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Liu YB, Wang Q, Song YL, Song XM, Fan YC, Kong L, Zhang JS, Li S, Lv YJ, Li ZY, Dai JY, Qiu ZK. Abnormal phosphorylation / dephosphorylation and Ca 2+ dysfunction in heart failure. Heart Fail Rev 2024; 29:751-768. [PMID: 38498262 DOI: 10.1007/s10741-024-10395-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/01/2024] [Indexed: 03/20/2024]
Abstract
Heart failure (HF) can be caused by a variety of causes characterized by abnormal myocardial systole and diastole. Ca2+ current through the L-type calcium channel (LTCC) on the membrane is the initial trigger signal for a cardiac cycle. Declined systole and diastole in HF are associated with dysfunction of myocardial Ca2+ function. This disorder can be correlated with unbalanced levels of phosphorylation / dephosphorylation of LTCC, endoplasmic reticulum (ER), and myofilament. Kinase and phosphatase activity changes along with HF progress, resulting in phased changes in the degree of phosphorylation / dephosphorylation. It is important to realize the phosphorylation / dephosphorylation differences between a normal and a failing heart. This review focuses on phosphorylation / dephosphorylation changes in the progression of HF and summarizes the effects of phosphorylation / dephosphorylation of LTCC, ER function, and myofilament function in normal conditions and HF based on previous experiments and clinical research. Also, we summarize current therapeutic methods based on abnormal phosphorylation / dephosphorylation and clarify potential therapeutic directions.
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Affiliation(s)
- Yan-Bing Liu
- Interventional Medical Center, The Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, Shandong Province, China
- Medical College, Qingdao University, Qingdao, China
| | - Qian Wang
- Medical College, Qingdao University, Qingdao, China
| | - Yu-Ling Song
- Department of Pediatrics, Huantai County Hospital of Traditional Chinese Medicine, Zibo, China
| | | | - Yu-Chen Fan
- Medical College, Qingdao University, Qingdao, China
| | - Lin Kong
- Medical College, Qingdao University, Qingdao, China
| | | | - Sheng Li
- Medical College, Qingdao University, Qingdao, China
| | - Yi-Ju Lv
- Medical College, Qingdao University, Qingdao, China
| | - Ze-Yang Li
- Medical College, Qingdao University, Qingdao, China
| | - Jing-Yu Dai
- Department of Oncology, The Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, Shandong Province, China.
| | - Zhen-Kang Qiu
- Interventional Medical Center, The Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, Shandong Province, China.
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Gross P, Johnson J, Romero CM, Eaton DM, Poulet C, Sanchez-Alonso J, Lucarelli C, Ross J, Gibb AA, Garbincius JF, Lambert J, Varol E, Yang Y, Wallner M, Feldsott EA, Kubo H, Berretta RM, Yu D, Rizzo V, Elrod J, Sabri A, Gorelik J, Chen X, Houser SR. Interaction of the Joining Region in Junctophilin-2 With the L-Type Ca 2+ Channel Is Pivotal for Cardiac Dyad Assembly and Intracellular Ca 2+ Dynamics. Circ Res 2021; 128:92-114. [PMID: 33092464 PMCID: PMC7790862 DOI: 10.1161/circresaha.119.315715] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
RATIONALE Ca2+-induced Ca2+ release (CICR) in normal hearts requires close approximation of L-type calcium channels (LTCCs) within the transverse tubules (T-tubules) and RyR (ryanodine receptors) within the junctional sarcoplasmic reticulum. CICR is disrupted in cardiac hypertrophy and heart failure, which is associated with loss of T-tubules and disruption of cardiac dyads. In these conditions, LTCCs are redistributed from the T-tubules to disrupt CICR. The molecular mechanism responsible for LTCCs recruitment to and from the T-tubules is not well known. JPH (junctophilin) 2 enables close association between T-tubules and the junctional sarcoplasmic reticulum to ensure efficient CICR. JPH2 has a so-called joining region that is located near domains that interact with T-tubular plasma membrane, where LTCCs are housed. The idea that this joining region directly interacts with LTCCs and contributes to LTCC recruitment to T-tubules is unknown. OBJECTIVE To determine if the joining region in JPH2 recruits LTCCs to T-tubules through direct molecular interaction in cardiomyocytes to enable efficient CICR. METHODS AND RESULTS Modified abundance of JPH2 and redistribution of LTCC were studied in left ventricular hypertrophy in vivo and in cultured adult feline and rat ventricular myocytes. Protein-protein interaction studies showed that the joining region in JPH2 interacts with LTCC-α1C subunit and causes LTCCs distribution to the dyads, where they colocalize with RyRs. A JPH2 with induced mutations in the joining region (mutPG1JPH2) caused T-tubule remodeling and dyad loss, showing that an interaction between LTCC and JPH2 is crucial for T-tubule stabilization. mutPG1JPH2 caused asynchronous Ca2+-release with impaired excitation-contraction coupling after β-adrenergic stimulation. The disturbed Ca2+ regulation in mutPG1JPH2 overexpressing myocytes caused calcium/calmodulin-dependent kinase II activation and altered myocyte bioenergetics. CONCLUSIONS The interaction between LTCC and the joining region in JPH2 facilitates dyad assembly and maintains normal CICR in cardiomyocytes.
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MESH Headings
- Animals
- Calcium/metabolism
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/metabolism
- Calcium Signaling
- Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism
- Cats
- Cells, Cultured
- Disease Models, Animal
- Excitation Contraction Coupling
- Humans
- Hypertrophy, Left Ventricular/metabolism
- Hypertrophy, Left Ventricular/pathology
- Hypertrophy, Left Ventricular/physiopathology
- Kinetics
- Male
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Mitochondria, Heart/metabolism
- Mitochondria, Heart/pathology
- Muscle Proteins/genetics
- Muscle Proteins/metabolism
- Mutation
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Organelle Biogenesis
- Protein Binding
- Protein Interaction Domains and Motifs
- Rats, Sprague-Dawley
- Ryanodine Receptor Calcium Release Channel
- Rats
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Affiliation(s)
- Polina Gross
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
| | - Jaslyn Johnson
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
| | - Carlos M. Romero
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
| | - Deborah M. Eaton
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
| | - Claire Poulet
- Imperial College London, Department of Cardiovascular Sciences, Imperial Centre for Translational and Experimental Medicine, National Heart and Lung Institute, London
| | - Jose Sanchez-Alonso
- Imperial College London, Department of Cardiovascular Sciences, Imperial Centre for Translational and Experimental Medicine, National Heart and Lung Institute, London
| | - Carla Lucarelli
- Imperial College London, Department of Cardiovascular Sciences, Imperial Centre for Translational and Experimental Medicine, National Heart and Lung Institute, London
| | - Jean Ross
- Bioimaging Center Research, Delaware Biotechnology Institute, Newark
| | - Andrew A. Gibb
- Lewis Katz Temple University School of Medicine, Center for Translational Medicine, Department of Pharmacology, Philadelphia
| | - Joanne F. Garbincius
- Lewis Katz Temple University School of Medicine, Center for Translational Medicine, Department of Pharmacology, Philadelphia
| | - Jonathan Lambert
- Lewis Katz Temple University School of Medicine, Center for Translational Medicine, Department of Pharmacology, Philadelphia
| | - Erdem Varol
- Columbia University, Center for Theoretical Neuroscience, Department of Statistics, New York, NY
| | - Yijun Yang
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
| | - Markus Wallner
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
- Medical University of Graz, Division of Cardiology, Graz, Austria
- Center for Biomarker Research in Medicine, CBmed GmbH, Graz, Austria
| | - Eric A. Feldsott
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
| | - Hajime Kubo
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
| | - Remus M. Berretta
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
| | - Daohai Yu
- Clinical Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia
| | - Victor Rizzo
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
| | - John Elrod
- Lewis Katz Temple University School of Medicine, Center for Translational Medicine, Department of Pharmacology, Philadelphia
| | - Abdelkarim Sabri
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
| | - Julia Gorelik
- Imperial College London, Department of Cardiovascular Sciences, Imperial Centre for Translational and Experimental Medicine, National Heart and Lung Institute, London
| | - Xiongwen Chen
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
| | - Steven R. Houser
- Lewis Katz Temple University School of Medicine, Cardiovascular Research Center, Department of Physiology, Philadelphia
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IRAG1 Deficient Mice Develop PKG1β Dependent Pulmonary Hypertension. Cells 2020; 9:cells9102280. [PMID: 33066124 PMCID: PMC7601978 DOI: 10.3390/cells9102280] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 10/09/2020] [Accepted: 10/11/2020] [Indexed: 02/07/2023] Open
Abstract
PKGs are serine/threonine kinases. PKG1 has two isoforms-PKG1α and β. Inositol trisphosphate receptor (IP3R)-associated cGMP-kinase substrate 1 (IRAG1) is a substrate for PKG1β. IRAG1 is also known to further interact with IP3RI, which mediates intracellular Ca2+ release. However, the role of IRAG1 in PH is not known. Herein, WT and IRAG1 KO mice were kept under normoxic or hypoxic (10% O2) conditions for five weeks. Animals were evaluated for echocardiographic variables and went through right heart catheterization. Animals were further sacrificed to prepare lungs and right ventricular (RV) for immunostaining, western blotting, and pulmonary artery smooth muscle cell (PASMC) isolation. IRAG1 is expressed in PASMCs and downregulated under hypoxic conditions. Genetic deletion of IRAG1 leads to RV hypertrophy, increase in RV systolic pressure, and RV dysfunction in mice. Absence of IRAG1 in lung and RV have direct impacts on PKG1β expression. Attenuated PKG1β expression in IRAG1 KO mice further dysregulates other downstream candidates of PKG1β in RV. IRAG1 KO mice develop PH spontaneously. Our results indicate that PKG1β signaling via IRAG1 is essential for the homeostasis of PASMCs and RV. Disturbing this signaling complex by deleting IRAG1 can lead to RV dysfunction and development of PH in mice.
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Rouhana S, Farah C, Roy J, Finan A, Rodrigues de Araujo G, Bideaux P, Scheuermann V, Saliba Y, Reboul C, Cazorla O, Aimond F, Richard S, Thireau J, Fares N. Early calcium handling imbalance in pressure overload-induced heart failure with nearly normal left ventricular ejection fraction. Biochim Biophys Acta Mol Basis Dis 2019; 1865:230-242. [DOI: 10.1016/j.bbadis.2018.08.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 07/13/2018] [Accepted: 08/02/2018] [Indexed: 02/07/2023]
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Pathological hypertrophy and cardiac dysfunction are linked to aberrant endogenous unsaturated fatty acid metabolism. PLoS One 2018; 13:e0193553. [PMID: 29494668 PMCID: PMC5832311 DOI: 10.1371/journal.pone.0193553] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 01/29/2018] [Indexed: 01/11/2023] Open
Abstract
Pathological cardiac hypertrophy leads to derangements in lipid metabolism that may contribute to the development of cardiac dysfunction. Since previous studies, using high saturated fat diets, have yielded inconclusive results, we investigated whether provision of a high-unsaturated fatty acid (HUFA) diet was sufficient to restore impaired lipid metabolism and normalize diastolic dysfunction in the pathologically hypertrophied heart. Male, Wistar rats were subjected to supra-valvar aortic stenosis (SVAS) or sham surgery. After 6 weeks, diastolic dysfunction and pathological hypertrophy was confirmed and both sham and SVAS rats were treated with either normolipidic or HUFA diet. At 18 weeks post-surgery, the HUFA diet failed to normalize decreased E/A ratios or attenuate measures of cardiac hypertrophy in SVAS animals. Enzymatic activity assays and gene expression analysis showed that both normolipidic and HUFA-fed hypertrophied hearts had similar increases in glycolytic enzyme activity and down-regulation of fatty acid oxidation genes. Mass spectrometry analysis revealed depletion of unsaturated fatty acids, primarily linoleate and oleate, within the endogenous lipid pools of normolipidic SVAS hearts. The HUFA diet did not restore linoleate or oleate in the cardiac lipid pools, but did maintain body weight and adipose mass in SVAS animals. Overall, these results suggest that, in addition to decreased fatty acid oxidation, aberrant unsaturated fatty acid metabolism may be a maladaptive signature of the pathologically hypertrophied heart. The HUFA diet is insufficient to reverse metabolic remodeling, diastolic dysfunction, or pathologically hypertrophy, possibly do to preferentially partitioning of unsaturated fatty acids to adipose tissue.
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Troupes CD, Wallner M, Borghetti G, Zhang C, Mohsin S, von Lewinski D, Berretta RM, Kubo H, Chen X, Soboloff J, Houser S. Role of STIM1 (Stromal Interaction Molecule 1) in Hypertrophy-Related Contractile Dysfunction. Circ Res 2017; 121:125-136. [PMID: 28592415 DOI: 10.1161/circresaha.117.311094] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 06/02/2017] [Accepted: 06/07/2017] [Indexed: 12/20/2022]
Abstract
RATIONALE Pathological increases in cardiac afterload result in myocyte hypertrophy with changes in myocyte electrical and mechanical phenotype. Remodeling of contractile and signaling Ca2+ occurs in pathological hypertrophy and is central to myocyte remodeling. STIM1 (stromal interaction molecule 1) regulates Ca2+ signaling in many cell types by sensing low endoplasmic reticular Ca2+ levels and then coupling to plasma membrane Orai channels to induce a Ca2+ influx pathway. Previous reports suggest that STIM1 may play a role in cardiac hypertrophy, but its role in electrical and mechanical phenotypic alterations is not well understood. OBJECTIVE To define the contributions of STIM1-mediated Ca2+ influx on electrical and mechanical properties of normal and diseased myocytes, and to determine whether Orai channels are obligatory partners for STIM1 in these processes using a clinically relevant large animal model of hypertrophy. METHODS AND RESULTS Cardiac hypertrophy was induced by slow progressive pressure overload in adult cats. Hypertrophied myocytes had increased STIM1 expression and activity, which correlated with altered Ca2+-handling and action potential (AP) prolongation. Exposure of hypertrophied myocytes to the Orai channel blocker BTP2 caused a reduction of AP duration and reduced diastolic Ca2+ spark rate. BTP2 had no effect on normal myocytes. Forced expression of STIM1 in cultured adult feline ventricular myocytes increased diastolic spark rate and prolonged AP duration. STIM1 expression produced an increase in the amount of Ca2+ stored within the sarcoplasmic reticulum and activated Ca2+/calmodulin-dependent protein kinase II. STIM1 expression also increased spark rates and induced spontaneous APs. STIM1 effects were eliminated by either BTP2 or by coexpression of a dominant negative Orai construct. CONCLUSIONS STIM1 can associate with Orai in cardiac myocytes to produce a Ca2+ influx pathway that can prolong the AP duration and load the sarcoplasmic reticulum and likely contributes to the altered electromechanical properties of the hypertrophied heart.
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Affiliation(s)
- Constantine D Troupes
- From the Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (C.D.T., M.W., G.B., C.Z., S.M., R.M.B., H.K., X.C., S.H.); Department of Cardiology, Medical University of Graz, Austria (D.v.L.); and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University School of Medicine, Philadelphia, PA (J.S.)
| | - Markus Wallner
- From the Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (C.D.T., M.W., G.B., C.Z., S.M., R.M.B., H.K., X.C., S.H.); Department of Cardiology, Medical University of Graz, Austria (D.v.L.); and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University School of Medicine, Philadelphia, PA (J.S.)
| | - Giulia Borghetti
- From the Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (C.D.T., M.W., G.B., C.Z., S.M., R.M.B., H.K., X.C., S.H.); Department of Cardiology, Medical University of Graz, Austria (D.v.L.); and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University School of Medicine, Philadelphia, PA (J.S.)
| | - Chen Zhang
- From the Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (C.D.T., M.W., G.B., C.Z., S.M., R.M.B., H.K., X.C., S.H.); Department of Cardiology, Medical University of Graz, Austria (D.v.L.); and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University School of Medicine, Philadelphia, PA (J.S.)
| | - Sadia Mohsin
- From the Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (C.D.T., M.W., G.B., C.Z., S.M., R.M.B., H.K., X.C., S.H.); Department of Cardiology, Medical University of Graz, Austria (D.v.L.); and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University School of Medicine, Philadelphia, PA (J.S.)
| | - Dirk von Lewinski
- From the Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (C.D.T., M.W., G.B., C.Z., S.M., R.M.B., H.K., X.C., S.H.); Department of Cardiology, Medical University of Graz, Austria (D.v.L.); and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University School of Medicine, Philadelphia, PA (J.S.)
| | - Remus M Berretta
- From the Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (C.D.T., M.W., G.B., C.Z., S.M., R.M.B., H.K., X.C., S.H.); Department of Cardiology, Medical University of Graz, Austria (D.v.L.); and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University School of Medicine, Philadelphia, PA (J.S.)
| | - Hajime Kubo
- From the Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (C.D.T., M.W., G.B., C.Z., S.M., R.M.B., H.K., X.C., S.H.); Department of Cardiology, Medical University of Graz, Austria (D.v.L.); and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University School of Medicine, Philadelphia, PA (J.S.)
| | - Xiongwen Chen
- From the Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (C.D.T., M.W., G.B., C.Z., S.M., R.M.B., H.K., X.C., S.H.); Department of Cardiology, Medical University of Graz, Austria (D.v.L.); and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University School of Medicine, Philadelphia, PA (J.S.)
| | - Jonathan Soboloff
- From the Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (C.D.T., M.W., G.B., C.Z., S.M., R.M.B., H.K., X.C., S.H.); Department of Cardiology, Medical University of Graz, Austria (D.v.L.); and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University School of Medicine, Philadelphia, PA (J.S.)
| | - Steven Houser
- From the Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (C.D.T., M.W., G.B., C.Z., S.M., R.M.B., H.K., X.C., S.H.); Department of Cardiology, Medical University of Graz, Austria (D.v.L.); and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University School of Medicine, Philadelphia, PA (J.S.).
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7
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Cao Y, Wu X, Wang X, Sun H, Lee I. Transmembrane dynamics of the Thr-5 phosphorylated sarcolipin pentameric channel. Arch Biochem Biophys 2016; 604:143-51. [PMID: 27378083 DOI: 10.1016/j.abb.2016.06.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Revised: 06/23/2016] [Accepted: 06/24/2016] [Indexed: 12/16/2022]
Abstract
Sarcolipin (SLN), an important membrane protein expressed in the sarcoplasmic reticulum (SR), regulates muscle contractions in cardiac and skeletal muscle. The phosphorylation at amino acid Thr5 of the SLN protein modulates the amount of Ca(2+) that passes through the SR. Using molecular dynamics simulation, we evaluated the phosphorylation at Thr5 of pentameric SLN (phospho-SLN) channel's energy barrier and pore characteristics by calculating the potential of mean force (PMF) along the channel pore and determining the diffusion coefficient. The results indicate that pentameric phospho-SLN promotes penetration of monovalent and divalent ions through the channel. The analysis of PMF, pore radius and diffusion coefficient indicates that Leu21 is the hydrophobic gate of the pentameric SLN channel. In the channel, water molecules near the Leu21 pore demonstrated a clear hydrated-dehydrated transition; however, the mutation of Leu21 to an Alanine (L21A) destroyed the hydrated-dehydrated transitions. These water-dynamic behaviors and PMF confirm that Leu21 is the key residue that regulates the ion permeability of the pentameric SLN channel. These results provide the structural-basis insights and molecular-dynamic information that are needed to understand the regulatory mechanisms of ion permeability in the pentameric SLN channel.
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Affiliation(s)
- Yipeng Cao
- Institute of Physics, Nankai University, No.94 Weijin Road, Tianjin, 300071, PR China
| | - Xue Wu
- Institute of Physics, Nankai University, No.94 Weijin Road, Tianjin, 300071, PR China
| | - Xinyu Wang
- Institute of Physics, Nankai University, No.94 Weijin Road, Tianjin, 300071, PR China
| | - Haiying Sun
- Institute of Physics, Nankai University, No.94 Weijin Road, Tianjin, 300071, PR China
| | - Imshik Lee
- Institute of Physics, Nankai University, No.94 Weijin Road, Tianjin, 300071, PR China.
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Ablorh NAD, Thomas DD. Phospholamban phosphorylation, mutation, and structural dynamics: a biophysical approach to understanding and treating cardiomyopathy. Biophys Rev 2015; 7:63-76. [PMID: 28509982 DOI: 10.1007/s12551-014-0157-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 11/26/2014] [Indexed: 01/16/2023] Open
Abstract
We review the recent development of novel biochemical and spectroscopic methods to determine the site-specific phosphorylation, expression, mutation, and structural dynamics of phospholamban (PLB), in relation to its function (inhibition of the cardiac calcium pump, SERCA2a), with specific focus on cardiac physiology, pathology, and therapy. In the cardiomyocyte, SERCA2a actively transports Ca2+ into the sarcoplasmic reticulum (SR) during relaxation (diastole) to create the concentration gradient that drives the passive efflux of Ca2+ required for cardiac contraction (systole). Unphosphorylated PLB (U-PLB) inhibits SERCA2a, but phosphorylation at S16 and/or T17 (producing P-PLB) changes the structure of PLB to relieve SERCA2a inhibition. Because insufficient SERCA2a activity is a hallmark of heart failure, SERCA2a activation, by gene therapy (Andino et al. 2008; Fish et al. 2013; Hoshijima et al. 2002; Jessup et al. 2011) or drug therapy (Ferrandi et al. 2013; Huang 2013; Khan et al. 2009; Rocchetti et al. 2008; Zhang et al. 2012), is a widely sought goal for treatment of heart failure. This review describes rational approaches to this goal. Novel biophysical assays, using site-directed labeling and high-resolution spectroscopy, have been developed to resolve the structural states of SERCA2a-PLB complexes in vitro and in living cells. Novel biochemical assays, using synthetic standards and multidimensional immunofluorescence, have been developed to quantitate PLB expression and phosphorylation states in cells and human tissues. The biochemical and biophysical properties of U-PLB, P-PLB, and mutant PLB will ultimately resolve the mechanisms of loss of inhibition and gain of inhibition to guide therapeutic development. These assays will be powerful tools for investigating human tissue samples from the Sydney Heart Bank, for the purpose of analyzing and diagnosing specific disorders.
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Affiliation(s)
- Naa-Adjeley D Ablorh
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA
| | - David D Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA.
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Barr LA, Makarewich CA, Berretta RM, Gao H, Troupes CD, Woitek F, Recchia F, Kubo H, Force T, Houser SR. Imatinib activates pathological hypertrophy by altering myocyte calcium regulation. Clin Transl Sci 2014; 7:360-7. [PMID: 24931551 DOI: 10.1111/cts.12173] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Imatinib mesylate is a selective tyrosine-kinase inhibitor used in the treatment of multiple cancers, most notably chronic myelogenous leukemia. There is evidence that imatinib can induce cardiotoxicity in cancer patients. Our hypothesis is that imatinib alters calcium regulatory mechanisms and can contribute to development of pathological cardiac hypertrophy. METHODS AND RESULTS Neonatal rat ventricular myocytes (NRVMs) were treated with clinical doses (low: 2 μM; high: 5 μM) of imatinib and assessed for molecular changes. Imatinib increased peak systolic Ca(2+) and Ca(2+) transient decay rates and Western analysis revealed significant increases in phosphorylation of phospholamban (Thr-17) and the ryanodine receptor (Ser-2814), signifying activation of calcium/calmodulin-dependent kinase II (CaMKII). Imatinib significantly increased NRVM volume as assessed by Coulter counter, myocyte surface area, and atrial natriuretic peptide abundance seen by Western. Imatinib induced cell death, but did not activate the classical apoptotic program as assessed by caspase-3 cleavage, indicating a necrotic mechanism of death in myocytes. We expressed AdNFATc3-green fluorescent protein in NRVMs and showed imatinib treatment significantly increased nuclear factor of activated T cells translocation that was inhibited by the calcineurin inhibitor FK506 or CaMKII inhibitors. CONCLUSION These data show that imatinib can activate pathological hypertrophic signaling pathways by altering intracellular Ca(2+) dynamics. This is likely a contributing mechanism for the adverse cardiac effects of imatinib.
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Affiliation(s)
- Larry A Barr
- Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
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Sikkel MB, Hayward C, MacLeod KT, Harding SE, Lyon AR. SERCA2a gene therapy in heart failure: an anti-arrhythmic positive inotrope. Br J Pharmacol 2014; 171:38-54. [PMID: 24138023 PMCID: PMC3874695 DOI: 10.1111/bph.12472] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2013] [Revised: 09/16/2013] [Accepted: 09/24/2013] [Indexed: 01/14/2023] Open
Abstract
Therapeutic options that directly enhance cardiomyocyte contractility in chronic heart failure (HF) therapy are currently limited and do not improve prognosis. In fact, most positive inotropic agents, such as β-adrenoreceptor agonists and PDE inhibitors, which have been assessed in HF patients, cause increased mortality as a result of arrhythmia and sudden cardiac death. Cardiac sarcoplasmic reticulum Ca(2)(+) -ATPase2a (SERCA2a) is a key protein involved in sequestration of Ca(2)(+) into the sarcoplasmic reticulum (SR) during diastole. There is a reduction of SERCA2a protein level and function in HF, which has been successfully targeted via viral transfection of the SERCA2a gene into cardiac tissue in vivo. This has enhanced cardiac contractility and reduced mortality in several preclinical models of HF. Theoretical concerns have been raised regarding the possibility of arrhythmogenic adverse effects of SERCA2a gene therapy due to enhanced SR Ca(2)(+) load and induction of SR Ca(2)(+) leak as a result. Contrary to these concerns, SERCA2a gene therapy in a wide variety of preclinical models, including acute ischaemia/reperfusion, chronic pressure overload and chronic myocardial infarction, has resulted in a reduction in ventricular arrhythmias. The potential mechanisms for this unexpected beneficial effect, as well as mechanisms of enhancement of cardiac contractile function, are reviewed in this article.
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Affiliation(s)
- Markus B Sikkel
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
| | - Carl Hayward
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
- NIHR Cardiovascular Biomedical Research Unit, Royal Brompton HospitalLondon, UK
| | - Kenneth T MacLeod
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
| | - Sian E Harding
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
| | - Alexander R Lyon
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
- NIHR Cardiovascular Biomedical Research Unit, Royal Brompton HospitalLondon, UK
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11
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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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12
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Liles JT, Ida KK, Joly KM, Chapo J, Plato CF. Age exacerbates chronic catecholamine-induced impairments in contractile reserve in the rat. Am J Physiol Regul Integr Comp Physiol 2011; 301:R491-9. [PMID: 21593430 DOI: 10.1152/ajpregu.00756.2010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Contractile reserve decreases with advancing age and chronic isoproterenol (ISO) administration is a well-characterized model of cardiac hypertrophy known to impair cardiovascular function. This study evaluated whether nonsenescent, mature adult rats are more susceptible to detrimental effects of chronic ISO administration than younger adult rats. Rats received daily injections of ISO (0.1 mg/kg sc) or vehicle for 3 wk. ISO induced a greater impairment in contractile reserve [maximum of left ventricular pressure development (Δ+dP/dt(max))] in mature adult ISO-treated (MA-ISO) than in young adult ISO-treated rats (YA-ISO) in response to infusions of mechanistically distinct inotropes (digoxin, milrinone; 20-200 μl·kg(-1)·min(-1)), while basal and agonist-induced changes in heart rate and systolic arterial pressure (SAP) were not different across groups. ISO decreased expression of the calcium handling protein, sarco(endo)plasmic reticulum Ca(2+)-ATPase-2a, in MA-ISO compared with YA, YA-ISO, and MA rats. Chronic ISO also induced greater increases in cardiac hypertrophy [left ventricular (LV) index: 33 ± 3 vs. 22 ± 5%] and caspase-3 activity (34 vs. 5%) in MA-ISO relative to YA-ISO rats. Moreover, β-myosin heavy chain (β-MHC) and atrial natriuretic factor (ANF) mRNA expression was significantly elevated in MA-ISO. These results demonstrate that adult rats develop greater impairments in systolic performance than younger rats when exposed to chronic catecholamine excess. Reduced contractile reserve may result from calcium dysregulation, increased caspase-3 activity, or increased β-MHC and ANF expression. Although several studies report age-related declines in systolic performance in older and senescent animals, the present study demonstrates that catecholamine excess induces reductions in systolic performance significantly earlier in life.
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Affiliation(s)
- John T Liles
- Gilead Sciences, Inc., 1651 Page Mill Road, Palo Alto, CA 94304, USA.
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13
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Schaeffer PJ, Desantiago J, Yang J, Flagg TP, Kovacs A, Weinheimer CJ, Courtois M, Leone TC, Nichols CG, Bers DM, Kelly DP. Impaired contractile function and calcium handling in hearts of cardiac-specific calcineurin b1-deficient mice. Am J Physiol Heart Circ Physiol 2009; 297:H1263-73. [PMID: 19700627 DOI: 10.1152/ajpheart.00152.2009] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To define the necessity of calcineurin (Cn) signaling for cardiac maturation and function, the postnatal phenotype of mice with cardiac-specific targeted ablation of the Cn B1 regulatory subunit (Ppp3r1) gene (csCnb1(-/-) mice) was characterized. csCnb1(-/-) mice develop a lethal cardiomyopathy, characterized by impaired postnatal growth of the heart and combined systolic and diastolic relaxation abnormalities, despite a lack of structural derangements. Notably, the csCnb1(-/-) hearts did not exhibit diastolic dilatation, despite the severe functional phenotype. Myocytes isolated from the mutant mice exhibited reduced rates of contraction/relaxation and abnormalities in calcium transients, consistent with altered sarcoplasmic reticulum loading. Levels of sarco(endo) plasmic reticulum Ca-ATPase 2a (Atp2a2) and phospholamban were normal, but phospholamban phosphorylation was markedly reduced at Ser(16) and Thr(17). In addition, levels of the Na/Ca exchanger (Slc8a1) were modestly reduced. These results define a novel mouse model of cardiac-specific Cn deficiency and demonstrate novel links between Cn signaling, postnatal growth of the heart, pathological ventricular remodeling, and excitation-contraction coupling.
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Affiliation(s)
- Paul J Schaeffer
- Departments of Medicine, Washington University School of Medicine, Center for Cardiovascular Research, St Louis, Missouri, USA
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14
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Haghighi K, Chen G, Sato Y, Fan GC, He S, Kolokathis F, Pater L, Paraskevaidis I, Jones WK, Dorn GW, Kremastinos DT, Kranias EG. A human phospholamban promoter polymorphism in dilated cardiomyopathy alters transcriptional regulation by glucocorticoids. Hum Mutat 2008; 29:640-7. [PMID: 18241046 DOI: 10.1002/humu.20692] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Depressed calcium handling by the sarcoplasmic reticulum (SR) Ca-ATPase and its regulator phospholamban (PLN) is a key characteristic of human and experimental heart failure. Accumulating evidence indicates that increases in the relative levels of PLN to Ca-ATPase in failing hearts and resulting inhibition of Ca sequestration during diastole, impairs contractility. Here, we identified a genetic variant in the PLN promoter region, which increases its expression and may serve as a genetic modifier in dilated cardiomyopathy (DCM). The variant AF177763.1:g.203A>C (at position -36 bp relative to the PLN transcriptional start site) was found only in the heterozygous form in 1 out of 296 normal subjects and in 22 out of 381 cardiomyopathy patients (heart failure at age of 18-44 years, ejection fraction=22+/-9%). In vitro analysis, using luciferase as a reporter gene in rat neonatal cardiomyocytes, indicated that the PLN-variant increased activity by 24% compared to the wild type. Furthermore, the g.203A>C substitution altered the specific sequence of the steroid receptor for the glucocorticoid nuclear receptor (GR)/transcription factor in the PLN promoter, resulting in enhanced binding to the mutated DNA site. These findings suggest that the g.203A>C genetic variant in the human PLN promoter may contribute to depressed contractility and accelerate functional deterioration in heart failure.
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Affiliation(s)
- Kobra Haghighi
- Department of Pharmacology and Cell Biophysics, University of Cincinnati, College of Medicine, Cincinnati, Ohio 45267-0575, USA
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15
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Rolim NPL, Medeiros A, Rosa KT, Mattos KC, Irigoyen MC, Krieger EM, Krieger JE, Negrão CE, Brum PC. Exercise training improves the net balance of cardiac Ca2+ handling protein expression in heart failure. Physiol Genomics 2007; 29:246-52. [PMID: 17244791 DOI: 10.1152/physiolgenomics.00188.2006] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The molecular basis of the beneficial effects associated with exercise training (ET) on overall ventricular function (VF) in heart failure (HF) remains unclear. We investigated potential Ca2+ handling abnormalities and whether ET would improve VF of mice lacking α2A- and α2C-adrenoceptors (α2A/α2CARKO) that have sympathetic hyperactivity-induced HF. A cohort of male wild-type (WT) and congenic α2A/α2CARKO mice in a C57BL/J genetic background (5–7 mo of age) was randomly assigned into untrained and trained groups. VF was assessed by two-dimensional guided M-mode echocardiography. Cardiac myocyte width and ventricular fibrosis were evaluated with a computer-assisted morphometric system. Sarcoplasmic reticulum Ca2+ ATPase (SERCA2), phospholamban (PLN), phospho-Ser16-PLN, phospho-Thr17-PLN, phosphatase 1 (PP1), and Na+-Ca2+ exchanger (NCX) were analyzed by Western blotting. ET consisted of 8-wk running sessions of 60 min, 5 days/wk. α2A/α2CARKO mice displayed exercise intolerance, systolic dysfunction, increased cardiac myocyte width, and ventricular fibrosis paralleled by decreased SERCA2 and increased NCX expression levels. ET in α2A/α2CARKO mice improved exercise tolerance and systolic function. ET slightly reduced cardiac myocyte width, but unchanged ventricular fibrosis in α2A/α2CARKO mice. ET significantly increased the expression of SERCA2 (20%) and phospho-Ser16-PLN (63%), phospho-Thr17-PLN (211%) in α2A/α2CARKO mice. Furthermore, ET restored NCX and PP1 expression in α2A/α2CARKO to untrained WT mice levels. Thus, we provide evidence that Ca2+ handling is impaired in this HF model and that overall VF improved upon ET, which was associated to changes in the net balance of cardiac Ca2+ handling proteins.
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Affiliation(s)
- Natale P L Rolim
- School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil
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16
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Mills GD, Harris DM, Chen X, Houser SR. Intracellular sodium determines frequency-dependent alterations in contractility in hypertrophied feline ventricular myocytes. Am J Physiol Heart Circ Physiol 2006; 292:H1129-38. [PMID: 17012360 DOI: 10.1152/ajpheart.00375.2006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hypertrophy and failure (H/F) in humans and large mammals are characterized by a change from a positive developed force-frequency relationship (+FFR) in normal myocardium to a flattened or negative developed force-frequency relationship (-FFR) in disease. Altered Ca(2+) homeostasis underlies this process, but the role of intracellular Na(+) concentration ([Na(+)](i)) in H/F and frequency-dependent contractility reserve is unclear. We hypothesized that altered [Na(+)](i) is central to the -FFR response in H/F feline myocytes. Aortic constriction caused left ventricular hypertrophy (LVH). We found that as pacing rate was increased, contraction magnitude was maintained in isolated control myocytes (CM) but decreased in LVH myocytes (LVH-M). Quiescent LVH-M had higher [Na(+)](i) than CM (LVH-M 13.3 +/- 0.3 vs. CM 8.9 +/- 0.2 mmol/l; P < 0.001) with 0.5-Hz pacing (LVH-M 14.9 +/- 0.5 vs. CM 10.8 +/- 0.4 mmol/l; P < 0.001) but were not different at 2.5 Hz (17.0 +/- 0.7 vs. control 16.0 +/- 0.7 mmol/l; not significant). [Na(+)](i) was altered by patch pipette dialysis to define the effect of [Na(+)](i) on contraction magnitude and action potential (AP) wave shape at slow and fast pacing rates. Using AP clamp, we showed that LVH-M require increased [Na(+)](i) and long diastolic intervals to maintain normal shortening. Finally, we determined the voltage dependence of contraction for Ca(2+) current (I(Ca))-triggered and Na(+)/Ca(2+) exchanger-mediated contractions and showed that there is a greater [Na(+)](i) dependence of contractility in LVH-M. These data show that increased [Na(+)](i) is essential for maintaining contractility at slow heart rates but contributes to small contractions at fast rates unless rate-dependent AP shortening is prevented, suggesting that altered [Na(+)](i) regulation is a critical contributor to abnormal contractility in disease.
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Affiliation(s)
- Geoffrey D Mills
- Temple University School of Medicine, 3400 N. Broad St., Philadelphia, PA 19140, USA
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Sheehan KA. A new look at phospholamban in pressure-overload hypertrophy. Am J Physiol Heart Circ Physiol 2006; 291:H23. [PMID: 16565314 DOI: 10.1152/ajpheart.00267.2006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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