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Fülöp GÁ, Oláh A, Csipo T, Kovács Á, Pórszász R, Veress R, Horváth B, Nagy L, Bódi B, Fagyas M, Helgadottir SL, Bánhegyi V, Juhász B, Bombicz M, Priksz D, Nanasi P, Merkely B, Édes I, Csanádi Z, Papp Z, Radovits T, Tóth A. Omecamtiv mecarbil evokes diastolic dysfunction and leads to periodic electromechanical alternans. Basic Res Cardiol 2021; 116:24. [PMID: 33844095 PMCID: PMC8041714 DOI: 10.1007/s00395-021-00866-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 03/31/2021] [Indexed: 01/31/2023]
Abstract
Omecamtiv mecarbil (OM) is a promising novel drug for improving cardiac contractility. We tested the therapeutic range of OM and identified previously unrecognized side effects. The Ca2+ sensitivity of isometric force production (pCa50) and force at low Ca2+ levels increased with OM concentration in human permeabilized cardiomyocytes. OM (1 µM) slowed the kinetics of contractions and relaxations and evoked an oscillation between normal and reduced intracellular Ca2+ transients, action potential lengths and contractions in isolated canine cardiomyocytes. Echocardiographic studies and left ventricular pressure-volume analyses demonstrated concentration-dependent improvements in cardiac systolic function at OM concentrations of 600-1200 µg/kg in rats. Administration of OM at a concentration of 1200 µg/kg was associated with hypotension, while doses of 600-1200 µg/kg were associated with the following aspects of diastolic dysfunction: decreases in E/A ratio and the maximal rate of diastolic pressure decrement (dP/dtmin) and increases in isovolumic relaxation time, left atrial diameter, the isovolumic relaxation constant Tau, left ventricular end-diastolic pressure and the slope of the end-diastolic pressure-volume relationship. Moreover, OM 1200 µg/kg frequently evoked transient electromechanical alternans in the rat in vivo in which normal systoles were followed by smaller contractions (and T-wave amplitudes) without major differences on the QRS complexes. Besides improving systolic function, OM evoked diastolic dysfunction and pulsus alternans. The narrow therapeutic window for OM may necessitate the monitoring of additional clinical safety parameters in clinical application.
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MESH Headings
- Action Potentials/drug effects
- Adult
- Animals
- Arrhythmias, Cardiac/chemically induced
- Arrhythmias, Cardiac/metabolism
- Arrhythmias, Cardiac/physiopathology
- Blood Pressure/drug effects
- Calcium Signaling/drug effects
- Cardiotonic Agents/toxicity
- Diastole
- Dogs
- Dose-Response Relationship, Drug
- Female
- Heart Rate/drug effects
- Humans
- Hypotension/chemically induced
- Hypotension/metabolism
- Hypotension/physiopathology
- Kinetics
- Male
- Myocardial Contraction/drug effects
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Rats, Inbred WKY
- Systole
- Urea/analogs & derivatives
- Urea/toxicity
- Ventricular Dysfunction, Left/chemically induced
- Ventricular Dysfunction, Left/metabolism
- Ventricular Dysfunction, Left/physiopathology
- Ventricular Function, Left/drug effects
- Rats
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Grants
- GINOP-2.3.2-15-2016-00043 Ministry for National Economy of Hungary, co-financed by the European Union and the European Regional Development Fund
- ÚNKP-18-3-III-DE-209 Ministry of Human Capacities of Hungary, co-financed by the European Union and the European Regional Development Fund
- ED_18-1-2019-0028, TKP2020-IKA-04 and TKP2020-NKA-04 The Thematic Excellence Programme of the Ministry for Innovation and Technology, also supported from the National Research, Development and Innovation Fund of Hungary
- FK 128809 National Research, Development and Innovation Fund of Hungary
- FK 128116 National Research, Development and Innovation Fund of Hungary
- K 134939 National Research, Development and Innovation Fund of Hungary.
- K 116940 and K 132623 National Research, Development and Innovation Fund of Hungary.
- Therapeutic Development thematic programme of the Semmelweis University Higher Education Institutional Excellence Programme of the Ministry for Innovation and Technology in Hungary
- 2020-4.1.1.-TKP2020, Therapeutic Development and Bioimaging thematic programme of the Semmelweis University The Thematic Excellence Programme of the Ministry for Innovation and Technology was also supported from the National Research, Development and Innovation Fund of Hungary
- The Thematic Excellence Programme of the Ministry for Innovation and Technology, also supported from the National Research, Development and Innovation Fund of Hungary
- The Thematic Excellence Programme of the Ministry for Innovation and Technology was also supported from the National Research, Development and Innovation Fund of Hungary
- University of Debrecen
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Affiliation(s)
- Gábor Á Fülöp
- Division of Clinical Physiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, 22 Móricz Zsigmond Street, 4032, Debrecen, Hungary
- Doctoral School of Kálmán Laki, University of Debrecen, Debrecen, Hungary
| | - Attila Oláh
- Heart and Vascular Center, Semmelweis University, Budapest, Hungary
| | - Tamas Csipo
- Division of Clinical Physiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, 22 Móricz Zsigmond Street, 4032, Debrecen, Hungary
- Doctoral School of Kálmán Laki, University of Debrecen, Debrecen, Hungary
| | - Árpád Kovács
- Division of Clinical Physiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, 22 Móricz Zsigmond Street, 4032, Debrecen, Hungary
- Division of Cardiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Róbert Pórszász
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Roland Veress
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - László Nagy
- Division of Clinical Physiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, 22 Móricz Zsigmond Street, 4032, Debrecen, Hungary
- Division of Cardiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Beáta Bódi
- Division of Clinical Physiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, 22 Móricz Zsigmond Street, 4032, Debrecen, Hungary
| | - Miklós Fagyas
- Division of Clinical Physiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, 22 Móricz Zsigmond Street, 4032, Debrecen, Hungary
- Division of Cardiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Solveig Lind Helgadottir
- Division of Clinical Physiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, 22 Móricz Zsigmond Street, 4032, Debrecen, Hungary
| | - Viktor Bánhegyi
- Division of Clinical Physiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, 22 Móricz Zsigmond Street, 4032, Debrecen, Hungary
- Doctoral School of Kálmán Laki, University of Debrecen, Debrecen, Hungary
| | - Béla Juhász
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Mariann Bombicz
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Daniel Priksz
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Peter Nanasi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Béla Merkely
- Heart and Vascular Center, Semmelweis University, Budapest, Hungary
| | - István Édes
- Division of Cardiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zoltán Csanádi
- Division of Cardiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zoltán Papp
- Division of Clinical Physiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, 22 Móricz Zsigmond Street, 4032, Debrecen, Hungary
- HAS-UD Vascular Biology and Myocardial Pathophysiology Research Group, Hungarian Academy of Sciences, Budapest, Hungary
| | - Tamás Radovits
- Heart and Vascular Center, Semmelweis University, Budapest, Hungary
| | - Attila Tóth
- Division of Clinical Physiology, Department of Cardiology, Faculty of Medicine, University of Debrecen, 22 Móricz Zsigmond Street, 4032, Debrecen, Hungary.
- HAS-UD Vascular Biology and Myocardial Pathophysiology Research Group, Hungarian Academy of Sciences, Budapest, Hungary.
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Kovács Á, Fülöp GÁ, Kovács A, Csípő T, Bódi B, Priksz D, Juhász B, Beke L, Hendrik Z, Méhes G, Granzier HL, Édes I, Fagyas M, Papp Z, Barta J, Tóth A. Renin overexpression leads to increased titin-based stiffness contributing to diastolic dysfunction in hypertensive mRen2 rats. Am J Physiol Heart Circ Physiol 2016; 310:H1671-82. [PMID: 27059079 DOI: 10.1152/ajpheart.00842.2015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 03/30/2016] [Indexed: 01/09/2023]
Abstract
Hypertension (HTN) is a major risk factor for heart failure. We investigated the influence of HTN on cardiac contraction and relaxation in transgenic renin overexpressing rats (carrying mouse Ren-2 renin gene, mRen2, n = 6). Blood pressure (BP) was measured. Cardiac contractility was characterized by echocardiography, cellular force measurements, and biochemical assays were applied to reveal molecular mechanisms. Sprague-Dawley (SD) rats (n = 6) were used as controls. Transgenic rats had higher circulating renin activity and lower cardiac angiotensin-converting enzyme two levels. Systolic BP was elevated in mRen2 rats (235.11 ± 5.32 vs. 127.03 ± 7.56 mmHg in SD, P < 0.05), resulting in increased left ventricular (LV) weight/body weight ratio (4.05 ± 0.09 vs. 2.77 ± 0.08 mg/g in SD, P < 0.05). Transgenic renin expression had no effect on the systolic parameters, such as LV ejection fraction, cardiomyocyte Ca(2+)-activated force, and Ca(2+) sensitivity of force production. In contrast, diastolic dysfunction was observed in mRen2 compared with SD rats: early and late LV diastolic filling ratio (E/A) was lower (1.14 ± 0.04 vs. 1.87 ± 0.08, P < 0.05), LV isovolumetric relaxation time was longer (43.85 ± 0.89 vs. 28.55 ± 1.33 ms, P < 0.05), cardiomyocyte passive tension was higher (1.74 ± 0.06 vs. 1.28 ± 0.18 kN/m(2), P < 0.05), and lung weight/body weight ratio was increased (6.47 ± 0.24 vs. 5.78 ± 0.19 mg/g, P < 0.05), as was left atrial weight/body weight ratio (0.21 ± 0.03 vs. 0.14 ± 0.03 mg/g, P < 0.05). Hyperphosphorylation of titin at Ser-12742 within the PEVK domain and a twofold overexpression of protein kinase C-α in mRen2 rats were detected. Our data suggest a link between the activation of renin-angiotensin-aldosterone system and increased titin-based stiffness through phosphorylation of titin's PEVK element, contributing to diastolic dysfunction.
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Affiliation(s)
- Árpád Kovács
- Division of Clinical Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Gábor Á Fülöp
- Division of Clinical Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Andrea Kovács
- Division of Clinical Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Tamás Csípő
- Division of Clinical Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Beáta Bódi
- Division of Clinical Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Dániel Priksz
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Béla Juhász
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Lívia Beke
- Department of Pathology, Medical Center, University of Debrecen, Debrecen, Hungary
| | - Zoltán Hendrik
- Department of Pathology, Medical Center, University of Debrecen, Debrecen, Hungary
| | - Gábor Méhes
- Department of Pathology, Medical Center, University of Debrecen, Debrecen, Hungary
| | - Henk L Granzier
- Department of Physiology, University of Arizona, Tucson, Arizona; and
| | - István Édes
- Department of Cardiology, Medical Center, University of Debrecen, Debrecen, Hungary; Research Center for Molecular Medicine, University of Debrecen, Debrecen, Hungary
| | - Miklós Fagyas
- Division of Clinical Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Department of Cardiology, Medical Center, University of Debrecen, Debrecen, Hungary
| | - Zoltán Papp
- Division of Clinical Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Research Center for Molecular Medicine, University of Debrecen, Debrecen, Hungary
| | - Judit Barta
- Department of Cardiology, Medical Center, University of Debrecen, Debrecen, Hungary;
| | - Attila Tóth
- Division of Clinical Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Research Center for Molecular Medicine, University of Debrecen, Debrecen, Hungary
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3
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Katrukha IA. Human cardiac troponin complex. Structure and functions. BIOCHEMISTRY (MOSCOW) 2014; 78:1447-65. [DOI: 10.1134/s0006297913130063] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Manning JR, Perkins SO, Sinclair EA, Gao X, Zhang Y, Newman G, Pyle WG, Schultz JEJ. Low molecular weight fibroblast growth factor-2 signals via protein kinase C and myofibrillar proteins to protect against postischemic cardiac dysfunction. Am J Physiol Heart Circ Physiol 2013; 304:H1382-96. [PMID: 23479264 DOI: 10.1152/ajpheart.00613.2012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Among its many biological roles, fibroblast growth factor-2 (FGF2) acutely protects the heart from dysfunction associated with ischemia/reperfusion (I/R) injury. Our laboratory has demonstrated that this is due to the activity of the low molecular weight (LMW) isoform of FGF2 and that FGF2-mediated cardioprotection relies on the activity of protein kinase C (PKC); however, which PKC isoforms are responsible for LMW FGF2-mediated cardioprotection, and their downstream targets, remain to be elucidated. To identify the PKC pathway(s) that contributes to postischemic cardiac recovery by LMW FGF2, mouse hearts expressing only LMW FGF2 (HMWKO) were bred to mouse hearts not expressing PKCα (PKCαKO) or subjected to a selective PKCε inhibitor (εV(1-2)) before and during I/R. Hearts only expressing LMW FGF2 showed significantly improved postischemic recovery of cardiac function following I/R (P < 0.05), which was significantly abrogated in the absence of PKCα (P < 0.05) or presence of PKCε inhibition (P < 0.05). Hearts only expressing LMW FGF2 demonstrated differences in actomyosin ATPase activity as well as increases in the phosphorylation of troponin I and T during I/R compared with wild-type hearts; several of these effects were dependent on PKCα activity. This evidence indicates that both PKCα and PKCε play a role in LMW FGF2-mediated protection from cardiac dysfunction and that PKCα signaling to the contractile apparatus is a key step in the mechanism of LMW FGF2-mediated protection against myocardial dysfunction.
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Affiliation(s)
- Janet R Manning
- Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
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5
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Yang FH, Pyle WG. Reduced cardiac CapZ protein protects hearts against acute ischemia–reperfusion injury and enhances preconditioning. J Mol Cell Cardiol 2012; 52:761-72. [DOI: 10.1016/j.yjmcc.2011.11.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 11/17/2011] [Accepted: 11/21/2011] [Indexed: 10/14/2022]
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6
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Tilley DG. G protein-dependent and G protein-independent signaling pathways and their impact on cardiac function. Circ Res 2011; 109:217-30. [PMID: 21737817 DOI: 10.1161/circresaha.110.231225] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
G protein-coupled receptors signal through a variety of mechanisms that impact cardiac function, including contractility and hypertrophy. G protein-dependent and G protein-independent pathways each have the capacity to initiate numerous intracellular signaling cascades to mediate these effects. G protein-dependent signaling has been studied for decades and great strides continue to be made in defining the intricate pathways and effectors regulated by G proteins and their impact on cardiac function. G protein-independent signaling is a relatively newer concept that is being explored more frequently in the cardiovascular system. Recent studies have begun to reveal how cardiac function may be regulated via G protein-independent signaling, especially with respect to the ever-expanding cohort of β-arrestin-mediated processes. This review primarily focuses on the impact of both G protein-dependent and β-arrestin-dependent signaling pathways on cardiac function, highlighting the most recent data that illustrate the comprehensive nature of these mechanisms of G protein-coupled receptor signaling.
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Affiliation(s)
- Douglas G Tilley
- Department of Pharmaceutical Sciences, Jefferson School of Pharmacy, and Center for Translational Medicine, Thomas Jefferson University, 1025 Walnut Street, 402 College Building, Philadelphia, PA 19107, USA.
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7
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Kooij V, Stienen GJM, van der Velden J. The role of protein kinase C-mediated phosphorylation of sarcomeric proteins in the heart-detrimental or beneficial? Biophys Rev 2011; 3:107. [PMID: 28510060 DOI: 10.1007/s12551-011-0050-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 06/08/2011] [Indexed: 10/18/2022] Open
Abstract
Protein kinase C (PKC) is a family of serine/threonine protein kinases, and alterations have been found in PKC isoform expression and localization in the failing heart. These alterations in PKC activation levels influence the PKC-mediated phosphorylation status of cellular target proteins involved in Ca2+-handling and sarcomeric contraction. The differences observed in the effects due to PKC-mediated phosphorylation may underlie part of the contractile dysfunction observed in the failing heart. It is therefore important to establish the beneficial and detrimental effects of this kinase in the healthy and failing heart. The function of PKC has been studied intensively; however, the complexity of the regulation of this kinase makes the interpretation of the different effects difficult. The main focus of this review is the (patho)physiological impact of phosphorylation of sarcomeric proteins, myosin light chain-2, troponin I and T, desmin, myosin binding protein-C, and titin by PKC.
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Affiliation(s)
- Viola Kooij
- Division of Cardiology, Johns Hopkins Bayview Proteomics Center, Johns Hopkins University, 5200 Eastern Avenue, MFL Bldg, Center Tower, Rm 601, Baltimore, MD, 21224, USA.
| | - Ger J M Stienen
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
| | - Jolanda van der Velden
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
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Chen WQ, Cai H, Zhang C, Ji XP, Zhang Y. Is overall blockade superior to selective blockade of adrenergic receptor subtypes in suppressing left ventricular remodeling in spontaneously hypertensive rats? Hypertens Res 2010; 33:1071-81. [PMID: 20668454 DOI: 10.1038/hr.2010.121] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
To test the hypothesis that nonselective blockade of adrenergic receptor (AR) subtypes is superior to selective blockade of AR subtypes in suppressing left ventricular (LV) remodeling induced by hypertension. Sixty-four spontaneously hypertensive rats (SHR) were randomly divided into four groups: bisoprolol-treated, propranolol-treated, carvedilol-treated and no treatment groups (n=16, each). Sixteen Wistar-Kyoto (WKY) rats served as a control group. Echocardiography and cardiac catheterization were carried out to record the mitral flow velocity ratio of E wave to A wave (E/A), LV mass index (LVMI), maximal rising (dp/dt(max)) and falling (-dp/dt(max)) rate of the LV pressure and LV relaxation time constant (τ). The mRNA and protein expression levels of AR, protein kinase(PK) and G-protein subtypes, intracellular free calcium (Ca) concentration and cardiocyte apoptoisis rate were determined. Three drug-treated groups showed higher velocity ratio of E wave to A wave (E/A) and -dp/dt(max) and lower systolic blood pressure (SBP), LVMI, τ, apoptosis rate and intracellular free Ca(2+) concentration than the no treatment group. The mRNA expression levels of AR-α(1B) in the carvedilol group were significantly lower than the other two drug-treated groups. The mRNA expression levels of AR-β(1), AR-β(2) and Gsα were significantly higher in the three drug-treated groups than in the no treatment group, with the expression levels of AR-β(2) being the highest in the carvedilol-treated group. The protein expression levels of PKA and PKC subtype α and δ were lower in the three drug-treated groups than in the no treatment group. Overall blockade of AR subtypes is not superior to selective blockade of AR subtypes in suppressing LV remodeling in SHR. Although carvedilol is the most effective in attenuating cardiocyte apoptosis, normalizing AR-α(1B) and Gsα expression and increasing AR-β(2) expression.
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Affiliation(s)
- Wen Qiang Chen
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Shandong University Qilu Hospital, Shandong, PR China
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Abstract
JPs (junctophilins) contribute to the formation of junctional membrane complexes in muscle cells by physically linking the t-tubule (transverse-tubule) and SR (sarcoplasmic reticulum) membranes. In humans with HCM (hypertrophic cardiomyopathy), mutations in JP2 are linked to altered Ca2+ signalling in cardiomyocytes; however, the effects of these mutations on skeletal muscle function have not been examined. In the present study, we investigated the role of the dominant-negative JP2-S165F mutation (which is associated with human HCM) in skeletal muscle. Consistent with the hypertrophy observed in human cardiac muscle, overexpression of JP2-S165F in primary mouse skeletal myotubes led to a significant increase in myotube diameter and resting cytosolic Ca2+ concentration. Single myotube Ca2+ imaging experiments showed reductions in both the excitation-contraction coupling gain and RyR (ryanodine receptor) 1-mediated Ca2+ release from the SR. Immunoprecipitation assays revealed defects in the PKC (protein kinase C)-mediated phosphorylation of the JP2-S165F mutant protein at Ser165 and in binding of JP2-S165F to the Ca2+ channel TRPC3 (transient receptor potential cation canonical-type channel 3) on the t-tubule membrane. Therefore both the hypertrophy and altered intracellular Ca2+ signalling in the JP2-S165F-expressing skeletal myotubes can be linked to altered phosphorylation of JP2 and/or altered cross-talk among Ca2+ channels on the t-tubule and SR membranes.
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Kooij V, Boontje N, Zaremba R, Jaquet K, dos Remedios C, Stienen GJM, van der Velden J. Protein kinase C alpha and epsilon phosphorylation of troponin and myosin binding protein C reduce Ca2+ sensitivity in human myocardium. Basic Res Cardiol 2009; 105:289-300. [PMID: 19655190 PMCID: PMC2807945 DOI: 10.1007/s00395-009-0053-z] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Revised: 07/20/2009] [Accepted: 07/22/2009] [Indexed: 12/01/2022]
Abstract
Previous studies indicated that the increase in protein kinase C (PKC)-mediated myofilament protein phosphorylation observed in failing myocardium might be detrimental for contractile function. This study was designed to reveal and compare the effects of PKCα- and PKCε-mediated phosphorylation on myofilament function in human myocardium. Isometric force was measured at different [Ca2+] in single permeabilized cardiomyocytes from failing human left ventricular tissue. Activated PKCα and PKCε equally reduced Ca2+ sensitivity in failing cardiomyocytes (ΔpCa50 = 0.08 ± 0.01). Both PKC isoforms increased phosphorylation of troponin I- (cTnI) and myosin binding protein C (cMyBP-C) in failing cardiomyocytes. Subsequent incubation of failing cardiomyocytes with the catalytic subunit of protein kinase A (PKA) resulted in a further reduction in Ca2+ sensitivity, indicating that the effects of both PKC isoforms were not caused by cross-phosphorylation of PKA sites. Both isozymes showed no effects on maximal force and only PKCα resulted in a modest significant reduction in passive force. Effects of PKCα were only minor in donor cardiomyocytes, presumably because of already saturated cTnI and cMyBP-C phosphorylation levels. Donor tissue could therefore be used as a tool to reveal the functional effects of troponin T (cTnT) phosphorylation by PKCα. Massive dephosphorylation of cTnT with alkaline phosphatase increased Ca2+ sensitivity. Subsequently, PKCα treatment of donor cardiomyocytes reduced Ca2+ sensitivity (ΔpCa50 = 0.08 ± 0.02) and solely increased phosphorylation of cTnT, but did not affect maximal and passive force. PKCα- and PKCε-mediated phosphorylation of cMyBP-C and cTnI as well as cTnT decrease myofilament Ca2+ sensitivity and may thereby reduce contractility and enhance relaxation of human myocardium.
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Affiliation(s)
- Viola Kooij
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands.
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11
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Glazer HP, Osipov RM, Clements RT, Sellke FW, Bianchi C. Hypercholesterolemia is associated with hyperactive cardiac mTORC1 and mTORC2 signaling. Cell Cycle 2009; 8:1738-46. [PMID: 19395857 DOI: 10.4161/cc.8.11.8619] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Nutritional excess and hyperlipidemia increase the heart's susceptibility to ischemic injury. Mammalian target of rapamycin (mTOR) controls the cellular response to nutritional status and may play a role in ischemic injury. To explore the effect of hypercholesterolemia on cardiac mTOR signaling, we assessed mTOR signaling in hypercholesterolemic swine (HC) that are also susceptible to increased cardiac ischemia-reperfusion injury. Yucatan pigs were fed a high-fat/high-cholesterol diet for 4 weeks to induce hypercholesterolemia, and mTOR signaling was measured by immunoblotting and immunofluorescence in the non-ischemic left ventricular area. Total myocardial mTOR and raptor levels were markedly increased in the HC group compared to the normocholesterolemic group, and directly correlated with serum cholesterol levels. mTOR exhibited intense perinuclear staining in myocytes only in the HC group. Hypercholesterolemia was associated with hyperactive signaling upstream and downstream of both mTOR complexes, including myocardial Akt, S6K1, 4EBP1, S6 and PKC-alpha, increased levels of cardiac hypertrophy markers, and a trend toward lower levels of myocardial autophagy. Hypercholesterolemia can now be added to the growing list of conditions associated with aberrant mTOR signaling. Hypercholesterolemia produces a unique profile of alterations in cardiac mTOR signaling, which is a potential target in cardiac diseases associated with hypercholesterolemia and nutritional excess.
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Affiliation(s)
- Hilary P Glazer
- Division of Cardiothoracic Surgery Research, Beth Israel Deaconess Medical Center & Harvard Medical School, Boston, MA 02215, USA
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