1
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Liu M, Zhao J, Lu Y, Chen Z, Feng X, Pan G. Gab1 Overexpression Attenuates Susceptibility to Ventricular Arrhythmias in Pressure Overloaded Heart Failure Mouse Hearts. Cardiovasc Drugs Ther 2024; 38:253-262. [PMID: 36374360 DOI: 10.1007/s10557-022-07394-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/14/2022] [Indexed: 11/16/2022]
Abstract
PURPOSE Grb2 associated binding protein 1 (Gab1) is an adaptor protein that is important for intracellular signal transduction which involved in several pathological process. However, the role of Gab1 in pressure overload-induced ventricular arrhythmias (VAs) remain poorly understood. In the current study, we aimed to test the role of Gab1 in VA susceptibility induced by pressure overload. METHODS We overexpressed Gab1 in the hearts using an adeno-associated virus 9 (AAV9) system through tail vein injection. Aortic banding (AB) surgery was performed in C57BL6/J mice to induce heart failure (HF). Four weeks following AB, histology, echocardiography, and biochemical analysis were conducted to investigate cardiac structural remodeling and electrophysiological studies were performed to check the electrical remodeling. Western blot analysis was used to explore the underlying mechanisms. RESULTS The mRNA and protein expression were downregulated in AB hearts compared to sham hearts. Gab1 overexpression significantly reversed AB-induced cardiac structural remodeling including ameliorated AB-induced cardiac dysfunction, cardiac fibrosis, and inflammatory response. Moreover, Gab1 overexpression also markedly alleviated AB-induced electrical remodeling including ion channel alterations and VA susceptibility. Mechanistically, we found that TLR4/MyD88/NF-κB contributes to the cardio protective effect of Gab1 overexpression on AB-induced VAs. CONCLUSIONS Our study manifested that Gab1 may serve as a promising anti-arrhythmic target via inhibiting TLR4/MyD88/NF-κB signaling pathway induced by AB.
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Affiliation(s)
- Mingxin Liu
- Department of Cardiology, Yueyang Central Hospital, No.39 Dongmaoling Road, Yueyang 414000, Hunan, China.
| | - Jianhua Zhao
- Department of Cardiology, Yueyang Central Hospital, No.39 Dongmaoling Road, Yueyang 414000, Hunan, China
| | - Yonghua Lu
- Department of Cardiology, Yueyang Central Hospital, No.39 Dongmaoling Road, Yueyang 414000, Hunan, China
| | - Zhi Chen
- Department of Cardiology, Yueyang Central Hospital, No.39 Dongmaoling Road, Yueyang 414000, Hunan, China
| | - Xiaojian Feng
- Department of Cardiology, Yueyang Central Hospital, No.39 Dongmaoling Road, Yueyang 414000, Hunan, China
| | - Gang Pan
- Department of Cardiology, Yueyang Central Hospital, No.39 Dongmaoling Road, Yueyang 414000, Hunan, China.
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2
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Van NTH, Kim WK, Nam JH. Challenges in the Therapeutic Targeting of KCa Channels: From Basic Physiology to Clinical Applications. Int J Mol Sci 2024; 25:2965. [PMID: 38474212 PMCID: PMC10932353 DOI: 10.3390/ijms25052965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/23/2024] [Accepted: 01/25/2024] [Indexed: 03/14/2024] Open
Abstract
Calcium-activated potassium (KCa) channels are ubiquitously expressed throughout the body and are able to regulate membrane potential and intracellular calcium concentrations, thereby playing key roles in cellular physiology and signal transmission. Consequently, it is unsurprising that KCa channels have been implicated in various diseases, making them potential targets for pharmaceutical interventions. Over the past two decades, numerous studies have been conducted to develop KCa channel-targeting drugs, including those for disorders of the central and peripheral nervous, cardiovascular, and urinary systems and for cancer. In this review, we synthesize recent findings regarding the structure and activating mechanisms of KCa channels. We also discuss the role of KCa channel modulators in therapeutic medicine. Finally, we identify the major reasons behind the delay in bringing these modulators to the pharmaceutical market and propose new strategies to promote their application.
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Affiliation(s)
- Nhung Thi Hong Van
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Republic of Korea;
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
| | - Woo Kyung Kim
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
- Department of Internal Medicine, Graduate School of Medicine, Dongguk University, Goyang 10326, Republic of Korea
| | - Joo Hyun Nam
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Republic of Korea;
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
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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] [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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Schmeckpeper J, Kim K, George SA, Blackwell DJ, Brennan JA, Efimov IR, Knollmann BC. RyR2 inhibition with dantrolene is antiarrhythmic, prevents further pathological remodeling, and improves cardiac function in chronic ischemic heart disease. J Mol Cell Cardiol 2023; 181:67-78. [PMID: 37285929 PMCID: PMC10526741 DOI: 10.1016/j.yjmcc.2023.05.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 04/30/2023] [Accepted: 05/31/2023] [Indexed: 06/09/2023]
Abstract
Diastolic Ca2+ leak due to cardiac ryanodine receptor (RyR2) hyperactivity has been widely documented in chronic ischemic heart disease (CIHD) and may contribute to ventricular tachycardia (VT) risk and progressive left-ventricular (LV) remodeling. Here we test the hypothesis that targeting RyR2 hyperactivity can suppress VT inducibility and progressive heart failure in CIHD by the RyR2 inhibitor dantrolene. METHODS AND RESULTS: CIHD was induced in C57BL/6 J mice by left coronary artery ligation. Four weeks later, mice were randomized to either acute or chronic (6 weeks via implanted osmotic pump) treatment with dantrolene or vehicle. VT inducibility was assessed by programmed stimulation in vivo and in isolated hearts. Electrical substrate remodeling was assessed by optical mapping. Ca2+ sparks and spontaneous Ca2+ releases were measured in isolated cardiomyocytes. Cardiac remodeling was quantified by histology and qRT-PCR. Cardiac function and contractility were measured using echocardiography. Compared to vehicle, acute dantrolene treatment reduced VT inducibility. Optical mapping demonstrated reentrant VT prevention by dantrolene, which normalized the shortened refractory period (VERP) and prolonged action potential duration (APD), preventing APD alternans. In single CIHD cardiomyocytes, dantrolene normalized RyR2 hyperactivity and prevented spontaneous intracellular Ca2+ release. Chronic dantrolene treatment not only reduced VT inducibility but also reduced peri-infarct fibrosis and prevented further progression of LV dysfunction in CIHD mice. CONCLUSIONS: RyR2 hyperactivity plays a mechanistic role for VT risk, post-infarct remodeling, and contractile dysfunction in CIHD mice. Our data provide proof of concept for the anti-arrhythmic and anti-remodeling efficacy of dantrolene in CIHD.
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Affiliation(s)
- Jeffrey Schmeckpeper
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Kyungsoo Kim
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Sharon A George
- Department of Biomedical Engineering, the George Washington University, Washington DC, USA; Department of Biomedical Engineering, Northwestern University, Chicago, IL, USA
| | - Daniel J Blackwell
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jaclyn A Brennan
- Department of Biomedical Engineering, the George Washington University, Washington DC, USA
| | - Igor R Efimov
- Department of Biomedical Engineering, the George Washington University, Washington DC, USA; Department of Biomedical Engineering, Northwestern University, Chicago, IL, USA
| | - Bjorn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA.
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Liu T, Li T, Xu D, Wang Y, Zhou Y, Wan J, Huang CLH, Tan X. Small-conductance calcium-activated potassium channels in the heart: expression, regulation and pathological implications. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220171. [PMID: 37122223 PMCID: PMC10150224 DOI: 10.1098/rstb.2022.0171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
Ca2+-activated K+ channels are critical to cellular Ca2+ homeostasis and excitability; they couple intracellular Ca2+ and membrane voltage change. Of these, the small, 4-14 pS, conductance SK channels include three, KCNN1-3 encoded, SK1/KCa2.1, SK2/KCa2.2 and SK3/KCa2.3, channel subtypes with characteristic, EC50 ∼ 10 nM, 40 pM, 1 nM, apamin sensitivities. All SK channels, particularly SK2 channels, are expressed in atrial, ventricular and conducting system cardiomyocytes. Pharmacological and genetic modification results have suggested that SK channel block or knockout prolonged action potential durations (APDs) and effective refractory periods (ERPs) particularly in atrial, but also in ventricular, and sinoatrial, atrioventricular node and Purkinje myocytes, correspondingly affect arrhythmic tendency. Additionally, mitochondrial SK channels may decrease mitochondrial Ca2+ overload and reactive oxygen species generation. SK channels show low voltage but marked Ca2+ dependences (EC50 ∼ 300-500 nM) reflecting their α-subunit calmodulin (CaM) binding domains, through which they may be activated by voltage-gated or ryanodine-receptor Ca2+ channel activity. SK function also depends upon complex trafficking and expression processes and associations with other ion channels or subunits from different SK subtypes. Atrial and ventricular clinical arrhythmogenesis may follow both increased or decreased SK expression through decreased or increased APD correspondingly accelerating and stabilizing re-entrant rotors or increasing incidences of triggered activity. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Ting Liu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Tao Li
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Cardiology, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Dandi Xu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Yan Wang
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Yafei Zhou
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Juyi Wan
- Department of Cardiovascular Surgery, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Christopher L-H Huang
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Physiological Laboratory and Department of Biochemistry, University of Cambridge, Cambridge CB2 3EG, UK
| | - Xiaoqiu Tan
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Cardiology, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Physiology, School of Basic Medical Sciences, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
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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] [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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7
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Chen M, Zhu T, Wu Z, Hu L, Wu Z, Liu Q, Zhou S. LL-VNS attenuates SK2 expression and incidence of arrhythmias following acute myocardial infarction in rats. Front Cardiovasc Med 2023; 9:1034888. [PMID: 36712237 PMCID: PMC9874093 DOI: 10.3389/fcvm.2022.1034888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 12/12/2022] [Indexed: 01/12/2023] Open
Abstract
Objectives Our previous study has demonstrated that low-level vagus nerve stimulation (LL-VNS) protects the heart against ventricular arrhythmias (VAs) induced by acute myocardial infarction (AMI). However, the potential mechanisms by which it influences ventricular electrophysiology remain unknown. Materials and methods Forty-five rats were divided into three groups: a Control group (sham AMI followed by sham LL-VNS, n = 15), an AMI group (AMI followed by sham LL-VSN for 60 mins, n = 15), and an AMI + LL-VNS group (AMI followed by LL-VSN for 60 mins, n = 15). Heart rate variability (HRV), ventricular effective refractory period (ERP), ventricular fibrillation threshold (VFT), and left stellate ganglion (LSG) activity were measured at baseline and during AMI. Finally, myocardial tissues were collected for tissue analysis. Results AMI directly induced hyperactivity in the LSG and reduced vagal tone as indexed by HRV. AMI also decreased VFT, and shortened ERP but increased ERP dispersion. AMI resulted in an increase in expression of ventricular small-conductance Ca2+-activated K+ (SK2). However, LL-VNS significantly mitigated or eliminated the effects of AMI. Conclusion LL-VNS altered the electrophysiological properties of the ventricles through inhibition of cardiac sympathetic nervous activity and reduction in SK2 expression.
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Affiliation(s)
- Mingxian Chen
- The Second Xiangya Hospital, Central South University, Changsha, China
| | - Tongjian Zhu
- Xiangyang Central Hospital, Xiangyang, Hubei, China
| | - Zhihong Wu
- The Second Xiangya Hospital, Central South University, Changsha, China
| | - Lin Hu
- The Second Xiangya Hospital, Central South University, Changsha, China
| | - Zhijian Wu
- The Second Xiangya Hospital, Central South University, Changsha, China
| | - Qiming Liu
- The Second Xiangya Hospital, Central South University, Changsha, China
| | - Shenghua Zhou
- The Second Xiangya Hospital, Central South University, Changsha, China,*Correspondence: Shenghua Zhou,
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8
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Abstract
Cardiac alternans arises from dynamical instabilities in the electrical and calcium cycling systems of the heart, and often precedes ventricular arrhythmias and sudden cardiac death. In this review, we integrate clinical observations with theory and experiment to paint a holistic portrait of cardiac alternans: the underlying mechanisms, arrhythmic manifestations and electrocardiographic signatures. We first summarize the cellular and tissue mechanisms of alternans that have been demonstrated both theoretically and experimentally, including 3 voltage-driven and 2 calcium-driven alternans mechanisms. Based on experimental and simulation results, we describe their relevance to mechanisms of arrhythmogenesis under different disease conditions, and their link to electrocardiographic characteristics of alternans observed in patients. Our major conclusion is that alternans is not only a predictor, but also a causal mechanism of potentially lethal ventricular and atrial arrhythmias across the full spectrum of arrhythmia mechanisms that culminate in functional reentry, although less important for anatomic reentry and focal arrhythmias.
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Affiliation(s)
- Zhilin Qu
- Departments of Medicine (Cardiology), Physiology, and Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA
| | - James N. Weiss
- Departments of Medicine (Cardiology), Physiology, and Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA
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9
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Qi D, Li W, Quan XQ, Gao Y, Wang J, Guo L, Zhao W, Liu T, Gao C, Yan GX. Alternating Early Afterdepolarizations Underlying Bradycardia-Dependent Macroscopic T Wave and Discordant Mechanical Alternans. Circ Arrhythm Electrophysiol 2023; 16:e011453. [PMID: 36595630 DOI: 10.1161/circep.122.011453] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
BACKGROUND Macroscopic T wave alternans (macro-TWA) often heralds the onset of Torsades de Pointes in patients with QT prolongation. However, the mechanisms underlying macro-TWA remain unclear. We examined the cellular and ionic basis for macro-TWA in rabbits with left ventricular hypertrophy (LVH). METHODS The renovascular hypertension model was used to induce LVH in rabbits. Action potentials were simultaneously recorded from epicardium and endocardium together with a transmural ECG and isometric contractility in arterially perfused left ventricular wedges. Late sodium current (INa-L) was recorded in single-isolated left ventricular myocytes with the whole cell patch-clamp technique. RESULTS Macro-TWA and accompanied mechanical alternans occurred spontaneously in 8 of 33 LVH rabbits (P<0.05, versus 0/15 in controls) and were induced by an INa-L enhancer ATX-II at 1 to 3 nM in additional 7. Macro-TWA and mechanical alternans occurred discordantly, that is, that longer QT interval and larger T wave were associated with weaker isometric contvractility. Alternating early afterdepolarizations in the endocardium caused macro-TWA in 12 of 15 LVH rabbits and, therefore, early afterdepolarization-dependent R-from-T extrasystoles and Torsades de Pointes always originated from the beats with longer QT and larger T wave during macro-TWA. INa-L density was significantly larger in LVH myocytes than that of control myocytes. Macro-TWA, mechanical alternans, R-from-T extrasystoles, and Torsades de Pointes were all abolished by INa-L blocker ranolazine or mexiletine. CONCLUSIONS LVH enhances INa-L density and promotes alternating early afterdepolarizations in the left ventricular endocardium that manifest as macro-TWA with discordant mechanical alternans. INa-L blockade abolishes macro-TWA, mechanical alternans, early afterdepolarization-dependent R-from-T extrasystoles, and Torsades de Pointes.
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Affiliation(s)
- Datun Qi
- Zhengzhou University People's Hospital and Central China Fuwai Hospital, Zhengzhou, China (D.Q., C.G., G.-X.Y.).,Lankenau Institute for Medical Research, Wynnewood, PA (D.Q., X.-Q.Q., Y.G., J.W., W.Z., G.-X.Y.)
| | - Wei Li
- Department of Cardiology, Xinhua Hospital, Shanghai, China (W.L.)
| | - Xiao-Qing Quan
- Lankenau Institute for Medical Research, Wynnewood, PA (D.Q., X.-Q.Q., Y.G., J.W., W.Z., G.-X.Y.)
| | - Yuan Gao
- Lankenau Institute for Medical Research, Wynnewood, PA (D.Q., X.-Q.Q., Y.G., J.W., W.Z., G.-X.Y.).,Henan University of Traditional Chinese Medicine, Zhengzhou, China (Y.G.)
| | - Jianyong Wang
- Lankenau Institute for Medical Research, Wynnewood, PA (D.Q., X.-Q.Q., Y.G., J.W., W.Z., G.-X.Y.).,TEDA International Cardiovascular Hospital, Tianjin, China (J.W.)
| | | | - Wenping Zhao
- Lankenau Institute for Medical Research, Wynnewood, PA (D.Q., X.-Q.Q., Y.G., J.W., W.Z., G.-X.Y.).,Affiliated Hospital of Hebei University, Baoding, China (W.Z.)
| | - Tong Liu
- Department of Cardiology, Second Hospital of Tianjin Medical University, China (T.L.)
| | - Chuanyu Gao
- Zhengzhou University People's Hospital and Central China Fuwai Hospital, Zhengzhou, China (D.Q., C.G., G.-X.Y.)
| | - Gan-Xin Yan
- Zhengzhou University People's Hospital and Central China Fuwai Hospital, Zhengzhou, China (D.Q., C.G., G.-X.Y.).,Lankenau Institute for Medical Research, Wynnewood, PA (D.Q., X.-Q.Q., Y.G., J.W., W.Z., G.-X.Y.).,Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA (G.-X.Y.)
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10
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Huang C, Song Z, Qu Z. Synchronization of spatially discordant voltage and calcium alternans in cardiac tissue. Phys Rev E 2022; 106:024406. [PMID: 36109882 DOI: 10.1103/physreve.106.024406] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Accepted: 07/18/2022] [Indexed: 06/01/2023]
Abstract
The heart is an excitable medium which is excited by membrane potential depolarization and propagation. Membrane potential depolarization brings in calcium (Ca) through the Ca channels to trigger intracellular Ca release for contraction of the heart. Ca also affects voltage via Ca-dependent ionic currents, and thus, voltage and Ca are bidirectionally coupled. It has been shown that the voltage subsystem or the Ca subsystem can generate its own dynamical instabilities which are affected by their bidirectional couplings, leading to complex dynamics of action potential and Ca cycling. Moreover, the dynamics become spatiotemporal in tissue in which cells are diffusively coupled through voltage. A widely investigated spatiotemporal dynamics is spatially discordant alternans (SDA) in which action potential duration (APD) or Ca amplitude exhibits temporally period-2 and spatially out-of-phase patterns, i.e., APD-SDA and Ca-SDA patterns, respectively. However, the mechanisms of formation, stability, and synchronization of APD-SDA and Ca-SDA patterns remain incompletely understood. In this paper, we use cardiac tissue models described by an amplitude equation, coupled iterated maps, and reaction-diffusion equations with detailed physiology (the ionic model) to perform analytical and computational investigations. We show that, when the Ca subsystem is stable, the Ca-SDA pattern always follows the APD-SDA pattern, and thus, they are always synchronized. When the Ca subsystem is unstable, synchronization of APD-SDA and Ca-SDA patterns depends on the stabilities of both subsystems, their coupling strengths, and the spatial scales of the initial Ca-SDA patterns. Spontaneous (initial condition-independent) synchronization is promoted by enhancing APD instability and reducing Ca instability as well as stronger Ca-to-APD and APD-to-Ca coupling, a pattern formation caused by dynamical instabilities. When Ca is more unstable and APD is less unstable or APD-to-Ca coupling is weak, synchronization of APD-SDA and Ca-SDA patterns is promoted by larger initially synchronized Ca-SDA clusters, i.e., initial condition-dependent synchronization. The synchronized APD-SDA and Ca-SDA patterns can be locked in-phase, antiphase, or quasiperiodic depending on the coupling relationship between APD and Ca. These theoretical and simulation results provide mechanistic insights into the APD-SDA and Ca-SDA dynamics observed in experimental studies.
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Affiliation(s)
- Chunli Huang
- School of Mathematics and Statistics, Guangdong University of Foreign Studies, Guangzhou 510420, China
- Department of Medicine, University of California, Los Angeles, California 90095, USA
| | - Zhen Song
- Peng Cheng Laboratory, Shenzhen, Guangdong, China
| | - Zhilin Qu
- Department of Medicine, University of California, Los Angeles, California 90095, USA
- Department of Computational Medicine, University of California, Los Angeles, California 90095, USA
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11
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The Inhibition of the Small-Conductance Ca2+-Activated Potassium Channels Decreases the Sinus Node Pacemaking during Beta-Adrenergic Activation. Pharmaceuticals (Basel) 2022; 15:ph15030313. [PMID: 35337111 PMCID: PMC8948633 DOI: 10.3390/ph15030313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 02/24/2022] [Accepted: 03/01/2022] [Indexed: 11/17/2022] Open
Abstract
Sinus pacemaking is based on tight cooperation of intracellular Ca2+ handling and surface membrane ion channels. An important player of this synergistic crosstalk could be the small-conductance Ca2+-activated K+-channel (ISK) that could contribute to the sinoatrial node (SAN) pacemaking driven by the intracellular Ca2+ changes under normal conditions and beta-adrenergic activation, however, the exact role is not fully clarified. SK2 channel expression was verified by immunoblot technique in rabbit SAN cells. Ionic currents and action potentials were measured by patch-clamp technique. The ECG R-R intervals were obtained by Langendorff-perfusion method on a rabbit heart. Apamin, a selective inhibitor of SK channels, was used during the experiments. Patch-clamp experiments revealed an apamin-sensitive current. When 100 nM apamin was applied, we found no change in the action potential nor in the ECG R-R interval. In experiments where isoproterenol was employed, apamin increased the cycle length of the SAN action potentials and enhanced the ECG R-R interval. Apamin did not amplify the cycle length variability or ECG R-R interval variability. Our data indicate that ISK has no role under normal condition, however, it moderately contributes to the SAN automaticity under beta-adrenergic activation.
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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] [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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Kani K, Fujiu K. Electrical Storm. Int Heart J 2021; 62:1195-1198. [PMID: 34853216 DOI: 10.1536/ihj.21-662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Kunihiro Kani
- Department of Cardiovascular Medicine, Graduate School of Medicine, The University of Tokyo
| | - Katsuhito Fujiu
- Department of Cardiovascular Medicine, Graduate School of Medicine, The University of Tokyo
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14
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Husti Z, Varró A, Baczkó I. Arrhythmogenic Remodeling in the Failing Heart. Cells 2021; 10:cells10113203. [PMID: 34831426 PMCID: PMC8623396 DOI: 10.3390/cells10113203] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 11/05/2021] [Accepted: 11/11/2021] [Indexed: 12/12/2022] Open
Abstract
Chronic heart failure is a clinical syndrome with multiple etiologies, associated with significant morbidity and mortality. Cardiac arrhythmias, including ventricular tachyarrhythmias and atrial fibrillation, are common in heart failure. A number of cardiac diseases including heart failure alter the expression and regulation of ion channels and transporters leading to arrhythmogenic electrical remodeling. Myocardial hypertrophy, fibrosis and scar formation are key elements of arrhythmogenic structural remodeling in heart failure. In this article, the mechanisms responsible for increased arrhythmia susceptibility as well as the underlying changes in ion channel, transporter expression and function as well as alterations in calcium handling in heart failure are discussed. Understanding the mechanisms of arrhythmogenic remodeling is key to improving arrhythmia management and the prevention of sudden cardiac death in patients with heart failure.
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Affiliation(s)
- Zoltán Husti
- Department of Pharmacology and Pharmacotherapy, University of Szeged, 6720 Szeged, Hungary; (Z.H.); (A.V.)
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, 6720 Szeged, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, University of Szeged, 6720 Szeged, Hungary; (Z.H.); (A.V.)
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, 6720 Szeged, Hungary
- ELKH-SZTE Research Group for Cardiovascular Pharmacology, Eötvös Loránd Research Network, 6720 Szeged, Hungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, 6720 Szeged, Hungary; (Z.H.); (A.V.)
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, 6720 Szeged, Hungary
- Correspondence:
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15
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Small conductance calcium activated K + channel inhibitor decreases stretch induced vulnerability to atrial fibrillation. IJC HEART & VASCULATURE 2021; 37:100898. [PMID: 34746364 PMCID: PMC8554272 DOI: 10.1016/j.ijcha.2021.100898] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/05/2021] [Accepted: 10/16/2021] [Indexed: 12/11/2022]
Abstract
Background Atrial dilation is an important risk factor for atrial fibrillation (AF) and animal studies have found that acute atrial dilation shortens the atrial effective refractory period (AERP) and increases the risk of AF. Stretch activated ion channels (SACs) and calcium channels play a role in this. The expression profile and calcium dependent activation makes the small conductance calcium activated K+ channel (KCa2.x) a candidate for coupling stretch induced increases in intracellular calcium through K+-efflux and thereby shortening of atrial refractoriness. Objectives We hypothesized that KCa2.x channel inhibitors can prevent the stretch induced shortening of AERP and protect the heart from AF. Methods The effect of KCa2 channel inhibitor (N-(pyridin-2-yl)-4-(pyridin-2-yl)thiazol-2-amine (ICA) 1 µM) was investigated using the isolated perfused rabbit heart preparation. To stretch the left atrium (LA) a balloon was inserted and inflated. AERP and action potential duration (APD) were recorded before and after atrial stretch. AF was induced by burst pacing the LA at different degrees of atrial stretch. Results Stretching of the LA by increasing the balloon pressure from 0 to 20 mmHg shortened the AERP by 8.6 ± 1 ms. In comparison, the KCa2 inhibitor ICA significantly attenuated the stretch induced shortening of AERP to 2.5 ± 1.1 ms. Total AF duration increased linearly with atrial balloon pressure. This relationship was not found in the presence of ICA. ICA lowered the incidence of AF induction and total AF duration. Conclusion The KCa2 channel inhibitor ICA attenuates the acute stretch induced shortening of AERP and decreases stretch induced vulnerability to AF.
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16
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Ledford HA, Park S, Muir D, Woltz RL, Ren L, Nguyen PT, Sirish P, Wang W, Sihn CR, George AL, Knollmann BC, Yamoah EN, Yarov-Yarovoy V, Zhang XD, Chiamvimonvat N. Different arrhythmia-associated calmodulin mutations have distinct effects on cardiac SK channel regulation. J Gen Physiol 2021; 152:211546. [PMID: 33211795 PMCID: PMC7681919 DOI: 10.1085/jgp.202012667] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 08/25/2020] [Accepted: 10/19/2020] [Indexed: 12/21/2022] Open
Abstract
Calmodulin (CaM) plays a critical role in intracellular signaling and regulation of Ca2+-dependent proteins and ion channels. Mutations in CaM cause life-threatening cardiac arrhythmias. Among the known CaM targets, small-conductance Ca2+-activated K+ (SK) channels are unique, since they are gated solely by beat-to-beat changes in intracellular Ca2+. However, the molecular mechanisms of how CaM mutations may affect the function of SK channels remain incompletely understood. To address the structural and functional effects of these mutations, we introduced prototypical human CaM mutations in human induced pluripotent stem cell–derived cardiomyocyte-like cells (hiPSC-CMs). Using structural modeling and molecular dynamics simulation, we demonstrate that human calmodulinopathy-associated CaM mutations disrupt cardiac SK channel function via distinct mechanisms. CaMD96V and CaMD130G mutants reduce SK currents through a dominant-negative fashion. By contrast, specific mutations replacing phenylalanine with leucine result in conformational changes that affect helix packing in the C-lobe, which disengage the interactions between apo-CaM and the CaM-binding domain of SK channels. Distinct mutant CaMs may result in a significant reduction in the activation of the SK channels, leading to a decrease in the key Ca2+-dependent repolarization currents these channels mediate. The findings in this study may be generalizable to other interactions of mutant CaMs with Ca2+-dependent proteins within cardiac myocytes.
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Affiliation(s)
- Hannah A Ledford
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA
| | - Seojin Park
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV
| | - Duncan Muir
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA
| | - Ryan L Woltz
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA
| | - Lu Ren
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA
| | - Phuong T Nguyen
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA
| | - Padmini Sirish
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA
| | - Wenying Wang
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV
| | - Choong-Ryoul Sihn
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Björn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Department of Medicine, School of Medicine, Vanderbilt University, Nashville, TN
| | - Ebenezer N Yamoah
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA
| | - Xiao-Dong Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA
| | - Nipavan Chiamvimonvat
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, Davis, CA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA
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17
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Veteto AB, Peana D, Lambert MD, McDonald KS, Domeier TL. Transient receptor potential vanilloid-4 contributes to stretch-induced hypercontractility and time-dependent dysfunction in the aged heart. Cardiovasc Res 2021; 116:1887-1896. [PMID: 31693106 DOI: 10.1093/cvr/cvz287] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 09/29/2019] [Accepted: 11/04/2019] [Indexed: 01/06/2023] Open
Abstract
AIMS Cardiovascular disease remains the greatest cause of mortality in Americans over 65. The stretch-activated transient receptor potential vanilloid-4 (TRPV4) ion channel is expressed in cardiomyocytes of the aged heart. This investigation tests the hypothesis that TRPV4 alters Ca2+ handling and cardiac function in response to increased ventricular preload and cardiomyocyte stretch. METHODS AND RESULTS Left ventricular maximal pressure (PMax) was monitored in isolated working hearts of Aged (24-27 months) mice following preload elevation from 5 to 20mmHg, with and without TRPV4 antagonist HC067047 (HC, 1 µmol/L). In preload responsive hearts, PMax prior to and immediately following preload elevation (i.e. Frank-Starling response) was similar between Aged and Aged+HC. Within 1 min following preload elevation, Aged hearts demonstrated secondary PMax augmentation (Aged>Aged+HC) suggesting a role for stretch-activated TRPV4 in cardiac hypercontractility. However, after 20 min at 20 mmHg Aged exhibited depressed PMax (Aged<Aged+HC) suggestive of TRPV4-dependent contractile dysfunction with sustained stretch. To examine stretch-induced Ca2+ homeostasis at the single-cell level, isolated cardiomyocytes were stretched 10-15% of slack length while measuring intracellular Ca2+ with fura-2. Uniaxial longitudinal stretch increased intracellular Ca2+ levels and triggered Ca2+ overload and terminal cellular contracture in Aged, but not Aged+HC. Preload elevation in hearts of young/middle-age (3-12 months) mice produced an initial PMax increase (Frank-Starling response) without secondary PMax augmentation, and cardiomyocyte stretch did not affect intracellular Ca2+ levels. Hearts of transgenic mice with cardiac-specific TRPV4 expression exhibited PMax similar to 3- to 12-month control mice prior to and immediately following preload elevation but displayed secondary PMax augmentation. Cardiomyocytes of mice with transgenic TRPV4 expression were highly sensitive to mechanical stimulation and exhibited elevated Ca2+ levels, Ca2+ overload, and terminal contracture upon cellular attachment and stretch. CONCLUSION TRPV4 contributes to a stretch-induced increase in cardiomyocyte Ca2+ and cardiac hypercontractility, yet sustained stretch leads to cardiomyocyte Ca2+ overload and contractile dysfunction in the aged heart.
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Affiliation(s)
- Adam B Veteto
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, 1 Hospital Drive, Columbia, MO 65212, USA
| | - Deborah Peana
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, 1 Hospital Drive, Columbia, MO 65212, USA
| | - Michelle D Lambert
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, 1 Hospital Drive, Columbia, MO 65212, USA
| | - Kerry S McDonald
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, 1 Hospital Drive, Columbia, MO 65212, USA
| | - Timothy L Domeier
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, 1 Hospital Drive, Columbia, MO 65212, USA
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18
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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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19
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Rahm AK, Wieder T, Gramlich D, Müller ME, Wunsch MN, El Tahry FA, Heimberger T, Sandke S, Weis T, Most P, Katus HA, Thomas D, Lugenbiel P. Differential regulation of K Ca 2.1 (KCNN1) K + channel expression by histone deacetylases in atrial fibrillation with concomitant heart failure. Physiol Rep 2021; 9:e14835. [PMID: 34111326 PMCID: PMC8191401 DOI: 10.14814/phy2.14835] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 01/12/2023] Open
Abstract
Atrial fibrillation (AF) with concomitant heart failure (HF) poses a significant therapeutic challenge. Mechanism‐based approaches may optimize AF therapy. Small‐conductance, calcium‐activated K+ (KCa, KCNN) channels contribute to cardiac action potential repolarization. KCNN1 exhibits predominant atrial expression and is downregulated in chronic AF patients with preserved cardiac function. Epigenetic regulation is suggested by AF suppression following histone deacetylase (HDAC) inhibition. We hypothesized that HDAC‐dependent KCNN1 remodeling contributes to arrhythmogenesis in AF complicated by HF. The aim of this study was to assess KCNN1 and HDAC1–7 and 9 transcript levels in AF/HF patients and in a pig model of atrial tachypacing‐induced AF with reduced left ventricular function. In HL‐1 atrial myocytes, tachypacing and anti‐Hdac siRNAs were employed to investigate effects on Kcnn1 mRNA levels. KCNN1 expression displayed side‐specific remodeling in AF/HF patients with upregulation in left and suppression in right atrium. In pigs, KCNN1 remodeling showed intermediate phenotypes. HDAC levels were differentially altered in humans and pigs, reflecting highly variable epigenetic regulation. Tachypacing recapitulated downregulation of Hdacs1, 3, 4, 6, and 7 with a tendency towards reduced Kcnn1 levels in vitro, indicating that atrial high rates induce remodeling. Finally, Kcnn1 expression was decreased by knockdown of Hdacs2, 3, 6, and 7 and enhanced by genetic Hdac9 inactivation, while anti‐Hdac1, 4, and 5 siRNAs did not affect Kcnn1 transcript levels. In conclusion, KCNN1 and HDAC expression is differentially remodeled in AF complicated by HF. Direct regulation of KCNN1 by HDACs in atrial myocytes provides a basis for mechanism‐based antiarrhythmic therapy.
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Affiliation(s)
- Ann-Kathrin Rahm
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Teresa Wieder
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany
| | - Dominik Gramlich
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Mara Elena Müller
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Maximilian N Wunsch
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Fadwa A El Tahry
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Tanja Heimberger
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Steffi Sandke
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Tanja Weis
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Patrick Most
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany
| | - Hugo A Katus
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Dierk Thomas
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Patrick Lugenbiel
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.,HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
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20
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Chen H, Jin Z, Fu Z, Xia F. SK2 channel deletion reduces susceptibility to bupivacaine-induced cardiotoxicity in mouse. Hum Exp Toxicol 2021; 40:1796-1802. [PMID: 33887967 DOI: 10.1177/09603271211010912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Bupivacaine is frequently used for regional anesthesia and postoperative analgesia. However, an inadvertent intravenous injection can cause severe cardiotoxicity, manifesting as arrhythmia, hypotension, and even cardiac asystole. The mechanism of bupivacaine-mediated cardiotoxicity remains unclear. SK2 knockout mice (SK) and wild-type mice (WT) were divided into four groups, with 12 mice per group. We determined the difference in bupivacaine cardiotoxicity between SK2 knockout and WT mice by measuring the time to the first arrhythmia (Tarrhythmia) and the time to asystole (Tasystole). Secondary indicators of cardiotoxicity were the time from the beginning of bupivacaine infusion to 20% prolongation of the QT interval (TQT) and the time to 20% widening of the QRS complex (TQRS). Tarrhythmia and Tasystole were significantly longer in the SK-bupi group than in the WT-bupi group (both P < 0.05). TQT and TQRS were longer in the SK-bupi group than in the WT-bupi group (all P < 0.05). The time to 25%, 50%, and 75% reduction in HR in the SK-bupi group was significantly longer than in the WT-bupi group (all P < 0.05). Knocking out the SK2 channel can reduce bupivacaine-induced cardiotoxicity in the mouse.
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Affiliation(s)
- H Chen
- Department of Anesthesiology, 89657First Affiliated Hospital, Wenzhou Medical University, Zhejiang, China
| | - Z Jin
- Department of Anesthesiology, 89657First Affiliated Hospital, Wenzhou Medical University, Zhejiang, China
| | - Z Fu
- Department of Pain Management, 66555Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - F Xia
- Department of Anesthesiology, 89657First Affiliated Hospital, Wenzhou Medical University, Zhejiang, China
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21
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The Small Conductance Calcium-Activated Potassium Channel Inhibitors NS8593 and UCL1684 Prevent the Development of Atrial Fibrillation Through Atrial-Selective Inhibition of Sodium Channel Activity. J Cardiovasc Pharmacol 2021; 76:164-172. [PMID: 32453071 DOI: 10.1097/fjc.0000000000000855] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The mechanisms underlying atrial-selective prolongation of effective refractory period (ERP) and suppression of atrial fibrillation (AF) by NS8593 and UCL1684, small conductance calcium-activated potassium (SK) channel blockers, are poorly defined. The purpose of the study was to confirm the effectiveness of these agents to suppress AF and to probe the underlying mechanisms. Transmembrane action potentials and pseudoelectrocardiograms were recorded from canine isolated coronary-perfused canine atrial and ventricular wedge preparations. Patch clamp techniques were used to record sodium channel current (INa) in atrial and ventricular myocytes and human embryonic kidney cells. In both atria and ventricles, NS8593 (3-10 µM) and UCL1684 (0.5 µM) did not significantly alter action potential duration, suggesting little to no SK channel inhibition. Both agents caused atrial-selective: (1) prolongation of ERP secondary to development of postrepolarization refractoriness, (2) reduction of Vmax, and (3) increase of diastolic threshold of excitation (all are sodium-mediated parameters). NS8593 and UCL1684 significantly reduced INa density in human embryonic kidney cells as well as in atrial but not in ventricular myocytes at physiologically relevant holding potentials. NS8593 caused a shift of steady-state inactivation to negative potentials in atrial but not ventricular cells. NS8593 and UCL1684 prevented induction of acetylcholine-mediated AF in 6/6 and 8/8 preparations, respectively. This anti-AF effect was associated with strong rate-dependent depression of excitability. The SK channel blockers, NS8593 and UCL1684, are effective in preventing the development of AF due to potent atrial-selective inhibition of INa, causing atrial-selective prolongation of ERP secondary to induction of postrepolarization refractoriness.
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22
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Takahashi M, Yokoshiki H, Mitsuyama H, Watanabe M, Temma T, Kamada R, Hagiwara H, Takahashi Y, Anzai T. SK channel blockade prevents hypoxia-induced ventricular arrhythmias through inhibition of Ca 2+/voltage uncoupling in hypertrophied hearts. Am J Physiol Heart Circ Physiol 2021; 320:H1456-H1469. [PMID: 33635168 DOI: 10.1152/ajpheart.00777.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 02/17/2021] [Indexed: 11/22/2022]
Abstract
Ventricular arrhythmia (VA) is the major cause of death in patients with left ventricular (LV) hypertrophy and/or acute ischemia. We hypothesized that apamin, a blocker of small-conductance Ca2+-activated K+ (SK) channels, alters Ca2+ handling and exhibits anti-arrhythmic effects in ventricular myocardium. Spontaneous hypertensive rats were used as a model of LV hypertrophy. A dual optical mapping of membrane potential (Vm) and intracellular calcium (Cai) was performed during global hypoxia (GH) on the Langendorff perfusion system. The majority of pacing-induced VAs during GH were initiated by triggered activities. Pretreatment of apamin (100 nmol/L) significantly inhibited the VA inducibility. Compared with SK channel blockers (apamin and NS8593), non-SK channel blockers (glibenclamide and 4-AP) did not exhibit anti-arrhythmic effects. Apamin prevented not only action potential duration (APD80) shortening (-18.7 [95% confidence interval, -35.2 to -6.05] ms vs. -2.75 [95% CI, -10.45 to 12.65] ms, P = 0.04) but also calcium transient duration (CaTD80) prolongation (14.52 [95% CI, 8.8-20.35] ms vs. 3.85 [95% CI, -3.3 to 12.1] ms, P < 0.01), thereby reducing CaTD80 - APD80, which denotes "Cai/Vm uncoupling" (33.22 [95% CI, 22-48.4] ms vs. 6.6 [95% CI, 0-14.85] ms, P < 0.01). The reduction of Cai/Vm uncoupling was attributable to less prolonged Ca2+ decay constant and suppression of diastolic Cai increase by apamin. The inhibition of VA inducibility and changes in APs/CaTs parameters caused by apamin was negated by the addition of ouabain, an inhibitor of Na+/K+ pump. Apamin attenuates APD shortening, Ca2+ handling abnormalities, and Cai/Vm uncoupling, leading to inhibition of VA occurrence in hypoxic hypertrophied hearts.NEW & NOTEWORTHY We demonstrated that hypoxia-induced ventricular arrhythmias were mainly initiated by Ca2+-loaded triggered activities in hypertrophied hearts. The blockades of small-conductance Ca2+-activated K+ channels, especially "apamin," showed anti-arrhythmic effects by alleviation of not only action potential duration shortening but also Ca2+ handling abnormalities, most notably the "Ca2+/voltage uncoupling."
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Affiliation(s)
- Masayuki Takahashi
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
- Department of Cardiovascular Medicine, National Hospital Organization Hokkaido Medical Center, Sapporo, Japan
| | - Hisashi Yokoshiki
- Department of Cardiovascular Medicine, Sapporo City General Hospital, Sapporo, Japan
| | - Hirofumi Mitsuyama
- Department of Cardiovascular Medicine, Hokkaido Ohno Memorial Hospital, Sapporo, Japan
| | - Masaya Watanabe
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Taro Temma
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Rui Kamada
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Hikaru Hagiwara
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Yumi Takahashi
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Toshihisa Anzai
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
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23
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Darkow E, Nguyen TT, Stolina M, Kari FA, Schmidt C, Wiedmann F, Baczkó I, Kohl P, Rajamani S, Ravens U, Peyronnet R. Small Conductance Ca 2 +-Activated K + (SK) Channel mRNA Expression in Human Atrial and Ventricular Tissue: Comparison Between Donor, Atrial Fibrillation and Heart Failure Tissue. Front Physiol 2021; 12:650964. [PMID: 33868017 PMCID: PMC8047327 DOI: 10.3389/fphys.2021.650964] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/01/2021] [Indexed: 12/25/2022] Open
Abstract
In search of more efficacious and safe pharmacological treatments for atrial fibrillation (AF), atria-selective antiarrhythmic agents have been promoted that target ion channels principally expressed in the atria. This concept allows one to engage antiarrhythmic effects in atria, but spares the ventricles from potentially proarrhythmic side effects. It has been suggested that cardiac small conductance Ca2+-activated K+ (SK) channels may represent an atria-selective target in mammals including humans. However, there are conflicting data concerning the expression of SK channels in different stages of AF, and recent findings suggest that SK channels are upregulated in ventricular myocardium when patients develop heart failure. To address this issue, RNA-sequencing was performed to compare expression levels of three SK channels (KCNN1, KCNN2, and KCNN3) in human atrial and ventricular tissue samples from transplant donor hearts (no cardiac disease), and patients with cardiac disease in sinus rhythm or with AF. In addition, for control purposes expression levels of several genes known to be either chamber-selective or differentially expressed in AF and heart failure were determined. In atria, as compared to ventricle from transplant donor hearts, we confirmed higher expression of KCNN1 and KCNA5, and lower expression of KCNJ2, whereas KCNN2 and KCNN3 were statistically not differentially expressed. Overall expression of KCNN1 was low compared to KCNN2 and KCNN3. Comparing atrial tissue from patients with AF to sinus rhythm samples we saw downregulation of KCNN2 in AF, as previously reported. When comparing ventricular tissue from heart failure patients to non-diseased samples, we found significantly increased ventricular expression of KCNN3 in heart failure, as previously published. The other channels showed no significant difference in expression in either disease. Our results add weight to the view that SK channels are not likely to be an atria-selective target, especially in failing human hearts, and modulators of these channels may prove to have less utility in treating AF than hoped. Whether targeting SK1 holds potential remains to be elucidated.
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Affiliation(s)
- Elisa Darkow
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany.,Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Freiburg im Breisgau, Germany.,Faculty of Biology, University of Freiburg, Freiburg im Breisgau, Germany
| | - Thong T Nguyen
- Genome Analysis Unit, Amgen Research, Amgen Inc., South San Francisco, CA, United States
| | - Marina Stolina
- Department of Cardiometabolic Disorders, Amgen Research, Amgen Inc., Thousand Oaks, CA, United States
| | - Fabian A Kari
- Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany.,Department of Cardiovascular Surgery, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany
| | - Constanze Schmidt
- Department of Cardiology, University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research) Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany
| | - Felix Wiedmann
- Department of Cardiology, University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research) Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany.,CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg im Breisgau, Germany
| | - Sridharan Rajamani
- Translational Safety and Bioanalytical Sciences, Amgen Research, Amgen Inc., South San Francisco, CA, United States
| | - Ursula Ravens
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
| | - Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
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24
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Zhang XD, Thai PN, Lieu DK, Chiamvimonvat N. Cardiac small-conductance calcium-activated potassium channels in health and disease. Pflugers Arch 2021; 473:477-489. [PMID: 33624131 PMCID: PMC7940285 DOI: 10.1007/s00424-021-02535-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 02/02/2021] [Accepted: 02/03/2021] [Indexed: 12/22/2022]
Abstract
Small-conductance Ca2+-activated K+ (SK, KCa2) channels are encoded by KCNN genes, including KCNN1, 2, and 3. The channels play critical roles in the regulation of cardiac excitability and are gated solely by beat-to-beat changes in intracellular Ca2+. The family of SK channels consists of three members with differential sensitivity to apamin. All three isoforms are expressed in human hearts. Studies over the past two decades have provided evidence to substantiate the pivotal roles of SK channels, not only in healthy heart but also with diseases including atrial fibrillation (AF), ventricular arrhythmia, and heart failure (HF). SK channels are prominently expressed in atrial myocytes and pacemaking cells, compared to ventricular cells. However, the channels are significantly upregulated in ventricular myocytes in HF and pulmonary veins in AF models. Interests in cardiac SK channels are further fueled by recent studies suggesting the possible roles of SK channels in human AF. Therefore, SK channel may represent a novel therapeutic target for atrial arrhythmias. Furthermore, SK channel function is significantly altered by human calmodulin (CaM) mutations, linked to life-threatening arrhythmia syndromes. The current review will summarize recent progress in our understanding of cardiac SK channels and the roles of SK channels in the heart in health and disease.
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Affiliation(s)
- Xiao-Dong Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA.
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA.
| | - Phung N Thai
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA
| | - Deborah K Lieu
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA
| | - Nipavan Chiamvimonvat
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA.
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA.
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, 95616, USA.
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25
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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] [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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26
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Weisbrod D. Small and Intermediate Calcium Activated Potassium Channels in the Heart: Role and Strategies in the Treatment of Cardiovascular Diseases. Front Physiol 2020; 11:590534. [PMID: 33329039 PMCID: PMC7719780 DOI: 10.3389/fphys.2020.590534] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 10/02/2020] [Indexed: 12/11/2022] Open
Abstract
Calcium-activated potassium channels are a heterogeneous family of channels that, despite their different biophysical characteristics, structures, and pharmacological signatures, play a role of transducer between the ubiquitous intracellular calcium signaling and the electric variations of the membrane. Although this family of channels was extensively described in various excitable and non-excitable tissues, an increasing amount of evidences shows their functional role in the heart. This review aims to focus on the physiological role and the contribution of the small and intermediate calcium-activated potassium channels in cardiac pathologies.
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27
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Song Z, Qu Z. Delayed global feedback in the genesis and stability of spatiotemporal excitation patterns in paced biological excitable media. PLoS Comput Biol 2020; 16:e1007931. [PMID: 33017392 PMCID: PMC7561267 DOI: 10.1371/journal.pcbi.1007931] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 10/15/2020] [Accepted: 07/22/2020] [Indexed: 12/23/2022] Open
Abstract
Biological excitable media, such as cardiac or neural cells and tissue, exhibit memory in which a change in the present excitation may affect the behaviors in the next excitation. For example, a change in calcium (Ca2+) concentration in a cell in the present excitation may affect the Ca2+ dynamics in the next excitation via bi-directional coupling between voltage and Ca2+, forming a delayed feedback loop. Since the Ca2+ dynamics inside the excitable cells are spatiotemporal while the membrane voltage is a global signal, the feedback loop is then a delayed global feedback (DGF) loop. In this study, we investigate the roles of DGF in the genesis and stability of spatiotemporal excitation patterns in periodically-paced excitable media using mathematical models with different levels of complexity: a model composed of coupled FitzHugh-Nagumo units, a 3-dimensional physiologically-detailed ventricular myocyte model, and a coupled map lattice model. We investigate the dynamics of excitation patterns that are temporal period-2 (P2) and spatially concordant or discordant, such as subcellular concordant or discordant Ca2+alternans in cardiac myocytes or spatially concordant or discordant Ca2+ and repolarization alternans in cardiac tissue. Our modeling approach allows both computer simulations and rigorous analytical treatments, which lead to the following results and conclusions. When DGF is absent, concordant and discordant P2 patterns occur depending on initial conditions with the discordant P2 patterns being spatially random. When the DGF is negative, only concordant P2 patterns exist. When the DGF is positive, both concordant and discordant P2 patterns can occur. The discordant P2 patterns are still spatially random, but they satisfy that the global signal exhibits a temporal period-1 behavior. The theoretical analyses of the coupled map lattice model reveal the underlying instabilities and bifurcations for the genesis, selection, and stability of spatiotemporal excitation patterns. Understanding the mechanisms of pattern formation in biological systems is of great importance. Here we investigate the dynamical mechanisms by which delayed global feedback affects excitation pattern formation and stability in periodically-paced biological excitable media, such as cardiac or neural cells and tissue. We focus on the formation and stability of the temporal period-2 and spatially in-phase and out-of-phase excitation patterns. Using models of different levels of complexity, we show that when the delayed global feedback is negative, only the spatially in-phase patterns are stable. When the feedback is positive, both spatially in-phase and out-of-phase patterns are stable, and the out-of-phase patterns are spatially random but satisfy that the global signals are temporal period-1 solutions.
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Affiliation(s)
- Zhen Song
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- Peng Cheng Laboratory, Shenzhen, China
- * E-mail: (ZS); (ZQ)
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Computational Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail: (ZS); (ZQ)
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28
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Sung YL, Lin TT, Syu JY, Hsu HJ, Lin KY, Liu YB, Lin SF. Reverse electromechanical modelling of diastolic dysfunction in spontaneous hypertensive rat after sacubitril/valsartan therapy. ESC Heart Fail 2020; 7:4040-4050. [PMID: 32969191 PMCID: PMC7755015 DOI: 10.1002/ehf2.13013] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 09/02/2020] [Accepted: 09/02/2020] [Indexed: 11/25/2022] Open
Abstract
Aims Hypertension is a significant risk for the development of left ventricular hypertrophy, diastolic dysfunction, followed by heart failure and sudden cardiac death. While therapy with sacubitril/valsartan (SV) reduces the risk of sudden cardiac death in patients with heart failure and systolic dysfunction, the effect on those with diastolic dysfunction remains unclear. We hypothesized that, in the animal model of hypertensive heart disease, treatment with SV reduces the susceptibility to ventricular arrhythmia. Methods and results Young adult female spontaneous hypertensive rats (SHRs) were randomly separated into three groups, which were SHRs, SHRs treated with valsartan, and SHRs treated with SV. In addition, the age‐matched and weight‐matched Wistar Kyoto rats were considered as controls, and there were 12 rats in each group. In vivo ventricular tachyarrhythmia induction and in vitro optical mapping were used to measure the inducibility of ventricular arrhythmias and to characterize the dynamic properties of electrical propagation. The level of small‐conductance Ca2+‐activated potassium channel type 2 (KCNN2) was analysed in cardiac tissue. Compared with SHR with left ventricular hypertrophy, treatment with SV significantly improved cardiac geometry (relative wall thickness, 0.68 ± 0.11 vs. 0.76 ± 0.13, P < 0.05) and diastolic dysfunction (isovolumetric relaxation time, 59.4 ± 3.2 vs. 70.5 ± 4.2 ms, P < 0.05; deceleration time of mitral E wave, 46 ± 4.8 vs. 42 ± 3.8, P < 0.05). The incidence of induced ventricular arrhythmia was significantly reduced in SHR treated with SV compared with SHR (ventricular tachycardia, 1.14 ± 0.32 vs. 2.91 ± 0.5 episodes per 10 stimuli, P < 0.001; ventricular fibrillation, 1.72 ± 0.31 vs. 5.81 ± 0.42 episodes per 10 stimuli, P < 0.001). The prolonged action potential duration (APD) and increase of the maximum slope of APD restitution were observed in SHR, while the treatment of SV improved the arrhythmogeneity (APD, 37.12 ± 6.18 vs. 92.41 ± 10.71 ms at 250 ms pacing cycle length, P < 0.001; max slope 0.29 ± 0.01 vs. 1.48 ± 0.04, P < 0.001). These effects were strongly associated with down‐regulation of KCNN2 (0.38 ± 0.07 vs. 0.74 ± 0.12 ng/ml, P < 0.001). The treatment of SV also decreased the level of N‐terminal pro‐B‐type natriuretic peptide, cardiac bridging integrator‐1, and intramyocardial fibrosis of SHR. Conclusions In conclusion, synergistic blockade of the neprilysin and the renin–angiotensin system by SV in SHRs results in KCNN2‐associated electrical remodelling in ventricle, which stabilizes electrical dynamics and attenuates arrhythmogenesis.
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Affiliation(s)
- Yen-Ling Sung
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan.,Department of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, Taiwan
| | - Ting-Tse Lin
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan.,Department of Internal Medicine, National Taiwan University Hospital Hsin-Chu Biomedical Park Branch, Hsinchu, Taiwan.,Department of Internal Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Jhen-Yang Syu
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Hung-Jui Hsu
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Kai-Yuan Lin
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Yen-Bin Liu
- Department of Internal Medicine, National Taiwan University College of Medicine, Taipei, Taiwan.,Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Shien-Fong Lin
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
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29
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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] [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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30
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Fei YD, Chen M, Guo S, Ueoka A, Chen Z, Rubart-von der Lohe M, Everett TH, Qu Z, Weiss JN, Chen PS. Simultaneous activation of the small conductance calcium-activated potassium current by acetylcholine and inhibition of sodium current by ajmaline cause J-wave syndrome in Langendorff-perfused rabbit ventricles. Heart Rhythm 2020; 18:98-108. [PMID: 32763429 DOI: 10.1016/j.hrthm.2020.07.036] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 07/24/2020] [Accepted: 07/30/2020] [Indexed: 01/06/2023]
Abstract
BACKGROUND Concomitant apamin-sensitive small conductance calcium-activated potassium current (IKAS) activation and sodium current inhibition induce J-wave syndrome (JWS) in rabbit hearts. Sudden death in JWS occurs predominantly in men at night when parasympathetic tone is strong. OBJECTIVE The purpose of this study was to test the hypotheses that acetylcholine (ACh), the parasympathetic transmitter, activates IKAS and causes JWS in the presence of ajmaline. METHODS We performed optical mapping in Langendorff-perfused rabbit hearts and whole-cell voltage clamp to determine IKAS in isolated ventricular cardiomyocytes. RESULTS ACh (1 μM) + ajmaline (2 μM) induced J-point elevations in all (6 male and 6 female) hearts from 0.01± 0.01 to 0.31 ± 0.05 mV (P<.001), which were reduced by apamin (specific IKAS inhibitor, 100 nM) to 0.14 ± 0.02 mV (P<.001). More J-point elevation was noted in male than in female hearts (P=.037). Patch clamp studies showed that ACh significantly (P<.001) activated IKAS in isolated male but not in female ventricular myocytes (n=8). Optical mapping studies showed that ACh induced action potential duration (APD) heterogeneity, which was more significant in right than in left ventricles. Apamin in the presence of ACh prolonged both APD at the level of 25% (P<.001) and APD at the level of 80% (P<.001) and attenuated APD heterogeneity. Ajmaline further increased APD heterogeneity induced by ACh. Ventricular arrhythmias were induced in 6 of 6 male and 1 of 6 female hearts (P=.015) in the presence of ACh and ajmaline, which was significantly suppressed by apamin in the former. CONCLUSION ACh activates ventricular IKAS. ACh and ajmaline induce JWS and facilitate the induction of ventricular arrhythmias more in male than in female ventricles.
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Affiliation(s)
- Yu-Dong Fei
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, XinHua Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Mu Chen
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, XinHua Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shuai Guo
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Akira Ueoka
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiovascular Medicine, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Zhenhui Chen
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Michael Rubart-von der Lohe
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine, Indianapolis, Indiana
| | - Thomas H Everett
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Zhilin Qu
- Department of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California
| | - James N Weiss
- Department of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Cedars-Sinai Medical Center, Los Angeles, California.
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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] [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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Wu AZ, Chen M, Yin D, Everett TH, Chen Z, Rubart M, Weiss JN, Qu Z, Chen PS. Sex-specific I KAS activation in rabbit ventricles with drug-induced QT prolongation. Heart Rhythm 2020; 18:88-97. [PMID: 32707174 DOI: 10.1016/j.hrthm.2020.07.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 06/30/2020] [Accepted: 07/13/2020] [Indexed: 01/23/2023]
Abstract
BACKGROUND Female sex is a known risk factor for drug-induced long QT syndrome (diLQTS). We recently demonstrated a sex difference in apamin-sensitive small-conductance Ca2+-activated K+ current (IKAS) activation during β-adrenergic stimulation. OBJECTIVE The purpose of this study was to test the hypothesis that there is a sex difference in IKAS in the rabbit models of diLQTS. METHODS We evaluated the sex difference in ventricular repolarization in 15 male and 22 female Langendorff-perfused rabbit hearts with optical mapping techniques during atrial pacing. HMR1556 (slowly activating delayed rectifier K+ current [IKs] blocker), E4031 (rapidly activating delayed rectifier K+ current [IKr] blocker) and sea anemone toxin (ATX-II, late Na+ current [INaL] activator) were used to simulate types 1-3 long QT syndrome, respectively. Apamin, an IKAS blocker, was then added to determine the magnitude of further QT prolongation. RESULTS HMR1556, E4031, and ATX-II led to the prolongation of action potential duration at 80% repolarization (APD80) in both male and female ventricles at pacing cycle lengths of 300-400 ms. Apamin further prolonged APD80 (pacing cycle length 350 ms) from 187.8±4.3 to 206.9±7.1 (P=.014) in HMR1556-treated, from 209.9±7.8 to 224.9±7.8 (P=.003) in E4031-treated, and from 174.3±3.3 to 188.1±3.0 (P=.0002) in ATX-II-treated female hearts. Apamin did not further prolong the APD80 in male hearts. The Cai transient duration (CaiTD) was significantly longer in diLQTS than baseline but without sex differences. Apamin did not change CaiTD. CONCLUSION We conclude that IKAS is abundantly increased in female but not in male ventricles with diLQTS. Increased IKAS helps preserve the repolarization reserve in female ventricles treated with IKs and IKr blockers or INaL activators.
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Affiliation(s)
- Adonis Z Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Michael Rubart
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine, Indianapolis, Indiana
| | - James N Weiss
- Departments of Medicine (Cardiology), Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | - Zhilin Qu
- Departments of Medicine (Cardiology), Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Cedars-Sinai Medical Center, Los Angeles, California.
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Turker I, Makiyama T, Ueyama T, Shimizu A, Yamakawa M, Chen P, Vatta M, Horie M, Ai T. Telethonin
variants found in Brugada syndrome, J‐wave pattern ECG, and ARVC reduce peak Na
v
1.5 currents in HEK‐293 cells. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2020; 43:838-846. [DOI: 10.1111/pace.13996] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 06/11/2020] [Accepted: 06/21/2020] [Indexed: 12/15/2022]
Affiliation(s)
- Isik Turker
- Department of Medicine Krannert Institute of Cardiology Indiana University School of Medicine Indianapolis Indiana
| | - Takeru Makiyama
- Cardiovascular Medicine Kyoto University Graduate School of Medicine Kyoto Japan
| | - Takeshi Ueyama
- Department of Cardiology Yamaguchi University School of Medical Science Yamaguchi Japan
| | - Akihiko Shimizu
- Department of Cardiology Yamaguchi University School of Medical Science Yamaguchi Japan
| | - Masaru Yamakawa
- Department of Pediatrics Kobe City Medical Center General Hospital Kobe Japan
| | - Peng‐Sheng Chen
- Department of Medicine Krannert Institute of Cardiology Indiana University School of Medicine Indianapolis Indiana
| | - Matteo Vatta
- Department of Medical and Molecular Genetics Indiana University School of Medicine Indianapolis Indiana
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine Shiga University of Medical Science Shiga Japan
| | - Tomohiko Ai
- Department of Medicine Krannert Institute of Cardiology Indiana University School of Medicine Indianapolis Indiana
- Department of Clinical Laboratory Medicine Juntendo University School of Medicine Tokyo Japan
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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] [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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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] [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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Landaw J, Zhang Z, Song Z, Liu MB, Olcese R, Chen PS, Weiss JN, Qu Z. Small-conductance Ca 2+-activated K + channels promote J-wave syndrome and phase 2 reentry. Heart Rhythm 2020; 17:1582-1590. [PMID: 32333974 DOI: 10.1016/j.hrthm.2020.04.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 03/30/2020] [Accepted: 04/10/2020] [Indexed: 12/14/2022]
Abstract
BACKGROUND Small-conductance Ca2+-activated potassium (SK) channels play complex roles in cardiac arrhythmogenesis. SK channels colocalize with L-type Ca2+ channels, yet how this colocalization affects cardiac arrhythmogenesis is unknown. OBJECTIVE The purpose of this study was to investigate the role of colocalization of SK channels with L-type Ca2+ channels in promoting J-wave syndrome and ventricular arrhythmias. METHODS We carried out computer simulations of single-cell and tissue models. SK channels in the model were assigned to preferentially sense Ca2+ in the bulk cytosol, subsarcolemmal space, or junctional cleft. RESULTS When SK channels sense Ca2+ in the bulk cytosol, the SK current (ISK) rises and decays slowly during an action potential, the action potential duration (APD) decreases as the maximum conductance increases, no complex APD dynamics and phase 2 reentry can be induced by ISK. When SK channels sense Ca2+ in the subsarcolemmal space or junctional cleft, ISK can rise and decay rapidly during an action potential in a spike-like pattern because of spiky Ca2+ transients in these compartments, which can cause spike-and-dome action potential morphology, APD alternans, J-wave elevation, and phase 2 reentry. Our results can account for the experimental finding that activation of ISK induced J-wave syndrome and phase 2 reentry in rabbit hearts. CONCLUSION Colocalization of SK channels with L-type Ca2+ channels so that they preferentially sense Ca2+ in the subsarcolemmal or junctional space may result in a spiky ISK, which can functionally play a similar role of the transient outward K+ current in promoting J-wave syndrome and ventricular arrhythmias.
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Affiliation(s)
- Julian Landaw
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhaoyang Zhang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhen Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Michael B Liu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Riccardo Olcese
- Department of Anesthesiology and Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - James N Weiss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
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Therapeutic Effects of Apamin as a Bee Venom Component for Non-Neoplastic Disease. Toxins (Basel) 2020; 12:toxins12030195. [PMID: 32204567 PMCID: PMC7150898 DOI: 10.3390/toxins12030195] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 03/15/2020] [Accepted: 03/17/2020] [Indexed: 02/06/2023] Open
Abstract
Bee venom is a natural toxin produced by honeybees and plays an important role in defending bee colonies. Bee venom has several kinds of peptides, including melittin, apamin, adolapamine, and mast cell degranulation peptides. Apamin accounts for about 2%-3% dry weight of bee venom and is a peptide neurotoxin that contains 18 amino acid residues that are tightly crosslinked by two disulfide bonds. It is well known for its pharmacological functions, which irreversibly block Ca2+-activated K+ (SK) channels. Apamin regulates gene expression in various signal transduction pathways involved in cell development. The aim of this study was to review the current understanding of apamin in the treatment of apoptosis, fibrosis, and central nervous system diseases, which are the pathological processes of various diseases. Apamin's potential therapeutic and pharmacological applications are also discussed.
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Cardiomyocyte calcium handling in health and disease: Insights from in vitro and in silico studies. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 157:54-75. [PMID: 32188566 DOI: 10.1016/j.pbiomolbio.2020.02.008] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 12/31/2019] [Accepted: 02/29/2020] [Indexed: 02/07/2023]
Abstract
Calcium (Ca2+) plays a central role in cardiomyocyte excitation-contraction coupling. To ensure an optimal electrical impulse propagation and cardiac contraction, Ca2+ levels are regulated by a variety of Ca2+-handling proteins. In turn, Ca2+ modulates numerous electrophysiological processes. Accordingly, Ca2+-handling abnormalities can promote cardiac arrhythmias via various mechanisms, including the promotion of afterdepolarizations, ion-channel modulation and structural remodeling. In the last 30 years, significant improvements have been made in the computational modeling of cardiomyocyte Ca2+ handling under physiological and pathological conditions. However, numerous questions involving the Ca2+-dependent regulation of different macromolecular complexes, cross-talk between Ca2+-dependent regulatory pathways operating over a wide range of time scales, and bidirectional interactions between electrophysiology and mechanics remain to be addressed by in vitro and in silico studies. A better understanding of disease-specific Ca2+-dependent proarrhythmic mechanisms may facilitate the development of improved therapeutic strategies. In this review, we describe the fundamental mechanisms of cardiomyocyte Ca2+ handling in health and disease, and provide an overview of currently available computational models for cardiomyocyte Ca2+ handling. Finally, we discuss important uncertainties and open questions about cardiomyocyte Ca2+ handling and highlight how synergy between in vitro and in silico studies may help to answer several of these issues.
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Yin D, Yang N, Tian Z, Wu AZ, Xu D, Chen M, Kamp NJ, Wang Z, Shen C, Chen Z, Lin SF, Rubart-von der Lohe M, Chen PS, Everett TH. Effects of ondansetron on apamin-sensitive small conductance calcium-activated potassium currents in pacing-induced failing rabbit hearts. Heart Rhythm 2019; 17:332-340. [PMID: 31513946 DOI: 10.1016/j.hrthm.2019.09.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Indexed: 12/16/2022]
Abstract
BACKGROUND Ondansetron, a widely prescribed antiemetic, has been implicated in drug-induced long QT syndrome. Recent patch clamp experiments have shown that ondansetron inhibits the apamin-sensitive small conductance calcium-activated potassium current (IKAS). OBJECTIVE The purpose of this study was to determine whether ondansetron causes action potential duration (APD) prolongation by IKAS inhibition. METHODS Optical mapping was performed in rabbit hearts with pacing-induced heart failure (HF) and in normal hearts before and after ondansetron (100 nM) infusion. APD at 80% repolarization (APD80) and arrhythmia inducibility were determined. Additional studies with ondansetron were performed in normal hearts perfused with hypokalemic Tyrode's (2.4 mM) solution before or after apamin administration. RESULTS The corrected QT interval in HF was 326 ms (95% confidence interval [CI] 306-347 ms) at baseline and 364 ms (95% CI 351-378 ms) after ondansetron infusion (P < .001). Ondansetron significantly prolonged APD80 in the HF group and promoted early afterdepolarizations, steepened the APD restitution curve, and increased ventricular vulnerability. Ventricular fibrillation was not inducible in HF ventricles at baseline, but after ondansetron infusion, ventricular fibrillation was induced in 5 of the 7 ventricles (P = .021). In hypokalemia, apamin prolonged APD80 from 163 ms (95% CI 146-180 ms) to 180 ms (95% CI 156-204 ms) (P = .018). Subsequent administration of ondansetron failed to further prolong APD80 (180 ms [95% CI 156-204 ms] vs 179 ms [95% CI 165-194 ms]; P = .789). The results were similar when ondansetron was administered first, followed by apamin. CONCLUSION Ondansetron is a specific IKAS blocker at therapeutic concentrations. Ondansetron may prolong the QT interval in HF by inhibiting small conductance calcium-activated potassium channels, which increases the vulnerability to ventricular arrhythmias.
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Affiliation(s)
- Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, the First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Na Yang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Gynecological and Obstetric Ultrasound, the First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Zhipeng Tian
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Central Hospital Affiliated to Shenyang Medical College, Shenyang, China
| | - Adonis Z Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Institute of Biomedical Engineering, National Chiao Tung University, Hsin-Chu, Taiwan
| | - Dongzhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Nicholas J Kamp
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Zhuo Wang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Changyu Shen
- Richard and Susan Smith Center for Outcomes Research in Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Institute of Biomedical Engineering, National Chiao Tung University, Hsin-Chu, Taiwan
| | | | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana.
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Lubberding AF, Sattler SM, Grunnet M, Sørensen US, Tfelt-Hansen J, Jespersen T. Arrhythmia development during inhibition of small-conductance calcium-activated potassium channels in acute myocardial infarction in a porcine model. Europace 2019; 21:1584-1593. [DOI: 10.1093/europace/euz223] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 07/22/2019] [Indexed: 12/19/2022] Open
Abstract
AbstractAims Acute myocardial infarction (AMI) is associated with intracellular Ca2+ build-up. In healthy ventricles, small conductance Ca2+-activated K+ (SK) channels are present but do not participate in repolarization. However, SK current is increased in chronic myocardial infarction and heart failure, and recently, SK channel inhibition was demonstrated to reduce arrhythmias in AMI rats. Hence, we hypothesized that SK channel inhibitors (NS8593 and AP14145) could reduce arrhythmia development during AMI in a porcine model.Methods and results Twenty-seven pigs were randomized 1:1:1 to control, NS8593, or AP14145. Haemodynamic and electrophysiological parameters [electrocardiogram (ECG) and monophasic action potentials (MAP)] were continuously recorded. A balloon was placed in the mid-left anterior descending artery, blinded to treatment. Infusion lasted from 10 min before occlusion until 30 min after. Occlusion was maintained for 1 h, followed by 2 h of reperfusion. Upon occlusion, cardiac output dropped similarly in all groups, while blood pressure remained stable. Heart rate decreased in the NS8593 and AP14145 groups. QRS duration increased upon occlusion in all groups but more prominently in AP14145-treated pigs. Inhibition of SK channels did not affect QT interval. Infarct MAP duration shortened comparably in all groups. Ventricular fibrillation developed in 4/9 control-, 4/9 AP14145-, and 2/9 NS8593-treated pigs. Ventricular tachycardia was rarely observed in either group, whereas ventricular extrasystoles occurred comparably in all groups.Conclusion Inhibition of SK channels was neither beneficial nor detrimental to ventricular arrhythmia development in the setting of AMI in this porcine model.
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Affiliation(s)
- Anniek F Lubberding
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Norre Alle 14, Copenhagen, Denmark
| | - Stefan M Sattler
- Department of Cardiology, Heart Centre, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, Copenhagen, Denmark
- Medical Department I, University Hospital Grosshadern, LMU, Marchioninistraße 15, Munich, Germany
| | | | | | - Jacob Tfelt-Hansen
- Department of Cardiology, Heart Centre, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, Copenhagen, Denmark
- Department of Forensic Medicine, Faculty of Medical Sciences, University of Copenhagen, Frederik V's Vej, Copenhagen, Denmark
| | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Norre Alle 14, Copenhagen, Denmark
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Peyronnet R, Ravens U. Atria-selective antiarrhythmic drugs in need of alliance partners. Pharmacol Res 2019; 145:104262. [PMID: 31059791 DOI: 10.1016/j.phrs.2019.104262] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 04/30/2019] [Accepted: 05/03/2019] [Indexed: 12/15/2022]
Abstract
Atria-selective antiarrhythmic drugs in need of alliance partners. Guideline-based treatment of atrial fibrillation (AF) comprises prevention of thromboembolism and stroke, as well as antiarrhythmic therapy by drugs, electrical rhythm conversion, ablation and surgical procedures. Conventional antiarrhythmic drugs are burdened with unwanted side effects including a propensity of triggering life-threatening ventricular fibrillation. In order to solve this therapeutic dilemma, 'atria-selective' antiarrhythmic drugs have been developed for the treatment of supraventricular arrhythmias. These drugs are designed to aim at atrial targets, taking advantage of differences in atrial and ventricular ion channel expression and function. However it is not clear, whether such drugs are sufficiently antiarrhythmic or whether they are in need of an alliance partner for clinical efficacy. Atria-selective Na+ channel blockers display fast dissociation kinetics and high binding affinity to inactivated channels. Compounds targeting atria-selective K+ channels include blockers of ultra rapid delayed rectifier (Kv1.5) or acetylcholine-activated inward rectifier K+ channels (Kir3.x), inward rectifying K+ channels (Kir2.x), Ca2+-activated K+ channels of small conductance (SK), weakly rectifying two-pore domain K+ channels (K2P), and transient receptor potential channels (TRP). Despite good antiarrhythmic data from in-vitro and animal model experiments, clinical efficacy of atria-selective antiarrhythmic drugs remains to be demonstrated. In the present review we will briefly summarize the novel compounds and their proposed antiarrhythmic action. In addition, we will discuss the evidence for putative improvement of antiarrhythmic efficacy and potency by addressing multiple pathophysiologically relevant targets as possible alliance partners.
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Affiliation(s)
- Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg Bad Krozingen, Medical Center, University of Freiburg, Freiburg, Germany; Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ursula Ravens
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg Bad Krozingen, Medical Center, University of Freiburg, Freiburg, Germany; Institute of Physiology, Medical Faculty TU Dresden, Dresden, Germany.
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Hamilton S, Polina I, Terentyeva R, Bronk P, Kim TY, Roder K, Clements RT, Koren G, Choi BR, Terentyev D. PKA phosphorylation underlies functional recruitment of sarcolemmal SK2 channels in ventricular myocytes from hypertrophic hearts. J Physiol 2019; 598:2847-2873. [PMID: 30771223 PMCID: PMC7496687 DOI: 10.1113/jp277618] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Accepted: 02/08/2019] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Small-conductance Ca2+ -activated K+ (SK) channels expressed in ventricular myocytes are dormant in health, yet become functional in cardiac disease. SK channels are voltage independent and their gating is controlled by intracellular [Ca2+ ] in a biphasic manner. Submicromolar [Ca2+ ] activates the channel via constitutively-bound calmodulin, whereas higher [Ca2+ ] exerts inhibitory effect during depolarization. Using a rat model of cardiac hypertrophy induced by thoracic aortic banding, we found that functional upregulation of SK2 channels in hypertrophic rat ventricular cardiomyocytes is driven by protein kinase A (PKA) phosphorylation. Using site-directed mutagenesis, we identified serine-465 as the site conferring PKA-dependent effects on SK2 channel function. PKA phosphorylation attenuates ISK rectification by reducing the Ca2+ /voltage-dependent inhibition of SK channels without changing their sensitivity to activating submicromolar [Ca2+ ]i . This mechanism underlies the functional recruitment of SK channels not only in cardiac disease, but also in normal physiology, contributing to repolarization under conditions of enhanced adrenergic drive. ABSTRACT Small-conductance Ca2+ -activated K+ (SK) channels expressed in ventricular myocytes (VMs) are dormant in health, yet become functional in cardiac disease. We aimed to test the hypothesis that post-translational modification of SK channels under conditions accompanied by enhanced adrenergic drive plays a central role in disease-related activation of the channels. We investigated this phenomenon using a rat model of hypertrophy induced by thoracic aortic banding (TAB). Western blot analysis using anti-pan-serine/threonine antibodies demonstrated enhanced phosphorylation of immunoprecipitated SK2 channels in VMs from TAB rats vs. Shams, which was reversible by incubation of the VMs with PKA inhibitor H89 (1 μmol L-1 ). Patch clamped VMs under basal conditions from TABs but not Shams exhibited outward current sensitive to the specific SK inhibitor apamin (100 nmol L-1 ), which was eliminated by inhibition of PKA (1 μmol L-1 ). Beta-adrenergic stimulation (isoproterenol, 100 nmol L-1 ) evoked ISK in VMs from Shams, resulting in shortening of action potentials in VMs and ex vivo optically mapped Sham hearts. Using adenoviral gene transfer, wild-type and mutant SK2 channels were overexpressed in adult rat VMs, revealing serine-465 as the site that elicits PKA-dependent phosphorylation effects on SK2 channel function. Concurrent confocal Ca2+ imaging experiments established that PKA phosphorylation lessens rectification of ISK via reduction Ca2+ /voltage-dependent inhibition of the channels at high [Ca2+ ] without affecting their sensitivity to activation by Ca2+ in the submicromolar range. In conclusion, upregulation of SK channels in diseased VMs is mediated by hyperadrenergic drive in cardiac hypertrophy, with functional effects on the channel conferred by PKA-dependent phosphorylation at serine-465.
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Affiliation(s)
- Shanna Hamilton
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Iuliia Polina
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Medical University of South Carolina, Department of Medicine, Division of Nephrology, Charleston, SC, USA
| | - Radmila Terentyeva
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Peter Bronk
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Tae Yun Kim
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Karim Roder
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Richard T Clements
- Department of Surgery, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Vascular Research Laboratory, Providence Veterans Affairs Medical Center, Providence, RI, USA
| | - Gideon Koren
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Bum-Rak Choi
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Dmitry Terentyev
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
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Kamada R, Yokoshiki H, Mitsuyama H, Watanabe M, Mizukami K, Tenma T, Takahashi M, Takada S, Anzai T. Arrhythmogenic β-adrenergic signaling in cardiac hypertrophy: The role of small-conductance calcium-activated potassium channels via activation of CaMKII. Eur J Pharmacol 2019; 844:110-117. [DOI: 10.1016/j.ejphar.2018.12.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 11/29/2018] [Accepted: 12/06/2018] [Indexed: 10/27/2022]
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Sendra-Ferrer M, Gonzalez MD. Ibutilide for the control of refractory ventricular tachycardia and ventricular fibrillation in patients with myocardial ischemia and hemodynamic instability. J Cardiovasc Electrophysiol 2018; 30:503-510. [PMID: 30580467 DOI: 10.1111/jce.13835] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Revised: 12/11/2018] [Accepted: 12/19/2018] [Indexed: 11/30/2022]
Abstract
INTRODUCTION Recurrent ventricular tachycardia (VT) and ventricular fibrillation (VF) in patients with myocardial ischemia requiring hemodynamic support can be refractory to available antiarrhythmic agents and even to cardioversion and defibrillation. The purpose of this study was to report the effect of intravenous ibutilide in patients with a VT and/or VF storm in the presence of incomplete revascularization requiring hemodynamic support. METHODS AND RESULTS Standard continuous telemetry and frequent 12-lead electrocardiograms were obtained to determine the effect of intravenous Ibutilide in these patients. We studied six consecutive patients (age 60 ± 12 years; five males) with incomplete revascularization and mechanical support (extracorporeal membrane of oxygenation = 2; left ventricular assist device = 4) with VT/VF refractory to lidocaine and amiodarone. Intravenous ibutilide was given as a last resort for management of their ventricular arrhythmias. Intravenous ibutilide (1-2 mg) allowed restoration of sinus rhythm in three patients with persistent VF that were refractory to multiple defibrillation shocks. When the 24-hour period before and after ibutilide administration was compared, this drug markedly reduced the number of required cardioversions/defibrillations in all patients from 20 ± 9 to 0.7 ± 0.8 shocks ( P = 0.036). CONCLUSIONS In patients with myocardial ischemia requiring hemodynamic support, intravenous Ibutilide demonstrates a potent antiarrhythmic effect and can facilitate defibrillation in patients with refractory VF.
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Affiliation(s)
- Mauricio Sendra-Ferrer
- Penn State University Heart and Vascular Institute, Penn State University College of Medicine, The Milton S. Hershey Medical Center, Hershey, Pennsylvania
| | - Mario D Gonzalez
- Penn State University Heart and Vascular Institute, Penn State University College of Medicine, The Milton S. Hershey Medical Center, Hershey, Pennsylvania
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Chen M, Xu DZ, Wu AZ, Guo S, Wan J, Yin D, Lin SF, Chen Z, Rubart-von der Lohe M, Everett TH, Qu Z, Weiss JN, Chen PS. Concomitant SK current activation and sodium current inhibition cause J wave syndrome. JCI Insight 2018; 3:122329. [PMID: 30429367 DOI: 10.1172/jci.insight.122329] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 07/17/2018] [Indexed: 12/18/2022] Open
Abstract
The mechanisms of J wave syndrome (JWS) are incompletely understood. Here, we showed that the concomitant activation of small-conductance calcium-activated potassium (SK) current (IKAS) and inhibition of sodium current by cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA) recapitulate the phenotypes of JWS in Langendorff-perfused rabbit hearts. CyPPA induced significant J wave elevation and frequent spontaneous ventricular fibrillation (SVF), as well as sinus bradycardia, atrioventricular block, and intraventricular conduction delay. IKAS activation by CyPPA resulted in heterogeneous shortening of action potential (AP) duration (APD) and repolarization alternans. CyPPA inhibited cardiac sodium current (INa) and decelerated AP upstroke and intracellular calcium transient. SVFs were typically triggered by short-coupled premature ventricular contractions, initiated with phase 2 reentry and originated more frequently from the right than the left ventricles. Subsequent IKAS blockade by apamin reduced J wave elevation and eliminated SVF. β-Adrenergic stimulation was antiarrhythmic in CyPPA-induced electrical storm. Like CyPPA, hypothermia (32.0°C) also induced J wave elevation and SVF. It facilitated negative calcium-voltage coupling and phase 2 repolarization alternans with spatial and electromechanical discordance, which were ameliorated by apamin. These findings suggest that IKAS activation contributes to the development of JWS in rabbit ventricles.
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Affiliation(s)
- Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Dong-Zhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Cardiovascular Division, Institute of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Adonis Z Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Shuai Guo
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Juyi Wan
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Department of Cardiothoracic Surgery, Affiliated Hospital of Southwest Medical University, Luzhou, China
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsin-Chu, Taiwan
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Michael Rubart-von der Lohe
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Zhilin Qu
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California, USA
| | - James N Weiss
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California, USA
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
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Wan J, Chen M, Wang Z, Everett TH, Rubart-von der Lohe M, Shen C, Qu Z, Weiss JN, Boyden PA, Chen PS. Small-conductance calcium-activated potassium current modulates the ventricular escape rhythm in normal rabbit hearts. Heart Rhythm 2018; 16:615-623. [PMID: 30445170 DOI: 10.1016/j.hrthm.2018.10.033] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Indexed: 10/27/2022]
Abstract
BACKGROUND The apamin-sensitive small-conductance calcium-activated K (SK) current IKAS modulates automaticity of the sinus node. IKAS blockade by apamin causes sinus bradycardia. OBJECTIVE The purpose of this study was to test the hypothesis that IKAS modulates ventricular automaticity. METHODS We tested the effects of apamin (100 nM) on ventricular escape rhythms in Langendorff-perfused rabbit ventricles with atrioventricular block (protocol 1) and on recorded transmembrane action potential of pseudotendons of superfused right ventricular endocardial preparations (protocol 2). RESULTS All preparations exhibited spontaneous ventricular escape rhythms. In protocol 1, apamin decreased the atrial rate from 186.2 ± 18.0 bpm to 163.8 ± 18.7 bpm (N = 6; P = .006) but accelerated the ventricular escape rate from 51.5 ± 10.7 bpm to 98.2 ± 25.4 bpm (P = .031). Three preparations exhibited bursts of nonsustained ventricular tachycardia and pauses, resulting in repeated burst termination pattern. In protocol 2, apamin increased the ventricular escape rate from 70.2 ± 13.1 bpm to 110.1 ± 2.2 bpm (P = .035). Spontaneous phase 4 depolarization was recorded from the pseudotendons in 6 of 10 preparations at baseline and in 3 in the presence of apamin. There were no changes of phase 4 slope (18.37 ± 3.55 mV/s vs 18.93 ± 3.26 mV/s, N = 3; P = .231, ), but the threshold of phase 0 activation (mV) reduced from -67.97 ± 1.53 to -75.26 ± 0.28 (P = .034). Addition of JTV-519, a ryanodine receptor 2 stabilizer, in 5 preparations reduced escape rate back to baseline. CONCLUSION Contrary to its bradycardic effect in the sinus node, IKAS blockade by apamin accelerates ventricular automaticity and causes repeated nonsustained ventricular tachycardia in normal ventricles. ryanodine receptor 2 blockade reversed the apamin effects on ventricular automaticity.
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Affiliation(s)
- Juyi Wan
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiothoracic Surgery, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan Province, China
| | - Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Zhuo Wang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | | | - Changyu Shen
- Richard and Susan Smith Center for Outcomes Research in Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Zhilin Qu
- Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | - James N Weiss
- Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | | | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana.
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Ko JS, Guo S, Hassel J, Celestino-Soper P, Lynnes TC, Tisdale JE, Zheng JJ, Taylor SE, Foroud T, Murray MD, Kovacs RJ, Li X, Lin SF, Chen Z, Vatta M, Chen PS, Rubart M. Ondansetron blocks wild-type and p.F503L variant small-conductance Ca 2+-activated K + channels. Am J Physiol Heart Circ Physiol 2018; 315:H375-H388. [PMID: 29677462 PMCID: PMC6139629 DOI: 10.1152/ajpheart.00479.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 04/11/2018] [Accepted: 04/11/2018] [Indexed: 01/24/2023]
Abstract
Apamin-sensitive small-conductance Ca2+-activated K+ (SK) current ( IKAS) is encoded by Ca2+-activated K+ channel subfamily N ( KCNN) genes. IKAS importantly contributes to cardiac repolarization in conditions associated with reduced repolarization reserve. To test the hypothesis that IKAS inhibition contributes to drug-induced long QT syndrome (diLQTS), we screened for KCNN variants among patients with diLQTS, determined the properties of heterologously expressed wild-type (WT) and variant KCNN channels, and determined if the 5-HT3 receptor antagonist ondansetron blocks IKAS. We searched 2,306,335 records in the Indiana Network for Patient Care and found 11 patients with diLQTS who had DNA available in the Indiana Biobank. DNA sequencing discovered a heterozygous KCNN2 variant (p.F503L) in a 52-yr-old woman presenting with corrected QT interval prolongation at baseline (473 ms) and further corrected QT interval lengthening (601 ms) after oral administration of ondansetron. That patient was also heterozygous for the p.S38G and p.P2835S variants of the QT-controlling genes KCNE1 and ankyrin 2, respectively. Patch-clamp experiments revealed that the p.F503L KCNN2 variant heterologously expressed in human embryonic kidney (HEK)-293 cells augmented Ca2+ sensitivity, increasing IKAS density. The fraction of total F503L-KCNN2 protein retained in the membrane was higher than that of WT KCNN2 protein. Ondansetron at nanomolar concentrations inhibited WT and p.F503L SK2 channels expressed in HEK-293 cells as well as native SK channels in ventricular cardiomyocytes. Ondansetron-induced IKAS inhibition was also demonstrated in Langendorff-perfused murine hearts. In conclusion, the heterozygous p.F503L KCNN2 variant increases Ca2+ sensitivity and IKAS density in transfected HEK-293 cells. Ondansetron at therapeutic (i.e., nanomolar) concentrations is a potent IKAS blocker. NEW & NOTEWORTHY We showed that ondansetron, a 5-HT3 receptor antagonist, blocks small-conductance Ca2+-activated K+ (SK) current. Ondansetron may be useful in controlling arrhythmias in which increased SK current is a likely contributor. However, its SK-blocking effects may also facilitate the development of drug-induced long QT syndrome.
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Affiliation(s)
- Jum-Suk Ko
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
- Wonkwang University School of Medicine and Hospital, Iksan, South Korea
| | - Shuai Guo
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Jonathan Hassel
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Patricia Celestino-Soper
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
| | - Ty C Lynnes
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
| | - James E Tisdale
- Department of Pharmacy Practice, College of Pharmacy, Purdue University , West Lafayette, Indiana
- Division of Clinical Pharmacology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | | | - Stanley E Taylor
- Department of Biostatistics, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Tatiana Foroud
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
| | - Michael D Murray
- Department of Pharmacy Practice, College of Pharmacy, Purdue University , West Lafayette, Indiana
- Regenstrief Institute , Indianapolis, Indiana
| | - Richard J Kovacs
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Xiaochun Li
- Department of Biostatistics, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Shien-Fong Lin
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
- Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan
| | - Zhenhui Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Matteo Vatta
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine , Indianapolis, Indiana
| | - Peng-Sheng Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Michael Rubart
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine , Indianapolis, Indiana
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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] [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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49
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Chen M, Yin D, Guo S, Xu DZ, Wang Z, Chen Z, Rubart-von der Lohe M, Lin SF, Everett Iv TH, Weiss JN, Chen PS. Sex-specific activation of SK current by isoproterenol facilitates action potential triangulation and arrhythmogenesis in rabbit ventricles. J Physiol 2018; 596:4299-4322. [PMID: 29917243 DOI: 10.1113/jp275681] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 06/11/2018] [Indexed: 01/09/2023] Open
Abstract
KEY POINTS It is unknown if a sex difference exists in cardiac apamin-sensitive small conductance Ca2+ -activated K+ (SK) current (IKAS ). There is no sex difference in IKAS in the basal condition. However, there is larger IKAS in female rabbit ventricles than in male during isoproterenol infusion. IKAS activation by isoproterenol leads to action potential triangulation in females, indicating its abundant activation at early phases of repolarization. IKAS activation in females induces negative Ca2+ -voltage coupling and promotes electromechanically discordant phase 2 repolarization alternans. IKAS is important in the mechanisms of ventricular fibrillation in females during sympathetic stimulation. ABSTRACT Sex has a large influence on cardiac electrophysiological properties. Whether sex differences exist in apamin-sensitive small conductance Ca2+ -activated K+ (SK) current (IKAS ) remains unknown. We performed optical mapping, transmembrane potential, patch clamp, western blot and immunostaining in 62 normal rabbit ventricles, including 32 females and 30 males. IKAS blockade by apamin only minimally prolonged action potential (AP) duration (APD) in the basal condition for both sexes, but significantly prolonged APD in the presence of isoproterenol in females. Apamin prolonged APD at the level of 25% repolarization (APD25 ) more prominently than APD at the level of 80% repolarization (APD80 ), consequently reversing isoproterenol-induced AP triangulation in females. In comparison, apamin prolonged APD to a significantly lesser extent in males and failed to restore the AP plateau during isoproterenol infusion. IKAS in males did not respond to the L-type calcium current agonist BayK8644, but was amplified by the casein kinase 2 (CK2) inhibitor 4,5,6,7-tetrabromobenzotriazole. In addition, whole-cell outward IKAS densities in ventricular cardiomyocytes were significantly larger in females than in males. SK channel subtype 2 (SK2) protein expression was higher and the CK2/SK2 ratio was lower in females than in males. IKAS activation in females induced negative intracellular Ca2+ -voltage coupling, promoted electromechanically discordant phase 2 repolarization alternans and facilitated ventricular fibrillation (VF). Apamin eliminated the negative Ca2+ -voltage coupling, attenuated alternans and reduced VF inducibility, phase singularities and dominant frequencies in females, but not in males. We conclude that β-adrenergic stimulation activates ventricular IKAS in females to a much greater extent than in males. IKAS activation plays an important role in ventricular arrhythmogenesis in females during sympathetic stimulation.
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Affiliation(s)
- Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shuai Guo
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Dong-Zhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Cardiovascular Division, Institute of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Zhuo Wang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Michael Rubart-von der Lohe
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan
| | - Thomas H Everett Iv
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - James N Weiss
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, CA, USA
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
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50
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Dobrev D. Sex-specific density of ventricular SK currents: is this a general feature of SK channel function? J Physiol 2018; 596:4287-4288. [PMID: 30019760 PMCID: PMC6138293 DOI: 10.1113/jp276663] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2024] Open
Affiliation(s)
- Dobromir Dobrev
- Institute of PharmacologyWest German Heart and Vascular CenterUniversity Duisburg‐EssenEssenGermany
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