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Keefe JA, Moore OM, Ho KS, Wehrens XHT. Role of Ca 2+ in healthy and pathologic cardiac function: from normal excitation-contraction coupling to mutations that cause inherited arrhythmia. Arch Toxicol 2023; 97:73-92. [PMID: 36214829 PMCID: PMC10122835 DOI: 10.1007/s00204-022-03385-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 09/15/2022] [Indexed: 01/19/2023]
Abstract
Calcium (Ca2+) ions are a key second messenger involved in the rhythmic excitation and contraction of cardiomyocytes throughout the heart. Proper function of Ca2+-handling proteins is required for healthy cardiac function, whereas disruption in any of these can cause cardiac arrhythmias. This comprehensive review provides a broad overview of the roles of Ca2+-handling proteins and their regulators in healthy cardiac function and the mechanisms by which mutations in these proteins contribute to inherited arrhythmias. Major Ca2+ channels and Ca2+-sensitive regulatory proteins involved in cardiac excitation-contraction coupling are discussed, with special emphasis on the function of the RyR2 macromolecular complex. Inherited arrhythmia disorders including catecholaminergic polymorphic ventricular tachycardia, long QT syndrome, Brugada syndrome, short QT syndrome, and arrhythmogenic right-ventricular cardiomyopathy are discussed with particular emphasis on subtypes caused by mutations in Ca2+-handling proteins.
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Affiliation(s)
- Joshua A Keefe
- Cardiovascular Research Institute, Baylor College of Medicine, One Baylor Plaza, BCM335, Houston, TX, 77030, USA.,Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Oliver M Moore
- Cardiovascular Research Institute, Baylor College of Medicine, One Baylor Plaza, BCM335, Houston, TX, 77030, USA.,Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Kevin S Ho
- Cardiovascular Research Institute, Baylor College of Medicine, One Baylor Plaza, BCM335, Houston, TX, 77030, USA.,Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Xander H T Wehrens
- Cardiovascular Research Institute, Baylor College of Medicine, One Baylor Plaza, BCM335, Houston, TX, 77030, USA. .,Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, 77030, USA. .,Department of Medicine, Baylor College of Medicine, Houston, TX, 77030, USA. .,Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA. .,Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA. .,Center for Space Medicine, Baylor College of Medicine, Houston, TX, 77030, USA.
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2
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Guarina L, Moghbel AN, Pourhosseinzadeh MS, Cudmore RH, Sato D, Clancy CE, Santana LF. Biological noise is a key determinant of the reproducibility and adaptability of cardiac pacemaking and EC coupling. J Gen Physiol 2022; 154:e202012613. [PMID: 35482009 PMCID: PMC9059386 DOI: 10.1085/jgp.202012613] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 03/16/2022] [Accepted: 04/07/2022] [Indexed: 12/23/2022] Open
Abstract
Each heartbeat begins with the generation of an action potential in pacemaking cells in the sinoatrial node. This signal triggers contraction of cardiac muscle through a process termed excitation-contraction (EC) coupling. EC coupling is initiated in dyadic structures of cardiac myocytes, where ryanodine receptors in the junctional sarcoplasmic reticulum come into close apposition with clusters of CaV1.2 channels in invaginations of the sarcolemma. Cooperative activation of CaV1.2 channels within these clusters causes a local increase in intracellular Ca2+ that activates the juxtaposed ryanodine receptors. A salient feature of healthy cardiac function is the reliable and precise beat-to-beat pacemaking and amplitude of Ca2+ transients during EC coupling. In this review, we discuss recent discoveries suggesting that the exquisite reproducibility of this system emerges, paradoxically, from high variability at subcellular, cellular, and network levels. This variability is attributable to stochastic fluctuations in ion channel trafficking, clustering, and gating, as well as dyadic structure, which increase intracellular Ca2+ variance during EC coupling. Although the effects of these large, local fluctuations in function and organization are sometimes negligible at the macroscopic level owing to spatial-temporal summation within and across cells in the tissue, recent work suggests that the "noisiness" of these intracellular Ca2+ events may either enhance or counterintuitively reduce variability in a context-dependent manner. Indeed, these noisy events may represent distinct regulatory features in the tuning of cardiac contractility. Collectively, these observations support the importance of incorporating experimentally determined values of Ca2+ variance in all EC coupling models. The high reproducibility of cardiac contraction is a paradoxical outcome of high Ca2+ signaling variability at subcellular, cellular, and network levels caused by stochastic fluctuations in multiple processes in time and space. This underlying stochasticity, which counterintuitively manifests as reliable, consistent Ca2+ transients during EC coupling, also allows for rapid changes in cardiac rhythmicity and contractility in health and disease.
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Affiliation(s)
- Laura Guarina
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | - Ariana Neelufar Moghbel
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | | | - Robert H. Cudmore
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | - Daisuke Sato
- Department of Pharmacology, University of California Davis School of Medicine, Davis, CA
| | - Colleen E. Clancy
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | - Luis Fernando Santana
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
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3
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Hutchings DC, Madders GWP, Niort BC, Bode EF, Waddell CA, Woods LS, Dibb KM, Eisner DA, Trafford AW. Interaction of background Ca 2+ influx, sarcoplasmic reticulum threshold and heart failure in determining propensity for Ca 2+ waves in sheep heart. J Physiol 2022; 600:2637-2650. [PMID: 35233776 PMCID: PMC9310721 DOI: 10.1113/jp282168] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 02/25/2022] [Indexed: 11/11/2022] Open
Abstract
Ventricular arrhythmias can cause death in heart failure (HF). A trigger is the occurrence of Ca2+ waves which activate a Na+ -Ca2+ exchange (NCX) current, leading to delayed after-depolarisations and triggered action potentials. Waves arise when sarcoplasmic reticulum (SR) Ca2+ content reaches a threshold and are commonly induced experimentally by raising external Ca2+ , although the mechanism by which this causes waves is unclear and was the focus of this study. Intracellular Ca2+ was measured in voltage-clamped ventricular myocytes from both control sheep and those subjected to rapid pacing to produce HF. Threshold SR Ca2+ content was determined by applying caffeine (10 mM) following a wave and integrating wave and caffeine-induced NCX currents. Raising external Ca2+ induced waves in a greater proportion of HF cells than control. The associated increase of SR Ca2+ content was smaller in HF due to a lower threshold. Raising external Ca2+ had no effect on total influx via the L-type Ca2+ current, ICa-L , and increased efflux on NCX. Analysis of sarcolemmal fluxes revealed substantial background Ca2+ entry which sustains Ca2+ efflux during waves in the steady state. Wave frequency and background Ca2+ entry were decreased by Gd3+ or the TRPC6 inhibitor BI 749327. These agents also blocked Mn2+ entry. Inhibiting connexin hemi-channels, TRPC1/4/5, L-type channels or NCX had no effect on background entry. In conclusion, raising external Ca2+ induces waves via a background Ca2+ influx through TRPC6 channels. The greater propensity to waves in HF results from increased background entry and decreased threshold SR content. KEY POINTS: Heart failure is a pro-arrhythmic state and arrhythmias are a major cause of death. At the cellular level, Ca2+ waves resulting in delayed after-depolarisations are a key trigger of arrhythmias. Ca2+ waves arise when the sarcoplasmic reticulum (SR) becomes overloaded with Ca2+ . We investigate the mechanism by which raising external Ca2+ causes waves, and how this is modified in heart failure. We demonstrate that a novel sarcolemmal background Ca2+ influx via the TRPC6 channel is responsible for SR Ca2+ overload and Ca2+ waves. The increased propensity for Ca2+ waves in heart failure results from an increase of background influx, and a lower threshold SR content. The results of the present study highlight a novel mechanism by which Ca2+ waves may arise in heart failure, providing a basis for future work and novel therapeutic targets.
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Affiliation(s)
- David C Hutchings
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK.,Manchester University NHS Foundation Trust, Manchester, UK
| | - George W P Madders
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Barbara C Niort
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Elizabeth F Bode
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Caitlin A Waddell
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Lori S Woods
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Katharine M Dibb
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - David A Eisner
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Andrew W Trafford
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
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4
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Gonano LA, Mattiazzi A. Targeting late ICaL to close the window to ventricular arrhythmias. J Gen Physiol 2021; 153:212726. [PMID: 34699586 PMCID: PMC8552155 DOI: 10.1085/jgp.202113009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Affiliation(s)
- Luis A Gonano
- Centro de Investigaciones Cardiovasculares Horacio Cingolani, CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares Horacio Cingolani, CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
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Vicente M, Salgado-Almario J, Collins MM, Martínez-Sielva A, Minoshima M, Kikuchi K, Domingo B, Llopis J. Cardioluminescence in Transgenic Zebrafish Larvae: A Calcium Imaging Tool to Study Drug Effects and Pathological Modeling. Biomedicines 2021; 9:biomedicines9101294. [PMID: 34680411 PMCID: PMC8533351 DOI: 10.3390/biomedicines9101294] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 09/07/2021] [Accepted: 09/20/2021] [Indexed: 01/12/2023] Open
Abstract
Zebrafish embryos and larvae have emerged as an excellent model in cardiovascular research and are amenable to live imaging with genetically encoded biosensors to study cardiac cell behaviours, including calcium dynamics. To monitor calcium ion levels in three to five days post-fertilization larvae, we have used bioluminescence. We generated a transgenic line expressing GFP-aequorin in the heart, Tg(myl7:GA), and optimized a reconstitution protocol to boost aequorin luminescence. The analogue diacetylh-coelenterazine enhanced light output and signal-to-noise ratio. With this cardioluminescence model, we imaged the time-averaged calcium levels and beat-to-beat calcium oscillations continuously for hours. As a proof-of-concept of the transgenic line, changes in ventricular calcium levels were observed by Bay K8644, an L-type calcium channel activator and with the blocker nifedipine. The β-adrenergic blocker propranolol decreased calcium levels, heart rate, stroke volume, and cardiac output, suggesting that larvae have a basal adrenergic tone. Zebrafish larvae treated with terfenadine for 24 h have been proposed as a model of heart failure. Tg(myl7:GA) larvae treated with terfenadine showed bradycardia, 2:1 atrioventricular block, decreased time-averaged ventricular calcium levels but increased calcium transient amplitude, and reduced cardiac output. As alterations of calcium signalling are involved in the pathogenesis of heart failure and arrhythmia, the GFP-aequorin transgenic line provides a powerful platform for understanding calcium dynamics.
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Affiliation(s)
- Manuel Vicente
- Physiology and Cell Dynamics Group, Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, C/Almansa 14, 02006 Albacete, Spain; (M.V.); (J.S.-A.); (A.M.-S.)
| | - Jussep Salgado-Almario
- Physiology and Cell Dynamics Group, Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, C/Almansa 14, 02006 Albacete, Spain; (M.V.); (J.S.-A.); (A.M.-S.)
| | - Michelle M. Collins
- Department of Anatomy, Physiology, and Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada;
| | - Antonio Martínez-Sielva
- Physiology and Cell Dynamics Group, Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, C/Almansa 14, 02006 Albacete, Spain; (M.V.); (J.S.-A.); (A.M.-S.)
| | - Masafumi Minoshima
- Department of Material and Life Science, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan; (M.M.); (K.K.)
| | - Kazuya Kikuchi
- Department of Material and Life Science, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan; (M.M.); (K.K.)
- WPI-Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
| | - Beatriz Domingo
- Physiology and Cell Dynamics Group, Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, C/Almansa 14, 02006 Albacete, Spain; (M.V.); (J.S.-A.); (A.M.-S.)
- Correspondence: (B.D.); (J.L.); Tel.: +34-967-599-315 (J.L.); +34-967-599-200 (ext. 2686) (B.D.)
| | - Juan Llopis
- Physiology and Cell Dynamics Group, Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, C/Almansa 14, 02006 Albacete, Spain; (M.V.); (J.S.-A.); (A.M.-S.)
- Correspondence: (B.D.); (J.L.); Tel.: +34-967-599-315 (J.L.); +34-967-599-200 (ext. 2686) (B.D.)
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6
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Hutchings DC, Pearman CM, Madders GWP, Woods LS, Eisner DA, Dibb KM, Trafford AW. PDE5 Inhibition Suppresses Ventricular Arrhythmias by Reducing SR Ca 2+ Content. Circ Res 2021; 129:650-665. [PMID: 34247494 PMCID: PMC8409902 DOI: 10.1161/circresaha.121.318473] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
[Figure: see text].
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Affiliation(s)
- David C Hutchings
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Charles M Pearman
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - George W P Madders
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Lori S Woods
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - David A Eisner
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Katharine M Dibb
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Andrew W Trafford
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
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7
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Yang HQ, Zhou P, Wang LP, Zhao YT, Ren YJ, Guo YB, Xu M, Wang SQ. Compartmentalized β1-adrenergic signalling synchronizes excitation-contraction coupling without modulating individual Ca2+ sparks in healthy and hypertrophied cardiomyocytes. Cardiovasc Res 2020; 116:2069-2080. [PMID: 32031586 DOI: 10.1093/cvr/cvaa013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 11/20/2019] [Accepted: 01/30/2020] [Indexed: 12/21/2022] Open
Abstract
AIMS β-adrenergic receptors (βARs) play pivotal roles in regulating cardiac excitation-contraction (E-C) coupling. Global signalling of β1ARs up-regulates both the influx of Ca2+ through sarcolemmal L-type Ca2+ channels (LCCs) and the release of Ca2+ from the sarcoplasmic reticulum (SR) through the ryanodine receptors (RyRs). However, we recently found that β2AR stimulation meditates 'offside compartmentalization', confining β1AR signalling into subsarcolemmal nanodomains without reaching SR proteins. In the present study, we aim to investigate the new question, whether and how compartmentalized β1AR signalling regulates cardiac E-C coupling. METHODS AND RESULTS By combining confocal Ca2+ imaging and patch-clamp techniques, we investigated the effects of compartmentalized βAR signalling on E-C coupling at both cellular and molecular levels. We found that simultaneous activation of β2 and β1ARs, in contrast to global signalling of β1ARs, modulated neither the amplitude and spatiotemporal properties of Ca2+ sparks nor the kinetics of the RyR response to LCC Ca2+ sparklets. Nevertheless, by up-regulating LCC current, compartmentalized β1AR signalling synchronized RyR Ca2+ release and increased the functional reserve (stability margin) of E-C coupling. In circumstances of briefer excitation durations or lower RyR responsivity, compartmentalized βAR signalling, by increasing the intensity of Ca2+ triggers, helped stabilize the performance of E-C coupling and enhanced the Ca2+ transient amplitude in failing heart cells. CONCLUSION Given that compartmentalized βAR signalling can be induced by stress-associated levels of catecholamines, our results revealed an important, yet unappreciated, heart regulation mechanism that is autoadaptive to varied stress conditions.
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Affiliation(s)
- Hua-Qian Yang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Rd, Beijing 100871, China
| | - Peng Zhou
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Rd, Beijing 100871, China
| | - Li-Peng Wang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Rd, Beijing 100871, China
| | - Yan-Ting Zhao
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Rd, Beijing 100871, China
| | - Yu-Jie Ren
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Rd, Beijing 100871, China
| | - Yun-Bo Guo
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Rd, Beijing 100871, China
| | - Ming Xu
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Rd, Beijing 100871, China
| | - Shi-Qiang Wang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Rd, Beijing 100871, China
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8
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Wacker C, Dams N, Schauer A, Ritzer A, Volk T, Wagner M. Region-specific mechanisms of corticosteroid-mediated inotropy in rat cardiomyocytes. Sci Rep 2020; 10:11604. [PMID: 32665640 PMCID: PMC7360564 DOI: 10.1038/s41598-020-68308-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 06/23/2020] [Indexed: 11/09/2022] Open
Abstract
Regional differences in ion channel activity in the heart control the sequence of repolarization and may contribute to differences in contraction. Corticosteroids such as aldosterone or corticosterone increase the L-type Ca2+ current (ICaL) in the heart via the mineralocorticoid receptor (MR). Here, we investigate the differential impact of corticosteroid-mediated increase in ICaL on action potentials (AP), ion currents, intracellular Ca2+ handling and contractility in endo- and epicardial myocytes of the rat left ventricle. Dexamethasone led to a similar increase in ICaL in endocardial and epicardial myocytes, while the K+ currents Ito and IK were unaffected. However, AP duration (APD) and AP-induced Ca2+ influx (QCa) significantly increased exclusively in epicardial myocytes, thus abrogating the normal differences between the groups. Dexamethasone increased Ca2+ transients, contractility and SERCA activity in both regions, the latter possibly due to a decrease in total phospholamban (PLB) and an increase PLBpThr17. These results suggest that corticosteroids are powerful modulators of ICaL, Ca2+ transients and contractility in both endo- and epicardial myocytes, while APD and QCa are increased in epicardial myocytes only. This indicates that increased ICaL and SERCA activity rather than QCa are the primary drivers of contractility by adrenocorticoids.
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Affiliation(s)
- Caroline Wacker
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Niklas Dams
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Alexander Schauer
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Anne Ritzer
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Tilmann Volk
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany. .,Muscle Research Center Erlangen (MURCE), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
| | - Michael Wagner
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany. .,Abteilung für Rhythmologie, Herzzentrum Dresden, Fetscherstraße 76, 01307, Dresden, Germany.
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9
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Two-variable nullcline analysis of ionic general equilibrium predicts calcium homeostasis in ventricular myocytes. PLoS Comput Biol 2020; 16:e1007572. [PMID: 32502205 PMCID: PMC7316341 DOI: 10.1371/journal.pcbi.1007572] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 06/25/2020] [Accepted: 05/05/2020] [Indexed: 01/16/2023] Open
Abstract
Ventricular contraction is roughly proportional to the amount of calcium released from the Sarcoplasmic Reticulum (SR) during systole. While it is rather straightforward to measure calcium levels and contractibility under different physiological conditions, the complexity of calcium handling during systole and diastole has made the prediction of its release at steady state impossible. Here we approach the problem analyzing the evolution of intracellular and extracellular calcium fluxes during a single beat which is away from homeostatic balance. Using an in-silico subcellular model of rabbit ventricular myocyte, we show that the high dimensional nonlinear problem of finding the steady state can be reduced to a two-variable general equilibrium condition where pre-systolic calcium level in the cytosol and in the SR must fulfill simultaneously two different equalities. This renders calcium homeostasis as a problem that can be studied in terms of its equilibrium structure, leading to precise predictions of steady state from single-beat measurements. We show how changes in ion channels modify the general equilibrium, as shocks would do in general equilibrium macroeconomic models. This allows us to predict when an enhanced entrance of calcium in the cell reduces its contractibility and explain why SERCA gene therapy, a change in calcium handling to treat heart failure, might fail to improve contraction even when it successfully increases SERCA expression. Cardiomyocytes, upon voltage excitation, release calcium, which leads to cell contraction. However, under some pathological conditions, calcium handling is impaired. Recently, SERCA gene therapy, whose aim is to improve Ca2+ sequestration by the Sarcoplasmic Reticulum (SR), has failed to improve the prognosis of patients with Heart Failure. This, together with recent counterintuitive results in calcium handling, has highlighted the need for a framework to understand calcium homeostasis across species and pathologies. We show here that the proper framework is a general equilibrium approach of two independent variables. The development of this framework allows us to find a possible mechanism for the failure of SERCA gene therapy even when it manages to increase Ca SERCA expression.
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10
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Lookin O, Butova X, Protsenko Y. The role of pacing rate in the modulation of mechano-induced immediate and delayed changes in the force and Ca-transient of cardiac muscle. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 159:34-45. [PMID: 32450183 DOI: 10.1016/j.pbiomolbio.2020.05.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 03/11/2020] [Accepted: 05/11/2020] [Indexed: 12/21/2022]
Abstract
Myocardial function is tuned by dynamic changes in length and load via mechano-calcium feedback. This regulation may be significantly affected by heart rhythm. We evaluated the mechano-induced modulation of contractility and Ca-transient (CaT) in the rat myocardium subjected to twitch-by-twitch shortening-re-lengthening (↓-↑) trains of different lengths (N = 1 … 720 cycles) at low (1 Hz) and near-physiological (3.5 Hz) pacing rates. Force/CaT characteristics were evaluated in the first post-train isometric twitch (immediate effect) and during slow changes (delayed maximal elevation/decrease) and compared with those of the pre-train twitch. The immediate inotropic effect was positive for N = 30 … 720 and negative for N = 1 … 20, while the delayed effect was always positive. The immediate and delayed inotropic effects were significantly higher at 3.5-Hz vs 1-Hz (P < 0.05). The prominent inotropism was accompanied by much smaller changes in the CaT diastolic level/amplitude. The shortening-re-lengthening train induced oscillations of the slow change in force at 3.5-Hz (always) and at 1-Hz (∼50% of muscles), which were dependent of the train length and independent of the pacing rate. We suggest that twitch-by-twitch shortening-re-lengthening of cardiac muscle decreases Ca2+ buffering by troponin C and elevates Ca2+ loading of the sarcoplasmic reticulum (SR); the latter cumulatively depends on the train length. A high pacing rate intensifies the cumulative transient shift in the SR Ca2+ loading, augmenting the post-train inotropic response and prolonging its recovery to the pre-train level. The pacing-dependent mechano-induced inotropic effects remain to be elucidated in the myocardium with impaired Ca handling.
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Affiliation(s)
- Oleg Lookin
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, 620049, 106 Pervomayskaya St., Yekaterinburg, Russia; Center for Fundamental Biotechnology and Bioengineering, Institute of Natural Sciences and Mathematics, Ural Federal University, 620002, 19 Mira St., Yekaterinburg, Russia.
| | - Xenia Butova
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, 620049, 106 Pervomayskaya St., Yekaterinburg, Russia; Center for Fundamental Biotechnology and Bioengineering, Institute of Natural Sciences and Mathematics, Ural Federal University, 620002, 19 Mira St., Yekaterinburg, Russia
| | - Yuri Protsenko
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, 620049, 106 Pervomayskaya St., Yekaterinburg, Russia
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11
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Lu S, Liao Z, Lu X, Katschinski DM, Mercola M, Chen J, Heller Brown J, Molkentin JD, Bossuyt J, Bers DM. Hyperglycemia Acutely Increases Cytosolic Reactive Oxygen Species via O-linked GlcNAcylation and CaMKII Activation in Mouse Ventricular Myocytes. Circ Res 2020; 126:e80-e96. [PMID: 32134364 DOI: 10.1161/circresaha.119.316288] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
RATIONALE Diabetes mellitus is a complex, multisystem disease, affecting large populations worldwide. Chronic CaMKII (Ca2+/calmodulin-dependent kinase II) activation may occur in diabetes mellitus and be arrhythmogenic. Diabetic hyperglycemia was shown to activate CaMKII by (1) O-linked attachment of N-acetylglucosamine (O-GlcNAc) at S280 leading to arrhythmia and (2) a reactive oxygen species (ROS)-mediated oxidation of CaMKII that can increase postinfarction mortality. OBJECTIVE To test whether high extracellular glucose (Hi-Glu) promotes ventricular myocyte ROS generation and the role played by CaMKII. METHODS AND RESULTS We tested how extracellular Hi-Glu influences ROS production in adult ventricular myocytes, using DCF (2',7'-dichlorodihydrofluorescein diacetate) and genetically targeted Grx-roGFP2 redox sensors. Hi-Glu (30 mmol/L) significantly increased the rate of ROS generation-an effect prevented in myocytes pretreated with CaMKII inhibitor KN-93 or from either global or cardiac-specific CaMKIIδ KO (knockout) mice. CaMKII KO or inhibition also prevented Hi-Glu-induced sarcoplasmic reticulum Ca2+ release events (Ca2+ sparks). Thus, CaMKII activation is required for Hi-Glu-induced ROS generation and sarcoplasmic reticulum Ca2+ leak in cardiomyocytes. To test the involvement of O-GlcNAc-CaMKII pathway, we inhibited GlcNAcylation removal by Thiamet G (ThmG), which mimicked the Hi-Glu-induced ROS production. Conversely, inhibition of GlcNAcylation (OSMI-1 [(αR)-α-[[(1,2-dihydro-2-oxo-6-quinolinyl)sulfonyl]amino]-N-(2-furanylmethyl)-2-methoxy-N-(2-thienylmethyl)-benzeneacetamide]) prevented ROS induction in response to either Hi-Glu or ThmG. Moreover, in a CRSPR-based knock-in mouse in which the functional GlcNAcylation site on CaMKIIδ was ablated (S280A), neither Hi-Glu nor ThmG induced myocyte ROS generation. So CaMKIIδ-S280 is required for the Hi-Glu-induced (and GlcNAc dependent) ROS production. To identify the ROS source(s), we used different inhibitors of NOX (NADPH oxidase) 2 (Gp91ds-tat peptide), NOX4 (GKT137831), mitochondrial ROS (MitoTempo), and NOS (NO synthase) pathway inhibitors (L-NAME, L-NIO, and L-NPA). Only NOX2 inhibition or KO prevented Hi-Glu/ThmG-induced ROS generation. CONCLUSIONS Diabetic hyperglycemia induces acute cardiac myocyte ROS production by NOX2 that requires O-GlcNAcylation of CaMKIIδ at S280. This novel ROS induction may exacerbate pathological consequences of diabetic hyperglycemia.
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Affiliation(s)
- Shan Lu
- From the Department of Pharmacology, University of California, Davis School of Medicine (S.L., Z.L., J.B., D.M.B.)
| | - Zhandi Liao
- From the Department of Pharmacology, University of California, Davis School of Medicine (S.L., Z.L., J.B., D.M.B.)
| | - Xiyuan Lu
- Department of Cardiology, Renji Hospital School of Medicine, Jiaotong University, Shanghai, China (X.L.)
| | - Dörthe M Katschinski
- Institute of Cardiovascular Physiology, University Medical Centre Göttingen, Germany (D.M.K.)
- German Center for Cardiovascular Research, Partner Site, Göttingen (D.M.K.)
| | - Mark Mercola
- Stanford Cardiovascular Institute and Department of Medicine, Stanford University, CA (M.M.)
| | - Ju Chen
- Department of Medicine (J.C.), University of California San Diego, La Jolla
| | - Joan Heller Brown
- Department of Pharmacology (J.H.B.), University of California San Diego, La Jolla
| | - Jeffery D Molkentin
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, OH (J.D.M.)
| | - Julie Bossuyt
- From the Department of Pharmacology, University of California, Davis School of Medicine (S.L., Z.L., J.B., D.M.B.)
| | - Donald M Bers
- From the Department of Pharmacology, University of California, Davis School of Medicine (S.L., Z.L., J.B., D.M.B.)
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12
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Lookin O, Protsenko Y. The lack of slow force response in failing rat myocardium: role of stretch-induced modulation of Ca-TnC kinetics. J Physiol Sci 2019; 69:345-357. [PMID: 30560346 PMCID: PMC10717443 DOI: 10.1007/s12576-018-0651-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 12/08/2018] [Indexed: 10/27/2022]
Abstract
The slow force response (SFR) to stretch is an important adaptive mechanism of the heart. The SFR may result in ~ 20-30% extra force but it is substantially attenuated in heart failure. We investigated the relation of SFR magnitude with Ca2+ transient decay in healthy (CONT) and monocrotaline-treated rats with heart failure (MCT). Right ventricular trabeculae were stretched from 85 to 95% of optimal length and held stretched for 10 min at 30 °C and 1 Hz. Isometric twitches and Ca2+ transients were collected on 2, 4, 6, 8, 10 min after stretch. The changes in peak tension and Ca2+ transient decay characteristics during SFR were evaluated as a percentage of the value measured immediately after stretch. The amount of Ca2+ utilized by TnC was indirectly evaluated using the methods of Ca2+ transient "bump" and "difference curve." The muscles of CONT rats produced positive SFR and they showed prominent functional relation between SFR magnitude and the magnitude (amplitude, integral intensity) of Ca2+ transient "bump" and "difference curve." The myocardium of MCT rats showed negative SFR to stretch (force decreased in time) which was not correlated well with the characteristics of Ca2+ transient decay, evaluated by the methods of "bump" and "difference curve." We conclude that the intracellular mechanisms of Ca2+ balancing during stretch-induced slow adaptation of myocardial contractility are disrupted in failing rat myocardium. The potential significance of our findings is that the deficiency of slow force response in diseased myocardium may be diminished under augmented kinetics of Ca-TnC interaction.
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Affiliation(s)
- Oleg Lookin
- Laboratory of Biological Motility, Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, 106 Pervomayskaya St., Yekaterinburg, 620049, Russian Federation.
- Ural Federal University, 19 Mira St., Yekaterinburg, 620002, Russian Federation.
| | - Yuri Protsenko
- Laboratory of Biological Motility, Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, 106 Pervomayskaya St., Yekaterinburg, 620049, Russian Federation
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13
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Denham NC, Pearman CM, Caldwell JL, Madders GWP, Eisner DA, Trafford AW, Dibb KM. Calcium in the Pathophysiology of Atrial Fibrillation and Heart Failure. Front Physiol 2018; 9:1380. [PMID: 30337881 PMCID: PMC6180171 DOI: 10.3389/fphys.2018.01380] [Citation(s) in RCA: 102] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 09/11/2018] [Indexed: 12/20/2022] Open
Abstract
Atrial fibrillation (AF) is commonly associated with heart failure. A bidirectional relationship exists between the two-AF exacerbates heart failure causing a significant increase in heart failure symptoms, admissions to hospital and cardiovascular death, while pathological remodeling of the atria as a result of heart failure increases the risk of AF. A comprehensive understanding of the pathophysiology of AF is essential if we are to break this vicious circle. In this review, the latest evidence will be presented showing a fundamental role for calcium in both the induction and maintenance of AF. After outlining atrial electrophysiology and calcium handling, the role of calcium-dependent afterdepolarizations and atrial repolarization alternans in triggering AF will be considered. The atrial response to rapid stimulation will be discussed, including the short-term protection from calcium overload in the form of calcium signaling silencing and the eventual progression to diastolic calcium leak causing afterdepolarizations and the development of an electrical substrate that perpetuates AF. The role of calcium in the bidirectional relationship between heart failure and AF will then be covered. The effects of heart failure on atrial calcium handling that promote AF will be reviewed, including effects on both atrial myocytes and the pulmonary veins, before the aspects of AF which exacerbate heart failure are discussed. Finally, the limitations of human and animal studies will be explored allowing contextualization of what are sometimes discordant results.
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Affiliation(s)
- Nathan C. Denham
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | | | | | | | | | | | - Katharine M. Dibb
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
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14
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Ferrantini C, Pioner JM, Mazzoni L, Gentile F, Tosi B, Rossi A, Belardinelli L, Tesi C, Palandri C, Matucci R, Cerbai E, Olivotto I, Poggesi C, Mugelli A, Coppini R. Late sodium current inhibitors to treat exercise-induced obstruction in hypertrophic cardiomyopathy: an in vitro study in human myocardium. Br J Pharmacol 2018; 175:2635-2652. [PMID: 29579779 PMCID: PMC6003658 DOI: 10.1111/bph.14223] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 03/07/2018] [Accepted: 03/08/2018] [Indexed: 12/19/2022] Open
Abstract
Background and Purpose In 30–40% of hypertrophic cardiomyopathy (HCM) patients, symptomatic left ventricular (LV) outflow gradients develop only during exercise due to catecholamine‐induced LV hypercontractility (inducible obstruction). Negative inotropic pharmacological options are limited to β‐blockers or disopyramide, with low efficacy and tolerability. We assessed the potential of late sodium current (INaL)‐inhibitors to treat inducible obstruction in HCM. Experimental Approach The electrophysiological and mechanical responses to β‐adrenoceptor stimulation were studied in human myocardium from HCM and control patients. Effects of INaL‐inhibitors (ranolazine and GS‐967) in HCM samples were investigated under conditions simulating rest and exercise. Key Results In cardiomyocytes and trabeculae from 18 surgical septal samples of patients with obstruction, the selective INaL‐inhibitor GS‐967 (0.5 μM) hastened twitch kinetics, decreased diastolic [Ca2+] and shortened action potentials, matching the effects of ranolazine (10μM). Mechanical responses to isoprenaline (inotropic and lusitropic) were comparable in HCM and control myocardium. However, isoprenaline prolonged action potentials in HCM myocardium, while it shortened them in controls. Unlike disopyramide, neither GS‐967 nor ranolazine reduced force at rest. However, in the presence of isoprenaline, they reduced Ca2+‐transient amplitude and twitch tension, while the acceleration of relaxation was maintained. INaL‐inhibitors were more effective than disopyramide in reducing contractility during exercise. Finally, INaL‐inhibitors abolished arrhythmias induced by isoprenaline. Conclusions and Implications Ranolazine and GS‐967 reduced septal myocardium tension during simulated exercise in vitro and therefore have the potential to ameliorate symptoms caused by inducible obstruction in HCM patients, with some advantages over disopyramide and β‐blockers.
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Affiliation(s)
- Cecilia Ferrantini
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.,Cardiomyopathy Unit, Careggi University Hospital, Florence, Italy
| | - Josè Manuel Pioner
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Luca Mazzoni
- Department NeuroFarBa, University of Florence, Florence, Italy
| | - Francesca Gentile
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Benedetta Tosi
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Alessandra Rossi
- Cardiomyopathy Unit, Careggi University Hospital, Florence, Italy
| | | | - Chiara Tesi
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Chiara Palandri
- Department NeuroFarBa, University of Florence, Florence, Italy
| | - Rosanna Matucci
- Department NeuroFarBa, University of Florence, Florence, Italy
| | | | - Iacopo Olivotto
- Cardiomyopathy Unit, Careggi University Hospital, Florence, Italy
| | - Corrado Poggesi
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
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15
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Genetic background dominates the susceptibility to ventricular arrhythmias in a murine model of β-adrenergic stimulation. Sci Rep 2018; 8:2312. [PMID: 29396505 PMCID: PMC5797149 DOI: 10.1038/s41598-018-20792-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 01/24/2018] [Indexed: 11/16/2022] Open
Abstract
In cardiovascular research, several mouse strains with differing genetic backgrounds are used to investigate mechanisms leading to and sustaining ventricular arrhythmias. The genetic background has been shown to affect the studied phenotype in other research fields. Surprisingly little is known about potential strain-specific susceptibilities towards ventricular arrhythmias in vivo. Here, we hypothesized that inter-strain differences reported in the responsiveness of the β-adrenergic pathway, which is relevant for the development of arrhythmias, translate into a strain-specific vulnerability. To test this hypothesis, we characterized responses to β-adrenergic blockade (metoprolol) and β-adrenergic stimulation (isoproterenol) in 4 mouse strains commonly employed in cardiovascular research (Balb/c, BS, C57Bl/6 and FVB) using telemetric ECG recordings. We report pronounced differences in the electrical vulnerability following isoproterenol: Balb/c mice developed the highest number and the most complex arrhythmias while BS mice were protected. Balb/c mice, therefore, seem to be the background of choice for experiments requiring the occurrence of arrhythmias while BS mice may give insight into electrical stability. Arrhythmias did not correlate with the basal β-adrenergic tone, with the response to β-adrenergic stimulation or with the absolute heart rates during β-adrenergic stimulation. Thus, genetic factors dominate the susceptibility to ventricular arrhythmias in this model of β-adrenergic stimulation.
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16
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Rocchetti M, Sala L, Dreizehnter L, Crotti L, Sinnecker D, Mura M, Pane LS, Altomare C, Torre E, Mostacciuolo G, Severi S, Porta A, De Ferrari GM, George AL, Schwartz PJ, Gnecchi M, Moretti A, Zaza A. Elucidating arrhythmogenic mechanisms of long-QT syndrome CALM1-F142L mutation in patient-specific induced pluripotent stem cell-derived cardiomyocytes. Cardiovasc Res 2017; 113:531-541. [PMID: 28158429 DOI: 10.1093/cvr/cvx006] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 01/15/2017] [Indexed: 12/29/2022] Open
Abstract
Aims Calmodulin (CaM) is a small protein, encoded by three genes (CALM1-3), exerting multiple Ca2+-dependent modulatory roles. A mutation (F142L) affecting only one of the six CALM alleles is associated with long QT syndrome (LQTS) characterized by recurrent cardiac arrests. This phenotypic severity is unexpected from the predicted allelic balance. In this work, the effects of heterozygous CALM1-F142L have been investigated in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) obtained from a LQTS patient carrying the F142L mutation, i.e. in the context of native allelic ratio and potential gene modifiers. Methods and Results Skin fibroblasts of the mutation carrier and two unrelated healthy subjects (controls) were reprogrammed to hiPSC and differentiated into hiPSC-CMs. Scanty IK1 expression, an hiPSC-CMs feature potentially biasing repolarization, was corrected by addition of simulated IK1 (Dynamic-Clamp). Abnormalities in repolarization rate-dependency (in single cells and cell aggregates), membrane currents and intracellular Ca2+ dynamics were evaluated as putative arrhythmogenic factors. CALM1-F142L prolonged repolarization, altered its rate-dependency and its response to isoproterenol. This was associated with severe impairment of Ca2+-dependent inactivation (CDI) of ICaL, resulting in augmented inward current during the plateau phase. As a result, the repolarization of mutant cells failed to adapt to high pacing rates, a finding well reproduced by using a recent hiPSC-CM action potential model. The mutation failed to affect IKs and INaL and changed If only marginally. Intracellular Ca2+ dynamics and Ca2+ store stability were not significantly modified. Mutation-induced repolarization abnormalities were reversed by verapamil. Conclusion The main functional derangement in CALM1-F142L was prolonged repolarization with altered rate-dependency and sensitivity to β-adrenergic stimulation. Impaired CDI of ICaL underlined the electrical abnormality, which was sensitive to ICaL blockade. High mutation penetrance was confirmed in the presence of the native genotype, implying strong dominance of effects.
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Affiliation(s)
- Marcella Rocchetti
- Department of Biotechnology and Bioscience, University of Milano-Bicocca, Milan, Italy
| | - Luca Sala
- Department of Biotechnology and Bioscience, University of Milano-Bicocca, Milan, Italy.,Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, IRCCS Istituto Auxologico Italiano, Milan, Italy
| | - Lisa Dreizehnter
- I. Medical Department - Cardiology, Klinikum Rechts der Isar- Technische Universität München, Munich, Germany
| | - Lia Crotti
- Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, IRCCS Istituto Auxologico Italiano, Milan, Italy.,Department of Molecular Medicine - Unit of Cardiology, University of Pavia, Pavia, Italy
| | - Daniel Sinnecker
- I. Medical Department - Cardiology, Klinikum Rechts der Isar- Technische Universität München, Munich, Germany
| | - Manuela Mura
- Department of Molecular Medicine - Unit of Cardiology, University of Pavia, Pavia, Italy.,Department of Cardiothoracic and Vascular Sciences - Coronary Care Unit and Laboratory of Clinical and Experimental Cardiology, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy
| | - Luna Simona Pane
- I. Medical Department - Cardiology, Klinikum Rechts der Isar- Technische Universität München, Munich, Germany
| | - Claudia Altomare
- Department of Biotechnology and Bioscience, University of Milano-Bicocca, Milan, Italy
| | - Eleonora Torre
- Department of Biotechnology and Bioscience, University of Milano-Bicocca, Milan, Italy
| | - Gaspare Mostacciuolo
- Department of Biotechnology and Bioscience, University of Milano-Bicocca, Milan, Italy
| | - Stefano Severi
- Biomedical Engineering Laboratory D.E.I, University of Bologna, Cesena, Italy
| | - Alberto Porta
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.,Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy
| | - Gaetano M De Ferrari
- Department of Molecular Medicine - Unit of Cardiology, University of Pavia, Pavia, Italy.,Department of Cardiothoracic and Vascular Sciences - Coronary Care Unit and Laboratory of Clinical and Experimental Cardiology, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Peter J Schwartz
- Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, IRCCS Istituto Auxologico Italiano, Milan, Italy
| | - Massimiliano Gnecchi
- Department of Molecular Medicine - Unit of Cardiology, University of Pavia, Pavia, Italy.,Department of Cardiothoracic and Vascular Sciences - Coronary Care Unit and Laboratory of Clinical and Experimental Cardiology, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy.,Department of Medicine, University of Cape Town, Cape Town, South Africa
| | - Alessandra Moretti
- I. Medical Department - Cardiology, Klinikum Rechts der Isar- Technische Universität München, Munich, Germany.,DZHK (German Centre for Cardiovascular Research) - Partner Site Munich Heart Alliance, Munich, Germany
| | - Antonio Zaza
- Department of Biotechnology and Bioscience, University of Milano-Bicocca, Milan, Italy
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17
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Clarke JD, Caldwell JL, Pearman CM, Eisner DA, Trafford AW, Dibb KM. Increased Ca buffering underpins remodelling of Ca 2+ handling in old sheep atrial myocytes. J Physiol 2017; 595:6263-6279. [PMID: 28752958 PMCID: PMC5621500 DOI: 10.1113/jp274053] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Accepted: 07/26/2017] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Ageing is associated with an increased risk of cardiovascular disease and arrhythmias, with the most common arrhythmia being found in the atria of the heart. Little is known about how the normal atria of the heart remodel with age and thus why dysfunction might occur. We report alterations to the atrial systolic Ca2+ transient that have implications for the function of the atrial in the elderly. We describe a novel mechanism by which increased Ca buffering can account for changes to systolic Ca2+ in the old atria. The present study helps us to understand how the processes regulating atrial contraction are remodelled during ageing and provides a basis for future work aiming to understand why dysfunction develops. ABSTRACT Many cardiovascular diseases, including those affecting the atria, are associated with advancing age. Arrhythmias, including those in the atria, can arise as a result of electrical remodelling or alterations in Ca2+ homeostasis. In the atria, age-associated changes in the action potential have been documented. However, little is known about remodelling of intracellular Ca2+ homeostasis in the healthy aged atria. Using single atrial myocytes from young and old Welsh Mountain sheep, we show the free Ca2+ transient amplitude and rate of decay of systolic Ca2+ decrease with age, whereas sarcoplasmic reticulum (SR) Ca content increases. An increase in intracellular Ca buffering explains both the decrease in Ca2+ transient amplitude and decay kinetics in the absence of any change in sarcoendoplasmic reticulum calcium transport ATPase function. Ageing maintained the integrated Ca2+ influx via ICa-L but decreased peak ICa-L . Decreased peak ICa-L was found to be responsible for the age-associated increase in SR Ca content but not the decrease in Ca2+ transient amplitude. Instead, decreased peak ICa-L offsets increased SR load such that Ca2+ release from the SR was maintained during ageing. The results of the present study highlight a novel mechanism by which increased Ca buffering decreases systolic Ca2+ in old atria. Furthermore, for the first time, we have shown that SR Ca content is increased in old atrial myocytes.
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Affiliation(s)
- Jessica D. Clarke
- Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Central Manchester Foundation Trust, 3.14 Core Technology FacilityUniversity of ManchesterManchesterUK
| | - Jessica L. Caldwell
- Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Central Manchester Foundation Trust, 3.14 Core Technology FacilityUniversity of ManchesterManchesterUK
| | - Charles M. Pearman
- Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Central Manchester Foundation Trust, 3.14 Core Technology FacilityUniversity of ManchesterManchesterUK
| | - David A. Eisner
- Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Central Manchester Foundation Trust, 3.14 Core Technology FacilityUniversity of ManchesterManchesterUK
| | - Andrew W. Trafford
- Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Central Manchester Foundation Trust, 3.14 Core Technology FacilityUniversity of ManchesterManchesterUK
| | - Katharine M. Dibb
- Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Central Manchester Foundation Trust, 3.14 Core Technology FacilityUniversity of ManchesterManchesterUK
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18
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Abstract
Cardiac contractility is regulated by changes in intracellular Ca concentration ([Ca2+]i). Normal function requires that [Ca2+]i be sufficiently high in systole and low in diastole. Much of the Ca needed for contraction comes from the sarcoplasmic reticulum and is released by the process of calcium-induced calcium release. The factors that regulate and fine-tune the initiation and termination of release are reviewed. The precise control of intracellular Ca cycling depends on the relationships between the various channels and pumps that are involved. We consider 2 aspects: (1) structural coupling: the transporters are organized within the dyad, linking the transverse tubule and sarcoplasmic reticulum and ensuring close proximity of Ca entry to sites of release. (2) Functional coupling: where the fluxes across all membranes must be balanced such that, in the steady state, Ca influx equals Ca efflux on every beat. The remainder of the review considers specific aspects of Ca signaling, including the role of Ca buffers, mitochondria, Ca leak, and regulation of diastolic [Ca2+]i.
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Affiliation(s)
- David A Eisner
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences Centre, University of Manchester, United Kingdom.
| | - Jessica L Caldwell
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences Centre, University of Manchester, United Kingdom
| | - Kornél Kistamás
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences Centre, University of Manchester, United Kingdom
| | - Andrew W Trafford
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences Centre, University of Manchester, United Kingdom
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19
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Wang YY, Mesirca P, Marqués-Sulé E, Zahradnikova A, Villejoubert O, D'Ocon P, Ruiz C, Domingo D, Zorio E, Mangoni ME, Benitah JP, Gómez AM. RyR2R420Q catecholaminergic polymorphic ventricular tachycardia mutation induces bradycardia by disturbing the coupled clock pacemaker mechanism. JCI Insight 2017; 2:91872. [PMID: 28422759 DOI: 10.1172/jci.insight.91872] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 03/09/2017] [Indexed: 01/14/2023] Open
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a lethal genetic arrhythmia that manifests syncope or sudden death in children and young adults under stress conditions. CPVT patients often present bradycardia and sino-atrial node (SAN) dysfunction. However, the mechanism remains unclear. We analyzed SAN function in two CPVT families and in a novel knock-in (KI) mouse model carrying the RyR2R420Q mutation. Humans and KI mice presented slower resting heart rate. Accordingly, the rate of spontaneous intracellular Ca2+ ([Ca2+]i) transients was slower in KI mouse SAN preparations than in WT, without any significant alteration in the "funny" current (If ). The L-type Ca2+ current was reduced in KI SAN cells in a [Ca2+]i-dependent way, suggesting that bradycardia was due to disrupted crosstalk between the "voltage" and "Ca2+" clock, and the mechanisms of pacemaking was induced by aberrant spontaneous RyR2- dependent Ca2+ release. This finding was consistent with a higher Ca2+ leak during diastolic periods produced by long-lasting Ca2+ sparks in KI SAN cells. Our results uncover a mechanism for the CPVT-causing RyR2 N-terminal mutation R420Q, and they highlight the fact that enhancing the Ca2+ clock may slow the heart rhythm by disturbing the coupling between Ca2+ and voltage clocks.
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Affiliation(s)
- Yue Yi Wang
- UMR-S 1180, Inserm, Université Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France
| | - Pietro Mesirca
- UMR-5203, CNRS, INSERM U1191, Institut de Génomique Fonctionnelle, Département de Physiologie, Université de Montpellier, Montpellier, France
| | - Elena Marqués-Sulé
- UMR-S 1180, Inserm, Université Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France.,Physiotherapy Department
| | - Alexandra Zahradnikova
- UMR-S 1180, Inserm, Université Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France
| | - Olivier Villejoubert
- UMR-S 1180, Inserm, Université Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France
| | - Pilar D'Ocon
- ERI BIOTECMED and Department of Pharmacology School, University of Valencia, Valencia, Spain
| | | | - Diana Domingo
- Cardiology Department, Hospital Universitario y Politécnico La Fe, Valencia, Spain
| | - Esther Zorio
- Cardiology Department, Hospital Universitario y Politécnico La Fe, Valencia, Spain
| | - Matteo E Mangoni
- UMR-5203, CNRS, INSERM U1191, Institut de Génomique Fonctionnelle, Département de Physiologie, Université de Montpellier, Montpellier, France
| | - Jean-Pierre Benitah
- UMR-S 1180, Inserm, Université Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France
| | - Ana María Gómez
- UMR-S 1180, Inserm, Université Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France
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20
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Rajagopal V, Bass G, Walker CG, Crossman DJ, Petzer A, Hickey A, Siekmann I, Hoshijima M, Ellisman MH, Crampin EJ, Soeller C. Examination of the Effects of Heterogeneous Organization of RyR Clusters, Myofibrils and Mitochondria on Ca2+ Release Patterns in Cardiomyocytes. PLoS Comput Biol 2015; 11:e1004417. [PMID: 26335304 PMCID: PMC4559435 DOI: 10.1371/journal.pcbi.1004417] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 06/26/2015] [Indexed: 11/18/2022] Open
Abstract
Spatio-temporal dynamics of intracellular calcium, [Ca2+]i, regulate the contractile function of cardiac muscle cells. Measuring [Ca2+]i flux is central to the study of mechanisms that underlie both normal cardiac function and calcium-dependent etiologies in heart disease. However, current imaging techniques are limited in the spatial resolution to which changes in [Ca2+]i can be detected. Using spatial point process statistics techniques we developed a novel method to simulate the spatial distribution of RyR clusters, which act as the major mediators of contractile Ca2+ release, upon a physiologically-realistic cellular landscape composed of tightly-packed mitochondria and myofibrils. We applied this method to computationally combine confocal-scale (~ 200 nm) data of RyR clusters with 3D electron microscopy data (~ 30 nm) of myofibrils and mitochondria, both collected from adult rat left ventricular myocytes. Using this hybrid-scale spatial model, we simulated reaction-diffusion of [Ca2+]i during the rising phase of the transient (first 30 ms after initiation). At 30 ms, the average peak of the simulated [Ca2+]i transient and of the simulated fluorescence intensity signal, F/F0, reached values similar to that found in the literature ([Ca2+]i ≈1 μM; F/F0≈5.5). However, our model predicted the variation in [Ca2+]i to be between 0.3 and 12.7 μM (~3 to 100 fold from resting value of 0.1 μM) and the corresponding F/F0 signal ranging from 3 to 9.5. We demonstrate in this study that: (i) heterogeneities in the [Ca2+]i transient are due not only to heterogeneous distribution and clustering of mitochondria; (ii) but also to heterogeneous local densities of RyR clusters. Further, we show that: (iii) these structure-induced heterogeneities in [Ca2+]i can appear in line scan data. Finally, using our unique method for generating RyR cluster distributions, we demonstrate the robustness in the [Ca2+]i transient to differences in RyR cluster distributions measured between rat and human cardiomyocytes. Calcium (Ca2+) acts as a signal for many functions in the heart cell, from its primary role in triggering contractions during the heartbeat to acting as a signal for cell growth. Cellular function is tightly coupled to its ultra-structural organization. Spatially-realistic and biophysics-based computational models can provide quantitative insights into structure-function relationships in Ca2+ signaling. We developed a novel computational model of a rat ventricular myocyte that integrates structural information from confocal and electron microscopy datasets that were independently acquired and includes: myofibrils (protein complexes that contract during the heartbeat), mitochondria (organelles that provide energy for contraction), and ryanodine receptors (RyR, ion channels that release the Ca2+ required to trigger myofibril contraction from intracellular stores). Using this model, we examined [Ca2+]i dynamics throughout the cell cross-section at a much higher resolution than previously possible. We estimated the size of structural maladaptation that would cause disease-related alterations in [Ca2+]i dynamics. Using our methods for data integration, we also tested whether reducing the density of RyRs in human cardiomyocytes (~40% relative to rat) would have a significant effect on [Ca2+]i. We found that Ca2+ release patterns between the two species are similar, suggesting Ca2+ dynamics are robust to variations in cell ultrastructure.
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Affiliation(s)
- Vijay Rajagopal
- Department of Mechanical Engineering, University of Melbourne, Melbourne, Australia
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne, Melbourne, Australia
- * E-mail:
| | - Gregory Bass
- Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne, Melbourne, Australia
| | - Cameron G. Walker
- Department of Engineering Science, University of Auckland, Auckland, New Zealand
| | - David J. Crossman
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Amorita Petzer
- School of Biological Sciences, University of Auckland, Auckland. New Zealand
| | - Anthony Hickey
- School of Biological Sciences, University of Auckland, Auckland. New Zealand
| | - Ivo Siekmann
- Department of Mechanical Engineering, University of Melbourne, Melbourne, Australia
| | - Masahiko Hoshijima
- Department of Medicine, University of California San Diego, San Diego, United States of America
- National Center for Microscopy and Imaging Research, University of California San Diego, San Diego, United States of America
| | - Mark H. Ellisman
- National Center for Microscopy and Imaging Research, University of California San Diego, San Diego, United States of America
| | - Edmund J. Crampin
- Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne, Melbourne, Australia
- School of Mathematics and Statistics, Faculty of Science, University of Melbourne, Melbourne, Australia
- School of Medicine, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, University of Melbourne, Melbourne, Australia
| | - Christian Soeller
- Department of Physiology, University of Auckland, Auckland, New Zealand
- Biomedical Physics, University of Exeter, Exeter, United Kingdom
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21
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Feridooni HA, Dibb KM, Howlett SE. How cardiomyocyte excitation, calcium release and contraction become altered with age. J Mol Cell Cardiol 2015; 83:62-72. [PMID: 25498213 DOI: 10.1016/j.yjmcc.2014.12.004] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 12/02/2014] [Accepted: 12/04/2014] [Indexed: 11/29/2022]
Abstract
Cardiovascular disease is the main cause of death globally, accounting for over 17 million deaths each year. As the incidence of cardiovascular disease rises markedly with age, the overall risk of cardiovascular disease is expected to increase dramatically with the aging of the population such that by 2030 it could account for over 23 million deaths per year. It is therefore vitally important to understand how the heart remodels in response to normal aging for at least two reasons: i) to understand why the aged heart is increasingly susceptible to disease; and ii) since it may be possible to modify treatment of disease in older adults if the underlying substrate upon which the disease first develops is fully understood. It is well known that age modulates cardiac function at the level of the individual cardiomyocyte. Generally, in males, aging reduces cell shortening, which is associated with a decrease in the amplitude of the systolic Ca(2+) transient. This may arise due to a decrease in peak L-type Ca(2+) current. Sarcoplasmic reticulum (SR) Ca(2+) load appears to be maintained during normal aging but evidence suggests that SR function is disrupted, such that the rate of sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA)-mediated Ca(2+) removal is reduced and the properties of SR Ca(2+) release in terms of Ca(2+) sparks are altered. Interestingly, Ca(2+) handling is modulated by age to a lesser degree in females. Here we review how cellular contraction is altered as a result of the aging process by considering expression levels and functional properties of key proteins involved in controlling intracellular Ca(2+). We consider how changes in both electrical properties and intracellular Ca(2+) handling may interact to modulate cardiomyocyte contraction. We also reflect on why cardiovascular risk may differ between the sexes by highlighting sex-specific variation in the age-associated remodeling process. This article is part of a Special Issue entitled CV Aging.
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Affiliation(s)
- Hirad A Feridooni
- Department of Pharmacology, Dalhousie University, PO Box 15000, 5850 College St, Halifax, NS B3H 4R2, Canada.
| | - Katharine M Dibb
- Institute of Cardiovascular Sciences, University of Manchester, Manchester, UK.
| | - Susan E Howlett
- Department of Pharmacology, Dalhousie University, PO Box 15000, 5850 College St, Halifax, NS B3H 4R2, Canada; Department of Medicine (Geriatric Medicine), Dalhousie University, PO Box 15000, 5850 College St, Halifax, NS B3H 4R2, Canada; Institute of Cardiovascular Sciences, University of Manchester, Manchester, UK.
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22
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Briant LJB, Paton JFR, Pickering AE, Champneys AR. Modelling the vascular response to sympathetic postganglionic nerve activity. J Theor Biol 2015; 371:102-16. [PMID: 25698230 PMCID: PMC4386929 DOI: 10.1016/j.jtbi.2015.01.037] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 01/22/2015] [Accepted: 01/27/2015] [Indexed: 11/17/2022]
Abstract
This paper explores the influence of burst properties of the sympathetic nervous system on arterial contractility. Specifically, a mathematical model is constructed of the pathway from action potential generation in a sympathetic postganglionic neurone to contraction of an arterial smooth muscle cell. The differential equation model is a synthesis of models of the individual physiological processes, and is shown to be consistent with physiological data. The model is found to be unresponsive to tonic (regular) stimulation at typical frequencies recorded in sympathetic efferents. However, when stimulated at the same average frequency, but with repetitive respiratory-modulated burst patterns, it produces marked contractions. Moreover, the contractile force produced is found to be highly dependent on the number of spikes in each burst. In particular, when the model is driven by preganglionic spike trains recorded from wild-type and spontaneously hypertensive rats (which have increased spiking during each burst) the contractile force was found to be 10-fold greater in the hypertensive case. An explanation is provided in terms of the summative increased release of noradrenaline. Furthermore, the results suggest the marked effect that hypertensive spike trains had on smooth muscle cell tone can provide a significant contribution to the pathology of hypertension. We model the sympathetic-driven contraction of a vascular smooth muscle cell. The cell is unresponsive to tonic stimulation at typical sympathetic frequencies. We quantify the force produced by the cell in response to sympathetic bursting. The response of the cell is strongly dependent on burst amplitude and duration. Recordings from hypertensive animals produce significant contractile forces.
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Affiliation(s)
- Linford J B Briant
- School of Physiology & Pharmacology, Medical Sciences Building, University Walk, University of Bristol, Bristol BS8 1TD, UK; Department of Engineering Mathematics, Merchant Venturers Building, Woodland Road, University of Bristol, Bristol BS8 1UB, UK
| | - Julian F R Paton
- School of Physiology & Pharmacology, Medical Sciences Building, University Walk, University of Bristol, Bristol BS8 1TD, UK
| | - Anthony E Pickering
- School of Physiology & Pharmacology, Medical Sciences Building, University Walk, University of Bristol, Bristol BS8 1TD, UK; Department of Anaesthesia, University Hospitals Bristol, Bristol BS2 8HW, UK
| | - Alan R Champneys
- Department of Engineering Mathematics, Merchant Venturers Building, Woodland Road, University of Bristol, Bristol BS8 1UB, UK.
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23
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Verkerk AO, van Borren MMGJ, van Ginneken ACG, Wilders R. Ca(2+) cycling properties are conserved despite bradycardic effects of heart failure in sinoatrial node cells. Front Physiol 2015; 6:18. [PMID: 25698973 PMCID: PMC4313601 DOI: 10.3389/fphys.2015.00018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Accepted: 01/12/2015] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND In animal models of heart failure (HF), heart rate decreases due to an increase in intrinsic cycle length (CL) of the sinoatrial node (SAN). Pacemaker activity of SAN cells is complex and modulated by the membrane clock, i.e., the ensemble of voltage gated ion channels and electrogenic pumps and exchangers, and the Ca(2+) clock, i.e., the ensemble of intracellular Ca(2+) ([Ca(2+)]i) dependent processes. HF in SAN cells results in remodeling of the membrane clock, but few studies have examined its effects on [Ca(2+)]i homeostasis. METHODS SAN cells were isolated from control rabbits and rabbits with volume and pressure overload-induced HF. [Ca(2+)]i concentrations, and action potentials (APs) and Na(+)-Ca(2+) exchange current (INCX) were measured using indo-1 and patch-clamp methodology, respectively. RESULTS The frequency of spontaneous [Ca(2+)]i transients was significantly lower in HF SAN cells (3.0 ± 0.1 (n = 40) vs. 3.4 ± 0.1 Hz (n = 45); mean ± SEM), indicating that intrinsic CL was prolonged. HF slowed the [Ca(2+)]i transient decay, which could be explained by the slower frequency and reduced sarcoplasmic reticulum (SR) dependent rate of Ca(2+) uptake. Other [Ca(2+)]i transient parameters, SR Ca(2+) content, INCX density, and INCX-[Ca(2+)]i relationship were all unaffected by HF. Combined AP and [Ca(2+)]i recordings demonstrated that the slower [Ca(2+)]i transient decay in HF SAN cells may result in increased INCX during the diastolic depolarization, but that this effect is likely counteracted by the HF-induced increase in intracellular Na(+). β-adrenergic and muscarinic stimulation were not changed in HF SAN cells, except that late diastolic [Ca(2+)]i rise, a prominent feature of the Ca(2+) clock, is lower during β-adrenergic stimulation. CONCLUSIONS HF SAN cells have a slower [Ca(2+)]i transient decay with limited effects on pacemaker activity. Reduced late diastolic [Ca(2+)]i rise during β-adrenergic stimulation may contribute to an impaired increase in intrinsic frequency in HF SAN cells.
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Affiliation(s)
- Arie O Verkerk
- Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
| | - Marcel M G J van Borren
- Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands ; Laboratory of Clinical Chemistry and Haematology, Rijnstate Hospital Arnhem, Netherlands
| | - Antoni C G van Ginneken
- Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
| | - Ronald Wilders
- Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
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24
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Clarke JD, Caldwell JL, Horn MA, Bode EF, Richards MA, Hall MCS, Graham HK, Briston SJ, Greensmith DJ, Eisner DA, Dibb KM, Trafford AW. Perturbed atrial calcium handling in an ovine model of heart failure: potential roles for reductions in the L-type calcium current. J Mol Cell Cardiol 2015; 79:169-79. [PMID: 25463272 PMCID: PMC4312356 DOI: 10.1016/j.yjmcc.2014.11.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 11/10/2014] [Accepted: 11/11/2014] [Indexed: 12/19/2022]
Abstract
Heart failure (HF) is commonly associated with reduced cardiac output and an increased risk of atrial arrhythmias particularly during β-adrenergic stimulation. The aim of the present study was to determine how HF alters systolic Ca(2+) and the response to β-adrenergic (β-AR) stimulation in atrial myocytes. HF was induced in sheep by ventricular tachypacing and changes in intracellular Ca(2+) concentration studied in single left atrial myocytes under voltage and current clamp conditions. The following were all reduced in HF atrial myocytes; Ca(2+) transient amplitude (by 46% in current clamped and 28% in voltage clamped cells), SR dependent rate of Ca(2+) removal (kSR, by 32%), L-type Ca(2+) current density (by 36%) and action potential duration (APD90 by 22%). However, in HF SR Ca(2+) content was increased (by 19%) when measured under voltage-clamp stimulation. Inhibiting the L-type Ca(2+) current (ICa-L) in control cells reproduced both the decrease in Ca(2+) transient amplitude and increase of SR Ca(2+) content observed in voltage-clamped HF cells. During β-AR stimulation Ca(2+) transient amplitude was the same in control and HF cells. However, ICa-L remained less in HF than control cells whilst SR Ca(2+) content was highest in HF cells during β-AR stimulation. The decrease in ICa-L that occurs in HF atrial myocytes appears to underpin the decreased Ca(2+) transient amplitude and increased SR Ca(2+) content observed in voltage-clamped cells.
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Affiliation(s)
- Jessica D Clarke
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Jessica L Caldwell
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Margaux A Horn
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Elizabeth F Bode
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Mark A Richards
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Mark C S Hall
- Liverpool Heart and Chest Hospital, Thomas Drive, Liverpool L14 3PE, UK
| | - Helen K Graham
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Sarah J Briston
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - David J Greensmith
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - David A Eisner
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Katharine M Dibb
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Andrew W Trafford
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK.
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Ferrantini C, Coppini R, Sacconi L, Tosi B, Zhang ML, Wang GL, de Vries E, Hoppenbrouwers E, Pavone F, Cerbai E, Tesi C, Poggesi C, ter Keurs HEDJ. Impact of detubulation on force and kinetics of cardiac muscle contraction. ACTA ACUST UNITED AC 2014; 143:783-97. [PMID: 24863933 PMCID: PMC4035744 DOI: 10.1085/jgp.201311125] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
T-tubule uncoupling from the plasma membrane leads to myocardial contractile abnormalities. Action potential–driven Ca2+ currents from the transverse tubules (t-tubules) trigger synchronous Ca2+ release from the sarcoplasmic reticulum of cardiomyocytes. Loss of t-tubules has been reported in cardiac diseases, including heart failure, but the effect of uncoupling t-tubules from the sarcolemma on cardiac muscle mechanics remains largely unknown. We dissected intact rat right ventricular trabeculae and compared force, sarcomere length, and intracellular Ca2+ in control trabeculae with trabeculae in which the t-tubules were uncoupled from the plasma membrane by formamide-induced osmotic shock (detubulation). We verified disconnection of a consistent fraction of t-tubules from the sarcolemma by two-photon fluorescence imaging of FM4-64–labeled membranes and by the absence of tubular action potential, which was recorded by random access multiphoton microscopy in combination with a voltage-sensitive dye (Di-4-AN(F)EPPTEA). Detubulation reduced the amplitude and prolonged the duration of Ca2+ transients, leading to slower kinetics of force generation and relaxation and reduced twitch tension (1 Hz, 30°C, 1.5 mM [Ca2+]o). No mechanical changes were observed in rat left atrial trabeculae after formamide shock, consistent with the lack of t-tubules in rodent atrial myocytes. Detubulation diminished the rate-dependent increase of Ca2+-transient amplitude and twitch force. However, maximal twitch tension at high [Ca2+]o or in post-rest potentiated beats was unaffected, although contraction kinetics were slower. The ryanodine receptor (RyR)2 Ca-sensitizing agent caffeine (200 µM), which increases the velocity of transverse Ca2+ release propagation in detubulated cardiomyocytes, rescued the depressed contractile force and the slower twitch kinetics of detubulated trabeculae, with negligible effects in controls. We conclude that partial loss of t-tubules leads to myocardial contractile abnormalities that can be rescued by enhancing and accelerating the propagation of Ca2+-induced Ca2+ release to orphan RyR2 clusters.
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Affiliation(s)
- Cecilia Ferrantini
- Center of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, ItalyCenter of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, Italy
| | - Raffaele Coppini
- Center of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, ItalyCenter of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, ItalyCenter of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, Italy
| | - Leonardo Sacconi
- Center of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, Italy National Institute of Optics, National Research Council, 50019 Sesto Fiorentino, Italy
| | - Benedetta Tosi
- Center of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, ItalyCenter of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, Italy
| | - Mei Luo Zhang
- Department of Cardiac Sciences of the Libin Institute at the Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Guo Liang Wang
- Department of Cardiac Sciences of the Libin Institute at the Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Ewout de Vries
- Department of Cardiac Sciences of the Libin Institute at the Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Ernst Hoppenbrouwers
- Department of Cardiac Sciences of the Libin Institute at the Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Francesco Pavone
- Center of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, ItalyCenter of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, Italy National Institute of Optics, National Research Council, 50019 Sesto Fiorentino, Italy
| | - Elisabetta Cerbai
- Center of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, ItalyCenter of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, ItalyCenter of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, Italy
| | - Chiara Tesi
- Center of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, ItalyCenter of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, Italy
| | - Corrado Poggesi
- Center of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, ItalyCenter of Molecular Medicine, Department of Experimental and Clinical Medicine, Division of Physiology, Department of NeuroFarBa, Division of Pharmacology, LENS, European Laboratory for Non-Linear Spectroscopy, and Department of Physics, University of Florence, 50121 Florence, Italy
| | - Henk E D J ter Keurs
- Department of Cardiac Sciences of the Libin Institute at the Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 1N4, Canada
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26
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Briston SJ, Dibb KM, Solaro RJ, Eisner DA, Trafford AW. Balanced changes in Ca buffering by SERCA and troponin contribute to Ca handling during β-adrenergic stimulation in cardiac myocytes. Cardiovasc Res 2014; 104:347-54. [PMID: 25183792 PMCID: PMC4240166 DOI: 10.1093/cvr/cvu201] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 07/24/2014] [Accepted: 08/25/2014] [Indexed: 01/01/2023] Open
Abstract
AIMS During activation of cardiac myocytes, less than 1% of cytosolic Ca is free; the rest is bound to buffers, largely SERCA, and troponin C. Signalling by phosphorylation, as occurs during β-adrenergic stimulation, changes the Ca-binding affinity of these proteins and may affect the systolic Ca transient. Our aim was to determine the effects of β-adrenergic stimulation on Ca buffering and to differentiate between the roles of SERCA and troponin. METHODS AND RESULTS Ca buffering was studied in cardiac myocytes from mice: wild-type (WT), phospholamban-knockout (PLN-KO), and mice expressing slow skeletal troponin I (ssTnI) that is not protein kinase A phosphorylatable. WT cells showed no change in Ca buffering in response to the β-adrenoceptor agonist isoproterenol (ISO). However, ISO decreased Ca buffering in PLN-KO myocytes, presumably unmasking the role of troponin. This effect was confirmed in WT cells in which SERCA activity was blocked with the application of thapsigargin. In contrast, ISO increased Ca buffering in ssTnI cells, presumably revealing the effect of an increase in Ca binding to SERCA. CONCLUSIONS These data indicate the individual roles played by SERCA and troponin in Ca buffering during β-adrenergic stimulation and that these two buffers effectively counterbalance each other so that Ca buffering remains constant during β-adrenergic stimulation, a factor which may be physiologically important. This study also emphasizes the importance of taking into account Ca buffering, particularly in disease states where Ca binding to myofilaments or SERCA may be altered.
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Affiliation(s)
- Sarah J Briston
- Unit of Cardiac Physiology, Manchester Academic Health Science Centre, Core Technology Facility, 46 Grafton St, Manchester M13 9NT, UK
| | - Katharine M Dibb
- Unit of Cardiac Physiology, Manchester Academic Health Science Centre, Core Technology Facility, 46 Grafton St, Manchester M13 9NT, UK
| | - R John Solaro
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, USA
| | - David A Eisner
- Unit of Cardiac Physiology, Manchester Academic Health Science Centre, Core Technology Facility, 46 Grafton St, Manchester M13 9NT, UK
| | - Andrew W Trafford
- Unit of Cardiac Physiology, Manchester Academic Health Science Centre, Core Technology Facility, 46 Grafton St, Manchester M13 9NT, UK
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27
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Greiser M, Kerfant BG, Williams GS, Voigt N, Harks E, Dibb KM, Giese A, Meszaros J, Verheule S, Ravens U, Allessie MA, Gammie JS, van der Velden J, Lederer WJ, Dobrev D, Schotten U. Tachycardia-induced silencing of subcellular Ca2+ signaling in atrial myocytes. J Clin Invest 2014; 124:4759-72. [PMID: 25329692 PMCID: PMC4347234 DOI: 10.1172/jci70102] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Accepted: 08/28/2014] [Indexed: 01/06/2023] Open
Abstract
Atrial fibrillation (AF) is characterized by sustained high atrial activation rates and arrhythmogenic cellular Ca2+ signaling instability; however, it is not clear how a high atrial rate and Ca2+ instability may be related. Here, we characterized subcellular Ca2+ signaling after 5 days of high atrial rates in a rabbit model. While some changes were similar to those in persistent AF, we identified a distinct pattern of stabilized subcellular Ca2+ signaling. Ca2+ sparks, arrhythmogenic Ca2+ waves, sarcoplasmic reticulum (SR) Ca2+ leak, and SR Ca2+ content were largely unaltered. Based on computational analysis, these findings were consistent with a higher Ca2+ leak due to PKA-dependent phosphorylation of SR Ca2+ channels (RyR2s), fewer RyR2s, and smaller RyR2 clusters in the SR. We determined that less Ca2+ release per [Ca2+]i transient, increased Ca2+ buffering strength, shortened action potentials, and reduced L-type Ca2+ current contribute to a stunning reduction of intracellular Na+ concentration following rapid atrial pacing. In both patients with AF and in our rabbit model, this silencing led to failed propagation of the [Ca2+]i signal to the myocyte center. We conclude that sustained high atrial rates alone silence Ca2+ signaling and do not produce Ca2+ signaling instability, consistent with an adaptive molecular and cellular response to atrial tachycardia.
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Affiliation(s)
- Maura Greiser
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Benoît-Gilles Kerfant
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - George S.B. Williams
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Niels Voigt
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Erik Harks
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Katharine M. Dibb
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Anne Giese
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Janos Meszaros
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Sander Verheule
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Ursula Ravens
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Maurits A. Allessie
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - James S. Gammie
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Jolanda van der Velden
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - W. Jonathan Lederer
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Dobromir Dobrev
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Ulrich Schotten
- Department of Physiology, Maastricht University, Maastricht, the Netherlands. Center for Biomedical Engineering and Technology, Laboratory of Molecular Cardiology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA. Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, Manchester, United Kingdom. Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany. Division of Cardiac Surgery, University of Maryland Medical Center, Baltimore, Maryland, USA. Laboratory for Physiology, VU University Medical Center, Amsterdam, the Netherlands
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Pereira L, Ruiz-Hurtado G, Rueda A, Mercadier JJ, Benitah JP, Gómez AM. Calcium signaling in diabetic cardiomyocytes. Cell Calcium 2014; 56:372-80. [PMID: 25205537 DOI: 10.1016/j.ceca.2014.08.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 07/24/2014] [Accepted: 08/07/2014] [Indexed: 12/18/2022]
Abstract
Diabetes mellitus is one of the most common medical conditions. It is associated to medical complications in numerous organs and tissues, of which the heart is one of the most important and most prevalent organs affected by this disease. In fact, cardiovascular complications are the most common cause of death among diabetic patients. At the end of the 19th century, the weakness of the heart in diabetes was noted as part of the general muscular weakness that exists in that disease. However, it was only in the eighties that diabetic cardiomyopathy was recognized, which comprises structural and functional abnormalities in the myocardium in diabetic patients even in the absence of coronary artery disease or hypertension. This disorder has been associated with both type 1 and type 2 diabetes, and is characterized by early-onset diastolic dysfunction and late-onset systolic dysfunction, in which alteration in Ca(2+) signaling is of major importance, since it controls not only contraction, but also excitability (and therefore is involved in rhythmic disorder), enzymatic activity, and gene transcription. Here we attempt to give a brief overview of Ca(2+) fluxes alteration reported on diabetes, and provide some new data on differential modulation of Ca(2+) handling alteration in males and females type 2 diabetic mice to promote further research. Due to space limitations, we apologize for those authors whose important work is not cited.
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Affiliation(s)
- Laetitia Pereira
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
| | - Gema Ruiz-Hurtado
- Unidad de Hipertensión, Instituto de Investigación i+12, Hospital Universitario 12 de Octubre, Madrid, Spain; Instituto Pluridisciplinar, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain
| | - Angélica Rueda
- Departamento de Bioquímica, Cinvestav-IPN, México, DF, Mexico
| | - Jean-Jacques Mercadier
- Inserm, UMR S769, Faculté de Pharmacie, Université Paris Sud, Labex LERMIT, DHU TORINO, Châtenay-Malabry, France; Université Paris Diderot - Sorbonne Paris Cité, Assistance Publique - Hôpitaux de Paris (AP-HP), France
| | - Jean-Pierre Benitah
- Inserm, UMR S769, Faculté de Pharmacie, Université Paris Sud, Labex LERMIT, DHU TORINO, Châtenay-Malabry, France
| | - Ana María Gómez
- Inserm, UMR S769, Faculté de Pharmacie, Université Paris Sud, Labex LERMIT, DHU TORINO, Châtenay-Malabry, France.
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29
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Greensmith DJ, Nirmalan M. The effects of tumor necrosis factor-alpha on systolic and diastolic function in rat ventricular myocytes. Physiol Rep 2013; 1:e00093. [PMID: 24303157 PMCID: PMC3831905 DOI: 10.1002/phy2.93] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Revised: 08/14/2013] [Accepted: 08/15/2013] [Indexed: 11/20/2022] Open
Abstract
The proinflammatory cytokine tumor necrosis factor-alpha (TNF-α) is associated with myocardial dysfunction observed in sepsis and septic shock. There are two fundamental components to this dysfunction. (1) systolic dysfunction; and (2) diastolic dysfunction. The aim of these experiments was to determine if any aspect of whole-heart dysfunction could be explained by alterations to global intracellular calcium ([Ca2+]i), contractility, and [Ca2+]i handling, by TNF-α, at the level of the individual rat myocyte. We took an integrative approach to simultaneously measure [Ca2+]i, contractility and sarcolemmal Ca fluxes using the Ca indicator fluo-3, video edge detection, and the perforated patch technique, respectively. All experiments were performed at 37°C. The effects of 50 ng/mL TNF-α were immediate and sustained. The amplitude of systolic [Ca2+]i was reduced by 31% and systolic shortening by 19%. Diastolic [Ca2+]i, myocyte length and relaxation rate were not affected, nor were the activity of the [Ca2+]i removal mechanisms. The reduction in systolic [Ca2+]i was associated with a 14% reduction in sarcoplasmic reticulum (SR) content and a 11% decrease in peak L-type Ca current (ICa-L). Ca influx was decreased by 7% associated with a more rapid ICa-L inactivation. These data show that at the level of the myocyte, TNF-α reduces SR Ca which underlies a reduction in systolic [Ca2+]i and thence shortening. Although these findings correlate well with aspects of systolic myocardial dysfunction seen in sepsis, in this model, acutely, TNF-α does not appear to provide a cellular mechanism for sepsis-related diastolic myocardial dysfunction.
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Affiliation(s)
- David J Greensmith
- Unit of Cardiac Physiology, Institute of Cardiovascular Science, Manchester Academic Health Science Centre, Core Technology Facility 46 Grafton Street, Manchester, M13 9NT, U.K
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30
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Shen X, Cannell MB, Ward ML. Effect of SR load and pH regulatory mechanisms on stretch-dependent Ca(2+) entry during the slow force response. J Mol Cell Cardiol 2013; 63:37-46. [PMID: 23880608 DOI: 10.1016/j.yjmcc.2013.07.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 06/11/2013] [Accepted: 07/11/2013] [Indexed: 12/22/2022]
Abstract
When cardiac muscle is stretched, there is an initial inotropic response that coincides with the stretch followed by a slower increase in twitch force that develops over several minutes (the "slow force response", or SFR). Unlike the initial response to stretch, the SFR is produced by an increase in Ca(2+) transient amplitude, but the cellular mechanisms that give rise to the increased transients are still debated. We have examined the relationship between the SFR, intracellular [Ca(2+)] and the inotropic state of right ventricular trabeculae from rat hearts at 37°C. The magnitude of the SFR varied with [Ca(2+)]o and stimulation frequency, so that the SFR was greatest for conditions associated with a reduced SR Ca(2+) content. The SFR was not blocked by the AT1 receptor blocker losartan, but was reduced by SN-6, an inhibitor of reverse mode Na(+)/Ca(2+)-exchange (NCX). The Na(+)/H(+)-exchange (NHE) inhibitor HOE642 had no effect in HCO3(-)-buffered solutions, but blocked 50% of the SFR in HCO3(-)-free solution. Inhibition of HCO3(-) transport by DIDS increased the SFR and made it sensitive to HOE642. The addition of cross-bridge cycle inhibitors (20mM BDM or 20μM blebbistatin) to the superfusate reduced the SFR as monitored by changes in Ca(2+). In HCO3(-)-free conditions, the SFR was associated with a slow acidification that was inhibited by BDM, and by stopping electrical stimulation. These results can be explained by stretch increasing metabolic demand and stimulating Na(+) entry via both NHE and the Na(+)/HCO3(-) transporters. This mechanism provides a novel link between inotropic state and stretch, as well as a way for the cell to compensate for increased acid load. The feedback mechanism between force and Ca(2+) transient amplitude that we describe is also limited by the degree of SR Ca(2+) load.
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Affiliation(s)
- Xin Shen
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand
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31
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Trafford AW, Clarke JD, Richards MA, Eisner DA, Dibb KM. Calcium signalling microdomains and the t-tubular system in atrial mycoytes: potential roles in cardiac disease and arrhythmias. Cardiovasc Res 2013; 98:192-203. [PMID: 23386275 DOI: 10.1093/cvr/cvt018] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The atria contribute 25% to ventricular stroke volume and are the site of the commonest cardiac arrhythmia, atrial fibrillation (AF). The initiation of contraction in the atria is similar to that in the ventricle involving a systolic rise of intracellular Ca(2+) concentration ([Ca(2+)](i)). There are, however, substantial inter-species differences in the way systolic Ca(2+) is regulated in atrial cells. These differences are a consequence of a well-developed and functionally relevant transverse (t)-tubule network in the atria of large mammals, including humans, and its virtual absence in smaller laboratory species such as the rat. Where T-tubules are absent, the systolic Ca(2+) transient results from a 'fire-diffuse-fire' sequential recruitment of Ca(2+) release sites from the cell edge to the centre and hence marked spatiotemporal heterogeneity of systolic Ca(2+). Conversely, the well-developed T-tubule network in large mammals ensures a near synchronous rise of [Ca(2+)](i). In addition to synchronizing the systolic rise of [Ca(2+)](i), the presence of T-tubules in the atria of large mammals, by virtue of localization of the L-type Ca(2+) channels and Na(+)-Ca(2+) exchanger antiporters on the T-tubules, may serve to, respectively, accelerate changes in the amplitude of the systolic Ca(2+) transient during inotropic manoeuvres and lower diastolic [Ca(2+)](i). On the other hand, the presence of T-tubules and hence wider cellular distribution of the Na(+)-Ca(2+) exchanger may predispose the atria of large mammals to Ca(2+)-dependent delayed afterdepolarizations (DADs); this may be a determining factor in why the atria of large mammals spontaneously develop and maintain AF.
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Affiliation(s)
- Andrew W Trafford
- Unit of Cardiac Physiology, Manchester Academic Health Science Centre, Institute of Cardiovascular Science, University of Manchester, 3.23 Core Technology Facility, 46 Grafton Street, Manchester M13 9PT, UK
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Dibb KM, Clarke JD, Eisner DA, Richards MA, Trafford AW. A functional role for transverse (t-) tubules in the atria. J Mol Cell Cardiol 2013; 58:84-91. [PMID: 23147188 DOI: 10.1016/j.yjmcc.2012.11.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 11/01/2012] [Indexed: 11/17/2022]
Abstract
Mammalian ventricular myocytes are characterised by the presence of an extensive transverse (t-) tubule network which is responsible for the synchronous rise of intracellular Ca(2+) concentration ([Ca(2+)]i) during systole. Disruption to the ventricular t-tubule network occurs in various cardiac pathologies and leads to heterogeneous changes of [Ca(2+)]i which are thought to contribute to the reduced contractility and increased susceptibility to arrhythmias of the diseased ventricle. Here we review evidence that, despite the long-held dogma of atrial cells having no or very few t-tubules, there is indeed an extensive and functionally significant t-tubule network present in atrial myocytes of large mammals including human. Moreover, the atrial t-tubule network is highly plastic in nature and undergoes far more extensive remodelling in heart disease than is the case in the ventricle with profound consequences for the resulting systolic Ca(2+) transient. In addition to considering the functional role of the t-tubule network in the healthy and diseased atria we also provide an overview of recent data concerning the putative factors controlling the formation of t-tubules and conclude by posing some important questions that currently remain to be addressed and whether or not targeting t-tubules offers potential novel therapeutic possibilities for heart disease.
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Affiliation(s)
- Katharine M Dibb
- Institute of Cardiovascular Sciences, Manchester Academic Health Science Centre, 3.08 Core Technology Facility, 46 Grafton Street, Manchester, M13 9PT, UK
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Stokke MK, Tovsrud N, Louch WE, Øyehaug L, Hougen K, Sejersted OM, Swift F, Sjaastad I. I(CaL) inhibition prevents arrhythmogenic Ca(2+) waves caused by abnormal Ca(2+) sensitivity of RyR or SR Ca(2+) accumulation. Cardiovasc Res 2013; 98:315-25. [PMID: 23417043 DOI: 10.1093/cvr/cvt037] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AIMS Arrhythmogenic Ca(2+) waves result from uncontrolled Ca(2+) release from the sarcoplasmic reticulum (SR) that occurs with increased Ca(2+) sensitivity of the ryanodine receptor (RyR) or excessive Ca(2+) accumulation during β-adrenergic stimulation. We hypothesized that inhibition of the L-type Ca(2+) current (I(CaL)) could prevent such Ca(2+) waves in both situations. METHODS AND RESULTS Ca(2+) waves were induced in mouse left ventricular cardiomyocytes by isoproterenol combined with caffeine to increase RyR Ca(2+) sensitivity. I(CaL) inhibition by verapamil (0.5 µM) reduced Ca(2+) wave probability in cardiomyocytes during electrostimulation, and during a 10 s rest period after ceasing stimulation. A separate type of Ca(2+) release events occurred during the decay phase of the Ca(2+) transient and was not prevented by verapamil. Verapamil decreased Ca(2+) spark frequency, but not in permeabilized cells, indicating that this was not due to direct effects on RyR. The antiarrhythmic effect of verapamil was due to reduced SR Ca(2+) content following I(CaL) inhibition. Computational modelling supported that the level of I(CaL) inhibition obtained experimentally was sufficient to reduce the SR Ca(2+) content. Ca(2+) wave prevention through reduced SR Ca(2+) content was also effective in heterozygous ankyrin B knockout mice with excessive SR Ca(2+) accumulation during β-adrenergic stimulation. CONCLUSION I(CaL) inhibition prevents diastolic Ca(2+) waves caused by increased Ca(2+) sensitivity of RyR or excessive SR Ca(2+) accumulation during β-adrenergic stimulation. In contrast, unstimulated early Ca(2+) release during the decay of the Ca(2+) transient is not prevented, and merits further study to understand the full antiarrhythmic potential of I(CaL) inhibition.
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Affiliation(s)
- Mathis K Stokke
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.
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34
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Calcium flux balance in the heart. J Mol Cell Cardiol 2012; 58:110-7. [PMID: 23220128 DOI: 10.1016/j.yjmcc.2012.11.017] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 11/08/2012] [Accepted: 11/22/2012] [Indexed: 11/22/2022]
Abstract
This article reviews the consequences of the need for the cardiac cell to be in calcium flux balance in the steady state. We first discuss how this steady state condition affects the control of resting [Ca(2+)]i. The next section considers how sarcoplasmic reticulum (SR) Ca content is controlled by a feedback mechanism whereby changes of SR Ca affect the amplitude of the Ca transient and this, in turn, controls sarcolemmal Ca fluxes. Subsequent sections review the effects of altering the activity of individual Ca handling proteins. Increasing the activity of the SR Ca-ATPase (SERCA) increases both the amplitude and rate constant of decay of the systolic Ca transient. The Ca flux balance condition requires that this must be achieved with no change of Ca efflux placing constraints on the magnitude of change of amplitude and decay rate. We analyze the quantitative dependence of Ca transient amplitude and SR content on SERCA activity. Increasing the open probability of the RyR during systole is predicted to have no steady state effect on the amplitude of the systolic Ca transient. We discuss the effects of changing the amplitude of the L-type Ca current in the context of both triggering Ca release from the SR and loading the cell with calcium. These manoeuvres are considered in the context of the effects of β-adrenergic stimulation. Finally, we review calcium flux balance in the presence of Ca waves.
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35
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Tencerová B, Zahradníková A, Gaburjáková J, Gaburjáková M. Luminal Ca2+ controls activation of the cardiac ryanodine receptor by ATP. ACTA ACUST UNITED AC 2012; 140:93-108. [PMID: 22851674 PMCID: PMC3409101 DOI: 10.1085/jgp.201110708] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The synergic effect of luminal Ca2+, cytosolic Ca2+, and cytosolic adenosine triphosphate (ATP) on activation of cardiac ryanodine receptor (RYR2) channels was examined in planar lipid bilayers. The dose–response of RYR2 gating activity to ATP was characterized at a diastolic cytosolic Ca2+ concentration of 100 nM over a range of luminal Ca2+ concentrations and, vice versa, at a diastolic luminal Ca2+ concentration of 1 mM over a range of cytosolic Ca2+ concentrations. Low level of luminal Ca2+ (1 mM) significantly increased the affinity of the RYR2 channel for ATP but without substantial activation of the channel. Higher levels of luminal Ca2+ (8–53 mM) markedly amplified the effects of ATP on the RYR2 activity by selectively increasing the maximal RYR2 activation by ATP, without affecting the affinity of the channel to ATP. Near-diastolic cytosolic Ca2+ levels (<500 nM) greatly amplified the effects of luminal Ca2+. Fractional inhibition by cytosolic Mg2+ was not affected by luminal Ca2+. In models, the effects of luminal and cytosolic Ca2+ could be explained by modulation of the allosteric effect of ATP on the RYR2 channel. Our results suggest that luminal Ca2+ ions potentiate the RYR2 gating activity in the presence of ATP predominantly by binding to a luminal site with an apparent affinity in the millimolar range, over which local luminal Ca2+ likely varies in cardiac myocytes.
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Affiliation(s)
- Barbora Tencerová
- Institute of Molecular Physiology and Genetics, Centre of Excellence for Cardiovascular Research, Slovak Academy of Sciences, 833 34 Bratislava, Slovak Republic
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Sankaranarayanan R, Venetucci L. Are the anti-arrhythmic effects of omega-3 fatty acids due to modulation of myocardial calcium handling? Front Physiol 2012; 3:373. [PMID: 23060805 PMCID: PMC3461578 DOI: 10.3389/fphys.2012.00373] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 08/30/2012] [Indexed: 11/15/2022] Open
Abstract
Both animal and clinical studies have demonstrated that omega-3 fatty acids have anti-arrhythmic properties. It has been suggested that these anti-arrhythmic effects are due to modulation of the activity of various myocardial calcium handling proteins such as ryanodine receptor (RyR), L-type calcium current and sodium/calcium exchanger. In this article, we review all the data available on the effects of omega-3 fatty acids on ventricular myocardial calcium handling. In addition we highlight some unanswered questions and discuss possible therapeutic benefits of omega-3 fatty acids.
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Affiliation(s)
- Rajiv Sankaranarayanan
- Cardiovascular Research Group, University of Manchester Manchester, UK ; Manchester Royal Infirmary, Manchester Heart Centre Manchester, UK
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37
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Ruiz-Hurtado G, Gómez-Hurtado N, Fernández-Velasco M, Calderón E, Smani T, Ordoñez A, Cachofeiro V, Boscá L, Díez J, Gómez AM, Delgado C. Cardiotrophin-1 induces sarcoplasmic reticulum Ca(2+) leak and arrhythmogenesis in adult rat ventricular myocytes. Cardiovasc Res 2012; 96:81-9. [PMID: 22787135 DOI: 10.1093/cvr/cvs234] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
AIMS Plasma levels of cardiotrophin-1 (CT-1) are elevated in several cardiovascular diseases and are correlated with the severity of the pathology. However, the mechanisms by which this inflammatory cytokine participates in the pathology of the heart are not completely understood. It is well established that alterations in intracellular calcium ([Ca(2+)](i)) handling are involved in cardiac dysfunction during heart failure, but it is unknown whether CT-1 modulates [Ca(2+)](i) handling in adult cardiomyocytes. Here we have analyzed for the first time the effects of CT-1 on [Ca(2+)](i) homeostasis in adult rat cardiomyocytes. METHODS AND RESULTS L-type calcium current (I(CaL)) was recorded using patch-clamp techniques, and [Ca(2+)](i) transients and Ca(2+) sparks were viewed by confocal microscopy. Treatment of cardiomyocytes with 1 nM CT-1 for 20-60 min induced a significant increase in I(CaL) density, [Ca(2+)](i) transients, and cell shortening compared with control cells. Our study reveals that CT-1 increases I(CaL) by a protein kinase A-dependent mechanism, and Ca(2+) sparks by a Ca(2+)/calmodulin kinase II-dependent and protein kinase A-independent mechanism. Cardiomyocytes treated with CT-1 exhibited a higher occurrence of arrhythmogenic behaviour, manifested as spontaneous Ca(2+) waves and aftercontractions. CONCLUSION Our findings provide evidence that cardiomyocytes treated with CT-1 present high spontaneous Ca(2+) release during diastole, a mechanism linked to arrhythmogenicity in the pathologic heart.
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Affiliation(s)
- Gema Ruiz-Hurtado
- Inserm, U769, IFR141, Labex Lermit, Université Paris 11, Chatenay-Malabry, France
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Ruiz-Hurtado G, Domínguez-Rodríguez A, Pereira L, Fernández-Velasco M, Cassan C, Lezoualc'h F, Benitah JP, Gómez AM. Sustained Epac activation induces calmodulin dependent positive inotropic effect in adult cardiomyocytes. J Mol Cell Cardiol 2012; 53:617-25. [PMID: 22910094 DOI: 10.1016/j.yjmcc.2012.08.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 07/15/2012] [Accepted: 08/07/2012] [Indexed: 01/30/2023]
Abstract
Cardiac actions of Epac (exchange protein directly activated by cAMP) are not completely elucidated. Epac induces cardiomyocytes hypertrophy, Ca(2+)/calmodulin protein kinase II (CaMKII) and excitation-transcription coupling in rat cardiac myocytes. Here we aimed to elucidate the pathway cascade involved in Epac sustained actions, as during the initiation of hypertrophy development, where β-adrenergic signaling is chronically stimulated. Rats were treated with the Epac selective activator 8-pCPT during 4 weeks and Ca(2+) signaling was analyzed in isolated cardiac myocytes by confocal microscopy. We observed a positive inotropic effect manifested by increased [Ca(2+)](i) transient amplitudes. In order to further analyze these actions, we incubated adult cardiomyocytes in the presence of 8-pCPT. The effects were similar to those obtained in-vivo and are blunted by Epac1 knock down. Interestingly, the increase in [Ca(2+)] transients was abolished by protein synthesis blockade or when the downstream effectors of calmodulin (CaMKII or calcineurin) were inhibited, pointing to calmodulin (CaM) as an important downstream protein in Epac sustained actions. In fact, CaM expression was enhanced by 8-pCPT treatment in isolated cells, as found by Western blots. Moreover, the 8-pCPT-induced, PKA-independent, positive inotropic effect was favored by enhanced extracellular Ca(2+) influx via L-type Ca(2+) channels. However, 8-pCPT also induced aberrant Ca(2+) release as Ca(2+) waves and extra [Ca(2+)](i) transients, suggesting proarrhythmic effect. These results provide new insights regarding Epac cardiac actions, suggesting an important role in the initial compensation of the heart to pathological stimuli during the initiation of cardiac hypertrophy, favoring contraction but also arrhythmia risk.
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Affiliation(s)
- Gema Ruiz-Hurtado
- Inserm, U769, Univ. Paris Sud, IFR141, Labex Lermit, Châtenay-Malabry, France
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Sobie EA, Lederer WJ. Dynamic local changes in sarcoplasmic reticulum calcium: physiological and pathophysiological roles. J Mol Cell Cardiol 2012; 52:304-11. [PMID: 21767546 PMCID: PMC3217160 DOI: 10.1016/j.yjmcc.2011.06.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 06/24/2011] [Accepted: 06/30/2011] [Indexed: 10/18/2022]
Abstract
Evidence obtained in recent years indicates that, in cardiac myocytes, release of Ca(2+) from the sarcoplasmic reticulum (SR) is regulated by changes in the concentration of Ca(2+) within the SR. In this review, we summarize recent advances in our understanding of this regulatory role, with a particular emphasis on dynamic and local changes in SR [Ca(2+)]. We focus on five important questions that are to some extent unresolved and controversial. These questions concern: (1) the importance of SR [Ca(2+)] depletion in the termination of Ca(2+) release; (2) the quantitative extent of depletion during local release events such as Ca(2+) sparks; (3) the influence of SR [Ca(2+)] refilling on release refractoriness and the propensity for pathological Ca(2+) release; (4) dynamic changes in SR [Ca(2+)] during propagating Ca(2+) waves; and (5) the speed of Ca(2+) diffusion within the SR. With each issue, we discuss data supporting alternative viewpoints, and we identify fundamental questions that are being actively investigated. We conclude with a discussion of experimental and computational advances that will help to resolve controversies. This article is part of a special issue entitled "Local Signaling in Myocytes."
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Affiliation(s)
- Eric A Sobie
- Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, NY, USA.
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Voigt N, Nattel S, Dobrev D. Proarrhythmic atrial calcium cycling in the diseased heart. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:1175-91. [PMID: 22453988 DOI: 10.1007/978-94-007-2888-2_53] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
During the last decades Ca(2+) has been found to play a crucial role in cardiac arrhythmias associated with heart failure and a number of congenital arrhythmia syndromes. Recent studies demonstrated that altered atrial Ca(2+) cycling may promote the initiation and maintenance of atrial fibrillation, the most common clinical arrhythmia that contributes significantly to population morbidity and mortality. This article describes physiological Ca(2+) cycling mechanisms in atrial cardiomyocytes and relates them to fundamental cellular proarrhythmic mechanisms involving Ca(2+) signaling abnormalities in the atrium during atrial fibrillation.
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Affiliation(s)
- Niels Voigt
- Division of Experimental Cardiology, Medical Faculty Mannheim, University of Heidelberg, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany.
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41
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Sjåland C, Lunde PK, Swift F, Munkvik M, Ericsson M, Lunde M, Boye S, Christensen G, Ellingsen Ø, Sejersted OM, Andersson KB. Slowed relaxation and preserved maximal force in soleus muscles of mice with targeted disruption of the Serca2 gene in skeletal muscle. J Physiol 2011; 589:6139-55. [PMID: 21946846 DOI: 10.1113/jphysiol.2011.211987] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Sarcoplasmic reticulum Ca(2+) ATPases (SERCAs) play a major role in muscle contractility by pumping Ca(2+) from the cytosol into the sarcoplasmic reticulum (SR) Ca(2+) store, allowing muscle relaxation and refilling of the SR with releasable Ca(2+). Decreased SERCA function has been shown to result in impaired muscle function and disease in human and animal models. In this study, we present a new mouse model with targeted disruption of the Serca2 gene in skeletal muscle (skKO) to investigate the functional consequences of reduced SERCA2 expression in skeletal muscle. SkKO mice were viable and basic muscle structure was intact. SERCA2 abundance was reduced in multiple muscles, and by as much as 95% in soleus muscle, having the highest content of slow-twitch fibres (40%). The Ca(2+) uptake rate was significantly reduced in SR vesicles in total homogenates. We did not find any compensatory increase in SERCA1 or SERCA3 abundance, or altered expression of several other Ca(2+)-handling proteins. Ultrastructural analysis revealed generally well-preserved muscle morphology, but a reduced volume of the longitudinal SR. In contracting soleus muscle in vitro preparations, skKO muscles were able to fully relax, but with a significantly slowed relaxation time compared to controls. Surprisingly, the maximal force and contraction rate were preserved, suggesting that skKO slow-twitch fibres may be able to contribute to the total muscle force despite loss of SERCA2 protein. Thus it is possible that SERCA-independent mechanisms can contribute to muscle contractile function.
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Affiliation(s)
- Cecilie Sjåland
- Institute for Experimental Medical Research, Oslo University Hospital, Ullevål, and University of Oslo, Oslo, Norway
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Briston SJ, Caldwell JL, Horn MA, Clarke JD, Richards MA, Greensmith DJ, Graham HK, Hall MCS, Eisner DA, Dibb KM, Trafford AW. Impaired β-adrenergic responsiveness accentuates dysfunctional excitation-contraction coupling in an ovine model of tachypacing-induced heart failure. J Physiol 2011; 589:1367-82. [PMID: 21242250 PMCID: PMC3082097 DOI: 10.1113/jphysiol.2010.203984] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Accepted: 01/10/2011] [Indexed: 01/08/2023] Open
Abstract
Reduced inotropic responsiveness is characteristic of heart failure (HF). This study determined the cellular Ca2+ homeostatic and molecular mechanisms causing the blunted β-adrenergic (β-AR) response in HF.We induced HF by tachypacing in sheep; intracellular Ca2+ concentration was measured in voltage-clamped ventricular myocytes. In HF, Ca2+ transient amplitude and peak L-type Ca2+ current (ICa-L) were reduced (to 70 ± 11% and 50 ± 3.7% of control, respectively, P <0.05) whereas sarcoplasmic reticulum (SR) Ca2+ content was unchanged. β-AR stimulation with isoprenaline (ISO) increased Ca2+ transient amplitude, ICa-L and SRCa2+ content in both cell types; however, the response of HF cells was markedly diminished (P <0.05).Western blotting revealed an increase in protein phosphatase levels (PP1, 158 ± 17% and PP2A, 188 ± 34% of control, P <0.05) and reduced phosphorylation of phospholamban in HF (Ser16, 30 ± 10% and Thr17, 41 ± 15% of control, P <0.05). The β-AR receptor kinase GRK-2 was also increased in HF (173 ± 38% of control, P <0.05). In HF, activation of adenylyl cyclase with forskolin rescued the Ca2+ transient, SR Ca2+ content and SR Ca2+ uptake rate to the same levels as control cells in ISO. In conclusion, the reduced responsiveness of the myocardium to β-AR agonists in HF probably arises as a consequence of impaired phosphorylation of key intracellular proteins responsible for regulating the SR Ca2+ content and therefore failure of the systolic Ca2+ transient to increase appropriately during β-AR stimulation.
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Affiliation(s)
- Sarah J Briston
- Unit of Cardiac Physiology, Manchester Academic Health Sciences Centre, University of Manchester, Manchester M13 9NT, UK
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43
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Stokke MK, Briston SJ, Jølle GF, Manzoor I, Louch WE, Øyehaug L, Christensen G, Eisner DA, Trafford AW, Sejersted OM, Sjaastad I. Ca2+ wave probability is determined by the balance between SERCA2-dependent Ca2+ reuptake and threshold SR Ca2+ content. Cardiovasc Res 2011; 90:503-12. [DOI: 10.1093/cvr/cvr013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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44
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Lee YS, Dun W, Boyden PA, Sobie EA. Complex and rate-dependent beat-to-beat variations in Ca2+ transients of canine Purkinje cells. J Mol Cell Cardiol 2011; 50:662-9. [PMID: 21232541 DOI: 10.1016/j.yjmcc.2010.12.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 12/09/2010] [Accepted: 12/31/2010] [Indexed: 11/29/2022]
Abstract
Purkinje fibers play an essential role in transmitting electrical impulses through the heart, but they may also serve as triggers for arrhythmias linked to defective intracellular calcium (Ca(2+)) regulation. Although prior studies have extensively characterized spontaneous Ca(2+) release in nondriven Purkinje cells, little attention has been paid to rate-dependent changes in Ca(2+) transients. Therefore we explored the behaviors of Ca(2+) transients at pacing rates ranging from 0.125 to 3 Hz in single canine Purkinje cells loaded with fluo3 and imaged with a confocal microscope. The experiments uncovered the following novel aspects of Ca(2+) regulation in Purkinje cells: 1) the cells exhibit a negative Ca(2+)-frequency relationship (at 2.5 Hz, Ca(2+) transient amplitude was 66 ± 6% smaller than that at 0.125 Hz); 2) sarcoplasmic reticulum (SR) Ca(2+) release occurs as a propagating wave at very low rates but is localized near the cell membrane at higher rates; 3) SR Ca(2+) load declines modestly (10 ± 5%) with an increase in pacing rate from 0.125 Hz to 2.5 Hz; 4) Ca(2+) transients show considerable beat-to-beat variability, with greater variability occurring at higher pacing rates. Analysis of beat-to-beat variability suggests that it can be accounted for by stochastic triggering of local Ca(2+) release events. Consistent with this hypothesis, an increase in triggering probability caused a decrease in the relative variability. These results offer new insight into how Ca(2+) release is normally regulated in Purkinje cells and provide clues regarding how disruptions in this regulation may lead to deleterious consequences such as arrhythmias.
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Affiliation(s)
- Young-Seon Lee
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, NY, USA
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45
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Thul R, Coombes S. Understanding cardiac alternans: a piecewise linear modeling framework. CHAOS (WOODBURY, N.Y.) 2010; 20:045102. [PMID: 21198114 DOI: 10.1063/1.3518362] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Cardiac alternans is a beat-to-beat alternation in action potential duration (APD) and intracellular calcium (Ca(2+)) cycling seen in cardiac myocytes under rapid pacing that is believed to be a precursor to fibrillation. The cellular mechanisms of these rhythms and the coupling between cellular Ca(2+) and voltage dynamics have been extensively studied leading to the development of a class of physiologically detailed models. These have been shown numerically to reproduce many of the features of myocyte response to pacing, including alternans, and have been analyzed mathematically using various approximation techniques that allow for the formulation of a low dimensional map to describe the evolution of APDs. The seminal work by Shiferaw and Karma is of particular interest in this regard [Shiferaw, Y. and Karma, A., "Turing instability mediated by voltage and calcium diffusion in paced cardiac cells," Proc. Natl. Acad. Sci. U.S.A. 103, 5670-5675 (2006)]. Here, we establish that the key dynamical behaviors of the Shiferaw-Karma model are arranged around a set of switches. These are shown to be the main elements for organizing the nonlinear behavior of the model. Exploiting this observation, we show that a piecewise linear caricature of the Shiferaw-Karma model, with a set of appropriate switching manifolds, can be constructed that preserves the physiological interpretation of the original model while being amenable to a systematic mathematical analysis. In illustration of this point, we formulate the dynamics of Ca(2+) cycling (in response to pacing) and compute the properties of periodic orbits in terms of a stroboscopic map that can be constructed without approximation. Using this, we show that alternans emerge via a period-doubling instability and track this bifurcation in terms of physiologically important parameters. We also show that when coupled to a spatially extended model for Ca(2+) transport, the model supports spatially varying patterns of alternans. We analyze the onset of this instability with a generalization of the master stability approach to accommodate the nonsmooth nature of our system.
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Affiliation(s)
- R Thul
- School of Mathematical Sciences, University of Nottingham, Nottingham, Nottinghamshire NG7 2RD, United Kingdom.
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46
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Liu N, Ruan Y, Denegri M, Bachetti T, Li Y, Colombi B, Napolitano C, Coetzee WA, Priori SG. Calmodulin kinase II inhibition prevents arrhythmias in RyR2(R4496C+/-) mice with catecholaminergic polymorphic ventricular tachycardia. J Mol Cell Cardiol 2010; 50:214-22. [PMID: 20937285 DOI: 10.1016/j.yjmcc.2010.10.001] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2010] [Revised: 09/28/2010] [Accepted: 10/04/2010] [Indexed: 11/18/2022]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease characterized by life-threatening arrhythmias elicited by adrenergic activation. CPVT is caused by mutations in the cardiac ryanodine receptor gene (RyR2). In vitro studies demonstrated that RyR2 mutations respond to sympathetic activation with an abnormal diastolic Ca(2+) leak from the sarcoplasmic reticulum; however the pathways that mediate the response to adrenergic stimulation have not been defined. In our RyR2(R4496C+/-) knock-in mouse model of CPVT we tested the hypothesis that inhibition of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) counteracts the effects of adrenergic stimulation resulting in an antiarrhythmic activity. CaMKII inhibition with KN-93 completely prevented catecholamine-induced sustained ventricular tachyarrhythmia in RyR2(R4496C+/-) mice, while the inactive congener KN-92 had no effect. In ventricular myocytes isolated from the hearts of RyR2(R4496C+/-) mice, CaMKII inhibition with an autocamtide-2 related inhibitory peptide or with KN-93 blunted triggered activity and transient inward currents induced by isoproterenol. Isoproterenol also enhanced the activity of the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA), increased spontaneous Ca(2+) release and spark frequency. CaMKII inhibition blunted each of these parameters without having an effect on the SR Ca(2+) content. Our data therefore indicate that CaMKII inhibition is an effective intervention to prevent arrhythmogenesis (both in vivo and in vitro) in the RyR2(R4496C+/-) knock-in mouse model of CPVT. Mechanistically, CAMKII inhibition acts on several elements of the EC coupling cascade, including an attenuation of SR Ca(2+) leak and blunting catecholamine-mediated SERCA activation. CaMKII inhibition may therefore represent a novel therapeutic target for patients with CPVT.
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Affiliation(s)
- Nian Liu
- Cardiovascular Genetics Program, The Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, USA
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Dobrev D, Voigt N, Wehrens XHT. The ryanodine receptor channel as a molecular motif in atrial fibrillation: pathophysiological and therapeutic implications. Cardiovasc Res 2010; 89:734-43. [PMID: 20943673 DOI: 10.1093/cvr/cvq324] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with substantial morbidity and mortality. It causes profound changes in sarcoplasmic reticulum (SR) Ca(2+) homeostasis, including ryanodine receptor channel dysfunction and diastolic SR Ca(2+) leak, which might contribute to both decreased contractile function and increased propensity to atrial arrhythmias. In this review, we will focus on the molecular basis of ryanodine receptor channel dysfunction and enhanced diastolic SR Ca(2+) leak in AF. The potential relevance of increased incidence of spontaneous SR Ca(2+) release for both AF induction and/or maintenance and the development of novel mechanism-based therapeutic approaches will be discussed.
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Affiliation(s)
- Dobromir Dobrev
- Division of Experimental Cardiology, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
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48
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Cooper PJ, Soeller C, Cannell MB. Excitation-contraction coupling in human heart failure examined by action potential clamp in rat cardiac myocytes. J Mol Cell Cardiol 2010; 49:911-7. [PMID: 20430038 DOI: 10.1016/j.yjmcc.2010.04.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2010] [Revised: 04/09/2010] [Accepted: 04/20/2010] [Indexed: 11/29/2022]
Abstract
The effect of the loss of the notch in the human action potential (AP) during heart failure was examined by voltage clamping rat ventricular myocytes with human APs and recording intracellular Ca(2+) with fluorescent dyes. Loss of the notch resulted in about a 50% reduction in the initial phase of the Ca(2+) transient due to reduced ability of the L-type Ca(2+) channel to trigger release. The failing human AP increased non-uniformity of cytosolic Ca(2+), with some cellular regions failing to elicit Ca(2+)-induced Ca(2+) release from the sarcoplasmic reticulum. In addition, there was an increase in the occurrence of late Ca(2+) sparks. Monte-Carlo simulations of spark activation by L-type Ca(2+) current supported the idea that the decreased synchrony of Ca(2+) spark production associated with the loss of the notch could be explained by reduced Ca(2+) influx from open Ca(2+) channels. We conclude that the notch of the AP is critical for efficient and synchronous EC coupling and that the loss of the notch will reduce the SR Ca(2+) release in heart failure, without changes in (for example) SR Ca(2+)-ATPase uptake.
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Affiliation(s)
- Patricia J Cooper
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
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49
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Stokke MK, Hougen K, Sjaastad I, Louch WE, Briston SJ, Enger UH, Andersson KB, Christensen G, Eisner DA, Sejersted OM, Trafford AW. Reduced SERCA2 abundance decreases the propensity for Ca2+ wave development in ventricular myocytes. Cardiovasc Res 2009; 86:63-71. [PMID: 20019150 DOI: 10.1093/cvr/cvp401] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS To describe the overall role of reduced sarcoplasmic reticulum Ca(2+) ATPase (SERCA2) for Ca(2+) wave development. METHODS AND RESULTS SERCA2 knockout [Serca2(flox/flox) Tg(alphaMHC-MerCreMer); KO] mice allowing inducible cardiomyocyte-specific disruption of the Serca2 gene in adult mice were compared with Serca(flox/flox) (FF) control mice. Six days after Serca2 gene disruption, SERCA2 protein abundance was reduced by 53% in KO compared with FF, whereas SERCA2 activity in field-stimulated, Fluo-5F AM-loaded cells was reduced by 42%. Baseline Ca(2+) content of the sarcoplasmic reticulum (SR) and Ca(2+) transient amplitude and rate constant of decay measured in whole-cell voltage-clamped cells were decreased in KO to 75, 81, and 69% of FF values. Ca(2+) waves developed in only 31% of KO cardiomyocytes compared with 57% of FF when external Ca(2+) was raised (10 mM), although SR Ca(2+) content needed for waves to develop was 79% of FF values. In addition, waves propagated at a 15% lower velocity in KO cells. Ventricular extrasystoles (VES) occurred with lower frequency in SERCA2 KO mice (KO: 3 +/- 1 VES/h vs. FF: 8 +/- 1 VES/h) (P < 0.05 for all results). CONCLUSION Reduced SERCA2 abundance resulted in decreased amplitude and decay rate of Ca(2+) transients, reduced SR Ca(2+) content, and decreased propensity for Ca(2+) wave development.
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Affiliation(s)
- Mathis K Stokke
- Institute for Experimental Medical Research, Oslo University Hospital, Ullevål, Kirkeveien 166, N-0407 Oslo, Norway.
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50
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Affiliation(s)
- Mark R. Fowler
- Faculty of Biomedical & Life Sciences, West Medical Building, University of Glasgow, United Kingdom
| | - Godfrey L. Smith
- Faculty of Biomedical & Life Sciences, West Medical Building, University of Glasgow, United Kingdom
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