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Yang Y, Lu X, Rong X, Jiang W, Lai D, Ma Y, Zhou K, Fu G, Xu S. Inhibition of the mevalonate pathway ameliorates anoxia-induced down-regulation of FKBP12.6 and intracellular calcium handling dysfunction in H9c2 cells. J Mol Cell Cardiol 2015; 80:166-74. [PMID: 25636197 DOI: 10.1016/j.yjmcc.2015.01.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 11/27/2014] [Accepted: 01/20/2015] [Indexed: 11/25/2022]
Abstract
Statins have beneficial pleiotropic effects beyond lipid lowering on the cardiovascular system. These cardio-protective effects are mediated through inhibition of the intracellular mevalonate pathway, by decreasing isoprenoid intermediate synthesis and the subsequent post-translational modification of small GTPases, such as Ras, Rho, and Rac. Impaired intracellular calcium handling is considered an important pathophysiologic mechanism responsible for cardiac dysfunction. Our study aimed at investigating the influence of mevalonate pathway, including its downstream small GTPases (Ras, RhoA, and Rac1) on anoxia-mediated alterations of calcium handling in H9c2 cardiomyocytes. Cultured H9c2 cardiomyocytes were exposed to acute anoxia after pretreatment with different drugs that specifically antagonize five key components in the mevalonate pathway, including 3-hydroxy-3-methylglutaryl-CoA reductase, farnesyl pyrophosphate synthase, Rho-kinase, Rac1 and Ras farnesyltransferase. Thereafter, we evaluated the effects of the mevalonate pathway on anoxia-induced cell death, expression of the sarcoplasmic reticulum calcium release channel (ryanodine receptor 2) and its regulator FK506-binding protein 12.6, as well as functional calcium release from intracellular calcium stores. Our experiments confirmed the role of prenylated proteins in regulating cardiomyocyte dysfunction, especially via RhoA- and Ras-related signaling pathways. Furthermore, our data demonstrated that inhibition of the mevalonate pathway could ameliorate anoxia-mediated calcium handling dysfunction with the up-regulated expression of FK506-binding protein 12.6 and consequently provided evidence for FK506-binding protein 12.6 as a "stabilizer" of ryanodine receptor 2.
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Affiliation(s)
- Ying Yang
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
| | - Xue Lu
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xiqing Rong
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Wenbing Jiang
- Department of Cardiology, Wenzhou People's Hospital, Wenzhou, Zhejiang, China
| | - Dongwu Lai
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yan Ma
- Department of Orthopedics, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Ke Zhou
- Department of Orthopedics, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Guosheng Fu
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Shiming Xu
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China; Institute of Translational Medicine, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
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Defective sarcoplasmic reticulum-mitochondria calcium exchange in aged mouse myocardium. Cell Death Dis 2014; 5:e1573. [PMID: 25522267 PMCID: PMC4454162 DOI: 10.1038/cddis.2014.526] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 10/21/2014] [Accepted: 11/04/2014] [Indexed: 02/06/2023]
Abstract
Mitochondrial alterations are critically involved in increased vulnerability to disease during aging. We investigated the contribution of mitochondria–sarcoplasmic reticulum (SR) communication in cardiomyocyte functional alterations during aging. Heart function (echocardiography) and ATP/phosphocreatine (NMR spectroscopy) were preserved in hearts from old mice (>20 months) with respect to young mice (5–6 months). Mitochondrial membrane potential and resting O2 consumption were similar in mitochondria from young and old hearts. However, maximal ADP-stimulated O2 consumption was specifically reduced in interfibrillar mitochondria from aged hearts. Second generation proteomics disclosed an increased mitochondrial protein oxidation in advanced age. Because energy production and oxidative status are regulated by mitochondrial Ca2+, we investigated the effect of age on mitochondrial Ca2+ uptake. Although no age-dependent differences were found in Ca2+ uptake kinetics in isolated mitochondria, mitochondrial Ca2+ uptake secondary to SR Ca2+ release was significantly reduced in cardiomyocytes from old hearts, and this effect was associated with decreased NAD(P)H regeneration and increased mitochondrial ROS upon increased contractile activity. Immunofluorescence and proximity ligation assay identified the defective communication between mitochondrial voltage-dependent anion channel and SR ryanodine receptor (RyR) in cardiomyocytes from aged hearts associated with altered Ca2+ handling. Age-dependent alterations in SR Ca2+ transfer to mitochondria and in Ca2+ handling could be reproduced in cardiomyoctes from young hearts after interorganelle disruption with colchicine, at concentrations that had no effect in aged cardiomyocytes or isolated mitochondria. Thus, defective SR–mitochondria communication underlies inefficient interorganelle Ca2+ exchange that contributes to energy demand/supply mistmach and oxidative stress in the aged heart.
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Role of Mitofusin-2 in mitochondrial localization and calcium uptake in skeletal muscle. Cell Calcium 2014; 57:14-24. [PMID: 25477138 DOI: 10.1016/j.ceca.2014.11.002] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 11/04/2014] [Indexed: 12/21/2022]
Abstract
As muscle contraction requires ATP and Ca(2+), skeletal muscle function is highly dependent on communication between two major intracellular organelles: mitochondria and sarcoplasmic reticulum (SR). In adult skeletal muscle, mitochondria located within the I-band of the sarcomere are connected to the SR by small ∼10 nm electron dense tethers that bridge the outer mitochondrial membrane to the region of SR that is ∼130 nm from the site of Ca(2+) release. However, the molecular composition of tethers and their precise impact on mitochondrial Ca(2+) uptake in skeletal muscle is unclear. Mitofusin-2 (Mfn2) is a transmembrane GTPase present in both mitochondria and ER/SR membranes that forms trans-dimers and participates in mitochondrial fusion. Here we evaluated the role Mfn2 plays in mitochondrial morphology, localization, and functional SR-mitochondrial Ca(2+) crosstalk in adult skeletal muscle. Compared to a non-targeting (CTRL) siRNA, in vivo electroporation of 400 nM Mfn2 siRNA (Mfn2 KD) into mouse footpads resulted in a marked acute reduction (67±3%) in Mfn2 protein levels in flexor digitorum brevis (FDB) muscles that occurred without a change in other key Ca(2+) regulatory proteins. Electron microscopy analyses revealed that Mfn2 knockdown resulted in a change in mitochondria morphology and mis-localization of some mitochondria from the I-band to the A-band region of the sarcomere. To assess the role of Mfn2 in SR-mitochondrial crosstalk, we measured mitochondrial Ca(2+) uptake and myoplasmic Ca(2+) transients with rhod-2 and mag-fluo-4, respectively, during repetitive high frequency tetanic stimulation (5×100 Hz tetani, 500 ms/tetani, 0.2 duty cycle) in CTRL and Mfn2 KD fibers. Mitochondrial Ca(2+) uptake during repetitive tetanic stimulation was significantly reduced (40%) in Mfn2 KD FDB fibers, which was accompanied by a parallel elevation in the global electrically evoked myoplasmic Ca(2+) transient. Mfn2 KD also resulted in a reduction of the mitochondrial membrane potential, which contributed to the observed decrease in activity-dependent mitochondrial Ca(2+) uptake. Consistent with this idea, a similar decrease in mitochondrial Ca(2+) uptake was also observed in wild type fibers following a comparable reduction in mitochondrial membrane potential induced by acute exposure to a low concentration (50 nM) of carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP). In addition, both global and mitochondrial Ca(2+) transients during repetitive tetanic stimulation were similarly reduced by both slow (EGTA) and fast (BAPTA) Ca(2+) chelating agents. Together, these results indicate that Mfn2 promotes proper mitochondrial morphology, localization, and membrane potential required for optimal activity-dependent mitochondrial Ca(2+) uptake and buffering of the global myoplasmic Ca(2+) transient in adult skeletal muscle.
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Sanmartín CD, Paula-Lima AC, García A, Barattini P, Hartel S, Núñez MT, Hidalgo C. Ryanodine receptor-mediated Ca(2+) release underlies iron-induced mitochondrial fission and stimulates mitochondrial Ca(2+) uptake in primary hippocampal neurons. Front Mol Neurosci 2014; 7:13. [PMID: 24653672 PMCID: PMC3949220 DOI: 10.3389/fnmol.2014.00013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 02/03/2014] [Indexed: 01/11/2023] Open
Abstract
Mounting evidence indicates that iron accumulation impairs brain function. We have reported previously that addition of sub-lethal concentrations of iron to primary hippocampal neurons produces Ca2+ signals and promotes cytoplasmic generation of reactive oxygen species. These Ca2+ signals, which emerge within seconds after iron addition, arise mostly from Ca2+ release through the redox-sensitive ryanodine receptor (RyR) channels present in the endoplasmic reticulum. We have reported also that addition of synaptotoxic amyloid-β oligomers to primary hippocampal neurons stimulates RyR-mediated Ca2+ release, generating long-lasting Ca2+ signals that activate Ca2+-sensitive cellular effectors and promote the disruption of the mitochondrial network. Here, we describe that 24 h incubation of primary hippocampal neurons with iron enhanced agonist-induced RyR-mediated Ca2+ release and promoted mitochondrial network fragmentation in 43% of neurons, a response significantly prevented by RyR inhibition and by the antioxidant agent N-acetyl-L-cysteine. Stimulation of RyR-mediated Ca2+ release by a RyR agonist promoted mitochondrial Ca2+ uptake in control neurons and in iron-treated neurons that displayed non-fragmented mitochondria, but not in neurons with fragmented mitochondria. Yet, the global cytoplasmic Ca2+ increase induced by the Ca2+ ionophore ionomycin prompted significant mitochondrial Ca2+ uptake in neurons with fragmented mitochondria, indicating that fragmentation did not prevent mitochondrial Ca2+ uptake but presumably decreased the functional coupling between RyR-mediated Ca2+ release and the mitochondrial Ca2+ uniporter. Taken together, our results indicate that stimulation of redox-sensitive RyR-mediated Ca2+ release by iron causes significant neuronal mitochondrial fragmentation, which presumably contributes to the impairment of neuronal function produced by iron accumulation.
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Affiliation(s)
- Carol D Sanmartín
- Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile Santiago, Chile ; Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile Santiago, Chile
| | - Andrea C Paula-Lima
- Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile Santiago, Chile ; Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile Santiago, Chile ; Institute for Research in Dental Sciences, Faculty of Dentistry, Universidad de Chile Santiago, Chile
| | - Alejandra García
- Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile Santiago, Chile
| | - Pablo Barattini
- Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile Santiago, Chile
| | - Steffen Hartel
- Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile Santiago, Chile ; Laboratory of Scientific Image Processing, Anatomy and Developmental Biology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile Santiago, Chile
| | - Marco T Núñez
- Department of Biology, Faculty of Sciences and Research Ring on Oxidative Stress in the Nervous System, Universidad de Chile Santiago, Chile
| | - Cecilia Hidalgo
- Center for Molecular Studies of the Cell, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile Santiago, Chile ; Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile Santiago, Chile ; Physiology and Biophysics Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile Santiago, Chile
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McCarron JG, Olson ML, Wilson C, Sandison ME, Chalmers S. Examining the role of mitochondria in Ca²⁺ signaling in native vascular smooth muscle. Microcirculation 2013; 20:317-29. [PMID: 23305516 PMCID: PMC3708117 DOI: 10.1111/micc.12039] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 01/07/2013] [Indexed: 01/18/2023]
Abstract
Mitochondrial Ca2+ uptake contributes important feedback controls to limit the time course of Ca2+signals. Mitochondria regulate cytosolic [Ca2+] over an exceptional breath of concentrations (∼200 nM to >10 μM) to provide a wide dynamic range in the control of Ca2+ signals. Ca2+ uptake is achieved by passing the ion down the electrochemical gradient, across the inner mitochondria membrane, which itself arises from the export of protons. The proton export process is efficient and on average there are less than three protons free within the mitochondrial matrix. To study mitochondrial function, the most common approaches are to alter the proton gradient and to measure the electrochemical gradient. However, drugs which alter the mitochondrial proton gradient may have substantial off target effects that necessitate careful consideration when interpreting their effect on Ca2+ signals. Measurement of the mitochondrial electrochemical gradient is most often performed using membrane potential sensitive fluorophores. However, the signals arising from these fluorophores have a complex relationship with the electrochemical gradient and are altered by changes in plasma membrane potential. Care is again needed in interpreting results. This review provides a brief description of some of the methods commonly used to alter and measure mitochondrial contribution to Ca2+ signaling in native smooth muscle.
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Affiliation(s)
- John G McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK.
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56
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Okada H, Lai NC, Kawaraguchi Y, Liao P, Copps J, Sugano Y, Okada-Maeda S, Banerjee I, Schilling JM, Gingras AR, Asfaw EK, Suarez J, Kang SM, Perkins GA, Au CG, Israeli-Rosenberg S, Manso AM, Liu Z, Milner DJ, Kaufman SJ, Patel HH, Roth DM, Hammond HK, Taylor SS, Dillmann WH, Goldhaber JI, Ross RS. Integrins protect cardiomyocytes from ischemia/reperfusion injury. J Clin Invest 2013; 123:4294-308. [PMID: 24091324 DOI: 10.1172/jci64216] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Accepted: 07/18/2013] [Indexed: 11/17/2022] Open
Abstract
Ischemic damage is recognized to cause cardiomyocyte (CM) death and myocardial dysfunction, but the role of cell-matrix interactions and integrins in this process has not been extensively studied. Expression of α7β1D integrin, the dominant integrin in normal adult CMs, increases during ischemia/reperfusion (I/R), while deficiency of β1 integrins increases ischemic damage. We hypothesized that the forced overexpression of integrins on the CM would offer protection from I/R injury. Tg mice with CM-specific overexpression of integrin α7β1D exposed to I/R had a substantial reduction in infarct size compared with that of α5β1D-overexpressing mice and WT littermate controls. Using isolated CMs, we found that α7β1D preserved mitochondrial membrane potential during hypoxia/reoxygenation (H/R) injury via inhibition of mitochondrial Ca2+ overload but did not alter H/R effects on oxidative stress. Therefore, we assessed Ca2+ handling proteins in the CM and found that β1D integrin colocalized with ryanodine receptor 2 (RyR2) in CM T-tubules, complexed with RyR2 in human and rat heart, and specifically bound to RyR2 amino acids 165-175. Integrins stabilized the RyR2 interdomain interaction, and this stabilization required integrin receptor binding to its ECM ligand. These data suggest that α7β1D integrin modifies Ca2+ regulatory pathways and offers a means to protect the myocardium from ischemic injury.
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57
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Cooper LL, Li W, Lu Y, Centracchio J, Terentyeva R, Koren G, Terentyev D. Redox modification of ryanodine receptors by mitochondria-derived reactive oxygen species contributes to aberrant Ca2+ handling in ageing rabbit hearts. J Physiol 2013; 591:5895-911. [PMID: 24042501 DOI: 10.1113/jphysiol.2013.260521] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Ageing is associated with a blunted response to sympathetic stimulation and an increased risk of arrhythmia and sudden cardiac death. Aberrant calcium (Ca(2+)) handling is an important contributor to the electrical and contractile dysfunction associated with ageing. Yet, the specific molecular mechanisms underlying abnormal Ca(2+) handling in ageing heart remain poorly understood. In this study, we used ventricular myocytes isolated from young (5-9 months) and old (4-6 years) rabbit hearts to test the hypothesis that changes in Ca(2+) homeostasis are caused by post-translational modification of ryanodine receptors (RyRs) by mitochondria-derived reactive oxygen species (ROS) generated in the ageing heart. Changes in parameters of Ca(2+) handling were determined by measuring cytosolic and intra-sarcoplasmic reticulum (SR) Ca(2+) dynamics in intact and permeabilized ventricular myocytes using confocal microscopy. We also measured age-related changes in ROS production and mitochondria membrane potential using a ROS-sensitive dye and a mitochondrial voltage-sensitive fluorescent indicator, respectively. In permeablized myocytes, ageing did not change SERCA activity and spark frequency but decreased spark amplitude and SR Ca(2+) load suggesting increased RyR activity. Treatment with the antioxidant dithiothreitol reduced RyR-mediated SR Ca(2+) leak in permeabilized myocytes from old rabbit hearts to the level comparable to young. Moreover, myocytes from old rabbits had more depolarized mitochondria membrane potential and increased rate of ROS production. Under β-adrenergic stimulation, Ca(2+) transient amplitude, SR Ca(2+) load, and latency of pro-arrhythmic spontaneous Ca(2+) waves (SCWs) were decreased while RyR-mediated SR Ca(2+) leak was increased in cardiomyocytes from old rabbits. Additionally, with β-adrenergic stimulation, scavenging of mitochondrial ROS in myocytes from old rabbit hearts restored redox status of RyRs, which reduced SR Ca(2+) leak, ablated most SCWs, and increased latency to levels comparable to young. These data indicate that an age-associated increase of ROS production by mitochondria leads to the thiol-oxidation of RyRs, which underlies the hyperactivity of RyRs and thereby shortened refractoriness of Ca(2+) release in cardiomyocytes from the ageing heart. This mechanism probably plays an important role in the increased incidence of arrhythmia and sudden death in the ageing population.
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Affiliation(s)
- Leroy L Cooper
- D. Terentyev: Cardiovascular Research Center, Rhode Island Hospital, Brown University School of Medicine, 1 Hoppin Street, West Coro-5, Providence, RI 02903, USA.
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58
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Eisner V, Csordás G, Hajnóczky G. Interactions between sarco-endoplasmic reticulum and mitochondria in cardiac and skeletal muscle - pivotal roles in Ca²⁺ and reactive oxygen species signaling. J Cell Sci 2013; 126:2965-78. [PMID: 23843617 DOI: 10.1242/jcs.093609] [Citation(s) in RCA: 156] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Mitochondria are strategically and dynamically positioned in the cell to spatially coordinate ATP production with energy needs and to allow the local exchange of material with other organelles. Interactions of mitochondria with the sarco-endoplasmic reticulum (SR/ER) have been receiving much attention owing to emerging evidence on the role these sites have in cell signaling, dynamics and biosynthetic pathways. One of the most important physiological and pathophysiological paradigms for SR/ER-mitochondria interactions is in cardiac and skeletal muscle. The contractile activity of these tissues has to be matched by mitochondrial ATP generation that is achieved, at least in part, by propagation of Ca(2+) signals from SR to mitochondria. However, the muscle has a highly ordered structure, providing only limited opportunity for mitochondrial dynamics and interorganellar interactions. This Commentary focuses on the latest advances in the structure, function and disease relevance of the communication between SR/ER and mitochondria in muscle. In particular, we discuss the recent demonstration of SR/ER-mitochondria tethers that are formed by multiple proteins, and local Ca(2+) transfer between SR/ER and mitochondria.
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Affiliation(s)
- Verónica Eisner
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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59
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Redpath CJ, Bou Khalil M, Drozdzal G, Radisic M, McBride HM. Mitochondrial hyperfusion during oxidative stress is coupled to a dysregulation in calcium handling within a C2C12 cell model. PLoS One 2013; 8:e69165. [PMID: 23861961 PMCID: PMC3704522 DOI: 10.1371/journal.pone.0069165] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 06/11/2013] [Indexed: 01/04/2023] Open
Abstract
Atrial Fibrillation is the most common sustained cardiac arrhythmia worldwide harming millions of people every year. Atrial Fibrillation (AF) abruptly induces rapid conduction between atrial myocytes which is associated with oxidative stress and abnormal calcium handling. Unfortunately this new equilibrium promotes perpetuation of the arrhythmia. Recently, in addition to being the major source of oxidative stress within cells, mitochondria have been observed to fuse, forming mitochondrial networks and attach to intracellular calcium stores in response to cellular stress. We sought to identify a potential role for rapid stimulation, oxidative stress and mitochondrial hyperfusion in acute changes to myocyte calcium handling. In addition we hoped to link altered calcium handling to increased sarcoplasmic reticulum (SR)-mitochondrial contacts, the so-called mitochondrial associated membrane (MAM). We selected the C2C12 murine myotube model as it has previously been successfully used to investigate mitochondrial dynamics and has a myofibrillar system similar to atrial myocytes. We observed that rapid stimulation of C2C12 cells resulted in mitochondrial hyperfusion and increased mitochondrial colocalisation with calcium stores. Inhibition of mitochondrial fission by transfection of mutant DRP1K38E resulted in similar effects on mitochondrial fusion, SR colocalisation and altered calcium handling. Interestingly the effects of 'forced fusion' were reversed by co-incubation with the reducing agent N-Acetyl cysteine (NAC). Subsequently we demonstrated that oxidative stress resulted in similar reversible increases in mitochondrial fusion, SR-colocalisation and altered calcium handling. Finally, we believe we have identified that myocyte calcium handling is reliant on baseline levels of reactive oxygen species as co-incubation with NAC both reversed and retarded myocyte response to caffeine induced calcium release and re-uptake. Based on these results we conclude that the coordinate regulation of mitochondrial fusion and MAM contacts may form a point source for stress-induced arrhythmogenesis. We believe that the MAM merits further investigation as a therapeutic target in AF-induced remodelling.
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Affiliation(s)
- Calum J Redpath
- Cellular Electrophysiology Laboratory, University of Ottawa Heart Institute, University of Ottawa, Ottawa, ON, Canada.
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60
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Louch WE, Stokke MK, Sjaastad I, Christensen G, Sejersted OM. No rest for the weary: diastolic calcium homeostasis in the normal and failing myocardium. Physiology (Bethesda) 2013; 27:308-23. [PMID: 23026754 DOI: 10.1152/physiol.00021.2012] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Following contraction of the heart, efficient relaxation (diastole) is essential for refilling the ventricles with blood. This review describes how ventricular relaxation is controlled by Ca(2+) homeostasis in cardiac muscle cells and how alterations in Ca(2+) cycling affect diastolic function in the normal and failing heart. These discussions illustrate that the diastolic phase is not simply a period of rest but rather involves highly regulated and dynamic Ca(2+) fluxes.
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Affiliation(s)
- William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.
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61
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62
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Patron M, Raffaello A, Granatiero V, Tosatto A, Merli G, De Stefani D, Wright L, Pallafacchina G, Terrin A, Mammucari C, Rizzuto R. The mitochondrial calcium uniporter (MCU): molecular identity and physiological roles. J Biol Chem 2013; 288:10750-8. [PMID: 23400777 DOI: 10.1074/jbc.r112.420752] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The direct measurement of mitochondrial [Ca(2+)] with highly specific probes demonstrated that major swings in organellar [Ca(2+)] parallel the changes occurring in the cytosol and regulate processes as diverse as aerobic metabolism and cell death by necrosis and apoptosis. Despite great biological relevance, insight was limited by the complete lack of molecular understanding. The situation has changed, and new perspectives have emerged following the very recent identification of the mitochondrial Ca(2+) uniporter, the channel allowing rapid Ca(2+) accumulation across the inner mitochondrial membrane.
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Affiliation(s)
- Maria Patron
- Department of Biomedical Sciences, University of Padua and the Institute of Neuroscience, Consiglio Nazionale delle Ricerche, 35131 Padua, Italy
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63
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Dorn GW, Maack C. SR and mitochondria: Calcium cross-talk between kissing cousins. J Mol Cell Cardiol 2013; 55:42-9. [DOI: 10.1016/j.yjmcc.2012.07.015] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 07/19/2012] [Accepted: 07/25/2012] [Indexed: 01/13/2023]
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64
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Shahzad T, Kasseckert SA, Iraqi W, Johnson V, Schulz R, Schlüter KD, Dörr O, Parahuleva M, Hamm C, Ladilov Y, Abdallah Y. Mechanisms involved in postconditioning protection of cardiomyocytes against acute reperfusion injury. J Mol Cell Cardiol 2013; 58:209-16. [PMID: 23328483 DOI: 10.1016/j.yjmcc.2013.01.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Revised: 12/26/2012] [Accepted: 01/07/2013] [Indexed: 12/12/2022]
Abstract
Experimental and clinical studies demonstrated that postconditioning confers protection against myocardial ischemia/reperfusion injury. However the underlying cellular mechanisms responsible for the beneficial effect of postconditioning are still poorly understood. The aim of the present study was to examine the role of cytosolic and mitochondrial Ca(2+)-handling. For this purpose adult rat cardiomyocytes were subjected to simulated in vitro ischemia (glucose-free hypoxia at pH6.4) followed by simulated reperfusion with a normoxic buffer (pH7.4; 2.5 mmol/L glucose). Postconditioning, i.e., 2 repetitive cycles of normoxic (5s) and hypoxic (2.5 min) superfusion, was applied during the first 5 min of reoxygenation. Mitochondrial membrane potential (ΔΨm), cytosolic and mitochondrial Ca(2+) concentrations, cytosolic pH and necrosis were analysed applying JC-1, fura-2, fura-2/manganese, BCECF and propidium iodide, respectively. Mitochondrial permeability transition pore (MPTP) opening was detected by calcein release. Hypoxic treatment led to a reduction of ΔΨm, an increase in cytosolic and mitochondrial Ca(2+) concentration, and acidification of cardiomyocytes. During the first minutes of reoxygenation, ΔΨm transiently recovered, but irreversibly collapsed after 7 min of reoxygenation, which was accompanied by MPTP opening. Simultaneously, mitochondrial Ca(2+) increased during reperfusion and cardiomyocytes developed spontaneous cytosolic Ca(2+) oscillations and severe contracture followed by necrosis after 25 min of reoxygenation. In postconditioned cells, the collapse in ΔΨm as well as the leak of calcein, the increase in mitochondrial Ca(2+), cytosolic Ca(2+) oscillations, contracture and necrosis were significantly reduced. Furthermore postconditioning delayed cardiomyocyte pH recovery. Postconditioning by hypoxia/reoxygenation was as protective as treatment with cyclosporine A. Combining cyclosporine A and postconditioning had no additive effect. The data of the present study demonstrate that postconditioning by hypoxia/reoxygenation prevents reperfusion injury by limiting mitochondrial Ca(2+) load and thus opening of the MPTP in isolated cardiomyocytes. These effects seem to be supported by postconditioning-induced delay in pH recovery and suppression of Ca(2+) oscillations.
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Affiliation(s)
- Tayyab Shahzad
- Department of Cardiology and Angiology, University Hospital Giessen and Marburg Klinikstr. 33, 35392 Giessen, Germany
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65
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Dedkova EN, Blatter LA. Calcium signaling in cardiac mitochondria. J Mol Cell Cardiol 2013; 58:125-33. [PMID: 23306007 DOI: 10.1016/j.yjmcc.2012.12.021] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 12/01/2012] [Accepted: 12/28/2012] [Indexed: 01/02/2023]
Abstract
Mitochondrial Ca signaling contributes to the regulation of cellular energy metabolism, and mitochondria participate in cardiac excitation-contraction coupling (ECC) through their ability to store Ca, shape the cytosolic Ca signals and generate ATP required for contraction. The mitochondrial inner membrane is equipped with an elaborate system of channels and transporters for Ca uptake and extrusion that allows for the decoding of cytosolic Ca signals, and the storage of Ca in the mitochondrial matrix compartment. Controversy, however remains whether the fast cytosolic Ca transients underlying ECC in the beating heart are transmitted rapidly into the matrix compartment or slowly integrated by the mitochondrial Ca transport machinery. This review summarizes established and novel findings on cardiac mitochondrial Ca transport and buffering, and discusses the evidence either supporting or arguing against the idea that Ca can be taken up rapidly by mitochondria during ECC.
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Affiliation(s)
- Elena N Dedkova
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL 60612, USA
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Lu X, Ginsburg KS, Kettlewell S, Bossuyt J, Smith GL, Bers DM. Measuring local gradients of intramitochondrial [Ca(2+)] in cardiac myocytes during sarcoplasmic reticulum Ca(2+) release. Circ Res 2012; 112:424-31. [PMID: 23243207 DOI: 10.1161/circresaha.111.300501] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
RATIONALE Mitochondrial [Ca(2+)] ([Ca(2+)](mito)) regulates mitochondrial energy production, provides transient Ca(2+) buffering under stress, and can be involved in cell death. Mitochondria are near the sarcoplasmic reticulum (SR) in cardiac myocytes, and evidence for crosstalk exists. However, quantitative measurements of [Ca(2+)](mito) are limited, and spatial [Ca(2+)](mito) gradients have not been directly measured. OBJECTIVE To directly measure local [Ca(2+)](mito) during normal SR Ca release in intact myocytes, and evaluate potential subsarcomeric spatial [Ca(2+)](mito) gradients. METHODS AND RESULTS Using the mitochondrially targeted inverse pericam indicator Mitycam, calibrated in situ, we directly measured [Ca(2+)](mito) during SR Ca(2+) release in intact rabbit ventricular myocytes by confocal microscopy. During steady state pacing, Δ[Ca(2+)](mito) amplitude was 29±3 nmol/L, rising rapidly (similar to cytosolic free [Ca(2+)]) but declining much more slowly. Taking advantage of the structural periodicity of cardiac sarcomeres, we found that [Ca(2+)](mito) near SR Ca(2+) release sites (Z-line) versus mid-sarcomere (M-line) reached a high peak amplitude (37±4 versus 26±4 nmol/L, respectively P<0.05) which occurred earlier in time. This difference was attributed to ends of mitochondria being physically closer to SR Ca(2+) release sites, because the mitochondrial Ca(2+) uniporter was homogeneously distributed, and elevated [Ca(2+)] applied laterally did not produce longitudinal [Ca(2+)](mito) gradients. CONCLUSIONS We developed methods to measure spatiotemporal [Ca(2+)](mito) gradients quantitatively during excitation-contraction coupling. The amplitude and kinetics of [Ca(2+)](mito) transients differ significantly from those in the cytosol and are respectively higher and faster near the Z-line versus M-line. This approach will help clarify SR-mitochondrial Ca(2+) signaling.
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Affiliation(s)
- Xiyuan Lu
- Department of Pharmacology, University of California, Davis, CA 95616, USA
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67
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GTPase of the immune-associated nucleotide-binding protein 5 (GIMAP5) regulates calcium influx in T-lymphocytes by promoting mitochondrial calcium accumulation. Biochem J 2012; 449:353-64. [DOI: 10.1042/bj20120516] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mature T-lymphocytes undergo spontaneous apoptosis in the biobreeding diabetes-prone strain of rats due to the loss of the functional GIMAP5 (GTPase of the immune-associated nucleotide-binding protein 5) protein. The mechanisms underlying the pro-survival function of GIMAP5 in T-cells have not yet been elucidated. We have previously shown that GIMAP5 deficiency in T-cells impairs Ca2+ entry via plasma membrane channels following exposure to thapsigargin or stimulation of the T-cell antigen receptor. In the present study we report that this reduced Ca2+ influx in GIMAP5-deficient T-cells is associated with the inability of their mitochondria to sequester Ca2+ following capacitative entry, which is required for sustained Ca2+ influx via the plasma membrane channels. Consistent with a role for GIMAP5 in regulating mitochondrial Ca2+, overexpression of GIMAP5 in HEK (human embryonic kidney)-293 cells resulted in increased Ca2+ accumulation within the mitochondria. Disruption of microtubules, but not the actin cytoskeleton, abrogated mitochondrial Ca2+ sequestration in primary rat T-cells, whereas both microtubules and actin cytoskeleton were needed for the GIMAP5-mediated increase in mitochondrial Ca2+ in HEK-293 cells. Moreover, GIMAP5 showed partial colocalization with tubulin in HEK-293 cells. On the basis of these findings, we propose that the pro-survival function of GIMAP5 in T-lymphocytes may be linked to its requirement to facilitate microtubule-dependent mitochondrial buffering of Ca2+ following capacitative entry.
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68
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Coupling of ryanodine receptor 2 and voltage-dependent anion channel 2 is essential for Ca2+ transfer from the sarcoplasmic reticulum to the mitochondria in the heart. Biochem J 2012; 447:371-9. [DOI: 10.1042/bj20120705] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The structural proximity and functional coupling between the SR (sarcoplasmic reticulum) and mitochondria have been suggested to occur in the heart. However, the molecular architecture involved in the SR–mitochondrial coupling remains unclear. In the present study, we performed various genetic and Ca2+-probing studies to resolve the proteins involved in the coupling process. By using the bacterial 2-hybrid, glutathione transferase pull-down, co-immunoprecipitation and immunocytochemistry assays, we found that RyR2 (ryanodine receptor type 2), which is physically associated with VDAC2 (voltage-dependent anion channel 2), was co-localized in SR–mitochondrial junctions. Furthermore, a fractionation study revealed that VDAC2 was co-localized with RyR2 only in the subsarcolemmal region. VDAC2 knockdown by targeted short hairpin RNA led to an increased diastolic [Ca2+] (calcium concentration) and abolishment of mitochondrial Ca2+ uptake. Collectively, the present study suggests that the coupling of VDAC2 with RyR2 is essential for Ca2+ transfer from the SR to mitochondria in the heart.
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69
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Hartman WR, Smelter DF, Sathish V, Karass M, Kim S, Aravamudan B, Thompson MA, Amrani Y, Pandya HC, Martin RJ, Prakash YS, Pabelick CM. Oxygen dose responsiveness of human fetal airway smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2012; 303:L711-9. [PMID: 22923637 DOI: 10.1152/ajplung.00037.2012] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Maintenance of blood oxygen saturation dictates supplemental oxygen administration to premature infants, but hyperoxia predisposes survivors to respiratory diseases such as asthma. Although much research has focused on oxygen effects on alveoli in the setting of bronchopulmonary dysplasia, the mechanisms by which oxygen affects airway structure or function relevant to asthma are still under investigation. We used isolated human fetal airway smooth muscle (fASM) cells from 18-20 postconceptual age lungs (canalicular stage) to examine oxygen effects on intracellular Ca(2+) ([Ca(2+)](i)) and cellular proliferation. fASM cells expressed substantial smooth muscle actin and myosin and several Ca(2+) regulatory proteins but not fibroblast or epithelial markers, profiles qualitatively comparable to adult human ASM. Fluorescence Ca(2+) imaging showed robust [Ca(2+)](i) responses to 1 μM acetylcholine (ACh) and 10 μM histamine (albeit smaller and slower than adult ASM), partly sensitive to zero extracellular Ca(2+). Compared with adult, fASM showed greater baseline proliferation. Based on this validation, we assessed fASM responses to 10% hypoxia through 90% hyperoxia and found enhanced proliferation at <60% oxygen but increased apoptosis at >60%, effects accompanied by appropriate changes in proliferative vs. apoptotic markers and enhanced mitochondrial fission at >60% oxygen. [Ca(2+)](i) responses to ACh were enhanced for <60% but blunted at >60% oxygen. These results suggest that hyperoxia has dose-dependent effects on structure and function of developing ASM, which could have consequences for airway diseases of childhood. Thus detrimental effects on ASM should be an additional consideration in assessing risks of supplemental oxygen in prematurity.
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70
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Abstract
During the past two decades calcium (Ca(2+)) accumulation in energized mitochondria has emerged as a biological process of utmost physiological relevance. Mitochondrial Ca(2+) uptake was shown to control intracellular Ca(2+) signalling, cell metabolism, cell survival and other cell-type specific functions by buffering cytosolic Ca(2+) levels and regulating mitochondrial effectors. Recently, the identity of mitochondrial Ca(2+) transporters has been revealed, opening new perspectives for investigation and molecular intervention.
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71
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George CH, Parthimos D, Silvester NC. A network-oriented perspective on cardiac calcium signaling. Am J Physiol Cell Physiol 2012; 303:C897-910. [PMID: 22843795 DOI: 10.1152/ajpcell.00388.2011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The normal contractile, electrical, and energetic function of the heart depends on the synchronization of biological oscillators and signal integrators that make up cellular signaling networks. In this review we interpret experimental data from molecular, cellular, and transgenic models of cardiac signaling behavior in the context of established concepts in cell network architecture and organization. Focusing on the cellular Ca(2+) handling machinery, we describe how the plasticity and adaptability of normal Ca(2+) signaling is dependent on dynamic network configurations that operate across a wide range of functional states. We consider how (mal)adaptive changes in signaling pathways restrict the dynamic range of the network such that it cannot respond appropriately to physiologic stimuli or perturbation. Based on these concepts, a model is proposed in which pathologic abnormalities in cardiac rhythm and contractility (e.g., arrhythmias and heart failure) arise as a consequence of progressive desynchronization and reduction in the dynamic range of the Ca(2+) signaling network. We discuss how a systems-level understanding of the network organization, cellular noise, and chaotic behavior may inform the design of new therapeutic modalities that prevent or reverse the disease-linked unraveling of the Ca(2+) signaling network.
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Affiliation(s)
- Christopher H George
- Wales Heart Research Institute and Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff Univ., Heath Park, Cardiff, Wales, UK CF14 4XN.
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72
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Yi M, Weaver D, Eisner V, Várnai P, Hunyady L, Ma J, Csordás G, Hajnóczky G. Switch from ER-mitochondrial to SR-mitochondrial calcium coupling during muscle differentiation. Cell Calcium 2012; 52:355-65. [PMID: 22784666 DOI: 10.1016/j.ceca.2012.05.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 05/25/2012] [Accepted: 05/28/2012] [Indexed: 11/26/2022]
Abstract
Emerging evidence indicates that mitochondria are locally coupled to endoplasmic reticulum (ER) Ca2+ release in myoblasts and to sarcoplasmic reticulum (SR) Ca2+ release in differentiated muscle fibers in order to regulate cytoplasmic calcium dynamics and match metabolism with cell activity. However, the mechanism of the developmental transition from ER to SR coupling remains unclear. We have studied mitochondrial sensing of IP3 receptor (IP3R)- and ryanodine receptor (RyR)-mediated Ca2+ signals in H9c2 myoblasts and differentiating myotubes, as well as the attendant changes in mitochondrial morphology. Mitochondria in myoblasts were largely elongated, luminally connected and relatively few in number, whereas the myotubes were densely packed with globular mitochondria that displayed limited luminal continuity. Vasopressin, an IP3-linked agonist, evoked a large cytoplasmic Ca2+ ([Ca2+]c) increase in myoblasts, whereas it elicited a smaller response in myotubes. Conversely, RyR-mediated Ca2+ release induced by caffeine, was not observed in myoblasts, but triggered a large [Ca2+]c signal in myotubes. Both the IP3R and the RyR-mediated [Ca2+]c rise was closely associated with a mitochondrial matrix Ca2+ ([Ca2+]m) signal. Every myotube that showed a [Ca2+]c spike also displayed a [Ca2+]m response. Addition of IP3 to permeabilized myoblasts and caffeine to permeabilized myotubes also resulted in a rapid [Ca2+]m rise, indicating that Ca2+ was delivered via local coupling of the ER/SR and mitochondria. Thus, as RyRs are expressed during muscle differentiation, the local connection between RyR and mitochondrial Ca2+ uptake sites also appears. When RyR1 was exogenously introduced to myoblasts by overexpression, the [Ca2+]m signal appeared together with the [Ca2+]c signal, however the mitochondrial morphology remained unchanged. Thus, RyR expression alone is sufficient to induce the steps essential for their alignment with mitochondrial Ca2+ uptake sites, whereas the mitochondrial proliferation and reshaping utilize either downstream or alternative pathways.
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Affiliation(s)
- Muqing Yi
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
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73
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Chen Y, Csordás G, Jowdy C, Schneider TG, Csordás N, Wang W, Liu Y, Kohlhaas M, Meiser M, Bergem S, Nerbonne JM, Dorn GW, Maack C. Mitofusin 2-containing mitochondrial-reticular microdomains direct rapid cardiomyocyte bioenergetic responses via interorganelle Ca(2+) crosstalk. Circ Res 2012; 111:863-75. [PMID: 22777004 DOI: 10.1161/circresaha.112.266585] [Citation(s) in RCA: 271] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
RATIONALE Mitochondrial Ca(2+) uptake is essential for the bioenergetic feedback response through stimulation of Krebs cycle dehydrogenases. Close association of mitochondria to the sarcoplasmic reticulum (SR) may explain efficient mitochondrial Ca(2+) uptake despite low Ca(2+) affinity of the mitochondrial Ca(2+) uniporter. However, the existence of such mitochondrial Ca(2+) microdomains and their functional role are presently unresolved. Mitofusin (Mfn) 1 and 2 mediate mitochondrial outer membrane fusion, whereas Mfn2 but not Mfn1 tethers endoplasmic reticulum to mitochondria in noncardiac cells. OBJECTIVE To elucidate roles for Mfn1 and 2 in SR-mitochondrial tethering, Ca(2+) signaling, and bioenergetic regulation in cardiac myocytes. METHODS AND RESULTS Fruit fly heart tubes deficient of the Drosophila Mfn ortholog MARF had increased contraction-associated and caffeine-sensitive Ca(2+) release, suggesting a role for Mfn in SR Ca(2+) handling. Whereas cardiac-specific Mfn1 ablation had no effects on murine heart function or Ca(2+) cycling, Mfn2 deficiency decreased cardiomyocyte SR-mitochondrial contact length by 30% and reduced the content of SR-associated proteins in mitochondria-associated membranes. This was associated with decreased mitochondrial Ca(2+) uptake (despite unchanged mitochondrial membrane potential) but increased steady-state and caffeine-induced SR Ca(2+) release. Accordingly, Ca(2+)-induced stimulation of Krebs cycle dehydrogenases during β-adrenergic stimulation was hampered in Mfn2-KO but not Mfn1-KO myocytes, evidenced by oxidation of the redox states of NAD(P)H/NAD(P)(+) and FADH(2)/FAD. CONCLUSIONS Physical tethering of SR and mitochondria via Mfn2 is essential for normal interorganelle Ca(2+) signaling in the myocardium, consistent with a requirement for SR-mitochondrial Ca(2+) signaling through microdomains in the cardiomyocyte bioenergetic feedback response to physiological stress.
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Affiliation(s)
- Yun Chen
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St Louis, MO 63110, USA
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74
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Abstract
Mitochondria may function as multiple separate organelles or as a single electrically coupled continuum to modulate changes in [Ca2+]c (cytoplasmic Ca2+ concentration) in various cell types. Mitochondria may also be tethered to the internal Ca2+ store or plasma membrane in particular parts of cells to facilitate the organelles modulation of local and global [Ca2+]c increases. Differences in the organization and positioning contributes significantly to the at times apparently contradictory reports on the way mitochondria modulate [Ca2+]c signals. In the present paper, we review the organization of mitochondria and the organelles role in Ca2+ signalling.
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75
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Csordás G, Várnai P, Golenár T, Sheu SS, Hajnóczky G. Calcium transport across the inner mitochondrial membrane: molecular mechanisms and pharmacology. Mol Cell Endocrinol 2012; 353:109-13. [PMID: 22123069 PMCID: PMC3295916 DOI: 10.1016/j.mce.2011.11.011] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 11/10/2011] [Accepted: 11/10/2011] [Indexed: 01/21/2023]
Abstract
Growing evidence supports that mitochondrial calcium uptake is important for cell metabolism, signaling and survival. However, both the molecular nature of the mitochondrial Ca(2+) transport sites and the calcium signals they respond to remained elusive. Recent RNA interference studies have identified new candidate proteins for Ca(2+) transport across the inner mitochondrial membrane, including LETM1, MCU, MICU1 and NCLX. The sensitivity of these factors to several drugs has been tested and in parallel, some new inhibitors of mitochondrial Ca(2+) uptake have been described. This paper provides an update on the pharmacological aspects of the molecular mechanisms of the inner mitochondrial membrane Ca(2+) transport.
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Affiliation(s)
- György Csordás
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
| | - Peter Várnai
- Department of Physiology, Semmelweis University Budapest, Hungary
| | - Tünde Golenár
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
| | - Shey-Shing Sheu
- Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107
| | - György Hajnóczky
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
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76
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Abdallah Y, Kasseckert SA, Iraqi W, Said M, Shahzad T, Erdogan A, Neuhof C, Gündüz D, Schlüter KD, Tillmanns H, Piper HM, Reusch HP, Ladilov Y. Interplay between Ca2+ cycling and mitochondrial permeability transition pores promotes reperfusion-induced injury of cardiac myocytes. J Cell Mol Med 2012; 15:2478-85. [PMID: 21199327 PMCID: PMC3822958 DOI: 10.1111/j.1582-4934.2010.01249.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Uncontrolled release of Ca2+ from the sarcoplasmic reticulum (SR) contributes to the reperfusion-induced cardiomyocyte injury, e.g. hypercontracture and necrosis. To find out the underlying cellular mechanisms of this phenomenon, we investigated whether the opening of mitochondrial permeability transition pores (MPTP), resulting in ATP depletion and reactive oxygen species (ROS) formation, may be involved. For this purpose, isolated cardiac myocytes from adult rats were subjected to simulated ischemia and reperfusion. MPTP opening was detected by calcein release and by monitoring the ΔΨm. Fura-2 was used to monitor cytosolic [Ca2+]i or mitochondrial calcium [Ca2+]m, after quenching the cytosolic compartment with MnCl2. Mitochondrial ROS [ROS]m production was detected with MitoSOX Red and mag-fura-2 was used to monitor Mg2+ concentration, which reflects changes in cellular ATP. Necrosis was determined by propidium iodide staining. Reperfusion led to a calcein release from mitochondria, ΔΨm collapse and disturbance of ATP recovery. Simultaneously, Ca2+ oscillations occurred, [Ca2+]m and [ROS]m increased, cells developed hypercontracture and underwent necrosis. Inhibition of the SR-driven Ca2+ cycling with thapsigargine or ryanodine prevented mitochondrial dysfunction, ROS formation and MPTP opening. Suppression of the mitochondrial Ca2+ uptake (Ru360) or MPTP (cyclosporine A) significantly attenuated Ca2+ cycling, hypercontracture and necrosis. ROS scavengers (2-mercaptopropionyl glycine or N-acetylcysteine) had no effect on these parameters, but reduced [ROS]m. In conclusion, MPTP opening occurs early during reperfusion and is due to the Ca2+ oscillations originating primarily from the SR and supported by MPTP. The interplay between Ca2+ cycling and MPTP promotes the reperfusion-induced cardiomyocyte hypercontracture and necrosis. Mitochondrial ROS formation is a result rather than a cause of MPTP opening.
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Affiliation(s)
- Yaser Abdallah
- Institute of Physiology, Justus Liebig University, Giessen, Germany
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77
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Kiviluoto S, Akl H, Vervliet T, Bultynck G, Parys JB, Missiaen L, De Smedt H. IP3 receptor-binding partners in cell-death mechanisms. ACTA ACUST UNITED AC 2012. [DOI: 10.1002/wmts.5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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78
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Mitochondrial involvement in carbachol-induced intracellular Ca2+ mobilization and contraction in rat gastric smooth muscle. Life Sci 2011; 89:757-64. [DOI: 10.1016/j.lfs.2011.08.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 06/27/2011] [Accepted: 07/27/2011] [Indexed: 11/22/2022]
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79
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Chen M, Wang Y, Hou T, Zhang H, Qu A, Wang X. Differential mitochondrial calcium responses in different cell types detected with a mitochondrial calcium fluorescent indicator, mito-GCaMP2. Acta Biochim Biophys Sin (Shanghai) 2011; 43:822-30. [PMID: 21880604 DOI: 10.1093/abbs/gmr075] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mitochondrial calcium plays a crucial role in mitochondrial metabolism, cell calcium handling, and cell death. However, some mechanisms concerning mitochondrial calcium regulation are still unknown, especially how mitochondrial calcium couples with cytosolic calcium. In this work, we constructed a novel mitochondrial calcium fluorescent indicator (mito-GCaMP2) by genetic manipulation. Mito-GCaMP2 was imported into mitochondria with high efficiency and the fluorescent signals co-localized with that of tetramethyl rhodamine methyl ester, a mitochondrial membrane potential indicator. The mitochondrial inhibitors specifically decreased the signals of mito-GCaMP2. The apparent K(d) of mito-GCaMP2 was 195.0 nmol/L at pH 8.0 in adult rat cardiomyocytes. Furthermore, we observed that mito-GCaMP2 preferred the alkaline pH surrounding of mitochondria. In HeLa cells, we found that mitochondrial calcium ([Ca(2+)](mito)) responded to the changes of cytosolic calcium ([Ca(2+)](cyto)) induced by histamine or thapasigargin. Moreover, external Ca(2+) (100 μmol/L) directly induced an increase of [Ca(2+)](mito) in permeabilized HeLa cells. However, in rat cardiomyocytes [Ca(2+)](mito) did not respond to cytosolic calcium transients stimulated by electric pacing or caffeine. In permeabilized cardiomyocytes, 600 nmol/L free Ca(2+) repeatedly increased the fluorescent signals of mito-GCaMP2, which excluded the possibility that mito-GCaMP2 lost its function in cardiomyocytes mitochondria. These results showed that the response of mitochondrial calcium is diverse in different cell lineages and suggested that mitochondria in cardiomyocytes may have a special defense mechanism to control calcium flux.
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Affiliation(s)
- Min Chen
- Yunnan Center for Disease Prevention and Control, Kunming, China.
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80
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Passive Ca2+ overload in H9c2 cardiac myoblasts: Assessment of cellular damage and cytosolic Ca2+ transients. Arch Biochem Biophys 2011; 512:175-82. [DOI: 10.1016/j.abb.2011.05.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 05/24/2011] [Accepted: 05/25/2011] [Indexed: 12/20/2022]
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81
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Hashitani H, Hashiatni H, Lang RJ, Suzuki H. Role of perinuclear mitochondria in the spatiotemporal dynamics of spontaneous Ca2+ waves in interstitial cells of Cajal-like cells of the rabbit urethra. Br J Pharmacol 2011; 161:680-94. [PMID: 20880405 DOI: 10.1111/j.1476-5381.2010.00902.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Although spontaneous Ca(2+) waves in interstitial cells of Cajal (ICC)-like cells (ICC-LCs) primarily arise from endoplasmic reticulum (ER) Ca(2+) release, the interactions among mitochondrial Ca(2+) buffering, cellular energetics and ER Ca(2+) release in determining the spatiotemporal dynamics of intracellular Ca(2+) remain to be elucidated. EXPERIMENTAL APPROACH Spontaneous Ca(2+) transients in freshly isolated ICC-LCs of the rabbit urethra were visualized using fluo-4 Ca(2+) imaging, while the intracellular distribution of mitochondria was viewed with MitoTracker Red. KEY RESULTS Spontaneous Ca(2+) waves invariably originated from the perinuclear region where clusters of mitochondria surround the nucleus. Perinuclear Ca(2+) dynamics were characterized by a gradual rise in basal Ca(2+) that preceded each regenerative Ca(2+) transient. Caffeine evoked oscillatory Ca(2+) waves originating from anywhere within ICC-LCs. Ryanodine or cyclopiazonic acid prevented Ca(2+) wave generation with a rise in basal Ca(2+), and subsequent caffeine evoked a single rudimentary Ca(2+) transient. Inhibition of glycolysis with 2-deoxy-glucose or carbonyl cyanide 3-chlorophenylhydrazone, a mitochondrial protonophore, increased basal Ca(2+) and abolished Ca(2+) waves. However, caffeine still induced oscillatory Ca(2+) transients. Mitochondrial Ca(2+) uptake inhibition with RU360 attenuated Ca(2+) wave amplitudes, while mitochondrial Ca(2+) efflux inhibition with CGP37157 suppressed the initial Ca(2+) rise to reduce Ca(2+) wave frequency. CONCLUSIONS AND IMPLICATIONS Perinuclear mitochondria in ICC-LCs play a dominant role in the spatial regulation of Ca(2+) wave generation and may regulate ER Ca(2+) release frequency by buffering Ca(2+) within microdomains between both organelles. Glycolysis inhibition reduced mitochondrial Ca(2+) buffering without critically disrupting ER function. Perinuclear mitochondria may function as sensors of intracellular metabolites.
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Affiliation(s)
- Hikaru Hashitani
- Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
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82
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Dittami GM, Rajguru SM, Lasher RA, Hitchcock RW, Rabbitt RD. Intracellular calcium transients evoked by pulsed infrared radiation in neonatal cardiomyocytes. J Physiol 2011; 589:1295-306. [PMID: 21242257 DOI: 10.1113/jphysiol.2010.198804] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Neonatal rat ventricular cardiomyocytes were used to investigate mechanisms underlying transient changes in intracellular free Ca2+ concentration ([Ca2+]i) evoked by pulsed infrared radiation (IR, 1862 nm). Fluorescence confocal microscopy revealed IR-evoked [Ca2+]i events with each IR pulse (3-4 ms pulse⁻¹, 9.1-11.6 J cm⁻² pulse⁻¹). IR-evoked [Ca2+]i events were distinct from the relatively large spontaneous [Ca2+]i transients, with IR-evoked events exhibiting smaller amplitudes (0.88 ΔF/F0 vs. 1.99 ΔF/F0) and shorter time constants (τ =0.64 s vs. 1.19 s, respectively). Both IR-evoked [Ca2+]i events and spontaneous [Ca2+]i transients could be entrained by the IR pulse (0.2-1 pulse s⁻¹), provided the IR dose was sufficient and the radiation was applied directly to the cell. Examination of IR-evoked events during peak spontaneous [Ca2+]i periods revealed a rapid drop in [Ca2+]i, often restoring the baseline [Ca2+]i concentration, followed by a transient increase in [Ca2+]i.Cardiomyocytes were challenged with pharmacological agents to examine potential contributors to the IR-evoked [Ca2+]i events. Three compounds proved to be the most potent, reversible inhibitors: (1) CGP-37157 (20 μM, n =12), an inhibitor of the mitochondrial Na+/Ca2+ exchanger (mNCX), (2) Ruthenium Red (40 μM, n =13), an inhibitor of the mitochondrial Ca2+ uniporter (mCU), and (3) 2-aminoethoxydiphenylborane (10 μM, n =6), an IP3 channel antagonist. Ryanodine blocked the spontaneous [Ca2+]i transients but did not alter the IR-evoked events in the same cells. This pharmacological array implicates mitochondria as the major intracellular store of Ca2+ involved in IR-evoked responses reported here. Results support the hypothesis that 1862 nm pulsed IR modulates mitochondrial Ca2+ transport primarily through actions on mCU and mNCX.
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Affiliation(s)
- Gregory M Dittami
- Department of Bioengineering, University of Utah, Salt Lake City, UT 84112, USA.
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83
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Giulivi C, Ross-Inta C, Omanska-Klusek A, Napoli E, Sakaguchi D, Barrientos G, Allen PD, Pessah IN. Basal bioenergetic abnormalities in skeletal muscle from ryanodine receptor malignant hyperthermia-susceptible R163C knock-in mice. J Biol Chem 2011; 286:99-113. [PMID: 20978128 PMCID: PMC3013050 DOI: 10.1074/jbc.m110.153247] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Revised: 10/13/2010] [Indexed: 12/25/2022] Open
Abstract
Malignant hyperthermia (MH) and central core disease in humans have been associated with mutations in the skeletal ryanodine receptor (RyR1). Heterozygous mice expressing the human MH/central core disease RyR1 R163C mutation exhibit MH when exposed to halothane or heat stress. Considering that many MH symptoms resemble those that could ensue from a mitochondrial dysfunction (e.g. metabolic acidosis and hyperthermia) and that MH-susceptible mice or humans have a higher than normal cytoplasmic Ca(2+) concentration at rest, we evaluated the role of mitochondria in skeletal muscle from R163C compared with wild type mice under basal (untriggered) conditions. R163C skeletal muscle exhibited a significant increase in matrix Ca(2+), increased reactive oxygen species production, lower expression of mitochondrial proteins, and higher mtDNA copy number. These changes, in conjunction with lower myoglobin and glycogen contents, Myh4 and GAPDH transcript levels, GAPDH activity, and lower glucose utilization suggested a switch to a compromised bioenergetic state characterized by both low oxidative phosphorylation and glycolysis. The shift in bioenergetic state was accompanied by a dysregulation of Ca(2+)-responsive signaling pathways regulated by calcineurin and ERK1/2. Chronically elevated resting Ca(2+) in R163C skeletal muscle elicited the maintenance of a fast-twitch fiber program and the development of insulin resistance-like phenotype as part of a metabolic adaptation to the R163C RyR1 mutation.
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Affiliation(s)
- Cecilia Giulivi
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California 95616, USA.
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84
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Wersinger E, Fuchs PA. Modulation of hair cell efferents. Hear Res 2010; 279:1-12. [PMID: 21187136 DOI: 10.1016/j.heares.2010.12.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Revised: 12/10/2010] [Accepted: 12/20/2010] [Indexed: 02/01/2023]
Abstract
Outer hair cells (OHCs) amplify the sound-evoked motion of the basilar membrane to enhance acoustic sensitivity and frequency selectivity. Medial olivocochlear (MOC) efferents inhibit OHCs to reduce the sound-evoked response of cochlear afferent neurons. OHC inhibition occurs through the activation of postsynaptic α9α10 nicotinic receptors tightly coupled to calcium-dependent SK2 channels that hyperpolarize the hair cell. MOC neurons are cholinergic but a number of other neurotransmitters and neuromodulators have been proposed to participate in efferent transmission, with emerging evidence for both pre- and postsynaptic effects. Cochlear inhibition in vivo is maximized by repetitive activation of the efferents, reflecting facilitation and summation of transmitter release onto outer hair cells. This review summarizes recent studies on cellular and molecular mechanisms of cholinergic inhibition and the regulation of those molecular components, in particular the involvement of intracellular calcium. Facilitation at the efferent synapse is compared in a variety of animals, as well as other possible mechanisms of modulation of ACh release. These results suggest that short-term plasticity contributes to effective cholinergic inhibition of hair cells.
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Affiliation(s)
- Eric Wersinger
- The Center for Hearing and Balance, Department of Otolaryngology Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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85
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Decuypere JP, Monaco G, Bultynck G, Missiaen L, De Smedt H, Parys JB. The IP(3) receptor-mitochondria connection in apoptosis and autophagy. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:1003-13. [PMID: 21146562 DOI: 10.1016/j.bbamcr.2010.11.023] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 11/24/2010] [Accepted: 11/25/2010] [Indexed: 01/08/2023]
Abstract
The amount of Ca(2+) taken up in the mitochondrial matrix is a crucial determinant of cell fate; it plays a decisive role in the choice of the cell between life and death. The Ca(2+) ions mainly originate from the inositol 1,4,5-trisphosphate (IP(3))-sensitive Ca(2+) stores of the endoplasmic reticulum (ER). The uptake of these Ca(2+) ions in the mitochondria depends on the functional properties and the subcellular localization of the IP(3) receptor (IP(3)R) in discrete domains near the mitochondria. To allow for an efficient transfer of the Ca(2+) ions from the ER to the mitochondria, structural interactions between IP(3)Rs and mitochondria are needed. This review will focus on the key proteins involved in these interactions, how they are regulated, and what are their physiological roles in apoptosis, necrosis and autophagy. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.
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Affiliation(s)
- Jean-Paul Decuypere
- Laboratory of Molecular and Cellular Signalling, Dept. Molecular and Cellular, campus Gasthuisberg O/N1 K.U.Leuven, Bus 802, B-3000 Leuven, Belgium
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86
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Neumann JT, Diaz-Sylvester PL, Fleischer S, Copello JA. CGP-37157 inhibits the sarcoplasmic reticulum Ca²+ ATPase and activates ryanodine receptor channels in striated muscle. Mol Pharmacol 2010; 79:141-7. [PMID: 20923851 DOI: 10.1124/mol.110.067165] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
7-Chloro-5-(2-chlorophenyl)-1,5-dihydro-4,1-benzothiazepin-2(3H)-one [CGP-37157 (CGP)], a benzothiazepine derivative of clonazepam, is commonly used as a blocker of the mitochondrial Na+/Ca²+ exchanger. However, evidence suggests that CGP could also affect other targets, such as L-type Ca²+ channels and plasmalemma Na+/Ca²+ exchanger. Here, we tested the possibility of a direct modulation of ryanodine receptor channels (RyRs) and/or sarco/endoplasmic reticulum Ca²+-stimulated ATPase (SERCA) by CGP. In the presence of ruthenium red (inhibitor of RyRs), CGP decreased SERCA-mediated Ca²+ uptake of cardiac and skeletal sarcoplasmic reticulum (SR) microsomes (IC₅₀ values of 6.6 and 9.9 μM, respectively). The CGP effects on SERCA activity correlated with a decreased V(max) of ATPase activity of SERCA-enriched skeletal SR fractions. CGP (≥ 5 μM) also increased RyR-mediated Ca²+ leak from skeletal SR microsomes. Planar bilayer studies confirmed that both cardiac and skeletal RyRs are directly activated by CGP (EC(50) values of 9.4 and 12.0 μM, respectively). In summary, we found that CGP inhibits SERCA and activates RyR channels. Hence, the action of CGP on cellular Ca²+ homeostasis reported in the literature of cardiac, skeletal muscle, and other nonmuscle systems requires further analysis to take into account the contribution of all CGP-sensitive Ca²+ transporters.
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Affiliation(s)
- Jake T Neumann
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois, USA
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87
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Hung CHL, Ho YS, Chang RCC. Modulation of mitochondrial calcium as a pharmacological target for Alzheimer's disease. Ageing Res Rev 2010; 9:447-56. [PMID: 20553970 DOI: 10.1016/j.arr.2010.05.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Revised: 05/14/2010] [Accepted: 05/19/2010] [Indexed: 12/20/2022]
Abstract
Perturbed neuronal calcium homeostasis is a prominent feature in Alzheimer's disease (AD). Mitochondria accumulate calcium ions (Ca(2+)) for cellular bioenergetic metabolism and suppression of mitochondrial motility within the cell. Excessive Ca(2+) uptake into mitochondria often leads to mitochondrial membrane permeabilization and induction of apoptosis. Ca(2+) is an interesting second messenger which can initiate both cellular life and death pathways in mitochondria. This review critically discusses the potential of manipulating mitochondrial Ca(2+) concentrations as a novel therapeutic opportunity for treating AD. This review also highlights the neuroprotective role of a number of currently available agents that modulate different mitochondrial Ca(2+) transport pathways. It is reasoned that these mitochondrial Ca(2+) modulators are most effective in combination with agents that increase the Ca(2+) buffering capacity of mitochondria. Modulation of mitochondrial Ca(2+) handling is a potential pharmacological target for future development of AD treatments.
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Affiliation(s)
- Clara Hiu-Ling Hung
- Laboratory of Neurodegenerative Diseases, Department of Anatomy, LKS Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong, China
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88
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Csordás G, Várnai P, Golenár T, Roy S, Purkins G, Schneider TG, Balla T, Hajnóczky G. Imaging interorganelle contacts and local calcium dynamics at the ER-mitochondrial interface. Mol Cell 2010; 39:121-32. [PMID: 20603080 DOI: 10.1016/j.molcel.2010.06.029] [Citation(s) in RCA: 555] [Impact Index Per Article: 39.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Revised: 04/09/2010] [Accepted: 06/14/2010] [Indexed: 12/11/2022]
Abstract
The ER-mitochondrial junction provides a local calcium signaling domain that is critical for both matching energy production with demand and the control of apoptosis. Here, we visualize ER-mitochondrial contact sites and monitor the localized [Ca(2+)] changes ([Ca(2+)](ER-mt)) using drug-inducible fluorescent interorganelle linkers. We show that all mitochondria have contacts with the ER, but plasma membrane (PM)-mitochondrial contacts are less frequent because of interleaving ER stacks in both RBL-2H3 and H9c2 cells. Single mitochondria display discrete patches of ER contacts and show heterogeneity in the ER-mitochondrial Ca(2+) transfer. Pericam-tagged linkers revealed IP(3)-induced [Ca(2+)](ER-mt) signals that exceeded 9 microM and endured buffering bulk cytoplasmic [Ca(2+)] increases. Altering linker length to modify the space available for the Ca(2+) transfer machinery had a biphasic effect on [Ca(2+)](ER-mt) signals. These studies provide direct evidence for the existence of high-Ca(2+) microdomains between the ER and mitochondria and suggest an optimal gap width for efficient Ca(2+) transfer.
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Affiliation(s)
- György Csordás
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
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89
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Ruiz A, Matute C, Alberdi E. Intracellular Ca2+ release through ryanodine receptors contributes to AMPA receptor-mediated mitochondrial dysfunction and ER stress in oligodendrocytes. Cell Death Dis 2010; 1:e54. [PMID: 21364659 PMCID: PMC3032558 DOI: 10.1038/cddis.2010.31] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Overactivation of ionotropic glutamate receptors in oligodendrocytes induces cytosolic Ca(2+) overload and excitotoxic death, a process that contributes to demyelination and multiple sclerosis. Excitotoxic insults cause well-characterized mitochondrial alterations and endoplasmic reticulum (ER) dysfunction, which is not fully understood. In this study, we analyzed the contribution of ER-Ca(2+) release through ryanodine receptors (RyRs) and inositol triphosphate receptors (IP(3)Rs) to excitotoxicity in oligodendrocytes in vitro. First, we observed that oligodendrocytes express all previously characterized RyRs and IP(3)Rs. Blockade of Ca(2+)-induced Ca(2+) release by TMB-8 following α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor-mediated insults attenuated both oligodendrocyte death and cytosolic Ca(2+) overload. In turn, RyR inhibition by ryanodine reduced as well the Ca(2+) overload whereas IP(3)R inhibition was ineffective. Furthermore, AMPA-triggered mitochondrial membrane depolarization, oxidative stress and activation of caspase-3, which in all instances was diminished by RyR inhibition. In addition, we observed that AMPA induced an ER stress response as revealed by α subunit of the eukaryotic initiation factor 2α phosphorylation, overexpression of GRP chaperones and RyR-dependent cleavage of caspase-12. Finally, attenuating ER stress with salubrinal protected oligodendrocytes from AMPA excitotoxicity. Together, these results show that Ca(2+) release through RyRs contributes to cytosolic Ca(2+) overload, mitochondrial dysfunction, ER stress and cell death following AMPA receptor-mediated excitotoxicity in oligodendrocytes.
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Affiliation(s)
- A Ruiz
- Centro de Investigación Biomédica en Red en Enfermedades Neurodegenerativas (CIBERNED), Universidad del País Vasco, Leioa, Spain
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90
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Ruiz-Meana M, Fernandez-Sanz C, Garcia-Dorado D. The SR-mitochondria interaction: a new player in cardiac pathophysiology. Cardiovasc Res 2010; 88:30-9. [DOI: 10.1093/cvr/cvq225] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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91
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Twig G, Liu X, Liesa M, Wikstrom JD, Molina AJA, Las G, Yaniv G, Hajnóczky G, Shirihai OS. Biophysical properties of mitochondrial fusion events in pancreatic beta-cells and cardiac cells unravel potential control mechanisms of its selectivity. Am J Physiol Cell Physiol 2010; 299:C477-87. [PMID: 20445168 DOI: 10.1152/ajpcell.00427.2009] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Studies in various types of cells find that, on average, each mitochondrion becomes involved in a fusion event every 15 min, depending on the cell type. As most contact events do not result in mitochondrial fusion, it is expected that properties of the individual mitochondrion determine the likelihood of a fusion event. However, apart from membrane potential, the properties that influence the likelihood of entering a fusion event are not known. Here, we tag and track individual mitochondria in H9c2, INS1, and primary beta-cells and determine the biophysical properties that increase the likelihood of a fusion event. We found that the probability for fusion is independent of contact duration and organelle dimensions, but it is influenced by organelle motility. Furthermore, the history of a previous fusion event of the individual mitochondrion influenced both the likelihood for a subsequent fusion event, as well as the site on the mitochondrion at which the fusion occurred. These observations unravel the specific properties that distinguish mitochondria that will enter fusion events from the ones that will not. Altogether, these properties may help to elucidate the molecular mechanisms that regulate fusion at the level of the single mitochondrion.
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Affiliation(s)
- Gilad Twig
- Evans Biomedical Research Center, Boston University, Boston, Massachusetts 02118, USA
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92
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Turner JD, Gaspers LD, Wang G, Thomas AP. Uncoupling protein-2 modulates myocardial excitation-contraction coupling. Circ Res 2010; 106:730-8. [PMID: 20056920 DOI: 10.1161/circresaha.109.206631] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
RATIONALE Uncoupling protein (UCP)2 is a mitochondrial inner membrane protein that is expressed in mammalian myocardium under normal conditions and upregulated in pathological states such as heart failure. UCP2 is thought to protect cardiomyocytes against oxidative stress by dissipating the mitochondrial proton gradient and mitochondrial membrane potential (DeltaPsi(m)), thereby reducing mitochondrial reactive oxygen species generation. However, in apparent conflict with its uncoupling role, UCP2 has also been proposed to be essential for mitochondrial Ca(2+) uptake, which could have a protective action by stimulating mitochondrial ATP production. OBJECTIVE The goal of this study was to better understand the role of myocardial UCP2 by examining the effects of UCP2 on bioenergetics, Ca(2+) homeostasis, and excitation-contraction coupling in neonatal cardiomyocytes. METHODS AND RESULTS Adenoviral-mediated expression of UCP2 caused a mild depression of DeltaPsi(m) and increased the basal rate of oxygen consumption but did not affect total cellular ATP levels. Mitochondrial Ca(2+) uptake was examined in permeabilized cells loaded with the mitochondria-selective Ca(2+) probe, rhod-2. UCP2 overexpression markedly inhibited mitochondrial Ca(2+) uptake. Pretreatment with the UCP2-specific inhibitor genipin largely reversed the effects UCP2 expression on mitochondrial Ca(2+) handling, bioenergetics, and oxygen utilization. Electrically evoked cytosolic Ca(2+) transients and spontaneous cytosolic Ca(2+) sparks were examined using fluo-based probes and confocal microscopy in line scan mode. UCP2 overexpression significantly prolonged the decay phase of [Ca(2+)](c) transients in electrically paced cells, increased [Ca(2+)](c) spark activity and increased the probability that Ca(2+) sparks propagated into Ca(2+) waves. This dysregulation results from a loss of the ability of mitochondria to suppress local Ca(2+)-induced Ca(2+) release activity of the sarcoplasmic reticulum. CONCLUSION Increases in UCP2 expression that lower DeltaPsi(m) and contribute to protection against oxidative stress, also have deleterious effects on beat-to-beat [Ca(2+)](c) handling and excitation-contraction coupling, which may contribute to the progression of heart disease.
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Affiliation(s)
- Jay D Turner
- Department of Pharmacology and Physiology, UMDNJ-New Jersey Medical School, Newark, NJ 07103, USA
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93
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Wu PC, Fann MJ, Kao LS. Characterization of Ca2+ signaling pathways in mouse adrenal medullary chromaffin cells. J Neurochem 2009; 112:1210-22. [PMID: 20002295 DOI: 10.1111/j.1471-4159.2009.06533.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In the present study, we characterized the Ca2+ responses and secretions induced by various secretagogues in mouse chromaffin cells. Activation of the acetylcholine receptor (AChR) by carbachol induced a transient intracellular Ca2+ concentration ([Ca2+](i)) increase followed by two phases of [Ca2+](i) decay and a burst of exocytic events. The contribution of the subtypes of AChRs to carbachol-induced responses was examined. Based on the results obtained by stimulating the cells with the nicotinic receptor (nAChR) agonist, 1,1-dimethyl-4-phenylpiperazinium iodide, high K(+) and the effects of thapsigargin, it appears that activation of nAChRs induces an extracellular Ca2+ influx, which in turn activate Ca(2+)-induced Ca2+ release via the ryanodine receptors. Muscarine, a muscarinic receptor (mAChRs) agonist, was found to induce [Ca2+](i) oscillation and sustained catecholamine release, possibly by activation of both the receptor- and store-operated Ca2+ entry pathways. The RT-PCR results showed that mouse chromaffin cells are equipped with messages for multiple subtypes of AChRs, ryanodine receptors and all known components of the receptor- and store-operated Ca2+ entry. Furthermore, results obtained by directly monitoring endoplasmic reticulum (ER) and mitochondrial Ca2+ concentration and by disabling mitochondrial Ca2+ uptake suggest that the ER acts as a Ca2+ source, while the mitochondria acts as a Ca2+ sink. Our results show that both nAChRs and mAChRs contribute to the initial carbachol-induced [Ca2+](i) increase which is further enhanced by the Ca2+ released from the ER mediated by Ca(2+)-induced Ca2+ release and mAChR activation. This information on the Ca2+ signaling pathways should lay a good foundation for future studies using mouse chromaffin cells as a model system.
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Affiliation(s)
- Pei-Chun Wu
- Molecular Medicine Program, National Yang-Ming University, Taipei, Taiwan
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94
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Zhang T, Guo T, Mishra S, Dalton ND, Kranias EG, Peterson KL, Bers DM, Brown JH. Phospholamban ablation rescues sarcoplasmic reticulum Ca(2+) handling but exacerbates cardiac dysfunction in CaMKIIdelta(C) transgenic mice. Circ Res 2009; 106:354-62. [PMID: 19959778 DOI: 10.1161/circresaha.109.207423] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
RATIONALE We previously showed that transgenic mice expressing Ca(2+)/calmodulin-dependent protein kinase II delta(C) (CaMKII-TG) develop dilated cardiomyopathy associated with increased ryanodine receptors (RyR2) phosphorylation, enhanced sarcoplasmic reticulum (SR) Ca(2+) leak and lowering of SR Ca(2+) load. We hypothesized that phospholamban (PLN) ablation would restore SR Ca(2+) load and prevent the decreased ventricular contractility, dilation and mortality seen in CaMKII-TG. OBJECTIVE Our objectives were to generate CaMKII-TG mice lacking PLN, determine whether the maladaptive effects of cardiac CaMKIIdelta(C) expression were corrected, and establish the mechanistic basis for these changes. METHODS AND RESULTS CaMKII-TG were crossed with PLN knockout (PLN-KO) mice to generate KO/TG mice. Myocytes from wild type (WT), CaMKII-TG, PLN-KO and KO/TG were compared. The decreased SR Ca(2+) load and twitch Ca(2+) transients seen in CaMKII-TG were normalized in KO/TG. Surprisingly the heart failure phenotype was exacerbated, as indicated by increased left ventricular dilation, decreased ventricular function, increased apoptosis and greater mortality. In KO/TG myocytes SR Ca(2+) sparks and leak were significantly increased, presumably because of the combined effects of restored SR Ca(2+) load and RyR2 phosphorylation. Mitochondrial Ca(2+) loading was increased in cardiomyocytes from KO/TG versus WT or CaMKII-TG mice and this was dependent on elevated SR Ca(2+) sparks. Cardiomyocytes from KO/TG showed poor viability, improved by inhibiting SR Ca(2+) release and mitochondrial Ca(2+) loading. CONCLUSIONS Normalizing cardiomyocyte SR Ca(2+) loading in the face of elevated CaMKII and RyR2 phosphorylation leads to enhanced SR Ca(2+) leak and mitochondrial Ca(2+) elevation, associated with exacerbated cell death, heart failure and mortality.
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Affiliation(s)
- Tong Zhang
- Department of Pharmacology, University of California, San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0636, USA
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95
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Janssen K, Horn S, Niemann MT, Daniel PT, Schulze-Osthoff K, Fischer U. Inhibition of the ER Ca2+ pump forces multidrug-resistant cells deficient in Bak and Bax into necrosis. J Cell Sci 2009; 122:4481-91. [PMID: 19920074 DOI: 10.1242/jcs.055772] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tumor cells deficient in the proapoptotic proteins Bak and Bax are resistant to chemotherapeutic drugs. Here, we demonstrate that murine embryonic fibroblasts deficient for both Bak and Bax are, however, efficiently killed by thapsigargin, a specific inhibitor of ER Ca(2+) pumps that induces ER stress by depleting ER Ca(2+) stores. In the presence of Bak and Bax, thapsigargin eliminates cells by release of mitochondrial cytochrome c and subsequent caspase activation, which leads to the proteolytic inactivation of the molecular necrosis switch PARP-1 and results in apoptosis. By contrast, in the absence of Bak and Bax, a failure to activate caspases results in PARP-1-mediated ATP depletion. The subsequent necrosis is not prevented by autophagy as an alternative energy source. Moreover, in cells deficient for both Bak and Bax, thapsigargin induces permanent mitochondrial damage by Ca(2+) overload, permeability transition and membrane rupture. Thus, even though deficiency in Bak and Bax protects these cells against apoptosis, it does not compromise necrosis induced by SERCA inhibitors. Importantly, thapsigargin induces caspase-independent cell death also in colon and prostate carcinoma cells deficient in Bak and Bax expression. Therefore, targeted application of ER stressors such as thapsigargin might be a promising approach for the treatment of Bak- and Bax-deficient, drug-resistant tumors.
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Affiliation(s)
- Katja Janssen
- Interfaculty Institute for Biochemistry, University of Tübingen, Tübingen, Germany
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96
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Rizzuto R, Marchi S, Bonora M, Aguiari P, Bononi A, De Stefani D, Giorgi C, Leo S, Rimessi A, Siviero R, Zecchini E, Pinton P. Ca(2+) transfer from the ER to mitochondria: when, how and why. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1787:1342-51. [PMID: 19341702 PMCID: PMC2730423 DOI: 10.1016/j.bbabio.2009.03.015] [Citation(s) in RCA: 344] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 03/21/2009] [Accepted: 03/24/2009] [Indexed: 10/25/2022]
Abstract
The heterogenous subcellular distribution of a wide array of channels, pumps and exchangers allows extracellular stimuli to induce increases in cytoplasmic Ca(2+) concentration ([Ca(2+)]c) with highly defined spatial and temporal patterns, that in turn induce specific cellular responses (e.g. contraction, secretion, proliferation or cell death). In this extreme complexity, the role of mitochondria was considered marginal, till the direct measurement with targeted indicators allowed to appreciate that rapid and large increases of the [Ca(2+)] in the mitochondrial matrix ([Ca(2+)]m) invariably follow the cytosolic rises. Given the low affinity of the mitochondrial Ca(2+) transporters, the close proximity to the endoplasmic reticulum (ER) Ca(2+)-releasing channels was shown to be responsible for the prompt responsiveness of mitochondria. In this review, we will summarize the current knowledge of: i) the mitochondrial and ER Ca(2+) channels mediating the ion transfer, ii) the structural and molecular foundations of the signaling contacts between the two organelles, iii) the functional consequences of the [Ca(2+)]m increases, and iv) the effects of oncogene-mediated signals on mitochondrial Ca(2+) homeostasis. Despite the rapid progress carried out in the latest years, a deeper molecular understanding is still needed to unlock the secrets of Ca(2+) signaling machinery.
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Affiliation(s)
- Rosario Rizzuto
- Dept. Biomedical Sciences, University of Padua, Via Colombo 3, Padua 35121, Italy.
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97
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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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98
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Mitochondrial 'kiss-and-run': interplay between mitochondrial motility and fusion-fission dynamics. EMBO J 2009; 28:3074-89. [PMID: 19745815 DOI: 10.1038/emboj.2009.255] [Citation(s) in RCA: 245] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Accepted: 07/30/2009] [Indexed: 02/07/2023] Open
Abstract
Visualizing mitochondrial fusion in real time, we identified two classes of fusion events in mammalian cells. In addition to complete fusion, we observed transient fusion events, wherein two mitochondria came into close apposition, exchanged soluble inter-membrane space and matrix proteins, and re-separated, preserving the original morphology. Transient fusion exhibited rapid kinetics of the sequential and separable mergers of the outer and inner membranes, but allowed only partial exchange of integral membrane proteins. When the inner membrane fusion protein Opa1 level was lowered or was greatly elevated, transient fusions could occur, whereas complete fusions disappeared. Furthermore, transient fusions began from oblique or lateral interactions of mitochondria associated with separate microtubules, whereas complete fusions resulted from longitudinal merging of organelles travelling along a single microtubule. In contrast to complete fusion, transient fusions both required and promoted mitochondrial motility. Transient fusions were also necessary and sufficient to support mitochondrial metabolism. Thus, Opa1 expression and cytoskeletal anchorage govern a novel form of fusion that has a distinct function in mitochondrial maintenance.
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Ruiz A, Matute C, Alberdi E. Endoplasmic reticulum Ca(2+) release through ryanodine and IP(3) receptors contributes to neuronal excitotoxicity. Cell Calcium 2009; 46:273-81. [PMID: 19747726 DOI: 10.1016/j.ceca.2009.08.005] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Accepted: 08/20/2009] [Indexed: 01/02/2023]
Abstract
Overactivation of ionotropic glutamate receptors induces a Ca(2+) overload into the cytoplasm that leads neurons to excitotoxic death, a process that has been linked to several neurodegenerative disorders. While the role of mitochondria and its involvement in excitotoxicity have been widely studied, the contribution of endoplasmic reticulum (ER), another crucial intracellular store in maintaining Ca(2+) homeostasis, is not fully understood. In this study, we analyzed the contribution of ER-Ca(2+) release through ryanodine (RyR) and IP(3) (IP(3)R) receptors to a neuronal in vitro model of excitotoxicity. NMDA induced a dose-dependent neuronal death, which was significantly decreased by ER-Ca(2+) release inhibitors in cortical neurons as well as in organotypic slices. Furthermore, ryanodine and 2APB, RyR and IP(3)R inhibitors respectively, attenuated NMDA-triggered intracellular Ca(2+) increase and oxidative stress, whereas 2APB reduced mitochondrial membrane depolarization and caspase-3 cleavage. Consistent with ER-Ca(2+) homeostasis disruption, we observed that NMDA-induced ER stress, characterized here by eIF2alpha phosphorylation and over-expression of GRP chaperones which were regulated by ER-Ca(2+) release inhibitors. These results demonstrate that Ca(2+) release from ER contributes to neuronal death by both promoting mitochondrial dysfunction and inducing specific stress and apoptosis pathways during excitotoxicity.
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Affiliation(s)
- Asier Ruiz
- Centro de Investigación Biomédica en Red en Enfermedades Neurodegenerativas (CIBERNED), Spain
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100
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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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