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Hennis K, Piantoni C, Biel M, Fenske S, Wahl-Schott C. Pacemaker Channels and the Chronotropic Response in Health and Disease. Circ Res 2024; 134:1348-1378. [PMID: 38723033 PMCID: PMC11081487 DOI: 10.1161/circresaha.123.323250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 05/13/2024]
Abstract
Loss or dysregulation of the normally precise control of heart rate via the autonomic nervous system plays a critical role during the development and progression of cardiovascular disease-including ischemic heart disease, heart failure, and arrhythmias. While the clinical significance of regulating changes in heart rate, known as the chronotropic effect, is undeniable, the mechanisms controlling these changes remain not fully understood. Heart rate acceleration and deceleration are mediated by increasing or decreasing the spontaneous firing rate of pacemaker cells in the sinoatrial node. During the transition from rest to activity, sympathetic neurons stimulate these cells by activating β-adrenergic receptors and increasing intracellular cyclic adenosine monophosphate. The same signal transduction pathway is targeted by positive chronotropic drugs such as norepinephrine and dobutamine, which are used in the treatment of cardiogenic shock and severe heart failure. The cyclic adenosine monophosphate-sensitive hyperpolarization-activated current (If) in pacemaker cells is passed by hyperpolarization-activated cyclic nucleotide-gated cation channels and is critical for generating the autonomous heartbeat. In addition, this current has been suggested to play a central role in the chronotropic effect. Recent studies demonstrate that cyclic adenosine monophosphate-dependent regulation of HCN4 (hyperpolarization-activated cyclic nucleotide-gated cation channel isoform 4) acts to stabilize the heart rate, particularly during rapid rate transitions induced by the autonomic nervous system. The mechanism is based on creating a balance between firing and recently discovered nonfiring pacemaker cells in the sinoatrial node. In this way, hyperpolarization-activated cyclic nucleotide-gated cation channels may protect the heart from sinoatrial node dysfunction, secondary arrhythmia of the atria, and potentially fatal tachyarrhythmia of the ventricles. Here, we review the latest findings on sinoatrial node automaticity and discuss the physiological and pathophysiological role of HCN pacemaker channels in the chronotropic response and beyond.
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Affiliation(s)
- Konstantin Hennis
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
| | - Chiara Piantoni
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
| | - Martin Biel
- Department of Pharmacy, Center for Drug Research (M.B., S.F.), Ludwig-Maximilians-Universität München, Germany
- German Centre for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Germany (M.B., S.F.)
| | - Stefanie Fenske
- Department of Pharmacy, Center for Drug Research (M.B., S.F.), Ludwig-Maximilians-Universität München, Germany
- German Centre for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Germany (M.B., S.F.)
| | - Christian Wahl-Schott
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
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2
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Ni M, Li Y, Wei J, Song Z, Wang H, Yao J, Chen YX, Belke D, Estillore JP, Wang R, Vallmitjana A, Benitez R, Hove-Madsen L, Feng W, Chen J, Roston TM, Sanatani S, Lehman A, Chen SRW. Increased Ca 2+ Transient Underlies RyR2-Related Left Ventricular Noncompaction. Circ Res 2023; 133:177-192. [PMID: 37325910 DOI: 10.1161/circresaha.123.322504] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 06/07/2023] [Indexed: 06/17/2023]
Abstract
BACKGROUND A loss-of-function cardiac ryanodine receptor (RyR2) mutation, I4855M+/-, has recently been linked to a new cardiac disorder termed RyR2 Ca2+ release deficiency syndrome (CRDS) as well as left ventricular noncompaction (LVNC). The mechanism by which RyR2 loss-of-function causes CRDS has been extensively studied, but the mechanism underlying RyR2 loss-of-function-associated LVNC is unknown. Here, we determined the impact of a CRDS-LVNC-associated RyR2-I4855M+/- loss-of-function mutation on cardiac structure and function. METHODS We generated a mouse model expressing the CRDS-LVNC-associated RyR2-I4855M+/- mutation. Histological analysis, echocardiography, ECG recording, and intact heart Ca2+ imaging were performed to characterize the structural and functional consequences of the RyR2-I4855M+/- mutation. RESULTS As in humans, RyR2-I4855M+/- mice displayed LVNC characterized by cardiac hypertrabeculation and noncompaction. RyR2-I4855M+/- mice were highly susceptible to electrical stimulation-induced ventricular arrhythmias but protected from stress-induced ventricular arrhythmias. Unexpectedly, the RyR2-I4855M+/- mutation increased the peak Ca2+ transient but did not alter the L-type Ca2+ current, suggesting an increase in Ca2+-induced Ca2+ release gain. The RyR2-I4855M+/- mutation abolished sarcoplasmic reticulum store overload-induced Ca2+ release or Ca2+ leak, elevated sarcoplasmic reticulum Ca2+ load, prolonged Ca2+ transient decay, and elevated end-diastolic Ca2+ level upon rapid pacing. Immunoblotting revealed increased level of phosphorylated CaMKII (Ca2+-calmodulin dependent protein kinases II) but unchanged levels of CaMKII, calcineurin, and other Ca2+ handling proteins in the RyR2-I4855M+/- mutant compared with wild type. CONCLUSIONS The RyR2-I4855M+/- mutant mice represent the first RyR2-associated LVNC animal model that recapitulates the CRDS-LVNC overlapping phenotype in humans. The RyR2-I4855M+/- mutation increases the peak Ca2+ transient by increasing the Ca2+-induced Ca2+ release gain and the end-diastolic Ca2+ level by prolonging Ca2+ transient decay. Our data suggest that the increased peak-systolic and end-diastolic Ca2+ levels may underlie RyR2-associated LVNC.
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Affiliation(s)
- Mingke Ni
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Alberta, Canada (M.N., Y.L., J.W., Z.S., H.W., J.Y., Y.-X.C., D.B., J.P.E., R.W., S.R.W.C.)
| | - Yanhui Li
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Alberta, Canada (M.N., Y.L., J.W., Z.S., H.W., J.Y., Y.-X.C., D.B., J.P.E., R.W., S.R.W.C.)
| | - Jinhong Wei
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Alberta, Canada (M.N., Y.L., J.W., Z.S., H.W., J.Y., Y.-X.C., D.B., J.P.E., R.W., S.R.W.C.)
- School of Medicine, Northwest University, Xi 'an, China (J.W.)
| | - Zhenpeng Song
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Alberta, Canada (M.N., Y.L., J.W., Z.S., H.W., J.Y., Y.-X.C., D.B., J.P.E., R.W., S.R.W.C.)
| | - Hui Wang
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Alberta, Canada (M.N., Y.L., J.W., Z.S., H.W., J.Y., Y.-X.C., D.B., J.P.E., R.W., S.R.W.C.)
| | - Jinjing Yao
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Alberta, Canada (M.N., Y.L., J.W., Z.S., H.W., J.Y., Y.-X.C., D.B., J.P.E., R.W., S.R.W.C.)
| | - Yong-Xiang Chen
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Alberta, Canada (M.N., Y.L., J.W., Z.S., H.W., J.Y., Y.-X.C., D.B., J.P.E., R.W., S.R.W.C.)
| | - Darrell Belke
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Alberta, Canada (M.N., Y.L., J.W., Z.S., H.W., J.Y., Y.-X.C., D.B., J.P.E., R.W., S.R.W.C.)
| | - John Paul Estillore
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Alberta, Canada (M.N., Y.L., J.W., Z.S., H.W., J.Y., Y.-X.C., D.B., J.P.E., R.W., S.R.W.C.)
| | - Ruiwu Wang
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Alberta, Canada (M.N., Y.L., J.W., Z.S., H.W., J.Y., Y.-X.C., D.B., J.P.E., R.W., S.R.W.C.)
| | - Alexander Vallmitjana
- Department of Automatic Control, Universitat Politècnica de Catalunya, Barcelona, Spain (A.V., R.B.)
| | - Raul Benitez
- Department of Automatic Control, Universitat Politècnica de Catalunya, Barcelona, Spain (A.V., R.B.)
- Institut de Recerca Sant Joan de Déu (IRSJD), Barcelona, Spain (R.B.)
| | - Leif Hove-Madsen
- Biomedical Research Institute Barcelona IIBB-CSIC, IIB Sant Pau and CIBERCV, Hospital de Sant Pau, Barcelona, Spain (L.H.-M.)
| | - Wei Feng
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla (W.F., J.C.)
| | - Ju Chen
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla (W.F., J.C.)
| | - Thomas M Roston
- Division of Pediatric Cardiology, Department of Pediatrics (T.M.R., S.S.), University of British Columbia, Vancouver, Canada
| | - Shubhayan Sanatani
- Division of Pediatric Cardiology, Department of Pediatrics (T.M.R., S.S.), University of British Columbia, Vancouver, Canada
| | - Anna Lehman
- Department of Medical Genetics (A.L.), University of British Columbia, Vancouver, Canada
| | - S R Wayne Chen
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Alberta, Canada (M.N., Y.L., J.W., Z.S., H.W., J.Y., Y.-X.C., D.B., J.P.E., R.W., S.R.W.C.)
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3
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Terrar DA. Timing mechanisms to control heart rhythm and initiate arrhythmias: roles for intracellular organelles, signalling pathways and subsarcolemmal Ca 2. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220170. [PMID: 37122228 PMCID: PMC10150226 DOI: 10.1098/rstb.2022.0170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
Rhythms of electrical activity in all regions of the heart can be influenced by a variety of intracellular membrane bound organelles. This is true both for normal pacemaker activity and for abnormal rhythms including those caused by early and delayed afterdepolarizations under pathological conditions. The influence of the sarcoplasmic reticulum (SR) on cardiac electrical activity is widely recognized, but other intracellular organelles including lysosomes and mitochondria also contribute. Intracellular organelles can provide a timing mechanism (such as an SR clock driven by cyclic uptake and release of Ca2+, with an important influence of intraluminal Ca2+), and/or can act as a Ca2+ store involved in signalling mechanisms. Ca2+ plays many diverse roles including carrying electric current, driving electrogenic sodium-calcium exchange (NCX) particularly when Ca2+ is extruded across the surface membrane causing depolarization, and activation of enzymes which target organelles and surface membrane proteins. Heart function is also influenced by Ca2+ mobilizing agents (cADP-ribose, nicotinic acid adenine dinucleotide phosphate and inositol trisphosphate) acting on intracellular organelles. Lysosomal Ca2+ release exerts its effects via calcium/calmodulin-dependent protein kinase II to promote SR Ca2+ uptake, and contributes to arrhythmias resulting from excessive beta-adrenoceptor stimulation. A separate arrhythmogenic mechanism involves lysosomes, mitochondria and SR. Interacting intracellular organelles, therefore, have profound effects on heart rhythms and NCX plays a central role. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Derek A Terrar
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
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4
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Landstrom AP, Yang Q, Sun B, Perelli RM, Bidzimou MT, Zhang Z, Aguilar-Sanchez Y, Alsina KM, Cao S, Reynolds JO, Word TA, van der Sangen NM, Wells Q, Kannankeril PJ, Ludwig A, Kim JJ, Wehrens XH. Reduction in Junctophilin 2 Expression in Cardiac Nodal Tissue Results in Intracellular Calcium-Driven Increase in Nodal Cell Automaticity. Circ Arrhythm Electrophysiol 2023; 16:e010858. [PMID: 36706317 PMCID: PMC9974897 DOI: 10.1161/circep.122.010858] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 01/06/2023] [Indexed: 01/29/2023]
Abstract
BACKGROUND Spontaneously depolarizing nodal cells comprise the pacemaker of the heart. Intracellular calcium (Ca2+) plays a critical role in mediating nodal cell automaticity and understanding this so-called Ca2+ clock is critical to understanding nodal arrhythmias. We previously demonstrated a role for Jph2 (junctophilin 2) in regulating Ca2+-signaling through inhibition of RyR2 (ryanodine receptor 2) Ca2+ leak in cardiac myocytes; however, its role in pacemaker function and nodal arrhythmias remains unknown. We sought to determine whether nodal Jph2 expression silencing causes increased sinoatrial and atrioventricular nodal cell automaticity due to aberrant RyR2 Ca2+ leak. METHODS A tamoxifen-inducible, nodal tissue-specific, knockdown mouse of Jph2 was achieved using a Cre-recombinase-triggered short RNA hairpin directed against Jph2 (Hcn4:shJph2). In vivo cardiac rhythm was monitored by surface ECG, implantable cardiac telemetry, and intracardiac electrophysiology studies. Intracellular Ca2+ imaging was performed using confocal-based line scans of isolated nodal cells loaded with fluorescent Ca2+ reporter Cal-520. Whole cell patch clamp was conducted on isolated nodal cells to determine action potential kinetics and sodium-calcium exchanger function. RESULTS Hcn4:shJph2 mice demonstrated a 40% reduction in nodal Jph2 expression, resting sinus tachycardia, and impaired heart rate response to pharmacologic stress. In vivo intracardiac electrophysiology studies and ex vivo optical mapping demonstrated accelerated junctional rhythm originating from the atrioventricular node. Hcn4:shJph2 nodal cells demonstrated increased and irregular Ca2+ transient generation with increased Ca2+ spark frequency and Ca2+ leak from the sarcoplasmic reticulum. This was associated with increased nodal cell AP firing rate, faster diastolic repolarization rate, and reduced sodium-calcium exchanger activity during repolarized states compared to control. Phenome-wide association studies of the JPH2 locus identified an association with sinoatrial nodal disease and atrioventricular nodal block. CONCLUSIONS Nodal-specific Jph2 knockdown causes increased nodal automaticity through increased Ca2+ leak from intracellular stores. Dysregulated intracellular Ca2+ underlies nodal arrhythmogenesis in this mouse model.
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Affiliation(s)
- Andrew P. Landstrom
- Dept of Pediatrics, Division of Cardiology, Duke Univ School of Medicine, Durham, NC
- Dept of Cell Biology, Duke Univ School of Medicine, Durham, NC
| | - Qixin Yang
- Dept of Pediatrics, Division of Cardiology, Duke Univ School of Medicine, Durham, NC
- Dept of Cardiology, The First Affiliated Hospital, College of Medicine, Zhejiang Univ, Hangzhou, China
| | - Bo Sun
- Dept of Pediatrics, Division of Cardiology, Duke Univ School of Medicine, Durham, NC
| | | | | | - Zhushan Zhang
- Dept of Cell Biology, Duke Univ School of Medicine, Durham, NC
| | - Yuriana Aguilar-Sanchez
- Integrative Molecular & Biomedical Sciences Program, Baylor College of Medicine, Houston, TX
| | - Katherina M. Alsina
- Integrative Molecular & Biomedical Sciences Program, Baylor College of Medicine, Houston, TX
| | - Shuyi Cao
- Dept of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX
| | - Julia O. Reynolds
- Dept of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX
| | - Tarah A. Word
- Dept of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX
| | | | - Quinn Wells
- Depts of Medicine, Pharmacology, and Biomedical Informatics, Vanderbilt Univ School of Medicine, Nashville, TN
| | - Prince J. Kannankeril
- Center for Pediatric Precision Medicine, Dept of Pediatrics, Vanderbilt Univ School of Medicine, Nashville, TN
| | - Andreas Ludwig
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Jeffrey J. Kim
- Dept of Pediatrics, Section of Cardiology, Baylor College of Medicine, Houston, TX
| | - Xander H.T. Wehrens
- Dept of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX
- Dept of Pediatrics, Section of Cardiology, Baylor College of Medicine, Houston, TX
- Depts of Neuroscience & Center for Space Medicine and the Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX
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5
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Demydenko K, Ekhteraei-Tousi S, Roderick HL. Inositol 1,4,5-trisphosphate receptors in cardiomyocyte physiology and disease. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210319. [PMID: 36189803 PMCID: PMC9527928 DOI: 10.1098/rstb.2021.0319] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The contraction of cardiac muscle underlying the pumping action of the heart is mediated by the process of excitation-contraction coupling (ECC). While triggered by Ca2+ entry across the sarcolemma during the action potential, it is the release of Ca2+ from the sarcoplasmic reticulum (SR) intracellular Ca2+ store via ryanodine receptors (RyRs) that plays the major role in induction of contraction. Ca2+ also acts as a key intracellular messenger regulating transcription underlying hypertrophic growth. Although Ca2+ release via RyRs is by far the greatest contributor to the generation of Ca2+ transients in the cardiomyocyte, Ca2+ is also released from the SR via inositol 1,4,5-trisphosphate (InsP3) receptors (InsP3Rs). This InsP3-induced Ca2+ release modifies Ca2+ transients during ECC, participates in directing Ca2+ to the mitochondria, and stimulates the transcription of genes underlying hypertrophic growth. Central to these specific actions of InsP3Rs is their localization to responsible signalling microdomains, the dyad, the SR-mitochondrial interface and the nucleus. In this review, the various roles of InsP3R in cardiac (patho)physiology and the mechanisms by which InsP3 signalling selectively influences the different cardiomyocyte cell processes in which it is involved will be presented. This article is part of the theme issue ‘The cardiomyocyte: new revelations on the interplay between architecture and function in growth, health, and disease’.
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Affiliation(s)
- Kateryna Demydenko
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Samaneh Ekhteraei-Tousi
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - H Llewelyn Roderick
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
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6
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Foster DB, Gu JM, Kim EH, Wolfson DW, O’Meally R, Cole RN, Cho HC. Tbx18 Orchestrates Cytostructural Transdifferentiation of Cardiomyocytes to Pacemaker Cells by Recruiting the Epithelial-Mesenchymal Transition Program. J Proteome Res 2022; 21:2277-2292. [PMID: 36006872 PMCID: PMC9552783 DOI: 10.1021/acs.jproteome.2c00133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Indexed: 11/29/2022]
Abstract
Previously, we reported that heterologous expression of an embryonic transcription factor, Tbx18, reprograms ventricular cardiomyocytes into induced pacemaker cells (Tbx18-iPMs), though the key pathways are unknown. Here, we have used a tandem mass tag proteomic approach to characterize the impact of Tbx18 on neonatal rat ventricular myocytes. Tbx18 expression triggered vast proteome remodeling. Tbx18-iPMs exhibited increased expression of known pacemaker ion channels, including Hcn4 and Cx45 as well as upregulation of the mechanosensitive ion channels Piezo1, Trpp2 (PKD2), and TrpM7. Metabolic pathways were broadly downregulated, as were ion channels associated with ventricular excitation-contraction coupling. Tbx18-iPMs also exhibited extensive intracellular cytoskeletal and extracellular matrix remodeling, including 96 differentially expressed proteins associated with the epithelial-to-mesenchymal transition (EMT). RNAseq extended coverage of low abundance transcription factors, revealing upregulation of EMT-inducing Snai1, Snai2, Twist1, Twist2, and Zeb2. Finally, network diffusion mapping of >200 transcriptional regulators indicates EMT and heart development factors occupy adjacent network neighborhoods downstream of Tbx18 but upstream of metabolic control factors. In conclusion, transdifferentiation of cardiac myocytes into pacemaker cells entails massive electrogenic, metabolic, and cytostructural remodeling. Structural changes exhibit hallmarks of the EMT. The results aid ongoing efforts to maximize the yield and phenotypic stability of engineered biological pacemakers.
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Affiliation(s)
- D. Brian Foster
- Division
of Cardiology, Department of Medicine, The
Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - Jin-mo Gu
- Department
of Pediatrics, Emory University, Atlanta, Georgia 30322, United States
| | - Elizabeth H. Kim
- Cedars-Sinai
Medical Center, Los Angeles, California 90048, United States
| | - David W. Wolfson
- Wallace
H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia 30332, United States
| | - Robert O’Meally
- Proteomics
Core Facility, The Johns Hopkins University
School of Medicine, Baltimore, Maryland 21205, United States
| | - Robert N. Cole
- Proteomics
Core Facility, The Johns Hopkins University
School of Medicine, Baltimore, Maryland 21205, United States
| | - Hee Cheol Cho
- Department
of Surgery, The Johns Hopkins University
School of Medicine, Baltimore, Maryland 21205, United States
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7
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Turner D, Kang C, Mesirca P, Hong J, Mangoni ME, Glukhov AV, Sah R. Electrophysiological and Molecular Mechanisms of Sinoatrial Node Mechanosensitivity. Front Cardiovasc Med 2021; 8:662410. [PMID: 34434970 PMCID: PMC8382116 DOI: 10.3389/fcvm.2021.662410] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 06/24/2021] [Indexed: 01/01/2023] Open
Abstract
The understanding of the electrophysiological mechanisms that underlie mechanosensitivity of the sinoatrial node (SAN), the primary pacemaker of the heart, has been evolving over the past century. The heart is constantly exposed to a dynamic mechanical environment; as such, the SAN has numerous canonical and emerging mechanosensitive ion channels and signaling pathways that govern its ability to respond to both fast (within second or on beat-to-beat manner) and slow (minutes) timescales. This review summarizes the effects of mechanical loading on the SAN activity and reviews putative candidates, including fast mechanoactivated channels (Piezo, TREK, and BK) and slow mechanoresponsive ion channels [including volume-regulated chloride channels and transient receptor potential (TRP)], as well as the components of mechanochemical signal transduction, which may contribute to SAN mechanosensitivity. Furthermore, we examine the structural foundation for both mechano-electrical and mechanochemical signal transduction and discuss the role of specialized membrane nanodomains, namely, caveolae, in mechanical regulation of both membrane and calcium clock components of the so-called coupled-clock pacemaker system responsible for SAN automaticity. Finally, we emphasize how these mechanically activated changes contribute to the pathophysiology of SAN dysfunction and discuss controversial areas necessitating future investigations. Though the exact mechanisms of SAN mechanosensitivity are currently unknown, identification of such components, their impact into SAN pacemaking, and pathological remodeling may provide new therapeutic targets for the treatment of SAN dysfunction and associated rhythm abnormalities.
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Affiliation(s)
- Daniel Turner
- Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, United States
| | - Chen Kang
- Cardiovascular Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Pietro Mesirca
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Juan Hong
- Cardiovascular Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Matteo E Mangoni
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Alexey V Glukhov
- Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, United States
| | - Rajan Sah
- Cardiovascular Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, United States
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8
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Morotti S, Ni H, Peters CH, Rickert C, Asgari-Targhi A, Sato D, Glukhov AV, Proenza C, Grandi E. Intracellular Na + Modulates Pacemaking Activity in Murine Sinoatrial Node Myocytes: An In Silico Analysis. Int J Mol Sci 2021; 22:5645. [PMID: 34073281 PMCID: PMC8198068 DOI: 10.3390/ijms22115645] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 05/21/2021] [Accepted: 05/25/2021] [Indexed: 12/19/2022] Open
Abstract
Background: The mechanisms underlying dysfunction in the sinoatrial node (SAN), the heart's primary pacemaker, are incompletely understood. Electrical and Ca2+-handling remodeling have been implicated in SAN dysfunction associated with heart failure, aging, and diabetes. Cardiomyocyte [Na+]i is also elevated in these diseases, where it contributes to arrhythmogenesis. Here, we sought to investigate the largely unexplored role of Na+ homeostasis in SAN pacemaking and test whether [Na+]i dysregulation may contribute to SAN dysfunction. Methods: We developed a dataset-specific computational model of the murine SAN myocyte and simulated alterations in the major processes of Na+ entry (Na+/Ca2+ exchanger, NCX) and removal (Na+/K+ ATPase, NKA). Results: We found that changes in intracellular Na+ homeostatic processes dynamically regulate SAN electrophysiology. Mild reductions in NKA and NCX function increase myocyte firing rate, whereas a stronger reduction causes bursting activity and loss of automaticity. These pathologic phenotypes mimic those observed experimentally in NCX- and ankyrin-B-deficient mice due to altered feedback between the Ca2+ and membrane potential clocks underlying SAN firing. Conclusions: Our study generates new testable predictions and insight linking Na+ homeostasis to Ca2+ handling and membrane potential dynamics in SAN myocytes that may advance our understanding of SAN (dys)function.
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Affiliation(s)
- Stefano Morotti
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA; (H.N.); (A.A.-T.); (D.S.)
| | - Haibo Ni
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA; (H.N.); (A.A.-T.); (D.S.)
| | - Colin H. Peters
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; (C.H.P.); (C.R.); (C.P.)
| | - Christian Rickert
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; (C.H.P.); (C.R.); (C.P.)
| | - Ameneh Asgari-Targhi
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA; (H.N.); (A.A.-T.); (D.S.)
| | - Daisuke Sato
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA; (H.N.); (A.A.-T.); (D.S.)
| | - Alexey V. Glukhov
- Department of Medicine, Cardiovascular Medicine, University of Wisconsin Madison School of Medicine and Public Health, Madison, WI 53705, USA;
| | - Catherine Proenza
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; (C.H.P.); (C.R.); (C.P.)
- Department of Medicine, Division of Cardiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Eleonora Grandi
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA; (H.N.); (A.A.-T.); (D.S.)
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9
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Burton RAB, Terrar DA. Emerging Evidence for cAMP-calcium Cross Talk in Heart Atrial Nanodomains Where IP 3-Evoked Calcium Release Stimulates Adenylyl Cyclases. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2021; 4:25152564211008341. [PMID: 37366374 PMCID: PMC10243587 DOI: 10.1177/25152564211008341] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 03/01/2021] [Accepted: 03/07/2021] [Indexed: 06/28/2023]
Abstract
Calcium handling is vital to normal physiological function in the heart. Human atrial arrhythmias, eg. atrial fibrillation, are a major morbidity and mortality burden, yet major gaps remain in our understanding of how calcium signaling pathways function and interact. Inositol trisphosphate (IP3) is a calcium-mobilizing second messenger and its agonist-induced effects have been observed in many tissue types. In the atria IP3 receptors (IR3Rs) residing on junctional sarcoplasmic reticulum augment cellular calcium transients and, when over-stimulated, lead to arrhythmogenesis. Recent studies have demonstrated that the predominant pathway for IP3 actions in atrial myocytes depends on stimulation of calcium-dependent forms of adenylyl cyclase (AC8 and AC1) by IP3-evoked calcium release from the sarcoplasmic reticulum. AC8 shows co-localisation with IP3Rs and AC1 appears to be nearby. These observations support crosstalk between calcium and cAMP pathways in nanodomains in atria. Similar mechanisms also appear to operate in the pacemaker region of the sinoatrial node. Here we discuss these significant advances in our understanding of atrial physiology and pathology, together with implications for the identification of potential novel targets and modulators for the treatment of atrial arrhythmias.
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Affiliation(s)
| | - Derek A. Terrar
- Department of Pharmacology, University of Oxford, Oxford, UK
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10
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Capel RA, Bose SJ, Collins TP, Rajasundaram S, Ayagama T, Zaccolo M, Burton RAB, Terrar DA. IP 3-mediated Ca 2+ release regulates atrial Ca 2+ transients and pacemaker function by stimulation of adenylyl cyclases. Am J Physiol Heart Circ Physiol 2020; 320:H95-H107. [PMID: 33064562 PMCID: PMC7864251 DOI: 10.1152/ajpheart.00380.2020] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Inositol trisphosphate (IP3) is a Ca2+-mobilizing second messenger shown to modulate atrial muscle contraction and is thought to contribute to atrial fibrillation. Cellular pathways underlying IP3 actions in cardiac tissue remain poorly understood, and the work presented here addresses the question whether IP3-mediated Ca2+ release from the sarcoplasmic reticulum is linked to adenylyl cyclase activity including Ca2+-stimulated adenylyl cyclases (AC1 and AC8) that are selectively expressed in atria and sinoatrial node (SAN). Immunocytochemistry in guinea pig atrial myocytes identified colocalization of type 2 IP3 receptors with AC8, while AC1 was located in close vicinity. Intracellular photorelease of IP3 by UV light significantly enhanced the amplitude of the Ca2+ transient (CaT) evoked by electrical stimulation of atrial myocytes (31 ± 6% increase 60 s after photorelease, n = 16). The increase in CaT amplitude was abolished by inhibitors of adenylyl cyclases (MDL-12,330) or protein kinase A (H89), showing that cAMP signaling is required for this effect of photoreleased IP3. In mouse, spontaneously beating right atrial preparations, phenylephrine, an α-adrenoceptor agonist with effects that depend on IP3-mediated Ca2+ release, increased the maximum beating rate by 14.7 ± 0.5%, n = 10. This effect was substantially reduced by 2.5 µmol/L 2-aminoethyl diphenylborinate and abolished by a low dose of MDL-12,330, observations which are again consistent with a functional interaction between IP3 and cAMP signaling involving Ca2+ stimulation of adenylyl cyclases in the SAN pacemaker. Understanding the interaction between IP3 receptor pathways and Ca2+-stimulated adenylyl cyclases provides important insights concerning acute mechanisms for initiation of atrial arrhythmias. NEW & NOTEWORTHY This study provides evidence supporting the proposal that IP3 signaling in cardiac atria and sinoatrial node involves stimulation of Ca2+-activated adenylyl cyclases (AC1 and AC8) by IP3-evoked Ca2+ release from junctional sarcoplasmic reticulum. AC8 and IP3 receptors are shown to be located close together, while AC1 is nearby. Greater understanding of these novel aspects of the IP3 signal transduction mechanism is important for future study in atrial physiology and pathophysiology, particularly atrial fibrillation.
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Affiliation(s)
- Rebecca A Capel
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Samuel J Bose
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Thomas P Collins
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Skanda Rajasundaram
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Thamali Ayagama
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Rebecca-Ann Beatrice Burton
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Derek A Terrar
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
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11
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Isoform-specific regulation of HCN4 channels by a family of endoplasmic reticulum proteins. Proc Natl Acad Sci U S A 2020; 117:18079-18090. [PMID: 32647060 DOI: 10.1073/pnas.2006238117] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ion channels in excitable cells function in macromolecular complexes in which auxiliary proteins modulate the biophysical properties of the pore-forming subunits. Hyperpolarization-activated, cyclic nucleotide-sensitive HCN4 channels are critical determinants of membrane excitability in cells throughout the body, including thalamocortical neurons and cardiac pacemaker cells. We previously showed that the properties of HCN4 channels differ dramatically in different cell types, possibly due to the endogenous expression of auxiliary proteins. Here, we report the discovery of a family of endoplasmic reticulum (ER) transmembrane proteins that associate with and modulate HCN4. Lymphoid-restricted membrane protein (LRMP, Jaw1) and inositol trisphosphate receptor-associated guanylate kinase substrate (IRAG, Mrvi1, and Jaw1L) are homologous proteins with small ER luminal domains and large cytoplasmic domains. Despite their homology, LRMP and IRAG have distinct effects on HCN4. LRMP is a loss-of-function modulator that inhibits the canonical depolarizing shift in the voltage dependence of HCN4 in response to the binding of cAMP. In contrast, IRAG causes a gain of HCN4 function by depolarizing the basal voltage dependence in the absence of cAMP. The mechanisms of action of LRMP and IRAG are independent of trafficking and cAMP binding, and they are specific to the HCN4 isoform. We also found that IRAG is highly expressed in the mouse sinoatrial node where computer modeling predicts that its presence increases HCN4 current. Our results suggest important roles for LRMP and IRAG in the regulation of cellular excitability, as tools for advancing mechanistic understanding of HCN4 channel function, and as possible scaffolds for coordination of signaling pathways.
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12
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MacDonald EA, Rose RA, Quinn TA. Neurohumoral Control of Sinoatrial Node Activity and Heart Rate: Insight From Experimental Models and Findings From Humans. Front Physiol 2020; 11:170. [PMID: 32194439 PMCID: PMC7063087 DOI: 10.3389/fphys.2020.00170] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 02/13/2020] [Indexed: 12/22/2022] Open
Abstract
The sinoatrial node is perhaps one of the most important tissues in the entire body: it is the natural pacemaker of the heart, making it responsible for initiating each-and-every normal heartbeat. As such, its activity is heavily controlled, allowing heart rate to rapidly adapt to changes in physiological demand. Control of sinoatrial node activity, however, is complex, occurring through the autonomic nervous system and various circulating and locally released factors. In this review we discuss the coupled-clock pacemaker system and how its manipulation by neurohumoral signaling alters heart rate, considering the multitude of canonical and non-canonical agents that are known to modulate sinoatrial node activity. For each, we discuss the principal receptors involved and known intracellular signaling and protein targets, highlighting gaps in our knowledge and understanding from experimental models and human studies that represent areas for future research.
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Affiliation(s)
- Eilidh A. MacDonald
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada
| | - Robert A. Rose
- Cumming School of Medicine, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada
| | - T. Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada
- School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada
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13
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Gilbert G, Demydenko K, Dries E, Puertas RD, Jin X, Sipido K, Roderick HL. Calcium Signaling in Cardiomyocyte Function. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a035428. [PMID: 31308143 DOI: 10.1101/cshperspect.a035428] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Rhythmic increases in intracellular Ca2+ concentration underlie the contractile function of the heart. These heart muscle-wide changes in intracellular Ca2+ are induced and coordinated by electrical depolarization of the cardiomyocyte sarcolemma by the action potential. Originating at the sinoatrial node, conduction of this electrical signal throughout the heart ensures synchronization of individual myocytes into an effective cardiac pump. Ca2+ signaling pathways also regulate gene expression and cardiomyocyte growth during development and in pathology. These fundamental roles of Ca2+ in the heart are illustrated by the prevalence of altered Ca2+ homeostasis in cardiovascular diseases. Indeed, heart failure (an inability of the heart to support hemodynamic needs), rhythmic disturbances, and inappropriate cardiac growth all share an involvement of altered Ca2+ handling. The prevalence of these pathologies, contributing to a third of all deaths in the developed world as well as to substantial morbidity makes understanding the mechanisms of Ca2+ handling and dysregulation in cardiomyocytes of great importance.
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Affiliation(s)
- Guillaume Gilbert
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - Kateryna Demydenko
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - Eef Dries
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - Rosa Doñate Puertas
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - Xin Jin
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - Karin Sipido
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - H Llewelyn Roderick
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
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14
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Yue X, Hazan A, Lotteau S, Zhang R, Torrente AG, Philipson KD, Ottolia M, Goldhaber JI. Na/Ca exchange in the atrium: Role in sinoatrial node pacemaking and excitation-contraction coupling. Cell Calcium 2020; 87:102167. [PMID: 32028091 DOI: 10.1016/j.ceca.2020.102167] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 01/21/2020] [Indexed: 01/14/2023]
Abstract
Na/Ca exchange is the dominant calcium (Ca) efflux mechanism in cardiac myocytes. Although our knowledge of exchanger function (NCX1 in the heart) was originally established using biochemical and electrophysiological tools such as cardiac sarcolemmal vesicles and the giant patch technique [1-4], many advances in our understanding of the physiological/pathophysiological roles of NCX1 in the heart have been obtained using a suite of genetically modified mice. Early mouse studies focused on modification of expression levels of NCX1 in the ventricles, with transgenic overexpressors, global NCX1 knockout (KO) mice (which were embryonic lethal if homozygous), and finally ventricular-specific NCX1 KO [5-12]. We found, to our surprise, that ventricular cardiomyocytes lacking NCX1 can survive and function by engaging a clever set of adaptations to minimize Ca entry, while maintaining contractile function through an increase in excitation-contraction (EC) coupling gain [5,6,13]. Having studied ventricular NCX1 ablation in detail, we more recently focused on elucidating the role of NCX1 in the atria through altering NCX1 expression. Using a novel atrial-specific NCX1 KO mouse, we found unexpected changes in atrial cell morphology and calcium handling, together with dramatic alterations in the function of sinoatrial node (SAN) pacemaker activity. In this review, we will discuss these findings and their implications for cardiac disease.
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Affiliation(s)
- Xin Yue
- Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Adina Hazan
- Smidt Heart Institute, Department of Cardiology, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Sabine Lotteau
- Smidt Heart Institute, Department of Cardiology, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Rui Zhang
- Smidt Heart Institute, Department of Cardiology, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Angelo G Torrente
- Institute for Functional Genomics, University of Montpellier, CNRS, INSERM, Montpellier, France
| | | | - Michela Ottolia
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, UCLA, Los Angeles, CA 90095, USA
| | - Joshua I Goldhaber
- Smidt Heart Institute, Department of Cardiology, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.
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15
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Abstract
The aim of this chapter is to discuss evidence concerning the many roles of calcium ions, Ca2+, in cell signaling pathways that control heart function. Before considering details of these signaling pathways, the control of contraction in ventricular muscle by Ca2+ transients accompanying cardiac action potentials is first summarized, together with a discussion of how myocytes from the atrial and pacemaker regions of the heart diverge from this basic scheme. Cell signaling pathways regulate the size and timing of the Ca2+ transients in the different heart regions to influence function. The simplest Ca2+ signaling elements involve enzymes that are regulated by cytosolic Ca2+. Particularly important examples to be discussed are those that are stimulated by Ca2+, including Ca2+-calmodulin-dependent kinase (CaMKII), Ca2+ stimulated adenylyl cyclases, Ca2+ stimulated phosphatase and NO synthases. Another major aspect of Ca2+ signaling in the heart concerns actions of the Ca2+ mobilizing agents, inositol trisphosphate (IP3), cADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate, (NAADP). Evidence concerning roles of these Ca2+ mobilizing agents in different regions of the heart is discussed in detail. The focus of the review will be on short term regulation of Ca2+ transients and contractile function, although it is recognized that Ca2+ regulation of gene expression has important long term functional consequences which will also be briefly discussed.
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16
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Learn from Your Elders: Developmental Biology Lessons to Guide Maturation of Stem Cell-Derived Cardiomyocytes. Pediatr Cardiol 2019; 40:1367-1387. [PMID: 31388700 PMCID: PMC6786957 DOI: 10.1007/s00246-019-02165-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Accepted: 07/16/2019] [Indexed: 02/07/2023]
Abstract
Human pluripotent stem cells (hPSCs) offer a multifaceted platform to study cardiac developmental biology, understand disease mechanisms, and develop novel therapies. Remarkable progress over the last two decades has led to methods to obtain highly pure hPSC-derived cardiomyocytes (hPSC-CMs) with reasonable ease and scalability. Nevertheless, a major bottleneck for the translational application of hPSC-CMs is their immature phenotype, resembling that of early fetal cardiomyocytes. Overall, bona fide maturation of hPSC-CMs represents one of the most significant goals facing the field today. Developmental biology studies have been pivotal in understanding the mechanisms to differentiate hPSC-CMs. Similarly, evaluation of developmental cues such as electrical and mechanical activities or neurohormonal and metabolic stimulations revealed the importance of these pathways in cardiomyocyte physiological maturation. Those signals cooperate and dictate the size and the performance of the developing heart. Likewise, this orchestra of stimuli is important in promoting hPSC-CM maturation, as demonstrated by current in vitro maturation approaches. Different shades of adult-like phenotype are achieved by prolonging the time in culture, electromechanical stimulation, patterned substrates, microRNA manipulation, neurohormonal or metabolic stimulation, and generation of human-engineered heart tissue (hEHT). However, mirroring this extremely dynamic environment is challenging, and reproducibility and scalability of these approaches represent the major obstacles for an efficient production of mature hPSC-CMs. For this reason, understanding the pattern behind the mechanisms elicited during the late gestational and early postnatal stages not only will provide new insights into postnatal development but also potentially offer new scalable and efficient approaches to mature hPSC-CMs.
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17
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Vinogradova TM, Tagirova Sirenko S, Lakatta EG. Unique Ca 2+-Cycling Protein Abundance and Regulation Sustains Local Ca 2+ Releases and Spontaneous Firing of Rabbit Sinoatrial Node Cells. Int J Mol Sci 2018; 19:ijms19082173. [PMID: 30044420 PMCID: PMC6121616 DOI: 10.3390/ijms19082173] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 07/20/2018] [Accepted: 07/23/2018] [Indexed: 11/16/2022] Open
Abstract
Spontaneous beating of the heart pacemaker, the sinoatrial node, is generated by sinoatrial node cells (SANC) and caused by gradual change of the membrane potential called diastolic depolarization (DD). Submembrane local Ca2+ releases (LCR) from sarcoplasmic reticulum (SR) occur during late DD and activate an inward Na+/Ca2+ exchange current, which accelerates the DD rate leading to earlier occurrence of an action potential. A comparison of intrinsic SR Ca2+ cycling revealed that, at similar physiological Ca2+ concentrations, LCRs are large and rhythmic in permeabilized SANC, but small and random in permeabilized ventricular myocytes (VM). Permeabilized SANC spontaneously released more Ca2+ from SR than VM, despite comparable SR Ca2+ content in both cell types. In this review we discuss specific patterns of expression and distribution of SR Ca2+ cycling proteins (SR Ca2+ ATPase (SERCA2), phospholamban (PLB) and ryanodine receptors (RyR)) in SANC and ventricular myocytes. We link ability of SANC to generate larger and rhythmic LCRs with increased abundance of SERCA2, reduced abundance of the SERCA inhibitor PLB. In addition, an increase in intracellular [Ca2+] increases phosphorylation of both PLB and RyR exclusively in SANC. The differences in SR Ca2+ cycling protein expression between SANC and VM provide insights into diverse regulation of intrinsic SR Ca2+ cycling that drives automaticity of SANC.
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Affiliation(s)
- Tatiana M Vinogradova
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, 251 Bayview Blvd, Room 8B-123, Baltimore, MD 21224, USA.
| | - Syevda Tagirova Sirenko
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, 251 Bayview Blvd, Room 8B-123, Baltimore, MD 21224, USA.
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, 251 Bayview Blvd, Room 8B-123, Baltimore, MD 21224, USA.
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18
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Barrett JN, Rincon S, Singh J, Matthewman C, Pasos J, Barrett EF, Rajguru SM. Pulsed infrared releases Ca 2+ from the endoplasmic reticulum of cultured spiral ganglion neurons. J Neurophysiol 2018; 120:509-524. [PMID: 29668377 DOI: 10.1152/jn.00740.2017] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Inner ear spiral ganglion neurons were cultured from day 4 postnatal mice and loaded with a fluorescent Ca2+ indicator (fluo-4, -5F, or -5N). Pulses of infrared radiation (IR; 1,863 nm, 200 µs, 200-250 Hz for 2-5 s, delivered via an optical fiber) produced a rapid, transient temperature increase of 6-12°C (above a baseline of 24-30°C). These IR pulse trains evoked transient increases in both nuclear and cytosolic Ca2+ concentration ([Ca2+]) of 0.20-1.4 µM, with a simultaneous reduction of [Ca2+] in regions containing endoplasmic reticulum (ER). IR-induced increases in cytosolic [Ca2+] continued in medium containing no added Ca2+ (±Ca2+ buffers) and low [Na+], indicating that the [Ca2+] increase was mediated by release from intracellular stores. Consistent with this hypothesis, the IR-induced [Ca2+] response was prolonged and eventually blocked by inhibition of ER Ca2+-ATPase with cyclopiazonic acid, and was also inhibited by a high concentration of ryanodine and by inhibitors of inositol (1,4,5)-trisphosphate (IP3)-mediated Ca2+ release (xestospongin C and 2-aminoethoxydiphenyl borate). The thermal sensitivity of the response suggested involvement of warmth-sensitive transient receptor potential (TRP) channels. The IR-induced [Ca2+] increase was inhibited by TRPV4 inhibitors (HC-067047 and GSK-2193874), and immunostaining of spiral ganglion cultures demonstrated the presence of TRPV4 and TRPM2 that colocalized with ER marker GRP78. These results suggest that the temperature sensitivity of IR-induced [Ca2+] elevations is conferred by TRP channels on ER membranes, which facilitate Ca2+ efflux into the cytosol and thereby contribute to Ca2+-induced Ca2+-release via IP3 and ryanodine receptors. NEW & NOTEWORTHY Infrared radiation-induced photothermal effects release Ca2+ from the endoplasmic reticulum of primary spiral ganglion neurons. This Ca2+ release is mediated by activation of transient receptor potential (TRPV4) channels and involves amplification by Ca2+-induced Ca2+-release. The neurons immunostained for warmth-sensitive channels, TRPV4 and TRPM2, which colocalize with endoplasmic reticulum. Pulsed infrared radiation provides a novel experimental tool for releasing intracellular Ca2+, studying Ca2+ regulatory mechanisms, and influencing neuronal excitability.
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Affiliation(s)
- John N Barrett
- Department of Physiology and Biophysics, University of Miami , Miami, Florida.,Neuroscience Program, University of Miami , Miami, Florida
| | - Samantha Rincon
- Department of Biomedical Engineering, University of Miami , Miami, Florida
| | - Jayanti Singh
- Department of Otolaryngology, University of Miami , Miami, Florida
| | | | - Julio Pasos
- Department of Otolaryngology, University of Miami , Miami, Florida
| | - Ellen F Barrett
- Department of Physiology and Biophysics, University of Miami , Miami, Florida.,Neuroscience Program, University of Miami , Miami, Florida
| | - Suhrud M Rajguru
- Department of Biomedical Engineering, University of Miami , Miami, Florida.,Department of Otolaryngology, University of Miami , Miami, Florida
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19
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Torrente AG, Zhang R, Wang H, Zaini A, Kim B, Yue X, Philipson KD, Goldhaber JI. Contribution of small conductance K + channels to sinoatrial node pacemaker activity: insights from atrial-specific Na + /Ca 2+ exchange knockout mice. J Physiol 2017; 595:3847-3865. [PMID: 28346695 DOI: 10.1113/jp274249] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 03/22/2017] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS Repolarizing currents through K+ channels are essential for proper sinoatrial node (SAN) pacemaking, but the influence of intracellular Ca2+ on repolarization in the SAN is uncertain. We identified all three isoforms of Ca2+ -activated small conductance K+ (SK) channels in the murine SAN. SK channel blockade slows repolarization and subsequent depolarization of SAN cells. In the atrial-specific Na+ /Ca2+ exchanger (NCX) knockout mouse, cellular Ca2+ accumulation during spontaneous SAN pacemaker activity produces intermittent hyperactivation of SK channels, leading to arrhythmic pauses alternating with bursts of pacing. These findings suggest that Ca2+ -sensitive SK channels can translate changes in cellular Ca2+ into a repolarizing current capable of modulating pacemaking. SK channels are a potential pharmacological target for modulating SAN rate or treating SAN dysfunction, particularly under conditions characterized by abnormal increases in diastolic Ca2+ . ABSTRACT Small conductance K+ (SK) channels have been implicated as modulators of spontaneous depolarization and electrical conduction that may be involved in cardiac arrhythmia. However, neither their presence nor their contribution to sinoatrial node (SAN) pacemaker activity has been investigated. Using quantitative PCR (q-PCR), immunostaining and patch clamp recordings of membrane current and voltage, we identified all three SK isoforms (SK1, SK2 and SK3) in mouse SAN. Inhibition of SK channels with the specific blocker apamin prolonged action potentials (APs) in isolated SAN cells. Apamin also slowed diastolic depolarization and reduced pacemaker rate in isolated SAN cells and intact tissue. We investigated whether the Ca2+ -sensitive nature of SK channels could explain arrhythmic SAN pacemaker activity in the atrial-specific Na+ /Ca2+ exchange (NCX) knockout (KO) mouse, a model of cellular Ca2+ overload. SAN cells isolated from the NCX KO exhibited higher SK current than wildtype (WT) and apamin prolonged their APs. SK blockade partially suppressed the arrhythmic burst pacing pattern of intact NCX KO SAN tissue. We conclude that SK channels have demonstrable effects on SAN pacemaking in the mouse. Their Ca2+ -dependent activation translates changes in cellular Ca2+ into a repolarizing current capable of modulating regular pacemaking. This Ca2+ dependence also promotes abnormal automaticity when these channels are hyperactivated by elevated Ca2+ . We propose SK channels as a potential target for modulating SAN rate, and for treating patients affected by SAN dysfunction, particularly in the setting of Ca2+ overload.
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Affiliation(s)
- Angelo G Torrente
- Cedars-Sinai Heart Institute, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA
| | - Rui Zhang
- Cedars-Sinai Heart Institute, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA
| | - Heidi Wang
- Cedars-Sinai Heart Institute, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA
| | - Audrey Zaini
- Cedars-Sinai Heart Institute, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA
| | - Brian Kim
- Cedars-Sinai Heart Institute, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA
| | - Xin Yue
- Cedars-Sinai Heart Institute, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA
| | - Kenneth D Philipson
- Department of Physiology, David Geffen School of Medicine at UCLA, 650 Charles Young Drive South, Los Angeles, CA, 90095-1751, USA
| | - Joshua I Goldhaber
- Cedars-Sinai Heart Institute, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA.,Department of Biomedical Sciences, Cedars-Sinai Medical Center, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA
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20
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Daniels RE, Haq KT, Miller LS, Chia EW, Miura M, Sorrentino V, McGuire JJ, Stuyvers BD. Cardiac expression of ryanodine receptor subtype 3; a strategic component in the intracellular Ca 2+ release system of Purkinje fibers in large mammalian heart. J Mol Cell Cardiol 2017; 104:31-42. [PMID: 28111173 DOI: 10.1016/j.yjmcc.2017.01.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 12/08/2016] [Accepted: 01/18/2017] [Indexed: 10/20/2022]
Abstract
BACKGROUND Three distinct Ca2+ release channels were identified in dog P-cells: the ryanodine receptor subtype 2 (RyR2) was detected throughout the cell, while the ryanodine receptor subtype 3 (RyR3) and inositol phosphate sensitive Ca2+ release channel (InsP3R) were found in the cell periphery. How each of these channels contributes to the Ca2+ cycling of P-cells is unclear. Recent modeling of Ca2+ mobilization in P-cells suggested that Ca2+ sensitivity of Ca2+induced Ca2+release (CICR) was larger at the P-cell periphery. Our study examined whether this numerically predicted region of Ca2+ release exists in live P-cells. We compared the regional Ca2+ dynamics with the arrangement of intracellular Ca2+ release (CR) channels. METHODS Gene expression of CR channels was measured by qPCR in Purkinje fibers and myocardium of adult Yucatan pig hearts. We characterized the CR channels protein expression in isolated P-cells by immuno-fluorescence, laser scanning confocal microscopy, and 3D reconstruction. The spontaneous Ca2+ activity and electrically-evoked Ca2+ mobilization were imaged by 2D spinning disk confocal microscopy. Functional regions of P-cell were differentiated by the characteristics of local Ca2+ events. We used the Ca2+ propagation velocities as indicators of channel Ca2+ sensitivity. RESULTS RyR2 gene expression was identical in Purkinje fibers and myocardium (6 hearts) while RyR3 and InsP3R gene expressions were, respectively, 100 and 16 times larger in the Purkinje fibers. Specific fluorescent immuno-staining of Ca2+ release channels revealed an intermediate layer of RyR3 expression between a near-membrane InsP3R-region and a central RyR2-region. We found that cell periphery produced two distinct forms of spontaneous Ca2+-transients: (1) large asymmetrical Ca2+ sparks under the membrane, and (2) typical Ca2+-wavelets propagating exclusively around the core of the cell. Larger cell-wide Ca2+ waves (CWWs) appeared occasionally traveling in the longitudinal direction through the core of Pcells. Large sparks arose in a micrometric space overlapping the InsP3R expression. The InsP3R antagonists 2-aminoethoxydiphenyl borate (2-APB; 3μM) and xestospongin C (XeC; 50μM) dramatically reduced their frequency. The Ca2+ wavelets propagated in a 5-10μm thick layered space which matched the intermediate zone of RyR3 expression. The wavelet incidence was unchanged by 2-APB or XeC, but was reduced by 60% in presence of the RyR3 antagonist dantrolene (10μM). The velocity of wavelets was two times larger (86±16μm/s; n=14) compared to CWWs' (46±10μm/s; n=11; P<0.05). Electric stimulation triggered a uniform and large elevation of Ca2+ concentration under the membrane which preceded the propagation of Ca2+ into the interior of the cell. Elevated Cai propagated at 150μm/s (147±34μm/s; n=5) through the region equivalent to the zone of RyR3 expression. This velocity dropped by 50% (75±24μm/s; n=5) in the central region wherein predominant RyR2 expression was detected. CONCLUSION We identified two layers of distinct Ca2+ release channels in the periphery of Pcell: an outer layer of InsP3Rs under the membrane and an inner layer of RyR3s. The propagation of Ca2+ events in these layers revealed that Ca2+ sensitivity of Ca2+ release was larger in the RyR3 layer compared to that of other sub-cellular regions. We propose that RyR3 expression in P-cells plays a role in the stability of electric function of Purkinje fibers.
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Affiliation(s)
- Rebecca E Daniels
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Kazi T Haq
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Lawson S Miller
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Elizabeth W Chia
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Masahito Miura
- Department of Clinical Physiology, Health Science, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Vincenzo Sorrentino
- Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy
| | - John J McGuire
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Bruno D Stuyvers
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada.
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Groschner K, Shrestha N, Fameli N. Cardiovascular and Hemostatic Disorders: SOCE in Cardiovascular Cells: Emerging Targets for Therapeutic Intervention. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 993:473-503. [PMID: 28900929 DOI: 10.1007/978-3-319-57732-6_24] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The discovery of the store-operated Ca2+ entry (SOCE) phenomenon is tightly associated with its recognition as a pathway of high (patho)physiological significance in the cardiovascular system. Early on, SOCE has been investigated primarily in non-excitable cell types, and the vascular endothelium received particular attention, while a role of SOCE in excitable cells, specifically cardiac myocytes and pacemakers, was initially ignored and remains largely enigmatic even to date. With the recent gain in knowledge on the molecular components of SOCE as well as their cellular organization within nanodomains, potential tissue/cell type-dependent heterogeneity of the SOCE machinery along with high specificity of linkage to downstream signaling pathways emerged for cardiovascular cells. The basis of precise decoding of cellular Ca2+ signals was recently uncovered to involve correct spatiotemporal organization of signaling components, and even minor disturbances in these assemblies trigger cardiovascular pathologies. With this chapter, we wish to provide an overview on current concepts of cellular organization of SOCE signaling complexes in cardiovascular cells with particular focus on the spatiotemporal aspects of coupling to downstream signaling and the potential disturbance of these mechanisms by pathogenic factors. The significance of these mechanistic concepts for the development of novel therapeutic strategies will be discussed.
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Affiliation(s)
- Klaus Groschner
- Institute of Biophysics, Medical University of Graz, Neue Stiftingtalstrasse 6/4, 8010, Graz, Austria.
| | - Niroj Shrestha
- Institute of Biophysics, Medical University of Graz, Neue Stiftingtalstrasse 6/4, 8010, Graz, Austria
| | - Nicola Fameli
- Institute of Biophysics, Medical University of Graz, Neue Stiftingtalstrasse 6/4, 8010, Graz, Austria
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
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Berridge MJ. The Inositol Trisphosphate/Calcium Signaling Pathway in Health and Disease. Physiol Rev 2016; 96:1261-96. [DOI: 10.1152/physrev.00006.2016] [Citation(s) in RCA: 377] [Impact Index Per Article: 47.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Many cellular functions are regulated by calcium (Ca2+) signals that are generated by different signaling pathways. One of these is the inositol 1,4,5-trisphosphate/calcium (InsP3/Ca2+) signaling pathway that operates through either primary or modulatory mechanisms. In its primary role, it generates the Ca2+ that acts directly to control processes such as metabolism, secretion, fertilization, proliferation, and smooth muscle contraction. Its modulatory role occurs in excitable cells where it modulates the primary Ca2+ signal generated by the entry of Ca2+ through voltage-operated channels that releases Ca2+ from ryanodine receptors (RYRs) on the internal stores. In carrying out this modulatory role, the InsP3/Ca2+ signaling pathway induces subtle changes in the generation and function of the voltage-dependent primary Ca2+ signal. Changes in the nature of both the primary and modulatory roles of InsP3/Ca2+ signaling are a contributory factor responsible for the onset of a large number human diseases.
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Affiliation(s)
- Michael J. Berridge
- Laboratory of Molecular Signalling, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, United Kingdom
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Greer-Short A, Poelzing S. Temporal response of ectopic activity in guinea pig ventricular myocardium in response to isoproterenol and acetylcholine. Front Physiol 2015; 6:278. [PMID: 26539122 PMCID: PMC4611207 DOI: 10.3389/fphys.2015.00278] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 09/21/2015] [Indexed: 12/16/2022] Open
Abstract
Both β adrenergic and muscarinic receptor stimulation independently potentiate arrhythmogenesis. However, the effect of simultaneous stimulation on arrhythmogenesis is not well known. The purpose of this study was to determine the temporal response of arrhythmia risk to individual and combined autonomic agonists. Guinea pig hearts were excised and Langendorff-perfused. The β adrenergic receptor and muscarinic receptor agonists were isoproterenol (ISO, 0.6 μM) and acetylcholine (ACh, 10 μM), respectively. All measurements with agonists occurred over 21 min. ISO induced ectopic activity for the first 8 min. ISO also transiently shortened and then prolonged R-R interval over a similar time course. ACh added after ISO transiently induced ectopic activity for 12 min, while R-R interval invariantly prolonged. ACh alone produced few ectopic beats, while invariantly prolonging R-R interval. In contrast to ISO alone, ISO following ACh significantly increased ectopic activity and shortened R-R interval for the duration of the experiment. Animals aged 17–19 months exhibited sustained arrhythmogenesis while those aged 11–14 did not. When ACh was removed in older hearts while ISO perfused, a transient increase in ectopic activity and decreased R-R interval was observed, similar to ISO alone. These data suggest that pre-treating with and maintaining ACh perfusion can sustain ISO sensitivity, in contrast to ISO perfusion alone.
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Affiliation(s)
- Amara Greer-Short
- Center for Heart and Regenerative Medicine, Virginia Tech Carilion Research Institute, Virginia Polytechnic Institute and State University Roanoke, VA, USA ; School of Biomedical Engineering and Sciences, Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University Blacksburg, VA, USA
| | - Steven Poelzing
- Center for Heart and Regenerative Medicine, Virginia Tech Carilion Research Institute, Virginia Polytechnic Institute and State University Roanoke, VA, USA ; School of Biomedical Engineering and Sciences, Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University Blacksburg, VA, USA
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