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Lei M, Salvage SC, Jackson AP, Huang CLH. Cardiac arrhythmogenesis: roles of ion channels and their functional modification. Front Physiol 2024; 15:1342761. [PMID: 38505707 PMCID: PMC10949183 DOI: 10.3389/fphys.2024.1342761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 01/22/2024] [Indexed: 03/21/2024] Open
Abstract
Cardiac arrhythmias cause significant morbidity and mortality and pose a major public health problem. They arise from disruptions in the normally orderly propagation of cardiac electrophysiological activation and recovery through successive cardiomyocytes in the heart. They reflect abnormalities in automaticity, initiation, conduction, or recovery in cardiomyocyte excitation. The latter properties are dependent on surface membrane electrophysiological mechanisms underlying the cardiac action potential. Their disruption results from spatial or temporal instabilities and heterogeneities in the generation and propagation of cellular excitation. These arise from abnormal function in their underlying surface membrane, ion channels, and transporters, as well as the interactions between them. The latter, in turn, form common regulatory targets for the hierarchical network of diverse signaling mechanisms reviewed here. In addition to direct molecular-level pharmacological or physiological actions on these surface membrane biomolecules, accessory, adhesion, signal transduction, and cytoskeletal anchoring proteins modify both their properties and localization. At the cellular level of excitation-contraction coupling processes, Ca2+ homeostatic and phosphorylation processes affect channel activity and membrane excitability directly or through intermediate signaling. Systems-level autonomic cellular signaling exerts both acute channel and longer-term actions on channel expression. Further upstream intermediaries from metabolic changes modulate the channels both themselves and through modifying Ca2+ homeostasis. Finally, longer-term organ-level inflammatory and structural changes, such as fibrotic and hypertrophic remodeling, similarly can influence all these physiological processes with potential pro-arrhythmic consequences. These normal physiological processes may target either individual or groups of ionic channel species and alter with particular pathological conditions. They are also potentially alterable by direct pharmacological action, or effects on longer-term targets modifying protein or cofactor structure, expression, or localization. Their participating specific biomolecules, often clarified in experimental genetically modified models, thus constitute potential therapeutic targets. The insights clarified by the physiological and pharmacological framework outlined here provide a basis for a recent modernized drug classification. Together, they offer a translational framework for current drug understanding. This would facilitate future mechanistically directed therapeutic advances, for which a number of examples are considered here. The latter are potentially useful for treating cardiac, in particular arrhythmic, disease.
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Affiliation(s)
- Ming Lei
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Samantha C. Salvage
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Antony P. Jackson
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Christopher L.-H. Huang
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
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2
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Rossi A, Giannoni A, Piacenti M. Prognostic value of right ventricular refractory period heterogeneity in Brugada syndrome. Independent predictor or part of something more complex? Author's reply. Europace 2022; 25:780-781. [PMID: 36548949 PMCID: PMC9935027 DOI: 10.1093/europace/euac249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Affiliation(s)
- Andrea Rossi
- Fondazione Toscana Gabriele Monasterio, via
Moruzzi 1, Pisa 56124, Italy
| | - Alberto Giannoni
- Corresponding author. Tel: +39-050-3152189, Fax: +39-050-3152109;
E-mail addresses: ;
| | - Marcello Piacenti
- Fondazione Toscana Gabriele Monasterio, via
Moruzzi 1, Pisa 56124, Italy
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3
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Rossi A, Giannoni A, Nesti M, Notarstefano P, Castiglione V, Solarino G, Teresi L, Mirizzi G, Russo V, Panchetti L, Startari U, Ripoli A, Gentile F, Santoro A, Botto N, Casolo G, Sieira J, Pieroni M, Santangeli P, Emdin M, Piacenti M. Prognostic value of right ventricular refractory period heterogeneity in Type-1 Brugada electrocardiographic pattern. Europace 2022; 25:651-659. [PMID: 36196034 PMCID: PMC9935005 DOI: 10.1093/europace/euac168] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 08/31/2022] [Indexed: 12/24/2022] Open
Abstract
AIMS To investigate the prognostic significance of heterogeneity in the refractoriness of right ventricular (RV) outflow tract (RVOT) and RV apex at the electrophysiological study (EPS) in Brugada syndrome (BrS). METHODS AND RESULTS A cohort of BrS patients (primary prevention) from five Italian centres was retrospectively analysed. Patients with spontaneous or drug-induced Type-1 electrocardiogram (ECG) + symptoms were offered an EPS for prognostic stratification. The primary endpoint was a composite of sudden cardiac death (SCD), resuscitated cardiac arrest, or appropriate intervention by the implantable cardioverter-defibrillator (ICD). Three hundred and seventy-two patients with BrS were evaluated (44 ± 15 years, 69% males, 23% with ICD): 4 SCDs and 17 ICD interventions occurred at follow-up (median 48, interquartile range: 36-60 months). Family history of SCD, syncope, and a spontaneous Type-1 ECG pattern were univariate predictors of the primary endpoint in the whole population. In patients undergoing EPS (n = 198, 53%, 44 ± 12 years, 71% males, 39% with ICD), 3 SCD and 15 ICD interventions occurred at follow-up. In this subset, the primary endpoint was not only predicted by ventricular tachycardia/fibrillation inducibility but also by a difference in the refractory period between RVOT and RV apex (ΔRPRVOT-apex) >60 ms. ΔRPRVOT-apex > 60 ms remained an independent predictor of SCD/ICD shock at bivariate analysis, even when adjusted for the other univariate predictors, showing the highest predictive power at C-statistic analysis (0.75, 95% confidence interval 0.63-0.86). CONCLUSIONS Heterogeneity of RV refractory periods is a strong, independent predictor of life-threatening arrhythmias in BrS patients, beyond VT/VF inducibility at EPS and common clinical predictors.
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Affiliation(s)
| | - Alberto Giannoni
- Corresponding author. Tel: +39 050 3153396; fax: +39 050 3152109.
E-mail address: ;
| | - Martina Nesti
- Cardiovascular and Neurological Department, San Donato
Hospital, Arezzo, Italy
| | | | - Vincenzo Castiglione
- Health Science Interdisciplinary Center, Scuola Superiore
Sant'Anna, Pisa, Italy
| | | | - Lucio Teresi
- Health Science Interdisciplinary Center, Scuola Superiore
Sant'Anna, Pisa, Italy
| | | | - Vincenzo Russo
- Department of Translational Medical Sciences, University of Campania Luigi
Vanvitelli, Monaldi Hospital, Naples, Italy
| | | | | | | | | | - Amato Santoro
- Cardiology Division, Azienda Ospedaliera Universitaria
Senese, Siena, Italy
| | | | | | - Juan Sieira
- Heart Rhythm Management Centre, Universitair Ziekenhuis
Brussel, Brussels, Belgium
| | - Maurizio Pieroni
- Cardiovascular and Neurological Department, San Donato
Hospital, Arezzo, Italy
| | - Pasquale Santangeli
- Electrophysiology Section, Cardiovascular Division, Hospital of the
University of Pennsylvania, Philadelphia, PA,
USA
| | - Michele Emdin
- Fondazione Toscana Gabriele Monasterio,
Pisa, Italy,Health Science Interdisciplinary Center, Scuola Superiore
Sant'Anna, Pisa, Italy
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Li Y, Lang S, Akin I, Zhou X, El-Battrawy I. Brugada Syndrome: Different Experimental Models and the Role of Human Cardiomyocytes From Induced Pluripotent Stem Cells. J Am Heart Assoc 2022; 11:e024410. [PMID: 35322667 PMCID: PMC9075459 DOI: 10.1161/jaha.121.024410] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Brugada syndrome (BrS) is an inherited and rare cardiac arrhythmogenic disease associated with an increased risk of ventricular fibrillation and sudden cardiac death. Different genes have been linked to BrS. The majority of mutations are located in the SCN5A gene, and the typical abnormal ECG is an elevation of the ST segment in the right precordial leads V1 to V3. The pathophysiological mechanisms of BrS were studied in different models, including animal models, heterologous expression systems, and human-induced pluripotent stem cell-derived cardiomyocyte models. Currently, only a few BrS studies have used human-induced pluripotent stem cell-derived cardiomyocytes, most of which have focused on genotype-phenotype correlations and drug screening. The combination of new technologies, such as clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 (CRISPR associated protein 9)-mediated genome editing and 3-dimensional engineered heart tissues, has provided novel insights into the pathophysiological mechanisms of the disease and could offer opportunities to improve the diagnosis and treatment of patients with BrS. This review aimed to compare different models of BrS for a better understanding of the roles of human-induced pluripotent stem cell-derived cardiomyocytes in current BrS research and personalized medicine at a later stage.
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Affiliation(s)
- Yingrui Li
- First Department of Medicine Medical Faculty Mannheim University Medical Centre Mannheim (UMM)University of Heidelberg Mannheim Germany
| | - Siegfried Lang
- First Department of Medicine Medical Faculty Mannheim University Medical Centre Mannheim (UMM)University of Heidelberg Mannheim Germany.,DZHK (German Center for Cardiovascular Research), Partner Site, Heidelberg-Mannheim Mannheim Germany
| | - Ibrahim Akin
- First Department of Medicine Medical Faculty Mannheim University Medical Centre Mannheim (UMM)University of Heidelberg Mannheim Germany.,DZHK (German Center for Cardiovascular Research), Partner Site, Heidelberg-Mannheim Mannheim Germany
| | - Xiaobo Zhou
- First Department of Medicine Medical Faculty Mannheim University Medical Centre Mannheim (UMM)University of Heidelberg Mannheim Germany.,Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province Institute of Cardiovascular Research Southwest Medical University Luzhou Sichuan China.,DZHK (German Center for Cardiovascular Research), Partner Site, Heidelberg-Mannheim Mannheim Germany
| | - Ibrahim El-Battrawy
- First Department of Medicine Medical Faculty Mannheim University Medical Centre Mannheim (UMM)University of Heidelberg Mannheim Germany.,DZHK (German Center for Cardiovascular Research), Partner Site, Heidelberg-Mannheim Mannheim Germany.,Department of Cardiology and Angiology Bergmannsheil Bochum Medical Clinic II Ruhr University Bochum Germany
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Sawa Y, Matsushita N, Sato S, Ishida N, Saito M, Sanbe A, Morino Y, Taira E, Obara M, Hirose M. Chronic HDAC6 Activation Induces Atrial Fibrillation Through Atrial Electrical and Structural Remodeling in Transgenic Mice. Int Heart J 2021; 62:616-626. [PMID: 34054002 DOI: 10.1536/ihj.20-703] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Atrial fibrillation (AF) is a relatively common complication of hypertension. Chronic hypertension induces cardiac HDAC6 catalytic activity. However, whether HDAC6 activation contributes to hypertension-induced AF is still uncertain. We examined whether chronic cardiac HDAC6 activation-induced atrial remodeling, leading to AF induction.The HDAC6 constitutively active transgenic (TG) (HDAC6 active TG) mouse overexpressing the active HDAC6 protein, specifically in cardiomyocytes, was created to examine the effects of chronic HDAC6 activation on atrial electrical and structural remodeling and AF induction in HDAC6 active TG and non-transgenic (NTG) mice. Left atrial burst pacing (S1S1 = 30 msec) for 15-30 sec significantly increased the frequency of sustained AF in HDAC6 active-TG mice compared with NTG mice. Left steady-state atrial pacing (S1S1 = 80 msec) decreased the atrial conduction velocity in isolated HDAC6 active TG compared with NTG mouse atria. The atrial size was similar between HDAC6 active TG and NTG mice. In contrast, atrial interstitial fibrosis increased in HDAC6 active TG compared with that of NTG mouse atria. While protein expression levels of both CX40 and CX43 were similar between HDAC6 active TG and NTG mouse atria, a heterogeneous distribution of CX40 and CX43 occurred in HDAC6 active-TG mouse atria but not in NTG mouse atria. Gene expression of interleukin 6 increased in HDAC6 active TG compared with NTG mouse atria.Chronic cardiac HDAC6 activation induced atrial electrical and structural remodeling, and sustained AF. Hypertension-induced cardiac HDAC6 catalytic activity may play important roles in the development of AF.
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Affiliation(s)
- Yohei Sawa
- Division of Molecular and Cellular Pharmacology, Department of Pathophysiology and Pharmacology, Iwate Medical University School of Pharmaceutical Science.,Division of Cardiology, Department of Internal Medicine, Iwate Medical University, School of Medicine
| | - Naoko Matsushita
- Division of Cardiology, Department of Internal Medicine, Iwate Medical University, School of Medicine
| | - Sachiko Sato
- Department of Pharmacology, Iwate Medical University, School of Medicine
| | - Nanae Ishida
- Division of Molecular and Cellular Pharmacology, Department of Pathophysiology and Pharmacology, Iwate Medical University School of Pharmaceutical Science
| | - Maki Saito
- Department of Pharmacy, Iryo Sosei University, School of Pharmaceutical Science
| | - Atsushi Sanbe
- Division of Pharmacotherapeutics, Department of Pathophysiology and Pharmacology, Iwate Medical University School of Pharmaceutical Science
| | - Yoshihiro Morino
- Division of Cardiology, Department of Internal Medicine, Iwate Medical University, School of Medicine
| | - Eiichi Taira
- Department of Pharmacology, Iwate Medical University, School of Medicine
| | - Mami Obara
- Department of Pharmacology, Iwate Medical University, School of Medicine
| | - Masamichi Hirose
- Division of Molecular and Cellular Pharmacology, Department of Pathophysiology and Pharmacology, Iwate Medical University School of Pharmaceutical Science
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Ahmad S, Valli H, Smyth R, Jiang AY, Jeevaratnam K, Matthews HR, Huang CL. Reduced cardiomyocyte Na + current in the age-dependent murine Pgc-1β -/- model of ventricular arrhythmia. J Cell Physiol 2019; 234:3921-3932. [PMID: 30146680 PMCID: PMC6492124 DOI: 10.1002/jcp.27183] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 07/12/2018] [Indexed: 12/27/2022]
Abstract
Peroxisome proliferator-activated receptor-γ coactivator-1 deficient (Pgc-1β-/- ) murine hearts model the increased, age-dependent, ventricular arrhythmic risks attributed to clinical conditions associated with mitochondrial energetic dysfunction. These were accompanied by compromised action potential (AP) upstroke rates and impaired conduction velocities potentially producing arrhythmic substrate. We tested a hypothesis implicating compromised Na+ current in these electrophysiological phenotypes by applying loose patch-clamp techniques in intact young and aged, wild-type (WT) and Pgc-1β-/- , ventricular cardiomyocyte preparations for the first time. This allowed conservation of their in vivo extracellular and intracellular conditions. Depolarising steps elicited typical voltage-dependent activating and inactivating inward Na+ currents with peak amplitudes increasing or decreasing with their respective activating or preceding inactivating voltage steps. Two-way analysis of variance associated Pgc-1β-/- genotype with independent reductions in maximum peak ventricular Na+ currents from -36.63 ± 2.14 (n = 20) and -35.43 ± 1.96 (n = 18; young and aged WT, respectively), to -29.06 ± 1.65 (n = 23) and -27.93 ± 1.63 (n = 20; young and aged Pgc-1β-/- , respectively) pA/μm2 (p < 0.0001), without independent effects of, or interactions with age. Voltages at half-maximal current V*, and steepness factors k in plots of voltage dependences of both Na+ current activation and inactivation, and time constants for its postrepolarisation recovery from inactivation, remained indistinguishable through all experimental groups. So were the activation and rectification properties of delayed outward (K+ ) currents, demonstrated from tail currents reflecting current recoveries from respective varying or constant voltage steps. These current-voltage properties directly implicate decreases specifically in maximum available Na+ current with unchanged voltage dependences and unaltered K+ current properties, in proarrhythmic reductions in AP conduction velocity in Pgc-1β-/- ventricles.
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Affiliation(s)
- Shiraz Ahmad
- Physiological LaboratoryUniversity of CambridgeCambridgeUnited Kingdom
| | - Haseeb Valli
- Physiological LaboratoryUniversity of CambridgeCambridgeUnited Kingdom
| | - Robert Smyth
- Physiological LaboratoryUniversity of CambridgeCambridgeUnited Kingdom
| | - Anita Y. Jiang
- Physiological LaboratoryUniversity of CambridgeCambridgeUnited Kingdom
| | - Kamalan Jeevaratnam
- Physiological LaboratoryUniversity of CambridgeCambridgeUnited Kingdom
- Department of Veterinary Pre‐clinical Sciences, Faculty of Health and Medical SciencesUniversity of SurreyGuildfordUnited Kingdom
- Department of Physiology, PU‐RCSI School of Medicine, Perdana UniversitySerdangMalaysia
| | - Hugh R. Matthews
- Physiological LaboratoryUniversity of CambridgeCambridgeUnited Kingdom
| | - Christopher L.‐H. Huang
- Physiological LaboratoryUniversity of CambridgeCambridgeUnited Kingdom
- Department of BiochemistryUniversity of CambridgeCambridgeUnited Kingdom
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7
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Ahmad S, Valli H, Chadda KR, Cranley J, Jeevaratnam K, Huang CLH. Ventricular pro-arrhythmic phenotype, arrhythmic substrate, ageing and mitochondrial dysfunction in peroxisome proliferator activated receptor-γ coactivator-1β deficient (Pgc-1β -/-) murine hearts. Mech Ageing Dev 2018; 173:92-103. [PMID: 29763629 PMCID: PMC6004599 DOI: 10.1016/j.mad.2018.05.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2017] [Revised: 04/19/2018] [Accepted: 05/11/2018] [Indexed: 12/24/2022]
Abstract
INTRODUCTION Ageing and age-related bioenergetic conditions including obesity, diabetes mellitus and heart failure constitute clinical ventricular arrhythmic risk factors. MATERIALS AND METHODS Pro-arrhythmic properties in electrocardiographic and intracellular recordings were compared in young and aged, peroxisome proliferator-activated receptor-γ coactivator-1β knockout (Pgc-1β-/-) and wild type (WT), Langendorff-perfused murine hearts, during regular and programmed stimulation (PES), comparing results by two-way ANOVA. RESULTS AND DISCUSSION Young and aged Pgc-1β-/- showed higher frequencies and durations of arrhythmic episodes through wider PES coupling-interval ranges than WT. Both young and old, regularly-paced, Pgc-1β-/- hearts showed slowed maximum action potential (AP) upstrokes, (dV/dt)max (∼157 vs. 120-130 V s-1), prolonged AP latencies (by ∼20%) and shortened refractory periods (∼58 vs. 51 ms) but similar AP durations (∼50 ms at 90% recovery) compared to WT. However, Pgc-1β-/- genotype and age each influenced extrasystolic AP latencies during PES. Young and aged WT ventricles displayed distinct, but Pgc-1β-/- ventricles displayed similar dependences of AP latency upon (dV/dt)max resembling aged WT. They also independently increased myocardial fibrosis. AP wavelengths combining activation and recovery terms paralleled contrasting arrhythmic incidences in Pgc-1β-/- and WT hearts. Mitochondrial dysfunction thus causes pro-arrhythmic Pgc-1β-/- phenotypes by altering AP conduction through reducing (dV/dt)max and causing age-dependent fibrotic change.
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Affiliation(s)
- Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, United Kingdom
| | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, United Kingdom
| | - Karan R Chadda
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, United Kingdom; Faculty of Health and Medical Sciences, University of Surrey, GU2 7AL, Guildford, Surrey, United Kingdom
| | - James Cranley
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, United Kingdom
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, GU2 7AL, Guildford, Surrey, United Kingdom; PU-RCSI School of Medicine, Perdana University, 43400, Serdang, Selangor Darul Ehsan, Malaysia
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, United Kingdom; Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW, United Kingdom.
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Salvage SC, Chandrasekharan KH, Jeevaratnam K, Dulhunty AF, Thompson AJ, Jackson AP, Huang CL. Multiple targets for flecainide action: implications for cardiac arrhythmogenesis. Br J Pharmacol 2018; 175:1260-1278. [PMID: 28369767 PMCID: PMC5866987 DOI: 10.1111/bph.13807] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 03/27/2017] [Accepted: 03/29/2017] [Indexed: 12/19/2022] Open
Abstract
Flecainide suppresses cardiac tachyarrhythmias including paroxysmal atrial fibrillation, supraventricular tachycardia and arrhythmic long QT syndromes (LQTS), as well as the Ca2+ -mediated, catecholaminergic polymorphic ventricular tachycardia (CPVT). However, flecainide can also exert pro-arrhythmic effects most notably following myocardial infarction and when used to diagnose Brugada syndrome (BrS). These divergent actions result from its physiological and pharmacological actions at multiple, interacting levels of cellular organization. These were studied in murine genetic models with modified Nav channel or intracellular ryanodine receptor (RyR2)-Ca2+ channel function. Flecainide accesses its transmembrane Nav 1.5 channel binding site during activated, open, states producing a use-dependent antagonism. Closing either activation or inactivation gates traps flecainide within the pore. An early peak INa related to activation of Nav channels followed by rapid de-activation, drives action potential (AP) upstrokes and their propagation. This is diminished in pro-arrhythmic conditions reflecting loss of function of Nav 1.5 channels, such as BrS, accordingly exacerbated by flecainide challenge. Contrastingly, pro-arrhythmic effects attributed to prolonged AP recovery by abnormal late INaL following gain-of-function modifications of Nav 1.5 channels in LQTS3 are reduced by flecainide. Anti-arrhythmic effects of flecainide that reduce triggering in CPVT models mediated by sarcoplasmic reticular Ca2+ release could arise from its primary actions on Nav channels indirectly decreasing [Ca2+ ]i through a reduced [Na+ ]i and/or direct open-state RyR2-Ca2+ channel antagonism. The consequent [Ca2+ ]i alterations could also modify AP propagation velocity and therefore arrhythmic substrate through its actions on Nav 1.5 channel function. This is consistent with the paradoxical differences between flecainide actions upon Na+ currents, AP conduction and arrhythmogenesis under circumstances of normal and increased RyR2 function. LINKED ARTICLES This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.
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Affiliation(s)
- Samantha C Salvage
- Department of BiochemistryUniversity of CambridgeCambridgeUK
- Physiological LaboratoryUniversity of CambridgeCambridgeUK
| | | | - Kamalan Jeevaratnam
- Faculty of Health and Medical SciencesUniversity of SurreyGuildfordUK
- School of MedicinePerdana University – Royal College of Surgeons IrelandSerdangSelangor Darul EhsanMalaysia
| | - Angela F Dulhunty
- Muscle Research Group, Eccles Institute of Neuroscience, John Curtin School of Medical ResearchAustralian National UniversityActonAustralia
| | | | | | - Christopher L‐H Huang
- Department of BiochemistryUniversity of CambridgeCambridgeUK
- Physiological LaboratoryUniversity of CambridgeCambridgeUK
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Valli H, Ahmad S, Sriharan S, Dean LD, Grace AA, Jeevaratnam K, Matthews HR, Huang CLH. Epac-induced ryanodine receptor type 2 activation inhibits sodium currents in atrial and ventricular murine cardiomyocytes. Clin Exp Pharmacol Physiol 2017; 45:278-292. [PMID: 29027245 PMCID: PMC5814738 DOI: 10.1111/1440-1681.12870] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 09/23/2017] [Accepted: 09/27/2017] [Indexed: 12/16/2022]
Abstract
Acute RyR2 activation by exchange protein directly activated by cAMP (Epac) reversibly perturbs myocyte Ca2+ homeostasis, slows myocardial action potential conduction, and exerts pro‐arrhythmic effects. Loose patch‐clamp studies, preserving in vivo extracellular and intracellular conditions, investigated Na+ current in intact cardiomyocytes in murine atrial and ventricular preparations following Epac activation. Depolarising steps to varying test voltages activated typical voltage‐dependent Na+ currents. Plots of peak current against depolarisation from resting potential gave pretreatment maximum atrial and ventricular currents of −20.23 ± 1.48 (17) and −29.8 ± 2.4 (10) pA/μm2 (mean ± SEM [n]). Challenge by 8‐CPT (1 μmol/L) reduced these currents to −11.21 ± 0.91 (12) (P < .004) and −19.3 ± 1.6 (11) pA/μm2 (P < .04) respectively. Currents following further addition of the RyR2 inhibitor dantrolene (10 μmol/L) (−19.91 ± 2.84 (13) and −26.6 ± 1.7 (17)), and dantrolene whether alone (−19.53 ± 1.97 (8) and −27.6 ± 1.9 (14)) or combined with 8‐CPT (−19.93 ± 2.59 (12) and −29.9 ± 2.5(11)), were indistinguishable from pretreatment values (all P >> .05). Assessment of the inactivation that followed by applying subsequent steps to a fixed voltage 100 mV positive to resting potential gave concordant results. Half‐maximal inactivation voltages and steepness factors, and time constants for Na+ current recovery from inactivation in double‐pulse experiments, were similar through all the pharmacological conditions. Intracellular sharp microelectrode membrane potential recordings in intact Langendorff‐perfused preparations demonstrated concordant variations in maximum rates of atrial and ventricular action potential upstroke, (dV/dt)max. We thus demonstrate an acute, reversible, Na+ channel inhibition offering a possible mechanism for previously reported pro‐arrhythmic slowing of AP propagation following modifications of Ca2+ homeostasis, complementing earlier findings from chronic alterations in Ca2+ homeostasis in genetically‐modified RyR2‐P2328S hearts.
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Affiliation(s)
- Haseeb Valli
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Sujan Sriharan
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Lydia D Dean
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Andrew A Grace
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Kamalan Jeevaratnam
- Physiological Laboratory, University of Cambridge, Cambridge, UK.,Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK.,PU-RCSI School of Medicine, Perdana University, Serdang, Selangor Darul Ehsan, Malaysia
| | - Hugh R Matthews
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Cambridge, UK.,Department of Biochemistry, University of Cambridge, Cambridge, UK
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Valli H, Ahmad S, Jiang AY, Smyth R, Jeevaratnam K, Matthews HR, Huang CLH. Cardiomyocyte ionic currents in intact young and aged murine Pgc-1β -/- atrial preparations. Mech Ageing Dev 2017; 169:1-9. [PMID: 29197478 PMCID: PMC5846848 DOI: 10.1016/j.mad.2017.11.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 11/11/2017] [Accepted: 11/28/2017] [Indexed: 12/19/2022]
Abstract
Energetically-deficient Pgc-1β−/− murine atria show age-dependent arrhythmia. Voltage clamp studies investigated their underlying membrane current changes. Pgc-1β−/− atria showed reduced inward Na+ currents with normal voltage-dependences. Outward repolarising K+ currents retained normal activation and rectification. A resulting slowed action potential conduction explains the arrhythmic phenotype.
Introduction Recent studies reported that energetically deficient murine Pgc-1β−/− hearts replicate age-dependent atrial arrhythmic phenotypes associated with their corresponding clinical conditions, implicating action potential (AP) conduction slowing consequent upon reduced AP upstroke rates. Materials and methods We tested a hypothesis implicating Na+ current alterations as a mechanism underlying these electrophysiological phenotypes. We applied loose patch-clamp techniques to intact young and aged, WT and Pgc-1β−/−, atrial cardiomyocyte preparations preserving their in vivo extracellular and intracellular conditions. Results and discussion Depolarising steps activated typical voltage-dependent activating and inactivating inward (Na+) currents whose amplitude increased or decreased with the amplitudes of the activating, or preceding inactivating, steps. Maximum values of peak Na+ current were independently influenced by genotype but not age or interacting effects of genotype and age on two-way ANOVA. Neither genotype, nor age, whether independently or interactively, influenced voltages at half-maximal current, or steepness factors, for current activation and inactivation, or time constants for recovery from inactivation following repolarisation. In contrast, delayed outward (K+) currents showed similar activation and rectification properties through all experimental groups. These findings directly demonstrate and implicate reduced Na+ in contrast to unchanged K+ current, as a mechanism for slowed conduction causing atrial arrhythmogenicity in Pgc-1β−/− hearts.
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Affiliation(s)
- Haseeb Valli
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom
| | - Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom
| | - Anita Y Jiang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom
| | - Robert Smyth
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom
| | - Kamalan Jeevaratnam
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom; Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, Surrey, United Kingdom; PU-RCSI School of Medicine, Perdana University, 43400 Serdang, Selangor Darul Ehsan, Malaysia
| | - Hugh R Matthews
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom; Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, United Kingdom.
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11
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McPheeters MT, Wang YT, Werdich AA, Jenkins MW, Laurita KR. An infrared optical pacing system for screening cardiac electrophysiology in human cardiomyocytes. PLoS One 2017; 12:e0183761. [PMID: 28837652 PMCID: PMC5570338 DOI: 10.1371/journal.pone.0183761] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 08/10/2017] [Indexed: 01/05/2023] Open
Abstract
Human cardiac myocytes derived from pluripotent stem cells (hCM) have invigorated interest in genetic disease mechanisms and cardiac safety testing; however, the technology to fully assess electrophysiological function in an assay that is amenable to high throughput screening has lagged. We describe a fully contactless system using optical pacing with an infrared (IR) laser and multi-site high fidelity fluorescence imaging to assess multiple electrophysiological parameters from hCM monolayers in a standard 96-well plate. Simultaneous multi-site action potentials (FluoVolt) or Ca2+ transients (Fluo4-AM) were measured, from which high resolution maps of conduction velocity and action potential duration (APD) were obtained in a single well. Energy thresholds for optical pacing were determined for cell plating density, laser spot size, pulse width, and wavelength and found to be within ranges reported previously for reliable pacing. Action potentials measured using FluoVolt and a microelectrode exhibited the same morphology and rate of depolarization. Importantly, we show that this can be achieved accurately with minimal damage to hCM due to optical pacing or fluorescence excitation. Finally, using this assay we demonstrate that hCM exhibit reproducible changes in repolarization and impulse conduction velocity for Flecainide and Quinidine, two well described reference compounds. In conclusion, we demonstrate a high fidelity electrophysiological screening assay that incorporates optical pacing with IR light to control beating rate of hCM monolayers.
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Affiliation(s)
- Matthew T. McPheeters
- Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States of America
- Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Yves T. Wang
- Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States of America
- Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Andreas A. Werdich
- Brigham and Women's Hospital/Harvard Medical School, Cardiovascular Division, Boston, Massachusetts, United States of America
| | - Michael W. Jenkins
- Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States of America
- Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Kenneth R. Laurita
- Brigham and Women's Hospital/Harvard Medical School, Cardiovascular Division, Boston, Massachusetts, United States of America
- Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio, United States of America
- Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail:
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12
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Osadchii OE. Role of abnormal repolarization in the mechanism of cardiac arrhythmia. Acta Physiol (Oxf) 2017; 220 Suppl 712:1-71. [PMID: 28707396 DOI: 10.1111/apha.12902] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In cardiac patients, life-threatening tachyarrhythmia is often precipitated by abnormal changes in ventricular repolarization and refractoriness. Repolarization abnormalities typically evolve as a consequence of impaired function of outward K+ currents in cardiac myocytes, which may be caused by genetic defects or result from various acquired pathophysiological conditions, including electrical remodelling in cardiac disease, ion channel modulation by clinically used pharmacological agents, and systemic electrolyte disorders seen in heart failure, such as hypokalaemia. Cardiac electrical instability attributed to abnormal repolarization relies on the complex interplay between a provocative arrhythmic trigger and vulnerable arrhythmic substrate, with a central role played by the excessive prolongation of ventricular action potential duration, impaired intracellular Ca2+ handling, and slowed impulse conduction. This review outlines the electrical activity of ventricular myocytes in normal conditions and cardiac disease, describes classical electrophysiological mechanisms of cardiac arrhythmia, and provides an update on repolarization-related surrogates currently used to assess arrhythmic propensity, including spatial dispersion of repolarization, activation-repolarization coupling, electrical restitution, TRIaD (triangulation, reverse use dependence, instability, and dispersion), and the electromechanical window. This is followed by a discussion of the mechanisms that account for the dependence of arrhythmic vulnerability on the location of the ventricular pacing site. Finally, the review clarifies the electrophysiological basis for cardiac arrhythmia produced by hypokalaemia, and gives insight into the clinical importance and pathophysiology of drug-induced arrhythmia, with particular focus on class Ia (quinidine, procainamide) and Ic (flecainide) Na+ channel blockers, and class III antiarrhythmic agents that block the delayed rectifier K+ channel (dofetilide).
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Affiliation(s)
- O. E. Osadchii
- Department of Health Science and Technology; University of Aalborg; Aalborg Denmark
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13
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Abstract
Cardiac arrhythmias can follow disruption of the normal cellular electrophysiological processes underlying excitable activity and their tissue propagation as coherent wavefronts from the primary sinoatrial node pacemaker, through the atria, conducting structures and ventricular myocardium. These physiological events are driven by interacting, voltage-dependent, processes of activation, inactivation, and recovery in the ion channels present in cardiomyocyte membranes. Generation and conduction of these events are further modulated by intracellular Ca2+ homeostasis, and metabolic and structural change. This review describes experimental studies on murine models for known clinical arrhythmic conditions in which these mechanisms were modified by genetic, physiological, or pharmacological manipulation. These exemplars yielded molecular, physiological, and structural phenotypes often directly translatable to their corresponding clinical conditions, which could be investigated at the molecular, cellular, tissue, organ, and whole animal levels. Arrhythmogenesis could be explored during normal pacing activity, regular stimulation, following imposed extra-stimuli, or during progressively incremented steady pacing frequencies. Arrhythmic substrate was identified with temporal and spatial functional heterogeneities predisposing to reentrant excitation phenomena. These could arise from abnormalities in cardiac pacing function, tissue electrical connectivity, and cellular excitation and recovery. Triggering events during or following recovery from action potential excitation could thereby lead to sustained arrhythmia. These surface membrane processes were modified by alterations in cellular Ca2+ homeostasis and energetics, as well as cellular and tissue structural change. Study of murine systems thus offers major insights into both our understanding of normal cardiac activity and its propagation, and their relationship to mechanisms generating clinical arrhythmias.
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Affiliation(s)
- Christopher L-H Huang
- Physiological Laboratory and the Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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14
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Tse G, Liu T, Li KHC, Laxton V, Chan YWF, Keung W, Li RA, Yan BP. Electrophysiological Mechanisms of Brugada Syndrome: Insights from Pre-clinical and Clinical Studies. Front Physiol 2016; 7:467. [PMID: 27803673 PMCID: PMC5067537 DOI: 10.3389/fphys.2016.00467] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 09/27/2016] [Indexed: 12/19/2022] Open
Abstract
Brugada syndrome (BrS), is a primary electrical disorder predisposing affected individuals to sudden cardiac death via the development of ventricular tachycardia and fibrillation (VT/VF). Originally, BrS was linked to mutations in the SCN5A, which encodes for the cardiac Na+ channel. To date, variants in 19 genes have been implicated in this condition, with 11, 5, 3, and 1 genes affecting the Na+, K+, Ca2+, and funny currents, respectively. Diagnosis of BrS is based on ECG criteria of coved- or saddle-shaped ST segment elevation and/or T-wave inversion with or without drug challenge. Three hypotheses based on abnormal depolarization, abnormal repolarization, and current-load-mismatch have been put forward to explain the electrophysiological mechanisms responsible for BrS. Evidence from computational modeling, pre-clinical, and clinical studies illustrates that molecular abnormalities found in BrS lead to alterations in excitation wavelength (λ), which ultimately elevates arrhythmic risk. A major challenge for clinicians in managing this condition is the difficulty in predicting the subset of patients who will suffer from life-threatening VT/VF. Several repolarization risk markers have been used thus far, but these neglect the contributions of conduction abnormalities in the form of slowing and dispersion. Indices incorporating both repolarization and conduction and based on the concept of λ have recently been proposed. These may have better predictive values than the existing markers.
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Affiliation(s)
- Gary Tse
- Department of Medicine and Therapeutics, Chinese University of Hong KongHong Kong, Hong Kong
- Li Ka Shing Institute of Health Sciences, Chinese University of Hong KongHong Kong, Hong Kong
| | - Tong Liu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical UniversityTianjin, China
| | - Ka H. C. Li
- Faculty of Medicine, Newcastle UniversityNewcastle, UK
| | - Victoria Laxton
- Intensive Care Department, Royal Brompton and Harefield NHS TrustLondon, UK
| | - Yin W. F. Chan
- School of Biological Sciences, University of CambridgeCambridge, UK
| | - Wendy Keung
- Stem Cell and Regenerative Medicine Consortium, Li Ka Shing Faculty of Medicine, The University of Hong KongPokfulam, Hong Kong
| | - Ronald A. Li
- Ming Wai Lau Centre for Reparative Medicine, Karolinska InstitutetSolna, Sweden
| | - Bryan P. Yan
- Department of Medicine and Therapeutics, Chinese University of Hong KongHong Kong, Hong Kong
- Department of Epidemiology and Preventive Medicine, Monash UniversityMelbourne, VIC, Australia
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15
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Ning F, Luo L, Ahmad S, Valli H, Jeevaratnam K, Wang T, Guzadhur L, Yang D, Fraser JA, Huang CLH, Ma A, Salvage SC. The RyR2-P2328S mutation downregulates Nav1.5 producing arrhythmic substrate in murine ventricles. Pflugers Arch 2015; 468:655-65. [PMID: 26545784 PMCID: PMC4792352 DOI: 10.1007/s00424-015-1750-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Revised: 09/25/2015] [Accepted: 10/19/2015] [Indexed: 01/05/2023]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) predisposes to ventricular arrhythmia due to altered Ca2+ homeostasis and can arise from ryanodine receptor (RyR2) mutations including RyR2-P2328S. Previous reports established that homozygotic murine RyR2-P2328S (RyR2S/S) hearts show an atrial arrhythmic phenotype associated with reduced action potential (AP) conduction velocity and sodium channel (Nav1.5) expression. We now relate ventricular arrhythmogenicity and slowed AP conduction in RyR2S/S hearts to connexin-43 (Cx43) and Nav1.5 expression and Na+ current (INa). Stimulation protocols applying extrasystolic S2 stimulation following 8 Hz S1 pacing at progressively decremented S1S2 intervals confirmed an arrhythmic tendency despite unchanged ventricular effective refractory periods (VERPs) in Langendorff-perfused RyR2S/S hearts. Dynamic pacing imposing S1 stimuli then demonstrated that progressive reductions of basic cycle lengths (BCLs) produced greater reductions in conduction velocity at equivalent BCLs and diastolic intervals in RyR2S/S than WT, but comparable changes in AP durations (APD90) and their alternans. Western blot analyses demonstrated that Cx43 protein expression in whole ventricles was similar, but Nav1.5 expression in both whole tissue and membrane fractions were significantly reduced in RyR2S/S compared to wild-type (WT). Loose patch-clamp studies similarly demonstrated reduced INa in RyR2S/S ventricles. We thus attribute arrhythmogenesis in RyR2S/S ventricles resulting from arrhythmic substrate produced by reduced conduction velocity to downregulated Nav1.5 reducing INa, despite normal determinants of repolarization and passive conduction. The measured changes were quantitatively compatible with earlier predictions of linear relationships between conduction velocity and the peak INa of the AP but nonlinear relationships between peak INa and maximum Na+ permeability.
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Affiliation(s)
- Feifei Ning
- Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University, No. 277 West Yanta Road, Xi'an, Shaanxi, 710061, People's Republic of China
| | - Ling Luo
- Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University, No. 277 West Yanta Road, Xi'an, Shaanxi, 710061, People's Republic of China
| | - Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Cambridge, CB2 3EG, UK
| | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Cambridge, CB2 3EG, UK
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Science, Duke of Kent Building, University of Surrey, Guildford, GU2 7TE, UK
- Perdana University-Royal College of Surgeons Ireland, 43400 Serdang, Selangor, Darul Ehsan, Malaysia
| | - Tingzhong Wang
- Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University, No. 277 West Yanta Road, Xi'an, Shaanxi, 710061, People's Republic of China
- Key Laboratory of Molecular Cardiology, Shaanxi Province, People's Republic of China
- Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University), Ministry of Education, Xi'an, People's Republic of China
| | - Laila Guzadhur
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK
- Niche Science and Technology, Falstaff House, Bardolph Road, Richmond, UK
| | - Dandan Yang
- Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University, No. 277 West Yanta Road, Xi'an, Shaanxi, 710061, People's Republic of China
| | - James A Fraser
- Physiological Laboratory, University of Cambridge, Cambridge, CB2 3EG, UK
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Cambridge, CB2 3EG, UK
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK
| | - Aiqun Ma
- Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University, No. 277 West Yanta Road, Xi'an, Shaanxi, 710061, People's Republic of China.
- Key Laboratory of Molecular Cardiology, Shaanxi Province, People's Republic of China.
- Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University), Ministry of Education, Xi'an, People's Republic of China.
| | - Samantha C Salvage
- Physiological Laboratory, University of Cambridge, Cambridge, CB2 3EG, UK.
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16
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Zaglia T, Pianca N, Borile G, Da Broi F, Richter C, Campione M, Lehnart SE, Luther S, Corrado D, Miquerol L, Mongillo M. Optogenetic determination of the myocardial requirements for extrasystoles by cell type-specific targeting of ChannelRhodopsin-2. Proc Natl Acad Sci U S A 2015; 112:E4495-504. [PMID: 26204914 PMCID: PMC4538656 DOI: 10.1073/pnas.1509380112] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Extrasystoles lead to several consequences, ranging from uneventful palpitations to lethal ventricular arrhythmias, in the presence of pathologies, such as myocardial ischemia. The role of working versus conducting cardiomyocytes, as well as the tissue requirements (minimal cell number) for the generation of extrasystoles, and the properties leading ectopies to become arrhythmia triggers (topology), in the normal and diseased heart, have not been determined directly in vivo. Here, we used optogenetics in transgenic mice expressing ChannelRhodopsin-2 selectively in either cardiomyocytes or the conduction system to achieve cell type-specific, noninvasive control of heart activity with high spatial and temporal resolution. By combining measurement of optogenetic tissue activation in vivo and epicardial voltage mapping in Langendorff-perfused hearts, we demonstrated that focal ectopies require, in the normal mouse heart, the simultaneous depolarization of at least 1,300-1,800 working cardiomyocytes or 90-160 Purkinje fibers. The optogenetic assay identified specific areas in the heart that were highly susceptible to forming extrasystolic foci, and such properties were correlated to the local organization of the Purkinje fiber network, which was imaged in three dimensions using optical projection tomography. Interestingly, during the acute phase of myocardial ischemia, focal ectopies arising from this location, and including both Purkinje fibers and the surrounding working cardiomyocytes, have the highest propensity to trigger sustained arrhythmias. In conclusion, we used cell-specific optogenetics to determine with high spatial resolution and cell type specificity the requirements for the generation of extrasystoles and the factors causing ectopies to be arrhythmia triggers during myocardial ischemia.
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MESH Headings
- Animals
- Arrhythmias, Cardiac/complications
- Arrhythmias, Cardiac/pathology
- Arrhythmias, Cardiac/physiopathology
- Cardiac Complexes, Premature/complications
- Cardiac Complexes, Premature/pathology
- Cardiac Complexes, Premature/physiopathology
- Channelrhodopsins
- Connexins/metabolism
- Coronary Vessels/pathology
- Coronary Vessels/physiopathology
- Electrophysiological Phenomena
- Humans
- Integrases/metabolism
- Ligation
- Male
- Mice, Inbred C57BL
- Mice, Transgenic
- Myocardial Ischemia/complications
- Myocardial Ischemia/pathology
- Myocardial Ischemia/physiopathology
- Myocardium/metabolism
- Myocardium/pathology
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Optogenetics/methods
- Organ Specificity
- Purkinje Fibers/metabolism
- Purkinje Fibers/pathology
- Purkinje Fibers/physiopathology
- Gap Junction alpha-5 Protein
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Affiliation(s)
- Tania Zaglia
- Department of Biomedical Sciences, University of Padova, 35122 Padova, Italy; Venetian Institute of Molecular Medicine, 35129 Padova, Italy
| | - Nicola Pianca
- Department of Biomedical Sciences, University of Padova, 35122 Padova, Italy; Venetian Institute of Molecular Medicine, 35129 Padova, Italy
| | - Giulia Borile
- Department of Biomedical Sciences, University of Padova, 35122 Padova, Italy; Venetian Institute of Molecular Medicine, 35129 Padova, Italy
| | | | - Claudia Richter
- Research Group Biomedical Physics, Max Planck Institute for Dynamics and Self-Organization, 37077 Gottingen, Germany
| | - Marina Campione
- Department of Biomedical Sciences, University of Padova, 35122 Padova, Italy; Neuroscience Institute, Consiglio Nazionale delle Ricerche, 35121 Padova, Italy
| | - Stephan E Lehnart
- Heart Research Center Göttingen, Clinic of Cardiology and Pulmonology, University Medical Center, 37077 Gottingen, Germany; German Centre for Cardiovascular Research, partner site Göttingen, 37077 Gottingen, Germany
| | - Stefan Luther
- Research Group Biomedical Physics, Max Planck Institute for Dynamics and Self-Organization, 37077 Gottingen, Germany; Heart Research Center Göttingen, Clinic of Cardiology and Pulmonology, University Medical Center, 37077 Gottingen, Germany; German Centre for Cardiovascular Research, partner site Göttingen, 37077 Gottingen, Germany; Institute for Nonlinear Dynamics, Georg-August-Universität Göttingen, 37077 Gottingen, Germany
| | - Domenico Corrado
- Department of Cardiologic, Thoracic and Vascular Sciences, University of Padova, 35128 Padova, Italy
| | - Lucile Miquerol
- Aix Marseille University, CNRS Institut de Biologie du Développement de Marseille UMR 7288, 13288 Marseille, France
| | - Marco Mongillo
- Department of Biomedical Sciences, University of Padova, 35122 Padova, Italy; Venetian Institute of Molecular Medicine, 35129 Padova, Italy; Neuroscience Institute, Consiglio Nazionale delle Ricerche, 35121 Padova, Italy;
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17
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Yang LZ, Zhu YC. Urocortin2 prolongs action potential duration and modulates potassium currents in guinea pig myocytes and HEK293 cells. Eur J Pharmacol 2015; 758:97-106. [DOI: 10.1016/j.ejphar.2015.03.078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2014] [Revised: 03/18/2015] [Accepted: 03/25/2015] [Indexed: 10/23/2022]
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18
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Salvage SC, King JH, Chandrasekharan KH, Jafferji DIG, Guzadhur L, Matthews HR, Huang CL, Fraser JA. Flecainide exerts paradoxical effects on sodium currents and atrial arrhythmia in murine RyR2-P2328S hearts. Acta Physiol (Oxf) 2015; 214:361-75. [PMID: 25850710 PMCID: PMC4510817 DOI: 10.1111/apha.12505] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 11/03/2014] [Accepted: 04/01/2015] [Indexed: 12/30/2022]
Abstract
Aims Cardiac ryanodine receptor mutations are associated with catecholaminergic polymorphic ventricular tachycardia (CPVT), and some, including RyR2-P2328S, also predispose to atrial fibrillation. Recent work associates reduced atrial Nav1.5 currents in homozygous RyR2-P2328S (RyR2S/S) mice with slowed conduction and increased arrhythmogenicity. Yet clinically, and in murine models, the Nav1.5 blocker flecainide reduces ventricular arrhythmogenicity in CPVT. We aimed to determine whether, and how, flecainide influences atrial arrhythmogenicity in RyR2S/S mice and their wild-type (WT) littermates. Methods We explored effects of 1 μm flecainide on WT and RyR2S/S atria. Arrhythmic incidence, action potential (AP) conduction velocity (CV), atrial effective refractory period (AERP) and AP wavelength (λ = CV × AERP) were measured using multi-electrode array recordings in Langendorff-perfused hearts; Na+ currents (INa) were recorded using loose patch clamping of superfused atria. Results RyR2S/S showed more frequent atrial arrhythmias, slower CV, reduced INa and unchanged AERP compared to WT. Flecainide was anti-arrhythmic in RyR2S/S but pro-arrhythmic in WT. It increased INa in RyR2S/S atria, whereas it reduced INa as expected in WT. It increased AERP while sparing CV in RyR2S/S, but reduced CV while sparing AERP in WT. Thus, RyR2S/S hearts have low λ relative to WT; flecainide then increases λ in RyR2S/S but decreases λ in WT. Conclusions Flecainide (1 μm) rescues the RyR2-P2328S atrial arrhythmogenic phenotype by restoring compromised INa and λ, changes recently attributed to increased sarcoplasmic reticular Ca2+ release. This contrasts with the increased arrhythmic incidence and reduced INa and λ with flecainide in WT.
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Affiliation(s)
- S. C. Salvage
- Physiological Laboratory University of Cambridge Cambridge UK
| | - J. H. King
- Physiological Laboratory University of Cambridge Cambridge UK
| | | | | | - L. Guzadhur
- Department of Biochemistry University of Cambridge Cambridge UK
| | - H. R. Matthews
- Physiological Laboratory University of Cambridge Cambridge UK
| | - C. L.‐H. Huang
- Physiological Laboratory University of Cambridge Cambridge UK
- Department of Biochemistry University of Cambridge Cambridge UK
| | - J. A. Fraser
- Physiological Laboratory University of Cambridge Cambridge UK
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19
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Matsushita N, Hirose M, Sanbe A, Kondo Y, Irie Y, Taira E. Nicorandil improves electrical remodelling, leading to the prevention of electrically induced ventricular tachyarrhythmia in a mouse model of desmin-related cardiomyopathy. Clin Exp Pharmacol Physiol 2014; 41:89-97. [PMID: 24117876 DOI: 10.1111/1440-1681.12185] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 09/26/2013] [Accepted: 09/30/2013] [Indexed: 11/28/2022]
Abstract
1. Transgenic (TG) mice overexpressing an arg120gly missense mutation in heat shock protein B5 (HSPB5; i.e. R120G TG mice) exhibit desmin-related cardiomyopathy. Recently, the cardioprotective effect of nicorandil has been shown to prolong the survival of R120G TG mice. However, whether the TG mice exhibit ventricular arrhythmias and whether nicorandil can inhibit these arrhythmias remain unknown. In the present study we examined the effects of chronic nicorandil administration on ventricular electrical remodelling and arrhythmias in R120G TG mice. 2. Mice were administered nicorandil (15 mg/kg per day) or vehicle (water) orally from 5 to 30 weeks of age. Electrocardiograms (ECG) and optical action potentials were recorded from R120G TG mouse hearts. In addition, the expression of ventricular connexin 43 and the cardiac Na(+) channel Nav1.5 was examined in TG mice. 3. All ECG parameters tested were prolonged in R120G TG compared with non-transgenic (NTG) mice. Nicorandil improved the prolonged P, PQ and QRS intervals in R120G TG mice. Interestingly, impulse conduction slowing and increases in the expression of total and phosphorylated connexin 43 and Nav1.5 were observed in ventricles from R120G TG compared with NTG mice. Nicorandil improved ventricular impulse conduction slowing and normalized the increased protein expression levels of total and phosphorylated connexin 43, but not of Nav1.5, in R120G TG mouse hearts. Electrical rapid pacing at the ventricle induced ventricular tachyarrhythmias (VT) in six of eight R120G TG mouse hearts, but not in any of the eight nicorandil-treated R120G TG mouse hearts (P < 0.05). 4. These findings demonstrate that nicorandil inhibits cardiac electrical remodelling and that the prevention of VT by nicorandil is associated with normalization of connexin 43 expression in this model.
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Affiliation(s)
- Naoko Matsushita
- Department of Molecular and Cellular Pharmacology, Iwate Medical University School of Pharmaceutical Sciences, Shiwa-gun, Iwate, Japan; Department of Pharmacology, Iwate Medical University School of Medicine, Shiwa-gun, Iwate, Japan
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20
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Bébarová M. Arrhythmogenesis in Brugada syndrome: impact and constrains of current concepts. Int J Cardiol 2013; 167:1760-71. [PMID: 23295036 DOI: 10.1016/j.ijcard.2012.12.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 11/15/2012] [Accepted: 12/06/2012] [Indexed: 01/13/2023]
Abstract
Brugada syndrome (BrS), an inherited arrhythmogenic disease first described in 1992, is characterized by ST segment elevations on the electrocardiogram in the right precordium and by a high occurrence of arrhythmias including the life-threatening ventricular tachycardia/fibrillation. Knowledge of the underlying mechanisms of formation of arrhythmogenic substrate in BrS is essential, namely for the risk stratification of BrS patients and their therapy which is still restrained almost exclusively to the implantation of cardioverter/defibrillator. In spite of many crucial findings in this field published within recent years, the final consistent view has not been established so far. Hence, BrS described 20 years ago remains an actual topic of both clinical and experimental studies. This review presents an overview of the current knowledge related to the pathogenesis of BrS arrhythmogenic substrate, namely of the genetic basis of BrS, functional consequences of mutations related to BrS, and arrhythmogenic mechanisms in BrS.
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Affiliation(s)
- Markéta Bébarová
- Department of Physiology, Faculty of Medicine, Masaryk University, Kamenice 5, 625 00 Brno, Bohunice, Czech Republic.
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21
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ZHANG YANMIN, WU JINGJING, JEEVARATNAM KAMALAN, KING JAMESH, GUZADHUR LAILA, REN XIAOLEI, GRACE ANDREWA, LEI MING, HUANG CHRISTOPHERLH, FRASER JAMESA. Conduction Slowing Contributes to Spontaneous Ventricular Arrhythmias in Intrinsically Active Murine RyR2-P2328S
Hearts. J Cardiovasc Electrophysiol 2012; 24:210-8. [DOI: 10.1111/jce.12015] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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22
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Derangeon M, Montnach J, Baró I, Charpentier F. Mouse Models of SCN5A-Related Cardiac Arrhythmias. Front Physiol 2012; 3:210. [PMID: 22737129 PMCID: PMC3381239 DOI: 10.3389/fphys.2012.00210] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 05/29/2012] [Indexed: 12/19/2022] Open
Abstract
Mutations of SCN5A gene, which encodes the α-subunit of the voltage-gated Na+ channel NaV1.5, underlie hereditary cardiac arrhythmic syndromes such as the type 3 long QT syndrome, cardiac conduction diseases, the Brugada syndrome, the sick sinus syndrome, a trial standstill, and numerous overlap syndromes. Patch-clamp studies in heterologous expression systems have provided important information to understand the genotype-phenotype relationships of these diseases. However, they could not clarify how SCN5A mutations can be responsible for such a large spectrum of diseases, for the late age of onset or the progressiveness of some of these diseases and for the overlapping syndromes. Genetically modified mice rapidly appeared as promising tools for understanding the pathophysiological mechanisms of cardiac SCN5A-related arrhythmic syndromes and several mouse models have been established. This review presents the results obtained on these models that, for most of them, recapitulate the clinical phenotypes of the patients. This includes two models knocked out for Nav1.5 β1 and β3 auxiliary subunits that are also discussed. Despite their own limitations that we point out, the mouse models still appear as powerful tools to elucidate the pathophysiological mechanisms of SCN5A-related diseases and offer the opportunity to investigate the secondary cellular consequences of SCN5A mutations such as the expression remodeling of other genes. This points out the potential role of these genes in the overall human phenotype. Finally, they constitute useful tools for addressing the role of genetic and environmental modifiers on cardiac electrical activity.
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