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Alvarez JAE, Jafri MS, Ullah A. Local Control Model of a Human Ventricular Myocyte: An Exploration of Frequency-Dependent Changes and Calcium Sparks. Biomolecules 2023; 13:1259. [PMID: 37627324 PMCID: PMC10452762 DOI: 10.3390/biom13081259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 08/07/2023] [Accepted: 08/15/2023] [Indexed: 08/27/2023] Open
Abstract
Calcium (Ca2+) sparks are the elementary events of excitation-contraction coupling, yet they are not explicitly represented in human ventricular myocyte models. A stochastic ventricular cardiomyocyte human model that adapts to intracellular Ca2+ ([Ca2+]i) dynamics, spark regulation, and frequency-dependent changes in the form of locally controlled Ca2+ release was developed. The 20,000 CRUs in this model are composed of 9 individual LCCs and 49 RyRs that function as couplons. The simulated action potential duration at 1 Hz steady-state pacing is ~0.280 s similar to human ventricular cell recordings. Rate-dependence experiments reveal that APD shortening mechanisms are largely contributed by the L-type calcium channel inactivation, RyR open fraction, and [Ca2+]myo concentrations. The dynamic slow-rapid-slow pacing protocol shows that RyR open probability during high pacing frequency (2.5 Hz) switches to an adapted "nonconducting" form of Ca2+-dependent transition state. The predicted force was also observed to be increased in high pacing, but the SR Ca2+ fractional release was lower due to the smaller difference between diastolic and systolic [Ca2+]SR. Restitution analysis through the S1S2 protocol and increased LCC Ca2+-dependent activation rate show that the duration of LCC opening helps modulate its effects on the APD restitution at different diastolic intervals. Ultimately, a longer duration of calcium sparks was observed in relation to the SR Ca2+ loading at high pacing rates. Overall, this study demonstrates the spontaneous Ca2+ release events and ion channel responses throughout various stimuli.
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Affiliation(s)
| | - M. Saleet Jafri
- School of Systems Biology, George Mason University, Fairfax, VA 22030, USA;
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 20201, USA
| | - Aman Ullah
- School of Systems Biology, George Mason University, Fairfax, VA 22030, USA;
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Palacios J, Paredes A, Cifuentes F, Catalán MA, García-Villalón AL, Borquez J, Simirgiotis MJ, Jones M, Foster A, Greensmith DJ. A hydroalcoholic extract of Senecio nutans SCh. Bip (Asteraceae); its effects on cardiac function and chemical characterization. JOURNAL OF ETHNOPHARMACOLOGY 2023; 300:115747. [PMID: 36152785 DOI: 10.1016/j.jep.2022.115747] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 09/07/2022] [Accepted: 09/18/2022] [Indexed: 06/16/2023]
Abstract
ETHNOPHARMACOLOGY RELEVANCE The plant Senecio nutans SCh. Bip. is used by Andean communities to treat altitude sickness. Recent evidence suggests it may produce vasodilation and negative cardiac inotropy, though the cellular mechanisms have not been elucidated. PURPOSE To determinate the mechanisms action of S. nutans on cardiovascular function in normotensive animals. METHODS The effect of the extract on rat blood pressure was measured with a transducer in the carotid artery and intraventricular pressure by a Langendorff system. The effects on sheep ventricular intracellular calcium handling and contractility were evaluated using photometry. Ultra-high-performance liquid-chromatography with diode array detection coupled with heated electrospray-ionization quadrupole-orbitrap mass spectrometric detection (UHPLC-DAD-ESI-Q-OT-MSn) was used for extract chemical characterization. RESULTS In normotensive rats, S. nutans (10 mg/kg) reduced mean arterial pressure (MAP) by 40% (p < 0.05), causing a dose-dependent coronary artery dilation and decreased left ventricular pressure. In isolated cells, S. nutans extract (1 μg/ml) rapidly reduced the [Ca2+]i transient amplitude and sarcomere shorting by 40 and 49% (p < 0.001), respectively. The amplitude of the caffeine evoked [Ca2+]i transient was reduced by 24% (p < 0.001), indicating reduced sarcoplasmic reticulum (SR) Ca2+ content. Sodium-calcium exchanger (NCX) activity increased by 17% (p < 0.05), while sarcoendoplasmic reticulum Ca2+-ATPase (SERCA) activity was decreased by 21% (p < 0.05). LC-MS results showed the presence of vitamin C, malic acid, and several antioxidant phenolic acids reported for the first time. Dihydroeuparin and 4-hydroxy-3-(3-methylbut-2-enyl) acetophenone were abundant in the extract. CONCLUSION In normotensive animals, S. nutans partially reduces MAP by decreasing heart rate and cardiac contractility. This negative inotropy is accounted for by decreased SERCA activity and increased NCX activity which reduces SR Ca2+ content. These results highlight the plant's potential as a source of novel cardio-active phytopharmaceuticals or nutraceuticals.
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Affiliation(s)
- Javier Palacios
- Laboratorio de Bioquímica Aplicada, Química y Farmacia, Facultad de Ciencias de la Salud, Universidad Arturo Prat, Iquique, 1110939, Chile.
| | - Adrián Paredes
- Departamento de Química, Facultad de Ciencias Básicas, Universidad de Antofagasta, Antofagasta, 1271155, Chile; Instituto Antofagasta (IA), Universidad de Antofagasta, Antofagasta, 1271155, Chile.
| | - Fredi Cifuentes
- Instituto Antofagasta (IA), Universidad de Antofagasta, Antofagasta, 1271155, Chile; Departamento de Biomédico, Facultad Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, 1271155, Chile.
| | - Marcelo A Catalán
- Instituto de Fisiología, Facultad de Medicina, Universidad Austral de Chile, Valdivia, 5090000, Chile.
| | | | - Jorge Borquez
- Departamento de Química, Facultad de Ciencias Básicas, Universidad de Antofagasta, Antofagasta, 1271155, Chile.
| | - Mario J Simirgiotis
- Center for Interdisciplinary Studies on the Nervous System (CISNe), Universidad Austral de Chile, Valdivia, 5090000, Chile.
| | - Matthew Jones
- Biomedical Research Centre, School of Science, Engineering and Environment, The University of Salford, Salford, United Kingdom.
| | - Amy Foster
- Biomedical Research Centre, School of Science, Engineering and Environment, The University of Salford, Salford, United Kingdom.
| | - David J Greensmith
- Biomedical Research Centre, School of Science, Engineering and Environment, The University of Salford, Salford, United Kingdom.
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Cely-Ortiz A, Felice JI, Díaz-Zegarra LA, Valverde CA, Federico M, Palomeque J, Wehrens XHT, Kranias EG, Aiello EA, Lascano EC, Negroni JA, Mattiazzi A. Determinants of Ca2+ release restitution: Insights from genetically altered animals and mathematical modeling. J Gen Physiol 2021; 152:152125. [PMID: 32986800 PMCID: PMC7594441 DOI: 10.1085/jgp.201912512] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 07/27/2020] [Accepted: 08/21/2020] [Indexed: 01/07/2023] Open
Abstract
Each heartbeat is followed by a refractory period. Recovery from refractoriness is known as Ca2+ release restitution (CRR), and its alterations are potential triggers of Ca2+ arrhythmias. Although the control of CRR has been associated with SR Ca2+ load and RYR2 Ca2+ sensitivity, the relative role of some of the determinants of CRR remains largely undefined. An intriguing point, difficult to dissect and previously neglected, is the possible independent effect of SR Ca2+ content versus the velocity of SR Ca2+ refilling on CRR. To assess these interrogations, we used isolated myocytes with phospholamban (PLN) ablation (PLNKO), knock-in mice with pseudoconstitutive CaMKII phosphorylation of RYR2 S2814 (S2814D), S2814D crossed with PLNKO mice (SDKO), and a previously validated human cardiac myocyte model. Restitution of cytosolic Ca2+ (Fura-2 AM) and L-type calcium current (ICaL; patch-clamp) was evaluated with a two-pulse (S1/S2) protocol. CRR and ICaL restitution increased as a function of the (S2-S1) coupling interval, following an exponential curve. When SR Ca2+ load was increased by increasing extracellular [Ca2+] from 2.0 to 4.0 mM, CRR and ICaL restitution were enhanced, suggesting that ICaL restitution may contribute to the faster CRR observed at 4.0 mM [Ca2+]. In contrast, ICaL restitution did not differ among the different mouse models. For a given SR Ca2+ load, CRR was accelerated in S2814D myocytes versus WT, but not in PLNKO and SDKO myocytes versus WT and S2814D, respectively. The model mimics all experimental data. Moreover, when the PLN ablation-induced decrease in RYR2 expression was corrected, the model revealed that CRR was accelerated in PLNKO and SDKO versus WT and S2814D myocytes, consistent with the enhanced velocity of refilling, SR [Ca2+] recovery, and CRR. We speculate that refilling rate might enhance CRR independently of SR Ca2+ load.
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Affiliation(s)
- Alejandra Cely-Ortiz
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Juan I Felice
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Leandro A Díaz-Zegarra
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Carlos A Valverde
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Marilén Federico
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Julieta Palomeque
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Xander H T Wehrens
- Departments of Molecular Physiology and Biophysics, Medicine (in Cardiology), Neuroscience, Pediatrics, Center for Space Medicine, Baylor College of Medicine, Cardiovascular Research Institute, Houston, TX
| | - Evangelia G Kranias
- Department of Pharmacology, University of Cincinnati College of Medicine, Cincinnati, OH
| | - Ernesto A Aiello
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Elena C Lascano
- Instituto de Medicina Traslacional, Trasplante y Bioingeniería, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Favaloro, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Jorge A Negroni
- Instituto de Medicina Traslacional, Trasplante y Bioingeniería, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Favaloro, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
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Caspofungin induces the release of Ca 2+ ions from internal stores by activating ryanodine receptor-dependent pathways in human tracheal epithelial cells. Sci Rep 2020; 10:11723. [PMID: 32678179 PMCID: PMC7367263 DOI: 10.1038/s41598-020-68626-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 06/25/2020] [Indexed: 11/09/2022] Open
Abstract
The antimycotic drug caspofungin is known to alter the cell function of cardiomyocytes and the cilia-bearing cells of the tracheal epithelium. The objective of this study was to investigate the homeostasis of intracellular Ca2+ concentration ([Ca2+]i) after exposure to caspofungin in isolated human tracheal epithelial cells. The [Ca2+]i was measured using the ratiometric fluoroprobe FURA-2 AM. We recorded two groups of epithelial cells with distinct responses to caspofungin exposure, which demonstrated either a rapid transient rise in [Ca2+]i or a sustained elevation of [Ca2+]i. Both patterns of Ca2+ kinetics were still observed when an influx of transmembraneous Ca2+ ions was pharmacologically inhibited. Furthermore, in extracellular buffer solutions without Ca2+ ions, caspofungin exposure still evoked this characteristic rise in [Ca2+]i. To shed light on the origin of the Ca2+ ions responsible for the elevation in [Ca2+]i we investigated the possible intracellular storage of Ca2+ ions. The depletion of mitochondrial Ca2+ stores using 25 µM 2,4-dinitrophenol (DNP) did not prevent the caspofungin-induced rise in [Ca2+]i, which was rapid and transient. However, the application of caffeine (30 mM) to discharge Ca2+ ions that were presumably stored in the endoplasmic reticulum (ER) prior to caspofungin exposure completely inhibited the caspofungin-induced changes in [Ca2+]i levels. When the ER-bound IP3 receptors were blocked by 2-APB (40 µM), we observed a delayed transient rise in [Ca2+]i as a response to the caspofungin. Inhibition of the ryanodine receptors (RyR) using 40 µM ryanodine completely prevented the caspofungin-induced elevation of [Ca2+]i. In summary, caspofungin has been shown to trigger an increase in [Ca2+]i independent from extracellular Ca2+ ions by liberating the Ca2+ ions stored in the ER, mainly via a RyR pathway.
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Puhl SL, Weeks KL, Güran A, Ranieri A, Boknik P, Kirchhefer U, Müller FU, Avkiran M. Role of type 2A phosphatase regulatory subunit B56α in regulating cardiac responses to β-adrenergic stimulation in vivo. Cardiovasc Res 2020; 115:519-529. [PMID: 30203051 PMCID: PMC6383118 DOI: 10.1093/cvr/cvy230] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 07/26/2018] [Accepted: 09/07/2018] [Indexed: 12/11/2022] Open
Abstract
AIMS B56α is a protein phosphatase 2A (PP2A) regulatory subunit that is highly expressed in the heart. We previously reported that cardiomyocyte B56α localizes to myofilaments under resting conditions and translocates to the cytosol in response to acute β-adrenergic receptor (β-AR) stimulation. Given the importance of reversible protein phosphorylation in modulating cardiac function during sympathetic stimulation, we hypothesized that loss of B56α in mice with targeted disruption of the gene encoding B56α (Ppp2r5a) would impact on cardiac responses to β-AR stimulation in vivo. METHODS AND RESULTS Cardiac phenotype of mice heterozygous (HET) or homozygous (HOM) for the disrupted Ppp2r5a allele and wild type (WT) littermates was characterized under basal conditions and following acute β-AR stimulation with dobutamine (DOB; 0.75 mg/kg i.p.) or sustained β-AR stimulation by 2-week infusion of isoproterenol (ISO; 30 mg/kg/day s.c.). Left ventricular (LV) wall thicknesses, chamber dimensions and function were assessed by echocardiography, and heart tissue collected for gravimetric, histological, and biochemical analyses. Western blot analysis revealed partial and complete loss of B56α protein in hearts from HET and HOM mice, respectively, and no changes in the expression of other PP2A regulatory, catalytic or scaffolding subunits. PP2A catalytic activity was reduced in hearts of both HET and HOM mice. There were no differences in the basal cardiac phenotype between genotypes. Acute DOB stimulation induced the expected inotropic response in WT and HET mice, which was attenuated in HOM mice. In contrast, DOB-induced increases in heart rate were unaffected by B56α deficiency. In WT mice, ISO infusion increased LV wall thicknesses, cardiomyocyte area and ventricular mass, without LV dilation, systolic dysfunction, collagen deposition or foetal gene expression. The hypertrophic response to ISO was blunted in mice deficient for B56α. CONCLUSION These findings identify B56α as a potential regulator of cardiac structure and function during β-AR stimulation.
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Affiliation(s)
- Sarah-Lena Puhl
- School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Research Excellence, St Thomas' Hospital, Westminster Bridge Road, London, UK.,Institute for Cardiovascular Prevention, Ludwig-Maximilians-University, Pettenkoferstrasse 9b, D-80336 Munich, Germany
| | - Kate L Weeks
- School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Research Excellence, St Thomas' Hospital, Westminster Bridge Road, London, UK.,Baker Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC, Australia
| | - Alican Güran
- School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Research Excellence, St Thomas' Hospital, Westminster Bridge Road, London, UK
| | - Antonella Ranieri
- School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Research Excellence, St Thomas' Hospital, Westminster Bridge Road, London, UK
| | - Peter Boknik
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Domagkstrasse 12, D-48149 Münster, Germany
| | - Uwe Kirchhefer
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Domagkstrasse 12, D-48149 Münster, Germany
| | - Frank U Müller
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Domagkstrasse 12, D-48149 Münster, Germany
| | - Metin Avkiran
- School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Research Excellence, St Thomas' Hospital, Westminster Bridge Road, London, UK
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Eisner DA, Caldwell JL, Trafford AW, Hutchings DC. The Control of Diastolic Calcium in the Heart: Basic Mechanisms and Functional Implications. Circ Res 2020; 126:395-412. [PMID: 31999537 PMCID: PMC7004450 DOI: 10.1161/circresaha.119.315891] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Normal cardiac function requires that intracellular Ca2+ concentration be reduced to low levels in diastole so that the ventricle can relax and refill with blood. Heart failure is often associated with impaired cardiac relaxation. Little, however, is known about how diastolic intracellular Ca2+ concentration is regulated. This article first discusses the reasons for this ignorance before reviewing the basic mechanisms that control diastolic intracellular Ca2+ concentration. It then considers how the control of systolic and diastolic intracellular Ca2+ concentration is intimately connected. Finally, it discusses the changes that occur in heart failure and how these may result in heart failure with preserved versus reduced ejection fraction.
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Affiliation(s)
- David A Eisner
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, University of Manchester, United Kingdom
| | - Jessica L Caldwell
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, University of Manchester, United Kingdom
| | - Andrew W Trafford
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, University of Manchester, United Kingdom
| | - David C Hutchings
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, University of Manchester, United Kingdom
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7
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Examining Cardiomyocyte Dysfunction Using Acute Chemical Induction of an Ageing Phenotype. Int J Mol Sci 2019; 21:ijms21010197. [PMID: 31892165 PMCID: PMC6982016 DOI: 10.3390/ijms21010197] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 12/21/2019] [Accepted: 12/23/2019] [Indexed: 11/18/2022] Open
Abstract
Much effort is focussed on understanding the structural and functional changes in the heart that underlie age-dependent deterioration of cardiac performance. Longitudinal studies, using aged animals, have pinpointed changes occurring to the contractile myocytes within the heart. However, whilst longitudinal studies are important, other experimental approaches are being advanced that can recapitulate the phenotypic changes seen during ageing. This study investigated the induction of an ageing cardiomyocyte phenotypic change by incubation of cells with hydroxyurea for several days ex vivo. Hydroxyurea incubation has been demonstrated to phenocopy age- and senescence-induced changes in neurons, but its utility for ageing studies with cardiac cells has not been examined. Incubation of neonatal rat ventricular myocytes with hydroxyurea for up to 7 days replicated specific aspects of cardiac ageing including reduced systolic calcium responses, increased alternans and a lesser ability of the cells to follow electrical pacing. Additional functional and structural changes were observed within the myocytes that pointed to ageing-like remodelling, including lipofuscin granule accumulation, reduced mitochondrial membrane potential, increased production of reactive oxygen species, and altered ultrastructure, such as mitochondria with disrupted cristae and disorganised myofibres. These data highlight the utility of alternative approaches for exploring cellular ageing whilst avoiding the costs and co-morbid factors that can affect longitudinal studies.
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Guth BD, Engwall M, Eldridge S, Foley CM, Guo L, Gintant G, Koerner J, Parish ST, Pierson JB, Ribeiro AJS, Zabka T, Chaudhary KW, Kanda Y, Berridge B. Considerations for an In Vitro, Cell-Based Testing Platform for Detection of Adverse Drug-Induced Inotropic Effects in Early Drug Development. Part 1: General Considerations for Development of Novel Testing Platforms. Front Pharmacol 2019; 10:884. [PMID: 31447679 PMCID: PMC6697071 DOI: 10.3389/fphar.2019.00884] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 07/15/2019] [Indexed: 01/10/2023] Open
Abstract
Drug-induced effects on cardiac contractility can be assessed through the measurement of the maximal rate of pressure increase in the left ventricle (LVdP/dtmax) in conscious animals, and such studies are often conducted at the late stage of preclinical drug development. Detection of such effects earlier in drug research using simpler, in vitro test systems would be a valuable addition to our strategies for identifying the best possible drug development candidates. Thus, testing platforms with reasonably high throughput, and affordable costs would be helpful for early screening purposes. There may also be utility for testing platforms that provide mechanistic information about how a given drug affects cardiac contractility. Finally, there could be in vitro testing platforms that could ultimately contribute to the regulatory safety package of a new drug. The characteristics needed for a successful cell or tissue-based testing platform for cardiac contractility will be dictated by its intended use. In this article, general considerations are presented with the intent of guiding the development of new testing platforms that will find utility in drug research and development. In the following article (part 2), specific aspects of using human-induced stem cell-derived cardiomyocytes for this purpose are addressed.
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Affiliation(s)
- Brian D Guth
- Department of Drug Discovery Sciences, Boehringer Ingelheim Pharma GmbH & Co KG, Biberach an der Riss, Germany.,PreClinical Drug Development Platform (PCDDP), North-West University, Potchefstroom, South Africa
| | - Michael Engwall
- Safety Pharmacology and Animal Research Center, Amgen Research, Thousand Oaks, CA, United States
| | - Sandy Eldridge
- Division of Cancer Treatment and Diagnosis, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States
| | - C Michael Foley
- Department of Integrative Pharmacology, Integrated Sciences and Technology, AbbVie, North Chicago, IL, United States
| | - Liang Guo
- Laboratory of Investigative Toxicology, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick, MD, United States
| | - Gary Gintant
- Department of Integrative Pharmacology, Integrated Sciences and Technology, AbbVie, North Chicago, IL, United States
| | - John Koerner
- Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, MD, United States
| | - Stanley T Parish
- Health and Environmental Sciences Institute, Washington, DC, United States
| | - Jennifer B Pierson
- Health and Environmental Sciences Institute, Washington, DC, United States
| | - Alexandre J S Ribeiro
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translation Sciences, Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, MD, United States
| | - Tanja Zabka
- Department of Safety Assessment, Genentech, South San Francisco, CA, United States
| | - Khuram W Chaudhary
- Global Safety Pharmacology, GlaxoSmithKline plc, Collegeville, PA, United States
| | - Yasunari Kanda
- Division of Pharmacology, National Institute of Health Sciences, Kanagawa, Japan
| | - Brian Berridge
- National Toxicology Program, National Institute of Environmental Health Sciences, Durham, NC, United States
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9
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Lawless M, Caldwell JL, Radcliffe EJ, Smith CER, Madders GWP, Hutchings DC, Woods LS, Church SJ, Unwin RD, Kirkwood GJ, Becker LK, Pearman CM, Taylor RF, Eisner DA, Dibb KM, Trafford AW. Phosphodiesterase 5 inhibition improves contractile function and restores transverse tubule loss and catecholamine responsiveness in heart failure. Sci Rep 2019; 9:6801. [PMID: 31043634 PMCID: PMC6494852 DOI: 10.1038/s41598-019-42592-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 03/26/2019] [Indexed: 12/13/2022] Open
Abstract
Heart failure (HF) is characterized by poor survival, a loss of catecholamine reserve and cellular structural remodeling in the form of disorganization and loss of the transverse tubule network. Indeed, survival rates for HF are worse than many common cancers and have not improved over time. Tadalafil is a clinically relevant drug that blocks phosphodiesterase 5 with high specificity and is used to treat erectile dysfunction. Using a sheep model of advanced HF, we show that tadalafil treatment improves contractile function, reverses transverse tubule loss, restores calcium transient amplitude and the heart's response to catecholamines. Accompanying these effects, tadalafil treatment normalized BNP mRNA and prevented development of subjective signs of HF. These effects were independent of changes in myocardial cGMP content and were associated with upregulation of both monomeric and dimerized forms of protein kinase G and of the cGMP hydrolyzing phosphodiesterases 2 and 3. We propose that the molecular switch for the loss of transverse tubules in HF and their restoration following tadalafil treatment involves the BAR domain protein Amphiphysin II (BIN1) and the restoration of catecholamine sensitivity is through reductions in G-protein receptor kinase 2, protein phosphatase 1 and protein phosphatase 2 A abundance following phosphodiesterase 5 inhibition.
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Affiliation(s)
- Michael Lawless
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Jessica L Caldwell
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Emma J Radcliffe
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Charlotte E R Smith
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - George W P Madders
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - David C Hutchings
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Lori S Woods
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Stephanie J Church
- Division of Cardiovascular Sciences, Centre for Advanced Discovery and Experimental Therapeutics, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Richard D Unwin
- Division of Cardiovascular Sciences, Centre for Advanced Discovery and Experimental Therapeutics, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Graeme J Kirkwood
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Lorenz K Becker
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Charles M Pearman
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Rebecca F Taylor
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - David A Eisner
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Katharine M Dibb
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom
| | - Andrew W Trafford
- Division of Cardiovascular Sciences, Unit of Cardiac Physiology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, United Kingdom.
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10
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Eisner DA. Ups and downs of calcium in the heart. J Physiol 2019; 596:19-30. [PMID: 29071725 DOI: 10.1113/jp275130] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 10/16/2017] [Indexed: 01/26/2023] Open
Abstract
Contraction and relaxation of the heart result from cyclical changes of intracellular Ca2+ concentration ([Ca2+ ]i ). The entry of Ca2+ into the cell via the L-type Ca2+ current leads to the release of more from the sarcoplasmic reticulum (SR). Compared to other regulatory mechanisms such as phosphorylation, Ca2+ signalling is very rapid. However, since Ca2+ cannot be destroyed, Ca2+ signalling can only be controlled by pumping across membranes. In the steady state, on each beat, the amount of Ca2+ released from the SR must equal that taken back and influx and efflux across the sarcolemma must be equal. Any imbalance in these fluxes will result in a change of SR Ca2+ content and this provides a mechanism for regulation of SR Ca2+ content. These flux balance considerations also explain why simply potentiating Ca2+ release from the SR has no maintained effect on the amplitude of the Ca2+ transient. A low diastolic [Ca2+ ]i is essential for cardiac relaxation, but the factors that control diastolic [Ca2+ ]i are poorly understood. Recent work suggests that flux balance is also important here. In particular, decreasing SR function decreases the amplitude of the systolic Ca2+ transient and the resulting decrease of Ca2+ efflux results in an increase of diastolic [Ca2+ ]i to maintain total efflux.
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Affiliation(s)
- David A Eisner
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, 3.18 Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, UK
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11
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Anesthetics, the Ryanodine Receptors, and the Heart. Anesthesiology 2017; 126:373-375. [PMID: 28079565 DOI: 10.1097/aln.0000000000001520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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12
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Mora MT, Ferrero JM, Romero L, Trenor B. Sensitivity analysis revealing the effect of modulating ionic mechanisms on calcium dynamics in simulated human heart failure. PLoS One 2017; 12:e0187739. [PMID: 29117223 PMCID: PMC5678731 DOI: 10.1371/journal.pone.0187739] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 10/25/2017] [Indexed: 12/27/2022] Open
Abstract
Abnormal intracellular Ca2+ handling is the major contributor to the depressed cardiac contractility observed in heart failure. The electrophysiological remodeling associated with this pathology alters both the action potential and the Ca2+ dynamics, leading to a defective excitation-contraction coupling that ends in mechanical dysfunction. The importance of maintaining a correct intracellular Ca2+ concentration requires a better understanding of its regulation by ionic mechanisms. To study the electrical activity and ionic homeostasis of failing myocytes, a modified version of the O’Hara et al. human action potential model was used, including electrophysiological remodeling. The impact of the main ionic transport mechanisms was analyzed using single-parameter sensitivity analyses, the first of which explored the modulation of electrophysiological characteristics related to Ca2+ exerted by the remodeled parameters. The second sensitivity analysis compared the potential consequences of modulating individual channel conductivities, as one of the main effects of potential drugs, on Ca2+ dynamic properties under both normal conditions and in heart failure. The first analysis revealed the important contribution of the sarcoplasmic reticulum Ca2+-ATPase (SERCA) dysfunction to the altered Ca2+ homeostasis, with the Na+/Ca2+ exchanger (NCX) and other Ca2+ cycling proteins also playing a significant role. Our results highlight the importance of improving the SR uptake function to increase Ca2+ content and restore Ca2+ homeostasis and contractility. The second sensitivity analysis highlights the different response of the failing myocyte versus the healthy myocyte to potential pharmacological actions on single channels. The result of modifying the conductances of the remodeled proteins such as SERCA and NCX in heart failure has less impact on Ca2+ modulation. These differences should be taken into account when designing drug therapies.
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Affiliation(s)
- Maria T. Mora
- Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, Valencia, Spain
| | - Jose M. Ferrero
- Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, Valencia, Spain
| | - Lucia Romero
- Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, Valencia, Spain
| | - Beatriz Trenor
- Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, Valencia, Spain
- * E-mail:
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13
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Colman MA, Pinali C, Trafford AW, Zhang H, Kitmitto A. A computational model of spatio-temporal cardiac intracellular calcium handling with realistic structure and spatial flux distribution from sarcoplasmic reticulum and t-tubule reconstructions. PLoS Comput Biol 2017; 13:e1005714. [PMID: 28859079 PMCID: PMC5597258 DOI: 10.1371/journal.pcbi.1005714] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 09/13/2017] [Accepted: 08/08/2017] [Indexed: 12/28/2022] Open
Abstract
Intracellular calcium cycling is a vital component of cardiac excitation-contraction coupling. The key structures responsible for controlling calcium dynamics are the cell membrane (comprising the surface sarcolemma and transverse-tubules), the intracellular calcium store (the sarcoplasmic reticulum), and the co-localisation of these two structures to form dyads within which calcium-induced-calcium-release occurs. The organisation of these structures tightly controls intracellular calcium dynamics. In this study, we present a computational model of intracellular calcium cycling in three-dimensions (3-D), which incorporates high resolution reconstructions of these key regulatory structures, attained through imaging of tissue taken from the sheep left ventricle using serial block face scanning electron microscopy. An approach was developed to model the sarcoplasmic reticulum structure at the whole-cell scale, by reducing its full 3-D structure to a 3-D network of one-dimensional strands. The model reproduces intracellular calcium dynamics during control pacing and reveals the high-resolution 3-D spatial structure of calcium gradients and intracellular fluxes in both the cytoplasm and sarcoplasmic reticulum. We also demonstrated the capability of the model to reproduce potentially pro-arrhythmic dynamics under perturbed conditions, pertaining to calcium-transient alternans and spontaneous release events. Comparison with idealised cell models emphasised the importance of structure in determining calcium gradients and controlling the spatial dynamics associated with calcium-transient alternans, wherein the probabilistic nature of dyad activation and recruitment was constrained. The model was further used to highlight the criticality in calcium spark propagation in relation to inter-dyad distances. The model presented provides a powerful tool for future investigation of structure-function relationships underlying physiological and pathophysiological intracellular calcium handling phenomena at the whole-cell. The approach allows for the first time direct integration of high-resolution images of 3-D intracellular structures with models of calcium cycling, presenting the possibility to directly assess the functional impact of structural remodelling at the cellular scale. The organisation of the membrane and sub-cellular structures of cells in the heart closely controls the coupling between its electrical and mechanical function. Computational models of the cellular calcium handling system, which is responsible for this electro-mechanical coupling, have been developed in recent years to study underlying structure-function relationships. Previous models have been largely idealised in structure; we present a new model which incorporates experimental data describing the high-resolution organisation of the primary structures involved in calcium dynamics. Significantly, the structure of the intracellular calcium store is modelled for the first time. The model is shown to reproduce calcium dynamics in control cells in both normal and abnormal conditions, demonstrating its suitability for future investigation of structure-function relationships. Thus, the model presented provides a powerful tool for the direct integration of experimentally acquired structural data in healthy and diseased cells and assessment of the role of structure in regulating normal and abnormal calcium dynamics.
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Affiliation(s)
- Michael A. Colman
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- School of Physics and Astronomy, Faculty of Engineering and Physical Sciences, University of Manchester, Manchester, United Kingdom
- * E-mail:
| | - Christian Pinali
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health Sciences, University of Manchester, Manchester, United Kingdom
| | - Andrew W. Trafford
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health Sciences, University of Manchester, Manchester, United Kingdom
| | - Henggui Zhang
- School of Physics and Astronomy, Faculty of Engineering and Physical Sciences, University of Manchester, Manchester, United Kingdom
| | - Ashraf Kitmitto
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health Sciences, University of Manchester, Manchester, United Kingdom
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14
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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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15
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Sankaranarayanan R, Kistamás K, Greensmith DJ, Venetucci LA, Eisner DA. Systolic [Ca 2+ ] i regulates diastolic levels in rat ventricular myocytes. J Physiol 2017; 595:5545-5555. [PMID: 28617952 PMCID: PMC5556151 DOI: 10.1113/jp274366] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 06/13/2017] [Indexed: 11/30/2022] Open
Abstract
KEY POINTS For the heart to function as a pump, intracellular calcium concentration ([Ca2+ ]i ) must increase during systole to activate contraction and then fall, during diastole, to allow the myofilaments to relax and the heart to refill with blood. The present study investigates the control of diastolic [Ca2+ ]i in rat ventricular myocytes. We show that diastolic [Ca2+ ]i is increased by manoeuvres that decrease sarcoplasmic reticulum function. This is accompanied by a decrease of systolic [Ca2+ ]i such that the time-averaged [Ca2+ ]i remains constant. We report that diastolic [Ca2+ ]i is controlled by the balance between Ca2+ entry and Ca2+ efflux during systole. The results of the present study identify a novel mechanism by which changes of the amplitude of the systolic Ca transient control diastolic [Ca2+ ]i . ABSTRACT The intracellular Ca concentration ([Ca2+ ]i ) must be sufficently low in diastole so that the ventricle is relaxed and can refill with blood. Interference with this will impair relaxation. The factors responsible for regulation of diastolic [Ca2+ ]i , in particular the relative roles of the sarcoplasmic reticulum (SR) and surface membrane, are unclear. We investigated the effects on diastolic [Ca2+ ]i that result from the changes of Ca cycling known to occur in heart failure. Experiments were performed using Fluo-3 in voltage clamped rat ventricular myocytes. Increasing stimulation frequency increased diastolic [Ca2+ ]i . This increase of [Ca2+ ]i was larger when SR function was impaired either by making the ryanodine receptor leaky (with caffeine or ryanodine) or by decreasing sarco/endoplasmic reticulum Ca-ATPase activity with thapsigargin. The increase of diastolic [Ca2+ ]i produced by interfering with the SR was accompanied by a decrease of the amplitude of the systolic Ca transient, such that there was no change of time-averaged [Ca2+ ]i . Time-averaged [Ca2+ ]i was increased by β-adrenergic stimulation with isoprenaline and increased in a saturating manner with increased stimulation frequency; average [Ca2+ ]i was a linear function of Ca entry per unit time. Diastolic and time-averaged [Ca2+ ]i were decreased by decreasing the L-type Ca current (with 50 μm cadmium chloride). We conclude that diastolic [Ca2+ ]i is controlled by the balance between Ca entry and efflux during systole. Furthermore, manoeuvres that decrease the amplitude of the Ca transient (without decreasing Ca influx) will therefore increase diastolic [Ca2+ ]i . This identifies a novel mechanism by which changes of the amplitude of the systolic Ca transient control diastolic [Ca2+ ]i .
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Affiliation(s)
- Rajiv Sankaranarayanan
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences CentreUniversity of ManchesterManchesterUK
| | - Kornél Kistamás
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences CentreUniversity of ManchesterManchesterUK
| | - David J. Greensmith
- Biomedical Research Centre, School of Environment and Life Sciences, Peel BuildingUniversity of SalfordSalfordUK
| | - Luigi A. Venetucci
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences CentreUniversity of ManchesterManchesterUK
| | - David A. Eisner
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences CentreUniversity of ManchesterManchesterUK
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16
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Gadeberg HC, Kong CHT, Bryant SM, James AF, Orchard CH. Sarcolemmal distribution of ICa and INCX and Ca 2+ autoregulation in mouse ventricular myocytes. Am J Physiol Heart Circ Physiol 2017; 313:H190-H199. [PMID: 28476922 PMCID: PMC5538864 DOI: 10.1152/ajpheart.00117.2017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 04/14/2017] [Accepted: 05/01/2017] [Indexed: 12/02/2022]
Abstract
This study shows that in contrast to the rat, mouse ventricular Na+/Ca2+ exchange current density is lower in the t-tubules than in the surface sarcolemma and Ca2+ current is predominantly located in the t-tubules. As a consequence, the t-tubules play a role in recovery (autoregulation) from reduced, but not increased, sarcoplasmic reticulum Ca2+ release. The balance of Ca2+ influx and efflux regulates the Ca2+ load of cardiac myocytes, a process known as autoregulation. Previous work has shown that Ca2+ influx, via L-type Ca2+ current (ICa), and efflux, via the Na+/Ca2+ exchanger (NCX), occur predominantly at t-tubules; however, the role of t-tubules in autoregulation is unknown. Therefore, we investigated the sarcolemmal distribution of ICa and NCX current (INCX), and autoregulation, in mouse ventricular myocytes using whole cell voltage-clamp and simultaneous Ca2+ measurements in intact and detubulated (DT) cells. In contrast to the rat, INCX was located predominantly at the surface membrane, and the hysteresis between INCX and Ca2+ observed in intact myocytes was preserved after detubulation. Immunostaining showed both NCX and ryanodine receptors (RyRs) at the t-tubules and surface membrane, consistent with colocalization of NCX and RyRs at both sites. Unlike INCX, ICa was found predominantly in the t-tubules. Recovery of the Ca2+ transient amplitude to steady state (autoregulation) after application of 200 µM or 10 mM caffeine was slower in DT cells than in intact cells. However, during application of 200 µM caffeine to increase sarcoplasmic reticulum (SR) Ca2+ release, DT and intact cells recovered at the same rate. It appears likely that this asymmetric response to changes in SR Ca2+ release is a consequence of the distribution of ICa, which is reduced in DT cells and is required to refill the SR after depletion, and NCX, which is little affected by detubulation, remaining available to remove Ca2+ when SR Ca2+ release is increased. NEW & NOTEWORTHY This study shows that in contrast to the rat, mouse ventricular Na+/Ca2+ exchange current density is lower in the t-tubules than in the surface sarcolemma and Ca2+ current is predominantly located in the t-tubules. As a consequence, the t-tubules play a role in recovery (autoregulation) from reduced, but not increased, sarcoplasmic reticulum Ca2+ release.
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Affiliation(s)
- Hanne C Gadeberg
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Cherrie H T Kong
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Simon M Bryant
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Andrew F James
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Clive H Orchard
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
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17
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Lascano E, Negroni J, Vila Petroff M, Mattiazzi A. Impact of RyR2 potentiation on myocardial function. Am J Physiol Heart Circ Physiol 2017; 312:H1105-H1109. [PMID: 28389603 DOI: 10.1152/ajpheart.00855.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 03/31/2017] [Accepted: 03/31/2017] [Indexed: 01/20/2023]
Abstract
This perspective attempts to shed light on an old and not yet solved controversy in cardiac physiology, i.e., the impact of increasing ryanodine receptor (RyR)2 open probability on myocardial function. Based on an already proven myocyte model, it was shown that increasing RyR2 open probability results in a purely short-lived increase in Ca2+ transient amplitude, and, therefore, it does not increase cardiac contractility. However, potentiation of RyR2 activity permanently enhances fractional Ca2+ release, shifting the intracellular Ca2+ transient versus sarcoplasmic reticulum (SR) Ca2+ content curve to a new state of higher efficiency. This would allow the heart to maintain a given contractility despite a decrease in SR Ca2+ content, to enhance contractility if SR Ca2+ content is simultaneously preserved or to successfully counteract the effects of a negative inotropic intervention.NEW & NOTEWORTHY Increasing ryanodine receptor (RyR)2 open probability does not increase cardiac contractility. However, RyR2 potentiation shifts the intracellular Ca2+ transient-sarcoplasmic reticulum (SR) Ca2+ content relationship toward an enhanced efficiency state, which may contribute to a positive inotropic effect, preserve contractility despite decreased SR Ca2+ content, or successfully counteract the effects of a negative inotropic action.
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Affiliation(s)
- E Lascano
- Instituto de Medicina Translacional, Transplante y Bioingeniería, Universidad Favaloro, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina; and
| | - J Negroni
- Instituto de Medicina Translacional, Transplante y Bioingeniería, Universidad Favaloro, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina; and
| | - M Vila Petroff
- Centro de Investigaciones Cardiovasculares, CCT-La Plata-CONICET, Facultad de Cs. Médicas, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
| | - A Mattiazzi
- Centro de Investigaciones Cardiovasculares, CCT-La Plata-CONICET, Facultad de Cs. Médicas, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
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18
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Jaimes R, Walton RD, Pasdois P, Bernus O, Efimov IR, Kay MW. A technical review of optical mapping of intracellular calcium within myocardial tissue. Am J Physiol Heart Circ Physiol 2016; 310:H1388-401. [PMID: 27016580 DOI: 10.1152/ajpheart.00665.2015] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 03/21/2016] [Indexed: 12/18/2022]
Abstract
Optical mapping of Ca(2+)-sensitive fluorescence probes has become an extremely useful approach and adopted by many cardiovascular research laboratories to study a spectrum of myocardial physiology and disease conditions. Optical mapping data are often displayed as detailed pseudocolor images, providing unique insight for interpreting mechanisms of ectopic activity, action potential and Ca(2+) transient alternans, tachycardia, and fibrillation. Ca(2+)-sensitive fluorescent probes and optical mapping systems continue to evolve in the ongoing effort to improve therapies that ease the growing worldwide burden of cardiovascular disease. In this technical review we provide an updated overview of conventional approaches for optical mapping of Cai (2+) within intact myocardium. In doing so, a brief history of Cai (2+) probes is provided, and nonratiometric and ratiometric Ca(2+) probes are discussed, including probes for imaging sarcoplasmic reticulum Ca(2+) and probes compatible with potentiometric dyes for dual optical mapping. Typical measurements derived from optical Cai (2+) signals are explained, and the analytics used to compute them are presented. Last, recent studies using Cai (2+) optical mapping to study arrhythmias, heart failure, and metabolic perturbations are summarized.
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Affiliation(s)
- Rafael Jaimes
- Department of Biomedical Engineering, The George Washington University. Washington, District of Columbia
| | - Richard D Walton
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; Institut National de la Santé et de la Recherche Médicale, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; and L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Philippe Pasdois
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; Institut National de la Santé et de la Recherche Médicale, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; and L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Olivier Bernus
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; Institut National de la Santé et de la Recherche Médicale, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; and L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Igor R Efimov
- Department of Biomedical Engineering, The George Washington University. Washington, District of Columbia; L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University. Washington, District of Columbia;
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19
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Torrente AG, Mesirca P, Neco P, Rizzetto R, Dubel S, Barrere C, Sinegger-Brauns M, Striessnig J, Richard S, Nargeot J, Gomez AM, Mangoni ME. L-type Cav1.3 channels regulate ryanodine receptor-dependent Ca2+ release during sino-atrial node pacemaker activity. Cardiovasc Res 2016; 109:451-61. [PMID: 26786159 DOI: 10.1093/cvr/cvw006] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 01/07/2016] [Indexed: 11/13/2022] Open
Abstract
AIMS Sino-atrial node (SAN) automaticity is an essential mechanism of heart rate generation that is still not completely understood. Recent studies highlighted the importance of intracellular Ca(2+) ([Ca(2+)]i) dynamics during SAN pacemaker activity. Nevertheless, the functional role of voltage-dependent L-type Ca(2+) channels in controlling SAN [Ca(2+)]i release is largely unexplored. Since Cav1.3 is the predominant L-type Ca(2+) channel isoform in SAN cells, we studied [Ca(2+)]i dynamics in isolated cells and ex vivo SAN preparations explanted from wild-type (WT) and Cav1.3 knockout (KO) mice (Cav1.3(-/-)). METHODS AND RESULTS We found that Cav1.3 deficiency strongly impaired [Ca(2+)]i dynamics, reducing the frequency of local [Ca(2+)]i release events and preventing their synchronization. This impairment inhibited the generation of Ca(2+) transients and delayed spontaneous activity. We also used action potentials recorded in WT SAN cells as voltage-clamp commands for Cav1.3(-/-) cells. Although these experiments showed abolished Ca(2+) entry through L-type Ca(2+) channels in the diastolic depolarization range of KO SAN cells, their sarcoplasmic reticulum Ca(2+) load remained normal. β-Adrenergic stimulation enhanced pacemaking of both genotypes, though, Cav1.3(-/-) SAN cells remained slower than WT. Conversely, we rescued pacemaker activity in Cav1.3(-/-) SAN cells and intact tissues through caffeine-mediated stimulation of Ca(2+)-induced Ca(2+) release. CONCLUSIONS Cav1.3 channels play a critical role in the regulation of [Ca(2+)]i dynamics, providing an unanticipated mechanism for triggering local [Ca(2+)]i releases and thereby controlling pacemaker activity. Our study also provides an additional pathophysiological mechanism for congenital SAN dysfunction and heart block linked to Cav1.3 loss of function in humans.
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Affiliation(s)
- Angelo Giovanni Torrente
- Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France
| | - Pietro Mesirca
- Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France
| | - Patricia Neco
- UMR-S 1180, Inserm, Univ. Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France Department of Pharmacology and Toxicology, Institute of Pharmacy
| | - Riccardo Rizzetto
- Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France
| | - Stefan Dubel
- Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France
| | - Christian Barrere
- Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France
| | - Martina Sinegger-Brauns
- Department of Pharmacology and Toxicology, Institute of Pharmacy Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Joerg Striessnig
- Department of Pharmacology and Toxicology, Institute of Pharmacy Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Sylvain Richard
- INSERM, U1046, Montpellier, France CNRS UMR 9214, PhyMedExp, University of Montpellier, France
| | - Joël Nargeot
- Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France
| | - Ana Maria Gomez
- UMR-S 1180, Inserm, Univ. Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France Department of Pharmacology and Toxicology, Institute of Pharmacy
| | - Matteo Elia Mangoni
- Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, 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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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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22
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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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