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Van NTH, Kim WK, Nam JH. Challenges in the Therapeutic Targeting of KCa Channels: From Basic Physiology to Clinical Applications. Int J Mol Sci 2024; 25:2965. [PMID: 38474212 PMCID: PMC10932353 DOI: 10.3390/ijms25052965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/23/2024] [Accepted: 01/25/2024] [Indexed: 03/14/2024] Open
Abstract
Calcium-activated potassium (KCa) channels are ubiquitously expressed throughout the body and are able to regulate membrane potential and intracellular calcium concentrations, thereby playing key roles in cellular physiology and signal transmission. Consequently, it is unsurprising that KCa channels have been implicated in various diseases, making them potential targets for pharmaceutical interventions. Over the past two decades, numerous studies have been conducted to develop KCa channel-targeting drugs, including those for disorders of the central and peripheral nervous, cardiovascular, and urinary systems and for cancer. In this review, we synthesize recent findings regarding the structure and activating mechanisms of KCa channels. We also discuss the role of KCa channel modulators in therapeutic medicine. Finally, we identify the major reasons behind the delay in bringing these modulators to the pharmaceutical market and propose new strategies to promote their application.
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Affiliation(s)
- Nhung Thi Hong Van
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Republic of Korea;
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
| | - Woo Kyung Kim
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
- Department of Internal Medicine, Graduate School of Medicine, Dongguk University, Goyang 10326, Republic of Korea
| | - Joo Hyun Nam
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Republic of Korea;
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
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2
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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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Herrera NT, Zhang X, Ni H, Maleckar MM, Heijman J, Dobrev D, Grandi E, Morotti S. Dual effects of the small-conductance Ca 2+-activated K + current on human atrial electrophysiology and Ca 2+-driven arrhythmogenesis: an in silico study. Am J Physiol Heart Circ Physiol 2023; 325:H896-H908. [PMID: 37624096 PMCID: PMC10659325 DOI: 10.1152/ajpheart.00362.2023] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 08/11/2023] [Accepted: 08/11/2023] [Indexed: 08/26/2023]
Abstract
By sensing changes in intracellular Ca2+, small-conductance Ca2+-activated K+ (SK) channels dynamically regulate the dynamics of the cardiac action potential (AP) on a beat-to-beat basis. Given their predominance in atria versus ventricles, SK channels are considered a promising atrial-selective pharmacological target against atrial fibrillation (AF), the most common cardiac arrhythmia. However, the precise contribution of SK current (ISK) to atrial arrhythmogenesis is poorly understood, and may potentially involve different mechanisms that depend on species, heart rates, and degree of AF-induced atrial remodeling. Both reduced and enhanced ISK have been linked to AF. Similarly, both SK channel up- and downregulation have been reported in chronic AF (cAF) versus normal sinus rhythm (nSR) patient samples. Here, we use our multiscale modeling framework to obtain mechanistic insights into the contribution of ISK in human atrial cardiomyocyte electrophysiology. We simulate several protocols to quantify how ISK modulation affects the regulation of AP duration (APD), Ca2+ transient, refractoriness, and occurrence of alternans and delayed afterdepolarizations (DADs). Our simulations show that ISK activation shortens the APD and atrial effective refractory period, limits Ca2+ cycling, and slightly increases the propensity for alternans in both nSR and cAF conditions. We also show that increasing ISK counteracts DAD development by enhancing the repolarization force that opposes the Ca2+-dependent depolarization. Taken together, our results suggest that increasing ISK in human atrial cardiomyocytes could promote reentry while protecting against triggered activity. Depending on the leading arrhythmogenic mechanism, ISK inhibition may thus be a beneficial or detrimental anti-AF strategy.NEW & NOTEWORTHY Using our established framework for human atrial myocyte simulations, we investigated the role of the small-conductance Ca2+-activated K+ current (ISK) in the regulation of cell function and the development of Ca2+-driven arrhythmias. We found that ISK inhibition, a promising atrial-selective pharmacological strategy against atrial fibrillation, counteracts the reentry-promoting abbreviation of atrial refractoriness, but renders human atrial myocytes more vulnerable to delayed afterdepolarizations, thus potentially increasing the propensity for ectopic (triggered) activity.
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Affiliation(s)
- Nathaniel T Herrera
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Xianwei Zhang
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Haibo Ni
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Mary M Maleckar
- Department of Computational Physiology, Simula Research Laboratory, Oslo, Norway
| | - Jordi Heijman
- Department of Cardiology, Faculty of Health, Medicine, and Life Sciences, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | - Dobromir Dobrev
- Faculty of Medicine, West German Heart and Vascular Center, Institute of Pharmacology, University Duisburg-Essen, Essen, Germany
- Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada
- Department of Integrative Physiology, Baylor College of Medicine, Houston, Texas, United States
| | - Eleonora Grandi
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Stefano Morotti
- Department of Pharmacology, University of California Davis, Davis, California, United States
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Linz B, Hesselkilde EM, Skarsfeldt MA, Hertel JN, Sattler SM, Yan Y, Tfelt-Hansen J, Diness JG, Bentzen BH, Linz D, Jespersen T. Pharmacological inhibition of SK-channels with AP14145 prevents atrial arrhythmogenic changes in a porcine model for obstructive respiratory events. J Cardiovasc Electrophysiol 2023; 34:126-134. [PMID: 36482155 PMCID: PMC10107889 DOI: 10.1111/jce.15769] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 11/02/2022] [Accepted: 11/07/2022] [Indexed: 12/13/2022]
Abstract
BACKGROUND Obstructive sleep apnea (OSA) creates a complex substrate for atrial fibrillation (AF), which is refractory to many clinically available pharmacological interventions. We investigated atrial antiarrhythmogenic properties and ventricular electrophysiological safety of small-conductance Ca2+ -activated K+ (SK)-channel inhibition in a porcine model for obstructive respiratory events. METHODS In spontaneously breathing pigs, obstructive respiratory events were simulated by intermittent negative upper airway pressure (INAP) applied via a pressure device connected to the intubation tube. INAP was applied for 75 s, every 10 min, three times before and three times during infusion of the SK-channel inhibitor AP14145. Atrial effective refractory periods (AERP) were acquired before (pre-INAP), during (INAP) and after (post-) INAP. AF-inducibility was determined by a S1S2 atrial pacing protocol. Ventricular arrhythmicity was evaluated by heart rate adjusted QT-interval duration (QT-paced) and electromechanical window (EMW) shortening. RESULTS During vehicle infusion, INAP transiently shortened AERP (pre-INAP: 135 ± 10 ms vs. post-INAP 101 ± 11 ms; p = .008) and increased AF-inducibility. QT-paced prolonged during INAP (pre-INAP 270 ± 7 ms vs. INAP 275 ± 7 ms; p = .04) and EMW shortened progressively throughout INAP and post-INAP (pre-INAP 80 ± 4 ms; INAP 59 ± 6 ms, post-INAP 46 ± 10 ms). AP14145 prolonged baseline AERP, partially prevented INAP-induced AERP-shortening and reduced AF-susceptibility. AP14145 did not alter QT-paced at baseline (pre-AP14145 270 ± 7 ms vs. AP14145 268 ± 6 ms, p = .83) or QT-paced and EMW-shortening during INAP. CONCLUSION In a pig model for obstructive respiratory events, the SK-channel-inhibitor AP14145 prevented INAP-associated AERP-shortening and AF-susceptibility without impairing ventricular electrophysiology. Whether SK-channels represent a target for OSA-related AF in humans warrants further study.
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Affiliation(s)
- Benedikt Linz
- Faculty of Health and Medical Sciences, Department of Biomedical Sciences, Cardiac Physiology Laboratory, Panum Institutet, University of Copenhagen, Copenhagen, Denmark
| | - Eva M Hesselkilde
- Faculty of Health and Medical Sciences, Department of Biomedical Sciences, Cardiac Physiology Laboratory, Panum Institutet, University of Copenhagen, Copenhagen, Denmark
| | - Mark A Skarsfeldt
- Faculty of Health and Medical Sciences, Department of Biomedical Sciences, Cardiac Physiology Laboratory, Panum Institutet, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
| | - Julie N Hertel
- Faculty of Health and Medical Sciences, Department of Biomedical Sciences, Cardiac Physiology Laboratory, Panum Institutet, University of Copenhagen, Copenhagen, Denmark
| | - Stefan M Sattler
- Faculty of Health and Medical Sciences, Department of Biomedical Sciences, Cardiac Physiology Laboratory, Panum Institutet, University of Copenhagen, Copenhagen, Denmark
| | - Yannan Yan
- Faculty of Health and Medical Sciences, Department of Biomedical Sciences, Cardiac Physiology Laboratory, Panum Institutet, University of Copenhagen, Copenhagen, Denmark
| | - Jacob Tfelt-Hansen
- The Department of Cardiology, The Heart Centre, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.,Department of Forensic Medicine, Faculty of Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Bo H Bentzen
- Faculty of Health and Medical Sciences, Department of Biomedical Sciences, Cardiac Physiology Laboratory, Panum Institutet, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
| | - Dominik Linz
- Faculty of Health and Medical Sciences, Department of Biomedical Sciences, Cardiac Physiology Laboratory, Panum Institutet, University of Copenhagen, Copenhagen, Denmark.,Centre for Heart Rhythm Disorders, South Australian Health and Medical Research Institute, Royal Adelaide Hospital, University of Adelaide, Adelaide, Australia.,Department of Cardiology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Thomas Jespersen
- Faculty of Health and Medical Sciences, Department of Biomedical Sciences, Cardiac Physiology Laboratory, Panum Institutet, University of Copenhagen, Copenhagen, Denmark
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Small conductance calcium activated K + channel inhibitor decreases stretch induced vulnerability to atrial fibrillation. IJC HEART & VASCULATURE 2021; 37:100898. [PMID: 34746364 PMCID: PMC8554272 DOI: 10.1016/j.ijcha.2021.100898] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/05/2021] [Accepted: 10/16/2021] [Indexed: 12/11/2022]
Abstract
Background Atrial dilation is an important risk factor for atrial fibrillation (AF) and animal studies have found that acute atrial dilation shortens the atrial effective refractory period (AERP) and increases the risk of AF. Stretch activated ion channels (SACs) and calcium channels play a role in this. The expression profile and calcium dependent activation makes the small conductance calcium activated K+ channel (KCa2.x) a candidate for coupling stretch induced increases in intracellular calcium through K+-efflux and thereby shortening of atrial refractoriness. Objectives We hypothesized that KCa2.x channel inhibitors can prevent the stretch induced shortening of AERP and protect the heart from AF. Methods The effect of KCa2 channel inhibitor (N-(pyridin-2-yl)-4-(pyridin-2-yl)thiazol-2-amine (ICA) 1 µM) was investigated using the isolated perfused rabbit heart preparation. To stretch the left atrium (LA) a balloon was inserted and inflated. AERP and action potential duration (APD) were recorded before and after atrial stretch. AF was induced by burst pacing the LA at different degrees of atrial stretch. Results Stretching of the LA by increasing the balloon pressure from 0 to 20 mmHg shortened the AERP by 8.6 ± 1 ms. In comparison, the KCa2 inhibitor ICA significantly attenuated the stretch induced shortening of AERP to 2.5 ± 1.1 ms. Total AF duration increased linearly with atrial balloon pressure. This relationship was not found in the presence of ICA. ICA lowered the incidence of AF induction and total AF duration. Conclusion The KCa2 channel inhibitor ICA attenuates the acute stretch induced shortening of AERP and decreases stretch induced vulnerability to AF.
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Investigational Anti-Atrial Fibrillation Pharmacology and Mechanisms by Which Antiarrhythmics Terminate the Arrhythmia: Where Are We in 2020? J Cardiovasc Pharmacol 2021; 76:492-505. [PMID: 33165131 PMCID: PMC7641178 DOI: 10.1097/fjc.0000000000000892] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Antiarrhythmic drugs remain the mainstay therapy for patients with atrial fibrillation (AF). A major disadvantage of the currently available anti-AF agents is the risk of induction of ventricular proarrhythmias. Aiming to reduce this risk, several atrial-specific or -selective ion channel block approaches have been introduced for AF suppression, but only the atrial-selective inhibition of the sodium channel has been demonstrated to be valid in both experimental and clinical studies. Among the other pharmacological anti-AF approaches, “upstream therapy” has been prominent but largely disappointing, and pulmonary delivery of anti-AF drugs seems to be promising. Major contradictions exist in the literature about the electrophysiological mechanisms of AF (ie, reentry or focal?) and the mechanisms by which anti-AF drugs terminate AF, making the search for novel anti-AF approaches largely empirical. Drug-induced termination of AF may or may not be associated with prolongation of the atrial effective refractory period. Anti-AF drug research has been largely based on the “suppress reentry” ideology; however, results of the AF mapping studies increasingly indicate that nonreentrant mechanism(s) plays an important role in the maintenance of AF. Also, the analysis of anti-AF drug-induced electrophysiological alterations during AF, conducted in the current study, leans toward the focal source as the prime mechanism of AF maintenance. More effort should be placed on the investigation of pharmacological suppression of the focal mechanisms.
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Rahm AK, Gramlich D, Wieder T, Müller ME, Schoeffel A, El Tahry FA, Most P, Heimberger T, Sandke S, Weis T, Ullrich ND, Korff T, Lugenbiel P, Katus HA, Thomas D. Trigger-Specific Remodeling of K Ca2 Potassium Channels in Models of Atrial Fibrillation. Pharmgenomics Pers Med 2021; 14:579-590. [PMID: 34045886 PMCID: PMC8144362 DOI: 10.2147/pgpm.s290291] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 04/06/2021] [Indexed: 11/23/2022] Open
Abstract
AIM Effective antiarrhythmic treatment of atrial fibrillation (AF) constitutes a major challenge, in particular, when concomitant heart failure (HF) is present. HF-associated atrial arrhythmogenesis is distinctly characterized by prolonged atrial refractoriness. Small-conductance, calcium-activated K+ (KCa, SK, KCNN) channels contribute to cardiac action potential repolarization and are implicated in AF susceptibility and therapy. The mechanistic impact of AF/HF-related triggers on atrial KCa channels is not known. We hypothesized that tachycardia, stretch, β-adrenergic stimulation, and hypoxia differentially determine KCa2.1-2.3 channel remodeling in atrial cells. METHODS KCNN1-3 transcript levels were assessed in AF/HF patients and in a pig model of atrial tachypacing-induced AF with reduced left ventricular function. HL-1 atrial myocytes were subjected to proarrhythmic triggers to investigate the effects on Kcnn mRNA and KCa channel protein. RESULTS Atrial KCNN1-3 expression was reduced in AF/HF patients. KCNN2 and KCNN3 suppression was recapitulated in the corresponding pig model. In contrast to human AF, KCNN1 remained unchanged in pigs. Channel- and stressor-specific remodeling was revealed in vitro. Lower expression levels of KCNN1/KCa2.1 were linked to stretch and β-adrenergic stimulation. Furthermore, KCNN3/KCa2.3 expression was suppressed upon tachypacing and hypoxia. Finally, KCNN2/KCa2.2 abundance was specifically enhanced by hypoxia. CONCLUSION Reduction of KCa2.1-2.3 channel expression might contribute to the action potential prolongation in AF complicated by HF. Subtype-specific KCa2 channel remodeling induced by tachypacing, stretch, β-adrenergic stimulation, or hypoxia is expected to differentially determine atrial remodeling, depending on patient-specific activation of each triggering factor. Stressor-dependent KCa2 regulation in atrial myocytes provides a starting point for mechanism-based antiarrhythmic therapy.
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Affiliation(s)
- Ann-Kathrin Rahm
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Dominik Gramlich
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Teresa Wieder
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
| | - Mara Elena Müller
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Axel Schoeffel
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
| | - Fadwa A El Tahry
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
| | - Patrick Most
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
| | - Tanja Heimberger
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Steffi Sandke
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Tanja Weis
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Nina D Ullrich
- Institute of Physiology and Pathophysiology, Department of Cardiovascular Physiology, Heidelberg University, Heidelberg, 69120, Germany
| | - Thomas Korff
- Institute of Physiology and Pathophysiology, Department of Cardiovascular Physiology, Heidelberg University, Heidelberg, 69120, Germany
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Mannheim, 68167, Germany
| | - Patrick Lugenbiel
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Hugo A Katus
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
| | - Dierk Thomas
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany
- HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany
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The Small Conductance Calcium-Activated Potassium Channel Inhibitors NS8593 and UCL1684 Prevent the Development of Atrial Fibrillation Through Atrial-Selective Inhibition of Sodium Channel Activity. J Cardiovasc Pharmacol 2021; 76:164-172. [PMID: 32453071 DOI: 10.1097/fjc.0000000000000855] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The mechanisms underlying atrial-selective prolongation of effective refractory period (ERP) and suppression of atrial fibrillation (AF) by NS8593 and UCL1684, small conductance calcium-activated potassium (SK) channel blockers, are poorly defined. The purpose of the study was to confirm the effectiveness of these agents to suppress AF and to probe the underlying mechanisms. Transmembrane action potentials and pseudoelectrocardiograms were recorded from canine isolated coronary-perfused canine atrial and ventricular wedge preparations. Patch clamp techniques were used to record sodium channel current (INa) in atrial and ventricular myocytes and human embryonic kidney cells. In both atria and ventricles, NS8593 (3-10 µM) and UCL1684 (0.5 µM) did not significantly alter action potential duration, suggesting little to no SK channel inhibition. Both agents caused atrial-selective: (1) prolongation of ERP secondary to development of postrepolarization refractoriness, (2) reduction of Vmax, and (3) increase of diastolic threshold of excitation (all are sodium-mediated parameters). NS8593 and UCL1684 significantly reduced INa density in human embryonic kidney cells as well as in atrial but not in ventricular myocytes at physiologically relevant holding potentials. NS8593 caused a shift of steady-state inactivation to negative potentials in atrial but not ventricular cells. NS8593 and UCL1684 prevented induction of acetylcholine-mediated AF in 6/6 and 8/8 preparations, respectively. This anti-AF effect was associated with strong rate-dependent depression of excitability. The SK channel blockers, NS8593 and UCL1684, are effective in preventing the development of AF due to potent atrial-selective inhibition of INa, causing atrial-selective prolongation of ERP secondary to induction of postrepolarization refractoriness.
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Qi MM, Qian LL, Wang RX. Modulation of SK Channels: Insight Into Therapeutics of Atrial Fibrillation. Heart Lung Circ 2021; 30:1130-1139. [PMID: 33642173 DOI: 10.1016/j.hlc.2021.01.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 01/12/2021] [Accepted: 01/31/2021] [Indexed: 11/19/2022]
Abstract
Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia in the world. Although much technological progress in the treatment of AF has been made, there is an urgent need for better treatment of AF due to its high rates of morbidity and mortality. The anti-arrhythmic drugs currently approved for marketing have significant limitations and side effects such as life-threatening ventricular arrhythmias and hypotension. The small conductance Ca2+-activated K+ channels (SK channels) are dependent on intracellular Ca2+ concentrations, which tightly integrate with membrane potential. Given the predominant expression in the atria of many species, including humans, they are now emerging as a therapeutic target for treating AF. This review aimed to illustrate the characteristics and function of SK channels. Moreover, it discussed the regulation of SK channels and their potential as a therapeutic target of AF.
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Affiliation(s)
- Miao-Miao Qi
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China
| | - Ling-Ling Qian
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China
| | - Ru-Xing Wang
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China.
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10
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Fenner MF, Gatta G, Sattler S, Kuiper M, Hesselkilde EM, Adler DMT, Smerup M, Schotten U, Sørensen U, Diness JG, Jespersen T, Verheule S, Van Hunnik A, Buhl R. Inhibition of Small-Conductance Calcium-Activated Potassium Current ( I K,Ca) Leads to Differential Atrial Electrophysiological Effects in a Horse Model of Persistent Atrial Fibrillation. Front Physiol 2021; 12:614483. [PMID: 33633584 PMCID: PMC7900437 DOI: 10.3389/fphys.2021.614483] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 01/08/2021] [Indexed: 12/13/2022] Open
Abstract
Background Small-conductance Ca2+-activated K+ (KCa2) channels have been proposed as a possible atrial-selective target to pharmacologically terminate atrial fibrillation (AF) and to maintain sinus rhythm. However, it has been hypothesized that the importance of the KCa2 current—and thereby the efficacy of small-conductance Ca2+-activated K+ current (IK,Ca) inhibition—might be negatively related to AF duration and the extent of AF-induced remodeling. Experimental Approach and Methods To address the hypothesis of the efficacy of IK,Ca inhibition being dependent on AF duration, the anti-arrhythmic properties of the IK,Ca inhibitor NS8593 (5 mg/kg) and its influence on atrial conduction were studied using epicardial high-density contact mapping in horses with persistent AF. Eleven Standardbred mares with tachypacing-induced persistent AF (42 ± 5 days of AF) were studied in an open-chest experiment. Unipolar AF electrograms were recorded and isochronal high-density maps analyzed to allow for the reconstruction of wave patterns and changes in electrophysiological parameters, such as atrial conduction velocity and AF cycle length. Atrial anti-arrhythmic properties and adverse effects of NS8593 on ventricular electrophysiology were evaluated by continuous surface ECG monitoring. Results IK,Ca inhibition by NS8593 administered intravenously had divergent effects on right and left AF complexity and propagation properties in this equine model of persistent AF. Despite global prolongation of AF cycle length, a slowing of conduction in the right atrium led to increased anisotropy and electrical dissociation, thus increasing AF complexity. In contrast, there was no significant change in AF complexity in the LA, and cardioversion of AF was not achieved. Conclusions Intra-atrial heterogeneity in response to IK,Ca inhibition by NS8593 was observed. The investigated dose of NS8593 increased the AF cycle length but was not sufficient to induce cardioversion. In terms of propagation properties during AF, IK,Ca inhibition by NS8593 led to divergent effects in the right and left atrium. This divergent behavior may have impeded the cardioversion success.
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Affiliation(s)
- Merle Friederike Fenner
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Giulia Gatta
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Stefan Sattler
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Marion Kuiper
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Eva Melis Hesselkilde
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ditte M T Adler
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Morten Smerup
- Department of Cardiothoracic Surgery, The Heart Centre, Copenhagen University Hospital, Copenhagen, Denmark
| | - Ulrich Schotten
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | | | | | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sander Verheule
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Arne Van Hunnik
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
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11
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The regulation of the small-conductance calcium-activated potassium current and the mechanisms of sex dimorphism in J wave syndrome. Pflugers Arch 2021; 473:491-506. [PMID: 33411079 DOI: 10.1007/s00424-020-02500-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 11/20/2020] [Accepted: 11/25/2020] [Indexed: 12/16/2022]
Abstract
Apamin-sensitive small-conductance calcium-activated potassium (SK) current (IKAS) plays an important role in cardiac repolarization under a variety of physiological and pathological conditions. The regulation of cardiac IKAS relies on SK channel expression, intracellular Ca2+, and interaction between SK channel and intracellular Ca2+. IKAS activation participates in multiple types of arrhythmias, including atrial fibrillation, ventricular tachyarrhythmias, and automaticity and conduction abnormality. Recently, sex dimorphisms in autonomic control have been noticed in IKAS activation, resulting in sex-differentiated action potential morphology and arrhythmogenesis. This review provides an update on the Ca2+-dependent regulation of cardiac IKAS and the role of IKAS on arrhythmias, with a special focus on sex differences in IKAS activation. We propose that sex dimorphism in autonomic control of IKAS may play a role in J wave syndrome.
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12
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Soattin L, Lubberding AF, Bentzen BH, Christ T, Jespersen T. Inhibition of Adenosine Pathway Alters Atrial Electrophysiology and Prevents Atrial Fibrillation. Front Physiol 2020; 11:493. [PMID: 32595514 PMCID: PMC7304385 DOI: 10.3389/fphys.2020.00493] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 04/23/2020] [Indexed: 01/13/2023] Open
Abstract
Background Adenosine leads to atrial action potential (AP) shortening through activation of adenosine 1 receptors (A1-R) and subsequent opening of G-protein-coupled inwardly rectifying K+ channels. Extracellular production of adenosine is drastically increased during stress and ischemia. Objective The aim of this study was to address whether the pharmacological blockade of endogenous production of adenosine and of its signaling prevents atrial fibrillation (AF). Methods The role of A1-R activation on atrial action potential duration, refractoriness, and AF vulnerability was investigated in rat isolated beating heart preparations (Langendorff) with an A1-R agonist [2-chloro-N6-cyclopentyladenosine (CCPA), 50 nM] and antagonist [1-butyl-3-(3-hydroxypropyl)-8-(3-noradamantyl)xanthine (PSB36), 40 nM]. Furthermore, to interfere with the endogenous adenosine release, the ecto-5′-nucleotidase (CD73) inhibitor was applied [5′-(α,β-methylene) diphosphate sodium salt (AMPCP), 500 μM]. Isolated trabeculae from human right atrial appendages (hRAAs) were used for comparison. Results As expected, CCPA shortened AP duration at 90% of repolarization (APD90) and effective refractory period (ERP) in rat atria. PSB36 prolonged APD90 and ERP in rat atria, and CD73 inhibition with AMPCP prolonged ERP in rats, confirming that endogenously produced amount of adenosine is sufficiently high to alter atrial electrophysiology. In human atrial appendages, CCPA shortened APD90, while PSB36 prolonged it. Rat hearts treated with CCPA are prone to AF. In contrast, PSB36 and AMPCP prevented AF events and reduced AF duration (vehicle, 11.5 ± 2.6 s; CCPA, 40.6 ± 16.1 s; PSB36, 6.5 ± 3.7 s; AMPCP, 3.0 ± 1.4 s; P < 0.0001). Conclusion A1-R activation by intrinsic adenosine release alters atrial electrophysiology and promotes AF. Inhibition of adenosine pathway protects atria from arrhythmic events.
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Affiliation(s)
- Luca Soattin
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Institute of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Anniek Frederike Lubberding
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bo Hjorth Bentzen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Torsten Christ
- Institute of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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13
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Peyronnet R, Ravens U. Atria-selective antiarrhythmic drugs in need of alliance partners. Pharmacol Res 2019; 145:104262. [PMID: 31059791 DOI: 10.1016/j.phrs.2019.104262] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 04/30/2019] [Accepted: 05/03/2019] [Indexed: 12/15/2022]
Abstract
Atria-selective antiarrhythmic drugs in need of alliance partners. Guideline-based treatment of atrial fibrillation (AF) comprises prevention of thromboembolism and stroke, as well as antiarrhythmic therapy by drugs, electrical rhythm conversion, ablation and surgical procedures. Conventional antiarrhythmic drugs are burdened with unwanted side effects including a propensity of triggering life-threatening ventricular fibrillation. In order to solve this therapeutic dilemma, 'atria-selective' antiarrhythmic drugs have been developed for the treatment of supraventricular arrhythmias. These drugs are designed to aim at atrial targets, taking advantage of differences in atrial and ventricular ion channel expression and function. However it is not clear, whether such drugs are sufficiently antiarrhythmic or whether they are in need of an alliance partner for clinical efficacy. Atria-selective Na+ channel blockers display fast dissociation kinetics and high binding affinity to inactivated channels. Compounds targeting atria-selective K+ channels include blockers of ultra rapid delayed rectifier (Kv1.5) or acetylcholine-activated inward rectifier K+ channels (Kir3.x), inward rectifying K+ channels (Kir2.x), Ca2+-activated K+ channels of small conductance (SK), weakly rectifying two-pore domain K+ channels (K2P), and transient receptor potential channels (TRP). Despite good antiarrhythmic data from in-vitro and animal model experiments, clinical efficacy of atria-selective antiarrhythmic drugs remains to be demonstrated. In the present review we will briefly summarize the novel compounds and their proposed antiarrhythmic action. In addition, we will discuss the evidence for putative improvement of antiarrhythmic efficacy and potency by addressing multiple pathophysiologically relevant targets as possible alliance partners.
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Affiliation(s)
- Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg Bad Krozingen, Medical Center, University of Freiburg, Freiburg, Germany; Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ursula Ravens
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg Bad Krozingen, Medical Center, University of Freiburg, Freiburg, Germany; Institute of Physiology, Medical Faculty TU Dresden, Dresden, Germany.
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14
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Skibsbye L, Bengaard AK, Uldum-Nielsen AM, Boddum K, Christ T, Jespersen T. Inhibition of Small Conductance Calcium-Activated Potassium (SK) Channels Prevents Arrhythmias in Rat Atria During β-Adrenergic and Muscarinic Receptor Activation. Front Physiol 2018; 9:510. [PMID: 29922167 PMCID: PMC5996028 DOI: 10.3389/fphys.2018.00510] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 04/20/2018] [Indexed: 01/18/2023] Open
Abstract
Sympathetic and vagal activation is linked to atrial arrhythmogenesis. Here we investigated the small conductance Ca2+-activated K+ (SK)-channel pore-blocker N-(pyridin-2-yl)-4-(pyridine-2-yl)thiazol-2-amine (ICA) on action potential (AP) and atrial fibrillation (AF) parameters in isolated rat atria during β-adrenergic [isoprenaline (ISO)] and muscarinic M2 [carbachol (CCh)] activation. Furthermore, antiarrhythmic efficacy of ICA was benchmarked toward the class-IC antiarrhythmic drug flecainide (Fleca). ISO increased the spontaneous beating frequency but did not affect other AP parameters. As expected, CCh hyperpolarized resting membrane potential (-6.2 ± 0.9 mV), shortened APD90 (24.2 ± 1.6 vs. 17.7 ± 1.1 ms), and effective refractory period (ERP; 20.0 ± 1.3 vs. 15.8 ± 1.3 ms). The duration of burst pacing triggered AF was unchanged in the presence of CCh compared to control atria (12.8 ± 5.3 vs. 11.2 ± 3.6 s), while β-adrenergic activation resulted in shorter AF durations (3.3 ± 1.7 s) and lower AF-frequency compared to CCh. Treatment with ICA (10 μM) in ISO -stimulated atria prolonged APD90 and ERP, while the AF burden was reduced (7.1 ± 5.5 vs. 0.1 ± 0.1 s). In CCh-stimulated atria, ICA treatment also resulted in APD90 and ERP prolongation and shorter AF durations. Fleca treatment in CCh-stimulated atria prolonged APD90 and ERP and abbreviated the AF duration to a similar extent as with ICA. Muscarinic activated atria constitutes a more arrhythmogenic substrate than β-adrenoceptor activated atria. Pharmacological inhibition of SK channels by ICA is effective under both conditions and equally efficacious to Fleca.
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Affiliation(s)
- Lasse Skibsbye
- Cardiac Physiology Laboratory, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anne K Bengaard
- Cardiac Physiology Laboratory, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - A M Uldum-Nielsen
- Cardiac Physiology Laboratory, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kim Boddum
- Cardiac Physiology Laboratory, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Torsten Christ
- Department of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, DZHK: German Centre for Cardiovascular Research, Hamburg, Germany
| | - Thomas Jespersen
- Cardiac Physiology Laboratory, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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15
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Gu M, Zhu Y, Yin X, Zhang DM. Small-conductance Ca 2+-activated K + channels: insights into their roles in cardiovascular disease. Exp Mol Med 2018; 50:1-7. [PMID: 29651007 PMCID: PMC5938042 DOI: 10.1038/s12276-018-0043-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Revised: 12/11/2017] [Accepted: 12/12/2017] [Indexed: 12/13/2022] Open
Abstract
Life-threatening malignant arrhythmias in pathophysiological conditions can increase the mortality and morbidity of patients with cardiovascular diseases. Cardiac electrical activity depends on the coordinated propagation of excitatory stimuli and the generation of action potentials in cardiomyocytes. Action potential formation results from the opening and closing of ion channels. Recent studies have indicated that small-conductance calcium-activated potassium (SK) channels play a critical role in cardiac repolarization in pathophysiological but not normal physiological conditions. The aim of this review is to describe the role of SK channels in healthy and diseased hearts, to suggest cardiovascular pathophysiologic targets for intervention, and to discuss studies of agents that target SK channels for the treatment of cardiovascular diseases.
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Affiliation(s)
- Mingxia Gu
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Jiangsu, 210006, Nanjing, China
- Department of Cardiology, Nanjing Central Hospital, Jiangsu, 210018, Nanjing, China
| | - Yanrong Zhu
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Jiangsu, 210006, Nanjing, China
| | - Xiaorong Yin
- Department of Cardiology, Nanjing Central Hospital, Jiangsu, 210018, Nanjing, China
| | - Dai-Min Zhang
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Jiangsu, 210006, Nanjing, China.
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16
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Diness JG, Skibsbye L, Simó-Vicens R, Santos JL, Lundegaard P, Citerni C, Sauter DRP, Bomholtz SH, Svendsen JH, Olesen SP, Sørensen US, Jespersen T, Grunnet M, Bentzen BH. Termination of Vernakalant-Resistant Atrial Fibrillation by Inhibition of Small-Conductance Ca 2+-Activated K + Channels in Pigs. Circ Arrhythm Electrophysiol 2017; 10:CIRCEP.117.005125. [PMID: 29018164 PMCID: PMC5647113 DOI: 10.1161/circep.117.005125] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 08/21/2017] [Indexed: 11/17/2022]
Abstract
Supplemental Digital Content is available in the text. Background Evidence has emerged that small-conductance Ca2+-activated K+ (SK) channels constitute a new target for treatment of atrial fibrillation (AF). SK channels are predominantly expressed in the atria as compared with the ventricles. Various marketed antiarrhythmic drugs are limited by ventricular adverse effects and efficacy loss as AF progresses. Methods and Results A total of 43 pigs were used for the studies. AF reversion in conscious long-term tachypaced pigs: Pigs were subjected to atrial tachypacing (7 Hz) until they developed sustained AF that could not be reverted by vernakalant 4 mg/kg (18.8±3.3 days of atrial tachypacing). When the SK channel inhibitor AP14145 was tested in these animals, vernakalant-resistant AF was reverted to sinus rhythm, and reinduction of AF by burst pacing (50 Hz) was prevented in 8 of 8 pigs. Effects on refractory period and AF duration in open chest pigs: The effects of AP14145 and vernakalant on the effective refractory periods and acute burst pacing-induced AF were examined in anaesthetized open chest pigs. Both vernakalant and AP14145 significantly prolonged atrial refractoriness and reduced AF duration without affecting the ventricular refractoriness or blood pressure in pigs subjected to 7 days atrial tachypacing, as well as in sham-operated control pigs. Conclusions SK currents play a role in porcine atrial repolarization, and pharmacological inhibition of these with AP14145 demonstrates antiarrhythmic effects in a vernakalant-resistant porcine model of AF. These results suggest SK channel blockers as potentially interesting anti-AF drugs.
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Affiliation(s)
- Jonas Goldin Diness
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.).
| | - Lasse Skibsbye
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Rafel Simó-Vicens
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Joana Larupa Santos
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Pia Lundegaard
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Carlotta Citerni
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Daniel Rafael Peter Sauter
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Sofia Hammami Bomholtz
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Jesper Hastrup Svendsen
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Søren-Peter Olesen
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Ulrik S Sørensen
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Thomas Jespersen
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Morten Grunnet
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
| | - Bo Hjorth Bentzen
- From the Acesion Pharma, Copenhagen, Denmark (J.G.D., R.S.-V., C.C., D.R.P.S., S.H.B., U.S.S., M.G., B.H.B.); Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark (L.S., J.L.S., P.L., D.R.P.S., S.-P.O., T.J., M.G., B.H.B.); and the Heart Centre, Rigshospitalet, Copenhagen, Denmark (J.H.S.)
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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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18
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Skibsbye L, Jespersen T, Christ T, Maleckar MM, van den Brink J, Tavi P, Koivumäki JT. Refractoriness in human atria: Time and voltage dependence of sodium channel availability. J Mol Cell Cardiol 2016; 101:26-34. [PMID: 27773652 DOI: 10.1016/j.yjmcc.2016.10.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 09/30/2016] [Accepted: 10/19/2016] [Indexed: 11/16/2022]
Abstract
BACKGROUND Refractoriness of cardiac cells limits maximum frequency of electrical activity and protects the heart from tonic contractions. Short refractory periods support major arrhythmogenic substrates and augmentation of refractoriness is therefore seen as a main mechanism of antiarrhythmic drugs. Cardiomyocyte excitability depends on availability of sodium channels, which involves both time- and voltage-dependent recovery from inactivation. This study therefore aims to characterise how sodium channel inactivation affects refractoriness in human atria. METHODS AND RESULTS Steady-state activation and inactivation parameters of sodium channels measured in vitro in isolated human atrial cardiomyocytes were used to parameterise a mathematical human atrial cell model. Action potential data were acquired from human atrial trabeculae of patients in either sinus rhythm or chronic atrial fibrillation. The ex vivo measurements of action potential duration, effective refractory period and resting membrane potential were well-replicated in simulations using this new in silico model. Notably, the voltage threshold potential at which refractoriness was observed was not different between sinus rhythm and chronic atrial fibrillation tissues and was neither affected by changes in frequency (1 vs. 3Hz). CONCLUSIONS Our results suggest a preferentially voltage-dependent, rather than time-dependent, effect with respect to refractoriness at physiologically relevant rates in human atria. However, as the resting membrane potential is hyperpolarized in chronic atrial fibrillation, the voltage-dependence of excitability dominates, profoundly increasing the risk for arrhythmia re-initiation and maintenance in fibrillating atria. Our results thereby highlight resting membrane potential as a potential target in pharmacological management of chronic atrial fibrillation.
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Affiliation(s)
- Lasse Skibsbye
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Torsten Christ
- Department of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Germany; DZ HK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck,Germany
| | - Mary M Maleckar
- Center for Cardiological Innovation and Center for Biomedical Computing, Simula Research Laboratory, Oslo, Norway
| | - Jonas van den Brink
- Center for Cardiological Innovation and Center for Biomedical Computing, Simula Research Laboratory, Oslo, Norway
| | - Pasi Tavi
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Jussi T Koivumäki
- Center for Cardiological Innovation and Center for Biomedical Computing, Simula Research Laboratory, Oslo, Norway; Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.
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19
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Antiarrhythmic effect of the Ca 2+-activated K + (SK) channel inhibitor ICA combined with either amiodarone or dofetilide in an isolated heart model of atrial fibrillation. Pflugers Arch 2016; 468:1853-1863. [PMID: 27722784 PMCID: PMC6763419 DOI: 10.1007/s00424-016-1883-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 08/13/2016] [Accepted: 08/27/2016] [Indexed: 12/22/2022]
Abstract
Dose is an important parameter in terms of both efficacy and adverse effects in pharmacological treatment of atrial fibrillation (AF). Both of the class III antiarrhythmics dofetilide and amiodarone have documented anti-AF effects. While dofetilide has dose-related ventricular side effects, amiodarone primarily has adverse non-cardiac effects. Pharmacological inhibition of small conductance Ca2+-activated K+ (SK) channels has recently been reported to be antiarrhythmic in a number of animal AF models. In a Langendorff model of acutely induced AF on guinea pig hearts, it was investigated whether a combination of the SK channel blocker N-(pyridin-2-yl)-4-(pyridin-2-yl)thiazol-2-amine (ICA) together with either dofetilide or amiodarone provided a synergistic effect. The duration of AF was reduced with otherwise subefficacious concentrations of either dofetilide or amiodarone when combined with ICA, also at a subefficacious concentration. At a concentration level effective as monotherapy, dofetilide produced a marked increase in the QT interval. This QT prolonging effect was absent when combined with ICA at non-efficacious monotherapy concentrations. The results thereby reveal that combination of subefficacious concentrations of an SK channel blocker and either dofetilide or amiodarone can maintain anti-AF properties, while the risk of ventricular arrhythmias is reduced.
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20
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Veeraraghavan R, Lin J, Keener JP, Gourdie R, Poelzing S. Potassium channels in the Cx43 gap junction perinexus modulate ephaptic coupling: an experimental and modeling study. Pflugers Arch 2016; 468:1651-61. [PMID: 27510622 DOI: 10.1007/s00424-016-1861-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 06/27/2016] [Accepted: 07/25/2016] [Indexed: 12/01/2022]
Abstract
It was recently demonstrated that cardiac sodium channels (Nav1.5) localized at the perinexus, an intercalated disc (ID) nanodomain associated with gap junctions (GJ), may contribute to electrical coupling between cardiac myocytes via an ephaptic mechanism. Impairment of ephaptic coupling by acute interstitial edema (AIE)-induced swelling of the perinexus was associated with arrhythmogenic, anisotropic conduction slowing. Given that Kir2.1 has also recently been reported to localize at intercalated discs, we hypothesized that Kir2.1 channels may reside within the perinexus and that inhibiting them may mitigate arrhythmogenic conduction slowing observed during AIE. Using gated stimulated emission depletion (gSTED) and stochastic optical reconstruction microscopy (STORM) super-resolution microscopy, we indeed find that a significant proportion of Kir2.1 channels resides within the perinexus. Moreover, whereas Nav1.5 inhibition during AIE exacerbated arrhythmogenic conduction slowing, inhibiting Kir2.1 channels during AIE preferentially increased transverse conduction velocity-decreasing anisotropy and ameliorating arrhythmia risk compared to AIE alone. Comparison of our results with a nanodomain computer model identified enrichment of both Nav1.5 and Kir2.1 at intercalated discs as key factors underlying the experimental observations. We demonstrate that Kir2.1 channels are localized within the perinexus alongside Nav1.5 channels. Further, targeting Kir2.1 modulates intercellular coupling between cardiac myocytes, anisotropy of conduction, and arrhythmia propensity in a manner consistent with a role for ephaptic coupling in cardiac conduction. For over half a century, electrical excitation in the heart has been thought to occur exclusively via gap junction-mediated ionic current flow between cells. Further, excitation was thought to depend almost exclusively on sodium channels with potassium channels being involved mainly in returning the cell to rest. Here, we demonstrate that sodium and potassium channels co-reside within nanoscale domains at cell-to-cell contact sites. Experimental and computer modeling results suggest a role for these channels in electrical coupling between cardiac muscle cells via an ephaptic mechanism working in tandem with gap junctions. This new insight into the mechanism of cardiac electrical excitation could pave the way for novel therapies against cardiac rhythm disturbances.
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Affiliation(s)
- Rengasayee Veeraraghavan
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, 2 Riverside Circle, Roanoke, VA, 24016, USA.
| | - Joyce Lin
- Department of Mathematics, California Polytechnic State University, San Luis Obispo, CA, USA
| | - James P Keener
- Department of Mathematics, University of Utah, 155 South 1400 East, Salt Lake City, UT, 84112, USA
| | - Robert Gourdie
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, 2 Riverside Circle, Roanoke, VA, 24016, USA.
- School of Biomedical Engineering and Sciences, Virginia Polytechnic University, Blacksburg, VA, USA.
| | - Steven Poelzing
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, 2 Riverside Circle, Roanoke, VA, 24016, USA.
- School of Biomedical Engineering and Sciences, Virginia Polytechnic University, Blacksburg, VA, USA.
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21
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Abstract
Any disturbance of electrical impulse formation in the heart and of impulse conduction or action potential (AP) repolarization can lead to rhythm disorders. Potassium (K(+)) channels play a prominent role in the AP repolarization process. In this review we describe the causes and mechanisms of proarrhythmic effects that arise as a response to blockers of cardiac K(+) channels. The largest and chemically most diverse groups of compound targets are Kv11.1 (hERG) and Kv7.1 (KvLQT1) channels. Finally, the proarrhythmic propensity of atrial-selective K(+) blockers inhibiting Kv1.5, Kir3.1/3.4, SK, and K2P channels is discussed.
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Affiliation(s)
- Lasse Skibsbye
- Danish Arrhythmia Research Centre, Faculty of Health and Medical Sciences, University of Copenhagen, 3 Blegdamsvej, 3 Copenhagen N DK-2200, Denmark
| | - Ursula Ravens
- Department of Pharmacology and Toxicology, Medical Faculty Carl Gustav Carus, Institut für Pharmakologie und Toxikologie, TU Dresden, Fetscherstrasse 74, Dresden D-01307, Germany.
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22
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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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23
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van der Heyden MA, Jespersen T. Pharmacological exploration of the resting membrane potential reserve: Impact on atrial fibrillation. Eur J Pharmacol 2016; 771:56-64. [DOI: 10.1016/j.ejphar.2015.11.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/06/2015] [Accepted: 11/16/2015] [Indexed: 12/24/2022]
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van Hunnik A, Lau DH, Zeemering S, Kuiper M, Verheule S, Schotten U. Antiarrhythmic effect of vernakalant in electrically remodeled goat atria is caused by slowing of conduction and prolongation of postrepolarization refractoriness. Heart Rhythm 2015; 13:964-72. [PMID: 26681610 DOI: 10.1016/j.hrthm.2015.12.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND Vernakalant inhibits several potassium currents and causes a rate- and voltage-dependent inhibition of the sodium current. OBJECTIVE The aim of this study was to evaluate the antiarrhythmic mechanism of vernakalant in normal and electrically remodeled atria. METHODS Fourteen goats were instrumented with electrodes on both atria. Drug effects on refractory period (ERP), conduction velocity (CV), and atrial fibrillation cycle length (AFCL) were determined in normal goats (control) and after 2 (2dAF) or 11 (11dAF) days of pacing-induced atrial fibrillation (AF) in awake goats. To evaluate the contribution of changes in conduction and ERP, the same experiments were performed with flecainide and AVE0118. In a subset of goats, monophasic action potentials were recorded during anesthesia. RESULTS Vernakalant dose-dependently prolonged ERP and decreased CV in CTL experiments. Both effects were maintained after 2dAF and 11dAF. After 11dAF, conduction slowed down by 8.2 ± 1.5 cm/s and AFCL increased by 55 ± 3 ms, leading to AF termination in 5 out of 9 goats. Monophasic action potential measurements revealed that ERP prolongation was due to enhanced postrepolarization refractoriness. During pacing, vernakalant had comparable effects on CV as flecainide, while effect on ERP was comparable to AVE0118. During AF, all compounds had comparable effects on median AFCL and ERP despite differences in their effects on CV during pacing. CONCLUSION The antiarrhythmic effect of vernakalant in the goat, at clinically relevant plasma concentrations, is based on both conduction slowing and ERP prolongation due to postrepolarization refractoriness. These electrophysiological effects were not affected by long-term electrical remodeling of the atria.
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Affiliation(s)
- Arne van Hunnik
- Department of Physiology, Faculty of Medicine, Maastricht University, Maastricht, The Netherlands
| | - Dennis H Lau
- Department of Physiology, Faculty of Medicine, Maastricht University, Maastricht, The Netherlands
| | - Stef Zeemering
- Department of Physiology, Faculty of Medicine, Maastricht University, Maastricht, The Netherlands
| | - Marion Kuiper
- Department of Physiology, Faculty of Medicine, Maastricht University, Maastricht, The Netherlands
| | - Sander Verheule
- Department of Physiology, Faculty of Medicine, Maastricht University, Maastricht, The Netherlands
| | - Ulrich Schotten
- Department of Physiology, Faculty of Medicine, Maastricht University, Maastricht, The Netherlands.
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25
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Christophersen P, Wulff H. Pharmacological gating modulation of small- and intermediate-conductance Ca(2+)-activated K(+) channels (KCa2.x and KCa3.1). Channels (Austin) 2015. [PMID: 26217968 DOI: 10.1080/19336950.2015.1071748] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
This short review discusses pharmacological modulation of the opening/closing properties (gating) of small- and intermediate-conductance Ca(2+)-activated K(+) channels (KCa2 and KCa3.1) with special focus on mechanisms-of-action, selectivity, binding sites, and therapeutic potentials. Despite KCa channel gating-modulation being a relatively novel field in drug discovery, efforts in this area have already revealed a surprising plethora of pharmacological sites-of-actions and channel subtype selectivity exerted by different chemical classes. The currently published positive modulators show that such molecules are potentially useful for the treatment of various neurodegenerative disorders such as ataxia, alcohol dependence, and epilepsy as well as hypertension. The negative KCa2 modulators are very effective agents for atrial fibrillation. The prediction is that further unraveling of the molecular details of gating pharmacology will allow for the design of even more potent and subtype selective KCa modulators entering into drug development for these indications.
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Affiliation(s)
| | - Heike Wulff
- b Department of Pharmacology ; University of California, Davis ; Davis , CA USA
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