1
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Tzialla C, Arossa A, Mannarino S, Orcesi S, Veggiotti P, Fiandrino G, Zuffardi O, Errichiello E. SCN2A and arrhythmia: A potential correlation? A case report and literature review. Eur J Med Genet 2022; 65:104639. [DOI: 10.1016/j.ejmg.2022.104639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Revised: 09/18/2022] [Accepted: 10/01/2022] [Indexed: 11/29/2022]
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2
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Epilepsy-Induced High Affinity Blockade of the Cardiac Sodium Current INa by Lamotrigine; A Potential for Acquired Arrythmias. Pharmaceuticals (Basel) 2022; 15:ph15101208. [PMID: 36297320 PMCID: PMC9609666 DOI: 10.3390/ph15101208] [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: 07/29/2022] [Revised: 09/20/2022] [Accepted: 09/22/2022] [Indexed: 11/30/2022] Open
Abstract
Lamotrigine is widely prescribed to treat bipolar neurological disorder and epilepsy. It exerts its antiepileptic action by blocking voltage-gated sodium channels in neurons. Recently, the US Food and Drug Administration issued a warning on the use of Lamotrigine after observations of conduction anomalies and Brugada syndrome patterns on the electrocardiograms of epileptic patients treated with the drug. Brugada syndrome and conduction disturbance are both associated with alterations of the cardiac sodium current (INa) kinetics and amplitude. In this study, we used the patch clamp technique on cardiomyocytes from epileptic rats to test the hypothesis that Lamotrigine also blocks INa in the heart. We found that Lamotrigine inhibited 60% of INa peak amplitude and reduced cardiac excitability in epileptic rats but had little effect in sham animals. Moreover, Lamotrigine inhibited 67% of INaL and, more importantly, prolonged the action potential refractory period in epileptic animals. Our results suggest that enhanced affinity of Lamotrigine for INa may in part explain the clinical phenotypes observed in epileptic patients.
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3
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Badr A, Hassinen M, Vornanen M. Spatial uniformity of action potentials indicates base-to-apex depolarization and repolarization of rainbow trout (Oncorhynchus mykiss) ventricle. J Exp Biol 2022; 225:276292. [PMID: 35950359 DOI: 10.1242/jeb.244466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 08/02/2022] [Indexed: 11/20/2022]
Abstract
The spatial pattern of electrical activation is crucial for a full understanding of fish heart function. However, it remains unclear whether there is regional variation in action potential (AP) morphologies and underlying ion currents. Because the direction of depolarization and spatial differences in the durations of ventricular APs set limits to potential patterns of ventricular repolarization, we determined AP morphologies, underlying ion currents, and ion channel expression in 4 different regions (spongy myocardium; and apex, base, and middle of the compact myocardium), and correlated them with in vivo electrocardiogram (ECG) in rainbow trout (Oncorhynchus mykiss). ECG recorded from 3 leads indicated that the depolarization and repolarization of AP propagate from base-to-apex, and the main depolarization axis of the ventricle is between +90° and +120°. AP shape was uniform across the whole ventricle, and little regional differences were found in density of repolarizing K+ currents or depolarizing Ca2+ and Na+ currents and the underlying transcripts of ion channels, providing compelling evidence for the suggested excitation pattern. The spatial uniformity of AP durations and base-to-apex propagation of activation with a relatively slow velocity of propagation indicates no special ventricular conduction pathway in the trout ventricle like the His-Purkinje system of mammalian hearts. The sequence of repolarization is solely determined by activation time without being affected by regional differences in AP duration.
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Affiliation(s)
- Ahmed Badr
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland.,Sohag University, Faculty of Science, Department of Zoology, 82524 Sohag, Egypt
| | - Minna Hassinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland
| | - Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland
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4
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Horváth B, Szentandrássy N, Almássy J, Dienes C, Kovács ZM, Nánási PP, Banyasz T. Late Sodium Current of the Heart: Where Do We Stand and Where Are We Going? Pharmaceuticals (Basel) 2022; 15:ph15020231. [PMID: 35215342 PMCID: PMC8879921 DOI: 10.3390/ph15020231] [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: 01/13/2022] [Revised: 02/07/2022] [Accepted: 02/09/2022] [Indexed: 02/05/2023] Open
Abstract
Late sodium current has long been linked to dysrhythmia and contractile malfunction in the heart. Despite the increasing body of accumulating information on the subject, our understanding of its role in normal or pathologic states is not complete. Even though the role of late sodium current in shaping action potential under physiologic circumstances is debated, it’s unquestioned role in arrhythmogenesis keeps it in the focus of research. Transgenic mouse models and isoform-specific pharmacological tools have proved useful in understanding the mechanism of late sodium current in health and disease. This review will outline the mechanism and function of cardiac late sodium current with special focus on the recent advances of the area.
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Affiliation(s)
- Balázs Horváth
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
| | - Norbert Szentandrássy
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
- Department of Basic Medical Sciences, Faculty of Dentistry, University of Debrecen, 4032 Debrecen, Hungary
| | - János Almássy
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
| | - Csaba Dienes
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
| | - Zsigmond Máté Kovács
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
| | - Péter P. Nánási
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
- Department of Dental Physiology and Pharmacology, University of Debrecen, 4032 Debrecen, Hungary
| | - Tamas Banyasz
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
- Correspondence: ; Tel.: +36-(52)-255-575; Fax: +36-(52)-255-116
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5
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Hézső T, Naveed M, Dienes C, Kiss D, Prorok J, Árpádffy-Lovas T, Varga R, Fujii E, Mercan T, Topal L, Kistamás K, Szentandrássy N, Almássy J, Jost N, Magyar J, Bányász T, Baczkó I, Varró A, Nánási PP, Virág L, Horváth B. Mexiletine-like cellular electrophysiological effects of GS967 in canine ventricular myocardium. Sci Rep 2021; 11:9565. [PMID: 33953276 PMCID: PMC8100105 DOI: 10.1038/s41598-021-88903-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Accepted: 03/26/2021] [Indexed: 12/14/2022] Open
Abstract
Enhancement of the late Na+ current (INaL) increases arrhythmia propensity in the heart, while suppression of the current is antiarrhythmic. GS967 is an agent considered as a selective blocker of INaL. In the present study, effects of GS967 on INaL and action potential (AP) morphology were studied in canine ventricular myocytes by using conventional voltage clamp, action potential voltage clamp and sharp microelectrode techniques. The effects of GS967 (1 µM) were compared to those of the class I/B antiarrhythmic compound mexiletine (40 µM). Under conventional voltage clamp conditions, INaL was significantly suppressed by GS967 and mexiletine, causing 80.4 ± 2.2% and 59.1 ± 1.8% reduction of the densities of INaL measured at 50 ms of depolarization, and 79.0 ± 3.1% and 63.3 ± 2.7% reduction of the corresponding current integrals, respectively. Both drugs shifted the voltage dependence of the steady-state inactivation curve of INaL towards negative potentials. GS967 and mexiletine dissected inward INaL profiles under AP voltage clamp conditions having densities, measured at 50% of AP duration (APD), of −0.37 ± 0.07 and −0.28 ± 0.03 A/F, and current integrals of −56.7 ± 9.1 and −46.6 ± 5.5 mC/F, respectively. Drug effects on peak Na+ current (INaP) were assessed by recording the maximum velocity of AP upstroke (V+max) in multicellular preparations. The offset time constant was threefold faster for GS967 than mexiletine (110 ms versus 289 ms), while the onset of the rate-dependent block was slower in the case of GS967. Effects on beat-to-beat variability of APD was studied in isolated myocytes. Beat-to-beat variability was significantly decreased by both GS967 and mexiletine (reduction of 42.1 ± 6.5% and 24.6 ± 12.8%, respectively) while their shortening effect on APD was comparable. It is concluded that the electrophysiological effects of GS967 are similar to those of mexiletine, but with somewhat faster offset kinetics of V+max block. However, since GS967 depressed V+max and INaL at the same concentration, the current view that GS967 represents a new class of drugs that selectively block INaL has to be questioned and it is suggested that GS967 should be classified as a class I/B antiarrhythmic agent.
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Affiliation(s)
- Tamás Hézső
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen, Hungary
| | - Muhammad Naveed
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, 6701, Szeged, Hungary
| | - Csaba Dienes
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen, Hungary
| | - Dénes Kiss
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen, Hungary
| | - János Prorok
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, 6701, Szeged, Hungary.,MTA-SZTE Research Group for Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - Tamás Árpádffy-Lovas
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, 6701, Szeged, Hungary
| | - Richárd Varga
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, 6701, Szeged, Hungary
| | - Erika Fujii
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen, Hungary
| | - Tanju Mercan
- Department of Biophysics, School of Medicine, Akdeniz University, Antalya, Turkey
| | - Leila Topal
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, 6701, Szeged, Hungary
| | - Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen, Hungary
| | - Norbert Szentandrássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen, Hungary.,Department of Basic Medical Sciences, Faculty of Dentistry, University of Debrecen, Debrecen, Hungary
| | - János Almássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen, Hungary
| | - Norbert Jost
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, 6701, Szeged, Hungary.,MTA-SZTE Research Group for Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - János Magyar
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen, Hungary.,Division of Sport Physiology, Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen, Hungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, 6701, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, 6701, Szeged, Hungary. .,MTA-SZTE Research Group for Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary. .,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary.
| | - Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen, Hungary. .,Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, Debrecen, Hungary.
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, 6701, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, 4012, Debrecen, Hungary.,Faculty of Pharmacy, University of Debrecen, Debrecen, Hungary
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6
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Plant LD, Xiong D, Romero J, Dai H, Goldstein SAN. Hypoxia Produces Pro-arrhythmic Late Sodium Current in Cardiac Myocytes by SUMOylation of Na V1.5 Channels. Cell Rep 2021; 30:2225-2236.e4. [PMID: 32075761 PMCID: PMC7054841 DOI: 10.1016/j.celrep.2020.01.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 12/03/2019] [Accepted: 01/07/2020] [Indexed: 01/08/2023] Open
Abstract
Acute cardiac hypoxia produces life-threatening elevations in late sodium current (ILATE) in the human heart. Here, we show the underlying mechanism: hypoxia induces rapid SUMOylation of NaV1.5 channels so they reopen when normally inactive, late in the action potential. NaV1.5 is SUMOylated only on lysine 442, and the mutation of that residue, or application of a deSUMOylating enzyme, prevents hypoxic reopenings. The time course of SUMOylation of single channels in response to hypoxia coincides with the increase in ILATE, a reaction that is complete in under 100 s. In human cardiac myocytes derived from pluripotent stem cells, hypoxia-induced ILATE is confirmed to be SUMO-dependent and to produce action potential prolongation, the pro-arrhythmic change observed in patients. The cardiac channel NaV1.5 passes pro-arrhythmic late sodium currents in response to hypoxia. Plant et al. demonstrate the pathophysiological mechanism to be rapid, hypoxia-induced monoSUMOylation of NaV1.5 channels. Blocking SUMOylation of lysine442 prevents hypoxia-induced late currents and attendant prolongation of the action potential in human cardiomyocytes derived from pluripotent stem cells.
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Affiliation(s)
- Leigh D Plant
- Department of Pharmaceutical Sciences, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
| | - Dazhi Xiong
- Departments of Pediatrics and Physiology & Biophysics, University of California, Irvine, 1001 Health Sciences Road, Irvine Hall, Irvine, CA 92697, USA
| | - Jesus Romero
- Departments of Pediatrics and Physiology & Biophysics, University of California, Irvine, 1001 Health Sciences Road, Irvine Hall, Irvine, CA 92697, USA
| | - Hui Dai
- Departments of Pediatrics and Physiology & Biophysics, University of California, Irvine, 1001 Health Sciences Road, Irvine Hall, Irvine, CA 92697, USA
| | - Steve A N Goldstein
- Departments of Pediatrics and Physiology & Biophysics, University of California, Irvine, 1001 Health Sciences Road, Irvine Hall, Irvine, CA 92697, USA.
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7
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Kistamás K, Hézső T, Horváth B, Nánási PP. Late sodium current and calcium homeostasis in arrhythmogenesis. Channels (Austin) 2020; 15:1-19. [PMID: 33258400 PMCID: PMC7757849 DOI: 10.1080/19336950.2020.1854986] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The cardiac late sodium current (INa,late) is the small sustained component of the sodium current active during the plateau phase of the action potential. Several studies demonstrated that augmentation of the current can lead to cardiac arrhythmias; therefore, INa,late is considered as a promising antiarrhythmic target. Fundamentally, enlarged INa,late increases Na+ influx into the cell, which, in turn, is converted to elevated intracellular Ca2+ concentration through the Na+/Ca2+ exchanger. The excessive Ca2+ load is known to be proarrhythmic. This review describes the behavior of the voltage-gated Na+ channels generating INa,late in health and disease and aims to discuss the physiology and pathophysiology of Na+ and Ca2+ homeostasis in context with the enhanced INa,late demonstrating also the currently accessible antiarrhythmic choices.
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Affiliation(s)
- Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary
| | - Tamás Hézső
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary
| | - Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary.,Department of Dental Physiology, Faculty of Dentistry, University of Debrecen , Debrecen, Hungary
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8
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Biet M, Ton AT, Delabre JF, Morin N, Dumaine R. In utero exposure to nicotine abolishes the postnatal response of the cardiac sodium current to isoproterenol in newborn rabbit atrium. Heart Rhythm 2020; 16:494-501. [PMID: 30929670 DOI: 10.1016/j.hrthm.2019.02.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Indexed: 01/13/2023]
Abstract
BACKGROUND In utero exposure to tobacco smoke is associated with sudden infant death syndrome (SIDS) and cardiac arrhythmias in newborns. The arrhythmogenic mechanisms seem linked to alterations of the cardiac sodium current (INa). We previously reported that in utero exposure to nicotine delays the postnatal development of the heart sinoatrial node in rabbits and altered expression of the sodium channels NaV1.5 and NaV1.1 in the atrium surrounding it. These channels react differently to sympathetic stimulation. OBJECTIVE The purpose of this study was to test whether nicotine altered the response of INa to stimulation by the β-adrenoreceptor agonist isoproterenol in atrial myocytes. Our hypothesis is that changes in the sympathetic response of sinoatrial node peripheral cells may create a substrate for arrhythmia. METHODS Using the patch-clamp technique we measured the effect of nicotine on the response of INa to adrenergic stimulation in isolated cardiomyocytes. RESULTS Isoproterenol increased INa by 50% in newborn sham rabbits but had no effect in newborn rabbits exposed to nicotine in utero. Our data also show that nicotine increases the late sodium current, an effect that may promote QT prolongation. CONCLUSION We provide the first evidence linking fetal exposure to nicotine to long-term alterations of INa response to isoproterenol. These changes may impair INa adaptation to sympathetic tone and prevent awakening from sleep apnea, thus leading to arrhythmias that could potentially be involved in SIDS. Our data also raise concerns about the use of nicotine replacement therapies for pregnant women.
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Affiliation(s)
- Michael Biet
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec, Canada
| | - Anh Tuan Ton
- Montreal Heart Institute, University of Montreal, Montréal, Quebec, Canada
| | - Jean-Francois Delabre
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec, Canada
| | - Nathalie Morin
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec, Canada
| | - Robert Dumaine
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec, Canada.
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9
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Varró A, Tomek J, Nagy N, Virág L, Passini E, Rodriguez B, Baczkó I. Cardiac transmembrane ion channels and action potentials: cellular physiology and arrhythmogenic behavior. Physiol Rev 2020; 101:1083-1176. [PMID: 33118864 DOI: 10.1152/physrev.00024.2019] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Cardiac arrhythmias are among the leading causes of mortality. They often arise from alterations in the electrophysiological properties of cardiac cells and their underlying ionic mechanisms. It is therefore critical to further unravel the pathophysiology of the ionic basis of human cardiac electrophysiology in health and disease. In the first part of this review, current knowledge on the differences in ion channel expression and properties of the ionic processes that determine the morphology and properties of cardiac action potentials and calcium dynamics from cardiomyocytes in different regions of the heart are described. Then the cellular mechanisms promoting arrhythmias in congenital or acquired conditions of ion channel function (electrical remodeling) are discussed. The focus is on human-relevant findings obtained with clinical, experimental, and computational studies, given that interspecies differences make the extrapolation from animal experiments to human clinical settings difficult. Deepening the understanding of the diverse pathophysiology of human cellular electrophysiology will help in developing novel and effective antiarrhythmic strategies for specific subpopulations and disease conditions.
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Affiliation(s)
- András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - Jakub Tomek
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Elisa Passini
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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10
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Susceptibility to Ventricular Arrhythmias Resulting from Mutations in FKBP1B, PXDNL, and SCN9A Evaluated in hiPSC Cardiomyocytes. Stem Cells Int 2020; 2020:8842398. [PMID: 32952569 PMCID: PMC7481990 DOI: 10.1155/2020/8842398] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/29/2020] [Accepted: 08/11/2020] [Indexed: 12/22/2022] Open
Abstract
Background We report an inherited cardiac arrhythmia syndrome consisting of Brugada and Early Repolarization Syndrome associated with variants in SCN9A, PXDNL, and FKBP1B. The proband inherited the 3 mutations and exhibited palpitations and arrhythmia-mediated syncope, whereas the parents and sister, who carried one or two of the mutations, were asymptomatic. Methods and Results We assessed the functional impact of these mutations in induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) derived from the proband and an unaffected family member. Current and voltage clamp recordings, as well as confocal microscopy analysis of Ca2+ transients, were evaluated in hiPSC-CMs from the proband and compared these results with hiPSC-CMs from undiseased controls. Genetic analysis using next-generation DNA sequencing revealed heterozygous mutations in SCN9A, PXDNL, and FKBP1B in the proband. The proband displayed right bundle branch block and exhibited episodes of syncope. The father carried a mutation in FKBP1B, whereas the mother and sister carried the SCN9A mutation. None of the 3 family members screened developed cardiac events. Action potential recordings from control hiPSC-CM showed spontaneous activity and a low upstroke velocity. In contrast, the hiPSC-CM from the proband showed irregular spontaneous activity. Confocal microscopy of the hiPSC-CM of the proband revealed low fluorescence intensity Ca2+ transients that were episodic in nature. Patch-clamp measurements in hiPSC-CM showed no difference in INa but reduced ICa in the proband compared with control. Coexpression of PXDNL-R391Q with SCN5A-WT displayed lower INa density compared to PXDNL-WT. In addition, coexpression of PXDNL-R391Q with KCND3-WT displayed significantly higher Ito density compared to PXDNL-WT. Conclusion SCN9A, PXDNL, and FKBP1B variants appeared to alter spontaneous activity in hiPSC-CM. Only the proband carrying all 3 mutations displayed the ERS/BrS phenotype, whereas one nor two mutations alone did not produce the clinical phenotype. Our results suggest a polygenic cause of the BrS/ERS arrhythmic phenotype due to mutations in these three gene variants caused a very significant loss of function of INa and ICa and gain of function of Ito.
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11
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Árpádffy-Lovas T, Husti Z, Baczkó I, Varró A, Virág L. Different effects of amiodarone and dofetilide on the dispersion of repolarization between well-coupled ventricular and Purkinje fibers 1. Can J Physiol Pharmacol 2020; 99:48-55. [PMID: 32692935 DOI: 10.1139/cjpp-2020-0234] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Increased transmural dispersion of repolarization is an established contributing factor to ventricular tachyarrhythmias. In this study, we evaluated the effect of chronic amiodarone treatment and acute administration of dofetilide in canine cardiac preparations containing electrotonically coupled Purkinje fibers (PFs) and ventricular muscle (VM) and compared the effects to those in uncoupled PF and VM preparations using the conventional microelectrode technique. Dispersion between PFs and VM was inferred from the difference in the respective action potential durations (APDs). In coupled preparations, amiodarone decreased the difference in APDs between PFs and VM, thus decreasing dispersion. In the same preparations, dofetilide increased the dispersion by causing a more pronounced prolongation in PFs. This prolongation was even more emphasized in uncoupled PF preparations, while the effect in VM was the same. In uncoupled preparations, amiodarone elicited no change on the difference in APDs. In conclusion, amiodarone decreased the dispersion between PFs and VM, while dofetilide increased it. The measured difference in APD between cardiac regions may be the affected by electrotonic coupling; thus, studying PFs and VM separately may lead to an over- or underestimation of dispersion.
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Affiliation(s)
- Tamás Árpádffy-Lovas
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Zoltán Husti
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary.,MTA-SZTE Research Group of Cardiovascular Pharmacology, Szeged, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary.,MTA-SZTE Research Group of Cardiovascular Pharmacology, Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary.,MTA-SZTE Research Group of Cardiovascular Pharmacology, Szeged, Hungary
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12
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Ebner J, Uhrin P, Szabo PL, Kiss A, Podesser BK, Todt H, Hilber K, Koenig X. Reduced Na+ current in Purkinje fibers explains cardiac conduction defects and arrhythmias in Duchenne muscular dystrophy. Am J Physiol Heart Circ Physiol 2020; 318:H1436-H1440. [DOI: 10.1152/ajpheart.00224.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Dystrophic cardiac Purkinje fibers have abnormally reduced Na+ current densities. This explains impaired ventricular conduction in the dystrophic heart.
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Affiliation(s)
- Janine Ebner
- Department of Neurophysiology-Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Pavel Uhrin
- Department of Vascular Biology and Thrombosis Research, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Petra L. Szabo
- Ludwig Boltzmann Institute for Cardiovascular Research at the Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Attila Kiss
- Ludwig Boltzmann Institute for Cardiovascular Research at the Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Bruno K. Podesser
- Ludwig Boltzmann Institute for Cardiovascular Research at the Center for Biomedical Research, Medical University of Vienna, Vienna, Austria
| | - Hannes Todt
- Department of Neurophysiology-Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Karlheinz Hilber
- Department of Neurophysiology-Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Xaver Koenig
- Department of Neurophysiology-Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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13
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Horváth B, Hézső T, Kiss D, Kistamás K, Magyar J, Nánási PP, Bányász T. Late Sodium Current Inhibitors as Potential Antiarrhythmic Agents. Front Pharmacol 2020; 11:413. [PMID: 32372952 PMCID: PMC7184885 DOI: 10.3389/fphar.2020.00413] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 03/18/2020] [Indexed: 12/19/2022] Open
Abstract
Based on recent findings, an increased late sodium current (INa,late) plays an important pathophysiological role in cardiac diseases, including rhythm disorders. The article first describes what is INa,late and how it functions under physiological circumstances. Next, it shows the wide range of cellular mechanisms that can contribute to an increased INa,late in heart diseases, and also discusses how the upregulated INa,late can play a role in the generation of cardiac arrhythmias. The last part of the article is about INa,late inhibiting drugs as potential antiarrhythmic agents, based on experimental and preclinical data as well as in the light of clinical trials.
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Affiliation(s)
- Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Faculty of Pharmacy, University of Debrecen, Debrecen, Hungary
| | - Tamás Hézső
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Dénes Kiss
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - János Magyar
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Division of Sport Physiology, University of Debrecen, Debrecen, Hungary
| | - Péter P. Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, Debrecen, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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14
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Hegyi B, Chen-Izu Y, Izu LT, Rajamani S, Belardinelli L, Bers DM, Bányász T. Balance Between Rapid Delayed Rectifier K + Current and Late Na + Current on Ventricular Repolarization: An Effective Antiarrhythmic Target? Circ Arrhythm Electrophysiol 2020; 13:e008130. [PMID: 32202931 PMCID: PMC7331791 DOI: 10.1161/circep.119.008130] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Rapid delayed rectifier K+ current (IKr) and late Na+ current (INaL) significantly shape the cardiac action potential (AP). Changes in their magnitudes can cause either long or short QT syndromes associated with malignant ventricular arrhythmias and sudden cardiac death. METHODS Physiological self AP-clamp was used to measure INaL and IKr during the AP in rabbit and porcine ventricular cardiomyocytes to test our hypothesis that the balance between IKr and INaL affects repolarization stability in health and disease conditions. RESULTS We found comparable amount of net charge carried by IKr and INaL during the physiological AP, suggesting that outward K+ current via IKr and inward Na+ current via INaL are in balance during physiological repolarization. Remarkably, IKr and INaL integrals in each control myocyte were highly correlated in both healthy rabbit and pig myocytes, despite high overall cell-to-cell variability. This close correlation was lost in heart failure myocytes from both species. Pretreatment with E-4031 to block IKr (mimicking long QT syndrome 2) or with sea anemone toxin II to impair Na+ channel inactivation (mimicking long QT syndrome 3) prolonged AP duration (APD); however, using GS-967 to inhibit INaL sufficiently restored APD to control in both cases. Importantly, INaL inhibition significantly reduced the beat-to-beat and short-term variabilities of APD. Moreover, INaL inhibition also restored APD and repolarization stability in heart failure. Conversely, pretreatment with GS-967 shortened APD (mimicking short QT syndrome), and E-4031 reverted APD shortening. Furthermore, the amplitude of AP alternans occurring at high pacing frequency was decreased by INaL inhibition, increased by IKr inhibition, and restored by combined INaL and IKr inhibitions. CONCLUSIONS Our data demonstrate that IKr and INaL are counterbalancing currents during the physiological ventricular AP and their integrals covary in individual myocytes. Targeting these ionic currents to normalize their balance may have significant therapeutic potential in heart diseases with repolarization abnormalities. Visual Overview: A visual overview is available for this article.
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Affiliation(s)
- Bence Hegyi
- Department of Pharmacology, University of California, Davis
| | - Ye Chen-Izu
- Department of Pharmacology, University of California, Davis
- Department of Biomedical Engineering, University of California, Davis
- Department of Internal Medicine/Cardiology, University of California, Davis
| | | | - Sridharan Rajamani
- Amgen, Inc., South San Francisco, University of Debrecen, Debrecen, Hungary
| | - Luiz Belardinelli
- InCarda Therapeutics, Inc., Newark, CA, University of Debrecen, Debrecen, Hungary
| | - Donald M. Bers
- Department of Pharmacology, University of California, Davis
| | - Tamás Bányász
- Department of Pharmacology, University of California, Davis
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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15
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Chu L, Greenstein JL, Winslow RL. Na + microdomains and sparks: Role in cardiac excitation-contraction coupling and arrhythmias in ankyrin-B deficiency. J Mol Cell Cardiol 2019; 128:145-157. [PMID: 30731085 DOI: 10.1016/j.yjmcc.2019.02.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 02/01/2019] [Accepted: 02/02/2019] [Indexed: 01/25/2023]
Abstract
Cardiac sodium (Na+) potassium ATPase (NaK) pumps, neuronal sodium channels (INa), and sodium calcium (Ca2+) exchangers (NCX1) may co-localize to form a Na+ microdomain. It remains controversial as to whether neuronal INa contributes to local Na+ accumulation, resulting in reversal of nearby NCX1 and influx of Ca2+ into the cell. Therefore, there has been great interest in the possible roles of a Na+ microdomain in cardiac Ca2+-induced Ca2+ release (CICR). In addition, the important role of co-localization of NaK and NCX1 in regulating localized Na+ and Ca2+ levels and CICR in ankyrin-B deficient (ankyrin-B+/-) cardiomyocytes has been examined in many recent studies. Altered Na+ dynamics may contribute to the appearance of arrhythmias, but the mechanisms underlying this relationship remain unclear. In order to investigate this, we present a mechanistic canine cardiomyocyte model which reproduces independent local dyadic junctional SR (JSR) Ca2+ release events underlying cell-wide excitation-contraction coupling, as well as a three-dimensional super-resolution model of the Ca2+ spark that describes local Na+ dynamics as governed by NaK pumps, neuronal INa, and NCX1. The model predicts the existence of Na+ sparks, which are generated by NCX1 and exhibit significantly slower dynamics as compared to Ca2+ sparks. Moreover, whole-cell simulations indicate that neuronal INa in the cardiac dyad plays a key role during the systolic phase. Rapid inward neuronal INa can elevate dyadic [Na+] to 35-40 mM, which drives reverse-mode NCX1 transport, and therefore promotes Ca2+ entry into the dyad, enhancing the trigger for JSR Ca2+ release. The specific role of decreased co-localization of NaK and NCX1 in ankyrin-B+/- cardiomyocytes was examined. Model results demonstrate that a reduction in the local NCX1- and NaK-mediated regulation of dyadic [Ca2+] and [Na+] results in an increase in Ca2+ spark activity during isoproterenol stimulation, which in turn stochastically activates NCX1 in the dyad. This alteration in NCX1/NaK co-localization interrupts the balance between NCX1 and NaK currents in a way that leads to enhanced depolarizing inward current during the action potential plateau, which ultimately leads to a higher probability of L-type Ca2+ channel reopening and arrhythmogenic early-afterdepolarizations.
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Affiliation(s)
- Lulu Chu
- Department of Biomedical Engineering and the Institute for Computational Medicine, The Johns Hopkins University School of Medicine and Whiting School of Engineering, 3400 N Charles Street, Baltimore, MD 21218, USA.
| | - Joseph L Greenstein
- Department of Biomedical Engineering and the Institute for Computational Medicine, The Johns Hopkins University School of Medicine and Whiting School of Engineering, 3400 N Charles Street, Baltimore, MD 21218, USA.
| | - Raimond L Winslow
- Department of Biomedical Engineering and the Institute for Computational Medicine, The Johns Hopkins University School of Medicine and Whiting School of Engineering, 3400 N Charles Street, Baltimore, MD 21218, USA.
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16
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Wang W, Mellor RL, Nerbonne JM, Balke CW. Regional differences in the expression of tetrodotoxin-sensitive inward Ca 2+ and outward Cs +/K + currents in mouse and human ventricles. Channels (Austin) 2019; 13:72-87. [PMID: 30704344 PMCID: PMC6380286 DOI: 10.1080/19336950.2019.1568146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Tetrodotoxin (TTX) sensitive inward Ca2+ currents, ICa(TTX), have been identified in cardiac myocytes from several species, although it is unclear if ICa(TTX) is expressed in all cardiac cell types, and if ICa(TTX) reflects Ca2+ entry through the main, Nav1.5-encoded, cardiac Na+ (Nav) channels. To address these questions, recordings were obtained with 2 mm Ca2+ and 0 mm Na+ in the bath and 120 mm Cs+ in the pipettes from myocytes isolated from adult mouse interventricular septum (IVS), left ventricular (LV) endocardium, apex, and epicardium and from human LV endocardium and epicardium. On membrane depolarizations from a holding potential of −100 mV, ICa(TTX) was identified in mouse IVS and LV endocardial myocytes and in human LV endocardial myocytes, whereas only TTX-sensitive outward Cs+/K+ currents were observed in mouse LV apex and epicardial myocytes and human LV epicardial myocytes. The inward Ca2+, but not the outward Cs+/K+, currents were blocked by mm concentrations of MTSEA, a selective blocker of cardiac Nav1.5-encoded Na+ channels. In addition, in Nav1.5-expressing tsA-201 cells, ICa(TTX) was observed in 3 (of 20) cells, and TTX-sensitive outward Cs+/K+ currents were observed in the other (17) cells. The time- and voltage-dependent properties of the TTX-sensitive inward Ca2+ and outward Cs+/K+ currents recorded in Nav1.5-expressing tsA-201 were indistinguishable from native currents in mouse and human cardiac myocytes. Overall, the results presented here suggest marked regional, cell type-specific, differences in the relative ion selectivity, and likely the molecular architecture, of native SCN5A-/Scn5a- (Nav1.5-) encoded cardiac Na+ channels in mouse and human ventricles.
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Affiliation(s)
- Wei Wang
- a Center for Cardiovascular Research, Department of Medicine, Cardiovascular Division , Washington University School of Medicine , St. Louis , MO , USA
| | - Rebecca L Mellor
- a Center for Cardiovascular Research, Department of Medicine, Cardiovascular Division , Washington University School of Medicine , St. Louis , MO , USA
| | - Jeanne M Nerbonne
- a Center for Cardiovascular Research, Department of Medicine, Cardiovascular Division , Washington University School of Medicine , St. Louis , MO , USA.,b John Cochran Veterans Administration Medical Center , St. Louis , MO , USA
| | - C William Balke
- a Center for Cardiovascular Research, Department of Medicine, Cardiovascular Division , Washington University School of Medicine , St. Louis , MO , USA.,b John Cochran Veterans Administration Medical Center , St. Louis , MO , USA
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17
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A Mathematical Model of the Human Cardiac Na + Channel. J Membr Biol 2019; 252:77-103. [PMID: 30637460 DOI: 10.1007/s00232-018-00058-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Accepted: 12/31/2018] [Indexed: 01/07/2023]
Abstract
Sodium ion channel is a membrane protein that plays an important role in excitable cells, as it is responsible for the initiation of action potentials. Understanding the electrical characteristics of sodium channels is essential in predicting their behavior under different physiological conditions. We investigated several Markov models for the human cardiac sodium channel NaV1.5 to derive a minimal mathematical model that describes the reported experimental data obtained using major voltage clamp protocols. We obtained simulation results for peak current-voltage relationships, the voltage dependence of normalized ion channel conductance, steady-state inactivation, activation and deactivation kinetics, fast and slow inactivation kinetics, and recovery from inactivation kinetics. Good agreement with the experimental data provides us with the mechanisms of the fast and slow inactivation of the human sodium channel and the coupling of its inactivation states to the closed and open states in the activation pathway.
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18
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Nunes D, Kuner T. Axonal sodium channel NaV1.2 drives granule cell dendritic GABA release and rapid odor discrimination. PLoS Biol 2018; 16:e2003816. [PMID: 30125271 PMCID: PMC6117082 DOI: 10.1371/journal.pbio.2003816] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 08/30/2018] [Accepted: 08/06/2018] [Indexed: 12/19/2022] Open
Abstract
Dendrodendritic synaptic interactions between olfactory bulb mitral and granule cells represent a key neuronal mechanism of odor discrimination. Dendritic release of gamma-aminobutyric acid (GABA) from granule cells contributes to stimulus-dependent, rapid, and accurate odor discrimination, yet the physiological mechanisms governing this release and its behavioral relevance are unknown. Here, we show that granule cells express the voltage-gated sodium channel α-subunit NaV1.2 in clusters distributed throughout the cell surface including dendritic spines. Deletion of NaV1.2 in granule cells abolished spiking and GABA release as well as inhibition of synaptically connected mitral cells (MCs). As a consequence, mice required more time to discriminate highly similar odorant mixtures, while odor discrimination learning remained unaffected. In conclusion, we show that expression of NaV1.2 in granule cells is crucial for physiological dendritic GABA release and rapid discrimination of similar odorants with high accuracy. Hence, our data indicate that neurotransmitter-releasing dendritic spines function just like axon terminals. In axonal nerve terminals, neurotransmitter release is triggered by a localized Ca2+ nanodomain generated by voltage-gated calcium channels in response to an action potential, which in turn is mediated by voltage-gated sodium channels. Dendritic neurotransmitter release has been thought to work differently, mainly depending on Ca2+ entering directly through N-methyl-D-aspartate (NMDA) receptors, a subtype of ligand-gated ion channel. To further investigate how dendritic neurotransmitter is released, we studied granule cells in the olfactory bulb of mice, which establish inhibitory dendrodendritic synapses with mitral cells. We show that granule cells express voltage-gated sodium channels predominantly localized in dendrites and spines. Down-regulation of these channels precludes action potential firing in granule cells and strongly reduces mitral cell inhibition. Behaviorally, these mice require more time to discriminate highly similar odorants at maximal accuracy. Therefore, the inhibition of mitral cells relies on neurotransmitter released from the dendrites of granule cells by a mechanism that resembles axonal neurotransmitter release much more than previously thought.
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Affiliation(s)
- Daniel Nunes
- Champalimaud Research, Champalimaud Centre for the Unknown, Lisbon, Portugal
- Functional Neuroanatomy Department, Institute for Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
- * E-mail: (DN); (TK)
| | - Thomas Kuner
- Functional Neuroanatomy Department, Institute for Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
- * E-mail: (DN); (TK)
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19
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Calloe K, Aistrup GL, Di Diego JM, Goodrow RJ, Treat JA, Cordeiro JM. Interventricular differences in sodium current and its potential role in Brugada syndrome. Physiol Rep 2018; 6:e13787. [PMID: 30009404 PMCID: PMC6046646 DOI: 10.14814/phy2.13787] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 06/14/2018] [Accepted: 06/15/2018] [Indexed: 12/19/2022] Open
Abstract
Brugada syndrome (BrS) is an inherited disease associated with ST elevation in the right precordial leads, polymorphic ventricular tachycardia (PVT), and sudden cardiac death in adults. Mutations in the cardiac sodium channel account for a large fraction of BrS cases. BrS manifests in the right ventricle (RV), which led us to examine the biophysical and molecular properties of sodium channel in myocytes isolated from the left (LV) and right ventricle. Patch clamp was used to record sodium current (INa ) in single canine RV and LV epicardial (epi) and endocardial (endo) myocytes. Action potentials were recorded from multicellular preparations and single cells. mRNA and proteins were determined using quantitative RT-PCR and Western blot. Although LV wedge preparations were thicker than RV wedges, transmural ECG recordings showed no difference in the width of the QRS complex or transmural conduction time. Action potential characteristics showed RV epi and endo had a lower Vmax compared with LV epi and endo cells. Peak INa density was significantly lower in epi and endo RV cells compared with epi and endo LV cells. Recovery from inactivation of INa in RV cells was slightly faster and half maximal steady-state inactivation was more positive. β2 and β4 mRNA was detected at very low levels in both ventricles, which was confirmed at the protein level. Our observations demonstrate that Vmax and Na+ current are smaller in RV, presumably due to differential Nav 1.5/β subunit expression. These results provide a potential mechanism for the right ventricular manifestation of BrS.
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Affiliation(s)
- Kirstine Calloe
- Department of Veterinary and Animal SciencesSection for Anatomy, Biochemistry and PhysiologyUniversity of CopenhagenFrederiksbergDenmark
| | - Gary L. Aistrup
- Department of Experimental CardiologyMasonic Medical Research LaboratoryUticaNew York
| | - José M. Di Diego
- Department of Experimental CardiologyMasonic Medical Research LaboratoryUticaNew York
- Lankenau Institute for Medical ResearchWynnewoodPennsylvania
| | - Robert J. Goodrow
- Department of Experimental CardiologyMasonic Medical Research LaboratoryUticaNew York
| | - Jacqueline A. Treat
- Department of Experimental CardiologyMasonic Medical Research LaboratoryUticaNew York
| | - Jonathan M. Cordeiro
- Department of Experimental CardiologyMasonic Medical Research LaboratoryUticaNew York
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20
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Song Y, Belardinelli L. Basal late sodium current is a significant contributor to the duration of action potential of guinea pig ventricular myocytes. Physiol Rep 2018; 5:e13295. [PMID: 28554967 PMCID: PMC5449569 DOI: 10.14814/phy2.13295] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 05/01/2017] [Accepted: 05/02/2017] [Indexed: 01/17/2023] Open
Abstract
In cardiac myocytes, an enhancement of late sodium current (INaL) under pathological conditions is known to cause prolongation of action potential duration (APD). This study investigated the contribution of INaL under basal, physiological conditions to the APD Whole-cell INaL and the APD of ventricular myocytes isolated from healthy adult guinea pigs were measured at 36°C. The INaL inhibitor GS967 or TTX was applied to block INaL The amplitude of basal INaL and the APD at 50% repolarization in myocytes stimulated at a frequency of 0.17 Hz were -0.24 ± 0.02 pA/pF and 229 ± 6 msec, respectively. GS967 (0.01-1 μmol/L) concentration dependently reduced the basal INaL by 18 ± 3-82 ± 4%. At the same concentrations, GS967 shortened the APD by 9 ± 2 to 25 ± 1%. Similarly, TTX at 0.1-10 μmol/L decreased the basal INaL by 13 ± 1-94 ± 1% and APD by 8 ± 1-31 ± 2%. There was a close correlation (R2 = 0.958) between the percentage inhibition of INaL and the percentage shortening of APD caused by either GS967 or TTX MTSEA (methanethiosulfonate ethylammonium, 2 mmol/L), a NaV1.5 channel blocker, reduced the INaL by 90 ± 5%, suggesting that the NaV1.5 channel isoform is the major contributor to the basal INaL KN-93 (10 μmol/L) and AIP (2 μmol/L), blockers of CaMKII, moderately reduced the basal INaL Thus, this study provides strong evidence that basal endogenous INaL is a significant contributor to the APD of cardiac myocytes. In addition, the basal INaL of guinea pig ventricular myocytes is mainly generated from NaV1.5 channel isoform and is regulated by CaMKII.
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Affiliation(s)
- Yejia Song
- University of Florida, Gainesville, Florida
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21
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Song Y, Belardinelli L. Enhanced basal late sodium current appears to underlie the age-related prolongation of action potential duration in guinea pig ventricular myocytes. J Appl Physiol (1985) 2017; 125:1329-1338. [PMID: 29357519 DOI: 10.1152/japplphysiol.00916.2017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Aging hearts have prolonged QT interval and are vulnerable to oxidative stress. Because the QT interval indirectly reflects the action potential duration (APD), we examined the hypotheses that 1) the APD of ventricular myocytes increases with age; 2) the age-related prolongation of APD is due to an enhancement of basal late Na+ current (INaL); 3) inhibition of INaL may protect aging hearts from arrhythmogenic effects of hydrogen peroxide (H2O2). Experiments were performed on ventricular myocytes isolated from one-month (young) and one-year (old) guinea pigs (GPs). The APD of myocytes from old GPs was significantly longer than that from young GPs and was shortened by the INaL inhibitors GS967 and tetrodotoxin. The magnitude of INaL was significantly larger in myocytes from old than from young GPs. The CaMKII inhibitors KN-93 and AIP and the NaV1.5-channel blocker MTSEA blocked the INaL. There were no significant differences between myocytes from young and old GPs in L-type Ca2+ current and the rapidly- and slowly-activating delayed rectifier K+ currents, although the inward rectifier K+ current was slightly decreased in myocytes from old GPs. H2O2 induced more early afterdepolarizations in myocytes from old than from young GPs. The effect of H2O2 was attenuated by GS967. The results suggest that 1) the APD of myocytes from old GPs is prolonged, 2) a CaMKII-mediated increase in NaV1.5-channel INaL is responsible for the prolongation of APD, and 3) Inhibition of INaL may be beneficial for maintaining electrical stability under oxidative stress in myocytes of old GPs.
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Affiliation(s)
- Yejia Song
- Medicine, University of Florida, United States
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22
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Biophysical comparison of sodium currents in native cardiac myocytes and human induced pluripotent stem cell-derived cardiomyocytes. J Pharmacol Toxicol Methods 2017; 90:19-30. [PMID: 29128504 DOI: 10.1016/j.vascn.2017.11.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 09/22/2017] [Accepted: 11/02/2017] [Indexed: 12/31/2022]
Abstract
INTRODUCTION Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are used for safety pharmacology and to investigate genetic diseases affecting cardiac ion channels. It is unclear whether adult myocytes or hiPSC-CMs are the better platform for cardiac safety pharmacology. We examined the biophysical and molecular properties of INa in adult myocytes and hiPSC-CMs. METHODS hiPSC-CMs were plated at low density. Atrial and ventricular cells were obtained from dog hearts. Whole cell patch clamp was used to record INa. RESULTS Voltage clamp recordings showed a large INa in all three cell types but different densities. Small differences in steady-state inactivation and recovery from inactivation were noted in the three cell types. Application of lidocaine to the three cell types showed a similar pattern of block of INa under voltage clamp; however, lidocaine produced different effects on AP waveform under current clamp. AP clamp experiments showed that application of ventricular or atrial cell waveforms to the same hiPSC-CM elicited a large INa while application of a sinoatrial node waveform elicited no INa. Molecular analysis of Na+ channel subunits showed SCN5A and SCN1B-4B were expressed in adult cells and iPSC-CMs. However, iPSC-CMs express both fetal (exon 6A) and adult (exon 6) isoforms of SCN5A. DISCUSSION There are major differences in INa density and smaller differences in other biophysical properties of INa in adult atrial, ventricular, and hiPSC-CMs. The depolarized maximum diastolic potential coupled with the presence of phase 4 depolarization limits the contribution of INa in hiPSC-CM action potentials. Our results suggest that hiPSC-CMs may be useful for drug screening of Na+ channel inhibitors under voltage clamp but not current clamp.
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23
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Ton AT, Biet M, Delabre JF, Morin N, Dumaine R. In-utero exposure to nicotine alters the development of the rabbit cardiac conduction system and provides a potential mechanism for sudden infant death syndrome. Arch Toxicol 2017; 91:3947-3960. [PMID: 28593499 DOI: 10.1007/s00204-017-2006-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 06/01/2017] [Indexed: 01/06/2023]
Abstract
In-utero exposure to tobacco smoke remains the highest risk factor for sudden infant death syndrome (SIDS). To alleviate the risks, nicotine replacement therapies are often prescribed to women who wish to quit smoking during their pregnancy. Cardiac arrhythmias is considered the final outcome leading to sudden death. Our goal in this study was to determine if exposing rabbit fetus to nicotine altered the cardiac conduction system of newborn kittens in a manner susceptible to cause SIDS. Using neuronal markers and a series of immunohistological and electrophysiological techniques we found that nicotine delayed the development of the cardiac pacemaker center (sinoatrial node) and decreased its innervation. At the molecular level, nicotine favored the expression of cardiac sodium channels with biophysical properties that will tend to slow heart rate and diminish electrical conduction. Our results show that alterations of the cardiac sodium current may contribute to the bradycardia, conduction disturbances and other cardiac arrhythmias often associated to SIDS and raise awareness on the use of replacement therapy during pregnancy.
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Affiliation(s)
- Anh Tuan Ton
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001 12th ave, Sherbrooke, QC, Canada
- Montreal Heart Institute, University of Montreal, Montréal, QC, Canada
| | - Michael Biet
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001 12th ave, Sherbrooke, QC, Canada
| | - Jean-Francois Delabre
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001 12th ave, Sherbrooke, QC, Canada
| | - Nathalie Morin
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001 12th ave, Sherbrooke, QC, Canada
| | - Robert Dumaine
- Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001 12th ave, Sherbrooke, QC, Canada.
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Barajas-Martinez H, Goodrow RJ, Hu D, Patel P, Desai M, Panama BK, Treat JA, Aistrup GL, Cordeiro JM. Biophysical and molecular comparison of sodium current in cells isolated from canine atria and pulmonary vein. Pflugers Arch 2017; 469:703-712. [PMID: 28243733 DOI: 10.1007/s00424-017-1956-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 02/08/2017] [Accepted: 02/10/2017] [Indexed: 11/25/2022]
Abstract
The collar of the pulmonary vein (PV) is the focal point for the initiation of atrial arrhythmias, but the mechanisms underlying how PV cells differ from neighboring left atrial tissue are unclear. We examined the biophysical and molecular properties of INa in cells isolated from the canine pulmonary sleeve and compared the properties to left atrial tissue. PV and left atrial myocytes were isolated and patch clamp techniques were used to record INa. Action potential recordings from either tissue type were made using high-resistance electrodes. mRNA was determined using quantitative RT-PCR and proteins were determined by Western blot. Analysis of the action potential characteristics showed that PV tissue had a lower Vmax compared with left atrial tissue. Fast INa showed that current density was slightly lower in PV cells compared with LA cells (-96 ± 18.7 pA/pF vs. -120 ± 6.7 pA/pF, respectively, p < 0.05). The recovery from inactivation of INa in PV cells was slightly slower but no marked difference in steady-state inactivation was noted. Analysis of late INa during a 225-ms pulse showed that late INa was significantly smaller in PV cells compared to LA cells at all measured time points into the pulse. These results suggest PV cells have lower density of both peak and late INa. Molecular analysis of Nav1.5 and the four beta subunits showed lower levels of Nav1.5 as well as Navβ1 subunits, confirming the biophysical findings. These data show that a lower density of INa may lead to depression of excitability and predispose the PV collar to re-entrant circuits under pathophysiological conditions.
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Affiliation(s)
- Hector Barajas-Martinez
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY, 13501, USA
| | - Robert J Goodrow
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY, 13501, USA
| | - Dan Hu
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY, 13501, USA
| | - Payal Patel
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY, 13501, USA
| | - Mayurika Desai
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY, 13501, USA
| | - Brian K Panama
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY, 13501, USA
| | - Jacqueline A Treat
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY, 13501, USA
| | - Gary L Aistrup
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY, 13501, USA
| | - Jonathan M Cordeiro
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY, 13501, USA.
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25
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Li W, Yu Y, Hou JW, Zhou ZW, Guo K, Zhang PP, Wang ZQ, Yan JH, Sun J, Zhou Q, Wang YP, Li YG. Larger rate dependence of late sodium current in cardiac Purkinje cells: A potential link to arrhythmogenesis. Heart Rhythm 2016; 14:422-431. [PMID: 27915058 DOI: 10.1016/j.hrthm.2016.11.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Indexed: 11/29/2022]
Abstract
BACKGROUND Purkinje cells (PCs) have a steeper rate dependence of repolarization and are more susceptible to arrhythmic activity than do ventricular myocytes (VMs). Late sodium current (INaL) is rate dependent and contributes to rate dependence of repolarization. OBJECTIVE This study sought to test our hypothesis that PCs have a larger rate dependence of INaL, contributing to their steeper rate dependence of repolarization and higher susceptibility to arrhythmic activity, than do VMs. METHODS INaL was recorded in isolated rabbit PCs and VMs with the whole-cell patch clamp technique. Action potential was examined using the microelectrode technique. RESULTS Compared with VMs, PCs exhibited a significantly larger rate dependence of INaL with a larger INaL to basic cycle length (BCL) slope. Moreover, PCs had a larger rate dependence of INaL decay and slower recovery kinetics. Interestingly, the larger rate dependence of INaL matched to a steeper rate dependence of action potential duration (APD) in PCs. The INaL blocker tetrodotoxin significantly blunted, while the INaL enhancer anemone toxin (ATX-II) significantly increased, the rate dependence of INaL and APD in PCs and VMs. In the presence of ATX-II, the rate dependence of INaL in PCs was markedly larger than that in VMs, causing a much steeper rate dependence of APD in PCs. Accordingly, PCs exhibited greater rate-dependent electrical instability and were more prone to ATX-II-induced early afterdepolarizations, which were completely inhibited by the INaL inhibitor ranolazine. CONCLUSION PCs have a significantly larger rate dependence of INaL than do VMs because of distinctive INaL decay and recovery kinetics, which contributes to their larger rate adaptation, and simultaneously predisposes them to a higher risk of arrhythmogenesis.
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Affiliation(s)
- Wei Li
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Ying Yu
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jian-Wen Hou
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhi-Wen Zhou
- Department of Cardiology, Shanghai Xuhui District Central Hospital/Shanghai Clinical Center of Chinese Academy of Sciences, Shanghai, China
| | - Kai Guo
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Peng-Pai Zhang
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhi-Quan Wang
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jian-Hua Yan
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jian Sun
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qing Zhou
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yue-Peng Wang
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yi-Gang Li
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
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26
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Liu J, Laksman Z, Backx PH. The electrophysiological development of cardiomyocytes. Adv Drug Deliv Rev 2016; 96:253-73. [PMID: 26788696 DOI: 10.1016/j.addr.2015.12.023] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 12/23/2015] [Accepted: 12/31/2015] [Indexed: 02/07/2023]
Abstract
The generation of human cardiomyocytes (CMs) from human pluripotent stem cells (hPSCs) has become an important resource for modeling human cardiac disease and for drug screening, and also holds significant potential for cardiac regeneration. Many challenges remain to be overcome however, before innovation in this field can translate into a change in the morbidity and mortality associated with heart disease. Of particular importance for the future application of this technology is an improved understanding of the electrophysiologic characteristics of CMs, so that better protocols can be developed and optimized for generating hPSC-CMs. Many different cell culture protocols are currently utilized to generate CMs from hPSCs and all appear to yield relatively “developmentally” immature CMs with highly heterogeneous electrical properties. These hPSC-CMs are characterized by spontaneous beating at highly variable rates with a broad range of depolarization-repolarization patterns, suggestive of mixed populations containing atrial, ventricular and nodal cells. Many recent studies have attempted to introduce approaches to promote maturation and to create cells with specific functional properties. In this review, we summarize the studies in which the electrical properties of CMs derived from stem cells have been examined. In order to place this information in a useful context, we also review the electrical properties of CMs as they transition from the developing embryo to the adult human heart. The signal pathways involved in the regulation of ion channel expression during development are also briefly considered.
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27
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Vigmond EJ, Stuyvers BD. Modeling our understanding of the His-Purkinje system. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2015; 120:179-88. [PMID: 26740015 DOI: 10.1016/j.pbiomolbio.2015.12.013] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 12/18/2015] [Accepted: 12/22/2015] [Indexed: 01/25/2023]
Abstract
The His-Purkinje System (HPS) is responsible for the rapid electric conduction in the ventricles. It relays electrical impulses from the atrioventricular node to the muscle cells and, thus, coordinates the contraction of ventricles in order to ensure proper cardiac pump function. The HPS has been implicated in the genesis of ventricular tachycardia and fibrillation as a source of ectopic beats, as well as forming distinct portions of reentry circuitry. Despite its importance, it remains much less well characterized, structurally and functionally, than the myocardium. Notably, important differences exist with regard to cell structure and electrophysiology, including ion channels, intracellular calcium handling, and gap junctions. Very few computational models address the HPS, and the majority of organ level modeling studies omit it. This review will provide an overview of our current knowledge of structure and function (including electrophysiology) of the HPS. We will review the most recent advances in modeling of the system from the single cell to the organ level, with considerations for relevant interspecies distinctions.
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Affiliation(s)
- Edward J Vigmond
- LIRYC, Institute of Electrophysiology and Cardiac Modeling, Hôpital Xavier Arnozan, avenue Haut-Lévèque, 33600 Pessac, France; Institut de Mathématiques de Bordeaux, Université de Bordeaux, 351, cours de la Libération, F 33 405 Talence, France; Department of Electrical and Computer Engineering, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.
| | - Bruno D Stuyvers
- LIRYC, Institute of Electrophysiology and Cardiac Modeling, Hôpital Xavier Arnozan, avenue Haut-Lévèque, 33600 Pessac, France; Université de Bordeaux, 351, cours de la Libération, F 33 405 Talence, France; Faculty of Medicine, Memorial University of Newfoundland, 300 Prince Phillip Drive, St. John's, NL A1B 3V6, Canada.
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28
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Hof T, Sallé L, Coulbault L, Richer R, Alexandre J, Rouet R, Manrique A, Guinamard R. TRPM4 non-selective cation channels influence action potentials in rabbit Purkinje fibres. J Physiol 2015; 594:295-306. [PMID: 26548780 DOI: 10.1113/jp271347] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 10/29/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The transient receptor potential melastatin 4 (TRPM4) inhibitor 9-phenanthrol reduces action potential duration in rabbit Purkinje fibres but not in ventricle. TRPM4-like single channel activity is observed in isolated rabbit Purkinje cells but not in ventricular cells. The TRPM4-like current develops during the notch and early repolarization phases of the action potential in Purkinje cells. ABSTRACT Transient receptor potential melastatin 4 (TRPM4) Ca(2+)-activated non-selective cation channel activity has been recorded in cardiomyocytes and sinus node cells from mammals. In addition, TRPM4 gene mutations are associated with human diseases of cardiac conduction, suggesting that TRPM4 plays a role in this aspect of cardiac function. Here we evaluate the TRPM4 contribution to cardiac electrophysiology of Purkinje fibres. Ventricular strips with Purkinje fibres were isolated from rabbit hearts. Intracellular microelectrodes recorded Purkinje fibre activity and the TRPM4 inhibitor 9-phenanthrol was applied to unmask potential TRPM4 contributions to the action potential. 9-Phenanthrol reduced action potential duration measured at the point of 50 and 90% repolarization with an EC50 of 32.8 and 36.1×10(-6) mol l(-1), respectively, but did not modulate ventricular action potentials. Inside-out patch-clamp recordings were used to monitor TRPM4 activity in isolated Purkinje cells. TRPM4-like single channel activity (conductance = 23.8 pS; equal permeability for Na(+) and K(+); sensitivity to voltage, Ca(2+) and 9-phenanthrol) was observed in 43% of patches from Purkinje cells but not from ventricular cells (0/16). Action potential clamp experiments performed in the whole-cell configuration revealed a transient inward 9-phenanthrol-sensitive current (peak density = -0.65 ± 0.15 pA pF(-1); n = 5) during the plateau phases of the Purkinje fibre action potential. These results show that TRPM4 influences action potential characteristics in rabbit Purkinje fibres and thus could modulate cardiac conduction and be involved in triggering arrhythmias.
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Affiliation(s)
- Thomas Hof
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Laurent Sallé
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Laurent Coulbault
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Romain Richer
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Joachim Alexandre
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - René Rouet
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Alain Manrique
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Romain Guinamard
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
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29
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Tse G, Yeo JM. Conduction abnormalities and ventricular arrhythmogenesis: The roles of sodium channels and gap junctions. IJC HEART & VASCULATURE 2015; 9:75-82. [PMID: 26839915 PMCID: PMC4695916 DOI: 10.1016/j.ijcha.2015.10.003] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 10/19/2015] [Indexed: 01/12/2023]
Abstract
Ventricular arrhythmias arise from disruptions in the normal orderly sequence of electrical activation and recovery of the heart. They can be categorized into disorders affecting predominantly cellular depolarization or repolarization, or those involving action potential (AP) conduction. This article briefly discusses the factors causing conduction abnormalities in the form of unidirectional conduction block and reduced conduction velocity (CV). It then examines the roles that sodium channels and gap junctions play in AP conduction. Finally, it synthesizes experimental results to illustrate molecular mechanisms of how abnormalities in these proteins contribute to such conduction abnormalities and hence ventricular arrhythmogenesis, in acquired pathologies such as acute ischaemia and heart failure, as well as inherited arrhythmic syndromes.
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Affiliation(s)
- Gary Tse
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Jie Ming Yeo
- School of Medicine, Imperial College London, SW7 2AZ, UK
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30
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Purkinje Cells as Sources of Arrhythmias in Long QT Syndrome Type 3. Sci Rep 2015; 5:13287. [PMID: 26289036 PMCID: PMC4542521 DOI: 10.1038/srep13287] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 07/16/2015] [Indexed: 12/27/2022] Open
Abstract
Long QT syndrome (LQTS) is characterized by ventricular arrhythmias and sudden cardiac death. Purkinje cells (PC) within the specialized cardiac conduction system have unique electrophysiological properties that we hypothesize may produce the primary sources of arrhythmia in heritable LQTS. LQTS type 3 (LQT3) transgenic mice harboring the ΔKPQ+/− mutation were crossed with Contactin2-EGFP BAC transgenic mice, which express a fluorescent reporter gene within the Purkinje fiber network. Isolated ventricular myocytes (VMs) (EGFP−) and PCs (EGFP+) from wild type and ΔKPQ mutant hearts were compared using the whole-cell patch clamp technique and microfluorimetry of calcium transients. Increased late sodium current was seen in ΔKPQ-PCs and ΔKPQ-VMs, with larger density in ΔKPQ-PCs. Marked prolongation of action potential duration of ΔKPQ-PCs was seen compared to ΔKPQ-VMs. ΔKPQ-PCs, but not ΔKPQ-VMs, exhibited frequent early afterdepolarizations, which corresponded to repetitive oscillations of intracellular calcium. Abnormalities in cell repolarization were reversed with exposure to mexiletine. We present the first direct experimental evidence that PCs are uniquely sensitive to LQT3 mutations, displaying electrophysiological behavior that is highly pro-arrhythmic.
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31
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Biet M, Morin N, Lessard-Beaudoin M, Graham RK, Duss S, Gagné J, Sanon NT, Carmant L, Dumaine R. Prolongation of Action Potential Duration and QT Interval During Epilepsy Linked to Increased Contribution of Neuronal Sodium Channels to Cardiac Late Na
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Current. Circ Arrhythm Electrophysiol 2015; 8:912-20. [DOI: 10.1161/circep.114.002693] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 06/01/2015] [Indexed: 11/16/2022]
Affiliation(s)
- Michael Biet
- From the Département de Pharmacologie et Physiologie, Université de Sherbrooke, Sherbrooke, Canada (M.B., N.M., M.L.-B., R.K.G., R.D.); and Department of Pediatrics, Centre de Recherche du CHU Sainte Justine, Université de Montréal, Montréal, Quebec, Canada (S.D., J.G., N.T.S., L.C.)
| | - Nathalie Morin
- From the Département de Pharmacologie et Physiologie, Université de Sherbrooke, Sherbrooke, Canada (M.B., N.M., M.L.-B., R.K.G., R.D.); and Department of Pediatrics, Centre de Recherche du CHU Sainte Justine, Université de Montréal, Montréal, Quebec, Canada (S.D., J.G., N.T.S., L.C.)
| | - Melissa Lessard-Beaudoin
- From the Département de Pharmacologie et Physiologie, Université de Sherbrooke, Sherbrooke, Canada (M.B., N.M., M.L.-B., R.K.G., R.D.); and Department of Pediatrics, Centre de Recherche du CHU Sainte Justine, Université de Montréal, Montréal, Quebec, Canada (S.D., J.G., N.T.S., L.C.)
| | - Rona K. Graham
- From the Département de Pharmacologie et Physiologie, Université de Sherbrooke, Sherbrooke, Canada (M.B., N.M., M.L.-B., R.K.G., R.D.); and Department of Pediatrics, Centre de Recherche du CHU Sainte Justine, Université de Montréal, Montréal, Quebec, Canada (S.D., J.G., N.T.S., L.C.)
| | - Sandra Duss
- From the Département de Pharmacologie et Physiologie, Université de Sherbrooke, Sherbrooke, Canada (M.B., N.M., M.L.-B., R.K.G., R.D.); and Department of Pediatrics, Centre de Recherche du CHU Sainte Justine, Université de Montréal, Montréal, Quebec, Canada (S.D., J.G., N.T.S., L.C.)
| | - Jonathan Gagné
- From the Département de Pharmacologie et Physiologie, Université de Sherbrooke, Sherbrooke, Canada (M.B., N.M., M.L.-B., R.K.G., R.D.); and Department of Pediatrics, Centre de Recherche du CHU Sainte Justine, Université de Montréal, Montréal, Quebec, Canada (S.D., J.G., N.T.S., L.C.)
| | - Nathalie T. Sanon
- From the Département de Pharmacologie et Physiologie, Université de Sherbrooke, Sherbrooke, Canada (M.B., N.M., M.L.-B., R.K.G., R.D.); and Department of Pediatrics, Centre de Recherche du CHU Sainte Justine, Université de Montréal, Montréal, Quebec, Canada (S.D., J.G., N.T.S., L.C.)
| | - Lionel Carmant
- From the Département de Pharmacologie et Physiologie, Université de Sherbrooke, Sherbrooke, Canada (M.B., N.M., M.L.-B., R.K.G., R.D.); and Department of Pediatrics, Centre de Recherche du CHU Sainte Justine, Université de Montréal, Montréal, Quebec, Canada (S.D., J.G., N.T.S., L.C.)
| | - Robert Dumaine
- From the Département de Pharmacologie et Physiologie, Université de Sherbrooke, Sherbrooke, Canada (M.B., N.M., M.L.-B., R.K.G., R.D.); and Department of Pediatrics, Centre de Recherche du CHU Sainte Justine, Université de Montréal, Montréal, Quebec, Canada (S.D., J.G., N.T.S., L.C.)
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Roger S, Gillet L, Le Guennec JY, Besson P. Voltage-gated sodium channels and cancer: is excitability their primary role? Front Pharmacol 2015; 6:152. [PMID: 26283962 PMCID: PMC4518325 DOI: 10.3389/fphar.2015.00152] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 07/09/2015] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (NaV) are molecular characteristics of excitable cells. Their activation, triggered by membrane depolarization, generates transient sodium currents that initiate action potentials in neurons and muscle cells. Sodium currents were discovered by Hodgkin and Huxley using the voltage clamp technique and reported in their landmark series of papers in 1952. It was only in the 1980's that sodium channel proteins from excitable membranes were molecularly characterized by Catterall and his collaborators. Non-excitable cells can also express NaV channels in physiological conditions as well as in pathological conditions. These NaV channels can sustain biological roles that are not related to the generation of action potentials. Interestingly, it is likely that the abnormal expression of NaV in pathological tissues can reflect the re-expression of a fetal phenotype. This is especially true in epithelial cancer cells for which these channels have been identified and sodium currents recorded, while it was not the case for cells from the cognate normal tissues. In cancers, the functional activity of NaV appeared to be involved in regulating the proliferative, migrative, and invasive properties of cells. This review is aimed at addressing the non-excitable roles of NaV channels with a specific emphasis in the regulation of cancer cell biology.
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Affiliation(s)
- Sébastien Roger
- Inserm UMR1069, Nutrition, Croissance et Cancer, Université François-Rabelais de Tours Tours, France ; Département de Physiologie Animale, UFR Sciences and Techniques, Université François-Rabelais de Tours Tours, France
| | - Ludovic Gillet
- Department of Clinical Research, University of Bern Bern, Switzerland
| | | | - Pierre Besson
- Inserm UMR1069, Nutrition, Croissance et Cancer, Université François-Rabelais de Tours Tours, France
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Gintant G. Cardiac Sodium Current (Na v1.5). METHODS AND PRINCIPLES IN MEDICINAL CHEMISTRY 2015. [DOI: 10.1002/9783527673643.ch12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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The genetic basis for inherited forms of sinoatrial dysfunction and atrioventricular node dysfunction. J Interv Card Electrophysiol 2015; 43:121-34. [PMID: 25863800 PMCID: PMC4486151 DOI: 10.1007/s10840-015-9998-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 03/13/2015] [Indexed: 01/01/2023]
Abstract
The sinoatrial node (SAN) and the atrioventricular node (AVN) are the anatomical and functional regions of the heart which play critical roles in the generation and conduction of the electrical impulse. Their functions are ensured by peculiar structural cytological properties and specific collections of ion channels. Impairment of SAN and AVN activity is generally acquired,but in some cases familial inheritance has been established and therefore a genetic cause is involved. In recent years, combined efforts of clinical practice and experimental basic science studies have identified and characterized several causative gene mutations associated with the nodal syndromes. Channelopathies, i.e., diseases associated with defective ion channels, remain the major cause of genetically determined nodal arrhythmias; however, it is becoming increasingly evident that mutations in other classes of regulatory and structural proteins also have profound pathophysiological roles. In this review, we will present some aspects of the genetic identification of the molecular mechanism underlying both SAN and AVN dysfunctions with a particular focus on mutations of the Na, pacemaker (HCN), and Ca channels. Genetic defects in regulatory proteins and calcium-handling proteins will be also considered. In conclusion, the identification of the genetic defects associated with familial nodal dysfunction is an essential step for implementing an appropriate therapeutic treatment.
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Balycheva M, Faggian G, Glukhov AV, Gorelik J. Microdomain-specific localization of functional ion channels in cardiomyocytes: an emerging concept of local regulation and remodelling. Biophys Rev 2015; 7:43-62. [PMID: 28509981 DOI: 10.1007/s12551-014-0159-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 12/18/2014] [Indexed: 12/26/2022] Open
Abstract
Cardiac excitation involves the generation of action potential by individual cells and the subsequent conduction of the action potential from cell to cell through intercellular gap junctions. Excitation of the cellular membrane results in opening of the voltage-gated L-type calcium ion (Ca2+) channels, thereby allowing a small amount of Ca2+ to enter the cell, which in turn triggers the release of a much greater amount of Ca2+ from the sarcoplasmic reticulum, the intracellular Ca2+ store, and gives rise to the systolic Ca2+ transient and contraction. These processes are highly regulated by the autonomic nervous system, which ensures the acute and reliable contractile function of the heart and the short-term modulation of this function upon changes in heart rate or workload. It has recently become evident that discrete clusters of different ion channels and regulatory receptors are present in the sarcolemma, where they form an interacting network and work together as a part of a macro-molecular signalling complex which in turn allows the specificity, reliability and accuracy of the autonomic modulation of the excitation-contraction processes by a variety of neurohormonal pathways. Disruption in subcellular targeting of ion channels and associated signalling proteins may contribute to the pathophysiology of a variety of cardiac diseases, including heart failure and certain arrhythmias. Recent methodological advances have made it possible to routinely image the topography of live cardiomyocytes, allowing the study of clustering functional ion channels and receptors as well as their coupling within a specific microdomain. In this review we highlight the emerging understanding of the functionality of distinct subcellular microdomains in cardiac myocytes (e.g. T-tubules, lipid rafts/caveolae, costameres and intercalated discs) and their functional role in the accumulation and regulation of different subcellular populations of sodium, Ca2+ and potassium ion channels and their contributions to cellular signalling and cardiac pathology.
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Affiliation(s)
- Marina Balycheva
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, 4th Floor National Heart and Lung Institute, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK.,Cardiosurgery Department, University of Verona School of Medicine, Verona, Italy
| | - Giuseppe Faggian
- Cardiosurgery Department, University of Verona School of Medicine, Verona, Italy
| | - Alexey V Glukhov
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, 4th Floor National Heart and Lung Institute, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK.
| | - Julia Gorelik
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, 4th Floor National Heart and Lung Institute, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK.
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Zimmer T, Haufe V, Blechschmidt S. Voltage-gated sodium channels in the mammalian heart. Glob Cardiol Sci Pract 2014; 2014:449-63. [PMID: 25780798 PMCID: PMC4355518 DOI: 10.5339/gcsp.2014.58] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 12/11/2014] [Indexed: 12/19/2022] Open
Abstract
Mammalian species express nine functional voltage-gated Na(+) channels. Three of them, the cardiac-specific isoform Nav1.5 and the neuronal isoforms Nav1.8 and Nav1.9, are relatively resistant to the neurotoxin tetrodotoxin (TTX; IC50 ≥ 1 μM). The other six isoforms are highly sensitive to TTX with IC50 values in the nanomolar range. These isoforms are expressed in the central nervous system (Nav1.1, Nav1.2, Nav1.3, Nav1.6), in the skeletal muscle (Nav1.4), and in the peripheral nervous system (Nav1.6, Nav1.7). The isoform Nav1.5, encoded by the SCN5A gene, is responsible for the upstroke of the action potential in the heart. Mutations in SCN5A are associated with a variety of life-threatening arrhythmias, like long QT syndrome type 3 (LQT3), Brugada syndrome (BrS) or cardiac conduction disease (CCD). Previous immunohistochemical and electrophysiological assays demonstrated the cardiac expression of neuronal and skeletal muscle Na(+) channels in the heart of various mammals, which led to far-reaching speculations on their function. However, when comparing the Na(+) channel mRNA patterns in the heart of various mammalian species, only minute quantities of transcripts for TTX-sensitive Na(+) channels were detectable in whole pig and human hearts, suggesting that these channels are not involved in cardiac excitation phenomena in higher mammals. This conclusion is strongly supported by the fact that mutations in TTX-sensitive Na(+) channels were associated with epilepsy or skeletal muscle diseases, rather than with a pathological cardiac phenotype. Moreover, previous data from TTX-intoxicated animals and from cases of human tetrodotoxication showed that low TTX dosages caused at most little alterations of both the cardiac output and the electrocardiogram. Recently, genome-wide association studies identified SCN10A, the gene encoding Nav1.8, as a determinant of cardiac conduction parameters, and mutations in SCN10A have been associated with BrS. These novel findings opened a fascinating new research area in the cardiac ion channel field, and the on-going debate on how SCN10A/Nav1.8 affects cardiac conduction is very exciting.
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Affiliation(s)
- Thomas Zimmer
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Kollegiengasse 9, 07743 Jena, Germany
| | | | - Steve Blechschmidt
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Kollegiengasse 9, 07743 Jena, Germany
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Mishra S, Reznikov V, Maltsev VA, Undrovinas NA, Sabbah HN, Undrovinas A. Contribution of sodium channel neuronal isoform Nav1.1 to late sodium current in ventricular myocytes from failing hearts. J Physiol 2014; 593:1409-27. [PMID: 25772296 DOI: 10.1113/jphysiol.2014.278259] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 10/03/2014] [Indexed: 01/06/2023] Open
Abstract
KEY POINTS Late Na(+) current (INaL) contributes to action potential remodelling and Ca(2+)/Na(+) changes in heart failure. The molecular identity of INaL remains unclear. The contributions of different Na(+) channel isoforms, apart from the cardiac isoform, remain unknown. We discovered and characterized a substantial contribution of neuronal isoform Nav1.1 to INaL. This new component is physiologically relevant to the control of action potential shape and duration, as well as to cell Ca(2+) dynamics, especially in heart failure. ABSTRACT Late Na(+) current (INaL) contributes to action potential (AP) duration and Ca(2+) handling in cardiac cells. Augmented INaL was implicated in delayed repolarization and impaired Ca(2+) handling in heart failure (HF). We tested if Na(+) channel (Nav) neuronal isoforms contribute to INaL and Ca(2+) cycling defects in HF in 17 dogs in which HF was achieved via sequential coronary artery embolizations. Six normal dogs served as control. Transient Na(+) current (INaT ) and INaL in left ventricular cardiomyocytes (VCMs) were recorded by patch clamp while Ca(2+) dynamics was monitored using Fluo-4. Virally delivered short interfering RNA (siRNA) ensured Nav1.1 and Nav1.5 post-transcriptional silencing. The expression of six Navs was observed in failing VCMs as follows: Nav1.5 (57.3%) > Nav1.2 (15.3%) > Nav1.1 (11.6%) > Nav2.1 (10.7%) > Nav1.3 (4.6%) > Nav1.6 (0.5%). Failing VCMs showed up-regulation of Nav1.1 expression, but reduction of Nav1.6 mRNA. A similar Nav expression pattern was found in samples from human hearts with ischaemic HF. VCMs with silenced Nav1.5 exhibited residual INaT and INaL (∼30% of control) with rightwardly shifted steady-state activation and inactivation. These currents were tetrodotoxin sensitive but resistant to MTSEA, a specific Nav1.5 blocker. The amplitude of the tetrodotoxin-sensitive INaL was 0.1709 ± 0.0299 pA pF(-1) (n = 7 cells) and the decay time constant was τ = 790 ± 76 ms (n = 5). This INaL component was lacking in VCMs with a silenced Nav1.1 gene, indicating that, among neuronal isoforms, Nav1.1 provides the largest contribution to INaL. At -10 mV this contribution is ∼60% of total INaL. Our further experimental and in silico examinations showed that this new Nav1.1 INaL component contributes to Ca(2+) accumulation in failing VCMs and modulates AP shape and duration. In conclusion, we have discovered an Nav1.1-originated INaL component in dog heart ventricular cells. This component is physiologically relevant to controlling AP shape and duration, as well as to cell Ca(2+) dynamics.
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Affiliation(s)
- Sudhish Mishra
- Department of Internal Medicine, Henry Ford Hospital, Detroit, MI, USA
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Horvath B, Bers DM. The late sodium current in heart failure: pathophysiology and clinical relevance. ESC Heart Fail 2014; 1:26-40. [PMID: 28834665 DOI: 10.1002/ehf2.12003] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 07/13/2014] [Accepted: 07/14/2014] [Indexed: 12/19/2022] Open
Abstract
Large and growing body of data suggest that an increased late sodium current (INa,late ) can have a significant pathophysiological role in heart failure and other heart diseases. The first goal of this article is to describe how INa,late functions under physiological circumstances. The second goal is to show the wide range of cellular mechanisms that can increase INa,late in cardiac disease, and also to describe how the up-regulated INa,late contributes to the pathophysiology of heart failure. The final section of the article discusses the possible use of INa,late -modifying drugs in heart failure, on the basis of experimental and preclinical data.
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Affiliation(s)
- Balazs Horvath
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Faculty of Pharmacy, University of Debrecen, Debrecen, Hungary
| | - Donald M Bers
- Department of Pharmacology, School of Medicine, University of California, Davis, CA, USA
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Bardai A, Blom MT, van Noord C, Verhamme KM, Sturkenboom MCJM, Tan HL. Sudden cardiac death is associated both with epilepsy and with use of antiepileptic medications. Heart 2014; 101:17-22. [PMID: 25031263 DOI: 10.1136/heartjnl-2014-305664] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
OBJECTIVE Epilepsy is associated with increased risk for sudden cardiac death (SCD). We aimed to establish, in a community based study, whether this association is mediated by epilepsy per se, use of antiepileptic medications (AEMs), or both. METHODS We studied SCD cases and age/sex matched controls in a case-control study in a large scale general practitioners' research database (n=478 661 patients). SCD risk for symptomatic epilepsy (seizure <2 years before SCD), stable epilepsy (no seizure <2 years before SCD), and use of AEMs (any indication) was determined. RESULTS We identified 926 SCD cases and 9832 controls. Fourteen cases had epilepsy. Epilepsy was associated with an increased SCD risk (cases 1.5%, controls 0.5%; adjusted OR 2.8, 95% CI 1.4 to 5.3). SCD risk was increased for symptomatic epilepsy (cases 0.9%, controls 0.1%; adjusted OR 5.8, 95% CI 2.1 to 15.6), but not with stable epilepsy (cases 0.6%, controls 0.4%; adjusted OR 1.6, 95% CI 0.7 to 4.1). AEM use was found in 23 cases and was associated with an increased SCD risk (cases 2.5%, controls 0.8%; adjusted OR overall 2.6, 95% CI 1.5 to 4.3) among symptomatic epilepsy cases (cases 0.9%, controls 0.1%; adjusted OR 6.4, 95% CI 2.4 to 17.4) and non-epilepsy cases (cases 1.0%, controls 0.4%; adjusted OR 2.3, 95% CI 1.01 to 5.2). Increased SCD risk was associated with sodium channel blocking AEMs (cases 1.6%, controls 0.4%; adjusted OR 2.8, 95% CI 1.1 to 7.2), but not with non-sodium channel blocking AEMs. Carbamazepine and gabapentin were associated with increased SCD risk (carbamazepine: cases 1.1%, controls 0.3%; adjusted OR 3.2, 95% CI 1.1 to 9.2; gabapentin: cases 0.3%, controls 0.1%; adjusted OR 5.7, 95% CI 1.2 to 27.9). CONCLUSIONS Epilepsy and AEM use are both associated with increased SCD risk in the general population. Poor seizure control contributes to increased SCD risk in epilepsy, while sodium channel blockade contributes to SCD susceptibility in AEM users.
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Affiliation(s)
- Abdennasser Bardai
- Department of Cardiology, Heart Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands Interuniversity Cardiology Institute Netherlands, Utrecht, The Netherlands Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Marieke T Blom
- Department of Cardiology, Heart Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Charlotte van Noord
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Katia M Verhamme
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Miriam C J M Sturkenboom
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands Department of Medical Informatics, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Hanno L Tan
- Department of Cardiology, Heart Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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Ono T, Hayashida M, Tezuka A, Hayakawa H, Ohno Y. Antagonistic effects of tetrodotoxin on aconitine-induced cardiac toxicity. J NIPPON MED SCH 2014; 80:350-61. [PMID: 24189353 DOI: 10.1272/jnms.80.350] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Aconitine, well-known for its high cardiotoxicity, causes severe arrhythmias, such as ventricular tachycardia and ventricular fibrillation, by opening membrane sodium channels. Tetrodotoxin, a membrane sodium-channel blocker, is thought to antagonize aconitine activity. Tetrodotoxin is a potent blocker of the skeletal muscle sodium-channel isoform Na(v)1.4 (IC50 10 nM), but micromolar concentrations of tetrodotoxin are required to inhibit the primary cardiac isoform Na(v)1.5. This suggests that substantial concentrations of tetrodotoxin are required to alleviate the cardiac toxicity caused by aconitine. To elucidate the interaction between aconitine and tetrodotoxin in the cardiovascular and respiratory systems, mixtures of aconitine and tetrodotoxin were simultaneously administered to mice, and the effects on electrocardiograms, breathing rates, and arterial oxygen saturation were examined. Compared with mice treated with aconitine alone, some mice treated with aconitine-tetrodotoxin mixtures showed lower mortality rates and delayed appearance of arrhythmia. The decreased breathing rates and arterial oxygen saturation observed in mice receiving aconitine alone were alleviated in mice that survived after receiving the aconitine-tetrodotoxin mixture; this result suggests that tetrodotoxin is antagonistic to aconitine. When the tetrodotoxin dose is greater than the dose that can block tetrodotoxin-sensitive sodium channels, which are excessively activated by aconitine, tetrodotoxin toxicity becomes prominent, and the mortality rate increases because of the respiratory effects of tetrodotoxin. In terms of cardiotoxicity, mice receiving the aconitine-tetrodotoxin mixture showed minor and shorter periods of change on electrocardiography. This finding can be explained by the recent discovery of tetrodotoxin-sensitive sodium-channel cardiac isoforms (Na(v)1.1, 1.2, 1.3, 1.4 and 1.6).
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41
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Biet M, Morin N, Benrezzak O, Naimi F, Bellanger S, Baillargeon JP, Chouinard L, Gallo-Payet N, Carpentier AC, Dumaine R. Lasting alterations of the sodium current by short-term hyperlipidemia as a mechanism for initiation of cardiac remodeling. Am J Physiol Heart Circ Physiol 2014; 306:H291-7. [DOI: 10.1152/ajpheart.00715.2013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Clinical and animal studies indicate that increased fatty acid delivery to lean tissues induces cardiac electrical remodeling and alterations of cellular calcium homeostasis. Since this may represent a mechanism initiating cardiac dysfunction during establishment of insulin resistance and diabetes or anaerobic cardiac metabolism (ischemia), we sought to determine if short-term exposure to high plasma concentration of fatty acid in vivo was sufficient to alter the cardiac sodium current ( INa) in dog ventricular myocytes. Our results show that delivery of triglycerides and nonesterified fatty acids by infusion of Intralipid + heparin (IH) for 8 h increased the amplitude of INa by 43% and shifted its activation threshold by −5 mV, closer to the resting membrane potential. Steady-state inactivation (availability) of the channels was reduced by IH with no changes in recovery from inactivation. As a consequence, INa “window” current, a strong determinant of intracellular Na+ and Ca2+ concentrations, was significantly increased. The results indicate that increased circulating fatty acids alter INa gating in manners consistent with an increased cardiac excitability and augmentation of intracellular calcium. Moreover, these changes could still be measured after the dogs were left to recover for 12 h after IH perfusion, suggesting lasting changes in INa. Our results indicate that fatty acids rapidly induce cardiac remodeling and suggest that this process may be involved in the development of cardiac dysfunctions associated to insulin resistance and diabetes.
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Affiliation(s)
- M. Biet
- Department of Physiology and Biophysics, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada; and
| | - N. Morin
- Department of Physiology and Biophysics, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada; and
| | - O. Benrezzak
- Department of Medecine (Endocrinology), Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - F. Naimi
- Department of Physiology and Biophysics, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada; and
| | - S. Bellanger
- Department of Physiology and Biophysics, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada; and
| | - J. P. Baillargeon
- Department of Medecine (Endocrinology), Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - L. Chouinard
- Department of Medecine (Endocrinology), Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - N. Gallo-Payet
- Department of Medecine (Endocrinology), Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - A. C. Carpentier
- Department of Medecine (Endocrinology), Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - R. Dumaine
- Department of Physiology and Biophysics, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada; and
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Jones DK, Ruben PC. Proton modulation of cardiac I Na: a potential arrhythmogenic trigger. Handb Exp Pharmacol 2014; 221:169-81. [PMID: 24737236 DOI: 10.1007/978-3-642-41588-3_8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Voltage-gated sodium (NaV) channels generate the upstroke and mediate duration of the ventricular action potential, thus they play a critical role in mediating cardiac excitability. Cardiac ischemia triggers extracellular pH to drop as low as pH 6.0, within just 10 min of its onset. Heightened proton concentrations reduce sodium conductance and alter the gating parameters of the cardiac-specific voltage-gated sodium channel, NaV1.5. Most notably, acidosis destabilizes fast inactivation, which plays a critical role in regulating action potential duration. The changes in NaV1.5 channel gating contribute to cardiac dysfunction during ischemia that can cause syncope, cardiac arrhythmia, and even sudden cardiac death. Understanding NaV channel modulation by protons is paramount to treatment and prevention of the deleterious effects of cardiac ischemia and other triggers of cardiac acidosis.
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Altered cardiac electrophysiology and SUDEP in a model of Dravet syndrome. PLoS One 2013; 8:e77843. [PMID: 24155976 PMCID: PMC3796479 DOI: 10.1371/journal.pone.0077843] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 09/04/2013] [Indexed: 12/04/2022] Open
Abstract
Objective Dravet syndrome is a severe form of intractable pediatric epilepsy with a high incidence of SUDEP: Sudden Unexpected Death in epilepsy. Cardiac arrhythmias are a proposed cause for some cases of SUDEP, yet the susceptibility and potential mechanism of arrhythmogenesis in Dravet syndrome remain unknown. The majority of Dravet syndrome patients have denovo mutations in SCN1A, resulting in haploinsufficiency. We propose that, in addition to neuronal hyperexcitability, SCN1A haploinsufficiency alters cardiac electrical function and produces arrhythmias, providing a potential mechanism for SUDEP. Methods Postnatal day 15-21 heterozygous SCN1A-R1407X knock-in mice, expressing a human Dravet syndrome mutation, were used to investigate a possible cardiac phenotype. A combination of single cell electrophysiology and invivo electrocardiogram (ECG) recordings were performed. Results We observed a 2-fold increase in both transient and persistent Na+ current density in isolated Dravet syndrome ventricular myocytes that resulted from increased activity of a tetrodotoxin-resistant Na+ current, likely Nav1.5. Dravet syndrome myocytes exhibited increased excitability, action potential duration prolongation, and triggered activity. Continuous radiotelemetric ECG recordings showed QT prolongation, ventricular ectopic foci, idioventricular rhythms, beat-to-beat variability, ventricular fibrillation, and focal bradycardia. Spontaneous deaths were recorded in 2 DS mice, and a third became moribund and required euthanasia. Interpretation These data from single cell and whole animal experiments suggest that altered cardiac electrical function in Dravet syndrome may contribute to the susceptibility for arrhythmogenesis and SUDEP. These mechanistic insights may lead to critical risk assessment and intervention in human patients.
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Abstract
An electrophysiological analysis of canine single ventricular myocardial (VM) and Purkinje (P) cells was carried out by means of whole cell voltage clamp method. The following results in VM versus P cells were obtained. INa3 was present, had a threshold negative to the fast activating-inactivating INa1, its slow inactivation was cut off by INa1, and contributed to Na+ influx at INa1 threshold. INa1 was smaller and had a less negative threshold. There was no comparable slowly inactivating INa2, accounting for the shorter action potential. Slope conductance at resting potential was about double and decreased to a minimum value at the larger and less negative IK1 peak. The negative slope region of I-V relation was smaller during fast ramps and larger during slow ramps than in P cells, occurred in the voltage range of IK1 block by Mg2+, was not affected by a lower Vh and TTX and was eliminated by Ba2+, in contrast to P cells. ICa was larger, peaked at positive potentials and was eliminated by Ni2+. Ito was much smaller, began at more positive values, was abolished by less negative Vh and by 4-aminopyridine, included a sustained current that 4-aminopyridine decreased but did not eliminate. Steeper ramps increased IK1 peak as well as the fall in outward current during repolarization, consistent with a time-dependent block and unblock of IK1 by polyamines. During repolarization, the positive slope region was consistently present and was similar in amplitude to IK1 peak, whereas it was small or altogether missing in P cells. The total outward current at positive potentials comprised a larger IK1 component whereas it included a larger Ito and sustained current in P cells. These and other results provide a better understanding of the mechanisms underlying the action potential of VM and P cells under normal and some abnormal (arrhythmias) conditions.
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Affiliation(s)
- M Vassalle
- Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, U.S.A
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Kaufmann SG, Westenbroek RE, Maass AH, Lange V, Renner A, Wischmeyer E, Bonz A, Muck J, Ertl G, Catterall WA, Scheuer T, Maier SK. Distribution and function of sodium channel subtypes in human atrial myocardium. J Mol Cell Cardiol 2013; 61:133-141. [PMID: 23702286 PMCID: PMC3906922 DOI: 10.1016/j.yjmcc.2013.05.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2012] [Revised: 04/25/2013] [Accepted: 05/10/2013] [Indexed: 12/16/2022]
Abstract
Voltage-gated sodium channels composed of a pore-forming α subunit and auxiliary β subunits are responsible for the upstroke of the action potential in cardiac muscle. However, their localization and expression patterns in human myocardium have not yet been clearly defined. We used immunohistochemical methods to define the level of expression and the subcellular localization of sodium channel α and β subunits in human atrial myocytes. Nav1.2 channels are located in highest density at intercalated disks where β1 and β3 subunits are also expressed. Nav1.4 and the predominant Nav1.5 channels are located in a striated pattern on the cell surface at the z-lines together with β2 subunits. Nav1.1, Nav1.3, and Nav1.6 channels are located in scattered puncta on the cell surface in a pattern similar to β3 and β4 subunits. Nav1.5 comprised approximately 88% of the total sodium channel staining, as assessed by quantitative immunohistochemistry. Functional studies using whole cell patch-clamp recording and measurements of contractility in human atrial cells and tissue showed that TTX-sensitive (non-Nav1.5) α subunit isoforms account for up to 27% of total sodium current in human atrium and are required for maximal contractility. Overall, our results show that multiple sodium channel α and β subunits are differentially localized in subcellular compartments in human atrial myocytes, suggesting that they play distinct roles in initiation and conduction of the action potential and in excitation-contraction coupling. TTX-sensitive sodium channel isoforms, even though expressed at low levels relative to TTX-sensitive Nav1.5, contribute substantially to total cardiac sodium current and are required for normal contractility. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".
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Affiliation(s)
- Susann G. Kaufmann
- Medizinische Klinik und Poliklinik I, Universitätsklinikum Würzburg, Würzburg, Germany
| | - Ruth E. Westenbroek
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7280, USA
| | - Alexander H. Maass
- Department of Cardiology, Thoraxcenter, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Volkmar Lange
- Thoracic Surgery, Hospital St. Raphael, Ostercappeln, Germany
| | - Andre Renner
- Thoracic and Cardiovascular Surgery, Heart and Diabetes Center, Bad Oeynhausen, Germany
| | | | | | - Jenny Muck
- Medizinische Klinik und Poliklinik I, Universitätsklinikum Würzburg, Würzburg, Germany
| | - Georg Ertl
- Medizinische Klinik und Poliklinik I, Universitätsklinikum Würzburg, Würzburg, Germany
| | - William A. Catterall
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7280, USA
| | - Todd Scheuer
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7280, USA
| | - Sebastian K.G. Maier
- Medizinische Klinik und Poliklinik I, Universitätsklinikum Würzburg, Würzburg, Germany
- Department of Medicine II, Hospital St. Elisabeth Straubing, Straubing, Germany
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Ottolia M, Torres N, Bridge JHB, Philipson KD, Goldhaber JI. Na/Ca exchange and contraction of the heart. J Mol Cell Cardiol 2013; 61:28-33. [PMID: 23770352 DOI: 10.1016/j.yjmcc.2013.06.001] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2013] [Revised: 05/30/2013] [Accepted: 06/04/2013] [Indexed: 12/19/2022]
Abstract
Sodium-calcium exchange (NCX) is the major calcium (Ca) efflux mechanism of ventricular cardiomyocytes. Consequently the exchanger plays a critical role in the regulation of cellular Ca content and hence contractility. Reductions in Ca efflux by the exchanger, such as those produced by elevated intracellular sodium (Na) in response to cardiac glycosides, raise sarcoplasmic reticulum (SR) Ca stores. The result is an increased Ca transient and cardiac contractility. Enhanced Ca efflux activity by the exchanger, for example during heart failure, may reduce diadic cleft Ca and excitation-contraction (EC) coupling gain. This aggravates the impaired contractility associated with SR Ca ATPase dysfunction and reduced SR Ca load in failing heart muscle. Recent data from our laboratories indicate that NCX can also impact the efficiency of EC coupling and contractility independent of SR Ca load through diadic cleft priming with Ca during the upstroke of the action potential. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".
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Affiliation(s)
- Michela Ottolia
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
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47
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Cavanaugh J, French JA. Post-partum variation in the expression of paternal care is unrelated to urinary steroid metabolites in marmoset fathers. Horm Behav 2013; 63:551-8. [PMID: 23439223 PMCID: PMC3746002 DOI: 10.1016/j.yhbeh.2013.02.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 02/11/2013] [Accepted: 02/12/2013] [Indexed: 11/17/2022]
Abstract
The organization and activation of maternal care are known to be highly regulated by hormones and there is growing evidence that expression of paternal care is also related to endocrine substrates. We examined the relationship between paternal behavior and steroid hormones in marmoset fathers (Callithrix geoffroyi) and evaluated whether hormone-paternal behavior relationships were altered by previous offspring-care experience in males. Based on previous findings, we predicted that testosterone, estradiol, and cortisol would decrease following the birth of offspring and would be lowest during the period of maximal infant carrying. Furthermore, we predicted that post-partum changes in carrying effort and hormone levels would be influenced by the level of offspring-care experience. Carrying effort and other paternal care behaviors underwent temporal changes over the post-partum period, but these patterns were not related to variation in hormone concentrations over the same period. There was a limited effect of offspring-care experience on hormone concentrations, but experience was found to play a role in the expression of paternal care, with experienced fathers engaging in significantly more infant allogrooming than inexperienced fathers. Furthermore, inexperienced fathers increased the frequency of food sharing in response to infant begging across the post-partum period, while experienced fathers displayed consistently low levels. We posit that a combination of experiential factors and an increased role for alloparents in offspring-care led to these changes. However, it appears that hormonal changes may not influence paternal responsiveness in white-faced marmoset fathers and that hormone-paternal behavior relationships are not critically dependent on a male's previous offspring-care experience.
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Affiliation(s)
- Jon Cavanaugh
- Callitrichid Research Center, Department of Psychology, University of Nebraska, Omaha, NE 68182, USA.
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48
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Role of “non-cardiac” voltage-gated sodium channels in cardiac cells. J Mol Cell Cardiol 2012; 53:589-90. [DOI: 10.1016/j.yjmcc.2012.08.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 08/02/2012] [Accepted: 08/07/2012] [Indexed: 11/18/2022]
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Biet M, Barajas-Martínez H, Ton AT, Delabre JF, Morin N, Dumaine R. About half of the late sodium current in cardiac myocytes from dog ventricle is due to non-cardiac-type Na+ channels. J Mol Cell Cardiol 2012; 53:593-8. [DOI: 10.1016/j.yjmcc.2012.06.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 05/31/2012] [Accepted: 06/20/2012] [Indexed: 10/28/2022]
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50
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Verkerk AO, Remme CA, Schumacher CA, Scicluna BP, Wolswinkel R, de Jonge B, Bezzina CR, Veldkamp MW. Functional Na
V
1.8 Channels in Intracardiac Neurons. Circ Res 2012; 111:333-43. [DOI: 10.1161/circresaha.112.274035] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rationale:
The
SCN10A
gene encodes the neuronal sodium channel isoform Na
V
1.8. Several recent genome-wide association studies have linked
SCN10A
to PR interval and QRS duration, strongly suggesting an as-yet unknown role for Na
V
1.8 in cardiac electrophysiology.
Objective:
To demonstrate the functional presence of
SCN10A
/Nav1.8 in intracardiac neurons of the mouse heart.
Methods and Results:
Immunohistochemistry on mouse tissue sections showed intense Na
V
1.8 labeling in dorsal root ganglia and intracardiac ganglia and only modest Na
V
1.8 expression within the myocardium. Immunocytochemistry further revealed substantial Na
V
1.8 staining in isolated neurons from murine intracardiac ganglia but no Na
V
1.8 expression in isolated ventricular myocytes. Patch-clamp studies demonstrated that the Na
V
1.8 blocker A-803467 (0.5–2 μmol/L) had no effect on either mean sodium current (I
Na
) density or I
Na
gating kinetics in isolated myocytes but significantly reduced I
Na
density in intracardiac neurons. Furthermore, A-803467 accelerated the slow component of current decay and shifted voltage dependence of inactivation toward more negative voltages, as expected for blockade of Na
V
1.8-based I
Na
. In line with these findings, A-803467 did not affect cardiomyocyte action potential upstroke velocity but markedly reduced action potential firing frequency in intracardiac neurons, confirming a functional role for Na
V
1.8 in cardiac neural activity.
Conclusions:
Our findings demonstrate the functional presence of
SCN10A
/Na
V
1.8 in intracardiac neurons, indicating a novel role for this neuronal sodium channel in regulation of cardiac electric activity.
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Affiliation(s)
- Arie O. Verkerk
- From the Department of Clinical and Experimental Cardiology (C.A.R., C.A.S., B.P.S., R.W., C.R.B., M.W.V.) and the Department of Anatomy, Embryology, and Physiology (A.O.V., B.d.J.), Heart Failure Research Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Carol Ann Remme
- From the Department of Clinical and Experimental Cardiology (C.A.R., C.A.S., B.P.S., R.W., C.R.B., M.W.V.) and the Department of Anatomy, Embryology, and Physiology (A.O.V., B.d.J.), Heart Failure Research Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Cees A. Schumacher
- From the Department of Clinical and Experimental Cardiology (C.A.R., C.A.S., B.P.S., R.W., C.R.B., M.W.V.) and the Department of Anatomy, Embryology, and Physiology (A.O.V., B.d.J.), Heart Failure Research Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Brendon P. Scicluna
- From the Department of Clinical and Experimental Cardiology (C.A.R., C.A.S., B.P.S., R.W., C.R.B., M.W.V.) and the Department of Anatomy, Embryology, and Physiology (A.O.V., B.d.J.), Heart Failure Research Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Rianne Wolswinkel
- From the Department of Clinical and Experimental Cardiology (C.A.R., C.A.S., B.P.S., R.W., C.R.B., M.W.V.) and the Department of Anatomy, Embryology, and Physiology (A.O.V., B.d.J.), Heart Failure Research Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Berend de Jonge
- From the Department of Clinical and Experimental Cardiology (C.A.R., C.A.S., B.P.S., R.W., C.R.B., M.W.V.) and the Department of Anatomy, Embryology, and Physiology (A.O.V., B.d.J.), Heart Failure Research Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Connie R. Bezzina
- From the Department of Clinical and Experimental Cardiology (C.A.R., C.A.S., B.P.S., R.W., C.R.B., M.W.V.) and the Department of Anatomy, Embryology, and Physiology (A.O.V., B.d.J.), Heart Failure Research Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Marieke W. Veldkamp
- From the Department of Clinical and Experimental Cardiology (C.A.R., C.A.S., B.P.S., R.W., C.R.B., M.W.V.) and the Department of Anatomy, Embryology, and Physiology (A.O.V., B.d.J.), Heart Failure Research Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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