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Ren AJ, Wei C, Liu YJ, Liu M, Wang P, Fan J, Wang K, Zhang S, Qin Z, Ren QX, Zheng Y, Chen YX, Xie Z, Gao L, Zhu Y, Zhang Y, Yang HT, Zhang WJ. ZBTB20 Regulates SERCA2a Activity and Myocardial Contractility Through Phospholamban. Circ Res 2024; 134:252-265. [PMID: 38166470 DOI: 10.1161/circresaha.123.323798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 12/20/2023] [Indexed: 01/04/2024]
Abstract
BACKGROUND Intracellular Ca2+ cycling determines myocardial contraction and relaxation in response to physiological demands. SERCA2a (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 2a) is responsible for the sequestration of cytosolic Ca2+ into intracellular stores during cardiac relaxation, and its activity is reversibly inhibited by PLN (phospholamban). However, the regulatory hierarchy of SERCA2a activity remains unclear. METHODS Cardiomyocyte-specific ZBTB20 knockout mice were generated by crossing ZBTB20flox mice with Myh6-Cre mice. Echocardiography, blood pressure measurements, Langendorff perfusion, histological analysis and immunohistochemistry, quantitative reverse transcription-PCR, Western blot analysis, electrophysiological measurements, and chromatin immunoprecipitation assay were performed to clarify the phenotype and elucidate the molecular mechanisms. RESULTS Specific ablation of ZBTB20 in cardiomyocyte led to a significant increase in basal myocardial contractile parameters both in vivo and in vitro, accompanied by an impairment in cardiac reserve and exercise capacity. Moreover, the cardiomyocytes lacking ZBTB20 showed an increase in sarcoplasmic reticular Ca2+ content and exhibited a remarkable enhancement in both SERCA2a activity and electrically stimulated contraction. Mechanistically, PLN expression was dramatically reduced in cardiomyocytes at the mRNA and protein levels by ZBTB20 deletion or silencing, and PLN overexpression could largely restore the basal contractility in ZBTB20-deficient cardiomyocytes. CONCLUSIONS These data point to ZBTB20 as a fine-tuning modulator of PLN expression and SERCA2a activity, thereby offering new perspective on the regulation of basal contractility in the mammalian heart.
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Affiliation(s)
- An-Jing Ren
- Department of Pathophysiology, Naval Medical University, Shanghai, China (A.-J.R., C.W., M.L., P.W., K.W., Z.Q., Q.-X.R., Y.-X.C., W.J.Z.)
- Experimental Teaching Center, College of Basic Medical Sciences, Naval Medical University, Shanghai, China (A.-J.R., J.F.)
| | - Chunchun Wei
- Department of Pathophysiology, Naval Medical University, Shanghai, China (A.-J.R., C.W., M.L., P.W., K.W., Z.Q., Q.-X.R., Y.-X.C., W.J.Z.)
| | - Ya-Jin Liu
- NHC Key Laboratory of Hormones and Development, Tianjin Key Laboratory of Metabolic Diseases, Tianjin Institute of Endocrinology and Chu Hsien-I Memorial Hospital, Tianjin Medical University Tianjin, China (Y.-J.L., Y. Zhu, W.J.Z.)
| | - Mengna Liu
- Department of Pathophysiology, Naval Medical University, Shanghai, China (A.-J.R., C.W., M.L., P.W., K.W., Z.Q., Q.-X.R., Y.-X.C., W.J.Z.)
| | - Ping Wang
- Department of Pathophysiology, Naval Medical University, Shanghai, China (A.-J.R., C.W., M.L., P.W., K.W., Z.Q., Q.-X.R., Y.-X.C., W.J.Z.)
| | - Juan Fan
- Experimental Teaching Center, College of Basic Medical Sciences, Naval Medical University, Shanghai, China (A.-J.R., J.F.)
| | - Kai Wang
- Department of Pathophysiology, Naval Medical University, Shanghai, China (A.-J.R., C.W., M.L., P.W., K.W., Z.Q., Q.-X.R., Y.-X.C., W.J.Z.)
| | - Sha Zhang
- Department of Cardiovascular Diseases, Changhai Hospital, Naval Medical University, Shanghai, China (S.Z.)
| | - Zhenbang Qin
- Department of Pathophysiology, Naval Medical University, Shanghai, China (A.-J.R., C.W., M.L., P.W., K.W., Z.Q., Q.-X.R., Y.-X.C., W.J.Z.)
| | - Qiu-Xiao Ren
- Department of Pathophysiology, Naval Medical University, Shanghai, China (A.-J.R., C.W., M.L., P.W., K.W., Z.Q., Q.-X.R., Y.-X.C., W.J.Z.)
| | - Yanjun Zheng
- CAS Key Laboratory of Tissue Microenvironment and Tumor, Laboratory of Molecular Cardiology, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, China (Y. Zheng, H.-T.Y.)
| | - Yu-Xia Chen
- Department of Pathophysiology, Naval Medical University, Shanghai, China (A.-J.R., C.W., M.L., P.W., K.W., Z.Q., Q.-X.R., Y.-X.C., W.J.Z.)
| | - Zhifang Xie
- Ministry of Education-Shanghai Key Laboratory of Children's Environmental Health, Institute of Early Life Health, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, China (Z.X.)
| | - Ling Gao
- Translational Medical Center for Stem Cell Therapy and Institute for Regenerative Medicine, Shanghai East Hospital, Tongji University School of Medicine, China (L.G.)
| | - Yi Zhu
- NHC Key Laboratory of Hormones and Development, Tianjin Key Laboratory of Metabolic Diseases, Tianjin Institute of Endocrinology and Chu Hsien-I Memorial Hospital, Tianjin Medical University Tianjin, China (Y.-J.L., Y. Zhu, W.J.Z.)
| | - Youyi Zhang
- Institute of Vascular Medicine, National Key Laboratory of Cardiovascular Homeostasis and Remodeling, Peking University Third Hospital, Beijing, China (Y. Zhang)
| | - Huang-Tian Yang
- CAS Key Laboratory of Tissue Microenvironment and Tumor, Laboratory of Molecular Cardiology, Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, China (Y. Zheng, H.-T.Y.)
| | - Weiping J Zhang
- Department of Pathophysiology, Naval Medical University, Shanghai, China (A.-J.R., C.W., M.L., P.W., K.W., Z.Q., Q.-X.R., Y.-X.C., W.J.Z.)
- NHC Key Laboratory of Hormones and Development, Tianjin Key Laboratory of Metabolic Diseases, Tianjin Institute of Endocrinology and Chu Hsien-I Memorial Hospital, Tianjin Medical University Tianjin, China (Y.-J.L., Y. Zhu, W.J.Z.)
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Hegner P, Drzymalski M, Biedermann A, Memmel B, Durczok M, Wester M, Floerchinger B, Provaznik Z, Schmid C, Zausig Y, Maier LS, Wagner S. SAR296968, a Novel Selective Na+/Ca2+ Exchanger Inhibitor, Improves Ca2+ Handling and Contractile Function in Human Atrial Cardiomyocytes. Biomedicines 2022; 10:biomedicines10081932. [PMID: 36009478 PMCID: PMC9406204 DOI: 10.3390/biomedicines10081932] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 07/30/2022] [Accepted: 08/04/2022] [Indexed: 11/16/2022] Open
Abstract
Background: In reverse-mode, cardiac sodium-calcium exchanger (NCX) can increase the cytoplasmic Ca2+ concentration in response to high intracellular Na+ levels, which may contribute to diastolic contractile dysfunction. Furthermore, increased spontaneous Ca2+ release from intracellular stores can activate forward mode NCX. The resulting transient inward current causes delayed afterdepolarization (DAD)-dependent arrhythmias. Moreover, recently, NCX has been associated with impaired relaxation and reduced cardiac function in heart failure with preserved ejection fraction (HFpEF). Since NCX is upregulated in human chronic atrial fibrillation (AF) as well as heart failure (HF), specific inhibition may have therapeutic potential. Objective: We tested the antiarrhythmic, lusitropic and inotropic effects of a novel selective NCX-inhibitor (SAR296968) in human atrial myocardium. Methods and Results: Right atrial appendage biopsies of 46 patients undergoing elective cardiac surgery in a predominant HFpEF cohort (n = 24/46) were investigated. In isolated human atrial cardiomyocytes, SAR296968 reduced the frequency of spontaneous SR Ca2+ release events and increased caffeine transient amplitude. In accordance, in isolated atrial trabeculae, SAR296968 enhanced the developed tension after a 30 s pause of electrical stimulation consistent with reduced diastolic sarcoplasmic reticulum (SR) Ca2+ leak. Moreover, compared to vehicle, SAR296968 decreased steady-state diastolic tension (at 1 Hz) without impairing developed systolic tension. Importantly, SAR296968 did not affect the safety parameters, such as resting membrane potential or action potential duration as measured by patch clamp. Conclusion: The novel selective NCX-inhibitor SAR296968 inhibits atrial pro-arrhythmic activity and improves diastolic and contractile function in human atrial myocardium, which may have therapeutic implications, especially for treatment of HFpEF.
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Affiliation(s)
- Philipp Hegner
- Department of Internal Medicine II, University Medical Center Regensburg, 93053 Regensburg, Germany
| | - Marzena Drzymalski
- Department of Internal Medicine II, University Medical Center Regensburg, 93053 Regensburg, Germany
| | - Alexander Biedermann
- Department of Internal Medicine II, University Medical Center Regensburg, 93053 Regensburg, Germany
| | - Bernadette Memmel
- Department of Internal Medicine II, University Medical Center Regensburg, 93053 Regensburg, Germany
| | - Melanie Durczok
- Department of Internal Medicine II, University Medical Center Regensburg, 93053 Regensburg, Germany
| | - Michael Wester
- Department of Internal Medicine II, University Medical Center Regensburg, 93053 Regensburg, Germany
| | - Bernhard Floerchinger
- Department of Cardiothoracic Surgery, University Medical Center Regensburg, 93053 Regensburg, Germany
| | - Zdenek Provaznik
- Department of Cardiothoracic Surgery, University Medical Center Regensburg, 93053 Regensburg, Germany
| | - Christof Schmid
- Department of Cardiothoracic Surgery, University Medical Center Regensburg, 93053 Regensburg, Germany
| | - York Zausig
- Department of Anesthesiology, University Medical Center Regensburg, 93053 Regensburg, Germany
- Department of Anesthesiology and Operative Intensive Care Medicine, Aschaffenburg-Alzenau Hospital, 63739 Aschaffenburg, Germany
| | - Lars S. Maier
- Department of Internal Medicine II, University Medical Center Regensburg, 93053 Regensburg, Germany
| | - Stefan Wagner
- Department of Internal Medicine II, University Medical Center Regensburg, 93053 Regensburg, Germany
- Correspondence: ; Tel.: +49-941-944-7206
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Njegic A, Wilson C, Cartwright EJ. Targeting Ca 2 + Handling Proteins for the Treatment of Heart Failure and Arrhythmias. Front Physiol 2020; 11:1068. [PMID: 33013458 PMCID: PMC7498719 DOI: 10.3389/fphys.2020.01068] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 08/04/2020] [Indexed: 12/18/2022] Open
Abstract
Diseases of the heart, such as heart failure and cardiac arrhythmias, are a growing socio-economic burden. Calcium (Ca2+) dysregulation is key hallmark of the failing myocardium and has long been touted as a potential therapeutic target in the treatment of a variety of cardiovascular diseases (CVD). In the heart, Ca2+ is essential for maintaining normal cardiac function through the generation of the cardiac action potential and its involvement in excitation contraction coupling. As such, the proteins which regulate Ca2+ cycling and signaling play a vital role in maintaining Ca2+ homeostasis. Changes to the expression levels and function of Ca2+-channels, pumps and associated intracellular handling proteins contribute to altered Ca2+ homeostasis in CVD. The remodeling of Ca2+-handling proteins therefore results in impaired Ca2+ cycling, Ca2+ leak from the sarcoplasmic reticulum and reduced Ca2+ clearance, all of which contributes to increased intracellular Ca2+. Currently, approved treatments for targeting Ca2+ handling dysfunction in CVD are focused on Ca2+ channel blockers. However, whilst Ca2+ channel blockers have been successful in the treatment of some arrhythmic disorders, they are not universally prescribed to heart failure patients owing to their ability to depress cardiac function. Despite the progress in CVD treatments, there remains a clear need for novel therapeutic approaches which are able to reverse pathophysiology associated with heart failure and arrhythmias. Given that heart failure and cardiac arrhythmias are closely associated with altered Ca2+ homeostasis, this review will address the molecular changes to proteins associated with both Ca2+-handling and -signaling; their potential as novel therapeutic targets will be discussed in the context of pre-clinical and, where available, clinical data.
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Affiliation(s)
- Alexandra Njegic
- Division of Cardiovascular Sciences, The University of Manchester, Manchester, United Kingdom.,Centre for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom
| | - Claire Wilson
- Division of Cardiovascular Sciences, The University of Manchester, Manchester, United Kingdom.,Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Elizabeth J Cartwright
- Division of Cardiovascular Sciences, The University of Manchester, Manchester, United Kingdom
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Li S, Chopra A, Keung W, Chan CWY, Costa KD, Kong CW, Hajjar RJ, Chen CS, Li RA. Sarco/endoplasmic reticulum Ca2+-ATPase is a more effective calcium remover than sodium-calcium exchanger in human embryonic stem cell-derived cardiomyocytes. Am J Physiol Heart Circ Physiol 2019; 317:H1105-H1115. [DOI: 10.1152/ajpheart.00540.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Human pluripotent stem cell (hPSCs)-derived ventricular (V) cardiomyocytes (CMs) display immature Ca2+–handing properties with smaller transient amplitudes and slower kinetics due to such differences in crucial Ca2+-handling proteins as the poor sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pump but robust Na+-Ca2+ exchanger (NCX) activities in human embryonic stem cell (ESC)-derived VCMs compared with adult. Despite their fundamental importance in excitation-contraction coupling, the relative contribution of SERCA and NCX to Ca2+-handling of hPSC-VCMs remains unexplored. We systematically altered the activities of SERCA and NCX in human embryonic stem cell-derived ventricular cardiomyocytes (hESC-VCMs) and their engineered microtissues, followed by examining the resultant phenotypic consequences. SERCA overexpression in hESC-VCMs shortened the decay of Ca2+ transient at low frequencies (0.5 Hz) without affecting the amplitude, SR Ca2+ content and Ca2+ baseline. Interestingly, short hairpin RNA-based NCX suppression did not prolong the transient decay, indicating a compensatory response for Ca2+ removal. Although hESC-VCMs and their derived microtissues exhibited negative frequency-transient/force responses, SERCA overexpression rendered them less negative at high frequencies (>2 Hz) by accelerating Ca2+ sequestration. We conclude that for hESC-VCMs and their microtissues, SERCA, rather than NCX, is the main Ca2+ remover during diastole; poor SERCA expression is the leading cause for immature negative-frequency/force responses, which can be partially reverted by forced expression. Combinatorial approach to mature calcium handling in hESC-VCMs may help shed further mechanistic insights. NEW & NOTEWORTHY In this study of human pluripotent stem cell-derived cardiomyocytes, we studied the role of sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) and Na+-Ca2+ exchanger (NCX) in Ca2+ handling. Our data support the notion that SERCA is more effective in cytosolic calcium removal than the NCX.
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Affiliation(s)
- Sen Li
- Dr. Li Dak-Sum Research Centre, The University of Hong Kong, Pokfulam, Hong Kong
- Stem Cell and Regenerative Medicine Consortium, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Anant Chopra
- Department of Bioengineering, Boston University, Boston, Massachusetts
- Harvard Wyss Institute for Biologically Inspired Engineering, Boston, Massachusetts
| | - Wendy Keung
- Dr. Li Dak-Sum Research Centre, The University of Hong Kong, Pokfulam, Hong Kong
- Stem Cell and Regenerative Medicine Consortium, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Camie W. Y. Chan
- Stem Cell and Regenerative Medicine Consortium, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Kevin D. Costa
- Cardiovascular Research Center, Icahn School of Medicine at Mount Sinai, Manhattan, New York
| | - Chi-Wing Kong
- Dr. Li Dak-Sum Research Centre, The University of Hong Kong, Pokfulam, Hong Kong
- Stem Cell and Regenerative Medicine Consortium, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Roger J. Hajjar
- Cardiovascular Research Center, Icahn School of Medicine at Mount Sinai, Manhattan, New York
| | - Christopher S. Chen
- Department of Bioengineering, Boston University, Boston, Massachusetts
- Harvard Wyss Institute for Biologically Inspired Engineering, Boston, Massachusetts
| | - Ronald A. Li
- Dr. Li Dak-Sum Research Centre, The University of Hong Kong, Pokfulam, Hong Kong
- Stem Cell and Regenerative Medicine Consortium, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
- Ming-Wai Lau Centre for Reparative Medicine, Karolinska Institutet, Hong Kong
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Pathophysiology of Calcium Mediated Ventricular Arrhythmias and Novel Therapeutic Options with Focus on Gene Therapy. Int J Mol Sci 2019; 20:ijms20215304. [PMID: 31653119 PMCID: PMC6862059 DOI: 10.3390/ijms20215304] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Revised: 10/16/2019] [Accepted: 10/21/2019] [Indexed: 12/19/2022] Open
Abstract
Cardiac arrhythmias constitute a major health problem with a huge impact on mortality rates and health care costs. Despite ongoing research efforts, the understanding of the molecular mechanisms and processes responsible for arrhythmogenesis remains incomplete. Given the crucial role of Ca2+-handling in action potential generation and cardiac contraction, Ca2+ channels and Ca2+ handling proteins represent promising targets for suppression of ventricular arrhythmias. Accordingly, we report the different roles of Ca2+-handling in the development of congenital as well as acquired ventricular arrhythmia syndromes. We highlight the therapeutic potential of gene therapy as a novel and innovative approach for future arrhythmia therapy. Furthermore, we discuss various promising cellular and mitochondrial targets for therapeutic gene transfer currently under investigation.
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Nakamura T, Fujita T, Kishimura M, Suita K, Hidaka Y, Cai W, Umemura M, Yokoyama U, Uechi M, Ishikawa Y. Vidarabine, an Anti-Herpes Virus Agent, Protects Against the Development of Heart Failure With Relatively Mild Side-Effects on Cardiac Function in a Canine Model of Pacing-Induced Dilated Cardiomyopathy. Circ J 2016; 80:2496-2505. [PMID: 27818454 DOI: 10.1253/circj.cj-16-0736] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND In heart failure patients, chronic hyperactivation of sympathetic signaling is known to exacerbate cardiac dysfunction. In this study, the cardioprotective effect of vidarabine, an anti-herpes virus agent, which we identified as a cardiac adenylyl cyclase inhibitor, in dogs with pacing-induced dilated cardiomyopathy (DCM) was evaluated. In addition, the adverse effects of vidarabine on basal cardiac function was compared to those of the β-blocker, carvedilol.Methods and Results:Vidarabine and carvedilol attenuated the development of pacing-induced systolic dysfunction significantly and with equal effectiveness. Both agents also inhibited the development of cardiac apoptosis and fibrosis and reduced the Na+-Ca2+exchanger-1 protein level in the heart. Importantly, carvedilol significantly enlarged the left ventricle and atrium; vidarabine, in contrast, did not. Vidarabine-treated dogs maintained cardiac response to β-AR stimulation better than carvedilol-treated dogs did. CONCLUSIONS Vidarabine may protect against pacing-induced DCM with less suppression of basal cardiac function than carvedilol in a dog model. (Circ J 2016; 80: 2496-2505).
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Affiliation(s)
- Takashi Nakamura
- Cardiovascular Research Institute, Yokohama City University Graduate School of Medicine
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Roe AT, Frisk M, Louch WE. Targeting cardiomyocyte Ca2+ homeostasis in heart failure. Curr Pharm Des 2015; 21:431-48. [PMID: 25483944 PMCID: PMC4475738 DOI: 10.2174/138161282104141204124129] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Accepted: 08/06/2014] [Indexed: 12/19/2022]
Abstract
Improved treatments for heart failure patients will require the development of novel therapeutic strategies that target basal disease
mechanisms. Disrupted cardiomyocyte Ca2+ homeostasis is recognized as a major contributor to the heart failure phenotype, as it
plays a key role in systolic and diastolic dysfunction, arrhythmogenesis, and hypertrophy and apoptosis signaling. In this review, we outline
existing knowledge of the involvement of Ca2+ homeostasis in these deficits, and identify four promising targets for therapeutic intervention:
the sarcoplasmic reticulum Ca2+ ATPase, the Na+-Ca2+ exchanger, the ryanodine receptor, and t-tubule structure. We discuss
experimental data indicating the applicability of these targets that has led to recent and ongoing clinical trials, and suggest future therapeutic
approaches.
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Affiliation(s)
| | | | - William E Louch
- Institute for Experimental Medical Research, Kirkeveien 166, 4.etg. Bygg 7, Oslo University Hospital Ullevål, 0407 Oslo, Norway.
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Gandhi A, Siedlecka U, Shah AP, Navaratnarajah M, Yacoub MH, Terracciano CM. The effect of SN-6, a novel sodium-calcium exchange inhibitor, on contractility and calcium handling in isolated failing rat ventricular myocytes. Cardiovasc Ther 2014; 31:e115-24. [PMID: 24106913 DOI: 10.1111/1755-5922.12045] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Specific Na(+) /Ca(2+) exchanger (NCX) inhibition is a potential strategy to correct reduced contractility and depleted sarcoplasmic reticulum (SR) Ca(2+) content in heart failure (HF). SN-6, a benzyloxyphenyl derivative and proposed selective NCX inhibitor, could be used for this purpose. This study aimed to evaluate the effects of SN-6 on contractility and Ca(2+) handling in normal and failing rat cardiomyocytes. EXPERIMENTAL APPROACH HF was induced in rats by coronary artery ligation. Left ventricular myocytes were isolated and superfused with increasing concentrations of SN-6. KEY RESULTS Sarcomere shortening, induced by field-stimulation, was reduced in amplitude with increasing concentrations of SN-6 compared with control solution. This effect was greater in failing cells. Kinetics of contractility (time to 90% peak and time to 50% relaxation) were significantly faster. Despite this, intracellular Ca(2+) transients demonstrated no change in the peak amplitude at low concentrations of SN-6, suggesting that SN-6 may affect myofilament sensitivity to Ca(2+) . Ten micro molar SN-6 significantly reduced peak Ca(2+) amplitude by 61.57% and 64.73% in normal and failing cells, respectively. Diastolic Ca(2+) was significantly increased at 1 μM SN-6. SR Ca(2+) content, assessed by rapid application of caffeine, was reduced in failing cells with 1 μM SN-6. Peak ICa , measured by whole-cell patch clamping, was significantly reduced in normal and failing myocytes at 1 μM SN-6. CONCLUSIONS AND IMPLICATIONS Our data suggest that SN-6 is not a selective inhibitor of NCX and impairs contractility and Ca(2+) handling. Its use, together with similar putative NCX blockers, in correcting the contractile abnormalities of heart failure requires further studies.
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Affiliation(s)
- Ajay Gandhi
- Cell Electrophysiology, Heart Science Centre, NHLI, Imperial College London, London, UK
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Sensitivity of rabbit ventricular action potential and Ca²⁺ dynamics to small variations in membrane currents and ion diffusion coefficients. BIOMED RESEARCH INTERNATIONAL 2013; 2013:565431. [PMID: 24222910 PMCID: PMC3814049 DOI: 10.1155/2013/565431] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Accepted: 08/19/2013] [Indexed: 12/19/2022]
Abstract
Little is known about how small variations in ionic currents and Ca²⁺ and Na⁺ diffusion coefficients impact action potential and Ca²⁺ dynamics in rabbit ventricular myocytes. We applied sensitivity analysis to quantify the sensitivity of Shannon et al. model (Biophys. J., 2004) to 5%-10% changes in currents conductance, channels distribution, and ion diffusion in rabbit ventricular cells. We found that action potential duration and Ca²⁺ peaks are highly sensitive to 10% increase in L-type Ca²⁺ current; moderately influenced by 10% increase in Na⁺-Ca²⁺ exchanger, Na⁺-K⁺ pump, rapid delayed and slow transient outward K⁺ currents, and Cl⁻ background current; insensitive to 10% increases in all other ionic currents and sarcoplasmic reticulum Ca²⁺ fluxes. Cell electrical activity is strongly affected by 5% shift of L-type Ca²⁺ channels and Na⁺-Ca²⁺ exchanger in between junctional and submembrane spaces while Ca²⁺-activated Cl⁻-channel redistribution has the modest effect. Small changes in submembrane and cytosolic diffusion coefficients for Ca²⁺, but not in Na⁺ transfer, may alter notably myocyte contraction. Our studies highlight the need for more precise measurements and further extending and testing of the Shannon et al. model. Our results demonstrate usefulness of sensitivity analysis to identify specific knowledge gaps and controversies related to ventricular cell electrophysiology and Ca²⁺ signaling.
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Wang J, Gao E, Chan TO, Zhang XQ, Song J, Shang X, Koch WJ, Feldman AM, Cheung JY. Induced overexpression of Na(+)/Ca(2+) exchanger does not aggravate myocardial dysfunction induced by transverse aortic constriction. J Card Fail 2013; 19:60-70. [PMID: 23273595 DOI: 10.1016/j.cardfail.2012.11.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 11/06/2012] [Accepted: 11/08/2012] [Indexed: 11/30/2022]
Abstract
BACKGROUND Alterations in expression and activity of cardiac Na(+)/Ca(2+) exchanger (NCX1) have been implicated in the pathogenesis of heart failure. METHODS AND RESULTS Using transgenic mice in which expression of rat NCX1 was induced at 5 weeks of age, we performed transverse aortic constriction (TAC) at 8 weeks and examined cardiac and myocyte function at 15-18 weeks after TAC (age 23-26 weeks). TAC induced left ventricular (LV) and myocyte hypertrophy and increased myocardial fibrosis in both wild-type (WT) and NCX1-overexpressed mice. NCX1 and phosphorylated ryanodine receptor expression was increased by TAC, whereas sarco(endo)plasmic reticulum Ca(2+)-ATPase levels were decreased by TAC. Action potential duration was prolonged by TAC, but to a greater extent in NCX1 myocytes. Na(+)/Ca(2+) exchange current was similar between WT-TAC and WT-sham myocytes, but was higher in NCX1-TAC myocytes. Both myocyte contraction and [Ca(2+)](i) transient amplitudes were reduced in WT-TAC myocytes, but restored to WT-sham levels in NCX1-TAC myocytes. Despite improvement in single myocyte contractility and Ca(2+) dynamics, induced NCX1 overexpression in TAC animals did not ameliorate LV hypertrophy, increase ejection fraction, or enhance inotropic (maximal first derivative of LV pressure rise, +dP/dt) responses to isoproterenol. CONCLUSIONS In pressure-overload hypertrophy, induced overexpression of NCX1 corrected myocyte contractile and [Ca(2+)](i) transient abnormalities but did not aggravate or improve myocardial dysfunction.
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Affiliation(s)
- Jufang Wang
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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11
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Louch WE, Stokke MK, Sjaastad I, Christensen G, Sejersted OM. No rest for the weary: diastolic calcium homeostasis in the normal and failing myocardium. Physiology (Bethesda) 2013; 27:308-23. [PMID: 23026754 DOI: 10.1152/physiol.00021.2012] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Following contraction of the heart, efficient relaxation (diastole) is essential for refilling the ventricles with blood. This review describes how ventricular relaxation is controlled by Ca(2+) homeostasis in cardiac muscle cells and how alterations in Ca(2+) cycling affect diastolic function in the normal and failing heart. These discussions illustrate that the diastolic phase is not simply a period of rest but rather involves highly regulated and dynamic Ca(2+) fluxes.
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Affiliation(s)
- William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.
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12
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Menick DR, Li MS, Chernysh O, Renaud L, Kimbrough D, Kasiganesan H, Mani SK. Transcriptional pathways and potential therapeutic targets in the regulation of Ncx1 expression in cardiac hypertrophy and failure. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 961:125-35. [PMID: 23224875 PMCID: PMC3624972 DOI: 10.1007/978-1-4614-4756-6_11] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Changes in cardiac gene expression contribute to the progression of heart failure by affecting cardiomyocyte growth, function, and survival. The Na(+)-Ca(2+) exchanger gene (Ncx1) is upregulated in hypertrophy and is often found elevated in end-stage heart failure. Studies have shown that the change in its expression contributes to contractile dysfunction. Several transcriptional pathways mediate Ncx1 expression in pathological cardiac remodeling. Both α-adrenergic receptor (α-AR) and β-adrenergic receptor (β-AR) signaling can play a role in the regulation of calcium homeostasis in the cardiomyocyte, but chronic activation in periods of cardiac stress contributes to heart failure by mechanisms which include Ncx1 upregulation. Our studies have even demonstrated that NCX1 can directly act as a regulator of "activity-dependent signal transduction" mediating changes in its own expression. Finally, we present evidence that histone deacetylases (HDACs) and histone acetyltransferases (HATs) act as master regulators of Ncx1 expression. We show that many of the transcription factors regulating Ncx1 expression are important in cardiac development and also in the regulation of many other genes in the so-called fetal gene program, which are activated by pathological stimuli. Importantly, studies have revealed that the transcriptional network regulating Ncx1 expression is also mediating many of the other changes in genetic remodeling contributing to the development of cardiac dysfunction and revealed potential therapeutic targets for the treatment of hypertrophy and failure.
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Kaese S, Verheule S. Cardiac electrophysiology in mice: a matter of size. Front Physiol 2012; 3:345. [PMID: 22973235 PMCID: PMC3433738 DOI: 10.3389/fphys.2012.00345] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Accepted: 08/09/2012] [Indexed: 12/27/2022] Open
Abstract
Over the last decade, mouse models have become a popular instrument for studying cardiac arrhythmias. This review assesses in which respects a mouse heart is a miniature human heart, a suitable model for studying mechanisms of cardiac arrhythmias in humans and in which respects human and murine hearts differ. Section I considers the issue of scaling of mammalian cardiac (electro) physiology to body mass. Then, we summarize differences between mice and humans in cardiac activation (section II) and the currents underlying the action potential in the murine working myocardium (section III). Changes in cardiac electrophysiology in mouse models of heart disease are briefly outlined in section IV, while section V discusses technical considerations pertaining to recording cardiac electrical activity in mice. Finally, section VI offers general considerations on the influence of cardiac size on the mechanisms of tachy-arrhythmias.
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Affiliation(s)
- Sven Kaese
- Division of Experimental and Clinical Electrophysiology, Department of Cardiology and Angiology, University Hospital Münster Münster, Germany
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Kumarswamy R, Lyon AR, Volkmann I, Mills AM, Bretthauer J, Pahuja A, Geers-Knörr C, Kraft T, Hajjar RJ, Macleod KT, Harding SE, Thum T. SERCA2a gene therapy restores microRNA-1 expression in heart failure via an Akt/FoxO3A-dependent pathway. Eur Heart J 2012; 33:1067-75. [PMID: 22362515 PMCID: PMC3341631 DOI: 10.1093/eurheartj/ehs043] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
AIMS Impaired myocardial sarcoplasmic reticulum calcium ATPase 2a (SERCA2a) activity is a hallmark of failing hearts, and SERCA2a gene therapy improves cardiac function in animals and patients with heart failure (HF). Deregulation of microRNAs has been demonstrated in HF pathophysiology. We studied the effects of therapeutic AAV9.SERCA2a gene therapy on cardiac miRNome expression and focused on regulation, expression, and function of miR-1 in reverse remodelled failing hearts. METHODS AND RESULTS We studied a chronic post-myocardial infarction HF model treated with AAV9.SERCA2a gene therapy. Heart failure resulted in a strong deregulation of the cardiac miRNome. miR-1 expression was decreased in failing hearts, but normalized in reverse remodelled hearts after AAV9.SERCA2a gene delivery. Increased Akt activation in cultured cardiomyocytes led to phosphorylation of FoxO3A and subsequent exclusion from the nucleus, resulting in miR-1 gene silencing. In vitro SERCA2a expression also rescued miR-1 in failing cardiomyocytes, whereas SERCA2a inhibition reduced miR-1 levels. In vivo, Akt and FoxO3A were highly phosphorylated in failing hearts, but reversed to normal by AAV9.SERCA2a, leading to cardiac miR-1 restoration. Likewise, enhanced sodium-calcium exchanger 1 (NCX1) expression during HF was normalized by SERCA2a gene therapy. Validation experiments identified NCX1 as a novel functional miR-1 target. CONCLUSION SERCA2a gene therapy of failing hearts restores miR-1 expression by an Akt/FoxO3A-dependent pathway, which is associated with normalized NCX1 expression and improved cardiac function.
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Affiliation(s)
- Regalla Kumarswamy
- Institute of Molecular and Translational Therapeutic Strategies, Hannover Medical School, Carl-Neuberg-Str 1, 30625 Hannover, Germany
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Song J, Gao E, Wang J, Zhang XQ, Chan TO, Koch WJ, Shang X, Joseph JI, Peterson BZ, Feldman AM, Cheung JY. Constitutive overexpression of phosphomimetic phospholemman S68E mutant results in arrhythmias, early mortality, and heart failure: potential involvement of Na+/Ca2+ exchanger. Am J Physiol Heart Circ Physiol 2011; 302:H770-81. [PMID: 22081699 DOI: 10.1152/ajpheart.00733.2011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Expression and activity of cardiac Na(+)/Ca(2+) exchanger (NCX1) are altered in many disease states. We engineered mice in which the phosphomimetic phospholemman S68E mutant (inhibits NCX1 but not Na(+)-K(+)-ATPase) was constitutively overexpressed in a cardiac-specific manner (conS68E). At 4-6 wk, conS68E mice exhibited severe bradycardia, ventricular arrhythmias, increased left ventricular (LV) mass, decreased cardiac output (CO), and ∼50% mortality compared with wild-type (WT) littermates. Protein levels of NCX1, calsequestrin, ryanodine receptor, and α(1)- and α(2)-subunits of Na(+)-K(+)-ATPase were similar, but sarco(endo)plasmic reticulum Ca(2+)-ATPase was lower, whereas L-type Ca(2+) channels were higher in conS68E hearts. Resting membrane potential and action potential amplitude were similar, but action potential duration was dramatically prolonged in conS68E myocytes. Diastolic intracellular Ca(2+) ([Ca(2+)](i)) was higher, [Ca(2+)](i) transient and maximal contraction amplitudes were lower, and half-time of [Ca(2+)](i) transient decline was longer in conS68E myocytes. Intracellular Na(+) reached maximum within 3 min after isoproterenol addition, followed by decline in WT but not in conS68E myocytes. Na(+)/Ca(2+) exchange, L-type Ca(2+), Na(+)-K(+)-ATPase, and depolarization-activated K(+) currents were decreased in conS68E myocytes. At 22 wk, bradycardia and increased LV mass persisted in conS68E survivors. Despite comparable baseline CO, conS68E survivors at 22 wk exhibited decreased chronotropic, inotropic, and lusitropic responses to isoproterenol. We conclude that constitutive overexpression of S68E mutant was detrimental, both in terms of depressed cardiac function and increased arrhythmogenesis.
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Affiliation(s)
- Jianliang Song
- Division of Nephrology, Thomas Jefferson Univ., 833 Chestnut St., Suite 700, Philadelphia, PA 19107, USA
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Varró A, Baczkó I. Cardiac ventricular repolarization reserve: a principle for understanding drug-related proarrhythmic risk. Br J Pharmacol 2011; 164:14-36. [PMID: 21545574 PMCID: PMC3171857 DOI: 10.1111/j.1476-5381.2011.01367.x] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 02/22/2011] [Accepted: 03/02/2011] [Indexed: 12/11/2022] Open
Abstract
Cardiac repolarization abnormalities can be caused by a wide range of cardiac and non-cardiac compounds and may lead to the development of life-threatening Torsades de Pointes (TdP) ventricular arrhythmias. Drug-induced torsades de pointes is associated with unexpected and unexplained sudden cardiac deaths resulting in the withdrawal of several compounds in the past. To better understand the mechanism of such unexpected sudden cardiac deaths, the concept of repolarization reserve has recently emerged. According to this concept, pharmacological, congenital or acquired impairment of one type of transmembrane ion channel does not necessarily result in excessive repolarization changes because other repolarizing currents can take over and compensate. In this review, the major factors contributing to repolarization reserve are discussed in the context of their clinical significance in physiological and pathophysiological conditions including drug administration, genetic defects, heart failure, diabetes mellitus, gender, renal failure, hypokalaemia, hypothyroidism and athletes' sudden deaths. In addition, pharmacological support of repolarization reserve as a possible therapeutic option is discussed. Some methods for the quantitative estimation of repolarization reserve are also recommended. It is concluded that repolarization reserve should be considered by safety pharmacologists to better understand, predict and prevent previously unexplained drug-induced sudden cardiac deaths.
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Affiliation(s)
- András Varró
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.
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Romero L, Carbonell B, Trenor B, Rodríguez B, Saiz J, Ferrero JM. Systematic characterization of the ionic basis of rabbit cellular electrophysiology using two ventricular models. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 107:60-73. [PMID: 21749896 DOI: 10.1016/j.pbiomolbio.2011.06.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Accepted: 06/27/2011] [Indexed: 01/08/2023]
Abstract
Several mathematical models of rabbit ventricular action potential (AP) have been proposed to investigate mechanisms of arrhythmias and excitation-contraction coupling. Our study aims at systematically characterizing how ionic current properties modulate the main cellular biomarkers of arrhythmic risk using two widely-used rabbit ventricular models, and comparing simulation results using the two models with experimental data available for rabbit. A sensitivity analysis of AP properties, Ca²⁺ and Na⁺ dynamics, and their rate dependence to variations (±15% and ±30%) in the main transmembrane current conductances and kinetics was performed using the Shannon et al. (2004) and the Mahajan et al. (2008a,b) AP rabbit models. The effects of severe transmembrane current blocks (up to 100%) on steady-state AP and calcium transients, and AP duration (APD) restitution curves were also simulated using both models. Our simulations show that, in both virtual rabbit cardiomyocytes, APD is significantly modified by most repolarization currents, AP triangulation is regulated mostly by the inward rectifier K⁺ current (I(K1)) whereas APD rate adaptation as well as [Na⁺](i) rate dependence is influenced by the Na⁺/K⁺ pump current (I(NaK)). In addition, steady-state [Ca²⁺](i) levels, APD restitution properties and [Ca²⁺](i) rate dependence are strongly dependent on I(NaK), the L-Type Ca²⁺ current (I(CaL)) and the Na⁺/Ca²⁺ exchanger current (I(NaCa)), although the relative role of these currents is markedly model dependent. Furthermore, our results show that simulations using both models agree with many experimentally-reported electrophysiological characteristics. However, our study shows that the Shannon et al. model mimics rabbit electrophysiology more accurately at normal pacing rates, whereas Mahajan et al. model behaves more appropriately at faster rates. Our results reinforce the usefulness of sensitivity analysis for further understanding of cellular electrophysiology and validation of cardiac AP models.
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Affiliation(s)
- Lucía Romero
- Instituto de Investigación Interuniversitario en Bioingeniería y Tecnología Orientada al Ser Humano (I3BH), Universitat Politècnica de València (UPV), Camino de Vera s/n, 46022 Valencia, Spain.
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18
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Activated expression of cardiac adenylyl cyclase 6 reduces dilation and dysfunction of the pressure-overloaded heart. Biochem Biophys Res Commun 2010; 405:349-55. [PMID: 21195051 DOI: 10.1016/j.bbrc.2010.12.113] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Accepted: 12/21/2010] [Indexed: 01/08/2023]
Abstract
BACKGROUND AND OBJECTIVE Cardiac-directed adenylyl cyclase 6 (AC6) expression attenuates left ventricular (LV) hypertrophy and dysfunction in cardiomyopathy, but its effects in the pressure-overloaded heart are unknown. METHODS Mice with cardiac-directed and regulated expression of AC6 underwent transaortic constriction (TAC) to induce LV pressure overload. Ten days prior to TAC, and for the duration of the 4 week study, cardiac myocyte AC6 expression was activated in one group (AC-On) but not the other (AC-Off). Multiple measures of LV systolic and diastolic function were obtained 4 weeks after TAC, and LV samples assessed for alterations in Ca2+ signaling. RESULTS LV contractility, as reflected in the end-systolic pressure-volume relationship (Emax), was increased (p=0.01) by activation of AC6 expression. In addition, diastolic function was improved (p<0.05) and LV dilation was reduced (p<0.05). LV samples from AC-On mice showed reduced protein expression of sodium/calcium exchanger (NCX1) (p<0.05), protein phosphatase 1 (PP1) (p<0.01), and increased phosphorylation of phospholamban (PLN) at Ser16 (p<0.05). Finally, sarcoplasmic reticulum (SR) Ca2+ content was increased in cardiac myocytes isolated from AC-On mice (p<0.05). CONCLUSIONS Activation of cardiac AC6 expression improves function of the pressure-overloaded and failing heart. The predominant mechanism for this favorable adaptation is improved Ca2+ handling, a consequence of increased PLN phosphorylation, reduced NCX1, reduced PP1 expression, and increased SR Ca2+ content.
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Kuster GM, Lancel S, Zhang J, Communal C, Trucillo MP, Lim CC, Pfister O, Weinberg EO, Cohen RA, Liao R, Siwik DA, Colucci WS. Redox-mediated reciprocal regulation of SERCA and Na+-Ca2+ exchanger contributes to sarcoplasmic reticulum Ca2+ depletion in cardiac myocytes. Free Radic Biol Med 2010; 48:1182-7. [PMID: 20132882 PMCID: PMC2847633 DOI: 10.1016/j.freeradbiomed.2010.01.038] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Revised: 01/14/2010] [Accepted: 01/27/2010] [Indexed: 11/21/2022]
Abstract
Myocardial failure is associated with increased oxidative stress and abnormal excitation-contraction coupling characterized by depletion of sarcoplasmic reticulum (SR) Ca(2+) stores and a reduction in Ca(2+)-transient amplitude. Little is known about the mechanisms whereby oxidative stress affects Ca(2+) handling and contractile function; however, reactive thiols may be involved. We used an in vitro cardiomyocyte system to test the hypothesis that short-term oxidative stress induces SR Ca(2+) depletion via redox-mediated regulation of sarcoendoplasmic reticulum Ca(2+)-ATPase (SERCA) and the sodium-Ca(2+) exchanger (NCX) and that this is associated with thiol oxidation. Adult rat ventricular myocytes paced at 5 Hz were superfused with H(2)O(2) (100 microM, 15 min). H(2)O(2) caused a progressive decrease in cell shortening followed by diastolic arrest, which was associated with decreases in SR Ca(2+) content, systolic [Ca(2+)](i), and Ca(2+)-transient amplitude, but no change in diastolic [Ca(2+)](i). H(2)O(2) caused reciprocal effects on the activities of SERCA (decreased) and NCX (increased). Pretreatment with the NCX inhibitor KB-R7943 before H(2)O(2) increased diastolic [Ca(2+)](i) and mimicked the effect of SERCA inhibition with thapsigargin. These functional effects were associated with oxidative modification of thiols on both SERCA and NCX. In conclusion, redox-mediated SR Ca(2+) depletion involves reciprocal regulation of SERCA and NCX, possibly via direct oxidative modification of both proteins.
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Affiliation(s)
- Gabriela M Kuster
- Cardiovascular Medicine Section, Department of Medicine, and Myocardial and Vascular Biology Units, Boston University Medical Center, Boston, MA 02118, USA
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20
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Mani SK, Egan EA, Addy BK, Grimm M, Kasiganesan H, Thiyagarajan T, Renaud L, Brown JH, Kern CB, Menick DR. beta-Adrenergic receptor stimulated Ncx1 upregulation is mediated via a CaMKII/AP-1 signaling pathway in adult cardiomyocytes. J Mol Cell Cardiol 2009; 48:342-51. [PMID: 19945464 DOI: 10.1016/j.yjmcc.2009.11.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 11/18/2009] [Accepted: 11/18/2009] [Indexed: 10/20/2022]
Abstract
The Na(+)-Ca(2+) exchanger gene (Ncx1) is upregulated in hypertrophy and is often found elevated in end-stage heart failure. Studies have shown that the change in its expression contributes to contractile dysfunction. beta-Adrenergic receptor (beta-AR) signaling plays an important role in the regulation of calcium homeostasis in the cardiomyocyte, but chronic activation in periods of cardiac stress contributes to heart failure by mechanisms which include Ncx1 upregulation. Here, using a Ca(2+)/calmodulin-dependent protein kinase II (CaMKIIdelta(c)) null mouse, we demonstrate that beta-AR-stimulated Ncx1 upregulation is dependent on CaMKII. beta-AR-stimulated Ncx1 expression is mediated by activator protein 1 (AP-1) factors and is independent of cAMP-response element-binding protein (CREB) activation. The MAP kinases (ERK1/2, JNK and p38) are not required for AP-1 factor activation. Chromatin immunoprecipitation demonstrates that beta-AR stimulation activates the ordered recruitment of JunB homodimers, which then are replaced by c-Jun homodimers binding to the proximal AP-1 elements of the endogenous Ncx1 promoter. In conclusion, this work has provided insight into the intracellular signaling pathways and transcription factors regulating Ncx1 gene expression in a chronically beta-AR-stimulated heart.
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Affiliation(s)
- Santhosh K Mani
- Division of Cardiology, Department of Medicine, Gazes Cardiac Research Institute, Medical University of South Carolina, 114 Doughty Street, Box 250773, Charleston, SC 29425, USA
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21
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Xu L, Kappler CS, Mani SK, Shepherd NR, Renaud L, Snider P, Conway SJ, Menick DR. Chronic administration of KB-R7943 induces up-regulation of cardiac NCX1. J Biol Chem 2009; 284:27265-72. [PMID: 19661061 DOI: 10.1074/jbc.m109.022855] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The NCX1 (sodium-calcium exchanger) is up-regulated in human heart failure and in many animal models of heart failure. The potential benefits and risks of therapeutically blocking NCX1 in heart failure and during ischemia-reperfusion are being actively investigated. In this study, we demonstrate that prolonged administration of the NCX1 inhibitor KB-R7943 resulted in the up-regulation of Ncx1 gene expression in both isolated adult cardiomyocytes and intact mouse hearts. Ncx1 up-regulation is mediated by the activation of p38. Importantly, p38 is not activated by KB-R7943 treatment in heart tubes from Ncx1(-/-) mice at 9.5 days postcoitum but is activated in heart tubes from Ncx1(+/+) mice. p38 activation does not appear to be in response to changes in cytosolic calcium concentration, [Ca(2+)](i). Interestingly, chronic KB-R7943 treatment in mice leads to the formation of an NCX1-p38 complex. Our study demonstrates for the first time that the electrogenic sarcolemma membrane cardiac NCX1 can act as a regulator of "activity-dependent signal transduction" leading to changes in gene expression.
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Affiliation(s)
- Lin Xu
- Department of Medicine, Gazes Cardiac Research Institute, Division of Cardiology, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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Chandrasekaran S, Peterson RE, Mani SK, Addy B, Buchholz AL, Xu L, Thiyagarajan T, Kasiganesan H, Kern CB, Menick DR. Histone deacetylases facilitate sodium/calcium exchanger up-regulation in adult cardiomyocytes. FASEB J 2009; 23:3851-64. [PMID: 19638401 DOI: 10.1096/fj.09-132415] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
It is becoming increasingly evident that histone deacetylases (HDACs) have a prominent role in the alteration of gene expression during the growth remodeling process of cardiac hypertrophy. HDACs are generally viewed as corepressors of gene expression. However, we demonstrate that class I and class II HDACs play an important role in the basal expression and up-regulation of the sodium calcium exchanger (Ncx1) gene in adult cardiomyocytes. Treatment with the HDAC inhibitor trichostatin A (TSA) prevented the pressure-overload-stimulated up-regulation of Ncx1 expression. Overexpression of HDAC5 resulted in the dose-dependent up-regulation of basal and alpha-adrenergic stimulated Ncx1 expression. We show that Nkx2.5 recruits HDAC5 to the Ncx1 promoter, where HDAC5 complexes with HDAC1. Nkx2.5 also interacts with transcriptional activator p300, which is recruited to the Ncx1 promoter. We demonstrate that when Nkx2.5 is acetylated, it is found associated with HDAC5, whereas deacetylated Nkx2.5 is in complex with p300. Notably, TSA treatment prevents p300 from being recruited to the endogenous Ncx1 promoter, resulting in the repression of Ncx1 expression. We propose a novel model for Ncx1 regulation in which deacetylation of Nkx2.5 is required for the recruitment of p300 and results in up-regulation of exchanger expression.
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Affiliation(s)
- Sangeetha Chandrasekaran
- Gazes Cardiac Research Institute, Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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Wang J, Chan TO, Zhang XQ, Gao E, Song J, Koch WJ, Feldman AM, Cheung JY. Induced overexpression of Na+/Ca2+ exchanger transgene: altered myocyte contractility, [Ca2+]i transients, SR Ca2+ contents, and action potential duration. Am J Physiol Heart Circ Physiol 2009; 297:H590-601. [PMID: 19525383 DOI: 10.1152/ajpheart.00190.2009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have produced mice in which expression of the rat cardiac Na(+)/Ca(2+) exchanger (NCX1) transgene was switched on when doxycycline was removed from the feed at 5 wk. At 8 to 10 wk, NCX1 expression in induced (Ind) mouse hearts was 2.5-fold higher but protein levels of sarco(endo)plasmic reticulum Ca(2+)-ATPase, alpha(1)- and alpha(2)-subunits of Na(+)-K(+)-ATPase, phospholamban, ryanodine receptor, calsequestrin, and unphosphorylated and phosphorylated phospholemman were unchanged compared with wild-type (WT) or noninduced (non-Ind) hearts. There was no cellular hypertrophy since WT, non-Ind, and Ind myocytes had similar whole cell membrane capacitance. In Ind myocytes, NCX1 current amplitude was approximately 42% higher, L-type Ca(2+) current amplitude was unchanged, and action potential duration was prolonged compared with WT or non-Ind myocytes. Contraction and intracellular Ca(2+) concentration ([Ca(2+)](i)) transient amplitudes in Ind myocytes were lower at 0.6, not different at 1.8, and higher at 5.0 mM extracellular Ca(2+) concentration ([Ca(2+)](o)) compared with WT or non-Ind myocytes. Despite similar Ca(2+) current amplitude and sarcoplasmic reticulum (SR) Ca(2+) uptake, SR Ca(2+) content at 5.0 mM [Ca(2+)](o) was significantly higher in Ind compared with non-Ind myocytes, indicating that NCX1 directly contributed to SR Ca(2+) loading. Echocardiography demonstrated that heart rate, left ventricular mass, ejection fraction, stroke volume, and cardiac output were similar among the three groups of animals. In vivo close-chest catheterization demonstrated similar contractility and relaxation among the three groups of mice, both at baseline and after stimulation with isoproterenol. We conclude that induced expression of NCX1 transgene resulted in altered [Ca(2+)](i) homeostasis, myocyte contractility, and action potential morphology. In addition, heart failure did not occur 3 to 5 wk after NCX1 transgene was induced to be expressed at levels found in diseased hearts.
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Affiliation(s)
- JuFang Wang
- Department of Medicine, Division of Nephrology, Center of Translational Medicine, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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Davis J, Westfall MV, Townsend D, Blankinship M, Herron TJ, Guerrero-Serna G, Wang W, Devaney E, Metzger JM. Designing heart performance by gene transfer. Physiol Rev 2008; 88:1567-651. [PMID: 18923190 DOI: 10.1152/physrev.00039.2007] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The birth of molecular cardiology can be traced to the development and implementation of high-fidelity genetic approaches for manipulating the heart. Recombinant viral vector-based technology offers a highly effective approach to genetically engineer cardiac muscle in vitro and in vivo. This review highlights discoveries made in cardiac muscle physiology through the use of targeted viral-mediated genetic modification. Here the history of cardiac gene transfer technology and the strengths and limitations of viral and nonviral vectors for gene delivery are reviewed. A comprehensive account is given of the application of gene transfer technology for studying key cardiac muscle targets including Ca(2+) handling, the sarcomere, the cytoskeleton, and signaling molecules and their posttranslational modifications. The primary objective of this review is to provide a thorough analysis of gene transfer studies for understanding cardiac physiology in health and disease. By comparing results obtained from gene transfer with those obtained from transgenesis and biophysical and biochemical methodologies, this review provides a global view of cardiac structure-function with an eye towards future areas of research. The data presented here serve as a basis for discovery of new therapeutic targets for remediation of acquired and inherited cardiac diseases.
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Affiliation(s)
- Jennifer Davis
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA
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Moon HS, Choi E, Hyun C. The Cardiac Sodium-Calcium Exchanger Gene (NCX-1) is a Potential Canine Cardiac Biomarker of Chronic Mitral Valvular Insufficiency. J Vet Intern Med 2008; 22:1360-5. [DOI: 10.1111/j.1939-1676.2008.0209.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Abstract
End-stage heart failure is characterized by a number of abnormalities at the cellular level, which include changes in excitation-contraction coupling, alterations in contractile proteins and activation/deactivation of signaling pathways. Even though many of these changes are adaptive to the high workload and stress in heart failure, a significant number of these alterations are deeply deleterious to the cardiac cell. In this article, we will review the changes in calcium cycling that occur in myopathic hearts and how they can be effectively targeted. We will also focus on protein misfolding in the setting of cardiac dysfunction.
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Zhang YH, Hancox JC. Regulation of cardiac Na+-Ca2+ exchanger activity by protein kinase phosphorylation--still a paradox? Cell Calcium 2008; 45:1-10. [PMID: 18614228 DOI: 10.1016/j.ceca.2008.05.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Revised: 04/14/2008] [Accepted: 05/27/2008] [Indexed: 11/18/2022]
Abstract
The cardiac Na+-Ca2+ exchanger (NCX) is an important regulator of intracellular ion homeostasis and cardiac function. Gaining insight into modulation of the NCX is therefore important in order to understand ion handling in the heart under physiological and pathological conditions. Typically, the functional contribution of the NCX is often regarded as "secondary" to the changes in luminal Na+ and Ca2+. Whilst it is well accepted that the NCX can be regulated by various factors, including the concentrations of transported ions, direct receptor-mediated modulation of the cardiac NCX is more controversial. Evidence from several different laboratories supports the notion that the cardiac NCX is a direct target of neurotransmitters and hormones and their downstream signalling pathways; however, the issue remains unresolved due to conflicting data showing a lack of direct modulation. The present review summarizes overall findings regarding the modulation of the cardiac NCX, in particular on molecular mechanisms of direct phosphorylation of NCX by beta-adrenergic/adenylate cyclase/protein kinase A and (for comparative purposes) on endothelin-1/protein kinase C signalling pathways. It also aims to consider whether it is currently possible to reconcile discrepancies between studies in the interpretation of the regulation of the cardiac NCX by agents stimulating the beta-adrenoceptor/PKA pathway.
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Affiliation(s)
- Yin Hua Zhang
- Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
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Wang W, Metzger JM. Parvalbumin isoforms for enhancing cardiac diastolic function. Cell Biochem Biophys 2008; 51:1-8. [PMID: 18458829 DOI: 10.1007/s12013-008-9011-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Accepted: 04/04/2008] [Indexed: 11/28/2022]
Abstract
Diastolic heart failure (DHF), characterized by depressed myocardial relaxation performance and poor ventricular filling, is a distinct form of heart failure accounting for nearly half of the heart failure patients with otherwise normal systolic performance. Defective intracellular calcium (Ca2+) cycling is an important mechanism underlying impaired relaxation in DHF. Recently, genetic manipulation of Ca2+ handling proteins in cardiac myocytes has been explored for its potential therapeutic application in DHF. Specifically, ectopic expression of the skeletal muscle Ca2+ binding protein parvalbumin (Parv) has been shown to accelerate myocardial relaxation in vitro and in vivo. Parv acts as a unique "delayed" Ca2+ buffer during diastole by promoting Ca2+ transient decay and sequestration and corrects diastolic dysfunction in an energy-independent manner. This brief review summarizes the rationale and development of Parv gene transfer approaches for DHF, and in particular, discusses the divergent effects of Parv isoforms on cardiac myocyte Ca2+ handling and contractile function with the long-range goal of alleviating diastolic dysfunction in DHF.
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Affiliation(s)
- Wang Wang
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, 1301 E. Catherine St., 7727 Medical Science II, Ann Arbor, MI 48109-0622, USA
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Kockskämper J, Seidlmayer L, Walther S, Hellenkamp K, Maier LS, Pieske B. Endothelin-1 enhances nuclear Ca2+ transients in atrial myocytes through Ins(1,4,5)P3-dependent Ca2+ release from perinuclear Ca2+ stores. J Cell Sci 2007; 121:186-95. [PMID: 18089647 DOI: 10.1242/jcs.021386] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nuclear Ca2+ plays a key role in the regulation of gene expression. Inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3)] might be an important regulator of nuclear Ca2+ but its contribution to nuclear Ca2+ signalling in adult cardiomyocytes remains elusive. We tested the hypothesis that endothelin-1 enhances nuclear Ca2+ concentration transients (CaTs) in rabbit atrial myocytes through Ins(1,4,5)P3-induced Ca(2+) release from perinuclear stores. Cytoplasmic and nuclear CaTs were measured simultaneously in electrically stimulated atrial myocytes using confocal Ca2+ imaging. Nuclear CaTs were significantly slower than cytoplasmic CaTs, indicative of compartmentalisation of intracellular Ca2+ signalling. Endothelin-1 elicited a preferential (10 nM) or a selective (0.1 nM) increase in nuclear versus cytoplasmic CaTs. This effect was abolished by inhibition of endothelin-1 receptors, phospholipase C and Ins(1,4,5)P3 receptors. Fractional Ca2+ release from the sarcoplasmic reticulum and perinuclear stores was increased by endothelin-1 at an otherwise unaltered Ca2+ load. Comparable increases of cytoplasmic CaTs induced by beta-adrenoceptor stimulation or elevation of extracellular Ca2+ could not mimic the endothelin-1 effects on nuclear CaTs, suggesting that endothelin-1 specifically modulates nuclear Ca2+ signalling. Thus, endothelin-1 enhances nuclear CaTs in atrial myocytes by increasing fractional Ca2+ release from perinuclear stores. This effect is mediated by the coupling of endothelin receptor A to PLC-Ins(1,4,5)P3 signalling and might contribute to excitation-transcription coupling.
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Affiliation(s)
- Jens Kockskämper
- Department of Cardiology and Pneumology, University Medicine Göttingen, Germany.
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Sag CM, Dybkova N, Neef S, Maier LS. Effects on recovery during acidosis in cardiac myocytes overexpressing CaMKII. J Mol Cell Cardiol 2007; 43:696-709. [DOI: 10.1016/j.yjmcc.2007.09.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Revised: 09/07/2007] [Accepted: 09/20/2007] [Indexed: 10/22/2022]
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Török TL. Electrogenic Na+/Ca2+-exchange of nerve and muscle cells. Prog Neurobiol 2007; 82:287-347. [PMID: 17673353 DOI: 10.1016/j.pneurobio.2007.06.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Revised: 04/12/2007] [Accepted: 06/12/2007] [Indexed: 12/19/2022]
Abstract
The plasma membrane Na(+)/Ca(2+)-exchanger is a bi-directional electrogenic (3Na(+):1Ca(2+)) and voltage-sensitive ion transport mechanism, which is mainly responsible for Ca(2+)-extrusion. The Na(+)-gradient, required for normal mode operation, is created by the Na(+)-pump, which is also electrogenic (3Na(+):2K(+)) and voltage-sensitive. The Na(+)/Ca(2+)-exchanger operational modes are very similar to those of the Na(+)-pump, except that the uncoupled flux (Na(+)-influx or -efflux?) is missing. The reversal potential of the exchanger is around -40 mV; therefore, during the upstroke of the AP it is probably transiently activated, leading to Ca(2+)-influx. The Na(+)/Ca(2+)-exchange is regulated by transported and non-transported external and internal cations, and shows ATP(i)-, pH- and temperature-dependence. The main problem in determining the role of Na(+)/Ca(2+)-exchange in excitation-secretion/contraction coupling is the lack of specific (mode-selective) blockers. During recent years, evidence has been accumulated for co-localisation of the Na(+)-pump, and the Na(+)/Ca(2+)-exchanger and their possible functional interaction in the "restricted" or "fuzzy space." In cardiac failure, the Na(+)-pump is down-regulated, while the exchanger is up-regulated. If the exchanger is working in normal mode (Ca(2+)-extrusion) during most of the cardiac cycle, upregulation of the exchanger may result in SR Ca(2+)-store depletion and further impairment in contractility. If so, a normal mode selective Na(+)/Ca(2+)-exchange inhibitor would be useful therapy for decompensation, and unlike CGs would not increase internal Na(+). In peripheral sympathetic nerves, pre-synaptic alpha(2)-receptors may regulate not only the VSCCs but possibly the reverse Na(+)/Ca(2+)-exchange as well.
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Affiliation(s)
- Tamás L Török
- Department of Pharmacodynamics, Semmelweis University, P.O. Box 370, VIII. Nagyvárad-tér 4, H-1445 Budapest, Hungary.
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Palomeque J, Petroff MV, Sapia L, Gende OA, Mundiña-Weilenmann C, Mattiazzi A. Multiple alterations in Ca2+ handling determine the negative staircase in a cellular heart failure model. J Card Fail 2007; 13:143-54. [PMID: 17395056 DOI: 10.1016/j.cardfail.2006.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 10/13/2006] [Accepted: 11/03/2006] [Indexed: 11/27/2022]
Abstract
BACKGROUND The flat or negative force frequency relationship (FFR) is a hallmark of the failing heart. Either decreases in SERCA2a expression, increases in Na(+)/Ca(2+) exchanger (NCX) expression or elevated Na(+)(i) have been independently proposed as mediators of the negative FFR. METHODS AND RESULTS To determine whether each one of these mechanisms is sufficient to account for the negative FFR of the failing heart or on the contrary, various mechanisms, acting in concert are required. SERCA2a was pharmacologically inhibited with thapsigargin (TG) or cyclopiazonic acid (CPA) or by using siRNA technology; Na(+)(i) was increased with either ouabain (Oua) or monensin and NCX protein was overexpressed by gene transfer (Ad.NCX), to mimic in nonfailing cat myocytes the phenotype of the failing heart and examine their effect on the FFR. The positive FFR of healthy myocytes remained unaffected after either SERCA2a inhibition, Na(+)(i) elevation, or NCX overexpression. However, the combination of TG + Oua, Oua + Ad.NCX, or TG + Ad.NCX, converted the positive FFR to negative. Moreover, the FFR became negative at lower frequencies, when the 3 interventions were combined. CONCLUSIONS Ca(2+) handling has to be altered at several levels to explain the negative FFR of the failing heart. These anomalies in Ca(2+) homeostasis acting in synergy have additive effects.
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Affiliation(s)
- Julieta Palomeque
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata 1900, Argentina
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Schillinger W, Teucher N, Christians C, Kohlhaas M, Sossalla S, Van Nguyen P, Schmidt AG, Schunck O, Nebendahl K, Maier LS, Zeitz O, Hasenfuss G. High intracellular Na+preserves myocardial function at low heart rates in isolated myocardium from failing hearts. Eur J Heart Fail 2006; 8:673-80. [PMID: 16540370 DOI: 10.1016/j.ejheart.2006.01.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2005] [Revised: 10/28/2005] [Accepted: 01/25/2006] [Indexed: 10/24/2022] Open
Abstract
We investigated the hypothesis that increased intracellular [Na+]i in heart failure contributes to preservation of SR Ca2+ load which may become particularly evident at slow heart rates. [Na+]i in SBFI-loaded myocytes from rabbits with pacing-induced heart failure (PHF) was significantly higher at each frequency as compared to Sham-operated animals. Furthermore, PHF rabbits demonstrated reduced SR Ca2+-ATPase protein levels (-37%, p < 0.04) but unchanged Na+/Ca2+ exchanger protein levels. At 0.25 Hz, isometric force was similar in cardiac trabeculae from PHF rabbits as compared to control (PHF, 3.6+/-1.3; Sham, 4.4+/-0.6 mN/mm2). Rapid cooling contractures (RCCs) were unchanged indicating preserved SR Ca2+ load at this frequency. In Sham, isometric twitch force increased with rising frequencies to 29.0+/-2.8 mN/mm2 at 3.0 Hz (p < 0.05) as compared to 0.25 Hz. RCCs showed a parallel increase by 186+/-47% (p < 0.01). In PHF, frequency-dependent increase in force (15.8+/-4.7 mN/mm2 at 3.0 Hz) and RCCs (increase by 70+/-40%) were significantly blunted. Thus, in PHF in rabbits SR Ca2+ load is preserved at low frequencies despite decreased SR Ca2+-ATPase expression. This may result from [Na+]i-dependent changes in Na+/Ca2+ exchanger activity.
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Affiliation(s)
- Wolfgang Schillinger
- Georg-August-Universität Göttingen, Herzzentrum, Kardiologie und Pneumologie, Robert-Koch-Str. 40, 37099 Göttingen, Germany.
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Münch G, Rosport K, Baumgartner C, Li Z, Wagner S, Bültmann A, Ungerer M. Functional alterations after cardiac sodium-calcium exchanger overexpression in heart failure. Am J Physiol Heart Circ Physiol 2006; 291:H488-95. [PMID: 16603685 DOI: 10.1152/ajpheart.01324.2005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The sodium-calcium exchanger (NCX) is discussed as one of the key proteins involved in heart failure. However, the causal role and the extent to which NCX contributes to contractile dysfunction during heart failure are poorly understood. NCX overexpression was induced by infection with an adenovirus coding for NCX, which coexpressed green fluorescence protein (GFP) (AdNCX) by ex vivo gene transfer to nonfailing and failing rabbit cardiomyocytes. Myocardial gene transfer in rabbits in vivo was achieved by adenoviral delivery via aortic cross-clamping. Peak cell shortening of cardiomyocytes was determined photo-optically. Hemodynamic parameters in vivo were determined by echocardiography (fractional shortening) and tip catheter [maximal first derivative of left ventricular (LV) pressure (dP/d tmax); maximal negative derivative of LV pressure (−dP/d tmax)]. Peak cell shortening was depressed after NCX gene delivery in isolated nonfailing and in failing cardiomyocytes. In nonfailing rabbits in vivo, basal systolic contractility (fractional shortening and dP/d tmax) and maximum rate of LV relaxation (−dP/d tmax) in vivo were largely unaffected after NCX overexpression. However, during heart failure, long-term NCX overexpression over 2 wk significantly improved fractional shortening and dP/d tmax compared with AdGFP-infected rabbits, both without inotropic stimulation and after β-adrenergic stimulation with isoproterenol. −dP/d tmax was also improved after NCX overexpression in the failing rabbits group. These results indicate that short-term effects of NCX overexpression impair contractility of isolated failing and nonfailing rabbit cardiomyocytes. NCX overexpression over 2 wk in vivo does not seem to affect myocardial contractility in nonfailing rabbits. Interestingly, in vivo overexpression of NCX decreased the progression of systolic and diastolic contractile dysfunction and improved β-adrenoceptor-mediated contractile reserve in heart failure in rabbits in vivo.
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Affiliation(s)
- Götz Münch
- Trigen GmbH, Fraunhoferstr. 9, D-82152 Martinsried, Germany.
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Smith GL, Elliott EEB, Kettlewell S, Currie S, Quinn FR. Na+/Ca2+ Exchanger Expression and Function in a Rabbit Model of Myocardial Infarction. J Cardiovasc Electrophysiol 2006; 17 Suppl 1:S57-S63. [PMID: 16686683 DOI: 10.1111/j.1540-8167.2006.00384.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
INTRODUCTION In general, sarcolemmal Na(+)/Ca(2+) exchanger (NCX) protein and activity is increased in hearts with ventricular dysfunction. However, in a subset of studies, reduced activity of NCX has been reported. Left ventricular dysfunction (LVD) was induced in the rabbit eight weeks after an apical myocardial infarction. METHODS Using single microelectrode voltage clamp to assess the NCX activity in isolated ventricular cells, a decrease in NCX activity by approximately 30% was observed. Immunoblot analysis indicated increased NCX protein levels by approximately 20% in the LVD group. The cause of this paradox is unknown. Overexpression of the protein sorcin increased the activity of NCX without affecting NCX protein levels. RESULTS Sorcin protein (dimer) levels were significantly lower in the LVD group (0.67+/-0.05 n=15, P<0.05) compared to sham (1.0+/-0.16, n=15). Sorcin monomer levels were not significantly different (sham: 1.0+/-0.26, LVD: 0.83+/-0.13). Mathematical modeling of NCX suggests that a reduction of NCX activity during diastole to that in LVD could be achieved by holding the diastolic membrane potential at -60 mV instead of -80 mV. Holding E(m) at -60 mV decreased NCX-mediated Ca(2+) efflux rates to values comparable to those seen in LVD and increased SR Ca(2+) content and peak systolic [Ca(2+)] in sham and LVD cardiomyocytes. CONCLUSIONS In conclusion, reduced sorcin expression may be linked to the lower NCX activity in the rabbit model of LVD. Reduced NCX activity during diastole increases SR Ca(2+) content and Ca(2+) transient amplitude.
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Affiliation(s)
- Godfrey L Smith
- Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, UK.
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Iwamoto T. Sodium–calcium exchange inhibitors: therapeutic potential in cardiovascular diseases. Future Cardiol 2005; 1:519-29. [DOI: 10.2217/14796678.1.4.519] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Intracellular calcium ions (Ca2+) are the key regulators in cardiac and arterial functions during the contraction–relaxation cycle. Myocyte Ca2+ imbalance thus produces mechanical dysfunction, electrical instability (arrhythmia) and muscle remodeling. The sodium–calcium exchanger (NCX) is one of the major Ca2+-handling proteins in myocytes. Evidence is currently accumulating to suggest that NCX1 is upregulated in various cardiovascular diseases. Recently developed benzyloxyphenyl NCX inhibitors effectively prevent myocardial ischemia/reperfusion injury and salt-sensitive hypertension in animal models. Furthermore, several experiments with genetically engineered mice provide compelling evidence that these diseases are triggered by pathologic Ca2+ entry through NCX1 in cardiac and arterial myocytes, respectively. Thus, NCX inhibitors may have therapeutic potential as novel cardiovascular drugs for myocardial reperfusion injury and salt-sensitive hypertension. However, the efficacy of NCX inhibitors, as well as the role of NCX1, in heart failure or arrhythmias requires more detailed study.
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Affiliation(s)
- Takahiro Iwamoto
- Fukuoka University, Department of Pharmacology, School of Medicine, Jonan-ku, Fukuoka 814-0180, Japan
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Hoshijima M. Gene therapy targeted at calcium handling as an approach to the treatment of heart failure. Pharmacol Ther 2005; 105:211-28. [PMID: 15737405 DOI: 10.1016/j.pharmthera.2004.10.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2004] [Accepted: 10/08/2004] [Indexed: 01/08/2023]
Abstract
Chronic congestive heart failure primarily of ischemic origin remains a leading cause of morbidity and mortality in the United States and other leading countries. The current main stream of therapy is, however, palliative and uses a complex regimen of drugs, the actions of which are not understood completely. On the other hand, unfavorable remodeling after cardiac injuries of multiple causes has been thought to lead to cardiac contractile dysfunction in heart failure, and a body of scientific evidence points to a central role of intrinsic defects in intracellular calcium handling in cardiomyocytes that arise from the distorted functions of several key regulatory molecules on plasma membrane or sarcoplasmic reticulum (SR), a muscle-specific intracellular membrane complex that stores calcium at high concentration. Accordingly, the initial appetite to use gene transfer strategies to modulate calcium regulatory proteins was to validate molecular targets for the development of new pharmaceuticals; however, remarkable therapeutic efficacies found in an initial series of studies using various heart failure animal models immediately promoted us to seek ways to directly apply gene transfer to cure clinical heart failure. The first part of this article reviews our up-to-date knowledge of various functional components to regulate calcium handling in cardiomyocytes, including beta-adrenergic receptor, L-type calcium channel, ryanodine receptor (RyR) and its associated proteins, sarco-endoplasmic reticulum calcium ATPase (SERCA), and phospholamban (PLN), and their abnormalities in failing hearts. A series of new somatic gene transfer attempts targeting calcium handling in cardiomyocytes are discussed thereafter.
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Affiliation(s)
- Masahiko Hoshijima
- University of California San Diego, Institute of Molecular Medicine, Department of Medicine, UCSD School of Medicine, UCSD0641, 9500 Gilman Dr., La Jolla, CA 92093, USA.
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Abstract
Heart failure remains a leading cause of worldwide morbidity and mortality. Despite recent advances in treatment and our increasing knowledge of pathophysiology and the molecular derangements involved in the failing heart, our ability to affect the underlying cardiac disease processes is limited. In recent years, there has been considerable interest in myocardial gene transfer as both an investigational and potential therapeutic modality. Ultimately, the goal of any such strategy is to reprogramme failing cardiac myocytes and correct the aberrant molecular events causing heart failure. So far, viral vectors have been utilised with success more frequently than any other method of gene delivery in animal models. Studies in animal models and in failing human cardiomyocytes in culture targeting specific molecular pathways, including the beta-adrenergic receptor cascade and the myocyte intracellular calcium handling system, have shown encouraging results and offer hope that gene manipulation may provide novel adjunctive therapeutic modalities for human heart failure.
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Affiliation(s)
- Jacob N Schroder
- Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA
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Stagg MA, Malik AH, MacLeod KT, Terracciano CMN. The effects of overexpression of the Na+/Ca2+ exchanger on calcium regulation in hypertrophied mouse cardiac myocytes. Cell Calcium 2005; 36:111-8. [PMID: 15193859 DOI: 10.1016/j.ceca.2004.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2003] [Revised: 11/04/2003] [Accepted: 01/06/2004] [Indexed: 11/23/2022]
Abstract
In cardiac hypertrophy and failure it has been shown that the amount of Na/Ca exchanger protein can increase. Several studies have investigated this modification in overt heart failure. However, the role of Na/Ca exchanger overexpression during the development of hypertrophy is unknown. To address this question we investigated Ca2+ regulation in an early stage of cardiac hypertrophy before signs of heart failure occurred and evaluated the role of Na/Ca exchanger overexpression. Cardiac hypertrophy was induced by a constant infusion of angiotensin II (Ang, 1 microg/min/kg) via an osmotic pump for 14 days. Thereafter, ventricular myocytes from either wild type (NON) or transgenic mice overexpressing the Na/Ca exchanger (TR) were isolated. Myocytes were loaded with indo-1 AM or fluo-4 AM to monitor cytoplasmic [Ca2+] with all experiments performed at 37 degrees C. In myocytes exposed to Ang there was an increase in cell capacitance of more than 20% indicating cellular hypertrophy. Ca2+ transients were prolonged in hypertrophied NON myocytes but not in TR myocytes. Action potentials had a less negative plateau in TR myocytes. Sarcoplasmic reticulum (SR) Ca2+ content, measured using rapid caffeine application, was greater in TR myocytes but unaffected by hypertrophy. Ca2+ spark frequency was significantly greater in TR. Na/Ca exchanger overexpression prevented the prolongation of the Ca2+ transient observed in hypertrophy and maintained a similar SR Ca2+ leak suggesting a compensatory role in Ca2+ regulation in hypertrophied cardiac myocytes from transgenic mice. We suggest this compensatory effect is mediated by increased SR Ca2+ content and faster Ca2+ removal via the Na/Ca exchanger.
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Affiliation(s)
- Mark A Stagg
- Cellular Electrophysiology, Heart Science Centre, Imperial College London, National Heart & Lung Institute, Harefield Hospital, Hill End Road Harefield, Middlesex UB9 6JH, UK.
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McCurley JM, Hanlon SU, Wei SK, Wedam EF, Michalski M, Haigney MC. Furosemide and the progression of left ventricular dysfunction in experimental heart failure. J Am Coll Cardiol 2004; 44:1301-7. [PMID: 15364336 DOI: 10.1016/j.jacc.2004.04.059] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2003] [Revised: 03/31/2004] [Accepted: 04/20/2004] [Indexed: 11/30/2022]
Abstract
OBJECTIVES We tested the hypothesis that furosemide accelerates the progression of left ventricular systolic dysfunction in a tachycardia-induced porcine model of heart failure. BACKGROUND Furosemide activates the renin-angiotensin-aldosterone system in patients with congestive heart failure (CHF). Such activation may contribute to CHF progression, but prospective data are lacking. METHODS Thirty-two Yorkshire pigs were randomized to furosemide (1 mg/kg intramuscularly daily, mean 16.1 +/- 0.9 mg) or placebo. Thereafter, a pacing model of heart failure was utilized to produce systolic dysfunction in both sets of animals (fractional shortening <0.16 by echocardiogram). The goal was to determine if furosemide would accelerate the progression of left ventricular dysfunction in the "treated" group. After sacrifice, sodium-calcium exchanger currents and their responsiveness to isoproterenol were measured during voltage clamp. All investigators were blinded to treatment assignment. RESULTS Furosemide shortened the time to left ventricular dysfunction (35.1 +/- 5.1 days in placebo versus 21.4 +/- 3.2 days for furosemide animals; p = 0.038, log-rank test). By day 14, aldosterone levels were significantly higher in furosemide animals (43.0 +/- 11.8 ng/dl vs. 17.6 +/- 4.5 ng/dl; p < 0.05). Serum sodium was reduced (133.0 +/- 0.9 mmol/l furosemide vs. 135.7 +/- 0.8 mmol/l placebo; p < 0.05), but no difference in norepinephrine, potassium, magnesium, creatinine, or urea nitrogen was present. Basal sodium-calcium exchanger currents were significantly increased and isoproterenol responsiveness depressed by furosemide. CONCLUSIONS Tachycardic pigs given furosemide had significant acceleration of both contractile and metabolic features of CHF, including left ventricular systolic dysfunction, elevated serum aldosterone levels, and altered calcium handling in a controlled experimental model of heart failure.
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Affiliation(s)
- John M McCurley
- Division of Cardiology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
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Bölck B, Münch G, Mackenstein P, Hellmich M, Hirsch I, Reuter H, Hattebuhr N, Weig HJ, Ungerer M, Brixius K, Schwinger RHG. Na+/Ca2+ exchanger overexpression impairs frequency- and ouabain-dependent cell shortening in adult rat cardiomyocytes. Am J Physiol Heart Circ Physiol 2004; 287:H1435-45. [PMID: 15165985 DOI: 10.1152/ajpheart.00397.2003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Na(+)/Ca(2+) exchanger (NCX) may influence cardiac function depending on its predominant mode of action, forward mode or reverse mode, during the contraction-relaxation cycle. The intracellular Na(+) concentration ([Na(+)](i)) and the duration of the action potential as well as the level of NCX protein expression regulate the mode of action of NCX. [Na(+)](i) and NCX expression have been reported to be increased in human heart failure. Nevertheless, the consequences of altered NCX expression in heart failure are still a matter of discussion. We aimed to characterize the influence of NCX expression on intracellular Ca(2+) transport in rat cardiomyocytes by adenoviral-mediated gene transfer. A five- to ninefold (dose dependent) overexpression of NCX protein was achieved after 48 h by somatic gene transfer (Ad.NCX.GFP) versus control (Ad.GFP). NCX activity, determined by Na(+) gradient-dependent (45)Ca(2+)-uptake, was significantly increased. The protein expressions of sarco(endo)plasmic reticulum Ca(2+)-ATPase, phospholamban, and calsequestrin were unaffected by NCX overexpression. Fractional shortening (FS) of isolated cardiomyocytes was significantly increased at low stimulation rates in Ad.NCX.GFP. After a step-wise enhancing frequency of stimulation to 3.0 Hz, FS remained unaffected in Ad.GFP cells but declined in Ad.NCX.GFP cells. The positive inotropic effect of the cardiac glycoside ouabain was less effective in Ad.NCX.GFP cells, whereas the positive inotropic effect of beta-adrenergic stimulation remained unchanged. In conclusion, NCX overexpression results in a reduced cell shortening at higher stimulation frequencies as well as after inhibition of sarcolemmal Na(+)-K(+)-ATPase, i.e., in conditions with enhanced [Na(+)](i). At low stimulation rates, increased NCX expression enhances both intracellular systolic Ca(2+) and contraction amplitude.
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Affiliation(s)
- Birgit Bölck
- Laboratory of Muscle Research and Molecular Cardiology, Dept. of Internal Medicine III, Univ. of Cologne, Joseph-Stelzmann Strasse 9, 50924 Cologne, Germany
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Abstract
In recent years there has been a rapid expansion in our understanding of the molecular biology that underpins human physiology. In the heart, elegant molecular pathways have been elucidated, and derangements in these pathways have been identified as factors in cardiac disease. However, as our understanding has grown, we have recognized that there exist only relatively crude tools to effect changes in molecular pathophysiology. The ultimate promise of gene therapy is to correct the molecular derangements that cause illness. To bring this promise to fruition in the clinical arena, many problems need to be solved, and chief among these remains reliable and robust delivery of genes to the target organ. To this end, viral vectors have been utilized with success more frequently than any other method of gene delivery. The use of these vectors in the heart has already offered promising novel benefit for human ischemic heart disease, and studies in animal models have given glimpses of hope that gene therapy may provide future therapeutic benefit in heart failure by improving cardiac function.
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Affiliation(s)
- Matthew L Williams
- Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA
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Abstract
In recent years, electrical remodeling has emerged as an important pathophysiologic mechanism in many types of cardiac pathology. Because clinical heart disease often involves both hypertrophic and failure phenotypes, identification of disease-specific mechanisms is essential. This review focuses on mechanisms of electrical remodeling in cardiac hypertrophy, emphasizing transmembrane Ca2+ fluxes and Ca(2+)-responsive signaling pathways. Where information is available, the remodeling of hypertrophy is contrasted with what is known about heart failure.
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Affiliation(s)
- Joseph A Hill
- Departments of Internal Medicine and Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-8573, USA.
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Quinn FR, Currie S, Duncan AM, Miller S, Sayeed R, Cobbe SM, Smith GL. Myocardial infarction causes increased expression but decreased activity of the myocardial Na+-Ca2+ exchanger in the rabbit. J Physiol 2003; 553:229-42. [PMID: 12949221 PMCID: PMC2343488 DOI: 10.1113/jphysiol.2003.050716] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Na+-Ca2+ exchanger (NCX) protein levels and activity were measured in myocardium from the basal region of the left ventricle of rabbit hearts with significant left ventricular dysfunction (LVD), 8-9 weeks after an apical infarction. NCX protein abundance was higher in the tissue homogenates (121 +/- 11%) and purified membrane fractions (143 +/- 12%) in the LVD compared to the sham-operated (sham) group. NCX mRNA was also higher in the LVD group (126%). Lower NCX protein expression was observed in the membrane fractions from the epicardium compared to the endocardium in both the sham and LVD groups. Transmembrane currents were recorded in isolated cardiomyocytes by single-electrode voltage clamp; [Ca2+]i was measured using Fura-2. Rapid application of 10 mmol l-1 caffeine was used to induce Ca2+ release from the sarcoplasmic reticulum. The subsequent NCX-mediated Ca2+ efflux rate constant was lower (70% of sham) in the LVD group. NCX currents were measured in cardiomyocytes dialysed with 250 nM Ca2+ (50 mmol l-1 EGTA). A lower NCX current (75% of sham) was observed in the LVD group. Lower NCX activity was also observed in cardiomyocytes isolated from the epicardium compared to the endocardium; a transmural difference that was also seen in the LVD group. Reduced activity despite increased protein expression may result from reduced Ca2+ sensitivity of the allosteric regulation of NCX. However, measurements indicated increased Ca2+ sensitivity in the LVD group. Cardiomyocytes from LVD hearts displayed a marked reduction in the transverse tubule area (59% of sham) and the surface area/volume ratio (80% of sham). Disrupted transverse tubule structure may contribute to the decrease in NCX activity despite increased protein expression in LVD.
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Affiliation(s)
- F R Quinn
- Division of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK
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47
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Plank DM, Yatani A, Ritsu H, Witt S, Glascock B, Lalli MJ, Periasamy M, Fiset C, Benkusky N, Valdivia HH, Sussman MA. Calcium dynamics in the failing heart: restoration by beta-adrenergic receptor blockade. Am J Physiol Heart Circ Physiol 2003; 285:H305-15. [PMID: 12649072 DOI: 10.1152/ajpheart.00425.2002] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Changes in calcium (Ca2+) regulation contribute to loss of contractile function in dilated cardiomyopathy. Clinical treatment using beta-adrenergic receptor antagonists (beta-blockers) slows deterioration of cardiac function in end-stage heart failure patients; however, the effects of beta-blocker treatment on Ca2+ dynamics in the failing heart are unknown. To address this issue, tropomodulin-overexpressing transgenic (TOT) mice, which suffer from dilated cardiomyopathy, were treated with a nonselective beta-receptor blocker (5 mg. kg-1. day-1 propranolol) for 2 wk. Ca2+ dynamics in isolated cardiomyocytes of TOT mice significantly improved after treatment compared with untreated TOT mice. Frequency-dependent diastolic and Ca2+ transient amplitudes were returned to normal in propranolol-treated TOT mice and but not in untreated TOT mice. Ca2+ kinetic measurements of time to peak and time decay of the caffeine-induced Ca2+ transient to 50% relaxation were also normalized. Immunoblot analysis of untreated TOT heart samples showed a 3.6-fold reduction of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA), whereas Na+/Ca2+ exchanger (NCX) concentrations were increased 2.6-fold relative to nontransgenic samples. Propranolol treatment of TOT mice reversed the alterations in SERCA and NCX protein levels but not potassium channels. Although restoration of Ca2+ dynamics occurred within 2 wk of beta-blockade treatment, evidence of functional improvement in cardiac contractility assessed by echocardiography took 10 wk to materialize. These results demonstrate that beta-adrenergic blockade restores Ca2+ dynamics and normalizes expression of Ca2+-handling proteins, eventually leading to improved hemodynamic function in cardiomyopathic hearts.
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Affiliation(s)
- David M Plank
- Divisions of Molecular Cardiovascular Biology, The Children's Hospital and Research Foundation, Cincinnati, OH 45229, USA
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48
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Bernecker OY, del Monte F, Hajjar RJ. Gene therapy for the treatment of heart failure--calcium signaling. Semin Thorac Cardiovasc Surg 2003; 15:268-76. [PMID: 12973704 DOI: 10.1016/s1043-0679(03)70006-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The knowledge of molecular mechanisms indicated in cardiac dysfunction has increased dramatically over the last decade and yields considerable potential for new treatment options in heart failure. Alterations in intracellular calcium signaling play a crucial role in the pathophysiology of heart failure, and in recent years, somatic gene transfer has been identified as an important tool to help understand the relative contribution of specific calcium-handling proteins in heart failure. This article reviews recent advances in gene delivery techniques aimed at global myocardial transfection and discusses molecular therapeutic targets identified within intracellular calcium signaling pathways in heart failure.
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Affiliation(s)
- Oliver Y Bernecker
- Program in Cardiovascular Gene Therapy, Cardiovascular Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
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Matsumoto T, Miura T, Miki T, Nishino Y, Nakamura Y, Shimamoto K. Does enhanced expression of the Na+-Ca2+ exchanger increase myocardial vulnerability to ischemia/reperfusion injury in rabbit hearts? Mol Cell Biochem 2003; 248:141-7. [PMID: 12870666 DOI: 10.1023/a:1024140419688] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Reverse-mode activation of the Na+-Ca2+ exchanger (NCX) at the time of reperfusion following ischemia contributes to Ca2+ overload and cardiomyocyte injury. The aim of the present study was to determine whether increased NCX in the myocardium that survived after infarction enhances its vulnerability to ischemia/reperfusion injury. Rabbits were divided into post-MI and sham groups and underwent ligation of the left circumflex coronary artery and sham operation, respectively. Two weeks later, hearts were isolated and perfused with crystalloid in the Langendorff mode with monitoring of left ventricular (LV) pressure. NCX level in the myocardium was determined by Western blotting. Myocardial stunning was induced by 5 episodes of 5-min global ischemia/5-min reperfusion. Using separate groups of hearts, myocardial infarction was induced by 30-min global ischemia/2-h reperfusion with or without treatment with 0.3 microM KB-R7943, a reverse-mode selective blocker of NCX. Heart weight-to-body weight ratio was 20% larger and NCX protein level was 60% higher in the post-MI group than in the sham group. However, there were no significant differences between severities of myocardial stunning after the repetitive ischemia/ reperfusion (18 +/- 7 vs. 25 +/- 2% reduction in LV developed pressure) and between infarct sizes after 30-min ischemia (59.1 +/- 4.1 vs. 63.0 +/- 4.5% of risk area) in the post-MI and sham groups. KB-R7943 limited infarct size in the post-MI group by 53%, and the extent of this protection was not different from that we have reported for hearts without previous infarcts (i.e. 45% reduction of infarct size). These results suggest that enhanced NCX expression does not necessarily increase myocardial vulnerability to myocardial stunning and infarction.
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Affiliation(s)
- Tomoaki Matsumoto
- Second Department of Internal Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan
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50
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MacNeill BD, Hayase M, Hajjar RJ. Targeting signaling pathways in heart failure by gene transfer. Curr Atheroscler Rep 2003; 5:178-85. [PMID: 12667429 DOI: 10.1007/s11883-003-0021-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Congestive heart failure represents an enormous clinical problem demanding effective therapeutic approaches. The varied etiologies of heart failure include abnormalities of ion handling, cellular signaling, neurohormonal control, and apoptosis, all of which are potentially amenable to genetic manipulation. Gene therapy holds the promise of retarding the progression, preventing, and perhaps reversing heart failure. Advances in our knowledge of possible targets, vectors, and delivery techniques have revolutionized this field in recent years, bringing us close to clinical application.
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Affiliation(s)
- Briain D MacNeill
- Cardiovascular Research Center, Massachusetts General Hospital - East, Building 149, 149 13th Street, Charlestown, MA 02129-2000, USA.
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