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Phungphong S, Kijtawornrat A, Wattanapermpool J, Bupha-Intr T. Improvement in cardiac function of ovariectomized rats by antioxidant tempol. Free Radic Biol Med 2020; 160:239-245. [PMID: 32763410 DOI: 10.1016/j.freeradbiomed.2020.06.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 05/27/2020] [Accepted: 06/06/2020] [Indexed: 12/13/2022]
Abstract
A rise in heart disease incidence in women after menopause has led to investigations into the role of female sex hormones on cardiac function. Although various adverse changes in cardiac contractile function following loss of female sex hormones have been reported, a clear mechanism of action has never been characterized. In order to examine whether an elevation in oxidative stress is a major cause of cardiac contractile dysfunction after female sex hormone deprivation, cardiac functions of ovariectomized rats with and without supplementation of superoxide scavenger tempol were compared to those of sham-operated controls. Chronic deprivation of female sex hormones reduced total oxidative capacity and increased plasma carbonyl protein content. Tempol supplementation of ovariectomized rats significantly ameliorated plasma oxidative stress status. Echocardiography demonstrated a significant decrease in left ventricular ejection fraction in ovariectomized rats, which was completely prevented by tempol supplementation. Decreased myocardial contractility occurs with reduced maximum myofilament force of contraction and amplitude of transient intracellular Ca2+ concentration, both phenomena completely attenuated by tempol supplementation. However, tempol only partially prevented shift of heart myosin heavy chain from dominant α-to β-isoform of ovariectomized rats. Immunoblot analysis of protein carbonylation indicated that tempol supplementation significantly reduced the level of cardiac myofibrillar proteins oxidation increased in ovariectomized rat heart. Taken together, the results indicate changes of cardiac contractile machinery following loss of female sex hormones were, in part, due to an increase in oxidative stress, and antioxidant supplementation could be considered another potential prevention measure in postmenopausal women.
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Affiliation(s)
- Sukanya Phungphong
- Department of Physiology, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
| | - Anusak Kijtawornrat
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | | | - Tepmanas Bupha-Intr
- Department of Physiology, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand.
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2
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Phungphong S, Kijtawornrat A, Kampaengsri T, Wattanapermpool J, Bupha-Intr T. Comparison of exercise training and estrogen supplementation on mast cell-mediated doxorubicin-induced cardiotoxicity. Am J Physiol Regul Integr Comp Physiol 2020; 318:R829-R842. [PMID: 32159365 DOI: 10.1152/ajpregu.00224.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cardiac inflammation has been proposed as one of the primary mechanisms of anthracycline-induced acute cardiotoxicity. A reduction in cardiac inflammation might also reduce cardiotoxicity. This study aimed to evaluate the potential of estrogen therapy and regular exercise on attenuating cardiac inflammation in the context of doxorubicin-induced cardiomyopathy. Ovariectomized rats were randomly allocated into estrogen supplementation, exercise training, and mast cell stabilizer treatment groups. Eight weeks after ovariectomy, rats received six cumulative doses of doxorubicin for two weeks. Echocardiography demonstrated a progressive decrease in ejection fraction in doxorubicin-treated rats without hypertrophic effect. This systolic defect was completely prevented by either estrogen supplementation or mast cell stabilizer treatment but not by regular exercise. As a heart disease indicator, increased β-myosin heavy chain expression induced by doxorubicin could only be prevented by estrogen supplementation. Decrease in shortening and intracellular Ca2+ transients of cardiomyocytes were due to absence of female sex hormones without further effects of doxorubicin. Again, estrogen supplementation and mast cell stabilizer treatment prevented these changes but exercise training did not. Histological analysis indicated that the hyperactivation of cardiac mast cells in ovariectomized rats was augmented by doxorubicin. Estrogen supplementation and mast cell stabilizer treatment completely prevented both increases in mast cell density and degranulation, whereas exercise training partially attenuated the hyperactivation. Our results, therefore, suggest that estrogen supplementation acts similarly to mast cell stabilizers in attenuating the effects of doxorubicin. Ineffectiveness of regular exercise in preventing the acute cardiotoxicity of doxorubicin might be due to a lesser effect on preventing cardiac inflammation.
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Affiliation(s)
- Sukanya Phungphong
- Department of Physiology, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Anusak Kijtawornrat
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand
| | | | | | - Tepmanas Bupha-Intr
- Department of Physiology, Faculty of Science, Mahidol University, Bangkok, Thailand
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Bildyug NB, Khaitlina SY. Redistribution of Sarcomeric Myosin and α-Actinin in Cardiomyocytes in Culture upon the Rearrangement of their Contractile Apparatus. ACTA ACUST UNITED AC 2019. [DOI: 10.1134/s1990519x1905002x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Bildyug N. Extracellular Matrix in Regulation of Contractile System in Cardiomyocytes. Int J Mol Sci 2019; 20:E5054. [PMID: 31614676 PMCID: PMC6834325 DOI: 10.3390/ijms20205054] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 10/07/2019] [Accepted: 10/09/2019] [Indexed: 12/16/2022] Open
Abstract
The contractile apparatus of cardiomyocytes is considered to be a stable system. However, it undergoes strong rearrangements during heart development as cells progress from their non-muscle precursors. Long-term culturing of mature cardiomyocytes is also accompanied by the reorganization of their contractile apparatus with the conversion of typical myofibrils into structures of non-muscle type. Processes of heart development as well as cell adaptation to culture conditions in cardiomyocytes both involve extracellular matrix changes, which appear to be crucial for the maturation of contractile apparatus. The aim of this review is to analyze the role of extracellular matrix in the regulation of contractile system dynamics in cardiomyocytes. Here, the remodeling of actin contractile structures and the expression of actin isoforms in cardiomyocytes during differentiation and adaptation to the culture system are described along with the extracellular matrix alterations. The data supporting the regulation of actin dynamics by extracellular matrix are highlighted and the possible mechanisms of such regulation are discussed.
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Affiliation(s)
- Natalya Bildyug
- Institute of Cytology, Russian Academy of Sciences, St-Petersburg 194064, Russia.
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Rattanasopa C, Kirk JA, Bupha-Intr T, Papadaki M, de Tombe PP, Wattanapermpool J. Estrogen but not testosterone preserves myofilament function from doxorubicin-induced cardiotoxicity by reducing oxidative modifications. Am J Physiol Heart Circ Physiol 2019; 316:H360-H370. [PMID: 30499711 PMCID: PMC6397386 DOI: 10.1152/ajpheart.00428.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Here, we aimed to explore sex differences and the impact of sex hormones on cardiac contractile properties in doxorubicin (DOX)-induced cardiotoxicity. Male and female Sprague-Dawley rats were subjected to sham surgery or gonadectomy and then treated or untreated with DOX (2 mg/kg) every other week for 10 wk. Estrogen preserved maximum active tension (Tmax) with DOX exposure, whereas progesterone and testosterone did not. The effects of sex hormones and DOX correlated with both altered myosin heavy chain isoform expression and myofilament protein oxidation, suggesting both as possible mechanisms. However, acute treatment with oxidative stress (H2O2) or a reducing agent (DTT) indicated that the effects on Tmax were mediated by reversible myofilament oxidative modifications and not only changes in myosin heavy chain isoforms. There were also sex differences in the DOX impact on myofilament Ca2+ sensitivity. DOX increased Ca2+ sensitivity in male rats only in the absence of testosterone and in female rats only in the presence of estrogen. Conversely, DOX decreased Ca2+ sensitivity in female rats in the absence of estrogen. In most instances, this mechanism was through altered phosphorylation of troponin I at Ser23/Ser24. However, there was an additional DOX-induced, estrogen-dependent, irreversible (by DTT) mechanism that altered Ca2+ sensitivity. Our data demonstrate sex differences in cardiac contractile responses to chronic DOX treatment. We conclude that estrogen protects against chronic DOX treatment in the heart, preserving myofilament function. NEW & NOTEWORTHY We identified sex differences in cardiotoxic effects of chronic doxorubicin (DOX) exposure on myofilament function. Estrogen, but not testosterone, decreases DOX-induced oxidative modifications on myofilaments to preserve maximum active tension. In rats, DOX exposure increased Ca2+ sensitivity in the presence of estrogen but decreased Ca2+ sensitivity in the absence of estrogen. In male rats, the DOX-induced shift in Ca2+ sensitivity involved troponin I phosphorylation; in female rats, this was through an estrogen-dependent mechanism.
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Affiliation(s)
- Chutima Rattanasopa
- 1Department of Physiology, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Jonathan A. Kirk
- 2Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Maywood, Illinois
| | - Tepmanas Bupha-Intr
- 1Department of Physiology, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Maria Papadaki
- 2Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Maywood, Illinois
| | - Pieter P. de Tombe
- 2Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Maywood, Illinois
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Shchepkin DV, Nikitina LV, Bershitsky SY, Kopylova GV. The isoforms of α-actin and myosin affect the Ca 2+ regulation of the actin-myosin interaction in the heart. Biochem Biophys Res Commun 2017. [PMID: 28623140 DOI: 10.1016/j.bbrc.2017.06.043] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Myocardium of mammals contains a wide range of isoforms of proteins that provides contractile function of the heart. These are two isoforms of ventricular and two of atrial myosin, α- and β-tropomyosin, and two isoforms of α-actin: cardiac and skeletal. We believe that the difference in the amino acid sequence of α-actin can affect the calcium regulation of the actin-myosin interaction. To test this hypothesis, we investigated effects of the isoforms of α-actin, cardiac and skeletal, and the isoforms of cardiac myosin on the calcium regulation of the actin-myosin interaction in an in vitro motility assay using reconstructed regulated thin filaments. The results show that isoforms of α-actin and the ratio of α/β-chains of Tpm differently affect the calcium regulation of the actin-myosin interaction in myocardium in dependence on cardiac myosin isoforms.
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Affiliation(s)
- Daniil V Shchepkin
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg 620049, Russia
| | - Larisa V Nikitina
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg 620049, Russia
| | - Sergey Y Bershitsky
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg 620049, Russia
| | - Galina V Kopylova
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg 620049, Russia.
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Vutthasathien P, Wattanapermpool J. Regular exercise improves cardiac contractile activation by modulating MHC isoforms and SERCA activity in orchidectomized rats. J Appl Physiol (1985) 2015; 119:831-9. [PMID: 26272317 DOI: 10.1152/japplphysiol.00224.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 08/10/2015] [Indexed: 11/22/2022] Open
Abstract
Data from the trial known as Testosterone in Older Men with Mobility Limitations (TOM) has indicated an association between testosterone administration and a greater risk for adverse cardiovascular events. We therefore propose that regular exercise is a cardioprotective alternative that prevents detrimental changes in contractile activation when a deficiency in male sex hormones exists. Ten-week-old orchidectomized (ORX) rats were subjected to a 9-wk treadmill running program at moderate intensity starting 1 wk after surgery. Although exercise-induced cardiac hypertrophy was observed both in rats that underwent ORX and sham surgery, regular exercise enhanced cardiac myofilament Ca(2+) sensitivity and myosin light-chain 2 phosphorylation only in rats that underwent a sham operation. Although the rats that had sham surgery and and given exercise exhibited no change in maximum developed tension, regular running prevented the suppression of maximum active tension in the hearts of ORX rats. Regular exercise also prevented a shift in myosin heavy chain (MHC) isoforms toward β-MHC, a reduction in sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) activity, and an increase in SERCA sensitivity in the hearts of ORX rats. Neither SERCA content nor its modulating component, phospholamban (PLB), was altered by exercise in either sham-operated or ORX rats. However, decreases in the phosphorylated Thr(17) form of PLB and the phosphorylated Thr(287) form of Ca(2+)/calmodulin-dependent kinase II in the hearts of ORX rats were abolished after regular exercise. These results thus support the use of regular running as a cardioprotective alternative to testosterone replacement in hypogonadal conditions.
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Monasky MM, Taglieri DM, Henze M, Warren CM, Utter MS, Soergel DG, Violin JD, Solaro RJ. The β-arrestin-biased ligand TRV120023 inhibits angiotensin II-induced cardiac hypertrophy while preserving enhanced myofilament response to calcium. Am J Physiol Heart Circ Physiol 2013; 305:H856-66. [PMID: 23873795 DOI: 10.1152/ajpheart.00327.2013] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
In the present study, we compared the cardioprotective effects of TRV120023, a novel angiotensin II (ANG II) type 1 receptor (AT1R) ligand, which blocks G protein coupling but stimulates β-arrestin signaling, against treatment with losartan, a conventional AT1R blocker in the treatment of cardiac hypertrophy and regulation of myofilament activity and phosphorylation. Rats were subjected to 3 wk of treatment with saline, ANG II, ANG II + losartan, ANG II + TRV120023, or TRV120023 alone. ANG II induced increased left ventricular mass compared with rats that received ANG II + losartan or ANG II + TRV120023. Compared with saline controls, ANG II induced a significant increase in pCa50 and maximum Ca(2+)-activated myofilament tension but reduced the Hill coefficient (nH). TRV120023 increased maximum tension and pCa50, although to lesser extent than ANG II. In contrast to ANG II, TRV120023 increased nH. Losartan blocked the effects of ANG II on pCa50 and nH and reduced maximum tension below that of saline controls. ANG II + TRV120023 showed responses similar to those of TRV120023 alone; compared with ANG II + losartan, ANG II + TRV120023 preserved maximum tension and increased both pCa50 and cooperativity. Tropomyosin phosphorylation was lower in myofilaments from saline-treated hearts compared with the other groups. Phosphorylation of cardiac troponin I was significantly reduced in ANG II + TRV120023 and TRV120023 groups versus saline controls, and myosin-binding protein C phosphorylation at Ser(282) was unaffected by ANG II or losartan but significantly reduced with TRV120023 treatment compared with all other groups. Our data indicate that TRV120023-related promotion of β-arrestin signaling and enhanced contractility involves a mechanism promoting the myofilament response to Ca(2+) via altered protein phosphorylation. Selective activation of β-arrestin-dependent pathways may provide advantages over conventional AT1R blockers.
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Affiliation(s)
- Michelle M Monasky
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois, Chicago, Illinois; and
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Jeong EM, Monasky MM, Gu L, Taglieri DM, Patel BG, Liu H, Wang Q, Greener I, Dudley SC, Solaro RJ. Tetrahydrobiopterin improves diastolic dysfunction by reversing changes in myofilament properties. J Mol Cell Cardiol 2013; 56:44-54. [PMID: 23247392 PMCID: PMC3666585 DOI: 10.1016/j.yjmcc.2012.12.003] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 10/22/2012] [Accepted: 12/05/2012] [Indexed: 01/13/2023]
Abstract
Despite the increasing prevalence of heart failure with preserved left ventricular function, there are no specific treatments, partially because the mechanism of impaired relaxation is incompletely understood. Evidence indicates that cardiac relaxation may depend on nitric oxide (NO), generated by NO synthase (NOS) requiring the co-factor tetrahydrobiopterin (BH(4)). Recently, we reported that hypertension-induced diastolic dysfunction was accompanied by cardiac BH(4) depletion, NOS uncoupling, a depression in myofilament cross-bridge kinetics, and S-glutathionylation of myosin binding protein C (MyBP-C). We hypothesized that the mechanism by which BH(4) ameliorates diastolic dysfunction is by preventing glutathionylation of MyBP-C and thus reversing changes of myofilament properties that occur during diastolic dysfunction. We used the deoxycorticosterone acetate (DOCA)-salt mouse model, which demonstrates mild hypertension, myocardial oxidative stress, and diastolic dysfunction. Mice were divided into two groups that received control diet and two groups that received BH(4) supplement for 7days after developing diastolic dysfunction at post-operative day 11. Mice were assessed by echocardiography. Left ventricular papillary detergent-extracted fiber bundles were isolated for simultaneous determination of force and ATPase activity. Sarcomeric protein glutathionylation was assessed by immunoblotting. DOCA-salt mice exhibited diastolic dysfunction that was reversed after BH(4) treatment. Diastolic sarcomere length (DOCA-salt 1.70±0.01 vs. DOCA-salt+BH(4) 1.77±0.01μm, P<0.001) and relengthening (relaxation constant, τ, DOCA-salt 0.28±0.02 vs. DOCA-salt+BH(4) 0.08±0.01, P<0.001) were also restored to control by BH(4) treatment. pCa(50) for tension increased in DOCA-salt compared to sham but reverted to sham levels after BH(4) treatment. Maximum ATPase rate and tension cost (ΔATPase/ΔTension) decreased in DOCA-salt compared to sham, but increased after BH(4) treatment. Cardiac MyBP-C glutathionylation increased in DOCA-salt compared to sham, but decreased with BH(4) treatment. MyBP-C glutathionylation correlated with the presence of diastolic dysfunction. Our results suggest that by depressing S-glutathionylation of MyBP-C, BH(4) ameliorates diastolic dysfunction by reversing a decrease in cross-bridge turnover kinetics. These data provide evidence for modulation of cardiac relaxation by post-translational modification of myofilament proteins.
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Affiliation(s)
- Euy-Myoung Jeong
- Department of Medicine, Section of Cardiology, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Michelle M. Monasky
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Lianzhi Gu
- Department of Medicine, Section of Cardiology, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Domenico M. Taglieri
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Bindiya G. Patel
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Hong Liu
- Department of Medicine, Section of Cardiology, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Qiongying Wang
- Department of Medicine, Section of Cardiology, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Ian Greener
- Department of Medicine, Section of Cardiology, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Samuel C. Dudley
- Department of Medicine, Section of Cardiology, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - R. John Solaro
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
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Shi T, Moravec CS, Perez DM. Novel proteins associated with human dilated cardiomyopathy: selective reduction in α(1A)-adrenergic receptors and increased desensitization proteins. J Recept Signal Transduct Res 2013; 33:96-106. [PMID: 23384050 DOI: 10.3109/10799893.2013.764897] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract Therapeutics to treat human heart failure (HF) and the identification of proteins associated with HF are still limited. We analyzed α(1)-adrenergic receptor (AR) subtypes in human HF and performed proteomic analysis on more uniform samples to identify novel proteins associated with human HF. Six failing hearts with end-stage dilated cardiomyopathy (DCM) and four non-failing heart controls were subjected to proteomic analysis. Out of 48 identified proteins, 26 proteins were redundant between samples. Ten of these 26 proteins were previously reported to be associated with HF. Of the newly identified proteins, we found several muscle proteins and mitochondrial/electron transport proteins, while novel were functionally similar to previous reports. However, we also found novel proteins involved in functional classes such as β-oxidation and G-protein coupled receptor signaling and desensitization not previously associated with HF. We also performed radioligand-binding studies on the heart samples and not only confirmed a large loss of β(1)-ARs in end-stage DCM, but also found a selective decrease in the α(1A)-AR subtype not previously reported. We have identified new proteins and functional categories associated with end-stage DCM. We also report that similar to the previously characterized loss of β(1)-AR in HF, there is also a concomitant loss of α(1A)-ARs, which are considered cardioprotective proteins.
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Affiliation(s)
- Ting Shi
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland, OH, USA
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Nikolova-Krstevski V, Leimena C, Xiao XH, Kesteven S, Tan JC, Yeo LS, Yu ZY, Zhang Q, Carlton A, Head S, Shanahan C, Feneley MP, Fatkin D. Nesprin-1 and actin contribute to nuclear and cytoskeletal defects in lamin A/C-deficient cardiomyopathy. J Mol Cell Cardiol 2010; 50:479-86. [PMID: 21156181 DOI: 10.1016/j.yjmcc.2010.12.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 11/30/2010] [Accepted: 12/01/2010] [Indexed: 10/18/2022]
Abstract
Lamin A/C mutations are the most common cause of familial dilated cardiomyopathy (DCM) but the pathogenetic mechanisms are incompletely understood. Nesprins are spectrin repeat-containing proteins that interact with lamin A/C and are components of the linker-of-nucleoskeleton-and-cytoskeleton (LINC) complex that connects the nuclear envelope to the actin cytoskeleton. Our aim was to determine whether changes in nesprin-1 and actin might contribute to DCM in homozygous Lmna knockout (Lmna(-/-)) mice. Here we find that Lmna(-/-) cardiomyocytes have altered nuclear envelope morphology, disorganization of nesprin-1 and heterogeneity in the distribution of nuclear and cytoskeletal actin. Functional interactions of nesprin-1 with nuclear G-actin and with the cytoskeletal γ-actin, α-cardiac actin and α-smooth muscle actin (α-SMA) isoforms were shown by immunoprecipitation and Western blotting. At 4-6 weeks of age, Lmna(-/-) mice had normal levels of γ-actin and α-cardiac actin, but α-SMA expression was increased by 50%. In contrast to the predominant vascular distribution of α-SMA in WT ventricular sections, α-SMA had a diffuse staining pattern in Lmna(-/-) sections. Osmotic swelling studies showed enhanced radial swelling in Lmna(-/-) cardiomyocytes indicative of cytoskeletal instability. The distensibility of Lmna(-/-) cardiomyocytes with osmotic stress was reduced by addition of α-SMA-specific fusion peptide. Our findings support a model in which uncoupling of the nucleus and cytoskeleton associated with disruption of the LINC complex promotes mechanical instability and defective force transmission in cardiomyocytes. Changes in the distribution and expression patterns of nuclear and cytoskeletal actin suggest that diverse transcriptional and structural defects may also contribute to DCM in Lmna(-/-) mice.
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Affiliation(s)
- Vesna Nikolova-Krstevski
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst NSW 2010, Australia
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Avner BS, Hinken AC, Yuan C, Solaro RJ. H2O2 alters rat cardiac sarcomere function and protein phosphorylation through redox signaling. Am J Physiol Heart Circ Physiol 2010; 299:H723-30. [PMID: 20562337 DOI: 10.1152/ajpheart.00050.2010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
ROS, such as H(2)O(2), are a component of pathological conditions in many organ systems and have been reported to be elevated in cardiac pathophysiology. The experiments presented here test the hypothesis that H(2)O(2) induces alterations in cardiac myofilament function by the posttranslational modification of sarcomeric proteins indirectly through PKC signaling. In vitro assessment of actomyosin Mg(2+)-ATPase activity of myofibrillar fractions showed blunted relative ATP consumption in the relaxed state (pCa 8.0) in response to treatment with 0.5 mM H(2)O(2) before myofilament isolation. The effect was attributable to downstream "redox signaling," inasmuch as the direct application of H(2)O(2) to isolated myofibrils did not alter Mg(2+)-ATPase activity. Ca(2+)-ATPase activity, which was used as a measure of myofibrillar myosin function, was unaffected by H(2)O(2). Functional experiments using rat cardiac trabeculae treated with 0.5 or 5 mM H(2)O(2) followed by detergent extraction of membranes demonstrated increased Ca(2+) sensitivity of force production, a faster rate of force redevelopment, and (for 5 mM) decreased maximum tension. Biochemical analysis of myocardial samples treated with 0.5 mM H(2)O(2) demonstrated increased phosphorylation of two sarcomeric proteins: cardiac troponin I and myosin-binding protein-C. These changes were eliminated by a general PKC inhibitor. However, H(2)O(2) and the general PKC activator PMA induced different phosphorylation patterns in cardiomyocytes in which PKC-delta was elevated by viral infection. These data provide evidence that PKC-dependent redox signaling affects the function of cardiac myofilaments and indicate modification of specific proteins through this signaling mechanism.
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Affiliation(s)
- Benjamin S Avner
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois, Chicago, Illinois 60612-7342, USA
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Jaeger MA, Sonnemann KJ, Fitzsimons DP, Prins KW, Ervasti JM. Context-dependent functional substitution of alpha-skeletal actin by gamma-cytoplasmic actin. FASEB J 2009; 23:2205-14. [PMID: 19279140 DOI: 10.1096/fj.09-129783] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We generated transgenic mice that overexpressed gamma-(cyto) actin 2000-fold above wild-type levels in skeletal muscle. gamma-(cyto) actin comprised 40% of total actin in transgenic skeletal muscle, with a concomitant 40% decrease in alpha-actin. Surprisingly, transgenic muscle was histologically and ultrastructurally identical to wild-type muscle despite near-stoichiometric incorporation of gamma-(cyto) actin into sarcomeric thin filaments. Furthermore, several parameters of muscle physiological performance in the transgenic animals were not different from wild type. Given these surprising results, we tested whether overexpression of gamma-(cyto) actin could rescue the early postnatal lethality in alpha-(sk) actin-null mice (Acta1(-/-)). By quantitative Western blot analysis, we found total actin levels were decreased by 35% in Acta1(-/-) muscle. Although transgenic overexpression of gamma-(cyto) actin on the Acta1(-/-) background restored total actin levels to wild type, resulting in thin filaments composed of 60% gamma-(cyto) actin and a 40% mixture of cardiac and vascular actin, the life span of transgenic Acta1(-/-) mice was not extended. These results indicate that sarcomeric thin filaments can accommodate substantial incorporation of gamma-(cyto) actin without functional consequences, yet gamma-(cyto) actin cannot fully substitute for alpha-(sk) actin.
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Affiliation(s)
- Michele A Jaeger
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 321 Church St. SE, Minneapolis, MN 55455, USA
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Rai R, Wong CCL, Xu T, Leu NA, Dong DW, Guo C, McLaughlin KJ, Yates JR, Kashina A. Arginyltransferase regulates alpha cardiac actin function, myofibril formation and contractility during heart development. Development 2008; 135:3881-9. [PMID: 18948421 DOI: 10.1242/dev.022723] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Post-translational arginylation mediated by arginyltransferase (Ate1) is essential for cardiovascular development and angiogenesis in mammals and directly affects myocardium structure in the developing heart. We recently showed that arginylation exerts a number of intracellular effects by modifying proteins involved in the functioning of the actin cytoskeleton and in cell motility. Here, we investigated the role of arginylation in the development and function of cardiac myocytes and their actin-containing structures during embryogenesis. Biochemical and mass spectrometry analyses showed that alpha cardiac actin undergoes arginylation at four sites during development. Ultrastructural analysis of the myofibrils in wild-type and Ate1 knockout mouse hearts showed that the absence of arginylation results in defects in myofibril structure that delay their development and affect the continuity of myofibrils throughout the heart, predicting defects in cardiac contractility. Comparison of cardiac myocytes derived from wild-type and Ate1 knockout mouse embryos revealed that the absence of arginylation results in abnormal beating patterns. Our results demonstrate cell-autonomous cardiac myocyte defects in arginylation knockout mice that lead to severe congenital abnormalities similar to those observed in human disease, and outline a new function of arginylation in the regulation of the actin cytoskeleton in cardiac myocytes.
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Affiliation(s)
- Reena Rai
- Department of Animal Biology and School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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15
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Daniels MCG, Naya T, Rundell VLM, de Tombe PP. Development of contractile dysfunction in rat heart failure: hierarchy of cellular events. Am J Physiol Regul Integr Comp Physiol 2007; 293:R284-92. [PMID: 17363676 DOI: 10.1152/ajpregu.00880.2006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The cellular mechanisms underlying the development of congestive heart failure (HF) are not well understood. Accordingly, we studied myocardial function in isolated right ventricular trabeculae from rats in which HF was induced by left ventricular myocardial infarction (MI). Both early-stage (12 wk post-MI; E-pMI) and late, end-stage HF (28 wk post-Mi; L-pMI) were studied. HF was associated with decreased sarcoplasmic reticulum Ca2+ ATPase protein levels (28% E-pMI; 52% L-pMI). HF affected neither sodium/calcium exchange, ryanodine receptor, nor phospholamban protein levels. Twitch force at saturating extracellular [Ca2+] was depressed in HF (30% E-pMI; 38% L-pMI), concomitant with a marked increase in sensitivity of twitch force toward extracellular [Ca2+] (26% E-pMI; 68% L-pMI). Ca2+-saturated myofilament force development in skinned trabeculae was unchanged in E-pMI but significantly depressed in L-pMI (45%). Tension-dependent ATP hydrolysis rate was depressed in L-pMI (49%), but not in E-pMI. Our results suggest a hierarchy of cellular events during the development of HF, starting with altered calcium homeostasis during the early phase followed by myofilament dysfunction at end-stage HF.
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Affiliation(s)
- Marcel C G Daniels
- Department of Physiology and Biophysics MC901, Center for Cardiovascular Research, University of Illinois at Chicago, 835 S. Wolcott Ave., Chicago, IL 60612, USA
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16
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Thawornkaiwong A, Pantharanontaga J, Wattanapermpool J. Hypersensitivity of myofilament response to Ca2+ in association with maladaptation of estrogen-deficient heart under diabetes complication. Am J Physiol Regul Integr Comp Physiol 2007; 292:R844-51. [PMID: 17038444 DOI: 10.1152/ajpregu.00365.2006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The amelioration of cardioprotective effect of estrogen in diabetes suggests potential interactive action of estrogen and insulin on myofilament activation. We compared Ca2+-dependent Mg2+-ATPase activity of isolated myofibrillar preparations from hearts of sham and 10-wk ovariectomized rats with or without simultaneous 8 wk-induction of diabetes and from diabetic-ovariectomized rats with estrogen and/or insulin supplementation. Similar magnitude of suppressed maximum myofibrillar ATPase activity was demonstrated in ovariectomized, diabetic, and diabetic-ovariectomized rat hearts. Such suppressed activity and the relative suppression in α-myosin heavy chain level in ovariectomy combined with diabetes could be completely restored by estrogen and insulin supplementation. Conversely, the myofilament Ca2+ hypersensitivity detected only in the ovariectomized but not diabetic group was also observed in diabetic-ovariectomized rats, which was restored upon estrogen supplementation. Binding kinetics of β1-adrenergic receptors and immunoblots of β1-adrenoceptors as well as heat shock 72 (HSP72) were analyzed to determine the association of changes in receptors and HSP72 to that of the myofilament response to Ca2+. The amount of β1-adrenoceptors significantly increased concomitant with Ca2+ hypersensitivity of the myofilament, without differences in the receptor binding affinity among the groups. In contrast, changes in HSP72 paralleled that of maximum myofibrillar ATPase activity. These results indicate that hypersensitivity of cardiac myofilament to Ca2+ is specifically induced in ovariectomized rats even under diabetes complication and that alterations in the expression of β1-adrenoceptors may, in part, play a mechanistic role underlying the cardioprotective effects of estrogen that act together with Ca2+ hypersensitivity of the myofilament in determining the gender difference in cardiac activation.
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Affiliation(s)
- Ariyaporn Thawornkaiwong
- Department of Physiology, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand
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17
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Hanft LM, Rybakova IN, Patel JR, Rafael-Fortney JA, Ervasti JM. Cytoplasmic gamma-actin contributes to a compensatory remodeling response in dystrophin-deficient muscle. Proc Natl Acad Sci U S A 2006; 103:5385-90. [PMID: 16565216 PMCID: PMC1459364 DOI: 10.1073/pnas.0600980103] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dystrophin mechanically links the costameric cytoskeleton and sarcolemma, yet dystrophin-deficient muscle exhibits abnormalities in cell signaling, gene expression, and contractile function that are not clearly understood. We generated new antibodies specific for cytoplasmic gamma-actin and confirmed that gamma-actin most predominantly localized to the sarcolemma and in a faint reticular lattice within normal muscle cells. However, we observed that gamma-actin levels were increased 10-fold at the sarcolemma and within the cytoplasm of striated muscle cells from dystrophin-deficient mdx mice. Transgenic overexpression of the dystrophin homologue utrophin, or functional dystrophin constructs in mdx muscle, restored gamma-actin to normal levels, whereas gamma-actin remained elevated in mdx muscle expressing nonfunctional dystrophin constructs. We conclude that increased cytoplasmic gamma-actin in dystrophin-deficient muscle may be a compensatory response to fortify the weakened costameric lattice through recruitment of parallel mechanical linkages. However, the presence of excessive myoplasmic gamma-actin may also contribute to altered cell signaling or gene expression in dystrophin-deficient muscle.
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Affiliation(s)
- Laurin M. Hanft
- *Department of Physiology, University of Wisconsin, Madison, WI 53706; and
| | - Inna N. Rybakova
- *Department of Physiology, University of Wisconsin, Madison, WI 53706; and
| | | | - Jill A. Rafael-Fortney
- Department of Molecular and Cellular Biochemistry, Ohio State University, Columbus, OH 43210
| | - James M. Ervasti
- *Department of Physiology, University of Wisconsin, Madison, WI 53706; and
- To whom correspondence should be addressed at:
Department of Physiology, University of Wisconsin, 127 Service Memorial Institute, 1300 University Avenue, Madison, WI 53706. E-mail:
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18
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Stelzer JE, Fitzsimons DP, Moss RL. Ablation of myosin-binding protein-C accelerates force development in mouse myocardium. Biophys J 2006; 90:4119-27. [PMID: 16513777 PMCID: PMC1459529 DOI: 10.1529/biophysj.105.078147] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Myosin-binding protein-C (MyBP-C) is a thick filament-associated protein that binds tightly to myosin. Given that cMyBP-C may act to modulate cooperative activation of the thin filament by constraining the availability of myosin cross-bridges for binding to actin, we investigated the role of MyBP-C in the regulation of cardiac muscle contraction. We assessed the Ca(2+) sensitivity of force (pCa(50)) and the activation dependence of the rate of force redevelopment (k(tr)) in skinned myocardium isolated from wild-type (WT) and cMyBP-C null (cMyBP-C(-/-)) mice. Mechanical measurements were performed at 22 degrees C in the absence and presence of a strong-binding, nonforce-generating analog of myosin subfragment-1 (NEM-S1). In the absence of NEM-S1, maximal force and k(tr) and the pCa(50) of isometric force did not differ between WT and cMyBP-C(-/-) myocardium; however, ablation of cMyBP-C-accelerated k(tr) at each submaximal force. Treatment of WT and cMyBP-C(-/-) myocardium with 3 muM NEM-S1 elicited similar increases in pCa(50,) but the effects of NEM-S1 to increase k(tr) at submaximal forces and thereby markedly reduce the activation dependence of k(tr) occurred to a greater degree in cMyBP-C(-/-) myocardium. Together, these results support the idea that cMyBP-C normally acts to constrain the interaction between myosin and actin, which in turn limits steady-state force development and the kinetics of cross-bridge interaction.
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Affiliation(s)
- Julian E Stelzer
- Department of Physiology, University of Wisconsin School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA.
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19
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Kumar A, Crawford K, Flick R, Klevitsky R, Lorenz JN, Bove KE, Robbins J, Lessard JL. Transgenic overexpression of cardiac actin in the mouse heart suggests coregulation of cardiac, skeletal and vascular actin expression. Transgenic Res 2005; 13:531-40. [PMID: 15672834 DOI: 10.1007/s11248-004-2823-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Previous studies have shown that depletion of cardiac actin by targeted disruption is associated with increased expression of alternative actins in the mouse heart. Here we have studied the effects of transgenic overexpression of cardiac actin using the alpha-myosin heavy chain promoter. Lines carrying 7 or 8 copies of the transgene showed a 2-fold increase in cardiac actin mRNA and also displayed decreased expression of skeletal and vascular actin in their hearts. In contrast, a line with more than 250 copies of the transgene did not show a similar decrease in the expression of skeletal and vascular actin despite a 3-fold increase in cardiac actin mRNA. While the low copy number transgenic mice displayed hearts that were similar to non-transgenic controls, the high copy number transgenic line showed larger hearts with distinct atrial enlargement and cardiomyocyte hypertrophy. Further, while the low copy number transgenic mouse hearts were mildly hypocontractile when compared with non-transgenic mouse hearts, the high copy number transgenic mouse hearts were significantly so. We conclude that in the presence of a small number of copies of the cardiac actin transgene, homeostatic mechanisms involved in maintaining actin levels are active and negatively regulate skeletal and vascular actin levels in the heart in response to increased expression of cardiac actin. However, these putative mechanisms are either inoperative in the high copy number transgenic line or are countered by the enhanced expression of skeletal and vascular actin during cardiomyocyte hypertrophy.
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Affiliation(s)
- A Kumar
- Division of Developmental Biology, University of Cincinnati, College of Medicine, Cincinnati, OH 45229, USA.
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20
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Abstract
Although well known as the location of the mechanism by which the cardiac sarcomere is activated by Ca2+ to generate force and shortening, the thin filament is now also recognized as a vital component determining the dynamics of contraction and relaxation. Molecular signaling in the thin filament involves steric, allosteric, and cooperative mechanisms that are modified by protein phosphorylation, sarcomere length and load, the chemical environment, and isoform composition. Approaches employing transgenesis and mutagenesis now permit investigation of these processes at the level of the systems biology of the heart. These studies reveal that the thin filaments are not merely slaves to the levels of Ca2+ determined by membrane channels, transporters and exchangers, but are actively involved in beat to beat control of cardiac function by neural and hormonal factors and by the Frank-Starling mechanism.
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Affiliation(s)
- Tomoyoshi Kobayashi
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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21
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Chaponnier C, Gabbiani G. Pathological situations characterized by altered actin isoform expression. J Pathol 2004; 204:386-95. [PMID: 15495226 DOI: 10.1002/path.1635] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Modulation of actin isoform expression is a well-established feature of developmental phenomena. As one might expect, it is also characteristic of several pathological situations that are the subject of the present review. alpha-Smooth muscle actin has proven to be a reliable marker for identifying (a) vascular smooth muscle cells during vascular development and vascular diseases, and (b) myofibroblasts during wound healing, fibrocontractive diseases, and stromal reaction to epithelial tumours. The hallmark of a differentiated myofibroblast relies on the acquisition of an organized contractile apparatus characterized by alpha-smooth muscle actin-expressing stress fibres. More and more data suggest that alpha-smooth muscle actin plays a direct role in myofibroblast contractile activity through its N-terminal domain AcEEED. Newly developed antibodies against alpha-skeletal and alpha-cardiac actins have allowed the detection of subpopulations of alpha-skeletal positive cardiomyocytes in adult, hypertrophic, and failing heart. These antibodies have also permitted us to identify the differentiation degree of malignant cells in tumours such as rhabdomyosarcoma. Whether the differential expression of actin isoforms in human diseases is functionally relevant is not yet fully established, although studies on human actin mutations, actin null mice, and the N-terminal end of alpha-smooth muscle actin support this possibility.
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Affiliation(s)
- Christine Chaponnier
- Department of Pathology and Immunology, CMU, University of Geneva, Geneva, Switzerland.
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22
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Rundell VLM, Manaves V, Martin AF, de Tombe PP. Impact of beta-myosin heavy chain isoform expression on cross-bridge cycling kinetics. Am J Physiol Heart Circ Physiol 2004; 288:H896-903. [PMID: 15471982 DOI: 10.1152/ajpheart.00407.2004] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Myosin heavy chain (MHC) isoforms alpha and beta have intrinsically different ATP hydrolysis activities (ATPase) and therefore cross-bridge cycling rates in solution. There is considerable evidence of altered MHC expression in rodent cardiac disease models; however, the effect of incremental beta-MHC expression over a wide range on the rate of high-strain, isometric cross-bridge cycling is yet to be ascertained. We treated male rats with 6-propyl-2-thiouracil (PTU; 0.8 g/l in drinking water) for short intervals (6, 11, 16, and 21 days) to generate cardiac MHC patterns in transition from predominantly alpha-MHC to predominantly beta-MHC. Steady-state calcium-dependent tension development and tension-dependent ATP consumption (tension cost; proportional to cross-bridge cycling) were measured in chemically permeabilized (skinned) right ventricular muscles at 20 degrees C. To assess dynamic cross-bridge cycling kinetics, the rate of force redevelopment (ktr) was determined after rapid release-restretch of fully activated muscles. MHC isoform content in each experimental muscle was measured by SDS-PAGE and densitometry. alpha-MHC content decreased significantly and progressively with length of PTU treatment [68 +/- 5%, 58 +/- 4%, 37 +/- 4%, and 27 +/- 6% for 6, 11, 16, and 21 days, respectively; P < 0.001 (ANOVA)]. Tension cost decreased, linearly, with decreased alpha-MHC content [6.7 +/- 0.4, 5.6 +/- 0.5, 4.0 +/- 0.4, and 3.9 +/- 0.3 ATPase/tension for 6, 11, 16, and 21 days, respectively; P < 0.001 (ANOVA)]. Likewise, ktr was significantly and progressively depressed with length of PTU treatment [11.1 +/- 0.6, 9.1 +/- 0.5, 8.2 +/- 0.7, and 6.2 +/- 0.3 s(-1) for 6, 11, 16, and 21 days, respectively; P < 0.05 (ANOVA)] Thus cross-bridge cycling, under high strain, for alpha-MHC is three times higher than for beta-MHC. Furthermore, under isometric conditions, alpha-MHC and beta-MHC cross bridges hydrolyze ATP independently of one another.
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Affiliation(s)
- Veronica L M Rundell
- Center for Cardiovascular Research, Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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23
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Marston SB, Redwood CS. Modulation of thin filament activation by breakdown or isoform switching of thin filament proteins: physiological and pathological implications. Circ Res 2004; 93:1170-8. [PMID: 14670832 DOI: 10.1161/01.res.0000105088.06696.17] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In the heart, the contractile apparatus is adapted to the specific demands of the organ for continuous rhythmic contraction. The specialized contractile properties of heart muscle are attributable to the expression of cardiac-specific isoforms of contractile proteins. This review describes the isoforms of the thin filament proteins actin and tropomyosin and the three troponin subunits found in human heart muscle, how the isoform profiles of these proteins change during development and disease, and the possible functional consequences of these changes. During development of the heart, there is a distinctive switch of isoform expression at or shortly after birth; however, during adult life, thin filament protein isoform composition seems to be stable despite protein turnover rates of 3 to 10 days. The pattern of isoforms of actin, tropomyosin, troponin I, troponin C, and troponin T is not affected by aging or heart disease (ischemia and dilated cardiomyopathy). The evidence for proteolysis of thin filament proteins in situ during ischemia and stunning is evaluated, and it is concluded that C-terminal cleavage of troponin I is a feature of irreversibly injured myocardium but may not play a role in reversible stunning.
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Affiliation(s)
- Steven B Marston
- Imperial College London, National Heart and Lung Institute, Dovehouse St, London SW3 6LY, UK.
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24
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Rundell VLM, Geenen DL, Buttrick PM, de Tombe PP. Depressed cardiac tension cost in experimental diabetes is due to altered myosin heavy chain isoform expression. Am J Physiol Heart Circ Physiol 2004; 287:H408-13. [PMID: 15001437 DOI: 10.1152/ajpheart.00049.2004] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cardiac disease in diabetes presents as impaired left ventricular contraction and relaxation; however, the mechanisms underlying contractile protein dysfunction during the progression of disease are unknown. Accordingly, we assessed Ca(2+)-dependent tension development and tension-dependent ATP consumption (tension cost) in a rat model early (6 wk) and late (12 wk) after the onset of diabetes (50 mg/kg iv streptozotocin) using mechanical force- and enzyme-coupled UV absorbance measurements. Myofilament Ca(2+) sensitivity and maximal tension were unchanged between groups at either time point. Cross-bridge cycling rate was significantly decreased in diabetes, as indexed by tension cost (early control 5.4 +/- 0.4 and early diabetes 4.2 +/- 0.3; and late control 6.0 +/- 0.2 and late diabetes 4.2 +/- 0.2; P < 0.05). Because rodent models of cardiac disease are confounded by altered myosin isoform distribution, myosin content was determined by SDS-PAGE and densitometry. The cardiac content of alpha-myosin in diabetes was decreased to 41% +/- 4.1 at 6 wk and 32.5% +/- 2.9 at 12 wk of diabetes (early control 77.8% +/- 3.3 and late control 73.6% +/- 2.5). Separate control experiments demonstrated a linear decrease in tension cost with decreased alpha-myosin content. Given this, the depression of tension cost in this rodent model of diabetes could be fully explained by the altered myosin isoform distribution.
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Affiliation(s)
- Veronica L M Rundell
- Center for Cardiovascular Research, Department of Physiology, University of Illinois at Chicago, 835 S. Wolcott (M/C 901 Chicago, IL 60612, USA
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