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Kjeldsen ST, Nissen SD, Saljic A, Hesselkilde EM, Carstensen H, Sattler SM, Jespersen T, Linz D, Hopster-Iversen C, Kutieleh R, Sanders P, Buhl R. Structural and electro-anatomical characterization of the equine pulmonary veins: implications for atrial fibrillation. J Vet Cardiol 2024; 52:1-13. [PMID: 38290222 DOI: 10.1016/j.jvc.2024.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 01/03/2024] [Accepted: 01/03/2024] [Indexed: 02/01/2024]
Abstract
INTRODUCTION/OBJECTIVES Spontaneous pulmonary vein (PV) activity triggers atrial fibrillation (AF) in humans. Although AF frequently occurs in horses, the origin remains unknown. This study investigated the structural and electro-anatomical properties of equine PVs to determine the potential presence of an arrhythmogenic substrate. ANIMALS, MATERIALS AND METHODS Endocardial three-dimensional electro-anatomical mapping (EnSite Precision) using high-density (HD) catheters was performed in 13 sedated horses in sinus rhythm. Left atrium (LA) access was obtained retrogradely through the carotid artery. Post-mortem, tissue was harvested from the LA, right atrium (RA), and PVs for histological characterization and quantification of ion channel expression using immunohistochemical analysis. RESULTS Geometry, activation maps, and voltage maps of the PVs were created and a median of four ostia were identified. Areas of reduced conduction were found at the veno-atrial junction. The mean myocardial sleeve length varied from 28 ± 13 to 49 ± 22 mm. The PV voltage was 1.2 ± 1.4 mV and lower than the LA (3.4 ± 0.9 mV, P < 0.001). The fibrosis percentage was higher in PV myocardium (26.1 ± 6.6 %) than LA (14.5 ± 5.0 %, P = 0.003). L-type calcium channel (CaV1.2) expression was higher in PVs than LA (P = 0.001). T-type calcium channels (CaV3.3), connexin-43, ryanodine receptor-2, and small conductance calcium-activated potassium channel-3 was expressed in PVs. CONCLUSIONS The veno-atrial junction had lower voltages, increased structural heterogeneity and areas of slower conduction. Myocardial sleeves had variable lengths, and a different ion channel expression compared to the atria. Heterogeneous properties of the PVs interacting with the adjacent LA likely provide the milieu for re-entry and AF initiation.
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Affiliation(s)
- S T Kjeldsen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, 2630 Taastrup, Denmark.
| | - S D Nissen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, 2630 Taastrup, Denmark
| | - A Saljic
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - E M Hesselkilde
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - H Carstensen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, 2630 Taastrup, Denmark
| | - S M Sattler
- Department of Cardiology, Herlev and Gentofte University Hospital, Gentofte Hospitalsvej 1, 2900 Hellerup, Denmark
| | - T Jespersen
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - D Linz
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark; Department of Cardiology, Maastricht University Medical Centre and Cardiovascular Research Institute Maastricht, Universiteitssingel 50, 632, 6229 ER Maastricht, Netherlands
| | - C Hopster-Iversen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, 2630 Taastrup, Denmark
| | - R Kutieleh
- Abbott Medical, 214 Greenhill Road, SA 5063, Australia
| | - P Sanders
- Centre for Heart Rhythm Disorders, Royal Adelaide Hospital and University of Adelaide, Port Rd, SA 5000, Australia
| | - R Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, 2630 Taastrup, Denmark
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2
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Holst AG, Tomcsányi J, Vestbjerg B, Grunnet M, Sørensen US, Diness JG, Bentzen BH, Edvardsson N, Hohnloser SH, Bhatt DL, Dorian P. Inhibition of the K Ca2 potassium channel in atrial fibrillation: a randomized phase 2 trial. Nat Med 2024; 30:106-111. [PMID: 38092897 PMCID: PMC10803288 DOI: 10.1038/s41591-023-02679-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 11/01/2023] [Indexed: 01/24/2024]
Abstract
Existing antiarrhythmic drugs to treat atrial fibrillation (AF) have incomplete efficacy, contraindications and adverse effects, including proarrhythmia. AP30663, an inhibitor of the KCa2 channel, has demonstrated AF efficacy in animals; however, its efficacy in humans with AF is unknown. Here we conducted a phase 2 trial in which patients with a current episode of AF lasting for 7 days or less were randomized to receive an intravenous infusion of 3 or 5 mg kg-1 AP30663 or placebo. The trial was prematurely discontinued because of slow enrollment during the coronavirus disease 2019 pandemic. The primary endpoint of the trial was cardioversion from AF to sinus rhythm within 90 min from the start of the infusion, analyzed with Bayesian statistics. Among 59 patients randomized and included in the efficacy analyses, the primary endpoint occurred in 42% (5 of 12), 55% (12 of 22) and 0% (0 of 25) of patients treated with 3 mg kg-1 AP30663, 5 mg kg-1 AP30663 or placebo, respectively. Both doses demonstrated more than 99.9% probability of superiority over placebo, surpassing the prespecified 95% threshold. The mean time to cardioversion, a secondary endpoint, was 47 (s.d. = 23) and 41 (s.d. = 24) minutes for 3 mg kg-1 and 5 mg kg-1 AP30663, respectively. AP30663 caused a transient increase in the QTcF interval, with a maximum mean effect of 37.7 ms for the 5 mg kg-1 dose. For both dose groups, no ventricular arrhythmias occurred and adverse event rates were comparable to the placebo group. AP30663 demonstrated AF cardioversion efficacy in patients with recent-onset AF episodes. KCa2 channel inhibition may be an attractive mechanism for rhythm control of AF that should be studied further in randomized trials. ClinicalTrials.gov registration: NCT04571385 .
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Affiliation(s)
| | - János Tomcsányi
- Cardiology Department, St. John of God Hospital, Budapest, Hungary
| | | | | | | | | | | | - Nils Edvardsson
- Acesion Pharma, Copenhagen, Denmark
- Department of Molecular and Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | | | - Deepak L Bhatt
- Mount Sinai Heart, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Paul Dorian
- Department of Medicine, Division of Cardiology, University of Toronto, St. Michael's Hospital, Toronto, Ontario, Canada
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3
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Giommi A, Gurgel ARB, Smith GL, Workman AJ. Does the small conductance Ca 2+-activated K + current I SK flow under physiological conditions in rabbit and human atrial isolated cardiomyocytes? J Mol Cell Cardiol 2023; 183:70-80. [PMID: 37704101 DOI: 10.1016/j.yjmcc.2023.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 08/16/2023] [Accepted: 09/02/2023] [Indexed: 09/15/2023]
Abstract
BACKGROUND The small conductance Ca2+-activated K+ current (ISK) is a potential therapeutic target for treating atrial fibrillation. AIM To clarify, in rabbit and human atrial cardiomyocytes, the intracellular [Ca2+]-sensitivity of ISK, and its contribution to action potential (AP) repolarisation, under physiological conditions. METHODS Whole-cell-patch clamp, fluorescence microscopy: to record ion currents, APs and [Ca2+]i; 35-37°C. RESULTS In rabbit atrial myocytes, 0.5 mM Ba2+ (positive control) significantly decreased whole-cell current, from -12.8 to -4.9 pA/pF (P < 0.05, n = 17 cells, 8 rabbits). By contrast, the ISK blocker apamin (100 nM) had no effect on whole-cell current, at any set [Ca2+]i (∼100-450 nM). The ISK blocker ICAGEN (1 μM: ≥2 x IC50) also had no effect on current over this [Ca2+]i range. In human atrial myocytes, neither 1 μM ICAGEN (at [Ca2+]i ∼ 100-450 nM), nor 100 nM apamin ([Ca2+]i ∼ 250 nM) affected whole-cell current (5-10 cells, 3-5 patients/group). APs were significantly prolonged (at APD30 and APD70) by 2 mM 4-aminopyridine (positive control) in rabbit atrial myocytes, but 1 μM ICAGEN had no effect on APDs, versus either pre-ICAGEN or time-matched controls. High concentration (10 μM) ICAGEN (potentially ISK-non-selective) moderately increased APD70 and APD90, by 5 and 26 ms, respectively. In human atrial myocytes, 1 μM ICAGEN had no effect on APD30-90, whether stimulated at 1, 2 or 3 Hz (6-9 cells, 2-4 patients/rate). CONCLUSION ISK does not flow in human or rabbit atrial cardiomyocytes with [Ca2+]i set within the global average diastolic-systolic range, nor during APs stimulated at physiological or supra-physiological (≤3 Hz) rates.
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Affiliation(s)
- Alessandro Giommi
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Aline R B Gurgel
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Godfrey L Smith
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Antony J Workman
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK.
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4
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Herrera NT, Zhang X, Ni H, Maleckar MM, Heijman J, Dobrev D, Grandi E, Morotti S. Dual effects of the small-conductance Ca 2+-activated K + current on human atrial electrophysiology and Ca 2+-driven arrhythmogenesis: an in silico study. Am J Physiol Heart Circ Physiol 2023; 325:H896-H908. [PMID: 37624096 PMCID: PMC10659325 DOI: 10.1152/ajpheart.00362.2023] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 08/11/2023] [Accepted: 08/11/2023] [Indexed: 08/26/2023]
Abstract
By sensing changes in intracellular Ca2+, small-conductance Ca2+-activated K+ (SK) channels dynamically regulate the dynamics of the cardiac action potential (AP) on a beat-to-beat basis. Given their predominance in atria versus ventricles, SK channels are considered a promising atrial-selective pharmacological target against atrial fibrillation (AF), the most common cardiac arrhythmia. However, the precise contribution of SK current (ISK) to atrial arrhythmogenesis is poorly understood, and may potentially involve different mechanisms that depend on species, heart rates, and degree of AF-induced atrial remodeling. Both reduced and enhanced ISK have been linked to AF. Similarly, both SK channel up- and downregulation have been reported in chronic AF (cAF) versus normal sinus rhythm (nSR) patient samples. Here, we use our multiscale modeling framework to obtain mechanistic insights into the contribution of ISK in human atrial cardiomyocyte electrophysiology. We simulate several protocols to quantify how ISK modulation affects the regulation of AP duration (APD), Ca2+ transient, refractoriness, and occurrence of alternans and delayed afterdepolarizations (DADs). Our simulations show that ISK activation shortens the APD and atrial effective refractory period, limits Ca2+ cycling, and slightly increases the propensity for alternans in both nSR and cAF conditions. We also show that increasing ISK counteracts DAD development by enhancing the repolarization force that opposes the Ca2+-dependent depolarization. Taken together, our results suggest that increasing ISK in human atrial cardiomyocytes could promote reentry while protecting against triggered activity. Depending on the leading arrhythmogenic mechanism, ISK inhibition may thus be a beneficial or detrimental anti-AF strategy.NEW & NOTEWORTHY Using our established framework for human atrial myocyte simulations, we investigated the role of the small-conductance Ca2+-activated K+ current (ISK) in the regulation of cell function and the development of Ca2+-driven arrhythmias. We found that ISK inhibition, a promising atrial-selective pharmacological strategy against atrial fibrillation, counteracts the reentry-promoting abbreviation of atrial refractoriness, but renders human atrial myocytes more vulnerable to delayed afterdepolarizations, thus potentially increasing the propensity for ectopic (triggered) activity.
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Affiliation(s)
- Nathaniel T Herrera
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Xianwei Zhang
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Haibo Ni
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Mary M Maleckar
- Department of Computational Physiology, Simula Research Laboratory, Oslo, Norway
| | - Jordi Heijman
- Department of Cardiology, Faculty of Health, Medicine, and Life Sciences, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | - Dobromir Dobrev
- Faculty of Medicine, West German Heart and Vascular Center, Institute of Pharmacology, University Duisburg-Essen, Essen, Germany
- Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada
- Department of Integrative Physiology, Baylor College of Medicine, Houston, Texas, United States
| | - Eleonora Grandi
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Stefano Morotti
- Department of Pharmacology, University of California Davis, Davis, California, United States
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5
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Heijman J, Zhou X, Morotti S, Molina CE, Abu-Taha IH, Tekook M, Jespersen T, Zhang Y, Dobrev S, Milting H, Gummert J, Karck M, Kamler M, El-Armouche A, Saljic A, Grandi E, Nattel S, Dobrev D. Enhanced Ca 2+-Dependent SK-Channel Gating and Membrane Trafficking in Human Atrial Fibrillation. Circ Res 2023; 132:e116-e133. [PMID: 36927079 PMCID: PMC10147588 DOI: 10.1161/circresaha.122.321858] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 03/08/2023] [Indexed: 03/18/2023]
Abstract
BACKGROUND Small-conductance Ca2+-activated K+ (SK)-channel inhibitors have antiarrhythmic effects in animal models of atrial fibrillation (AF), presenting a potential novel antiarrhythmic option. However, the regulation of SK-channels in human atrial cardiomyocytes and its modification in patients with AF are poorly understood and were the object of this study. METHODS Apamin-sensitive SK-channel current (ISK) and action potentials were recorded in human right-atrial cardiomyocytes from sinus rhythm control (Ctl) patients or patients with (long-standing persistent) chronic AF (cAF). RESULTS ISK was significantly higher, and apamin caused larger action potential prolongation in cAF- versus Ctl-cardiomyocytes. Sensitivity analyses in an in silico human atrial cardiomyocyte model identified IK1 and ISK as major regulators of repolarization. Increased ISK in cAF was not associated with increases in mRNA/protein levels of SK-channel subunits in either right- or left-atrial tissue homogenates or right-atrial cardiomyocytes, but the abundance of SK2 at the sarcolemma was larger in cAF versus Ctl in both tissue-slices and cardiomyocytes. Latrunculin-A and primaquine (anterograde and retrograde protein-trafficking inhibitors) eliminated the differences in SK2 membrane levels and ISK between Ctl- and cAF-cardiomyocytes. In addition, the phosphatase-inhibitor okadaic acid reduced ISK amplitude and abolished the difference between Ctl- and cAF-cardiomyocytes, indicating that reduced calmodulin-Thr80 phosphorylation due to increased protein phosphatase-2A levels in the SK-channel complex likely contribute to the greater ISK in cAF-cardiomyocytes. Finally, rapid electrical activation (5 Hz, 10 minutes) of Ctl-cardiomyocytes promoted SK2 membrane-localization, increased ISK and reduced action potential duration, effects greatly attenuated by apamin. Latrunculin-A or primaquine prevented the 5-Hz-induced ISK-upregulation. CONCLUSIONS ISK is upregulated in patients with cAF due to enhanced channel function, mediated by phosphatase-2A-dependent calmodulin-Thr80 dephosphorylation and tachycardia-dependent enhanced trafficking and targeting of SK-channel subunits to the sarcolemma. The observed AF-associated increases in ISK, which promote reentry-stabilizing action potential duration shortening, suggest an important role for SK-channels in AF auto-promotion and provide a rationale for pursuing the antiarrhythmic effects of SK-channel inhibition in humans.
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Affiliation(s)
- Jordi Heijman
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Xiaobo Zhou
- First Department of Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany and DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, Mannheim, Germany
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Collaborative Innovation Center for Prevention of Cardiovascular Diseases, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| | - Stefano Morotti
- Department of Pharmacology, University of California, Davis, CA, USA
| | - Cristina E. Molina
- Institute of Experimental Cardiovascular Research, University Medical Center Hamburg-Eppendorf and DZHK (German Center for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | - Issam H. Abu-Taha
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Marcel Tekook
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Yiqiao Zhang
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Shokoufeh Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Hendrik Milting
- Erich and Hanna Klessmann Institute, Heart and Diabetes Center NRW, University Hospital of the Ruhr-University Bochum, Bad Oeynhausen, Germany
| | - Jan Gummert
- Erich and Hanna Klessmann Institute, Heart and Diabetes Center NRW, University Hospital of the Ruhr-University Bochum, Bad Oeynhausen, Germany
| | - Matthias Karck
- Department of Cardiac Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Markus Kamler
- Department of Thoracic and Cardiovascular Surgery, West German Heart and Vascular Center Essen, University Hospital Essen, Germany
| | - Ali El-Armouche
- Institute of Pharmacology, Dresden University of Technology, Germany
| | - Arnela Saljic
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, CA, USA
| | - Stanley Nattel
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
- Department of Medicine, Montreal Heart Institute and Université de Montréal
- Department of Pharmacology and Therapeutics, McGill University Montreal, Canada
- IHU LIRYC and Fondation Bordeaux Université, Bordeaux, France
| | - Dobromir Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
- Department of Medicine, Montreal Heart Institute and Université de Montréal
- Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX, USA
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6
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van Herck IGM, Seutin V, Bentzen BH, Marrion NV, Edwards AG. Gating kinetics and pharmacological properties of small-conductance Ca 2+-activated potassium channels. Biophys J 2023; 122:1143-1157. [PMID: 36760125 PMCID: PMC10111258 DOI: 10.1016/j.bpj.2023.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 11/20/2022] [Accepted: 02/06/2023] [Indexed: 02/11/2023] Open
Abstract
Small-conductance (SK) calcium-activated potassium channels are a promising treatment target in atrial fibrillation. However, the functional properties that differentiate SK inhibitors remain poorly understood. The objective of this study was to determine how two unrelated SK channel inhibitors, apamin and AP14145, impact SK channel function in excised inside-out single-channel recordings. Surprisingly, both apamin and AP14145 exert much of their inhibition by inducing a class of very-long-lived channel closures (apamin: τc,vl = 11.8 ± 7.1 s, and AP14145: τc,vl = 10.3 ± 7.2 s), which were never observed under control conditions. Both inhibitors also induced changes to the three closed and two open durations typical of normal SK channel gating. AP14145 shifted the open duration distribution to favor longer open durations, whereas apamin did not alter open-state kinetics. AP14145 also prolonged the two shortest channel closed durations (AP14145: τc,s = 3.50 ± 0.81 ms, and τc,i = 32.0 ± 6.76 ms versus control: τc,s = 1.59 ± 0.19 ms, and τc,i = 13.5 ± 1.17 ms), thus slowing overall gating kinetics within bursts of channel activity. In contrast, apamin accelerated intraburst gating kinetics by shortening the two shortest closed durations (τc,s = 0.75 ± 0.10 ms and τc,i = 5.08 ± 0.49 ms) and inducing periods of flickery activity. Finally, AP14145 introduced a unique form of inhibition by decreasing unitary current amplitude. SK channels exhibited two clearly distinguishable amplitudes (control: Ahigh = 0.76 ± 0.03 pA, and Alow = 0.54 ± 0.03 pA). AP14145 both reduced the fraction of patches exhibiting the higher amplitude (AP14145: 4/9 patches versus control: 16/16 patches) and reduced the mean low amplitude (0.38 ± 0.03 pA). Here, we have demonstrated that both inhibitors introduce very long channel closures but that each also exhibits unique effects on other components of SK gating kinetics and unitary current. The combination of these effects is likely to be critical for understanding the functional differences of each inhibitor in the context of cyclical Ca2+-dependent channel activation in vivo.
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Affiliation(s)
- Ilsbeth G M van Herck
- Computational Physiology Department, Simula Research Laboratory, Oslo, Norway; Institute of Informatics, University of Oslo, Oslo, Norway
| | - Vincent Seutin
- Neurophysiology Unit, GIGA Neurosciences, University of Liège, Liège, Belgium
| | - Bo H Bentzen
- Acesion Pharma, Copenhagen, Denmark; Biomedical Institute, University of Copenhagen, Copenhagen, Denmark
| | - Neil V Marrion
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Andrew G Edwards
- Computational Physiology Department, Simula Research Laboratory, Oslo, Norway; Department of Pharmacology, University of California, Davis, California.
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Naseem MU, Gurrola-Briones G, Romero-Imbachi MR, Borrego J, Carcamo-Noriega E, Beltrán-Vidal J, Zamudio FZ, Shakeel K, Possani LD, Panyi G. Characterization and Chemical Synthesis of Cm39 (α-KTx 4.8): A Scorpion Toxin That Inhibits Voltage-Gated K + Channel K V1.2 and Small- and Intermediate-Conductance Ca 2+-Activated K + Channels K Ca2.2 and K Ca3.1. Toxins (Basel) 2023; 15:41. [PMID: 36668861 PMCID: PMC9866218 DOI: 10.3390/toxins15010041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/22/2022] [Accepted: 12/27/2022] [Indexed: 01/06/2023] Open
Abstract
A novel peptide, Cm39, was identified in the venom of the scorpion Centruroides margaritatus. Its primary structure was determined. It consists of 37 amino acid residues with a MW of 3980.2 Da. The full chemical synthesis and proper folding of Cm39 was obtained. Based on amino acid sequence alignment with different K+ channel inhibitor scorpion toxin (KTx) families and phylogenetic analysis, Cm39 belongs to the α-KTx 4 family and was registered with the systematic number of α-KTx 4.8. Synthetic Cm39 inhibits the voltage-gated K+ channel hKV1.2 with high affinity (Kd = 65 nM). The conductance-voltage relationship of KV1.2 was not altered in the presence of Cm39, and the analysis of the toxin binding kinetics was consistent with a bimolecular interaction between the peptide and the channel; therefore, the pore blocking mechanism is proposed for the toxin-channel interaction. Cm39 also inhibits the Ca2+-activated KCa2.2 and KCa3.1 channels, with Kd = 502 nM, and Kd = 58 nM, respectively. However, the peptide does not inhibit hKV1.1, hKV1.3, hKV1.4, hKV1.5, hKV1.6, hKV11.1, mKCa1.1 K+ channels or the hNaV1.5 and hNaV1.4 Na+ channels at 1 μM concentrations. Understanding the unusual selectivity profile of Cm39 motivates further experiments to reveal novel interactions with the vestibule of toxin-sensitive channels.
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Affiliation(s)
- Muhammad Umair Naseem
- Department of Biophysics and Cell Biology, Faculty of Medicine, Research Center for Molecular Medicine, University of Debrecen, Egyetem ter. 1, 4032 Debrecen, Hungary
| | - Georgina Gurrola-Briones
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnologia, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca 62210, Morelos, Mexico
| | - Margarita R. Romero-Imbachi
- Grupo de Investigaciones Herpetológicas y Toxinológicas, Centro de Investigaciones Biomédicas, Departamento de Biología, Facultad de Ciencias Naturales, Exactas y de la Educación, Universidad del Cauca, Sector Tulcan, Calle 2 N 3N-100, Popayán 190002, Cauca, Colombia
| | - Jesus Borrego
- Department of Biophysics and Cell Biology, Faculty of Medicine, Research Center for Molecular Medicine, University of Debrecen, Egyetem ter. 1, 4032 Debrecen, Hungary
| | - Edson Carcamo-Noriega
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnologia, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca 62210, Morelos, Mexico
| | - José Beltrán-Vidal
- Grupo de Investigaciones Herpetológicas y Toxinológicas, Centro de Investigaciones Biomédicas, Departamento de Biología, Facultad de Ciencias Naturales, Exactas y de la Educación, Universidad del Cauca, Sector Tulcan, Calle 2 N 3N-100, Popayán 190002, Cauca, Colombia
| | - Fernando Z. Zamudio
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnologia, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca 62210, Morelos, Mexico
| | - Kashmala Shakeel
- Department of Biophysics and Cell Biology, Faculty of Medicine, Research Center for Molecular Medicine, University of Debrecen, Egyetem ter. 1, 4032 Debrecen, Hungary
| | - Lourival Domingos Possani
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnologia, Universidad Nacional Autónoma de México, Av. Universidad 2001, Cuernavaca 62210, Morelos, Mexico
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, Research Center for Molecular Medicine, University of Debrecen, Egyetem ter. 1, 4032 Debrecen, Hungary
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Kanaporis G, Blatter LA. Activation of small conductance Ca 2+ -activated K + channels suppresses Ca 2+ transient and action potential alternans in ventricular myocytes. J Physiol 2023; 601:51-67. [PMID: 36426548 PMCID: PMC9878619 DOI: 10.1113/jp283870] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 11/22/2022] [Indexed: 11/27/2022] Open
Abstract
At the cellular level, cardiac alternans is observed as beat-to-beat alternations in contraction strength, action potential (AP) morphology and Ca2+ transient (CaT) amplitude, and is a risk factor for cardiac arrhythmia. The (patho)physiological roles of small conductance Ca2+ -activated K+ (SK) channels in ventricles are poorly understood. We tested the hypothesis that in single rabbit ventricular myocytes pharmacological modulation of SK channels plays a causative role for the development of pacing-induced CaT and AP duration (APD) alternans. SK channel blockers (apamin, UCL1684) had only a minor effect on AP repolarization. However, SK channel activation by NS309 resulted in significant APD shortening, demonstrating that functional SK channels are well expressed in ventricular myocytes. The effects of NS309 were prevented or reversed by apamin and UCL1684, indicating that NS309 acted on SK channels. SK channel activation abolished or reduced the degree of pacing-induced CaT and APD alternans. Inhibition of KV 7.1 (with HMR1556) and KV 11.1 (with E4031) channels was used to mimic conditions of long QT syndromes type-1 and type-2, respectively. Both HMR1556 and E4031 enhanced CaT alternans that was prevented by SK channel activation. In AP voltage-clamped cells the SK channel activator had no effect on CaT alternans, confirming that suppression of CaT alternans was caused by APD shortening. APD shortening contributed to protection from alternans by lowering sarcoplasmic reticulum Ca2+ content and curtailing Ca2+ release. The data suggest that SK activation could be a potential intervention to avert development of alternans with important ramifications for arrhythmia prevention and therapy for patients with long QT syndrome. KEY POINTS: At the cellular level, cardiac alternans is observed as beat-to-beat alternations in contraction strength, action potential (AP) morphology and intracellular Ca2+ release amplitude, and is a risk factor for cardiac arrhythmia. The (patho)physiological roles of small conductance Ca2+ -activated K+ (SK) channels in ventricles are poorly understood. We investigated whether pharmacological modulation of SK channels affects the development of cardiac alternans in normal ventricular cells and in cells with drug-induced long QT syndrome (LQTS). While SK channel blockers have only a minor effect on AP morphology, their activation leads to AP shortening and abolishes or reduces the degree of pacing-induced Ca2+ and AP alternans. AP shortening contributed to protection against alternans by lowering sarcoplasmic reticulum Ca2+ content and curtailing Ca2+ release. The data suggest SK activation as a potential intervention to avert the development of alternans with important ramifications for arrhythmia prevention for patients with LQTS.
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Affiliation(s)
- Giedrius Kanaporis
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, Illinois, USA
| | - Lothar A Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, Illinois, USA
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Buhl R, Hesselkilde EM, Carstensen H, Hopster‐Iversen C, van Loon G, Decloedt A, Van Steenkiste G, Marr C, Reef VB, Schwarzwald CC, Mitchell KJ, Nostell K, Nogradi N, Nielsen SS, Carlson J, Platonov P. Atrial fibrillatory rate as predictor of recurrence of atrial fibrillation in horses treated medically or with electrical cardioversion. Equine Vet J 2022; 54:1013-1022. [PMID: 34957586 PMCID: PMC9787611 DOI: 10.1111/evj.13551] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 12/20/2021] [Indexed: 12/30/2022]
Abstract
BACKGROUND The recurrence rate of atrial fibrillation (AF) in horses after cardioversion to sinus rhythm (SR) is relatively high. Atrial fibrillatory rate (AFR) derived from surface ECG is considered a biomarker for electrical remodelling and could potentially be used for the prediction of successful AF cardioversion and AF recurrence. OBJECTIVES Evaluate if AFR was associated with successful treatment and could predict AF recurrence in horses. STUDY DESIGN Retrospective multicentre study. METHODS Electrocardiograms (ECG) from horses with persistent AF admitted for cardioversion with either medical treatment (quinidine) or transvenous electrical cardioversion (TVEC) were included. Bipolar surface ECG recordings were analysed by spatiotemporal cancellation of QRST complexes and calculation of AFR from the remaining atrial signal. Kaplan-Meier survival curve and Cox regression analyses were performed to assess the relationship between AFR and the risk of AF recurrence. RESULTS Of the 195 horses included, 74 received quinidine treatment and 121 were treated with TVEC. Ten horses did not cardiovert to SR after quinidine treatment and AFR was higher in these, compared with the horses that successfully cardioverted to SR (median [interquartile range]), (383 [367-422] vs 351 [332-389] fibrillations per minute (fpm), P < .01). Within the first 180 days following AF cardioversion, 12% of the quinidine and 34% of TVEC horses had AF recurrence. For the horses successfully cardioverted with TVEC, AFR above 380 fpm was significantly associated with AF recurrence (hazard ratio = 2.4, 95% confidence interval 1.2-4.8, P = .01). MAIN LIMITATIONS The treatment groups were different and not randomly allocated, therefore the two treatments cannot be compared. Medical records and the follow-up strategy varied between the centres. CONCLUSIONS High AFR is associated with failure of quinidine cardioversion and AF recurrence after successful TVEC. As a noninvasive marker that can be retrieved from surface ECG, AFR can be clinically useful in predicting the probability of responding to quinidine treatment as well as maintaining SR after electrical cardioversion.
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Affiliation(s)
- Rikke Buhl
- Department of Veterinary Clinical SciencesFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Eva M. Hesselkilde
- Department of Veterinary Clinical SciencesFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Helena Carstensen
- Department of Veterinary Clinical SciencesFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Charlotte Hopster‐Iversen
- Department of Veterinary Clinical SciencesFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Gunther van Loon
- Equine CardioteamDepartment of Large Animal Internal MedicineGhent UniversityMerelbekeBelgium
| | - Annelies Decloedt
- Equine CardioteamDepartment of Large Animal Internal MedicineGhent UniversityMerelbekeBelgium
| | - Glenn Van Steenkiste
- Equine CardioteamDepartment of Large Animal Internal MedicineGhent UniversityMerelbekeBelgium
| | | | - Virginia B. Reef
- Department of Clinical Studies New Bolton CenterUniversity of Pennsylvania School of Veterinary MedicineKennett SquarePennsylvaniaUSA
| | | | | | - Katarina Nostell
- Department of Clinical SciencesFaculty of Veteirnary SciencesSwedish University of Agricultural SciencesUppsalaSweden
| | | | - Søren S. Nielsen
- Department of Veterinary SciencesFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
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Premont A, Saadeh K, Edling C, Lewis R, Marr CM, Jeevaratnam K. Cardiac ion channel expression in the equine model - In-silico prediction utilising RNA sequencing data from mixed tissue samples. Physiol Rep 2022; 10:e15273. [PMID: 35880716 PMCID: PMC9316921 DOI: 10.14814/phy2.15273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 03/19/2022] [Accepted: 04/03/2022] [Indexed: 06/15/2023] Open
Abstract
Understanding cardiomyocyte ion channel expression is crucial to understanding normal cardiac electrophysiology and underlying mechanisms of cardiac pathologies particularly arrhythmias. Hitherto, equine cardiac ion channel expression has rarely been investigated. Therefore, we aim to predict equine cardiac ion channel gene expression. Raw RNAseq data from normal horses from 9 datasets was retrieved from ArrayExpress and European Nucleotide Archive and reanalysed. The normalised (FPKM) read counts for a gene in a mix of tissue were hypothesised to be the average of the expected expression in each tissue weighted by the proportion of the tissue in the mix. The cardiac-specific expression was predicted by estimating the mean expression in each other tissues. To evaluate the performance of the model, predicted gene expression values were compared to the human cardiac gene expression. Cardiac-specific expression could be predicted for 91 ion channels including most expressed Na+ channels, K+ channels and Ca2+ -handling proteins. These revealed interesting differences from what would be expected based on human studies. These differences included predominance of NaV 1.4 rather than NaV 1.5 channel, and RYR1, SERCA1 and CASQ1 rather than RYR2, SERCA2, CASQ2 Ca2+ -handling proteins. Differences in channel expression not only implicate potentially different regulatory mechanisms but also pathological mechanisms of arrhythmogenesis.
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Affiliation(s)
- Antoine Premont
- Faculty of Health and Medical SciencesUniversity of SurreyGuildfordSurreyUK
| | - Khalil Saadeh
- Faculty of Health and Medical SciencesUniversity of SurreyGuildfordSurreyUK
- School of Clinical MedicineUniversity of CambridgeCambridgeUK
| | - Charlotte Edling
- Faculty of Health and Medical SciencesUniversity of SurreyGuildfordSurreyUK
| | - Rebecca Lewis
- Faculty of Health and Medical SciencesUniversity of SurreyGuildfordSurreyUK
| | - Celia M. Marr
- Faculty of Health and Medical SciencesUniversity of SurreyGuildfordSurreyUK
- School of Clinical MedicineUniversity of CambridgeCambridgeUK
- Rossdales Equine Hospital and Diagnostic CentreExningSuffolkUK
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11
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Weis R, Carstensen H, Sattler SM, Buhl R, Hesselkilde EM. Electrocardiographic Changes in a Horse with Induced Myocardial Infarction. Animals (Basel) 2022; 12:ani12101272. [PMID: 35625118 PMCID: PMC9137605 DOI: 10.3390/ani12101272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 05/06/2022] [Accepted: 05/10/2022] [Indexed: 11/18/2022] Open
Abstract
Simple Summary During acute myocardial infarction (AMI), the electrophysiological changes are clearly visible on the 12-lead electrocardiogram (ECG), and are as such, an important diagnostic tool in human cardiology. Similar to humans, changes are seen on the ECG in both pigs and dogs, but so far, this has not been studied in horses, despite equine cardiology being a growing field. This study aimed to investigate the ECG changes seen with a 12-lead ECG in a horse with induced myocardial infarction. The ECG changes observed in this case report were comparable to other species with AMI and showed similar patterns throughout the different phases of occlusion. The results could, therefore, indicate that a 12-lead ECG can be used to detect signs of ischemic heart disease, such as AMI, in horses, while they also potentially elucidate certain translational connections between human and veterinary medicine. Abstract During acute myocardial infarction (AMI), the ischemia and necrosis of the infarcted tissue result in local electrophysiological changes, which bring about deviations of the ST segment and T wave. In this case report, the aim was to investigate whether these changes could be detected with a 12-lead electrocardiogram (ECG) during acute occlusion of the coronary artery in a 15-year-old Standardbred mare (scheduled for euthanasia due to non-cardiac health problems). The left anterior descending (LAD) coronary artery was occluded using an angioplasty balloon catheter guided through the carotid artery. Two coronary occlusions of 30 min were induced, separated by a 10-min reperfusion phase. AMI led to ST deviations and T-wave amplitude changes (maximum ST deviation was 1.98 mV; T-wave amplitude increased from 6.58 to 9.25 mV). The ST segment almost returned to the baseline during the reperfusion phase. The ECG changes seen after the infarction were comparable to those reported in other species with AMI, suggesting that the 12-lead-ECG can potentially be used to detect signs of myocardial infarction in horses.
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Affiliation(s)
- Rikke Weis
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630 Taastrup, Denmark; (R.W.); (H.C.); (E.M.H.)
| | - Helena Carstensen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630 Taastrup, Denmark; (R.W.); (H.C.); (E.M.H.)
| | - Stefan M. Sattler
- Department of Cardiology, Gentofte University Hospital, Gentofte Hospitalsvej 1, 2900 Hellerup, Denmark;
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630 Taastrup, Denmark; (R.W.); (H.C.); (E.M.H.)
- Correspondence:
| | - Eva M. Hesselkilde
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630 Taastrup, Denmark; (R.W.); (H.C.); (E.M.H.)
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12
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Yang B, Jiang Q, He S, Li T, Ou X, Chen T, Fan X, Jiang F, Zeng X, Huang CLH, Lei M, Tan X. Ventricular SK2 upregulation following angiotensin II challenge: Modulation by p21-activated kinase-1. J Mol Cell Cardiol 2022; 164:110-125. [PMID: 34774547 DOI: 10.1016/j.yjmcc.2021.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 10/15/2021] [Accepted: 11/03/2021] [Indexed: 12/11/2022]
Abstract
Effects of hypertrophic challenge on small-conductance, Ca2+-activated K+(SK2) channel expression were explored in intact murine hearts, isolated ventricular myocytes and neonatal rat cardiomyocytes (NRCMs). An established experimental platform applied angiotensin II (Ang II) challenge in the presence and absence of reduced p21-activated kinase (PAK1) (PAK1cko vs. PAK1f/f, or shRNA-PAK1 interference) expression. SK2 current contributions were detected through their sensitivity to apamin block. Ang II treatment increased such SK2 contributions to optically mapped action potential durations (APD80) and their heterogeneity, and to patch-clamp currents. Such changes were accentuated in PAK1cko compared to PAK1f/f, intact hearts and isolated cardiomyocytes. They paralleled increased histological and echocardiographic hypertrophic indices, reduced cardiac contractility, and increased SK2 protein expression, changes similarly greater with PAK1cko than PAK1f/f. In NRCMs, Ang II challenge replicated such increases in apamin-sensitive SK patch clamp currents as well as in real-time PCR and western blot measures of SK2 mRNA and protein expression and cell hypertrophy. Furthermore, the latter were enhanced by shRNA-PAK1 interference and mitigated by the PAK1 agonist FTY720. Increased CaMKII and CREB phosphorylation accompanied these effects. These were rescued by both FTY720 as well as the CaMKII inhibitor KN93, but not its inactive analogue KN92. Such CREB then specifically bound to the KCNN2 promoter sequence in luciferase assays. These findings associate Ang II induced hypertrophy with increased SK2 expression brought about by a CaMKII/CREB signaling convergent with the PAK1 pathway thence upregulating the KCNN2 promoter activity. SK2 may then influence cardiac electrophysiology under conditions of cardiac hypertrophy and failure.
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Affiliation(s)
- Binbin Yang
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Oral & Maxillofacial Reconstruction and Regeneration Laboratory, The Affiliated Stomatology Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Qin Jiang
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Shicheng He
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Tao Li
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Xianhong Ou
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Tangting Chen
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Xuehui Fan
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Feng Jiang
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Xiaorong Zeng
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Christopher L-H Huang
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Physiological Laboratory and Department of Biochemistry, University of Cambridge, Cambridge CB2 3EG, UK
| | - Ming Lei
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
| | - Xiaoqiu Tan
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China.
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13
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Ji D, Fleig A, Horgen FD, Feng ZP, Sun HS. Modulators of TRPM7 and its potential as a drug target for brain tumours. Cell Calcium 2021; 101:102521. [PMID: 34953296 DOI: 10.1016/j.ceca.2021.102521] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 12/14/2021] [Accepted: 12/15/2021] [Indexed: 12/14/2022]
Abstract
TRPM7 is a non-selective divalent cation channel with an alpha-kinase domain. Corresponding with its broad expression, TRPM7 has a role in a wide range of cell functions, including proliferation, migration, and survival. Growing evidence shows that TRPM7 is also aberrantly expressed in various cancers, including brain cancers. Because ion channels have widespread tissue distribution and result in extensive physiological consequences when dysfunctional, these proteins can be compelling drug targets. In fact, ion channels comprise the third-largest drug target type, following enzymes and receptors. Literature has shown that suppression of TRPM7 results in inhibition of migration, invasion, and proliferation in several human brain tumours. Therefore, TRPM7 presents a potential target for therapeutic brain tumour interventions. This article reviews current literature on TRPM7 as a potential drug target in the context of brain tumours and provides an overview of various selective and non-selective modulators of the channel relevant to pharmacology, oncology, and ion channel function.
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Affiliation(s)
- Delphine Ji
- Department of Surgery, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8; Department of Physiology, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8
| | - Andrea Fleig
- Center for Biomedical Research at The Queen's Medical Center and John A. Burns School of Medicine and Cancer Center at the University of Hawaii, Honolulu, Hawaii 96813, USA
| | - F David Horgen
- Department of Natural Sciences, Hawaii Pacific University, Kaneohe, Hawaii 96744, USA
| | - Zhong-Ping Feng
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8.
| | - Hong-Shuo Sun
- Department of Surgery, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8; Department of Physiology, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8; Department of Pharmacology, Temerty Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8; Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, Ontario, Canada M5S 3M2.
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14
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Premont A, Balthes S, Marr CM, Jeevaratnam K. Fundamentals of arrhythmogenic mechanisms and treatment strategies for equine atrial fibrillation. Equine Vet J 2021; 54:262-282. [PMID: 34564902 DOI: 10.1111/evj.13518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 09/13/2021] [Accepted: 09/16/2021] [Indexed: 11/26/2022]
Abstract
Atrial fibrillation (AF) is the most common pathological arrhythmia in horses. Although it is not usually a life-threatening condition on its own, it can cause poor performance and make the horse unsafe to ride. It is a complex multifactorial disease influenced by both genetic and environmental factors including exercise training, comorbidities or ageing. The interactions between all these factors in horses are still not completely understood and the pathophysiology of AF remains poorly defined. Exciting progress has been recently made in equine cardiac electrophysiology in terms of diagnosis and documentation methods such as cardiac mapping, implantable electrocardiogram (ECG) recording devices or computer-based ECG analysis that will hopefully improve our understanding of this disease. The available pharmaceutical and electrophysiological treatments have good efficacy and lead to a good prognosis for AF, but recurrence is a frequent issue that veterinarians have to face. This review aims to summarise our current understanding of equine cardiac electrophysiology and pathophysiology of equine AF while providing an overview of the mechanism of action for currently available treatments for equine AF.
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Affiliation(s)
- Antoine Premont
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
| | - Samantha Balthes
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
| | - Celia M Marr
- Rossdales Equine Hospital and Diagnostic Centre, Newmarket, UK
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15
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Saljic A, Friederike Fenner M, Winters J, Flethøj M, Eggert Eggertsen C, Carstensen H, Dalgas Nissen S, Melis Hesselkilde E, van Hunnik A, Schotten U, Sørensen U, Jespersen T, Verheule S, Buhl R. Increased fibroblast accumulation in the equine heart following persistent atrial fibrillation. Int J Cardiol Heart Vasc 2021; 35:100842. [PMID: 34355058 PMCID: PMC8322305 DOI: 10.1016/j.ijcha.2021.100842] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 06/30/2021] [Accepted: 07/06/2021] [Indexed: 01/06/2023]
Abstract
Persistent atrial fibrillation is associated with increased fibroblast accumulation. Six weeks of persistent AF is not associated with structural remodeling. Fibroblasts are potentially contributing to alteration in atrial electrophysiology.
Background Fibroblasts maintain the extracellular matrix homeostasis and may couple to cardiomyocytes through gap junctions and thereby increase the susceptibility to slow conduction and cardiac arrhythmias, such as atrial fibrillation (AF). In this study, we used an equine model of persistent AF to characterize structural changes and the role of fibroblasts in the development of an arrhythmogenic substrate for AF. Material and methods Eleven horses were subjected to atrial tachypacing until self-sustained AF developed and were kept in AF for six weeks. Horses in sinus rhythm (SR) served as control. In terminal open-chest experiments conduction velocity (CV) was measured. Tissue was harvested and stained from selected sites. Automated image analysis was performed to assess fibrosis, fibroblasts, capillaries and various cardiomyocyte characteristics. Results Horses in SR showed a rate-dependent slowing of CV, while in horses with persistent AF this rate-dependency was completely abolished (CV•basic cycle length relation p = 0.0295). Overall and interstitial amounts of fibrosis were unchanged, but an increased fibroblast count was found in left atrial appendage, Bachmann's bundle, intraatrial septum and pulmonary veins (p < 0.05 for all) in horses with persistent AF. The percentage of α-SMA expressing fibroblasts remained the same between the groups. Conclusion Persistent AF resulted in fibroblast accumulation in several regions, particularly in the left atrial appendage. The increased number of fibroblasts could be a mediator of altered electrophysiology during AF. Targeting the fibroblast proliferation and differentiation could potentially serve as a novel therapeutic target slowing down the structural remodeling associated with AF.
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Affiliation(s)
- Arnela Saljic
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark
| | - Merle Friederike Fenner
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, DK-2630 Taastrup, Denmark.,Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Grønnegårdsvej 7, 1870 Frederiksberg, Denmark
| | - Joris Winters
- Department of Physiology, Maastricht University, Maastricht, Netherlands
| | - Mette Flethøj
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, DK-2630 Taastrup, Denmark
| | - Caroline Eggert Eggertsen
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark
| | - Helena Carstensen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, DK-2630 Taastrup, Denmark
| | - Sarah Dalgas Nissen
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark
| | - Eva Melis Hesselkilde
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark
| | - Arne van Hunnik
- Department of Physiology, Maastricht University, Maastricht, Netherlands
| | - Ulrich Schotten
- Department of Physiology, Maastricht University, Maastricht, Netherlands
| | | | - Thomas Jespersen
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark
| | - Sander Verheule
- Department of Physiology, Maastricht University, Maastricht, Netherlands
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Agrovej 8, DK-2630 Taastrup, Denmark
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Abstract
The physiological heart function is controlled by a well-orchestrated interplay of different ion channels conducting Na+, Ca2+ and K+. Cardiac K+ channels are key players of cardiac repolarization counteracting depolarizating Na+ and Ca2+ currents. In contrast to Na+ and Ca2+, K+ is conducted by many different channels that differ in activation/deactivation kinetics as well as in their contribution to different phases of the action potential. Together with modulatory subunits these K+ channel α-subunits provide a wide range of repolarizing currents with specific characteristics. Moreover, due to expression differences, K+ channels strongly influence the time course of the action potentials in different heart regions. On the other hand, the variety of different K+ channels increase the number of possible disease-causing mutations. Up to now, a plethora of gain- as well as loss-of-function mutations in K+ channel forming or modulating proteins are known that cause severe congenital cardiac diseases like the long-QT-syndrome, the short-QT-syndrome, the Brugada syndrome and/or different types of atrial tachyarrhythmias. In this chapter we provide a comprehensive overview of different K+ channels in cardiac physiology and pathophysiology.
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Qi MM, Qian LL, Wang RX. Modulation of SK Channels: Insight Into Therapeutics of Atrial Fibrillation. Heart Lung Circ 2021; 30:1130-1139. [PMID: 33642173 DOI: 10.1016/j.hlc.2021.01.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 01/12/2021] [Accepted: 01/31/2021] [Indexed: 11/19/2022]
Abstract
Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia in the world. Although much technological progress in the treatment of AF has been made, there is an urgent need for better treatment of AF due to its high rates of morbidity and mortality. The anti-arrhythmic drugs currently approved for marketing have significant limitations and side effects such as life-threatening ventricular arrhythmias and hypotension. The small conductance Ca2+-activated K+ channels (SK channels) are dependent on intracellular Ca2+ concentrations, which tightly integrate with membrane potential. Given the predominant expression in the atria of many species, including humans, they are now emerging as a therapeutic target for treating AF. This review aimed to illustrate the characteristics and function of SK channels. Moreover, it discussed the regulation of SK channels and their potential as a therapeutic target of AF.
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Affiliation(s)
- Miao-Miao Qi
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China
| | - Ling-Ling Qian
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China
| | - Ru-Xing Wang
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China.
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18
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Saljic A, Jespersen T, Buhl R. Anti-arrhythmic investigations in large animal models of atrial fibrillation. Br J Pharmacol 2021; 179:838-858. [PMID: 33624840 DOI: 10.1111/bph.15417] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 02/10/2021] [Accepted: 02/11/2021] [Indexed: 12/13/2022] Open
Abstract
Atrial fibrillation (AF) constitutes an increasing health problem in the aging population. Animal models reflecting human phenotypes are needed to understand the mechanisms of AF, as well as to test new pharmacological interventions. In recent years, a number of large animal models, primarily pigs, goats, dog and horses have been used in AF research. These animals can to a certain extent recapitulate the human pathophysiological characteristics and serve as valuable tools in investigating new pharmacological interventions for treating AF. This review focuses on anti-arrhythmic investigations in large animals. Initially, spontaneous AF in small and large mammals is discussed. This is followed by a short presentation of frequently used methods for inducing short- and long-term AF. The major focus of the review is on anti-arrhythmic compounds either frequently used in the human clinic (ranolazine, flecainide, vernakalant and amiodarone) or being promising new AF medicine candidates (IK,Ach , ISK,Ca and IK2P blockers).
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Affiliation(s)
- Arnela Saljic
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Jespersen
- Laboratory of Cardiac Physiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
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19
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Fenner MF, Gatta G, Sattler S, Kuiper M, Hesselkilde EM, Adler DMT, Smerup M, Schotten U, Sørensen U, Diness JG, Jespersen T, Verheule S, Van Hunnik A, Buhl R. Inhibition of Small-Conductance Calcium-Activated Potassium Current ( I K,Ca) Leads to Differential Atrial Electrophysiological Effects in a Horse Model of Persistent Atrial Fibrillation. Front Physiol 2021; 12:614483. [PMID: 33633584 PMCID: PMC7900437 DOI: 10.3389/fphys.2021.614483] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 01/08/2021] [Indexed: 12/13/2022] Open
Abstract
Background Small-conductance Ca2+-activated K+ (KCa2) channels have been proposed as a possible atrial-selective target to pharmacologically terminate atrial fibrillation (AF) and to maintain sinus rhythm. However, it has been hypothesized that the importance of the KCa2 current—and thereby the efficacy of small-conductance Ca2+-activated K+ current (IK,Ca) inhibition—might be negatively related to AF duration and the extent of AF-induced remodeling. Experimental Approach and Methods To address the hypothesis of the efficacy of IK,Ca inhibition being dependent on AF duration, the anti-arrhythmic properties of the IK,Ca inhibitor NS8593 (5 mg/kg) and its influence on atrial conduction were studied using epicardial high-density contact mapping in horses with persistent AF. Eleven Standardbred mares with tachypacing-induced persistent AF (42 ± 5 days of AF) were studied in an open-chest experiment. Unipolar AF electrograms were recorded and isochronal high-density maps analyzed to allow for the reconstruction of wave patterns and changes in electrophysiological parameters, such as atrial conduction velocity and AF cycle length. Atrial anti-arrhythmic properties and adverse effects of NS8593 on ventricular electrophysiology were evaluated by continuous surface ECG monitoring. Results IK,Ca inhibition by NS8593 administered intravenously had divergent effects on right and left AF complexity and propagation properties in this equine model of persistent AF. Despite global prolongation of AF cycle length, a slowing of conduction in the right atrium led to increased anisotropy and electrical dissociation, thus increasing AF complexity. In contrast, there was no significant change in AF complexity in the LA, and cardioversion of AF was not achieved. Conclusions Intra-atrial heterogeneity in response to IK,Ca inhibition by NS8593 was observed. The investigated dose of NS8593 increased the AF cycle length but was not sufficient to induce cardioversion. In terms of propagation properties during AF, IK,Ca inhibition by NS8593 led to divergent effects in the right and left atrium. This divergent behavior may have impeded the cardioversion success.
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Affiliation(s)
- Merle Friederike Fenner
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Giulia Gatta
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Stefan Sattler
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Marion Kuiper
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Eva Melis Hesselkilde
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ditte M T Adler
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Morten Smerup
- Department of Cardiothoracic Surgery, The Heart Centre, Copenhagen University Hospital, Copenhagen, Denmark
| | - Ulrich Schotten
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | | | | | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sander Verheule
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Arne Van Hunnik
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
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20
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Chen M, Fei Y, Chen TZ, Li YG, Chen PS. The regulation of the small-conductance calcium-activated potassium current and the mechanisms of sex dimorphism in J wave syndrome. Pflugers Arch 2021; 473:491-506. [PMID: 33411079 DOI: 10.1007/s00424-020-02500-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 11/20/2020] [Accepted: 11/25/2020] [Indexed: 12/16/2022]
Abstract
Apamin-sensitive small-conductance calcium-activated potassium (SK) current (IKAS) plays an important role in cardiac repolarization under a variety of physiological and pathological conditions. The regulation of cardiac IKAS relies on SK channel expression, intracellular Ca2+, and interaction between SK channel and intracellular Ca2+. IKAS activation participates in multiple types of arrhythmias, including atrial fibrillation, ventricular tachyarrhythmias, and automaticity and conduction abnormality. Recently, sex dimorphisms in autonomic control have been noticed in IKAS activation, resulting in sex-differentiated action potential morphology and arrhythmogenesis. This review provides an update on the Ca2+-dependent regulation of cardiac IKAS and the role of IKAS on arrhythmias, with a special focus on sex differences in IKAS activation. We propose that sex dimorphism in autonomic control of IKAS may play a role in J wave syndrome.
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21
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Dudem S, Sergeant GP, Thornbury KD, Hollywood MA. Calcium-Activated K(+) Channels (K(Ca)) and Therapeutic Implications. Handb Exp Pharmacol 2021; 267:379-416. [PMID: 33945030 DOI: 10.1007/164_2021_459] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Potassium channels are the most diverse and ubiquitous family of ion channels found in cells. The Ca2+ and voltage gated members form a subfamily that play a variety of roles in both excitable and non-excitable cells and are further classified on the basis of their single channel conductance to form the small conductance (SK), intermediate conductance (IK) and big conductance (BK) K+ channels.In this chapter, we will focus on the mechanisms underlying the gating of BK channels, whose function is modified in different tissues by different splice variants as well as the expanding array of regulatory accessory subunits including β, γ and LINGO subunits. We will examine how BK channels are modified by these regulatory subunits and describe how the channel gating is altered by voltage and Ca2+ whilst setting this in context with the recently published structures of the BK channel. Finally, we will discuss how BK and other calcium-activated channels are modulated by novel ion channel modulators and describe some of the challenges associated with trying to develop compounds with sufficient efficacy, potency and selectivity to be of therapeutic benefit.
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22
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Decloedt A, Van Steenkiste G, Vera L, Buhl R, van Loon G. Atrial fibrillation in horses Part 2: Diagnosis, treatment and prognosis. Vet J 2020; 268:105594. [PMID: 33468306 DOI: 10.1016/j.tvjl.2020.105594] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 10/27/2020] [Accepted: 12/10/2020] [Indexed: 10/22/2022]
Abstract
Atrial fibrillation (AF) is suspected by an irregularly irregular rhythm during auscultation at rest and should be confirmed by electrocardiography. Heart rate monitoring is potentially interesting for AF detection by horse owners, based on the disproportionally high heart rate during exercise or increased heart rate variability. Echocardiography and laboratory analysis are useful to identify underlying cardiac disease. Horses with severe cardiac disease should not undergo cardioversion due to the risk of recurrence. Cardioversion is recommended especially in horses performing high intensity exercise or showing average maximal heart rates higher than 220 beats per min or abnormal ventricular complexes during exercise or stress. Pharmacological cardioversion can be performed using quinidine sulphate administered orally, with an overall mean reported success rate around 80%. Other therapeutic drugs have been described such as flecainide, amiodarone or novel atrial specific compounds. Transvenous electrical cardioversion (TVEC) is performed by delivering a shock between two cardioversion catheters positioned in the left pulmonary artery and right atrium, with a success rate of >95%. After cardioversion, most horses return to their previous level of performance. However, the recurrence rate after pharmacological or electrical cardioversion is up to 39%. Recurrence has been related to previous unsuccessful treatment attempts, valvular regurgitation and the presence of atrial premature depolarisations or low atrial contractile function after cardioversion. Large atrial size and long AF duration have also been suggested as risk factors. Different approaches for preventing recurrence have been described such as the administration of sotalol, however, large clinical studies have not been published.
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Affiliation(s)
- Annelies Decloedt
- Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Belgium.
| | - Glenn Van Steenkiste
- Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Belgium
| | - Lisse Vera
- Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Belgium
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Gunther van Loon
- Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Belgium
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23
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Wong CK, Tse HF. New methodological approaches to atrial fibrillation drug discovery. Expert Opin Drug Discov 2020; 16:319-329. [PMID: 33016154 DOI: 10.1080/17460441.2021.1826432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
INTRODUCTION Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice and rhythm control using pharmacological agents is required in selected patients. Nonetheless, current medication is only modestly efficacious and associated with significant cardiovascular and systemic side effects. More efficacious and safe drugs are required to restore and maintain sinus rhythm in patients with AF. AREAS COVERED In this review, several potential drug targets are discussed including trans-membrane ion channels, intracellular calcium signaling, gap junction signaling, atrial inflammation and fibrosis, and the autonomic nervous system. New tools and methodologies for AF drug development are also reviewed including gene therapy, genome-guided therapy, stem cell technologies, tissue engineering, and optogenetics. EXPERT OPINION In recent decades, there has been an increased understanding of the underlying pathogenesis of AF. As a result, there is a gradual paradigm shift from focusing only on trans-membrane ion channel inhibition to developing therapeutic agents that target other underlying arrhythmogenic mechanisms. Gene therapy and genome-guided therapy are emerging as novel treatments for AF with some success in proof-of-concept studies. Recent advances in stem cell technology, tissue engineering, and optogenetics may allow more effective in-vitro drug screening than conventional methodologies.
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Affiliation(s)
- Chun-Ka Wong
- Cardiology Division, Department of Medicine, The University of Hong Kong, Hong Kong, SAR China
| | - Hung-Fat Tse
- Cardiology Division, Department of Medicine, The University of Hong Kong, Hong Kong, SAR China
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24
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Abstract
The transient receptor potential cation channel, subfamily M, member 7 (TRPM7) is a ubiquitously expressed membrane protein, which forms a channel linked to a cytosolic protein kinase. Genetic inactivation of TRPM7 in animal models uncovered the critical role of TRPM7 in early embryonic development, immune responses, and the organismal balance of Zn2+, Mg2+, and Ca2+. TRPM7 emerged as a new therapeutic target because malfunctions of TRPM7 have been associated with anoxic neuronal death, tissue fibrosis, tumour progression, and giant platelet disorder. Recently, several laboratories have identified pharmacological compounds allowing to modulate either channel or kinase activity of TRPM7. Among other small molecules, NS8593 has been defined as a potent negative gating regulator of the TRPM7 channel. Consequently, several groups applied NS8593 to investigate cellular pathways regulated by TRPM7. Here, we summarize the progress in this research area. In particular, two notable milestones have been reached in the assessment of TRPM7 druggability. Firstly, several laboratories demonstrated that NS8593 treatment reliably mirrors prominent phenotypes of cells manipulated by genetic inactivation of TRPM7. Secondly, it has been shown that NS8593 allows us to probe the therapeutic potential of TRPM7 in animal models of human diseases. Collectively, these studies employing NS8593 may serve as a blueprint for the preclinical assessment of TRPM7-targeting drugs.
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25
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Bronk P, Kim TY, Polina I, Hamilton S, Terentyeva R, Roder K, Koren G, Terentyev D, Choi BR. Impact of I SK Voltage and Ca 2+/Mg 2+-Dependent Rectification on Cardiac Repolarization. Biophys J 2020; 119:690-704. [PMID: 32668235 DOI: 10.1016/j.bpj.2020.06.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 06/02/2020] [Accepted: 06/10/2020] [Indexed: 10/24/2022] Open
Abstract
Cardiac small conductance Ca2+-activated K+ (SK) channels are activated solely by Ca2+, but the SK current (ISK) is inwardly rectified. However, the impact of inward rectification in shaping action potentials (APs) in ventricular cardiomyocytes under β-adrenergic stimulation or in disease states remains undefined. Two processes underlie this inward rectification: an intrinsic rectification caused by an electrostatic energy barrier from positively charged amino acids at the inner pore and a voltage-dependent Ca2+/Mg2+ block. Thus, Ca2+ has a biphasic effect on ISK, activating at low [Ca2+] yet inhibiting ISK at high [Ca2+]. We examined the effect of ISK rectification on APs in rat cardiomyocytes by simultaneously recording whole-cell apamin-sensitive currents and Ca2+ transients during an AP waveform and developed a computer model of SK channels with rectification features. The typical profile of ISK during AP clamp included an initial peak (mean 1.6 pA/pF) followed by decay to the point that submembrane [Ca2+] reached ∼10 μM. During the rest of the AP stimulus, ISK either plateaued or gradually increased as the cell repolarized and submembrane [Ca2+] decreased further. We used a six-state gating model combined with intrinsic and Ca2+/Mg2+-dependent rectification to simulate ISK and investigated the relative contributions of each type of rectification to AP shape. This SK channel model replicates key features of ISK recording during AP clamp showing that intrinsic rectification limits ISK at high Vm during the early and plateau phase of APs. Furthermore, the initial rise of Ca2+ transients activates, but higher [Ca2+] blocks SK channels, yielding a transient outward-like ISK trajectory. During the decay phase of Ca2+, the Ca2+-dependent block is released, causing ISK to rise again and contribute to repolarization. Therefore, ISK is an important repolarizing current, and the rectification characteristics of an SK channel determine its impact on early, plateau, and repolarization phases of APs.
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26
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Gal P, Klaassen ES, Bergmann KR, Saghari M, Burggraaf J, Kemme MJB, Sylvest C, Sørensen U, Bentzen BH, Grunnet M, Diness JG, Edvardsson N. First Clinical Study with AP30663 - a K Ca 2 Channel Inhibitor in Development for Conversion of Atrial Fibrillation. Clin Transl Sci 2020; 13:1336-1344. [PMID: 32725783 PMCID: PMC7719388 DOI: 10.1111/cts.12835] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 05/22/2020] [Indexed: 11/30/2022] Open
Abstract
Pharmacological cardioversion of atrial fibrillation (AF) is frequently inefficacious. AP30663, a small conductance Ca2+ activated K+ (KCa2) channel blocker, prolonged the atrial effective refractory period in preclinical studies and subsequently converted AF into normal sinus rhythm. This first‐in‐human study evaluated the safety and tolerability, and pharmacokinetic (PK) and pharmacodynamic (PD) effects were explored. Forty‐seven healthy male volunteers (23.7 ± 3.0 years) received AP30663 intravenously in ascending doses. Due to infusion site reactions, changes to the formulation and administration were implemented in the latter 24 volunteers. Extractions from a 24‐hour continuous electrocardiogram were used to evaluate the PD effect of AP30663. Data were analyzed with a repeated measure analysis of covariance, noncompartmental analysis, and concentration‐effect analysis. In total, 33 of 34 adverse events considered related to AP30663 exposure were related to the infusion site, mild in severity, and temporary in nature, although full recovery took up to 110 days. After formulation and administration changes, the local infusion site reaction remained, but the median duration was shorter despite higher dose levels. AP30663 displayed a less than dose proportional increase in peak plasma concentration (Cmax) and a terminal half‐life of around 5 hours. In healthy volunteers, no effect of AP30663 was observed on electrocardiographic parameters, other than a concentration‐dependent effect on the corrected QT Fridericia’s formula interval (+18.8 ± 4.3 ms for the highest dose level compared with time matched placebo). In conclusion, administration of AP30663, a novel KCa2 channel inhibitor, was safe and well‐tolerated systemically in humans, supporting further development in patients with AF undergoing cardioversion.
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Affiliation(s)
- Pim Gal
- Centre for Human Drug Research, Leiden, The Netherlands.,Leiden University Medical Centre, Leiden, The Netherlands
| | | | | | - Mahdi Saghari
- Centre for Human Drug Research, Leiden, The Netherlands
| | - Jacobus Burggraaf
- Centre for Human Drug Research, Leiden, The Netherlands.,Leiden University Medical Centre, Leiden, The Netherlands.,Leiden Academic Center for Drug Research, Leiden, The Netherlands
| | | | | | | | | | | | | | - Nils Edvardsson
- Acesion Pharma ApS, Copenhagen, Denmark.,Department of Molecular and Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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27
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Fenner MF, Carstensen H, Dalgas Nissen S, Melis Hesselkilde E, Scott Lunddahl C, Adler Hess Jensen M, Loft-Andersen AV, Sattler SM, Platonov P, El-Haou S, Jackson C, Tang R, Kirby R, Ford J, Schotten U, Milnes J, Svane Sørensen U, Jespersen T, Buhl R. Effect of selective I K,ACh inhibition by XAF-1407 in an equine model of tachypacing-induced persistent atrial fibrillation. Br J Pharmacol 2020; 177:3778-3794. [PMID: 32436234 DOI: 10.1111/bph.15100] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 03/20/2020] [Accepted: 05/01/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND AND PURPOSE Inhibition of the G-protein gated ACh-activated inward rectifier potassium current, IK,ACh may be an effective atrial selective treatment strategy for atrial fibrillation (AF). Therefore, the anti-arrhythmic and electrophysiological properties of a novel putatively potent and highly specific IK,ACh inhibitor, XAF-1407 (3-methyl-1-[5-phenyl-4-[4-(2-pyrrolidin-1-ylethoxymethyl)-1-piperidyl]thieno[2,3-d]pyrimidin-6-yl]azetidin-3-ol), were characterised for the first time in vitro and investigated in horses with persistent AF. EXPERIMENTAL APPROACH The pharmacological ion channel profile of XAF-1407 was investigated using cell lines expressing relevant ion channels. In addition, eleven horses were implanted with implantable cardioverter defibrillators enabling atrial tachypacing into self-sustained AF. The electrophysiological effects of XAF-1407 were investigated after serial cardioversions over a period of 1 month. Cardioversion success, drug-induced changes of atrial tissue refractoriness, and ventricular electrophysiology were assessed at baseline (day 0) and days 3, 5, 11, 17, and 29 after AF induction. KEY RESULTS XAF-1407 potently and selectively inhibited Kir 3.1/3.4 and Kir 3.4/3.4, underlying the IK,ACh current. XAF-1407 treatment in horses prolonged atrial effective refractory period as well as decreased atrial fibrillatory rate significantly (~20%) and successfully cardioverted AF, although with a decreasing efficacy over time. XAF-1407 shortened atrioventricular-nodal refractoriness, without effect on QRS duration. QTc prolongation (4%) within 15 min of drug infusion was observed, however, without any evidence of ventricular arrhythmia. CONCLUSION AND IMPLICATIONS XAF-1407 efficiently cardioverted sustained tachypacing-induced AF of short duration in horses without notable side effects. This supports IK,ACh inhibition as a potentially safe treatment of paroxysmal AF in horses, suggesting potential clinical value for other species including humans.
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Affiliation(s)
- Merle Friederike Fenner
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Helena Carstensen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Sarah Dalgas Nissen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Eva Melis Hesselkilde
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Christine Scott Lunddahl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Maja Adler Hess Jensen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Ameli Victoria Loft-Andersen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Stefan Michael Sattler
- Department of Cardiology, The Heart Centre, Copenhagen University Hospital, Copenhagen, Denmark.,Department of Medicine I, University Hospital Munich, Campus Grosshadern, Ludwig-Maximilians University Munich (LMU), Munich, Germany
| | - Pyotr Platonov
- Arrhythmia Clinic, Skåne University Hospital and Department of Cardiology, Clinical Sciences, Lund University, Lund, Sweden
| | | | | | | | | | | | - Ulrich Schotten
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, The Netherlands
| | | | | | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
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28
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Yu Y, Luo D, Li Z, Zhang J, Li F, Qiao J, Yu F, Li M. Inhibitory Effects of Dronedarone on Small Conductance Calcium Activated Potassium Channels in Patients with Chronic Atrial Fibrillation: Comparison to Amiodarone. Med Sci Monit 2020; 26:e924215. [PMID: 32470968 PMCID: PMC7282350 DOI: 10.12659/msm.924215] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Dysfunction of small conductance calcium activated potassium (SK) channels plays a vital role in atrial arrhythmogenesis. Amiodarone and dronedarone are the most effective class III antiarrhythmic drugs. It is unclear whether the antiarrhythmic effect of amiodarone and dronedarone is related to SK channel inhibition. MATERIAL AND METHODS Tissue samples were obtained from the right atria of 46 patients with normal sinus rhythm and 39 patients with chronic atrial fibrillation. Isolated atrial myocytes were obtained by enzymatic dissociation. KCNN2 (SK2) channels were transiently expressed in human embryonic kidney (HEK)-293 cells. SK currents were recorded using whole-cell conventional patch clamp techniques. RESULTS Amiodarone and dronedarone showed a concentration-dependent inhibitory effect on SK currents (IKAS) in atrial myocytes from normal sinus rhythm patients and chronic atrial fibrillation patients. The suppressed efficacy of dronedarone and amiodarone on IKAS was greater in atrial myocytes from chronic atrial fibrillation patients than that from normal sinus rhythm patients. Furthermore, in patients with chronic atrial fibrillation, the IC₅₀ value was 2.42 µM with dronedarone and 8.03 µM with amiodarone. In HEK-293 cells with transiently transfected SK2 channels, both dronedarone and amiodarone had a dose-dependent inhibitory effect on IKAS. The IC₅₀ value was 1.7 µM with dronedarone and 7.2 µM with amiodarone in cells from patients with chronic atrial fibrillation. Compared to amiodarone, dronedarone is more efficacy to inhibit IKAS and could be a potential intervention for patients with chronic atrial fibrillation. CONCLUSIONS Dronedarone provides a great degree of IKAS inhibition in atrial myocytes from chronic atrial fibrillation than amiodarone. IKAS might be a potential target of amiodarone and dronedarone for the management of chronic atrial fibrillation.
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Affiliation(s)
- Yiyan Yu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland).,Department of Electrocardiography, The Affiliated Traditional Chinese Medicine Hospital of Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Dan Luo
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Zhiyi Li
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Juan Zhang
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Fang Li
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Jie Qiao
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Fengxu Yu
- Department of Cardiothoracic Surgery, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Miaoling Li
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland).,Department of Cardiothoracic Surgery, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China (mainland)
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Diness JG, Abildgaard L, Bomholtz SH, Skarsfeldt MA, Edvardsson N, Sørensen US, Grunnet M, Bentzen BH. Inhibition of K Ca2 Channels Decreased the Risk of Ventricular Arrhythmia in the Guinea Pig Heart During Induced Hypokalemia. Front Pharmacol 2020; 11:749. [PMID: 32508659 PMCID: PMC7251152 DOI: 10.3389/fphar.2020.00749] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 05/06/2020] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Hypokalemia reduces the cardiac repolarization reserve. This prolongs the QT-interval and increases the risk of ventricular arrhythmia; a risk that is exacerbated by administration of classical class 3 anti-arrhythmic agents.Small conductance Ca2+-activated K+-channels (KCa2) are a promising new atrial selective target for treatment of atrial fibrillation. Under physiological conditions KCa2 plays a minor role in ventricular repolarization. However, this might change under hypokalemia because of concomitant increases in ventriculay -60r intracellur Ca2+. PURPOSE To study the effects of pharmacological KCa2 channel inhibition by the compounds AP14145, ICA, or AP30663 under hypokalemic conditions as compared to dofetilide and hypokalemia alone time-matched controls (TMC). METHODS The current at +10 mV was compared in HEK293 cells stably expressing KCa2.3 perfused first with normo- and then hypokalemic solutions (4 mM K+ and 2.5 mM K+, respectively). Guinea pig hearts were isolated and perfused with normokalemic (4 mM K+) Krebs-Henseleit solution, followed by perfusion with drug or vehicle control. The perfusion was then changed to hypokalemic solution (2.5 mM K+) in presence of drug. 30 animals were randomly assigned to 5 groups: ICA, AP14145, AP30663, dofetilide, or TMC. QT-interval, the interval from the peak to the end of the T wave (Tp-Te), ventricular effective refractory period (VERP), arrhythmia score, and ventricular fibrillation (VF) incidence were recorded. RESULTS Hypokalemia slightly increased KCa2.3 current compared to normokalemia. Application of KCa2 channel inhibitors and dofetilide prolonged the QT interval corrected for heart rate. Dofetilide, but none of the KCa2 channel inhibitors increased Tp-Te during hypokalemia. During hypokalemia 4/6 hearts in the TMC group developed VF (two spontaneously, two by S1S2 stimulation) whereas 5/6 hearts developed VF in the dofetilide group (two spontaneously, three by S1S2 stimulation). In comparison, 0/6, 1/6, and 1/6 hearts developed VF when treated with the KCa2 channel inhibitors AP30663, ICA, or AP14145, respectively. CONCLUSION Hypokalemia was associated with an increased incidence of VF, an effect that also seen in the presence of dofetilide. In comparison, the structurally and functionally different KCa2 channel inhibitors, ICA, AP14145, and AP30663 protected the heart from hypokalemia induced VF. These results support that KCa2 inhibition may be associated with a better safety and tolerability profile than dofetilide.
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Affiliation(s)
| | | | - Sofia Hammami Bomholtz
- Acesion Pharma, Copenhagen, Denmark
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Mark Alexander Skarsfeldt
- Acesion Pharma, Copenhagen, Denmark
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nils Edvardsson
- Acesion Pharma, Copenhagen, Denmark
- Department of Molecular and Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | | | | | - Bo Hjorth Bentzen
- Acesion Pharma, Copenhagen, Denmark
- Department of Molecular and Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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Bentzen BH, Bomholtz SH, Simó-Vicens R, Folkersen L, Abildgaard L, Speerschneider T, Muthukumarasamy KM, Edvardsson N, Sørensen US, Grunnet M, Diness JG. Mechanisms of Action of the KCa2-Negative Modulator AP30663, a Novel Compound in Development for Treatment of Atrial Fibrillation in Man. Front Pharmacol 2020; 11:610. [PMID: 32477117 PMCID: PMC7232560 DOI: 10.3389/fphar.2020.00610] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 04/20/2020] [Indexed: 12/17/2022] Open
Abstract
Aims Small conductance Ca2+-activated K+ channels (SK channels, KCa2) are a new target for treatment of atrial fibrillation (AF). AP30663 is a small molecule inhibitor of KCa2 channels that is currently in clinical development for treatment of AF. The aim of this study is to present the electrophysiological profile and mechanism of action of AP30663 and its efficacy in prolonging atrial refractoriness in rodents, and by bioinformatic analysis investigate if genetic variants in KCNN2 or KCNN3 influence the expression level of these in human heart tissue. Methods and Results Whole-cell and inside-out patch-clamp recordings of heterologously expressed KCa2 channels revealed that AP30663 inhibits KCa2 channels with minor effects on other relevant cardiac ion channels. AP30663 modulates the KCa2.3 channel by right-shifting the Ca2+-activation curve. In isolated guinea pig hearts AP30663 significantly prolonged the atrial effective refractory period (AERP) with minor effects on the QT-interval corrected for heart rate. Similarly, in anaesthetized rats 5 and 10 mg/kg of AP30663 changed the AERP to 130.7±5.4% and 189.9±18.6 of baseline values. The expression quantitative trait loci analyses revealed that the genome wide association studies for AF SNP rs13376333 in KCNN3 is associated with increased mRNA expression of KCNN3 in human atrial appendage tissue. Conclusions AP30663 is a novel negative allosteric modulator of KCa2 channels that concentration-dependently prolonged rodent atrial refractoriness with minor effects on the QT-interval. Moreover, AF associated SNPs in KCNN3 influence KCNN3 mRNA expression in human atrial tissue. These properties support continued development of AP30663 for treatment of AF in man.
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Affiliation(s)
- Bo Hjorth Bentzen
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sofia Hammami Bomholtz
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rafel Simó-Vicens
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lasse Folkersen
- Institute of Biological Psychiatry, Sankt Hans Hospital, Roskilde, Denmark
| | | | - Tobias Speerschneider
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kalai Mangai Muthukumarasamy
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nils Edvardsson
- Acesion Pharma, Copenhagen, Denmark.,Department of Molecular and Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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Citerni C, Kirchhoff J, Olsen LH, Sattler SM, Grunnet M, Edvardsson N, Bentzen BH, Diness JG. Inhibition of K Ca2 and K v11.1 Channels in Pigs With Left Ventricular Dysfunction. Front Pharmacol 2020; 11:556. [PMID: 32435191 PMCID: PMC7219273 DOI: 10.3389/fphar.2020.00556] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 04/14/2020] [Indexed: 12/17/2022] Open
Abstract
Background Inhibition of KCa2 channels, conducting IKCa, can convert atrial fibrillation (AF) to sinus rhythm and protect against its induction. IKCa inhibition has been shown to possess functional atrial selectivity with minor effects on ventricles. Under pathophysiological conditions with ventricular remodeling, however, inhibiting IKCa can exhibit both proarrhythmic and antiarrhythmic ventricular effects. The aim of this study was to evaluate the effects of the IKCa inhibitor AP14145, when given before or after the IKr blocker dofetilide, on cardiac function and ventricular proarrhythmia markers in pigs with or without left ventricular dysfunction (LVD). Methods Landrace pigs were randomized into an AF group (n = 6) and two control groups: SHAM1 (n = 8) and SHAM2 (n = 4). AF pigs were atrially tachypaced (A-TP) for 43 ± 4 days until sustained AF and LVD developed. A-TP and SHAM1 pigs received 20 mg/kg AP14145 followed by 100 µg/kg dofetilide whereas SHAM2 pigs received the same drugs in the opposite order. Proarrhythmic markers such as short-term variability of QT (STVQT) and RR (STVRR) intervals, and the number of premature ventricular complexes (PVCs) were measured at baseline and after administration of drugs. The influence on cardiac function was assessed by measuring cardiac output, stroke volume, and relevant echocardiographic parameters. Results IKCa inhibition by AP14145 did not increase STVQT or STVRR in any of the pigs. IKr inhibition by dofetilide markedly increased STVQT in the A-TP pigs, but not in SHAM operated pigs. Upon infusion of AP14145 the number of PVCs decreased or remained unchanged both when AP14145 was infused after baseline and after dofetilide. Conversely, the number of PVCs increased or remained unchanged upon dofetilide infusion. Neither AP14145 nor dofetilide affected relevant echocardiographic parameters, cardiac output, or stroke volume in any of the groups. Conclusion IKCa inhibition with AP14145 was not proarrhythmic in healthy pigs, or in the presence of LVD resulting from A-TP. In pigs already challenged with 100 µg/kg dofetilide there were no signs of proarrhythmia when 20 mg/kg AP14145 were infused. KCa2 channel inhibition did not affect cardiac function, implying that KCa2 inhibitors can be administered safely also in the presence of LV dysfunction.
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Affiliation(s)
- Carlotta Citerni
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
| | | | - Lisbeth Høier Olsen
- Department of Veterinary Disease Biology, University of Copenhagen, Frederiksberg, Denmark
| | - Stefan Michael Sattler
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Department of Cardiology, Heart Center, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | | | - Nils Edvardsson
- Acesion Pharma, Copenhagen, Denmark.,Department of Molecular and Clinical Medicine, Sahlgrenska Academy at Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Bo Hjorth Bentzen
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
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Diness JG, Kirchhoff JE, Speerschneider T, Abildgaard L, Edvardsson N, Sørensen US, Grunnet M, Bentzen BH. The K Ca2 Channel Inhibitor AP30663 Selectively Increases Atrial Refractoriness, Converts Vernakalant-Resistant Atrial Fibrillation and Prevents Its Reinduction in Conscious Pigs. Front Pharmacol 2020; 11:159. [PMID: 32180722 PMCID: PMC7059611 DOI: 10.3389/fphar.2020.00159] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 02/07/2020] [Indexed: 12/20/2022] Open
Abstract
AIMS To describe the effects of the KCa2 channel inhibitor AP30663 in pigs regarding tolerability, cardiac electrophysiology, pharmacokinetics, atrial functional selectivity, effectiveness in cardioversion of tachy-pacing induced vernakalant-resistant atrial fibrillation (AF), and prevention of reinduction of AF. METHODS AND RESULTS Six healthy pigs with implanted pacemakers and equipped with a Holter monitor were used to compare the effects of increasing doses (0, 5, 10, 15, 20, and 25 mg/kg) of AP30663 on the right atrial effective refractory period (AERP) and on various ECG parameters, including the QT interval. Ten pigs with implanted neurostimulators were long-term atrially tachypaced (A-TP) until sustained vernakalant-resistant AF was present. 20 mg/kg AP30663 was tested to discover if it could successfully convert vernakalant-resistant AF to sinus rhythm (SR) and protect against reinduction of AF. Seven anesthetized pigs were used for pharmacokinetic experiments. Two pigs received an infusion of 20 mg/kg AP30663 over 60 min while five pigs received 5 mg/kg AP30663 over 30 min. Blood samples were collected before, during, and after infusion on AP30663. AP30663 was well-tolerated and prominently increased the AERP in pigs with little effect on ventricular repolarization. Furthermore, it converted A-TP induced AF that had become unresponsive to vernakalant, and it prevented reinduction of AF in pigs. Both a >30 ms increase of the AERP and conversion of AF occurred in different pigs at a free plasma concentration level of around 1.0-1.4 µM of AP30663, which was achieved at a dose level of 5 mg/kg. CONCLUSION AP30663 has shown properties in animals that would be of clinical interest in man.
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Affiliation(s)
| | | | - Tobias Speerschneider
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lea Abildgaard
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
| | - Nils Edvardsson
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
- Department of Molecular and Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Ulrik S. Sørensen
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
| | - Morten Grunnet
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
| | - Bo Hjorth Bentzen
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Hesselkilde EZ, Carstensen H, Flethøj M, Fenner M, Kruse DD, Sattler SM, Tfelt-Hansen J, Pehrson S, Braunstein TH, Carlson J, Platonov PG, Jespersen T, Buhl R. Longitudinal study of electrical, functional and structural remodelling in an equine model of atrial fibrillation. BMC Cardiovasc Disord 2019; 19:228. [PMID: 31638896 PMCID: PMC6805623 DOI: 10.1186/s12872-019-1210-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 09/26/2019] [Indexed: 08/26/2023] Open
Abstract
Background Large animal models are important in atrial fibrillation (AF) research, as they can be used to study the pathophysiology of AF and new therapeutic approaches. Unlike other animal models, horses spontaneously develop AF and could therefore serve as a bona fide model in AF research. We therefore aimed to study the electrical, functional and structural remodelling caused by chronic AF in a horse model. Method Nine female horses were included in the study, with six horses tachypaced into self-sustained AF and three that served as a time-matched sham-operated control group. Acceleration in atrial fibrillatory rate (AFR), changes in electrocardiographic and echocardiographic variables and response to medical treatment (flecainide 2 mg/kg) were recorded over a period of 2 months. At the end of the study, changes in ion channel expression and fibrosis were measured and compared between the two groups. Results AFR increased from 299 ± 33 fibrillations per minute (fpm) to 376 ± 12 fpm (p < 0.05) and atrial function (active left atrial fractional area change) decreased significantly during the study (p < 0.05). No changes were observed in heart rate or ventricular function. The AF group had more atrial fibrosis compared to the control group (p < 0.05). No differences in ion channel expression were observed. Conclusion Horses with induced AF show signs of atrial remodelling that are similar to humans and other animal models.
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Affiliation(s)
- Eva Zander Hesselkilde
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630, Taastrup, Denmark
| | - Helena Carstensen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630, Taastrup, Denmark
| | - Mette Flethøj
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630, Taastrup, Denmark
| | - Merle Fenner
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630, Taastrup, Denmark
| | - Ditte Dybvald Kruse
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Stefan M Sattler
- Department of Cardiology, The Heart Centre, Copenhagen University Hospital, Blegdamsvej 9, 2100, Copenhagen, Denmark.,Department of Medicine I, University Hospital Munich, Campus Grosshadern, Ludwig-Maximilians University Munich (LMU), Munich, Germany
| | - Jacob Tfelt-Hansen
- Department of Cardiology, The Heart Centre, Copenhagen University Hospital, Blegdamsvej 9, 2100, Copenhagen, Denmark.,Department of Forensic Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Frederik V's vej 11, 2100, Copenhagen, Denmark
| | - Steen Pehrson
- Department of Cardiology, The Heart Centre, Copenhagen University Hospital, Blegdamsvej 9, 2100, Copenhagen, Denmark
| | - Thomas Hartig Braunstein
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Jonas Carlson
- Department of Cardiology, Clinical Sciences, Arrhythmia Clinic, Skåne University Hospital, Lund University, 21185, Lund, Sweden
| | - Pyotr G Platonov
- Department of Cardiology, Clinical Sciences, Arrhythmia Clinic, Skåne University Hospital, Lund University, 21185, Lund, Sweden
| | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630, Taastrup, Denmark.
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Kalstø SM, Siland JE, Rienstra M, Christophersen IE. Atrial Fibrillation Genetics Update: Toward Clinical Implementation. Front Cardiovasc Med 2019; 6:127. [PMID: 31552271 PMCID: PMC6743416 DOI: 10.3389/fcvm.2019.00127] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 08/12/2019] [Indexed: 12/16/2022] Open
Abstract
Atrial fibrillation (AF) is the most common heart rhythm disorder worldwide and may have serious cardiovascular health consequences. AF is associated with increased risk of stroke, dementia, heart failure, and death. There are several known robust, clinical risk predictors for AF, such as male sex, increasing age, and hypertension; however, during the last couple of decades, a substantive genetic component has also been established. Over the last 10 years, the discovery of novel AF-related genetic variants has accelerated, increasing our understanding of mechanisms behind AF. Current studies are focusing on mapping the polygenic structure of AF, improving risk prediction, therapeutic development, and patient-specific management. Nevertheless, it is still difficult for clinicians to interpret the role of genetics in AF prediction and management. Here, we provide an overview of relevant topics within the genetics of AF and attempt to provide some guidance on how to interpret genetic advances and their implementation into clinical decision-making.
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Affiliation(s)
- Silje Madeleine Kalstø
- Department of Medical Research, Bærum Hospital, Vestre Viken Hospital Trust, Rud, Norway
| | - Joylene Elisabeth Siland
- Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Michiel Rienstra
- Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Ingrid E Christophersen
- Department of Medical Research, Bærum Hospital, Vestre Viken Hospital Trust, Rud, Norway.,The Department of Medical Genetics, Oslo University Hospital, Oslo, Norway
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Shamsaldeen YA, Culliford L, Clout M, James AF, Ascione R, Hancox JC, Marrion NV. Role of SK channel activation in determining the action potential configuration in freshly isolated human atrial myocytes from the SKArF study. Biochem Biophys Res Commun 2019; 512:684-690. [PMID: 30922569 DOI: 10.1016/j.bbrc.2019.03.074] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 03/13/2019] [Indexed: 10/27/2022]
Abstract
Inhibition of SK channel function is being pursued in animal models as a possible therapeutic approach to treat atrial fibrillation (AF). However, the pharmacology of SK channels in human atria is unclear. SK channel function is inhibited by both apamin and UCL1684, with the former discriminating between SK channel subtypes. In this proof-of-principle study, the effects of apamin and UCL1684 on right atrial myocytes freshly isolated from patients in sinus rhythm undergoing elective cardiac surgery were investigated. Outward current evoked from voltage clamped human atrial myocytes was reduced by these two inhibitors of SK channel function. In contrast, membrane current underlying the atrial action potential was affected significantly only by UCL1684 and not by apamin. This pharmacology mirrors that observed in mouse atria, suggesting that mammalian atria possess two populations of SK channels, with only one population contributing to the action potential waveform. Immuno-visualization of the subcellular localization of SK2 and SK3 subunits showed a high degree of colocalization, consistent with the formation of heteromeric SK2/SK3 channels. These data reveal that human atrial myocytes express two SK channel subtypes, one exhibiting an unusual pharmacology. These channels contribute to the atrial action potential waveform and might be a target for novel therapeutic approaches to treat supraventricular arrhythmic conditions such as atrial fibrillation.
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Affiliation(s)
- Yousif A Shamsaldeen
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, BS8 1TD, UK
| | - Lucy Culliford
- Clinical Trials and Evaluation Unit, Bristol Trials Centre, Bristol Medical School, University of Bristol, Bristol, UK
| | - Madeleine Clout
- Clinical Trials and Evaluation Unit, Bristol Trials Centre, Bristol Medical School, University of Bristol, Bristol, UK
| | - Andrew F James
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, BS8 1TD, UK
| | - Raimondo Ascione
- Translational Biomedical Research Centre, Faculty of Health Sciences, University of Bristol, UK
| | - Jules C Hancox
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, BS8 1TD, UK
| | - Neil V Marrion
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, BS8 1TD, UK.
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Carstensen H, Hesselkilde EZ, Haugaard MM, Flethøj M, Carlson J, Pehrson S, Jespersen T, Platonov PG, Buhl R. Effects of dofetilide and ranolazine on atrial fibrillatory rate in a horse model of acutely induced atrial fibrillation. J Cardiovasc Electrophysiol 2019; 30:596-606. [PMID: 30661267 PMCID: PMC6849868 DOI: 10.1111/jce.13849] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 12/21/2018] [Accepted: 01/04/2019] [Indexed: 12/19/2022]
Abstract
INTRODUCTION The atrial fibrillatory rate is a potential biomarker in the study of antiarrhythmic drug effects on atrial fibrillation (AF). The purpose of this study was to evaluate whether dose-dependent changes in the atrial fibrillatory rate can be monitored on surface electrocardiography (ECG) following treatment with dofetilide, ranolazine, and a combination of the two in an acute model of AF in horses. METHODS AND RESULTS Eight horses were subjected to pacing-induced AF on 4 separate days. Saline (control), dofetilide, ranolazine, or a combination of dofetilide and ranolazine was administered in four incremental doses. Atrial fibrillatory activity was extracted from surface ECGs using spatiotemporal QRST cancellation. The mean atrial fibrillatory rate before drug infusion was 297 ± 27 fpm. Dofetilide reduced the atrial fibrillatory rate following the infusion of low doses (0.89 µg/kg, P < 0.05) and within 5 minutes preceding cardioversion (P < 0.05). Cardioversion with ranolazine was preceded by a reduction in the atrial fibrillatory rate in the last minute (P < 0.05). The combination of drugs reduced the atrial fibrillatory rate in a similar manner to dofetilide used alone. A trend toward a lower atrial fibrillatory rate before drug infusion was found among horses cardioverting on low doses of the drugs. CONCLUSION The atrial fibrillatory rate derived from surface ECGs showed a difference in the mode of action on AF between dofetilide and ranolazine. Dofetilide reduced the atrial fibrillatory rate, whereas ranolazine displayed a cardioverting mechanism that was distinct from a slowing of the fibrillatory process.
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Affiliation(s)
- Helena Carstensen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Eva Zander Hesselkilde
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Maria Mathilde Haugaard
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Mette Flethøj
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Jonas Carlson
- Department of Cardiology, Clinical Sciences, Lund University, Lund, Sweden
| | - Steen Pehrson
- Department of Cardiology, The Heart Centre, Copenhagen University Hospital, Taastrup, Denmark
| | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Pyotr G Platonov
- Department of Cardiology, Clinical Sciences, Lund University, Lund, Sweden.,Arrhythmia Clinic, Skåne University Hospital, Lund, Sweden
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
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Carstensen H, Kjær L, Haugaard MM, Flethøj M, Hesselkilde EZ, Kanters JK, Pehrson S, Buhl R, Jespersen T. Antiarrhythmic Effects of Combining Dofetilide and Ranolazine in a Model of Acutely Induced Atrial Fibrillation in Horses. J Cardiovasc Pharmacol 2018; 71:26-35. [PMID: 29068807 DOI: 10.1097/FJC.0000000000000541] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Supplemental Digital Content is Available in the Text. Background: Antiarrhythmic compounds against atrial fibrillation (AF) often have reduced efficacy and may display cardiac and/or noncardiac toxicity. Efficacy can be improved by combining 2 compounds with distinct mechanisms, and it may be possible to use lower doses of each compound, thereby reducing the likelihood of adverse side effects. The purpose of this study was to investigate whether the effective doses of dofetilide and ranolazine can be reduced if the drugs are combined. Methods: Dofetilide, ranolazine, and a combination of these were administered in 4 incremental dosing regimens to horses with acutely pacing-induced AF. Time to cardioversion, atrial effective refractory period, and AF vulnerability and duration were assessed. Results: Of 8 horses, 6 cardioverted to sinus rhythm after infusion with a combination of 0.889 μg/kg dofetilide and 0.104 mg/kg ranolazine. Two horses cardioverted with 0.104 mg/kg ranolazine alone, and 3 cardioverted with 0.889 μg/kg dofetilide alone. The combination therapy decreased AF vulnerability (P < 0.05) and AF duration (P < 0.05). No change in atrial effective refractory period was detected with any of the drugs. Conclusions: The combination of dofetilide and ranolazine showed increased antiarrhythmic effects on acutely induced AF in horses, affecting time to cardioversion, AF vulnerability, and AF duration.
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Ling TY, Yi F, Lu T, Wang XL, Sun X, Willis MS, Wu LQ, Shen WK, Adelman JP, Lee HC. F-box protein-32 down-regulates small-conductance calcium-activated potassium channel 2 in diabetic mouse atria. J Biol Chem 2019; 294:4160-4168. [PMID: 30635400 DOI: 10.1074/jbc.ra118.003837] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 12/28/2018] [Indexed: 11/06/2022] Open
Abstract
Diabetes mellitus (DM) is an independent risk factor for atrial fibrillation, but the underlying ionic mechanism for this association remains unclear. We recently reported that expression of the small-conductance calcium-activated potassium channel 2 (SK2, encoded by KCCN2) in atria from diabetic mice is significantly down-regulated, resulting in reduced SK currents in atrial myocytes from these mice. We also reported that the level of SK2 mRNA expression is not reduced in DM atria but that the ubiquitin-proteasome system (UPS), a major mechanism of intracellular protein degradation, is activated in vascular smooth muscle cells in DM. This suggests a possible role of the UPS in reduced SK currents. To test this possibility, we examined the role of the UPS in atrial SK2 down-regulation in DM. We found that a muscle-specific E3 ligase, F-box protein 32 (FBXO-32, also called atrogin-1), was significantly up-regulated in diabetic mouse atria. Enhanced FBXO-32 expression in atrial cells significantly reduced SK2 protein expression, and siRNA-mediated FBXO-32 knockdown increased SK2 protein expression. Furthermore, co-transfection of SK2 with FBXO-32 complementary DNA in HEK293 cells significantly reduced SK2 expression, whereas co-transfection with atrogin-1ΔF complementary DNA (a nonfunctional FBXO-32 variant in which the F-box domain is deleted) did not have any effects on SK2. These results indicate that FBXO-32 contributes to SK2 down-regulation and that the F-box domain is essential for FBXO-32 function. In conclusion, DM-induced SK2 channel down-regulation appears to be due to an FBXO-32-dependent increase in UPS-mediated SK2 protein degradation.
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Affiliation(s)
- Tian-You Ling
- From the Department of Cardiology, Ruijin Hospital, Shanghai JiaoTong University School of Medicine, Shanghai 200025, China.,the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Fu Yi
- the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905, .,the Department of Cardiovascular Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Tong Lu
- the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Xiao-Li Wang
- the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Xiaojing Sun
- the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Monte S Willis
- the Department of Pathology and Laboratory Medicine, Indiana Center for Musculoskeletal Health, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Li-Qun Wu
- From the Department of Cardiology, Ruijin Hospital, Shanghai JiaoTong University School of Medicine, Shanghai 200025, China
| | - Win-Kuang Shen
- the Department of Cardiovascular Diseases, Mayo Clinic, Phoenix, Arizona 85259, and
| | - John P Adelman
- the Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239
| | - Hon-Chi Lee
- the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota 55905,
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Vagos M, van Herck IGM, Sundnes J, Arevalo HJ, Edwards AG, Koivumäki JT. Computational Modeling of Electrophysiology and Pharmacotherapy of Atrial Fibrillation: Recent Advances and Future Challenges. Front Physiol 2018; 9:1221. [PMID: 30233399 PMCID: PMC6131668 DOI: 10.3389/fphys.2018.01221] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 08/13/2018] [Indexed: 12/19/2022] Open
Abstract
The pathophysiology of atrial fibrillation (AF) is broad, with components related to the unique and diverse cellular electrophysiology of atrial myocytes, structural complexity, and heterogeneity of atrial tissue, and pronounced disease-associated remodeling of both cells and tissue. A major challenge for rational design of AF therapy, particularly pharmacotherapy, is integrating these multiscale characteristics to identify approaches that are both efficacious and independent of ventricular contraindications. Computational modeling has long been touted as a basis for achieving such integration in a rapid, economical, and scalable manner. However, computational pipelines for AF-specific drug screening are in their infancy, and while the field is progressing quite rapidly, major challenges remain before computational approaches can fill the role of workhorse in rational design of AF pharmacotherapies. In this review, we briefly detail the unique aspects of AF pathophysiology that determine requirements for compounds targeting AF rhythm control, with emphasis on delimiting mechanisms that promote AF triggers from those providing substrate or supporting reentry. We then describe modeling approaches that have been used to assess the outcomes of drugs acting on established AF targets, as well as on novel promising targets including the ultra-rapidly activating delayed rectifier potassium current, the acetylcholine-activated potassium current and the small conductance calcium-activated potassium channel. Finally, we describe how heterogeneity and variability are being incorporated into AF-specific models, and how these approaches are yielding novel insights into the basic physiology of disease, as well as aiding identification of the important molecular players in the complex AF etiology.
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Affiliation(s)
- Márcia Vagos
- Computational Physiology Department, Simula Research Laboratory, Lysaker, Norway
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Ilsbeth G. M. van Herck
- Computational Physiology Department, Simula Research Laboratory, Lysaker, Norway
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Joakim Sundnes
- Computational Physiology Department, Simula Research Laboratory, Lysaker, Norway
- Center for Cardiological Innovation, Oslo, Norway
| | - Hermenegild J. Arevalo
- Computational Physiology Department, Simula Research Laboratory, Lysaker, Norway
- Center for Cardiological Innovation, Oslo, Norway
| | - Andrew G. Edwards
- Computational Physiology Department, Simula Research Laboratory, Lysaker, Norway
- Center for Cardiological Innovation, Oslo, Norway
| | - Jussi T. Koivumäki
- BioMediTech Institute and Faculty of Biomedical Sciences and Engineering, Tampere University of Technology, Tampere, Finland
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
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Carstensen H, Hesselkilde EZ, Fenner M, Loft-Andersen AV, Flethøj M, Kanters JK, Sattler SM, Tfelt-Hansen J, Pehrson S, Jespersen T, Buhl R. Time-dependent antiarrhythmic effects of flecainide on induced atrial fibrillation in horses. J Vet Intern Med 2018; 32:1708-1717. [PMID: 30133839 PMCID: PMC6189357 DOI: 10.1111/jvim.15287] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 05/31/2018] [Accepted: 06/26/2018] [Indexed: 11/28/2022] Open
Abstract
Background Pharmacological treatment of atrial fibrillation (AF) in horses can be challenging because of low efficacy and adverse effects. Flecainide has been tested with variable efficacy. Objective To test whether the efficacy of flecainide is dependent on AF duration. Animals Nine Standardbred mares. Methods Factorial study design. All horses were instrumented with a pacemaker and assigned to a control or an AF group. On day 0, all horses were in sinus rhythm and received 2 mg/kg flecainide IV. Atrial fibrillation subsequently was induced in the AF group by pacemaker stimulation. On days 3, 9, 27, and 55, flecainide was administered to all horses, regardless of heart rhythm. Results All horses in AF cardioverted to sinus rhythm on days 3 and 9. On day 27, 5/6 horses cardioverted, whereas only 2/6 cardioverted on day 55. The time from the start of flecainide infusion to cardioversion (range, 3–185 min, log transformed) showed linear correlation with the cumulative duration of AF (r2 = .80, P < .0001). Flecainide induced abnormal QRS complexes in 4/6 AF horses and 1/3 controls. A positive correlation was found between heart rate before flecainide infusion and number of abnormal QRS complexes (0.14, P < .05). One horse suffered from cardiac arrest and died after flecainide infusion. Conclusions and Clinical Importance Flecainide is effective for cardioversion of short‐term induced AF, but the effect decreases with AF duration. Controlling heart rate may minimize adverse effects caused by flecainide, but the drug should be used with great caution.
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Affiliation(s)
- Helena Carstensen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Eva Z Hesselkilde
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Merle Fenner
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Ameli V Loft-Andersen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Mette Flethøj
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Jørgen K Kanters
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, København, Denmark
| | - Stefan M Sattler
- Department of Cardiology, The Heart Centre, Copenhagen University Hospital, København, Denmark.,Department of Medicine I, University Hospital Munich, Campus Grosshadern, Ludwig-Maximilians University Munich (LMU), Munich, Germany
| | - Jacob Tfelt-Hansen
- Department of Cardiology, The Heart Centre, Copenhagen University Hospital, København, Denmark.,Department of Forensic Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, København, Denmark
| | - Steen Pehrson
- Department of Cardiology, The Heart Centre, Copenhagen University Hospital, København, Denmark
| | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, København, Denmark
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
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Tenma T, Mitsuyama H, Watanabe M, Kakutani N, Otsuka Y, Mizukami K, Kamada R, Takahashi M, Takada S, Sabe H, Tsutsui H, Yokoshiki H. Small-conductance Ca2+-activated K+ channel activation deteriorates hypoxic ventricular arrhythmias via CaMKII in cardiac hypertrophy. Am J Physiol Heart Circ Physiol 2018; 315:H262-H272. [DOI: 10.1152/ajpheart.00636.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The molecular and electrophysiological mechanisms of acute ischemic ventricular arrhythmias in hypertrophied hearts are not well known. We hypothesized that small-conductance Ca2+-activated K+ (SK) channels are activated during hypoxia via the Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent pathway. We used normotensive Wistar-Kyoto (WKY) rats and spontaneous hypertensive rats (SHRs) as a model of cardiac hypertrophy. The inhibitory effects of SK channels and ATP-sensitive K+ channels on electrophysiological changes and genesis of arrhythmias during simulated global hypoxia (GH) were evaluated. Hypoxia-induced abbreviation of action potential duration (APD) occurred earlier in ventricles from SHRs versus. WKY rats. Apamin, a SK channel blocker, prevented this abbreviation in SHRs in both the early and delayed phase of GH, whereas in WKY rats only the delayed phase was prevented. In contrast, SHRs were less sensitive to glibenclamide, a ATP-sensitive K+ channel blocker, which inhibited the APD abbreviation in both phases of GH in WKY rats. SK channel blockers (apamin and UCL-1684) reduced the incidence of hypoxia-induced sustained ventricular arrhythmias in SHRs but not in WKY rats. Among three SK channel isoforms, SK2 channels were directly coimmunoprecipitated with CaMKII phosphorylated at Thr286 (p-CaMKII). We conclude that activation of SK channels leads to the APD abbreviation and sustained ventricular arrhythmias during simulated hypoxia, especially in hypertrophied hearts. This mechanism may result from p-CaMKII-bound SK2 channels and reveal new molecular targets to prevent lethal ventricular arrhythmias during acute hypoxia in cardiac hypertrophy. NEW & NOTEWORTHY We now show a new pathophysiological role of small-conductance Ca2+-activated K+ channels, which shorten the action potential duration and induce ventricular arrhythmias during hypoxia. We also demonstrate that small-conductance Ca2+-activated K+ channels interact with phosphorylated Ca2+/calmodulin-dependent protein kinase II at Thr286 in hypertrophied hearts.
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Affiliation(s)
- Taro Tenma
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Hirofumi Mitsuyama
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Masaya Watanabe
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Naoya Kakutani
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Yutaro Otsuka
- Department of Molecular Biology, Graduate School of Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Kazuya Mizukami
- Department of Cardiovascular Medicine, National Hospital Organization Hokkaido Medical Center, Sapporo, Hokkaido, Japan
| | - Rui Kamada
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Masayuki Takahashi
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Shingo Takada
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Hisataka Sabe
- Department of Molecular Biology, Graduate School of Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Hiroyuki Tsutsui
- Department of Cardiovascular Medicine, Kyusyu University Graduate School of Medicine, Fukuoka, Kyusyu, Japan
| | - Hisashi Yokoshiki
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
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Stowe DF, Yang M, Heisner JS, Camara AKS. Endogenous and Agonist-induced Opening of Mitochondrial Big Versus Small Ca2+-sensitive K+ Channels on Cardiac Cell and Mitochondrial Protection. J Cardiovasc Pharmacol 2017; 70:314-28. [PMID: 28777255 DOI: 10.1097/FJC.0000000000000524] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Both big (BKCa) and small (SKCa) conductance Ca-sensitive K channels are present in mammalian cardiac cell mitochondria (m). We used pharmacological agonists and antagonists of BKCa and SKCa channels to examine the importance of endogenous opening of these channels and the relative contribution of either or both of these channels to protect against contractile dysfunction and reduce infarct size after ischemia reperfusion (IR) injury through a mitochondrial protective mechanism. After global cardiac IR injury of ex vivo perfused Guinea pig hearts, we found the following: both agonists NS1619 (for BKCa) and DCEB (for SKCa) improved contractility; BKCa antagonist paxilline (PAX) alone or with SKCa antagonist NS8593 worsened contractility and enhanced infarct size; both antagonists PAX and NS8593 obliterated protection by their respective agonists; BKCa and SKCa antagonists did not block protection afforded by SKCa and BKCa agonists, respectively; and all protective effects by the agonists were blocked by scavenging superoxide anions (O2) with Mn(III) tetrakis (4-benzoic acid) porphyrin (TBAP). Contractile function was inversely associated with global infarct size. In in vivo rats, infusion of NS8593, PAX, or both antagonists enhanced regional infarct size while infusion of either NS1619 or DCEB reduced infarct size. In cardiac mitochondria isolated from ex vivo hearts after IR, combined SKCa and BKCa agonists improved respiratory control index and Ca retention capacity compared with IR alone, whereas the combined antagonists did not alter respiratory control index but worsened Ca retention capacity. Although the differential protective bioenergetics effects of endogenous or exogenous BKCa and SKCa channel opening remain unclear, each channel likely responds to different sensing Ca concentrations and voltage gradients over time during oxidative stress-induced injury to individually or together protect cardiac mitochondria and myocytes.
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Skibsbye L, Bengaard AK, Uldum-Nielsen AM, Boddum K, Christ T, Jespersen T. Inhibition of Small Conductance Calcium-Activated Potassium (SK) Channels Prevents Arrhythmias in Rat Atria During β-Adrenergic and Muscarinic Receptor Activation. Front Physiol 2018; 9:510. [PMID: 29922167 PMCID: PMC5996028 DOI: 10.3389/fphys.2018.00510] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 04/20/2018] [Indexed: 01/18/2023] Open
Abstract
Sympathetic and vagal activation is linked to atrial arrhythmogenesis. Here we investigated the small conductance Ca2+-activated K+ (SK)-channel pore-blocker N-(pyridin-2-yl)-4-(pyridine-2-yl)thiazol-2-amine (ICA) on action potential (AP) and atrial fibrillation (AF) parameters in isolated rat atria during β-adrenergic [isoprenaline (ISO)] and muscarinic M2 [carbachol (CCh)] activation. Furthermore, antiarrhythmic efficacy of ICA was benchmarked toward the class-IC antiarrhythmic drug flecainide (Fleca). ISO increased the spontaneous beating frequency but did not affect other AP parameters. As expected, CCh hyperpolarized resting membrane potential (-6.2 ± 0.9 mV), shortened APD90 (24.2 ± 1.6 vs. 17.7 ± 1.1 ms), and effective refractory period (ERP; 20.0 ± 1.3 vs. 15.8 ± 1.3 ms). The duration of burst pacing triggered AF was unchanged in the presence of CCh compared to control atria (12.8 ± 5.3 vs. 11.2 ± 3.6 s), while β-adrenergic activation resulted in shorter AF durations (3.3 ± 1.7 s) and lower AF-frequency compared to CCh. Treatment with ICA (10 μM) in ISO -stimulated atria prolonged APD90 and ERP, while the AF burden was reduced (7.1 ± 5.5 vs. 0.1 ± 0.1 s). In CCh-stimulated atria, ICA treatment also resulted in APD90 and ERP prolongation and shorter AF durations. Fleca treatment in CCh-stimulated atria prolonged APD90 and ERP and abbreviated the AF duration to a similar extent as with ICA. Muscarinic activated atria constitutes a more arrhythmogenic substrate than β-adrenoceptor activated atria. Pharmacological inhibition of SK channels by ICA is effective under both conditions and equally efficacious to Fleca.
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Affiliation(s)
- Lasse Skibsbye
- Cardiac Physiology Laboratory, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anne K Bengaard
- Cardiac Physiology Laboratory, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - A M Uldum-Nielsen
- Cardiac Physiology Laboratory, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kim Boddum
- Cardiac Physiology Laboratory, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Torsten Christ
- Department of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, DZHK: German Centre for Cardiovascular Research, Hamburg, Germany
| | - Thomas Jespersen
- Cardiac Physiology Laboratory, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Fan X, Yu Y, Lan H, Ou X, Yang L, Li T, Cao J, Zeng X, Li M. Ca2+/Calmodulin-Dependent Protein Kinase II (CaMKII) Increases Small-Conductance Ca2+-Activated K+ Current in Patients with Chronic Atrial Fibrillation. Med Sci Monit 2018; 24:3011-3023. [PMID: 29737974 PMCID: PMC5963316 DOI: 10.12659/msm.909684] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Background Increased small-conductance Ca2+-activated K+ current (SK), abnormal intracellular Ca2+ handling, and enhanced expression and activity of Ca2+/calmodulin-dependent protein kinase II (CaMKII) have been found in clinical and/or experimental models of atrial fibrillation (AF), but the cumulative effect of these phenomena and their mechanisms in AF are still unclear. This study aimed to test the hypothesis that CaMKII increases SK current in human chronic AF. Material/Methods Right atrial appendage tissues from patients with either sinus rhythm (SR) or AF and neonatal rat atrial myocytes were used. Patch clamp, qRT-PCR, and Western blotting techniques were used to perform the study. Results Compared to SR, the apamin-sensitive SK current (IKAS) was significantly increased, but the mRNA and protein levels of SK1, SK2, and SK3 were significantly decreased. In AF, the steady-state Ca2+ response curve of IKAS was shifted leftward and the [Ca2+]i level was significantly increased. CaMKII inhibitors (KN-93 or autocamtide-2-related inhibitory peptide (AIP)) reduced the IKAS in both AF and SR. The inhibitory effect of KN-93 or AIP on IKAS was greater in AF than in SR. The expression levels of calmodulin, CaMKII, and autophosphorylated CaMKII at Thr287 (but not at Thr286) were significantly increased in AF. Furthermore, KN-93 inhibited the expression of (Thr287)p-CaMKII and SK2 in neonatal rat atrial myocytes. Conclusions SK current is increased via the enhanced activation of CaMKII in patients with AF. This finding may explain the difference between SK current and channels expression in AF, and thus may provide a therapeutic target for AF.
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Affiliation(s)
- Xuehui Fan
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Yiyan Yu
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Huan Lan
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Xianhong Ou
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Lijie Yang
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Tao Li
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Jiming Cao
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Xiaorong Zeng
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Miaoling Li
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
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Hesselkilde EZ, Carstensen H, Haugaard MM, Carlson J, Pehrson S, Jespersen T, Buhl R, Platonov PG. Effect of flecainide on atrial fibrillatory rate in a large animal model with induced atrial fibrillation. BMC Cardiovasc Disord 2017; 17:289. [PMID: 29221440 PMCID: PMC5723027 DOI: 10.1186/s12872-017-0720-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 11/24/2017] [Indexed: 11/25/2022] Open
Abstract
Background Atrial fibrillatory cycle length has been considered one of the indices of atrial electrical remodelling during atrial fibrillation (AF), which can be assessed from surface ECG by computer-assisted calculation of atrial fibrillatory rate (AFR). Horses have been suggested as a bona fide model for AF studies since horses too, develop lone AF, however data on AF characteristics in horses are extremely sparse and non-invasive characterization of AF complexity using surface ECG processing has not been reported. Aim The aim was to study characteristics of induced AF and its modification by flecainide. Methods The study group consisted on 3 horses with spontaneous persistent AF and 13 with pace-induced AF. Seven horses were treated with saline (control) and eight with flecainide (2 mg/kg). ECGs were analysed using spatiotemporal cancellation of QRST complexes and calculation of AFR from the residual atrial signal. Results At AF onset, AFR was 295 ± 52 fibrillations per minute (fpm) in the horses with induced AF treated with flecainide, 269 ± 36 fpm in the control group (ns), and 364 ± 26 fpm in the horses with spontaneous persistent AF (P < 0.05 compared to the control group). Flecainide caused a decrease in AFR in all animals and restored sinus rhythm in the animals with induced AF. In the control animals, AFR increased from 269 ± 36 fpm to a plateau of 313 ± 14 fpm before decreasing to 288 ± 28 fpm during the last 10% of the AF episodes preceding spontaneous conversion (P < 0.05). Conclusion AFR in horses with induced AF resembles AFR in humans with paroxysmal AF. Flecainide caused a rapid decrease in AFR in all horses, further supporting the method to be a non-invasive technique to study the effect of antiarrhythmic compounds.
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Affiliation(s)
- Eva Z Hesselkilde
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630, Taastrup, Denmark
| | - Helena Carstensen
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630, Taastrup, Denmark
| | - Maria M Haugaard
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630, Taastrup, Denmark
| | - Jonas Carlson
- Department of Cardiology, Lund University, 21185, Lund, Sweden
| | - Steen Pehrson
- Department of Cardiology, The Heart Centre, University of Copenhagen, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark
| | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Højbakkegaard Allé 5, 2630, Taastrup, Denmark.
| | - Pyotr G Platonov
- Arrhythmia Clinic, Skåne University Hospital and Department of Cardiology, Clinical Sciences, Lund University, 21185, Lund, Sweden
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Simó-Vicens R, Kirchhoff JE, Dolce B, Abildgaard L, Speerschneider T, Sørensen US, Grunnet M, Diness JG, Bentzen BH. A new negative allosteric modulator, AP14145, for the study of small conductance calcium-activated potassium (K Ca 2) channels. Br J Pharmacol 2017; 174:4396-4408. [PMID: 28925012 DOI: 10.1111/bph.14043] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 09/08/2017] [Accepted: 09/13/2017] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND AND PURPOSE Small conductance calcium-activated potassium (KCa 2) channels represent a promising atrial-selective target for treatment of atrial fibrillation. Here, we establish the mechanism of KCa 2 channel inhibition by the new compound AP14145. EXPERIMENTAL APPROACH Using site-directed mutagenesis, binding determinants for AP14145 inhibition were explored. AP14145 selectivity and mechanism of action were investigated by patch-clamp recordings of heterologously expressed KCa 2 channels. The biological efficacy of AP14145 was assessed by measuring atrial effective refractory period (AERP) prolongation in anaesthetized rats, and a beam walk test was performed in mice to determine acute CNS-related effects of the drug. KEY RESULTS AP14145 was found to be an equipotent negative allosteric modulator of KCa 2.2 and KCa 2.3 channels (IC50 = 1.1 ± 0.3 μM). The presence of AP14145 (10 μM) increased the EC50 of Ca2+ on KCa 2.3 channels from 0.36 ± 0.02 to 1.2 ± 0.1 μM. The inhibitory effect strongly depended on two amino acids, S508 and A533 in the channel. AP14145 concentration-dependently prolonged AERP in rats. Moreover, AP14145 (10 mg·kg-1 ) did not trigger any apparent CNS effects in mice. CONCLUSIONS AND IMPLICATIONS AP14145 is a negative allosteric modulator of KCa 2.2 and KCa 2.3 channels that shifted the calcium dependence of channel activation, an effect strongly dependent on two identified amino acids. AP14145 prolonged AERP in rats and did not trigger any acute CNS effects in mice. The understanding of how KCa 2 channels are inhibited, at the molecular level, will help further development of drugs targeting KCa 2 channels.
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Affiliation(s)
- Rafel Simó-Vicens
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
| | | | - Bernardo Dolce
- Department of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | | | | | | | | | | | - Bo H Bentzen
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
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Diness JG, Skibsbye L, Simó-Vicens R, Santos JL, Lundegaard P, Citerni C, Sauter DRP, Bomholtz SH, Svendsen JH, Olesen SP, Sørensen US, Jespersen T, Grunnet M, Bentzen BH. Termination of Vernakalant-Resistant Atrial Fibrillation by Inhibition of Small-Conductance Ca 2+-Activated K + Channels in Pigs. Circ Arrhythm Electrophysiol 2017; 10:CIRCEP.117.005125. [PMID: 29018164 PMCID: PMC5647113 DOI: 10.1161/circep.117.005125] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 08/21/2017] [Indexed: 11/17/2022]
Abstract
Supplemental Digital Content is available in the text. Background Evidence has emerged that small-conductance Ca2+-activated K+ (SK) channels constitute a new target for treatment of atrial fibrillation (AF). SK channels are predominantly expressed in the atria as compared with the ventricles. Various marketed antiarrhythmic drugs are limited by ventricular adverse effects and efficacy loss as AF progresses. Methods and Results A total of 43 pigs were used for the studies. AF reversion in conscious long-term tachypaced pigs: Pigs were subjected to atrial tachypacing (7 Hz) until they developed sustained AF that could not be reverted by vernakalant 4 mg/kg (18.8±3.3 days of atrial tachypacing). When the SK channel inhibitor AP14145 was tested in these animals, vernakalant-resistant AF was reverted to sinus rhythm, and reinduction of AF by burst pacing (50 Hz) was prevented in 8 of 8 pigs. Effects on refractory period and AF duration in open chest pigs: The effects of AP14145 and vernakalant on the effective refractory periods and acute burst pacing-induced AF were examined in anaesthetized open chest pigs. Both vernakalant and AP14145 significantly prolonged atrial refractoriness and reduced AF duration without affecting the ventricular refractoriness or blood pressure in pigs subjected to 7 days atrial tachypacing, as well as in sham-operated control pigs. Conclusions SK currents play a role in porcine atrial repolarization, and pharmacological inhibition of these with AP14145 demonstrates antiarrhythmic effects in a vernakalant-resistant porcine model of AF. These results suggest SK channel blockers as potentially interesting anti-AF drugs.
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Affiliation(s)
- Jonas Goldin Diness
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.).
| | - Lasse Skibsbye
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Rafel Simó-Vicens
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Joana Larupa Santos
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Pia Lundegaard
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Carlotta Citerni
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Daniel Rafael Peter Sauter
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Sofia Hammami Bomholtz
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Jesper Hastrup Svendsen
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Søren-Peter Olesen
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Ulrik S Sørensen
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Thomas Jespersen
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Morten Grunnet
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Bo Hjorth Bentzen
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
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Chen KH, Liu H, Sun HY, Jin MW, Xiao GS, Wang Y, Li GR. The Natural Flavone Acacetin Blocks Small Conductance Ca 2+-Activated K + Channels Stably Expressed in HEK 293 Cells. Front Pharmacol 2017; 8:716. [PMID: 29081746 PMCID: PMC5646423 DOI: 10.3389/fphar.2017.00716] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2017] [Accepted: 09/25/2017] [Indexed: 01/06/2023] Open
Abstract
The natural flavone acacetin inhibits several voltage-gated potassium currents in atrial myocytes, and has anti-atrial fibrillation (AF) effect in experimental AF models. The present study investigates whether acacetin inhibits the Ca2+-activated potassium (KCa) currents, including small conductance (SKCa1, SKCa2, and SKCa3), intermediate conductance (IKCa), and large-conductance (BKCa) channels stably expressed in HEK 293 cells. The effects of acacetin on these KCa channels were determined with a whole-cell patch voltage-clamp technique. The results showed that acacetin inhibited the three subtype SKCa channel currents in concentration-dependent manner with IC50 of 12.4 μM for SKCa1, 10.8 μM for SKCa2, and 11.6 μM for SKCa3. Site-directed mutagenesis of SKCa3 channels generated the mutants H490N, S512T, H521N, and A537V. Acacetin inhibited the mutants with IC50 of 118.5 μM for H490N, 275.2 μM for S512T, 15.3 μM for H521N, and 10.6 μM for A537V, suggesting that acacetin interacts with the P-loop helix of SKCa3 channel. However, acacetin at 3–10 μM did not decrease, but induced a slight increase of BKCa (+70 mV) by 8% at 30 μM. These results demonstrate the novel information that acacetin remarkably inhibits SKCa channels, but not IKCa or BKCa channels, which suggests that blockade of SKCa by acacetin likely contributes to its anti-AF property previously observed in experimental AF.
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Affiliation(s)
- Kui-Hao Chen
- Department of Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, Hong Kong.,Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hui Liu
- Department of Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, Hong Kong.,Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hai-Ying Sun
- Department of Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, Hong Kong
| | - Man-Wen Jin
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Guo-Sheng Xiao
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
| | - Yan Wang
- Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
| | - Gui-Rong Li
- Department of Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, Hong Kong.,Xiamen Cardiovascular Hospital, Xiamen University, Xiamen, China
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49
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Simó-Vicens R, Sauter DRP, Grunnet M, Diness JG, Bentzen BH. Effect of antiarrhythmic drugs on small conductance calcium - activated potassium channels. Eur J Pharmacol 2017; 803:118-123. [PMID: 28322838 DOI: 10.1016/j.ejphar.2017.03.039] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 03/16/2017] [Accepted: 03/17/2017] [Indexed: 10/19/2022]
Abstract
Atrial fibrillation (AF) is the most common type of arrhythmia. Current pharmacological treatment for AF is moderately effective and/or increases the risk of serious ventricular adverse effects. To avoid ventricular adverse effects, a new target has been considered, the small conductance calcium-activated K+ channels (KCa2.X, SK channels). In the heart, KCa2.X channels are functionally more important in atria compared to ventricles, and pharmacological inhibition of the channel confers atrial selective prolongation of the cardiac action potential and converts AF to sinus rhythm in animal models of AF. Whether antiarrhythmic drugs (AADs) recommended for treating AF target KCa2.X channels is unknown. To this end, we tested a large number of AADs on the human KCa2.2 and KCa2.3 channels to assess their effect on this new target using automated whole-cell patch clamp. Of the AADs recommended for treatment of AF only dofetilide and propafenone inhibited hKCa2.X channels, with no subtype selectivity. The calculated IC50 were 90±10µmol/l vs 60±10µmol/l for dofetilide and 42±4µmol/l vs 80±20µmol/l for propafenone (hKCa2.3 vs hKCa2.2). Whether this inhibition has clinical importance for their antiarrhythmic effect is unlikely, as the calculated IC50 values are very high compared to the effective free therapeutic plasma concentration of the drugs when used for AF treatment, 40,000-fold for dofetilide and 140-fold higher for propafenone.
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Affiliation(s)
- Rafel Simó-Vicens
- Biomedical Institute, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark; Acesion Pharma, Ole Maaløes Vej 3, DK-2200 Copenhagen, Denmark
| | - Daniel R P Sauter
- Biomedical Institute, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark; Acesion Pharma, Ole Maaløes Vej 3, DK-2200 Copenhagen, Denmark
| | - Morten Grunnet
- Acesion Pharma, Ole Maaløes Vej 3, DK-2200 Copenhagen, Denmark
| | - Jonas G Diness
- Acesion Pharma, Ole Maaløes Vej 3, DK-2200 Copenhagen, Denmark
| | - Bo H Bentzen
- Biomedical Institute, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark; Acesion Pharma, Ole Maaløes Vej 3, DK-2200 Copenhagen, Denmark.
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50
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Hundahl LA, Sattler SM, Skibsbye L, Diness JG, Tfelt-Hansen J, Jespersen T. Pharmacological blockade of small conductance Ca 2+-activated K + channels by ICA reduces arrhythmic load in rats with acute myocardial infarction. Pflugers Arch 2017; 469:739-50. [PMID: 28285409 DOI: 10.1007/s00424-017-1962-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 02/07/2017] [Accepted: 02/20/2017] [Indexed: 01/02/2023]
Abstract
Acute myocardial infarction (AMI) with development of ventricular fibrillation (VF) is a common cause of sudden cardiac death (SCD). At present, no pharmacological treatment has successfully been able to prevent VF in the acute stage of AMI. This study investigates the antiarrhythmic effect of inhibiting small conductance Ca2+-activated K+ (SK) channels using the pore blocker N-(pyridin-2-yl)-4-(pyridin-2-yl)thiazol-2-amine (ICA) in AMI rats. Acute coronary ligation was performed in 26 anesthetized rats, and ECG, monophasic action potentials (MAPs), and ventricular effective refractory period (vERP) were recorded. Rats were randomized into four groups: (i) 3 mg/kg i.v. ICA with AMI (AMI-ICA-group, n = 9), (ii) vehicle with AMI (AMI-vehicle-group, n = 9), (iii) vehicle with sham operation (sham-vehicle-group, n = 8), and (iv) 3 mg/kg i.v. ICA with sham operation (sham-ICA-group, n = 6). At the end of experiments, hearts were stained for the non-perfused area at risk (AAR). AMI resulted in the development of ventricular tachycardia (VT) in all AMI-vehicle and AMI-ICA rats; however, ICA significantly decreased VT duration. VF occurred in 44% of AMI-vehicle rats but not in AMI-ICA rats. Monophasic action potential duration at 80% repolarization (MAPD80) in the ischemic area decreased rapidly in both AMI-vehicle and AMI-ICA rats. However, 5 min after occlusion, MAPD80 returned to baseline in AMI-ICA rats but not in AMI-vehicle rats. The vERP was prolonged in the AMI-ICA group compared to AMI-vehicle after ligation. AAR was similar between the AMI-vehicle group and the AMI-ICA group. In rats with AMI, ICA reduces the burden of arrhythmia.
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