1
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Banach K, Blatter LA. The 'Reverse FDUF' Mechanism of Atrial Excitation-Contraction Coupling Sustains Calcium Alternans-A Hypothesis. Biomolecules 2022; 13:biom13010007. [PMID: 36671392 PMCID: PMC9855423 DOI: 10.3390/biom13010007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 12/07/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
Cardiac calcium alternans is defined as beat-to-beat alternations of Ca transient (CaT) amplitude and has been linked to cardiac arrhythmia, including atrial fibrillation. We investigated the mechanism of atrial alternans in isolated rabbit atrial myocytes using high-resolution line scan confocal Ca imaging. Alternans was induced by increasing the pacing frequency until stable alternans was observed (1.6-2.5 Hz at room temperature). In atrial myocytes, action potential-induced Ca release is initiated in the cell periphery and subsequently propagates towards the cell center by Ca-induced Ca release (CICR) in a Ca wave-like fashion, driven by the newly identified 'fire-diffuse-uptake-fire' (FDUF) mechanism. The development of CaT alternans was accompanied by characteristic changes of the spatio-temporal organization of the CaT. During the later phase of the CaT, central [Ca]i exceeded peripheral [Ca]i that was indicative of a reversal of the subcellular [Ca]i gradient from centripetal to centrifugal. This gradient reversal resulted in a reversal of CICR propagation, causing a secondary Ca release during the large-amplitude alternans CaT, thereby prolonging the CaT, enhancing Ca-release refractoriness and reducing Ca release on the subsequent beat, thus enhancing the degree of CaT alternans. Here, we propose the 'reverse FDUF' mechanism as a novel cellular mechanism of atrial CaT alternans, which explains how the uncoupling of central from peripheral Ca release leads to the reversal of propagating CICR and to alternans.
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Affiliation(s)
- Kathrin Banach
- Department of Internal Medicine/Cardiology, Rush University Medical Center, Chicago, IL 60612, USA
| | - Lothar A. Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, IL 60612, USA
- Correspondence:
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2
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Sadredini M, Haugsten Hansen M, Frisk M, Louch WE, Lehnart SE, Sjaastad I, Stokke MK. CaMKII inhibition has dual effects on spontaneous Ca 2+ release and Ca 2+ alternans in ventricular cardiomyocytes from mice with a gain-of-function RyR2 mutation. Am J Physiol Heart Circ Physiol 2021; 321:H446-H460. [PMID: 34270372 DOI: 10.1152/ajpheart.00011.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In conditions with abnormally increased activity of the cardiac ryanodine receptor (RyR2), Ca2+/calmodulin-dependent protein kinase II (CaMKII) can contribute to a further destabilization of RyR2 that results in triggered arrhythmias. Therefore, inhibition of CaMKII in such conditions has been suggested as a strategy to suppress RyR2 activity and arrhythmias. However, suppression of RyR2 activity can lead to the development of arrhythmogenic Ca2+ alternans. The aim of this study was to test whether the suppression of RyR2 activity caused by inhibition of CaMKII increases propensity for Ca2+ alternans. We studied spontaneous Ca2+ release events and Ca2+ alternans in isolated left ventricular cardiomyocytes from mice carrying the gain-of-function RyR2 mutation RyR2-R2474S and from wild-type mice. CaMKII inhibition by KN-93 effectively decreased the frequency of spontaneous Ca2+ release events in RyR2-R2474S cardiomyocytes exposed to the β-adrenoceptor agonist isoprenaline. However, KN-93-treated RyR2-R2474S cardiomyocytes also showed increased propensity for Ca2+ alternans and increased Ca2+ alternans ratio compared with both an inactive analog of KN-93 and with vehicle-treated controls. This increased propensity for Ca2+ alternans was explained by prolongation of Ca2+ release refractoriness. Importantly, the increased propensity for Ca2+ alternans in KN-93-treated RyR2-R2474S cardiomyocytes did not surpass that of wild type. In conclusion, inhibition of CaMKII efficiently reduces spontaneous Ca2+ release but promotes Ca2+ alternans in RyR2-R2474S cardiomyocytes with a gain-of-function RyR2 mutation. The dominant effect in RyR2-R2474S is to reduce spontaneous Ca2+ release, which supports this intervention as a therapeutic strategy in this specific condition. However, future studies on CaMKII inhibition in conditions with increased propensity for Ca2+ alternans should include investigation of both phenomena.NEW & NOTEWORTHY Genetically increased RyR2 activity promotes arrhythmogenic Ca2+ release. Inhibition of CaMKII suppresses RyR2 activity and arrhythmogenic Ca2+ release. Suppression of RyR2 activity prolongs refractoriness of Ca2+ release. Prolonged refractoriness of Ca2+ release leads to arrhythmogenic Ca2+ alternans. CaMKII inhibition promotes Ca2+ alternans by prolonging Ca2+ release refractoriness.
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Affiliation(s)
- Mani Sadredini
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Marie Haugsten Hansen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Michael Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Stephan E Lehnart
- Department of Cardiology and Pulmonology, Heart Research Center Göttingen, University Medical Center Göttingen, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany.,DZHK (German Centre for Cardiovascular Research), Göttingen, Germany
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Mathis Korseberg Stokke
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway.,Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
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3
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MUW researcher of the month. Wien Klin Wochenschr 2021; 133:741-742. [PMID: 34241679 DOI: 10.1007/s00508-021-01919-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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4
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Kulkarni K, Walton RD, Armoundas AA, Tolkacheva EG. Clinical Potential of Beat-to-Beat Diastolic Interval Control in Preventing Cardiac Arrhythmias. J Am Heart Assoc 2021; 10:e020750. [PMID: 34027678 PMCID: PMC8483541 DOI: 10.1161/jaha.121.020750] [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: 11/16/2022]
Abstract
Life‐threatening ventricular arrhythmias and sudden cardiac death are often preceded by cardiac alternans, a beat‐to‐beat oscillation in the T‐wave morphology or duration. However, given the spatiotemporal and structural complexity of the human heart, designing algorithms to effectively suppress alternans and prevent fatal rhythms is challenging. Recently, an antiarrhythmic constant diastolic interval pacing protocol was proposed and shown to be effective in suppressing alternans in 0‐, 1‐, and 2‐dimensional in silico studies as well as in ex vivo whole heart experiments. Herein, we provide a systematic review of the electrophysiological conditions and mechanisms that enable constant diastolic interval pacing to be an effective antiarrhythmic pacing strategy. We also demonstrate a successful translation of the constant diastolic interval pacing protocol into an ECG‐based real‐time control system capable of modulating beat‐to‐beat cardiac electrical activity and preventing alternans. Furthermore, we present evidence of the clinical utility of real‐time alternans suppression in reducing arrhythmia susceptibility in vivo. We provide a comprehensive overview of this promising pacing technique, which can potentially be translated into a clinically viable device that could radically improve the quality of life of patients experiencing abnormal cardiac rhythms.
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Affiliation(s)
- Kanchan Kulkarni
- IHU-LIRYC, Electrophysiology and Heart Modeling InstituteFondation Bordeaux Université Pessac, Bordeaux France.,Centre de Recherche Cardio-Thoracique de Bordeaux University of Bordeaux France.,Centre de Recherche Cardio-Thoracique de Bordeaux INSERM Bordeaux France
| | - Richard D Walton
- IHU-LIRYC, Electrophysiology and Heart Modeling InstituteFondation Bordeaux Université Pessac, Bordeaux France.,Centre de Recherche Cardio-Thoracique de Bordeaux University of Bordeaux France.,Centre de Recherche Cardio-Thoracique de Bordeaux INSERM Bordeaux France
| | - Antonis A Armoundas
- Cardiovascular Research Center Massachusetts General Hospital Boston MA.,Institute for Medical Engineering and Science Massachusetts Institute of Technology Cambridge MA
| | - Elena G Tolkacheva
- Department of Biomedical Engineering University of Minnesota-Twin Cities Minneapolis MN
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5
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Szlovák J, Tomek J, Zhou X, Tóth N, Veress R, Horváth B, Szentandrássy N, Levijoki J, Papp JG, Herring N, Varró A, Eisner DA, Rodriguez B, Nagy N. Blockade of sodium‑calcium exchanger via ORM-10962 attenuates cardiac alternans. J Mol Cell Cardiol 2021; 153:111-122. [PMID: 33383036 PMCID: PMC8035081 DOI: 10.1016/j.yjmcc.2020.12.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Revised: 12/08/2020] [Accepted: 12/21/2020] [Indexed: 12/27/2022]
Abstract
Repolarization alternans, a periodic oscillation of long-short action potential duration, is an important source of arrhythmogenic substrate, although the mechanisms driving it are insufficiently understood. Despite its relevance as an arrhythmia precursor, there are no successful therapies able to target it specifically. We hypothesized that blockade of the sodium‑calcium exchanger (NCX) could inhibit alternans. The effects of the selective NCX blocker ORM-10962 were evaluated on action potentials measured with microelectrodes from canine papillary muscle preparations, and calcium transients measured using Fluo4-AM from isolated ventricular myocytes paced to evoke alternans. Computer simulations were used to obtain insight into the drug's mechanisms of action. ORM-10962 attenuated cardiac alternans, both in action potential duration and calcium transient amplitude. Three morphological types of alternans were observed, with differential response to ORM-10962 with regards to APD alternans attenuation. Analysis of APD restitution indicates that calcium oscillations underlie alternans formation. Furthermore, ORM-10962 did not markedly alter APD restitution, but increased post-repolarization refractoriness, which may be mediated by indirectly reduced L-type calcium current. Computer simulations reproduced alternans attenuation via ORM-10962, suggesting that it is acts by reducing sarcoplasmic reticulum release refractoriness. This results from the ORM-10962-induced sodium‑calcium exchanger block accompanied by an indirect reduction in L-type calcium current. Using a computer model of a heart failure cell, we furthermore demonstrate that the anti-alternans effect holds also for this disease, in which the risk of alternans is elevated. Targeting NCX may therefore be a useful anti-arrhythmic strategy to specifically prevent calcium driven alternans.
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Affiliation(s)
- Jozefina Szlovák
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Hungary
| | - Jakub Tomek
- Department of Physiology, Anatomy, and Genetics, University of Oxford, United Kingdom; Department of Computer Science, University of Oxford, United Kingdom.
| | - Xin Zhou
- Department of Computer Science, University of Oxford, United Kingdom
| | - Noémi Tóth
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Hungary
| | - Roland Veress
- Department of Physiology, Faculty of Medicine, University of Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Hungary; Faculty of Pharmacy, University of Debrecen, Hungary
| | | | | | - Julius Gy Papp
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - Neil Herring
- Department of Physiology, Anatomy, and Genetics, University of Oxford, United Kingdom
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - David A Eisner
- Unit of Cardiac Physiology, Manchester Academic Health Science Centre, University of Manchester, Core Technology Facility, Manchester, UK
| | - Blanca Rodriguez
- Department of Computer Science, University of Oxford, United Kingdom
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
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6
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Pandey V, Xie LH, Qu Z, Song Z. Mitochondrial depolarization promotes calcium alternans: Mechanistic insights from a ventricular myocyte model. PLoS Comput Biol 2021; 17:e1008624. [PMID: 33493168 PMCID: PMC7861552 DOI: 10.1371/journal.pcbi.1008624] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 02/04/2021] [Accepted: 12/10/2020] [Indexed: 01/08/2023] Open
Abstract
Mitochondria are vital organelles inside the cell and contribute to intracellular calcium (Ca2+) dynamics directly and indirectly via calcium exchange, ATP generation, and production of reactive oxygen species (ROS). Arrhythmogenic Ca2+ alternans in cardiac myocytes has been observed in experiments under abnormal mitochondrial depolarization. However, complex signaling pathways and Ca2+ cycling between mitochondria and cytosol make it difficult in experiments to reveal the underlying mechanisms of Ca2+ alternans under abnormal mitochondrial depolarization. In this study, we use a newly developed spatiotemporal ventricular myocyte computer model that integrates mitochondrial Ca2+ cycling and complex signaling pathways to investigate the mechanisms of Ca2+ alternans during mitochondrial depolarization. We find that elevation of ROS in response to mitochondrial depolarization plays a critical role in promoting Ca2+ alternans. Further examination reveals that the redox effect of ROS on ryanodine receptors and sarco/endoplasmic reticulum Ca2+-ATPase synergistically promote alternans. Upregulation of mitochondrial Ca2+ uniporter promotes Ca2+ alternans via Ca2+-dependent mitochondrial permeability transition pore opening. Due to their relatively slow kinetics, oxidized Ca2+/calmodulin-dependent protein kinase II activation and ATP do not play significant roles acutely in the genesis of Ca2+ alternans after mitochondrial depolarization, but their roles can be significant in the long term, mainly through their effects on sarco/endoplasmic reticulum Ca2+-ATPase activity. In conclusion, mitochondrial depolarization promotes Ca2+ alternans acutely via the redox effect of ROS and chronically by ATP reduction. It suppresses Ca2+ alternans chronically through oxidized Ca2+/calmodulin-dependent protein kinase II activation.
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Affiliation(s)
- Vikas Pandey
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
| | - Lai-Hua Xie
- Department of Cell Biology and Molecular Medicine, Rutgers, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
| | - Zhen Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Peng Cheng Laboratory, Shenzhen, Guangdong, China
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7
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Song Z, Xie LH, Weiss JN, Qu Z. A Spatiotemporal Ventricular Myocyte Model Incorporating Mitochondrial Calcium Cycling. Biophys J 2019; 117:2349-2360. [PMID: 31623883 PMCID: PMC6990377 DOI: 10.1016/j.bpj.2019.09.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 07/19/2019] [Accepted: 09/09/2019] [Indexed: 12/27/2022] Open
Abstract
Intracellular calcium (Ca2+) cycling dynamics in cardiac myocytes are spatiotemporally generated by stochastic events arising from a spatially distributed network of coupled Ca2+ release units that interact with an intertwined mitochondrial network. In this study, we developed a spatiotemporal ventricular myocyte model that integrates mitochondria-related Ca2+ cycling components into our previously developed ventricular myocyte model consisting of a three-dimensional Ca2+ release unit network. Mathematical formulations of mitochondrial membrane potential, mitochondrial Ca2+ cycling, mitochondrial permeability transition pore stochastic opening and closing, intracellular reactive oxygen species signaling, and oxidized Ca2+/calmodulin-dependent protein kinase II signaling were incorporated into the model. We then used the model to simulate the effects of mitochondrial depolarization on mitochondrial Ca2+ cycling, Ca2+ spark frequency, and Ca2+ amplitude, which agree well with experimental data. We also simulated the effects of the strength of mitochondrial Ca2+ uniporters and their spatial localization on intracellular Ca2+ cycling properties, which substantially affected diastolic and systolic Ca2+ levels in the mitochondria but exhibited only a small effect on sarcoplasmic reticulum and cytosolic Ca2+ levels under normal conditions. We show that mitochondrial depolarization can cause Ca2+ waves and Ca2+ alternans, which agrees with previous experimental observations. We propose that this new, to our knowledge, spatiotemporal ventricular myocyte model, incorporating properties of mitochondrial Ca2+ cycling and reactive-oxygen-species-dependent signaling, will be useful for investigating the effects of mitochondria on intracellular Ca2+ cycling and action potential dynamics in ventricular myocytes.
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Affiliation(s)
- Zhen Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
| | - Lai-Hua Xie
- Department of Cell Biology and Molecular Medicine, Rutgers New Jersey Medical School, Newark, New Jersey
| | - James N Weiss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
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8
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Exploring Impaired SERCA Pump-Caused Alternation Occurrence in Ischemia. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2019; 2019:8237071. [PMID: 31827590 PMCID: PMC6885202 DOI: 10.1155/2019/8237071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 10/08/2019] [Indexed: 12/24/2022]
Abstract
Impaired sarcoplasmic reticulum (SR) calcium transport ATPase (SERCA) gives rise to Ca2+ alternans and changes of the Ca2+release amount. These changes in Ca2+ release amount can reveal the mechanism underlying how the interaction between Ca2+ release and Ca2+ uptake induces Ca2+ alternans. This study of alternans by calculating the values of Ca2+ release properties with impaired SERCA has not been explored before. Here, we induced Ca2+ alternans by using an impaired SERCA pump under ischemic conditions. The results showed that the recruitment and refractoriness of the Ca2+ release increased as Ca2+ alternans occurred. This indicates triggering Ca waves. As the propagation of Ca waves is linked to the occurrence of Ca2+ alternans, the “threshold” for Ca waves reflects the key factor in Ca2+ alternans development, and it is still controversial nowadays. We proposed the ratio between the diastolic network SR (NSR) Ca content (Cansr) and the cytoplasmic Ca content (Cai) (Cansr/Cai) as the “threshold” of Ca waves and Ca2+ alternans. Diastolic Cansr, Cai, and their ratio were recorded at the onset of Ca2+ alternans. Compared with certain Cansr and Cai, the “threshold” of the ratio can better explain the comprehensive effects of the Ca2+ release and the Ca2+ uptake on Ca2+ alternans onset. In addition, these ratios are related with the function of SERCA pumps, which vary with different ischemic conditions. Thus, values of these ratios could be used to differentiate Ca2+ alternans from different ischemic cases. This agrees with some experimental results. Therefore, the certain value of diastolic Cansr/Cai can be the better “threshold” for Ca waves and Ca2+ alternans.
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9
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Kulkarni K, Merchant FM, Kassab MB, Sana F, Moazzami K, Sayadi O, Singh JP, Heist EK, Armoundas AA. Cardiac Alternans: Mechanisms and Clinical Utility in Arrhythmia Prevention. J Am Heart Assoc 2019; 8:e013750. [PMID: 31617437 PMCID: PMC6898836 DOI: 10.1161/jaha.119.013750] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Kanchan Kulkarni
- Cardiovascular Research CenterMassachusetts General HospitalBostonMA
| | | | - Mohamad B. Kassab
- Cardiovascular Research CenterMassachusetts General HospitalBostonMA
| | - Furrukh Sana
- Cardiovascular Research CenterMassachusetts General HospitalBostonMA
| | - Kasra Moazzami
- Cardiovascular Research CenterMassachusetts General HospitalBostonMA
| | - Omid Sayadi
- Cardiovascular Research CenterMassachusetts General HospitalBostonMA
| | - Jagmeet P. Singh
- Cardiology DivisionCardiac Arrhythmia ServiceMassachusetts General HospitalBostonMA
| | - E. Kevin Heist
- Cardiology DivisionCardiac Arrhythmia ServiceMassachusetts General HospitalBostonMA
| | - Antonis A. Armoundas
- Cardiovascular Research CenterMassachusetts General HospitalBostonMA
- Institute for Medical Engineering and ScienceMassachusetts Institute of TechnologyCambridgeMA
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10
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Hamilton S, Terentyev D. Proarrhythmic Remodeling of Calcium Homeostasis in Cardiac Disease; Implications for Diabetes and Obesity. Front Physiol 2018. [PMID: 30425651 DOI: 10.3389/fphys.2018.01517, 10.3389/fpls.2018.01517] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
A rapid growth in the incidence of diabetes and obesity has transpired to a major heath issue and economic burden in the postindustrial world, with more than 29 million patients affected in the United States alone. Cardiovascular defects have been established as the leading cause of mortality and morbidity of diabetic patients. Over the last decade, significant progress has been made in delineating mechanisms responsible for the diminished cardiac contractile function and enhanced propensity for malignant cardiac arrhythmias characteristic of diabetic disease. Rhythmic cardiac contractility relies upon the precise interplay between several cellular Ca2+ transport protein complexes including plasmalemmal L-type Ca2+ channels (LTCC), Na+-Ca2+ exchanger (NCX1), Sarco/endoplasmic Reticulum (SR) Ca2+-ATPase (SERCa2a) and ryanodine receptors (RyR2s), the SR Ca2+ release channels. Here we provide an overview of changes in Ca2+ homeostasis in diabetic ventricular myocytes and discuss the therapeutic potential of targeting Ca2+ handling proteins in the prevention of diabetes-associated cardiomyopathy and arrhythmogenesis.
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Affiliation(s)
- Shanna Hamilton
- Department of Medicine, The Warren Alpert Medical School of Brown University, Providence, RI, United States.,Cardiovascular Research Center, Rhode Island Hospital, Providence, RI, United States
| | - Dmitry Terentyev
- Department of Medicine, The Warren Alpert Medical School of Brown University, Providence, RI, United States.,Cardiovascular Research Center, Rhode Island Hospital, Providence, RI, United States
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11
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Hamilton S, Terentyev D. Proarrhythmic Remodeling of Calcium Homeostasis in Cardiac Disease; Implications for Diabetes and Obesity. Front Physiol 2018; 9:1517. [PMID: 30425651 PMCID: PMC6218530 DOI: 10.3389/fphys.2018.01517] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 10/09/2018] [Indexed: 12/28/2022] Open
Abstract
A rapid growth in the incidence of diabetes and obesity has transpired to a major heath issue and economic burden in the postindustrial world, with more than 29 million patients affected in the United States alone. Cardiovascular defects have been established as the leading cause of mortality and morbidity of diabetic patients. Over the last decade, significant progress has been made in delineating mechanisms responsible for the diminished cardiac contractile function and enhanced propensity for malignant cardiac arrhythmias characteristic of diabetic disease. Rhythmic cardiac contractility relies upon the precise interplay between several cellular Ca2+ transport protein complexes including plasmalemmal L-type Ca2+ channels (LTCC), Na+-Ca2+ exchanger (NCX1), Sarco/endoplasmic Reticulum (SR) Ca2+-ATPase (SERCa2a) and ryanodine receptors (RyR2s), the SR Ca2+ release channels. Here we provide an overview of changes in Ca2+ homeostasis in diabetic ventricular myocytes and discuss the therapeutic potential of targeting Ca2+ handling proteins in the prevention of diabetes-associated cardiomyopathy and arrhythmogenesis.
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Affiliation(s)
- Shanna Hamilton
- Department of Medicine, The Warren Alpert Medical School of Brown University, Providence, RI, United States.,Cardiovascular Research Center, Rhode Island Hospital, Providence, RI, United States
| | - Dmitry Terentyev
- Department of Medicine, The Warren Alpert Medical School of Brown University, Providence, RI, United States.,Cardiovascular Research Center, Rhode Island Hospital, Providence, RI, United States
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12
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Hamilton S, Terentyev D. Proarrhythmic Remodeling of Calcium Homeostasis in Cardiac Disease; Implications for Diabetes and Obesity. Front Physiol 2018; 9:1517. [PMID: 30425651 PMCID: PMC6218530 DOI: 10.3389/fphys.2018.01517,+10.3389/fpls.2018.01517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/06/2022] Open
Abstract
A rapid growth in the incidence of diabetes and obesity has transpired to a major heath issue and economic burden in the postindustrial world, with more than 29 million patients affected in the United States alone. Cardiovascular defects have been established as the leading cause of mortality and morbidity of diabetic patients. Over the last decade, significant progress has been made in delineating mechanisms responsible for the diminished cardiac contractile function and enhanced propensity for malignant cardiac arrhythmias characteristic of diabetic disease. Rhythmic cardiac contractility relies upon the precise interplay between several cellular Ca2+ transport protein complexes including plasmalemmal L-type Ca2+ channels (LTCC), Na+-Ca2+ exchanger (NCX1), Sarco/endoplasmic Reticulum (SR) Ca2+-ATPase (SERCa2a) and ryanodine receptors (RyR2s), the SR Ca2+ release channels. Here we provide an overview of changes in Ca2+ homeostasis in diabetic ventricular myocytes and discuss the therapeutic potential of targeting Ca2+ handling proteins in the prevention of diabetes-associated cardiomyopathy and arrhythmogenesis.
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Affiliation(s)
- Shanna Hamilton
- Department of Medicine, The Warren Alpert Medical School of Brown University, Providence, RI, United States,Cardiovascular Research Center, Rhode Island Hospital, Providence, RI, United States
| | - Dmitry Terentyev
- Department of Medicine, The Warren Alpert Medical School of Brown University, Providence, RI, United States,Cardiovascular Research Center, Rhode Island Hospital, Providence, RI, United States,*Correspondence: Dmitry Terentyev,
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13
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Tomek J, Tomková M, Zhou X, Bub G, Rodriguez B. Modulation of Cardiac Alternans by Altered Sarcoplasmic Reticulum Calcium Release: A Simulation Study. Front Physiol 2018; 9:1306. [PMID: 30283355 PMCID: PMC6156530 DOI: 10.3389/fphys.2018.01306] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 08/29/2018] [Indexed: 11/29/2022] Open
Abstract
Background: Cardiac alternans is an important precursor to arrhythmia, facilitating formation of conduction block, and re-entry. Diseased hearts were observed to be particularly vulnerable to alternans, mainly in heart failure or after myocardial infarction. Alternans is typically linked to oscillation of calcium cycling, particularly in the sarcoplasmic reticulum (SR). While the role of SR calcium reuptake in alternans is well established, the role of altered calcium release by ryanodine receptors has not yet been studied extensively. At the same time, there is strong evidence that calcium release is abnormal in heart failure and other heart diseases, suggesting that these changes might play a pro-alternans role. Aims: To demonstrate how changes to intracellular calcium release dynamics and magnitude affect alternans vulnerability. Methods: We used the state-of-the-art Heijman–Rudy and O’Hara–Rudy computer models of ventricular myocyte, given their detailed representation of calcium handling and their previous utility in alternans research. We modified the models to obtain precise control over SR release dynamics and magnitude, allowing for the evaluation of these properties in alternans formation and suppression. Results: Shorter time to peak SR release and shorter release duration decrease alternans vulnerability by improved refilling of releasable calcium within junctional SR; conversely, slow release promotes alternans. Modulating the total amount of calcium released, we show that sufficiently increased calcium release may surprisingly prevent alternans via a mechanism linked to the functional depletion of junctional SR during release. We show that this mechanism underlies differences between “eye-type” and “fork-type” alternans, which were observed in human in vivo and in silico. We also provide a detailed explanation of alternans formation in the given computer models, termed “sarcoplasmic reticulum calcium cycling refractoriness.” The mechanism relies on the steep SR load–release relationship, combined with relatively limited rate of junctional SR refilling. Conclusion: Both altered dynamics and magnitude of SR calcium release modulate alternans vulnerability. In particular, slow dynamics of SR release, such as those observed in heart failure, promote alternans. Therefore, acceleration of intracellular calcium release, e.g., via synchronization of calcium sparks, may inhibit alternans in failing hearts and reduce arrhythmia occurrence.
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Affiliation(s)
- Jakub Tomek
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Markéta Tomková
- Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Xin Zhou
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Gil Bub
- Department of Physiology, McGill University, Montreal, QC, Canada
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
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14
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Sun B, Wei J, Zhong X, Guo W, Yao J, Wang R, Vallmitjana A, Benitez R, Hove-Madsen L, Chen SRW. The cardiac ryanodine receptor, but not sarcoplasmic reticulum Ca 2+-ATPase, is a major determinant of Ca 2+ alternans in intact mouse hearts. J Biol Chem 2018; 293:13650-13661. [PMID: 29986885 DOI: 10.1074/jbc.ra118.003760] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Revised: 07/06/2018] [Indexed: 11/06/2022] Open
Abstract
Sarcoplasmic reticulum (SR) Ca2+ cycling is governed by the cardiac ryanodine receptor (RyR2) and SR Ca2+-ATPase (SERCA2a). Abnormal SR Ca2+ cycling is thought to be the primary cause of Ca2+ alternans that can elicit ventricular arrhythmias and sudden cardiac arrest. Although alterations in either RyR2 or SERCA2a function are expected to affect SR Ca2+ cycling, whether and to what extent altered RyR2 or SERCA2a function affects Ca2+ alternans is unclear. Here, we employed a gain-of-function RyR2 variant (R4496C) and the phospholamban-knockout (PLB-KO) mouse model to assess the effect of genetically enhanced RyR2 or SERCA2a function on Ca2+ alternans. Confocal Ca2+ imaging revealed that RyR2-R4496C shortened SR Ca2+ release refractoriness and markedly suppressed rapid pacing-induced Ca2+ alternans. Interestingly, despite enhancing RyR2 function, intact RyR2-R4496C hearts exhibited no detectable spontaneous SR Ca2+ release events during pacing. Unlike for RyR2, enhancing SERCA2a function by ablating PLB exerted a relatively minor effect on Ca2+ alternans in intact hearts expressing RyR2 WT or a loss-of-function RyR2 variant, E4872Q, that promotes Ca2+ alternans. Furthermore, partial SERCA2a inhibition with 3 μm 2,5-di-tert-butylhydroquinone (tBHQ) also had little impact on Ca2+ alternans, whereas strong SERCA2a inhibition with 10 μm tBHQ markedly reduced the amplitude of Ca2+ transients and suppressed Ca2+ alternans in intact hearts. Our results demonstrate that enhanced RyR2 function suppresses Ca2+ alternans in the absence of spontaneous Ca2+ release and that RyR2, but not SERCA2a, is a key determinant of Ca2+ alternans in intact working hearts, making RyR2 an important therapeutic target for cardiac alternans.
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Affiliation(s)
- Bo Sun
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Jinhong Wei
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Xiaowei Zhong
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Wenting Guo
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Jinjing Yao
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Ruiwu Wang
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Alexander Vallmitjana
- the Department of Automatic Control, Universitat Politècnica de Catalunya, Barcelona 08034, Spain, and
| | - Raul Benitez
- the Department of Automatic Control, Universitat Politècnica de Catalunya, Barcelona 08034, Spain, and
| | - Leif Hove-Madsen
- the Biomedical Research Institute of Barcelona (IIBB), CSIC, Sant Pau, Hospital de Sant Pau, Barcelona 08025, Spain
| | - S R Wayne Chen
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada,
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15
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Kanaporis G, Blatter LA. Alternans in atria: Mechanisms and clinical relevance. MEDICINA-LITHUANIA 2017; 53:139-149. [PMID: 28666575 DOI: 10.1016/j.medici.2017.04.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 04/25/2017] [Indexed: 12/29/2022]
Abstract
Atrial fibrillation is the most common sustained arrhythmia and its prevalence is rapidly rising with the aging of the population. Cardiac alternans, defined as cyclic beat-to-beat alternations in contraction force, action potential (AP) duration and intracellular Ca2+ release at constant stimulation rate, has been associated with the development of ventricular arrhythmias. Recent clinical data also provide strong evidence that alternans plays a central role in arrhythmogenesis in atria. The aim of this article is to review the mechanisms that are responsible for repolarization alternans and contribute to the transition from spatially concordant alternans to the more arrhythmogenic spatially discordant alternans in atria.
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Affiliation(s)
- Giedrius Kanaporis
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, USA.
| | - Lothar A Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, USA
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16
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Kurz FT, Aon MA, O'Rourke B, Armoundas AA. Functional Implications of Cardiac Mitochondria Clustering. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 982:1-24. [PMID: 28551779 PMCID: PMC7003720 DOI: 10.1007/978-3-319-55330-6_1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The spatio-temporal organization of mitochondria in cardiac myocytes facilitates myocyte-wide, cluster-bound, mitochondrial inner membrane potential oscillatory depolarizations, commonly triggered by metabolic or oxidative stressors. Local intermitochondrial coupling can be mediated by reactive oxygen species (ROS) that activate inner membrane pores to initiate a ROS-induced-ROS-release process that produces synchronized limit cycle oscillations of mitochondrial clusters within the whole mitochondrial network. The network's dynamic organization, structure and function can be assessed by quantifying dynamic local coupling constants and dynamic functional clustering coefficients, both providing information about the network's response to external stimuli. In addition to its special organization, the mitochondrial network of cardiac myocytes exhibits substrate-sensitive coupling constants and clustering coefficients. The myocyte's ability to form functional clusters of synchronously oscillating mitochondria is sensitive to conditions such as substrate availability (e.g., glucose, pyruvate, β-hydroxybutyrate), antioxidant status, respiratory chain activity, or history of oxidative challenge (e.g., ischemia-reperfusion). This underscores the relevance of quantitative methods to characterize the network's functional status as a way to assess the myocyte's resilience to pathological stressors.
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Affiliation(s)
- Felix T Kurz
- Department of Neuroradiology, Heidelberg University Hospital, Heidelberg, Germany.
- Massachusetts General Hospital, Cardiovascular Research Center, Harvard Medical School, Charlestown, MA, USA.
| | - Miguel A Aon
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Brian O'Rourke
- Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Antonis A Armoundas
- Department of Neuroradiology, Heidelberg University Hospital, Heidelberg, Germany.
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17
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Harada M, Melka J, Sobue Y, Nattel S. Metabolic Considerations in Atrial Fibrillation ― Mechanistic Insights and Therapeutic Opportunities ―. Circ J 2017; 81:1749-1757. [DOI: 10.1253/circj.cj-17-1058] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Jonathan Melka
- Department of Medicine and Research Center, Montreal Heart Institute
- Université de Montréal
- Department of Pharmacology and Therapeutics, McGill University
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen
| | - Yoshihiro Sobue
- Department of Medicine and Research Center, Montreal Heart Institute
- Université de Montréal
- Department of Pharmacology and Therapeutics, McGill University
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen
| | - Stanley Nattel
- Department of Medicine and Research Center, Montreal Heart Institute
- Université de Montréal
- Department of Pharmacology and Therapeutics, McGill University
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen
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