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Shen J, Fu H, Ding Y, Yuan Z, Xiang Z, Ding M, Huang M, Peng Y, Li T, Zha K, Ye Q. The role of iron overload and ferroptosis in arrhythmia pathogenesis. IJC HEART & VASCULATURE 2024; 52:101414. [PMID: 38694269 PMCID: PMC11060960 DOI: 10.1016/j.ijcha.2024.101414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Revised: 04/20/2024] [Accepted: 04/23/2024] [Indexed: 05/04/2024]
Abstract
Ferroptosis is a newly discovered form of programmed cell death triggered by intracellular iron overload, which leads to the accumulation of lipid peroxides in various cells. It has been implicated in the pathogenesis and progression of various diseases, including tumors, neurological disorders, and cardiovascular diseases. The intricate mechanism underlying ferroptosis involves an imbalance between the oxidation and antioxidant systems, disturbances in iron metabolism, membrane lipid peroxidation, and dysregulation of amino acid metabolism. We highlight the key molecular mechanisms governing iron overload and ferroptosis, and discuss potential molecular pathways linking ferroptosis with arrhythmias.
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Affiliation(s)
- Jingsong Shen
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Hengsong Fu
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Yanling Ding
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Ziyang Yuan
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Zeming Xiang
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Miao Ding
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Min Huang
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Yongquan Peng
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Tao Li
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
- Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou 646000, China
| | - Kelan Zha
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Qiang Ye
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
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Samuel TJ, Lai S, Schär M, Wu KC, Steinberg AM, Wei AC, Anderson M, Tomaselli GF, Gerstenblith G, Bottomley PA, Weiss RG. Myocardial ATP depletion detected noninvasively predicts sudden cardiac death risk in heart failure patients. JCI Insight 2022; 7:157557. [PMID: 35579938 PMCID: PMC9309047 DOI: 10.1172/jci.insight.157557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 05/06/2022] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Sudden cardiac death (SCD) remains a worldwide public health problem in need of better noninvasive predictive tools. Current guidelines for primary preventive SCD therapies, such as implantable cardioverter defibrillators (ICDs), are based on left ventricular ejection fraction (LVEF), but these guidelines are imprecise: fewer than 5% of ICDs deliver lifesaving therapy per year. Impaired cardiac metabolism and ATP depletion cause arrhythmias in experimental models, but to our knowledge a link between arrhythmias and cardiac energetic abnormalities in people has not been explored, nor has the potential for metabolically predicting clinical SCD risk. METHODS We prospectively measured myocardial energy metabolism noninvasively with phosphorus magnetic resonance spectroscopy in patients with no history of significant arrhythmias prior to scheduled ICD implantation for primary prevention in the setting of reduced LVEF (≤35%). RESULTS By 2 different analyses, low myocardial ATP significantly predicted the composite of subsequent appropriate ICD firings for life-threatening arrhythmias and cardiac death over approximately 10 years. Life-threatening arrhythmia risk was approximately 3-fold higher in patients with low ATP and independent of established risk factors, including LVEF. In patients with normal ATP, rates of appropriate ICD firings were several-fold lower than reported rates of ICD complications and inappropriate firings. CONCLUSION To the best of our knowledge, these are the first data linking in vivo myocardial ATP depletion and subsequent significant arrhythmic events in people, suggesting an energetic component to clinical life-threatening ventricular arrhythmogenesis. The findings support investigation of metabolic strategies that limit ATP loss to treat or prevent life-threatening cardiac arrhythmias and herald noninvasive metabolic imaging as a complementary SCD risk stratification tool. TRIAL REGISTRATION ClinicalTrials.gov NCT00181233. FUNDING This work was supported by the DW Reynolds Foundation, the NIH (grants HL61912, HL056882, HL103812, HL132181, HL140034), and Russell H. Morgan and Clarence Doodeman endowments at Johns Hopkins.
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Affiliation(s)
- T Jake Samuel
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, United States of America
| | - Shenghan Lai
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, United States of America
| | - Michael Schär
- Division of Magnetic Resonance Research, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, United States of America
| | - Katherine C Wu
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, United States of America
| | - Angela M Steinberg
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, United States of America
| | - An-Chi Wei
- Department of Electrical Engineering, National Taiwan University, Tapei, Taiwan
| | - Mark Anderson
- Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, United States of America
| | - Gordon F Tomaselli
- Division of Cardiology, Department of Medicine, The Albert Einstein College of Medicine, Bronx, United States of America
| | - Gary Gerstenblith
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, United States of America
| | - Paul A Bottomley
- Division of Magnetic Resonance Research, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, United States of America
| | - Robert G Weiss
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, United States of America
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Yurista SR, Silljé HHW, Rienstra M, de Boer RA, Westenbrink BD. Sodium-glucose co-transporter 2 inhibition as a mitochondrial therapy for atrial fibrillation in patients with diabetes? Cardiovasc Diabetol 2020; 19:5. [PMID: 31910841 PMCID: PMC6945755 DOI: 10.1186/s12933-019-0984-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 12/26/2019] [Indexed: 02/07/2023] Open
Abstract
While patients with type 2 diabetes mellitus (T2DM) are at increased risk to develop atrial fibrillation (AF), the mechanistic link between T2DM and AF-susceptibility remains unclear. Common co-morbidities of T2DM, particularly hypertension, may drive AF in the setting of T2DM. But direct mechanisms may also explain this relation, at least in part. In this regard, recent evidence suggests that mitochondrial dysfunction drives structural, electrical and contractile remodelling of atrial tissue in patients T2DM. Mitochondrial dysfunction may therefore be the mechanistic link between T2DM and AF and could also serve as a therapeutic target. An elegant series of experiments published in Cardiovascular Diabetology provide compelling new evidence to support this hypothesis. Using a model of high fat diet (HFD) and low-dose streptozotocin (STZ) injection, Shao et al. provide data that demonstrate a direct association between mitochondrial dysfunction and the susceptibility to develop AF. But the authors also demonstrated that the sodium-glucose co-transporter 2 inhibitors (SGLT2i) empagliflozin has the capacity to restore mitochondrial function, ameliorate electrical and structural remodelling and prevent AF. These findings provide a new horizon in which mitochondrial targeted therapies could serve as a new class of antiarrhythmic drugs.
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Affiliation(s)
- Salva R Yurista
- Department of Cardiology, University of Groningen, University Medical Center Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands
| | - Herman H W Silljé
- Department of Cardiology, University of Groningen, University Medical Center Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands
| | - Michiel Rienstra
- Department of Cardiology, University of Groningen, University Medical Center Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands
| | - Rudolf A de Boer
- Department of Cardiology, University of Groningen, University Medical Center Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands
| | - B Daan Westenbrink
- Department of Cardiology, University of Groningen, University Medical Center Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands.
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4
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Treinys R, Kanaporis G, Fischmeister R, Jurevičius J. Metabolic Inhibition Induces Transient Increase of L-type Ca 2+ Current in Human and Rat Cardiac Myocytes. Int J Mol Sci 2019; 20:ijms20061501. [PMID: 30917498 PMCID: PMC6471217 DOI: 10.3390/ijms20061501] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 03/15/2019] [Accepted: 03/23/2019] [Indexed: 01/17/2023] Open
Abstract
Metabolic inhibition is a common condition observed during ischemic heart disease and heart failure. It is usually accompanied by a reduction in L-type Ca2+ channel (LTCC) activity. In this study, however, we show that metabolic inhibition results in a biphasic effect on LTCC current (ICaL) in human and rat cardiac myocytes: an initial increase of ICaL is observed in the early phase of metabolic inhibition which is followed by the more classical and strong inhibition. We studied the mechanism of the initial increase of ICaL in cardiac myocytes during β-adrenergic stimulation by isoprenaline, a non-selective agonist of β-adrenergic receptors. The whole-cell patch⁻clamp technique was used to record the ICaL in single cardiac myocytes. The initial increase of ICaL was induced by a wide range of metabolic inhibitors (FCCP, 2,4-DNP, rotenone, antimycin A). In rat cardiomyocytes, the initial increase of ICaL was eliminated when the cells were pre-treated with thapsigargin leading to the depletion of Ca2+ from the sarcoplasmic reticulum (SR). Similar results were obtained when Ca2+ release from the SR was blocked with ryanodine. These data suggest that the increase of ICaL in the early phase of metabolic inhibition is due to a reduced calcium dependent inactivation (CDI) of LTCCs. This was further confirmed in human atrial myocytes where FCCP failed to induce the initial stimulation of ICaL when Ca2+ was replaced by Ba2+, eliminating CDI of LTCCs. We conclude that the initial increase in ICaL observed during the metabolic inhibition in human and rat cardiomyocytes is a consequence of an acute reduction of Ca2+ release from SR resulting in reduced CDI of LTCCs.
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Affiliation(s)
- Rimantas Treinys
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania.
| | - Giedrius Kanaporis
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania.
| | - Rodolphe Fischmeister
- INSERM UMR-S 1180, Univ Paris-Sud, Université Paris-Saclay, Châtenay-Malabry F-92296, France.
| | - Jonas Jurevičius
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania.
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5
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Wit AL. Basic Electrophysiologic Mechanisms of Sudden Cardiac Death Caused by Acute Myocardial Ischemia and Infarction. Card Electrophysiol Clin 2017; 9:525-536. [PMID: 29173399 DOI: 10.1016/j.ccep.2017.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Sudden cardiac death caused by acute ischemia results from electrophysiologic changes in myocardium deprived of its blood supply. These changes include a reduction in resting potential and phase 0 depolarization and an increase in intercellular resistivity that slow conduction, cause conduction block, and lead to reentrant excitation and ventricular fibrillation. Reperfusion of a coronary artery after a short period of occlusion leads to similar changes.
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Affiliation(s)
- Andrew L Wit
- Department of Pharmacology, College of Physicians and Surgeons of Columbia University, 630 West 168(th) Street, New York, NY 10032, USA.
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6
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Kanaporis G, Treinys R, Fischmeister R, Jurevičius J. Metabolic inhibition reduces cardiac L-type Ca2+ channel current due to acidification caused by ATP hydrolysis. PLoS One 2017; 12:e0184246. [PMID: 28859158 PMCID: PMC5578678 DOI: 10.1371/journal.pone.0184246] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Accepted: 08/21/2017] [Indexed: 01/14/2023] Open
Abstract
Metabolic stress evoked by myocardial ischemia leads to impairment of cardiac excitation and contractility. We studied the mechanisms by which metabolic inhibition affects the activity of L-type Ca2+ channels (LTCCs) in frog ventricular myocytes. Metabolic inhibition induced by the protonophore FCCP (as well as by 2,4- dinitrophenol, sodium azide or antimycin A) resulted in a dose-dependent reduction of LTCC current (ICa,L) which was more pronounced during β-adrenergic stimulation with isoprenaline. ICa,L was still reduced by metabolic inhibition even in the presence of 3 mM intracellular ATP, or when the cell was dialysed with cAMP or ATP-γ-S to induce irreversible thiophosphorylation of LTCCs, indicating that reduction in ICa,L is not due to ATP depletion and/or reduced phosphorylation of the channels. However, the effect of metabolic inhibition on ICa,L was strongly attenuated when the mitochondrial F1F0-ATP-synthase was blocked by oligomycin or when the cells were dialysed with the non-hydrolysable ATP analogue AMP-PCP. Moreover, increasing the intracellular pH buffering capacity or intracellular dialysis of the myocytes with an alkaline solution strongly attenuated the inhibitory effect of FCCP on ICa,L. Thus, our data demonstrate that metabolic inhibition leads to excessive ATP hydrolysis by the mitochondrial F1F0-ATP-synthase operating in the reverse mode and this results in intracellular acidosis causing the suppression of ICa,L. Limiting ATP break-down by F1F0-ATP-synthase and the consecutive development of intracellular acidosis might thus represent a potential therapeutic approach for maintaining a normal cardiac function during ischemia.
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Affiliation(s)
- Giedrius Kanaporis
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Rimantas Treinys
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Rodolphe Fischmeister
- INSERM UMR-S 1180, Univ Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France
| | - Jonas Jurevičius
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
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7
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Yang KC, Kyle JW, Makielski JC, Dudley SC. Mechanisms of sudden cardiac death: oxidants and metabolism. Circ Res 2015; 116:1937-55. [PMID: 26044249 PMCID: PMC4458707 DOI: 10.1161/circresaha.116.304691] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Accepted: 02/09/2015] [Indexed: 02/07/2023]
Abstract
Ventricular arrhythmia is the leading cause of sudden cardiac death (SCD). Deranged cardiac metabolism and abnormal redox state during cardiac diseases foment arrhythmogenic substrates through direct or indirect modulation of cardiac ion channel/transporter function. This review presents current evidence on the mechanisms linking metabolic derangement and excessive oxidative stress to ion channel/transporter dysfunction that predisposes to ventricular arrhythmias and SCD. Because conventional antiarrhythmic agents aiming at ion channels have proven challenging to use, targeting arrhythmogenic metabolic changes and redox imbalance may provide novel therapeutics to treat or prevent life-threatening arrhythmias and SCD.
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Affiliation(s)
- Kai-Chien Yang
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.)
| | - John W Kyle
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.)
| | - Jonathan C Makielski
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.).
| | - Samuel C Dudley
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.).
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8
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Miller L, Greensmith DJ, Sankaranarayanan R, O'Neill SC, Eisner DA. The effect of 2,5-di-(tert-butyl)-1,4-benzohydroquinone (TBQ) on intracellular Ca2+ handling in rat ventricular myocytes. Cell Calcium 2015; 58:208-14. [PMID: 26120055 PMCID: PMC4509554 DOI: 10.1016/j.ceca.2015.05.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 05/20/2015] [Accepted: 05/25/2015] [Indexed: 11/16/2022]
Abstract
The suitability of TBQ as a specific inhibitor of SERCA was investigated. TBQ decreased SERCA activity in a concentration dependent manner. TBQ inhibited the calcium current. TBQ activated an outward current consistent with an ATP-dependent potassium channel. TBQ cannot be used as a specific inhibitor of SERCA in rat cardiac myocytes.
2,5-Di-(tert-butyl)-1,4-benzohydroquinone (TBQ) is a reversible inhibitor of SERCA, potentially making it a useful tool to study the effects of SERCA inhibition in cardiac cells. However, it is unknown if TBQ also has effects on other components of ventricular Ca handling. The aim of these experiments was to characterise the effects of TBQ on Ca handling in rat ventricular myocytes and assess its suitability as a specific inhibitor of SERCA. This was achieved by voltage clamp via perforated patch and [Ca2+]i measurement using Fluo-3 AM. TBQ produced a fully reversible, concentration dependent decrease in the rate of systolic Ca decay. 10 μM TBQ decreased the amplitude of the systolic Ca transient by 48 ± 5% and the rate of decay by 54 ± 6%. SR Ca content was also reduced by 62 ± 4%. However, 10 μM TBQ also decreased the peak L-type Ca current by 23 ± 7%. At higher concentrations (100 μM), TBQ also activated an outward current with a current–voltage relationship consistent with a potassium current. This outward current was abolished by Glibenclamide (100 μM). These data show that TBQ can be used to reversibly inhibit SERCA. However, at concentrations that decrease SERCA activity, TBQ also decreases the L-type Ca current and (at higher concentrations) activates an outward current which appears to be an ATP dependent potassium current. We conclude that TBQ cannot be used as a specific inhibitor of SERCA in rat ventricular myocytes.
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Affiliation(s)
- L Miller
- Unit of Cardiac Physiology, Institute of Cardiovascular Sciences, 3.06 Core Technology Facility, 46 Grafton Street, Manchester M13 9NT, United Kingdom
| | - D J Greensmith
- Biomedical Research Centre, School of Environment and Life Sciences, University of Salford, G.35 Peel Building, Salford M5 4WT, United Kingdom.
| | - R Sankaranarayanan
- Unit of Cardiac Physiology, Institute of Cardiovascular Sciences, 3.06 Core Technology Facility, 46 Grafton Street, Manchester M13 9NT, United Kingdom
| | - S C O'Neill
- Unit of Cardiac Physiology, Institute of Cardiovascular Sciences, 3.06 Core Technology Facility, 46 Grafton Street, Manchester M13 9NT, United Kingdom
| | - D A Eisner
- Unit of Cardiac Physiology, Institute of Cardiovascular Sciences, 3.06 Core Technology Facility, 46 Grafton Street, Manchester M13 9NT, United Kingdom
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Effects of dantrolene on arrhythmogenicity in isolated regional ischemia-reperfusion rabbit hearts with or without pacing-induced heart failure. BIOMED RESEARCH INTERNATIONAL 2015; 2015:532820. [PMID: 25789321 PMCID: PMC4350948 DOI: 10.1155/2015/532820] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 12/29/2014] [Accepted: 01/05/2015] [Indexed: 11/17/2022]
Abstract
Dantrolene was reported to suppress ventricular fibrillation (VF) in failing hearts with acute myocardial infarction, but its antiarrhythmic efficacy in regional ischemia-reperfusion (IR) hearts remains debatable. Heart failure (HF) was induced by right ventricular pacing. The IR rabbit model was created by coronary artery ligation for 30 min, followed by reperfusion for 15 min in vivo in both HF and non-HF groups (n = 9 in each group). Simultaneous voltage and intracellular Ca2+ (Cai) optical mapping was then performed in isolated Langendorff-perfused hearts. Electrophysiological studies were conducted and VF inducibility was evaluated by dynamic pacing. Dantrolene (10 μM) was administered after baseline studies. The HF group had a higher VF inducibility than the control group. Dantrolene had both antiarrhythmic (prolonged action potential duration (APD) and effective refractory period) and proarrhythmic effects (slowed conduction velocity, steepened APD restitution slope, and enhanced arrhythmogenic alternans induction) but had no significant effects on ventricular premature beat (VPB) suppression and VF inducibility in both groups. A higher VF conversion rate in the non-HF group was likely due to greater APD prolonging effects in smaller hearts compared to the HF group. The lack of significant effects on VPB suppression by dantrolene suggests that triggered activity might not be the dominant mechanism responsible for VPB induction in the IR model.
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10
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Yang KC, Bonini MG, Dudley SC. Mitochondria and arrhythmias. Free Radic Biol Med 2014; 71:351-361. [PMID: 24713422 PMCID: PMC4096785 DOI: 10.1016/j.freeradbiomed.2014.03.033] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Revised: 03/21/2014] [Accepted: 03/24/2014] [Indexed: 12/31/2022]
Abstract
Mitochondria are essential to providing ATP, thereby satisfying the energy demand of the incessant electrical activity and contractile action of cardiac muscle. Emerging evidence indicates that mitochondrial dysfunction can adversely affect cardiac electrical functioning by impairing the intracellular ion homeostasis and membrane excitability through reduced ATP production and excessive reactive oxygen species (ROS) generation, resulting in increased propensity to cardiac arrhythmias. In this review, the molecular mechanisms linking mitochondrial dysfunction to cardiac arrhythmias are discussed with an emphasis on the impact of increased mitochondrial ROS on the cardiac ion channels and transporters that are critical to maintaining normal electromechanical functioning of the cardiomyocytes. The potential of using mitochondria-targeted antioxidants as a novel antiarrhythmia therapy is highlighted.
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Affiliation(s)
- Kai-Chien Yang
- Lifespan Cardiovascular Institute, Providence VA Medical Center, and Brown University, Providence, RI 02903, USA
| | - Marcelo G Bonini
- Department of Medicine/Cardiology, University of Illinois at Chicago, Chicago, IL 60612, USA; Department of Pathology, and University of Illinois at Chicago, Chicago, IL 60612, USA; Department of Pharmacology, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Samuel C Dudley
- Lifespan Cardiovascular Institute, Providence VA Medical Center, and Brown University, Providence, RI 02903, USA.
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11
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Guo A, Zhang C, Wei S, Chen B, Song LS. Emerging mechanisms of T-tubule remodelling in heart failure. Cardiovasc Res 2013; 98:204-15. [PMID: 23393229 DOI: 10.1093/cvr/cvt020] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Cardiac excitation-contraction coupling occurs primarily at the sites of transverse (T)-tubule/sarcoplasmic reticulum junctions. The orderly T-tubule network guarantees the instantaneous excitation and synchronous activation of nearly all Ca(2+) release sites throughout the large ventricular myocyte. Because of the critical roles played by T-tubules and the array of channels and transporters localized to the T-tubule membrane network, T-tubule architecture has recently become an area of considerable research interest in the cardiovascular field. This review will focus on the current knowledge regarding normal T-tubule structure and function in the heart, T-tubule remodelling in the transition from compensated hypertrophy to heart failure, and the impact of T-tubule remodelling on myocyte Ca(2+) handling function. In the last section, we discuss the molecular mechanisms underlying T-tubule remodelling in heart disease.
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Affiliation(s)
- Ang Guo
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
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12
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Jeong EM, Liu M, Sturdy M, Gao G, Varghese ST, Sovari AA, Dudley SC. Metabolic stress, reactive oxygen species, and arrhythmia. J Mol Cell Cardiol 2011; 52:454-63. [PMID: 21978629 DOI: 10.1016/j.yjmcc.2011.09.018] [Citation(s) in RCA: 162] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2011] [Revised: 08/20/2011] [Accepted: 09/19/2011] [Indexed: 02/07/2023]
Abstract
Cardiac arrhythmias can cause sudden cardiac death (SCD) and add to the current heart failure (HF) health crisis. Nevertheless, the pathological processes underlying arrhythmias are unclear. Arrhythmic conditions are associated with systemic and cardiac oxidative stress caused by reactive oxygen species (ROS). In excitable cardiac cells, ROS regulate both cellular metabolism and ion homeostasis. Increasing evidence suggests that elevated cellular ROS can cause alterations of the cardiac sodium channel (Na(v)1.5), abnormal Ca(2+) handling, changes of mitochondrial function, and gap junction remodeling, leading to arrhythmogenesis. This review summarizes our knowledge of the mechanisms by which ROS may cause arrhythmias and discusses potential therapeutic strategies to prevent arrhythmias by targeting ROS and its consequences. This article is part of a Special Issue entitled "Local Signaling in Myocytes".
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Affiliation(s)
- Euy-Myoung Jeong
- Section of Cardiology, University of Illinois at Chicago, Chicago, IL 60612, USA.
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Calderón-Sánchez EM, Ruiz-Hurtado G, Smani T, Delgado C, Benitah JP, Gómez AM, Ordóñez A. Cardioprotective action of urocortin in postconditioning involves recovery of intracellular calcium handling. Cell Calcium 2011; 50:84-90. [DOI: 10.1016/j.ceca.2011.05.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 05/03/2011] [Accepted: 05/10/2011] [Indexed: 10/18/2022]
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14
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Affiliation(s)
- Andreas S Barth
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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15
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Gusev K, Niggli E. Modulation of the local SR Ca2+ release by intracellular Mg2+ in cardiac myocytes. ACTA ACUST UNITED AC 2009; 132:721-30. [PMID: 19029377 PMCID: PMC2585859 DOI: 10.1085/jgp.200810119] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In cardiac muscle, Ca2+-induced Ca2+ release (CICR) from the sarcoplasmic reticulum (SR) defines the amplitude and time course of the Ca2+ transient. The global elevation of the intracellular Ca2+ concentration arises from the spatial and temporal summation of elementary Ca2+ release events, Ca2+ sparks. Ca2+ sparks represent the concerted opening of a group of ryanodine receptors (RYRs), which are under the control of several modulatory proteins and diffusible cytoplasmic factors (e.g., Ca2+, Mg2+, and ATP). Here, we examined by which mechanism the free intracellular Mg2+ ([Mg2+]free) affects various Ca2+ spark parameters in permeabilized mouse ventricular myocytes, such as spark frequency, duration, rise time, and full width, at half magnitude and half maximal duration. Varying the levels of free ATP and Mg2+ in specifically designed solutions allowed us to separate the inhibition of RYRs by Mg2+ from the possible activation by ATP and Mg2+-ATP via the adenine binding site of the channel. Changes in [Mg2+]free generally led to biphasic alterations of the Ca2+ spark frequency. For example, lowering [Mg2+]free resulted in an abrupt increase of spark frequency, which slowly recovered toward the initial level, presumably as a result of SR Ca2+ depletion. Fitting the Ca2+ spark inhibition by [Mg2+]free with a Hill equation revealed a Ki of 0.1 mM. In conclusion, our results support the notion that local Ca2+ release and Ca2+ sparks are modulated by Mg2+ in the intracellular environment. This seems to occur predominantly by hindering Ca2+-dependent activation of the RYRs through competitive Mg2+ occupancy of the high-affinity activation site of the channels. These findings help to characterize CICR in cardiac muscle under normal and pathological conditions, where the levels of Mg2+ and ATP can change.
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Affiliation(s)
- Konstantin Gusev
- Department of Physiology, University of Bern, 3012 Bern, Switzerland
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16
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Shirokova N, Niggli E. Studies of RyR function in situ. Methods 2008; 46:183-93. [PMID: 18848990 DOI: 10.1016/j.ymeth.2008.09.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 09/12/2008] [Indexed: 10/21/2022] Open
Abstract
The ryanodine receptors (RyRs) are intracellular Ca2+ release channels of the sarcoplasmic reticulum (SR) involved in many cellular responses, including muscle excitation-contraction coupling. Multiple biochemical and biophysical methods are available to study RyR functions. However, most of them are somewhat limited because they can only be used to examine channels which are purified from the SR and no longer in their natural environment. In this review we discuss optical methods for studying RyR functions in situ. We describe several techniques for the investigation of local (microscopic) intracellular Ca2+ signals (a.k.a Ca2+ sparks) by means of confocal microscopy and flash photolysis of caged compounds. We discuss how these studies can and will continue to contribute to our understanding of RyR function in physiological and pathological conditions.
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Affiliation(s)
- Natalia Shirokova
- Department of Pharmacology & Physiology, UMDNJ-New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07103, USA.
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17
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Abstract
We investigated the effect of combined inhibition of oxidative and glycolytic metabolism on L-type Ca(2+) channels (LCCs) and Ca(2+) spikes in isolated patch-clamped rabbit ventricular myocytes. Metabolic inhibition (MI) reduced LCC open probability, increased null probability, increased first latency, and decreased open time but left conductance unchanged. These results explain the reduction in macroscopic Ca(2+) current observed during MI. MI also produced a gradual reduction in action potential duration at 90% repolarization (APD(90)), a clear decline in spike probability, and an increase in spike latency and variance. These effects are consistent with the changes we observed in LCC activity. MI had no effect on the amplitude or time to peak of Ca(2+) spikes until APD(90) reached 10% of control, suggesting preserved sarcoplasmic reticulum Ca(2+) stores and ryanodine receptor (RyR) conductance in those couplons that remained functioning. Ca(2+) spikes disappeared completely when APD(90) reached <2% of control, although in two cells, spikes were reactivated in a highly synchronized fashion by very short action potentials. This reactivation is probably due to the increased driving force for Ca(2+) entry through a reduced number of LCCs that remain open during early repolarization. The enlarged single channel flux produced by rapid repolarization is apparently sufficient to trigger RyRs whose Ca(2+) sensitivity is likely reduced by MI. We suggest that loss of coupling fidelity during MI is explained by loss of LCC activity (possibly mediated by Ca(2+)-calmodulin kinase II activity). In addition, the results are consistent with loss of RyR activity, which can be mitigated under conditions likely to enlarge the trigger.
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18
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Huizar JF, Warren MD, Shvedko AG, Kalifa J, Moreno J, Mironov S, Jalife J, Zaitsev AV. Three distinct phases of VF during global ischemia in the isolated blood-perfused pig heart. Am J Physiol Heart Circ Physiol 2007; 293:H1617-28. [PMID: 17545483 DOI: 10.1152/ajpheart.00130.2007] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Changes in ventricular fibrillation (VF) organization occurring after the onset of global ischemia are relevant to defibrillation and survival but remain poorly understood. We hypothesized that ischemia-specific dynamic instability of the action potential (AP) causes a loss of spatiotemporal periodicity of propagation and broadening of the electrocardiogram (ECG) frequency spectrum during VF in the ischemic myocardium. We recorded voltage-sensitive fluorescence of di-4-ANEPPS (anterior left ventricle, 35 x 35 mm, 64 x 64 pixels) and the volume-conducted ECG in six blood-perfused hearts during 10 min of VF and global ischemia. We used coefficient of variation (CV) to estimate variability of AP amplitude, AP duration, and diastolic interval (CV-APA, CV-APD, and CV-DI, respectively). We computed excitation median frequency (Median_F), spectral width of the AP and ECG (SpW-AP and SpW-ECG, respectively), wavebreak incidence (WBI), and recurrence of propagation direction (RPD). We found three distinct phases of local VF dynamics: "relatively periodic" (<or=1 min, high Median_F, moderate AP variability, high WBI, low RPD), "highly periodic" (1-2 min, reduced Median_F, low AP variability, low WBI, high RPD), and "aperiodic" (3-10 min, low Median_F, high AP variability, high WBI, low RPD). In one experiment, spontaneous conversion from the aperiodic to the highly periodic phase occurred after 5 min of ischemia. The SpW-ECG was correlated with SpW-AP, CV-APD, and CV-APA. We conclude that 1) at least three distinct phases of VF dynamics are present in our model, and 2) the newly described aperiodic phase is related to ischemia-specific dynamic instability of the AP shape, which underlies broadening of the ECG spectrum during VF evolution.
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Affiliation(s)
- Jose F Huizar
- Institute for Cardiovascular Research, State University of New York Upstate Medical University, Syracuse, New York, USA
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19
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Szentandrássy N, Pérez-Bido MR, Alonzo E, Negretti N, O'Neill SC. Protein kinase A is activated by the n-3 polyunsaturated fatty acid eicosapentaenoic acid in rat ventricular muscle. J Physiol 2007; 582:349-58. [PMID: 17510185 PMCID: PMC1976381 DOI: 10.1113/jphysiol.2007.132753] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
During cardiac ischaemia antiarrhythmic n-3 polyunsaturated fatty acids (PUFAs) are released following activation of phospholipase A2, if they are in the diet prior to ischaemia. Here we show a positive lusitropic effect of one such PUFA, eicosapentaenoic acid (EPA) in the antiarrhythmic concentration range in Langendorff hearts and isolated rat ventricular myocytes due to activation of protein kinase A (PKA). Several different approaches indicated activation of PKA by EPA (5-10 micromol l(-1)): the time constant of decay of the systolic Ca2+ transient decreased to 65.3 +/- 5.0% of control, Western blot analysis showed a fourfold increase in phospholamban phosphorylation, and PKA activity increased by 21.0 +/- 7.3%. In addition myofilament Ca2+ sensitivity was reduced in EPA; this too may have resulted from PKA activation. We also found that EPA inhibited L-type Ca2+ current by 38.7 +/- 3.9% but this increased to 63.3 +/- 3.4% in 10 micromol l(-1) H89 (to inhibit PKA), providing further evidence of activation of PKA by EPA. PKA inhibition also prevented the lusitropic effect of EPA on the systolic Ca2+ transient and contraction. Our measurements show, however, PKA activation in EPA cannot be explained by increased cAMP levels and alternative mechanisms for PKA activation are discussed. The combined lusitropic effect and inhibition of contraction by EPA may, respectively, combat diastolic dysfunction in ischaemic cardiac muscle and promote cell survival by preserving ATP. This is a further level of protection for the heart in addition to the well-documented antiarrhythmic qualities of these fatty acids.
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Affiliation(s)
- Norbert Szentandrássy
- Department of Medicine, University of Manchester, Core Technology Facility, Grafton Street, Manchester M13 9PT, UK
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20
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Dworschak M, Breukelmann D, Hannon JD. The effect of isoflurane during reoxygenation on the sarcoplasmic reticulum and cellular injury in isolated ventricular myocytes. Life Sci 2006; 78:888-93. [PMID: 16137699 DOI: 10.1016/j.lfs.2005.05.088] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2005] [Accepted: 05/31/2005] [Indexed: 11/17/2022]
Abstract
In contrast to pretreatment with isoflurane its benefit when applied during reperfusion in rat hearts was only modest. As cellular injury during reoxygenation is greatly determined by sarcoplasmic reticulum (SR) calcium [Ca2+] handling we investigated the effect of isoflurane after simulated ischemia in rat ventricular myocytes. Hypoxic metabolic inhibition was induced by exposure to an acidic medium (pH: 6.3) containing deoxyglucose. Ambient pO2 was reduced to <15 mm Hg. After 30 min, cells were reoxygenated for 30 min with a glucose containing medium (pH: 7.4) in air (Air) or in the presence of isoflurane (Iso), or two SR blockers, i.e. either 3 microM ryanodine (Rya) or 10 microM of cyclopiazonic acid (CPA). During inhibition, diastolic cytosolic calcium ([Ca2+]i) increased and systolic cell shortening decreased. [Ca2+]i further increased in all groups towards the end of reoxygenation. However, [Ca2+]i in the Iso and the Rya group climbed twice as high as in the Air and the CPA group (P < 0.05). Hypercontracture occurred in 23% and 18% in the Iso and the Rya and in 10% and 9% in the Air and the CPA group, respectively (P < 0.05). Cell relengthening and shortening was impaired in Iso, Rya, and CPA treated cells (P < 0.05 vs. Air). Isoflurane given solely during reoxygenation appears to augment cellular injury. Its action seems to be blockade of SR Ca2+ release and Ca2+ efflux. SR Ca2+ overload induces spontaneous Ca2+ oscillations that cause hypercontracture. However, [Ca2+]i does not independently govern cellular systolic and diastolic dysfunction.
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Affiliation(s)
- Martin Dworschak
- Department of Anaesthesiology and General Intensive Care, Division of Cardiothoracic and Vascular Anaesthesia and Intensive Care, University Hospital Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
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21
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Chen M, Zhou JJ, Kam KWL, Qi JS, Yan WY, Wu S, Wong TM. Roles of KATP channels in delayed cardioprotection and intracellular Ca(2+) in the rat heart as revealed by kappa-opioid receptor stimulation with U50488H. Br J Pharmacol 2004; 140:750-8. [PMID: 14534156 PMCID: PMC1574065 DOI: 10.1038/sj.bjp.0705475] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The effect of preconditioning with U50488 H (UP), a selective kappa-opioid receptor (kappa-OR) agonist, on infarct size and intracellular Ca2+ ([Ca2+]i) in the heart subjected to ischaemic insults were studied and evaluated. U50488 H administered intravenously reduced the infarct size 18-48 h after administration in isolated hearts subjected to regional ischaemia/reperfusion (I/R). The effect was dose dependent. A peak effect was reached at 10 mg x kg-1 U50488 H and at 24 h after administration. The effect of 10 mg x kg-1 U50488 H at 24 h after administration was abolished by nor-binaltorphimine (nor-BNI), a selective kappa-OR antagonist, indicating the effect was kappa-OR mediated. The infarct reducing effect of U50488 H was attenuated when a selective blocker of mitochondrial (5-hydroxydecanoic acid, 5-HD) or sarcolemmal (HRM-1098) ATP-sensitive potassium channel (KATP) was coadministered with U50488 H 24 h before ischaemia or when 5-HD was administered just before ischaemia. U50488 H also attenuated the elevation in [Ca2+]i and reduction in electrically induced [Ca2+]i transient in cardiomyocytes subjected to ischaemic insults. The effects were reversed by blockade of KATP channel, which abolished the protective effect of preconditioning with U50488 H. The results indicated that mitochondrial KATP channel serves as both a trigger and a mediator, while sarcolemmal KATP channel as a trigger only, of delayed cardioprotection of kappa-OR stimulation. The effects of these channels may result from prevention/attenuation of [Ca2+]i overload induced by ischaemic insults.
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MESH Headings
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer/antagonists & inhibitors
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer/pharmacology
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer/therapeutic use
- Animals
- Calcium/antagonists & inhibitors
- Calcium/metabolism
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Coronary Circulation/drug effects
- Coronary Vessels/injuries
- Dose-Response Relationship, Drug
- Heart/drug effects
- Heart/physiology
- Heart Rate/drug effects
- Heart Rate/physiology
- Injections, Intravenous
- Ischemic Preconditioning, Myocardial/methods
- Male
- Myocardial Infarction/complications
- Myocardial Infarction/drug therapy
- Myocardial Reperfusion Injury/complications
- Myocardial Reperfusion Injury/drug therapy
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Naltrexone/analogs & derivatives
- Naltrexone/pharmacology
- Potassium Channel Blockers/metabolism
- Potassium Channel Blockers/pharmacology
- Potassium Channel Blockers/therapeutic use
- Potassium Channels/classification
- Potassium Channels/drug effects
- Potassium Channels/physiology
- Rats/physiology
- Rats, Sprague-Dawley
- Receptors, Opioid, kappa/antagonists & inhibitors
- Receptors, Opioid, kappa/drug effects
- Receptors, Opioid, kappa/metabolism
- Time Factors
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Affiliation(s)
- Mai Chen
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Jing-Jun Zhou
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Kenneth Wan-Lung Kam
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Jian-Song Qi
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Wing-Yi Yan
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Song Wu
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Tak-Ming Wong
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
- Author for correspondence:
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22
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Eisner DA, Díaz ME, O'Neill SC, Trafford AW. Physiological and pathological modulation of ryanodine receptor function in cardiac muscle. Cell Calcium 2004; 35:583-9. [PMID: 15110148 DOI: 10.1016/j.ceca.2004.01.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2003] [Accepted: 01/12/2004] [Indexed: 11/22/2022]
Abstract
Calcium release from the sarcoplasmic reticulum (SR) in cardiac muscle occurs through a specialised release channel, the ryanodine receptor, RyR, via the process of Ca-induced Ca release (CICR). The open probability of the RyR is increased by elevation of cytoplasmic Ca concentration ([Ca(2+)](i)). However, in addition to Ca, other modulators affect the RyR open probability. Agents which increase the RyR opening during systole produce a transient increase of systolic [Ca(2+)](i) followed by a return to the initial level due to a compensating decrease of SR Ca content. Increasing RyR opening during diastole decreases SR Ca content and thereby decreases systolic [Ca(2+)](i). We therefore conclude that potentiation of RyR opening will, if anything, decrease systolic [Ca(2+)](i). The effects of specific examples of modulators of the RyR, such as phosphorylation, metabolic changes, heart failure and polyunsaturated fatty acids, are discussed.
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Affiliation(s)
- D A Eisner
- Unit of Cardiac Physiology, University of Manchester, 1.524 Stopford Building, Oxford Road, Manchester M13 9PT, UK.
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23
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O'Neill SC, Miller L, Hinch R, Eisner DA. Interplay between SERCA and sarcolemmal Ca2+ efflux pathways controls spontaneous release of Ca2+ from the sarcoplasmic reticulum in rat ventricular myocytes. J Physiol 2004; 559:121-8. [PMID: 15194743 PMCID: PMC1665077 DOI: 10.1113/jphysiol.2003.058917] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Waves of calcium-induced calcium release occur in a variety of cell types and have been implicated in the origin of cardiac arrhythmias. We have investigated the effects of inhibiting the SR Ca(2+)-ATPase (SERCA) with the reversible inhibitor 2',5'-di(tert-butyl)-1,4-benzohydroquinone (TBQ) on the properties of these waves. Cardiac myocytes were voltage clamped at a constant potential between -65 and -40 mV and spontaneous waves evoked by increasing external Ca(2+) concentration to 4 mm. Application of 100 microm TBQ decreased the frequency of waves. This was associated with increases of resting [Ca(2+)](i), the time constant of decay of [Ca(2+)](i) and the integral of the accompanying Na(+)-Ca(2+) exchange current. There was also a decrease in propagation velocity of the waves. There was an increase of the calculated Ca(2+) efflux per wave. The SR Ca(2+) content when a wave was about to propagate decreased to 91.7 +/- 3.2%. The period between waves increased in direct proportion to the Ca(2+) efflux per wave meaning that TBQ had no effect on the Ca(2+) efflux per unit time. We conclude that (i) decreased wave frequency is not a direct consequence of decreased Ca(2+) pumping by SERCA between waves but, rather, to more Ca(2+) loss on each wave; (ii) inhibiting SERCA increases the chance of spontaneous Ca(2+) release propagating at a given SR content.
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Affiliation(s)
- S C O'Neill
- Unit of Cardiac Physiology, 1.525 Stopford Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK. stephen.c.o'
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24
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del Monte F, Lebeche D, Guerrero JL, Tsuji T, Doye AA, Gwathmey JK, Hajjar RJ. Abrogation of ventricular arrhythmias in a model of ischemia and reperfusion by targeting myocardial calcium cycling. Proc Natl Acad Sci U S A 2004; 101:5622-7. [PMID: 15044708 PMCID: PMC397450 DOI: 10.1073/pnas.0305778101] [Citation(s) in RCA: 163] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Abnormal intracellular Ca(2+) cycling plays an important role in cardiac dysfunction and ventricular arrhythmias in the setting of heart failure and transient cardiac ischemia followed by reperfusion (I/R). We hypothesized that overexpression of the sarcoplasmic reticulum Ca(2+) ATPase pump (SERCA2a) may improve both contractile dysfunction and ventricular arrhythmias. Continuous ECG recordings were obtained in 46 conscious rats after adenoviral gene transfer of either SERCA2a or the reporter gene beta-galactosidase (beta gal) or parvalbumin (PV), as early as 48 h before and 48 h after 30 min ligation of the left anterior descending artery by using an implantable telemetry system. Sham-operated animals were used for comparison for hemodynamic measurements, whereas within-animal baseline was used for electrocardiographic and echocardiographic parameters. All episodes of nonsustained ventricular tachycardia (VT) and ventricular fibrillation (VF) were counted, and their durations were summed by telemetry. I/R decreased regional cardiac wall thickening as well as the maximal rate of left ventricular pressure rise (+dP/dt) and ventricular pressure fall (-dP/dt). SERCA2a restored regional wall thickening and +dP/dt and -dP/dt to levels seen preoperatively. Regional-wall motion and anterior-wall thickening were improved in the SERCA2a animals, as assessed by echocardiography and piezoelectric crystals. To assess whether these effects are SERCA2a specific, we overexpressed a skeletal-muscle protein, PV, to examine whether Ca(2+) buffering alone can mitigate ventricular arrhythmias. During the first hour after I/R, the rate of nonsustained VT plus VF was 16 +/- 5 episodes per h (n = 6) in the Ad.beta gal group, 22 +/- 6 in the Ad.PV group, and 4 +/- 2(n = 6, P < 0.01) in the Ad.SERCA2a group. The decrease in VT plus VF in the Ad.SERCA2a group was consistent throughout the 48 h of monitoring. These results show that improving intracellular Ca(2+) handling by overexpression of SERCA2a restores contractile function and reduces ventricular arrhythmias during I/R.
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Affiliation(s)
- Federica del Monte
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA 02114, USA.
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25
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O'Neill SC, Eisner DA. pH-dependent and -independent effects inhibit Ca(2+)-induced Ca2+ release during metabolic blockade in rat ventricular myocytes. J Physiol 2003; 550:413-8. [PMID: 12766236 PMCID: PMC2343052 DOI: 10.1113/jphysiol.2003.042846] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We have investigated the role of changes of intracellular pH (pHi) in the effects of metabolic blockade (cyanide plus 2-deoxyglucose) on Ca2+ release from the sarcoplasmic reticulum (SR) in rat ventricular myocytes. pHi and cell length were measured simultaneously. Metabolic blockade decreased the frequency of Ca2+ waves, an effect previously shown to be due to inhibition of Ca2+ release from the SR. This was accompanied by an intracellular acidification. Intracellular acidification was produced in the absence of metabolic inhibition by application of sodium butyrate. A maintained intracellular acidosis produced a decrease of wave frequency. A hysteresis between pHi and wave frequency was observed such that during the onset of the acidification the wave frequency decreased more than in the steady state. Comparison of the steady state relationship between pHi and wave frequency showed that the decrease of wave frequency produced by metabolic blockade was greater than could be accounted for simply by the accompanying decrease of pHi. In other experiments the buffering power of the solution was increased. Under these conditions, metabolic blockade produced no change of pHi but the decrease of wave frequency persisted. We conclude that, although intracellular acidification occurs during metabolic blockade, it is not responsible for most of the inhibition of Ca2+ release from the SR.
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Affiliation(s)
- S C O'Neill
- Unit of Cardiac Physiology, Stopford Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK. stephen.c.o'
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26
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Tsujii E, Tanaka H, Oyamada M, Fujita K, Hamamoto T, Takamatsu T. In situ visualization of the intracellular Ca2+ dynamics at the border of the acute myocardial infarct. Mol Cell Biochem 2003; 248:135-9. [PMID: 12870665 DOI: 10.1023/a:1024188302849] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Ischemic insult to the heart produces myocyte Ca2+ ([Ca2+]i) overload. However, little is known about spatiotemporal changes in [Ca2+]i within the ischemic heart in situ at the cellular level. Using real-time confocal microscopy, we successfully visualized [Ca2+]i dynamics at the border zone on the subepicardial myocardium of the heart 2 h after coronary ligations followed by loading with fluo 3/AM. Three distinct regions were identified in the acute infarcted heart. In intact regions, the myocytes showed spatially uniform Ca2+ transients synchronously to QRS complex in the electrocardiogram. The myocytes at the infarcted regions showed no fluorescence intensity (FI). At the border zones between the intact and infarcted regions, Ca2+ waves emerged sporadically and randomly, instead of Ca2+ transients, at a mean frequency of 11.5 +/- 8.5 min/cell with a propagation velocity of 151.0 +/- 35.7 microm/sec along the longitudinal axis of the individual myocytes. In addition, some myocytes within the border zone exhibited homogeneously high static FI, indicating severe Ca2+ overload. In summary, we provided the first direct evidence of abnormal [Ca2+]i dynamics in acute infarcted hearts at the cellular level. The observed diversity in spatiotemporal [Ca2+]i dynamics at the border zone may contribute to the arrhythmias or contractile failure in acute myocardial infarction.
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Affiliation(s)
- Eiji Tsujii
- Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine, Kyoto, Japan
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27
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Ju YK, Allen DG. Early effects of metabolic inhibition on intracellular Ca2+ in toad pacemaker cells: involvement of Ca2+ stores. Am J Physiol Heart Circ Physiol 2003; 284:H1087-94. [PMID: 12595299 DOI: 10.1152/ajpheart.00755.2002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The early effects of metabolic inhibition on intracellular Ca(2+) concentration ([Ca(2+)](i)), Ca(2+) current, and sarcoplasmic reticulum (SR) Ca(2+) content were studied in single pacemaker cells from the sinus venosus of the cane toad. The amplitude of the spontaneous elevations of systolic [Ca(2+)](i) (Ca(2+) transients) was reduced after 5-min exposure to 2 mM NaCN from 338 +/- 30 to 189 +/- 37 nM (P < 0.005, n = 9), and the spontaneous firing rate was reduced from 27 +/- 2 to 12 +/- 4 beats/min (P < 0.002, n = 9). It has been proposed that CN(-) acts by inhibition of cytochrome P-450, resulting in a reduction of cAMP and Ca(2+) current. To test this proposal, we used clotrimazole, a cytochrome P-450 inhibitor, which also decreased the Ca(2+) transients and firing rate. CN(-) caused an insignificant fall of Ca(2+) current (23 +/- 11%) but a substantial reduction of SR Ca(2+) content (by 65 +/- 5%), whereas clotrimazole produced a larger reduction of Ca(2+) current and did not affect the SR Ca(2+) content. Thus the main effect of CN(-) does not seem to be through inhibition of cytochrome P-450. In conclusion, CN(-) appears to reduce Ca(2+) release from the SR mainly by reducing SR Ca(2+) content. A likely cause of the decreased SR content is reduced Ca(2+) uptake by the SR pump.
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Affiliation(s)
- Yue-Kun Ju
- Department of Physiology and Institute for Biomedical Research, University of Sydney, New South Wales 2006, Australia
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28
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Kockskämper J, Blatter LA. Subcellular Ca2+ alternans represents a novel mechanism for the generation of arrhythmogenic Ca2+ waves in cat atrial myocytes. J Physiol 2002; 545:65-79. [PMID: 12433950 PMCID: PMC2290652 DOI: 10.1113/jphysiol.2002.025502] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Ca(2+) alternans is a potentially arrhythmogenic beat-to-beat alternation of the amplitude of the action potential-induced [Ca(2+)](i) transient in cardiac myocytes. Despite its pathophysiological significance the cellular mechanisms underlying Ca(2+) alternans are poorly understood. Recent evidence, however, points to the modulation of Ca(2+)-induced Ca(2+) release (CICR) from the sarcoplasmic reticulum (SR) by localized alterations in energy metabolism as an important determinant of Ca(2+) alternans. We therefore studied the subcellular properties of Ca(2+) alternans in field-stimulated cat atrial myocytes employing fast two-dimensional fluorescence confocal microscopy. Ca(2+) alternans was elicited by an increase in stimulation frequency or by metabolic interventions targeting glycolysis. Marked subcellular variations in the time of onset, the magnitude, and the phase of alternans were observed. Longitudinal and transverse gradients of Ca(2+) alternans were found as well as neighbouring subcellular regions alternating out-of-phase. Moreover, focal inhibition of glycolysis resulted in spatially restricted Ca(2+) alternans. When two adjacent regions within a myocyte alternated out-of-phase, steep [Ca(2+)](i) gradients developed at their border giving rise to delayed propagating Ca(2+) waves. The results demonstrate that Ca(2+) alternans is a subcellular phenomenon caused by modulation of SR Ca(2+) release, which is mediated, at least in part, by local inhibition of energy metabolism. The generation of arrhythmogenic Ca(2+) waves by subcellular variations in the phase of Ca(2+) alternans represents a novel mechanism for the development of atrial disrhythmias.
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Affiliation(s)
- Jens Kockskämper
- Department of Physiology, Stritch School of Medicine, Loyola University Chicago, 2160 South First Avenue, Maywood, IL 60153, USA
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Ho JCS, Wu S, Kam KWL, Sham JSK, Wong TM. Effects of pharmacological preconditioning with U50488H on calcium homeostasis in rat ventricular myocytes subjected to metabolic inhibition and anoxia. Br J Pharmacol 2002; 137:739-48. [PMID: 12411403 PMCID: PMC1573565 DOI: 10.1038/sj.bjp.0704945] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The effects of pharmacological preconditioning with U50488H (U(50)), a selective kappa-opioid receptor agonist, on Ca(2+) homeostasis in rat ventricular myocytes subjected for 9 min to metabolic inhibition (MI) and anoxia (A), consequences of ischaemia, were studied and compared with those of preconditioning with brief periods of MI/A. 2. Precondition with 30 micro M of U(50) for three cycles of 1 min each cycle separated by 3 min of recovery (UP) significantly increased the percentage of non-blue cells following MI/A. The effect of UP is the same as that of preconditioning with an inhibitor of glycolysis and an oxygen scavenger for three 1-min cycles separated by three-minute recovery (MI/AP). The results indicate that like MI/AP, UP also confers cardioprotection. 3. MI/A increased intracellular Ca(2+) ([Ca(2+)](i)) and reduced the amplitude of caffeine-induced [Ca(2+)](i) transients, an indication of Ca(2+) content in the sarcoplasmic reticulum (SR). MI/A also reduced the electrically-induced [Ca(2+)](i) transient, that indicates Ca(2+)-release during excitation-contraction coupling, and Ca(2+) sparks in unstimulated myocytes, that indicates spontaneous Ca(2+)-release from SR. It also prolonged the decline of the electrically-induced [Ca(2+)](i) transient and slowed down the recovery of the electrically-induced [Ca(2+)](i) transient after administration of caffeine. In addition, MI/A prolonged the decline of caffeine induced [Ca(2+)](i) transient, an indication of Na(+)-Ca(2+) exchange activity, and UP prevented it. So UP, that confers cardioprotection, prevented the changes induced by MI/A. With the exception of Ca(2+)-spark, which was not studied, the effects of MI/AP are the same as those of UP. 4. It is concluded that pharmacological preconditioning with U(50), that confers immediate cardioprotection, prevents changes of Ca(2+) homeostasis altered by MI/A in the rat heart. This may be responsible, at least partly, for the cardioprotective action. 5. The study also provided evidence that MI/A causes mobilization of Ca(2+) from SR to cytoplasm causing Ca(2+)-overload which may be due to reduced Ca(2+)-uptake by SR. MI/A also reduces spontaneous and electrically induced Ca(2+) release from SR.
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Affiliation(s)
- J C S Ho
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - S Wu
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
- Institute of Cardiovascular Science and Medicine, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - K W L Kam
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - J S K Sham
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, U.S.A
| | - T M Wong
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
- Institute of Cardiovascular Science and Medicine, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
- Author for correspondence:
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Smith GL, O'Neill SC. A comparison of the effects of ATP and tetracaine on spontaneous Ca(2+) release from rat permeabilised cardiac myocytes. J Physiol 2001; 534:37-47. [PMID: 11432990 PMCID: PMC2278685 DOI: 10.1111/j.1469-7793.2001.00037.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. Fluo-3 fluorescence measurements were made in isolated beta-escin permeablised rat cardiac myocytes using confocal microscopy. Perfusion of a mock intracellular solution containing 0.22-0.23 microM Ca(2+) and 5 mM ATP elicited regular waves of Ca(2+) (approximately every 5 s) due to spontaneous release of Ca(2+) from the sarcoplasmic reticulum (SR). 2. An approximately linear relationship was noted between Ca(2+) wave velocity (v) and amplitude (sigma). Under the control conditions the ratio of velocity to amplitude (v/sigma) varied little and was 99.8 +/- 2.5 m s(-1) microM(-1) (n = 78). 3. Reduction of [ATP] in the bathing solution to 0.5 and 0.2 mM ATP progressively decreased Ca(2+) wave frequency and propagation velocity while increasing the amplitude. The changes in Ca(2+) wave characteristics in 0.5 mM ATP were similar to those observed during perfusion with 50 microM tetracaine. In 0.2 mM ATP the decline of [Ca(2+)] during a Ca(2+) wave was slowed suggesting a lowered rate of Ca(2+) re-uptake by the SR Ca(2+) pump. 4. Reduction of [ATP] to 0.1 mM abolished Ca(2+) waves after 15-20 s. Returning the [ATP] to 5 mM caused a burst of high frequency and large amplitude waves. Mean velocity of the first wave on returning to 5 mM ATP was larger than normal but the v/sigma value was 32 +/- 6 % of control (n = 6). In the similar burst on removal of 100 microM tetracaine v/sigma was higher than control (166 +/- 9 %, n = 6). 5. Rapid application of caffeine (10 mM) was used to assess the SR Ca(2+) content. This showed that SR Ca(2+) increased as [ATP] was reduced or [tetracaine] was increased. The highest SR Ca(2+) content was observed after perfusion with 0.1 mM ATP, which was 245 +/- 15 % of control values. 6. Returning [ATP] from 0.1 mM to 5 mM caused a burst of high frequency, large amplitude Ca(2+) waves. But recovery after incubation with 300 microM tetracaine resulted in SR Ca(2+) release with no coherent wave pattern. The reason for this discrepancy is discussed.
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Affiliation(s)
- G L Smith
- Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
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