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Sule RO, Phinney BS, Salemi MR, Gomes AV. Mitochondrial and Proteasome Dysfunction Occurs in the Hearts of Mice Treated with Triazine Herbicide Prometryn. Int J Mol Sci 2023; 24:15266. [PMID: 37894945 PMCID: PMC10607192 DOI: 10.3390/ijms242015266] [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: 09/05/2023] [Revised: 10/07/2023] [Accepted: 10/10/2023] [Indexed: 10/29/2023] Open
Abstract
Prometryn is a methylthio-s-triazine herbicide used to control the growth of annual broadleaf and grass weeds in many cultivated plants. Significant traces of prometryn are documented in the environment, mainly in waters, soil, and plants used for human and domestic consumption. Previous studies have shown that triazine herbicides have carcinogenic potential in humans. However, there is limited information about the effects of prometryn on the cardiac system in the literature, or the mechanisms and signaling pathways underlying any potential cytotoxic effects are not known. It is important to understand the possible effects of exogenous compounds such as prometryn on the heart. To determine the mechanisms and signaling pathways affected by prometryn (185 mg/kg every 48 h for seven days), we performed proteomic profiling of male mice heart with quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS) using ten-plex tandem mass tag (TMT) labeling. The data suggest that several major pathways, including energy metabolism, protein degradation, fatty acid metabolism, calcium signaling, and antioxidant defense system were altered in the hearts of prometryn-treated mice. Proteasome and immunoproteasome activity assays and expression levels showed proteasome dysfunction in the hearts of prometryn-treated mice. The results suggest that prometryn induced changes in mitochondrial function and various signaling pathways within the heart, particularly affecting stress-related responses.
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Affiliation(s)
- Rasheed O. Sule
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, One Shields Ave., Davis, CA 95616, USA
- Center for Mitochondrial and Epigenomic Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Brett S. Phinney
- Proteomics Core Facility, University of California, Davis, Davis, CA 95616, USA; (B.S.P.); (M.R.S.)
| | - Michelle R. Salemi
- Proteomics Core Facility, University of California, Davis, Davis, CA 95616, USA; (B.S.P.); (M.R.S.)
| | - Aldrin V. Gomes
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, One Shields Ave., Davis, CA 95616, USA
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA 95616, USA
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MacLeod KT. Changes in cellular Ca 2+ and Na + regulation during the progression towards heart failure. J Physiol 2023; 601:905-921. [PMID: 35946572 PMCID: PMC10952717 DOI: 10.1113/jp283082] [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] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 08/02/2022] [Indexed: 11/08/2022] Open
Abstract
In adapting to disease and loss of tissue, the heart shows great phenotypic plasticity that involves changes to its structure, composition and electrophysiology. Together with parallel whole body cardiovascular adaptations, the initial decline in cardiac function resulting from the insult is compensated. However, in the long term, the heart muscle begins to fail and patients with this condition have a very poor prognosis, with many dying from disturbances of rhythm. The surviving myocytes of these hearts gain Na+ , which is positively inotropic because of alterations to Ca2+ fluxes mediated by the Na+ /Ca2+ exchange, but compromises Ca2+ -dependent energy metabolism in mitochondria. Uptake of Ca2+ into the sarcoplasmic reticulum (SR) is reduced because of diminished function of SR Ca2+ ATPases. The result of increased Ca2+ influx and reduced SR Ca2+ uptake is an increase in the diastolic cytosolic Ca2+ concentration, which promotes spontaneous SR Ca2+ release and induces delayed afterdepolarisations. Action potential duration prolongs because of increased late Na+ current and changes in expression and function of other ion channels and transporters increasing the probability of the formation of early afterdepolarisations. There is a reduction in T-tubule density and so the normal spatial arrangements required for efficient excitation-contraction coupling are compromised and lead to temporal delays in Ca2+ release from the SR. Therefore, the structural and electrophysiological responses that occur to provide compensation do so at the expense of (1) increasing the likelihood of arrhythmogenesis; (2) activating hypertrophic, apoptotic and Ca2+ signalling pathways; and (3) decreasing the efficiency of SR Ca2+ release.
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Affiliation(s)
- Kenneth T. MacLeod
- National Heart & Lung InstituteImperial Centre for Translational and Experimental MedicineImperial CollegeHammersmith HospitalLondonUK
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Pitsch M, Kant S, Mytzka C, Leube RE, Krusche CA. Autophagy and Endoplasmic Reticulum Stress during Onset and Progression of Arrhythmogenic Cardiomyopathy. Cells 2021; 11:96. [PMID: 35011658 PMCID: PMC8750195 DOI: 10.3390/cells11010096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 12/20/2021] [Accepted: 12/23/2021] [Indexed: 11/16/2022] Open
Abstract
Arrhythmogenic cardiomyopathy (AC) is a heritable, potentially lethal disease without a causal therapy. AC is characterized by focal cardiomyocyte death followed by inflammation and progressive formation of connective tissue. The pathomechanisms leading to structural disease onset and progression, however, are not fully elucidated. Recent studies revealed that dysregulation of autophagy and endoplasmic/sarcoplasmic reticulum (ER/SR) stress plays an important role in cardiac pathophysiology. We therefore examined the temporal and spatial expression patterns of autophagy and ER/SR stress indicators in murine AC models by qRT-PCR, immunohistochemistry, in situ hybridization and electron microscopy. Cardiomyocytes overexpressing the autophagy markers LC3 and SQSTM1/p62 and containing prominent autophagic vacuoles were detected next to regions of inflammation and fibrosis during onset and chronic disease progression. mRNAs of the ER stress markers Chop and sXbp1 were elevated in both ventricles at disease onset. During chronic disease progression Chop mRNA was upregulated in right ventricles. In addition, reduced Ryr2 mRNA expression together with often drastically enlarged ER/SR cisternae further indicated SR dysfunction during this disease phase. Our observations support the hypothesis that locally altered autophagy and enhanced ER/SR stress play a role in AC pathogenesis both at the onset and during chronic progression.
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Affiliation(s)
| | | | | | - Rudolf E. Leube
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany; (M.P.); (S.K.); (C.M.)
| | - Claudia A. Krusche
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany; (M.P.); (S.K.); (C.M.)
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Gaburjakova J, Almassy J, Gaburjakova M. Luminal addition of non-permeant Eu 3+ interferes with luminal Ca 2+ regulation of the cardiac ryanodine receptor. Bioelectrochemistry 2020; 132:107449. [PMID: 31918058 DOI: 10.1016/j.bioelechem.2019.107449] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 12/17/2019] [Accepted: 12/17/2019] [Indexed: 10/25/2022]
Abstract
Dysregulation of the cardiac ryanodine receptor (RYR2) by luminal Ca2+ has been implicated in a life-threatening, stress-induced arrhythmogenic disease. The mechanism of luminal Ca2+-mediated RYR2 regulation is under debate, and it has been attributed to Ca2+ binding on the cytosolic face (the Ca2+ feedthrough mechanism) and/or the luminal face of the RYR2 channel (the true luminal mechanism). The molecular nature and location of the luminal Ca2+ site is unclear. At the single-channel level, we directly probed the RYR2 luminal face by Eu3+, considering the non-permeant nature of trivalent cations and their high binding affinities for Ca2+ sites. Without affecting essential determinants of the Ca2+ feedthrough mechanism, we found that luminal Eu3+ competitively antagonized the activation effect of luminal Ca2+ on RYR2 responsiveness to cytosolic caffeine, and no appreciable effect was observed for luminal Ba2+ (mimicking the absence of luminal Ca2+). Importantly, luminal Eu3+ caused no changes in RYR2 gating. Our results indicate that two distinct Ca2+ sites (available for luminal Ca2+ even when the channel is closed) are likely involved in the true luminal mechanism. One site facing the lumen regulates channel responsiveness to caffeine, while the other site, presumably positioned in the channel pore, governs the gating behavior.
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Affiliation(s)
- Jana Gaburjakova
- Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dubravska Cesta 9, 840 05 Bratislava, Slovak Republic.
| | - Janos Almassy
- Department of Physiology, Faculty of Medicine, University of Debrecen, PO Box 400, Debrecen 4002, Hungary.
| | - Marta Gaburjakova
- Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dubravska Cesta 9, 840 05 Bratislava, Slovak Republic.
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Highly variable contractile performance correlates with myocyte content in trabeculae from failing human hearts. Sci Rep 2018; 8:2957. [PMID: 29440728 PMCID: PMC5811450 DOI: 10.1038/s41598-018-21199-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 01/16/2018] [Indexed: 12/24/2022] Open
Abstract
Heart failure (HF) is defined by compromised contractile function and is associated with changes in excitation-contraction (EC) coupling and cardiomyocyte organisation. Tissue level changes often include fibrosis, while changes within cardiomyocytes often affect structures critical to EC coupling, including the ryanodine receptor (RyR), the associated protein junctophilin-2 (JPH2) and the transverse tubular system architecture. Using a novel approach, we aimed to directly correlate the influence of structural alterations with force development in ventricular trabeculae from failing human hearts. Trabeculae were excised from explanted human hearts in end-stage failure and immediately subjected to force measurements. Following functional experiments, each trabecula was fixed, sectioned and immuno-stained for structural investigations. Peak stress was highly variable between trabeculae from both within and between failing hearts and was strongly correlated with the cross-sectional area occupied by myocytes (MCSA), rather than total trabecula cross-sectional area. At the cellular level, myocytes exhibited extensive microtubule densification which was linked via JPH2 to time-to-peak stress. Trabeculae fractional MCSA variability was much higher than that in adjacent free wall samples. Together, these findings identify several structural parameters implicated in functional impairment in human HF and highlight the structural variability of ventricular trabeculae which should be considered when interpreting functional data.
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De Pauw M, Mubagwa K, Hodeige D, Borgers M, Flameng W, Van de Voorde J, Heyndrickx GR. Response to exercise and mechanical efficiency in non-ischaemic stunning, induced by short-term rapid pacing in dogs: a role for calcium? Acta Physiol (Oxf) 2017; 219:768-780. [PMID: 26560191 DOI: 10.1111/apha.12629] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 06/02/2015] [Accepted: 11/04/2015] [Indexed: 11/28/2022]
Abstract
AIM Rapid pacing (RP) is a regularly used model to induce heart failure in dogs. The aim of the study was to evaluate Ca2+ handling, left ventricular (LV) contractile response during Ca2+ administration compared to exercise, as well as oxygen consumption and mechanical efficiency after 48 h of RP. METHODS Fifty-three mongrel dogs were instrumented to measure LV pressure, LV fractional shortening, regional wall thickening and coronary blood flow. Contractile reserve was measured with isoproterenol and intravenous (IV) Ca2+ administration. To assess the function of the sarcoplasmic reticulum (SR), post-extrasystolic potentiation (PESP) and SR Ca2+ uptake were measured. A graded treadmill test was performed in baseline and after RP (n = 14). In a separate group of animals (n = 5), myocardial performance and oxygen consumption were measured using a wide range of loading conditions. RESULTS Left ventricular contractility was significantly decreased upon cessation of pacing. The contractile response to isoproterenol was blunted compared to a preserved response to IV Ca2+ . Post-extrasystolic potentiation was slightly increased after RP. Maximal velocity (Vmax ) of SR Ca2+ uptake was unchanged. Contractile response during exercise is attenuated after RP. External work is reduced, whereas oxygen consumption is preserved, provoking a reduced mechanical efficiency. CONCLUSION Forty-eight-hours RP provokes a reversible LV dysfunction, while the SR function and response to exogenous Ca2+ are preserved. This is compatible with an intracellular functional remodelling to counteract Ca2+ overload provoked by RP. Left ventricular dysfunction is accompanied by a reduced contractile reserve, but an unchanged oxygen consumption, illustrating an alteration in oxygen utilization.
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Affiliation(s)
- M. De Pauw
- The Department of Cardiology; Ghent University Hospital; Ghent Belgium
| | - K. Mubagwa
- Unit of Experimental Cardiac Surgery; Department of Cardiovascular Sciences; University of Leuven; Leuven Belgium
| | - D. Hodeige
- University of Louvain Medical School Brussels; Brussels Belgium
| | - M. Borgers
- The Janssen Research Foundation; Beerse Belgium
| | - W. Flameng
- Unit of Experimental Cardiac Surgery; Department of Cardiovascular Sciences; University of Leuven; Leuven Belgium
| | | | - G. R. Heyndrickx
- University of Louvain Medical School Brussels; Brussels Belgium
- Cardiovascular Center Aalst; Aalst Belgium
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Kirk JA, Chakir K, Lee KH, Karst E, Holewinski RJ, Pironti G, Tunin RS, Pozios I, Abraham TP, de Tombe P, Rockman HA, Van Eyk JE, Craig R, Farazi TG, Kass DA. Pacemaker-induced transient asynchrony suppresses heart failure progression. Sci Transl Med 2017; 7:319ra207. [PMID: 26702095 DOI: 10.1126/scitranslmed.aad2899] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Uncoordinated contraction from electromechanical delay worsens heart failure pathophysiology and prognosis, but restoring coordination with biventricular pacing, known as cardiac resynchronization therapy (CRT), improves both. However, not every patient qualifies for CRT. We show that heart failure with synchronous contraction is improved by inducing dyssynchrony for 6 hours daily by right ventricular pacing using an intracardiac pacing device, in a process we call pacemaker-induced transient asynchrony (PITA). In dogs with heart failure induced by 6 weeks of atrial tachypacing, PITA (starting on week 3) suppressed progressive cardiac dilation as well as chamber and myocyte dysfunction. PITA enhanced β-adrenergic responsiveness in vivo and normalized it in myocytes. Myofilament calcium response declined in dogs with synchronous heart failure, which was accompanied by sarcomere disarray and generation of myofibers with severely reduced function, and these changes were absent in PITA-treated hearts. The benefits of PITA were not replicated when the same number of right ventricular paced beats was randomly distributed throughout the day, indicating that continuity of dyssynchrony exposure is necessary to trigger the beneficial biological response upon resynchronization. These results suggest that PITA could bring the benefits of CRT to the many heart failure patients with synchronous contraction who are not CRT candidates.
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Affiliation(s)
- Jonathan A Kirk
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Khalid Chakir
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Kyoung Hwan Lee
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | | | - Ronald J Holewinski
- Advanced Clinical Biosystems Research Institute, Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Gianluigi Pironti
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710, USA
| | - Richard S Tunin
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Iraklis Pozios
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Theodore P Abraham
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Pieter de Tombe
- Department of Cell and Molecular Physiology, Loyola University Stritch School of Medicine, Maywood, IL 60153, USA
| | - Howard A Rockman
- Department of Medicine, Duke University School of Medicine, Durham, NC 27710, USA
| | - Jennifer E Van Eyk
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. Advanced Clinical Biosystems Research Institute, Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Roger Craig
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | | | - David A Kass
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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8
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Weinberg SH. Impaired Sarcoplasmic Reticulum Calcium Uptake and Release Promote Electromechanically and Spatially Discordant Alternans: A Computational Study. CLINICAL MEDICINE INSIGHTS-CARDIOLOGY 2016; 10:1-15. [PMID: 27385917 PMCID: PMC4920205 DOI: 10.4137/cmc.s39709] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 05/26/2016] [Accepted: 05/27/2016] [Indexed: 02/01/2023]
Abstract
Cardiac electrical dynamics are governed by cellular-level properties, such as action potential duration (APD) restitution and intracellular calcium (Ca) handling, and tissue-level properties, including conduction velocity restitution and cell-cell coupling. Irregular dynamics at the cellular level can lead to instabilities in cardiac tissue, including alternans, a beat-to-beat alternation in the action potential and/or the intracellular Ca transient. In this study, we incorporate a detailed single cell coupled map model of Ca cycling and bidirectional APD-Ca coupling into a spatially extended tissue model to investigate the influence of sarcoplasmic reticulum (SR) Ca uptake and release properties on alternans and conduction block. We find that an intermediate SR Ca uptake rate and larger SR Ca release resulted in the widest range of stimulus periods that promoted alternans. However, both reduced SR Ca uptake and release promote arrhythmogenic spatially and electromechanically discordant alternans, suggesting a complex interaction between SR Ca handling and alternans characteristics at the cellular and tissue level.
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Affiliation(s)
- Seth H Weinberg
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
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9
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Gopinathannair R, Etheridge SP, Marchlinski FE, Spinale FG, Lakkireddy D, Olshansky B. Arrhythmia-Induced Cardiomyopathies: Mechanisms, Recognition, and Management. J Am Coll Cardiol 2016; 66:1714-28. [PMID: 26449143 DOI: 10.1016/j.jacc.2015.08.038] [Citation(s) in RCA: 206] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 07/28/2015] [Accepted: 08/17/2015] [Indexed: 12/19/2022]
Abstract
Arrhythmia-induced cardiomyopathy (AIC) is a potentially reversible condition in which left ventricular dysfunction is induced or mediated by atrial or ventricular arrhythmias. Cellular and extracellular changes in response to the culprit arrhythmia have been identified, but specific pathophysiological mechanisms remain unclear. Early recognition of AIC and prompt treatment of the culprit arrhythmia using pharmacological or ablative techniques result in symptom resolution and recovery of ventricular function. Although cardiomyopathy in response to an arrhythmia may take months to years to develop, recurrent arrhythmia can result in rapid decline in ventricular function with development of heart failure, suggesting residual ultrastructural abnormalities. Reports of sudden death in patients with normalized left ventricular ejection fraction cast doubt on the complete reversibility of this condition. Several aspects of AIC, including specific pathophysiological mechanisms, predisposing factors, optimal therapeutic strategies to prevent ultrastructural changes, and long-term risk of sudden death remain unresolved and need further research.
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Affiliation(s)
- Rakesh Gopinathannair
- Division of Cardiovascular Medicine, University of Louisville, Louisville, Kentucky.
| | - Susan P Etheridge
- Division of Pediatric Cardiology, University of Utah, Salt Lake City, Utah
| | | | - Francis G Spinale
- Department of Internal Medicine, University of South Carolina, Charleston, South Carolina
| | | | - Brian Olshansky
- Mercy Heart and Vascular Institute, Mercy Medical Center North Iowa, Mason City, Iowa
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Roe AT, Frisk M, Louch WE. Targeting cardiomyocyte Ca2+ homeostasis in heart failure. Curr Pharm Des 2015; 21:431-48. [PMID: 25483944 PMCID: PMC4475738 DOI: 10.2174/138161282104141204124129] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Accepted: 08/06/2014] [Indexed: 12/19/2022]
Abstract
Improved treatments for heart failure patients will require the development of novel therapeutic strategies that target basal disease
mechanisms. Disrupted cardiomyocyte Ca2+ homeostasis is recognized as a major contributor to the heart failure phenotype, as it
plays a key role in systolic and diastolic dysfunction, arrhythmogenesis, and hypertrophy and apoptosis signaling. In this review, we outline
existing knowledge of the involvement of Ca2+ homeostasis in these deficits, and identify four promising targets for therapeutic intervention:
the sarcoplasmic reticulum Ca2+ ATPase, the Na+-Ca2+ exchanger, the ryanodine receptor, and t-tubule structure. We discuss
experimental data indicating the applicability of these targets that has led to recent and ongoing clinical trials, and suggest future therapeutic
approaches.
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Affiliation(s)
| | | | - William E Louch
- Institute for Experimental Medical Research, Kirkeveien 166, 4.etg. Bygg 7, Oslo University Hospital Ullevål, 0407 Oslo, Norway.
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Lavorato M, Huang TQ, Iyer VR, Perni S, Meissner G, Franzini-Armstrong C. Dyad content is reduced in cardiac myocytes of mice with impaired calmodulin regulation of RyR2. J Muscle Res Cell Motil 2015; 36:205-14. [DOI: 10.1007/s10974-015-9405-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 01/24/2015] [Indexed: 11/27/2022]
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Affiliation(s)
- Gerd Heusch
- Institut für Pathophysiologie, Universitätsklinikum Essen
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Zahradníková A, Valent I, Zahradník I. Frequency and release flux of calcium sparks in rat cardiac myocytes: a relation to RYR gating. ACTA ACUST UNITED AC 2010; 136:101-16. [PMID: 20548054 PMCID: PMC2894546 DOI: 10.1085/jgp.200910380] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cytosolic calcium concentration in resting cardiac myocytes locally fluctuates as a result of spontaneous microscopic Ca2+ releases or abruptly rises as a result of an external trigger. These processes, observed as calcium sparks, are fundamental for proper function of cardiac muscle. In this study, we analyze how the characteristics of spontaneous and triggered calcium sparks are related to cardiac ryanodine receptor (RYR) gating. We show that the frequency of spontaneous sparks and the probability distribution of calcium release flux quanta of triggered sparks correspond quantitatively to predictions of an allosteric homotetrameric model of RYR gating. This model includes competitive binding of Ca2+ and Mg2+ ions to the RYR activation sites and allosteric interaction between divalent ion binding and channel opening. It turns out that at rest, RYRs are almost fully occupied by Mg2+. Therefore, spontaneous sparks are most frequently evoked by random openings of the highly populated but rarely opening Mg4RYR and CaMg3RYR forms, whereas triggered sparks are most frequently evoked by random openings of the less populated but much more readily opening Ca2Mg2RYR and Ca3MgRYR forms. In both the spontaneous and the triggered sparks, only a small fraction of RYRs in the calcium release unit manages to open during the spark because of the limited rate of Mg2+ unbinding. This mechanism clarifies the unexpectedly low calcium release flux during elementary release events and unifies the theory of calcium signaling in resting and contracting cardiac myocytes.
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Affiliation(s)
- Alexandra Zahradníková
- Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, 833 34 Bratislava, Slovak Republic.
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15
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Abstract
Regulation of Calcium (Ca) cycling by the sarcoplasmic reticulum (SR) underlies the control of cardiac contraction during excitation-contraction (E-C) coupling. Moreover, alterations in E-C coupling occurring in cardiac hypertrophy and heart failure are characterized by abnormal Ca-cycling through the SR network. A large body of evidence points to the central role of: a) SERCA and its regulator phospholamban (PLN) in the modulation of cardiac relaxation; b) calsequestrin in the regulation of SR Ca-load; and c) the ryanodine receptor (RyR) Ca-channel in the control of SR Ca-release. The levels or activity of these key Ca-handling proteins are altered in cardiomyopathies, and these changes have been linked to the deteriorated cardiac function and remodeling. Furthermore, genetic variants in these SR Ca-cycling proteins have been identified, which may predispose to heart failure or fatal arrhythmias. This chapter concentrates on the pivotal role of SR Ca-cycling proteins in health and disease with specific emphasis on their recently reported genetic modifiers.
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Kittleson MM, Lowenstein CJ, Hare JM. Novel pathogenetic mechanisms in myocarditis: nitric oxide signaling. Heart Fail Clin 2007; 1:345-61. [PMID: 17386859 DOI: 10.1016/j.hfc.2005.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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17
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Armoundas AA, Rose J, Aggarwal R, Stuyvers BD, O’Rourke B, Kass DA, Marbán E, Shorofsky SR, Tomaselli GF, Balke CW. Cellular and molecular determinants of altered Ca2+ handling in the failing rabbit heart: primary defects in SR Ca2+ uptake and release mechanisms. Am J Physiol Heart Circ Physiol 2006; 292:H1607-18. [PMID: 17122195 PMCID: PMC2711877 DOI: 10.1152/ajpheart.00525.2006] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Myocytes from the failing myocardium exhibit depressed and prolonged intracellular Ca(2+) concentration ([Ca(2+)](i)) transients that are, in part, responsible for contractile dysfunction and unstable repolarization. To better understand the molecular basis of the aberrant Ca(2+) handling in heart failure (HF), we studied the rabbit pacing tachycardia HF model. Induction of HF was associated with action potential (AP) duration prolongation that was especially pronounced at low stimulation frequencies. L-type calcium channel current (I(Ca,L)) density (-0.964 +/- 0.172 vs. -0.745 +/- 0.128 pA/pF at +10 mV) and Na(+)/Ca(2+) exchanger (NCX) currents (2.1 +/- 0.8 vs. 2.3 +/- 0.8 pA/pF at +30 mV) were not different in myocytes from control and failing hearts. The amplitude of peak [Ca(2+)](i) was depressed (at +10 mV, 0.72 +/- 0.07 and 0.56 +/- 0.04 microM in normal and failing hearts, respectively; P < 0.05), with slowed rates of decay and reduced Ca(2+) spark amplitudes (P < 0.0001) in myocytes isolated from failing vs. control hearts. Inhibition of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA)2a revealed a greater reliance on NCX to remove cytosolic Ca(2+) in myocytes isolated from failing vs. control hearts (P < 0.05). mRNA levels of the alpha(1C)-subunit, ryanodine receptor (RyR), and NCX were unchanged from controls, while SERCA2a and phospholamban (PLB) were significantly downregulated in failing vs. control hearts (P < 0.05). alpha(1C) protein levels were unchanged, RyR, SERCA2a, and PLB were significantly downregulated (P < 0.05), while NCX protein was significantly upregulated (P < 0.05). These results support a prominent role for the sarcoplasmic reticulum (SR) in the pathogenesis of HF, in which abnormal SR Ca(2+) uptake and release synergistically contribute to the depressed [Ca(2+)](i) and the altered AP profile phenotype.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Gordon F. Tomaselli
- Correspondence to: Gordon F. Tomaselli, M.D., Johns Hopkins University, Division of Cardiology, 844 Ross Building, 720 Rutland Avenue, Baltimore, MD 21205, Phone: (410) 955-2774, Fax: (410) 502-2096, E-mail:
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Saliaris AP, Amado LC, Minhas KM, Schuleri KH, Lehrke S, St John M, Fitton T, Barreiro C, Berry C, Zheng M, Kozielski K, Eneboe V, Brawn J, Hare JM. Chronic allopurinol administration ameliorates maladaptive alterations in Ca2+ cycling proteins and beta-adrenergic hyporesponsiveness in heart failure. Am J Physiol Heart Circ Physiol 2006; 292:H1328-35. [PMID: 17071724 DOI: 10.1152/ajpheart.00461.2006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Xanthine oxidase (XO) activity contributes to both abnormal excitation-contraction (EC) coupling and cardiac remodeling in heart failure (HF). beta-Adrenergic hyporesponsiveness and abnormalities in Ca(2+) cycling proteins are mechanistically linked features of the HF phenotype. Accordingly, we hypothesized that XO influences beta-adrenergic responsiveness and expression of genes whose products participate in deranged EC coupling. We measured inotropic (dP/dt(max)), lusitropic (tau), and vascular (elastance; E(a)) responses to beta-adrenergic (beta-AR) stimulation with dobutamine in conscious dogs administered allopurinol (100 mg po daily) or placebo during a 4-wk induction of pacing HF. With HF induction, the decreases in both baseline and dobutamine-stimulated inotropic responses were offset by allopurinol. Additionally, allopurinol converted a vasoconstrictor effect to dobutamine to a vasodilator response and enhanced both lusitropic and preload reducing effects. To assess molecular correlates for this phenotype, we measured myocardial sarcoplasmic reticulum Ca(2+)-ATPase 2a (SERCA), phospholamban (PLB), phosphorylated PLB (P-PLB), and Na(+)/Ca(2+) transporter (NCX) gene expression and protein. Although SERCA mRNA and protein concentrations did not change with HF, both PLB and NCX were upregulated (P < 0.05). Additionally, P-PLB and protein kinase A activity were greatly reduced. Allopurinol ameliorated all of these molecular alterations and preserved the PLB-to-SERCA ratio. Preventing maladaptive alterations of Ca(2+) cycling proteins represents a novel mechanism for XO inhibition-mediated preservation of cardiac function in HF, raising the possibility that anti-oxidant therapies for HF may ameliorate transcriptional changes associated with adverse cardiac remodeling and beta-adrenergic hyporesponsiveness.
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19
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Yano M, Yamamoto T, Ikeda Y, Matsuzaki M. Mechanisms of Disease: ryanodine receptor defects in heart failure and fatal arrhythmia. ACTA ACUST UNITED AC 2006; 3:43-52. [PMID: 16391617 DOI: 10.1038/ncpcardio0419] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Accepted: 09/27/2005] [Indexed: 11/08/2022]
Abstract
Abnormal regulation of intracellular Ca(2+) by sarcoplasmic reticulum plays a part in the mechanism underlying contractile and relaxation dysfunction in heart failure (HF). The protein-kinase-A-mediated hyperphosphorylation of ryanodine receptors in the sarcoplasmic reticulum has been shown to cause the dissociation of FKBP12.6 (also known as calstabin-2) from ryanodine receptors in HF. In addition, several disease-linked mutations in the ryanodine receptors have been reported in patients with catecholaminergic polymorphic ventricular tachycardia or arrhythmogenic right ventricular cardiomyopathy type 2. The unique distribution of these mutation sites has led to the concept that the interaction among the putative regulatory domains within the ryanodine receptors has a key role in regulating channel opening. The knowledge gained from various studies of ryanodine receptors under pathologic conditions might lead to the development of new pharmacological or genetic strategies for the treatment of HF or cardiac arrhythmia. In this review, we focus on the role of the Ca(2+)-release channel, the ryanodine receptor, in the pathogenesis of HF and fatal arrhythmia, and the possibility of developing new therapeutic strategies for targeting this receptor.
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Affiliation(s)
- Masafumi Yano
- Department of Medical Bioregulation, Division of Cardiovascular Medicine, Yamaguchi University Graduate School of Medicine, Yamaguchi, Japan
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20
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Sathish V, Xu A, Karmazyn M, Sims SM, Narayanan N. Mechanistic basis of differences in Ca2+ -handling properties of sarcoplasmic reticulum in right and left ventricles of normal rat myocardium. Am J Physiol Heart Circ Physiol 2006; 291:H88-96. [PMID: 16461368 DOI: 10.1152/ajpheart.01372.2005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study investigated Ca2+ -cycling properties of sarcoplasmic reticulum (SR) in right ventricle (RV) and left ventricle (LV) of normal rat myocardium. Intracellular Ca2+ transients and contractile function were monitored in freshly isolated myocytes from RV and LV. SR in RV displayed nearly fourfold lower rates of ATP-energized Ca2+ uptake in vitro than SR of LV. The Ca2+ concentration required for half-maximal activation of Ca2+ transport was nearly twofold higher in SR of RV. The lower Ca2+ -sequestering activity of SR in RV was accompanied by a matching decrement in Ca2+ -induced phosphoenzyme formation during the catalytic cycle of the Ca2+ -pumping ATPase (SERCA2). Western immunoblot analysis showed that protein levels of Ca2+ -ATPase and its inhibitor phospholamban (PLN) were only approximately 15% lower in SR of RV than in SR of LV. Coimmunoprecipitation experiments revealed that PLN-bound, functionally inert Ca2+ -ATPase molecules in SR of RV greatly exceed (> 50%) that in SR of LV. Endogenous Ca2+/calmodulin-dependent protein kinase-mediated phosphorylation of SR substrates did not abolish the huge disparity in SR Ca2+ pump function between RV and LV. Intracellular Ca2+ transients, evoked by electrical field stimulation, were significantly prolonged in RV myocytes compared with LV myocytes, mainly because of slow decay of intracellular Ca2+ concentration. The slow decay of intracellular Ca2+ concentration in RV and consequent decrease in the speed of RV relaxation may promote temporal synchrony of the end of diastole in RV and LV. The preponderance of functionally silent SR Ca2+ pumps in RV reflects a higher diastolic reserve required to protect and maintain RV function in the face of a sudden rise in afterload or resistance in the pulmonary circulation.
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Affiliation(s)
- V Sathish
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada N6A 5C1
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21
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Bin G, Fen QY, Hua LX, Hong ZB, Zheng PY, Shu TC. Dysfunction of myocardial sarcoplasmic reticulum in rats with myocardial calcification. Life Sci 2005; 77:966-79. [PMID: 15964313 DOI: 10.1016/j.lfs.2004.12.037] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Accepted: 12/21/2004] [Indexed: 11/24/2022]
Abstract
We investigated the relationship between cardiac dysfunction and Ca2+ transport in the myocardial sarcoplasmic reticulum (SR) during the pathogenesis of cardiovascular calcification in rats. The possible mechanism of SR dysfunction was explored by detecting the alteration of the nitric oxide/nitric oxide synthase (NO/NOS) pathway in the SR. Using the vitamin D plus nicotine (VDN treatment for 2 week and 6 week) experimental model of cardiac calcification, cardiac function and sarcoplasmic reticulum function were measured. Inhibition of cardiac functions in vivo (peak rate of contraction and peak rate of relaxation, P < 0.05 or P < 0.01) were observed in all calcification groups, simultaneously, Ca2+ release and uptake in the SR as well as the Ca2+ release channel and Ca2+ pump activity were inhibited. Myocardial Ca2+ concentration and cardiac and SR dysfunction were inversely related (P < 0.05). The specific NO/NOS pathway (NO production, NOS activity and nNOS expression in the SR) was upregulated in the SR and associated with calcification (both 2- and 6 week VDN groups). These results indicate that cardiac dysfunction associated with myocardial calcification might be mediated by SR dysfunction, which may result from an impaired SR-specific NO/NOS pathway.
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Affiliation(s)
- Geng Bin
- Institute of Cardiovascular Research, Peking University First Hospital, Beijing, 100034, China
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22
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Eisner DA, Díaz ME, O'Neill SC, Trafford AW. Physiological and pathological modulation of ryanodine receptor function in cardiac muscle. Cell Calcium 2004; 35:583-9. [PMID: 15110148 DOI: 10.1016/j.ceca.2004.01.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2003] [Accepted: 01/12/2004] [Indexed: 11/22/2022]
Abstract
Calcium release from the sarcoplasmic reticulum (SR) in cardiac muscle occurs through a specialised release channel, the ryanodine receptor, RyR, via the process of Ca-induced Ca release (CICR). The open probability of the RyR is increased by elevation of cytoplasmic Ca concentration ([Ca(2+)](i)). However, in addition to Ca, other modulators affect the RyR open probability. Agents which increase the RyR opening during systole produce a transient increase of systolic [Ca(2+)](i) followed by a return to the initial level due to a compensating decrease of SR Ca content. Increasing RyR opening during diastole decreases SR Ca content and thereby decreases systolic [Ca(2+)](i). We therefore conclude that potentiation of RyR opening will, if anything, decrease systolic [Ca(2+)](i). The effects of specific examples of modulators of the RyR, such as phosphorylation, metabolic changes, heart failure and polyunsaturated fatty acids, are discussed.
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Affiliation(s)
- D A Eisner
- Unit of Cardiac Physiology, University of Manchester, 1.524 Stopford Building, Oxford Road, Manchester M13 9PT, UK.
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23
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Erenberg FG, Banerjee A. Systolic and diastolic properties of univentricular hearts in children: insights from physiologic indices that reflect calcium cycling. Pediatr Res 2003; 54:885-91. [PMID: 12930909 DOI: 10.1203/01.pdr.0000090930.17613.d8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Physiologic indices that reflect intracellular Ca2+ cycling were chosen to evaluate contraction and relaxation properties of the univentricular heart. We hypothesized that these indices would be impaired in univentricular hearts. With advances in surgical palliation, an increasing number of children are surviving with univentricular hearts supporting the systemic circulation. Similar to the adult failing heart, single ventricles may also manifest impaired Ca2+ cycling, which may have important therapeutic implications. In our study, we did not actually measure Ca2+ uptake or transients in the cardiac myocyte. Rather, we used previously validated physiologic indices that are known to reflect Ca2+ cycling. Sixteen children were studied, eight with single ventricles (SV) and eight as matched control subjects. Systolic properties were studied using maximal derivative of ventricular pressure (dP/dtmax), force-frequency relationship, and mechanical restitution. Diastolic properties were assessed using time constant of relaxation (tau) and the relaxation-frequency relationship. The critical HR (HRcrit) was assessed from the force-frequency relationship and relaxation-frequency relationship. DP/dtmax and tau were calculated from micromanometric tracings at increasing HRs, generated by right atrial pacing. In SV patients, dP/dtmax was lower than in the control group at each matched HR, and the force-frequency relationship was shifted downward. Restitution of contractility was slower in patients with SV. Tau was similar in both groups at lower HRs but significantly prolonged in the SV group at faster HRs. In the SV, HRcrit was significantly shifted to the left. These findings indicate impaired systolic and diastolic properties of univentricular heart, especially at increased HRs. Because these physiologic indices reflect Ca2+ cycling, it is speculated that the phenomenon of Ca2+ cycling may be impaired in the myocytes of univentricular hearts.
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Affiliation(s)
- Francine G Erenberg
- Division of Pediatric Cardiology, Children's Hospital Medical Center, Cincinnati, Ohio, USA
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24
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Kim YK, Kim SJ, Yatani A, Huang Y, Castelli G, Vatner DE, Liu J, Zhang Q, Diaz G, Zieba R, Thaisz J, Drusco A, Croce C, Sadoshima J, Condorelli G, Vatner SF. Mechanism of enhanced cardiac function in mice with hypertrophy induced by overexpressed Akt. J Biol Chem 2003; 278:47622-8. [PMID: 13129932 DOI: 10.1074/jbc.m305909200] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Transgenic mice with cardiac-specific overexpression of active Akt (TG) not only exhibit hypertrophy but also show enhanced left ventricular (LV) function. In 3-4-month-old TG, heart/body weight was increased by 60% and LV ejection fraction was elevated (84 +/- 2%, p < 0.01) compared with nontransgenic littermates (wild type (WT)) (73 +/- 1%). An increase in isolated ventricular myocyte contractile function (% contraction) in TG compared with WT (6.1 +/- 0.2 versus 3.5 +/- 0.2%, p < 0.01) was associated with increased Fura-2 Ca2+ transients (396 +/- 50 versus 250 +/- 24 nmol/liter, p < 0.05). The rate of relaxation (+dL/dt) was also enhanced in TG (214 +/- 15 versus 98 +/- 18 microm/s, p < 0.01). L-type Ca2+ current (ICa) density was increased in TG compared with WT (-9.0 +/- 0.3 versus 7.2 +/- 0.3 pA/pF, p < 0.01). Sarcoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) protein levels were increased (p < 0.05) by 6.6-fold in TG, which could be recapitulated in vitro by adenovirus-mediated overexpression of Akt in cultured adult ventricular myocytes. Conversely, inhibiting SERCA with either ryanodine or thapsigargin affected myocyte contraction and relaxation and Ca2+ channel kinetics more in TG than in WT. Thus, myocytes from mice with overexpressed Akt demonstrated enhanced contractility and relaxation, Fura-2 Ca2+ transients, and Ca2+ channel currents. Furthermore, increased protein expression of SERCA2a plays an important role in mediating enhanced LV function by Akt. Up-regulation of SERCA2a expression and enhanced LV myocyte contraction and relaxation in Akt-induced hypertrophy is opposite to the down-regulation of SERCA2a and reduced contractile function observed in many other forms of LV hypertrophy.
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Affiliation(s)
- Young-Kwon Kim
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, University of Medicine and Dentistry New Jersey, New Jersey Medical School, Newark, New Jersey 07101-1709, USA
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25
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Affiliation(s)
- Gerd Hasenfuss
- Department of Cardiology and Pneumology, University of Göttingen, Robert-Koch-Strasse 40, 37075 Göttingen, Germany.
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26
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Choudhary G, Dudley SC. Heart failure, oxidative stress, and ion channel modulation. CONGESTIVE HEART FAILURE (GREENWICH, CONN.) 2002; 8:148-55. [PMID: 12045383 DOI: 10.1111/j.1527-5299.2002.00716.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The balance of reactive oxygen species (ROS) and nitric oxide, the cell redox state, appears to be important in the mechanisms of heart failure. This balance has significant impact on calcium-handling proteins, affecting excitation-contraction coupling. Both ROS and nitric oxide appear to be elevated in heart failure and are accompanied by significant impairments in the number and function of calcium-handling proteins. These proteins contain sulfhydryl groups or disulfide linkages involving cysteine residues, making them susceptible to the action of oxidizing-reducing agents and nitrosylation, thereby altering their properties. Initial increases in nitric oxide may be an adaptive response to myocardial dysfunction, elevated cytokines, and increases in ROS, while a further increase in nitric oxide and overwhelming ROS can be damaging. Abundant nitric oxide and ROS can cause formation of peroxynitrite, a strong oxidant, or nitric oxide can activate alternate pathways aiding the ROS, causing impaired calcium handling contributing to contractile dysfunction.
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Affiliation(s)
- Gaurav Choudhary
- Department of Medicine, Division of Cardiology, Emory University, Atlanta, GA, USA
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27
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Excitation-Contraction Coupling in Cardiac Muscle. MOLECULAR CONTROL MECHANISMS IN STRIATED MUSCLE CONTRACTION 2002. [DOI: 10.1007/978-94-015-9926-9_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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28
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Engelhardt S, Boknik P, Keller U, Neumann J, Lohse MJ, Hein L. Early impairment of calcium handling and altered expression of junctin in hearts of mice overexpressing the beta1-adrenergic receptor. FASEB J 2001; 15:2718-20. [PMID: 11606476 DOI: 10.1096/fj.01-0107fje] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Chronic stimulation of cardiac beta1-adrenergic receptors contributes to disease progression and mortality in patients and animal models of heart failure. To search for the mechanism of adrenergic impairment of cardiac function in vivo, we studied transgenic mice with cardiac-specific overexpression of beta1-adrenergic receptors. Transgenic mice with cardiac overexpression of beta1-adrenergic receptors showed progressive left ventricular fibrosis starting at 4 months of age. Left ventricular catheterization revealed a modest enhancement of contractility and relaxation at 2 months of age, followed by progressive dysfunction in both parameters and ultimately cardiac failure. When the effects of endogenous catecholamines were blocked by the b-receptor antagonist propranolol, maximal rate of contractility (dp/dtmax) and maximal rate of relaxation (dp/dtmin) were significantly blunted in 2-month-old beta1-receptor transgenic mice. Isolated cardiomyocytes from these animals displayed markedly altered calcium transients with significant prolongation of the intracellular calcium transient compared with nontransgenic littermates. We determined the expression of sarcoplasmic reticulum proteins involved in calcium handling by RNase protection assay and by immunoblotting. Although the expression of calsequestrin, triadin, and phospholamban was not altered, we observed a progressive decrease in junctin abundance in beta1-receptor transgenic mice (Pbeta1-adrenergic receptors.
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MESH Headings
- Animals
- Blood Pressure/physiology
- Blotting, Western
- Calcium/metabolism
- Calcium-Binding Proteins/genetics
- Calcium-Binding Proteins/metabolism
- Calcium-Transporting ATPases/genetics
- Calcium-Transporting ATPases/metabolism
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Gene Expression Regulation
- Gene Expression Regulation, Developmental
- Humans
- Hypertrophy, Left Ventricular/genetics
- Hypertrophy, Left Ventricular/metabolism
- Hypertrophy, Left Ventricular/physiopathology
- Membrane Proteins
- Mice
- Mice, Transgenic
- Mixed Function Oxygenases
- Muscle Proteins/genetics
- Muscle Proteins/metabolism
- Myocardial Contraction/physiology
- Myocardium/cytology
- Myocardium/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Adrenergic, beta-1/genetics
- Receptors, Adrenergic, beta-1/physiology
- Sarcoplasmic Reticulum/metabolism
- Sarcoplasmic Reticulum Calcium-Transporting ATPases
- Time Factors
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Affiliation(s)
- S Engelhardt
- Institut für Pharmakologie und Toxikologie, Universität Würzburg, Germany; and, Institut für Pharmakologie und Toxikologie, Universität Münster, Germany
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29
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Armoundas AA, Wu R, Juang G, Marbán E, Tomaselli GF. Electrical and structural remodeling of the failing ventricle. Pharmacol Ther 2001; 92:213-30. [PMID: 11916538 DOI: 10.1016/s0163-7258(01)00171-1] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Heart failure (HF) is a complex disease that presents a major public health challenge to Western society. The prevalence of HF increases with age in the elderly population, and the societal disease burden will increase with prolongation of life expectancy. HF is initially characterized by an adaptive increase of neurohumoral activation to compensate for reduction of cardiac output. This leads to a combination of neurohumoral activation and mechanical stress in the failing heart that trigger a cascade of maladaptive electrical and structural events that impair both the systolic and diastolic function of the heart.
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Affiliation(s)
- A A Armoundas
- Division of Molecular Cardiobiology, Johns Hopkins University, Ross 844, 720 Rutland Avenue, Baltimore, MD 21205, USA.
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30
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Milnes JT, MacLeod KT. Reduced ryanodine receptor to dihydropyridine receptor ratio may underlie slowed contraction in a rabbit model of left ventricular cardiac hypertrophy. J Mol Cell Cardiol 2001; 33:473-85. [PMID: 11181016 DOI: 10.1006/jmcc.2000.1320] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiac hypertrophy is associated with contractile dysfunction, a feature of which is a slowing of the time to reach peak contraction. We have examined the main mechanisms involved in the initiation of contraction and investigated if their functions are changed during cardiac hypertrophy. Cardiac hypertrophy was induced by constriction of the ascending aorta in the rabbit. After 6 weeks left ventricular myocytes were isolated or left ventricular and septal mixed membrane preparations were produced for electrophysiological and radioligand binding studies, respectively. Aortic constriction resulted in a 24% and 23% increase in heart weight to body weight ratio and cell capacitance, respectively. Action potential duration and time-to-reach 50% and 90% peak contraction (TTP(50)and TTP(90), respectively) were significantly prolonged in myocytes from hypertrophied hearts. The prolongation of TTP(50)and TTP(90)could not be explained by altered peak calcium current density or SR calcium content which were unchanged in hypertrophy. Radioligand binding studies performed on tissue preparations from the same hearts, revealed a 34% reduction in ryanodine receptor (RYR) density with no change in dihydropyridine receptor (DHPR) density. This resulted in a reduction in the ratio of RYR to DHPR from 4.4:1 to 3.3:1 in hypertrophy. Ryanodine receptor Ca(2+)-sensitivity was unchanged between sham operated and hypertrophied groups. A reduction in the ratio of RYRs to DHPRs may result in a degree of "functional uncoupling" causing defective release of Ca(2+)from the SR. These findings may underlie the slowed TTP of myocyte contraction in hypertrophy.
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Affiliation(s)
- J T Milnes
- Dept. Cardiac Medicine, National Heart and Lung Institute, Imperial College School of Medicine, Dovehouse Street, London, SW3 6LY, UK
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31
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Laurent CE, Cardinal R, Rousseau G, Vermeulen M, Bouchard C, Wilkinson M, Armour JA, Bouvier M. Functional desensitization to isoproterenol without reducing cAMP production in canine failing cardiocytes. Am J Physiol Regul Integr Comp Physiol 2001; 280:R355-64. [PMID: 11208562 DOI: 10.1152/ajpregu.2001.280.2.r355] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To corroborate alterations in the functional responses to beta-adrenergic receptor (beta-AR) stimulation with changes in beta-AR signaling in failing cardiomyocytes, contractile and L-type Ca(2+) current responses to isoproterenol along with stimulated cAMP generation were compared among cardiomyocytes isolated from canines with tachycardia-induced heart failure or healthy hearts. The magnitude of shortening of failing cardiomyocytes was significantly depressed (by 22 +/- 4.4%) under basal conditions, and the maximal response to isoproterenol was significantly reduced (by 45 +/- 18%). Similar results were obtained when the responses in the rate of contraction and rate of relaxation to isoproterenol were considered. The L-type Ca(2+) current amplitude measured in failing cardiomyocytes under basal conditions was unchanged, but the responses to isoproterenol were significantly reduced compared with healthy cells. Isoproterenol-stimulated cAMP generation was similar in sarcolemmal membranes derived from the homogenates of failing (45 +/- 6.8) and healthy cardiomyocytes (52 +/- 8.5 pmol cAMP. mg protein(-1). min(-1)). However, stimulated cAMP generation was found to be significantly reduced when the membranes were derived from the homogenates of whole tissue (failing: 67 +/- 8.1 vs. healthy: 140 +/- 27.8 pmol cAMP. mg protein(-1). min(-1)). Total beta-AR density was not reduced in membranes derived from either whole tissue or isolated cardiomyocyte homogenates, but the beta(1)/beta(2) ratio was significantly reduced in the former (failing: 45/55 vs. healthy: 72/28) without being altered in the latter (failing: 72/28, healthy: 77/23). We thus conclude that, in tachycardia-induced heart failure, reduction in the functional responses of isolated cardiomyocytes to beta-AR stimulation may be attributed to alterations in the excitation-contraction machinery rather than to limitation of cAMP generation.
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Affiliation(s)
- C E Laurent
- Département de Pharmacologie, Faculté de Médecine, Université de Montréal, Québec H3C 3J7, Canada
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32
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Wang YG, Benedict WJ, Hüser J, Samarel AM, Blatter LA, Lipsius SL. Brief rapid pacing depresses contractile function via Ca(2+)/PKC-dependent signaling in cat ventricular myocytes. Am J Physiol Heart Circ Physiol 2001; 280:H90-8. [PMID: 11123222 DOI: 10.1152/ajpheart.2001.280.1.h90] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study is to determine the effects of brief rapid pacing (RP; approximately 200-240 beats/min for approximately 5 min) on contractile function in ventricular myocytes. RP was followed by a sustained inhibition of peak systolic cell shortening (-44 +/- 4%) that was not due to changes in diastolic cell length, membrane voltage, or L-type Ca(2+) current (I(Ca,L)). During RP, baseline and peak intracellular Ca(2+) concentration ([Ca(2+)](i)) increased markedly. After RP, Ca(2+) transients were similar to control. The effects of RP on cell shortening were not prevented by 1 microM calpain inhibitor I, 25 microM L-N(5)-(1-iminoethyl)-orthinthine, or 100 microM N(G)-monomethyl-L-arginine. However, RP-induced inhibition of cell shortening was prevented by lowering extracellular [Ca(2+)] (0.5 mM) during RP or exposure to chelerythrine (2-4 microM), a protein kinase C (PKC) inhibitor, or LY379196 (30 nM), a selective inhibitor of PKC-beta. Exposure to phorbol ester (200 nM phorbol 12-myristate 13-acetate) inhibited cell shortening (-46 +/- 7%). Western blots indicated that cat myocytes express PKC-alpha, -delta, and -epsilon as well as PKC-beta. These findings suggest that brief RP of ventricular myocytes depresses contractility at the myofilament level via Ca(2+)/PKC-dependent signaling. These findings may provide insight into the mechanisms of contractile dysfunction that follow paroxysmal tachyarrhythmias.
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Affiliation(s)
- Y G Wang
- Department of Physiology, Stritch School of Medicine, Loyola University Chicago and Cardiovascular Institute, Maywood, Illinois 60153, USA
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33
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Ono K, Yano M, Ohkusa T, Kohno M, Hisaoka T, Tanigawa T, Kobayashi S, Kohno M, Matsuzaki M. Altered interaction of FKBP12.6 with ryanodine receptor as a cause of abnormal Ca(2+) release in heart failure. Cardiovasc Res 2000; 48:323-31. [PMID: 11054478 DOI: 10.1016/s0008-6363(00)00191-7] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
OBJECTIVE Little information is available as to the Ca(2+) release function of the sarcoplasmic reticulum (SR) in heart failure. We assessed whether the alteration in this function in heart failure is related to a change in the role of FK binding protein (FKBP), which is tightly coupled with the cardiac ryanodine receptor (RyR) and recently identified as a modulatory protein acting to stabilize the gating function of RyR. METHODS SR vesicles were isolated from dog LV muscles [normal (N), n=6; heart failure induced by 3-weeks pacing (HF), n=6]. The time course of the SR Ca(2+) release was continuously monitored using a stopped-flow apparatus, and [3H]ryanodine-binding and [3H]dihydro-FK506-binding assays were also performed. RESULTS FK506, which specifically binds to FKBP12.6 and dissociates it from RyR, decreased the polylysine-induced enhancement of [3H]ryanodine-binding by 38% in N (P<0.05) but it had no effect in HF. In HF, the rate constant for the polylysine-induced Ca(2+) release from the SR was 61% smaller than in N. FK506 decreased the rate constant for the polylysine-induced Ca(2+) release by 67% in N (P<0.05) but had no effect in HF. The [3H]dihydro-FK506-binding assay revealed that the number (B(max)) of FKBPs was decreased by 83% in HF (P<0.05), while the K(d) value was unchanged. FK506 did not significantly change SR Ca(2+.)-ATPase activity in either N or HF. CONCLUSIONS In HF, the number of FKBPs showed a tremendous decrease; this may underlie the RyR-channel instability and the impairment of the Ca(2+) release function of RyR seen in the failing heart.
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Affiliation(s)
- K Ono
- Second Department of Internal Medicine, Yamaguchi University School of Medicine, 1-1-1 Minamikogushi, Ube, 755-8505, Yamaguchi, Japan
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Takahashi N, Atsumi H, Nakada S, Takeishi Y, Tomoike H. Alterations in the inotropic responses to forskolin and Ca2+ and reduced gene expressions of Ca2+-signaling proteins induced by chronic volume overload in rabbits. JAPANESE CIRCULATION JOURNAL 2000; 64:861-7. [PMID: 11110432 DOI: 10.1253/jcj.64.861] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Volume overload results in eccentric cardiac hypertrophy, but it is still unknown how this mechanical overload modulates the inotropic response to exogenous Ca2+ or adenylyl cyclase stimulation. Inotropic responsiveness in vivo and the levels of gene expression of Ca2+ signaling proteins were studied in rabbit hearts hypertrophied as a result of volume overload at 4 and 12 weeks after arteriovenous shunt formation. In sham-operated control rabbits, left ventricular (LV)+dP/dt was augmented in response to graded doses of CaCl2. Dose-related changes of LV+dP/dt to CaCl2 were attenuated significantly in shunt rabbits with volume overload. Forskolin dose-dependently augmented LV+dP/dt in sham rabbits, which was also attenuated significantly in rabbits with volume overload. The mRNA levels of dihydropyridine receptor, Na+/Ca2+ exchanger, sarcoplasmic reticulum Ca2+-ATPase, and ryanodine receptor decreased significantly at 4 and 12 weeks in the volume-overload rabbits compared with the sham rabbits, but the mRNA levels of phospholamban and calsequestrin remained unchanged. Chronic volume overload alters contractile responsiveness to Ca2+ or adenylyl cyclase stimulation, and downregulation of steady state mRNA levels of Ca2+ signaling proteins might be, at least in part, related to this pathologic process.
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Affiliation(s)
- N Takahashi
- The First Department of Internal Medicine, Yamagata University School of Medicine, Japan
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Hoit BD, Kadambi VJ, Tramuta DA, Ball N, Kranias EG, Walsh RA. Influence of sarcoplasmic reticulum calcium loading on mechanical and relaxation restitution. Am J Physiol Heart Circ Physiol 2000; 278:H958-63. [PMID: 10710365 DOI: 10.1152/ajpheart.2000.278.3.h958] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mechanical and relaxation restitution represent the restoration of contractile force and relaxation, respectively, in premature beats having progressively longer extrasystolic intervals (ESI); these phenomena are related to intracellular activator Ca(2+) by poorly defined mechanisms. We tested the hypothesis that the level of phospholamban [which modulates the affinity of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase for Ca(2+), and thus the SR Ca(2+) load] may be an important determinant of both mechanical and relaxation restitution. Five mice with ablation of the phospholamban (PLB) gene (PLBKO), eight isogenic wild-type controls (129SvJ), eleven mice with PLB overexpression (PLBOE), and nine isogenic wild-type (FVB/N) controls were anesthetized and instrumented with a 1.4-Fr Millar catheter in the left ventricle and a 1-Fr pacemaker in the right atrium. At a cycle length of 200 ms, extrastimuli with increasing ESI were introduced, and the peak rates of left ventricular isovolumic contraction (+/-dP/dt(max)) were normalized and fit to monoexponential equations. In a subset, the protocols were repeated after ryanodine (4 ng/g) was administered to deplete SR Ca(2+) stores. The time constant of mechanical restitution in PLBKO was significantly shorter [6.3 +/- 1.2 (SE) vs. 47.7 +/- 7.6 ms] and began earlier (50 +/- 10 vs. 70 +/- 19 ms) than in 129SvJ. In contrast, the time constant of mechnical restitution was significantly longer (80.3 +/- 7.6 vs. 54.1 +/- 9.2 ms) in PLBOE than in FVB/N. The time constant of relaxation restitution was less in PLBKO than in 129SvJ (26.2 +/- 9.9 vs. 44.6 +/- 3.3, P < 0.05) but was similar in PLBOE and FVB/N (21.1 +/- 6.3 vs. 20.5 +/- 5.7 ms). Intravenous ryanodine decreased significantly the time constants of mechanical restitution in PLBOE, 129SvJ, and FVB/N but was lethal in PLBKO. In contrast, ryanodine increased the time constant of relaxation restitution. Thus 1) the phospholamban level is a critical determinant of mechanical restitution and (to a lesser extent) relaxation restitution in these transgenic models, and 2) ryanodine differentially affects mechanical and relaxation restitution. Furthermore, our data suggest a dissociation of processes within the SR that govern contraction and relaxation.
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Affiliation(s)
- B D Hoit
- Division of Cardiology, University of Cincinnati Medical Center, Cincinnati 45267-0575, Ohio.
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Sato N, Asai K, Okumura S, Takagi G, Shannon RP, Fujita-Yamaguchi Y, Ishikawa Y, Vatner SF, Vatner DE. Mechanisms of desensitization to a PDE inhibitor (milrinone) in conscious dogs with heart failure. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:H1699-705. [PMID: 10330256 DOI: 10.1152/ajpheart.1999.276.5.h1699] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The goal of this study was to determine the extent to which the effects of milrinone were desensitized in heart failure (HF) and to determine the mechanisms, i.e., whether these effects could be ascribed to changes in cAMP or phosphodiesterase (PDE) activity in HF. Accordingly, we examined the effects of milrinone in seven conscious dogs before and after HF was induced by rapid ventricular pacing at 240 beats/min. The dogs were chronically instrumented for measurements of left ventricular (LV) pressure and first derivative of LV pressure (dP/dt), arterial pressure, LV internal diameter, and wall thickness. Milrinone (10 micrograms . kg-1. min-1 iv) increased LV dP/dt by 1,854 +/- 157 from 2,701 +/- 105 mmHg/s (P < 0.05) before HF. After HF the increase in LV dP/dt in response to milrinone was attenuated significantly (P < 0.05); it increased by 615 +/- 67 from 1,550 +/- 107 mmHg/s, indicating marked desensitization. In the presence of ganglionic blockade the increases in LV dP/dt (+445 +/- 65 mmHg/s) in response to milrinone were markedly less (P < 0.01), and milrinone increased LV dP/dt even less in HF (+240 +/- 65 mmHg/s). cAMP and PDE activity were measured in endocardial and epicardial layers in normal and failing myocardium. cAMP was decreased significantly (P < 0.05) in LV endocardium (-26%) but not significantly in LV epicardium (-14%). PDE activity was also decreased significantly (P < 0.05) in LV endocardium (-18%) but not in LV epicardium (-4%). Thus significant desensitization to milrinone was observed in conscious dogs with HF. The major effect was autonomically mediated. The biochemical mechanism appears to be due in part to the modest reductions in PDE activity in failing myocardium, which, in turn, may be a compensatory mechanism to maintain cAMP levels in HF. Reductions in cAMP and PDE levels were restricted to the subendocardium, suggesting that the increased wall stress and reduced coronary reserve play a role in mediating these changes.
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Affiliation(s)
- N Sato
- Cardiovascular and Pulmonary Research Institute, Allegheny University of the Health Sciences, Pittsburgh, Pennsylvania 15212, USA
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Palmer BM, Valent S, Holder EL, Weinberger HD, Bies RD. Microtubules modulate cardiomyocyte beta-adrenergic response in cardiac hypertrophy. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:H1707-16. [PMID: 9815078 DOI: 10.1152/ajpheart.1998.275.5.h1707] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of microtubules in modulating cardiomyocyte beta-adrenergic response was investigated in rats with cardiac hypertrophy. Male Sprague-Dawley rats underwent stenosis of the abdominal aorta (hypertensive, HT) or sham operation (normotensive, NT). Echocardiography and isolated left ventricular cardiomyocyte dimensions demonstrated cardiac hypertrophy in the HT rats after 30 wk. Cardiomyocyte microtubule fraction was assayed by high-speed centrifugation and Western blot. In contrast to previous reports of increased microtubules after acute pressure overload, microtubule fraction for HT was significantly lower than that for NT. Cardiomyocytes were exposed to either 1 microM colchicine, 10 microM taxol, or equivalent volume of vehicle. Colchicine decreased microtubules, and taxol increased microtubules in both groups. Cardiomyocyte cytosolic calcium ([Ca2+]c) and shortening/relaxation dynamics were assessed during exposure to increasing isoproterenol concentrations. The beta-adrenergic response for these variables in the HT group was blunted compared with NT. However, increased microtubule assembly by taxol partially recovered the normal beta-adrenergic response for time to peak [Ca2+]c, time to peak shortening, and mechanical relaxation variables. Microtubule assembly may play a significant role in determining cardiomyocyte beta-adrenergic response in chronic cardiac hypertrophy.
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Affiliation(s)
- B M Palmer
- Department of Kinesiology and Applied Physiology, University of Colorado at Boulder, Boulder, Colorado 80309, USA
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Ueyama T, Ohkusa T, Yano M, Matsuzaki M. Growth hormone preserves cardiac sarcoplasmic reticulum Ca2+ release channels (ryanodine receptors) and enhances cardiac function in cardiomyopathic hamsters. Cardiovasc Res 1998; 40:64-73. [PMID: 9876318 DOI: 10.1016/s0008-6363(98)00095-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
OBJECTIVE Growth hormone (GH) improves cardiac function in experimental models of heart failure and human dilated cardiomyopathy. However, the mechanism by which GH increases myocardial contractility is not entirely clear. Our aim was to examine the effects of GH on cardiac function and cardiac sarcoplasmic reticulum Ca2+ release channels (ryanodine receptors, RyR) in the hearts of UM-X7.1 cardiomyopathic hamsters during the development of heart failure. METHODS Experimental and healthy control hamsters were examined at the age of 20 weeks. Recombinant human GH (2 mg/kg/day, s.c.) or vehicle was then administered for 3 weeks. We examined (i) the in vivo left ventricular (LV) size and LV systolic function using transthoracic echocardiography, (ii) the density (Bmax) and affinity (Kd) of high-affinity [3H] ryanodine binding sites in crude homogenates from normal and cardiomyopathic hamster hearts. RESULTS Vehicle-treated UM-X7.1 hamsters exhibited significant increases in left ventricular end-diastolic diameter and end-systolic diameter (LVESd), and a significant decrease in LV fractional shortening (FS). GH-treatment attenuated the increase in LVESd and reduced the LV chamber size, and also significantly increased LVFS. Vehicle-treated UM-X7.1 hamsters exhibited a significantly lower Bmax than control hamsters (0.34 +/- 0.04 vs 0.44 +/- 0.06 pmol/mg, p < 0.05), and the treatment with GH in UM-X7.1 hamsters significantly attenuated the reduction of Bmax (0.42 +/- 0.03 pmol/mg vs vehicle-treated group (0.34 +/- 0.04 pmol/mg), p < 0.05). Kd did not differ significantly between the experimental groups. In normal control hamsters, GH treatment with this dose did not significantly enhance LV systolic function or the density of RyRs. There was no significant difference in terms of the connective-tissue volume-fraction, myocyte size and capillary density between the GH- and vehicle-treated groups of UM-X7.1 hamsters. CONCLUSIONS GH treatment may improve cardiac function by preserving the density of RyRs and enhancing cellular function in cardiomyopathic hamster hearts.
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Affiliation(s)
- T Ueyama
- Second Department of Internal Medicine, Yamaguchi University School of Medicine, Japan
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Yao A, Su Z, Nonaka A, Zubair I, Spitzer KW, Bridge JH, Muelheims G, Ross J, Barry WH. Abnormal myocyte Ca2+ homeostasis in rabbits with pacing-induced heart failure. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:H1441-8. [PMID: 9746495 DOI: 10.1152/ajpheart.1998.275.4.h1441] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To determine whether there are abnormalities in myocyte excitation-contraction coupling and intracellular Ca2+ concentration ([Ca2+]i) homeostasis in pacing-induced heart failure (PF), we measured L-type Ca2+ current (ICa,L) and Na+/Ca2+ exchanger current (INa/Ca) with voltage clamp and measured intracellular Na+ concentration ([Na+]i) and [Ca2+]i with the use of sodium-binding benzofuran isophthalate (SBFI) and fluo 3 in ventricular myocytes isolated from control and paced rabbits. The peak systolic and diastolic levels and the amplitude of electrically stimulated [Ca2+]i transients (0.25 Hz, extracellular Ca2+ concentration = 1.08 mM) were significantly less in PF myocytes. Also, there was prolongation of the times to peak and decline of [Ca2+]i transients. ICa,L density was markedly decreased in PF myocytes. INa/Ca at -40 mV elicited by rapid exposure to 0 Na+ solution with a rapid solution switcher was significantly reduced in PF myocytes, suggesting that the function of the Na+/Ca2+ exchanger is impaired in these myocytes. In PF myocytes the decline of the [Ca2+]i transient when the Na+/Ca2+ exchanger was abruptly disabled was markedly prolonged compared with the decline in control myocytes, consistent with depressed sarcoplasmic reticulum (SR) Ca2+-ATPase function. RNase protection assay showed decreased levels of Na+/Ca2+ exchanger and SR Ca2+-ATPase mRNA in PF hearts, consistent with the function studies. We conclude that the functions of L-type Ca2+ channels, Na+/Ca2+ exchanger, and SR Ca2+-ATPase are impaired in myocytes from rabbit hearts with failure induced by rapid pacing. These abnormalities result in reduced [Ca2+]i transients and systolic and diastolic dysfunction and appear to account for the abnormal ventricular function observed.
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Affiliation(s)
- A Yao
- Division of Cardiology, University of Utah Health Sciences Center, Salt Lake City, Utah 84132, USA
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40
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Chu G, Ferguson DG, Edes I, Kiss E, Sato Y, Kranias EG. Phospholamban ablation and compensatory responses in the mammalian heart. Ann N Y Acad Sci 1998; 853:49-62. [PMID: 10603936 DOI: 10.1111/j.1749-6632.1998.tb08256.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phospholamban is a low molecular weight phosphoprotein in cardiac sarcoplasmic reticulum. The regulatory role of phospholamban in vivo has recently been elucidated by targeting the gene of this protein in embryonic stem cells and generating phospholamban-deficient mice. The phospholamban knockout hearts exhibited significantly enhanced contractile parameters and attenuated responses to beta-agonists. The hyperdynamic cardiac function of the phospholamban knockout mice was not accompanied by any cytoarchitectural abnormalities or alterations in the expression levels of the cardiac sarcoplasmic reticulum Ca(2+)-ATPase, calsequestrin, Na(+)-Ca2+ exchanger, or the contractile proteins. Furthermore, the attenuation of the cardiac responses to beta-agonists was not due to alterations in the phosphorylation levels of the other key cardiac phosphoproteins in the phospholamban knockout hearts. However, ablation of phospholamban was associated with down-regulation of the ryanodine receptor, which suggests that a cross-talk between cardiac sarcoplasmic reticulum Ca2+ uptake and Ca2+ release occurred in an attempt to maintain Ca2+ homeostasis in these hyperdynamic phospholamban knockout hearts.
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Affiliation(s)
- G Chu
- Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Ohio 45267-0575, USA
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Shoshan-Barmatz V, Ashley RH. The structure, function, and cellular regulation of ryanodine-sensitive Ca2+ release channels. INTERNATIONAL REVIEW OF CYTOLOGY 1998; 183:185-270. [PMID: 9666568 DOI: 10.1016/s0074-7696(08)60145-x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The fundamental biological process of Ca2+ signaling is known to be important in most eukaryotic cells, and inositol 1,2,5-trisphosphate and ryanodine receptors, intracellular Ca2+ release channels encoded by two distantly related gene families, are central to this phenomenon. Ryanodine receptors in the sarcoplasmic reticulum of skeletal and cardiac muscle have a predominant role in excitation-contraction coupling, but the channels are also present in the endoplasmic reticulum of noncontractile tissues including the central nervous system and the immune system. In all, three highly homologous ryanodine receptor isoforms have been identified, all very large proteins which assemble as (homo)tetramers of approximately 2 MDa. They contain large cytoplasmically disposed regulatory domains and are always associated with other structural or regulatory proteins, including calmodulin and immunophilins, which can have marked effects on channel function. The type 1 isoform in skeletal muscle is electromechanically coupled to surface membrane voltage sensors, whereas the remaining isoforms appear to be activated solely by endogenous cytoplasmic second messengers or other ligands, including Ca2+ itself ("Ca(2+)-induced Ca2+ release"). This review concentrates on ryanodine receptor structure-function relationships as probed by a variety of methods and on the molecular mechanisms of channel modulation at the cellular level (including evidence for the regulation of gene expression and transcription). It also touches on the relevance of ryanodine receptors to complex cellular functions and disease.
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Affiliation(s)
- V Shoshan-Barmatz
- Department of Life Sciences, Ben-Gurion University, Beer-Sheva, Israel
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McCall E, Ginsburg KS, Bassani RA, Shannon TR, Qi M, Samarel AM, Bers DM. Ca flux, contractility, and excitation-contraction coupling in hypertrophic rat ventricular myocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:H1348-60. [PMID: 9575940 DOI: 10.1152/ajpheart.1998.274.4.h1348] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Left ventricular hypertrophy (approximately 40%) was induced in rats by banding of the abdominal aorta. After 16 wk, ventricular homogenates were prepared for biochemical measurements and ventricular myocytes were isolated for functional studies. In myocytes, the effects of banding on intracellular Ca handling, contraction, and excitation-contraction (E-C) coupling were determined using indo 1 fluorescence and whole cell voltage clamp. After steady-state field or voltage-clamp stimulation to load the sarcoplasmic reticulum (SR), SR Ca content assessed by caffeine-induced Ca transients was the same in sham and banded groups. Despite this, cell shortening amplitudes were significantly depressed in the banded group, suggesting altered contractile properties. In banded rats, the SR Ca-adenosinetriphosphatase (Ca-ATPase) mRNA level was reduced, as was homogenate thapsigargin-sensitive SR Ca-ATPase, but cytosolic free Ca concentration ([Ca]i) decline attributed to SR Ca-ATPase activity in intact cells was not slowed. Banding also reduced Na/Ca exchange mRNA level but did not affect either Na-dependent sarcolemmal 45Ca transport in homogenate or the rate of [Ca]i decline in intact cells attributed to Na/Ca exchange (during caffeine-induced contractures). Banding also did not change the rate of [Ca]i decline mediated by the combined function of the mitochondrial Ca uptake and sarcolemmal Ca-ATPase in intact cells. Ca current (ICa) density and voltage dependence were the same in sham and banded groups. Ryanodine receptor mRNA, protein content, and ryanodine affinity were also unchanged in the banded group. At 1 mM extracellular Ca concentration ([Ca]o), banding did not affect E-C coupling efficacy in intact cells under voltage clamp (i.e., same contraction for given ICa and SR Ca load). However, when [Ca]o was reduced to 0.5 mM, the efficacy of E-C coupling was greatly depressed in the banded group (even though ICa and SR Ca content were matched). In summary, unloaded myocyte contraction was depressed in these hypertrophic hearts, but Ca transport was little altered, at 1 mM [Ca]o. However, reduction of [Ca]o to 0.5 mM appears to unmask a depressed fractional SR Ca release in response to a given ICa trigger and SR Ca load.
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Affiliation(s)
- E McCall
- Department of Physiology, Loyola University Medical Center, Maywood, Illinois 60153, USA
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Yamakado T, Yamada N, Tarumi T, Nakamura M, Nakano T. Left ventricular inotropic and lusitropic responses to pacing-induced tachycardia in patients with varying degrees of ventricular dysfunction. Am Heart J 1998; 135:584-91. [PMID: 9539471 DOI: 10.1016/s0002-8703(98)70271-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND In the failing human heart contractile reserve during tachycardia is attenuated or absent. However, it is not known whether during tachycardia diminished inotropic reserve depends on the degree of ventricular dysfunction or lusitropic reserve is also diminished in patients with left ventricular (LV) dysfunction. METHODS We studied 18 patients with dilated cardiomyopathy or mildly depressed LV function and 13 subjects in a control group (ejection fraction 0.67+/-0.09). The patients were classified into two groups based on whether their ejection fraction was less than or more than 0.40 (group 1, ejection fraction 0.27+/-0.05; group 2, ejection fraction 0.49+/-0.07). LV pressures were measured with a catheter-tip manometer during incremental right atrial pacing up to a heart rate of 150 beats/min. RESULTS With incremental pacing LV peak positive dP/dt rose progressively in both the normal group and in group 2, but the increase was less for group 2 than for the normal group; in group 1 the increase was slight or absent. In contrast, a significant and progressive decrease occurred in the time constant of LV relaxation in all three groups. Although their values remained significantly different at each heart rate, no intergroup differences in absolute or percent changes were present. CONCLUSIONS These findings suggest that during tachycardia LV inotropic reserve may be diminished depending on the degree of ventricular dysfunction, and lusitropic reserve may be preserved in patients with depressed function despite an attenuated inotropic response.
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Affiliation(s)
- T Yamakado
- First Department of Internal Medicine, Mie University, Tsu, Japan
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Affiliation(s)
- G Hasenfuss
- Medizinische Klinik III, Universität Freiburg, Germany.
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Ueyama T, Ohkusa T, Hisamatsu Y, Nakamura Y, Yamamoto T, Yano M, Matsuzaki M. Alterations in cardiac SR Ca(2+)-release channels during development of heart failure in cardiomyopathic hamsters. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:H1-7. [PMID: 9458845 DOI: 10.1152/ajpheart.1998.274.1.h1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The cardiomyopathic Syrian hamster develops a progressive cardiomyopathy characterized by cellular necrosis, hypertrophy, cardiac dilatation, and congestive heart failure. This study aimed to identify alterations in cardiac mechanical function and in the cellular content of sarcoplasmic reticulum (SR) Ca(2+)-release channels (ryanodine receptors, RyR) in the heart of the UM-X7.1 cardiomyopathic hamster during the development of heart failure. Experimental and healthy control hamsters were examined at 8, 18, and 28 wk of age. The UM-X7.1 hamsters had developed left ventricular (LV) hypertrophy at 8 wk and a marked LV dilatation at 18-28 wk. During the latter stage, the UM-X7.1 hamster hearts showed global hypokinesis. Equilibrium binding assays of high-affinity sites for [3H]ryanodine were performed in ventricular homogenate preparations. There was no significant difference between the two groups in the maximum number of [3H]ryanodine binding sites (Bmax) at either 8 or 18 wk of age, although the cardiac pump function was impaired in UM-X7.1 hamsters at 18 wk of age. By 28 wk, Bmax was significantly lower in the UM-X7.1 hamsters. Quantitative immunoblot assay revealed that the content of RyR protein in cardiomyopathic hearts, which was increased at the early stage, declined to below normal as heart failure advanced. These results suggest that the number of RyR in the UM-X7.1 cardiomyopathic hamsters was preserved at both the hypertrophic and early stages of heart failure with a possibly compensatory increase in the level of protein expression, although the cardiac function already showed a tendency to be impaired.
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Affiliation(s)
- T Ueyama
- Second Department of Internal Medicine, Yamaguchi University School of Medicine, Japan
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Ryu KH, Tanaka N, Dalton N, Mao L, Rockman HA, Milano CA, Ross J. Force-frequency relations in the failing rabbit heart and responses to adrenergic stimulation. J Card Fail 1997; 3:27-39. [PMID: 9110253 DOI: 10.1016/s1071-9164(97)90006-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Recent experiments have documented the importance of beta-adrenergic regulation of the force-frequency relation (FFR) in the normal and failing heart. As in isolated human cardiac muscle, a descending limb of the FFR occurs at high frequencies in the intact rabbit heart, and therefore a new model of atrial pacing-induced heart failure was developed in the rabbit. Responses of the FFR to beta-adrenergic stimulation were then assessed in the conscious state before and after the induction of heart failure. METHODS AND RESULTS Rapid atrial pacing for an average of 19.5 days in instrumented rabbits produced severe left ventricular dilation with reduced cardiac output (echocardiography) and depressed myocardial contractility and relaxation rate (left ventricular dP/dt, catheter-tip micromanometer), associated with reductions in beta-adrenergic receptor density and adenylyl cyclase activity. Before heart failure, heart rate was slowed in the conscious animal from 280 +/- 30 (SD) to about 225 beats/min using a sinus node inhibitor (zatebradine), and heart rate was then increased in steps by atrial pacing from 250 to 450 beats/min; the heart rate-versus-left ventricular dP/dtmax (FFR) response showed an ascending response (increasing contractility), with a descending limb at rates greater than 375 beats/min, and dobutamine infusion amplified the ascending limb of the FFR (increased slope) and attenuated the descending limb. In heart failure the basal FFR was severely depressed with a descending limb over 350 beats/min; dobutamine shifted the FFR upward somewhat without change in the slope of the ascending limb, whereas dobutamine prevented the descending limb of the FFR. Similar responses were observed in the relations between heart rate and cardiac output. CONCLUSIONS A new model of heart failure in the conscious rabbit was developed using rapid atrial pacing and applied to study force-frequency effects. In heart failure, normal beta-adrenergic amplification of the ascending limb of the FFR by dobutamine was absent, but a marked descending limb of the FFR at higher heart rates was prevented by dobutamine. Observed reductions in components of the beta-adrenergic receptor system likely were responsible for impaired beta-adrenergic FFR amplification, but the mechanism(s) for the descending limb and its correction by dobutamine are not yet established. These responses of the FFR may influence importantly the ability of the failing heart to respond to exercise and stress.
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Affiliation(s)
- K H Ryu
- Department of Medicine, University of California San Diego, La Jolla 92093-0613, USA
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47
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Isoform Diversity and Regulation of Organellar-Type Ca2+-Transport ATPases. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s1569-2558(08)60156-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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48
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Zheng L, Wibo M, Kolár F, Godfraind T. Calcium channels and cation transport ATPases in cardiac hypertrophy induced by aortic constriction in newborn rats. Mol Cell Biochem 1996; 163-164:23-9. [PMID: 8974036 DOI: 10.1007/bf00408637] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Cardiac enlargement due to gradual pressure overload was induced by abdominal aortic constriction in 2-day-old rats. On day 90, the functional performance of the left ventricle was assessed by acute load test (ligation of ascending aorta) in open-chest anaesthetized animals. Two subgroups, designated compensated and decompensated hypertrophy (CH and DH), were distinguished on the basis of the functional reserve of left ventricle, which was significantly impaired in DH but not in CH, and of right ventricle weight, which was markedly increased in DH but not significantly modified in CH. In total particulate fractions prepared from hypertrophied left ventricles, the levels (per g tissue) of sarcoplasmic reticulum Ca(2+)-transport systems were decreased, either slightly (by 13-16%: [3H]ryanodine binding) or moderately (by 28%: thapsigargin-sensitive Ca(2+)-ATPase activity). The number of sarcolemmal L-type Ca2+ channels ([3H]PN200-110 binding) was not modified significantly, while that of beta 1-adrenoceptors ([3H]CGP-12177 binding) was reduced, especially in the DH group (by 39%). Na+,K(+)-ATPase activity was reduced by 28% in CH and 41% in DH. [3H]Ouabain binding experiments (saturation and dissociation) indicated the existence of two high-affinity binding sites, attributable to the Na+, K(+)-ATPase alpha 3 and alpha 2 subunit isoforms; while the relatively minor alpha 3 component did not change significantly in hypertrophied ventricles, the alpha 2 component was markedly down-regulated, decreasing by 57% in CH and 82% in DH.
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Affiliation(s)
- L Zheng
- Laboratoire de Pharmacologie, Université Catholique de Louvain, Brussels, Belgium
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49
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Gengo PJ. Physiologic and emerging pathophysiologic role of cardiac calcium channels. Heart Fail Rev 1996. [DOI: 10.1007/bf00126379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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50
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Vatner DE, Sato N, Ishikawa Y, Kiuchi K, Shannon RP, Vatner SF. Beta-adrenoceptor desensitization during the development of canine pacing-induced heart failure. Clin Exp Pharmacol Physiol 1996; 23:688-92. [PMID: 8886492 DOI: 10.1111/j.1440-1681.1996.tb01760.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
1. The goal of this review is to emphasize four major points regarding the development of catecholamine desensitization in heart failure (HF). 2. Catecholamine desensitization occurs prior to the development of HF (i.e. after 1 day of rapid pacing, physiological responses to beta-adrenoceptor stimulation are depressed by over 50%, yet no evidence of HF is observed for 3-4 weeks of rapid pacing). 3. Multiple mechanisms in the beta-adrenoceptor cascade are involved. In HF there are decreases in beta 1-adrenoceptors, high affinity beta-adrenoceptors, adenylyl cyclase activity and messenger RNA and increases in Gi. 4. Not all mechanisms appear simultaneously (i.e. early decreases occur in high affinity beta-adrenoceptors and adenylyl cyclase; late increases in Gi and decreases in beta-adrenoceptor density evolves). 5. Mechanisms distal to cAMP generation also play a role (i.e. alterations in ryanodine receptor binding and excitation-contraction coupling also occur).
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Affiliation(s)
- D E Vatner
- Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA
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