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Giommi A, Gurgel ARB, Smith GL, Workman AJ. Does the small conductance Ca 2+-activated K + current I SK flow under physiological conditions in rabbit and human atrial isolated cardiomyocytes? J Mol Cell Cardiol 2023; 183:70-80. [PMID: 37704101 DOI: 10.1016/j.yjmcc.2023.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 08/16/2023] [Accepted: 09/02/2023] [Indexed: 09/15/2023]
Abstract
BACKGROUND The small conductance Ca2+-activated K+ current (ISK) is a potential therapeutic target for treating atrial fibrillation. AIM To clarify, in rabbit and human atrial cardiomyocytes, the intracellular [Ca2+]-sensitivity of ISK, and its contribution to action potential (AP) repolarisation, under physiological conditions. METHODS Whole-cell-patch clamp, fluorescence microscopy: to record ion currents, APs and [Ca2+]i; 35-37°C. RESULTS In rabbit atrial myocytes, 0.5 mM Ba2+ (positive control) significantly decreased whole-cell current, from -12.8 to -4.9 pA/pF (P < 0.05, n = 17 cells, 8 rabbits). By contrast, the ISK blocker apamin (100 nM) had no effect on whole-cell current, at any set [Ca2+]i (∼100-450 nM). The ISK blocker ICAGEN (1 μM: ≥2 x IC50) also had no effect on current over this [Ca2+]i range. In human atrial myocytes, neither 1 μM ICAGEN (at [Ca2+]i ∼ 100-450 nM), nor 100 nM apamin ([Ca2+]i ∼ 250 nM) affected whole-cell current (5-10 cells, 3-5 patients/group). APs were significantly prolonged (at APD30 and APD70) by 2 mM 4-aminopyridine (positive control) in rabbit atrial myocytes, but 1 μM ICAGEN had no effect on APDs, versus either pre-ICAGEN or time-matched controls. High concentration (10 μM) ICAGEN (potentially ISK-non-selective) moderately increased APD70 and APD90, by 5 and 26 ms, respectively. In human atrial myocytes, 1 μM ICAGEN had no effect on APD30-90, whether stimulated at 1, 2 or 3 Hz (6-9 cells, 2-4 patients/rate). CONCLUSION ISK does not flow in human or rabbit atrial cardiomyocytes with [Ca2+]i set within the global average diastolic-systolic range, nor during APs stimulated at physiological or supra-physiological (≤3 Hz) rates.
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Affiliation(s)
- Alessandro Giommi
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Aline R B Gurgel
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Godfrey L Smith
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Antony J Workman
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK.
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Liu T, Li T, Xu D, Wang Y, Zhou Y, Wan J, Huang CLH, Tan X. Small-conductance calcium-activated potassium channels in the heart: expression, regulation and pathological implications. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220171. [PMID: 37122223 PMCID: PMC10150224 DOI: 10.1098/rstb.2022.0171] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 12/25/2022] [Indexed: 05/02/2023] Open
Abstract
Ca2+-activated K+ channels are critical to cellular Ca2+ homeostasis and excitability; they couple intracellular Ca2+ and membrane voltage change. Of these, the small, 4-14 pS, conductance SK channels include three, KCNN1-3 encoded, SK1/KCa2.1, SK2/KCa2.2 and SK3/KCa2.3, channel subtypes with characteristic, EC50 ∼ 10 nM, 40 pM, 1 nM, apamin sensitivities. All SK channels, particularly SK2 channels, are expressed in atrial, ventricular and conducting system cardiomyocytes. Pharmacological and genetic modification results have suggested that SK channel block or knockout prolonged action potential durations (APDs) and effective refractory periods (ERPs) particularly in atrial, but also in ventricular, and sinoatrial, atrioventricular node and Purkinje myocytes, correspondingly affect arrhythmic tendency. Additionally, mitochondrial SK channels may decrease mitochondrial Ca2+ overload and reactive oxygen species generation. SK channels show low voltage but marked Ca2+ dependences (EC50 ∼ 300-500 nM) reflecting their α-subunit calmodulin (CaM) binding domains, through which they may be activated by voltage-gated or ryanodine-receptor Ca2+ channel activity. SK function also depends upon complex trafficking and expression processes and associations with other ion channels or subunits from different SK subtypes. Atrial and ventricular clinical arrhythmogenesis may follow both increased or decreased SK expression through decreased or increased APD correspondingly accelerating and stabilizing re-entrant rotors or increasing incidences of triggered activity. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Ting Liu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Tao Li
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Cardiology, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Dandi Xu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Yan Wang
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Yafei Zhou
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Juyi Wan
- Department of Cardiovascular Surgery, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Christopher L.-H. Huang
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Physiological Laboratory and Department of Biochemistry, University of Cambridge, Cambridge CB2 3EG, UK
| | - Xiaoqiu Tan
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Cardiology, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Physiology, School of Basic Medical Sciences, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
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Polyák A, Topal L, Zombori-Tóth N, Tóth N, Prorok J, Kohajda Z, Déri S, Demeter-Haludka V, Hegyi P, Venglovecz V, Ágoston G, Husti Z, Gazdag P, Szlovák J, Árpádffy-Lovas T, Naveed M, Sarusi A, Jost N, Virág L, Nagy N, Baczkó I, Farkas AS, Varró A. Cardiac electrophysiological remodeling associated with enhanced arrhythmia susceptibility in a canine model of elite exercise. eLife 2023; 12:80710. [PMID: 36815557 PMCID: PMC10014074 DOI: 10.7554/elife.80710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 02/16/2023] [Indexed: 02/24/2023] Open
Abstract
The health benefits of regular physical exercise are well known. Even so, there is increasing evidence that the exercise regimes of elite athletes can evoke cardiac arrhythmias including ventricular fibrillation and even sudden cardiac death (SCD). The mechanism of exercise-induced arrhythmia and SCD is poorly understood. Here, we show that chronic training in a canine model (12 sedentary and 12 trained dogs) that mimics the regime of elite athletes induces electrophysiological remodeling (measured by ECG, patch-clamp, and immunocytochemical techniques) resulting in increases of both the trigger and the substrate for ventricular arrhythmias. Thus, 4 months sustained training lengthened ventricular repolarization (QTc: 237.1±3.4 ms vs. 213.6±2.8 ms, n=12; APD90: 472.8±29.6 ms vs. 370.1±32.7 ms, n=29 vs. 25), decreased transient outward potassium current (6.4±0.5 pA/pF vs. 8.8±0.9 pA/pF at 50 mV, n=54 vs. 42), and increased the short-term variability of repolarization (29.5±3.8 ms vs. 17.5±4.0 ms, n=27 vs. 18). Left ventricular fibrosis and HCN4 protein expression were also enhanced. These changes were associated with enhanced ectopic activity (number of escape beats from 0/hr to 29.7±20.3/hr) in vivo and arrhythmia susceptibility (elicited ventricular fibrillation: 3 of 10 sedentary dogs vs. 6 of 10 trained dogs). Our findings provide in vivo, cellular electrophysiological and molecular biological evidence for the enhanced susceptibility to ventricular arrhythmia in an experimental large animal model of endurance training.
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Affiliation(s)
- Alexandra Polyák
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | - Leila Topal
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | - Noémi Zombori-Tóth
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | - Noémi Tóth
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | - János Prorok
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
- ELKH-SZTE Research Group for Cardiovascular Pharmacology, Eötvös Loránd Research NetworkSzegedHungary
| | - Zsófia Kohajda
- ELKH-SZTE Research Group for Cardiovascular Pharmacology, Eötvös Loránd Research NetworkSzegedHungary
| | - Szilvia Déri
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | | | - Péter Hegyi
- Centre for Translational Medicine and Institute of Pancreatic Diseases, Semmelweis UniversityBudapestHungary
- Institute for Translational Medicine, Medical School, University of PécsPécsHungary
- Translational Pancreatology Research Group, Interdisciplinary Centre of Excellence for Research Development and Innovation, University of SzegedSzegedHungary
| | - Viktória Venglovecz
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | - Gergely Ágoston
- Institute of Family Medicine, University of SzegedSzegedHungary
| | - Zoltán Husti
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | - Péter Gazdag
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | - Jozefina Szlovák
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | - Tamás Árpádffy-Lovas
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | - Muhammad Naveed
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | - Annamária Sarusi
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
| | - Norbert Jost
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
- ELKH-SZTE Research Group for Cardiovascular Pharmacology, Eötvös Loránd Research NetworkSzegedHungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of SzegedSzegedHungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of SzegedSzegedHungary
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
- ELKH-SZTE Research Group for Cardiovascular Pharmacology, Eötvös Loránd Research NetworkSzegedHungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of SzegedSzegedHungary
| | - Attila S Farkas
- Department of Internal Medicine, Cardiology ward, University of SzegedSzegedHungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, University of SzegedSzegedHungary
- ELKH-SZTE Research Group for Cardiovascular Pharmacology, Eötvös Loránd Research NetworkSzegedHungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of SzegedSzegedHungary
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Kanaporis G, Blatter LA. Activation of small conductance Ca 2+ -activated K + channels suppresses Ca 2+ transient and action potential alternans in ventricular myocytes. J Physiol 2023; 601:51-67. [PMID: 36426548 PMCID: PMC9878619 DOI: 10.1113/jp283870] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 11/22/2022] [Indexed: 11/27/2022] Open
Abstract
At the cellular level, cardiac alternans is observed as beat-to-beat alternations in contraction strength, action potential (AP) morphology and Ca2+ transient (CaT) amplitude, and is a risk factor for cardiac arrhythmia. The (patho)physiological roles of small conductance Ca2+ -activated K+ (SK) channels in ventricles are poorly understood. We tested the hypothesis that in single rabbit ventricular myocytes pharmacological modulation of SK channels plays a causative role for the development of pacing-induced CaT and AP duration (APD) alternans. SK channel blockers (apamin, UCL1684) had only a minor effect on AP repolarization. However, SK channel activation by NS309 resulted in significant APD shortening, demonstrating that functional SK channels are well expressed in ventricular myocytes. The effects of NS309 were prevented or reversed by apamin and UCL1684, indicating that NS309 acted on SK channels. SK channel activation abolished or reduced the degree of pacing-induced CaT and APD alternans. Inhibition of KV 7.1 (with HMR1556) and KV 11.1 (with E4031) channels was used to mimic conditions of long QT syndromes type-1 and type-2, respectively. Both HMR1556 and E4031 enhanced CaT alternans that was prevented by SK channel activation. In AP voltage-clamped cells the SK channel activator had no effect on CaT alternans, confirming that suppression of CaT alternans was caused by APD shortening. APD shortening contributed to protection from alternans by lowering sarcoplasmic reticulum Ca2+ content and curtailing Ca2+ release. The data suggest that SK activation could be a potential intervention to avert development of alternans with important ramifications for arrhythmia prevention and therapy for patients with long QT syndrome. KEY POINTS: At the cellular level, cardiac alternans is observed as beat-to-beat alternations in contraction strength, action potential (AP) morphology and intracellular Ca2+ release amplitude, and is a risk factor for cardiac arrhythmia. The (patho)physiological roles of small conductance Ca2+ -activated K+ (SK) channels in ventricles are poorly understood. We investigated whether pharmacological modulation of SK channels affects the development of cardiac alternans in normal ventricular cells and in cells with drug-induced long QT syndrome (LQTS). While SK channel blockers have only a minor effect on AP morphology, their activation leads to AP shortening and abolishes or reduces the degree of pacing-induced Ca2+ and AP alternans. AP shortening contributed to protection against alternans by lowering sarcoplasmic reticulum Ca2+ content and curtailing Ca2+ release. The data suggest SK activation as a potential intervention to avert the development of alternans with important ramifications for arrhythmia prevention for patients with LQTS.
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Affiliation(s)
- Giedrius Kanaporis
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, Illinois, USA
| | - Lothar A Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, Illinois, USA
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5
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The Inhibition of the Small-Conductance Ca2+-Activated Potassium Channels Decreases the Sinus Node Pacemaking during Beta-Adrenergic Activation. Pharmaceuticals (Basel) 2022; 15:ph15030313. [PMID: 35337111 PMCID: PMC8948633 DOI: 10.3390/ph15030313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 02/24/2022] [Accepted: 03/01/2022] [Indexed: 11/17/2022] Open
Abstract
Sinus pacemaking is based on tight cooperation of intracellular Ca2+ handling and surface membrane ion channels. An important player of this synergistic crosstalk could be the small-conductance Ca2+-activated K+-channel (ISK) that could contribute to the sinoatrial node (SAN) pacemaking driven by the intracellular Ca2+ changes under normal conditions and beta-adrenergic activation, however, the exact role is not fully clarified. SK2 channel expression was verified by immunoblot technique in rabbit SAN cells. Ionic currents and action potentials were measured by patch-clamp technique. The ECG R-R intervals were obtained by Langendorff-perfusion method on a rabbit heart. Apamin, a selective inhibitor of SK channels, was used during the experiments. Patch-clamp experiments revealed an apamin-sensitive current. When 100 nM apamin was applied, we found no change in the action potential nor in the ECG R-R interval. In experiments where isoproterenol was employed, apamin increased the cycle length of the SAN action potentials and enhanced the ECG R-R interval. Apamin did not amplify the cycle length variability or ECG R-R interval variability. Our data indicate that ISK has no role under normal condition, however, it moderately contributes to the SAN automaticity under beta-adrenergic activation.
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6
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Yang B, Jiang Q, He S, Li T, Ou X, Chen T, Fan X, Jiang F, Zeng X, Huang CLH, Lei M, Tan X. Ventricular SK2 upregulation following angiotensin II challenge: Modulation by p21-activated kinase-1. J Mol Cell Cardiol 2022; 164:110-125. [PMID: 34774547 DOI: 10.1016/j.yjmcc.2021.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 10/15/2021] [Accepted: 11/03/2021] [Indexed: 12/11/2022]
Abstract
Effects of hypertrophic challenge on small-conductance, Ca2+-activated K+(SK2) channel expression were explored in intact murine hearts, isolated ventricular myocytes and neonatal rat cardiomyocytes (NRCMs). An established experimental platform applied angiotensin II (Ang II) challenge in the presence and absence of reduced p21-activated kinase (PAK1) (PAK1cko vs. PAK1f/f, or shRNA-PAK1 interference) expression. SK2 current contributions were detected through their sensitivity to apamin block. Ang II treatment increased such SK2 contributions to optically mapped action potential durations (APD80) and their heterogeneity, and to patch-clamp currents. Such changes were accentuated in PAK1cko compared to PAK1f/f, intact hearts and isolated cardiomyocytes. They paralleled increased histological and echocardiographic hypertrophic indices, reduced cardiac contractility, and increased SK2 protein expression, changes similarly greater with PAK1cko than PAK1f/f. In NRCMs, Ang II challenge replicated such increases in apamin-sensitive SK patch clamp currents as well as in real-time PCR and western blot measures of SK2 mRNA and protein expression and cell hypertrophy. Furthermore, the latter were enhanced by shRNA-PAK1 interference and mitigated by the PAK1 agonist FTY720. Increased CaMKII and CREB phosphorylation accompanied these effects. These were rescued by both FTY720 as well as the CaMKII inhibitor KN93, but not its inactive analogue KN92. Such CREB then specifically bound to the KCNN2 promoter sequence in luciferase assays. These findings associate Ang II induced hypertrophy with increased SK2 expression brought about by a CaMKII/CREB signaling convergent with the PAK1 pathway thence upregulating the KCNN2 promoter activity. SK2 may then influence cardiac electrophysiology under conditions of cardiac hypertrophy and failure.
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Affiliation(s)
- Binbin Yang
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Oral & Maxillofacial Reconstruction and Regeneration Laboratory, The Affiliated Stomatology Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Qin Jiang
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Shicheng He
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Tao Li
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Xianhong Ou
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Tangting Chen
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Xuehui Fan
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Feng Jiang
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Xiaorong Zeng
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Christopher L-H Huang
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Physiological Laboratory and Department of Biochemistry, University of Cambridge, Cambridge CB2 3EG, UK
| | - Ming Lei
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
| | - Xiaoqiu Tan
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, China; Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, China.
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Husti Z, Varró A, Baczkó I. Arrhythmogenic Remodeling in the Failing Heart. Cells 2021; 10:cells10113203. [PMID: 34831426 PMCID: PMC8623396 DOI: 10.3390/cells10113203] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 11/05/2021] [Accepted: 11/11/2021] [Indexed: 12/12/2022] Open
Abstract
Chronic heart failure is a clinical syndrome with multiple etiologies, associated with significant morbidity and mortality. Cardiac arrhythmias, including ventricular tachyarrhythmias and atrial fibrillation, are common in heart failure. A number of cardiac diseases including heart failure alter the expression and regulation of ion channels and transporters leading to arrhythmogenic electrical remodeling. Myocardial hypertrophy, fibrosis and scar formation are key elements of arrhythmogenic structural remodeling in heart failure. In this article, the mechanisms responsible for increased arrhythmia susceptibility as well as the underlying changes in ion channel, transporter expression and function as well as alterations in calcium handling in heart failure are discussed. Understanding the mechanisms of arrhythmogenic remodeling is key to improving arrhythmia management and the prevention of sudden cardiac death in patients with heart failure.
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Affiliation(s)
- Zoltán Husti
- Department of Pharmacology and Pharmacotherapy, University of Szeged, 6720 Szeged, Hungary; (Z.H.); (A.V.)
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, 6720 Szeged, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, University of Szeged, 6720 Szeged, Hungary; (Z.H.); (A.V.)
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, 6720 Szeged, Hungary
- ELKH-SZTE Research Group for Cardiovascular Pharmacology, Eötvös Loránd Research Network, 6720 Szeged, Hungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, 6720 Szeged, Hungary; (Z.H.); (A.V.)
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, 6720 Szeged, Hungary
- Correspondence:
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Verkerk AO, Marchal GA, Zegers JG, Kawasaki M, Driessen AHG, Remme CA, de Groot JR, Wilders R. Patch-Clamp Recordings of Action Potentials From Human Atrial Myocytes: Optimization Through Dynamic Clamp. Front Pharmacol 2021; 12:649414. [PMID: 33912059 PMCID: PMC8072333 DOI: 10.3389/fphar.2021.649414] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 02/18/2021] [Indexed: 11/29/2022] Open
Abstract
Introduction: Atrial fibrillation (AF) is the most common cardiac arrhythmia. Consequently, novel therapies are being developed. Ultimately, the impact of compounds on the action potential (AP) needs to be tested in freshly isolated human atrial myocytes. However, the frequent depolarized state of these cells upon isolation seriously hampers reliable AP recordings. Purpose: We assessed whether AP recordings from single human atrial myocytes could be improved by providing these cells with a proper inward rectifier K+ current (IK1), and consequently with a regular, non-depolarized resting membrane potential (RMP), through “dynamic clamp”. Methods: Single myocytes were enzymatically isolated from left atrial appendage tissue obtained from patients with paroxysmal AF undergoing minimally invasive surgical ablation. APs were elicited at 1 Hz and measured using perforated patch-clamp methodology, injecting a synthetic IK1 to generate a regular RMP. The injected IK1 had strong or moderate rectification. For comparison, a regular RMP was forced through injection of a constant outward current. A wide variety of ion channel blockers was tested to assess their modulatory effects on AP characteristics. Results: Without any current injection, RMPs ranged from −9.6 to −86.2 mV in 58 cells. In depolarized cells (RMP positive to −60 mV), RMP could be set at −80 mV using IK1 or constant current injection and APs could be evoked upon stimulation. AP duration differed significantly between current injection methods (p < 0.05) and was shortest with constant current injection and longest with injection of IK1 with strong rectification. With moderate rectification, AP duration at 90% repolarization (APD90) was similar to myocytes with regular non-depolarized RMP, suggesting that a synthetic IK1 with moderate rectification is the most appropriate for human atrial myocytes. Importantly, APs evoked using each injection method were still sensitive to all drugs tested (lidocaine, nifedipine, E-4031, low dose 4-aminopyridine, barium, and apamin), suggesting that the major ionic currents of the atrial cells remained functional. However, certain drug effects were quantitatively dependent on the current injection approach used. Conclusion: Injection of a synthetic IK1 with moderate rectification facilitates detailed AP measurements in human atrial myocytes. Therefore, dynamic clamp represents a promising tool for testing novel antiarrhythmic drugs.
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Affiliation(s)
- Arie O Verkerk
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands.,Department of Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Gerard A Marchal
- Department of Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Jan G Zegers
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Makiri Kawasaki
- Department of Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Antoine H G Driessen
- Department of Cardiothoracic Surgery, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Carol Ann Remme
- Department of Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Joris R de Groot
- Department of Cardiology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Ronald Wilders
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
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Takahashi M, Yokoshiki H, Mitsuyama H, Watanabe M, Temma T, Kamada R, Hagiwara H, Takahashi Y, Anzai T. SK channel blockade prevents hypoxia-induced ventricular arrhythmias through inhibition of Ca 2+/voltage uncoupling in hypertrophied hearts. Am J Physiol Heart Circ Physiol 2021; 320:H1456-H1469. [PMID: 33635168 DOI: 10.1152/ajpheart.00777.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 02/17/2021] [Indexed: 11/22/2022]
Abstract
Ventricular arrhythmia (VA) is the major cause of death in patients with left ventricular (LV) hypertrophy and/or acute ischemia. We hypothesized that apamin, a blocker of small-conductance Ca2+-activated K+ (SK) channels, alters Ca2+ handling and exhibits anti-arrhythmic effects in ventricular myocardium. Spontaneous hypertensive rats were used as a model of LV hypertrophy. A dual optical mapping of membrane potential (Vm) and intracellular calcium (Cai) was performed during global hypoxia (GH) on the Langendorff perfusion system. The majority of pacing-induced VAs during GH were initiated by triggered activities. Pretreatment of apamin (100 nmol/L) significantly inhibited the VA inducibility. Compared with SK channel blockers (apamin and NS8593), non-SK channel blockers (glibenclamide and 4-AP) did not exhibit anti-arrhythmic effects. Apamin prevented not only action potential duration (APD80) shortening (-18.7 [95% confidence interval, -35.2 to -6.05] ms vs. -2.75 [95% CI, -10.45 to 12.65] ms, P = 0.04) but also calcium transient duration (CaTD80) prolongation (14.52 [95% CI, 8.8-20.35] ms vs. 3.85 [95% CI, -3.3 to 12.1] ms, P < 0.01), thereby reducing CaTD80 - APD80, which denotes "Cai/Vm uncoupling" (33.22 [95% CI, 22-48.4] ms vs. 6.6 [95% CI, 0-14.85] ms, P < 0.01). The reduction of Cai/Vm uncoupling was attributable to less prolonged Ca2+ decay constant and suppression of diastolic Cai increase by apamin. The inhibition of VA inducibility and changes in APs/CaTs parameters caused by apamin was negated by the addition of ouabain, an inhibitor of Na+/K+ pump. Apamin attenuates APD shortening, Ca2+ handling abnormalities, and Cai/Vm uncoupling, leading to inhibition of VA occurrence in hypoxic hypertrophied hearts.NEW & NOTEWORTHY We demonstrated that hypoxia-induced ventricular arrhythmias were mainly initiated by Ca2+-loaded triggered activities in hypertrophied hearts. The blockades of small-conductance Ca2+-activated K+ channels, especially "apamin," showed anti-arrhythmic effects by alleviation of not only action potential duration shortening but also Ca2+ handling abnormalities, most notably the "Ca2+/voltage uncoupling."
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Affiliation(s)
- Masayuki Takahashi
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
- Department of Cardiovascular Medicine, National Hospital Organization Hokkaido Medical Center, Sapporo, Japan
| | - Hisashi Yokoshiki
- Department of Cardiovascular Medicine, Sapporo City General Hospital, Sapporo, Japan
| | - Hirofumi Mitsuyama
- Department of Cardiovascular Medicine, Hokkaido Ohno Memorial Hospital, Sapporo, Japan
| | - Masaya Watanabe
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Taro Temma
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Rui Kamada
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Hikaru Hagiwara
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Yumi Takahashi
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Toshihisa Anzai
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
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10
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Darkow E, Nguyen TT, Stolina M, Kari FA, Schmidt C, Wiedmann F, Baczkó I, Kohl P, Rajamani S, Ravens U, Peyronnet R. Small Conductance Ca 2 +-Activated K + (SK) Channel mRNA Expression in Human Atrial and Ventricular Tissue: Comparison Between Donor, Atrial Fibrillation and Heart Failure Tissue. Front Physiol 2021; 12:650964. [PMID: 33868017 PMCID: PMC8047327 DOI: 10.3389/fphys.2021.650964] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/01/2021] [Indexed: 12/25/2022] Open
Abstract
In search of more efficacious and safe pharmacological treatments for atrial fibrillation (AF), atria-selective antiarrhythmic agents have been promoted that target ion channels principally expressed in the atria. This concept allows one to engage antiarrhythmic effects in atria, but spares the ventricles from potentially proarrhythmic side effects. It has been suggested that cardiac small conductance Ca2+-activated K+ (SK) channels may represent an atria-selective target in mammals including humans. However, there are conflicting data concerning the expression of SK channels in different stages of AF, and recent findings suggest that SK channels are upregulated in ventricular myocardium when patients develop heart failure. To address this issue, RNA-sequencing was performed to compare expression levels of three SK channels (KCNN1, KCNN2, and KCNN3) in human atrial and ventricular tissue samples from transplant donor hearts (no cardiac disease), and patients with cardiac disease in sinus rhythm or with AF. In addition, for control purposes expression levels of several genes known to be either chamber-selective or differentially expressed in AF and heart failure were determined. In atria, as compared to ventricle from transplant donor hearts, we confirmed higher expression of KCNN1 and KCNA5, and lower expression of KCNJ2, whereas KCNN2 and KCNN3 were statistically not differentially expressed. Overall expression of KCNN1 was low compared to KCNN2 and KCNN3. Comparing atrial tissue from patients with AF to sinus rhythm samples we saw downregulation of KCNN2 in AF, as previously reported. When comparing ventricular tissue from heart failure patients to non-diseased samples, we found significantly increased ventricular expression of KCNN3 in heart failure, as previously published. The other channels showed no significant difference in expression in either disease. Our results add weight to the view that SK channels are not likely to be an atria-selective target, especially in failing human hearts, and modulators of these channels may prove to have less utility in treating AF than hoped. Whether targeting SK1 holds potential remains to be elucidated.
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Affiliation(s)
- Elisa Darkow
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany.,Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Freiburg im Breisgau, Germany.,Faculty of Biology, University of Freiburg, Freiburg im Breisgau, Germany
| | - Thong T Nguyen
- Genome Analysis Unit, Amgen Research, Amgen Inc., South San Francisco, CA, United States
| | - Marina Stolina
- Department of Cardiometabolic Disorders, Amgen Research, Amgen Inc., Thousand Oaks, CA, United States
| | - Fabian A Kari
- Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany.,Department of Cardiovascular Surgery, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany
| | - Constanze Schmidt
- Department of Cardiology, University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research) Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany
| | - Felix Wiedmann
- Department of Cardiology, University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research) Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany.,CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg im Breisgau, Germany
| | - Sridharan Rajamani
- Translational Safety and Bioanalytical Sciences, Amgen Research, Amgen Inc., South San Francisco, CA, United States
| | - Ursula Ravens
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
| | - Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
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11
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Zhang XD, Thai PN, Lieu DK, Chiamvimonvat N. Cardiac small-conductance calcium-activated potassium channels in health and disease. Pflugers Arch 2021; 473:477-489. [PMID: 33624131 PMCID: PMC7940285 DOI: 10.1007/s00424-021-02535-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 02/02/2021] [Accepted: 02/03/2021] [Indexed: 12/22/2022]
Abstract
Small-conductance Ca2+-activated K+ (SK, KCa2) channels are encoded by KCNN genes, including KCNN1, 2, and 3. The channels play critical roles in the regulation of cardiac excitability and are gated solely by beat-to-beat changes in intracellular Ca2+. The family of SK channels consists of three members with differential sensitivity to apamin. All three isoforms are expressed in human hearts. Studies over the past two decades have provided evidence to substantiate the pivotal roles of SK channels, not only in healthy heart but also with diseases including atrial fibrillation (AF), ventricular arrhythmia, and heart failure (HF). SK channels are prominently expressed in atrial myocytes and pacemaking cells, compared to ventricular cells. However, the channels are significantly upregulated in ventricular myocytes in HF and pulmonary veins in AF models. Interests in cardiac SK channels are further fueled by recent studies suggesting the possible roles of SK channels in human AF. Therefore, SK channel may represent a novel therapeutic target for atrial arrhythmias. Furthermore, SK channel function is significantly altered by human calmodulin (CaM) mutations, linked to life-threatening arrhythmia syndromes. The current review will summarize recent progress in our understanding of cardiac SK channels and the roles of SK channels in the heart in health and disease.
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Affiliation(s)
- Xiao-Dong Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA.
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA.
| | - Phung N Thai
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA
| | - Deborah K Lieu
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA
| | - Nipavan Chiamvimonvat
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA.
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA.
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, 95616, USA.
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12
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Wu AZ, Chen M, Yin D, Everett TH, Chen Z, Rubart M, Weiss JN, Qu Z, Chen PS. Sex-specific I KAS activation in rabbit ventricles with drug-induced QT prolongation. Heart Rhythm 2021; 18:88-97. [PMID: 32707174 PMCID: PMC7796981 DOI: 10.1016/j.hrthm.2020.07.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 06/30/2020] [Accepted: 07/13/2020] [Indexed: 01/23/2023]
Abstract
BACKGROUND Female sex is a known risk factor for drug-induced long QT syndrome (diLQTS). We recently demonstrated a sex difference in apamin-sensitive small-conductance Ca2+-activated K+ current (IKAS) activation during β-adrenergic stimulation. OBJECTIVE The purpose of this study was to test the hypothesis that there is a sex difference in IKAS in the rabbit models of diLQTS. METHODS We evaluated the sex difference in ventricular repolarization in 15 male and 22 female Langendorff-perfused rabbit hearts with optical mapping techniques during atrial pacing. HMR1556 (slowly activating delayed rectifier K+ current [IKs] blocker), E4031 (rapidly activating delayed rectifier K+ current [IKr] blocker) and sea anemone toxin (ATX-II, late Na+ current [INaL] activator) were used to simulate types 1-3 long QT syndrome, respectively. Apamin, an IKAS blocker, was then added to determine the magnitude of further QT prolongation. RESULTS HMR1556, E4031, and ATX-II led to the prolongation of action potential duration at 80% repolarization (APD80) in both male and female ventricles at pacing cycle lengths of 300-400 ms. Apamin further prolonged APD80 (pacing cycle length 350 ms) from 187.8±4.3 to 206.9±7.1 (P=.014) in HMR1556-treated, from 209.9±7.8 to 224.9±7.8 (P=.003) in E4031-treated, and from 174.3±3.3 to 188.1±3.0 (P=.0002) in ATX-II-treated female hearts. Apamin did not further prolong the APD80 in male hearts. The Cai transient duration (CaiTD) was significantly longer in diLQTS than baseline but without sex differences. Apamin did not change CaiTD. CONCLUSION We conclude that IKAS is abundantly increased in female but not in male ventricles with diLQTS. Increased IKAS helps preserve the repolarization reserve in female ventricles treated with IKs and IKr blockers or INaL activators.
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Affiliation(s)
- Adonis Z Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Michael Rubart
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine, Indianapolis, Indiana
| | - James N Weiss
- Departments of Medicine (Cardiology), Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | - Zhilin Qu
- Departments of Medicine (Cardiology), Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Cedars-Sinai Medical Center, Los Angeles, California.
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13
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Increased Ca 2+ content of the sarcoplasmic reticulum provides arrhythmogenic trigger source in swimming-induced rat athlete's heart model. Sci Rep 2020; 10:19596. [PMID: 33177643 PMCID: PMC7658201 DOI: 10.1038/s41598-020-76496-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 10/21/2020] [Indexed: 12/17/2022] Open
Abstract
Sudden cardiac death among top athletes is very rare, however, it is 2–4 times more frequent than in the age-matched control population. In the present study, the electrophysiological consequences of long-term exercise training were investigated on Ca2+ homeostasis and ventricular repolarization, together with the underlying alterations of ion channel expression, in a rat athlete's heart model. 12-week swimming exercise-trained and control Wistar rats were used. Electrophysiological data were obtained by using ECG, patch clamp and fluorescent optical measurements. Protein and mRNA levels were determined by the Western immunoblot and qRT-PCR techniques. Animals in the trained group exhibited significantly lower resting heart rate, higher incidence of extrasystoles and spontaneous Ca2+ release events. The Ca2+ content of the sarcoplasmic reticulum (SR) and the Ca2+ transient amplitude were significantly larger in the trained group. Intensive physical training is associated with elevated SR Ca2+ content, which could be an important part of physiological cardiac adaptation mechanism to training. However, it may also sensitize the heart for the development of spontaneous Ca2+ release and extrasystoles. Training-associated remodeling may promote elevated incidence of life threatening arrhythmias in top athletes.
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14
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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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15
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Baczkó I, Hornyik T, Brunner M, Koren G, Odening KE. Transgenic Rabbit Models in Proarrhythmia Research. Front Pharmacol 2020; 11:853. [PMID: 32581808 PMCID: PMC7291951 DOI: 10.3389/fphar.2020.00853] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 05/22/2020] [Indexed: 12/23/2022] Open
Abstract
Drug-induced proarrhythmia constitutes a potentially lethal side effect of various drugs. Most often, this proarrhythmia is mechanistically linked to the drug's potential to interact with repolarizing cardiac ion channels causing a prolongation of the QT interval in the ECG. Despite sophisticated screening approaches during drug development, reliable prediction of proarrhythmia remains very challenging. Although drug-induced long-QT-related proarrhythmia is often favored by conditions or diseases that impair the individual's repolarization reserve, most cellular, tissue, and whole animal model systems used for drug safety screening are based on normal, healthy models. In recent years, several transgenic rabbit models for different types of long QT syndromes (LQTS) with differences in the extent of impairment in repolarization reserve have been generated. These might be useful for screening/prediction of a drug's potential for long-QT-related proarrhythmia, particularly as different repolarizing cardiac ion channels are impaired in the different models. In this review, we summarize the electrophysiological characteristics of the available transgenic LQTS rabbit models, and the pharmacological proof-of-principle studies that have been performed with these models—highlighting the advantages and disadvantages of LQTS models for proarrhythmia research. In the end, we give an outlook on potential future directions and novel models.
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Affiliation(s)
- István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Tibor Hornyik
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.,Department of Cardiology and Angiology I, Heart Center, University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Brunner
- Department of Cardiology and Angiology I, Heart Center, University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Department of Cardiology and Medical Intensive Care, St. Josefskrankenhaus, Freiburg, Germany
| | - Gideon Koren
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, RI, United States
| | - Katja E Odening
- Department of Cardiology and Angiology I, Heart Center, University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Translational Cardiology, Department of Cardiology, Inselspital, Bern University Hospital, Bern, Switzerland.,Institute of Physiology, University of Bern, Bern, Switzerland
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16
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Yu Y, Luo D, Li Z, Zhang J, Li F, Qiao J, Yu F, Li M. Inhibitory Effects of Dronedarone on Small Conductance Calcium Activated Potassium Channels in Patients with Chronic Atrial Fibrillation: Comparison to Amiodarone. Med Sci Monit 2020; 26:e924215. [PMID: 32470968 PMCID: PMC7282350 DOI: 10.12659/msm.924215] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Dysfunction of small conductance calcium activated potassium (SK) channels plays a vital role in atrial arrhythmogenesis. Amiodarone and dronedarone are the most effective class III antiarrhythmic drugs. It is unclear whether the antiarrhythmic effect of amiodarone and dronedarone is related to SK channel inhibition. MATERIAL AND METHODS Tissue samples were obtained from the right atria of 46 patients with normal sinus rhythm and 39 patients with chronic atrial fibrillation. Isolated atrial myocytes were obtained by enzymatic dissociation. KCNN2 (SK2) channels were transiently expressed in human embryonic kidney (HEK)-293 cells. SK currents were recorded using whole-cell conventional patch clamp techniques. RESULTS Amiodarone and dronedarone showed a concentration-dependent inhibitory effect on SK currents (IKAS) in atrial myocytes from normal sinus rhythm patients and chronic atrial fibrillation patients. The suppressed efficacy of dronedarone and amiodarone on IKAS was greater in atrial myocytes from chronic atrial fibrillation patients than that from normal sinus rhythm patients. Furthermore, in patients with chronic atrial fibrillation, the IC₅₀ value was 2.42 µM with dronedarone and 8.03 µM with amiodarone. In HEK-293 cells with transiently transfected SK2 channels, both dronedarone and amiodarone had a dose-dependent inhibitory effect on IKAS. The IC₅₀ value was 1.7 µM with dronedarone and 7.2 µM with amiodarone in cells from patients with chronic atrial fibrillation. Compared to amiodarone, dronedarone is more efficacy to inhibit IKAS and could be a potential intervention for patients with chronic atrial fibrillation. CONCLUSIONS Dronedarone provides a great degree of IKAS inhibition in atrial myocytes from chronic atrial fibrillation than amiodarone. IKAS might be a potential target of amiodarone and dronedarone for the management of chronic atrial fibrillation.
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Affiliation(s)
- Yiyan Yu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland).,Department of Electrocardiography, The Affiliated Traditional Chinese Medicine Hospital of Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Dan Luo
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Zhiyi Li
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Juan Zhang
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Fang Li
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Jie Qiao
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Fengxu Yu
- Department of Cardiothoracic Surgery, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Miaoling Li
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiology Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland).,Department of Cardiothoracic Surgery, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China (mainland)
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17
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Kohajda Z, Loewe A, Tóth N, Varró A, Nagy N. The Cardiac Pacemaker Story-Fundamental Role of the Na +/Ca 2+ Exchanger in Spontaneous Automaticity. Front Pharmacol 2020; 11:516. [PMID: 32410993 PMCID: PMC7199655 DOI: 10.3389/fphar.2020.00516] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 04/01/2020] [Indexed: 01/01/2023] Open
Abstract
The electrophysiological mechanism of the sinus node automaticity was previously considered exclusively regulated by the so-called "funny current". However, parallel investigations increasingly emphasized the importance of the Ca2+-homeostasis and Na+/Ca2+ exchanger (NCX). Recently, increasing experimental evidence, as well as insight through mechanistic in silico modeling demonstrates the crucial role of the exchanger in sinus node pacemaking. NCX had a key role in the exciting story of discovery of sinus node pacemaking mechanisms, which recently settled with a consensus on the coupled-clock mechanism after decades of debate. This review focuses on the role of the Na+/Ca2+ exchanger from the early results and concepts to recent advances and attempts to give a balanced summary of the characteristics of the local, spontaneous, and rhythmic Ca2+ releases, the molecular control of the NCX and its role in the fight-or-flight response. Transgenic animal models and pharmacological manipulation of intracellular Ca2+ concentration and/or NCX demonstrate the pivotal function of the exchanger in sinus node automaticity. We also highlight where specific hypotheses regarding NCX function have been derived from computational modeling and require experimental validation. Nonselectivity of NCX inhibitors and the complex interplay of processes involved in Ca2+ handling render the design and interpretation of these experiments challenging.
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Affiliation(s)
- Zsófia Kohajda
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Axel Loewe
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Noémi Tóth
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - András Varró
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Norbert Nagy
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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18
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Kohajda Z, Tóth N, Szlovák J, Loewe A, Bitay G, Gazdag P, Prorok J, Jost N, Levijoki J, Pollesello P, Papp JG, Varró A, Nagy N. Novel Na +/Ca 2+ Exchanger Inhibitor ORM-10962 Supports Coupled Function of Funny-Current and Na +/Ca 2+ Exchanger in Pacemaking of Rabbit Sinus Node Tissue. Front Pharmacol 2020; 10:1632. [PMID: 32063850 PMCID: PMC7000430 DOI: 10.3389/fphar.2019.01632] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 12/13/2019] [Indexed: 01/01/2023] Open
Abstract
Background and Purpose The exact mechanism of spontaneous pacemaking is not fully understood. Recent results suggest tight cooperation between intracellular Ca2+ handling and sarcolemmal ion channels. An important player of this crosstalk is the Na+/Ca2+ exchanger (NCX), however, direct pharmacological evidence was unavailable so far because of the lack of a selective inhibitor. We investigated the role of the NCX current in pacemaking and analyzed the functional consequences of the If-NCX coupling by applying the novel selective NCX inhibitor ORM-10962 on the sinus node (SAN). Experimental Approach Currents were measured by patch-clamp, Ca2+-transients were monitored by fluorescent optical method in rabbit SAN cells. Action potentials (AP) were recorded from rabbit SAN tissue preparations. Mechanistic computational data were obtained using the Yaniv et al. SAN model. Key Results ORM-10962 (ORM) marginally reduced the SAN pacemaking cycle length with a marked increase in the diastolic Ca2+ level as well as the transient amplitude. The bradycardic effect of NCX inhibition was augmented when the funny-current (If) was previously inhibited and vice versa, the effect of If was augmented when the Ca2+ handling was suppressed. Conclusion and Implications We confirmed the contribution of the NCX current to cardiac pacemaking using a novel NCX inhibitor. Our experimental and modeling data support a close cooperation between If and NCX providing an important functional consequence: these currents together establish a strong depolarization capacity providing important safety factor for stable pacemaking. Thus, after individual inhibition of If or NCX, excessive bradycardia or instability cannot be expected because each of these currents may compensate for the reduction of the other providing safe and rhythmic SAN pacemaking.
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Affiliation(s)
- Zsófia Kohajda
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Noémi Tóth
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Jozefina Szlovák
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Axel Loewe
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Gergő Bitay
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Péter Gazdag
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - János Prorok
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Norbert Jost
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | | | | | - Julius Gy Papp
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - András Varró
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Norbert Nagy
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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Asfaw TN, Tyan L, Glukhov AV, Bondarenko VE. A compartmentalized mathematical model of mouse atrial myocytes. Am J Physiol Heart Circ Physiol 2020; 318:H485-H507. [PMID: 31951471 DOI: 10.1152/ajpheart.00460.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Various experimental mouse models are extensively used to research human diseases, including atrial fibrillation, the most common cardiac rhythm disorder. Despite this, there are no comprehensive mathematical models that describe the complex behavior of the action potential and [Ca2+]i transients in mouse atrial myocytes. Here, we develop a novel compartmentalized mathematical model of mouse atrial myocytes that combines the action potential, [Ca2+]i dynamics, and β-adrenergic signaling cascade for a subpopulation of right atrial myocytes with developed transverse-axial tubule system. The model consists of three compartments related to β-adrenergic signaling (caveolae, extracaveolae, and cytosol) and employs local control of Ca2+ release. It also simulates ionic mechanisms of action potential generation and describes atrial-specific Ca2+ handling as well as frequency dependences of the action potential and [Ca2+]i transients. The model showed that the T-type Ca2+ current significantly affects the later stage of the action potential, with little effect on [Ca2+]i transients. The block of the small-conductance Ca2+-activated K+ current leads to a prolongation of the action potential at high intracellular Ca2+. Simulation results obtained from the atrial model cells were compared with those from ventricular myocytes. The developed model represents a useful tool to study complex electrical properties in the mouse atria and could be applied to enhance the understanding of atrial physiology and arrhythmogenesis.NEW & NOTEWORTHY A new compartmentalized mathematical model of mouse right atrial myocytes was developed. The model simulated action potential and Ca2+ dynamics at baseline and after stimulation of the β-adrenergic signaling system. Simulations showed that the T-type Ca2+ current markedly prolonged the later stage of atrial action potential repolarization, with a minor effect on [Ca2+]i transients. The small-conductance Ca2+-activated K+ current block resulted in prolongation of the action potential only at the relatively high intracellular Ca2+.
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Affiliation(s)
- Tesfaye Negash Asfaw
- Department of Mathematics and Statistics, Georgia State University, Atlanta, Georgia
| | - Leonid Tyan
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin
| | - Alexey V Glukhov
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin
| | - Vladimir E Bondarenko
- Department of Mathematics and Statistics, Georgia State University, Atlanta, Georgia.,Neuroscience Institute, Georgia State University, Atlanta, Georgia
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20
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Yin D, Yang N, Tian Z, Wu AZ, Xu D, Chen M, Kamp NJ, Wang Z, Shen C, Chen Z, Lin SF, Rubart-von der Lohe M, Chen PS, Everett TH. Effects of ondansetron on apamin-sensitive small conductance calcium-activated potassium currents in pacing-induced failing rabbit hearts. Heart Rhythm 2019; 17:332-340. [PMID: 31513946 DOI: 10.1016/j.hrthm.2019.09.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Indexed: 12/16/2022]
Abstract
BACKGROUND Ondansetron, a widely prescribed antiemetic, has been implicated in drug-induced long QT syndrome. Recent patch clamp experiments have shown that ondansetron inhibits the apamin-sensitive small conductance calcium-activated potassium current (IKAS). OBJECTIVE The purpose of this study was to determine whether ondansetron causes action potential duration (APD) prolongation by IKAS inhibition. METHODS Optical mapping was performed in rabbit hearts with pacing-induced heart failure (HF) and in normal hearts before and after ondansetron (100 nM) infusion. APD at 80% repolarization (APD80) and arrhythmia inducibility were determined. Additional studies with ondansetron were performed in normal hearts perfused with hypokalemic Tyrode's (2.4 mM) solution before or after apamin administration. RESULTS The corrected QT interval in HF was 326 ms (95% confidence interval [CI] 306-347 ms) at baseline and 364 ms (95% CI 351-378 ms) after ondansetron infusion (P < .001). Ondansetron significantly prolonged APD80 in the HF group and promoted early afterdepolarizations, steepened the APD restitution curve, and increased ventricular vulnerability. Ventricular fibrillation was not inducible in HF ventricles at baseline, but after ondansetron infusion, ventricular fibrillation was induced in 5 of the 7 ventricles (P = .021). In hypokalemia, apamin prolonged APD80 from 163 ms (95% CI 146-180 ms) to 180 ms (95% CI 156-204 ms) (P = .018). Subsequent administration of ondansetron failed to further prolong APD80 (180 ms [95% CI 156-204 ms] vs 179 ms [95% CI 165-194 ms]; P = .789). The results were similar when ondansetron was administered first, followed by apamin. CONCLUSION Ondansetron is a specific IKAS blocker at therapeutic concentrations. Ondansetron may prolong the QT interval in HF by inhibiting small conductance calcium-activated potassium channels, which increases the vulnerability to ventricular arrhythmias.
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Affiliation(s)
- Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, the First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Na Yang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Gynecological and Obstetric Ultrasound, the First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Zhipeng Tian
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Central Hospital Affiliated to Shenyang Medical College, Shenyang, China
| | - Adonis Z Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Institute of Biomedical Engineering, National Chiao Tung University, Hsin-Chu, Taiwan
| | - Dongzhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Nicholas J Kamp
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Zhuo Wang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Changyu Shen
- Richard and Susan Smith Center for Outcomes Research in Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Institute of Biomedical Engineering, National Chiao Tung University, Hsin-Chu, Taiwan
| | | | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana.
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21
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Kamada R, Yokoshiki H, Mitsuyama H, Watanabe M, Mizukami K, Tenma T, Takahashi M, Takada S, Anzai T. Arrhythmogenic β-adrenergic signaling in cardiac hypertrophy: The role of small-conductance calcium-activated potassium channels via activation of CaMKII. Eur J Pharmacol 2019; 844:110-117. [DOI: 10.1016/j.ejphar.2018.12.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 11/29/2018] [Accepted: 12/06/2018] [Indexed: 10/27/2022]
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22
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Wan J, Chen M, Wang Z, Everett TH, Rubart-von der Lohe M, Shen C, Qu Z, Weiss JN, Boyden PA, Chen PS. Small-conductance calcium-activated potassium current modulates the ventricular escape rhythm in normal rabbit hearts. Heart Rhythm 2018; 16:615-623. [PMID: 30445170 DOI: 10.1016/j.hrthm.2018.10.033] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Indexed: 10/27/2022]
Abstract
BACKGROUND The apamin-sensitive small-conductance calcium-activated K (SK) current IKAS modulates automaticity of the sinus node. IKAS blockade by apamin causes sinus bradycardia. OBJECTIVE The purpose of this study was to test the hypothesis that IKAS modulates ventricular automaticity. METHODS We tested the effects of apamin (100 nM) on ventricular escape rhythms in Langendorff-perfused rabbit ventricles with atrioventricular block (protocol 1) and on recorded transmembrane action potential of pseudotendons of superfused right ventricular endocardial preparations (protocol 2). RESULTS All preparations exhibited spontaneous ventricular escape rhythms. In protocol 1, apamin decreased the atrial rate from 186.2 ± 18.0 bpm to 163.8 ± 18.7 bpm (N = 6; P = .006) but accelerated the ventricular escape rate from 51.5 ± 10.7 bpm to 98.2 ± 25.4 bpm (P = .031). Three preparations exhibited bursts of nonsustained ventricular tachycardia and pauses, resulting in repeated burst termination pattern. In protocol 2, apamin increased the ventricular escape rate from 70.2 ± 13.1 bpm to 110.1 ± 2.2 bpm (P = .035). Spontaneous phase 4 depolarization was recorded from the pseudotendons in 6 of 10 preparations at baseline and in 3 in the presence of apamin. There were no changes of phase 4 slope (18.37 ± 3.55 mV/s vs 18.93 ± 3.26 mV/s, N = 3; P = .231, ), but the threshold of phase 0 activation (mV) reduced from -67.97 ± 1.53 to -75.26 ± 0.28 (P = .034). Addition of JTV-519, a ryanodine receptor 2 stabilizer, in 5 preparations reduced escape rate back to baseline. CONCLUSION Contrary to its bradycardic effect in the sinus node, IKAS blockade by apamin accelerates ventricular automaticity and causes repeated nonsustained ventricular tachycardia in normal ventricles. ryanodine receptor 2 blockade reversed the apamin effects on ventricular automaticity.
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Affiliation(s)
- Juyi Wan
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiothoracic Surgery, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan Province, China
| | - Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Zhuo Wang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | | | - Changyu Shen
- Richard and Susan Smith Center for Outcomes Research in Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Zhilin Qu
- Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | - James N Weiss
- Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | | | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana.
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23
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Tenma T, Mitsuyama H, Watanabe M, Kakutani N, Otsuka Y, Mizukami K, Kamada R, Takahashi M, Takada S, Sabe H, Tsutsui H, Yokoshiki H. Small-conductance Ca2+-activated K+ channel activation deteriorates hypoxic ventricular arrhythmias via CaMKII in cardiac hypertrophy. Am J Physiol Heart Circ Physiol 2018; 315:H262-H272. [DOI: 10.1152/ajpheart.00636.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The molecular and electrophysiological mechanisms of acute ischemic ventricular arrhythmias in hypertrophied hearts are not well known. We hypothesized that small-conductance Ca2+-activated K+ (SK) channels are activated during hypoxia via the Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent pathway. We used normotensive Wistar-Kyoto (WKY) rats and spontaneous hypertensive rats (SHRs) as a model of cardiac hypertrophy. The inhibitory effects of SK channels and ATP-sensitive K+ channels on electrophysiological changes and genesis of arrhythmias during simulated global hypoxia (GH) were evaluated. Hypoxia-induced abbreviation of action potential duration (APD) occurred earlier in ventricles from SHRs versus. WKY rats. Apamin, a SK channel blocker, prevented this abbreviation in SHRs in both the early and delayed phase of GH, whereas in WKY rats only the delayed phase was prevented. In contrast, SHRs were less sensitive to glibenclamide, a ATP-sensitive K+ channel blocker, which inhibited the APD abbreviation in both phases of GH in WKY rats. SK channel blockers (apamin and UCL-1684) reduced the incidence of hypoxia-induced sustained ventricular arrhythmias in SHRs but not in WKY rats. Among three SK channel isoforms, SK2 channels were directly coimmunoprecipitated with CaMKII phosphorylated at Thr286 (p-CaMKII). We conclude that activation of SK channels leads to the APD abbreviation and sustained ventricular arrhythmias during simulated hypoxia, especially in hypertrophied hearts. This mechanism may result from p-CaMKII-bound SK2 channels and reveal new molecular targets to prevent lethal ventricular arrhythmias during acute hypoxia in cardiac hypertrophy. NEW & NOTEWORTHY We now show a new pathophysiological role of small-conductance Ca2+-activated K+ channels, which shorten the action potential duration and induce ventricular arrhythmias during hypoxia. We also demonstrate that small-conductance Ca2+-activated K+ channels interact with phosphorylated Ca2+/calmodulin-dependent protein kinase II at Thr286 in hypertrophied hearts.
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Affiliation(s)
- Taro Tenma
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Hirofumi Mitsuyama
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Masaya Watanabe
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Naoya Kakutani
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Yutaro Otsuka
- Department of Molecular Biology, Graduate School of Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Kazuya Mizukami
- Department of Cardiovascular Medicine, National Hospital Organization Hokkaido Medical Center, Sapporo, Hokkaido, Japan
| | - Rui Kamada
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Masayuki Takahashi
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Shingo Takada
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Hisataka Sabe
- Department of Molecular Biology, Graduate School of Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Hiroyuki Tsutsui
- Department of Cardiovascular Medicine, Kyusyu University Graduate School of Medicine, Fukuoka, Kyusyu, Japan
| | - Hisashi Yokoshiki
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
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Fan X, Yu Y, Lan H, Ou X, Yang L, Li T, Cao J, Zeng X, Li M. Ca2+/Calmodulin-Dependent Protein Kinase II (CaMKII) Increases Small-Conductance Ca2+-Activated K+ Current in Patients with Chronic Atrial Fibrillation. Med Sci Monit 2018; 24:3011-3023. [PMID: 29737974 PMCID: PMC5963316 DOI: 10.12659/msm.909684] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Background Increased small-conductance Ca2+-activated K+ current (SK), abnormal intracellular Ca2+ handling, and enhanced expression and activity of Ca2+/calmodulin-dependent protein kinase II (CaMKII) have been found in clinical and/or experimental models of atrial fibrillation (AF), but the cumulative effect of these phenomena and their mechanisms in AF are still unclear. This study aimed to test the hypothesis that CaMKII increases SK current in human chronic AF. Material/Methods Right atrial appendage tissues from patients with either sinus rhythm (SR) or AF and neonatal rat atrial myocytes were used. Patch clamp, qRT-PCR, and Western blotting techniques were used to perform the study. Results Compared to SR, the apamin-sensitive SK current (IKAS) was significantly increased, but the mRNA and protein levels of SK1, SK2, and SK3 were significantly decreased. In AF, the steady-state Ca2+ response curve of IKAS was shifted leftward and the [Ca2+]i level was significantly increased. CaMKII inhibitors (KN-93 or autocamtide-2-related inhibitory peptide (AIP)) reduced the IKAS in both AF and SR. The inhibitory effect of KN-93 or AIP on IKAS was greater in AF than in SR. The expression levels of calmodulin, CaMKII, and autophosphorylated CaMKII at Thr287 (but not at Thr286) were significantly increased in AF. Furthermore, KN-93 inhibited the expression of (Thr287)p-CaMKII and SK2 in neonatal rat atrial myocytes. Conclusions SK current is increased via the enhanced activation of CaMKII in patients with AF. This finding may explain the difference between SK current and channels expression in AF, and thus may provide a therapeutic target for AF.
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Affiliation(s)
- Xuehui Fan
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Yiyan Yu
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Huan Lan
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Xianhong Ou
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Lijie Yang
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Tao Li
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Jiming Cao
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Xiaorong Zeng
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Miaoling Li
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
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Comerma-Steffensen SG, Carvacho I, Hedegaard ER, Simonsen U. Small and Intermediate Calcium-Activated Potassium Channel Openers Improve Rat Endothelial and Erectile Function. Front Pharmacol 2017; 8:660. [PMID: 28993731 PMCID: PMC5619997 DOI: 10.3389/fphar.2017.00660] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 09/05/2017] [Indexed: 12/13/2022] Open
Abstract
Modulation of endothelial calcium-activated potassium (KCa) channels has been proposed as an approach to restore endothelial function. The present study investigated whether novel openers of KCa channels with small (KCa2.x) and intermediate (KCa3.1) conductance, NS309 and NS4591, improve endothelium-dependent relaxation and erectile function. Rat corpus cavernosum (CC) strips were mounted for isometric tension recording and processed for immunoblotting. Mean arterial pressure (MAP), intracavernosal pressure (ICP), and electrocardiographic (ECG) measurements were conducted in anesthetized rats. Immunoblotting revealed the presence of KCa2.3 and large KCa conductance (KCa1.1) channels in the corpus cavernosum. NS309 and NS4591 increased current in CC endothelial cells in whole cell patch clamp experiments. Relaxation induced by NS309 (<1 μM) was inhibited by endothelial cell removal and high extracellular potassium. An inhibitor of nitric oxide (NO) synthase, and blockers of KCa2.x and KCa1.1 channels, apamin and iberiotoxin also inhibited NS309 relaxation. Incubation with NS309 (0.5 μM) markedly enhanced acetylcholine relaxation. Basal erectile function (ICP/MAP) increased during administration of NS309. Increases in ICP/MAP after cavernous nerve stimulation with NS309 were unchanged, whereas NS4591 significantly improved erectile function. Administration of NS309 and NS4591 caused small changes in the electrocardiogram, but neither arrhythmic events nor prolongation of the QTc interval were observed. The present study suggests that openers of KCa2.x and KCa3.1 channels improve endothelial and erectile function. The effects of NS309 and NS4591 on heart rate and ECG are small, but will require additional safety studies before evaluating whether activation of KCa2.3 channels has a potential for treatment of erectile dysfunction.
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Affiliation(s)
- Simon G. Comerma-Steffensen
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus UniversityAarhus, Denmark
- Animal Physiology, Department of Biomedical Sciences, Veterinary Sciences Faculty, Central University of VenezuelaMaracay, Venezuela
| | - Ingrid Carvacho
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus UniversityAarhus, Denmark
- Department of Biology and Chemistry, Faculty of Basic Sciences, Universidad Católica del MauleTalca, Chile
| | - Elise R. Hedegaard
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus UniversityAarhus, Denmark
| | - Ulf Simonsen
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus UniversityAarhus, Denmark
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Harmer SC, Tinker A. The impact of recent advances in genetics in understanding disease mechanisms underlying the long QT syndromes. Biol Chem 2017; 397:679-93. [PMID: 26910742 DOI: 10.1515/hsz-2015-0306] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 02/18/2016] [Indexed: 11/15/2022]
Abstract
Long QT syndrome refers to a characteristic abnormality of the electrocardiogram and it is associated with a form of ventricular tachycardia known as torsade-de-pointes and sudden arrhythmic death. It can occur as part of a hereditary syndrome or can be acquired usually because of drug administration. Here we review recent genetic, molecular and cellular discoveries and outline how they have furthered our understanding of this disease. Specifically we focus on compound mutations, genome wide association studies of QT interval, modifier genes and the therapeutic implications of this recent work.
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Reher TA, Wang Z, Hsueh CH, Chang PC, Pan Z, Kumar M, Patel J, Tan J, Shen C, Chen Z, Fishbein MC, Rubart M, Boyden P, Chen PS. Small-Conductance Calcium-Activated Potassium Current in Normal Rabbit Cardiac Purkinje Cells. J Am Heart Assoc 2017; 6:JAHA.117.005471. [PMID: 28550095 PMCID: PMC5669169 DOI: 10.1161/jaha.117.005471] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Background Purkinje cells (PCs) are important in cardiac arrhythmogenesis. Whether small‐conductance calcium‐activated potassium (SK) channels are present in PCs remains unclear. We tested the hypotheses that subtype 2 SK (SK2) channel proteins and apamin‐sensitive SK currents are abundantly present in PCs. Methods and Results We studied 25 normal rabbit ventricles, including 13 patch‐clamp studies, 4 for Western blotting, and 8 for immunohistochemical staining. Transmembrane action potentials were recorded in current‐clamp mode using the perforated‐patch technique. For PCs, the apamin (100 nmol/L) significantly prolonged action potential duration measured to 80% repolarization by an average of 10.4 ms (95% CI, 0.11–20.72) (n=9, P=0.047). Voltage‐clamp study showed that apamin‐sensitive SK current density was significantly larger in PCs compared with ventricular myocytes at potentials ≥0 mV. Western blotting of SK2 expression showed that the SK2 protein expression in the midmyocardium was 58% (P=0.028) and the epicardium was 50% (P=0.018) of that in the pseudotendons. Immunostaining of SK2 protein showed that PCs stained stronger than ventricular myocytes. Confocal microscope study showed SK2 protein was distributed to the periphery of the PCs. Conclusions SK2 proteins are more abundantly present in the PCs than in the ventricular myocytes of normal rabbit ventricles. Apamin‐sensitive SK current is important in ventricular repolarization of normal PCs.
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Affiliation(s)
- Thomas A Reher
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Zhuo Wang
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN.,Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Chia-Hsiang Hsueh
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Po-Cheng Chang
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Zhenwei Pan
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Mohineesh Kumar
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Jheel Patel
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Jian Tan
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Changyu Shen
- Smith Center for Outcomes Research in Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Zhenhui Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
| | - Michael C Fishbein
- Department of Pathology and Laboratory Medicine, UCLA Medical Center, Los Angeles, CA
| | - Michael Rubart
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN
| | - Penelope Boyden
- Department of Pharmacology, Columbia University, New York, NY
| | - Peng-Sheng Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indianapolis, IN
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Hundahl LA, Tfelt-Hansen J, Jespersen T. Rat Models of Ventricular Fibrillation Following Acute Myocardial Infarction. J Cardiovasc Pharmacol Ther 2017; 22:514-528. [PMID: 28381093 DOI: 10.1177/1074248417702894] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A number of animal models have been designed in order to unravel the underlying mechanisms of acute ischemia-induced arrhythmias and to test compounds and interventions for antiarrhythmic therapy. This is important as acute myocardial infarction (AMI) continues to be the major cause of sudden cardiac death, and we are yet to discover safe and effective treatments of the lethal arrhythmias occurring in the acute setting. Animal models therefore continue to be relevant for our understanding and treatment of acute ischemic arrhythmias. This review discusses the applicability of the rat as a model for ventricular arrhythmias occurring during the acute phase of AMI. It provides a description of models developed, advantages and disadvantages of rats, as well as an overview of the most important interventions investigated and the relevance for human pathophysiology.
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Affiliation(s)
- Laura A Hundahl
- 1 Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jacob Tfelt-Hansen
- 2 Department of Cardiology, Heart Centre, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Thomas Jespersen
- 1 Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Pharmacological blockade of small conductance Ca 2+-activated K + channels by ICA reduces arrhythmic load in rats with acute myocardial infarction. Pflugers Arch 2017; 469:739-750. [PMID: 28285409 DOI: 10.1007/s00424-017-1962-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 02/07/2017] [Accepted: 02/20/2017] [Indexed: 01/02/2023]
Abstract
Acute myocardial infarction (AMI) with development of ventricular fibrillation (VF) is a common cause of sudden cardiac death (SCD). At present, no pharmacological treatment has successfully been able to prevent VF in the acute stage of AMI. This study investigates the antiarrhythmic effect of inhibiting small conductance Ca2+-activated K+ (SK) channels using the pore blocker N-(pyridin-2-yl)-4-(pyridin-2-yl)thiazol-2-amine (ICA) in AMI rats. Acute coronary ligation was performed in 26 anesthetized rats, and ECG, monophasic action potentials (MAPs), and ventricular effective refractory period (vERP) were recorded. Rats were randomized into four groups: (i) 3 mg/kg i.v. ICA with AMI (AMI-ICA-group, n = 9), (ii) vehicle with AMI (AMI-vehicle-group, n = 9), (iii) vehicle with sham operation (sham-vehicle-group, n = 8), and (iv) 3 mg/kg i.v. ICA with sham operation (sham-ICA-group, n = 6). At the end of experiments, hearts were stained for the non-perfused area at risk (AAR). AMI resulted in the development of ventricular tachycardia (VT) in all AMI-vehicle and AMI-ICA rats; however, ICA significantly decreased VT duration. VF occurred in 44% of AMI-vehicle rats but not in AMI-ICA rats. Monophasic action potential duration at 80% repolarization (MAPD80) in the ischemic area decreased rapidly in both AMI-vehicle and AMI-ICA rats. However, 5 min after occlusion, MAPD80 returned to baseline in AMI-ICA rats but not in AMI-vehicle rats. The vERP was prolonged in the AMI-ICA group compared to AMI-vehicle after ligation. AAR was similar between the AMI-vehicle group and the AMI-ICA group. In rats with AMI, ICA reduces the burden of arrhythmia.
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Abstract
Long QT syndrome (LQTS) exhibits great phenotype variability among family members carrying the same mutation, which can be partially attributed to genetic factors. We functionally analyzed the KCNH2 (encoding for Kv11.1 or hERG channels) and TBX20 (encoding for the transcription factor Tbx20) variants found by next-generation sequencing in two siblings with LQTS in a Spanish family of African ancestry. Affected relatives harbor a heterozygous mutation in KCNH2 that encodes for p.T152HfsX180 Kv11.1 (hERG). This peptide, by itself, failed to generate any current when transfected into Chinese hamster ovary (CHO) cells but, surprisingly, exerted "chaperone-like" effects over native hERG channels in both CHO cells and mouse atrial-derived HL-1 cells. Therefore, heterozygous transfection of native (WT) and p.T152HfsX180 hERG channels generated a current that was indistinguishable from that generated by WT channels alone. Some affected relatives also harbor the p.R311C mutation in Tbx20. In human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), Tbx20 enhanced human KCNH2 gene expression and hERG currents (IhERG) and shortened action-potential duration (APD). However, Tbx20 did not modify the expression or activity of any other channel involved in ventricular repolarization. Conversely, p.R311C Tbx20 did not increase KCNH2 expression in hiPSC-CMs, which led to decreased IhERG and increased APD. Our results suggest that Tbx20 controls the expression of hERG channels responsible for the rapid component of the delayed rectifier current. On the contrary, p.R311C Tbx20 specifically disables the Tbx20 protranscriptional activity over KCNH2 Therefore, TBX20 can be considered a KCNH2-modifying gene.
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Abstract
Despite the epidemiological scale of atrial fibrillation, current treatment strategies are of limited efficacy and safety. Ideally, novel drugs should specifically correct the pathophysiological mechanisms responsible for atrial fibrillation with no other cardiac or extracardiac actions. Atrial-selective drugs are directed toward cellular targets with sufficiently different characteristics in atria and ventricles to modify only atrial function. Several potassium (K+) channels with either predominant expression in atria or distinct electrophysiological properties in atria and ventricles can serve as atrial-selective drug targets. These channels include the ultra-rapidly activating, delayed outward-rectifying Kv1.5 channel conducting IKur, the acetylcholine-activated inward-rectifying Kir3.1/Kir3.4 channel conducting IK,ACh, the Ca2+-activated K+ channels of small conductance (SK) conducting ISK, and the two pore domain K+ (K2P) channels TWIK-1, TASK-1 and TASK-3 that are responsible for voltage-independent background currents ITWIK-1, ITASK-1, and ITASK-3. Here, we briefly review the characteristics of these K+ channels and their roles in atrial fibrillation. The antiarrhythmic potential of drugs targeting the described channels is discussed as well as their putative value in treatment of atrial fibrillation.
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Affiliation(s)
- Ursula Ravens
- Institute of Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg, Germany; Department of Cardiology and Angiology I, University Heart Center Freiburg-Bad Krozingen, Freiburg, Germany; Department of Physiology, Medical Faculty Carl-Gustav-Carus, TU Dresden, Dresden, Germany.
| | - Katja E Odening
- Institute of Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg, Germany; Department of Cardiology and Angiology I, University Heart Center Freiburg-Bad Krozingen, Freiburg, Germany
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Abstract
Small-conductance Ca2+-activated potassium (SK) channels are relative newcomers within the field of cardiac electrophysiology. In recent years, an increased focus has been given to these channels because they might constitute a relatively atrial-selective target. This review will give a general introduction to SK channels followed by their proposed function in the heart under normal and pathophysiological conditions. It is revealed how antiarrhythmic effects can be obtained by SK channel inhibition in a number of species in situations of atrial fibrillation. On the contrary, the beneficial effects of SK channel inhibition in situations of heart failure are questionable and still needs investigation. The understanding of cardiac SK channels is rapidly increasing these years, and it is hoped that this will clarify whether SK channel inhibition has potential as a new anti–atrial fibrillation principle.
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Yu CC, Chia-Ti T, Chen PL, Wu CK, Chiu FC, Chiang FT, Chen PS, Chen CL, Lin LY, Juang JM, Ho LT, Lai LP, Yang WS, Lin JL. KCNN2 polymorphisms and cardiac tachyarrhythmias. Medicine (Baltimore) 2016; 95:e4312. [PMID: 27442679 PMCID: PMC5265796 DOI: 10.1097/md.0000000000004312] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Potassium calcium-activated channel subfamily N member 2 (KCNN2) encodes an integral membrane protein that forms small-conductance calcium-activated potassium (SK) channels. Recent studies in animal models show that SK channels are important in atrial and ventricular repolarization and arrhythmogenesis. However, the importance of SK channels in human arrhythmia remains unclear. The purpose of the present study was to test the association between genetic polymorphism of the SK2 channel and the occurrence of cardiac tachyarrhythmias in humans. We enrolled 327 Han Chinese, including 72 with clinically significant ventricular tachyarrhythmias (VTa) who had a history of aborted sudden cardiac death (SCD) or unexplained syncope, 98 with a history of atrial fibrillation (AF), and 144 normal controls. We genotyped 12 representative tag single nucleotide polymorphisms (SNPs) across a 141-kb genetic region containing the KCNN2 gene; these captured the full haplotype information. The rs13184658 and rs10076582 variants of KCNN2 were associated with VTa in both the additive and dominant models (odds ratio [OR] 2.89, 95% confidence interval [CI] = 1.505-5.545, P = 0.001; and OR 2.55, 95% CI = 1.428-4.566, P = 0.002, respectively). After adjustment for potential risk factors, the association remained significant. The population attributable risks of these 2 variants of VTa were 17.3% and 10.6%, respectively. One variant (rs13184658) showed weak but significant association with AF in a dominant model (OR 1.91, CI = 1.025-3.570], P = 0.042). There was a significant association between the KCNN2 variants and clinically significant VTa. These findings suggest an association between KCNN2 and VTa; it also appears that KCNN2 variants may be adjunctive markers for risk stratification in patients susceptible to SCD.
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Affiliation(s)
- Chih-Chieh Yu
- Department of Internal Medicine, National Taiwan University Hospital
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University
| | - Tsai Chia-Ti
- Department of Internal Medicine, National Taiwan University Hospital
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University
| | - Pei-Lung Chen
- Department of Internal Medicine, National Taiwan University Hospital
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University
- Department of Medical Genetics, National Taiwan University Hospital
- Graduate Institute of Medical Genomics and Proteomics, College of Medicine
- Research Center for Developmental Biology and Regenerative Medicine, National Taiwan University, Taipei
| | - Cho-Kai Wu
- Department of Internal Medicine, National Taiwan University Hospital
| | - Fu-Chun Chiu
- Department of Internal Medicine, National Taiwan University Hospital, Yun-Lin Branch, Yun-Lin, Taiwan
| | - Fu-Tien Chiang
- Department of Internal Medicine, National Taiwan University Hospital
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Chi-Ling Chen
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University
- Graduate Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan
| | - Lian-Yu Lin
- Department of Internal Medicine, National Taiwan University Hospital
| | - Jyh-Ming Juang
- Department of Internal Medicine, National Taiwan University Hospital
| | - Li-Ting Ho
- Department of Internal Medicine, National Taiwan University Hospital
| | - Ling-Ping Lai
- Department of Internal Medicine, National Taiwan University Hospital
| | - Wei-Shiung Yang
- Department of Internal Medicine, National Taiwan University Hospital
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University
- Graduate Institute of Medical Genomics and Proteomics, College of Medicine
- Research Center for Developmental Biology and Regenerative Medicine, National Taiwan University, Taipei
- Correspondence: Jiunn-Lee Lin, Wei-Shiung Yang, Department of Internal Medicine, National Taiwan University Hospital, No. 7, Chung San South Road, Taipei City 100, Taiwan (R.O.C.) (e-mail: , )
| | - Jiunn-Lee Lin
- Department of Internal Medicine, National Taiwan University Hospital
- Correspondence: Jiunn-Lee Lin, Wei-Shiung Yang, Department of Internal Medicine, National Taiwan University Hospital, No. 7, Chung San South Road, Taipei City 100, Taiwan (R.O.C.) (e-mail: , )
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Baczkó I, Jost N, Virág L, Bősze Z, Varró A. Rabbit models as tools for preclinical cardiac electrophysiological safety testing: Importance of repolarization reserve. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 121:157-68. [PMID: 27208697 DOI: 10.1016/j.pbiomolbio.2016.05.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 05/01/2016] [Indexed: 01/26/2023]
Abstract
It is essential to more reliably assess the pro-arrhythmic liability of compounds in development. Current guidelines for pre-clinical and clinical testing of drug candidates advocate the use of healthy animals/tissues and healthy individuals and focus on the test compound's ability to block the hERG current and prolong cardiac ventricular repolarization. Also, pre-clinical safety tests utilize several species commonly used in cardiac electrophysiological studies. In this review, important species differences in cardiac ventricular repolarizing ion currents are considered, followed by the discussion on electrical remodeling associated with chronic cardiovascular diseases that leads to altered ion channel and transporter expression and densities in pathological settings. We argue that the choice of species strongly influences experimental outcome and extrapolation of results to human clinical settings. We suggest that based on cardiac cellular electrophysiology, the rabbit is a useful species for pharmacological pro-arrhythmic investigations. In addition to healthy animals and tissues, the use of animal models (e.g. those with impaired repolarization reserve) is suggested that more closely resemble subsets of patients exhibiting increased vulnerability towards the development of ventricular arrhythmias and sudden cardiac death.
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Affiliation(s)
- István Baczkó
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary.
| | - Norbert Jost
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Dóm tér 12., 6720 Szeged, Hungary
| | - László Virág
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary
| | - Zsuzsanna Bősze
- Rabbit Genome and Biomodel Group, NARIC-Agricultural Biotechnology Institute, 2100 Gödöllő, Hungary
| | - András Varró
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Dóm tér 12., 6720 Szeged, Hungary
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Horváth B, Váczi K, Hegyi B, Gönczi M, Dienes B, Kistamás K, Bányász T, Magyar J, Baczkó I, Varró A, Seprényi G, Csernoch L, Nánási PP, Szentandrássy N. Sarcolemmal Ca(2+)-entry through L-type Ca(2+) channels controls the profile of Ca(2+)-activated Cl(-) current in canine ventricular myocytes. J Mol Cell Cardiol 2016; 97:125-39. [PMID: 27189885 DOI: 10.1016/j.yjmcc.2016.05.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 04/20/2016] [Accepted: 05/10/2016] [Indexed: 12/15/2022]
Abstract
Ca(2+)-activated Cl(-) current (ICl(Ca)) mediated by TMEM16A and/or Bestrophin-3 may contribute to cardiac arrhythmias. The true profile of ICl(Ca) during an actual ventricular action potential (AP), however, is poorly understood. We aimed to study the profile of ICl(Ca) systematically under physiological conditions (normal Ca(2+) cycling and AP voltage-clamp) as well as in conditions designed to change [Ca(2+)]i. The expression of TMEM16A and/or Bestrophin-3 in canine and human left ventricular myocytes was examined. The possible spatial distribution of these proteins and their co-localization with Cav1.2 was also studied. The profile of ICl(Ca), identified as a 9-anthracene carboxylic acid-sensitive current under AP voltage-clamp conditions, contained an early fast outward and a late inward component, overlapping early and terminal repolarizations, respectively. Both components were moderately reduced by ryanodine, while fully abolished by BAPTA, but not EGTA. [Ca(2+)]i was monitored using Fura-2-AM. Setting [Ca(2+)]i to the systolic level measured in the bulk cytoplasm (1.1μM) decreased ICl(Ca), while application of Bay K8644, isoproterenol, and faster stimulation rates increased the amplitude of ICl(Ca). Ca(2+)-entry through L-type Ca(2+) channels was essential for activation of ICl(Ca). TMEM16A and Bestrophin-3 showed strong co-localization with one another and also with Cav1.2 channels, when assessed using immunolabeling and confocal microscopy in both canine myocytes and human ventricular myocardium. Activation of ICl(Ca) in canine ventricular cells requires Ca(2+)-entry through neighboring L-type Ca(2+) channels and is only augmented by SR Ca(2+)-release. Substantial activation of ICl(Ca) requires high Ca(2+) concentration in the dyadic clefts which can be effectively buffered by BAPTA, but not EGTA.
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Affiliation(s)
- Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Faculty of Pharmacy, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Krisztina Váczi
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Bence Hegyi
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Mónika Gönczi
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; MTA-DE Momentum, Laboratory of Protein Dynamics, Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Beatrix Dienes
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - János Magyar
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Division of Sport Physiology, Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, H-6720 Szeged, Dóm tér 12, P.O. Box 427, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, H-6720 Szeged, Dóm tér 12, P.O. Box 427, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, H-6720 Szeged, Dóm tér 12, P.O. Box 427, Hungary
| | - György Seprényi
- Department of Medical Biology, Faculty of Medicine, University of Szeged, H-6720 Szeged, Somogyi Béla utca 4, P.O. Box 427, Hungary
| | - László Csernoch
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Norbert Szentandrássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary.
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Yu CC, Ko JS, Ai T, Tsai WC, Chen Z, Rubart M, Vatta M, Everett TH, George AL, Chen PS. Arrhythmogenic calmodulin mutations impede activation of small-conductance calcium-activated potassium current. Heart Rhythm 2016; 13:1716-23. [PMID: 27165696 DOI: 10.1016/j.hrthm.2016.05.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Indexed: 01/27/2023]
Abstract
BACKGROUND Apamin-sensitive small-conductance calcium-activated potassium (SK) channels are gated by intracellular Ca(2+) through a constitutive interaction with calmodulin. OBJECTIVE We hypothesize that arrhythmogenic human calmodulin mutations impede activation of SK channels. METHODS We studied 5 previously published calmodulin mutations (N54I, N98S, D96V, D130G, and F90L). Plasmids encoding either wild-type or mutant calmodulin were transiently transfected into human embryonic kidney 293 cells that stably express subtype 2 of SK protein channels (SK2 cells). Whole-cell voltage-clamp recording was used to determine apamin-sensitive current densities. We also performed optical mapping studies in normal murine hearts to determine the effects of apamin in hearts with (n=7) or without (n=3) pretreatment with sea anemone toxin. RESULTS SK2 cells transfected with wild-type calmodulin exhibited an apamin-sensitive current density of 33.6 pA/pF (31.4-36.5 pA/pF) (median and confidence interval 25th-75th percentile), which was significantly higher than that observed for cells transfected with N54I (17.0 pA/pF [14.0-27.7 pA/pF]; P = .016), F90L (22.6 pA/pF [20.3-24.3 pA/pF]; P = .011), D96V (13.0 pA/pF [10.9-15.8 pA/pF]; P = .003), N98S (13.7 pA/pF [8.8-20.4 pA/pF]; P = .005), and D130G (17.6 pA/pF [13.8-24.6 pA/pF]; P = .003). The decrease in SK2 current densities was not associated with a decrease in membrane protein expression or intracellular distribution of the channel protein. Apamin increased the ventricular action potential duration at 80% repolarization (from 79.6 ms [63.4-93.3 ms] to 121.8 ms [97.9-127.2 ms]; P = .010) in hearts pretreated with anemone toxin but not in control hearts. CONCLUSION Human arrhythmogenic calmodulin mutations impede the activation of SK2 channels in human embryonic kidney 293 cells.
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Affiliation(s)
- Chih-Chieh Yu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Jum-Suk Ko
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Iksan, Korea
| | - Tomohiko Ai
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Department of Molecular Pathogenesis, Medical Research Institute; Department of Emergency Medicine, Tokyo Medical and Dental University, Tokyo, Japan
| | - Wen-Chin Tsai
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Hualien Tzu-Chi General Hospital, Hualien City, Taiwan
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana
| | - Michael Rubart
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Department of Pediatrics, Riley Heart Research Center
| | - Matteo Vatta
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana; Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana.
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Hancox JC, James AF, Marrion NV, Zhang H, Thomas D. Novel ion channel targets in atrial fibrillation. Expert Opin Ther Targets 2016; 20:947-58. [DOI: 10.1517/14728222.2016.1159300] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Jules C. Hancox
- School of Physiology, Pharmacology and Neuroscience, University Walk, Bristol, UK
| | - Andrew F. James
- School of Physiology, Pharmacology and Neuroscience, University Walk, Bristol, UK
| | - Neil V. Marrion
- School of Physiology, Pharmacology and Neuroscience, University Walk, Bristol, UK
| | - Henggui Zhang
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
| | - Dierk Thomas
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany
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Bragança B, Oliveira-Monteiro N, Ferreirinha F, Lima PA, Faria M, Fontes-Sousa AP, Correia-de-Sá P. Ion Fluxes through KCa2 (SK) and Cav1 (L-type) Channels Contribute to Chronoselectivity of Adenosine A1 Receptor-Mediated Actions in Spontaneously Beating Rat Atria. Front Pharmacol 2016; 7:45. [PMID: 27014060 PMCID: PMC4780064 DOI: 10.3389/fphar.2016.00045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 02/18/2016] [Indexed: 11/24/2022] Open
Abstract
Impulse generation in supraventricular tissue is inhibited by adenosine and acetylcholine via the activation of A1 and M2 receptors coupled to inwardly rectifying GIRK/KIR3.1/3.4 channels, respectively. Unlike M2 receptors, bradycardia produced by A1 receptors activation predominates over negative inotropy. Such difference suggests that other ion currents may contribute to adenosine chronoselectivity. In isolated spontaneously beating rat atria, blockade of KCa2/SK channels with apamin and Cav1 (L-type) channels with nifedipine or verapamil, sensitized atria to the negative inotropic action of the A1 agonist, R-PIA, without affecting the nucleoside negative chronotropy. Patch-clamp experiments in the whole-cell configuration mode demonstrate that adenosine, via A1 receptors, activates the inwardly-rectifying GIRK/KIR3.1/KIR3.4 current resulting in hyperpolarization of atrial cardiomyocytes, which may slow down heart rate. Conversely, the nucleoside inactivates a small conductance Ca2+-activated KCa2/SK outward current, which eventually reduces the repolarizing force and thereby prolong action potentials duration and Ca2+ influx into cardiomyocytes. Immunolocalization studies showed that differences in A1 receptors distribution between the sinoatrial node and surrounding cardiomyocytes do not afford a rationale for adenosine chronoselectivity. Immunolabelling of KIR3.1, KCa2.2, KCa2.3, and Cav1 was also observed throughout the right atrium. Functional data indicate that while both A1 and M2 receptors favor the opening of GIRK/KIR3.1/3.4 channels modulating atrial chronotropy, A1 receptors may additionally restrain KCa2/SK activation thereby compensating atrial inotropic depression by increasing the time available for Ca2+ influx through Cav1 (L-type) channels.
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Affiliation(s)
- Bruno Bragança
- Laboratório de Farmacologia e Neurobiologia - Center for Drug Discovery and Innovative Medicines (MedInUP), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto (UP) Porto, Portugal
| | - Nádia Oliveira-Monteiro
- Laboratório de Farmacologia e Neurobiologia - Center for Drug Discovery and Innovative Medicines (MedInUP), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto (UP) Porto, Portugal
| | - Fátima Ferreirinha
- Laboratório de Farmacologia e Neurobiologia - Center for Drug Discovery and Innovative Medicines (MedInUP), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto (UP) Porto, Portugal
| | - Pedro A Lima
- Departamento de Química e Bioquímica, Faculdade de Ciências, Centro de Química e Bioquímica, Universidade de Lisboa Lisboa, Portugal
| | - Miguel Faria
- Laboratório de Farmacologia e Neurobiologia - Center for Drug Discovery and Innovative Medicines (MedInUP), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto (UP) Porto, Portugal
| | - Ana P Fontes-Sousa
- Laboratório de Farmacologia e Neurobiologia - Center for Drug Discovery and Innovative Medicines (MedInUP), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto (UP) Porto, Portugal
| | - Paulo Correia-de-Sá
- Laboratório de Farmacologia e Neurobiologia - Center for Drug Discovery and Innovative Medicines (MedInUP), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto (UP) Porto, Portugal
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Karppinen S, Rapila R, Naumenko N, Tuomainen T, Koivumäki JT, Hänninen SL, Korhonen T, Tavi P. Ca(2+) -activated K(+) current is essential for maintaining excitability and gene transcription in early embryonic cardiomyocytes. Acta Physiol (Oxf) 2016; 216:101-11. [PMID: 26095188 DOI: 10.1111/apha.12540] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 11/11/2014] [Accepted: 06/03/2015] [Indexed: 01/06/2023]
Abstract
AIM Activity of early embryonic cardiomyocytes relies on spontaneous Ca(2+) oscillations that are induced by interplay between sarcoplasmic reticulum (SR) - Ca(2+) release and ion currents of the plasma membrane. In a variety of cell types, Ca(2+) -activated K(+) current (IK(Ca) ) serves as a link between Ca(2+) signals and membrane voltage. This study aimed to determine the role of IK (Ca) in developing cardiomyocytes. METHODS Ion currents and membrane voltage of embryonic (E9-11) mouse cardiomyocytes were measured by patch clamp; [Ca(2+) ]i signals by confocal microscopy. Transcription of specific genes was measured with RT-qPCR and Ca(2+) -dependent transcriptional activity using NFAT-luciferase assay. Myocyte structure was assessed with antibody labelling and confocal microscopy. RESULTS E9-11 cardiomyocytes express small conductance (SK) channel subunits SK2 and SK3 and have a functional apamin-sensitive K(+) current, which is also sensitive to changes in cytosolic [Ca(2+) ]i . In spontaneously active cardiomyocytes, inhibition of IK (Ca) changed action and resting potentials, reduced SR Ca(2+) load and suppressed the amplitude and the frequency of spontaneously evoked Ca(2+) oscillations. Apamin caused dose-dependent suppression of NFAT-luciferase reporter activity, induced downregulation of a pattern of genes vital for cardiomyocyte development and triggered changes in the myocyte morphology. CONCLUSION The results show that apamin-sensitive IK (Ca) is required for maintaining excitability and activity of the developing cardiomyocytes as well as having a fundamental role in promoting Ca(2+) - dependent gene expression.
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Affiliation(s)
- S. Karppinen
- Department of Biotechnology and Molecular Medicine; A.I. Virtanen Institute for Molecular Sciences; University of Eastern Finland; Kuopio Finland
| | - R. Rapila
- Department of Biotechnology and Molecular Medicine; A.I. Virtanen Institute for Molecular Sciences; University of Eastern Finland; Kuopio Finland
| | - N. Naumenko
- Department of Biotechnology and Molecular Medicine; A.I. Virtanen Institute for Molecular Sciences; University of Eastern Finland; Kuopio Finland
| | - T. Tuomainen
- Department of Biotechnology and Molecular Medicine; A.I. Virtanen Institute for Molecular Sciences; University of Eastern Finland; Kuopio Finland
| | - J. T. Koivumäki
- Department of Biotechnology and Molecular Medicine; A.I. Virtanen Institute for Molecular Sciences; University of Eastern Finland; Kuopio Finland
| | - S. L. Hänninen
- Department of Biotechnology and Molecular Medicine; A.I. Virtanen Institute for Molecular Sciences; University of Eastern Finland; Kuopio Finland
- Institute of Biomedicine; Department of Physiology and Biocenter Oulu; University of Oulu; Oulu Finland
| | - T. Korhonen
- Department of Biotechnology and Molecular Medicine; A.I. Virtanen Institute for Molecular Sciences; University of Eastern Finland; Kuopio Finland
| | - P. Tavi
- Department of Biotechnology and Molecular Medicine; A.I. Virtanen Institute for Molecular Sciences; University of Eastern Finland; Kuopio Finland
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Mizukami K, Yokoshiki H, Mitsuyama H, Watanabe M, Tenma T, Takada S, Tsutsui H. Small-conductance Ca2+-activated K+ current is upregulated via the phosphorylation of CaMKII in cardiac hypertrophy from spontaneously hypertensive rats. Am J Physiol Heart Circ Physiol 2015; 309:H1066-74. [DOI: 10.1152/ajpheart.00825.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 08/12/2015] [Indexed: 01/09/2023]
Abstract
Left ventricular hypertrophy is associated with an increased risk of ventricular arrhythmias. However, the underlying molecular basis is poorly understood. It has been reported that small-conductance Ca2+-activated K+ (SK) channels are involved in the pathogenesis of ventricular arrhythmias in heart failure. The present study aimed to test the hypothesis that SK channel activity is increased via the Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent pathway in hypertensive cardiac hypertrophy. Normotensive Wistar-Kyoto (WKY) rats and spontaneous hypertensive rats (SHRs) were used. Whole cell membrane currents were recorded in isolated ventricular myocytes by the patch-clamp method, and apamin-sensitive K+ current ( IKAS), which is inhibited by apamin (100 nM), an SK channel blocker, was evaluated. IKAS at 40 mV was present in SHRs, whereas it was hardly detectable in WKY rats (0.579 ± 0.046 vs. 0.022 ± 0.062 pA/pF, both n = 6, P < 0.05). IKAS was almost completely abolished by 1 μM KN-93, a CaMKII inhibitor, in SHRs. Optical recordings of left ventricular anterior wall action potentials revealed that apamin prolonged the late phase of repolarization only in SHRs. Western blot analysis of SK channel protein isoforms demonstrated that SK2 was significantly increased in SHRs compared with WKY rats (SK2/GAPDH: 0.66 ± 0.07 vs. 0.40 ± 0.02, both n = 6, P < 0.05), whereas SK1 and SK3 did not differ between groups. In addition, autophosphorylated CaMKII was significantly increased in SHRs (phosphorylated CaMKII/GAPDH: 0.80 ± 0.06 vs. 0.58 ± 0.06, both n = 6, P < 0.05) despite a comparable total amount of CaMKII between groups. In conclusion, SK channels are upregulated via the enhanced activation of CaMKII in cardiac hypertrophy in SHRs.
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Affiliation(s)
- Kazuya Mizukami
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Hisashi Yokoshiki
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Hirofumi Mitsuyama
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Masaya Watanabe
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Taro Tenma
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Shingo Takada
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Hiroyuki Tsutsui
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
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Chan YH, Tsai WC, Ko JS, Yin D, Chang PC, Rubart M, Weiss JN, Everett TH, Lin SF, Chen PS. Small-Conductance Calcium-Activated Potassium Current Is Activated During Hypokalemia and Masks Short-Term Cardiac Memory Induced by Ventricular Pacing. Circulation 2015; 132:1377-86. [PMID: 26362634 DOI: 10.1161/circulationaha.114.015125] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Accepted: 06/11/2015] [Indexed: 01/26/2023]
Abstract
BACKGROUND Hypokalemia increases the vulnerability to ventricular fibrillation. We hypothesize that the apamin-sensitive small-conductance calcium-activated potassium current (IKAS) is activated during hypokalemia and that IKAS blockade is proarrhythmic. METHODS AND RESULTS Optical mapping was performed in 23 Langendorff-perfused rabbit ventricles with atrioventricular block and either right or left ventricular pacing during normokalemia or hypokalemia. Apamin prolonged the action potential duration (APD) measured to 80% repolarization (APD80) by 26 milliseconds (95% confidence interval [CI], 14-37) during normokalemia and by 54 milliseconds (95% CI, 40-68) during hypokalemia (P=0.01) at a 1000-millisecond pacing cycle length. In hypokalemic ventricles, apamin increased the maximal slope of APD restitution, the pacing cycle length threshold of APD alternans, the pacing cycle length for wave-break induction, and the area of spatially discordant APD alternans. Apamin significantly facilitated the induction of sustained ventricular fibrillation (from 3 of 9 hearts to 9 of 9 hearts; P=0.009). Short-term cardiac memory was assessed by the slope of APD80 versus activation time. The slope increased from 0.01 (95% CI, -0.09 to 0.12) at baseline to 0.34 (95% CI, 0.23-0.44) after apamin (P<0.001) during right ventricular pacing and from 0.07 (95% CI, -0.05 to 0.20) to 0.54 (95% CI, 0.06-1.03) after apamin infusion (P=0.045) during left ventricular pacing. Patch-clamp studies confirmed increased IKAS in isolated rabbit ventricular myocytes during hypokalemia (P=0.038). CONCLUSIONS Hypokalemia activates IKAS to shorten APD and maintain repolarization reserve at late activation sites during ventricular pacing. IKAS blockade prominently lengthens the APD at late activation sites and facilitates ventricular fibrillation induction.
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Affiliation(s)
- Yi-Hsin Chan
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Wei-Chung Tsai
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Jum-Suk Ko
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Dechun Yin
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Po-Cheng Chang
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Michael Rubart
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - James N Weiss
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Thomas H Everett
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Shien-Fong Lin
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Peng-Sheng Chen
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.).
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Zhang XD, Lieu DK, Chiamvimonvat N. Small-conductance Ca2+ -activated K+ channels and cardiac arrhythmias. Heart Rhythm 2015; 12:1845-51. [PMID: 25956967 PMCID: PMC4662728 DOI: 10.1016/j.hrthm.2015.04.046] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Indexed: 01/04/2023]
Abstract
Small-conductance Ca2+ -activated K+ (SK, KCa2) channels are unique in that they are gated solely by changes in intracellular Ca2+ and, hence, function to integrate intracellular Ca2+ and membrane potentials on a beat-to-beat basis. Recent studies have provided evidence for the existence and functional significance of SK channels in the heart. Indeed, our knowledge of cardiac SK channels has been greatly expanded over the past decade. Interests in cardiac SK channels are further driven by recent studies suggesting the critical roles of SK channels in human atrial fibrillation, the SK channel as a possible novel therapeutic target in atrial arrhythmias, and upregulation of SK channels in heart failure in animal models and in human heart failure. However, there remain critical gaps in our knowledge. Specifically, blockade of SK channels in cardiac arrhythmias has been shown to be both antiarrhythmic and proarrhythmic. This contemporary review provides an overview of the literature on the role of cardiac SK channels in cardiac arrhythmias and serves as a discussion platform for the current clinical perspectives. At the translational level, development of SK channel blockers as a new therapeutic strategy in the treatment of atrial fibrillation and the possible proarrhythmic effects merit further considerations and investigations.
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Affiliation(s)
- Xiao-Dong Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, California.
| | - Deborah K Lieu
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, California
| | - Nipavan Chiamvimonvat
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, California; Department of Veterans Affairs, Northern California Health Care System, Mather, California.
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Abstract
Optimal cardiac function depends on proper timing of excitation and contraction in various regions of the heart, as well as on appropriate heart rate. This is accomplished via specialized electrical properties of various components of the system, including the sinoatrial node, atria, atrioventricular node, His-Purkinje system, and ventricles. Here we review the major regionally determined electrical properties of these cardiac regions and present the available data regarding the molecular and ionic bases of regional cardiac function and dysfunction. Understanding these differences is of fundamental importance for the investigation of arrhythmia mechanisms and pharmacotherapy.
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Affiliation(s)
- Daniel C Bartos
- Department of Pharmacology, University of California Davis, Davis, California, USA
| | - Eleonora Grandi
- Department of Pharmacology, University of California Davis, Davis, California, USA
| | - Crystal M Ripplinger
- Department of Pharmacology, University of California Davis, Davis, California, USA
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Yu CC, Corr C, Shen C, Shelton R, Yadava M, Rhea IB, Straka S, Fishbein MC, Chen Z, Lin SF, Lopshire JC, Chen PS. Small conductance calcium-activated potassium current is important in transmural repolarization of failing human ventricles. Circ Arrhythm Electrophysiol 2015; 8:667-76. [PMID: 25908692 DOI: 10.1161/circep.114.002296] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 04/13/2015] [Indexed: 12/23/2022]
Abstract
BACKGROUND The transmural distribution of apamin-sensitive small conductance Ca(2+)-activated K(+) (SK) current (IKAS) in failing human ventricles remains unclear. METHODS AND RESULTS We optically mapped left ventricular wedge preparations from 12 failing native hearts and 2 rejected cardiac allografts explanted during transplant surgery. We determined transmural action potential duration (APD) before and after 100 nmol/L apamin administration in all wedges and after sequential administration of apamin, chromanol, and E4031 in 4 wedges. Apamin prolonged APD from 363 ms (95% confidence interval [CI], 341-385) to 409 (95% CI, 385-434; P<0.001) in all hearts, and reduced the transmural conduction velocity from 36 cm/s (95% CI, 30-42) to 32 cm/s (95% CI, 27-37; P=0.001) in 12 native failing hearts at 1000 ms pacing cycle length (PCL). The percent APD prolongation is negatively correlated with baseline APD and positively correlated with PCL. Only 1 wedge had M-cell islands. The percentages of APD prolongation in the last 4 hearts at 2000 ms PCL after apamin, chromanol, and E4031 were 9.1% (95% CI, 3.9-14.2), 17.3% (95% CI, 3.1-31.5), and 35.9% (95% CI, 15.7-56.1), respectively. Immunohistochemical staining of subtype 2 of SK protein showed increased expression in intercalated discs of myocytes. CONCLUSIONS SK current is important in the transmural repolarization in failing human ventricles. The magnitude of IKAS is positively correlated with the PCL, but negatively correlated with APD when PCL is fixed. There is abundant subtype 2 of SK protein in the intercalated discs of myocytes.
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Affiliation(s)
- Chih-Chieh Yu
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.)
| | - Christopher Corr
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.)
| | - Changyu Shen
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.)
| | - Richard Shelton
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.)
| | - Mrinal Yadava
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.)
| | - Isaac B Rhea
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.)
| | - Susan Straka
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.)
| | - Michael C Fishbein
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.)
| | - Zhenhui Chen
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.)
| | - Shien-Fong Lin
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.)
| | - John C Lopshire
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.)
| | - Peng-Sheng Chen
- From the Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology (C.-C.Y., C.C., R.S., M.Y., I.B.R., S.S., Z.C., S.-F.L., J.C.L., P.-S.C.) and Department of Biostatistics (C.S.), Indiana University School of Medicine, Indianapolis; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan (C.-C.Y.); Fairbanks School of Public Health, School of Medicine, Indiana University, Indianapolis (C.S.); Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at University of California, Los Angeles (M.C.F.); Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.); and Department of Medicine, Roudebush Veterans Affairs Medical Center, Indianapolis, IN (J.C.L.).
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SK channels and ventricular arrhythmias in heart failure. Trends Cardiovasc Med 2015; 25:508-14. [PMID: 25743622 DOI: 10.1016/j.tcm.2015.01.010] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Revised: 01/19/2015] [Accepted: 01/20/2015] [Indexed: 12/18/2022]
Abstract
Small-conductance Ca(2+)-activated K(+) (SK) currents are important in the repolarization of normal atrial (but not ventricular) cardiomyocytes. However, recent studies showed that the SK currents are upregulated in failing ventricular cardiomyocytes, along with increased SK channel protein expression and enhanced sensitivity to intracellular Ca(2+). The SK channel activation may be either anti-arrhythmic or pro-arrhythmic, depending on the underlying clinical situations. While the SK channel is a new target of anti-arrhythmic therapy, drug safety is still one of the major concerns.
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Hancock JM, Weatherall KL, Choisy SC, James AF, Hancox JC, Marrion NV. Selective activation of heteromeric SK channels contributes to action potential repolarization in mouse atrial myocytes. Heart Rhythm 2015; 12:1003-15. [PMID: 25620048 DOI: 10.1016/j.hrthm.2015.01.027] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Indexed: 11/15/2022]
Abstract
BACKGROUND Activation of small conductance calcium-activated potassium (SK) channels is proposed to contribute to repolarization of the action potential in atrial myocytes. This role is controversial, as these cardiac SK channels appear to exhibit an uncharacteristic pharmacology. OBJECTIVES The objectives of this study were to resolve whether activation of SK channels contributes to atrial action potential repolarization and to determine the likely subunit composition of the channel. METHODS The effect of 2 SK channel inhibitors was assessed on outward current evoked in voltage clamp and on action potential duration in perforated patch and whole-cell current clamp recording from acutely isolated mouse atrial myocytes. The presence of SK channel subunits was assessed using immunocytochemistry. RESULTS A significant component of outward current was reduced by the SK channel blockers apamin and UCL1684. Block by apamin displayed a sensitivity indicating that this current was carried by homomeric SK2 channels. Action potential duration was significantly prolonged by UCL1684, but not by apamin. This effect was accompanied by an increase in beat-to-beat variability and action potential triangulation. This pharmacology was matched by that of expressed heteromeric SK2-SK3 channels in HEK293 cells. Immunocytochemistry showed that atrial myocytes express both SK2 and SK3 channels with an overlapping expression pattern. CONCLUSION Only proposed heteromeric SK2-SK3 channels are physiologically activated to contribute to action potential repolarization, which is indicated by the difference in pharmacology of evoked outward current and prolongation of atrial action potential duration. The effect of blocking this channel on the action potential suggests that SK channel inhibition during cardiac function has the potential to be proarrhythmic.
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Affiliation(s)
- Jane M Hancock
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Kate L Weatherall
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Stéphanie C Choisy
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Andrew F James
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Jules C Hancox
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Neil V Marrion
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom.
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Burashnikov A, Belardinelli L, Antzelevitch C. Inhibition of IKr potentiates development of atrial-selective INa block leading to effective suppression of atrial fibrillation. Heart Rhythm 2014; 12:836-44. [PMID: 25546810 DOI: 10.1016/j.hrthm.2014.12.033] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Indexed: 12/19/2022]
Abstract
BACKGROUND The availability of safe and effective drugs for the management of atrial fibrillation (AF) remains an unmet medical need. OBJECTIVES The purpose of this study was to test the hypothesis that the inhibition of the rapidly activating delayed rectifier potassium current (IKr) greatly potentiates the development of atrial-selective sodium channel current (INa) block, leading to more effective suppression of AF. METHODS Electrophysiological and anti-AF effects of highly selective INa and IKr blockers (lidocaine and E-4031) individually and in combination were determined in canine coronary-perfused atrial and ventricular preparations. Acetylcholine (1 µM) was used to induce persistent AF. RESULTS Lidocaine (10 µM) caused a relatively small abbreviation of the action potential duration measured at 90% repolarization in both atria and ventricles, but caused atrial-selective prolongation of the effective refractory period owing to the induction of post-repolarization refractoriness. Lidocaine also caused modest atrial-selective depression of other INa-mediated parameters including excitability, maximum rate of rise of the action potential upstroke, and conduction time. E-4031 (1 µM) prolonged the action potential duration measured at 90% repolarization and effective refractory period in an atrial-predominant manner. A combination of lidocaine and E-4031 caused a greater atrial-selective depression of INa-mediated parameters. Persistent acetylcholine-mediated AF developed in 100% of atria under control conditions, in 80% (4 of 5) after pretreatment with lidocaine (10 µM), in 100% (4 of 4) after E-4031 (1 µM), and in only 14% (1 of 7) after the combination of lidocaine and E-4031. CONCLUSION Our results provide a proof of concept that IKr block greatly potentiates the effects of rapidly dissociating INa blockers to depress sodium channel-dependent parameters in the canine atria but not in the ventricles, thus contributing significantly to suppression of AF.
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Haugaard MM, Hesselkilde EZ, Pehrson S, Carstensen H, Flethøj M, Præstegaard KF, Sørensen US, Diness JG, Grunnet M, Buhl R, Jespersen T. Pharmacologic inhibition of small-conductance calcium-activated potassium (SK) channels by NS8593 reveals atrial antiarrhythmic potential in horses. Heart Rhythm 2014; 12:825-35. [PMID: 25542425 DOI: 10.1016/j.hrthm.2014.12.028] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Indexed: 11/28/2022]
Abstract
BACKGROUND Small-conductance calcium-activated potassium (SK) channels have been found to play an important role in atrial repolarization and atrial fibrillation (AF). OBJECTIVE The purpose of this study was to investigate the existence and functional role of SK channels in the equine heart. METHODS Cardiac biopsies were analyzed to investigate the expression level of the most prominent cardiac ion channels, with special focus on SK channels, in the equine heart. Subcellular distribution of SK isoform 2 (SK2) was assessed by immunohistochemistry and confocal microscopy. The electrophysiologic and anti-AF effects of the relative selective SK channel inhibitor NS8593 (5 mg/kg IV) were evaluated in anesthetized horses, focusing on the potential of NS8593 to terminate acute pacing-induced AF, drug-induced changes in atrial effective refractory period, AF duration and vulnerability, and ventricular depolarization and repolarization times. RESULTS Analysis revealed equivalent mRNA transcript levels of the 3 SK channel isoforms in atria compared to ventricles. Immunohistochemistry and confocal microscopy displayed a widespread distribution of SK2 in both atrial and ventricular cardiomyocytes. NS8593 terminated all induced AF episodes (duration ≥15 minutes), caused pronounced prolongation of atrial effective refractory period, and reduced AF duration and vulnerability. QRS duration and QTc interval were not affected by treatment. CONCLUSION SK channels are widely distributed in atrial and ventricular cardiomyocytes and contribute to atrial repolarization. Inhibition by NS8593 terminates pacing-induced AF of short duration and decreases AF duration and vulnerability without affecting ventricular conduction and repolarization. Thus, inhibition by NS8593 demonstrates clear atrial antiarrhythmic properties in healthy horses.
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Affiliation(s)
- Maria Mathilde Haugaard
- Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Eva Zander Hesselkilde
- Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Steen Pehrson
- Department of Cardiology, The Heart Centre, Copenhagen University Hospital, Taastrup, Denmark
| | - Helena Carstensen
- Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Mette Flethøj
- Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kirstine Færgemand Præstegaard
- Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | | | | | - Rikke Buhl
- Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Jespersen
- Danish National Foundation Research Centre in Arrhythmias (DARC) and Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Schmitt N, Grunnet M, Olesen SP. Cardiac potassium channel subtypes: new roles in repolarization and arrhythmia. Physiol Rev 2014; 94:609-53. [PMID: 24692356 DOI: 10.1152/physrev.00022.2013] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K+ channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K+ channels drive the late repolarization of the ventricle with some redundancy, and in atria this repolarization reserve is supplemented by the fairly atrial-specific KV1.5, Kir3, KCa, and K2P channels. The role of the latter two subtypes in atria is currently being clarified, and several findings indicate that they could constitute targets for new pharmacological treatment of atrial fibrillation. The interplay between the different K+ channel subtypes in both atria and ventricle is dynamic, and a significant up- and downregulation occurs in disease states such as atrial fibrillation or heart failure. The underlying posttranscriptional and posttranslational remodeling of the individual K+ channels changes their activity and significance relative to each other, and they must be viewed together to understand their role in keeping a stable heart rhythm, also under menacing conditions like attacks of reentry arrhythmia.
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