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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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Liantonio A, Bertini M, Mele A, Balla C, Dinoi G, Selvatici R, Mele M, De Luca A, Gualandi F, Imbrici P. Brugada Syndrome: More than a Monogenic Channelopathy. Biomedicines 2023; 11:2297. [PMID: 37626795 PMCID: PMC10452102 DOI: 10.3390/biomedicines11082297] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 08/10/2023] [Accepted: 08/15/2023] [Indexed: 08/27/2023] Open
Abstract
Brugada syndrome (BrS) is an inherited cardiac channelopathy first diagnosed in 1992 but still considered a challenging disease in terms of diagnosis, arrhythmia risk prediction, pathophysiology and management. Despite about 20% of individuals carrying pathogenic variants in the SCN5A gene, the identification of a polygenic origin for BrS and the potential role of common genetic variants provide the basis for applying polygenic risk scores for individual risk prediction. The pathophysiological mechanisms are still unclear, and the initial thinking of this syndrome as a primary electrical disease is evolving towards a partly structural disease. This review focuses on the main scientific advancements in the identification of biomarkers for diagnosis, risk stratification, pathophysiology and therapy of BrS. A comprehensive model that integrates clinical and genetic factors, comorbidities, age and gender, and perhaps environmental influences may provide the opportunity to enhance patients' quality of life and improve the therapeutic approach.
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Affiliation(s)
- Antonella Liantonio
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (A.L.); (A.M.); (G.D.); (M.M.); (A.D.L.)
| | - Matteo Bertini
- Cardiological Center, Sant’Anna University Hospital of Ferrara, 44121 Ferrara, Italy; (M.B.); (C.B.)
| | - Antonietta Mele
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (A.L.); (A.M.); (G.D.); (M.M.); (A.D.L.)
| | - Cristina Balla
- Cardiological Center, Sant’Anna University Hospital of Ferrara, 44121 Ferrara, Italy; (M.B.); (C.B.)
| | - Giorgia Dinoi
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (A.L.); (A.M.); (G.D.); (M.M.); (A.D.L.)
| | - Rita Selvatici
- Medical Genetics Unit, Department of Mother and Child, Sant’Anna University Hospital of Ferrara, 44121 Ferrara, Italy;
| | - Marco Mele
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (A.L.); (A.M.); (G.D.); (M.M.); (A.D.L.)
- Cardiothoracic Department, Policlinico Riuniti Foggia, 71122 Foggia, Italy
| | - Annamaria De Luca
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (A.L.); (A.M.); (G.D.); (M.M.); (A.D.L.)
| | - Francesca Gualandi
- Medical Genetics Unit, Department of Mother and Child, Sant’Anna University Hospital of Ferrara, 44121 Ferrara, Italy;
| | - Paola Imbrici
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (A.L.); (A.M.); (G.D.); (M.M.); (A.D.L.)
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3
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Huang CLH, Lei M. Cardiomyocyte electrophysiology and its modulation: current views and future prospects. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220160. [PMID: 37122224 PMCID: PMC10150219 DOI: 10.1098/rstb.2022.0160] [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: 01/16/2023] [Accepted: 03/10/2023] [Indexed: 05/02/2023] Open
Abstract
Normal and abnormal cardiac rhythms are of key physiological and clinical interest. This introductory article begins from Sylvio Weidmann's key historic 1950s microelectrode measurements of cardiac electrophysiological activity and Singh & Vaughan Williams's classification of cardiotropic targets. It then proceeds to introduce the insights into cardiomyocyte function and its regulation that subsequently emerged and their therapeutic implications. We recapitulate the resulting view that surface membrane electrophysiological events underlying cardiac excitation and its initiation, conduction and recovery constitute the final common path for the cellular mechanisms that impinge upon this normal or abnormal cardiac electrophysiological activity. We then consider progress in the more recently characterized successive regulatory hierarchies involving Ca2+ homeostasis, excitation-contraction coupling and autonomic G-protein signalling and their often reciprocal interactions with the surface membrane events, and their circadian rhythms. Then follow accounts of longer-term upstream modulation processes involving altered channel expression, cardiomyocyte energetics and hypertrophic and fibrotic cardiac remodelling. Consideration of these developments introduces each of the articles in this Phil. Trans. B theme issue. The findings contained in these articles translate naturally into recent classifications of cardiac electrophysiological targets and drug actions, thereby encouraging future iterations of experimental cardiac electrophysiological discovery, and testing directed towards clinical management. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Christopher L.-H. Huang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Ming Lei
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
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4
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Cheng J, Wei W, Fang Y, Zhou N, Wu Q, Zhao Q. Sudden cardiac death and cardiac sodium channel diseases. JOURNAL OF FORENSIC SCIENCE AND MEDICINE 2022. [DOI: 10.4103/jfsm.jfsm_123_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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5
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Yuan M, Guo Y, Xia H, Xu H, Deng H, Yuan L. Novel SCN5A and GPD1L Variants Identified in Two Unrelated Han-Chinese Patients With Clinically Suspected Brugada Syndrome. Front Cardiovasc Med 2021; 8:758903. [PMID: 34957250 PMCID: PMC8692717 DOI: 10.3389/fcvm.2021.758903] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Accepted: 10/29/2021] [Indexed: 12/25/2022] Open
Abstract
Brugada syndrome (BrS) is a complexly genetically patterned, rare, malignant, life-threatening arrhythmia disorder. It is autosomal dominant in most cases and characterized by identifiable electrocardiographic patterns, recurrent syncope, nocturnal agonal respiration, and other symptoms, including sudden cardiac death. Over the last 2 decades, a great number of variants have been identified in more than 36 pathogenic or susceptibility genes associated with BrS. The present study used the combined method of whole exome sequencing and Sanger sequencing to identify pathogenic variants in two unrelated Han-Chinese patients with clinically suspected BrS. Minigene splicing assay was used to evaluate the effects of the splicing variant. A novel heterozygous splicing variant c.2437-2A>C in the sodium voltage-gated channel alpha subunit 5 gene (SCN5A) and a novel heterozygous missense variant c.161A>T [p.(Asp54Val)] in the glycerol-3-phosphate dehydrogenase 1 like gene (GPD1L) were identified in these two patients with BrS-1 and possible BrS-2, respectively. Minigene splicing assay indicated the deletion of 15 and 141 nucleotides in exon 16, resulting in critical amino acid deletions. These findings expand the variant spectrum of SCN5A and GPD1L, which can be beneficial to genetic counseling and prenatal diagnosis.
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Affiliation(s)
- Meng Yuan
- Center for Experimental Medicine, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Yi Guo
- Department of Medical Information, School of Life Sciences, Central South University, Changsha, China
| | - Hong Xia
- Department of Emergency, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Hongbo Xu
- Center for Experimental Medicine, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Hao Deng
- Center for Experimental Medicine, The Third Xiangya Hospital, Central South University, Changsha, China.,Department of Neurology, The Third Xiangya Hospital, Central South University, Changsha, China.,Disease Genome Research Center, Central South University, Changsha, China
| | - Lamei Yuan
- Center for Experimental Medicine, The Third Xiangya Hospital, Central South University, Changsha, China.,Department of Neurology, The Third Xiangya Hospital, Central South University, Changsha, China.,Disease Genome Research Center, Central South University, Changsha, China
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6
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Dongol Y, Choi PM, Wilson DT, Daly NL, Cardoso FC, Lewis RJ. Voltage-Gated Sodium Channel Modulation by a New Spider Toxin Ssp1a Isolated From an Australian Theraphosid. Front Pharmacol 2021; 12:795455. [PMID: 35002728 PMCID: PMC8740163 DOI: 10.3389/fphar.2021.795455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 11/22/2021] [Indexed: 11/13/2022] Open
Abstract
Given the important role of voltage-gated sodium (NaV) channel-modulating spider toxins in elucidating the function, pharmacology, and mechanism of action of therapeutically relevant NaV channels, we screened the venom from Australian theraphosid species against the human pain target hNaV1.7. Using assay-guided fractionation, we isolated a 33-residue inhibitor cystine knot (ICK) peptide (Ssp1a) belonging to the NaSpTx1 family. Recombinant Ssp1a (rSsp1a) inhibited neuronal hNaV subtypes with a rank order of potency hNaV1.7 > 1.6 > 1.2 > 1.3 > 1.1. rSsp1a inhibited hNaV1.7, hNaV1.2 and hNaV1.3 without significantly altering the voltage-dependence of activation, inactivation, or delay in recovery from inactivation. However, rSsp1a demonstrated voltage-dependent inhibition at hNaV1.7 and rSsp1a-bound hNaV1.7 opened at extreme depolarizations, suggesting rSsp1a likely interacted with voltage-sensing domain II (VSD II) of hNaV1.7 to trap the channel in its resting state. Nuclear magnetic resonance spectroscopy revealed key structural features of Ssp1a, including an amphipathic surface with hydrophobic and charged patches shown by docking studies to comprise the interacting surface. This study provides the basis for future structure-function studies to guide the development of subtype selective inhibitors.
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Affiliation(s)
- Yashad Dongol
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Phil M. Choi
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - David T. Wilson
- Centre for Molecular Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, Australia
| | - Norelle L. Daly
- Centre for Molecular Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, Australia
| | - Fernanda C. Cardoso
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Richard J. Lewis
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
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7
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Takla M, Edling CE, Zhang K, Saadeh K, Tse G, Salvage SC, Huang CL, Jeevaratnam K. Transcriptional profiles of genes related to electrophysiological function in Scn5a +/- murine hearts. Physiol Rep 2021; 9:e15043. [PMID: 34617689 PMCID: PMC8495800 DOI: 10.14814/phy2.15043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/13/2021] [Accepted: 08/13/2021] [Indexed: 11/24/2022] Open
Abstract
The Scn5a gene encodes the major pore-forming Nav 1.5 (α) subunit, of the voltage-gated Na+ channel in cardiomyocytes. The key role of Nav 1.5 in action potential initiation and propagation in both atria and ventricles predisposes organisms lacking Scn5a or carrying Scn5a mutations to cardiac arrhythmogenesis. Loss-of-function Nav 1.5 genetic abnormalities account for many cases of the human arrhythmic disorder Brugada syndrome (BrS) and related conduction disorders. A murine model with a heterozygous Scn5a deletion recapitulates many electrophysiological phenotypes of BrS. This study examines the relationships between its Scn5a+/- genotype, resulting transcriptional changes, and the consequent phenotypic presentations of BrS. Of 62 selected protein-coding genes related to cardiomyocyte electrophysiological or homeostatic function, concentrations of mRNA transcribed from 15 differed significantly from wild type (WT). Despite halving apparent ventricular Scn5a transcription heterozygous deletion did not significantly downregulate its atrial expression, raising possibilities of atria-specific feedback mechanisms. Most of the remaining 14 genes whose expression differed significantly between WT and Scn5a+/- animals involved Ca2+ homeostasis specifically in atrial tissue, with no overlap with any ventricular changes. All statistically significant changes in expression were upregulations in the atria and downregulations in the ventricles. This investigation demonstrates the value of future experiments exploring for and clarifying links between transcriptional control of Scn5a and of genes whose protein products coordinate Ca2+ regulation and examining their possible roles in BrS.
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Affiliation(s)
- Michael Takla
- Faculty of Health and Medical ScienceUniversity of SurreyGuildfordUK
- Christ’s CollegeUniversity of CambridgeCambridgeUK
| | | | - Kevin Zhang
- Faculty of Health and Medical ScienceUniversity of SurreyGuildfordUK
- School of MedicineImperial College LondonLondonUK
| | - Khalil Saadeh
- Faculty of Health and Medical ScienceUniversity of SurreyGuildfordUK
- Clinical SchoolUniversity of CambridgeCambridgeUK
| | - Gary Tse
- Faculty of Health and Medical ScienceUniversity of SurreyGuildfordUK
- Second Hospital of Tianjin Medical UniversityTianjinChina
| | | | - Christopher L.‐H. Huang
- Faculty of Health and Medical ScienceUniversity of SurreyGuildfordUK
- Department of BiochemistryUniversity of CambridgeCambridgeUK
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8
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Nguyen LKC, Shimizu A, Soh JEC, Komeno M, Sato A, Ogita H. Transmembrane protein 168 mutation reduces cardiomyocyte cell surface expression of Nav1.5 through αB-crystallin intracellular dynamics. J Biochem 2021; 170:577-585. [PMID: 34086898 DOI: 10.1093/jb/mvab066] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 06/01/2021] [Indexed: 11/14/2022] Open
Abstract
Transmembrane protein 168 (TMEM168) was found to be localized on the nuclear membrane. A heterozygous mutation (c.1616G>A, p. R539Q) in TMEM168 was identified in patients with Brugada syndrome. This mutation reduced expression of cardiomyocyte sodium channel Nav1.5 via Nedd4-2 E3 ubiquitin ligase-induced ubiquitination and degradation. However, the detailed molecular mechanism provoked by the TMEM168 mutant remains unclear. Here, we demonstrated that small heat shock protein αB-crystallin, which can bind to Nav1.5 and Nedd4-2 and interfere with the association of both proteins, was strongly recruited from the cell surface to the perinuclear region because of the much higher interaction of αB-crystallin with the TMEM168 mutant than with wild-type TMEM168. Following knockdown of αB-crystallin in HL-1 cardiomyocytes, the interaction of Nav1.5 with Nedd4-2 was increased, despite a reduction of the expression level of Nav1.5. Moreover, αB-crystallin-mediated reduction of Nav1.5 expression was rescued in the presence of a proteasome inhibitor MG-132, suggesting the importance of the αB-crystallin-modulated ubiquitin-proteasome system for the stability of Nav1.5 expression. Collectively, the balance of molecular interactions among Nav1.5, Nedd4-2, and αB-crystallin plays a role in the regulation of cardiomyocyte cell surface expression of Nav1.5, and the TMEM168 mutant disturbs this balance, resulting in a decrease in Nav1.5 expression.
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Affiliation(s)
- Le Kim Chi Nguyen
- Division of Molecular Medical Biochemistry, Department of Biochemistry and Molecular Biology, Shiga University of Medical Science
| | - Akio Shimizu
- Division of Molecular Medical Biochemistry, Department of Biochemistry and Molecular Biology, Shiga University of Medical Science
| | - Joanne Ern Chi Soh
- Division of Molecular Medical Biochemistry, Department of Biochemistry and Molecular Biology, Shiga University of Medical Science
| | - Masahiro Komeno
- Division of Molecular Medical Biochemistry, Department of Biochemistry and Molecular Biology, Shiga University of Medical Science
| | - Akira Sato
- Division of Molecular Medical Biochemistry, Department of Biochemistry and Molecular Biology, Shiga University of Medical Science
| | - Hisakazu Ogita
- Division of Molecular Medical Biochemistry, Department of Biochemistry and Molecular Biology, Shiga University of Medical Science
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9
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Bonet-Luz E, Lyle JV, Huang CLH, Zhang Y, Nandi M, Jeevaratnam K, Aston PJ. Symmetric Projection Attractor Reconstruction analysis of murine electrocardiograms: Retrospective prediction of Scn5a +/- genetic mutation attributable to Brugada syndrome. Heart Rhythm O2 2021; 1:368-375. [PMID: 33748801 PMCID: PMC7962089 DOI: 10.1016/j.hroo.2020.08.007] [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] [Indexed: 11/09/2022] Open
Abstract
Background Life-threatening arrhythmias resulting from genetic mutations are often missed in current electrocardiogram (ECG) analysis. We combined a new method for ECG analysis that uses all the waveform data with machine learning to improve detection of such mutations from short ECG signals in a mouse model. Objective We sought to detect consequences of Na+ channel deficiencies known to compromise action potential conduction in comparisons of Scn5a+/- mutant and wild-type mice using short ECG signals, examining novel and standard features derived from lead I and II ECG recordings by machine learning algorithms. Methods Lead I and II ECG signals from anesthetized wild-type and Scn5a+/- mutant mice of length 130 seconds were analyzed by extracting various groups of features, which were used by machine learning to classify the mice as wild-type or mutant. The features used were standard ECG intervals and amplitudes, as well as features derived from attractors generated using the novel Symmetric Projection Attractor Reconstruction method, which reformulates the whole signal as a bounded, symmetric 2-dimensional attractor. All the features were also combined as a single feature group. Results Classification of genotype using the attractor features gave higher accuracy than using either the ECG intervals or the intervals and amplitudes. However, the highest accuracy (96%) was obtained using all the features. Accuracies for different subgroups of the data were obtained and compared. Conclusion Detection of the Scn5a+/- mutation from short mouse ECG signals with high accuracy is possible using our Symmetric Projection Attractor Reconstruction method.
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Affiliation(s)
- Esther Bonet-Luz
- Department of Mathematics, University of Surrey, Guildford, United Kingdom
| | - Jane V Lyle
- Department of Mathematics, University of Surrey, Guildford, United Kingdom
| | - Christopher L-H Huang
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Yanmin Zhang
- Department of Paediatric Cardiology, Shaanxi Institute for Pediatric Diseases, Affiliate Children's Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Manasi Nandi
- School of Cancer and Pharmaceutical Sciences, Faculty of Life Sciences & Medicine, King's College London, London, United Kingdom
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Philip J Aston
- Department of Mathematics, University of Surrey, Guildford, United Kingdom
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10
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Saadeh K, Fazmin IT. Mitochondrial Dysfunction Increases Arrhythmic Triggers and Substrates; Potential Anti-arrhythmic Pharmacological Targets. Front Cardiovasc Med 2021; 8:646932. [PMID: 33659284 PMCID: PMC7917191 DOI: 10.3389/fcvm.2021.646932] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Accepted: 01/26/2021] [Indexed: 12/31/2022] Open
Abstract
Incidence of cardiac arrhythmias increases significantly with age. In order to effectively stratify arrhythmic risk in the aging population it is crucial to elucidate the relevant underlying molecular mechanisms. The changes underlying age-related electrophysiological disruption appear to be closely associated with mitochondrial dysfunction. Thus, the present review examines the mechanisms by which age-related mitochondrial dysfunction promotes arrhythmic triggers and substrate. Namely, via alterations in plasmalemmal ionic currents (both sodium and potassium), gap junctions, cellular Ca2+ homeostasis, and cardiac fibrosis. Stratification of patients' mitochondrial function status permits application of appropriate anti-arrhythmic therapies. Here, we discuss novel potential anti-arrhythmic pharmacological interventions that specifically target upstream mitochondrial function and hence ameliorates the need for therapies targeting downstream changes which have constituted traditional antiarrhythmic therapy.
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Affiliation(s)
- Khalil Saadeh
- School of Clinical Medicine, University of Cambridge, Cambridge, United Kingdom.,Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Ibrahim Talal Fazmin
- School of Clinical Medicine, University of Cambridge, Cambridge, United Kingdom.,Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Royal Papworth Hospital NHS Foundation Trust, Cambridge, United Kingdom
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11
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Pearman CM, Denham NC, Mills RW, Ding WY, Modi SS, Hall MCS, Todd DM, Mahida S. Relationship between sodium channel function and clinical phenotype in SCN5A variants associated with Brugada syndrome. Hum Mutat 2020; 41:2195-2204. [PMID: 33131149 PMCID: PMC7756571 DOI: 10.1002/humu.24128] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 09/23/2020] [Accepted: 10/09/2020] [Indexed: 12/19/2022]
Abstract
The identification of a pathogenic SCN5A variant confers an increased risk of conduction defects and ventricular arrhythmias (VA) in Brugada syndrome (BrS). However, specific aspects of sodium channel function that influence clinical phenotype have not been defined. A systematic literature search identified SCN5A variants associated with BrS. Sodium current (INa) functional parameters (peak current, decay, steady‐state activation and inactivation, and recovery from inactivation) and clinical features (conduction abnormalities [CA], spontaneous VA or family history of sudden cardiac death [SCD], and spontaneous BrS electrocardiogram [ECG]) were extracted. A total of 561 SCN5A variants associated with BrS were identified, for which data on channel function and clinical phenotype were available in 142. In the primary analysis, no relationship was found between any aspect of channel function and CA, VA/SCD, or spontaneous BrS ECG pattern. Sensitivity analyses including only variants graded pathogenic or likely pathogenic suggested that reduction in peak current and positive shift in steady‐state activation were weakly associated with CA and VA/SCD, although sensitivity and specificity remained low. The relationship between in vitro assessment of channel function and BrS clinical phenotype is weak. The assessment of channel function does not enhance risk stratification. Caution is needed when extrapolating functional testing to the likelihood of variant pathogenicity.
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Affiliation(s)
- Charles M Pearman
- Department of Cardiac Electrophysiology and Inherited Cardiac Conditions, Liverpool Heart and Chest Hospital, Liverpool, UK.,Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Science Centre, Core Technology Facility, University of Manchester, Manchester, UK
| | - Nathan C Denham
- Department of Cardiac Electrophysiology and Inherited Cardiac Conditions, Liverpool Heart and Chest Hospital, Liverpool, UK.,Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Science Centre, Core Technology Facility, University of Manchester, Manchester, UK
| | - Robert W Mills
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA
| | - Wern Y Ding
- Department of Cardiac Electrophysiology and Inherited Cardiac Conditions, Liverpool Heart and Chest Hospital, Liverpool, UK.,Liverpool Centre for Cardiovascular Science, Faculty of Life Sciences, University of Liverpool, Liverpool, UK
| | - Simon S Modi
- Department of Cardiac Electrophysiology and Inherited Cardiac Conditions, Liverpool Heart and Chest Hospital, Liverpool, UK
| | - Mark C S Hall
- Department of Cardiac Electrophysiology and Inherited Cardiac Conditions, Liverpool Heart and Chest Hospital, Liverpool, UK
| | - Derick M Todd
- Department of Cardiac Electrophysiology and Inherited Cardiac Conditions, Liverpool Heart and Chest Hospital, Liverpool, UK
| | - Saagar Mahida
- Department of Cardiac Electrophysiology and Inherited Cardiac Conditions, Liverpool Heart and Chest Hospital, Liverpool, UK.,Liverpool Centre for Cardiovascular Science, Faculty of Life Sciences, University of Liverpool, Liverpool, UK
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12
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Saadeh K, Achercouk Z, Fazmin IT, Nantha Kumar N, Salvage SC, Edling CE, Huang CLH, Jeevaratnam K. Protein expression profiles in murine ventricles modeling catecholaminergic polymorphic ventricular tachycardia: effects of genotype and sex. Ann N Y Acad Sci 2020; 1478:63-74. [PMID: 32713021 DOI: 10.1111/nyas.14426] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 05/27/2020] [Accepted: 06/15/2020] [Indexed: 12/12/2022]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is associated with mutations in the cardiac ryanodine receptor (RyR2). These result in stress-induced ventricular arrhythmic episodes, with clinical symptoms and prognosis reported more severe in male than female patients. Murine homozygotic RyR2-P2328S (RyR2S/S ) hearts replicate the proarrhythmic CPVT phenotype of abnormal sarcoplasmic reticular Ca2+ leak and disrupted Ca2+ homeostasis. In addition, RyR2S/S hearts show decreased myocardial action potential conduction velocities (CV), all features implicated in arrhythmic trigger and substrate. The present studies explored for independent and interacting effects of RyR2S/S genotype and sex on expression levels of molecular determinants of Ca2+ homeostasis (CASQ2, FKBP12, SERCA2a, NCX1, and CaV 1.2) and CV (NaV 1.5, Connexin (Cx)-43, phosphorylated-Cx43, and TGF-β1) in mice. Expression levels of Ca2+ homeostasis proteins were not altered, hence implicating abnormal RyR2 function alone in disrupted cytosolic Ca2+ homeostasis. Furthermore, altered NaV 1.5, phosphorylated Cx43, and TGF-β1 expression were not implicated in the development of slowed CV. By contrast, decreased Cx43 expression correlated with slowed CV, in female, but not male, RyR2S/S mice. The CV changes may reflect acute actions of the increased cytosolic Ca2+ on NaV 1.5 and Cx43 function.
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Affiliation(s)
- Khalil Saadeh
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,School of Clinical Medicine, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom
| | - Zakaria Achercouk
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Ibrahim T Fazmin
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,School of Clinical Medicine, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom
| | - Nakulan Nantha Kumar
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Samantha C Salvage
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Charlotte E Edling
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Christopher L-H Huang
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
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13
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Jeevaratnam K. Chloroquine and hydroxychloroquine for COVID-19: implications for cardiac safety. EUROPEAN HEART JOURNAL. CARDIOVASCULAR PHARMACOTHERAPY 2020; 6:256-257. [PMID: 32347923 PMCID: PMC7197554 DOI: 10.1093/ehjcvp/pvaa041] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [MESH Headings] [Download PDF] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 04/15/2020] [Accepted: 04/21/2020] [Indexed: 12/17/2022]
Affiliation(s)
- Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, UK
- Physiological Laboratory, University of Cambridge, Cambridge, UK
- Corresponding author. Tel: +44 1483 682395,
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14
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Huang CLH, Wu L, Jeevaratnam K, Lei M. Update on antiarrhythmic drug pharmacology. J Cardiovasc Electrophysiol 2020; 31:579-592. [PMID: 31930579 DOI: 10.1111/jce.14347] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 12/22/2019] [Accepted: 01/03/2020] [Indexed: 12/28/2022]
Abstract
Cardiac arrhythmias constitute a major public health problem. Pharmacological intervention remains mainstay to their clinical management. This, in turn, depends upon systematic drug classification schemes relating their molecular, cellular, and systems effects to clinical indications and therapeutic actions. This approach was first pioneered in the 1960s Vaughan-Williams classification. Subsequent progress in cardiac electrophysiological understanding led to a lag between the fundamental science and its clinical translation, partly addressed by The working group of the European Society of Cardiology (1991), which, however, did not emerge with formal classifications. We here utilize the recent Revised Oxford Classification Scheme to review antiarrhythmic drug pharmacology. We survey drugs and therapeutic targets offered by the more recently characterized ion channels, transporters, receptors, intracellular Ca2+ handling, and cell signaling molecules. These are organized into their strategic roles in cardiac electrophysiological function. Following analysis of the arrhythmic process itself, we consider (a) pharmacological agents directly targeting membrane function, particularly the Na+ and K+ ion channels underlying depolarizing and repolarizing events in the cardiac action potential. (b) We also consider agents that modify autonomic activity that, in turn, affects both the membrane and (c) the Ca2+ homeostatic and excitation-contraction coupling processes linking membrane excitation to contractile activation. Finally, we consider (d) drugs acting on more upstream energetic and structural remodeling processes currently the subject of clinical trials. Such systematic correlations of drug actions and arrhythmic mechanisms at different molecular to systems levels of cardiac function will facilitate current and future antiarrhythmic therapy.
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Affiliation(s)
- Christopher L-H Huang
- Department of Biochemistry and Physiological Laboratory, University of Cambridge, Cambridge, UK.,Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China.,Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
| | - Lin Wu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China.,Department of Cardiology, Peking University First Hospital, Beijing, China
| | | | - Ming Lei
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China.,Department of Pharmacology, University of Oxford, Oxford, UK
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15
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Finlay M, Bhar-Amato J, Ng KE, Santos D, Orini M, Vyas V, Taggart P, Grace AA, Huang CLH, Lambiase PD, Tinker A. Autonomic modulation of the electrical substrate in mice haploinsufficient for cardiac sodium channels: a model of the Brugada syndrome. Am J Physiol Cell Physiol 2019; 317:C576-C583. [PMID: 31291141 DOI: 10.1152/ajpcell.00028.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A murine line haploinsufficient in the cardiac sodium channel has been used to model human Brugada syndrome: a disease causing sudden cardiac death due to lethal ventricular arrhythmias. We explored the effects of cholinergic tone on electrophysiological parameters in wild-type and genetically modified, heterozygous, Scn5a+/- knockout mice. Scn5a+/- ventricular slices showed longer refractory periods than wild-type both at baseline and during isoprenaline challenge. Scn5a+/- hearts also showed lower conduction velocities and increased mean increase in delay than did littermate controls at baseline and blunted responses to isoprenaline challenge. Carbachol exerted limited effects but reversed the effects of isoprenaline with coapplication. Scn5a+/- mice showed a reduction in conduction reserve in that isoprenaline no longer increased conduction velocity, and this was not antagonized by muscarinic agonists.
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Affiliation(s)
- Malcolm Finlay
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Justine Bhar-Amato
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Keat-Eng Ng
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Diogo Santos
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Michele Orini
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Vishal Vyas
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Peter Taggart
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Andrew A Grace
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Christopher L-H Huang
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Pier D Lambiase
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Andrew Tinker
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
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16
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Rao P, Liu Z, Duan H, Dang S, Li H, Zhong L, Wang X, Wang L, Wang X. Pretreatment with neuregulin-1 improves cardiac electrophysiological properties in a rat model of myocardial infarction. Exp Ther Med 2019; 17:3141-3149. [PMID: 30936986 PMCID: PMC6434250 DOI: 10.3892/etm.2019.7306] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 02/01/2019] [Indexed: 12/22/2022] Open
Abstract
Neuregulin-1 (NRG-1) is considered to be a potential therapeutic agent for cardiovascular diseases due to its diverse protective effects. The aim of the present study was to investigate the effect of NRG-1 on cardiac electrophysiology in rats with myocardial infarction (MI). The rats were randomly divided into three groups: The sham operation group (SO; n=8); MI group (n=8); and the MI with recombinant human NRG (rhNRG)-1 administration group (NRG-1 group; 10 µg/kg; n=8). A rat MI model was established via ligation of the left anterior descending coronary artery. The rats in the NRG-1 group received a 10 µg/kg rhNRG-1 injection through the tail vein 30 min prior to ligation. Following 24 h of intervention, the field potential (FP) parameters, including the interspike interval (ISI), field potential duration (FPD), FPrise, FPmin, FPmax and conduction velocity (CV), were measured using microelectrode array technology. Subsequently, burst pacing was performed to assess ventricular arrhythmia (VA) susceptibility in the left ventricle. FP parameters in the MI group were significantly different when compared with those observed in the SO group. ISI, FPD, FPrise and FPmax in the infarct, peri-infarct and normal zones, as well as the CV of the infarct and peri-infarct zones, were all significantly decreased, and FPmin in the normal zone was increased (P<0.05). However, when compared with the MI group, NRG-1 prolonged the ISI and FPD in the 3 zones, and increased FPrise in the infarct zone, FPmax in the normal zone and CV in the peri-infarct zone; it also decreased FPmin in the normal zone (P<0.05). Furthermore, the incidence of VA was significantly reduced in the NRG-1 group when compared with the MI group (P<0.05). In conclusion, NRG-1 improved cardiac electrophysiological properties and reduced VA susceptibility in acute MI.
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Affiliation(s)
- Panpan Rao
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China.,Cardiovascular Research Institute, Wuhan University, Wuhan, Hubei 430060, P.R. China.,Hubei Key Laboratory of Cardiology, Wuhan Pulmonary Hospital, Wuhan, Hubei 430060, P.R. China
| | - Ziqiang Liu
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China.,Cardiovascular Research Institute, Wuhan University, Wuhan, Hubei 430060, P.R. China.,Hubei Key Laboratory of Cardiology, Wuhan Pulmonary Hospital, Wuhan, Hubei 430060, P.R. China
| | - Huinan Duan
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China.,Department of Cardiology, Wuhan Pulmonary Hospital, Wuhan, Hubei 430060, P.R. China
| | - Song Dang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China.,Cardiovascular Research Institute, Wuhan University, Wuhan, Hubei 430060, P.R. China.,Hubei Key Laboratory of Cardiology, Wuhan Pulmonary Hospital, Wuhan, Hubei 430060, P.R. China
| | - Haitao Li
- Department of Cardiology, Hainan General Hospital, Haikou, Hainan 570100, P.R. China
| | - Liang Zhong
- Department of Anesthesiology, Wuhan Medical and Healthcare Center for Women and Children, Wuhan, Hubei 430015, P.R. China
| | - Xin Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China.,Cardiovascular Research Institute, Wuhan University, Wuhan, Hubei 430060, P.R. China.,Hubei Key Laboratory of Cardiology, Wuhan Pulmonary Hospital, Wuhan, Hubei 430060, P.R. China
| | - Long Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China.,Hubei Key Laboratory of Cardiology, Wuhan Pulmonary Hospital, Wuhan, Hubei 430060, P.R. China.,Department of Anesthesiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China
| | - Xi Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China.,Cardiovascular Research Institute, Wuhan University, Wuhan, Hubei 430060, P.R. China.,Hubei Key Laboratory of Cardiology, Wuhan Pulmonary Hospital, Wuhan, Hubei 430060, P.R. China
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17
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Chadda KR, Ajijola OA, Vaseghi M, Shivkumar K, Huang CLH, Jeevaratnam K. Ageing, the autonomic nervous system and arrhythmia: From brain to heart. Ageing Res Rev 2018; 48:40-50. [PMID: 30300712 DOI: 10.1016/j.arr.2018.09.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 08/21/2018] [Accepted: 09/30/2018] [Indexed: 02/08/2023]
Abstract
An ageing myocardium possesses significant electrophysiological alterations that predisposes the elderly patient to arrhythmic risk. Whilst these alterations are intrinsic to the cardiac myocytes, they are modulated by the cardiac autonomic nervous system (ANS) and consequently, ageing of the cardiac ANS is fundamental to the development of arrhythmias. A systems-based approach that incorporates the influence of the cardiac ANS could lead to better mechanistic understanding of how arrhythmogenic triggers and substrates interact spatially and temporally to produce sustained arrhythmia and why its incidence increases with age. Despite the existence of physiological oscillations of ANS activity on the heart, pathological oscillations can lead to defective activation and recovery properties of the myocardium. Such changes can be attributable to the decrease in functionality and structural alterations to ANS specific receptors in the myocardium with age. These altered ANS adaptive responses can occur either as a normal ageing process or accelerated in the presence of specific cardiac pathologies, such as genetic mutations or neurodegenerative conditions. Targeted intervention that seek to manipulate the ageing ANS influence on the myocardium may prove to be an efficacious approach for the management of arrhythmia in the ageing population.
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Affiliation(s)
- Karan R Chadda
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7AL, United Kingdom; Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, United Kingdom
| | - Olujimi A Ajijola
- UCLA Cardiac Arrhythmia Center, UCLA Health System/David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Marmar Vaseghi
- UCLA Cardiac Arrhythmia Center, UCLA Health System/David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Kalyanam Shivkumar
- UCLA Cardiac Arrhythmia Center, UCLA Health System/David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, United Kingdom; Department of Biochemistry, Hopkins Building, University of Cambridge, Cambridge, CB2 1QW, United Kingdom
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7AL, United Kingdom; Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, United Kingdom.
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18
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Chadda KR, Edling CE, Valli H, Ahmad S, Huang CLH, Jeevaratnam K. Gene and Protein Expression Profile of Selected Molecular Targets Mediating Electrophysiological Function in Pgc-1α Deficient Murine Atria. Int J Mol Sci 2018; 19:ijms19113450. [PMID: 30400228 PMCID: PMC6274828 DOI: 10.3390/ijms19113450] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 10/25/2018] [Accepted: 10/29/2018] [Indexed: 12/27/2022] Open
Abstract
Increases in the prevalence of obesity, insulin resistance, and metabolic syndrome has led to the increase of atrial fibrillation (AF) cases in the developed world. These AF risk factors are associated with mitochondrial dysfunction, previously modelled using peroxisome proliferator activated receptor-γ (PPARγ) coactivator-1 (Pgc-1)-deficient murine cardiac models. We explored gene and protein expression profiles of selected molecular targets related to electrophysiological function in murine Pgc-1α−/− atria. qPCR analysis surveyed genes related to Na+-K+-ATPase, K+ conductance, hyperpolarisation-activated cyclic nucleotide-gated (Hcn), Na+ channels, Ca2+ channels, and indicators for adrenergic and cholinergic receptor modulation. Western blot analysis for molecular targets specific to conduction velocity (Nav1.5 channel and gap junctions) was performed. Transcription profiles revealed downregulation of molecules related to Na+-K+-ATPase transport, Hcn-dependent pacemaker function, Na+ channel-dependent action potential activation and propagation, Ca2+ current generation, calsequestrin-2 dependent Ca2+ homeostasis, and adrenergic α1D dependent protection from hypertrophic change. Nav1.5 channel protein expression but not gap junction expression was reduced in Pgc-1α−/− atria compared to WT. Nav1.5 reduction reflects corresponding reduction in its gene expression profile. These changes, as well as the underlying Pgc-1α−/− alteration, suggest potential pharmacological targets directed towards either upstream PGC-1 signalling mechanisms or downstream ion channel changes.
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Affiliation(s)
- Karan R Chadda
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, UK.
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
| | - Charlotte E Edling
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, UK.
| | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
| | - Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
- Department of Biochemistry, Hopkins Building, University of Cambridge, Cambridge CB2 1QW, UK.
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, UK.
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
- School of Medicine, Perdana University-Royal College of Surgeons Ireland, Serdang 43400, Malaysia.
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19
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Wang W, Zhang S, Ni H, Garratt CJ, Boyett MR, Hancox JC, Zhang H. Mechanistic insight into spontaneous transition from cellular alternans to arrhythmia-A simulation study. PLoS Comput Biol 2018; 14:e1006594. [PMID: 30500818 PMCID: PMC6291170 DOI: 10.1371/journal.pcbi.1006594] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 12/12/2018] [Accepted: 10/23/2018] [Indexed: 02/01/2023] Open
Abstract
Cardiac electrical alternans (CEA), manifested as T-wave alternans in ECG, is a clinical biomarker for predicting cardiac arrhythmias and sudden death. However, the mechanism underlying the spontaneous transition from CEA to arrhythmias remains incompletely elucidated. In this study, multiscale rabbit ventricular models were used to study the transition and a potential role of INa in perpetuating such a transition. It was shown CEA evolved into either concordant or discordant action potential (AP) conduction alternans in a homogeneous one-dimensional tissue model, depending on tissue AP duration and conduction velocity (CV) restitution properties. Discordant alternans was able to cause conduction failure in the model, which was promoted by impaired sodium channel with either a reduced or increased channel current. In a two-dimensional homogeneous tissue model, a combined effect of rate- and curvature-dependent CV broke-up alternating wavefronts at localised points, facilitating a spontaneous transition from CEA to re-entry. Tissue inhomogeneity or anisotropy further promoted break-up of re-entry, leading to multiple wavelets. Similar observations have also been seen in human atrial cellular and tissue models. In conclusion, our results identify a mechanism by which CEA spontaneously evolves into re-entry without a requirement for premature ventricular complexes or pre-existing tissue heterogeneities, and demonstrated the important pro-arrhythmic role of impaired sodium channel activity. These findings are model-independent and have potential human relevance.
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Affiliation(s)
- Wei Wang
- Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, United Kingdom
| | - Shanzhuo Zhang
- School of Computer Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Haibo Ni
- Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, United Kingdom
| | - Clifford J. Garratt
- Manchester Heart Centre, Manchester Royal Infirmary, Manchester, United Kingdom
| | - Mark R. Boyett
- Manchester Heart Centre, Manchester Royal Infirmary, Manchester, United Kingdom
| | - Jules C. Hancox
- Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, United Kingdom
- School of Physiology, Pharmacology and Neuroscience, and Cardiovascular Research Laboratories, School of Medical Sciences, University of Bristol, Bristol, United Kingdom
| | - Henggui Zhang
- Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, United Kingdom
- School of Computer Science and Technology, Harbin Institute of Technology, Harbin, China
- 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
- Space Institute of Southern China, Shenzhen, China
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20
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Abstract
BACKGROUND Among his major cardiac electrophysiological contributions, Miles Vaughan Williams (1918-2016) provided a classification of antiarrhythmic drugs that remains central to their clinical use. METHODS We survey implications of subsequent discoveries concerning sarcolemmal, sarcoplasmic reticular, and cytosolic biomolecules, developing an expanded but pragmatic classification that encompasses approved and potential antiarrhythmic drugs on this centenary of his birth. RESULTS We first consider the range of pharmacological targets, tracking these through to cellular electrophysiological effects. We retain the original Vaughan Williams Classes I through IV but subcategorize these divisions in light of more recent developments, including the existence of Na+ current components (for Class I), advances in autonomic (often G protein-mediated) signaling (for Class II), K+ channel subspecies (for Class III), and novel molecular targets related to Ca2+ homeostasis (for Class IV). We introduce new classes based on additional targets, including channels involved in automaticity, mechanically sensitive ion channels, connexins controlling electrotonic cell coupling, and molecules underlying longer-term signaling processes affecting structural remodeling. Inclusion of this widened range of targets and their physiological sequelae provides a framework for a modernized classification of established antiarrhythmic drugs based on their pharmacological targets. The revised classification allows for the existence of multiple drug targets/actions and for adverse, sometimes actually proarrhythmic, effects. The new scheme also aids classification of novel drugs under investigation. CONCLUSIONS We emerge with a modernized classification preserving the simplicity of the original Vaughan Williams framework while aiding our understanding and clinical management of cardiac arrhythmic events and facilitating future developments in this area.
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Affiliation(s)
- Ming Lei
- Department of Pharmacology, University of Oxford, United Kingdom (M.L., D.A.T.)
- Key Laboratory of Medical Electrophysiology of the Ministry of Education and Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China (M.L., L.W.)
| | - Lin Wu
- Department of Cardiology, Peking University First Hospital, Beijing, China (L.W.)
- Key Laboratory of Medical Electrophysiology of the Ministry of Education and Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China (M.L., L.W.)
| | - Derek A Terrar
- Department of Pharmacology, University of Oxford, United Kingdom (M.L., D.A.T.)
| | - Christopher L-H Huang
- Physiological Laboratory (C.L.-H.H.), University of Cambridge, United Kingdom
- Department of Biochemistry (C.L.-H.H.). University of Cambridge, United Kingdom
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21
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Wang Y, Yang E, Wells MM, Bondarenko V, Woll K, Carnevale V, Granata D, Klein ML, Eckenhoff RG, Dailey WP, Covarrubias M, Tang P, Xu Y. Propofol inhibits the voltage-gated sodium channel NaChBac at multiple sites. J Gen Physiol 2018; 150:1317-1331. [PMID: 30018039 PMCID: PMC6122922 DOI: 10.1085/jgp.201811993] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Revised: 05/02/2018] [Accepted: 06/15/2018] [Indexed: 12/24/2022] Open
Abstract
Voltage-gated sodium (NaV) channels are important targets of general anesthetics, including the intravenous anesthetic propofol. Electrophysiology studies on the prokaryotic NaV channel NaChBac have demonstrated that propofol promotes channel activation and accelerates activation-coupled inactivation, but the molecular mechanisms of these effects are unclear. Here, guided by computational docking and molecular dynamics simulations, we predict several propofol-binding sites in NaChBac. We then strategically place small fluorinated probes at these putative binding sites and experimentally quantify the interaction strengths with a fluorinated propofol analogue, 4-fluoropropofol. In vitro and in vivo measurements show that 4-fluoropropofol and propofol have similar effects on NaChBac function and nearly identical anesthetizing effects on tadpole mobility. Using quantitative analysis by 19F-NMR saturation transfer difference spectroscopy, we reveal strong intermolecular cross-relaxation rate constants between 4-fluoropropofol and four different regions of NaChBac, including the activation gate and selectivity filter in the pore, the voltage sensing domain, and the S4-S5 linker. Unlike volatile anesthetics, 4-fluoropropofol does not bind to the extracellular interface of the pore domain. Collectively, our results show that propofol inhibits NaChBac at multiple sites, likely with distinct modes of action. This study provides a molecular basis for understanding the net inhibitory action of propofol on NaV channels.
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Affiliation(s)
- Yali Wang
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Elaine Yang
- Department of Neuroscience and Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College and Jefferson College of Biomedical Sciences, Thomas Jefferson University, Philadelphia, PA
| | - Marta M Wells
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Computational and Systems Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Vasyl Bondarenko
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Kellie Woll
- Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, PA
| | - Vincenzo Carnevale
- Institute for Computational Molecular Science, College of Science and Technology, Temple University, Philadelphia, PA
| | - Daniele Granata
- Institute for Computational Molecular Science, College of Science and Technology, Temple University, Philadelphia, PA
| | - Michael L Klein
- Institute for Computational Molecular Science, College of Science and Technology, Temple University, Philadelphia, PA
| | - Roderic G Eckenhoff
- Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, PA
| | - William P Dailey
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA
| | - Manuel Covarrubias
- Department of Neuroscience and Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College and Jefferson College of Biomedical Sciences, Thomas Jefferson University, Philadelphia, PA
| | - Pei Tang
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Computational and Systems Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Yan Xu
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA
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22
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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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Ahmad S, Valli H, Salvage SC, Grace AA, Jeevaratnam K, Huang CLH. Age-dependent electrocardiographic changes in Pgc-1β deficient murine hearts. Clin Exp Pharmacol Physiol 2017; 45:174-186. [PMID: 28949414 PMCID: PMC5814877 DOI: 10.1111/1440-1681.12863] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 07/06/2017] [Accepted: 09/19/2017] [Indexed: 01/08/2023]
Abstract
Increasing evidence implicates chronic energetic dysfunction in human cardiac arrhythmias. Mitochondrial impairment through Pgc-1β knockout is known to produce a murine arrhythmic phenotype. However, the cumulative effect of this with advancing age and its electrocardiographic basis have not been previously studied. Young (12-16 weeks) and aged (>52 weeks), wild type (WT) (n = 5 and 8) and Pgc-1β-/- (n = 9 and 6), mice were anaesthetised and used for electrocardiographic (ECG) recordings. Time intervals separating successive ECG deflections were analysed for differences between groups before and after β1-adrenergic (intraperitoneal dobutamine 3 mg/kg) challenge. Heart rates before dobutamine challenge were indistinguishable between groups. The Pgc-1β-/- genotype however displayed compromised nodal function in response to adrenergic challenge. This manifested as an impaired heart rate response suggesting a functional defect at the level of the sino-atrial node, and a negative dromotropic response suggesting an atrioventricular conduction defect. Incidences of the latter were most pronounced in the aged Pgc-1β-/- mice. Moreover, Pgc-1β-/- mice displayed electrocardiographic features consistent with the existence of a pro-arrhythmic substrate. Firstly, ventricular activation was prolonged in these mice consistent with slowed action potential conduction and is reported here for the first time. Additionally, Pgc-1β-/- mice had shorter repolarisation intervals. These were likely attributable to altered K+ conductance properties, ultimately resulting in a shortened QTc interval, which is also known to be associated with increased arrhythmic risk. ECG analysis thus yielded electrophysiological findings bearing on potential arrhythmogenicity in intact Pgc-1β-/- systems in widespread cardiac regions.
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Affiliation(s)
- Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Samantha C Salvage
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Andrew A Grace
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Kamalan Jeevaratnam
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, United Kingdom.,PU-RCSI School of Medicine, Perdana University, Selangor Darul Ehsan, Malaysia
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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24
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Persson PB, Bondke Persson A. Borders and beyond. Acta Physiol (Oxf) 2017; 221:84-86. [PMID: 28795790 DOI: 10.1111/apha.12935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- P. B. Persson
- Charité - Universitätsmedizin Berlin; corporate member of Freie Universität Berlin; Humboldt-Universität zu Berlin, and Berlin Institute of Health; Berlin Germany
- Institute of Vegetative Physiology; Berlin Germany
| | - A. Bondke Persson
- Charité - Universitätsmedizin Berlin; corporate member of Freie Universität Berlin; Humboldt-Universität zu Berlin, and Berlin Institute of Health; Berlin Germany
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25
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Jeevaratnam K, Chadda KR, Salvage SC, Valli H, Ahmad S, Grace AA, Huang CLH. Ion channels, long QT syndrome and arrhythmogenesis in ageing. Clin Exp Pharmacol Physiol 2017; 44 Suppl 1:38-45. [PMID: 28024120 PMCID: PMC5763326 DOI: 10.1111/1440-1681.12721] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 12/18/2016] [Accepted: 12/19/2016] [Indexed: 01/08/2023]
Abstract
Ageing is associated with increased prevalences of both atrial and ventricular arrhythmias, reflecting disruption of the normal sequence of ion channel activation and inactivation generating the propagated cardiac action potential. Experimental models with specific ion channel genetic modifications have helped clarify the interacting functional roles of ion channels and how their dysregulation contributes to arrhythmogenic processes at the cellular and systems level. They have also investigated interactions between these ion channel abnormalities and age-related processes in producing arrhythmic tendency. Previous reviews have explored the relationships between age and loss-of-function Nav 1.5 mutations in producing arrhythmogenicity. The present review now explores complementary relationships arising from gain-of-function Nav 1.5 mutations associated with long QT3 (LQTS3). LQTS3 patients show increased risks of life-threatening ventricular arrhythmias, particularly after 40 years of age, consistent with such interactions between the ion channel abnormailities and ageing. In turn clinical evidence suggests that ageing is accompanied by structural, particularly fibrotic, as well as electrophysiological change. These abnormalities may result from biochemical changes producing low-grade inflammation resulting from increased production of reactive oxygen species and superoxide. Experimental studies offer further insights into the underlying mechanisms underlying these phenotypes. Thus, studies in genetically modified murine models for LQTS implicated action potential recovery processes in arrhythmogenesis resulting from functional ion channel abnormalities. In addition, ageing wild type (WT) murine models demonstrated both ion channel alterations and fibrotic changes with ageing. Murine models then suggested evidence for interactions between ageing and ion channel mutations and provided insights into potential arrhythmic mechanisms inviting future exploration.
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Affiliation(s)
- Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK.,School of Medicine, Perdana University-Royal College of Surgeons Ireland, Serdang, Selangor Darul Ehsan, Malaysia
| | - Karan R Chadda
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK.,Physiological Laboratory, University of Cambridge, Cambridge, UK
| | | | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Andrew A Grace
- Division of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Cambridge, UK.,Division of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Cambridge, UK
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Ahmad S, Valli H, Edling CE, Grace AA, Jeevaratnam K, Huang CLH. Effects of ageing on pro-arrhythmic ventricular phenotypes in incrementally paced murine Pgc-1β -/- hearts. Pflugers Arch 2017; 469:1579-1590. [PMID: 28821956 PMCID: PMC5691113 DOI: 10.1007/s00424-017-2054-3] [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: 07/14/2017] [Revised: 08/02/2017] [Accepted: 08/03/2017] [Indexed: 01/07/2023]
Abstract
A range of chronic clinical conditions accompany cardiomyocyte energetic dysfunction and constitute independent risk factors for cardiac arrhythmia. We investigated pro-arrhythmic and arrhythmic phenotypes in energetically deficient C57BL mice with genetic ablation of the mitochondrial promoter peroxisome proliferator-activated receptor-γ coactivator-1β (Pgc-1β), a known model of ventricular arrhythmia. Pro-arrhythmic and cellular action potential (AP) characteristics were compared in intact Langendorff-perfused hearts from young (12–16 week) and aged (> 52 week), wild-type (WT) and Pgc-1β−/− mice. Simultaneous electrocardiographic and intracellular microelectrode recordings were made through successive trains of 100 regular stimuli at progressively incremented heart rates. Aged Pgc-1β−/− hearts displayed an increased incidence of arrhythmia compared to other groups. Young and aged Pgc-1β−/− hearts showed higher incidences of alternans in both AP activation (maximum AP upshoot velocity (dV/dt)max and latency), recovery (action potential duration (APD90) and resting membrane potential (RMP) characteristics compared to WT hearts. This was particularly apparent at lower pacing frequencies. These findings accompanied reduced (dV/dt)max and increased AP latency values in the Pgc-1β−/− hearts. APs observed prior to termination of the protocol showed lower (dV/dt)max and longer AP latencies, but indistinguishable APD90 and RMPs in arrhythmic compared to those in non-arrhythmic hearts. APD restitution analysis showed that Pgc-1β−/− and WT hearts showed similar limiting gradients. However, Pgc-1β−/− hearts had shortened plateau AP wavelengths, particularly in aged Pgc-1β−/− hearts. Pgc-1β−/− hearts therefore show pro-arrhythmic instabilities attributable to altered AP conduction and activation rather than recovery characteristics.
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Affiliation(s)
- Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK.
| | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
| | - Charlotte E Edling
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7AL, UK
| | - Andrew A Grace
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW, UK
| | - Kamalan Jeevaratnam
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7AL, UK
- 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, UK.
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW, UK.
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27
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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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28
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Tse G, Wong ST, Tse V, Yeo JM. Depolarization vs. repolarization: what is the mechanism of ventricular arrhythmogenesis underlying sodium channel haploinsufficiency in mouse hearts? Acta Physiol (Oxf) 2016; 218:234-235. [PMID: 27084434 DOI: 10.1111/apha.12694] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- G. Tse
- School of Biomedical Sciences; Li Ka Shing Faculty of Medicine; University of Hong Kong; Hong Kong Hong Kong
| | - S. T. Wong
- Faculty of Medicine; Imperial College London; London UK
| | - V. Tse
- Department of Physiology; McGill University; Montreal QC Canada
| | - J. M. Yeo
- Faculty of Medicine; Imperial College London; London UK
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29
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Choy L, Yeo JM, Tse V, Chan SP, Tse G. Cardiac disease and arrhythmogenesis: Mechanistic insights from mouse models. IJC HEART & VASCULATURE 2016; 12:1-10. [PMID: 27766308 PMCID: PMC5064289 DOI: 10.1016/j.ijcha.2016.05.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 05/02/2016] [Indexed: 12/19/2022]
Abstract
The mouse is the second mammalian species, after the human, in which substantial amount of the genomic information has been analyzed. With advances in transgenic technology, mutagenesis is now much easier to carry out in mice. Consequently, an increasing number of transgenic mouse systems have been generated for the study of cardiac arrhythmias in ion channelopathies and cardiomyopathies. Mouse hearts are also amenable to physical manipulation such as coronary artery ligation and transverse aortic constriction to induce heart failure, radiofrequency ablation of the AV node to model complete AV block and even implantation of a miniature pacemaker to induce cardiac dyssynchrony. Last but not least, pharmacological models, despite being simplistic, have enabled us to understand the physiological mechanisms of arrhythmias and evaluate the anti-arrhythmic properties of experimental agents, such as gap junction modulators, that may be exert therapeutic effects in other cardiac diseases. In this article, we examine these in turn, demonstrating that primary inherited arrhythmic syndromes are now recognized to be more complex than abnormality in a particular ion channel, involving alterations in gene expression and structural remodelling. Conversely, in cardiomyopathies and heart failure, mutations in ion channels and proteins have been identified as underlying causes, and electrophysiological remodelling are recognized pathological features. Transgenic techniques causing mutagenesis in mice are extremely powerful in dissecting the relative contributions of different genes play in producing disease phenotypes. Mouse models can serve as useful systems in which to explore how protein defects contribute to arrhythmias and direct future therapy.
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Affiliation(s)
- Lois Choy
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Jie Ming Yeo
- School of Medicine, Imperial College London, SW7 2AZ, UK
| | - Vivian Tse
- Department of Physiology, McGill University, Canada
| | - Shing Po Chan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Gary Tse
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
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30
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Affiliation(s)
- Pontus B. Persson
- Institute of Vegetative Physiology; Charité-Universitaetsmedizin Berlin; Berlin Germany
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