151
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Griffiths EJ, Balaska D, Cheng WHY. The ups and downs of mitochondrial calcium signalling in the heart. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:856-64. [PMID: 20188059 DOI: 10.1016/j.bbabio.2010.02.022] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 02/18/2010] [Accepted: 02/18/2010] [Indexed: 12/17/2022]
Abstract
Regulation of intramitochondrial free calcium ([Ca2+]m) is critical in both physiological and pathological functioning of the heart. The full extent and importance of the role of [Ca2+]m is becoming apparent as evidenced by the increasing interest and work in this area over the last two decades. However, controversies remain, such as the existence of beat-to-beat mitochondrial Ca2+ transients; the role of [Ca2+]m in modulating whole-cell Ca2+ signalling; whether or not an increase in [Ca2+]m is essential to couple ATP supply and demand; and the role of [Ca2+]m in cell death by both necrosis and apoptosis, especially in formation of the mitochondrial permeability transition pore. The role of [Ca2+]m in heart failure is an area that has also recently been highlighted. [Ca2+]m can now be measured reasonably specifically in intact cells and hearts thanks to developments in fluorescent indicators and targeted proteins and more sensitive imaging technology. This has revealed interactions of the mitochondrial Ca2+ transporters with those of the sarcolemma and sarcoplasmic reticulum, and has gone a long way to bringing the mitochondrial Ca2+ transporters to the forefront of cardiac research. Mitochondrial Ca2+ uptake occurs via the ruthenium red sensitive Ca2+ uniporter (mCU), and efflux via an Na+/Ca2+ exchanger (mNCX). The purification and cloning of the transporters, and development of more specific inhibitors, would produce a step-change in our understanding of the role of these apparently critical but still elusive proteins. In this article we will summarise the key physiological roles of [Ca2+]m in ATP production and cell Ca2+ signalling in both adult and neonatal hearts, as well as highlighting some of the controversies in these areas. We will also briefly discuss recent ideas on the interactions of nitric oxide with [Ca2+]m.
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Affiliation(s)
- Elinor J Griffiths
- Department of Biochemistry and Bristol Heart Institute, University of Bristol, School of Medical Sciences, University Walk, Bristol BS8 1TD, UK.
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152
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Yaniv Y, Juhaszova M, Nuss HB, Wang S, Zorov DB, Lakatta EG, Sollott SJ. Matching ATP supply and demand in mammalian heart: in vivo, in vitro, and in silico perspectives. Ann N Y Acad Sci 2010; 1188:133-42. [PMID: 20201896 PMCID: PMC2943203 DOI: 10.1111/j.1749-6632.2009.05093.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although the heart rapidly adapts cardiac output to match the body's circulatory demands, the regulatory mechanisms ensuring that sufficient ATP is available to perform the required cardiac work are not completely understood. Two mechanisms have been suggested to serve as key regulators: (1) ADP and Pi concentrations--ATP utilization/hydrolysis in the cytosol increases ADP and Pi fluxes to mitochondria and hence the amount of available substrates for ATP production increases; and (2) Ca2+ concentration--ATP utilization/hydrolysis is coupled to changes in free cytosolic calcium and mitochondrial calcium, the latter controlling Ca2+-dependent activation of mitochondrial enzymes taking part in ATP production. Here we discuss the evolving perspectives of each of the putative regulatory mechanisms and the precise molecular targets (dehydrogenase enzymes, ATP synthase) based on existing experimental and theoretical evidence. The data synthesis can generate novel hypotheses and experimental designs to solve the ongoing enigma of energy supply-demand matching in the heart.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Gerontology Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, Maryland 21224-6825, USA
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153
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Ryu SY, Beutner G, Dirksen RT, Kinnally KW, Sheu SS. Mitochondrial ryanodine receptors and other mitochondrial Ca2+ permeable channels. FEBS Lett 2010; 584:1948-55. [PMID: 20096690 DOI: 10.1016/j.febslet.2010.01.032] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2009] [Revised: 01/11/2010] [Accepted: 01/18/2010] [Indexed: 01/06/2023]
Abstract
Ca(2+) channels that underlie mitochondrial Ca(2+) transport first reported decades ago have now just recently been precisely characterized electrophysiologically. Numerous data indicate that mitochondrial Ca(2+) uptake via these channels regulates multiple intracellular processes by shaping cytosolic and mitochondrial Ca(2+) transients, as well as altering the cellular metabolic and redox state. On the other hand, mitochondrial Ca(2+) overload also initiates a cascade of events that leads to cell death. Thus, characterization of mitochondrial Ca(2+) channels is central to a comprehensive understanding of cell signaling. Here, we discuss recent progresses in the biophysical and electrophysiological characterization of several distinct mitochondrial Ca(2+) channels.
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Affiliation(s)
- Shin-Young Ryu
- Department of Pharmacology and Physiology, and Mitochondrial Research Innovation Group, University of Rochester Medical Center, Rochester, NY 14642, USA
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154
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Lukyanenko V, Chikando A, Lederer WJ. Mitochondria in cardiomyocyte Ca2+ signaling. Int J Biochem Cell Biol 2009; 41:1957-71. [PMID: 19703657 PMCID: PMC3522519 DOI: 10.1016/j.biocel.2009.03.011] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Revised: 03/20/2009] [Accepted: 03/26/2009] [Indexed: 10/20/2022]
Abstract
Ca(2+) signaling is of vital importance to cardiac cell function and plays an important role in heart failure. It is based on sarcolemmal, sarcoplasmic reticulum and mitochondrial Ca(2+) cycling. While the first two are well characterized, the latter remains unclear, controversial and technically challenging. In mammalian cardiac myocytes, Ca(2+) influx through L-type calcium channels in the sarcolemmal membrane triggers Ca(2+) release from the nearby junctional sarcoplasmic reticulum to produce Ca(2+) sparks. When this triggering is synchronized by the cardiac action potential, a global [Ca(2+)](i) transient arises from coordinated Ca(2+) release events. The ends of intermyofibrillar mitochondria are located within 20 nm of the junctional sarcoplasmic reticulum and thereby experience a high local [Ca(2+)] during the Ca(2+) release process. Both local and global Ca(2+) signals may thus influence calcium signaling in mitochondria and, reciprocally, mitochondria may contribute to the local control of calcium signaling. In addition to the intermyofibrillar mitochondria, morphologically distinct mitochondria are also located in the perinuclear and subsarcolemmal regions of the cardiomyocyte and thus experience a different local [Ca(2+)]. Here we review the literature in regard to several issues of broad interest: (1) the ultrastructural basis for mitochondrion - sarcoplasmic reticulum cross-signaling; (2) mechanisms of sarcoplasmic reticulum signaling; (3) mitochondrial calcium signaling; and (4) the possible interplay of calcium signaling between the sarcoplasmic reticulum and adjacent mitochondria. Finally, this review discusses experimental findings and mathematical models of cardiac calcium signaling between the sarcoplasmic reticulum and mitochondria, identifies weaknesses in these models, and suggests strategies and approaches for future investigations.
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Affiliation(s)
- Valeriy Lukyanenko
- Medical Biotechnology Center, University of Maryland Biotechnology Institute, Baltimore, MD 21201, USA.
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155
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Wenzel S, Tastan I, Abdallah Y, Schreckenberg R, Schlüter KD. Aldosterone improves contractile function of adult rat ventricular cardiomyocytes in a non-acute way: potential relationship to the calcium paradox of aldosteronism. Basic Res Cardiol 2009; 105:247-56. [PMID: 19763404 DOI: 10.1007/s00395-009-0059-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 08/19/2009] [Accepted: 08/21/2009] [Indexed: 10/20/2022]
Abstract
Heart failure is accompanied by electrolyte disturbance including reduced calcium and sodium in the extracellular milieu but increased calcium within cells, a phenomenon called "calcium paradox". Aldosteronism is considered as part of this disorder. Aldosterone antagonism is known to reduce cardiac mortality on top of standard therapies such as antagonism of the renin-angiotensin-system. However, the effect of aldosterone on cardiac function under basal conditions and conditions more closely related to those seen in heart failure remains elusive. In order to address this question the function of isolated cardiomyocytes was determined as unloaded cell shortening. Cardiomyocytes were isolated from adult rat hearts and cultured for 24 h in the presence of aldosterone. Thereafter, cell shortening was determined in cells that were electrically paced (0.5-2.0 Hz). The effect of aldosterone on cell shortening was investigated under basal and maximal inotropic stimulation, preincubation with angiotensin II and myocytes from spontaneously hypertensive rats. The composition of the culture medium was modified according to the extracellular milieu found in patients with end-stage heart failure. Aldosterone increased cell shortening in a frequency-dependent way under basal conditions and conditions of low calcium. It potentiated the effect of beta-adrenoceptor stimulation, increased the formation of oxygen radicals, and increased diastolic and systolic calcium. In conclusion, chronic exposure to aldosterone improves the function of cardiomyocytes under basal conditions and electrolyte disturbances that mimic the situation found in heart failure patients.
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Affiliation(s)
- Sibylle Wenzel
- Physiologisches Institut, Justus-Liebig-University Giessen, Aulweg 129, 35392 Giessen, Germany
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156
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Toischer K, Lehnart SE, Tenderich G, Milting H, Körfer R, Schmitto JD, Schöndube FA, Kaneko N, Loughrey CM, Smith GL, Hasenfuss G, Seidler T. K201 improves aspects of the contractile performance of human failing myocardium via reduction in Ca2+ leak from the sarcoplasmic reticulum. Basic Res Cardiol 2009; 105:279-87. [PMID: 19718543 PMCID: PMC2807967 DOI: 10.1007/s00395-009-0057-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Revised: 08/06/2009] [Accepted: 08/20/2009] [Indexed: 11/30/2022]
Abstract
In heart failure, intracellular Ca2+ leak from cardiac ryanodine receptors (RyR2s) leads to a loss of Ca2+ from the sarcoplasmic reticulum (SR) potentially contributing to decreased function. Experimental data suggest that the 1,4-benzothiazepine K201 (JTV-519) may stabilise RyR2s and thereby reduce detrimental intracellular Ca2+ leak. Whether K201 exerts beneficial effects in human failing myocardium is unknown. Therefore, we have studied the effects of K201 on muscle preparations from failing human hearts. K201 (0.3 microM; extracellular [Ca2+]e 1.25 mM) showed no effects on contractile function and micromolar concentrations resulted in negative inotropic effects (K201 1 microM; developed tension -9.8 +/- 2.5% compared to control group; P < 0.05). Interestingly, K201 (0.3 microM) increased the post-rest potentiation (PRP) of failing myocardium after 120 s, indicating an increased SR Ca2+ load. At high [Ca2+]e concentrations (5 mmol/L), K201 increased PRP already at shorter rest intervals (30 s). Strikingly, treatment with K201 (0.3 microM) prevented diastolic dysfunction (diastolic tension at 5 mmol/L [Ca2+]e normalised to 1 mmol/L [Ca2+]e: control 1.26 +/- 0.06, K201 1.01 +/- 0.03, P < 0.01). In addition at high [Ca2+]e) K201 (0.3 microM) treatment significantly improved systolic function [developed tension +27 +/- 8% (K201 vs. control); P < 0.05]. The beneficial effects on diastolic and systolic functions occurred throughout the physiological frequency range of the human heart rate from 1 to 3 Hz. Upon elevated intracellular Ca2+ concentration, systolic and diastolic contractile functions of terminally failing human myocardium are improved by K201.
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Affiliation(s)
- Karl Toischer
- Abteilung Kardiologie und Pneumologie, Georg-August-Universität, Göttingen, Germany.
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157
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Zhang S, Tong AL, Zhang Y, Nie M, Li YX, Wang H. Heteroplasmy level of the mitochondrial tRNaLeu(UUR) A3243G mutation in a Chinese family is positively associated with earlier age-of-onset and increasing severity of diabetes. ACTA ACUST UNITED AC 2009; 24:20-5. [PMID: 19382419 DOI: 10.1016/s1001-9294(09)60053-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To investigate the mutations of mitochondrial genome in a pedigree with suspected maternally inherited diabetes and deafness and to explore the correlations between the mutations and clinical features. METHODS Genomic DNA was isolated from blood leucocytes of each member of the pedigree. The mitochondrial genome was amplified with 24-pair primers that could cover the entire mitochondrial DNA. Direct sequencing of PCR products was used to identify any mitochondrial DNA mutations. RESULTS Family members on the maternal side all harbored the tRNALeu(UUR) A3243G mutation. The paternal side family members did not have the mutation. The age-of-onset of diabetes of the 4 maternal side family members was 15, 41, 44, and 65 years old, and their corresponding heteroplasmy level of the mutation was 34.5%, 14.9%, 14.6%, and 5.9%, respectively. The age-of-onset of diabetes and heteroplasmy level of A3243G mutation were negatively correlated with a correlation coefficient of -0.980 (P = 0.02). Meanwhile, patient with high heteroplasmy level of A3243G mutation had relatively low severity of disease. Moreover, 6 reported polymorphisms and 2 new variants were found. CONCLUSIONS The main cause of diabetes in this pedigree is the tRNALeu(UUR) A3243G mutation. However, other gene variants may contribute to its pathogenicity. The heteroplasmy level of the tRNALeu(UUR) A3243G mutation is positively associated with earlier age-of-onset and increasing severity of diabetes.
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Affiliation(s)
- Shi Zhang
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
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158
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Ruiz-Meana M, Abellán A, Miró-Casas E, Agulló E, Garcia-Dorado D. Role of sarcoplasmic reticulum in mitochondrial permeability transition and cardiomyocyte death during reperfusion. Am J Physiol Heart Circ Physiol 2009; 297:H1281-9. [PMID: 19684187 DOI: 10.1152/ajpheart.00435.2009] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is solid evidence that a sudden change in mitochondrial membrane permeability (mitochondrial permeability transition, MPT) plays a critical role in reperfusion-induced myocardial necrosis. We hypothesized that sarcoplasmic reticulum (SR) Ca(2+) cycling may induce partial MPT in microdomains of close anatomic proximity between mitochondria and SR, resulting in hypercontracture and cell death. MPT (mitochondrial calcein release), cell length, and sarcolemmal rupture (Trypan blue and lactate dehydrogenase release) were measured in adult rat cardiomyocytes submitted to simulated ischemia (NaCN/2-deoxyglucose, pH 6.4) and reperfusion. On simulated reperfusion, 83 +/- 2% of myocytes developed hypercontracture. In 22 +/- 6% of cases, hypercontracture was associated with sarcolemmal disruption [Trypan blue(+)]. During simulated reperfusion there was a 25% release of cyclosporin A-sensitive mitochondrial calcein (with respect to total mitochondrial calcein content). Simultaneous blockade of SR Ca(2+) uptake and release with thapsigargin and ryanodine, respectively, significantly reduced mitochondrial calcein release, hypercontracture, and cell death during simulated reperfusion. SR Ca(2+) blockers delayed mitochondrial Ca(2+) uptake in digitonin-permeabilized cardiomyocytes but did not have any effect on isolated mitochondria. Pretreatment with colchicine to disrupt microtubule network reduced the degree of fluorescent overlap between SR and mitochondria and abolished the protective effect of SR Ca(2+) blockers on MPT, hypercontracture, and cell death during reperfusion. We conclude that SR Ca(2+) cycling during reperfusion facilitates partial mitochondrial permeabilization due to the close anatomic proximity between both organelles, favoring hypercontracture and cell death.
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Affiliation(s)
- Marisol Ruiz-Meana
- Servicio de Cardiologia, Hospital Universitari Vall d'Hebron, 08035 Barcelona, Spain
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159
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Calcium upregulation by percutaneous administration of gene therapy in cardiac disease (CUPID Trial), a first-in-human phase 1/2 clinical trial. J Card Fail 2009; 15:171-81. [PMID: 19327618 DOI: 10.1016/j.cardfail.2009.01.013] [Citation(s) in RCA: 342] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2008] [Revised: 01/26/2009] [Accepted: 01/26/2009] [Indexed: 12/11/2022]
Abstract
BACKGROUND SERCA2a deficiency is commonly seen in advanced heart failure (HF). This study is designed to investigate safety and biological effects of enzyme replacement using gene transfer in patients with advanced HF. METHODS AND RESULTS A total of 9 patients with advanced HF (New York Heart Association [NYHA] Class III/IV, ejection fraction [EF] < or = 30%, maximal oxygen uptake [VO2 max] <16 mL.kg.min, with maximal pharmacological and device therapy) received a single intracoronary infusion of AAV1/SERCA2a in the open-label portion of this ongoing study. Doses administered ranged from 1.4 x 10(11) to 3 x 10(12) DNase resistant particles per patient. We present 6- to 12-month follow-up data for these patients. AAV1/SERCA2a demonstrated an acceptable safety profile in this advanced HF population. Of the 9 patients treated, several demonstrated improvements from baseline to month 6 across a number of parameters important in HF, including symptomatic (NYHA and Minnesota Living with Heart Failure Questionnaire, 5 patients), functional (6-minute walk test and VO2 max, 4 patients), biomarker (NT-ProBNP, 2 patients), and LV function/remodeling (EF and end-systolic volume, 5 patients). Of note, 2 patients who failed to improve had preexisting anti-AAV1 neutralizing antibodies. CONCLUSIONS Quantitative evidence of biological activity across a number of parameters important for assessing HF status could be detected in several patients without preexisting neutralizing antibodies in this open-label study, although the number of patients in each cohort is too small to conduct statistical analyses. These findings support the initiation of the Phase 2 double-blind, placebo-controlled portion of this study.
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160
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Lemasters JJ, Theruvath TP, Zhong Z, Nieminen AL. Mitochondrial calcium and the permeability transition in cell death. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1395-401. [PMID: 19576166 DOI: 10.1016/j.bbabio.2009.06.009] [Citation(s) in RCA: 477] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 06/15/2009] [Accepted: 06/17/2009] [Indexed: 12/17/2022]
Abstract
Dysregulation of Ca(2+) has long been implicated to be important in cell injury. A Ca(2+)-linked process important in necrosis and apoptosis (or necrapoptosis) is the mitochondrial permeability transition (MPT). In the MPT, large conductance permeability transition (PT) pores open that make the mitochondrial inner membrane abruptly permeable to solutes up to 1500 Da. The importance of Ca(2+) in MPT induction varies with circumstance. Ca(2+) overload is sufficient to induce the MPT. By contrast after ischemia-reperfusion to cardiac myocytes, Ca(2+) overload is the consequence of bioenergetic failure after the MPT rather than its cause. In other models, such as cytotoxicity from Reye-related agents and storage-reperfusion injury to liver grafts, Ca(2+) appears to be permissive to MPT onset. Lastly in oxidative stress, increased mitochondrial Ca(2+) and ROS generation act synergistically to produce the MPT and cell death. Thus, the exact role of Ca(2+) for inducing the MPT and cell death depends on the particular biologic setting.
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Affiliation(s)
- John J Lemasters
- Center for Cell Death, Injury and Regeneration, Medical University of South Carolina, Charleston, SC 29425, USA.
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161
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Murgia M, Giorgi C, Pinton P, Rizzuto R. Controlling metabolism and cell death: at the heart of mitochondrial calcium signalling. J Mol Cell Cardiol 2009; 46:781-8. [PMID: 19285982 PMCID: PMC2851099 DOI: 10.1016/j.yjmcc.2009.03.003] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 03/05/2009] [Accepted: 03/06/2009] [Indexed: 10/21/2022]
Abstract
Transient increases in intracellular calcium concentration activate and coordinate a wide variety of cellular processes in virtually every cell type. This review describes the main homeostatic mechanisms that control Ca(2+) transients, focusing on the mitochondrial checkpoint. We subsequently extend this paradigm to the cardiomyocyte and to the interplay between cytosol, endoplasmic reticulum and mitochondria that occurs beat-to-beat in excitation-contraction coupling. The mechanisms whereby mitochondria decode fast cytosolic calcium spikes are discussed in the light of the results obtained with recombinant photoproteins targeted to the mitochondrial matrix of contracting cardiomyocytes. Mitochondrial calcium homeostasis is then highlighted as a crucial point of convergence of the environmental signals that mediate cardiac cell death, both by necrosis and by apoptosis. Altogether we point to a role of the mitochondrion as an integrator of calcium signalling and a fundamental decision maker in cardiomyocyte metabolism and survival.
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Affiliation(s)
- Marta Murgia
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35121 Padua, Italy
| | - Carlotta Giorgi
- Department of Experimental and Diagnostic Medicine, Section of General Pathology, Interdisciplinary Center for the Study of Inflammation (ICSI) and Emilia Romagna Laboratory BioPharmaNet, University of Ferrara, Via Borsari 46, 44100 Ferrara; Italy
| | - Paolo Pinton
- Department of Experimental and Diagnostic Medicine, Section of General Pathology, Interdisciplinary Center for the Study of Inflammation (ICSI) and Emilia Romagna Laboratory BioPharmaNet, University of Ferrara, Via Borsari 46, 44100 Ferrara; Italy
| | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35121 Padua, Italy
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162
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Epoxyeicosatrienoic acids limit damage to mitochondrial function following stress in cardiac cells. J Mol Cell Cardiol 2009; 46:867-75. [DOI: 10.1016/j.yjmcc.2009.02.028] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2008] [Revised: 02/19/2009] [Accepted: 02/24/2009] [Indexed: 11/23/2022]
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163
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Mitochondrial calcium transport in the heart: Physiological and pathological roles. J Mol Cell Cardiol 2009; 46:789-803. [DOI: 10.1016/j.yjmcc.2009.03.001] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 02/28/2009] [Accepted: 03/03/2009] [Indexed: 12/20/2022]
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164
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Balaban RS. The role of Ca(2+) signaling in the coordination of mitochondrial ATP production with cardiac work. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1334-41. [PMID: 19481532 DOI: 10.1016/j.bbabio.2009.05.011] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Revised: 04/23/2009] [Accepted: 05/13/2009] [Indexed: 12/18/2022]
Abstract
The heart is capable of balancing the rate of mitochondrial ATP production with utilization continuously over a wide range of activity. This results in a constant phosphorylation potential despite a large change in metabolite turnover. The molecular mechanisms responsible for generating this energy homeostasis are poorly understood. The best candidate for a cytosolic signaling molecule reflecting ATP hydrolysis is Ca(2+). Since Ca(2+) initiates and powers muscle contraction as well as serves as the primary substrate for SERCA, Ca(2+) is an ideal feed-forward signal for priming ATP production. With the sarcoplasmic reticulum to cytosolic Ca(2+) gradient near equilibrium with the free energy of ATP, cytosolic Ca(2+) release is exquisitely sensitive to the cellular energy state providing a feedback signal. Thus, Ca(2+) can serve as a feed-forward and feedback regulator of ATP production. Consistent with this notion is the correlation of cytosolic and mitochondrial Ca(2+) with work in numerous preparations as well as the localization of mitochondria near Ca(2+) release sites. How cytosolic Ca(2+) signaling might regulate oxidative phosphorylation is a focus of this review. The relevant Ca(2+) sensitive sites include several dehydrogenases and substrate transporters together with a post-translational modification of F1-FO-ATPase and cytochrome oxidase. Thus, Ca(2+) apparently activates both the generation of the mitochondrial membrane potential as well as utilization to produce ATP. This balanced activation extends the energy homeostasis observed in the cytosol into the mitochondria matrix in the never resting heart.
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Affiliation(s)
- Robert S Balaban
- Laboratory of Cardiac Energetics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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165
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Andrienko TN, Picht E, Bers DM. Mitochondrial free calcium regulation during sarcoplasmic reticulum calcium release in rat cardiac myocytes. J Mol Cell Cardiol 2009; 46:1027-36. [PMID: 19345225 DOI: 10.1016/j.yjmcc.2009.03.015] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Revised: 03/08/2009] [Accepted: 03/21/2009] [Indexed: 11/18/2022]
Abstract
Cardiac mitochondria can take up Ca(2+), competing with Ca(2+) transporters like the sarcoplasmic reticulum (SR) Ca(2+)-ATPase. Rapid mitochondrial [Ca(2+)] transients have been reported to be synchronized with normal cytosolic [Ca(2+)](i) transients. However, most intra-mitochondrial free [Ca(2+)] ([Ca(2+)](mito)) measurements have been uncalibrated, and potentially contaminated by non-mitochondrial signals. Here we measured calibrated [Ca(2+)](mito) in single rat myocytes using the ratiometric Ca(2+) indicator fura-2 AM and plasmalemmal permeabilization by saponin (to eliminate cytosolic fura-2). The steady-state [Ca(2+)](mito) dependence on [Ca(2+)](i) (with 5 mM EGTA) was sigmoid with [Ca(2+)](mito)<[Ca(2+)](i) for [Ca(2+)](i) below 475 nM. With low [EGTA] (50 microM) and 150 nM [Ca(2+)](i) (+/-15 mM Na(+)) cyclical spontaneous SR Ca(2+) release occurred (5-15/min). Changes in [Ca(2+)](mito) during individual [Ca(2+)](i) transients were small ( approximately 2-10 nM/beat), but integrated gradually to steady-state. Inhibition SR Ca(2+) handling by thapsigargin, 2 mM tetracaine or 10 mM caffeine all stopped the progressive rise in [Ca(2+)](mito) and spontaneous Ca(2+) transients (confirming that SR Ca(2+) releases caused the [Ca(2+)](mito) rise). Confocal imaging of local [Ca(2+)](mito) (using rhod-2) showed that [Ca(2+)](mito) rose rapidly with a delay after SR Ca(2+) release (with amplitude up to 10 nM), but declined much more slowly than [Ca(2+)](i) (time constant 2.8+/-0.7 s vs. 0.19+/-0.06 s). Total Ca(2+) uptake for larger [Ca(2+)](mito) transients was approximately 0.5 micromol/L cytosol (assuming 100:1 mitochondrial Ca(2+) buffering), consistent with prior indirect estimates from [Ca(2+)](i) measurements, and corresponds to approximately 1% of the SR Ca(2+) uptake during a normal Ca(2+) transient. Thus small phasic [Ca(2+)](mito) transients and gradually integrating [Ca(2+)](mito) signals occur during repeating [Ca(2+)](i) transients.
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Affiliation(s)
- Tatyana N Andrienko
- Department of Pharmacology, University of California Davis, Davis, CA 95616-8636, USA
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166
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Miyamoto S, Murphy AN, Brown JH. Akt mediated mitochondrial protection in the heart: metabolic and survival pathways to the rescue. J Bioenerg Biomembr 2009; 41:169-80. [PMID: 19377835 PMCID: PMC2732429 DOI: 10.1007/s10863-009-9205-y] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cardiomyocyte death is now recognized as a critical factor in the development of heart disease. Mitochondria are not only responsible for energy production to ensure that cardiac output meets the body's energy demands, but they serve as critical integrators of cell survival signals. Numerous stressors are known to induce cell death by necrosis and/or apoptosis mediated through mitochondrial dysregulation. Anti- and pro-apoptotic Bcl-2 family proteins regulate apoptosis by controlling mitochondrial outer membrane permeability, whereas opening of the mitochondrial permeability transition pore (PT-pore) induces large amplitude permeability of the inner membrane and consequent rupture of the outer membrane. Akt is one of the best described survival kinases activated by receptor ligands and its activation preserves mitochondrial integrity and protects cardiomyocytes against necrotic and apoptotic death. The mechanisms responsible for Akt-mediated mitochondrial protection have not been fully elucidated. There is, however, accumulating evidence that multiple Akt target molecules, recruited through both transcriptional and post-transcriptional mechanisms, directly impinge upon and protect mitochondria. In this review we discuss mechanisms by which Akt activation can effect changes at the mitochondria that protect cardiomyocytes and attenuate pathophysiological responses of the heart.
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Affiliation(s)
- Shigeki Miyamoto
- Department of Pharmacology, University of California, 9500 Gilman Dr., La Jolla, San Diego, CA 92093-0636, USA.
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167
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Liu T, O’Rourke B. Regulation of mitochondrial Ca2+ and its effects on energetics and redox balance in normal and failing heart. J Bioenerg Biomembr 2009; 41:127-32. [PMID: 19390955 PMCID: PMC2946065 DOI: 10.1007/s10863-009-9216-8] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Ca(2+) has been well accepted as a signal that coordinates changes in cytosolic workload with mitochondrial energy metabolism in cardiomyocytes. During increased work, Ca(2+) is accumulated in mitochondria and stimulates ATP production to match energy supply and demand. The kinetics of mitochondrial Ca(2+) ([Ca(2+)](m)) uptake remains unclear, and we review the debate on this subject in this article. [Ca(2+)](m) has multiple targets in oxidative phosphorylation including the F1/FO ATPase, the adenine nucleotide translocase, and Ca(2+)-sensitive dehydrogenases (CaDH) of the tricarboxylic acid (TCA) cycle. The well established effect of [Ca(2+)](m) is to activate CaDHs of the TCA cycle to increase NADH production. Maintaining NADH level is not only critical to keep a high oxidative phosphorylation rate during increased cardiac work, but is also necessary for the reducing system of the cell to maintain its reactive oxygen species (ROS) -scavenging capacity. Further, we review recent data demonstrating the deleterious effects of elevated Na(+) in cardiac pathology by blunting [Ca(2+)](m) accumulation.
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Affiliation(s)
- Ting Liu
- Institute of Molecular Cardiobiology, Division of Cardiology, The Johns Hopkins University, Baltimore, MD, USA
| | - Brian O’Rourke
- Institute of Molecular Cardiobiology, The Johns Hopkins University, 720 Rutland Ave., 1060 Ross Bldg., Baltimore, MD 21205-2195, USA,
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168
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Cortassa S, O'Rourke B, Winslow RL, Aon MA. Control and regulation of mitochondrial energetics in an integrated model of cardiomyocyte function. Biophys J 2009; 96:2466-78. [PMID: 19289071 PMCID: PMC2989151 DOI: 10.1016/j.bpj.2008.12.3893] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Accepted: 12/01/2008] [Indexed: 01/14/2023] Open
Abstract
Understanding the regulation and control of complex networks of reactions requires analytical tools that take into account the interactions between individual network components controlling global network function. Here, we apply a generalized matrix method of control analysis to calculate flux and concentration control coefficients, as well as response coefficients, in an integrated model of excitation-contraction (EC) coupling and mitochondrial energetics (ECME model) in the cardiac ventricular myocyte. Control and regulation of oxygen consumption (V(O2)) was first assessed in a mitochondrion model, and then in the integrated cardiac myocyte model under resting and working conditions. The results demonstrate that in the ECME model, control of respiration is distributed among cytoplasmic ATPases and mitochondrial processes. The magnitude of control by cytoplasmic ATPases increases under working conditions. The model prediction that the respiratory chain exerts strong positive control on V(O2) (control coefficient 0.89) was corroborated experimentally in cardiac trabeculae utilizing the inhibitor titration method. In the model, mitochondrial respiration displayed the highest response coefficients with respect to the concentration of cytoplasmic ATP. This was due to the high elasticity of ANT flux toward ATP in the cytoplasm. The analysis reveals the complex interdependence of sarcolemmal, cytoplasmic, and mitochondrial processes that contribute to the control of energy supply and demand in the heart. Moreover, by visualizing the structure of control of the metabolic network of the myocyte, we provide support for the emerging concept of control by diffuse loops, in which action on the network (e.g., by a pharmacological agent) may bring about changes in processes without obvious direct mechanistic links between them.
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Affiliation(s)
- Sonia Cortassa
- Division of Cardiology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA.
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169
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The metabolic modulators, Etomoxir and NVP-LAB121, fail to reverse pressure overload induced heart failure in vivo. Basic Res Cardiol 2009; 104:547-57. [DOI: 10.1007/s00395-009-0015-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Revised: 02/23/2009] [Accepted: 02/25/2009] [Indexed: 10/21/2022]
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170
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Abstract
The transmembrane sodium gradient is essential for both excitability of the cardiac cell and the regulation of the cytoplasmic concentrations of Ca and protons. In addition, movements of Na across the mitochondrial membrane affect matrix protons and calcium. In the first part of the review, we discuss the most important pathways responsible for sarcolemmal and mitochondrial sodium movements. The bulk of the review considers the changes of intracellular Na concentration ([Na(+)](i)) that occur in disease, specifically, ischemia, reperfusion, and heart failure. We review evidence implicating the increase of intracellular sodium to either increased influx of sodium (via either sodium channels or sodium/hydrogen exchange) or, alternatively, to decreased efflux on the Na/K pump. Although much has been learned about sodium regulation in the heart, there are still many unanswered questions, particularly concerning mitochondrial Na regulation.
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Affiliation(s)
- Elizabeth Murphy
- Translational Medicine Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD 20892, USA.
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171
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Hünlich M, Hasenfuss G. Effects of the NO donor sodium nitroprusside on oxygen consumption and energetics in rabbit myocardium. Basic Res Cardiol 2009; 104:359-65. [PMID: 19190952 PMCID: PMC3085761 DOI: 10.1007/s00395-009-0777-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Accepted: 12/22/2008] [Indexed: 12/05/2022]
Abstract
Nitric oxide (NO) has influence on various cellular functions. Little is known of the influence of NO on myocardial energetics. In the present study oxygen consumption and mechanical parameters of isometrically contracting rabbit papillary muscles (1 Hz stimulation frequency) were investigated at varying interventions while maintaining physiological conditions (37°C; 2.5 mM Ca2+) to study the effects of NO on energetics. The NO donor sodium nitroprusside (SNP) showed a negative inotropic effect. SNP decreased the maximal force in normal rabbit muscle strips by 30%, the force time integral (FTI) by 40% and the relaxation time by 20%. In addition the oxygen consumption decreased by 60%, a notably disproportional decrease compared to the mechanical parameters. Consequently, the economy as a ratio of FTI and oxygen consumption is significantly increased by SNP. In contrast the negative inotropic effect due to a reduction in extracellular Calcium (Ca2+) from 2.5 to 1.25 mM reduced FTI and oxygen consumption proportionally by 40% and did not change economy. The effect of NO on force and oxygen consumption could be reproduced by the application of the cyclic guanosine monophosphate (cGMP) analogue 8-bromo-cGMP. In summary, NO increased the economy of isometrically contracting papillary muscles. The improvement in contraction economy under NO seems to be mediated by cGMP as the secondary messenger and maybe due to alterations of the crossbridge cycle.
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Affiliation(s)
- Mark Hünlich
- Universitätsklinik Göttingen, Abteilung für Kardiologie, Robert-Koch-Strasse 40, 37099, Göttingen, Germany.
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172
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Griffiths EJ, Rutter GA. Mitochondrial calcium as a key regulator of mitochondrial ATP production in mammalian cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1324-33. [PMID: 19366607 DOI: 10.1016/j.bbabio.2009.01.019] [Citation(s) in RCA: 264] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Revised: 01/23/2009] [Accepted: 01/27/2009] [Indexed: 12/30/2022]
Abstract
Mitochondrial Ca(2+) transport was initially considered important only in buffering of cytosolic Ca(2+) by acting as a "sink" under conditions of Ca(2+) overload. The main regulator of ATP production was considered to be the relative concentrations of high energy phosphates. However, work by Denton and McCormack in the 1970s and 1980s showed that free intramitochondrial Ca(2+) ([Ca(2+)](m)) activated dehydrogenase enzymes in mitochondria, leading to increased NADH and hence ATP production. This leads them to propose a scheme, subsequently termed a "parallel activation model" whereby increases in energy demand, such as hormonal stimulation or increased workload in muscle, produced an increase in cytosolic [Ca(2+)] that was relayed by the mitochondrial Ca(2+) transporters into the matrix to give an increase in [Ca(2+)](m). This then stimulated energy production to meet the increased energy demand. With the development of methods for measuring [Ca(2+)](m) in living cells that proved [Ca(2+)](m) changed over a dynamic physiological range rather than simply soaking up excess cytosolic [Ca(2+)], this model has now gained widespread acceptance. However, work by ourselves and others using targeted probes to measure changes in both [Ca(2+)] and [ATP] in different cell compartments has revealed variations in the interrelationships between these two in different tissues, suggesting that metabolic regulation by Ca(2+) is finely tuned to the demands and function of the individual organ.
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Affiliation(s)
- Elinor J Griffiths
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.
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173
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Willems PHGM, Smeitink JAM, Koopman WJH. Mitochondrial dynamics in human NADH:ubiquinone oxidoreductase deficiency. Int J Biochem Cell Biol 2009; 41:1773-82. [PMID: 19703648 DOI: 10.1016/j.biocel.2009.01.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Revised: 01/12/2009] [Accepted: 01/15/2009] [Indexed: 10/21/2022]
Abstract
Mitochondrial NADH:ubiquinone oxidoreductase or complex I (CI) is a frequently affected enzyme in cases of mitochondrial disorders. However, the cytopathological mechanism of the associated pediatric syndromes is poorly understood. Evidence in the literature suggests a connection between mitochondrial metabolism and morphology. Previous quantitative analysis of mitochondrial structure in cultured fibroblasts of 14 patients revealed that mitochondria were fragmented and/or less branched in patients with severe CI deficiency. These patient cells also displayed greatly increased levels of reactive oxygen species (ROS) and marked aberrations in mitochondrial and cellular Ca(2+)/ATP handling upon hormone stimulation. Here, we discuss the interrelationship between these parameters and demonstrate that the hormone-induced increase in mitochondrial Ca(2+) and ATP concentration, as well as the rate of cytosolic Ca(2+) removal, are not related to mitochondrial length and/or degree of branching, but decrease as a function of the number of mitochondria per cell. This suggests that the amount of mitochondria, and not their shape, is important for Ca(2+)-induced stimulation of mitochondrial ATP generation to feed cytosolic ATP-demanding processes.
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Affiliation(s)
- Peter H G M Willems
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Medical Centre, Nijmegen, The Netherlands
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174
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Valsecchi F, Esseling JJ, Koopman WJH, Willems PHGM. Calcium and ATP handling in human NADH:ubiquinone oxidoreductase deficiency. Biochim Biophys Acta Mol Basis Dis 2009; 1792:1130-7. [PMID: 19171191 DOI: 10.1016/j.bbadis.2009.01.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Accepted: 01/04/2009] [Indexed: 02/07/2023]
Abstract
Proper cell functioning requires precise coordination between mitochondrial ATP production and local energy demand. Ionic calcium (Ca(2+)) plays a central role in this coupling because it activates mitochondrial oxidative phosphorylation (OXPHOS) during hormonal and electrical cell stimulation. To determine how mitochondrial dysfunction affects cytosolic and mitochondrial Ca(2+)/ATP handling, we performed life-cell quantification of these parameters in fibroblast cell lines derived from healthy subjects and patients with isolated deficiency of the first OXPHOS complex (CI). In resting patient cells, CI deficiency was associated with a normal mitochondrial ([ATP](m)) and cytosolic ([ATP](c)) ATP concentration, a normal cytosolic Ca(2+) concentration ([Ca(2+)](c)), but a reduced Ca(2+) content of the endoplasmic reticulum (ER). Furthermore, cellular NAD(P)H levels were increased, mitochondrial membrane potential was slightly depolarized, reactive oxygen species (ROS) levels were elevated and mitochondrial shape was altered. Upon stimulation with bradykinin (Bk), the peak increases in [Ca(2+)](c), mitochondrial Ca(2+) concentration ([Ca(2+)](m)), [ATP](c) and [ATP](m) were reduced in patient cells. In agreement with these results, ATP-dependent Ca(2+) removal from the cytosol was slower. Here, we review the interconnection between cytosolic, endoplasmic reticular and mitochondrial Ca(2+) and ATP handling, and summarize our findings in patient fibroblasts in an integrative model.
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Affiliation(s)
- Federica Valsecchi
- Department of Membrane Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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175
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Zhao W, Fan GC, Zhang ZG, Bandyopadhyay A, Zhou X, Kranias EG. Protection of peroxiredoxin II on oxidative stress-induced cardiomyocyte death and apoptosis. Basic Res Cardiol 2008; 104:377-89. [PMID: 19030911 DOI: 10.1007/s00395-008-0764-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Accepted: 10/28/2008] [Indexed: 12/28/2022]
Abstract
Peroxiredoxin II, a cytosolic isoform of the antioxidant enzyme family, has been implicated in cancer-associated cell death and apoptosis, but its functional role in the heart remains to be elucidated. Interestingly, the expression levels of peroxiredoxin II were decreased in mouse hearts upon ischemia-reperfusion, while they were elevated in two genetically modified hyperdynamic hearts with phospholamban ablation or protein phosphatase 1 inhibitor 1 overexpression. To delineate the functional significance of altered peroxiredoxin II expression, adenoviruses encoding sense or antisense peroxiredoxin II were generated; cardiomyocytes were infected, and then subjected to H(2)O(2) treatment to mimic oxidative stress-induced cell death and apoptosis. H(2)O(2) stimulation resulted in a significant decrease of endogenous peroxiredoxin II expression, along with reduced cell viability in control cells. However, overexpression of peroxiredoxin II significantly protected from H(2)O(2)-induced apoptosis and necrosis, while downregulation of this enzyme promoted the detrimental effects of oxidative stress in cardiomyocytes. The beneficial effects of peroxiredoxin II were associated with increased Bcl-2 expression, decreased expression of Bax and attenuated activity of caspases 3, 9 and 12. Furthermore, there were no significant alterations in the expression levels of the other five isoforms of peroxiredoxin, as well as active catalase or glutathione peroxidase-1 after ischemia-reperfusion or H(2)O(2) treatment. These findings suggest that peroxiredoxin II may be a unique antioxidant in the cardiac system and may represent a potential target for cardiac protection from oxidative stress-induced injury.
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Affiliation(s)
- Wen Zhao
- Dept. of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0575, USA
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176
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Modulation of L-type Ca2+ channel current density and inactivation by β-adrenergic stimulation during murine cardiac embryogenesis. Basic Res Cardiol 2008; 104:295-306. [DOI: 10.1007/s00395-008-0755-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Accepted: 09/22/2008] [Indexed: 10/21/2022]
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177
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Effects of atorvastatin on calcium-regulating proteins: a possible mechanism to repair cardiac dysfunction in spontaneously hypertensive rats. Basic Res Cardiol 2008; 104:258-68. [PMID: 18836677 DOI: 10.1007/s00395-008-0751-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Accepted: 09/10/2008] [Indexed: 10/21/2022]
Abstract
Previous clinical and experimental studies have demonstrated that statins, the inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, can improve left ventricular function in damaged hearts. Also, the normal expression of Ca(2+) regulatory proteins is critical for efficient myocardial function. However, it is still unclear whether the beneficial effect of statins on cardiac function is associated with alterations of Ca(2+) regulatory proteins. In this study, we investigated the effect of atorvastatin on cardiac function in spontaneously hypertensive rats (SHRs), focusing in particular on its impact on the expression of sarcoplasmic reticulum Ca(2+)-adenosine triphosphatase (SERCA2a), phospholamban (PLB) and its phosphorylated form (phosphorylated PLB), all of which are Ca(2+) regulatory proteins in myocardium. SHRs showed decreases in gene expression of SERCA2a and phosphorylated PLB, and reduction in SERCA activity in the left ventricular myocardium, as well as reduced cardiac function, compared to age-matched Wistar Kyoto rats (WKYs). Furthermore, we showed that in SHRs atorvastatin preserved cardiac dysfunction accompanied by positive alterations in calcium regulatory proteins, with up-regulation in expression of SERCA2a and phosphorylated PLB, and with improvement of SERCA activity. Thus, atorvastatin has positive effects on calcium regulatory proteins, which may be one of the mechanisms of the beneficial effect of statins on cardiac function in spontaneously hypertensive rats.
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178
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Jaleel N, Nakayama H, Chen X, Kubo H, MacDonnell S, Zhang H, Berretta R, Robbins J, Cribbs L, Molkentin JD, Houser SR. Ca2+ influx through T- and L-type Ca2+ channels have different effects on myocyte contractility and induce unique cardiac phenotypes. Circ Res 2008; 103:1109-19. [PMID: 18832749 DOI: 10.1161/circresaha.108.185611] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
T-type Ca(2+) channels (TTCCs) are expressed in the developing heart, are not present in the adult ventricle, and are reexpressed in cardiac diseases involving cardiac dysfunction and premature, arrhythmogenic death. The goal of this study was to determine the functional role of increased Ca(2+) influx through reexpressed TTCCs in the adult heart. A mouse line with cardiac-specific, conditional expression of the alpha1G-TTCC was used to increase Ca(2+) influx through TTCCs. alpha1G hearts had mild increases in contractility but no cardiac histopathology or premature death. This contrasts with the pathological phenotype of a previously studied mouse with increased Ca(2+) influx through the L-type Ca(2+) channel (LTCC) secondary to overexpression of its beta2a subunit. Although alpha1G and beta2a myocytes had similar increases in Ca(2+) influx, alpha1G myocytes had smaller increases in contraction magnitude, and, unlike beta2a myocytes, there were no increases in sarcoplasmic reticulum Ca(2+) loading. Ca(2+) influx through TTCCs also did not induce normal sarcoplasmic reticulum Ca(2+) release. alpha1G myocytes had changes in LTCC, SERCA2a, and phospholamban abundance, which appear to be adaptations that help maintain Ca(2+) homeostasis. Immunostaining suggested that the majority of alpha1G-TTCCs were on the surface membrane. Osmotic shock, which selectively eliminates T-tubules, induced a greater reduction in L- versus TTCC currents. These studies suggest that T- and LTCCs are in different portions of the sarcolemma (surface membrane versus T-tubules) and that Ca(2+) influx through these channels induce different effects on myocyte contractility and lead to distinct cardiac phenotypes.
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Affiliation(s)
- Naser Jaleel
- Department of Physiology, Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, Pa., USA
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179
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García-Pérez C, Hajnóczky G, Csordás G. Physical coupling supports the local Ca2+ transfer between sarcoplasmic reticulum subdomains and the mitochondria in heart muscle. J Biol Chem 2008; 283:32771-80. [PMID: 18790739 DOI: 10.1074/jbc.m803385200] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In many cell types, transfer of Ca(2+) released via ryanodine receptors (RyR) to the mitochondrial matrix is locally supported by high [Ca(2+)] microdomains at close contacts between the sarcoplasmic reticulum (SR) and mitochondria. Here we studied whether the close contacts were secured via direct physical coupling in cardiac muscle using isolated rat heart mitochondria (RHMs). "Immuno-organelle chemistry" revealed RyR2 and calsequestrin-positive SR particles associated with mitochondria in both crude and Percoll-purified "heavy" mitochondrial fractions (cRHM and pRHM), to a smaller extent in the latter one. Mitochondria-associated vesicles were also visualized by electron microscopy in the RHMs. Western blot analysis detected greatly reduced presence of SR markers (calsequestrin, SERCA2a, and phospholamban) in pRHM, suggesting that the mitochondria-associated particles represented a small subfraction of the SR. Fluorescence calcium imaging in rhod2-loaded cRHM revealed mitochondrial matrix [Ca(2+)] ([Ca(2+)](m)) responses to caffeine-induced Ca(2+) release that were prevented when thapsigargin was added to predeplete the SR or by mitochondrial Ca(2+) uptake inhibitors. Importantly, caffeine failed to increase [Ca(2+)] in the large volume of the incubation medium, suggesting that local Ca(2+) transfer between the SR particles and mitochondria mediated the [Ca(2+)](m) signal. Despite the substantially reduced SR presence, pRHM still displayed a caffeine-induced [Ca(2+)](m) rise comparable with the one recorded in cRHM. Thus, a relatively small fraction of the total SR is physically coupled and transfers Ca(2+) locally to the mitochondria in cardiac muscle. The transferred Ca(2+) stimulates dehydrogenase activity and affects mitochondrial membrane permeabilization, indicating the broad significance of the physical coupling in mitochondrial function.
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Affiliation(s)
- Cecilia García-Pérez
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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180
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Effects of unipolar stimulation on voltage and calcium distributions in the isolated rabbit heart. Basic Res Cardiol 2008; 103:537-51. [PMID: 18642125 DOI: 10.1007/s00395-008-0740-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2008] [Accepted: 07/02/2008] [Indexed: 12/23/2022]
Abstract
BACKGROUND The effect of electric stimulation on the polarization of cardiac tissue (virtual electrode effect) is well known; the corresponding response of intracellular calcium concentration ([Ca(2+)](i)) and its dependence on coupling interval between conditioning stimulus (S1) and test stimulus (S2) has yet to be elucidated. OBJECTIVE Because uncovering the transmembrane potential (V(m))-[Ca(2+)](i) relationship during an electric shock is imperative for understanding arrhythmia induction and defibrillation, we aimed to study simultaneous V(m) and [Ca(2+)](i) responses to strong unipolar stimulation. METHODS We used a dual-camera optical system to image concurrently V (m) and [Ca(2+)](i) responses to unipolar stimulation (20 ms +/- 20 mA) in Langendorff-perfused rabbit hearts. RH-237 and Rhod-2 fluorescent dyes were used to measure V(m) and [Ca(2+)](i), respectively. The S1-S2 interval ranged from 10 to 170 ms to examine stimulation during the action potential. RESULTS The [Ca(2+)](i) deflections were less pronounced than changes in V(m) for all S1-S2 intervals. For cathodal stimulation, [Ca(2+)](i) at the central virtual cathode region increased with prolongation of S1-S2 interval. For anodal stimulation, [Ca(2+)](i) at the central virtual anode area decreased with shortening of the S1-S2 interval. At very short S1-S2 intervals (10-20 ms), when S2 polarization was superimposed on the S1 action potential upstroke, the [Ca(2+)](i) distribution did not follow V(m) and produced a more complex pattern. After S2 termination [Ca(2+)](i) exhibited three outcomes in a manner similar to V(m): non-propagating response, break stimulation, and make stimulation. CONCLUSIONS Changes in the [Ca(2+)](i) distribution correlate with the behavior of the V (m) distribution for S1-S2 coupling intervals longer than 20 ms; at shorter intervals S2 creates more heterogeneous [Ca(2+)](i) distribution in comparison with V(m). Stimulation in diastole and at very short coupling intervals caused V(m)-[Ca(2+)](i) uncoupling at the regions of positive polarization (virtual cathode).
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181
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Liu T, O'Rourke B. Enhancing mitochondrial Ca2+ uptake in myocytes from failing hearts restores energy supply and demand matching. Circ Res 2008; 103:279-88. [PMID: 18599868 DOI: 10.1161/circresaha.108.175919] [Citation(s) in RCA: 181] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Mitochondrial ATP production is continually adjusted to energy demand through coordinated increases in oxidative phosphorylation and NADH production mediated by mitochondrial Ca2+([Ca2+]m). Elevated cytosolic Na+ impairs [Ca2+]m accumulation during rapid pacing of myocytes, resulting in a decrease in NADH/NAD+ redox potential. Here, we determined 1) if accentuating [Ca2+]m accumulation prevents the impaired NADH response at high [Na+]i; 2) if [Ca2+]m handling and NADH/NAD+ balance during stimulation is impaired with heart failure (induced by aortic constriction); and 3) if inhibiting [Ca2+]m efflux improves NADH/NAD+ balance in heart failure. [Ca2+]m and NADH were recorded in cells at rest and during voltage clamp stimulation (4Hz) with either 5 or 15 mmol/L [Na+]i. Fast [Ca2+]m transients and a rise in diastolic [Ca2+]m were observed during electric stimulation. [Ca2+]m accumulation was [Na+]i-dependent; less [Ca2+]m accumulated in cells with 15 Na+ versus 5 mmol/L Na+ and NADH oxidation was evident at 15 mmol/L Na+, but not at 5 mmol/L Na+. Treatment with either the mitochondrial Na+/Ca2+ exchange inhibitor CGP-37157 (1 micromol/L) or raising cytosolic Pi (2 mmol/L) enhanced [Ca2+]m accumulation and prevented the NADH oxidation at 15 mmol/L [Na+]i. In heart failure myocytes, resting [Na+]i increased from 5.2+/-1.4 to 16.8+/-3.1mmol/L and net NADH oxidation was observed during pacing, whereas NADH was well matched in controls. Treatment with CGP-37157 or lowering [Na+]i prevented the impaired NADH response in heart failure. We conclude that high [Na+]i (at levels observed in heart failure) has detrimental effects on mitochondrial bioenergetics, and this impairment can be prevented by inhibiting the mitochondrial Na+/Ca2+ exchanger.
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Affiliation(s)
- Ting Liu
- Division of Cardiology, The Johns Hopkins University, Baltimore, MD, USA
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182
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Skyschally A, Gres P, Caster P, Sand A, Boengler K, Schulz R, Heusch G. Reduced calcium responsiveness characterizes contractile dysfunction following coronary microembolization. Basic Res Cardiol 2008; 103:552-9. [DOI: 10.1007/s00395-008-0732-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Accepted: 05/14/2008] [Indexed: 02/03/2023]
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183
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Slow contractions characterize failing rat hearts. Basic Res Cardiol 2008; 103:328-44. [DOI: 10.1007/s00395-008-0719-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Accepted: 02/08/2008] [Indexed: 10/22/2022]
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Myocardial adaptation of energy metabolism to elevated preload depends on calcineurin activity : a proteomic approach. Basic Res Cardiol 2008; 103:232-43. [PMID: 18274801 PMCID: PMC3085746 DOI: 10.1007/s00395-008-0696-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Accepted: 01/08/2008] [Indexed: 11/18/2022]
Abstract
Chronic hemodynamic overload on the heart results in pathological myocardial hypertrophy, eventually followed by heart failure. Phosphatase calcineurin is a crucial mediator of this response. Little is known, however, about the role of calcineurin in response to acute alterations in loading conditions of the heart, where it could be mediating beneficial adaptational processes. We therefore analyzed proteome changes following a short-term increase in preload in rabbit myocardium in the absence or presence of the calcineurin inhibitor cyclosporine A. Rabbit right ventricular isolated papillary muscles were cultivated in a muscle chamber system under physiological conditions and remained either completely unloaded or were stretched to a preload of 3 mN/mm2, while performing isotonic contractions (zero afterload). After 6 h, proteome changes were detected by two-dimensional gel electrophoresis and ESI-MS/MS. We identified 28 proteins that were upregulated by preload compared to the unloaded group (at least 1.75-fold regulation, all P < 0.05). Specifically, mechanical load upregulated a variety of enzymes involved in energy metabolism (i.e., aconitase, pyruvate kinase, fructose bisphosphate aldolase, ATP synthase alpha chain, acetyl-CoA acetyltransferase, NADH ubiquinone oxidoreductase, ubiquinol cytochrome c reductase, hydroxyacyl-CoA dehydrogenase). Cyclosporine A treatment (1 µmol/l) abolished the preload-induced upregulation of these proteins. We demonstrate for the first time that an acute increase in the myocardial preload causes upregulation of metabolic enzymes, thereby increasing the capacity of the myocardium to generate ATP production. This short-term adaptation to enhanced mechanical load appears to critically depend on calcineurin phosphatase activity.
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Bigelow DJ. Nitrotyrosine-modified SERCA2: a cellular sensor of reactive nitrogen species. Pflugers Arch 2008; 457:701-10. [DOI: 10.1007/s00424-007-0429-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 12/06/2007] [Accepted: 12/10/2007] [Indexed: 12/31/2022]
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O'Rourke B, Maack C. The role of Na dysregulation in cardiac disease and how it impacts electrophysiology. ACTA ACUST UNITED AC 2007; 4:207-217. [PMID: 18650959 DOI: 10.1016/j.ddmod.2007.11.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Ca(2+) is well known as the central player in cardiac cell physiology, mediating Ca(2+) activation of myosin ATPase and contraction, the stimulation of Ca(2+)-activated signaling pathways and modulation of mitochondrial energy production. Abnormalities of Ca(2+) handling are a well-studied mechanism of decompensation in heart failure. Less appreciated is the role of cytosolic Na(+) (Na(i) (+)), which can dramatically influence the transfer rates and distribution of Ca(2+) among the intracellular compartments of the myocyte. Since Na(i) (+) can vary widely under different physiological and pathological conditions, and its effects depend on multiple ion gradients and membrane electrical potentials, unraveling the global influence of Na(i) (+) on cell function is complex, requiring an integrative view of cardiomyocyte physiology. Here, we discuss how abnormal Na(i) (+) regulation not only influences the cytosolic Ca(2+) transient and the cellular action potential but also alters mitochondrial Ca(2+) uptake and the balance of energy supply and demand of the cardiomyocyte, which may contribute to oxidative stress and cardiac decompensation. The implications for sudden cardiac death and the potential for novel therapeutic interventions are discussed.
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Affiliation(s)
- Brian O'Rourke
- The Johns Hopkins University, Institute of Molecular Cardiobiology, Division of Cardiology, Baltimore, MD, USA
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