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Hohendanner F, McCulloch AD, Blatter LA, Michailova AP. Calcium and IP3 dynamics in cardiac myocytes: experimental and computational perspectives and approaches. Front Pharmacol 2014; 5:35. [PMID: 24639654 PMCID: PMC3944219 DOI: 10.3389/fphar.2014.00035] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 02/18/2014] [Indexed: 11/22/2022] Open
Abstract
Calcium plays a crucial role in excitation-contraction coupling (ECC), but it is also a pivotal second messenger activating Ca2+-dependent transcription factors in a process termed excitation-transcription coupling (ETC). Evidence accumulated over the past decade indicates a pivotal role of inositol 1,4,5-trisphosphate receptor (IP3R)-mediated Ca2+ release in the regulation of cytosolic and nuclear Ca2+ signals. IP3 is generated by stimulation of plasma membrane receptors that couple to phospholipase C (PLC), liberating IP3 from phosphatidylinositol 4,5-bisphosphate (PIP2). An intriguing aspect of IP3 signaling is the presence of the entire PIP2-PLC-IP3 signaling cascade as well as the presence of IP3Rs at the inner and outer membranes of the nuclear envelope (NE) which functions as a Ca2+ store. The observation that the nucleus is surrounded by its own putative Ca2+ store raises the possibility that nuclear IP3-dependent Ca2+ release plays a critical role in ETC. This provides a potential mechanism of regulation that acts locally and autonomously from the global cytosolic Ca2+ signal underlying ECC. Moreover, there is evidence that: (i) the sarcoplasmic reticulum (SR) and NE are a single contiguous Ca2+ store; (ii) the nuclear pore complex is the major gateway for Ca2+ and macromolecules to pass between the cytosol and the nucleoplasm; (iii) the inner membrane of the NE hosts key Ca2+ handling proteins including the Na+/Ca2+ exchanger (NCX)/GM1 complex, ryanodine receptors (RyRs), nicotinic acid adenine dinucleotide phosphate receptors (NAADPRs), Na+/K+ ATPase, and Na+/H+ exchanger. Thus, it appears that the nucleus represents a Ca2+ signaling domain equipped with its own ion channels and transporters that allow for complex local Ca2+ signals. Many experimental and modeling approaches have been used for the study of intracellular Ca2+ signaling but the key to the understanding of the dual role of Ca2+ mediating ECC and ECT lays in quantitative differences of local [Ca2+] in the nuclear and cytosolic compartment. In this review, we discuss the state of knowledge regarding the origin and the physiological implications of nuclear Ca2+ transients in different cardiac cell types (adult atrial and ventricular myocytes) as well as experimental and mathematical approaches to study Ca2+ and IP3 signaling in the cytosol and nucleus. In particular, we focus on the concept that highly localized Ca2+ signals are required to translocate and activate Ca2+-dependent transcription factors (e.g., nuclear factor of activated T-cells, NFAT; histone deacetylase, HDAC) through phosphorylation/dephosphorylation processes.
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Affiliation(s)
- Felix Hohendanner
- Department of Molecular Biophysics and Physiology, Rush University Medical Center Chicago, IL, USA
| | - Andrew D McCulloch
- Department of Bioengineering, University of California San Diego La Jolla, CA, USA
| | - Lothar A Blatter
- Department of Molecular Biophysics and Physiology, Rush University Medical Center Chicago, IL, USA
| | - Anushka P Michailova
- Department of Bioengineering, University of California San Diego La Jolla, CA, USA
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Bartlett PJ, Gaspers LD, Pierobon N, Thomas AP. Calcium-dependent regulation of glucose homeostasis in the liver. Cell Calcium 2014; 55:306-16. [PMID: 24630174 DOI: 10.1016/j.ceca.2014.02.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Revised: 02/07/2014] [Accepted: 02/08/2014] [Indexed: 02/09/2023]
Abstract
A major role of the liver is to integrate multiple signals to maintain normal blood glucose levels. The balance between glucose storage and mobilization is primarily regulated by the counteracting effects of insulin and glucagon. However, numerous signals converge in the liver to ensure energy demand matches the physiological status of the organism. Many circulating hormones regulate glycogenolysis, gluconeogenesis and mitochondrial metabolism by calcium-dependent signaling mechanisms that manifest as cytosolic Ca(2+) oscillations. Stimulus-strength is encoded in the Ca(2+) oscillation frequency, and also by the range of intercellular Ca(2+) wave propagation in the intact liver. In this article, we describe how Ca(2+) oscillations and waves can regulate glucose output and oxidative metabolism in the intact liver; how multiple stimuli are decoded though Ca(2+) signaling at the organ level, and the implications of Ca(2+) signal dysregulation in diseases such as metabolic syndrome and non-alcoholic fatty liver disease.
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Affiliation(s)
- Paula J Bartlett
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA.
| | - Lawrence D Gaspers
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Nicola Pierobon
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Andrew P Thomas
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
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53
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Pierro C, Cook SJ, Foets TCF, Bootman MD, Roderick HL. Oncogenic K-Ras suppresses IP₃-dependent Ca²⁺ release through remodelling of the isoform composition of IP₃Rs and ER luminal Ca²⁺ levels in colorectal cancer cell lines. J Cell Sci 2014; 127:1607-19. [PMID: 24522186 DOI: 10.1242/jcs.141408] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The GTPase Ras is a molecular switch engaged downstream of G-protein-coupled receptors and receptor tyrosine kinases that controls multiple cell-fate-determining signalling pathways. Ras signalling is frequently deregulated in cancer, underlying associated changes in cell phenotype. Although Ca(2+) signalling pathways control some overlapping functions with Ras, and altered Ca(2+) signalling pathways are emerging as important players in oncogenic transformation, how Ca(2+) signalling is remodelled during transformation and whether it has a causal role remains unclear. We have investigated Ca(2+) signalling in two human colorectal cancer cell lines and their isogenic derivatives in which the allele encoding oncogenic K-Ras (G13D) was deleted by homologous recombination. We show that agonist-induced Ca(2+) release from the endoplasmic reticulum (ER) intracellular Ca(2+) stores is enhanced by loss of K-Ras(G13D) through an increase in the Ca(2+) content of the ER store and a modification of the abundance of inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) subtypes. Consistently, uptake of Ca(2+) into mitochondria and sensitivity to apoptosis was enhanced as a result of K-Ras(G13D) loss. These results suggest that suppression of Ca(2+) signalling is a common response to naturally occurring levels of K-Ras(G13D), and that this contributes to a survival advantage during oncogenic transformation.
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Affiliation(s)
- Cristina Pierro
- Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT UK
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Sankar N, deTombe PP, Mignery GA. Calcineurin-NFATc regulates type 2 inositol 1,4,5-trisphosphate receptor (InsP3R2) expression during cardiac remodeling. J Biol Chem 2014; 289:6188-98. [PMID: 24415751 DOI: 10.1074/jbc.m113.495242] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In heart, the type 2 inositol 1,4,5-triphosphate receptor (InsP3R2) is the predominant isoform expressed and is localized in the nuclear membrane of ventricular myocytes. InsP3R2-mediated Ca(2+) release regulates hypertrophy specific gene expression by modulating CaMKIIδ, histone deacetylase, and calcineurin-NFATc signaling pathways. InsP3R2 protein is a hypertrophy specific marker and is overexpressed in heart failure animal models and in humans. However, the regulation of InsP3R2 mRNA and protein expression during cardiac hypertrophy and heart failure is not known. Here we show the transcriptional regulation of the Itpr2 gene in adult cardiomyocytes. Our data demonstrates that, InsP3R2 mRNA and protein expression is activated by hypertrophic agonists and attenuated by InsP3R inhibitors 2-aminoethoxyldiphenyl borate and xestospongin-C. The Itpr2 promoter is regulated by the calcineurin-NFATc signaling pathway. NFATc1 regulates Itpr2 gene expression by directly binding to the Itpr2 promoter. The calcineurin-NFATc mediated up-regulation of the Itpr2 promoter was attenuated by cyclosporine-A. InsP3R2 mRNA and protein expression was up-regulated in calcineurin-A transgenic mice and in human heart failure. Collectively, our data suggests that ITPR2 and hypertrophy specific gene expression is regulated, in part, by a positive feedback regulation between InsP3R2 and calcineurin-NFATc signaling pathways.
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Affiliation(s)
- Natesan Sankar
- From the Department of Cell & Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois 60153
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55
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Kapoor N, Maxwell JT, Mignery GA, Will D, Blatter LA, Banach K. Spatially defined InsP3-mediated signaling in embryonic stem cell-derived cardiomyocytes. PLoS One 2014; 9:e83715. [PMID: 24409283 PMCID: PMC3883750 DOI: 10.1371/journal.pone.0083715] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 11/06/2013] [Indexed: 11/19/2022] Open
Abstract
The functional role of inositol 1,4,5-trisphosphate (InsP3) signaling in cardiomyocytes is not entirely understood but it was linked to an increased propensity for triggered activity. The aim of this study was to determine how InsP3 receptors can translate Ca(2+) release into a depolarization of the plasma membrane and consequently arrhythmic activity. We used embryonic stem cell-derived cardiomyocytes (ESdCs) as a model system since their spontaneous electrical activity depends on InsP3-mediated Ca(2+) release. [InsP3]i was monitored with the FRET-based InsP3-biosensor FIRE-1 (Fluorescent InsP3 Responsive Element) and heterogeneity in sub-cellular [InsP3]i was achieved by targeted expression of FIRE-1 in the nucleus (FIRE-1nuc) or expression of InsP3 5-phosphatase (m43) localized to the plasma membrane. Spontaneous activity of ESdCs was monitored simultaneously as cytosolic Ca(2+) transients (Fluo-4/AM) and action potentials (current clamp). During diastole, the diastolic depolarization was paralleled by an increase of [Ca(2+)]i and spontaneous activity was modulated by [InsP3]i. A 3.7% and 1.7% increase of FIRE-1 FRET ratio and 3.0 and 1.5 fold increase in beating frequency was recorded upon stimulation with endothelin-1 (ET-1, 100 nmol/L) or phenylephrine (PE, 10 µmol/L), respectively. Buffering of InsP3 by FIRE-1nuc had no effect on the basal frequency while attenuation of InsP3 signaling throughout the cell (FIRE-1), or at the plasma membrane (m43) resulted in a 53.7% and 54.0% decrease in beating frequency. In m43 expressing cells the response to ET-1 was completely suppressed. Ca(2+) released from InsP3Rs is more effective than Ca(2+) released from RyRs to enhance INCX. The results support the hypothesis that in ESdCs InsP3Rs form a functional signaling domain with NCX that translates Ca(2+) release efficiently into a depolarization of the membrane potential.
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Affiliation(s)
- Nidhi Kapoor
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - Joshua T. Maxwell
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois, United States of America
| | - Gregory A. Mignery
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois, United States of America
| | - David Will
- Center for Cardiovascular Research, Dept. of Medicine, Section of Cardiology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Lothar A. Blatter
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois, United States of America
| | - Kathrin Banach
- Center for Cardiovascular Research, Dept. of Medicine, Section of Cardiology, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail:
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Tagashira H, Bhuiyan MS, Shioda N, Fukunaga K. Fluvoxamine rescues mitochondrial Ca2+ transport and ATP production through σ(1)-receptor in hypertrophic cardiomyocytes. Life Sci 2013; 95:89-100. [PMID: 24373833 DOI: 10.1016/j.lfs.2013.12.019] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Revised: 11/19/2013] [Accepted: 12/12/2013] [Indexed: 01/15/2023]
Abstract
AIMS We previously reported that fluvoxamine, a selective serotonin reuptake inhibitor with high affinity for the σ1-receptor (σ1R), ameliorates cardiac hypertrophy and dysfunction via σ1R stimulation. Although σ1R on non-cardiomyocytes interacts with the IP3 receptor (IP3R) to promote mitochondrial Ca(2+) transport, little is known about its physiological and pathological relevance in cardiomyocytes. MAIN METHODS Here we performed Ca(2+) imaging and measured ATP production to define the role of σ1Rs in regulating sarcoplasmic reticulum (SR)-mitochondrial Ca(2+) transport in neonatal rat ventricular cardiomyocytes treated with angiotensin II to promote hypertrophy. KEY FINDING These cardiomyocytes exhibited imbalances in expression levels of σ1R and IP3R and impairments in both phenylephrine-induced mitochondrial Ca(2+) mobilization from the SR and ATP production. Interestingly, σ1R stimulation with fluvoxamine rescued impaired mitochondrial Ca(2+) mobilization and ATP production, an effect abolished by treatment of cells with the σ1R antagonist, NE-100. Under physiological conditions, fluvoxamine stimulation of σ1Rs suppressed intracellular Ca(2+) mobilization through IP3Rs and ryanodine receptors (RyRs). In vivo, chronic administration of fluvoxamine to TAC mice also rescued impaired ATP production. SIGNIFICANCE These results suggest that σ1R stimulation with fluvoxamine promotes SR-mitochondrial Ca(2+) transport and mitochondrial ATP production, whereas σ1R stimulation suppresses intracellular Ca(2+) overload through IP3Rs and RyRs. These mechanisms likely underlie in part the anti-hypertrophic and cardioprotective action of the σ1R agonists including fluvoxamine.
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Affiliation(s)
- Hideaki Tagashira
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Md Shenuarin Bhuiyan
- Division of Molecular Cardiovascular Biology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Norifumi Shioda
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Kohji Fukunaga
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
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Lee H, Yoo YS, Lee D, Song EJ. Cholesterol induces cardiac hypertrophy by activating the AKT pathway. J Steroid Biochem Mol Biol 2013; 138:307-13. [PMID: 23907017 DOI: 10.1016/j.jsbmb.2013.07.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 06/27/2013] [Accepted: 07/22/2013] [Indexed: 01/01/2023]
Abstract
Cardiac hypertrophy leads to decompensated heart function, predisposition to heart failure, and sudden death due to physiological and pathological stimuli. Although high cholesterol is considered a principal risk factor for atherosclerosis and heart disease, it has not been shown whether cholesterol itself is sufficient to cause cardiac hypertrophy. In this study, we investigated whether cholesterol induces cardiac hypertrophy, and identified cellular mechanisms underlying hypertrophic responses using H9c2 cells as a model system. Here we show that cholesterol loading significantly increased the cellular surface area and upregulated hypertrophy marker gene, β-myosin-heavy chain (β-MHC). Cholesterol loading alone activated the extracellular signal-regulated kinase (ERK)/mitogen activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K)/AKT pathways. Conversely, cholesterol induced hypertrophic characteristic features such as increase in cellular surface area, and the expression of β-MHC mRNA is markedly inhibited by LY294002, a PI3K kinase inhibitor. These results suggest that cholesterol may play a key role in the development of cardiac hypertrophy through the activation of the PI3K/AKT pathway activation.
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Affiliation(s)
- Hyunjung Lee
- Molecular Recognition Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea; Department of Life & Pharmaceutical Sciences Ewha Womans University, Daehyun-dong, Seodaemun-gu, Seoul 120-750, Republic of Korea
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Chen YH, Pai CW, Huang SW, Chang SN, Lin LY, Chiang FT, Lin JL, Hwang JJ, Tsai CT. Inactivation of Myosin binding protein C homolog in zebrafish as a model for human cardiac hypertrophy and diastolic dysfunction. J Am Heart Assoc 2013; 2:e000231. [PMID: 24047589 PMCID: PMC3835223 DOI: 10.1161/jaha.113.000231] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Background Sudden cardiac death due to malignant ventricular arrhythmia is a devastating manifestation of cardiac hypertrophy. Sarcomere protein myosin binding protein C is functionally related to cardiac diastolic function and hypertrophy. Zebrafish is a better model to study human electrophysiology and arrhythmia than rodents because of the electrophysiological characteristics similar to those of humans. Methods and Results We established a zebrafish model of cardiac hypertrophy and diastolic dysfunction by genetic knockdown of myosin binding protein C gene (mybpc3) and investigated the electrophysiological phenotypes in this model. We found expression of zebrafish mybpc3 restrictively in the heart and slow muscle, and mybpc3 gene was evolutionally conservative with sequence homology between zebrafish and human mybpc3 genes. Zebrafish with genetic knockdown of mybpc3 by morpholino showed ventricular hypertrophy with increased myocardial wall thickness and diastolic heart failure, manifesting as decreased ventricular diastolic relaxation velocity, pericardial effusion, and dilatation of the atrium. In terms of electrophysiological phenotypes, mybpc3 knockdown fish had a longer ventricular action potential duration and slower ventricular diastolic calcium reuptake, both of which are typical electrophysiological features in human cardiac hypertrophy and heart failure. Impaired calcium reuptake resulted in increased susceptibility to calcium transient alternans and action potential duration alternans, which have been proved to be central to the genesis of malignant ventricular fibrillation and a sensitive marker of sudden cardiac death. Conclusions mybpc3 knockdown in zebrafish recapitulated the morphological, mechanical, and electrophysiological phenotypes of human cardiac hypertrophy and diastolic heart failure. Our study also first demonstrated arrhythmogenic cardiac alternans in cardiac hypertrophy.
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Affiliation(s)
- Yau-Hung Chen
- Department of Chemistry, Tamkang University, Taipei, Taiwan
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59
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Roderick HL, Knollmann BC. Inositol 1,4,5-trisphosphate receptors: "exciting" players in cardiac excitation-contraction coupling? Circulation 2013; 128:1273-5. [PMID: 23983251 PMCID: PMC3885819 DOI: 10.1161/circulationaha.113.005157] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- H. Llewelyn Roderick
- Babraham Institute, Babraham Research Campus, Babraham, Cambridge, UK, CB22 3AT. Office:+ 44 (0)1223 496489,
| | - Björn C. Knollmann
- Dept. of Medicine, Vanderbilt University, Medical Center, Nashville, TN, USA, Office: (615) 343-6493, Fax: (615) 343-4522,
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Signore S, Sorrentino A, Ferreira-Martins J, Kannappan R, Shafaie M, Del Ben F, Isobe K, Arranto C, Wybieralska E, Webster A, Sanada F, Ogórek B, Zheng H, Liu X, Del Monte F, D'Alessandro DA, Wunimenghe O, Michler RE, Hosoda T, Goichberg P, Leri A, Kajstura J, Anversa P, Rota M. Inositol 1, 4, 5-trisphosphate receptors and human left ventricular myocytes. Circulation 2013; 128:1286-97. [PMID: 23983250 DOI: 10.1161/circulationaha.113.002764] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
BACKGROUND Little is known about the function of inositol 1,4,5-trisphosphate receptors (IP3Rs) in the adult heart experimentally. Moreover, whether these Ca(2+) release channels are present and play a critical role in human cardiomyocytes remains to be defined. IP3Rs may be activated after Gαq-protein-coupled receptor stimulation, affecting Ca(2+) cycling, enhancing myocyte performance, and potentially favoring an increase in the incidence of arrhythmias. METHODS AND RESULTS IP3R function was determined in human left ventricular myocytes, and this analysis was integrated with assays in mouse myocytes to identify the mechanisms by which IP3Rs influence the electric and mechanical properties of the myocardium. We report that IP3Rs are expressed and operative in human left ventricular myocytes. After Gαq-protein-coupled receptor activation, Ca(2+) mobilized from the sarcoplasmic reticulum via IP3Rs contributes to the decrease in resting membrane potential, prolongation of the action potential, and occurrence of early afterdepolarizations. Ca(2+) transient amplitude and cell shortening are enhanced, and extrasystolic and dysregulated Ca(2+) elevations and contractions become apparent. These alterations in the electromechanical behavior of human cardiomyocytes are coupled with increased isometric twitch of the myocardium and arrhythmic events, suggesting that Gαq-protein-coupled receptor activation provides inotropic reserve, which is hampered by electric instability and contractile abnormalities. Additionally, our findings support the notion that increases in Ca(2+) load by IP3Rs promote Ca(2+) extrusion by forward-mode Na(+)/Ca(2+) exchange, an important mechanism of arrhythmic events. CONCLUSIONS The Gαq-protein/coupled receptor/IP3R axis modulates the electromechanical properties of the human myocardium and its propensity to develop arrhythmias.
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Affiliation(s)
- Sergio Signore
- Departments of Anesthesia and Medicine and Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (S.S., A.S., J.F.-M., R.K., M.S., F.D.B., K.I., C.A., E.W., A.W., F.S., B.O., H.Z., X.L., T.H., P.G., A.L., J.K., P.A., M.R.); Cardiovascular Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (F.d.M.); and Department of Cardiovascular and Thoracic Surgery, Montefiore Medical Center, Albert Einstein College of Medicine, New York, NY (D.A.D., O.W., R.E.M.)
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Schwoerer AP, Neef S, Broichhausen I, Jacubeit J, Tiburcy M, Wagner M, Biermann D, Didié M, Vettel C, Maier LS, Zimmermann WH, Carrier L, Eschenhagen T, Volk T, El-Armouche A, Ehmke H. Enhanced Ca²+ influx through cardiac L-type Ca²+ channels maintains the systolic Ca²+ transient in early cardiac atrophy induced by mechanical unloading. Pflugers Arch 2013; 465:1763-73. [PMID: 23842739 PMCID: PMC3898408 DOI: 10.1007/s00424-013-1316-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 06/13/2013] [Accepted: 06/18/2013] [Indexed: 11/04/2022]
Abstract
Cardiac atrophy as a consequence of mechanical unloading develops following exposure to microgravity or prolonged bed rest. It also plays a central role in the reverse remodelling induced by left ventricular unloading in patients with heart failure. Surprisingly, the intracellular Ca2+ transients which are pivotal to electromechanical coupling and to cardiac plasticity were repeatedly found to remain unaffected in early cardiac atrophy. To elucidate the mechanisms underlying the preservation of the Ca2+ transients, we investigated Ca2+ cycling in cardiomyocytes from mechanically unloaded (heterotopic abdominal heart transplantation) and control (orthotopic) hearts in syngeneic Lewis rats. Following 2 weeks of unloading, sarcoplasmic reticulum (SR) Ca2+ content was reduced by ~55 %. Atrophic cardiac myocytes also showed a much lower frequency of spontaneous diastolic Ca2+ sparks and a diminished systolic Ca2+ release, even though the expression of ryanodine receptors was increased by ~30 %. In contrast, current clamp recordings revealed prolonged action potentials in endocardial as well as epicardial myocytes which were associated with a two to fourfold higher sarcolemmal Ca2+ influx under action potential clamp. In addition, Cav1.2 subunits which form the pore of L-type Ca2+ channels (LTCC) were upregulated in atrophic myocardium. These data suggest that in early cardiac atrophy induced by mechanical unloading, an augmented sarcolemmal Ca2+ influx through LTCC fully compensates for a reduced systolic SR Ca2+ release to preserve the Ca2+ transient. This interplay involves an electrophysiological remodelling as well as changes in the expression of cardiac ion channels.
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Affiliation(s)
- A. P. Schwoerer
- Department of Cellular and Integrative Physiology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
| | - S. Neef
- Department of Cardiology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
| | - I. Broichhausen
- Department of Cellular and Integrative Physiology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
| | - J. Jacubeit
- Department of Cellular and Integrative Physiology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
| | - M. Tiburcy
- Institute of Pharmacology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - M. Wagner
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - D. Biermann
- Department of Cardiovascular Surgery, Center for Cardiology and Cardiovascular Surgery, University Heart Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
| | - M. Didié
- Department of Cardiology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- Institute of Pharmacology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - C. Vettel
- Institute of Pharmacology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - L. S. Maier
- Department of Cardiology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - W. H. Zimmermann
- Institute of Pharmacology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - L. Carrier
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
- Inserm, U974; CNRS, UMR7215; UPMC UM76, Institut de Myologie, Paris, 75013 France
| | - T. Eschenhagen
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
| | - T. Volk
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - A. El-Armouche
- Institute of Pharmacology, Heart Research Center, Georg-August-University Goettingen, Goettingen, Germany
- DZHK (German Centre for Cardiovascular Research)—Goettingen, Goettingen, Germany
| | - H. Ehmke
- Department of Cellular and Integrative Physiology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistr 52, 20246 Hamburg, Germany
- DZHK (German Centre for Cardiovascular Research)—Hamburg/Kiel/Luebeck, Hamburg, Germany
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Drawnel FM, Archer CR, Roderick HL. The role of the paracrine/autocrine mediator endothelin-1 in regulation of cardiac contractility and growth. Br J Pharmacol 2013; 168:296-317. [PMID: 22946456 DOI: 10.1111/j.1476-5381.2012.02195.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Revised: 08/23/2012] [Accepted: 08/28/2012] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED Endothelin-1 (ET-1) is a critical autocrine and paracrine regulator of cardiac physiology and pathology. Produced locally within the myocardium in response to diverse mechanical and neurohormonal stimuli, ET-1 acutely modulates cardiac contractility. During pathological cardiovascular conditions such as ischaemia, left ventricular hypertrophy and heart failure, myocyte expression and activity of the entire ET-1 system is enhanced, allowing the peptide to both initiate and maintain maladaptive cellular responses. Both the acute and chronic effects of ET-1 are dependent on the activation of intracellular signalling pathways, regulated by the inositol-trisphosphate and diacylglycerol produced upon activation of the ET(A) receptor. Subsequent stimulation of protein kinases C and D, calmodulin-dependent kinase II, calcineurin and MAPKs modifies the systolic calcium transient, myofibril function and the activity of transcription factors that coordinate cellular remodelling. The precise nature of the cellular response to ET-1 is governed by the timing, localization and context of such signals, allowing the peptide to regulate both cardiomyocyte physiology and instigate disease. LINKED ARTICLES This article is part of a themed section on Endothelin. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.168.issue-1.
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Affiliation(s)
- Faye M Drawnel
- Babraham Research Campus, Babraham Institute, Cambridge, UK
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63
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Stroma cell-derived factor-1α signaling enhances calcium transients and beating frequency in rat neonatal cardiomyocytes. PLoS One 2013; 8:e56007. [PMID: 23460790 PMCID: PMC3584107 DOI: 10.1371/journal.pone.0056007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 01/03/2013] [Indexed: 11/19/2022] Open
Abstract
Stroma cell-derived factor-1α (SDF-1α) is a cardioprotective chemokine, acting through its G-protein coupled receptor CXCR4. In experimental acute myocardial infarction, administration of SDF-1α induces an early improvement of systolic function which is difficult to explain solely by an anti-apoptotic and angiogenic effect. We wondered whether SDF-1α signaling might have direct effects on calcium transients and beating frequency. Primary rat neonatal cardiomyocytes were culture-expanded and characterized by immunofluorescence staining. Calcium sparks were studied by fluorescence microscopy after calcium loading with the Fluo-4 acetoxymethyl ester sensor. The cardiomyocyte enriched cellular suspension expressed troponin I and CXCR4 but was vimentin negative. Addition of SDF-1α in the medium increased cytoplasmic calcium release. The calcium response was completely abolished by using a neutralizing anti-CXCR4 antibody and partially suppressed and delayed by preincubation with an inositol triphosphate receptor (IP3R) blocker, but not with a ryanodine receptor (RyR) antagonist. Calcium fluxes induced by caffeine, a RyR agonist, were decreased by an IP3R blocker. Treatment with forskolin or SDF-1α increased cardiomyocyte beating frequency and their effects were additive. In vivo, treatment with SDF-1α increased left ventricular dP/dtmax. These results suggest that in rat neonatal cardiomyocytes, the SDF-1α/CXCR4 signaling increases calcium transients in an IP3-gated fashion leading to a positive chronotropic and inotropic effect.
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64
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Horn T, Ullrich ND, Egger M. 'Eventless' InsP3-dependent SR-Ca2+ release affecting atrial Ca2+ sparks. J Physiol 2013; 591:2103-11. [PMID: 23381902 DOI: 10.1113/jphysiol.2012.247288] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Augmented inositol 1,4,5-trisphosphate receptor (InsP3R) function has been linked to a variety of cardiac pathologies, including cardiac arrhythmia. The contribution of inositol 1,4,5-trisphosphate-induced Ca(2+) release (IP3ICR) in excitation-contraction coupling (ECC) under physiological conditions, as well as under cellular remodelling, remains controversial. Here we test the hypothesis that local IP3ICR directly affects ryanodine receptor (RyR) function and subsequent Ca(2+)-induced Ca(2+) release in atrial myocytes. IP3ICR was evoked by UV-flash photolysis of caged InsP3 under whole-cell configuration of the voltage-clamp technique in atrial myocytes isolated from C57/BL6 mice. Photolytic release of InsP3 was accompanied by a significant increase in the Ca(2+) release event frequency (4.14 ± 0.72 vs. 6.20 ± 0.76 events (100 μm)(-1) s(-1)). These individual photolytically triggered Ca(2+) release events were identified as Ca(2+) sparks, which originated from RyR openings. This was verified by Ca(2+) spark analysis and pharmacological separation between RyR and InsP3R-dependent sarcoplasmic reticulum (SR)-Ca(2+) release (2-aminoethoxydiphenyl borate, xestospongin C, tetracaine). Significant SR-Ca(2+) flux but eventless SR-Ca(2+) release through InsP3R were characterized using SR-Ca(2+) leak/SR-Ca(2+) load measurements. These results strongly support the idea that IP3ICR can effectively modulate RyR openings and Ca(2+) spark probability. We conclude that eventless and highly efficient InsP3-dependent SR-Ca(2+) flux is the main mechanism of functional cross-talk between InsP3Rs and RyRs, which may be an important factor in the modulation of ECC sensitivity.
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Affiliation(s)
- Tamara Horn
- Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland
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65
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Ruhle B, Trebak M. Emerging roles for native Orai Ca2+ channels in cardiovascular disease. CURRENT TOPICS IN MEMBRANES 2013; 71:209-35. [PMID: 23890117 DOI: 10.1016/b978-0-12-407870-3.00009-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Orai proteins form highly calcium (Ca(2+))-selective channels located in the plasma membrane of both nonexcitable and excitable cells, where they make important contributions to many cellular processes. The well-characterized Ca(2+) release-activated Ca(2+) current is mediated by Orai1 multimers and is activated, upon depletion of inositol 1,4,5-trisphosphate-sensitive stores, by direct interaction of Orai1 with the endoplasmic reticulum Ca(2+) sensor, stromal interaction molecule 1 (STIM1). This pathway is known as capacitative Ca(2+) entry or store-operated Ca(2+) entry. While most investigations have focused on STIM1 and Orai1 in their store-dependent mode, emerging evidence suggests that Orai1 and Orai3 heteromultimeric channels can form store-independent Ca(2+)-selective channels. The role of store-dependent and store-independent channels in excitation-transcription coupling and the pathological remodeling of the cardiovascular system are beginning to come forth. Recent evidence suggests that STIM/Orai-generated Ca(2+) signaling couples to gene transcription and subsequent phenotypic changes associated with the processes of cardiac and vascular remodeling. This short review will explore the contributions of native Orai channels to heart and vessel physiology and their role in cardiovascular diseases.
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Affiliation(s)
- Brian Ruhle
- Nanobioscience Constellation, The College of Nanoscale Science and Engineering, University at Albany-State University of New York, Albany, NY, USA
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66
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Tjondrokoesoemo A, Li N, Lin PH, Pan Z, Ferrante CJ, Shirokova N, Brotto M, Weisleder N, Ma J. Type 1 inositol (1,4,5)-trisphosphate receptor activates ryanodine receptor 1 to mediate calcium spark signaling in adult mammalian skeletal muscle. J Biol Chem 2012; 288:2103-9. [PMID: 23223241 DOI: 10.1074/jbc.m112.425975] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Functional coupling between inositol (1,4,5)-trisphosphate receptor (IP(3)R) and ryanodine receptor (RyR) represents a critical component of intracellular Ca(2+) signaling in many excitable cells; however, the role of this mechanism in skeletal muscle remains elusive. In skeletal muscle, RyR-mediated Ca(2+) sparks are suppressed in resting conditions, whereas application of transient osmotic stress can trigger activation of Ca(2+) sparks that are restricted to the periphery of the fiber. Here we show that onset of these spatially confined Ca(2+) sparks involves interaction between activation of IP(3)R and RyR near the sarcolemmal membrane. Pharmacological prevention of IP(3) production or inhibition of IP(3)R channel activity abolishes stress-induced Ca(2+) sparks in skeletal muscle. Although genetic ablation of the type 2 IP(3)R does not appear to affect Ca(2+) sparks in skeletal muscle, specific silencing of the type 1 IP(3)R leads to ablation of stress-induced Ca(2+) sparks. Our data indicate that membrane-delimited signaling involving cross-talk between IP(3)R1 and RyR1 contributes to Ca(2+) spark activation in skeletal muscle.
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Affiliation(s)
- Andoria Tjondrokoesoemo
- Department of Physiology and Biophysics, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA
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67
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Nakayama H, Fujio Y. [Ca2+-mediated pathogenesis in the heart]. Nihon Yakurigaku Zasshi 2012; 140:270-274. [PMID: 23229633 DOI: 10.1254/fpj.140.270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
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68
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Tencerová B, Zahradníková A, Gaburjáková J, Gaburjáková M. Luminal Ca2+ controls activation of the cardiac ryanodine receptor by ATP. ACTA ACUST UNITED AC 2012; 140:93-108. [PMID: 22851674 PMCID: PMC3409101 DOI: 10.1085/jgp.201110708] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The synergic effect of luminal Ca2+, cytosolic Ca2+, and cytosolic adenosine triphosphate (ATP) on activation of cardiac ryanodine receptor (RYR2) channels was examined in planar lipid bilayers. The dose–response of RYR2 gating activity to ATP was characterized at a diastolic cytosolic Ca2+ concentration of 100 nM over a range of luminal Ca2+ concentrations and, vice versa, at a diastolic luminal Ca2+ concentration of 1 mM over a range of cytosolic Ca2+ concentrations. Low level of luminal Ca2+ (1 mM) significantly increased the affinity of the RYR2 channel for ATP but without substantial activation of the channel. Higher levels of luminal Ca2+ (8–53 mM) markedly amplified the effects of ATP on the RYR2 activity by selectively increasing the maximal RYR2 activation by ATP, without affecting the affinity of the channel to ATP. Near-diastolic cytosolic Ca2+ levels (<500 nM) greatly amplified the effects of luminal Ca2+. Fractional inhibition by cytosolic Mg2+ was not affected by luminal Ca2+. In models, the effects of luminal and cytosolic Ca2+ could be explained by modulation of the allosteric effect of ATP on the RYR2 channel. Our results suggest that luminal Ca2+ ions potentiate the RYR2 gating activity in the presence of ATP predominantly by binding to a luminal site with an apparent affinity in the millimolar range, over which local luminal Ca2+ likely varies in cardiac myocytes.
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Affiliation(s)
- Barbora Tencerová
- Institute of Molecular Physiology and Genetics, Centre of Excellence for Cardiovascular Research, Slovak Academy of Sciences, 833 34 Bratislava, Slovak Republic
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69
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Domínguez-Rodríguez A, Ruiz-Hurtado G, Benitah JP, Gómez AM. The other side of cardiac Ca(2+) signaling: transcriptional control. Front Physiol 2012; 3:452. [PMID: 23226134 PMCID: PMC3508405 DOI: 10.3389/fphys.2012.00452] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 11/12/2012] [Indexed: 12/19/2022] Open
Abstract
Ca2+ is probably the most versatile signal transduction element used by all cell types. In the heart, it is essential to activate cellular contraction in each heartbeat. Nevertheless Ca2+ is not only a key element in excitation-contraction coupling (EC coupling), but it is also a pivotal second messenger in cardiac signal transduction, being able to control processes such as excitability, metabolism, and transcriptional regulation. Regarding the latter, Ca2+ activates Ca2+-dependent transcription factors by a process called excitation-transcription coupling (ET coupling). ET coupling is an integrated process by which the common signaling pathways that regulate EC coupling activate transcription factors. Although ET coupling has been extensively studied in neurons and other cell types, less is known in cardiac muscle. Some hints have been found in studies on the development of cardiac hypertrophy, where two Ca2+-dependent enzymes are key actors: Ca2+/Calmodulin kinase II (CaMKII) and phosphatase calcineurin, both of which are activated by the complex Ca2+/Calmodulin. The question now is how ET coupling occurs in cardiomyocytes, where intracellular Ca2+ is continuously oscillating. In this focused review, we will draw attention to location of Ca2+ signaling: intranuclear ([Ca2+]n) or cytoplasmic ([Ca2+]c), and the specific ionic channels involved in the activation of cardiac ET coupling. Specifically, we will highlight the role of the 1,4,5 inositol triphosphate receptors (IP3Rs) in the elevation of [Ca2+]n levels, which are important to locally activate CaMKII, and the role of transient receptor potential channels canonical (TRPCs) in [Ca2+]c, needed to activate calcineurin (Cn).
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70
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Drawnel FM, Wachten D, Molkentin JD, Maillet M, Aronsen JM, Swift F, Sjaastad I, Liu N, Catalucci D, Mikoshiba K, Hisatsune C, Okkenhaug H, Andrews SR, Bootman MD, Roderick HL. Mutual antagonism between IP(3)RII and miRNA-133a regulates calcium signals and cardiac hypertrophy. J Cell Biol 2012; 199:783-98. [PMID: 23166348 PMCID: PMC3514786 DOI: 10.1083/jcb.201111095] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 10/25/2012] [Indexed: 11/22/2022] Open
Abstract
Inositol 1,4,5'-triphosphate receptor II (IP(3)RII) calcium channel expression is increased in both hypertrophic failing human myocardium and experimentally induced models of the disease. The ectopic calcium released from these receptors induces pro-hypertrophic gene expression and may promote arrhythmias. Here, we show that IP(3)RII expression was constitutively restrained by the muscle-specific miRNA, miR-133a. During the hypertrophic response to pressure overload or neurohormonal stimuli, miR-133a down-regulation permitted IP(3)RII levels to increase, instigating pro-hypertrophic calcium signaling and concomitant pathological remodeling. Using a combination of in vivo and in vitro approaches, we demonstrated that IP(3)-induced calcium release (IICR) initiated the hypertrophy-associated decrease in miR-133a. In this manner, hypertrophic stimuli that engage IICR set a feed-forward mechanism in motion whereby IICR decreased miR-133a expression, further augmenting IP(3)RII levels and therefore pro-hypertrophic calcium release. Consequently, IICR can be considered as both an initiating event and a driving force for pathological remodeling.
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Affiliation(s)
- Faye M. Drawnel
- Babraham Institute, Babraham, Cambridge CB22 3AT, England, UK
| | - Dagmar Wachten
- Babraham Institute, Babraham, Cambridge CB22 3AT, England, UK
- Department of Molecular Sensory Systems, Center of Advanced European Studies and Research, 53175 Bonn, Germany
| | - Jeffery D. Molkentin
- Department of Pediatrics, University of Cincinnati, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229
| | - Marjorie Maillet
- Department of Pediatrics, University of Cincinnati, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229
| | - Jan Magnus Aronsen
- Institute for Experimental Medical Research, Faculty of Medicine, Oslo University Hospital, 0407 Oslo, Norway
- Bjørknes College, 0456 Oslo, Norway
| | - Fredrik Swift
- Institute for Experimental Medical Research, Faculty of Medicine, Oslo University Hospital, 0407 Oslo, Norway
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Faculty of Medicine, Oslo University Hospital, 0407 Oslo, Norway
| | - Ning Liu
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX 75390
| | - Daniele Catalucci
- Humanitas Clinical and Research Center, 20089 Rozzano, Milan, Italy
- Institute of Genetic and Biomedical Research, Milan Section, National Research Council, 20138 Milan, Italy
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Wako, Saitama 531-0198, Japan
| | - Chihiro Hisatsune
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Wako, Saitama 531-0198, Japan
| | | | | | | | - H. Llewelyn Roderick
- Babraham Institute, Babraham, Cambridge CB22 3AT, England, UK
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, England, UK
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71
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Increased mechanically-induced ectopy in the hypertrophied heart. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:331-9. [DOI: 10.1016/j.pbiomolbio.2012.07.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Accepted: 07/11/2012] [Indexed: 02/04/2023]
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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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73
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Yi M, Weaver D, Eisner V, Várnai P, Hunyady L, Ma J, Csordás G, Hajnóczky G. Switch from ER-mitochondrial to SR-mitochondrial calcium coupling during muscle differentiation. Cell Calcium 2012; 52:355-65. [PMID: 22784666 DOI: 10.1016/j.ceca.2012.05.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 05/25/2012] [Accepted: 05/28/2012] [Indexed: 11/26/2022]
Abstract
Emerging evidence indicates that mitochondria are locally coupled to endoplasmic reticulum (ER) Ca2+ release in myoblasts and to sarcoplasmic reticulum (SR) Ca2+ release in differentiated muscle fibers in order to regulate cytoplasmic calcium dynamics and match metabolism with cell activity. However, the mechanism of the developmental transition from ER to SR coupling remains unclear. We have studied mitochondrial sensing of IP3 receptor (IP3R)- and ryanodine receptor (RyR)-mediated Ca2+ signals in H9c2 myoblasts and differentiating myotubes, as well as the attendant changes in mitochondrial morphology. Mitochondria in myoblasts were largely elongated, luminally connected and relatively few in number, whereas the myotubes were densely packed with globular mitochondria that displayed limited luminal continuity. Vasopressin, an IP3-linked agonist, evoked a large cytoplasmic Ca2+ ([Ca2+]c) increase in myoblasts, whereas it elicited a smaller response in myotubes. Conversely, RyR-mediated Ca2+ release induced by caffeine, was not observed in myoblasts, but triggered a large [Ca2+]c signal in myotubes. Both the IP3R and the RyR-mediated [Ca2+]c rise was closely associated with a mitochondrial matrix Ca2+ ([Ca2+]m) signal. Every myotube that showed a [Ca2+]c spike also displayed a [Ca2+]m response. Addition of IP3 to permeabilized myoblasts and caffeine to permeabilized myotubes also resulted in a rapid [Ca2+]m rise, indicating that Ca2+ was delivered via local coupling of the ER/SR and mitochondria. Thus, as RyRs are expressed during muscle differentiation, the local connection between RyR and mitochondrial Ca2+ uptake sites also appears. When RyR1 was exogenously introduced to myoblasts by overexpression, the [Ca2+]m signal appeared together with the [Ca2+]c signal, however the mitochondrial morphology remained unchanged. Thus, RyR expression alone is sufficient to induce the steps essential for their alignment with mitochondrial Ca2+ uptake sites, whereas the mitochondrial proliferation and reshaping utilize either downstream or alternative pathways.
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Affiliation(s)
- Muqing Yi
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
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74
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Nuclear inositol 1,4,5-trisphosphate is a necessary and conserved signal for the induction of both pathological and physiological cardiomyocyte hypertrophy. J Mol Cell Cardiol 2012; 53:475-86. [PMID: 22766271 DOI: 10.1016/j.yjmcc.2012.06.017] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 06/20/2012] [Accepted: 06/21/2012] [Indexed: 01/08/2023]
Abstract
It is well established that inositol 1,4,5-trisphosphate (IP3) dependent Ca(2+) signaling plays a crucial role in cardiomyocyte hypertrophy. However, it is not yet known whether nuclear IP3 represents a Ca(2+) mobilizing pathway involved in this process. The goal of the current work was to investigate the specific role of nuclear IP3 in cardiomyocyte hypertrophic response. In this work, we used an adenovirus construct that selectively buffers IP3 in the nuclear region of neonatal cardiomyocytes. We showed for the first time that nuclear IP3 mediates endothelin-1 (ET-1) induced hypertrophy. We also found that both calcineurin (Cn)/nuclear factor of activated T Cells (NFAT) and histone deacetylase-5 (HDAC5) pathways require nuclear IP3 to mediate pathological cardiomyocyte growth. Additionally, we found that nuclear IP3 buffering inhibited insulin-like growth factor-1 (IGF-1) induced hypertrophy and prevented reexpression of fetal gene program. Together, these results demonstrated that nuclear IP3 is an essential and a conserved signal for both pathological and physiological forms of cardiomyocyte hypertrophy.
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Cherry EM, Fenton FH, Gilmour RF. Mechanisms of ventricular arrhythmias: a dynamical systems-based perspective. Am J Physiol Heart Circ Physiol 2012; 302:H2451-63. [PMID: 22467299 PMCID: PMC3378269 DOI: 10.1152/ajpheart.00770.2011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 03/26/2012] [Indexed: 01/23/2023]
Abstract
Defining the cellular electrophysiological mechanisms for ventricular tachyarrhythmias is difficult, given the wide array of potential mechanisms, ranging from abnormal automaticity to various types of reentry and kk activity. The degree of difficulty is increased further by the fact that any particular mechanism may be influenced by the evolving ionic and anatomic environments associated with many forms of heart disease. Consequently, static measures of a single electrophysiological characteristic are unlikely to be useful in establishing mechanisms. Rather, the dynamics of the electrophysiological triggers and substrates that predispose to arrhythmia development need to be considered. Moreover, the dynamics need to be considered in the context of a system, one that displays certain predictable behaviors, but also one that may contain seemingly stochastic elements. It also is essential to recognize that even the predictable behaviors of this complex nonlinear system are subject to small changes in the state of the system at any given time. Here we briefly review some of the short-, medium-, and long-term alterations of the electrophysiological substrate that accompany myocardial disease and their potential impact on the initiation and maintenance of ventricular arrhythmias. We also provide examples of cases in which small changes in the electrophysiological substrate can result in rather large differences in arrhythmia outcome. These results suggest that an interrogation of cardiac electrical dynamics is required to provide a meaningful assessment of the immediate risk for arrhythmia development and for evaluating the effects of putative antiarrhythmic interventions.
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Affiliation(s)
- Elizabeth M Cherry
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401, USA
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76
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García-Rúa V, Otero MF, Lear PV, Rodríguez-Penas D, Feijóo-Bandín S, Noguera-Moreno T, Calaza M, Álvarez-Barredo M, Mosquera-Leal A, Parrington J, Brugada J, Portolés M, Rivera M, González-Juanatey JR, Lago F. Increased expression of fatty-acid and calcium metabolism genes in failing human heart. PLoS One 2012; 7:e37505. [PMID: 22701570 PMCID: PMC3368932 DOI: 10.1371/journal.pone.0037505] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Accepted: 04/19/2012] [Indexed: 01/08/2023] Open
Abstract
Background Heart failure (HF) involves alterations in metabolism, but little is known about cardiomyopathy-(CM)-specific or diabetes-independent alterations in gene expression of proteins involved in fatty-acid (FA) uptake and oxidation or in calcium-(Ca2+)-handling in the human heart. Methods RT-qPCR was used to quantify mRNA expression and immunoblotting to confirm protein expression in left-ventricular myocardium from patients with HF (n = 36) without diabetes mellitus of ischaemic (ICM, n = 16) or dilated (DCM, n = 20) cardiomyopathy aetiology, and non-diseased donors (CTL, n = 6). Results Significant increases in mRNA of genes regulating FA uptake (CD36) and intracellular transport (Heart-FA-Binding Protein (HFABP)) were observed in HF patients vs CTL. Significance was maintained in DCM and confirmed at protein level, but not in ICM. mRNA was higher in DCM than ICM for peroxisome-proliferator-activated-receptor-alpha (PPARA), PPAR-gamma coactivator-1-alpha (PGC1A) and CD36, and confirmed at the protein level for PPARA and CD36. Transcript and protein expression of Ca2+-handling genes (Two-Pore-Channel 1 (TPCN1), Two-Pore-Channel 2 (TPCN2), and Inositol 1,4,5-triphosphate Receptor type-1 (IP3R1)) increased in HF patients relative to CTL. Increases remained significant for TPCN2 in all groups but for TPCN1 only in DCM. There were correlations between FA metabolism and Ca2+-handling genes expression. In ICM there were six correlations, all distinct from those found in CTL. In DCM there were also six (all also different from those found in CTL): three were common to and three distinct from ICM. Conclusion DCM-specific increases were found in expression of several genes that regulate FA metabolism, which might help in the design of aetiology-specific metabolic therapies in HF. Ca2+-handling genes TPCN1 and TPCN2 also showed increased expression in HF, while HF- and CM-specific positive correlations were found among several FA and Ca2+-handling genes.
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Affiliation(s)
- Vanessa García-Rúa
- Laboratory of Cellular and Molecular Cardiology, Santiago Institute of Biomedical Research (IDIS), University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
| | - Manuel Francisco Otero
- Laboratory of Cellular and Molecular Cardiology, Santiago Institute of Biomedical Research (IDIS), University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
- Department of Clinical Chemistry, University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
| | - Pamela Virginia Lear
- Laboratory of Cellular and Molecular Cardiology, Santiago Institute of Biomedical Research (IDIS), University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
| | - Diego Rodríguez-Penas
- Laboratory of Cellular and Molecular Cardiology, Santiago Institute of Biomedical Research (IDIS), University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
| | - Sandra Feijóo-Bandín
- Laboratory of Cellular and Molecular Cardiology, Santiago Institute of Biomedical Research (IDIS), University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
| | - Teresa Noguera-Moreno
- Unit of Biostatistical Research, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Manuel Calaza
- Laboratory 10, Santiago Institute of Biomedical Research (IDIS), University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
| | - María Álvarez-Barredo
- Department of Cardiology, University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
| | - Ana Mosquera-Leal
- Laboratory of Cellular and Molecular Cardiology, Santiago Institute of Biomedical Research (IDIS), University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
| | - John Parrington
- Department of Pharmacology, Oxford University, Oxford, United Kingdom
| | - Josep Brugada
- Cardiology Department, Thorax Institute, Hospital Clinic, Barcelona, Spain
| | | | | | - José Ramón González-Juanatey
- Laboratory of Cellular and Molecular Cardiology, Santiago Institute of Biomedical Research (IDIS), University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
- Department of Cardiology, University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
| | - Francisca Lago
- Laboratory of Cellular and Molecular Cardiology, Santiago Institute of Biomedical Research (IDIS), University of Santiago de Compostela Clinical Hospital (CHUS), Santiago de Compostela, Spain
- * E-mail:
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77
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Electrical Remodeling in Dyssynchrony and Resynchronization. J Cardiovasc Transl Res 2012; 5:170-9. [DOI: 10.1007/s12265-012-9348-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2011] [Accepted: 01/10/2012] [Indexed: 12/31/2022]
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78
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Li D, Lee CW, Buckler K, Parekh A, Herring N, Paterson DJ. Abnormal intracellular calcium homeostasis in sympathetic neurons from young prehypertensive rats. Hypertension 2012; 59:642-9. [PMID: 22252398 DOI: 10.1161/hypertensionaha.111.186460] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Hypertension is associated with cardiac noradrenergic hyperactivity, although it is not clear whether this precedes or follows the development of hypertension itself. We hypothesized that Ca(2+) homeostasis in postganglionic sympathetic neurons is impaired in spontaneously hypertensive rats (SHRs) and may occur before the development of hypertension. The depolarization-induced rise in intracellular free calcium concentration ([Ca(2+)](i); measured using fura-2-acetoxymethyl ester) was significantly larger in cultured sympathetic neurons from prehypertensive SHRs than in age matched normotensive Wistar-Kyoto rats. The decay of the [Ca(2+)](i) transient was also faster in SHRs. The endoplasmic reticulum Ca(2+) content and caffeine-induced [Ca(2+)](i) amplitude were significantly greater in the young SHRs. Lower protein levels of phospholamban and more copies of ryanodine receptor mRNA were also observed in the young SHRs. Depleting the endoplasmic reticulum Ca(2+) store did not alter the difference of the evoked [Ca(2+)](i) transient and decay time between young SHRs and Wistar-Kyoto rats. However, removing mitochondrial Ca(2+) buffering abolished these differences. A lower mitochondrial membrane potential was also observed in young SHR sympathetic neurons. This resulted in impaired mitochondrial Ca(2+) uptake and release, which might partly be responsible for the increased [Ca(2+)](i) transient and faster decay in SHR sympathetic neurons. This Ca(2+) phenotype seen in early development in cardiac stellate and superior cervical ganglion neurons may contribute to the sympathetic hyperresponsiveness that precedes the onset of hypertension.
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Affiliation(s)
- Dan Li
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy, and Genetics, Oxford, UK.
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79
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Stokke M, Rivelsrud F, Sjaastad I, Sejersted O, Swift F. Fra global til lokal - ny forståelse av den elektromekaniske koblingen i hjertet. TIDSSKRIFT FOR DEN NORSKE LEGEFORENING 2012; 132:1457-60. [DOI: 10.4045/tidsskr.11.1353] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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80
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Fearnley CJ, Roderick HL, Bootman MD. Calcium signaling in cardiac myocytes. Cold Spring Harb Perspect Biol 2011; 3:a004242. [PMID: 21875987 DOI: 10.1101/cshperspect.a004242] [Citation(s) in RCA: 186] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Calcium (Ca(2+)) is a critical regulator of cardiac myocyte function. Principally, Ca(2+) is the link between the electrical signals that pervade the heart and contraction of the myocytes to propel blood. In addition, Ca(2+) controls numerous other myocyte activities, including gene transcription. Cardiac Ca(2+) signaling essentially relies on a few critical molecular players--ryanodine receptors, voltage-operated Ca(2+) channels, and Ca(2+) pumps/transporters. These moieties are responsible for generating Ca(2+) signals upon cellular depolarization, recovery of Ca(2+) signals following cellular contraction, and setting basal conditions. Whereas these are the central players underlying cardiac Ca(2+) fluxes, networks of signaling mechanisms and accessory proteins impart complex regulation on cardiac Ca(2+) signals. Subtle changes in components of the cardiac Ca(2+) signaling machinery, albeit through mutation, disease, or chronic alteration of hemodynamic demand, can have profound consequences for the function and phenotype of myocytes. Here, we discuss mechanisms underlying Ca(2+) signaling in ventricular and atrial myocytes. In particular, we describe the roles and regulation of key participants involved in Ca(2+) signal generation and reversal.
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Affiliation(s)
- Claire J Fearnley
- Laboratory of Signalling and Cell Fate, The Babraham Institute, Babraham, Cambridge CB22 3AT, United Kingdom
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81
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Pereira L, Ruiz-Hurtado G, Morel E, Laurent AC, Métrich M, Domínguez-Rodríguez A, Lauton-Santos S, Lucas A, Benitah JP, Bers DM, Lezoualc'h F, Gómez AM. Epac enhances excitation-transcription coupling in cardiac myocytes. J Mol Cell Cardiol 2011; 52:283-91. [PMID: 22056318 DOI: 10.1016/j.yjmcc.2011.10.016] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Accepted: 10/19/2011] [Indexed: 12/28/2022]
Abstract
Epac is a guanine nucleotide exchange protein that is directly activated by cAMP, but whose cardiac cellular functions remain unclear. It is important to understand cardiac Epac signaling, because it is activated in parallel to classical cAMP-dependent signaling via protein kinase A. In addition to activating contraction, Ca(2+) is a key cardiac transcription regulator (excitation-transcription coupling). It is unknown how myocyte Ca(2+) signals are decoded in cardiac myocytes to control nuclear transcription. We examine Epac actions on cytosolic ([Ca(2+)](i)) and intranuclear ([Ca(2+)](n)) Ca(2+) homeostasis, focusing on whether Epac alters [Ca(2+)](n) and activates a prohypertrophic program in cardiomyocytes. Adult rat cardiomyocytes, loaded with fluo-3 were viewed by confocal microscopy during electrical field stimulation at 1Hz. Acute Epac activation by 8-pCPT increased Ca(2+) sparks and diastolic [Ca(2+)](i), but decreased systolic [Ca(2+)](i). The effects on diastolic [Ca(2+)](i) and Ca(2+) spark frequency were dependent on phospholipase C (PLC), inositol 1,4,5 triphosphate receptor (IP(3)R) and CaMKII activation. Interestingly, Epac preferentially increased [Ca(2+)](n) during both diastole and systole, correlating with the perinuclear expression pattern of Epac. Moreover, Epac activation induced histone deacetylase 5 (HDAC5) nuclear export, with consequent activation of the prohypertrophic transcription factor MEF2. These data provide the first evidence that the cAMP-binding protein Epac modulates cardiac nuclear Ca(2+) signaling by increasing [Ca(2+)](n) through PLC, IP(3)R and CaMKII activation, and initiates a prohypertrophic program via HDAC5 nuclear export and subsequent activation of the transcription factor MEF2.
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Affiliation(s)
- Laetitia Pereira
- Inserm, U637, Université de Montpellier 1, Université de Montpellier 2, France
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82
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Nakamura TY, Jeromin A, Mikoshiba K, Wakabayashi S. Neuronal Calcium Sensor-1 Promotes Immature Heart Function and Hypertrophy by Enhancing Ca
2+
Signals. Circ Res 2011; 109:512-23. [DOI: 10.1161/circresaha.111.248864] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rationale:
Neuronal calcium sensor-1 (NCS-1) regulates various neuronal functions. Although it is expressed in the heart, very little is known about its cardiac functions.
Objective:
This study aimed to identify the physiological and pathological roles of NCS-1 in the heart.
Methods and Results:
We characterized the cardiac functions of knockout mice (
Ncs1
−/−
) and identified NCS-1 as a novel regulator of cardiac Ca
2+
signaling, specifically in immature and hypertrophic hearts. NCS-1 was highly expressed in young hearts, and its deletion decreased survival and contractile function in young mice. Intracellular Ca
2+
levels and sarcoplasmic reticulum Ca
2+
content were significantly lower in
Ncs1
−/−
myocytes than in wild-type cells. This was due to reduced Ca
2+
/calmodulin-dependent protein kinase II (CaMKII) activity in
Ncs1
−/−
myocytes, which led to reduced sarcoplasmic reticulum Ca
2+
uptake and release. NCS-1 physically and functionally interacted with inositol 1,4,5-trisphosphate receptors (IP
3
Rs) in the heart. In addition, IP
3
R stimulation resulted in phosphorylation of CaMKII-δ, which was enhanced by NCS-1 overexpression. These results suggest that a functional link exists between NCS-1, IP
3
R function, and CaMKII activation that may affect global Ca
2+
signals in the immature heart. Furthermore, NCS-1 was upregulated in hypertrophic hearts, and hormone-induced hypertrophy was largely prevented in
Ncs1
−/−
hearts. Inhibitors of IP
3
Rs, CaMKII, and calcineurin all prevented NCS-1–induced hypertrophy, which suggests the involvement of these pathways.
Conclusions:
NCS-1 is an important regulator of immature heart function and hypertrophy, and it functions in part by promoting IP
3
R function, followed by CaMKII-dependent signal activation.
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Affiliation(s)
- Tomoe Y. Nakamura
- From the Department of Molecular Physiology (T.Y.N., S.W.), National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan; Banyan Biomarkers, Inc (A.J.), Alachua, FL; and Laboratory for Developmental Neurobiology (K.M.), RIKEN Brain Science Institute, Saitama, Japan
| | - Andreas Jeromin
- From the Department of Molecular Physiology (T.Y.N., S.W.), National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan; Banyan Biomarkers, Inc (A.J.), Alachua, FL; and Laboratory for Developmental Neurobiology (K.M.), RIKEN Brain Science Institute, Saitama, Japan
| | - Katsuhiko Mikoshiba
- From the Department of Molecular Physiology (T.Y.N., S.W.), National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan; Banyan Biomarkers, Inc (A.J.), Alachua, FL; and Laboratory for Developmental Neurobiology (K.M.), RIKEN Brain Science Institute, Saitama, Japan
| | - Shigeo Wakabayashi
- From the Department of Molecular Physiology (T.Y.N., S.W.), National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan; Banyan Biomarkers, Inc (A.J.), Alachua, FL; and Laboratory for Developmental Neurobiology (K.M.), RIKEN Brain Science Institute, Saitama, Japan
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83
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Della-Morte D, Beecham A, Rundek T, Wang L, McClendon MS, Slifer S, Blanton SH, Di Tullio MR, Sacco RL. A follow-up study for left ventricular mass on chromosome 12p11 identifies potential candidate genes. BMC MEDICAL GENETICS 2011; 12:100. [PMID: 21791083 PMCID: PMC3199748 DOI: 10.1186/1471-2350-12-100] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 07/26/2011] [Indexed: 11/14/2022]
Abstract
Background Left ventricular mass (LVM) is an important risk factor for cardiovascular disease. Previously we found evidence for linkage to chromosome 12p11 in Dominican families, with a significant increase in a subset of families with high average waist circumference (WC). In the present study, we use association analysis to further study the genetic effect on LVM. Methods Association analysis with LVM was done in the one LOD critical region of the linkage peak in an independent sample of 897 Caribbean Hispanics. Genotype data were available on 7085 SNPs from 23 to 53 MB on chromosome 12p11. Adjustment was made for vascular risk factors and population substructure using an additive genetic model. Subset analysis by WC was performed to test for a difference in genetic effects between the high and low WC subsets. Results In the overall analysis, the most significant association was found to rs10743465, downstream of the SOX5 gene (p = 1.27E-05). Also, 19 additional SNPs had nominal p < 0.001. In the subset analysis, the most significant difference in genetic effect between those with high and low WC occurred with rs1157480 (p = 1.37E-04 for the difference in β coefficients), located upstream of TMTC1. Twelve additional SNPs in or near 6 genes had p < 0.001. Conclusions The current study supports previously identified evidence by linkage for a genetic effect on LVM on chromosome 12p11 using association analysis in population-based Caribbean Hispanic cohort. SOX5 may play an important role in the regulation of LVM. An interaction of TMTC1 with abdominal obesity may contribute to phenotypic variation of LVM.
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Affiliation(s)
- David Della-Morte
- Department of Neurology, Evelyn F. McKnight Brain Institute, Miller School of Medicine, University of Miami, Miami, FL, USA
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84
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Logantha SJRJ, Cruickshank SF, Rowan EG, Drummond RM. Spontaneous and electrically evoked Ca2+ transients in cardiomyocytes of the rat pulmonary vein. Cell Calcium 2011; 48:150-60. [PMID: 20817251 DOI: 10.1016/j.ceca.2010.08.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 08/02/2010] [Accepted: 08/04/2010] [Indexed: 10/19/2022]
Abstract
The pulmonary vein is surrounded by an external sleeve of cardiomyocytes that are widely recognised to play an important role in atrial fibrillation. While intracellular Ca(2+) is thought to influence the electrical activity of cardiomyocytes, there have been relatively few studies examining Ca(2+) signalling in these cells. Therefore, using fluo-4 and fluorescence imaging microscopy, we have investigated Ca(2+) signalling in an intact section of the rat pulmonary vein. Under resting conditions cardiomyocytes displayed spontaneous Ca(2+) transients, which were variable in amplitude and had a frequency of 1.6±0.03Hz. The Ca(2+) transients were asynchronous amongst neighbouring cardiomyocytes and tended to propagate throughout the cell as a wave. Removing extracellular Ca(2+) produced a slight reduction in the amplitude and frequency of the spontaneous Ca(2+) transients; however, ryanodine (20μM) had a much greater effect on the amplitude and reduced the frequency by 94±2%. Blocking IP(3) receptors with 2-aminoethoxydiphenyl borate (20μM) also reduced the amplitude and frequency (by 73±11%) of these events, indicating the importance of Ca(2+) release from the SR. Electrical field stimulation of the pulmonary vein produced Ca(2+) transients in cardiomyocytes that were significantly reduced by either voltage-gated Ca(2+) channel blockers or ryanodine.
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Affiliation(s)
- Sunil Jit R J Logantha
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
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85
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Unraveling the secrets of a double life: contractile versus signaling Ca2+ in a cardiac myocyte. J Mol Cell Cardiol 2011; 52:317-22. [PMID: 21600216 DOI: 10.1016/j.yjmcc.2011.05.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2011] [Revised: 04/27/2011] [Accepted: 05/03/2011] [Indexed: 11/21/2022]
Abstract
No other inorganic molecule known in biology is considered as versatile as Ca(2+). In a vast majority of cell types, Ca(2+) acts as a universal second messenger underlying critical cellular processes varying from gene transcription to cell death. Although the role of Ca(2+) in myocyte contraction has been known for over a century, it was only more recently that this divalent cation has been implicated in mediating reactive signal transduction to promote cardiac hypertrophy. However, it remains unclear how Ca(2+)-dependent signaling pathways are regulated/activated in a cardiac myocyte given the prevailing conditions throughout the cytosol where Ca(2+) concentration oscillates between 100 nM and upwards of 1-2 μM during each contractile cycle. In this review we will examine three hypotheses put forward to explain how Ca(2+) might still function as a hypertrophic signaling molecule in cardiac myocytes and discuss the current literature that supports each of these views. This article is part of a special issue entitled "Local Signaling in Myocytes."
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86
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Bootman MD, Smyrnias I, Thul R, Coombes S, Roderick HL. Atrial cardiomyocyte calcium signalling. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:922-34. [DOI: 10.1016/j.bbamcr.2011.01.030] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 01/21/2011] [Accepted: 01/25/2011] [Indexed: 11/25/2022]
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87
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Cartwright EJ, Mohamed T, Oceandy D, Neyses L. Calcium signaling dysfunction in heart disease. Biofactors 2011; 37:175-81. [PMID: 21674639 DOI: 10.1002/biof.149] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 12/30/2010] [Indexed: 11/09/2022]
Abstract
In the heart, Ca(2+) is crucial for the regulation of contraction and intracellular signaling, processes, which are vital to the functioning of the healthy heart. Ca(2+) -activated signaling pathways must function against a background of large, rapid, and tightly regulated changes in intracellular free Ca(2+) concentrations during each contraction and relaxation cycle. This review highlights a number of proteins that regulate signaling Ca(2+) in both normal and pathological conditions including cardiac hypertrophy and heart failure, and discusses how these pathways are not regulated by the marked elevation in free intracellular calcium ([Ca(2+) ](i)) during contraction but require smaller sustained increases in Ca(2+) concentration. In addition, we present published evidence that the pool of Ca(2+) that regulates signaling is compartmentalized into distinct cellular microdomains and is thus distinct from that regulating contraction.
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Affiliation(s)
- Elizabeth J Cartwright
- Cardiovascular Medicine Research Group, Manchester Academic Health Science Centre, University of Manchester, UK.
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88
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Dorenkamp M, Breitwieser C, Morguet AJ, Seegers J, Behrens S, Zabel M. T-wave alternans testing in pacemaker patients: comparison of pacing modes and long-term prognostic relevance. Pacing Clin Electrophysiol 2011; 34:1054-62. [PMID: 21501180 DOI: 10.1111/j.1540-8159.2011.03101.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND T-wave alternans (TWA) is a useful method for identifying patients who are at risk for sudden cardiac death. We aimed to determine the effects of different pacing modes on test results and long-term prognostic relevance of TWA in patients following a dual-chamber (DDD) pacemaker implantation. METHODS Sixty-three patients (mean age 68 ± 13 years) with structural heart disease and recently implanted DDD pacemakers were enrolled. Left ventricular (LV) function was normal or moderately impaired (mean LV ejection fraction 61 ± 13%). All patients underwent sequential TWA testing using atrial and ventricular pacing. RESULTS During atrial pacing requiring physiologic conduction to the ventricles, 21% of TWA tests were positive, 43% negative, and 36% indeterminate. When using right ventricular (RV) pacing in the same patients, 19% of tests were positive, 40% negative, and 41% indeterminate. When positive and indeterminate tests were grouped as nonnegative, the concordance between atrial and ventricular pacing was 62% (κ= 0.22). After a mean follow-up of 5.9 ± 1.9 years, 18 (29%) patients had died. Improved survival was predicted by a negative TWA test using atrial pacing (P = 0.028), but not with ventricular pacing (P = 0.722). CONCLUSIONS In patients with dual-chamber pacemakers, there is a low concordance of TWA test results between atrial pacing with intrinsic conduction to the ventricles and apical RV pacing via pacemaker electrode. However, TWA during atrial pacing clearly exerts long-term prognostic relevance in a patient group with preserved LV function and structural heart disease.
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Affiliation(s)
- Marc Dorenkamp
- Department of Cardiology and Pneumology, Heart Center, Georg-August-University of Göttingen, Göttingen, Germany.
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89
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Landstrom AP, Kellen CA, Dixit SS, van Oort RJ, Garbino A, Weisleder N, Ma J, Wehrens XHT, Ackerman MJ. Junctophilin-2 expression silencing causes cardiocyte hypertrophy and abnormal intracellular calcium-handling. Circ Heart Fail 2011; 4:214-23. [PMID: 21216834 DOI: 10.1161/circheartfailure.110.958694] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Junctophilin-2 (JPH2), a protein expressed in the junctional membrane complex, is necessary for proper intracellular calcium (Ca(2+)) signaling in cardiac myocytes. Downregulation of JPH2 expression in a model of cardiac hypertrophy was recently associated with defective coupling between plasmalemmal L-type Ca(2+) channels and sarcoplasmic reticular ryanodine receptors. However, it remains unclear whether JPH2 expression is altered in patients with hypertrophic cardiomyopathy (HCM). In addition, the effects of downregulation of JPH2 expression on intracellular Ca(2+) handling are presently poorly understood. We sought to determine whether loss of JPH2 expression is noted among patients with HCM and whether expression silencing might perturb Ca(2+) handling in a prohypertrophic manner. METHODS AND RESULTS JPH2 expression was reduced in flash-frozen human cardiac tissue procured from patients with HCM compared with ostensibly healthy traumatic death victims. Partial silencing of JPH2 expression in HL-1 cells by a small interfering RNA probe targeted to murine JPH2 mRNA (shJPH2) resulted in myocyte hypertrophy and increased expression of known markers of cardiac hypertrophy. Whereas expression levels of major Ca(2+)-handling proteins were unchanged, shJPH2 cells demonstrated depressed maximal Ca(2+) transient amplitudes that were insensitive to L-type Ca(2+) channel activation with JPH2 knockdown. Further, reduced caffeine-triggered sarcoplasmic reticulum store Ca(2+) levels were observed with potentially increased total Ca(2+) stores. Spontaneous Ca(2+) oscillations were elicited at a higher extracellular [Ca(2+)] and with decreased frequency in JPH2 knockdown cells. CONCLUSIONS Our results show that JPH2 levels are reduced in patients with HCM. Reduced JPH2 expression results in reduced excitation-contraction coupling gain as well as altered Ca(2+) homeostasis, which may be associated with prohypertrophic remodeling.
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Affiliation(s)
- Andrew P Landstrom
- Department of Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN 55905, USA
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90
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Nakayama H, Bodi I, Maillet M, DeSantiago J, Domeier TL, Mikoshiba K, Lorenz JN, Blatter LA, Bers DM, Molkentin JD. The IP3 receptor regulates cardiac hypertrophy in response to select stimuli. Circ Res 2010; 107:659-66. [PMID: 20616315 DOI: 10.1161/circresaha.110.220038] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
RATIONALE Inositol 1,4,5-trisphosphate (IP(3)) is a second messenger that regulates intracellular Ca(2+) release through IP(3) receptors located in the sarco(endo)plasmic reticulum of cardiac myocytes. Many prohypertrophic G protein-coupled receptor (GPCR) signaling events lead to IP(3) liberation, although its importance in transducing the hypertrophic response has not been established in vivo. OBJECTIVE Here, we generated conditional, heart-specific transgenic mice with both gain- and loss-of-function for IP(3) receptor signaling to examine its hypertrophic growth effects following pathological and physiological stimulation. METHODS AND RESULTS Overexpression of the mouse type-2 IP(3) receptor (IP(3)R2) in the heart generated mild baseline cardiac hypertrophy at 3 months of age. Isolated myocytes from overexpressing lines showed increased Ca(2+) transients and arrhythmias in response to endothelin-1 stimulation. Although low levels of IP(3)R2 overexpression failed to augment/synergize cardiac hypertrophy following 2 weeks of pressure-overload stimulation, such levels did enhance hypertrophy following 2 weeks of isoproterenol infusion, in response to Galphaq overexpression, and/or in response to exercise stimulation. To inhibit IP(3) signaling in vivo, we generated transgenic mice expressing an IP(3) chelating protein (IP(3)-sponge). IP(3)-sponge transgenic mice abrogated cardiac hypertrophy in response to isoproterenol and angiotensin II infusion but not pressure-overload stimulation. Mechanistically, IP(3)R2-enhanced cardiac hypertrophy following isoproterenol infusion was significantly reduced in the calcineurin-Abeta-null background. CONCLUSION These results indicate that IP(3)-mediated Ca(2+) release plays a central role in regulating cardiac hypertrophy downstream of GPCR signaling, in part, through a calcineurin-dependent mechanism.
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Affiliation(s)
- Hiroyuki Nakayama
- Howard Hughes Medical Institute, Cincinnati Children's Hospital Medical Center, 240 Albert Sabin Way, Cincinnati, OH 45229-3039, USA
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91
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Røsjø H, Husberg C, Dahl MB, Stridsberg M, Sjaastad I, Finsen AV, Carlson CR, Oie E, Omland T, Christensen G. Chromogranin B in heart failure: a putative cardiac biomarker expressed in the failing myocardium. Circ Heart Fail 2010; 3:503-11. [PMID: 20519641 DOI: 10.1161/circheartfailure.109.867747] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Chromogranin B (CgB) is a member of the granin protein family. Because CgB is often colocalized with chromogranin A (CgA), a recently discovered cardiac biomarker, we hypothesized that CgB is regulated during heart failure (HF) development. METHODS AND RESULTS CgB regulation was investigated in patients with chronic HF and in a post-myocardial infarction HF mouse model. Animals were phenotypically characterized by echocardiography and euthanized 1 week after myocardial infarction. CgB mRNA levels were 5.2-fold increased in the noninfarcted part of the left ventricle of HF animals compared with sham-operated animals (P<0.001). CgB mRNA level in HF animals correlated closely with animal lung weight (r=0.74, P=0.04) but not with CgA mRNA levels (r=0.20, P=0.61). CgB protein levels were markedly increased in both the noninfarcted (110%) and the infarcted part of the left ventricle (70%) but unaltered in other tissues investigated. Myocardial CgB immunoreactivity was confined to cardiomyocytes. Norepinephrine, angiotensin II, and transforming growth factor-beta increased CgB gene expression in cardiomyocytes. Circulating CgB levels were increased in HF animals (median levels in HF animals versus sham, 1.23 [interquartile range, 1.03 to 1.93] versus 0.98 [0.90 to 1.04] nmol/L; P=0.003) and in HF patients (HF patients versus control, 1.66 [1.48 to 1.85] versus 1.47 [1.39 to 1.58] nmol/L; P=0.007), with levels increasing in proportion to New York Heart Association functional class (P=0.03 for trend). Circulating CgB levels were only modestly correlated with CgA (r=0.31, P=0.009) and B-type natriuretic peptide levels (r=0.27, P=0.014). CONCLUSIONS CgB production is increased and regulated in proportion to disease severity in the left ventricle and circulation during HF development.
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Affiliation(s)
- Helge Røsjø
- Medical Division and EpiGen, Institute of Clinical Epidemiology and Molecular Biology, Akershus University Hospital, Lørenskog, Norway.
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92
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Xiao J, Liang D, Zhao H, Liu Y, Zhang H, Lu X, Liu Y, Li J, Peng L, Chen YH. 2-Aminoethoxydiphenyl borate, a inositol 1,4,5-triphosphate receptor inhibitor, prevents atrial fibrillation. Exp Biol Med (Maywood) 2010; 235:862-8. [PMID: 20472714 DOI: 10.1258/ebm.2010.009362] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The expression of the inositol 1,4,5-triphosphate receptor (IP3R) is upregulated and the function of IP3R also increases during atrial fibrillation (AF). 2-Aminoethoxydiphenyl borate (2-APB) is a membrane-permeable inhibitor of IP3R. However, the effect of 2-APB on AF is unknown. The aim of the present study is to explore the effects of 2-APB on AF. In vitro rabbit heart models of ischemia-, stretch- and cholinergic agitation-induced AF were developed. Fura-2-acetoxymethyl (Fura-2-AM) and Mg2+-Fura-2-AM were used to monitor alterations of intracellular Ca2+ and ATP, respectively, in HL-1 cells, an atrial muscle cell line, under chemical ischemia or cholinergic agitation. The results showed that inhibition of IP3R significantly reduced the incidence and its probability of being sustained in all three types of AF. IP3R inhibition ameliorated the cytoplasmic Ca2+ overload and energy compromise resulting from chemical ischemia or cholinergic agitation. Thus, IP3R inhibition may be a novel target for AF treatment, and IP3R may be an important molecule in the context of different kinds of AF.
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Affiliation(s)
- Junjie Xiao
- Department of Cardiology, Tongji Hospital, Tongji University School of Medicine, Tongji University, 389 Xin Cun Road, Shanghai, China
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93
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There goes the neighborhood: pathological alterations in T-tubule morphology and consequences for cardiomyocyte Ca2+ handling. J Biomed Biotechnol 2010; 2010:503906. [PMID: 20396394 PMCID: PMC2852607 DOI: 10.1155/2010/503906] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2009] [Accepted: 01/15/2010] [Indexed: 12/19/2022] Open
Abstract
T-tubules are invaginations of the cardiomyocyte membrane into the cell interior which form a tortuous network. T-tubules provide proximity between the electrically excitable cell membrane and the sarcoplasmic reticulum, the main intracellular Ca2+ store. Tight coupling between the rapidly spreading action potential and Ca2+ release units in the SR membrane ensures synchronous Ca2+ release throughout the cardiomyocyte. This is a requirement for rapid and powerful contraction. In recent years, it has become clear that T-tubule structure and composition are altered in several pathological states which may importantly contribute to contractile defects in these conditions. In this review, we describe the “neighborhood” of proteins in the dyadic cleft which locally controls cardiomyocyte Ca2+ homeostasis and how alterations in T-tubule structure and composition may alter this neighborhood during heart failure, atrial fibrillation, and diabetic cardiomyopathy. Based on this evidence, we propose that T-tubules have the potential to serve as novel therapeutic targets.
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94
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Abstract
PURPOSE OF REVIEW We focus on the molecular and cellular basis of excitability, conduction and electrical remodeling in heart failure with dyssynchronous left ventricular contraction (DHF) and its restoration by cardiac resynchronization therapy (CRT) using a canine tachy-pacing heart failure model. RECENT FINDINGS The electrophysiological hallmark of cells and tissues isolated from failing hearts is prolongation of action potential duration (APD) and conduction slowing. In human studies and a number of animal models of heart failure, functional downregulation of K currents and alterations in depolarizing Na and Ca currents and transporters are demonstrated. Alterations in intercellular ion channels and extracellular matrix contribute to heterogeneity of APD and conduction slowing. The changes in cellular and tissue function are regionally heterogeneous, particularly in the DHF. Furthermore, beta-adrenergic signaling and modulation of ionic currents is blunted in heart failure. CRT partially reverses the DHF-induced downregulation of K current and improves Na channel gating. CRT significantly improves Ca homeostasis, especially in lateral myocytes, and restores the DHF-induced blunted beta-adrenergic receptor responsiveness. CRT abbreviates DHF-induced prolongation of APD in the lateral myocytes, reduces the left ventricular regional gradient of APD and suppresses development of early afterdepolarizations. SUMMARY CRT partially restores DHF-induced electrophysiological remodeling, abnormal Ca homeostasis, blunted beta-adrenergic responsiveness, and regional heterogeneity of APD, and thus may suppress ventricular arrhythmias and contribute to the mortality benefit of CRT as well as improving mechanical performance of the heart.
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95
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Aiba T, Tomaselli GF, Shimizu W. Electrophysiological Remodeling in Heart Failure Dyssynchrony vs. Resynchronization. J Arrhythm 2010. [DOI: 10.1016/s1880-4276(10)80011-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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96
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Role of ryanodine receptor subtypes in initiation and formation of calcium sparks in arterial smooth muscle: comparison with striated muscle. J Biomed Biotechnol 2009; 2009:135249. [PMID: 20029633 PMCID: PMC2793424 DOI: 10.1155/2009/135249] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Accepted: 09/22/2009] [Indexed: 11/17/2022] Open
Abstract
Calcium sparks represent local, rapid, and transient calcium release events from a cluster of ryanodine receptors (RyRs) in the sarcoplasmic reticulum. In arterial smooth muscle cells (SMCs), calcium sparks activate calcium-dependent potassium channels causing decrease in the global intracellular [Ca2+] and oppose vasoconstriction. This is in contrast to cardiac and skeletal muscle, where spatial and temporal summation of calcium sparks leads to global increases in intracellular [Ca2+] and myocyte contraction. We summarize the present data on local RyR calcium signaling in arterial SMCs in comparison to striated muscle and muscle-specific differences in coupling between L-type calcium channels and RyRs. Accordingly, arterial SMC Ca(v)1.2 L-type channels regulate intracellular calcium stores content, which in turn modulates calcium efflux though RyRs. Downregulation of RyR2 up to a certain degree is compensated by increased SR calcium content to normalize calcium sparks. This indirect coupling between Ca(v)1.2 and RyR in arterial SMCs is opposite to striated muscle, where triggering of calcium sparks is controlled by rapid and direct cross-talk between Ca(v)1.1/Ca(v)1.2 L-type channels and RyRs. We discuss the role of RyR isoforms in initiation and formation of calcium sparks in SMCs and their possible molecular binding partners and regulators, which differ compared to striated muscle.
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