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Kumar V, Bermea KC, Kumar D, Singh A, Verma A, Kaileh M, Sen R, Lakatta EG, Adamo L. RelA-mediated signaling connects adaptation to chronic cardiomyocyte stress with myocardial and systemic inflammation in the ADCY8 model of accelerated aging. GeroScience 2024; 46:4243-4262. [PMID: 38499959 PMCID: PMC11335706 DOI: 10.1007/s11357-024-01121-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Accepted: 03/01/2024] [Indexed: 03/20/2024] Open
Abstract
Mice with cardiac-specific overexpression of adenylyl cyclase (AC) type 8 (TGAC8) are under a constant state of severe myocardial stress. They have a remarkable ability to adapt to this stress, but they eventually develop accelerated cardiac aging and experience reduced longevity. We have previously demonstrated through bioinformatics that constitutive adenylyl cyclase activation in TGAC8 mice is associated with the activation of inflammation-related signaling pathways. However, the immune response associated with chronic myocardial stress in the TGAC8 mouse remains unexplored. Here we demonstrate that chronic activation of adenylyl cyclase in cardiomyocytes of TGAC8 mice results in activation of cell-autonomous RelA-mediated NF-κB signaling. This is associated with non-cell-autonomous activation of proinflammatory and age-associated signaling in myocardial endothelial cells and myocardial smooth muscle cells, expansion of myocardial immune cells, increase in serum levels of inflammatory cytokines, and changes in the size or composition of lymphoid organs. All these changes precede the appearance of cardiac fibrosis. We provide evidence indicating that RelA activation in cardiomyocytes with chronic activation of adenylyl cyclase is mediated by calcium-protein Kinase A (PKA) signaling. Using a model of chronic cardiomyocyte stress and accelerated aging, we highlight a novel, calcium/PKA/RelA-dependent connection between cardiomyocyte stress, myocardial inflammation, and systemic inflammation. These findings suggest that RelA-mediated signaling in cardiomyocytes might be an adaptive response to stress that, when chronically activated, ultimately contributes to both cardiac and systemic aging.
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Affiliation(s)
- Vikas Kumar
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute On Aging, National Institutes of Health, 251 Bayview Boulevard, Suite 100, Baltimore, MD, 21224, USA
- Department of Medicine, NYU Grossman School of Medicine, New York, NY, 10016, USA
| | - Kevin Christian Bermea
- Division of Cardiology, Department of Medicine, Johns Hopkins School of Medicine, Ross Research Building - Room 809, 720 Rutland Avenue, Baltimore, MD, 21205, USA
| | - Dhaneshwar Kumar
- Immunoregulation Section, Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, Bethesda, MD, USA
| | - Amit Singh
- Laboratory of Molecular Biology & Immunology, Intramural Research Program, National Institute On Aging, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Anjali Verma
- Laboratory of Clinical Investigation, Intramural Research Program, National Institute On Aging, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Mary Kaileh
- Laboratory of Molecular Biology & Immunology, Intramural Research Program, National Institute On Aging, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Ranjan Sen
- Laboratory of Molecular Biology & Immunology, Intramural Research Program, National Institute On Aging, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute On Aging, National Institutes of Health, 251 Bayview Boulevard, Suite 100, Baltimore, MD, 21224, USA.
| | - Luigi Adamo
- Division of Cardiology, Department of Medicine, Johns Hopkins School of Medicine, Ross Research Building - Room 809, 720 Rutland Avenue, Baltimore, MD, 21205, USA.
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Kumar V, Bermea KC, Kumar D, Singh A, Verma A, Kaileh M, Sen R, Lakatta EG, Adamo L. Cardiomyocyte-specific adenylyl cyclase type-8 overexpression induces cell-autonomous activation of RelA and non-cell-autonomous myocardial and systemic inflammation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.15.549173. [PMID: 37790465 PMCID: PMC10542148 DOI: 10.1101/2023.07.15.549173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Mice with cardiac-specific overexpression of adenylyl cyclase (AC) type 8 (TG AC8 ) are under a constant state of severe myocardial stress and have been shown to have a remarkable ability to adapt to this stress. However, they eventually develop accelerated cardiac aging and cardiac fibrosis, and experience reduced longevity. Here we show that young (3-month-old) TG AC8 animals are characterized by a broad and extensive inflammatory state, that precedes the development of cardiac fibrosis. We demonstrate that activation of ACVIII in the cardiomyocytes results in cell-autonomous RelA-mediated NF-κB signaling. This is associated with non-cell-autonomous activation of proinflammatory and age-associated signaling in myocardial endothelial cells, increases in serum levels of inflammatory cytokines, changes in myocardial immune cells, and changes in the size or composition of lymphoid organs. Finally, we provide evidence suggesting that ACVIII-driven RelA activation in cardiomyocytes might be mediated by calcium-Protein Kinase A (PKA) signaling. Our findings highlight a novel mechanistic connection between cardiomyocyte stress, myocardial para-inflammation, systemic inflammation, and aging, and therefore point to novel potential therapeutic targets to reduce age-associated myocardial deterioration.
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Loh KWZ, Hu Z, Soong TW. Modulation of Ca V1.2 Channel Function by Interacting Proteins and Post-Translational Modifications: Implications in Cardiovascular Diseases and COVID-19. Handb Exp Pharmacol 2023. [PMID: 36764970 DOI: 10.1007/164_2023_636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CaV1.2 calcium channel is the primary conduit for Ca2+ influx into cardiac and smooth muscles that underscores its importance in the pathogenesis of hypertension, atherosclerosis, myocardial infarction, and heart failure. But, a few controversies still remain. Therefore, exploring new ways to modulate CaV1.2 channel activity will augment the arsenal of CaV1.2 channel-based therapeutics for treatment of cardiovascular diseases. Here, we will mainly introduce a couple of emerging CaV1.2 channel interacting proteins, such as Galectin-1 and Cereblon, and discuss their roles in hypertension and heart failure through fine-tuning CaV1.2 channel activity. Of current interest, we will also evaluate the implication of the role of CaV1.2 channel in SARS-CoV-2 infection and the potential treatments of COVID-19-related cardiovascular symptoms.
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Affiliation(s)
- Kelvin Wei Zhern Loh
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Cardiovascular Diseases Translational Research Programme, National University of Singapore, Singapore, Singapore
| | - Zhenyu Hu
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Cardiovascular Diseases Translational Research Programme, National University of Singapore, Singapore, Singapore
| | - Tuck Wah Soong
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. .,Cardiovascular Diseases Translational Research Programme, National University of Singapore, Singapore, Singapore. .,Healthy Longevity Translational Research Programme, National University of Singapore, Singapore, Singapore.
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Shexiang Baoxin Pills Could Alleviate Isoproterenol-Induced Heart Failure Probably through its Inhibition of CaV1.2 Calcium Channel Currents. Biochem Res Int 2022; 2022:5498023. [DOI: 10.1155/2022/5498023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 10/08/2022] [Accepted: 10/22/2022] [Indexed: 11/11/2022] Open
Abstract
Heart failure (HF) affects millions of patients in the world. Shexiang Baoxin Pills (SXB) are extensively applied to treat coronary artery diseases and HF in Chinese hospitals. However, there are still no explanations for why SXB protects against HF. To assess the protective role, we created the HF model in rats by isoproterenol (ISO) subcutaneous injection, 85 milligrams per kilogram body weight for seven days. Four groups were implemented: CON (control), ISO (HF disease group), CAP (captopril, positive drug treatment), and SXB groups. Echocardiography was used to evaluate rats’ HF in vivo. The human CaV1.2 (hCaV1.2) channel currents were detected in tsA-201 cells by patch clamp technique. Five different concentrations of SXB (5, 10, 30, 50, and 100 mg/L) were chosen in this study. The results showed that SXB increased cardiac systolic function and inhibited rats’ cardiac hypertrophy and myocardial fibrosis induced by ISO. Subsequently, it was found that SXB was inhibited by the peak amplitudes of hCaV1.2 channel current (
). The SXB half inhibitory dosage was 9.09 mg/L. The steady-state activation curve was 22.8 mV depolarization shifted; while the inactivation curve and the recovery from inactivation were not affected significantly. In conclusion, these results indicated that SXB inhibited ISO-induced HF in rats and inhibited the hCaV1.2 channel current. The present study paved the way for SXB to protect itself from HF.
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Lotteau S, Zhang R, Hazan A, Grabar C, Gonzalez D, Aynaszyan S, Philipson KD, Ottolia M, Goldhaber JI. Acute Genetic Ablation of Cardiac Sodium/Calcium Exchange in Adult Mice: Implications for Cardiomyocyte Calcium Regulation, Cardioprotection, and Arrhythmia. J Am Heart Assoc 2021; 10:e019273. [PMID: 34472363 PMCID: PMC8649274 DOI: 10.1161/jaha.120.019273] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Background Sodium‐calcium (Ca2+) exchanger isoform 1 (NCX1) is the dominant Ca2+ efflux mechanism in cardiomyocytes and is critical to maintaining Ca2+ homeostasis during excitation‐contraction coupling. NCX1 activity has been implicated in the pathogenesis of cardiovascular diseases, but a lack of specific NCX1 blockers complicates experimental interpretation. Our aim was to develop a tamoxifen‐inducible NCX1 knockout (KO) mouse to investigate compensatory adaptations of acute ablation of NCX1 on excitation‐contraction coupling and intracellular Ca2+ regulation, and to examine whether acute KO of NCX1 confers resistance to triggered arrhythmia and ischemia/reperfusion injury. Methods and Results We used the α‐myosin heavy chain promoter (Myh6)‐MerCreMer promoter to create a tamoxifen‐inducible cardiac‐specific NCX1 KO mouse. Within 1 week of tamoxifen injection, NCX1 protein expression and current were dramatically reduced. Diastolic Ca2+ increased despite adaptive reductions in Ca2+ current and action potential duration and compensatory increases in excitation‐contraction coupling gain, sarcoplasmic reticulum Ca2+ ATPase 2 and plasma membrane Ca2+ ATPase. As these adaptations progressed over 4 weeks, diastolic Ca2+ normalized and SR Ca2+ load increased. Left ventricular function remained normal, but mild fibrosis and hypertrophy developed. Transcriptomics revealed modification of cardiovascular‐related gene networks including cell growth and fibrosis. NCX1 KO reduced spontaneous action potentials triggered by delayed afterdepolarizations and reduced scar size in response to ischemia/reperfusion. Conclusions Tamoxifen‐inducible NCX1 KO mice adapt to acute genetic ablation of NCX1 by reducing Ca2+ influx, increasing alternative Ca2+ efflux pathways, and increasing excitation‐contraction coupling gain to maintain contractility at the cost of mild Ca2+‐activated hypertrophy and fibrosis and decreased survival. Nevertheless, KO myocytes are protected against spontaneous action potentials and ischemia/reperfusion injury.
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Affiliation(s)
- Sabine Lotteau
- Smidt Heart Institute Cedars-Sinai Medical Center Los Angeles CA
| | - Rui Zhang
- Smidt Heart Institute Cedars-Sinai Medical Center Los Angeles CA
| | - Adina Hazan
- Smidt Heart Institute Cedars-Sinai Medical Center Los Angeles CA
| | - Christina Grabar
- Smidt Heart Institute Cedars-Sinai Medical Center Los Angeles CA
| | - Devina Gonzalez
- Smidt Heart Institute Cedars-Sinai Medical Center Los Angeles CA
| | | | - Kenneth D Philipson
- Department of Physiology David Geffen School of Medicine at UCLA Los Angeles CA
| | - Michela Ottolia
- Division of Molecular Medicine Department of Anesthesiology and Perioperative Medicine David Geffen School of Medicine at UCLA Los Angeles CA
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Zhang XH, Morad M. Ca 2+ signaling of human pluripotent stem cells-derived cardiomyocytes as compared to adult mammalian cardiomyocytes. Cell Calcium 2020; 90:102244. [PMID: 32585508 PMCID: PMC7483365 DOI: 10.1016/j.ceca.2020.102244] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 06/10/2020] [Accepted: 06/11/2020] [Indexed: 12/23/2022]
Abstract
Human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CMs) have been extensively used for in vitro modeling of human cardiovascular disease, drug screening and pharmacotherapy, but little rigorous studies have been reported on their biophysical or Ca2+ signaling properties. There is also considerable concern as to the level of their maturity and whether they can serve as reliable models for adult human cardiac myocytes. Ultrastructural difference such as lack of t-tubular network, their polygonal shapes, disorganized sarcomeric myofilament, and their rhythmic automaticity, among others, have been cited as evidence for immaturity of hiPSC-CMs. In this review, we will deal with Ca2+ signaling, its regulation, and its stage of maturity as compared to the mammalian adult cardiomyocytes. We shall summarize the data on functional aspects of Ca2+signaling and its parameters that include: L-type calcium channel (Cav1.2), ICa-induced Ca2+release, CICR, and its parameters, cardiac Na/Ca exchanger (NCX1), the ryanodine receptors (RyR2), sarco-reticular Ca2+pump, SERCA2a/PLB, and the contribution of mitochondrial Ca2+ to hiPSC-CMs excitation-contraction (EC)-coupling as compared with adult mammalian cardiomyocytes. The comparative studies suggest that qualitatively hiPSC-CMs have similar Ca2+signaling properties as those of adult cardiomyocytes, but quantitative differences do exist. This review, we hope, will allow the readers to judge for themselves to what extent Ca2+signaling of hiPSC-CMs represents the adult form of this signaling pathway, and whether these cells can be used as good models of human cardiomyocytes.
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Affiliation(s)
- Xiao-Hua Zhang
- Cardiac Signaling Center of University of South Carolina, Medical University of South Carolina, Clemson University, Charleston SC, United States
| | - Martin Morad
- Cardiac Signaling Center of University of South Carolina, Medical University of South Carolina, Clemson University, Charleston SC, United States.
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Regulation of cardiovascular calcium channel activity by post-translational modifications or interacting proteins. Pflugers Arch 2020; 472:653-667. [PMID: 32435990 DOI: 10.1007/s00424-020-02398-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Revised: 05/04/2020] [Accepted: 05/06/2020] [Indexed: 02/08/2023]
Abstract
Voltage-gated calcium channels are the major pathway for Ca2+ influx to initiate the contraction of smooth and cardiac muscles. Alterations of calcium channel function have been implicated in multiple cardiovascular diseases, such as hypertension, atrial fibrillation, and long QT syndrome. Post-translational modifications do expand cardiovascular calcium channel structure and function to affect processes such as channel trafficking or polyubiquitination by two E3 ubiquitin ligases, Ret finger protein 2 (Rfp2) or murine double minute 2 protein (Mdm2). Additionally, biophysical property such as Ca2+-dependent inactivation (CDI) could be altered through binding of calmodulin, or channel activity could be modulated via S-nitrosylation by nitric oxide and phosphorylation by protein kinases or by interacting protein partners, such as galectin-1 and Rem. Understanding how cardiovascular calcium channel function is post-translationally remodeled under distinctive disease conditions will provide better information about calcium channel-related disease mechanisms and improve the development of more selective therapeutic agents for cardiovascular diseases.
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Wang Y, Li C, Shi L, Chen X, Cui C, Huang J, Chen B, Hall DD, Pan Z, Lu M, Hong J, Song LS, Zhao S. Integrin β1D Deficiency-Mediated RyR2 Dysfunction Contributes to Catecholamine-Sensitive Ventricular Tachycardia in Arrhythmogenic Right Ventricular Cardiomyopathy. Circulation 2020; 141:1477-1493. [PMID: 32122157 DOI: 10.1161/circulationaha.119.043504] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a hereditary heart disease characterized by fatty infiltration, life-threatening arrhythmias, and increased risk of sudden cardiac death. The guideline for management of ARVC in patients is to improve quality of life by reducing arrhythmic symptoms and to prevent sudden cardiac death. However, the mechanism underlying ARVC-associated cardiac arrhythmias remains poorly understood. METHODS Using protein mass spectrometry analyses, we identified that integrin β1 is downregulated in ARVC hearts without changes to Ca2+-handling proteins. As adult cardiomyocytes express only the β1D isoform, we generated a cardiac specific β1D knockout mouse model and performed functional imaging and biochemical analyses to determine the consequences of integrin β1D loss on function in the heart in vivo and in vitro. RESULTS Integrin β1D deficiency and RyR2 Ser-2030 hyperphosphorylation were detected by Western blotting in left ventricular tissues from patients with ARVC but not in patients with ischemic or hypertrophic cardiomyopathy. Using lipid bilayer patch clamp single channel recordings, we found that purified integrin β1D protein could stabilize RyR2 function by decreasing RyR2 open probability, mean open time, and increasing mean close time. Also, β1D knockout mice exhibited normal cardiac function and morphology but presented with catecholamine-sensitive polymorphic ventricular tachycardia, consistent with increased RyR2 Ser-2030 phosphorylation and aberrant Ca2+ handling in β1D knockout cardiomyocytes. Mechanistically, we revealed that loss of DSP (desmoplakin) induces integrin β1D deficiency in ARVC mediated through an ERK1/2 (extracellular signal-regulated kinase 1 and 2)-fibronectin-ubiquitin/lysosome pathway. CONCLUSIONS Our data suggest that integrin β1D deficiency represents a novel mechanism underlying the increased risk of ventricular arrhythmias in patients with ARVC.
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Affiliation(s)
- Yihui Wang
- State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (Y.W., C.L., X.C., C.C., M.L., S.Z.)
| | - Chunyan Li
- State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (Y.W., C.L., X.C., C.C., M.L., S.Z.)
| | - Ling Shi
- Department of Pharmacology, College of Pharmacy, and State-Province Key Laboratories of Biomedicine-Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education, Harbin Medical University, Heilongjiang, China (L.S., Z.P.)
| | - Xiuyu Chen
- State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (Y.W., C.L., X.C., C.C., M.L., S.Z.)
| | - Chen Cui
- State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (Y.W., C.L., X.C., C.C., M.L., S.Z.)
| | | | - Biyi Chen
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa, Iowa City (B.C., D.D.H., L.-S.S.)
| | - Duane D Hall
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa, Iowa City (B.C., D.D.H., L.-S.S.)
| | - Zhenwei Pan
- Department of Pharmacology, College of Pharmacy, and State-Province Key Laboratories of Biomedicine-Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education, Harbin Medical University, Heilongjiang, China (L.S., Z.P.)
| | - Minjie Lu
- State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (Y.W., C.L., X.C., C.C., M.L., S.Z.)
| | - Jiang Hong
- Department of Cardiology, Fujian Institute of Coronary Heart Disease, Fujian Medical University Union Hospital, China (J.H.)
- Shanghai General Hospital, Shanghai Jiaotong University School of Medicine, China (J.H.)
| | - Long-Sheng Song
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa, Iowa City (B.C., D.D.H., L.-S.S.)
- Fraternal Order of Eagles Diabetes Research Center, Carver College of Medicine, University of Iowa, Iowa City (L.-S.S.)
- Department of Veterans Affairs Medical Center, Iowa City, IA (L.-S.S.)
| | - Shihua Zhao
- State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (Y.W., C.L., X.C., C.C., M.L., S.Z.)
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Liu QH, Qiao X, Zhang LJ, Wang J, Zhang L, Zhai XW, Ren XZ, Li Y, Cao XN, Feng QL, Cao JM, Wu BW. I K1 Channel Agonist Zacopride Alleviates Cardiac Hypertrophy and Failure via Alterations in Calcium Dyshomeostasis and Electrical Remodeling in Rats. Front Pharmacol 2019; 10:929. [PMID: 31507422 PMCID: PMC6718093 DOI: 10.3389/fphar.2019.00929] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 07/22/2019] [Indexed: 01/08/2023] Open
Abstract
Intracellular Ca2+ overload, prolongation of the action potential duration (APD), and downregulation of inward rectifier potassium (IK1) channel are hallmarks of electrical remodeling in cardiac hypertrophy and heart failure (HF). We hypothesized that enhancement of IK1 currents is a compensation for IK1 deficit and a novel modulation for cardiac Ca2+ homeostasis and pathological remodeling. In adult Sprague-Dawley (SD) rats in vivo, cardiac hypertrophy was induced by isoproterenol (Iso) injection (i.p., 3 mg/kg/d) for 3, 10, and 30 days. Neonatal rat ventricular myocytes (NRVMs) were isolated from 1 to 3 days SD rat pups and treated with 1 μmol/L Iso for 24 h in vitro. The effects of zacopride, a selective IK1/Kir2.1 channel agonist, on cardiac remodeling/hypertrophy were observed in the settings of 15 μg/kg in vivo and 1 μmol/L in vitro. After exposing to Iso for 3 days and 10 days, rat hearts showed distinct concentric hypertrophy and fibrosis and enhanced pumping function (P < 0.01 or P < 0.05), then progressed to dilatation and dysfunction post 30 days. Compared with the age-matched control, cardiomyocytes exhibited higher cytosolic Ca2+ (P < 0.01 or P < 0.05) and lower SR Ca2+ content (P < 0.01 or P < 0.05) all through 3, 10, and 30 days of Iso infusion. The expressions of Kir2.1 and SERCA2 were downregulated, while p-CaMKII, p-RyR2, and cleaved caspase-3 were upregulated. Iso-induced electrophysiological abnormalities were also manifested with resting potential (RP) depolarization (P < 0.01), APD prolongation (P < 0.01) in adult cardiomyocytes, and calcium overload in cultured NRVMs (P < 0.01). Zacopride treatment effectively retarded myocardial hypertrophy and fibrosis, preserved the expression of Kir2.1 and some key players in Ca2+ homeostasis, normalized the RP (P < 0.05), and abbreviated APD (P < 0.01), thus lowered cytosolic [Ca2 +]i (P < 0.01 or P < 0.05). IK1channel blocker BaCl2 or chloroquine largely reversed the cardioprotection of zacopride. We conclude that cardiac electrical remodeling is concurrent with structural remodeling. By enhancing cardiac IK1, zacopride prevents Iso-induced electrical remodeling around intracellular Ca2+ overload, thereby attenuates cardiac structural disorder and dysfunction. Early electrical interventions may provide protection on cardiac remodeling.
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Affiliation(s)
- Qing-Hua Liu
- Department of Pathophysiology, Shanxi Medical University, Taiyuan, China
| | - Xi Qiao
- Department of Pathophysiology, Shanxi Medical University, Taiyuan, China
| | - Li-Jun Zhang
- Department of Pathophysiology, Shanxi Medical University, Taiyuan, China
| | - Jin Wang
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Li Zhang
- Clinical Laboratory, Children's Hospital of Shanxi, Taiyuan, China
| | - Xu-Wen Zhai
- Clinical Skills Teaching Simulation Hospital, Shanxi Medical University, Taiyuan, China
| | - Xiao-Ze Ren
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Yu Li
- Department of Internal Medicine, The Hospital of Beijing Sports University, Beijing, China
| | - Xiao-Na Cao
- Department of Internal Medicine, The Hospital of Beijing Sports University, Beijing, China
| | - Qi-Long Feng
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Ji-Min Cao
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Bo-Wei Wu
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University, Taiyuan, China
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10
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Stewart BD, Scott CE, McCoy TP, Yin G, Despa F, Despa S, Kekenes-Huskey PM. Computational modeling of amylin-induced calcium dysregulation in rat ventricular cardiomyocytes. Cell Calcium 2017; 71:65-74. [PMID: 29604965 DOI: 10.1016/j.ceca.2017.11.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 11/30/2017] [Accepted: 11/30/2017] [Indexed: 01/08/2023]
Abstract
Hyperamylinemia is a condition that accompanies obesity and precedes type II diabetes, and it is characterized by above-normal blood levels of amylin, the pancreas-derived peptide. Human amylin oligomerizes easily and can deposit in the pancreas [1], brain [2], and heart [3], where they have been associated with calcium dysregulation. In the heart, accumulating evidence suggests that human amylin oligomers form moderately cation-selective [4,5] channels that embed in the cell sarcolemma (SL). The oligomers increase membrane conductance in a concentration-dependent manner [5], which is correlated with elevated cytosolic Ca2+. These findings motivate our core hypothesis that non-selective inward Ca2+ conduction afforded by human amylin oligomers increase cytosolic and sarcoplasmic reticulum (SR) Ca2+ load, which thereby magnifies intracellular Ca2+ transients. Questions remain however regarding the mechanism of amylin-induced Ca2+ dysregulation, including whether enhanced SL Ca2+ influx is sufficient to elevate cytosolic Ca2+ load [6], and if so, how might amplified Ca2+ transients perturb Ca2+-dependent cardiac pathways. To investigate these questions, we modified a computational model of cardiomyocytes Ca2+ signaling to reflect experimentally-measured changes in SL membrane permeation and decreased sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) function stemming from acute and transgenic human amylin peptide exposure. With this model, we confirmed the hypothesis that increasing SL permeation alone was sufficient to enhance Ca2+ transient amplitudes. Our model indicated that amplified cytosolic transients are driven by increased Ca2+ loading of the SR and that greater fractional release may contribute to the Ca2+-dependent activation of calmodulin, which could prime the activation of myocyte remodeling pathways. Importantly, elevated Ca2+ in the SR and dyadic space collectively drive greater fractional SR Ca2+ release for human amylin expressing rats (HIP) and acute amylin-exposed rats (+Amylin) mice, which contributes to the inotropic rise in cytosolic Ca2+ transients. These findings suggest that increased membrane permeation induced by oligomeratization of amylin peptide in cell sarcolemma contributes to Ca2+ dysregulation in pre-diabetes.
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Affiliation(s)
- Bradley D Stewart
- Department of Chemistry, University of Kentucky, 505 Rose St. Chemistry-Physics Building, Lexington, KY 40506, USA
| | - Caitlin E Scott
- Department of Chemistry, University of Kentucky, 505 Rose St. Chemistry-Physics Building, Lexington, KY 40506, USA
| | - Thomas P McCoy
- Department of Family & Community Nursing, University of North Carolina - Greensboro, 1008 Administration Dr. McIver Building, Greensboro, NC 27412, USA
| | - Guo Yin
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, UK Medical Center, MN 150, Lexington, KY 40536, USA
| | - Florin Despa
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, UK Medical Center, MN 150, Lexington, KY 40536, USA
| | - Sanda Despa
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, UK Medical Center, MN 150, Lexington, KY 40536, USA.
| | - Peter M Kekenes-Huskey
- Department of Chemistry, University of Kentucky, 505 Rose St. Chemistry-Physics Building, Lexington, KY 40506, USA.
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Alternative Splicing of L-type Ca V1.2 Calcium Channels: Implications in Cardiovascular Diseases. Genes (Basel) 2017; 8:genes8120344. [PMID: 29186814 PMCID: PMC5748662 DOI: 10.3390/genes8120344] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 11/09/2017] [Accepted: 11/21/2017] [Indexed: 01/28/2023] Open
Abstract
L-type CaV1.2 calcium channels are the major pathway for Ca2+ influx to initiate the contraction of smooth and cardiac muscles. Alteration of CaV1.2 channel function has been implicated in multiple cardiovascular diseases, such as hypertension and cardiac hypertrophy. Alternative splicing is a post-transcriptional mechanism that expands CaV1.2 channel structures to modify function, pharmacological and biophysical property such as calcium/voltage-dependent inactivation (C/VDI), or to influence its post-translational modulation by interacting proteins such as Galectin-1. Alternative splicing has generated functionally diverse CaV1.2 isoforms that can be developmentally regulated in the heart, or under pathophysiological conditions such as in heart failure. More importantly, alternative splicing of certain exons of CaV1.2 has been reported to be regulated by splicing factors such as RNA-binding Fox-1 homolog 1/2 (Rbfox 1/2), polypyrimidine tract-binding protein (PTBP1) and RNA-binding motif protein 20 (RBM20). Understanding how CaV1.2 channel function is remodelled in disease will provide better information to guide the development of more targeted approaches to discover therapeutic agents for cardiovascular diseases.
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Zhang C, Chen B, Wang Y, Guo A, Tang Y, Khataei T, Shi Y, Kutschke WJ, Zimmerman K, Weiss RM, Liu J, Benson CJ, Hong J, Ma J, Song LS. MG53 is dispensable for T-tubule maturation but critical for maintaining T-tubule integrity following cardiac stress. J Mol Cell Cardiol 2017; 112:123-130. [PMID: 28822805 DOI: 10.1016/j.yjmcc.2017.08.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 08/13/2017] [Accepted: 08/14/2017] [Indexed: 01/28/2023]
Abstract
The cardiac transverse (T)-tubule membrane system is the safeguard for cardiac function and undergoes dramatic remodeling in response to cardiac stress. However, the mechanism by which cardiomyocytes repair damaged T-tubule network remains unclear. In the present study, we tested the hypothesis that MG53, a muscle-specific membrane repair protein, antagonizes T-tubule damage to protect against maladaptive remodeling and thereby loss of excitation-contraction coupling and cardiac function. Using MG53-knockout (MG53-KO) mice, we first established that deficiency of MG53 had no impact on maturation of the T-tubule network in developing hearts. Additionally, MG53 ablation did not influence T-tubule integrity in unstressed adult hearts as late as 10months of age. Following left ventricular pressure overload-induced cardiac stress, MG53 protein levels were increased by approximately three-fold in wild-type mice, indicating that pathological stress induces a significant upregulation of MG53. MG53-deficient mice had worsened T-tubule disruption and pronounced dysregulation of Ca2+ handling properties, including decreased Ca2+ transient amplitude and prolonged time to peak and decay. Moreover, MG53 deficiency exacerbated cardiac hypertrophy and dysfunction and decreased survival following cardiac stress. Our data suggest MG53 is not required for T-tubule development and maintenance in normal physiology. However, MG53 is essential to preserve T-tubule integrity and thereby Ca2+ handling properties and cardiac function under pathological cardiac stress.
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Affiliation(s)
- Caimei Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Biyi Chen
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Yihui Wang
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA; Shanghai First People's Hospital, Shanghai Jiaotong University, Shanghai 200080, China
| | - Ang Guo
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Yiqun Tang
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA; Department of Clinical Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Tahsin Khataei
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Yun Shi
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - William J Kutschke
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Kathy Zimmerman
- Department of Veterans Affairs Medical Center, Iowa City, IA 52242, USA
| | - Robert M Weiss
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | - Jie Liu
- Department of Pathophysiology, School of Medicine, Shenzhen University, Shenzhen 518060, China
| | - Christopher J Benson
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA; Department of Veterans Affairs Medical Center, Iowa City, IA 52242, USA
| | - Jiang Hong
- Shanghai First People's Hospital, Shanghai Jiaotong University, Shanghai 200080, China
| | - Jianjie Ma
- Department of Surgery, Ohio State University Medical Center, Columbus, OH 43212, USA
| | - Long-Sheng Song
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA; Department of Veterans Affairs Medical Center, Iowa City, IA 52242, USA.
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13
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Exclusion of alternative exon 33 of Ca V1.2 calcium channels in heart is proarrhythmogenic. Proc Natl Acad Sci U S A 2017; 114:E4288-E4295. [PMID: 28490495 DOI: 10.1073/pnas.1617205114] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Alternative splicing changes the CaV1.2 calcium channel electrophysiological property, but the in vivo significance of such altered channel function is lacking. Structure-function studies of heterologously expressed CaV1.2 channels could not recapitulate channel function in the native milieu of the cardiomyocyte. To address this gap in knowledge, we investigated the role of alternative exon 33 of the CaV1.2 calcium channel in heart function. Exclusion of exon 33 in CaV1.2 channels has been reported to shift the activation potential -10.4 mV to the hyperpolarized direction, and increased expression of CaV1.2Δ33 channels was observed in rat myocardial infarcted hearts. However, how a change in CaV1.2 channel electrophysiological property, due to alternative splicing, might affect cardiac function in vivo is unknown. To address these questions, we generated mCacna1c exon 33-/--null mice. These mice contained CaV1.2Δ33 channels with a gain-of-function that included conduction of larger currents that reflects a shift in voltage dependence and a modest increase in single-channel open probability. This altered channel property underscored the development of ventricular arrhythmia, which is reflected in significantly more deaths of exon 33-/- mice from β-adrenergic stimulation. In vivo telemetric recordings also confirmed increased frequencies in premature ventricular contractions, tachycardia, and lengthened QT interval. Taken together, the significant decrease or absence of exon 33-containing CaV1.2 channels is potentially proarrhythmic in the heart. Of clinical relevance, human ischemic and dilated cardiomyopathy hearts showed increased inclusion of exon 33. However, the possible role that inclusion of exon 33 in CaV1.2 channels may play in the pathogenesis of human heart failure remains unclear.
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Moreno C, Hermosilla T, Morales D, Encina M, Torres-Díaz L, Díaz P, Sarmiento D, Simon F, Varela D. Cavβ2 transcription start site variants modulate calcium handling in newborn rat cardiomyocytes. Pflugers Arch 2015; 467:2473-84. [PMID: 26265381 DOI: 10.1007/s00424-015-1723-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 07/17/2015] [Indexed: 12/21/2022]
Abstract
In the heart, the main pathway for calcium influx is mediated by L-type calcium channels, a multi-subunit complex composed of the pore-forming subunit CaV1.2 and the auxiliary subunits CaVα2δ1 and CaVβ2. To date, five distinct CaVβ2 transcriptional start site (TSS) variants (CaVβ2a-e) varying only in the composition and length of the N-terminal domain have been described, each of them granting distinct biophysical properties to the L-type current. However, the physiological role of these variants in Ca(2+) handling in the native tissue has not been explored. Our results show that four of these variants are present in neonatal rat cardiomyocytes. The contribution of those CaVβ2 TSS variants on endogenous L-type current and Ca(2+) handling was explored by adenoviral-mediated overexpression of each CaVβ2 variant in cultured newborn rat cardiomyocytes. As expected, all CaVβ2 TSS variants increased L-type current density and produced distinctive changes on L-type calcium channel (LTCC) current activation and inactivation kinetics. The characteristics of the induced calcium transients were dependent on the TSS variant overexpressed. Moreover, the amplitude of the calcium transients varied depending on the subunit involved, being higher in cardiomyocytes transduced with CaVβ2a and smaller in CaVβ2d. Interestingly, the contribution of Ca(2+) influx and Ca(2+) release on total calcium transients, as well as the sarcoplasmic calcium content, was found to be TSS-variant-dependent. Remarkably, determination of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) messenger RNA (mRNA) abundance and cell size change indicates that CaVβ2 TSS variants modulate the cardiomyocyte hypertrophic state. In summary, we demonstrate that expression of individual CaVβ2 TSS variants regulates calcium handling in cardiomyocytes and, consequently, has significant repercussion in the development of hypertrophy.
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Affiliation(s)
- Cristian Moreno
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Tamara Hermosilla
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Danna Morales
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Matías Encina
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Leandro Torres-Díaz
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Pablo Díaz
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Daniela Sarmiento
- Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Avenida Republica 239, Santiago, Chile
| | - Felipe Simon
- Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Avenida Republica 239, Santiago, Chile.,Millennium Institute on Immunology and Immunotherapy, Santiago, Chile
| | - Diego Varela
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile.
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15
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KCNE2 modulates cardiac L-type Ca2+ channel. J Mol Cell Cardiol 2014; 72:208-18. [DOI: 10.1016/j.yjmcc.2014.03.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 03/05/2014] [Accepted: 03/18/2014] [Indexed: 11/19/2022]
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Viola HM, Jordan MC, Roos KP, Hool LC. Decreased myocardial injury and improved contractility after administration of a peptide derived against the alpha-interacting domain of the L-type calcium channel. J Am Heart Assoc 2014; 3:e000961. [PMID: 24958783 PMCID: PMC4309103 DOI: 10.1161/jaha.114.000961] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Background Myocardial infarction remains the leading cause of morbidity and mortality associated with coronary artery disease. The L‐type calcium channel (ICa‐L) is critical to excitation and contraction. Activation of the channel also alters mitochondrial function. Here, we investigated whether application of a alpha‐interacting domain/transactivator of transcription (AID‐TAT) peptide, which immobilizes the auxiliary β2 subunit of the channel and decreases metabolic demand, could alter mitochondrial function and myocardial injury. Methods and Results Treatment with AID‐TAT peptide decreased ischemia‐reperfusion injury in guinea‐pig hearts ex vivo (n=11) and in rats in vivo (n=9) assessed with uptake of nitroblue tetrazolium, release of creatine kinase, and lactate dehydrogenase. Contractility (assessed with catheterization of the left ventricle) was improved after application of AID‐TAT peptide in hearts ex vivo (n=6) and in vivo (n=8) up to 12 weeks before sacrifice. In search of the mechanism for the effect, we found that intracellular calcium ([Ca2+]i, Fura‐2), superoxide production (dihydroethidium fluorescence), mitochondrial membrane potential (Ψm, JC‐1 fluorescence), reduced nicotinamide adenine dinucleotide production, and flavoprotein oxidation (autofluorescence) are decreased after application of AID‐TAT peptide. Conclusions Application of AID‐TAT peptide significantly decreased infarct size and supported contractility up to 12 weeks postcoronary artery occlusion as a result of a decrease in metabolic demand during reperfusion.
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Affiliation(s)
- Helena M Viola
- School of Anatomy, Physiology and Human Biology, The University of Western Australia, Crawley, WA, Australia (H.M.V., L.C.H.)
| | - Maria C Jordan
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA (M.C.J., K.P.R.)
| | - Kenneth P Roos
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA (M.C.J., K.P.R.)
| | - Livia C Hool
- School of Anatomy, Physiology and Human Biology, The University of Western Australia, Crawley, WA, Australia (H.M.V., L.C.H.)
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Wu CYC, Chen B, Jiang YP, Jia Z, Martin DW, Liu S, Entcheva E, Song LS, Lin RZ. Calpain-dependent cleavage of junctophilin-2 and T-tubule remodeling in a mouse model of reversible heart failure. J Am Heart Assoc 2014; 3:e000527. [PMID: 24958777 PMCID: PMC4309042 DOI: 10.1161/jaha.113.000527] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Background A highly organized transverse tubule (T‐tubule) network is necessary for efficient Ca2+‐induced Ca2+ release and synchronized contraction of ventricular myocytes. Increasing evidence suggests that T‐tubule remodeling due to junctophilin‐2 (JP‐2) downregulation plays a critical role in the progression of heart failure. However, the mechanisms underlying JP‐2 dysregulation remain incompletely understood. Methods and Results A mouse model of reversible heart failure that is driven by conditional activation of the heterotrimeric G protein Gαq in cardiac myocytes was used in this study. Mice with activated Gαq exhibited disruption of the T‐tubule network and defects in Ca2+ handling that culminated in heart failure compared with wild‐type mice. Activation of Gαq/phospholipase Cβ signaling increased the activity of the Ca2+‐dependent protease calpain, leading to the proteolytic cleavage of JP‐2. A novel calpain cleavage fragment of JP‐2 is detected only in hearts with constitutive Gαq signaling to phospholipase Cβ. Termination of the Gαq signal was followed by normalization of the JP‐2 protein level, repair of the T‐tubule network, improvements in Ca2+ handling, and reversal of heart failure. Treatment of mice with a calpain inhibitor prevented Gαq‐dependent JP‐2 cleavage, T‐tubule disruption, and the development of heart failure. Conclusions Disruption of the T‐tubule network in heart failure is a reversible process. Gαq‐dependent activation of calpain and subsequent proteolysis of JP‐2 appear to be the molecular mechanism that leads to T‐tubule remodeling, Ca2+ handling dysfunction, and progression to heart failure in this mouse model.
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Affiliation(s)
- Chia-Yen C Wu
- Department of Physiology and Biophysics and Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY (C.Y.C.W., Y.P.J., S.L., E.E., R.Z.L.)
| | - Biyi Chen
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA (B.C., L.S.S.)
| | - Ya-Ping Jiang
- Department of Physiology and Biophysics and Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY (C.Y.C.W., Y.P.J., S.L., E.E., R.Z.L.)
| | - Zhiheng Jia
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY (Z.J., E.E.)
| | - Dwight W Martin
- Department of Medicine and Proteomics Center, Stony Brook University, Stony Brook, NY (D.W.M.)
| | - Shengnan Liu
- Department of Physiology and Biophysics and Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY (C.Y.C.W., Y.P.J., S.L., E.E., R.Z.L.)
| | - Emilia Entcheva
- Department of Physiology and Biophysics and Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY (C.Y.C.W., Y.P.J., S.L., E.E., R.Z.L.) Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY (Z.J., E.E.)
| | - Long-Sheng Song
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA (B.C., L.S.S.)
| | - Richard Z Lin
- Department of Physiology and Biophysics and Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY (C.Y.C.W., Y.P.J., S.L., E.E., R.Z.L.) Department of Veterans Affairs Medical Center, Northport, NY (R.Z.L.)
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Abstract
PDZ (PSD-95/Disc large/Zonula occludens-1) protein interaction domains bind to cytoplasmic protein C-termini of transmembrane proteins. In order to identify new interaction partners of the voltage-gated L-type Ca2+ channel 1.2 and the plasma membrane Ca2+ ATPase 4b (PMCA4b), we used PDZ domain arrays probing for 124 PDZ domains. We confirmed this by GST pull-downs and immunoprecipitations. In PDZ arrays, strongest interactions with 1.2 and PMCA4b were found for the PDZ domains of SAP-102, MAST-205, MAGI-1, MAGI-2, MAGI-3, and ZO-1. We observed binding of the 1.2 C-terminus to PDZ domains of NHERF1/2, Mint-2, and CASK. PMCA4b was observed to interact with Mint-2 and its known interactions with Chapsyn-110 and CASK were confirmed. Furthermore, we validated interaction of 1.2 and PMCA4b with NHERF1/2, CASK, MAST-205 and MAGI-3 via immunoprecipitation. We also verified the interaction of 1.2 and nNOS and hypothesized that nNOS overexpression might reduce Ca2+ influx through 1.2. To address this, we measured Ca2+ currents in HEK 293 cells co-expressing 1.2 and nNOS and observed reduced voltage-dependent 1.2 activation. Taken together, we conclude that 1.2 and PMCA4b bind promiscuously to various PDZ domains, and that our data provides the basis for further investigation of the physiological consequences of these interactions.
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Viola HM, Davies SMK, Filipovska A, Hool LC. L-type Ca(2+) channel contributes to alterations in mitochondrial calcium handling in the mdx ventricular myocyte. Am J Physiol Heart Circ Physiol 2013; 304:H767-75. [PMID: 23335798 DOI: 10.1152/ajpheart.00700.2012] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The L-type Ca(2+) channel is the main route for calcium entry into cardiac myocytes, and it is essential for contraction. Alterations in whole cell L-type Ca(2+) channel current and Ca(2+) homeostasis have been implicated in the development of cardiomyopathies. Cytoskeletal proteins can influence whole cell L-type Ca(2+) current and mitochondrial function. Duchenne muscular dystrophy is a fatal X-linked disease that leads to progressive muscle weakness due to the absence of cytoskeletal protein dystrophin. This includes dilated cardiomyopathy, but the mechanisms are not well understood. We sought to identify the effect of alterations in whole cell L-type Ca(2+) channel current on mitochondrial function in the murine model of Duchenne muscular dystrophy (mdx). Activation of the L-type Ca(2+) channel with the dihydropyridine agonist BayK(-) caused a significantly larger increase in cytosolic Ca(2+) in mdx vs. wild-type (wt) ventricular myocytes. Consistent with elevated cytosolic Ca(2+), resting mitochondrial Ca(2+), NADH, and mitochondrial superoxide were significantly greater in mdx vs. wt myocytes. Activation of the channel with BayK(-) caused a further increase in mitochondrial Ca(2+), NADH, and superoxide in mdx myocytes. The ratios of the increases were similar to the ratios recorded in wt myocytes. In mitochondria isolated from 8-wk-old mdx hearts, respiration and mitochondrial electron transport chain complex activity were similar to mitochondria isolated from wt hearts. We conclude that mitochondria function at a higher level of resting calcium in the intact mdx myocyte and activation of the L-type Ca(2+) channel contributes to alterations in calcium handling by the mitochondria. This perturbation may contribute to the development of cardiomyopathy.
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Affiliation(s)
- Helena M Viola
- School of Anatomy, Physiology and Human Biology, University of Western Australia, Crawley, Western Australia, Australia
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Chang W, Lim S, Song BW, Lee CY, Park MS, Chung YA, Yoon C, Lee SY, Ham O, Park JH, Choi E, Maeng LS, Hwang KC. Phorbol myristate acetate differentiates human adipose-derived mesenchymal stem cells into functional cardiogenic cells. Biochem Biophys Res Commun 2012; 424:740-6. [PMID: 22809507 DOI: 10.1016/j.bbrc.2012.07.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 07/09/2012] [Indexed: 01/20/2023]
Abstract
To achieve effective regeneration of injured myocardium, it is important to find physiological way of improving the cardiogenic differentiation of stem cells. Previous studies demonstrated that cardiomyocytes from bone marrow-derived mesenchymal stem cells (BMSCs) activated with phorbolmyristate acetate (PMA), a protein kinase C (PKC) activator, restore electromechanical function in infarcted rat hearts. In this study, we investigated the effect of PMA on cardiogenic differentiation of adipose-derived MSCs (ASCs) for clinical applications. To confirm the effect of PMA, ASCs treated with 1μM PMA were grown for nine days. The expression of cardiac-specific markers (cardiac troponin T, myosin light chain, myosin heavy chain) in PMA-treated MSCs was demonstrated by immunocytochemistry. Alhough few α(1A) receptors exist in ASCs, α(1)-adrenergic receptor subtypes were preferentially expressed in PMA-treated ASCs. Moreover, expression of the β-adrenergic and muscarinic receptors increased in PMA-treated ASCs compared to normal cells. The mRNA levels of Ca(2+)-related factors (SERCA 2a; sarcoplasmic reticulum Ca(2+)-ATPase, LTCC; L-type Ca(2+) channel) in treated ASCs were similar to the levels in cardiomyocytes. Following the transplantation of chemically activated cardiogenic ASCs into infarcted myocardium, histological analysis showed that infarct size, interstitial fibrosis, and apoptotic index were markedly decreased and cardiac function was restored. In conclusion, PMA might induce the cardiogenic differentiation of human ASCs as well as BMSCs. This result suggests successful use of human ASCs in cardiac regeneration therapy.
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Affiliation(s)
- Woochul Chang
- Institute of Catholic Integrative Medicine, Incheon St. Mary's Hospital, The Catholic University of Korea College of Medicine, Incheon 403-720, Republic of Korea
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Abstract
A wide range of Ca2+ signalling systems deliver the spatial and temporal Ca2+ signals necessary to control the specific functions of different cell types. Release of Ca2+ by InsP3 (inositol 1,4,5-trisphosphate) plays a central role in many of these signalling systems. Ongoing transcriptional processes maintain the integrity and stability of these cell-specific signalling systems. However, these homoeostatic systems are highly plastic and can undergo a process of phenotypic remodelling, resulting in the Ca2+ signals being set either too high or too low. Such subtle dysregulation of Ca2+ signals have been linked to some of the major diseases in humans such as cardiac disease, schizophrenia, bipolar disorder and Alzheimer's disease.
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Chen B, Guo A, Gao Z, Wei S, Xie YP, Chen SRW, Anderson ME, Song LS. In situ confocal imaging in intact heart reveals stress-induced Ca(2+) release variability in a murine catecholaminergic polymorphic ventricular tachycardia model of type 2 ryanodine receptor(R4496C+/-) mutation. Circ Arrhythm Electrophysiol 2012; 5:841-9. [PMID: 22722659 DOI: 10.1161/circep.111.969733] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
BACKGROUND Catecholaminergic polymorphic ventricular tachycardia is directly linked to mutations in proteins (eg, type 2 ryanodine receptor [RyR2](R4496C)) responsible for intracellular Ca(2+) homeostasis in the heart. However, the mechanism of Ca(2+) release dysfunction underlying catecholaminergic polymorphic ventricular tachycardia has only been investigated in isolated cells but not in the in situ undisrupted myocardium. METHODS AND RESULTS We investigated in situ myocyte Ca(2+) dynamics in intact Langendorff-perfused hearts (ex vivo) from wild-type and RyR2(R4496C+/-) mice using laser scanning confocal microscopy. We found that myocytes from both wild-type and RyR2(R4496C+/-) hearts displayed uniform, synchronized Ca(2+) transients. Ca(2+) transients from beat to beat were comparable in amplitude with identical activation and decay kinetics in wild-type and RyR2(R4496C+/-) hearts, suggesting that excitation-contraction coupling between the sarcolemmal Ca(2+) channels and mutated RyR2(R4496C+/-) channels remains intact under baseline resting conditions. On adrenergic stimulation, RyR2(R4496C+/-) hearts exhibited a high degree of Ca(2+) release variability. The varied pattern of Ca(2+) release was absent in single isolated myocytes, independent of cell cycle length, synchronized among neighboring myocytes, and correlated with catecholaminergic polymorphic ventricular tachycardia. A similar pattern of action potential variability, which was synchronized among neighboring myocytes, was also revealed under adrenergic stress in intact hearts but not in isolated myocytes. CONCLUSIONS Our studies using an in situ confocal imaging approach suggest that mutated RyR2s are functionally normal at rest but display a high degree of Ca(2+) release variability on intense adrenergic stimulation. Ca(2+) release variability is a Ca(2+) release abnormality, resulting from electric defects rather than the failure of the Ca(2+) release response to action potentials in mutated ventricular myocytes. Our data provide important insights into Ca(2+) release and electric dysfunction in an established model of catecholaminergic polymorphic ventricular tachycardia.
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Affiliation(s)
- Biyi Chen
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
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Tang H, Viola HM, Filipovska A, Hool LC. Ca(v)1.2 calcium channel is glutathionylated during oxidative stress in guinea pig and ischemic human heart. Free Radic Biol Med 2011; 51:1501-11. [PMID: 21810465 DOI: 10.1016/j.freeradbiomed.2011.07.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 06/21/2011] [Accepted: 07/10/2011] [Indexed: 11/16/2022]
Abstract
Glutathionylation as a posttranslational modification of proteins is becoming increasingly recognized, but its role in many diseases has not been demonstrated. Oxidative stress and alterations in calcium homeostasis are associated with the development of cardiac hypertrophy. Because the cardiac L-type Ca(2+) channel can be persistently activated after exposure to H(2)O(2), the aim of this study was to determine whether alterations in channel function were associated with glutathionylation of the α(1C) subunit (Ca(v)1.2) channel protein. Immunoblot analysis indicated that Ca(v)1.2 protein is significantly glutathionylated after exposure to H(2)O(2) and glutathione in vitro and after ischemia-reperfusion injury. L-type Ca(2+) channel macroscopic current and intracellular calcium were significantly increased in myocytes after exposure to oxidized glutathione and reversed by glutaredoxin. The increase in current correlated with an increase in open probability of the channel assessed as changes in single-channel activity after exposing the human long N-terminal Ca(v)1.2 to H(2)O(2) or oxidized glutathione. We also demonstrate that the Ca(v)1.2 channel is significantly glutathionylated in ischemic human heart. We conclude that oxidative stress is associated with an increase in glutathionylation of the Ca(v)1.2 channel protein. We suggest that the associated constitutive activity contributes to the development of pathology in ischemic heart disease.
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Affiliation(s)
- Helen Tang
- School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, WA 6009, Australia
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24
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Völkers M, Weidenhammer C, Herzog N, Qiu G, Spaich K, Wegner FV, Peppel K, Müller OJ, Schinkel S, Rabinowitz JE, Hippe HJ, Brinks H, Katus HA, Koch WJ, Eckhart AD, Friedrich O, Most P. The inotropic peptide βARKct improves βAR responsiveness in normal and failing cardiomyocytes through G(βγ)-mediated L-type calcium current disinhibition. Circ Res 2011; 108:27-39. [PMID: 21106943 PMCID: PMC4013502 DOI: 10.1161/circresaha.110.225201] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Accepted: 11/15/2010] [Indexed: 12/20/2022]
Abstract
RATIONALE The G(βγ)-sequestering peptide β-adrenergic receptor kinase (βARK)ct derived from the G-protein-coupled receptor kinase (GRK)2 carboxyl terminus has emerged as a promising target for gene-based heart failure therapy. Enhanced downstream cAMP signaling has been proposed as the underlying mechanism for increased β-adrenergic receptor (βAR) responsiveness. However, molecular targets mediating improved cardiac contractile performance by βARKct and its impact on G(βγ)-mediated signaling have yet to be fully elucidated. OBJECTIVE We sought to identify G(βγ)-regulated targets and signaling mechanisms conveying βARKct-mediated enhanced βAR responsiveness in normal (NC) and failing (FC) adult rat ventricular cardiomyocytes. METHODS AND RESULTS Assessing viral-based βARKct gene delivery with electrophysiological techniques, analysis of contractile performance, subcellular Ca²(+) handling, and site-specific protein phosphorylation, we demonstrate that βARKct enhances the cardiac L-type Ca²(+) channel (LCC) current (I(Ca)) both in NCs and FCs on βAR stimulation. Mechanistically, βARKct augments I(Ca) by preventing enhanced inhibitory interaction between the α1-LCC subunit (Cav1.2α) and liberated G(βγ) subunits downstream of activated βARs. Despite improved βAR contractile responsiveness, βARKct neither increased nor restored cAMP-dependent protein kinase (PKA) and calmodulin-dependent kinase II signaling including unchanged protein kinase (PK)Cε, extracellular signal-regulated kinase (ERK)1/2, Akt, ERK5, and p38 activation both in NCs and FCs. Accordingly, although βARKct significantly increases I(Ca) and Ca²(+) transients, being susceptible to suppression by recombinant G(βγ) protein and use-dependent LCC blocker, βARKct-expressing cardiomyocytes exhibit equal basal and βAR-stimulated sarcoplasmic reticulum Ca²(+) load, spontaneous diastolic Ca²(+) leakage, and survival rates and were less susceptible to field-stimulated Ca²(+) waves compared with controls. CONCLUSION Our study identifies a G(βγ)-dependent signaling pathway attenuating cardiomyocyte I(Ca) on βAR as molecular target for the G(βγ)-sequestering peptide βARKct. Targeted interruption of this inhibitory signaling pathway by βARKct confers improved βAR contractile responsiveness through increased I(Ca) without enhancing regular or restoring abnormal cAMP-signaling. βARKct-mediated improvement of I(Ca) rendered cardiomyocytes neither susceptible to βAR-induced damage nor arrhythmogenic sarcoplasmic reticulum Ca²(+) leakage.
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Affiliation(s)
- Mirko Völkers
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Christian Weidenhammer
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Nicole Herzog
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Gang Qiu
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Kristin Spaich
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Frederic V Wegner
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Karsten Peppel
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Oliver J Müller
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Stefanie Schinkel
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Joseph E Rabinowitz
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Hans-Jorg Hippe
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Henriette Brinks
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Hugo A Katus
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Walter J Koch
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Andrea D Eckhart
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Oliver Friedrich
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
| | - Patrick Most
- Center for Molecular and Translational Cardiology (M.V, C.W., N.H., K.S., P.M.), Department of Internal Medicine III (O.J.M, S.S., H.J.H., H.A.K.), Division of Cardiology, INF 350, University of Heidelberg, 69120 Heidelberg, Germany; Institute of Physiology and Pathophysiology (F.W., O.F.) Medical Biophysics, INF 326, University of Heidelberg, 69120 Heidelberg, Germany; George Zallie & Family Laboratory for Cardiovascular Gene Therapy (J.E.R., H.B., W.J.K.), Eugene Feiner Laboratory for Vascular Biology and Thrombosis (A.D.E.), Laboratory for Cardiac Stem Cell and Gene Therapy (G.Q., K.P., P.M.), Center for Translational Medicine, Thomas Jefferson University, 19107 Philadelphia, PA, USA
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25
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Abstract
Calcium ions play fundamental roles in many cellular processes in virtually all type of cells. The use of Ca(2+) sensitive fluorescent indicators has proven to be an indispensable tool for studying the spatio-temporal dynamics of intracellular calcium ([Ca(2+)](i)). With the aid of laser scanning confocal microscopy and new generation of Ca(2+) indicators, highly localized, short-lived Ca(2+) signals, namely Ca(2+) sparks, were revealed as elementary Ca(2+) release events during excitation-contraction coupling in cardiomyocytes. Since the discovery of Ca(2+) sparks in 1993, the demonstration of dynamic Ca(2+) micro-domains in living cardiomyocytes has revolutionized our understanding of Ca(2+)-mediated signal transduction in normal and diseased hearts. In this chapter, we have described a commonly used method for recording local and global Ca(2+) signals in cardiomyocytes using the fluorescent indicator fluo-4 acetoxymethyl (AM) and laser scanning confocal microscopy.
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Affiliation(s)
- Silvia Guatimosim
- Department of Physiology and Biophysics, ICB, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
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Shah AP, Siedlecka U, Gandhi A, Navaratnarajah M, Al-Saud SA, Yacoub MH, Terracciano CM. Genetic background affects function and intracellular calcium regulation of mouse hearts. Cardiovasc Res 2010; 87:683-93. [PMID: 20413651 DOI: 10.1093/cvr/cvq111] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS The genetic background is currently under close scrutiny when determining cardiovascular disease progression and response to therapy. However, this factor is rarely considered in physiological studies, where it could influence the normal behaviour and adaptive responses of the heart. We aim to test the hypothesis that genetic strain variability is associated with differences in excitation-contraction coupling mechanisms, in particular those involved in cytoplasmic Ca(2+) regulation, and that they are concomitant to differences in whole-heart function and cell morphology. METHODS AND RESULTS We studied 8- to 10-week-old male C57BL/6, BALB/C, FVB, and SV129 mice. Echocardiography and radiotelemetry were used to assess cardiac function in vivo. FVB mice had increased left ventricular ejection fraction and fractional shortening with significantly faster heart rate (HR) and lack of diurnal variation of HR. Confocal microscopy, sarcomere length tracking, and epifluorescence were used to investigate cell volume, t-tubule density, contractility, and Ca(2+) handling in isolated ventricular myocytes. Sarcomere relaxation and time-to-peak of the Ca(2+) transient were prolonged in BALB/C myocytes, with more frequent Ca(2+) sparks and significantly higher sarcoplasmic reticulum (SR) Ca(2+) leak. There were no strain differences in the contribution of different Ca(2+) extrusion mechanisms. SV129 had reduced SR Ca(2+) leak with elevated SR Ca(2+) content and smaller cell volume and t-tubule density compared with myocytes from other strains. CONCLUSION These results demonstrate that a different genetic background is associated with physiological differences in cardiac function in vivo and differences in morphology, contractility, and Ca(2+) handling at the cellular level.
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Affiliation(s)
- Adarsh P Shah
- Laboratory of Cell Electrophysiology, Heart Science Centre, National Heart and Lung Institute, Imperial College London, Harefield Hospital, Harefield, Middlesex UB9 6JH, UK
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Anti-arrhythmic effects of cyclopiazonic acid in Langendorff-perfused murine hearts. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2009; 98:281-8. [PMID: 19351518 DOI: 10.1016/j.pbiomolbio.2009.01.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We investigated the effects of reducing sarcoplasmic reticular (SR) Ca(2+) stores using the Ca(2+)-ATPase inhibitor cyclopiazonic acid (CPA) in Langendorff-perfused mouse hearts exposed to different pro-arrhythmic agents all known to produce Ca(2+)-mediated arrhythmogenesis. CPA (100 and 150 nM) produced progressive (beginning over approximately 1 min) and significant (P<0.0001) reductions in peak amplitudes of Ca(2+) transients evoked by regular stimulation in isolated Fluo-3 loaded myocytes from F/F(0)=3.2+/-0.16 (n=12 cells) to 1.62+/-0.012 (n=6 cells) and 1.53+/-0.06 (n=12 cells), respectively, consistent with previous reports describing reductions of store Ca(2+) in other cell systems. The corresponding effects of CPA were then examined in intact hearts exposed to isoproterenol (100 nM), elevated extracellular [Ca(2+)] (5mM) and caffeine (1mM). All three agents produced ventricular tachycardia either when added alone or simultaneously with CPA during programmed electrical stimulation. However, arrhythmogenicity was not observed when such agents were added approximately 10 min after introduction of CPA. CPA thus antagonized this Ca(2+)-mediated arrhythmogenesis but only under circumstances of SR Ca(2+) depletion. These alterations in arrhythmogenic tendency took place despite an absence of alterations in electrogram and monophasic action potential characteristics. This was in sharp contrast to previous observations in murine, DeltaKPQ-Scn5a (LQT3) and KCNE1(-/-) (LQT5), systems where re-entry has been implicated in arrhythmogenesis.
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Thiel WH, Chen B, Hund TJ, Koval OM, Purohit A, Song LS, Mohler PJ, Anderson ME. Proarrhythmic defects in Timothy syndrome require calmodulin kinase II. Circulation 2008; 118:2225-34. [PMID: 19001023 DOI: 10.1161/circulationaha.108.788067] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Timothy syndrome (TS) is a disease of excessive cellular Ca(2+) entry and life-threatening arrhythmias caused by a mutation in the primary cardiac L-type Ca(2+) channel (Ca(V)1.2). The TS mutation causes loss of normal voltage-dependent inactivation of Ca(V)1.2 current (I(Ca)). During cellular Ca(2+) overload, the calmodulin-dependent protein kinase II (CaMKII) causes arrhythmias. We hypothesized that CaMKII is a part of the proarrhythmic mechanism in TS. METHODS AND RESULTS We developed an adult rat ventricular myocyte model of TS (G406R) by lentivirus-mediated transfer of wild-type and TS Ca(V)1.2. The exogenous Ca(V)1.2 contained a mutation (T1066Y) conferring dihydropyridine resistance, so we could silence endogenous Ca(V)1.2 with nifedipine and maintain peak I(Ca) at control levels in infected cells. TS Ca(V)1.2-infected ventricular myocytes exhibited the signature voltage-dependent inactivation loss under Ca(2+) buffering conditions, not permissive for CaMKII activation. In physiological Ca(2+) solutions, TS Ca(V)1.2-expressing ventricular myocytes exhibited increased CaMKII activity and a proarrhythmic phenotype that included action potential prolongation, increased I(Ca) facilitation, and afterdepolarizations. Intracellular dialysis of a CaMKII inhibitory peptide, but not a control peptide, reversed increases in I(Ca) facilitation, normalized the action potential, and prevented afterdepolarizations. We developed a revised mathematical model that accounts for CaMKII-dependent and CaMKII-independent effects of the TS mutation. CONCLUSIONS In TS, the loss of voltage-dependent inactivation is an upstream initiating event for arrhythmia phenotypes that are ultimately dependent on CaMKII activation.
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Steady-state coupling of plasma membrane calcium entry to extrusion revealed by novel L-type calcium channel block. Cell Calcium 2008; 44:353-62. [DOI: 10.1016/j.ceca.2008.01.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Shemarova IV, Kuznetsov SV, Demina IN, Nesterov VP. Peculiarities of Ca2+-regulation of functional activity of myocardium of frog Rana temporaria. J EVOL BIOCHEM PHYS+ 2008. [DOI: 10.1134/s0022093008010064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Hullin R, Matthes J, von Vietinghoff S, Bodi I, Rubio M, D'Souza K, Friedrich Khan I, Rottländer D, Hoppe UC, Mohacsi P, Schmitteckert E, Gilsbach R, Bünemann M, Hein L, Schwartz A, Herzig S. Increased expression of the auxiliary beta(2)-subunit of ventricular L-type Ca(2)+ channels leads to single-channel activity characteristic of heart failure. PLoS One 2007; 2:e292. [PMID: 17356701 PMCID: PMC1808423 DOI: 10.1371/journal.pone.0000292] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2006] [Accepted: 02/19/2007] [Indexed: 11/25/2022] Open
Abstract
Background Increased activity of single ventricular L-type Ca2+-channels (L-VDCC) is a hallmark in human heart failure. Recent findings suggest differential modulation by several auxiliary β-subunits as a possible explanation. Methods and Results By molecular and functional analyses of human and murine ventricles, we find that enhanced L-VDCC activity is accompanied by altered expression pattern of auxiliary L-VDCC β-subunit gene products. In HEK293-cells we show differential modulation of single L-VDCC activity by coexpression of several human cardiac β-subunits: Unlike β1 or β3 isoforms, β2a and β2b induce a high-activity channel behavior typical of failing myocytes. In accordance, β2-subunit mRNA and protein are up-regulated in failing human myocardium. In a model of heart failure we find that mice overexpressing the human cardiac CaV1.2 also reveal increased single-channel activity and sarcolemmal β2 expression when entering into the maladaptive stage of heart failure. Interestingly, these animals, when still young and non-failing (“Adaptive Phase”), reveal the opposite phenotype, viz: reduced single-channel activity accompanied by lowered β2 expression. Additional evidence for the cause-effect relationship between β2-subunit expression and single L-VDCC activity is provided by newly engineered, double-transgenic mice bearing both constitutive CaV1.2 and inducible β2 cardiac overexpression. Here in non-failing hearts induction of β2-subunit overexpression mimicked the increase of single L-VDCC activity observed in murine and human chronic heart failure. Conclusions Our study presents evidence of the pathobiochemical relevance of β2-subunits for the electrophysiological phenotype of cardiac L-VDCC and thus provides an explanation for the single L-VDCC gating observed in human and murine heart failure.
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Affiliation(s)
- Roger Hullin
- Department of Cardiology, Swiss Heart Center Bern, University Hospital, Bern, Switzerland
- * To whom correspondence should be addressed. E-mail: (RH); (SH); (AS)
| | - Jan Matthes
- Department of Pharmacology, University of Cologne, Cologne, Germany
| | - Sibylle von Vietinghoff
- Department of Pharmacology, University of Wuerzburg, Wuerzburg, Germany
- Franz Volhard Clinic, Nephrology/Hypertension Section, Medical Faculty of the Charité, Berlin, Germany
| | - Ilona Bodi
- University of Cincinnati College of Medicine, Institute of Molecular Pharmacology and Biophysics, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Marta Rubio
- University of Cincinnati College of Medicine, Institute of Molecular Pharmacology and Biophysics, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Karen D'Souza
- University of Cincinnati College of Medicine, Institute of Molecular Pharmacology and Biophysics, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Ismail Friedrich Khan
- Department of Pharmacology, University of Cologne, Cologne, Germany
- Center of Molecular Medicine, University of Cologne, Cologne, Germany
| | | | - Uta C. Hoppe
- Center of Molecular Medicine, University of Cologne, Cologne, Germany
| | - Paul Mohacsi
- Department of Cardiology, Swiss Heart Center Bern, University Hospital, Bern, Switzerland
| | - Eva Schmitteckert
- Department of Pharmacology, University of Wuerzburg, Wuerzburg, Germany
| | - Ralf Gilsbach
- Department of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany
| | - Moritz Bünemann
- Department of Pharmacology, University of Wuerzburg, Wuerzburg, Germany
| | - Lutz Hein
- Department of Pharmacology, University of Wuerzburg, Wuerzburg, Germany
- Department of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany
| | - Arnold Schwartz
- University of Cincinnati College of Medicine, Institute of Molecular Pharmacology and Biophysics, University of Cincinnati, Cincinnati, Ohio, United States of America
- * To whom correspondence should be addressed. E-mail: (RH); (SH); (AS)
| | - Stefan Herzig
- Department of Pharmacology, University of Cologne, Cologne, Germany
- Center of Molecular Medicine, University of Cologne, Cologne, Germany
- * To whom correspondence should be addressed. E-mail: (RH); (SH); (AS)
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Tappia PS, Dent MR, Aroutiounova N, Babick AP, Weiler H. Gender differences in the modulation of cardiac gene expression by dietary conjugated linoleic acid isomersThis paper is one of a selection of papers published in this Special Issue, entitled The Cellular and Molecular Basis of Cardiovascular Dysfunction, Dhalla 70th Birthday Tribute. Can J Physiol Pharmacol 2007; 85:465-75. [PMID: 17612656 DOI: 10.1139/y06-104] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In an earlier study, we showed that dietary conjugated linoleic acid (CLA) isomers can exert differential effects on heart function in male and female rats, but the underlying mechanisms for these actions are not known. Cardiomyocyte Ca2+ cycling is a key event in normal cardiac contractile function and defects in Ca2+ cycling are associated with cardiac dysfunction and heart disease. We therefore hypothesized that abnormalities in the sarcolemmal (SL) and sarcoplasmic reticulum (SR)-mediated regulation of intracellular Ca2+ contribute to altered cardiac contractile function of male and female rats owing to dietary CLA isomers. Healthy male and female Sprague–Dawley rats were fed different CLA isomers, (cis-9, trans-11 (c9,t11) and trans-10, cis-12 (t10,c12)) individually and in combination (50:50 mix as triglyceride or fatty acids) from 4 to 20 weeks of age. We determined the mRNA levels of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) 2a, ryanodine receptor, phospholamban, calsequestrin, Na+–Ca2+-exchanger (NCX), and L-type Ca2+ channel in the left ventricle (LV) by RT-PCR. The SR function was assessed by measurement of Ca2+-uptake and -release. Significant gender differences were seen in the LV NCX, L-type Ca2+ channel, and ryanodine receptor mRNA expression levels in control male and female rats. Dietary CLA isomers in the various forms induced changes in the mRNA levels of SERCA 2a, NCX, and L-type Ca2+ channel in the LV of both male and female hearts. Whereas protein contents of the Ca2+ cycling proteins were altered, changes in SR Ca2+-uptake and -release were also detected in both male and female rats in response to dietary CLA. The results of this study demonstrate that long-term dietary supplementation can modulate cardiac gene expression and SR function in a gender-related manner and may, in part, contribute to altered cardiac contractility.
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Affiliation(s)
- Paramjit S Tappia
- Institute of Cardiovascular Sciences, St. Boniface Hospital Research Centre and Department of Human Nutritional Sciences, Faculties of Human Ecology and Medicine, University of Manitoba, 351 Tache Avenue, Winnipeg, MB R2H 2A6, Canada.
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Gaburjakova J, Gaburjakova M. Comparison of the effects exerted by luminal Ca2+ on the sensitivity of the cardiac ryanodine receptor to caffeine and cytosolic Ca2+. J Membr Biol 2007; 212:17-28. [PMID: 17206514 DOI: 10.1007/s00232-006-7018-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2005] [Revised: 08/07/2006] [Indexed: 10/23/2022]
Abstract
Ca(2+) released from the sarcoplasmic reticulum (SR) via ryanodine receptor type 2 (RYR2) is the key determinant of cardiac contractility. Although activity of RYR2 channels is primary controlled by Ca(2+) entry through the plasma membrane, there is growing evidence that Ca(2+) in the lumen of the SR can also be effectively involved in the regulation of RYR2 channel function. In the present study, we investigated the effect of luminal Ca(2+) on the response of RYR2 channels reconstituted into a planar lipid membrane to caffeine and Ca(2+) added to the cytosolic side of the channel. We performed two sets of experiments when the channel was exposed to either luminal Ba(2+) or Ca(2+). The given ion served also as a charge carrier. Luminal Ca(2+) effectively shifted the EC(50) for caffeine sensitivity to a lower concentration but did not modify the response of RYR2 channels to cytosolic Ca(2+). Importantly, luminal Ca(2+) exerted an effect on channel gating kinetics. Both the open and closed dwell times were considerably prolonged over the whole range (response to caffeine) or the partial range (response to cytosolic Ca(2+)) of open probability. Our results provide strong evidence that an alteration of the gating kinetics is the result of the interaction of luminal Ca(2+) with the luminally located Ca(2+) regulatory sites on the RYR2 channel complex.
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Affiliation(s)
- Jana Gaburjakova
- Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Vlarska 5, 833 34, Bratislava, Slovak Republic
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34
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Moosmang S, Lenhardt P, Haider N, Hofmann F, Wegener JW. Mouse models to study L-type calcium channel function. Pharmacol Ther 2006; 106:347-55. [PMID: 15922017 DOI: 10.1016/j.pharmthera.2004.12.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/16/2004] [Indexed: 10/25/2022]
Abstract
Calcium influx through voltage gated L-type Ca2+ channels has evolved as one of the most widely used transmembrane signalling mechanisms in eukaryotic organisms. Although pharmacological inhibitors of L-type Ca2+ channels have an important place in medical therapy, the full therapeutic potential of the 4 L-type Ca2+ channel subtypes has not been explored yet. To dissect the physiological relevance of the L-type Ca2+ channel subtype diversity, gene-targeted mouse models carrying deletions of these channels ("knockout mice") have been generated. This review focuses on recent data from studies in mice lacking the Ca(v)1.2 and Ca(v)1.3 pore subunits, which have elucidated some of the roles of L-type Ca2+ channels as mediators of signalling between cell membrane and intracellular processes like blood pressure regulation, smooth muscle contractility, insulin secretion, cardiac development, and learning and memory.
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Affiliation(s)
- Sven Moosmang
- Institut für Pharmakologie, Technische Universität München, Biedersteiner Strasse 29, 80802, München, Germany.
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Rubio M, Bodi I, Fuller-Bicer GA, Hahn HS, Periasamy M, Schwartz A. Sarcoplasmic reticulum adenosine triphosphatase overexpression in the L-type Ca2+ channel mouse results in cardiomyopathy and Ca2+ -induced arrhythmogenesis. J Cardiovasc Pharmacol Ther 2006; 10:235-49. [PMID: 16382260 DOI: 10.1177/107424840501000404] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
BACKGROUND Overexpression of the L-type voltage-dependent calcium channel alpha(1C)-subunit (L-VDCC OE) in transgenic mice results in adaptive hypertrophy followed by a maladaptive phase associated with a decrease in sarcoplasmic reticulum adenosine triphosphatase (SERCA)2a expression at 8 to 10 months of age. Overexpressing SERCA to manipulate calcium (Ca(2+)) cycling and prevent pathologic phenotypes in some models of heart failure has been proven to be a promising genetic strategy. OBJECTIVE In this study we investigated whether genetic manipulation that increases Ca(2+) uptake into the sarcoplasmic reticulum by overexpressing SERCA1a (skeletal muscle specific) into the L-VDCC OE background could restore or further deteriorate Ca(2+) cycling, contractile dysfunction, and electrical remodeling in the heart failure phenotype. RESULTS We found that the survival rate of L-VDCC OE/SERCA1a OE double transgenic mice decreased by 50%. L-VDCC OE/SERCA1a OE mice displayed an accelerated phenotype of severe dilation of both ventricles associated with deteriorated left ventricular function. Voltage clamp experiments revealed enhanced increased inward Ca(2+) current density and decreased the transient outward potassium current. Action potential duration in double transgenic ventricular myocytes was prolonged, and isoproterenol induced early after depolarization. These mice demonstrated a high incidence of spontaneous left ventricular arrhythmia. Expression of the proarrhythmic signaling protein Ca(2+)/calmodulin-dependent kinase II (CaMKII) was increased while connexin43 expression was decreased, defining an important putative mechanism in the electrophysiologic disturbances and mortality. CONCLUSIONS Despite previous reports of improved cardiac function in heart failure models after SERCA intervention, our results advocate the need to elucidate the involvement of augmented Ca(2+) cycling in arrhythmogenesis.
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Affiliation(s)
- Marta Rubio
- Institute of Molecular Pharmacology and Biophysics, University of Cincinnati Medical Center, Cincinnati, OH 45267-0828, USA
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Abstract
In cardiac cells, Ca2+ signals appear as brief transients responsible for controlling both contraction and transcription. Information may be encoded in these digital signals through changes in both frequency and shape. An increase in Ca2+ signalling contributes to a process of phenotypic remodelling during hypertrophy. The increase in Ca2+ that drives the larger contractions may be responsible for switching on a second process of signalosome remodelling to down-regulate the Ca2+ signalling pathway. It is a change in the properties of the Ca2+ transient that seems to carry the information responsible for the remodelling of the cardiac gene transcription programme that leads first to hypertrophy and then to congestive heart failure.
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Takemori K, Ishida H, Dote K, Yamamoto K, Ito H. Prophylactic effects of an N- and L-type Ca2+ antagonist, cilnidipine, against cardiac hypertrophy and dysfunction in stroke-prone, spontaneously hypertensive rats. Can J Physiol Pharmacol 2006; 83:785-90. [PMID: 16333380 DOI: 10.1139/y05-067] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To clarify the beneficial effects of cilnidipine, an L- and N-type calcium channel blocker, which were clinically observed against diastolic dysfunction in hypertrophied hearts of hypertensive patients, we investigated the effects of cilnidipine on cardiac remodeling and enhanced gene expression in stroke-prone, spontaneously hypertensive rats in comparison with that of captopril, a well-known angiotensin-converting enzyme inhibitor, at threshold doses with little blood pressure lowering effect. The expression of type III collagen and beta/alpha-myosin heavy chain as well as transforming growth factor-beta, and basic fibroblast growth factor were suppressed by both treatments, indicating the prevention or amelioration of cardiac dysfunction. Such beneficial effects were much more intense with cilnidipine treatment than in captopril. These results indicate that Ca2+ is a key factor in the pathogenesis of cardiac remodeling in hypertension. One possible beneficial effect of cilnidipine in the prevention of cardiac dysfunction may be due to the decreased amount of growth factors such as transforming growth factor-beta and basic fibroblast growth factor via direct action for Ca2+ influx and also via inhibition of local renin-angiotensin system in the myocardium.
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Affiliation(s)
- Kumiko Takemori
- Department of Pathology, Kinki University School of Medicine, Osaka, Japan
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Bodi I, Mikala G, Koch SE, Akhter SA, Schwartz A. The L-type calcium channel in the heart: the beat goes on. J Clin Invest 2006; 115:3306-17. [PMID: 16322774 PMCID: PMC1297268 DOI: 10.1172/jci27167] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Sydney Ringer would be overwhelmed today by the implications of his simple experiment performed over 120 years ago showing that the heart would not beat in the absence of Ca2+. Fascination with the role of Ca2+ has proliferated into all aspects of our understanding of normal cardiac function and the progression of heart disease, including induction of cardiac hypertrophy, heart failure, and sudden death. This review examines the role of Ca2+ and the L-type voltage-dependent Ca2+ channels in cardiac disease.
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Affiliation(s)
- Ilona Bodi
- Institute of Molecular Pharmacology and Biophysics, University of Cincinnati College of Medicine, Ohio 45267, USA
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Lebeche D, Dalal R, Jang M, del Monte F, Hajjar RJ. Transgenic Models of Heart Failure: Elucidation of the Molecular Mechanisms of Heart Disease. Heart Fail Clin 2005; 1:219-36. [PMID: 17386848 DOI: 10.1016/j.hfc.2005.03.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Djamel Lebeche
- Massachusetts General Hospital, Charlestown, MA 02129, USA.
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Brette F, Leroy J, Le Guennec JY, Sallé L. Ca2+ currents in cardiac myocytes: Old story, new insights. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2005; 91:1-82. [PMID: 16503439 DOI: 10.1016/j.pbiomolbio.2005.01.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Calcium is a ubiquitous second messenger which plays key roles in numerous physiological functions. In cardiac myocytes, Ca2+ crosses the plasma membrane via specialized voltage-gated Ca2+ channels which have two main functions: (i) carrying depolarizing current by allowing positively charged Ca2+ ions to move into the cell; (ii) triggering Ca2+ release from the sarcoplasmic reticulum. Recently, it has been suggested than Ca2+ channels also participate in excitation-transcription coupling. The purpose of this review is to discuss the physiological roles of Ca2+ currents in cardiac myocytes. Next, we describe local regulation of Ca2+ channels by cyclic nucleotides. We also provide an overview of recent studies investigating the structure-function relationship of Ca2+ channels in cardiac myocytes using heterologous system expression and transgenic mice, with descriptions of the recently discovered Ca2+ channels alpha(1D) and alpha(1E). We finally discuss the potential involvement of Ca2+ currents in cardiac pathologies, such as diseases with autoimmune components, and cardiac remodeling.
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Affiliation(s)
- Fabien Brette
- School of Biomedical Sciences, University of Leeds, Worsley Building Leeds, LS2 9NQ, UK.
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41
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Naguro I, Adachi-Akahane S, Ichijo H. Calcium signalingvia voltage-dependent L-type Ca2+ channels. ACTA ACUST UNITED AC 2004. [DOI: 10.1002/sita.200400035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Melendez J, Turner C, Avraham H, Steinberg SF, Schaefer E, Sussman MA. Cardiomyocyte apoptosis triggered by RAFTK/pyk2 via Src kinase is antagonized by paxillin. J Biol Chem 2004; 279:53516-23. [PMID: 15322113 DOI: 10.1074/jbc.m408475200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Altered cellular adhesion and apoptotic signaling in cardiac remodeling requires coordinated regulation of multiple constituent proteins that comprise cytoskeletal focal adhesions. One such protein activated by cardiac remodeling is related adhesion focal tyrosine kinase (RAFTK, also known as pyk2). Adenoviral-mediated expression of RAFTK in neonatal rat cardiomyocytes involves concurrent increases in phosphorylation of Src, c-Jun N-terminal kinase, and p38 leading to characteristic apoptotic changes including cleavage of poly(ADP-ribose) polymerase, caspase-3 activation, and increased DNA laddering. DNA laddering was decreased by mutation of the Tyr(402) Src-binding site in RAFTK, suggesting a central role for Src activity in apoptotic cell death that was confirmed by adenoviral-mediated Src expression. Multiple apoptotic signaling cascades are recruited by RAFTK as demonstrated by prevention of apoptosis using caspase-3 inhibitor IV (caspase-3 specific inhibitor), PP2 (Src-specific kinase inhibitor), or Csk (cellular negative regulator for Src), as well as dominant negative constructs for p38beta or MKP-1. These RAFTK-mediated phenotypic characteristics are prevented by concurrent expression of wild-type or a phosphorylation-deficient paxillin mutated at Tyr(31) and Tyr(118). Wild-type or mutant paxillin protein accumulation in the cytoplasm has no overt effect upon cell structure, but paxillin accumulation prevents losses of myofibril organization as well as focal adhesion kinase, vinculin, and paxillin protein levels mediated by RAFTK. Apoptotic signaling cascade inhibition by paxillin indicates interruption of signaling proximal to but downstream of RAFTK activity. Chronic RAFTK activation in cardiac remodeling may represent a maladaptive reactive response that can be modulated by paxillin, opening up novel possibilities for inhibition of cardiomyocyte apoptosis and structural degeneration in heart failure.
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Affiliation(s)
- Jaime Melendez
- The Children's Hospital Research Foundation, Division of Molecular Cardiovascular Biology, Cincinnati, OH 45229, USA
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Abstract
Genetic engineering has already provided critical data on the Ca-induced Ca(2+) release (CICR) hypothesis issues and promises even greater future insights. The two approaches employed thus far are (1) the construction of transgenic animal models with deletion or overexpression of Ca(2+) signaling proteins, and (2) direct structure-function studies of these proteins in artificial systems. In our laboratory both approaches have provided some insight into molecular modulation of CICR and the pathophysiology arising from the deletion or overactivity of these proteins. Probing the cytoplasmic segments of the carboxyl c-terminal tail of Ca(2+) channel, we identified two calcium sensing and calmodulin binding domains (LA and K) that have been implicated in Ca(2+)-induced inactivation of Ca(2+) channels. Introducing these peptides into atrial myocytes, where a large fraction of Ca(2+) release sites are unassociated with the dihydropyridine receptors (DHPRs) (no t-tubules), suggests that LA, but not K motif, increases the sensitivity of RyRs to Ca(2+), is responsible for the higher frequency of Ca(2+) sparks in the peripheral sites, and provides for the voltage dependence of CICR. Genetic overexpression or deletion of the primary proteins of the Ca(2+) signaling cascade also provides supportive evidence for the Ca(2+) current (I(Ca))-gated CICR mechanism, generates some novel and unexpected cardiac phenotypes in transgenic mice, and suggests that Ca(2+) signaling defects can trigger compensatory molecular mechanisms that underlie the observed cardiac phenotype and pathophysiology.
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Affiliation(s)
- Martin Morad
- Pharmacology and Medicine, Georgetown University, 4000 Reservoir Rd., Washington, DC 20057, USA.
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Wu Y, Kimbrough JT, Colbran RJ, Anderson ME. Calmodulin kinase is functionally targeted to the action potential plateau for regulation of L-type Ca2+ current in rabbit cardiomyocytes. J Physiol 2004; 554:145-55. [PMID: 14678498 PMCID: PMC1664743 DOI: 10.1113/jphysiol.2003.053314] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
L-type Ca2+ current (ICa-L) triggers Ca2+ release from the sarcoplasmic reticulum (SR) and both SR and ICa-L are potential sources of intracellular Ca2+ (Ca2+i) for feedback regulation of ICa-L. Ca2+i bound to calmodulin (Ca2+-CaM) can inhibit ICa-L, while Ca2+-CaM can also activate Ca2+-CaM-dependent protein kinase II (CaMK) to increase ICa. However, it is not known whether ICa-L or the SR is the primary source of Ca2+ for ICa-L regulation. The L-type Ca2+ channel C terminus is implicated as a critical transduction element for ICa-L responses to Ca2+-CaM and CaMK, and the C terminus undergoes voltage-dependent steric changes, suggesting that Ca2+i control of ICa-L may also be regulated by cell membrane potential. We developed conditions to separately test the relationship of Ca2+-CaM and CaMK to ICa-L and SR Ca2+i release during voltage clamp conditions modelled upon time and voltage domains relevant to the cardiac action potential. Here we show that CaMK increases ICa-L after brief positive conditioning pulses, whereas Ca2+-CaM reduces ICa-L over a broad range of positive and negative conditioning potentials. SR Ca2+ release was required for both Ca2+-CaM and CaMK ICa-L responses after strongly positive conditioning pulses (+10 and +40 mV), while Ca2+i from ICa-L was sufficient for Ca2+-CaM during weaker depolarizations. These findings show that ICa-L responses to CaMK are voltage dependent and suggest a new model of L-type Ca2+ channel regulation where voltage-dependent changes control ICa-L responses to Ca2+-CaM and CaMK signalling.
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Affiliation(s)
- Yuejin Wu
- Department of Internal Medicine, Vanderbilt University Medical Center, Nashville, TN 37232-6300, USA
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45
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Groner F, Rubio M, Schulte-Euler P, Matthes J, Khan IFY, Bodi I, Koch SE, Schwartz A, Herzig S. Single-channel gating and regulation of human L-type calcium channels in cardiomyocytes of transgenic mice. Biochem Biophys Res Commun 2004; 314:878-84. [PMID: 14741718 DOI: 10.1016/j.bbrc.2003.12.174] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Overexpression of human cardiac L-type Ca(2+) channel pores (hCa(v)1.2) in mice causes heart failure. Earlier studies showed Ca(v)1.2-mRNA increase by 2.8-fold, but whole-cell current density enhancement by </=1.5-fold only. Three possible explanations were examined: (1) poor translation of hCa(v)1.2 and of its accessory subunits, (2) altered sarcolemmal insertion of functional channels, and (3) lower single-channel activity of overexpressed channels. Western blots revealed a 2.7-fold increase of Ca(v)1.2 protein in transgenic myocytes, but less enhanced expression of beta(1a) and beta(1b) subunits. beta(2) and alpha(2)/delta were significantly lowered. Density of functional channels was increased by 3.0-fold. Single-channel gating was impaired in transgenic cardiomyocytes: open probability and ensemble average currents were reduced by 60%. Furthermore, channels of transgenic myocytes were not stimulated by 8-Br-cAMP, in contrast to wild-types. Expression of malcomposed, dysfunctional L-type Ca(2+) channels in murine cardiomyocytes overexpressing hCa(v)1.2 explains the moderate enhancement of whole-cell currents and illustrates compensatory mechanisms in a transgenic disease model.
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Affiliation(s)
- Ferdi Groner
- Department of Pharmacology, University of Cologne, 50931, Köln, Germany
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46
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Oudit GY, Sun H, Trivieri MG, Koch SE, Dawood F, Ackerley C, Yazdanpanah M, Wilson GJ, Schwartz A, Liu PP, Backx PH. L-type Ca2+ channels provide a major pathway for iron entry into cardiomyocytes in iron-overload cardiomyopathy. Nat Med 2003; 9:1187-94. [PMID: 12937413 DOI: 10.1038/nm920] [Citation(s) in RCA: 347] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2003] [Accepted: 08/01/2003] [Indexed: 01/12/2023]
Abstract
Under conditions of iron overload, which are now reaching epidemic proportions worldwide, iron-overload cardiomyopathy is the most important prognostic factor in patient survival. We hypothesize that in iron-overload disorders, iron accumulation in the heart depends on ferrous iron (Fe2+) permeation through the L-type voltage-dependent Ca2+ channel (LVDCC), a promiscuous divalent cation transporter. Iron overload in mice was associated with increased mortality, systolic and diastolic dysfunction, bradycardia, hypotension, increased myocardial fibrosis and elevated oxidative stress. Treatment with LVDCC blockers (CCBs; amlodipine and verapamil) at therapeutic levels inhibited the LVDCC current in cardiomyocytes, attenuated myocardial iron accumulation and oxidative stress, improved survival, prevented hypotension and preserved heart structure and function. Consistent with the role of LVDCCs in myocardial iron uptake, iron-overloaded transgenic mice with cardiac-specific overexpression of the LVDCC alpha1-subunit had twofold higher myocardial iron and oxidative stress levels, as well as greater impairment in cardiac function, compared with littermate controls; LVDCC blockade was again protective. Our results indicate that cardiac LVDCCs are key transporters of iron into cardiomyocytes under iron-overloaded conditions, and potentially represent a new therapeutic target to reduce the cardiovascular burden from iron overload.
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Affiliation(s)
- Gavin Y Oudit
- Heart and Stroke/Richard Lewar Centre of Excellence, Departments of Medicine and Physiology, University of Toronto, Ontario M5S 3E2, Canada
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Berridge MJ, Bootman MD, Roderick HL. Calcium signalling: dynamics, homeostasis and remodelling. Nat Rev Mol Cell Biol 2003; 4:517-29. [PMID: 12838335 DOI: 10.1038/nrm1155] [Citation(s) in RCA: 3917] [Impact Index Per Article: 186.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Ca2+ is a highly versatile intracellular signal that operates over a wide temporal range to regulate many different cellular processes. An extensive Ca2+-signalling toolkit is used to assemble signalling systems with very different spatial and temporal dynamics. Rapid highly localized Ca2+ spikes regulate fast responses, whereas slower responses are controlled by repetitive global Ca2+ transients or intracellular Ca2+ waves. Ca2+ has a direct role in controlling the expression patterns of its signalling systems that are constantly being remodelled in both health and disease.
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Affiliation(s)
- Michael J Berridge
- Laboratory of Molecular Signalling, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK.
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Bodi I, Muth JN, Hahn HS, Petrashevskaya NN, Rubio M, Koch SE, Varadi G, Schwartz A. Electrical remodeling in hearts from a calcium-dependent mouse model of hypertrophy and failure: complex nature of K+ current changes and action potential duration. J Am Coll Cardiol 2003; 41:1611-22. [PMID: 12742305 DOI: 10.1016/s0735-1097(03)00244-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
OBJECTIVES This study was designed to identify possible electrical remodeling (ER) in transgenic (Tg) mice with over-expressed L-type Ca(2+) channels. Transient outward K(+) current (I(to)) and action potential duration (APD) were studied in 2-, 4-, 8-, and 9- to 12-month-old mice to determine linkage to ventricular remodeling (VR), ER, and heart failure (HF). BACKGROUND Prolongation of APD and reduction in current density of I(to) are thought to be hallmarks of VR and HF. Mechanisms are not understood. METHODS Patch-clamp, perfused hearts, echocardiography, and Western blots were employed using 2-, 4-, 8-, and 9- to 12-month-old Tg mice. RESULTS Transgenic mice developed slow VR statistically manifesting at four months and continuing through death at 12 to 14 months, despite a slight up-regulation of I(to). A slight decrease or no change in APD was observed up to eight months; however, at 9 to 12 months, a small increase in APD was detected. Early afterdepolarizations were observed after application of 4-aminopyridine in Tg mice. No change was detected in protein of Kv4.3 and Kv4.2 up to eight months. At 9 to 12 months, Tg mice showed a slight decrease (41.4 +/- 6.9%, p < 0.05) in Kv4.2, consistent with a decrease in I(to). Surprisingly, Kv1.4 (the "fetal" K(+)-channel form) was up-regulated, and restitution of I(to) was slowed. Echocardiography revealed cardiac enlargement with impaired chamber function in hearts that were taken from the older animals. CONCLUSIONS Contrary to accepted dogma, APD and I(to) in a mouse model of hypertrophy and HF are not hallmarks of pathophysiology. We suggest that [Ca(2+)](i) (i.e., [Ca(2+)] concentration) is the primary factor in triggering cardiac enlargement and arrhythmogenesis.
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Affiliation(s)
- Ilona Bodi
- Institute of Molecular Pharmacology and Biophysics, Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0828, USA
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Sah R, Ramirez RJ, Oudit GY, Gidrewicz D, Trivieri MG, Zobel C, Backx PH. Regulation of cardiac excitation-contraction coupling by action potential repolarization: role of the transient outward potassium current (I(to)). J Physiol 2003; 546:5-18. [PMID: 12509475 PMCID: PMC2342473 DOI: 10.1113/jphysiol.2002.026468] [Citation(s) in RCA: 204] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The cardiac action potential (AP) is critical for initiating and coordinating myocyte contraction. In particular, the early repolarization period of the AP (phase 1) strongly influences the time course and magnitude of the whole-cell intracellular Ca(2+) transient by modulating trans-sarcolemmal Ca(2+) influx through L-type Ca(2+) channels (I(Ca,L)) and Na-Ca exchangers (I(Ca,NCX)). The transient outward potassium current (I(to)) has kinetic properties that make it especially effective in modulating the trajectory of phase 1 repolarization and thereby cardiac excitation-contraction coupling (ECC). The magnitude of I(to) varies greatly during cardiac development, between different regions of the heart, and is invariably reduced as a result of heart disease, leading to corresponding variations in ECC. In this article, we review evidence supporting a modulatory role of I(to) in ECC through its influence on I(Ca,L), and possibly I(Ca,NCX). We also discuss differential effects of I(to) on ECC between different species, between different regions of the heart and in heart disease.
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Affiliation(s)
- Rajan Sah
- Department of Physiology, University of Toronto, Heart & Stroke/Richard Lewar Centre, Room 68, Fitzgerald Building, 150 College Street, Toronto, Ontario, M5S 3E2, Canada
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