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Yu G, Chakrabarti S, Tischenko M, Chen AL, Wang Z, Cho H, French BA, Naga Prasad SV, Chen Q, Wang QK. Gene therapy targeting protein trafficking regulator MOG1 in mouse models of Brugada syndrome, arrhythmias, and mild cardiomyopathy. Sci Transl Med 2022; 14:eabf3136. [PMID: 35675436 DOI: 10.1126/scitranslmed.abf3136] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Brugada syndrome (BrS) is a fatal arrhythmia that causes an estimated 4% of all sudden death in high-incidence areas. SCN5A encodes cardiac sodium channel NaV1.5 and causes 25 to 30% of BrS cases. Here, we report generation of a knock-in (KI) mouse model of BrS (Scn5aG1746R/+). Heterozygous KI mice recapitulated some of the clinical features of BrS, including an ST segment abnormality (a prominent J wave) on electrocardiograms and development of spontaneous ventricular tachyarrhythmias (VTs), seizures, and sudden death. VTs were caused by shortened cardiac action potential duration and late phase 3 early afterdepolarizations associated with reduced sodium current density (INa) and increased Kcnd3 and Cacna1c expression. We developed a gene therapy using adeno-associated virus serotype 9 (AAV9) vector-mediated MOG1 delivery for up-regulation of MOG1, a chaperone that binds to NaV1.5 and traffics it to the cell surface. MOG1 was chosen for gene therapy because the large size of the SCN5A coding sequence (6048 base pairs) exceeds the packaging capacity of AAV vectors. AAV9-MOG1 gene therapy increased cell surface expression of NaV1.5 and ventricular INa, reversed up-regulation of Kcnd3 and Cacna1c expression, normalized cardiac action potential abnormalities, abolished J waves, and blocked VT in Scn5aG1746R/+ mice. Gene therapy also rescued the phenotypes of cardiac arrhythmias and contractile dysfunction in heterozygous humanized KI mice with SCN5A mutation p.D1275N. Using a small chaperone protein may have broad implications for targeting disease-causing genes exceeding the size capacity of AAV vectors.
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Affiliation(s)
- Gang Yu
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan 430074, P. R. China.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Susmita Chakrabarti
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Miroslava Tischenko
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Ai-Lan Chen
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Cardiology, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong 511436, P. R. China
| | - Zhijie Wang
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan 430074, P. R. China.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Hyosuk Cho
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Brent A French
- Department of Biomedical Engineering, University of Virginia Health System, Charlottesville, VA 22903, USA
| | - Sathyamangla V Naga Prasad
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Qiuyun Chen
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA
| | - Qing K Wang
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan 430074, P. R. China.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA.,Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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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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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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Feridooni HA, Kane AE, Ayaz O, Boroumandi A, Polidovitch N, Tsushima RG, Rose RA, Howlett SE. The impact of age and frailty on ventricular structure and function in C57BL/6J mice. J Physiol 2017; 595:3721-3742. [PMID: 28502095 DOI: 10.1113/jp274134] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 03/23/2017] [Indexed: 12/25/2022] Open
Abstract
KEY POINTS Heart size increases with age (called hypertrophy), and its ability to contract declines. However, these reflect average changes that may not be present, or present to the same extent, in all older individuals. That aging happens at different rates is well accepted clinically. People who are aging rapidly are frail and frailty is measured with a 'frailty index'. We quantified frailty with a validated mouse frailty index tool and evaluated the impacts of age and frailty on cardiac hypertrophy and contractile dysfunction. Hypertrophy increased with age, while contractions, calcium currents and calcium transients declined; these changes were graded by frailty scores. Overall health status, quantified as frailty, may promote maladaptive changes associated with cardiac aging and facilitate the development of diseases such as heart failure. To understand age-related changes in heart structure and function, it is essential to know both chronological age and the health status of the animal. ABSTRACT On average, cardiac hypertrophy and contractile dysfunction increase with age. Still, individuals age at different rates and their health status varies from fit to frail. We investigated the influence of frailty on age-dependent ventricular remodelling. Frailty was quantified as deficit accumulation in adult (≈7 months) and aged (≈27 months) C57BL/6J mice by adapting a validated frailty index (FI) tool. Hypertrophy and contractile function were evaluated in Langendorff-perfused hearts; cellular correlates/mechanisms were investigated in ventricular myocytes. FI scores increased with age. Mean cardiac hypertrophy increased with age, but values in the adult and aged groups overlapped. When plotted as a function of frailty, hypertrophy was graded by FI score (r = 0.67-0.55, P < 0.0003). Myocyte area also correlated positively with FI (r = 0.34, P = 0.03). Left ventricular developed pressure (LVDP) plus rates of pressure development (+dP/dt) and decay (-dP/dt) declined with age and this was graded by frailty (r = -0.51, P = 0.0007; r = -0.48, P = 0.002; r = -0.56, P = 0.0002 for LVDP, +dP/dt and -dP/dt). Smaller, slower contractions graded by FI score were also seen in ventricular myocytes. Contractile dysfunction in cardiomyocytes isolated from frail mice was attributable to parallel changes in underlying Ca2+ transients. These changes were not due to reduced sarcoplasmic reticulum stores, but were graded by smaller Ca2+ currents (r = -0.40, P = 0.008), lower gain (r = -0.37, P = 0.02) and reduced expression of Cav1.2 protein (r = -0.68, P = 0.003). These results show that cardiac hypertrophy and contractile dysfunction in naturally aging mice are graded by overall health and suggest that frailty, in addition to chronological age, can help explain heterogeneity in cardiac aging.
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Affiliation(s)
- H A Feridooni
- Department of Pharmacology, Dalhousie University, PO Box 15000, 5850 College St, B3H 4R2, Halifax, NS, Canada
| | - A E Kane
- Department of Pharmacology, Dalhousie University, PO Box 15000, 5850 College St, B3H 4R2, Halifax, NS, Canada
| | - O Ayaz
- Department of Pharmacology, Dalhousie University, PO Box 15000, 5850 College St, B3H 4R2, Halifax, NS, Canada
| | - A Boroumandi
- Department of Biology, Muscle Health Research Centre, York University, 4700 Keele St, Toronto, ON, Canada, M3J 1P3
| | - N Polidovitch
- Department of Biology, Muscle Health Research Centre, York University, 4700 Keele St, Toronto, ON, Canada, M3J 1P3
| | - R G Tsushima
- Department of Biology, Muscle Health Research Centre, York University, 4700 Keele St, Toronto, ON, Canada, M3J 1P3
| | - R A Rose
- Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, 5850 College St, B3H 4R2, Halifax, NS, Canada
| | - S E Howlett
- Department of Pharmacology, Dalhousie University, PO Box 15000, 5850 College St, B3H 4R2, Halifax, NS, Canada.,Department of Medicine (Geriatric Medicine), Dalhousie University, PO Box 15000, 5850 College St, B3H 4R2, Halifax, NS, Canada
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Speerschneider T, Grubb S, Olesen SP, Calloe K, Thomsen MB. Ventricular repolarization time, location of pacing stimulus and current pulse amplitude conspire to determine arrhythmogenicity in mice. Acta Physiol (Oxf) 2017; 219:660-668. [PMID: 27459728 DOI: 10.1111/apha.12761] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 04/13/2016] [Accepted: 07/22/2016] [Indexed: 11/29/2022]
Abstract
AIM In this study, we investigate the impact of altered action potential durations (APD) on ventricular repolarization time and proarrhythmia in mice with and without genetic deletion of the K+ -channel-interacting protein 2 (KChIP2-/- and WT respectively). Moreover, we examine the interrelationship between the dispersion of repolarization time and current pulse amplitude in provoking ventricular arrhythmia. METHODS Intracardiac pacing in anesthetized mice determined refractory periods and proarrhythmia susceptibility. Regional activation time (AT), APD and repolarization time (=AT + APD) were measured in isolated hearts using floating microelectrodes. RESULTS Proarrhythmia in WT and KChIP2-/- was not sensitive to changes in refractory periods. Action potentials were longer in KChIP2-/- hearts compared to WT hearts. Isolated WT hearts had large apico-basal dispersion of repolarization time, whereas hearts from KChIP2-/- mice had large left-to-right ventricular dispersion of repolarization time. Pacing from the right ventricle in KChIP2-/- mice in vivo revealed significant lower current pulse amplitudes needed to induce arrhythmias in these mice. CONCLUSION Large heterogeneity of repolarization time is proarrhythmic when pacing is delivered from the location of earlier repolarization time. Ventricular repolarization time, location of the pacing stimulus and the amplitude of the stimulating current pulse are critical parameters underlying arrhythmia vulnerability.
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Affiliation(s)
- T. Speerschneider
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - S. Grubb
- Department of Veterinary Clinical and Animal Science; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - S. P. Olesen
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - K. Calloe
- Department of Veterinary Clinical and Animal Science; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - M. B. Thomsen
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
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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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Koivumäki JT, Clark RB, Belke D, Kondo C, Fedak PWM, Maleckar MMC, Giles WR. Na(+) current expression in human atrial myofibroblasts: identity and functional roles. Front Physiol 2014; 5:275. [PMID: 25147525 PMCID: PMC4124488 DOI: 10.3389/fphys.2014.00275] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 07/07/2014] [Indexed: 12/19/2022] Open
Abstract
In the mammalian heart fibroblasts have important functional roles in both healthy conditions and diseased states. During pathophysiological challenges, a closely related myofibroblast cell population emerges, and can have distinct, significant roles. Recently, it has been reported that human atrial myofibroblasts can express a Na+ current, INa. Some of the biophysical properties and molecular features suggest that this INa is due to expression of Nav 1.5, the same Na+ channel α subunit that generates the predominant INa in myocytes from adult mammalian heart. In principle, expression of Nav 1.5 could give rise to regenerative action potentials in the fibroblasts/myofibroblasts. This would suggest an active as opposed to passive role for fibroblasts/myofibroblasts in both the “trigger” and the “substrate” components of cardiac rhythm disturbances. Our goals in this preliminary study were: (i) to confirm and extend the electrophysiological characterization of INa in a human atrial fibroblast/myofibroblast cell population maintained in conventional 2-D tissue culture; (ii) to identify key molecular properties of the α and β subunits of these Na+ channel(s); (iii) to define the biophysical and pharmacological properties of this INa; (iv) to integrate the available multi-disciplinary data, and attempt to illustrate its functional consequences, using a mathematical model in which the human atrial myocyte is coupled via connexins to fixed numbers of fibroblasts/myofibroblasts in a syncytial arrangement. Our experimental findings confirm that a significant fraction (approximately 40–50%) of these human atrial myofibroblasts can express INa. However, our data suggest that INa may be generated by a combination of Nav 1.9, Nav 1.2, and Nav 1.5. Our results, when complemented with mathematical modeling, provide a background for re-evaluating pharmacological management of supraventricular rhythm disorders, e.g., persistent atrial fibrillation.
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Affiliation(s)
- Jussi T Koivumäki
- Simula Research Laboratory, Center for Biomedical Computing and Center for Cardiological Innovation Oslo, Norway
| | - Robert B Clark
- Faculty of Kinesiology, University of Calgary Calgary, AB, Canada
| | - Darrell Belke
- Faculty of Kinesiology, University of Calgary Calgary, AB, Canada
| | - Colleen Kondo
- Faculty of Kinesiology, University of Calgary Calgary, AB, Canada
| | - Paul W M Fedak
- Division of Cardiothoracic Surgery, Department of Cardiac Sciences, University of Calgary Calgary, AB, Canada
| | - Mary M C Maleckar
- Simula Research Laboratory, Center for Biomedical Computing and Center for Cardiological Innovation Oslo, Norway
| | - Wayne R Giles
- Faculty of Kinesiology, University of Calgary Calgary, AB, Canada
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Bryant S, Kimura TE, Kong CHT, Watson JJ, Chase A, Suleiman MS, James AF, Orchard CH. Stimulation of ICa by basal PKA activity is facilitated by caveolin-3 in cardiac ventricular myocytes. J Mol Cell Cardiol 2014; 68:47-55. [PMID: 24412535 PMCID: PMC3980375 DOI: 10.1016/j.yjmcc.2013.12.026] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 12/22/2013] [Accepted: 12/31/2013] [Indexed: 12/14/2022]
Abstract
L-type Ca channels (LTCC), which play a key role in cardiac excitation–contraction coupling, are located predominantly at the transverse (t-) tubules in ventricular myocytes. Caveolae and the protein caveolin-3 (Cav-3) are also present at the t-tubules and have been implicated in localizing a number of signaling molecules, including protein kinase A (PKA) and β2-adrenoceptors. The present study investigated whether disruption of Cav-3 binding to its endogenous binding partners influenced LTCC activity. Ventricular myocytes were isolated from male Wistar rats and LTCC current (ICa) recorded using the whole-cell patch-clamp technique. Incubation of myocytes with a membrane-permeable peptide representing the scaffolding domain of Cav-3 (C3SD) reduced basal ICa amplitude in intact, but not detubulated, myocytes, and attenuated the stimulatory effects of the β2-adrenergic agonist zinterol on ICa. The PKA inhibitor H-89 also reduced basal ICa; however, the inhibitory effects of C3SD and H-89 on basal ICa amplitude were not summative. Under control conditions, myocytes stained with antibody against phosphorylated LTCC (pLTCC) displayed a striated pattern, presumably reflecting localization at the t-tubules. Both C3SD and H-89 reduced pLTCC staining at the z-lines but did not affect staining of total LTCC or Cav-3. These data are consistent with the idea that the effects of C3SD and H-89 share a common pathway, which involves PKA and is maximally inhibited by H-89, and suggest that Cav-3 plays an important role in mediating stimulation of ICa at the t-tubules via PKA-induced phosphorylation under basal conditions, and in response to β2-adrenoceptor stimulation. Basal L type calcium current was reduced by interfering with caveolin-3 binding. L type calcium current is tonically regulated by PKA phosphorylation. Interfering with caveolin-3 binding reduced beta2 adrenergic stimulation of ICa.
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Affiliation(s)
- Simon Bryant
- School of Physiology and Pharmacology, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Tomomi E Kimura
- School of Physiology and Pharmacology, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Cherrie H T Kong
- School of Physiology and Pharmacology, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Judy J Watson
- School of Physiology and Pharmacology, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Anabelle Chase
- School of Physiology and Pharmacology, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - M Saadeh Suleiman
- School of Physiology and Pharmacology, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Andrew F James
- School of Physiology and Pharmacology, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK.
| | - Clive H Orchard
- School of Physiology and Pharmacology, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK.
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King JH, Wickramarachchi C, Kua K, Du Y, Jeevaratnam K, Matthews HR, Grace AA, Huang CLH, Fraser JA. Loss of Nav1.5 expression and function in murine atria containing the RyR2-P2328S gain-of-function mutation. Cardiovasc Res 2013; 99:751-9. [PMID: 23723061 DOI: 10.1093/cvr/cvt141] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
AIMS Recent studies reported slowed conduction velocity (CV) in murine hearts homozygous for the gain-of-function RyR2-P2328S mutation (RyR2(S/S)) and associated this with an increased incidence of atrial and ventricular arrhythmias. The present experiments determined mechanisms contributing to the reduced atrial CV. METHODS AND RESULTS The determinants of CV were investigated in murine RyR2(S/S) hearts and compared with those in wild-type (WT) and slow-conducting Scn5a(+/-) hearts. Picrosirius red staining demonstrated increased fibrosis only in Scn5a(+/-) hearts. Immunoblot assays showed similar expressions of Cx43 and Cx40 levels in the three genotypes. In contrast, Nav1.5 expression was reduced in both RyR2(S/S) and Scn5a(+/-) atria. These findings correlated with intracellular microelectrode and loose-patch-clamp studies. Microelectrode measurements showed reduced maximum rates of depolarization in Scn5a(+/-) and RyR2(S/S) atria compared with WT, despite similar diastolic membrane potentials. Loose-patch-clamp measurements demonstrated reduced peak Na(+) currents (INa) in the Scn5a(+/-) and RyR2(S/S) atria relative to WT, with similar normalized current-voltage relationships. In WT atria, reduction in INa could be produced by treatment with high extracellular Ca(2+), caffeine, or cyclopiazonic acid, each expected to produce an acute increase in [Ca(2+)]i. CONCLUSION RyR2(S/S) atria show reduced levels of Nav1.5 expression and Na(+) channel function. Reduced Na(+) channel function was also observed in WT atria, following acute increases in [Ca(2+)]i. Taken together, the results suggest that raised [Ca(2+)]i produces both acute and chronic inhibition of Na(+) channel function. These findings may help explain the relationship between altered Ca(2+) homeostasis, CV, and the maintenance of common arrhythmias such as atrial fibrillation.
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Affiliation(s)
- James H King
- Physiological Laboratory, University of Cambridge, UK
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Luo T, Chang CX, Zhou X, Gu SK, Jiang TM, Li YM. Characterization of atrial histopathological and electrophysiological changes in a mouse model of aging. Int J Mol Med 2012; 31:138-46. [PMID: 23135407 DOI: 10.3892/ijmm.2012.1174] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 10/04/2012] [Indexed: 11/06/2022] Open
Abstract
The detailed mechanisms of age-related atrial structural and electrophysiological changes remain elusive. Small animal models have recently been used for the investigation of atrial tachyarrhythmia. In this study, we investigated the hypothesis that atrial structural and electrical characterization with aging provides a substrate for atrial fibrillation using a mouse model of aging. Male Kunming mice aged 2 (young), 12 (middle-aged) and 24 months (aged) were used in this study. A surface electrocardiogram and sinus node recovery time (SNRT) were recorded at baseline. Atrial fibrillation (AF) inducibility and duration were measured by a transesophageal electrode catheter. Collagen content was assessed by the collagen volume fraction. Whole cell configuration using the patch clamp technique was performed for the transient outward potassium (Ito) and ultra-rapid delayed rectifier potassium (Ikur) currents. P-wave duration, SNRT and rate-corrected SNRT were longer in the aged group than in the remaining 2 groups, paralleled by inducibility significantly being increased in the aged group. The right atrium had significantly higher levels of fibrosis than the left atrium in all the groups (P<0.05), whereas the extent of fibrosis in the left atrium had a higher positive correlation with age relative to the right atrium (P<0.05). Moreover, in old age, the dispersion of left relative to right atrium repolarization and augmented Ito currents contributed to vulnerability to AF. Nevertheless, Ikur currents in the atrial myocytes showed no age-related changes. The present study demonstrates that in addition to the structural alterations, aging can also cause integrative and cellular electrophysiological changes in a mouse model of aging, facilitating AF initiation and maintenance.
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Affiliation(s)
- Tao Luo
- Graduate School of Medicine, Tianjin Medical University, Tianjin, PR China
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