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Cation transport by the respiratory NADH:quinone oxidoreductase (complex I): facts and hypotheses. Biochem Soc Trans 2014; 41:1280-7. [PMID: 24059520 DOI: 10.1042/bst20130024] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The respiratory complex I (electrogenic NADH:quinone oxidoreductase) has been considered to act exclusively as a H+ pump. This was questioned when the search for the NADH-driven respiratory Na+ pump in Klebsiella pneumoniae initiated by Peter Dimroth led to the discovery of a Na+-translocating complex in this enterobacterium. The 3D structures of complex I from different organisms support the idea that the mechanism of cation transport by complex I involves conformational changes of the membrane-bound NuoL, NuoM and NuoN subunits. In vitro methods to follow Na+ transport were compared with in vivo approaches to test whether complex I, or its individual NuoL, NuoM or NuoN subunits, extrude Na+ from the cytoplasm to the periplasm of bacterial host cells. The truncated NuoL subunit of the Escherichia coli complex I which comprises amino acids 1-369 exhibits Na+ transport activity in vitro. This observation, together with an analysis of putative cation channels in NuoL, suggests that there exists in NuoL at least one continuous pathway for cations lined by amino acid residues from transmembrane segments 3, 4, 5, 7 and 8. Finally, we discuss recent studies on Na+ transport by mitochondrial complex I with respect to its putative role in the cycling of Na+ ions across the inner mitochondrial membrane.
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102
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Molecular mechanism and physiological role of active-deactive transition of mitochondrial complex I. Biochem Soc Trans 2014; 41:1325-30. [PMID: 24059527 PMCID: PMC3990385 DOI: 10.1042/bst20130088] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The unique feature of mitochondrial complex I is the so-called A/D transition (active–deactive transition). The A-form catalyses rapid oxidation of NADH by ubiquinone (k ~104 min−1) and spontaneously converts into the D-form if the enzyme is idle at physiological temperatures. Such deactivation occurs in vitro in the absence of substrates or in vivo during ischaemia, when the ubiquinone pool is reduced. The D-form can undergo reactivation given both NADH and ubiquinone availability during slow (k ~1–10 min−1) catalytic turnover(s). We examined known conformational differences between the two forms and suggested a mechanism exerting A/D transition of the enzyme. In addition, we discuss the physiological role of maintaining the enzyme in the D-form during the ischaemic period. Accumulation of the D-form of the enzyme would prevent reverse electron transfer from ubiquinol to FMN which could lead to superoxide anion generation. Deactivation would also decrease the initial burst of respiration after oxygen reintroduction. Therefore the A/D transition could be an intrinsic protective mechanism for lessening oxidative damage during the early phase of reoxygenation. Exposure of Cys39 of mitochondrially encoded subunit ND3 makes the D-form susceptible for modification by reactive oxygen species and nitric oxide metabolites which arrests the reactivation of the D-form and inhibits the enzyme. The nature of thiol modification defines deactivation reversibility, the reactivation timescale, the status of mitochondrial bioenergetics and therefore the degree of recovery of the ischaemic tissues after reoxygenation.
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103
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Katoh D, Hongo K, Ito K, Yoshino T, Kayama Y, Kawai M, Date T, Yoshimura M. Corticosteroids increase intracellular free sodium ion concentration via glucocorticoid receptor pathway in cultured neonatal rat cardiomyocytes. INTERNATIONAL JOURNAL OF CARDIOLOGY. HEART & VESSELS 2014; 3:49-56. [PMID: 29450170 PMCID: PMC5801272 DOI: 10.1016/j.ijchv.2014.03.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 03/03/2014] [Indexed: 11/27/2022]
Abstract
Background Glucocorticoids as well as mineralocorticoid have been shown to play essential roles in the regulation of electrical and mechanical activities in cardiomyocytes. Excess of these hormones is an independent risk factor for cardiovascular disease. Intracellular sodium ([Na+]i) kinetics are involved in cardiac diseases, including ischemia, heart failure and hypertrophy. However, intrinsic mediators that regulate [Na+]i in cardiomyocytes have not been widely discussed. Moreover, the quantitative estimation of altered [Na+]i in cultured cardiomyocytes and the association between the level of [Na+]i and the severity of pathological conditions, such as hypertrophy, have not been precisely reported. Methods and results We herein demonstrate the quantitative estimation of [Na+]i in cultured neonatal rat cardiomyocytes following 24 h of treatment with corticosterone, aldosterone and dexamethasone. The physiological concentration of glucocorticoids increased [Na+]i up to approximately 2.5 mM (an almost 1.5-fold increase compared to the control) in a dose-dependent manner; this effect was blocked by a glucocorticoid receptor (GR) antagonist but not a mineralocorticoid receptor antagonist. Furthermore, glucocorticoids induced cardiac hypertrophy, and the hypertrophic gene expression was positively and significantly correlated with the level of [Na+]i. Dexamethasone induced the upregulation of Na+/Ca2 + exchanger 1 at the mRNA and protein levels. Conclusions The physiological concentration of glucocorticoids increases [Na+]i via GR. The dexamethasone-induced upregulation of NCX1 is partly involved in the glucocorticoid-induced alteration of [Na+]i in cardiomyocytes. These results provide new insight into the mechanisms by which glucocorticoid excess within a physiological concentration contributes to the development of cardiac pathology.
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Affiliation(s)
- Daisuke Katoh
- Division of Cardiology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo 105-8461, Japan
| | - Kenichi Hongo
- Division of Cardiology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo 105-8461, Japan
| | - Keiichi Ito
- Division of Cardiology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo 105-8461, Japan
| | - Takuya Yoshino
- Division of Cardiology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo 105-8461, Japan
| | - Yosuke Kayama
- Division of Cardiology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo 105-8461, Japan
| | - Makoto Kawai
- Division of Cardiology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo 105-8461, Japan
| | - Taro Date
- Division of Cardiology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo 105-8461, Japan
| | - Michihiro Yoshimura
- Division of Cardiology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo 105-8461, Japan
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104
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Babot M, Birch A, Labarbuta P, Galkin A. Characterisation of the active/de-active transition of mitochondrial complex I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1083-92. [PMID: 24569053 PMCID: PMC4331042 DOI: 10.1016/j.bbabio.2014.02.018] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 02/14/2014] [Accepted: 02/17/2014] [Indexed: 12/12/2022]
Abstract
Oxidation of NADH in the mitochondrial matrix of aerobic cells is catalysed by mitochondrial complex I. The regulation of this mitochondrial enzyme is not completely understood. An interesting characteristic of complex I from some organisms is the ability to adopt two distinct states: the so-called catalytically active (A) and the de-active, dormant state (D). The A-form in situ can undergo de-activation when the activity of the respiratory chain is limited (i.e. in the absence of oxygen). The mechanisms and driving force behind the A/D transition of the enzyme are currently unknown, but several subunits are most likely involved in the conformational rearrangements: the accessory subunit 39 kDa (NDUFA9) and the mitochondrially encoded subunits, ND3 and ND1. These three subunits are located in the region of the quinone binding site. The A/D transition could represent an intrinsic mechanism which provides a fast response of the mitochondrial respiratory chain to oxygen deprivation. The physiological role of the accumulation of the D-form in anoxia is most probably to protect mitochondria from ROS generation due to the rapid burst of respiration following reoxygenation. The de-activation rate varies in different tissues and can be modulated by the temperature, the presence of free fatty acids and divalent cations, the NAD+/NADH ratio in the matrix, the presence of nitric oxide and oxygen availability. Cysteine-39 of the ND3 subunit, exposed in the D-form, is susceptible to covalent modification by nitrosothiols, ROS and RNS. The D-form in situ could react with natural effectors in mitochondria or with pharmacological agents. Therefore the modulation of the re-activation rate of complex I could be a way to ameliorate the ischaemia/reperfusion damage. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference. Guest Editors: Manuela Pereira and Miguel Teixeira. The potential mechanism of complex I A/D transition is discussed. An —SH group exposed in the D-form is susceptible to covalent modification. The role of A/D transition in tissue response to ischaemia is proposed.
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Affiliation(s)
- Marion Babot
- Queen's University Belfast, School of Biological Sciences, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK
| | - Amanda Birch
- Queen's University Belfast, School of Biological Sciences, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK
| | - Paola Labarbuta
- Queen's University Belfast, School of Biological Sciences, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK
| | - Alexander Galkin
- Queen's University Belfast, School of Biological Sciences, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK.
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105
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Zhao ZG, Zhang LL, Niu CY, Zhang J. Exogenous normal lymph reduces liver injury induced by lipopolysaccharides in rats. Braz J Med Biol Res 2014; 47:128-34. [PMID: 24519128 PMCID: PMC4051182 DOI: 10.1590/1414-431x20133280] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 10/11/2013] [Indexed: 11/30/2022] Open
Abstract
The liver is one of the target organs damaged by septic shock, wherein the spread
of endotoxins begins. This study aimed to investigate the effects of exogenous
normal lymph (ENL) on lipopolysaccharide (LPS)-induced liver injury in rats.
Male Wistar rats were randomly divided into sham, LPS, and LPS+ENL groups. LPS
(15 mg/kg) was administered intravenously via the left jugular vein to the LPS
and LPS+ENL groups. At 15 min after the LPS injection, saline or ENL without
cell components (5 mL/kg) was administered to the LPS and LPS+ENL groups,
respectively, at a rate of 0.5 mL/min. Hepatocellular injury indices and hepatic
histomorphology, as well as levels of P-selectin, intercellular adhesion
molecule 1 (ICAM-1), myeloperoxidase (MPO), and
Na+-K+-ATPase, were assessed in hepatic tissues. Liver
tissue damage occurred after LPS injection. All levels of alanine
aminotransferase (ALT) and aspartate aminotransferase (AST) in plasma as well as
the wet/dry weight ratio of hepatic tissue in plasma increased. Similarly,
P-selectin, ICAM-1, and MPO levels in hepatic tissues were elevated, whereas
Na+-K+-ATPase activity in hepatocytes decreased. ENL
treatment lessened hepatic tissue damage and decreased levels of AST, ALT,
ICAM-1, and MPO. Meanwhile, the treatment increased the activity of
Na+-K+-ATPase. These results indicated that ENL could
alleviate LPS-induced liver injury, thereby suggesting an alternative
therapeutic strategy for the treatment of liver injury accompanied by severe
infection or sepsis.
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Affiliation(s)
- Z G Zhao
- Institute of Microcirculation, Hebei North University, Zhangjiakou, China, Institute of Microcirculation, Hebei North University, Zhangjiakou, Hebei, China
| | - L L Zhang
- Institute of Microcirculation, Hebei North University, Zhangjiakou, China, Institute of Microcirculation, Hebei North University, Zhangjiakou, Hebei, China
| | - C Y Niu
- Institute of Microcirculation, Hebei North University, Zhangjiakou, China, Institute of Microcirculation, Hebei North University, Zhangjiakou, Hebei, China
| | - J Zhang
- Institute of Microcirculation, Hebei North University, Zhangjiakou, China, Institute of Microcirculation, Hebei North University, Zhangjiakou, Hebei, China
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106
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Kim D, Ryu HG, Ahn KH. Recent development of two-photon fluorescent probes for bioimaging. Org Biomol Chem 2014; 12:4550-66. [DOI: 10.1039/c4ob00431k] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Fluorescent probes are essential tools for studying biological systems.
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Affiliation(s)
- Dokyoung Kim
- Department of Chemistry and Center for Electro-Photo Behaviors in Advanced Molecular Systems
- Gyungbuk, Korea 790-784
| | - Hye Gun Ryu
- Department of Chemistry and Center for Electro-Photo Behaviors in Advanced Molecular Systems
- Gyungbuk, Korea 790-784
| | - Kyo Han Ahn
- Department of Chemistry and Center for Electro-Photo Behaviors in Advanced Molecular Systems
- Gyungbuk, Korea 790-784
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107
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Corradi F, Paolini L, De Caterina R. Ranolazine in the prevention of anthracycline cardiotoxicity. Pharmacol Res 2014; 79:88-102. [DOI: 10.1016/j.phrs.2013.11.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2013] [Revised: 11/06/2013] [Accepted: 11/06/2013] [Indexed: 12/19/2022]
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108
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Katoh D, Hongo K, Ito K, Yoshino T, Kayama Y, Komukai K, Kawai M, Date T, Yoshimura M. A technique for quantifying intracellular free sodium ion using a microplate reader in combination with sodium-binding benzofuran isophthalate and probenecid in cultured neonatal rat cardiomyocytes. BMC Res Notes 2013; 6:556. [PMID: 24369990 PMCID: PMC3879185 DOI: 10.1186/1756-0500-6-556] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 12/18/2013] [Indexed: 11/16/2022] Open
Abstract
Background Intracellular sodium ([Na+]i) kinetics are involved in cardiac diseases including ischemia, heart failure, and hypertrophy. Because [Na+]i plays a crucial role in modulating the electrical and contractile activity in the heart, quantifying [Na+]i is of great interest. Using fluorescent microscopy with sodium-binding benzofuran isophthalate (SBFI) is the most commonly used method for measuring [Na+]i. However, one limitation associated with this technique is that the test cannot simultaneously evaluate the effects of several types or various concentrations of compounds on [Na+]i. Moreover, there are few reports on the long-term effects of compounds on [Na+]i in cultured cells, although rapid changes in [Na+]i during a period of seconds or several minutes have been widely discussed. Findings We established a novel technique for quantifying [Na+]i in cultured neonatal rat cardiomyocytes attached to a 96-well plate using a microplate reader in combination with SBFI and probenecid. We showed that probenecid is indispensable for the accurate measurement because it prevents dye leakage from the cells. We further confirmed the reliability of this system by quantifying the effects of ouabain, which is known to transiently alter [Na+]i. To illustrate the utility of the new method, we also examined the chronic effects of aldosterone on [Na+]i in cultured cardiomyocytes. Conclusions Our technique can rapidly measure [Na+]i with accuracy and sensitivity comparable to the traditional microscopy based method. The results demonstrated that this 96-well plate based measurement has merits, especially for screening test of compounds regulating [Na+]i, and is useful to elucidate the mechanisms and consequences of altered [Na+]i handling in cardiomyocytes.
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Affiliation(s)
- Daisuke Katoh
- Division of Cardiology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo 105-8461, Japan.
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109
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Gauthier LD, Greenstein JL, O'Rourke B, Winslow RL. An integrated mitochondrial ROS production and scavenging model: implications for heart failure. Biophys J 2013; 105:2832-42. [PMID: 24359755 PMCID: PMC3882515 DOI: 10.1016/j.bpj.2013.11.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Revised: 08/30/2013] [Accepted: 11/05/2013] [Indexed: 12/27/2022] Open
Abstract
It has been observed experimentally that cells from failing hearts exhibit elevated levels of reactive oxygen species (ROS) upon increases in energetic workload. One proposed mechanism for this behavior is mitochondrial Ca(2+) mismanagement that leads to depletion of ROS scavengers. Here, we present a computational model to test this hypothesis. Previously published models of ROS production and scavenging were combined and reparameterized to describe ROS regulation in the cellular environment. Extramitochondrial Ca(2+) pulses were applied to simulate frequency-dependent changes in cytosolic Ca(2+). Model results show that decreased mitochondrial Ca(2+)uptake due to mitochondrial Ca(2+) uniporter inhibition (simulating Ru360) or elevated cytosolic Na(+), as in heart failure, leads to a decreased supply of NADH and NADPH upon increasing cellular workload. Oxidation of NADPH leads to oxidation of glutathione (GSH) and increased mitochondrial ROS levels, validating the Ca(2+) mismanagement hypothesis. The model goes on to predict that the ratio of steady-state [H2O2]m during 3Hz pacing to [H2O2]m at rest is highly sensitive to the size of the GSH pool. The largest relative increase in [H2O2]m in response to pacing is shown to occur when the total GSH and GSSG is close to 1 mM, whereas pool sizes below 0.9 mM result in high resting H2O2 levels, a quantitative prediction only possible with a computational model.
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Affiliation(s)
- Laura D Gauthier
- Institute for Computational Medicine and Department of Biomedical Engineering, The Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, Maryland.
| | - Joseph L Greenstein
- Institute for Computational Medicine and Department of Biomedical Engineering, The Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, Maryland
| | - Brian O'Rourke
- Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore Maryland
| | - Raimond L Winslow
- Institute for Computational Medicine and Department of Biomedical Engineering, The Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, Maryland
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110
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Coppini R, Ferrantini C, Mazzoni L, Sartiani L, Olivotto I, Poggesi C, Cerbai E, Mugelli A. Regulation of intracellular Na(+) in health and disease: pathophysiological mechanisms and implications for treatment. Glob Cardiol Sci Pract 2013; 2013:222-42. [PMID: 24689024 PMCID: PMC3963757 DOI: 10.5339/gcsp.2013.30] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 09/01/2013] [Indexed: 12/19/2022] Open
Abstract
Transmembrane sodium (Na+) fluxes and intracellular sodium homeostasis are central players in the physiology of the cardiac myocyte, since they are crucial for both cell excitability and for the regulation of the intracellular calcium concentration. Furthermore, Na+ fluxes across the membrane of mitochondria affect the concentration of protons and calcium in the matrix, regulating mitochondrial function. In this review we first analyze the main molecular determinants of sodium fluxes across the sarcolemma and the mitochondrial membrane and describe their role in the physiology of the healthy myocyte. In particular we focus on the interplay between intracellular Ca2+ and Na+. A large part of the review is dedicated to discuss the changes of Na+ fluxes and intracellular Na+ concentration([Na+]i) occurring in cardiac disease; we specifically focus on heart failure and hypertrophic cardiomyopathy, where increased intracellular [Na+]i is an established determinant of myocardial dysfunction. We review experimental evidence attributing the increase of [Na+]i to either decreased Na+ efflux (e.g. via the Na+/K+ pump) or increased Na+ influx into the myocyte (e.g. via Na+ channels). In particular, we focus on the role of the “late sodium current” (INaL), a sustained component of the fast Na+ current of cardiac myocytes, which is abnormally enhanced in cardiac diseases and contributes to both electrical and contractile dysfunction. We analyze the pathophysiological role of INaL enhancement in heart failure and hypertrophic cardiomyopathy and the consequences of its pharmacological modulation, highlighting the clinical implications. The central role of Na+ fluxes and intracellular Na+ physiology and pathophysiology of cardiac myocytes has been highlighted by a large number of recent works. The possibility of modulating Na+ inward fluxes and [Na+]i with specific INaL inhibitors, such as ranolazine, has made Na+a novel suitable target for cardiac therapy, potentially capable of addressing arrhythmogenesis and diastolic dysfunction in severe conditions such as heart failure and hypertrophic cardiomyopathy.
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Affiliation(s)
- Raffaele Coppini
- Department NeuroFarBa, Division of Pharmacology, University of Florence, Italy
| | - Cecilia Ferrantini
- Department of Clinical and Experimental Medicine, division of Physiology, University of Florence, Italy
| | - Luca Mazzoni
- Department NeuroFarBa, Division of Pharmacology, University of Florence, Italy
| | - Laura Sartiani
- Department NeuroFarBa, Division of Pharmacology, University of Florence, Italy
| | - Iacopo Olivotto
- Referral Center for Cardiomyopathies, Careggi University Hospital, Florence, Italy
| | - Corrado Poggesi
- Department of Clinical and Experimental Medicine, division of Physiology, University of Florence, Italy
| | - Elisabetta Cerbai
- Department NeuroFarBa, Division of Pharmacology, University of Florence, Italy
| | - Alessandro Mugelli
- Department NeuroFarBa, Division of Pharmacology, University of Florence, Italy
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111
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Şehirli AÖ, Koyun D, Tetik Ş, Özsavcı D, Yiğiner Ö, Çetinel Ş, Tok OE, Kaya Z, Akkiprik M, Kılıç E, Şener G. Melatonin protects against ischemic heart failure in rats. J Pineal Res 2013; 55:138-48. [PMID: 23551402 DOI: 10.1111/jpi.12054] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 03/08/2013] [Indexed: 10/27/2022]
Abstract
Ischemic injury, which occurs as a result of sympathetic hyperactivity, plays an important role in heart failure. Melatonin is thought to have antiatherogenic, antioxidant, and vasodilatory effects. In this study, we investigated whether melatonin protects against ischemic heart failure (HF). In Wistar albino rats, HF was induced by left anterior descending (LAD) coronary artery ligation and rats were treated with either vehicle or melatonin (10 mg/kg) for 4 weeks. At the end of this period, echocardiographic measurements were recorded and the rats were decapitated to obtain plasma and cardiac tissue samples. Lactate dehydrogenase, creatine kinase, aspartate aminotransferase, alanine aminotransferase, and lysosomal enzymes (β-D-glucuronidase, β-galactosidase, β-D-N-acetyl-glucosaminidase, acid phosphatase, and cathepsin-D) were studied in plasma samples, while malondialdehyde and glutathione levels and Na+, K+-ATPase, caspase-3 and myeloperoxidase activities were determined in the cardiac samples. Sarco/endoplasmic reticulum calcium ATPase (SERCA) and caveolin-3 levels in cardiac tissues were evaluated using Western blot analyses. Furthermore, caveolin-3 levels were also determined by histological analyses. In the vehicle-treated HF group, cardiotoxicity resulted in decreased cardiac Na+, K+-ATPase and SERCA activities, GSH contents and caveolin-3 levels, while plasma LDH, CK, and lysosomal enzyme activities and cardiac MDA and Myeloperoxidase (MPO) activities were found to be increased. On the other hand, melatonin treatment reversed all the functional and biochemical changes. The present results demonstrate that Mel ameliorates ischemic heart failure in rats. These observations highlight that melatonin is a promising supplement for improving defense mechanisms in the heart against oxidative stress caused by heart failure.
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Affiliation(s)
- Ahmet Özer Şehirli
- Department of Pharmacology, School of Pharmacy, Marmara University, Istanbul, Turkey
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112
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Li J, Xu L, Ye J, Li X, Zhang D, Liang D, Xu X, Qi M, Li C, Zhang H, Wang J, Liu Y, Zhang Y, Zhou Z, Liang X, Li J, Peng L, Zhu W, Chen YH. Aberrant dynamin 2-dependent Na(+) /H(+) exchanger-1 trafficking contributes to cardiomyocyte apoptosis. J Cell Mol Med 2013; 17:1119-27. [PMID: 23837875 PMCID: PMC4118171 DOI: 10.1111/jcmm.12086] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 05/13/2013] [Indexed: 02/05/2023] Open
Abstract
Sarcolemmal Na+/H+ exchanger 1 (NHE1) activity is essential for the intracellular pH (pHi) homeostasis in cardiac myocytes. Emerging evidence indicates that sarcolemmal NHE1 dysfunction was closely related to cardiomyocyte death, but it remains unclear whether defective trafficking of NHE1 plays a role in the vital cellular signalling processes. Dynamin (DNM), a large guanosine triphosphatase (GTPase), is best known for its roles in membrane trafficking events. Herein, using co-immunoprecipitation, cell surface biotinylation and confocal microscopy techniques, we investigated the potential regulation on cardiac NHE1 activity by DNM. We identified that DNM2, a cardiac isoform of DNM, directly binds to NHE1. Overexpression of a wild-type DNM2 or a dominant-negative DNM2 mutant with defective GTPase activity in adult rat ventricular myocytes (ARVMs) facilitated or retarded the internalization of sarcolemmal NHE1, whereby reducing or increasing its activity respectively. Importantly, the increased NHE1 activity associated with DNM2 deficiency led to ARVMs apoptosis, as demonstrated by cell viability, terminal deoxynucleotidyl transferase–mediated dUTP nick-end labelling assay, Bcl-1/Bax expression and caspase-3 activity, which were effectively rescued by pharmacological inhibition of NHE1 with zoniporide. Thus, our results demonstrate that disruption of the DNM2-dependent retrograde trafficking of NHE1 contributes to cardiomyocyte apoptosis.
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Affiliation(s)
- Jun Li
- Key Laboratory of Arrhythmias of the Ministry of Education of China, East Hospital, Tongji University School of Medicine, Shanghai, China; Institute of Medical Genetics, Tongji University, Shanghai, China
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113
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Myocardial energetics in heart failure. Basic Res Cardiol 2013; 108:358. [PMID: 23740216 DOI: 10.1007/s00395-013-0358-9] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/24/2013] [Accepted: 05/09/2013] [Indexed: 12/12/2022]
Abstract
It has become common sense that the failing heart is an "engine out of fuel". However, undisputable evidence that, indeed, the failing heart is limited by insufficient ATP supply is currently lacking. Over the last couple of years, an increasingly complex picture of mechanisms evolved that suggests that potentially metabolic intermediates and redox state could play the more dominant roles for signaling that eventually results in left ventricular remodeling and contractile dysfunction. In the pathophysiology of heart failure, mitochondria emerge in the crossfire of defective excitation-contraction coupling and increased energetic demand, which may provoke oxidative stress as an important upstream mediator of cardiac remodeling and cell death. Thus, future therapies may be guided towards restoring defective ion homeostasis and mitochondrial redox shifts rather than aiming solely at improving the generation of ATP.
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114
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Boyman L, Williams GSB, Khananshvili D, Sekler I, Lederer WJ. NCLX: the mitochondrial sodium calcium exchanger. J Mol Cell Cardiol 2013; 59:205-13. [PMID: 23538132 PMCID: PMC3951392 DOI: 10.1016/j.yjmcc.2013.03.012] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 03/15/2013] [Indexed: 11/18/2022]
Abstract
The free Ca(2+) concentration within the mitochondrial matrix ([Ca(2+)]m) regulates the rate of ATP production and other [Ca(2+)]m sensitive processes. It is set by the balance between total Ca(2+) influx (through the mitochondrial Ca(2+) uniporter (MCU) and any other influx pathways) and the total Ca(2+) efflux (by the mitochondrial Na(+)/Ca(2+) exchanger and any other efflux pathways). Here we review and analyze the experimental evidence reported over the past 40years which suggest that in the heart and many other mammalian tissues a putative Na(+)/Ca(2+) exchanger is the major pathway for Ca(2+) efflux from the mitochondrial matrix. We discuss those reports with respect to a recent discovery that the protein product of the human FLJ22233 gene mediates such Na(+)/Ca(2+) exchange across the mitochondrial inner membrane. Among its many functional similarities to other Na(+)/Ca(2+) exchanger proteins is a unique feature: it efficiently mediates Li(+)/Ca(2+) exchange (as well as Na(+)/Ca(2+) exchange) and was therefore named NCLX. The discovery of NCLX provides both the identity of a novel protein and new molecular means of studying various unresolved quantitative aspects of mitochondrial Ca(2+) movement out of the matrix. Quantitative and qualitative features of NCLX are discussed as is the controversy regarding the stoichiometry of the NCLX Na(+)/Ca(2+) exchange, the electrogenicity of NCLX, the [Na(+)]i dependency of NCLX and the magnitude of NCLX Ca(2+) efflux. Metabolic features attributable to NCLX and the physiological implication of the Ca(2+) efflux rate via NCLX during systole and diastole are also briefly discussed.
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Affiliation(s)
- Liron Boyman
- Center for Biomedical Engineering and Technology and Dept. Physiology, University of Maryland School of Medicine, Baltimore, MD 21201
| | - George S. B. Williams
- Center for Biomedical Engineering and Technology and Dept. Physiology, University of Maryland School of Medicine, Baltimore, MD 21201
- School of Systems Biology, College of Science, George Mason University, Manassas, VA 20110
| | - Daniel Khananshvili
- Sackler School of Medicine, Department of Physiology and Pharmacology, Tel-Aviv University, Ramat-Aviv 69978, Israel
| | - Israel Sekler
- Goldman Medical School, Dept. Biology & Neurobiology, Ben Gurion University of the Negev, P.O.B. 653, Beer-Sheva 84105, Israel
| | - W. J. Lederer
- Center for Biomedical Engineering and Technology and Dept. Physiology, University of Maryland School of Medicine, Baltimore, MD 21201
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115
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Madelin G, Regatte RR. Biomedical applications of sodium MRI in vivo. J Magn Reson Imaging 2013; 38:511-29. [PMID: 23722972 DOI: 10.1002/jmri.24168] [Citation(s) in RCA: 166] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 03/12/2013] [Indexed: 12/13/2022] Open
Abstract
In this article we present an up-to-date overview of the potential biomedical applications of sodium magnetic resonance imaging (MRI) in vivo. Sodium MRI is a subject of increasing interest in translational imaging research as it can give some direct and quantitative biochemical information on the tissue viability, cell integrity and function, and therefore not only help the diagnosis but also the prognosis of diseases and treatment outcomes. It has already been applied in vivo in most human tissues, such as brain for stroke or tumor detection and therapeutic response, in breast cancer, in articular cartilage, in muscle, and in kidney, and it was shown in some studies that it could provide very useful new information not available through standard proton MRI. However, this technique is still very challenging due to the low detectable sodium signal in biological tissue with MRI and hardware/software limitations of the clinical scanners. The article is divided in three parts: 1) the role of sodium in biological tissues, 2) a short review on sodium magnetic resonance, and 3) a review of some studies on sodium MRI on different organs/diseases to date.
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Affiliation(s)
- Guillaume Madelin
- New York University Langone Medical Center, Department of Radiology, Center for Biomedical Imaging, New York, NY 10016, USA.
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116
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Zhao ZG, Niu CY, Zhang LL, Zhang J, Han R, Zhang YP, Hou YL. Exogenous normal lymph alleviates lipopolysaccharide-induced acute kidney injury in rats. Ren Fail 2013; 35:806-11. [PMID: 23713704 DOI: 10.3109/0886022x.2013.794680] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Acute kidney injury (AKI) is a common pathological process which occurs in hemorrhage, intoxication, etc. It has been shown that the lymphatic circulation plays an important regulatory role in the pathogenesis of hemorrhage shock, and that exogenous normal lymph (ENL) has a beneficial effect on multiple organ injuries. In the present study, we investigated the effect of ENL on lipopolysaccharide (LPS)-induced AKI in rats. METHODS The AKI was induced by the jugular vein injection of LPS (iv, 15 mg/kg). After 15 min of LPS injection, saline or ENL without cell components (5 mL/kg) was iv infused at the speed of 0.5 mL per minute. Then, the renal function indices in plasma and renal histomorphology, and the levels of P-selectin, intercellular adhesion molecule-1 (ICAM-1), myeloperoxidase (MPO) and Na(+)-K(+)-ATPase in renal tissue were assessed at 3 or 6 h after LPS injection. RESULTS LPS induced a severe kidney injury including increased levels of urea, creatinine in plasma, aggrandized activities of ICAM-1 and MPO in renal tissue, and decreased the Na(+)-K(+)-ATPase activity in renal cells. These deleterious effects of LPS were significantly ameliorated by ENL treatment. CONCLUSION The present results indicate that ENL protect against LPS-induced AKI, suggesting an alternative therapeutic strategy for treatment of kidney injury accompanied with severe infection or sepsis.
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Affiliation(s)
- Zi-Gang Zhao
- Institute of Microcirculation, Hebei North University, Zhangjiakou, Hebei, PR China
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117
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Despa S, Bers DM. Na⁺ transport in the normal and failing heart - remember the balance. J Mol Cell Cardiol 2013; 61:2-10. [PMID: 23608603 DOI: 10.1016/j.yjmcc.2013.04.011] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Revised: 03/22/2013] [Accepted: 04/11/2013] [Indexed: 12/12/2022]
Abstract
In the heart, intracellular Na(+) concentration ([Na(+)]i) is a key modulator of Ca(2+) cycling, contractility and cardiac myocyte metabolism. Several Na(+) transporters are electrogenic, thus they both contribute to shaping the cardiac action potential and at the same time are affected by it. [Na(+)]i is controlled by the balance between Na(+) influx through various pathways, including the Na(+)/Ca(2+) exchanger and Na(+) channels, and Na(+) extrusion via the Na(+)/K(+)-ATPase. [Na(+)]i is elevated in HF due to a combination of increased entry through Na(+) channels and/or Na(+)/H(+) exchanger and reduced activity of the Na(+)/K(+)-ATPase. Here we review the major Na(+) transport pathways in cardiac myocytes and how they participate in regulating [Na(+)]i in normal and failing hearts. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes."
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Affiliation(s)
- Sanda Despa
- Department of Pharmacology, University of California, Davis, CA, USA.
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118
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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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119
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Pelin M, Ponti C, Sosa S, Gibellini D, Florio C, Tubaro A. Oxidative stress induced by palytoxin in human keratinocytes is mediated by a H+-dependent mitochondrial pathway. Toxicol Appl Pharmacol 2013; 266:1-8. [DOI: 10.1016/j.taap.2012.10.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Revised: 09/26/2012] [Accepted: 10/15/2012] [Indexed: 01/15/2023]
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120
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Belliard A, Sottejeau Y, Duan Q, Karabin JL, Pierre SV. Modulation of cardiac Na+,K+-ATPase cell surface abundance by simulated ischemia-reperfusion and ouabain preconditioning. Am J Physiol Heart Circ Physiol 2012; 304:H94-103. [PMID: 23086991 DOI: 10.1152/ajpheart.00374.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Na(+),K(+)-ATPase and cell survival were investigated in a cellular model of ischemia-reperfusion (I/R)-induced injury and protection by ouabain-induced preconditioning (OPC). Rat neonatal cardiac myocytes were subjected to 30 min of substrate and coverslip-induced ischemia followed by 30 min of simulated reperfusion. This significantly compromised cell viability as documented by lactate dehydrogenase release and Annexin V/propidium iodide staining. Total Na(+),K(+)-ATPase α(1)- and α(3)-polypeptide expression remained unchanged, but cell surface biotinylation and immunostaining studies revealed that α(1)-cell surface abundance was significantly decreased. Na(+),K(+)-ATPase-activity in crude homogenates and (86)Rb(+) transport in live cells were both significantly decreased by about 30% after I/R. OPC, induced by a 4-min exposure to 10 μM ouabain that ended 8 min before the beginning of ischemia, increased cell viability in a PKCε-dependent manner. This was comparable with the protective effect of OPC previously reported in intact heart preparations. OPC prevented I/R-induced decrease of Na(+),K(+)-ATPase activity and surface expression. This model also revealed that Na(+),K(+)-ATPase-mediated (86)Rb(+) uptake was not restored to control levels in the OPC group, suggesting that the increased viability was not conferred by an increased Na(+),K(+)-ATPase-mediated ion transport capacity at the cell membrane. Consistent with this observation, transient expression of an internalization-resistant mutant form of Na(+),K(+)-ATPase α(1) known to have increased surface abundance without increased ion transport activity successfully reduced I/R-induced cell death. These results suggest that maintenance of Na(+),K(+)-ATPase cell surface abundance is critical to myocyte survival after an ischemic attack and plays a role in OPC-induced protection. They further suggest that the protection conferred by increased surface expression of Na(+),K(+)-ATPase may be independent of ion transport.
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Affiliation(s)
- Aude Belliard
- Department of Biochemistry, College of Medicine, University of Toledo, 3000 Arlington Ave., Toledo, OH 43614, USA
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121
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Roberts PG, Hirst J. The deactive form of respiratory complex I from mammalian mitochondria is a Na+/H+ antiporter. J Biol Chem 2012; 287:34743-51. [PMID: 22854968 PMCID: PMC3464577 DOI: 10.1074/jbc.m112.384560] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 07/23/2012] [Indexed: 11/21/2022] Open
Abstract
In mitochondria, complex I (NADH:ubiquinone oxidoreductase) uses the redox potential energy from NADH oxidation by ubiquinone to transport protons across the inner membrane, contributing to the proton-motive force. However, in some prokaryotes, complex I may transport sodium ions instead, and three subunits in the membrane domain of complex I are closely related to subunits from the Mrp family of Na(+)/H(+) antiporters. Here, we define the relationship between complex I from Bos taurus heart mitochondria, a close model for the human enzyme, and sodium ion transport across the mitochondrial inner membrane. In accord with current consensus, we exclude the possibility of redox-coupled Na(+) transport by B. taurus complex I. Instead, we show that the "deactive" form of complex I, which is formed spontaneously when enzyme turnover is precluded by lack of substrates, is a Na(+)/H(+) antiporter. The antiporter activity is abolished upon reactivation by the addition of substrates and by the complex I inhibitor rotenone. It is specific for Na(+) over K(+), and it is not exhibited by complex I from the yeast Yarrowia lipolytica, which thus has a less extensive deactive transition. We propose that the functional connection between the redox and transporter modules of complex I is broken in the deactive state, allowing the transport module to assert its independent properties. The deactive state of complex I is formed during hypoxia, when respiratory chain turnover is slowed, and may contribute to determining the outcome of ischemia-reperfusion injury.
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Affiliation(s)
- Philippa G. Roberts
- From The Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, United Kingdom
| | - Judy Hirst
- From The Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, United Kingdom
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122
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Kohlhaas M, Maack C. Interplay of defective excitation-contraction coupling, energy starvation, and oxidative stress in heart failure. Trends Cardiovasc Med 2012; 21:69-73. [PMID: 22626245 DOI: 10.1016/j.tcm.2012.03.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
In chronic heart failure, maladaptive remodeling of the left ventricle (LV) with systolic and diastolic dysfunction underlies the inability of the heart to pump sufficient blood to supply the body with blood and oxygen. Three integral aspects of this maladaptive LV remodeling are (1) defects in excitation-contraction (EC) coupling, particularly of cellular Ca(2+) and Na(+) homeostasis; (2) an energetic deficit; and (3) oxidative stress. Although these three aspects are often investigated separately from each other, their close and dynamic interplay are increasingly recognized. Central to this novel approach are mitochondria, which are the main source for cellular ATP, but also for reactive oxygen species, and their function is critically regulated by Ca(2+) and Na(+). Here, we review recent advances in our understanding of how maladaptive changes of EC coupling can contribute to the energetic deficit and oxidative stress, which may initiate a vicious cycle leading to progressive cardiac dysfunction.
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Affiliation(s)
- Michael Kohlhaas
- Medizinische Klinik und Poliklinik, Innere Medizin III, Universitätsklinikum des Saarlandes, 66421 Homburg/Saar, Germany
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123
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Koltsova SV, Trushina Y, Haloui M, Akimova OA, Tremblay J, Hamet P, Orlov SN. Ubiquitous [Na+]i/[K+]i-sensitive transcriptome in mammalian cells: evidence for Ca(2+)i-independent excitation-transcription coupling. PLoS One 2012; 7:e38032. [PMID: 22666440 PMCID: PMC3362528 DOI: 10.1371/journal.pone.0038032] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 04/29/2012] [Indexed: 12/21/2022] Open
Abstract
Stimulus-dependent elevation of intracellular Ca2+ ([Ca2+]i) affects the expression of numerous genes – a phenomenon known as excitation-transcription coupling. Recently, we found that increases in [Na+]i trigger c-Fos expression via a novel Ca2+i-independent pathway. In the present study, we identified ubiquitous and tissue-specific [Na+]i/[K+]i-sensitive transcriptomes by comparative analysis of differentially expressed genes in vascular smooth muscle cells from rat aorta (RVSMC), the human adenocarcinoma cell line HeLa, and human umbilical vein endothelial cells (HUVEC). To augment [Na+]i and reduce [K+]i, cells were treated for 3 hrs with the Na+,K+-ATPase inhibitor ouabain or placed for the same time in the K+-free medium. Employing Affymetrix-based technology, we detected changes in expression levels of 684, 737 and 1839 transcripts in HeLa, HUVEC and RVSMC, respectively, that were highly correlated between two treatments (p<0.0001; R2>0.62). Among these Na+i/K+i-sensitive genes, 80 transcripts were common for all three types of cells. To establish if changes in gene expression are dependent on increases in [Ca2+]i, we performed identical experiments in Ca2+-free media supplemented with extracellular and intracellular Ca2+ chelators. Surprisingly, this procedure elevated rather than decreased the number of ubiquitous and cell-type specific Na+i/K+i-sensitive genes. Among the ubiquitous Na+i/K+i-sensitive genes whose expression was regulated independently of the presence of Ca2+ chelators by more than 3-fold, we discovered several transcription factors (Fos, Jun, Hes1, Nfkbia), interleukin-6, protein phosphatase 1 regulatory subunit, dual specificity phosphatase (Dusp8), prostaglandin-endoperoxide synthase 2, cyclin L1, whereas expression of metallopeptidase Adamts1, adrenomedulin, Dups1, Dusp10 and Dusp16 was detected exclusively in Ca2+-depleted cells. Overall, our findings indicate that Ca2+i-independent mechanisms of excitation-transcription coupling are involved in transcriptomic alterations triggered by elevation of the [Na+]i/[K+]i ratio. There results likely have profound implications for normal and pathological regulation of mammalian cells, including sustained excitation of neuronal cells, intensive exercise and ischemia-triggered disorders.
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Affiliation(s)
- Svetlana V. Koltsova
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM) – Technopôle Angus, Montreal, PQ, Canada
- Institute of General Pathology and Pathophysiology, Russian Academy of Medical Sciences, Moscow, Russia
| | - Yulia Trushina
- Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Mounsif Haloui
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM) – Technopôle Angus, Montreal, PQ, Canada
| | - Olga A. Akimova
- Institute of General Pathology and Pathophysiology, Russian Academy of Medical Sciences, Moscow, Russia
- Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Johanne Tremblay
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM) – Technopôle Angus, Montreal, PQ, Canada
- Department of Medicine, Université de Montréal, Montreal, PQ, Canada
| | - Pavel Hamet
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM) – Technopôle Angus, Montreal, PQ, Canada
- Department of Medicine, Université de Montréal, Montreal, PQ, Canada
| | - Sergei N. Orlov
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM) – Technopôle Angus, Montreal, PQ, Canada
- Department of Medicine, Université de Montréal, Montreal, PQ, Canada
- * E-mail:
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124
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β-Adrenergic Regulation of the Cardiac Na+-K+ ATPase Mediated by Oxidative Signaling. Trends Cardiovasc Med 2012; 22:83-7. [DOI: 10.1016/j.tcm.2012.06.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 06/29/2012] [Accepted: 06/29/2012] [Indexed: 11/24/2022]
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125
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Palty R, Sekler I. The mitochondrial Na(+)/Ca(2+) exchanger. Cell Calcium 2012; 52:9-15. [PMID: 22430014 DOI: 10.1016/j.ceca.2012.02.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 02/24/2012] [Accepted: 02/27/2012] [Indexed: 01/20/2023]
Abstract
Powered by the steep mitochondrial membrane potential Ca(2+) permeates into the mitochondria via the Ca(2+) uniporter and is then extruded by a mitochondrial Na(+)/Ca(2+) exchanger. This mitochondrial Ca(2+) shuttling regulates the rate of ATP production and participates in cellular Ca(2+) signaling. Despite the fact that the exchanger was functionally identified 40 years ago its molecular identity remained a mystery. Early studies on isolated mitochondria and intact cells characterized the functional properties of a mitochondrial Na(+)/Ca(2+) exchanger, and showed that it possess unique functional fingerprints such as Li(+)/Ca(2+) exchange and that it is displaying selective sensitivity to inhibitors. Purification of mitochondria proteins combined with functional reconstitution led to the isolation of a polypeptide candidate of the exchanger but failed to molecularly identify it. A turning point in the search for the exchanger molecule came with the recent cloning of the last member of the Na(+)/Ca(2+) exchanger superfamily termed NCLX (Na(+)/Ca(2+)/Li(+) exchanger). NCLX is localized in the inner mitochondria membrane and its expression is linked to mitochondria Na(+)/Ca(2+) exchange matching the functional fingerprints of the putative mitochondrial Na(+)/Ca(2+) exchanger. Thus NCLX emerges as the long sought mitochondria Na(+)/Ca(2+) exchanger and provide a critical molecular handle to study mitochondrial Ca(2+) signaling and transport. Here we summarize some of the main topics related to the molecular properties of the Na(+)/Ca(2+) exchanger, beginning with the early days of its functional identification, its kinetic properties and regulation, and culminating in its molecular identification.
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Affiliation(s)
- Raz Palty
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA 94720, USA.
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126
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Gillespie D, Chen H, Fill M. Is ryanodine receptor a calcium or magnesium channel? Roles of K+ and Mg2+ during Ca2+ release. Cell Calcium 2012; 51:427-33. [PMID: 22387011 DOI: 10.1016/j.ceca.2012.02.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 01/30/2012] [Accepted: 02/01/2012] [Indexed: 11/19/2022]
Abstract
The ryanodine receptor (RyR) is a poorly selective channel that mediates Ca(2+) release from intracellular Ca(2+) stores. How RyR's selectivity between the physiological cations K(+), Mg(2+), and Ca(2+) affects single-channel Ca(2+) current amplitude is examined using a recent model of RyR permeation. It is found that K(+) provides the vast majority of the countercurrent (through RyR itself) that is needed to prevent the sarcoplasmic reticulum (SR) membrane potential from changing and stopping Ca(2+) release. Moreover, intra-pore competition between Ca(2+) and Mg(2+) defines single RyR Ca(2+) current amplitude. Since both [Mg(2+)] and [Ca(2+)](SR) can change during pathophysiological conditions, the RyR unitary Ca(2+) current amplitude during Ca(2+) release may change significantly due to this Ca(2+)/Mg(2+) competition. Compared to the classic action of Mg(2+) on RyR open probability, these Ca(2+) current amplitude changes have as large or larger effects on overall RyR Ca(2+) mobilization. A new aspect of RyR divalent versus monovalent selectivity is also identified where this kind of selectivity decreases as divalent concentration increases.
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Affiliation(s)
- Dirk Gillespie
- Department of Molecular Biophysics and Physiology, Section of Cellular Signaling, Rush University Medical Center, Chicago, IL 60612, United States.
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127
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Wojtovich AP, Sherman TA, Nadtochiy SM, Urciuoli WR, Brookes PS, Nehrke K. SLO-2 is cytoprotective and contributes to mitochondrial potassium transport. PLoS One 2011; 6:e28287. [PMID: 22145034 PMCID: PMC3228735 DOI: 10.1371/journal.pone.0028287] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Accepted: 11/04/2011] [Indexed: 11/19/2022] Open
Abstract
Mitochondrial potassium channels are important mediators of cell protection against stress. The mitochondrial large-conductance "big" K(+) channel (mBK) mediates the evolutionarily-conserved process of anesthetic preconditioning (APC), wherein exposure to volatile anesthetics initiates protection against ischemic injury. Despite the role of the mBK in cardioprotection, the molecular identity of the channel remains unknown. We investigated the attributes of the mBK using C. elegans and mouse genetic models coupled with measurements of mitochondrial K(+) transport and APC. The canonical Ca(2+)-activated BK (or "maxi-K") channel SLO1 was dispensable for both mitochondrial K(+) transport and APC in both organisms. Instead, we found that the related but physiologically-distinct K(+) channel SLO2 was required, and that SLO2-dependent mitochondrial K(+) transport was triggered directly by volatile anesthetics. In addition, a SLO2 channel activator mimicked the protective effects of volatile anesthetics. These findings suggest that SLO2 contributes to protection from hypoxic injury by increasing the permeability of the mitochondrial inner membrane to K(+).
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Affiliation(s)
- Andrew P. Wojtovich
- Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Teresa A. Sherman
- Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Sergiy M. Nadtochiy
- Department of Anesthesiology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - William R. Urciuoli
- Department of Anesthesiology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Paul S. Brookes
- Department of Anesthesiology, University of Rochester Medical Center, Rochester, New York, United States of America
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Keith Nehrke
- Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York, United States of America
- * E-mail:
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Carro J, Rodríguez JF, Laguna P, Pueyo E. A human ventricular cell model for investigation of cardiac arrhythmias under hyperkalaemic conditions. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2011; 369:4205-32. [PMID: 21969673 DOI: 10.1098/rsta.2011.0127] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In this study, several modifications were introduced to a recently proposed human ventricular action potential (AP) model so as to render it suitable for the study of ventricular arrhythmias. These modifications were driven by new sets of experimental data available from the literature and the analysis of several well-established cellular arrhythmic risk biomarkers, namely AP duration at 90 per cent repolarization (APD(90)), AP triangulation, calcium dynamics, restitution properties, APD(90) adaptation to abrupt heart rate changes, and rate dependence of intracellular sodium and calcium concentrations. The proposed methodology represents a novel framework for the development of cardiac cell models. Five stimulation protocols were applied to the original model and the ventricular AP model developed here to compute the described arrhythmic risk biomarkers. In addition, those models were tested in a one-dimensional fibre in which hyperkalaemia was simulated by increasing the extracellular potassium concentration, [K(+)](o). The effective refractory period (ERP), conduction velocity (CV) and the occurrence of APD alternans were investigated. Results show that modifications improved model behaviour as verified by: (i) AP triangulation well within experimental limits (the difference between APD at 50 and 90 per cent repolarization being 78.1 ms); (ii) APD(90) rate adaptation dynamics characterized by fast and slow time constants within physiological ranges (10.1 and 105.9 s); and (iii) maximum S1S2 restitution slope in accordance with experimental data (S(S1S2)=1.0). In simulated tissues under hyperkalaemic conditions, APD(90) progressively shortened with the degree of hyperkalaemia, whereas ERP increased once a threshold in [K(+)](o) was reached ([K(+)](o)≈6 mM). CV decreased with [K(+)](o), and conduction was blocked for [K(+)](o)>10.4 mM. APD(90) alternans were observed for [K(+)](o)>9.8 mM. Those results adequately reproduce experimental observations. This study demonstrated the value of basing the development of AP models on the computation of arrhythmic risk biomarkers, as opposed to joining together independently derived ion channel descriptions to produce a whole-cell AP model, with the new framework providing a better picture of the model performance under a variety of stimulation conditions. On top of replicating experimental data at single-cell level, the model developed here was able to predict the occurrence of APD(90) alternans and areas of conduction block associated with high [K(+)](o) in tissue, which is of relevance for the investigation of the arrhythmogenic substrate in ischaemic hearts.
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Affiliation(s)
- Jesús Carro
- Aragón Institute of Engineering Research (I3A), IIS Aragón, Universidad de Zaragoza, Spain
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129
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Chikando AC, Kettlewell S, Williams GS, Smith G, Lederer WJ. Ca2+ dynamics in the mitochondria - state of the art. J Mol Cell Cardiol 2011; 51:627-31. [PMID: 21864537 PMCID: PMC3814218 DOI: 10.1016/j.yjmcc.2011.08.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 08/05/2011] [Accepted: 08/06/2011] [Indexed: 01/24/2023]
Abstract
The importance of [Ca2+] in the mitochondrial matrix, [Ca2+]mito, had been proposed by early work of Carafoli and others [1 ], [2 ] and [3 ]. The key suggestion in the 1970s [4 ] was that regulatory [Ca2+]mito played a role in controlling the rate of activation of tricarboxylic acid cycle dehydrogenases, important in the regulation of ATP production by the electron transport chain (ETC) during oxidative phosphorylation. This view is now established [5 ] and [6 ] and the key questions currently debated are to what extent do the mitochondria acquire and release Ca2+, and what impact do mitochondria have on the dynamic Ca2+ signal in the cardiac ventricular myocyte [7 ]. Although investigations of Ca2+ dynamics in mitochondria have been problematic, disparate and inconclusive, they have also been both provocative and exciting. A recent special issue of this journal presented contrasting perspectives on the speed, extent and mechanisms of changes in [Ca2+]mito, and how these changes may influence cellular spatio-temporal [Ca2+]i dynamics [8 ]. An audio discussion is also available online [9 ]. The uncertain nature of the signaling pathways is noted in Table 1 (see below) which shows mitochondrial proteins and processes that are of current focus and which remain contentious. Each of the “items” listed is largely unsettled, or is a “work in progress”. There may be advocates for opposing positions noted or recent discoveries that must still be tested at multiple levels by diverse laboratories. Currently, the first item, the mitochondrial sodium/calcium exchanger (NCLX) [10 ], appears the most solid with respect to the molecular identification and physiological function, whereas, the recently described candidates of the mitochondrial Ca2+ uniporter (MCU) [11 ] and [12 ] still need to be verified and broadly examined by the scientific community.
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130
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Kadenbach B, Ramzan R, Moosdorf R, Vogt S. The role of mitochondrial membrane potential in ischemic heart failure. Mitochondrion 2011; 11:700-6. [DOI: 10.1016/j.mito.2011.06.001] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 05/13/2011] [Accepted: 06/08/2011] [Indexed: 11/16/2022]
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131
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Zhao ZG, Niu CY, Zhang YP, Han R, Hou YL, Wang XR, Jiang H, Du ST, Lu B. The Mechanism of Spleen Injury in Rabbits with Acute Renal Failure. Ren Fail 2011; 33:418-25. [DOI: 10.3109/0886022x.2011.568145] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
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132
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Abstract
Two-photon microscopy (TPM) has become an indispensible tool in biology and medicine owing to the capability of imaging the intact tissue for a long period of time. To make it a versatile tool in biology, a variety of two-photon probes for specific applications are needed. In this context, many research groups are developing two-photon probes for various applications. In this Focus Review, we summarize recent results on model studies and selected examples of two-photon probes that can detect intracellular free metal ions in live cells and tissues to provide a guideline for the design of useful two-photon probes for various in vivo imaging applications.
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Affiliation(s)
- Hwan Myung Kim
- Division of Energy Systems Research, Ajou University, Suwon, 443-749 Korea.
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133
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Wei AC, Liu T, Cortassa S, Winslow RL, O'Rourke B. Mitochondrial Ca2+ influx and efflux rates in guinea pig cardiac mitochondria: low and high affinity effects of cyclosporine A. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:1373-81. [PMID: 21362444 DOI: 10.1016/j.bbamcr.2011.02.012] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Revised: 02/14/2011] [Accepted: 02/17/2011] [Indexed: 12/12/2022]
Abstract
Ca(2+) plays a central role in energy supply and demand matching in cardiomyocytes by transmitting changes in excitation-contraction coupling to mitochondrial oxidative phosphorylation. Matrix Ca(2+) is controlled primarily by the mitochondrial Ca(2+) uniporter and the mitochondrial Na(+)/Ca(2+) exchanger, influencing NADH production through Ca(2+)-sensitive dehydrogenases in the Krebs cycle. In addition to the well-accepted role of the Ca(2+)-triggered mitochondrial permeability transition pore in cell death, it has been proposed that the permeability transition pore might also contribute to physiological mitochondrial Ca(2+) release. Here we selectively measure Ca(2+) influx rate through the mitochondrial Ca(2+) uniporter and Ca(2+) efflux rates through Na(+)-dependent and Na(+)-independent pathways in isolated guinea pig heart mitochondria in the presence or absence of inhibitors of mitochondrial Na(+)/Ca(2+) exchanger (CGP 37157) or the permeability transition pore (cyclosporine A). cyclosporine A suppressed the negative bioenergetic consequences (ΔΨ(m) loss, Ca(2+) release, NADH oxidation, swelling) of high extramitochondrial Ca(2+) additions, allowing mitochondria to tolerate total mitochondrial Ca(2+) loads of >400nmol/mg protein. For Ca(2+) pulses up to 15μM, Na(+)-independent Ca(2+) efflux through the permeability transition pore accounted for ~5% of the total Ca(2+) efflux rate compared to that mediated by the mitochondrial Na(+)/Ca(2+) exchanger (in 5mM Na(+)). Unexpectedly, we also observed that cyclosporine A inhibited mitochondrial Na(+)/Ca(2+) exchanger-mediated Ca(2+) efflux at higher concentrations (IC(50)=2μM) than those required to inhibit the permeability transition pore, with a maximal inhibition of ~40% at 10μM cyclosporine A, while having no effect on the mitochondrial Ca(2+) uniporter. The results suggest a possible alternative mechanism by which cyclosporine A could affect mitochondrial Ca(2+) load in cardiomyocytes, potentially explaining the paradoxical toxic effects of cyclosporine A at high concentrations. This article is part of a Special Issue entitled: Mitochondria and Cardioprotection.
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Affiliation(s)
- An-Chi Wei
- Department of Biomedical Engineering, Institute of Computational Medicine, The Johns Hopkins University, Baltimore MD 21205-2195, USA
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Abstract
Sodium ((23)Na) imaging has a place somewhere between (1)H-MRI and MR spectroscopy (MRS). Like MRS it potentially provides information on metabolic processes, but only one single resonance of ionic (23)Na is observed. Therefore pulse sequences do not need to code for a chemical shift dimension, allowing (23)Na images to be obtained at high resolutions as compared to MRS. In this chapter the biological significance of sodium in the brain will be discussed, as well as methods for observing it with (23)Na-MRI. Many vital cellular processes and interactions in excitable tissues depend on the maintenance of a low intracellular and high extracellular sodium concentration. Healthy cells maintain this concentration gradient at the cost of energy. Leaky cell membranes or an impaired energy metabolism immediately leads to an increase in cytosolic total tissue sodium. This makes sodium a biomarker for ischemia, cancer, excessive tissue activation, or tissue damage as might be caused by ablation therapy. Special techniques allow quantification of tissue sodium for the monitoring of disease or therapy in longitudinal studies or preferential observation of the intracellular component of the tissue sodium. New methods and high-field magnet technology provide new opportunities for (23)Na-MRI in clinical and biomedical research.
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Affiliation(s)
- Ronald Ouwerkerk
- Cardiovascular Imaging, National Institute of Diabetes and Digestive and Kidney Disease, National Institute of Health, Bethesda, MD, USA.
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Costa F, de Lurdes Baeta M, Saraiva D, Verissimo MT, Ramos F. Evolution of Mineral Contents in Tomato Fruits During the Ripening Process After Harvest. FOOD ANAL METHOD 2010. [DOI: 10.1007/s12161-010-9179-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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136
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Pierre SV, Belliard A, Sottejeau Y. Modulation of Na(+)-K(+)-ATPase cell surface abundance through structural determinants on the α1-subunit. Am J Physiol Cell Physiol 2010; 300:C42-8. [PMID: 21048163 DOI: 10.1152/ajpcell.00386.2010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Through their ion-pumping and non-ion-pumping functions, Na(+)-K(+)-ATPase protein complexes at the plasma membrane are critical to intracellular homeostasis and to the physiological and pharmacological actions of cardiotonic steroids. Alteration of the abundance of Na(+)-K(+)-ATPase units at the cell surface is one of the mechanisms for Na(+)-K(+)-ATPase regulation in health and diseases that has been closely examined over the past few decades. We here summarize these findings, with emphasis on studies that explicitly tested the involvement of defined regions or residues on the Na(+)-K(+)-ATPase α1 polypeptide. We also report new findings on the effect of manipulating Na(+)-K(+)-ATPase membrane abundance by targeting one of these defined regions: a dileucine motif of the form [D/E]XXXL[L/I]. In this study, opossum kidney cells stably expressing rat α1 Na(+)-K(+)-ATPase or a mutant where the motif was disrupted (α1-L499V) were exposed to 30 min of substrate/coverslip-induced-ischemia followed by reperfusion (I-R). Biotinylation studies suggested that I-R itself acted as an inducer of Na(+)-K(+)-ATPase internalization and that surface expression of the mutant was higher than the native Na(+)-K(+)-ATPase before and after ischemia. Annexin V/propidium iodide staining and lactate dehydrogenase release suggested that I-R injury was reduced in α1-L499V-expressing cells compared with α1-expressing cells. Hence, modulation of Na(+)-K(+)-ATPase cell surface abundance through structural determinants on the α-subunit is an important mechanism of regulation of cellular Na(+)-K(+)-ATPase in various physiological and pathophysiological conditions, with a significant impact on cell survival in face of an ischemic stress.
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Affiliation(s)
- Sandrine V Pierre
- Department of Physiology and Pharmacology, University of Toledo College of Medicine, Ohio 43614-2598, USA.
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137
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Kumar S, Flacke JP, Kostin S, Appukuttan A, Reusch HP, Ladilov Y. SLC4A7 sodium bicarbonate co-transporter controls mitochondrial apoptosis in ischaemic coronary endothelial cells. Cardiovasc Res 2010; 89:392-400. [PMID: 20962104 DOI: 10.1093/cvr/cvq330] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AIMS Bicarbonate transport has been shown to participate in apoptosis under ischaemic stress. However, the precise transporting mechanisms involved in ischaemic apoptosis are unknown and were thus the aim of the present study. METHODS AND RESULTS Rat coronary endothelial cells (EC) were exposed to simulated in vitro ischaemia for 2 h, and apoptosis was subsequently determined by chromatin staining and caspase-3 activity analysis. By examining the expression of bicarbonate transporters (BT) in EC by reverse transcriptase polymerase chain reaction and western blotting, a marked expression of the electroneutral sodium bicarbonate co-transporter (SLC4A7) was defined. To analyse the potential role of this transporter during apoptosis, a selective inhibitor (S0859, Sanofi-Aventis) was applied. Treatment with S0859 significantly increased caspase-3 activity and elevated the number of apoptotic EC. These results were comparable with an unselective inhibition of all BT due to withdrawal of bicarbonate in the anoxic medium. Knockdown of SLC4A7 in EC by transfecting appropriate siRNA similarly increased apoptosis of EC under simulated ischaemia. The initial characterization of the participating mechanisms of SLC4A7-dependent apoptosis revealed an activation of the mitochondrial pathway of apoptosis, i.e. cleavage of caspase-9 and binding of Bax to mitochondria. In contrast, no activation of the endoplasmic reticulum-dependent pathway (caspase-12 cleavage) or the extrinsic apoptotic pathway (caspase-8 cleavage) was found. Finally, a mitochondrial localization of SLC4A7 was demonstrated. CONCLUSION The electroneutral sodium bicarbonate co-transporter SLC4A7 localizes in mitochondria and suppresses the ischaemia-induced activation of the mitochondrial pathway of apoptosis in coronary EC.
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Affiliation(s)
- Sanjeev Kumar
- Department of Clinical Pharmacology, Ruhr-University Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany
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138
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Kozoriz MG, Church J, Ozog MA, Naus CC, Krebs C. Temporary sequestration of potassium by mitochondria in astrocytes. J Biol Chem 2010; 285:31107-19. [PMID: 20667836 DOI: 10.1074/jbc.m109.082073] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Increases in extracellular potassium concentration ([K(+)](o)), which can occur during neuronal activity and under pathological conditions such as ischemia, lead to a variety of potentially detrimental effects on neuronal function. Although astrocytes are known to contribute to the clearance of excess K(+)(o), the mechanisms are not fully understood. We examined the potential role of mitochondria in sequestering K(+) in astrocytes. Astrocytes were loaded with the fluorescent K(+) indicator PBFI and release of K(+) from mitochondria into the cytoplasm was examined after uncoupling the mitochondrial membrane potential with carbonyl cyanide m-chlorophenylhydrazone (CCCP). Under the experimental conditions employed, transient applications of elevated [K(+)](o) led to increases in K(+) within mitochondria, as assessed by increases in the magnitudes of cytoplasmic [K(+)] ([K(+)](i)) transients evoked by brief exposures to CCCP. When mitochondrial K(+) sequestration was impaired by prolonged application of CCCP, there was a robust increase in [K(+)](i) upon exposure to elevated [K(+)](o). Blockade of plasmalemmal K(+) uptake routes by ouabain, Ba(2+), or a mixture of voltage-activated K(+) channel inhibitors reduced K(+) uptake into mitochondria. Also, reductions in mitochondrial K(+) uptake occurred in the presence of mito-K(ATP) channel inhibitors. Rises in [K(+)](i) evoked by brief applications of CCCP following exposure to high [K(+)](o) were also reduced by gap junction blockers and in astrocytes isolated from connexin43-null mice, suggesting that connexins also play a role in K(+) uptake into astrocyte mitochondria. We conclude that mitochondria play a key role in K(+)(o) handling by astrocytes.
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Affiliation(s)
- Michael G Kozoriz
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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139
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Carafoli E. The fateful encounter of mitochondria with calcium: how did it happen? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:595-606. [PMID: 20385096 DOI: 10.1016/j.bbabio.2010.03.024] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Revised: 03/29/2010] [Accepted: 03/30/2010] [Indexed: 01/09/2023]
Abstract
A number of findings in the 1950s had offered indirect indications that mitochondria could accumulate Ca2+. In 1961, the phenomenon was directly demonstrated using isolated mitochondria: the uptake process was driven by respiratory chain activity or by the hydrolysis of added ATP. It could be accompanied by the simultaneous uptake of inorganic phosphate, in which case precipitates of hydroxyapatite were formed in the matrix, buffering its free Ca2+ concentration. The properties of the uptake process were established in the 1960s and 1970s: the uptake of Ca2+ occurred electrophoretically on a carrier that has not yet been molecularly identified, and was released from mitochondria via a Na+/Ca2+ antiporter. A H+/Ca2+ release exchanger was also found to operate in some mitochondrial types. The permeability transition pore was later also found to mediate the efflux of Ca2+ from mitochondria. In the mitochondrial matrix two TCA cycle dehydrogenases and pyruvate dehydrogenase phosphate phosphatase were found to be regulated in the matrix by the cycling of Ca2+ across the inner membrane. In conditions of cytoplasmic Ca2+ overload mitochondria could store for a time large amounts of precipitated Ca2+-phosphate, thus permitting cells to survive situations of Ca2+ emergency. The uptake process was found to have very low affinity for Ca2+: since the bulk concentration of Ca2+ in the cytoplasm is in the low to mid-nM range, it became increasingly difficult to postulate a role of mitochondria in the regulation of cytoplsmic Ca2+. A number of findings had nevertheless shown that energy linked Ca2+ transport occurred efficiently in mitochondria of various tissues in situ. The paradox was only solved in the 1990s, when it was found that the concentration of Ca2+ in the cytoplasm is not uniform: perimitochondrial micropools are created by the agonist-promoted discharge of Ca2+ from vicinal stores in which the concentration of Ca2+ is high enough to activate the low affinity mitochondrial uniporter. Mitochondria thus regained center stage as important regulators of cytoplasmic Ca2+ (not only of their own internal Ca2+). Their Ca2+ uptake systems was found to react very rapidly to cytoplasmic Ca2+ demands, even in the 150-200 msec time scale of processes like the contraction and relaxation of heart. An important recent development in the area of mitochondrial Ca2+ transport is its involvement in the disease process. Ca2+ signaling defects are now gaining increasing importance in the pathogenesis of diseases, e.g., neurodegenerative diseases. Since mitochondria have now regained a central role in the regulation of cytoplasmic Ca2+, dysfunctions of their Ca2+ controlling systems have expectedly been found to be involved in the pathogenesis of numerous disease processes.
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Affiliation(s)
- Ernesto Carafoli
- Department of Biochemistry and Venetian Institute of Molecular Medicine, University of Padova, Italy.
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140
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Miura T, Miki T, Yano T. Role of the gap junction in ischemic preconditioning in the heart. Am J Physiol Heart Circ Physiol 2010; 298:H1115-25. [DOI: 10.1152/ajpheart.00879.2009] [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] [Indexed: 12/27/2022]
Abstract
The gap junction plays roles not only in electrical coupling of cardiomyocytes but also in intercellular transport of biologically active substances. Furthermore, the gap junction participates in decision making on cell survival versus cell death in various types of cells, and a part of reperfusion injury in the heart has been indicated to be gap junction mediated. The contribution of gap junction communication (GJC) and/or mitochondrial “hemichannels” to protective signaling during the trigger phase of ischemic preconditioning (IPC) is suggested by observations that IPC failed to protect the heart when GJC was blocked during IPC. Although ischemia suppresses both electrical and chemical GJC, chemical GJC persists for a considerable time after electrical GJC is lost. IPC facilitates the ischemia-induced suppression of chemical GJC, whereas IPC delays the reduction of electrical GJC after ischemia. The inhibition of GJC during sustained ischemia and reperfusion by GJC blockers mimics the effect of IPC on myocardial necrosis. IPC induces distinct effects on the interaction of connexin-43 with protein kinases, and the phosphorylation of connexin-43 at Ser368 by PKCε is a primary mechanism of inhibition of chemical GJC by IPC. Several lines of evidence support the notion that the modulation of GJC is a part of the mechanism of IPC-induced protection against myocardial necrosis and arrhythmias, though what percentage of IPC protection is attributable to the inhibition of GJC during ischemia-reperfusion still remains unclear.
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Affiliation(s)
- Tetsuji Miura
- Division of Cardiology, Second Department of Internal Medicine, Sapporo Medical University, School of Medicine, Sapporo, Japan
| | - Takayuki Miki
- Division of Cardiology, Second Department of Internal Medicine, Sapporo Medical University, School of Medicine, Sapporo, Japan
| | - Toshiyuki Yano
- Division of Cardiology, Second Department of Internal Medicine, Sapporo Medical University, School of Medicine, Sapporo, Japan
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Kohlhaas M, Liu T, Knopp A, Zeller T, Ong MF, Böhm M, O'Rourke B, Maack C. Elevated cytosolic Na+ increases mitochondrial formation of reactive oxygen species in failing cardiac myocytes. Circulation 2010; 121:1606-13. [PMID: 20351235 DOI: 10.1161/circulationaha.109.914911] [Citation(s) in RCA: 251] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND Oxidative stress is causally linked to the progression of heart failure, and mitochondria are critical sources of reactive oxygen species in failing myocardium. We previously observed that in heart failure, elevated cytosolic Na(+) ([Na(+)](i)) reduces mitochondrial Ca(2+) ([Ca(2+)](m)) by accelerating Ca(2+) efflux via the mitochondrial Na(+)/Ca(2+) exchanger. Because the regeneration of antioxidative enzymes requires NADPH, which is indirectly regenerated by the Krebs cycle, and Krebs cycle dehydrogenases are activated by [Ca(2+)](m), we speculated that in failing myocytes, elevated [Na(+)](i) promotes oxidative stress. METHODS AND RESULTS We used a patch-clamp-based approach to simultaneously monitor cytosolic and mitochondrial Ca(2+) and, alternatively, mitochondrial H(2)O(2) together with NAD(P)H in guinea pig cardiac myocytes. Cells were depolarized in a voltage-clamp mode (3 Hz), and a transition of workload was induced by beta-adrenergic stimulation. During this transition, NAD(P)H initially oxidized but recovered when [Ca(2+)](m) increased. The transient oxidation of NAD(P)H was closely associated with an increase in mitochondrial H(2)O(2) formation. This reactive oxygen species formation was potentiated when mitochondrial Ca(2+) uptake was blocked (by Ru360) or Ca(2+) efflux was accelerated (by elevation of [Na(+)](i)). In failing myocytes, H(2)O(2) formation was increased, which was prevented by reducing mitochondrial Ca(2+) efflux via the mitochondrial Na(+)/Ca(2+) exchanger. CONCLUSIONS Besides matching energy supply and demand, mitochondrial Ca(2+) uptake critically regulates mitochondrial reactive oxygen species production. In heart failure, elevated [Na(+)](i) promotes reactive oxygen species formation by reducing mitochondrial Ca(2+) uptake. This novel mechanism, by which defects in ion homeostasis induce oxidative stress, represents a potential drug target to reduce reactive oxygen species production in the failing heart.
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Affiliation(s)
- Michael Kohlhaas
- Universitätsklinikum des Saarlandes, Klinik für Innere Medizin III, 66421 Homburg, Germany
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142
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Kim MK, Lim CS, Hong JT, Han JH, Jang HY, Kim HM, Cho BR. Sodium-ion-selective two-photon fluorescent probe for in vivo imaging. Angew Chem Int Ed Engl 2010; 49:364-7. [PMID: 19998298 DOI: 10.1002/anie.200904835] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Mi Kyung Kim
- Division of Energy Systems Research, Ajou University, Suwon, 443-749, Korea
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143
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Griffiths EJ, Balaska D, Cheng WHY. The ups and downs of mitochondrial calcium signalling in the heart. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:856-64. [PMID: 20188059 DOI: 10.1016/j.bbabio.2010.02.022] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 02/18/2010] [Accepted: 02/18/2010] [Indexed: 12/17/2022]
Abstract
Regulation of intramitochondrial free calcium ([Ca2+]m) is critical in both physiological and pathological functioning of the heart. The full extent and importance of the role of [Ca2+]m is becoming apparent as evidenced by the increasing interest and work in this area over the last two decades. However, controversies remain, such as the existence of beat-to-beat mitochondrial Ca2+ transients; the role of [Ca2+]m in modulating whole-cell Ca2+ signalling; whether or not an increase in [Ca2+]m is essential to couple ATP supply and demand; and the role of [Ca2+]m in cell death by both necrosis and apoptosis, especially in formation of the mitochondrial permeability transition pore. The role of [Ca2+]m in heart failure is an area that has also recently been highlighted. [Ca2+]m can now be measured reasonably specifically in intact cells and hearts thanks to developments in fluorescent indicators and targeted proteins and more sensitive imaging technology. This has revealed interactions of the mitochondrial Ca2+ transporters with those of the sarcolemma and sarcoplasmic reticulum, and has gone a long way to bringing the mitochondrial Ca2+ transporters to the forefront of cardiac research. Mitochondrial Ca2+ uptake occurs via the ruthenium red sensitive Ca2+ uniporter (mCU), and efflux via an Na+/Ca2+ exchanger (mNCX). The purification and cloning of the transporters, and development of more specific inhibitors, would produce a step-change in our understanding of the role of these apparently critical but still elusive proteins. In this article we will summarise the key physiological roles of [Ca2+]m in ATP production and cell Ca2+ signalling in both adult and neonatal hearts, as well as highlighting some of the controversies in these areas. We will also briefly discuss recent ideas on the interactions of nitric oxide with [Ca2+]m.
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Affiliation(s)
- Elinor J Griffiths
- Department of Biochemistry and Bristol Heart Institute, University of Bristol, School of Medical Sciences, University Walk, Bristol BS8 1TD, UK.
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Kim M, Lim C, Hong J, Han J, Jang H, Kim H, Cho B. Sodium‐Ion‐Selective Two‐Photon Fluorescent Probe for In Vivo Imaging. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200904835] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Mi Kyung Kim
- Division of Energy Systems Research, Ajou University, Suwon, 443‐749 (Korea), Fax: (+82) 31‐219‐1615
| | - Chang Su Lim
- Department of Chemistry, Korea University, 1‐Anamdong, Seoul, 136‐701 (Korea), Fax: (+82) 2‐3290‐3544
| | - Jong Tae Hong
- Division of Energy Systems Research, Ajou University, Suwon, 443‐749 (Korea), Fax: (+82) 31‐219‐1615
| | - Ji Hee Han
- Department of Chemistry, Korea University, 1‐Anamdong, Seoul, 136‐701 (Korea), Fax: (+82) 2‐3290‐3544
| | - Hye‐Young Jang
- Division of Energy Systems Research, Ajou University, Suwon, 443‐749 (Korea), Fax: (+82) 31‐219‐1615
| | - Hwan Myung Kim
- Division of Energy Systems Research, Ajou University, Suwon, 443‐749 (Korea), Fax: (+82) 31‐219‐1615
| | - Bong Rae Cho
- Department of Chemistry, Korea University, 1‐Anamdong, Seoul, 136‐701 (Korea), Fax: (+82) 2‐3290‐3544
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145
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Løfgren B, Povlsen JA, Rasmussen LE, Støttrup NB, Solskov L, Krarup PM, Kristiansen SB, Bøtker HE, Nielsen TT. Amino acid transamination is crucial for ischaemic cardioprotection in normal and preconditioned isolated rat hearts--focus on L-glutamate. Exp Physiol 2009; 95:140-52. [PMID: 19717487 DOI: 10.1113/expphysiol.2009.049452] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have found that cardioprotection by l-glutamate mimics protection by classical ischaemic preconditioning (IPC). We investigated whether the effect of IPC involves amino acid transamination and whether IPC modulates myocardial glutamate metabolism. In a glucose-perfused, isolated rat heart model subjected to 40 min global no-flow ischaemia and 120 min reperfusion, the effects of IPC (2 cycles of 5 min ischaemia and 5 min reperfusion) and continuous glutamate (20 mm) administration during reperfusion on infarct size and haemodynamic recovery were studied. The effect of inhibiting amino acid transamination was evaluated by adding the amino acid transaminase inhibitor amino-oxyacetate (AOA; 0.025 mm) during reperfusion. Changes in coronary effluent, interstitial (microdialysis) and intracellular glutamate ([GLUT](i)) concentrations were measured. Ischaemic preconditioning and postischaemic glutamate administration reduced infarct size to the same extent (41 and 40%, respectively; P < 0.05 for both), without showing an additive effect. Amino-oxyacetate abolished infarct reduction by IPC and glutamate, and increased infarct size in both control and IPC hearts in a dose-dependent manner. Ischaemic preconditioning increased [GLUT](i) before ischaemia (P < 0.01) and decreased the release of glutamate during the first 10 min of reperfusion (P = 0.03). A twofold reduction in [GLUT](i) from the preischaemic state to 45 min of reperfusion (P = 0.0001) suggested increased postischaemic glutamate utilization in IPC hearts. While IPC and AOA changed haemodynamics in accordance with infarct size, glutamate decreased haemodynamic recovery despite reduced infarct size. In conclusion, ischaemic cardioprotection of the normal and IPC-protected heart depends on amino acid transamination and activity of the malate-aspartate shuttle during reperfusion. Underlying mechanisms of IPC include myocardial glutamate metabolism.
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Affiliation(s)
- Bo Løfgren
- Department of Cardiology B, Arhus University Hospital, Skejby, 8200 Arhus N, Denmark
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146
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Gurung IS, Kalin A, Grace AA, Huang CLH. Activation of purinergic receptors by ATP induces ventricular tachycardia by membrane depolarization and modifications of Ca2+ homeostasis. J Mol Cell Cardiol 2009; 47:622-33. [PMID: 19679135 DOI: 10.1016/j.yjmcc.2009.08.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2009] [Revised: 07/31/2009] [Accepted: 08/01/2009] [Indexed: 11/24/2022]
Abstract
Cardiac myocytes are continuously exposed to extracellular nucleotides secreted by the myocytes themselves, nerve terminals, or platelets and other blood cells during coronary perfusion, and the concentrations of such extracellular nucleotides are known to increase during cardiac ischemia and hypoxia. The effects of the extracellular nucleotides ATP, ADP, UTP, and adenosine on ventricular arrhythmogenic properties were explored in 36 Langendorff-perfused mouse hearts using monophasic action potential recording. Extracellular nucleotides induced arrhythmic phenomena in form of ectopic activity and ventricular tachycardia in a potency order of ATP (n=7) > ADP (n=5) > UTP (n=3) approximately adenosine (n=3). The purinergic receptor antagonists suramin and pyridoxal phosphate-6-azo(benzene-2,4-disulphonic acid) reduced the incidence of ATP-triggered arrhythmias. In isolated ventricular myocytes, ATP induced sustained increases in diastolic Ca2+ and triggered multiple Ca2+ waves, which were inhibited by suramin but not by the L-type Ca2+ channel antagonist nifedipine. In whole-cell patch clamp experiments, extracellular ATP induced two distinct types of inward currents, which were inhibited by suramin and PPADS, suggesting activation of P2X receptors. ATP also induced delayed after-depolarizations and ectopic action potentials in current clamped ventricular myocytes. In conclusion, extracellular ATP activates purinergic receptors and induces arrhythmic activity through modifications of Ca2+ homeostasis and an activation of depolarizing membrane currents.
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Affiliation(s)
- Iman S Gurung
- Department of Biochemistry, Hopkins Building; University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW, UK.
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147
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Romero L, Pueyo E, Fink M, Rodríguez B. Impact of ionic current variability on human ventricular cellular electrophysiology. Am J Physiol Heart Circ Physiol 2009; 297:H1436-45. [PMID: 19648254 DOI: 10.1152/ajpheart.00263.2009] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Abnormalities in repolarization and its rate dependence are known to be related to increased proarrhythmic risk. A number of repolarization-related electrophysiological properties are commonly used as preclinical biomarkers of arrhythmic risk. However, the variability and complexity of repolarization mechanisms make the use of cellular biomarkers to predict arrhythmic risk preclinically challenging. Our goal is to investigate the role of ionic current properties and their variability in modulating cellular biomarkers of arrhythmic risk to improve risk stratification and identification in humans. A systematic investigation into the sensitivity of the main preclinical biomarkers of arrhythmic risk to changes in ionic current conductances and kinetics was performed using computer simulations. Four stimulation protocols were applied to the ten Tusscher and Panfilov human ventricular model to quantify the impact of +/-15 and +/-30% variations in key model parameters on action potential (AP) properties, Ca(2+) and Na(+) dynamics, and their rate dependence. Simulations show that, in humans, AP duration is moderately sensitive to changes in all repolarization current conductances and in L-type Ca(2+) current (I(CaL)) and slow component of the delayed rectifier current (I(Ks)) inactivation kinetics. AP triangulation, however, is strongly dependent only on inward rectifier K(+) current (I(K1)) and delayed rectifier current (I(Kr)) conductances. Furthermore, AP rate dependence (i.e., AP duration rate adaptation and restitution properties) and intracellular Ca(2+) and Na(+) levels are highly sensitive to both I(CaL) and Na(+)/K(+) pump current (I(NaK)) properties. This study provides quantitative insights into the sensitivity of preclinical biomarkers of arrhythmic risk to variations in ionic current properties in humans. The results show the importance of sensitivity analysis as a powerful method for the in-depth validation of mathematical models in cardiac electrophysiology.
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Affiliation(s)
- Lucía Romero
- Instituto de Investigación Interuniversitario en Bioingeniería y Tecnología Orientada al Ser Humano, Universidad Politécnica de Valencia, Valencia, Spain.
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