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Nag S, Gollapudi SK, Del Rio CL, Spudich JA, McDowell R. Mavacamten, a precision medicine for hypertrophic cardiomyopathy: From a motor protein to patients. SCIENCE ADVANCES 2023; 9:eabo7622. [PMID: 37506209 DOI: 10.1126/sciadv.abo7622] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 06/23/2023] [Indexed: 07/30/2023]
Abstract
Hypertrophic cardiomyopathy (HCM) is a primary myocardial disorder characterized by left ventricular hypertrophy, hyperdynamic contraction, and impaired relaxation of the heart. These functional derangements arise directly from altered sarcomeric function due to either mutations in genes encoding sarcomere proteins, or other defects such as abnormal energetics. Current treatment options do not directly address this causal biology but focus on surgical and extra-sarcomeric (sarcolemmal) pharmacological symptomatic relief. Mavacamten (formerly known as MYK-461), is a small molecule designed to regulate cardiac function at the sarcomere level by selectively but reversibly inhibiting the enzymatic activity of myosin, the fundamental motor of the sarcomere. This review summarizes the mechanism and translational progress of mavacamten from proteins to patients, describing how the mechanism of action and pharmacological characteristics, involving both systolic and diastolic effects, can directly target pathophysiological derangements within the cardiac sarcomere to improve cardiac structure and function in HCM. Mavacamten was approved by the Food and Drug Administration in April 2022 for the treatment of obstructive HCM and now goes by the commercial name of Camzyos. Full information about the risks, limitations, and side effects can be found at www.accessdata.fda.gov/drugsatfda_docs/label/2022/214998s000lbl.pdf.
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Affiliation(s)
- Suman Nag
- MyoKardia Inc., a wholly owned subsidiary of Bristol Myers Squibb, Brisbane, CA 94005, USA
| | - Sampath K Gollapudi
- MyoKardia Inc., a wholly owned subsidiary of Bristol Myers Squibb, Brisbane, CA 94005, USA
| | - Carlos L Del Rio
- MyoKardia Inc., a wholly owned subsidiary of Bristol Myers Squibb, Brisbane, CA 94005, USA
- Cardiac Consulting, 1630 S Delaware St. #56426, San Mateo, CA 94403, USA
| | | | - Robert McDowell
- MyoKardia Inc., a wholly owned subsidiary of Bristol Myers Squibb, Brisbane, CA 94005, USA
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Shintani SA. Does the Hyperthermal Sarcomeric Oscillations Manifested by Body Temperature Support the Periodic Ventricular Dilation With Each Heartbeat? Front Physiol 2022; 13:846206. [PMID: 35418878 PMCID: PMC8996058 DOI: 10.3389/fphys.2022.846206] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 03/14/2022] [Indexed: 11/30/2022] Open
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3
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Waddingham MT, Tsuchimochi H, Sonobe T, Asano R, Jin H, Ow CPC, Schwenke DO, Katare R, Aoyama K, Umetani K, Hoshino M, Uesugi K, Shirai M, Ogo T, Pearson JT. Using Synchrotron Radiation Imaging Techniques to Elucidate the Actions of Hexarelin in the Heart of Small Animal Models. Front Physiol 2022; 12:766818. [PMID: 35126171 PMCID: PMC8814524 DOI: 10.3389/fphys.2021.766818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 11/23/2021] [Indexed: 11/13/2022] Open
Abstract
The majority of the conventional techniques that are utilized for investigating the pathogenesis of cardiovascular disease in preclinical animal models do not permit microlevel assessment of in situ cardiomyocyte and microvascular functions. Therefore, it has been difficult to establish whether cardiac dysfunction in complex multiorgan disease states, such as heart failure with preserved ejection fraction and pulmonary hypertension, have their origins in microvascular dysfunction or rather in the cardiomyocyte. Herein, we describe our approach of utilizing synchrotron radiation microangiography to, first, ascertain whether the growth hormone secretagogue (GHS) hexarelin is a vasodilator in the coronary circulation of normal and anesthetized Sprague-Dawley rats, and next investigate if hexarelin is able to prevent the pathogenesis of right ventricle (RV) dysfunction in pulmonary hypertension in the sugen chronic hypoxia model rat. We show that acute hexarelin administration evokes coronary microvascular dilation through GHS-receptor 1a and nitric oxide, and through endothelium-derived hyperpolarization. Previous work indicated that chronic exogenous administration of ghrelin largely prevented the pathogenesis of pulmonary hypertension in chronic hypoxia and in monocrotaline models. Unexpectedly, chronic hexarelin administration prior to sugen chronic hypoxia did not prevent RV hypertrophy or RV cardiomyocyte relaxation impairment. Small-angle X-ray scattering revealed that super relaxed myosin filaments contributed to diastolic dysfunction, and that length-dependent activation might contribute to sustained contractility of the RV. Thus, synchrotron-based imaging approaches can reveal novel insights into cardiac and coronary functions in vivo.
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Affiliation(s)
- Mark T. Waddingham
- Department of Advanced Medical Research for Pulmonary Hypertension, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Hirotsugu Tsuchimochi
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Japan
| | - Takashi Sonobe
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Japan
| | - Ryotaro Asano
- Department of Advanced Medical Research for Pulmonary Hypertension, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Huiling Jin
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Japan
| | - Connie P. C. Ow
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Japan
| | - Daryl O. Schwenke
- Department of Physiology, School of Biomedical Sciences, Heart Otago, University of Otago, Dunedin, New Zealand
| | - Rajesh Katare
- Department of Physiology, School of Biomedical Sciences, Heart Otago, University of Otago, Dunedin, New Zealand
| | - Kohki Aoyama
- Japan Synchrotron Radiation Research Institute, Harima, Japan
| | - Keiji Umetani
- Japan Synchrotron Radiation Research Institute, Harima, Japan
| | - Masato Hoshino
- Japan Synchrotron Radiation Research Institute, Harima, Japan
| | - Kentaro Uesugi
- Japan Synchrotron Radiation Research Institute, Harima, Japan
| | - Mikiyasu Shirai
- Department of Advanced Medical Research for Pulmonary Hypertension, National Cerebral and Cardiovascular Center, Suita, Japan
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Japan
| | - Takeshi Ogo
- Department of Advanced Medical Research for Pulmonary Hypertension, National Cerebral and Cardiovascular Center, Suita, Japan
| | - James T. Pearson
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Japan
- Department of Physiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
- *Correspondence: James T. Pearson
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Ma W, Henze M, Anderson RL, Gong H, Wong FL, Del Rio CL, Irving T. The Super-Relaxed State and Length Dependent Activation in Porcine Myocardium. Circ Res 2021; 129:617-630. [PMID: 34365814 DOI: 10.1161/circresaha.120.318647] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Weikang Ma
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago (W.M., H.G., T.I.)
| | - Marcus Henze
- MyoKardia Inc, Brisbane, CA (M.H., R.L.A., F.L.W., C.L.d.R.)
| | | | - Henry Gong
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago (W.M., H.G., T.I.)
| | - Fiona L Wong
- MyoKardia Inc, Brisbane, CA (M.H., R.L.A., F.L.W., C.L.d.R.)
| | | | - Thomas Irving
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago (W.M., H.G., T.I.)
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Regazzoni F, Dedè L, Quarteroni A. Biophysically detailed mathematical models of multiscale cardiac active mechanics. PLoS Comput Biol 2020; 16:e1008294. [PMID: 33027247 PMCID: PMC7571720 DOI: 10.1371/journal.pcbi.1008294] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 10/19/2020] [Accepted: 08/27/2020] [Indexed: 11/19/2022] Open
Abstract
We propose four novel mathematical models, describing the microscopic mechanisms of force generation in the cardiac muscle tissue, which are suitable for multiscale numerical simulations of cardiac electromechanics. Such models are based on a biophysically accurate representation of the regulatory and contractile proteins in the sarcomeres. Our models, unlike most of the sarcomere dynamics models that are available in the literature and that feature a comparable richness of detail, do not require the time-consuming Monte Carlo method for their numerical approximation. Conversely, the models that we propose only require the solution of a system of PDEs and/or ODEs (the most reduced of the four only involving 20 ODEs), thus entailing a significant computational efficiency. By focusing on the two models that feature the best trade-off between detail of description and identifiability of parameters, we propose a pipeline to calibrate such parameters starting from experimental measurements available in literature. Thanks to this pipeline, we calibrate these models for room-temperature rat and for body-temperature human cells. We show, by means of numerical simulations, that the proposed models correctly predict the main features of force generation, including the steady-state force-calcium and force-length relationships, the length-dependent prolongation of twitches and increase of peak force, the force-velocity relationship. Moreover, they correctly reproduce the Frank-Starling effect, when employed in multiscale 3D numerical simulation of cardiac electromechanics.
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Affiliation(s)
- Francesco Regazzoni
- MOX - Dipartimento di Matematica, Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Luca Dedè
- MOX - Dipartimento di Matematica, Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Alfio Quarteroni
- MOX - Dipartimento di Matematica, Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133 Milano, Italy
- Mathematics Institute, École Polytechnique Fédérale de Lausanne, Av. Piccard, CH-1015 Lausanne, Switzerland (Professor Emeritus)
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Waddingham MT, Sonobe T, Tsuchimochi H, Edgley AJ, Sukumaran V, Chen YC, Hansra SS, Schwenke DO, Umetani K, Aoyama K, Yagi N, Kelly DJ, Gaderi S, Herwig M, Kolijn D, Mügge A, Paulus WJ, Ogo T, Shirai M, Hamdani N, Pearson JT. Diastolic dysfunction is initiated by cardiomyocyte impairment ahead of endothelial dysfunction due to increased oxidative stress and inflammation in an experimental prediabetes model. J Mol Cell Cardiol 2019; 137:119-131. [DOI: 10.1016/j.yjmcc.2019.10.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 10/10/2019] [Accepted: 10/18/2019] [Indexed: 12/19/2022]
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7
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β-Arrestin mediates the Frank-Starling mechanism of cardiac contractility. Proc Natl Acad Sci U S A 2016; 113:14426-14431. [PMID: 27911784 DOI: 10.1073/pnas.1609308113] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The Frank-Starling law of the heart is a physiological phenomenon that describes an intrinsic property of heart muscle in which increased cardiac filling leads to enhanced cardiac contractility. Identified more than a century ago, the Frank-Starling relationship is currently known to involve length-dependent enhancement of cardiac myofilament Ca2+ sensitivity. However, the upstream molecular events that link cellular stretch to the length-dependent myofilament Ca2+ sensitivity are poorly understood. Because the angiotensin II type 1 receptor (AT1R) and the multifunctional transducer protein β-arrestin have been shown to mediate mechanosensitive cellular signaling, we tested the hypothesis that these two proteins are involved in the Frank-Starling mechanism of the heart. Using invasive hemodynamics, we found that mice lacking β-arrestin 1, β-arrestin 2, or AT1R were unable to generate a Frank-Starling force in response to changes in cardiac volume. Although wild-type mice pretreated with the conventional AT1R blocker losartan were unable to enhance cardiac contractility with volume loading, treatment with a β-arrestin-biased AT1R ligand to selectively activate β-arrestin signaling preserved the Frank-Starling relationship. Importantly, in skinned muscle fiber preparations, we found markedly impaired length-dependent myofilament Ca2+ sensitivity in β-arrestin 1, β-arrestin 2, and AT1R knockout mice. Our data reveal β-arrestin 1, β-arrestin 2, and AT1R as key regulatory molecules in the Frank-Starling mechanism, which potentially can be targeted therapeutically with β-arrestin-biased AT1R ligands.
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Kobirumaki-Shimozawa F, Oyama K, Shimozawa T, Mizuno A, Ohki T, Terui T, Minamisawa S, Ishiwata S, Fukuda N. Nano-imaging of the beating mouse heart in vivo: Importance of sarcomere dynamics, as opposed to sarcomere length per se, in the regulation of cardiac function. ACTA ACUST UNITED AC 2016; 147:53-62. [PMID: 26712849 PMCID: PMC4692490 DOI: 10.1085/jgp.201511484] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
¡Vive la différence! In cardiac contraction, the reduction in sarcomere length—rather than length itself—determines contractile force. Sarcomeric contraction in cardiomyocytes serves as the basis for the heart’s pump functions in mammals. Although it plays a critical role in the circulatory system, myocardial sarcomere length (SL) change has not been directly measured in vivo under physiological conditions because of technical difficulties. In this study, we developed a high speed (100–frames per second), high resolution (20-nm) imaging system for myocardial sarcomeres in living mice. Using this system, we conducted three-dimensional analysis of sarcomere dynamics in left ventricular myocytes during the cardiac cycle, simultaneously with electrocardiogram and left ventricular pressure measurements. We found that (a) the working range of SL was on the shorter end of the resting distribution, and (b) the left ventricular–developed pressure was positively correlated with the SL change between diastole and systole. The present findings provide the first direct evidence for the tight coupling of sarcomere dynamics and ventricular pump functions in the physiology of the heart.
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Affiliation(s)
- Fuyu Kobirumaki-Shimozawa
- Department of Cell Physiology and Department of Anesthesiology, The Jikei University School of Medicine, Minato-ku, Tokyo 105-8461, Japan
| | - Kotaro Oyama
- Department of Cell Physiology and Department of Anesthesiology, The Jikei University School of Medicine, Minato-ku, Tokyo 105-8461, Japan Department of Physics and Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Togo Shimozawa
- Department of Physics and Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Akari Mizuno
- Department of Physics and Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Takashi Ohki
- Department of Physics and Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Takako Terui
- Department of Cell Physiology and Department of Anesthesiology, The Jikei University School of Medicine, Minato-ku, Tokyo 105-8461, Japan
| | - Susumu Minamisawa
- Department of Cell Physiology and Department of Anesthesiology, The Jikei University School of Medicine, Minato-ku, Tokyo 105-8461, Japan
| | - Shin'ichi Ishiwata
- Department of Physics and Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan Waseda Bioscience Research Institute in Singapore, Waseda University, Helios, Singapore 138667
| | - Norio Fukuda
- Department of Cell Physiology and Department of Anesthesiology, The Jikei University School of Medicine, Minato-ku, Tokyo 105-8461, Japan
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9
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Shimozawa T, Hirokawa E, Kobirumaki-Shimozawa F, Oyama K, Shintani SA, Terui T, Kushida Y, Tsukamoto S, Fujii T, Ishiwata S, Fukuda N. In vivo cardiac nano-imaging: A new technology for high-precision analyses of sarcomere dynamics in the heart. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 124:31-40. [PMID: 27664770 DOI: 10.1016/j.pbiomolbio.2016.09.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 09/15/2016] [Accepted: 09/20/2016] [Indexed: 12/01/2022]
Abstract
The cardiac pump function is a result of a rise in intracellular Ca2+ and the ensuing sarcomeric contractions [i.e., excitation-contraction (EC) coupling] in myocytes in various locations of the heart. In order to elucidate the heart's mechanical properties under various settings, cardiac imaging is widely performed in today's clinical as well as experimental cardiology by using echocardiogram, magnetic resonance imaging and computed tomography. However, because these common techniques detect local myocardial movements at a spatial resolution of ∼100 μm, our knowledge on the sub-cellular mechanisms of the physiology and pathophysiology of the heart in vivo is limited. This is because (1) EC coupling occurs in the μm partition in a myocyte and (2) cardiac sarcomeres generate active force upon a length change of ∼100 nm on a beat-to-beat basis. Recent advances in optical technologies have enabled measurements of intracellular Ca2+ dynamics and sarcomere length displacements at high spatial and temporal resolution in the beating heart of living rodents. Future studies with these technologies are warranted to open a new era in cardiac research.
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Affiliation(s)
- Togo Shimozawa
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Sinjuku-ku, Tokyo 162-8480, Japan
| | - Erisa Hirokawa
- Department of Cell Physiology, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan
| | - Fuyu Kobirumaki-Shimozawa
- Department of Cell Physiology, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan
| | - Kotaro Oyama
- Department of Cell Physiology, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan
| | - Seine A Shintani
- Department of Physics, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033, Japan
| | - Takako Terui
- Department of Anesthesiology, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan
| | - Yasuharu Kushida
- Department of Cell Physiology, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan
| | - Seiichi Tsukamoto
- Department of Cell Physiology, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan
| | - Teruyuki Fujii
- Department of Cell Physiology, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan
| | - Shin'ichi Ishiwata
- Department of Physics, Faculty of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Norio Fukuda
- Department of Cell Physiology, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan.
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Waddingham MT, Edgley AJ, Astolfo A, Inagaki T, Fujii Y, Du CK, Zhan DY, Tsuchimochi H, Yagi N, Kelly DJ, Shirai M, Pearson JT. Chronic Rho-kinase inhibition improves left ventricular contractile dysfunction in early type-1 diabetes by increasing myosin cross-bridge extension. Cardiovasc Diabetol 2015; 14:92. [PMID: 26194354 PMCID: PMC4509700 DOI: 10.1186/s12933-015-0256-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 06/25/2015] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Impaired actin-myosin cross-bridge (CB) dynamics correlate with impaired left ventricular (LV) function in early diabetic cardiomyopathy (DCM). Elevated expression and activity of Rho kinase (ROCK) contributes to the development of DCM. ROCK targets several sarcomeric proteins including myosin light chain 2, myosin binding protein-C (MyBP-C), troponin I (TnI) and troponin T that all have important roles in regulating CB dynamics and contractility of the myocardium. Our aim was to examine if chronic ROCK inhibition prevents impaired CB dynamics and LV dysfunction in a rat model of early diabetes, and whether these changes are associated with changes in myofilament phosphorylation state. METHODS Seven days post-diabetes induction (65 mg/kg ip, streptozotocin), diabetic rats received the ROCK inhibitor, fasudil (10 mg/kg/day ip) or vehicle for 14 days. Rats underwent cardiac catheterization to assess LV function simultaneous with X-ray diffraction using synchrotron radiation to assess in situ CB dynamics. RESULTS Compared to controls, diabetic rats developed mild systolic and diastolic dysfunction, which was attenuated by fasudil. End-diastolic and systolic myosin proximity to actin filaments were significantly reduced in diabetic rats (P < 0.05). In all rats there was an inverse correlation between ROCK1 expression and the extension of myosin CB in diastole, with the lowest ROCK expression in control and fasudil-treated diabetic rats. In diabetic and fasudil-treated diabetic rats changes in relative phosphorylation of TnI and MyBP-C were not significant from controls. CONCLUSIONS Our results demonstrate a clear role for ROCK in the development of LV dysfunction and impaired CB dynamics in early DCM.
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Affiliation(s)
- Mark T Waddingham
- Department of Medicine, St. Vincent's Hospital, University of Melbourne, Melbourne, VIC, Australia.
| | - Amanda J Edgley
- Department of Medicine, St. Vincent's Hospital, University of Melbourne, Melbourne, VIC, Australia. .,Department of Physiology, Monash University, Clayton, VIC, Australia.
| | - Alberto Astolfo
- Australian Synchrotron, Clayton, VIC, Australia. .,Department of Medical Physics and Bioengineering, University College of London, London, England, UK.
| | - Tadakatsu Inagaki
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka, Japan.
| | - Yutaka Fujii
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka, Japan.
| | - Cheng-Kun Du
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka, Japan.
| | - Dong-Yun Zhan
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka, Japan.
| | - Hirotsugu Tsuchimochi
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka, Japan.
| | - Naoto Yagi
- Japan Synchrotron Radiation Research Institute, Harima, Hyogo, Japan.
| | - Darren J Kelly
- Department of Medicine, St. Vincent's Hospital, University of Melbourne, Melbourne, VIC, Australia.
| | - Mikiyasu Shirai
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka, Japan.
| | - James T Pearson
- Department of Physiology, Monash University, Clayton, VIC, Australia. .,Australian Synchrotron, Clayton, VIC, Australia. .,Monash Biomedical Imaging Facility, Monash University, Clayton, VIC, Australia.
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11
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Higuchi T, Miyagawa S, Pearson JT, Fukushima S, Saito A, Tsuchimochi H, Sonobe T, Fujii Y, Yagi N, Astolfo A, Shirai M, Sawa Y. Functional and Electrical Integration of Induced Pluripotent Stem Cell-Derived Cardiomyocytes in a Myocardial Infarction Rat Heart. Cell Transplant 2015; 24:2479-89. [PMID: 25606821 DOI: 10.3727/096368914x685799] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In vitro expanded beating cardiac myocytes derived from induced pluripotent stem cells (iPSC-CMs) are a promising source of therapy for cardiac regeneration. Meanwhile, the cell sheet method has been shown to potentially maximize survival, functionality, and integration of the transplanted cells into the heart. It is thus hypothesized that transplanted iPSC-CMs in a cell sheet manner may contribute to functional recovery via direct mechanical effects on the myocardial infarction (MI) heart. F344/NJcl-rnu/rnu rats were left coronary artery ligated (n = 30), followed by transplantation of Dsred-labeled iPSC-CM cell sheets of murine origin over the infarct heart surface. Effects of the treatment were assessed, including in vivo molecular/cellular evaluations using a synchrotron radiation scattering technique. Ejection fraction and activation recovery interval were significantly greater from day 3 onward after iPSC-CM transplantation compared to those after sham operation. A number of transplanted iPSC-CMs were present on the heart surface expressing cardiac myosin or connexin 43 over 2 weeks, assessed by immunoconfocal microscopy, while mitochondria in the transplanted iPSC-CMs gradually showed mature structure as assessed by electron microscopy. Of note, X-ray diffraction identified 1,0 and 1,1 equatorial reflections attributable to myosin and actin-myosin lattice planes typical of organized cardiac muscle fibers within the transplanted cell sheets at 4 weeks, suggesting cyclic systolic myosin mass transfer to actin filaments in the transplanted iPSC-CMs. Transplantation of iPSC-CM cell sheets into the heart yielded functional and electrical recovery with cyclic contraction of transplanted cells in the rat MI heart, indicating that this strategy may be a promising cardiac muscle replacement therapy.
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Affiliation(s)
- Takahiro Higuchi
- Department of Cardiac Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
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Jenkins MJ, Pearson JT, Schwenke DO, Edgley AJ, Sonobe T, Fujii Y, Ishibashi-Ueda H, Kelly DJ, Yagi N, Shirai M. Myosin heads are displaced from actin filaments in the in situ beating rat heart in early diabetes. Biophys J 2013; 104:1065-72. [PMID: 23473489 DOI: 10.1016/j.bpj.2013.01.037] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 12/06/2012] [Accepted: 01/02/2013] [Indexed: 01/13/2023] Open
Abstract
Diabetes is independently associated with a specific cardiomyopathy, characterized by impaired cardiac muscle relaxation and force development. Using synchrotron radiation small-angle x-ray scattering, this study investigated in the in situ heart and in real-time whether changes in cross-bridge disposition and myosin interfilament spacing underlie the early development of diabetic cardiomyopathy. Experiments were conducted using anesthetized Sprague-Dawley rats 3 weeks after treatment with either vehicle (control) or streptozotocin (diabetic). Diffraction patterns were recorded during baseline and dobutamine infusions simultaneous with ventricular pressure-volumetry. From these diffraction patterns myosin mass transfer to actin filaments was assessed as the change in intensity ratio (I(1,0)/I(1,1)). In diabetic hearts cross-bridge disposition was most notably abnormal in the diastolic phase (p < 0.05) and to a lesser extent the systolic phase (p < 0.05). In diabetic rats only, there was a transmural gradient of contractile depression. Elevated diabetic end-diastolic intensity ratios were correlated with the suppression of diastolic function (p < 0.05). Furthermore, the expected increase in myosin head transfer by dobutamine was significantly blunted in diabetic animals (p < 0.05). Interfilament spacing did not differ between groups. We reveal that impaired cross-bridge disposition and radial transfer may thus underlie the early decline in ventricular function observed in diabetic cardiomyopathy.
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Affiliation(s)
- Mathew J Jenkins
- Department of Medicine, St. Vincent's Hospital, University of Melbourne, Melbourne, Australia
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Shirai M, Schwenke DO, Tsuchimochi H, Umetani K, Yagi N, Pearson JT. Synchrotron radiation imaging for advancing our understanding of cardiovascular function. Circ Res 2013; 112:209-21. [PMID: 23287456 DOI: 10.1161/circresaha.111.300096] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Synchrotron radiation (SR) is increasingly being used for micro-level and nano-level functional imaging in in vivo animal experiments. This review focuses on the methodology that enables repeated and regional assessment of vessel internal diameter and flow in the resistance vessels of different organ systems. In particular, SR absorption microangiography approaches offer unique opportunities for real-time in vivo vascular imaging in small animals, even during dynamic motion of the heart and lungs. We also describe recent progress in the translation of multiple phase-contrast imaging techniques from ex vivo to in vivo small-animal studies. Furthermore, we also review the utility of SR for multiple pinpoint (dimensions 0.2×0.2 mm) assessments of myocardial function at the cross-bridge level in different regions of the heart using small-angle X-ray scattering, resulting from increases in SR flux at modern facilities. Finally, we present cases for the use of complementary SR approaches to study cardiovascular function, particularly the pathological changes associated with disease using small-animal models.
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Affiliation(s)
- Mikiyasu Shirai
- National Cerebral and Cardiovascular Center Research Institute, Suita, Japan.
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Elevated vascular resistance and afterload reduce the cardiac output response to dobutamine in early growth-restricted rats in adulthood. Br J Nutr 2011; 106:1374-82. [PMID: 21736800 DOI: 10.1017/s0007114511001784] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Epidemiological studies have linked intra-uterine growth restriction (IUGR) with an increased risk of CVD later in life. The aim of the present study was to examine the effect of maternal protein restriction on cardiac function in adulthood during dobutamine (DOB) stimulation. IUGR was induced in Wistar Kyoto dams through administration of a low-protein diet (LPD; 8.7 % casein) during pregnancy and lactation; the control group received a normal-protein diet (NPD; 20 % casein). At 14 weeks of age, cardiac function was assessed in male and female NPD (eight females and eight males) and LPD offspring (ten females and ten males) by pressure volumetry using an anaesthetised closed-chest approach. We determined mean arterial pressure (MAP), heart rate and left ventricular pressure-volume indices under baseline conditions and DOB stimulation (2 and 4 μg/kg per min). During β-adrenergic activation in LPD offspring, increases in cardiac output (CO, P < 0.018) and stroke volume (SV, P < 0.005) were attenuated in comparison with NPD offspring, while increases in ejection fraction and the maximal rate of ventricular pressure development were not affected. LPD females maintained a smaller end-diastolic volume (P < 0.017). MAP did not differ between the groups and did not change significantly during DOB infusion. Arterial elastance and total peripheral resistance decreased in all rats but remained significantly elevated in LPD offspring (P < 0.015 and < 0.01). Early growth restriction did not affect ventricular contractility but led to an increased afterload and impaired the ability to increase SV and CO during β-adrenergic stimulation.
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Cazorla O, Lacampagne A. Regional variation in myofilament length-dependent activation. Pflugers Arch 2011; 462:15-28. [DOI: 10.1007/s00424-011-0933-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 02/01/2011] [Accepted: 02/03/2011] [Indexed: 12/17/2022]
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Enhanced length-dependent Ca2+ activation in fish cardiomyocytes permits a large operating range of sarcomere lengths. J Mol Cell Cardiol 2010; 48:917-24. [PMID: 20170661 DOI: 10.1016/j.yjmcc.2010.02.008] [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: 12/15/2009] [Revised: 01/15/2010] [Accepted: 02/08/2010] [Indexed: 02/08/2023]
Abstract
Fish myocytes continue to develop active tension when stretched to sarcomere lengths (SLs) on the descending limb of the mammalian length-tension relationship. A greater length-dependent activation in fish than mammals could account for this because the increase in Ca(2+) sensitivity may overcome the tendency for force to fall due to reduced cross-bridge availability at SLs above optimal myofilament overlap. We stretched skinned fish and rat ventricular myocytes over a wide range of SLs, including those on the descending limb of the mammalian length-tension relationship. We found that fish myocytes developed greater active tension than rat myocytes at physiological Ca(2+) concentrations at long SLs as a result of a higher Ca(2+) sensitivity and a steeper relationship between Ca(2+) sensitivity and SL. We also investigated the diastolic properties of fish and rat myocytes at long SLs by measuring titin-based passive tension, titin isoform expression and titin phosphorylation. Fish myocytes produced higher titin-based passive tension despite expressing a higher proportion of a long N2BA-like isoform (38.0+/-2% of total vs 0% in rat). However, titin phosphorylation in fish myocytes was lower than in rat, which may explain some of the difference in passive tension between species. The high level of titin-based passive tension and the differential phosphorylation of sarcomeric proteins in fish myocytes may contribute to the enhanced length-dependent activation and underlie the extended range of in vivo stroke volumes found in fish compared with mammals.
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Colson BA, Locher MR, Bekyarova T, Patel JR, Fitzsimons DP, Irving TC, Moss RL. Differential roles of regulatory light chain and myosin binding protein-C phosphorylations in the modulation of cardiac force development. J Physiol 2010; 588:981-93. [PMID: 20123786 DOI: 10.1113/jphysiol.2009.183897] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Phosphorylation of myosin regulatory light chain (RLC) by myosin light chain kinase (MLCK) and myosin binding protein-C (cMyBP-C) by protein kinase A (PKA) independently accelerate the kinetics of force development in ventricular myocardium. However, while MLCK treatment has been shown to increase the Ca(2+) sensitivity of force (pCa(50)), PKA treatment has been shown to decrease pCa(50), presumably due to cardiac troponin I phosphorylation. Further, MLCK treatment increases Ca(2+)-independent force and maximum Ca(2+)-activated force, whereas PKA treatment has no effect on either force. To investigate the structural basis underlying the kinase-specific differential effects on steady-state force, we used synchrotron low-angle X-ray diffraction to compare equatorial intensity ratios (I(1,1)/I(1,0)) to assess the proximity of myosin cross-bridge mass relative to actin and to compare lattice spacings (d(1,0)) to assess the inter-thick filament spacing in skinned myocardium following treatment with either MLCK or PKA. As we showed previously, PKA phosphorylation of cMyBP-C increases I(1,1)/I(1,0) and, as hypothesized, treatment with MLCK also increased I(1,1)/I(1,0), which can explain the accelerated rates of force development during activation. Importantly, interfilament spacing was reduced by 2 nm (3.5%) with MLCK treatment, but did not change with PKA treatment. Thus, RLC or cMyBP-C phosphorylation increases the proximity of cross-bridges to actin, but only RLC phosphorylation affects lattice spacing, which suggests that RLC and cMyBP-C modulate the kinetics of force development by similar structural mechanisms; however, the effect of RLC phosphorylation to increase the Ca(2+) sensitivity of force is mediated by a distinct mechanism, most probably involving changes in interfilament spacing.
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Affiliation(s)
- Brett A Colson
- Department of Physiology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53711, USA.
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Sela G, Landesberg A. The external work-pressure time integral relationships and the afterload dependence of Frank-Starling mechanism. J Mol Cell Cardiol 2009; 47:544-51. [PMID: 19463830 DOI: 10.1016/j.yjmcc.2009.05.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Accepted: 05/13/2009] [Indexed: 11/19/2022]
Abstract
The mechanisms underlying the Frank-Starling Law of the heart are elusive and the prevalent notion suggests that it is afterload independent. However, isolated fiber studies reveal that the afterload determines cardiac function through cross-bridge dependent mechanisms. The study explores the roles of the afterload, in situ. The LV was exposed by left-thoracotomy in adult sheep (72.6+/-8.2 kg, n=8). Pressure transducers were inserted into the LV and aorta, a flowmeter was placed around the aortic root, and the LV volume was assessed by sonocrystals. Occluders around the aorta and the inferior vena cava enabled control of the afterload and preload. Different afterloads were imposed by partial aortic occlusions. Transient inferior vena cava occlusions (IVCOs) were preformed whenever the afterload was steady. A highly linear relationship was found between the external work (EW) and pressure time integral (PTI) (R(2)=0.98+/-0.01) during each transient IVCO (n=48). The slope of the EW-PTI relationship (WPTiR) was preload independent since, for any given afterload, the EW and PTI lay on a straight line. Interestingly, the slope of the WPTiR was afterload dependant: The slope was 33.3+/-4.1 mJ/mmHg.s at baselines and decreased by 1.0+/-0.50 mJ/mmHg.s with every 1 mmHg.min/L increase in the peripheral resistance. A unique WPTiR was obtained during both the occlusion and release phases of each IVCO, while two distinct EW-preload or PTI-preload relationships were observed. The novel WPTiR ties the Frank (pressure development) and Starling (EW production) phenomena together. The dependence of the WPTiR on the afterload highlights the adaptive control of the Frank-Starling mechanisms to changes in the afterload.
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Affiliation(s)
- Gali Sela
- Heart System Research Center, Faculty of Biomedical Engineering, Technion-IIT, Haifa 32000 Israel
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20
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Colson BA, Bekyarova T, Locher MR, Fitzsimons DP, Irving TC, Moss RL. Protein kinase A-mediated phosphorylation of cMyBP-C increases proximity of myosin heads to actin in resting myocardium. Circ Res 2008; 103:244-51. [PMID: 18599866 PMCID: PMC2810832 DOI: 10.1161/circresaha.108.178996] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Protein kinase A-mediated (PKA) phosphorylation of cardiac myosin binding protein C (cMyBP-C) accelerates the kinetics of cross-bridge cycling and may relieve the tether-like constraint of myosin heads imposed by cMyBP-C. We favor a mechanism in which cMyBP-C modulates cross-bridge cycling kinetics by regulating the proximity and interaction of myosin and actin. To test this idea, we used synchrotron low-angle x-ray diffraction to measure interthick filament lattice spacing and the equatorial intensity ratio, I(11)/I(10), in skinned trabeculae isolated from wild-type and cMyBP-C null (cMyBP-C(-/-)) mice. In wild-type myocardium, PKA treatment appeared to result in radial or azimuthal displacement of cross-bridges away from the thick filaments as indicated by an increase (approximately 50%) in I(11)/I(10) (0.22+/-0.03 versus 0.33+/-0.03). Conversely, PKA treatment did not affect cross-bridge disposition in mice lacking cMyBP-C, because there was no difference in I(11)/I(10) between untreated and PKA-treated cMyBP-C(-/-) myocardium (0.40+/-0.06 versus 0.42+/-0.05). Although lattice spacing did not change after treatment in wild-type (45.68+/-0.84 nm versus 45.64+/-0.64 nm), treatment of cMyBP-C(-/-) myocardium increased lattice spacing (46.80+/-0.92 nm versus 49.61+/-0.59 nm). This result is consistent with the idea that the myofilament lattice expands after PKA phosphorylation of cardiac troponin I, and when present, cMyBP-C, may stabilize the lattice. These data support our hypothesis that tethering of cross-bridges by cMyBP-C is relieved by phosphorylation of PKA sites in cMyBP-C, thereby increasing the proximity of cross-bridges to actin and increasing the probability of interaction with actin on contraction.
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Affiliation(s)
- Brett A Colson
- Department of Physiology, University of Wisconsin Medical School, Madison, WI, USA.
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Terui T, Sodnomtseren M, Matsuba D, Udaka J, Ishiwata S, Ohtsuki I, Kurihara S, Fukuda N. Troponin and titin coordinately regulate length-dependent activation in skinned porcine ventricular muscle. ACTA ACUST UNITED AC 2008; 131:275-83. [PMID: 18299397 PMCID: PMC2248715 DOI: 10.1085/jgp.200709895] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We investigated the molecular mechanism by which troponin (Tn) regulates the Frank-Starling mechanism of the heart. Quasi-complete reconstitution of thin filaments with rabbit fast skeletal Tn (sTn) attenuated length-dependent activation in skinned porcine left ventricular muscle, to a magnitude similar to that observed in rabbit fast skeletal muscle. The rate of force redevelopment increased upon sTn reconstitution at submaximal levels, coupled with an increase in Ca2+ sensitivity of force, suggesting the acceleration of cross-bridge formation and, accordingly, a reduction in the fraction of resting cross-bridges that can potentially produce additional active force. An increase in titin-based passive force, induced by manipulating the prehistory of stretch, enhanced length-dependent activation, in both control and sTn-reconstituted muscles. Furthermore, reconstitution of rabbit fast skeletal muscle with porcine left ventricular Tn enhanced length-dependent activation, accompanied by a decrease in Ca2+ sensitivity of force. These findings demonstrate that Tn plays an important role in the Frank-Starling mechanism of the heart via on–off switching of the thin filament state, in concert with titin-based regulation.
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Affiliation(s)
- Takako Terui
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo 105-8461, Japan.
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Ait Mou Y, le Guennec JY, Mosca E, de Tombe PP, Cazorla O. Differential contribution of cardiac sarcomeric proteins in the myofibrillar force response to stretch. Pflugers Arch 2008; 457:25-36. [PMID: 18449562 DOI: 10.1007/s00424-008-0501-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Revised: 03/18/2008] [Accepted: 03/18/2008] [Indexed: 11/24/2022]
Abstract
The present study examined the contribution of myofilament contractile proteins to regional function in guinea pig myocardium. We investigated the effect of stretch on myofilament contractile proteins, Ca(2+) sensitivity, and cross-bridge cycling kinetics (K (tr)) of force in single skinned cardiomyocytes isolated from the sub-endocardial (ENDO) or sub-epicardial (EPI) layer. As observed in other species, ENDO cells were stiffer, and Ca(2+) sensitivity of force at long sarcomere length was higher compared with EPI cells. Maximal K (tr) was unchanged by stretch, but was higher in EPI cells possibly due to a higher alpha-MHC content. Submaximal Ca(2+)-activated K (tr) increased only in ENDO cells with stretch. Stretch of skinned ENDO muscle strips induced increased phosphorylation in both myosin-binding protein C and myosin light chain 2. We concluded that transmural MHC isoform expression and differential regulatory protein phosphorylation by stretch contributes to regional differences in stretch modulation of activation in guinea pig left ventricle.
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Affiliation(s)
- Younss Ait Mou
- INSERM, U 637, Université MONTPELLIER I, UFR de Médecine, F-34295, Montpellier, France
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23
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dos Remedios CG. The regulation of muscle contraction: as in life, it keeps getting more complex. Biophys J 2007; 93:4097-8. [PMID: 17890400 PMCID: PMC2098728 DOI: 10.1529/biophysj.107.117762] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- C G dos Remedios
- Muscle Research Unit, Bosch Institute, The University of Sydney, Sydney, Australia.
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Affiliation(s)
- R John Solaro
- Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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