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Hitsumoto T, Tsukamoto O, Matsuoka K, Li J, Liu L, Kuramoto Y, Higo S, Ogawa S, Fujino N, Yoshida S, Kioka H, Kato H, Hakui H, Saito Y, Okamoto C, Inoue H, Hyejin J, Ueda K, Segawa T, Nishimura S, Asano Y, Asanuma H, Tani A, Imamura R, Komagawa S, Kanai T, Takamura M, Sakata Y, Kitakaze M, Haruta JI, Takashima S. Restoration of Cardiac Myosin Light Chain Kinase Ameliorates Systolic Dysfunction by Reducing Superrelaxed Myosin. Circulation 2023; 147:1902-1918. [PMID: 37128901 PMCID: PMC10270284 DOI: 10.1161/circulationaha.122.062885] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Accepted: 04/05/2023] [Indexed: 05/03/2023]
Abstract
BACKGROUND Cardiac-specific myosin light chain kinase (cMLCK), encoded by MYLK3, regulates cardiac contractility through phosphorylation of ventricular myosin regulatory light chain. However, the pathophysiological and therapeutic implications of cMLCK in human heart failure remain unclear. We aimed to investigate whether cMLCK dysregulation causes cardiac dysfunction and whether the restoration of cMLCK could be a novel myotropic therapy for systolic heart failure. METHODS We generated the knock-in mice (Mylk3+/fs and Mylk3fs/fs) with a familial dilated cardiomyopathy-associated MYLK3 frameshift mutation (MYLK3+/fs) that had been identified previously by us (c.1951-1G>T; p.P639Vfs*15) and the human induced pluripotent stem cell-derived cardiomyocytes from the carrier of the mutation. We also developed a new small-molecule activator of cMLCK (LEUO-1154). RESULTS Both mice (Mylk3+/fs and Mylk3fs/fs) showed reduced cMLCK expression due to nonsense-mediated messenger RNA decay, reduced MLC2v (ventricular myosin regulatory light chain) phosphorylation in the myocardium, and systolic dysfunction in a cMLCK dose-dependent manner. Consistent with this result, myocardium from the mutant mice showed an increased ratio of cardiac superrelaxation/disordered relaxation states that may contribute to impaired cardiac contractility. The phenotypes observed in the knock-in mice were rescued by cMLCK replenishment through the AAV9_MYLK3 vector. Human induced pluripotent stem cell-derived cardiomyocytes with MYLK3+/fs mutation reduced cMLCK expression by 50% and contractile dysfunction, accompanied by an increased superrelaxation/disordered relaxation ratio. CRISPR-mediated gene correction, or cMLCK replenishment by AAV9_MYLK3 vector, successfully recovered cMLCK expression, the superrelaxation/disordered relaxation ratio, and contractile dysfunction. LEUO-1154 increased human cMLCK activity ≈2-fold in the Vmax for ventricular myosin regulatory light chain phosphorylation without affecting the Km. LEUO-1154 treatment of human induced pluripotent stem cell-derived cardiomyocytes with MYLK3+/fs mutation restored the ventricular myosin regulatory light chain phosphorylation level and superrelaxation/disordered relaxation ratio and improved cardiac contractility without affecting calcium transients, indicating that the cMLCK activator acts as a myotrope. Finally, human myocardium from advanced heart failure with a wide variety of causes had a significantly lower MYLK3/PPP1R12B messenger RNA expression ratio than control hearts, suggesting an altered balance between myosin regulatory light chain kinase and phosphatase in the failing myocardium, irrespective of the causes. CONCLUSIONS cMLCK dysregulation contributes to the development of cardiac systolic dysfunction in humans. Our strategy to restore cMLCK activity could form the basis of a novel myotropic therapy for advanced systolic heart failure.
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Affiliation(s)
- Tatsuro Hitsumoto
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Osamu Tsukamoto
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Ken Matsuoka
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Junjun Li
- Department of Cardiovascular Surgery (J.L., L.L.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Li Liu
- Department of Cardiovascular Surgery (J.L., L.L.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Yuki Kuramoto
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Shuichiro Higo
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Shou Ogawa
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Noboru Fujino
- Department of Cardiovascular Medicine, Graduate School of Medical Science, Kanazawa University. Kanazawa, Ishikawa, Japan (N.F., S.Y., M.T.)
| | - Shohei Yoshida
- Department of Cardiovascular Medicine, Graduate School of Medical Science, Kanazawa University. Kanazawa, Ishikawa, Japan (N.F., S.Y., M.T.)
| | - Hidetaka Kioka
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Hisakazu Kato
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Hideyuki Hakui
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Yuki Saito
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Chisato Okamoto
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Hijiri Inoue
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Jo Hyejin
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Kyoko Ueda
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Takatsugu Segawa
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
| | - Shunsuke Nishimura
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | - Yoshihiro Asano
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
- Department of Genomic Medicine, National Cerebral and Cardiovascular Center, Osaka, Japan (Y.A.)
| | - Hiroshi Asanuma
- Department of Internal Medicine, Meiji University of Integrative Medicine, Nantan, Kyoto, Japan (H.A.)
| | - Akiyoshi Tani
- Compound Library Screening Center (A.T.), Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Riyo Imamura
- Drug Discovery Initiative, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan (R.I.)
| | - Shinsuke Komagawa
- Lead Explorating Units (S.K., T.K., J.-i.H.), Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Toshio Kanai
- Lead Explorating Units (S.K., T.K., J.-i.H.), Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Masayuki Takamura
- Department of Cardiovascular Medicine, Graduate School of Medical Science, Kanazawa University. Kanazawa, Ishikawa, Japan (N.F., S.Y., M.T.)
| | - Yasushi Sakata
- Department of Cardiology (Y.K., S.H., S.O., H. Kioka, HY.H., S.N., Y.A., Y.S.), Osaka University Graduate School of Medicine. Suita, Osaka, Japan
| | | | - Jun-ichi Haruta
- Lead Explorating Units (S.K., T.K., J.-i.H.), Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Seiji Takashima
- Department of Medical Biochemistry, Osaka University Graduate School of Medicine/Frontier Biosciences, Suita, Osaka, Japan (T.H., O.T., K.M., H. Kioka, H. Kato, H.H., Y.S., C.O., H.I., J.H., K.U., T.S., S.N., S.T.)
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Wehrens M, de Leeuw AE, Wright-Clark M, Eding JEC, Boogerd CJ, Molenaar B, van der Kraak PH, Kuster DWD, van der Velden J, Michels M, Vink A, van Rooij E. Single-cell transcriptomics provides insights into hypertrophic cardiomyopathy. Cell Rep 2022; 39:110809. [PMID: 35545053 DOI: 10.1016/j.celrep.2022.110809] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 01/25/2022] [Accepted: 04/21/2022] [Indexed: 11/24/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is a genetic heart disease that is characterized by unexplained segmental hypertrophy that is usually most pronounced in the septum. While sarcomeric gene mutations are often the genetic basis for HCM, the mechanistic origin for the heterogeneous remodeling remains largely unknown. A better understanding of the gene networks driving the cardiomyocyte (CM) hypertrophy is required to improve therapeutic strategies. Patients suffering from HCM often receive a septal myectomy surgery to relieve outflow tract obstruction due to hypertrophy. Using single-cell RNA sequencing (scRNA-seq) on septal myectomy samples from patients with HCM, we identify functional links between genes, transcription factors, and cell size relevant for HCM. The data show the utility of using scRNA-seq on the human hypertrophic heart, highlight CM heterogeneity, and provide a wealth of insights into molecular events involved in HCM that can eventually contribute to the development of enhanced therapies.
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Affiliation(s)
- Martijn Wehrens
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW) and University Medical Center, Utrecht, the Netherlands
| | - Anne E de Leeuw
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW) and University Medical Center, Utrecht, the Netherlands
| | - Maya Wright-Clark
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW) and University Medical Center, Utrecht, the Netherlands; Department of Cardiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Joep E C Eding
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW) and University Medical Center, Utrecht, the Netherlands
| | - Cornelis J Boogerd
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW) and University Medical Center, Utrecht, the Netherlands
| | - Bas Molenaar
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW) and University Medical Center, Utrecht, the Netherlands
| | - Petra H van der Kraak
- Department of Pathology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Diederik W D Kuster
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
| | - Jolanda van der Velden
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
| | - Michelle Michels
- Department of Cardiology, Erasmus MC, Rotterdam, the Netherlands
| | - Aryan Vink
- Department of Pathology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Eva van Rooij
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW) and University Medical Center, Utrecht, the Netherlands; Department of Cardiology, University Medical Center Utrecht, Utrecht, the Netherlands.
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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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Markandran K, Yu H, Song W, Lam DTUH, Madathummal MC, Ferenczi MA. Functional and Molecular Characterisation of Heart Failure Progression in Mice and the Role of Myosin Regulatory Light Chains in the Recovery of Cardiac Muscle Function. Int J Mol Sci 2021; 23:ijms23010088. [PMID: 35008512 PMCID: PMC8745055 DOI: 10.3390/ijms23010088] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 12/07/2021] [Accepted: 12/14/2021] [Indexed: 02/07/2023] Open
Abstract
Heart failure (HF) as a result of myocardial infarction (MI) is a major cause of fatality worldwide. However, the cause of cardiac dysfunction succeeding MI has not been elucidated at a sarcomeric level. Thus, studying the alterations within the sarcomere is necessary to gain insights on the fundamental mechansims leading to HF and potentially uncover appropriate therapeutic targets. Since existing research portrays regulatory light chains (RLC) to be mediators of cardiac muscle contraction in both human and animal models, its role was further explored In this study, a detailed characterisation of the physiological changes (i.e., isometric force, calcium sensitivity and sarcomeric protein phosphorylation) was assessed in an MI mouse model, between 2D (2 days) and 28D post-MI, and the changes were related to the phosphorylation status of RLCs. MI mouse models were created via complete ligation of left anterior descending (LAD) coronary artery. Left ventricular (LV) papillary muscles were isolated and permeabilised for isometric force and Ca2+ sensitivity measurement, while the LV myocardium was used to assay sarcomeric proteins’ (RLC, troponin I (TnI) and myosin binding protein-C (MyBP-C)) phosphorylation levels and enzyme (myosin light chain kinase (MLCK), zipper interacting protein kinase (ZIPK) and myosin phosphatase target subunit 2 (MYPT2)) expression levels. Finally, the potential for improving the contractility of diseased cardiac papillary fibres via the enhancement of RLC phosphorylation levels was investigated by employing RLC exchange methods, in vitro. RLC phosphorylation and isometric force potentiation were enhanced in the compensatory phase and decreased in the decompensatory phase of HF failure progression, respectively. There was no significant time-lag between the changes in RLC phosphorylation and isometric force during HF progression, suggesting that changes in RLC phosphorylation immediately affect force generation. Additionally, the in vitro increase in RLC phosphorylation levels in 14D post-MI muscle segments (decompensatory stage) enhanced its force of isometric contraction, substantiating its potential in HF treatment. Longitudinal observation unveils potential mechanisms involving MyBP-C and key enzymes regulating RLC phosphorylation, such as MLCK and MYPT2 (subunit of MLCP), during HF progression. This study primarily demonstrates that RLC phosphorylation is a key sarcomeric protein modification modulating cardiac function. This substantiates the possibility of using RLCs and their associated enzymes to treat HF.
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Affiliation(s)
- Kasturi Markandran
- Lee Kong Chian School of Medicine, Nanyang Technological University, Experimental Medicine Building, 59 Nanyang Drive, Singapore 636921, Singapore; (K.M.); (H.Y.); (W.S.); (D.T.U.H.L.); (M.C.M.)
| | - Haiyang Yu
- Lee Kong Chian School of Medicine, Nanyang Technological University, Experimental Medicine Building, 59 Nanyang Drive, Singapore 636921, Singapore; (K.M.); (H.Y.); (W.S.); (D.T.U.H.L.); (M.C.M.)
| | - Weihua Song
- Lee Kong Chian School of Medicine, Nanyang Technological University, Experimental Medicine Building, 59 Nanyang Drive, Singapore 636921, Singapore; (K.M.); (H.Y.); (W.S.); (D.T.U.H.L.); (M.C.M.)
| | - Do Thuy Uyen Ha Lam
- Lee Kong Chian School of Medicine, Nanyang Technological University, Experimental Medicine Building, 59 Nanyang Drive, Singapore 636921, Singapore; (K.M.); (H.Y.); (W.S.); (D.T.U.H.L.); (M.C.M.)
- Laboratory of Precision Disease Therapeutics, Genome Institute of Singapore, 60 Biopolis Street, Singapore 138672, Singapore
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, 10 Medical Drive, Singapore 117597, Singapore
| | - Mufeeda Changaramvally Madathummal
- Lee Kong Chian School of Medicine, Nanyang Technological University, Experimental Medicine Building, 59 Nanyang Drive, Singapore 636921, Singapore; (K.M.); (H.Y.); (W.S.); (D.T.U.H.L.); (M.C.M.)
- A*STAR Microscopy Platform—Electron Microscopy, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore
| | - Michael A. Ferenczi
- Lee Kong Chian School of Medicine, Nanyang Technological University, Experimental Medicine Building, 59 Nanyang Drive, Singapore 636921, Singapore; (K.M.); (H.Y.); (W.S.); (D.T.U.H.L.); (M.C.M.)
- Brunel Medical School, Brunel University London, Kingston Lane, Uxbridge UB8 3PH, UK
- Correspondence:
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Regulatory Light Chains in Cardiac Development and Disease. Int J Mol Sci 2021; 22:ijms22094351. [PMID: 33919432 PMCID: PMC8122660 DOI: 10.3390/ijms22094351] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/14/2021] [Accepted: 04/17/2021] [Indexed: 12/18/2022] Open
Abstract
The role of regulatory light chains (RLCs) in cardiac muscle function has been elucidated progressively over the past decade. The RLCs are among the earliest expressed markers during cardiogenesis and persist through adulthood. Failing hearts have shown reduced RLC phosphorylation levels and that restoring baseline levels of RLC phosphorylation is necessary for generating optimal force of muscle contraction. The signalling mechanisms triggering changes in RLC phosphorylation levels during disease progression remain elusive. Uncovering this information may provide insights for better management of heart failure patients. Given the cardiac chamber-specific expression of RLC isoforms, ventricular RLCs have facilitated the identification of mature ventricular cardiomyocytes, opening up possibilities of regenerative medicine. This review consolidates the standing of RLCs in cardiac development and disease and highlights knowledge gaps and potential therapeutic advancements in targeting RLCs.
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Schmid M, Toepfer CN. Cardiac myosin super relaxation (SRX): a perspective on fundamental biology, human disease and therapeutics. Biol Open 2021; 10:bio057646. [PMID: 33589442 PMCID: PMC7904003 DOI: 10.1242/bio.057646] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The fundamental basis of muscle contraction 'the sliding filament model' (Huxley and Niedergerke, 1954; Huxley and Hanson, 1954) and the 'swinging, tilting crossbridge-sliding filament mechanism' (Huxley, 1969; Huxley and Brown, 1967) nucleated a field of research that has unearthed the complex and fascinating role of myosin structure in the regulation of contraction. A recently discovered energy conserving state of myosin termed the super relaxed state (SRX) has been observed in filamentous myosins and is central to modulating force production and energy use within the sarcomere. Modulation of myosin function through SRX is a rapidly developing theme in therapeutic development for both cardiovascular disease and infectious disease. Some 70 years after the first discoveries concerning muscular function, modulation of myosin SRX may bring the first myosin targeted small molecule to the clinic, for treating hypertrophic cardiomyopathy (Olivotto et al., 2020). An often monogenic disease HCM afflicts 1 in 500 individuals, and can cause heart failure and sudden cardiac death. Even as we near therapeutic translation, there remain many questions about the governance of muscle function in human health and disease. With this review, we provide a broad overview of contemporary understanding of myosin SRX, and explore the complexities of targeting this myosin state in human disease.This article has an associated Future Leaders to Watch interview with the authors of the paper.
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Affiliation(s)
- Manuel Schmid
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, UK
| | - Christopher N Toepfer
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, UK
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
- Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
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In-silico human electro-mechanical ventricular modelling and simulation for drug-induced pro-arrhythmia and inotropic risk assessment. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 159:58-74. [PMID: 32710902 PMCID: PMC7848595 DOI: 10.1016/j.pbiomolbio.2020.06.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 06/08/2020] [Accepted: 06/28/2020] [Indexed: 12/28/2022]
Abstract
Human-based computational modelling and simulation are powerful tools to accelerate the mechanistic understanding of cardiac patho-physiology, and to develop and evaluate therapeutic interventions. The aim of this study is to calibrate and evaluate human ventricular electro-mechanical models for investigations on the effect of the electro-mechanical coupling and pharmacological action on human ventricular electrophysiology, calcium dynamics, and active contraction. The most recent models of human ventricular electrophysiology, excitation-contraction coupling, and active contraction were integrated, and the coupled models were calibrated using human experimental data. Simulations were then conducted using the coupled models to quantify the effects of electro-mechanical coupling and drug exposure on electrophysiology and force generation in virtual human ventricular cardiomyocytes and tissue. The resulting calibrated human electro-mechanical models yielded active tension, action potential, and calcium transient metrics that are in agreement with experiments for endocardial, epicardial, and mid-myocardial human samples. Simulation results correctly predicted the inotropic response of different multichannel action reference compounds and demonstrated that the electro-mechanical coupling improves the robustness of repolarisation under drug exposure compared to electrophysiology-only models. They also generated additional evidence to explain the partial mismatch between in-silico and in-vitro experiments on drug-induced electrophysiology changes. The human calibrated and evaluated modelling and simulation framework constructed in this study opens new avenues for future investigations into the complex interplay between the electrical and mechanical cardiac substrates, its modulation by pharmacological action, and its translation to tissue and organ models of cardiac patho-physiology.
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Pitoulis FG, Watson SA, Perbellini F, Terracciano CM. Myocardial slices come to age: an intermediate complexity in vitro cardiac model for translational research. Cardiovasc Res 2020; 116:1275-1287. [PMID: 31868875 PMCID: PMC7243278 DOI: 10.1093/cvr/cvz341] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 10/31/2019] [Accepted: 12/19/2019] [Indexed: 12/17/2022] Open
Abstract
Although past decades have witnessed significant reductions in mortality of heart failure together with advances in our understanding of its cellular, molecular, and whole-heart features, a lot of basic cardiac research still fails to translate into clinical practice. In this review we examine myocardial slices, a novel model in the translational arena. Myocardial slices are living ultra-thin sections of heart tissue. Slices maintain the myocardium's native function (contractility, electrophysiology) and structure (multicellularity, extracellular matrix) and can be prepared from animal and human tissue. The discussion begins with the history and current advances in the model, the different interlaboratory methods of preparation and their potential impact on results. We then contextualize slices' advantages and limitations by comparing it with other cardiac models. Recently, sophisticated methods have enabled slices to be cultured chronically in vitro while preserving the functional and structural phenotype. This is more timely now than ever where chronic physiologically relevant in vitro platforms for assessment of therapeutic strategies are urgently needed. We interrogate the technological developments that have permitted this, their limitations, and future directions. Finally, we look into the general obstacles faced by the translational field, and how implementation of research systems utilizing slices could help in resolving these.
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Affiliation(s)
- Fotios G Pitoulis
- Laboratory of Cell Electrophysiology, Department of Myocardial Function, Imperial College London, National Heart and Lung Institute, 4th Floor ICTEM Building Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Samuel A Watson
- Laboratory of Cell Electrophysiology, Department of Myocardial Function, Imperial College London, National Heart and Lung Institute, 4th Floor ICTEM Building Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Filippo Perbellini
- Laboratory of Cell Electrophysiology, Department of Myocardial Function, Imperial College London, National Heart and Lung Institute, 4th Floor ICTEM Building Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
- Hannover Medical School, Institute of Molecular and Translational Therapeutic Strategies, Hannover, Germany
| | - Cesare M Terracciano
- Laboratory of Cell Electrophysiology, Department of Myocardial Function, Imperial College London, National Heart and Lung Institute, 4th Floor ICTEM Building Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
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9
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Intact myocardial preparations reveal intrinsic transmural heterogeneity in cardiac mechanics. J Mol Cell Cardiol 2020; 141:11-16. [PMID: 32201175 PMCID: PMC7246333 DOI: 10.1016/j.yjmcc.2020.03.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 03/16/2020] [Accepted: 03/18/2020] [Indexed: 01/31/2023]
Abstract
Determining transmural mechanical properties in the heart provides a foundation to understand physiological and pathophysiological cardiac mechanics. Although work on mechanical characterisation has begun in isolated cells and permeabilised samples, the mechanical profile of living individual cardiac layers has not been examined. Myocardial slices are 300 μm-thin sections of heart tissue with preserved cellular stoichiometry, extracellular matrix, and structural architecture. This allows for cardiac mechanics assays in the context of an intact in vitro organotypic preparation. In slices obtained from the subendocardium, midmyocardium and subepicardium of rats, a distinct pattern in transmural contractility is found that is different from that observed in other models. Slices from the epicardium and midmyocardium had a higher active tension and passive tension than the endocardium upon stretch. Differences in total myocyte area coverage, and aspect ratio between layers underlined the functional readouts, while no differences were found in total sarcomeric protein and phosphoprotein between layers. Such intrinsic heterogeneity may orchestrate the normal pumping of the heart in the presence of transmural strain and sarcomere length gradients in the in vivo heart. The myocardial slice preparation is an intact cardiac model allowing the study of transmural properties. Mechanical behaviour is cardiac layer dependent. Structural differences in cardiomyocyte density, orientation, and aspect ratio may contribute to these findings.
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10
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van der Velden J, Stienen GJM. Cardiac Disorders and Pathophysiology of Sarcomeric Proteins. Physiol Rev 2019; 99:381-426. [PMID: 30379622 DOI: 10.1152/physrev.00040.2017] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The sarcomeric proteins represent the structural building blocks of heart muscle, which are essential for contraction and relaxation. During recent years, it has become evident that posttranslational modifications of sarcomeric proteins, in particular phosphorylation, tune cardiac pump function at rest and during exercise. This delicate, orchestrated interaction is also influenced by mutations, predominantly in sarcomeric proteins, which cause hypertrophic or dilated cardiomyopathy. In this review, we follow a bottom-up approach starting from a description of the basic components of cardiac muscle at the molecular level up to the various forms of cardiac disorders at the organ level. An overview is given of sarcomere changes in acquired and inherited forms of cardiac disease and the underlying disease mechanisms with particular reference to human tissue. A distinction will be made between the primary defect and maladaptive/adaptive secondary changes. Techniques used to unravel functional consequences of disease-induced protein changes are described, and an overview of current and future treatments targeted at sarcomeric proteins is given. The current evidence presented suggests that sarcomeres not only form the basis of cardiac muscle function but also represent a therapeutic target to combat cardiac disease.
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Affiliation(s)
- Jolanda van der Velden
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, Amsterdam , The Netherlands ; and Department of Physiology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Ger J M Stienen
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, Amsterdam , The Netherlands ; and Department of Physiology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
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11
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van Duin RWB, Houweling B, Uitterdijk A, Duncker DJ, Merkus D. Pulmonary vasodilation by phosphodiesterase 5 inhibition is enhanced and nitric oxide independent in early pulmonary hypertension after myocardial infarction. Am J Physiol Heart Circ Physiol 2017; 314:H170-H179. [PMID: 28986358 DOI: 10.1152/ajpheart.00370.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Myocardial infarction (MI) may result in pulmonary hypertension (PH). Inhibition of phosphodiesterase 5 (PDE5), the enzyme responsible for the breakdown of cGMP in vascular smooth muscle, has become part of the contemporary therapeutic armamentarium for pulmonary arterial hypertension and may also be beneficial for PH secondary to MI. Nitric oxide (NO) is an important activator of cGMP synthesis and can be enhanced in early PH and decreased in severe PH. In the present study, we investigated if PDE5 inhibition ameliorates pulmonary hemodynamics in swine with PH secondary to MI and whether NO is essential. The PDE5 inhibitor EMD360527 was administered in awake, chronically instrumented swine with or without MI. At rest, PDE5 inhibition produced pulmonary vasodilation as evidenced by a decrease in pulmonary vascular resistance, which was more pronounced in MI ( n = 5) compared with normal swine ( n = 10, P ≤ 0.01) and was accompanied by an increase in stroke volume in MI swine. Both pulmonary vasodilation and increased stroke volume were maintained during exercise, suggesting that this therapy may improve exercise capacity in patients with PH secondary to MI. Interestingly, prior inhibition of NO significantly enhanced ( P ≤ 0.01) pulmonary vasodilation by PDE5 inhibition in both normal ( n = 8) and MI swine ( n = 5, P ≤ 0.05 vs. normal). This suggests that the increased vasodilator responses to PDE5 inhibition after MI were not due to an increase in NO-induced cGMP production. These observations indicate that PDE5 inhibition represents an interesting pharmacotherapeutic approach in early PH after a recent MI to prevent overt PH. NEW & NOTEWORTHY This research article is the first to describe that pulmonary vasodilation to phosphodiesterase 5 inhibition is enhanced and nitric oxide independent in resting and exercising swine with pulmonary hypertension as a result of myocardial infarction. This suggests that phosphodiesterase 5 inhibition can normalize pulmonary hemodynamics in postcapillary pulmonary hypertension after a recent myocardial infarction and may improve exercise capacity.
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Affiliation(s)
- Richard W B van Duin
- Division of Experimental Cardiology, Department of Cardiology, Thoraxcenter, Cardiovascular Research School COEUR, Erasmus MC, Rotterdam , The Netherlands
| | - Birgit Houweling
- Division of Experimental Cardiology, Department of Cardiology, Thoraxcenter, Cardiovascular Research School COEUR, Erasmus MC, Rotterdam , The Netherlands
| | - André Uitterdijk
- Division of Experimental Cardiology, Department of Cardiology, Thoraxcenter, Cardiovascular Research School COEUR, Erasmus MC, Rotterdam , The Netherlands
| | - Dirk J Duncker
- Division of Experimental Cardiology, Department of Cardiology, Thoraxcenter, Cardiovascular Research School COEUR, Erasmus MC, Rotterdam , The Netherlands
| | - Daphne Merkus
- Division of Experimental Cardiology, Department of Cardiology, Thoraxcenter, Cardiovascular Research School COEUR, Erasmus MC, Rotterdam , The Netherlands
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12
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Gregorich ZR, Cai W, Lin Z, Chen AJ, Peng Y, Kohmoto T, Ge Y. Distinct sequences and post-translational modifications in cardiac atrial and ventricular myosin light chains revealed by top-down mass spectrometry. J Mol Cell Cardiol 2017; 107:13-21. [PMID: 28427997 DOI: 10.1016/j.yjmcc.2017.04.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 04/15/2017] [Indexed: 01/01/2023]
Abstract
Myosin is the principal component of the thick filaments that, through interactions with the actin thin filaments, mediates force production during muscle contraction. Myosin is a hexamer, consisting of two heavy chains, each associated with an essential (ELC) and a regulatory (RLC) light chain, which bind the lever-arm of the heavy chain and play important modulatory roles in striated muscle contraction. Nevertheless, a comprehensive assessment of the sequences of the ELC and RLC isoforms, as well as their post-translational modifications, in the heart remains lacking. Herein, utilizing top-down high-resolution mass spectrometry (MS), we have comprehensively characterized the sequences and N-terminal modifications of the atrial and ventricular isoforms of the myosin light chains from human and swine hearts, as well as the sites of phosphorylation in the swine proteins. In addition to the correction of disparities in the database sequences of the swine proteins, we show for the first time that, whereas the ventricular isoforms of the ELC and RLC are methylated at their N-termini, which is consistent with previous studies, the atrial isoforms of the ELC and RLC from both human and swine are Nα-methylated and Nα-acetylated, respectively. Furthermore, top-down MS with electron capture dissociation enabled localization of the sites of phosphorylation in swine RLC isoforms from the ventricles and atria to Ser14 and Ser22, respectively. Collectively, these results provide new insights into the sequences and modifications of myosin light chain isoforms in the human and swine hearts, which will pave the way for a better understanding of their functional roles in cardiac physiology and pathophysiology.
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Affiliation(s)
- Zachery R Gregorich
- Molecular and Cellular Pharmacology Training Program, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Wenxuan Cai
- Molecular and Cellular Pharmacology Training Program, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Ziqing Lin
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Albert J Chen
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Ying Peng
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Takushi Kohmoto
- Department of Surgery, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Ying Ge
- Molecular and Cellular Pharmacology Training Program, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705, USA; Human Proteomics Program, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
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13
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Chang AN, Kamm KE, Stull JT. Role of myosin light chain phosphatase in cardiac physiology and pathophysiology. J Mol Cell Cardiol 2016; 101:35-43. [PMID: 27742556 DOI: 10.1016/j.yjmcc.2016.10.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 10/07/2016] [Accepted: 10/10/2016] [Indexed: 11/18/2022]
Abstract
Maintenance of contractile performance of the heart is achieved in part by the constitutive 40% phosphorylation of myosin regulatory light chain (RLC) in sarcomeres. The importance of this extent of RLC phosphorylation for optimal cardiac performance becomes apparent when various mouse models and resultant phenotypes are compared. The absence or attenuation of RLC phosphorylation results in poor performance leading to heart failure, whereas increased RLC phosphorylation is associated with cardiac protection from stresses. Although information is limited, RLC phosphorylation appears compromised in human heart failure which is consistent with data from mouse studies. The extent of cardiac RLC phosphorylation is determined by the balanced activities of cardiac myosin light chain kinases and phosphatases, the regulatory mechanisms of which are now emerging. This review thusly focuses on kinases that may participate in phosphorylating RLC to make the substrate for cardiac myosin light chain phosphatases, in addition to providing perspectives on the family of myosin light chain phosphatases and involved signaling mechanisms. Because biochemical and physiological information about cardiac myosin light chain phosphatase is sparse, such studies represent an emerging area of investigation in health and disease.
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Affiliation(s)
- Audrey N Chang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Kristine E Kamm
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - James T Stull
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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14
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Behunin SM, Lopez-Pier MA, Birch CL, McKee LAK, Danilo C, Khalpey Z, Konhilas JP. LKB1/Mo25/STRAD uniquely impacts sarcomeric contractile function and posttranslational modification. Biophys J 2016; 108:1484-1494. [PMID: 25809261 DOI: 10.1016/j.bpj.2015.02.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 01/27/2015] [Accepted: 02/02/2015] [Indexed: 01/17/2023] Open
Abstract
The myocardium undergoes extensive metabolic and energetic remodeling during the progression of cardiac disease. Central to remodeling are changes in the adenine nucleotide pool. Fluctuations in these pools can activate AMP-activated protein kinase (AMPK), the central regulator of cellular energetics. Binding of AMP to AMPK not only allosterically activates AMPK but also promotes phosphorylation of AMPK by an upstream kinase complex, LKB1/Mo25/STRAD (liver kinase B 1, mouse protein 25, STE-related adaptor protein). AMPK phosphorylation by the LKB1 complex results in a substantial increase in AMPK activity. Molecular targeting by the LKB1 complex depends on subcellular localization and transcriptional expression. Yet, little is known about the ability of the LKB1 complex to modulate targeting of AMPK after activation. Accordingly, we hypothesized that differing stoichiometric ratios of LKB1 activator complex to AMPK would uniquely impact myofilament function. Demembranated rat cardiac trabeculae were incubated with varying ratios of the LKB1 complex to AMPK or the LKB1 complex alone. After incubation, we measured the Ca(2+) sensitivity of tension, rate constant for tension redevelopment, maximum tension generation, length-dependent activation, cooperativity, and sarcomeric protein phosphorylation status. We found that the Ca(2+) sensitivity of tension and cross-bridge dynamics were dependent on the LKB1 complex/AMPK ratio. We also found that the LKB1 complex desensitizes and suppresses myofilament function independently of AMPK. A phospho-proteomic analysis of myofilament proteins revealed site-specific changes in cardiac Troponin I (cTnI) phosphorylation, as well as a unique distribution of cTnI phosphospecies that were dependent on the LKB1 complex/ AMPK ratio. Fibers treated with the LKB1 complex alone did not alter cTnI phosphorylation or phosphospecies distribution. However, LKB1 complex treatment independent of AMPK increased phosphorylation of myosin-binding protein C. Therefore, we conclude that the LKB1/AMPK signaling axis is able to alter muscle function through multiple mechanisms.
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Affiliation(s)
- Samantha M Behunin
- Sarver Molecular Cardiovascular Research Program, Department of Physiology, University of Arizona, Tucson, Arizona
| | - Marissa A Lopez-Pier
- Sarver Molecular Cardiovascular Research Program, Department of Physiology, University of Arizona, Tucson, Arizona
| | - Camille L Birch
- Sarver Molecular Cardiovascular Research Program, Department of Physiology, University of Arizona, Tucson, Arizona
| | - Laurel A K McKee
- Sarver Molecular Cardiovascular Research Program, Department of Physiology, University of Arizona, Tucson, Arizona
| | - Christiane Danilo
- Sarver Molecular Cardiovascular Research Program, Department of Physiology, University of Arizona, Tucson, Arizona
| | - Zain Khalpey
- Department of Surgery, University of Arizona, Tucson, Arizona
| | - John P Konhilas
- Sarver Molecular Cardiovascular Research Program, Department of Physiology, University of Arizona, Tucson, Arizona.
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15
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Gregorich ZR, Peng Y, Lane NM, Wolff JJ, Wang S, Guo W, Guner H, Doop J, Hacker TA, Ge Y. Comprehensive assessment of chamber-specific and transmural heterogeneity in myofilament protein phosphorylation by top-down mass spectrometry. J Mol Cell Cardiol 2015; 87:102-12. [PMID: 26268593 DOI: 10.1016/j.yjmcc.2015.08.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 08/04/2015] [Accepted: 08/08/2015] [Indexed: 11/28/2022]
Abstract
The heart is characterized by a remarkable degree of heterogeneity, the basis of which is a subject of active investigation. Myofilament protein post-translational modifications (PTMs) represent a critical mechanism regulating cardiac contractility, and emerging evidence shows that pathological cardiac conditions induce contractile heterogeneity that correlates with transmural variations in the modification status of myofilament proteins. Nevertheless, whether there exists basal heterogeneity in myofilament protein PTMs in the heart remains unclear. Here we have systematically assessed chamber-specific and transmural variations in myofilament protein PTMs, specifically, the phosphorylation of cardiac troponin I (cTnI), cardiac troponin T (cTnT), tropomyosin (Tpm), and myosin light chain 2 (MLC2). We show that the phosphorylation of cTnI and αTm vary in the different chambers of the heart, whereas the phosphorylation of MLC2 and cTnT does not. In contrast, no significant transmural differences were observed in the phosphorylation of any of the myofilament proteins analyzed. These results highlight the importance of appropriate tissue sampling-particularly for studies aimed at elucidating disease mechanisms and biomarker discovery-in order to minimize potential variations arising from basal heterogeneity in myofilament PTMs in the heart.
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Affiliation(s)
- Zachery R Gregorich
- Molecular Pharmacology Training Program, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Ying Peng
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Nicole M Lane
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA; Cellular and Molecular Pathology Training Program, University of Wisconsin-Madison, Madison, WI 53706, USA
| | | | - Sijian Wang
- Department of Biostatistics & Medical Informatics, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Statistics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Wei Guo
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Huseyin Guner
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA; Human Proteomics Program, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Justin Doop
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Timothy A Hacker
- Department of Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Ying Ge
- Molecular Pharmacology Training Program, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA; Cellular and Molecular Pathology Training Program, University of Wisconsin-Madison, Madison, WI 53706, USA; Human Proteomics Program, University of Wisconsin-Madison, Madison, WI 53706, USA.
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16
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Manders E, Bogaard HJ, Handoko ML, van de Veerdonk MC, Keogh A, Westerhof N, Stienen GJM, Dos Remedios CG, Humbert M, Dorfmüller P, Fadel E, Guignabert C, van der Velden J, Vonk-Noordegraaf A, de Man FS, Ottenheijm CAC. Contractile dysfunction of left ventricular cardiomyocytes in patients with pulmonary arterial hypertension. J Am Coll Cardiol 2014; 64:28-37. [PMID: 24998125 DOI: 10.1016/j.jacc.2014.04.031] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 04/16/2014] [Indexed: 10/25/2022]
Abstract
BACKGROUND After lung transplantation, increased left ventricular (LV) filling can lead to LV failure, increasing the risk of post-operative complications and mortality. LV dysfunction in pulmonary arterial hypertension (PAH) is characterized by a reduced LV ejection fraction and impaired diastolic function. OBJECTIVES The pathophysiology of LV dysfunction in PAH is incompletely understood. This study sought to assess the contribution of atrophy and contractility of cardiomyocytes to LV dysfunction in PAH patients. METHODS LV function was assessed by cardiac magnetic resonance imaging. In addition, LV biopsies were obtained in 9 PAH patients and 10 donors. The cross-sectional area (CSA) and force-generating capacity of isolated single cardiomyocytes was investigated. RESULTS Magnetic resonance imaging analysis revealed a significant reduction in LV ejection fraction in PAH patients, indicating a reduction in LV contractility. The CSA of LV cardiomyocytes of PAH patients was significantly reduced (~30%), indicating LV cardiomyocyte atrophy. The maximal force-generating capacity, normalized to cardiomyocyte CSA, was significantly reduced (~25%). Also, a reduction in the number of available myosin-based cross-bridges was found to cause the contractile weakness of cardiomyocytes. This finding was supported by protein analyses, which showed an ~30% reduction in the myosin/actin ratio in cardiomyocytes from PAH patients. Finally, the phosphorylation level of sarcomeric proteins was reduced in PAH patients, which was accompanied by increased calcium sensitivity of force generation. CONCLUSIONS The contractile function and the CSA of LV cardiomyocytes is substantially reduced in PAH patients. We propose that these changes contribute to the reduced in vivo contractility of the LV in PAH patients.
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Affiliation(s)
- Emmy Manders
- Department of Pulmonology, Vrije Universiteit (VU) University Medical Center, Amsterdam, the Netherlands; Department of Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Harm-Jan Bogaard
- Department of Pulmonology, Vrije Universiteit (VU) University Medical Center, Amsterdam, the Netherlands
| | - M Louis Handoko
- Department of Physiology, VU University Medical Center, Amsterdam, the Netherlands; Cardiology Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, the Netherlands
| | - Marielle C van de Veerdonk
- Department of Pulmonology, Vrije Universiteit (VU) University Medical Center, Amsterdam, the Netherlands
| | - Anne Keogh
- Heart Transplant Unit, St. Vincent's Hospital, Sydney, Australia
| | - Nico Westerhof
- Department of Pulmonology, Vrije Universiteit (VU) University Medical Center, Amsterdam, the Netherlands; Department of Physiology, VU University Medical Center, Amsterdam, the Netherlands
| | - Ger J M Stienen
- Department of Physiology, VU University Medical Center, Amsterdam, the Netherlands; Department of Physics and Astronomy, VU University, Amsterdam, the Netherlands
| | | | - Marc Humbert
- University of Paris-Sud, Faculté de Médecine, Le Kremlin-Bicêtre, France; Assistance Publique-Hôpitaux de Paris, Service de Pneumologie, Département Hospitalo-Universitaire, Thorax Innovation (DHU TORINO), Hôpital Bicêtre, Le Kremlin-Bicêtre, France; Inserm U999, Laboratoire d'Excellence en Recherche sur le Médicament et l'Innovation Thérapeutique (LabEx LERMIT), Centre Chirurgical Marie Lannelongue, Le Plessis-Robinson, France
| | - Peter Dorfmüller
- University of Paris-Sud, Faculté de Médecine, Le Kremlin-Bicêtre, France; Inserm U999, Laboratoire d'Excellence en Recherche sur le Médicament et l'Innovation Thérapeutique (LabEx LERMIT), Centre Chirurgical Marie Lannelongue, Le Plessis-Robinson, France; Service d'Anatomie Pathologique, Centre Chirurgical Marie Lannelongue, Le Plessis-Robinson, France
| | - Elie Fadel
- University of Paris-Sud, Faculté de Médecine, Le Kremlin-Bicêtre, France; Inserm U999, Laboratoire d'Excellence en Recherche sur le Médicament et l'Innovation Thérapeutique (LabEx LERMIT), Centre Chirurgical Marie Lannelongue, Le Plessis-Robinson, France; Service de Chirurgie Thoracique, Centre Chirurgical Marie Lannelongue, Le Plessis-Robinson, France
| | - Christophe Guignabert
- University of Paris-Sud, Faculté de Médecine, Le Kremlin-Bicêtre, France; Inserm U999, Laboratoire d'Excellence en Recherche sur le Médicament et l'Innovation Thérapeutique (LabEx LERMIT), Centre Chirurgical Marie Lannelongue, Le Plessis-Robinson, France
| | - Jolanda van der Velden
- Department of Physiology, VU University Medical Center, Amsterdam, the Netherlands; ICIN Netherlands Heart Institute, Utrecht, the Netherlands
| | - Anton Vonk-Noordegraaf
- Department of Pulmonology, Vrije Universiteit (VU) University Medical Center, Amsterdam, the Netherlands
| | - Frances S de Man
- Department of Pulmonology, Vrije Universiteit (VU) University Medical Center, Amsterdam, the Netherlands.
| | - Coen A C Ottenheijm
- Department of Physiology, VU University Medical Center, Amsterdam, the Netherlands.
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17
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Haynes P, Campbell KS. Myocardial hypertrophy reduces transmural variation in mitochondrial function. Front Physiol 2014; 5:178. [PMID: 24847280 PMCID: PMC4019838 DOI: 10.3389/fphys.2014.00178] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 04/17/2014] [Indexed: 11/13/2022] Open
Affiliation(s)
- Premi Haynes
- Department of Physiology, Center for Muscle Biology, University of Kentucky Lexington, KY, USA
| | - Kenneth S Campbell
- Department of Physiology, Center for Muscle Biology, University of Kentucky Lexington, KY, USA
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Duncker DJ, van Deel ED, de Waard MC, de Boer M, Merkus D, van der Velden J. Exercise training in adverse cardiac remodeling. Pflugers Arch 2014; 466:1079-91. [PMID: 24573174 DOI: 10.1007/s00424-014-1464-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 01/27/2014] [Accepted: 01/28/2014] [Indexed: 12/14/2022]
Abstract
Cardiac remodeling in response to a myocardial infarction or chronic pressure-overload is an independent risk factor for the development of heart failure. In contrast, cardiac remodeling produced by regular physical exercise is associated with a decreased risk for heart failure. There is evidence that exercise training has a beneficial effect on disease progression and survival in patients with cardiac remodeling and dysfunction, but concern has also been expressed that exercise training may aggravate pathological remodeling and dysfunction. Here we present studies from our laboratory into the effects of exercise training on pathological cardiac remodeling and dysfunction in mice. The results indicate that even in the presence of a large infarct, exercise training exerts beneficial effects on the heart. These effects were mimicked in part by endothelial nitric oxide synthase (eNOS) overexpression and abrogated by eNOS deficiency, demonstrating the importance of nitric oxide signaling in mediating the cardiac effects of exercise. Exercise prior to a myocardial infarction was also cardioprotective. In contrast, exercise tended to aggravate pathological cardiac remodeling and dysfunction in the setting of pressure-overload produced by an aortic stenosis. These observations emphasize the critical importance of the underlying pathological stimulus for cardiac hypertrophy and remodeling, in determining the effects of exercise training. Future studies are needed to define the influence of exercise type, intensity and duration in different models and severities of pathological cardiac remodeling. Together such studies will aid in optimizing the therapy of exercise training in the setting of cardiovascular disease.
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Affiliation(s)
- Dirk J Duncker
- Division of Experimental Cardiology, Department of Cardiology, Thoraxcenter Erasmus MC University Medical Center Rotterdam, PO Box 2040, 3000, CA, Rotterdam, The Netherlands,
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19
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Haynes P, Nava KE, Lawson BA, Chung CS, Mitov MI, Campbell SG, Stromberg AJ, Sadayappan S, Bonnell MR, Hoopes CW, Campbell KS. Transmural heterogeneity of cellular level power output is reduced in human heart failure. J Mol Cell Cardiol 2014; 72:1-8. [PMID: 24560668 DOI: 10.1016/j.yjmcc.2014.02.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 01/22/2014] [Accepted: 02/11/2014] [Indexed: 01/04/2023]
Abstract
Heart failure is associated with pump dysfunction and remodeling but it is not yet known if the condition affects different transmural regions of the heart in the same way. We tested the hypotheses that the left ventricles of non-failing human hearts exhibit transmural heterogeneity of cellular level contractile properties, and that heart failure produces transmural region-specific changes in contractile function. Permeabilized samples were prepared from the sub-epicardial, mid-myocardial, and sub-endocardial regions of the left ventricular free wall of non-failing (n=6) and failing (n=10) human hearts. Power, an in vitro index of systolic function, was higher in non-failing mid-myocardial samples (0.59±0.06μWmg(-1)) than in samples from the sub-epicardium (p=0.021) and the sub-endocardium (p=0.015). Non-failing mid-myocardial samples also produced more isometric force (14.3±1.33kNm(-2)) than samples from the sub-epicardium (p=0.008) and the sub-endocardium (p=0.026). Heart failure reduced power (p=0.009) and force (p=0.042) but affected the mid-myocardium more than the other transmural regions. Fibrosis increased with heart failure (p=0.021) and mid-myocardial tissue from failing hearts contained more collagen than matched sub-epicardial (p<0.001) and sub-endocardial (p=0.043) samples. Power output was correlated with the relative content of actin and troponin I, and was also statistically linked to the relative content and phosphorylation of desmin and myosin light chain-1. Non-failing human hearts exhibit transmural heterogeneity of contractile properties. In failing organs, region-specific fibrosis produces the greatest contractile deficits in the mid-myocardium. Targeting fibrosis and sarcomeric proteins in the mid-myocardium may be particularly effective therapies for heart failure.
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Affiliation(s)
- Premi Haynes
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Kristofer E Nava
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Benjamin A Lawson
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Charles S Chung
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Mihail I Mitov
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Stuart G Campbell
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | | | - Sakthivel Sadayappan
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University, Chicago, USA
| | - Mark R Bonnell
- Division of Cardiothoracic Surgery, University of Kentucky, Lexington, KY, USA
| | - Charles W Hoopes
- Division of Cardiothoracic Surgery, University of Kentucky, Lexington, KY, USA
| | - Kenneth S Campbell
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA.
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20
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Merkus D, Duncker DJ. Perspectives: Coronary microvascular dysfunction in post-infarct remodelled myocardium. Eur Heart J Suppl 2014. [DOI: 10.1093/eurheartj/sut016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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21
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Kramer SP, Powell DK, Haggerty CM, Binkley CM, Mattingly AC, Cassis LA, Epstein FH, Fornwalt BK. Obesity reduces left ventricular strains, torsion, and synchrony in mouse models: a cine displacement encoding with stimulated echoes (DENSE) cardiovascular magnetic resonance study. J Cardiovasc Magn Reson 2013; 15:109. [PMID: 24380567 PMCID: PMC3882783 DOI: 10.1186/1532-429x-15-109] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 12/11/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Obesity affects a third of adults in the US and results in an increased risk of cardiovascular mortality. While the mechanisms underlying this increased risk are not well understood, animal models of obesity have shown direct effects on the heart such as steatosis and fibrosis, which may affect cardiac function. However, the effect of obesity on cardiac function in animal models is not well-defined. We hypothesized that diet-induced obesity in mice reduces strain, torsion, and synchrony in the left ventricle (LV). METHODS Ten 12-week-old C57BL/6 J mice were randomized to a high-fat or low-fat diet. After 5 months on the diet, mice were imaged with a 7 T ClinScan using a cine DENSE protocol. Three short-axis and two long-axis slices were acquired for quantification of strains, torsion and synchrony in the left ventricle. RESULTS Left ventricular mass was increased by 15% (p = 0.032) with no change in volumes or ejection fraction. Subepicardial strain was lower in the obese mice with a 40% reduction in circumferential strain (p = 0.008) a 53% reduction in radial strain (p = 0.032) and a trend towards a 19% reduction in longitudinal strain (p = 0.056). By contrast, subendocardial strain was modestly reduced in the obese mice in the circumferential direction by 12% (p = 0.028), and no different in the radial (p = 0.690) or longitudinal (p = 0.602) directions. Peak torsion was reduced by 34% (p = 0.028). Synchrony of contraction was also reduced (p = 0.032) with a time delay in the septal-to-lateral direction. CONCLUSIONS Diet-induced obesity reduces left ventricular strains and torsion in mice. Reductions in cardiac strain are mostly limited to the subepicardium, with relative preservation of function in the subendocardium. Diet-induced obesity also leads to reduced synchrony of contraction and hypertrophy in mouse models.
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MESH Headings
- Animals
- Biomechanical Phenomena
- Diet, High-Fat
- Disease Models, Animal
- Hypertrophy, Left Ventricular/diagnosis
- Hypertrophy, Left Ventricular/etiology
- Hypertrophy, Left Ventricular/physiopathology
- Magnetic Resonance Imaging, Cine
- Mice
- Mice, Inbred C57BL
- Myocardial Contraction
- Obesity/complications
- Obesity/diagnosis
- Obesity/physiopathology
- Predictive Value of Tests
- Stress, Mechanical
- Stroke Volume
- Time Factors
- Torsion, Mechanical
- Ventricular Dysfunction, Left/diagnosis
- Ventricular Dysfunction, Left/etiology
- Ventricular Dysfunction, Left/physiopathology
- Ventricular Function, Left
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Affiliation(s)
- Sage P Kramer
- Departments of Pediatrics, Physiology and Medicine, University of Kentucky, 800 Rose St, MN-150, Lexington, KY 40536, USA
| | - David K Powell
- Departments of Pediatrics, Physiology and Medicine, University of Kentucky, 800 Rose St, MN-150, Lexington, KY 40536, USA
| | - Christopher M Haggerty
- Departments of Pediatrics, Physiology and Medicine, University of Kentucky, 800 Rose St, MN-150, Lexington, KY 40536, USA
| | - Cassi M Binkley
- Departments of Pediatrics, Physiology and Medicine, University of Kentucky, 800 Rose St, MN-150, Lexington, KY 40536, USA
| | - Andrea C Mattingly
- Departments of Pediatrics, Physiology and Medicine, University of Kentucky, 800 Rose St, MN-150, Lexington, KY 40536, USA
| | - Lisa A Cassis
- Department of Molecular and Biomedical Pharmacology, University of Kentucky, Lexington, KY, USA
| | - Frederick H Epstein
- Departments of Biomedical Engineering and Radiology, University of Virginia, Charlottesville, VA, USA
| | - Brandon K Fornwalt
- Departments of Pediatrics, Physiology and Medicine, University of Kentucky, 800 Rose St, MN-150, Lexington, KY 40536, USA
- Graduate Center for Biomedical Engineering, University of Kentucky, Lexington, KY, USA
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22
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Chung CS, Campbell KS. Temperature and transmural region influence functional measurements in unloaded left ventricular cardiomyocytes. Physiol Rep 2013; 1:e00158. [PMID: 24400159 PMCID: PMC3871472 DOI: 10.1002/phy2.158] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 10/18/2013] [Accepted: 10/23/2013] [Indexed: 12/21/2022] Open
Abstract
Intact cardiomyocytes are increasingly being used to investigate the molecular mechanisms of contraction and to screen new therapeutic compounds. The function of the cardiomyocytes is often measured from the calcium transients and sarcomere length profiles. We studied the role of experimental temperature and transmural region on indices of function in freshly isolated, unloaded cardiomyocytes. Intact cardiomyocytes were isolated from the subendocardium, midmyocardium, and subepicardium of 3-month-old Sprague-Dawley rats. Myocytes from each region were studied at 25°C, 31°C, and 37°C. Cytosolic calcium transients were measured using Fura-2 fluorescence, whereas sarcomere length shortening and relengthening profiles were measured using high-speed video capture. For both the calcium transients and sarcomere length profiles, the time to peak and the time to half relaxation decreased significantly with increasing temperature. Increasing temperature also raised the minimum and maximum calcium levels of all cells. Of note, there was a reduced coefficient of variation (standard deviation divided by the mean) at higher temperatures for calcium fluorescence amplitudes, time to peak calcium, and rates of sarcomeric shortening and relengthening. The amplitudes and minimum of the calcium transients were significantly dependent on transmural region, and several sarcomere length parameters exhibited statistical interactions between temperature and transmural region. Together, these results show that biological variability can be reduced by performing experiments at 37°C rather than at room temperature, and by isolating cells from a specific transmural region. Adopting these procedures will improve the statistical power of subsequent analyses and increase the efficiency of future experiments.
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Affiliation(s)
- Charles S Chung
- Department of Physiology and Center for Muscle Biology, University of Kentucky Lexington, Kentucky
| | - Kenneth S Campbell
- Department of Physiology and Center for Muscle Biology, University of Kentucky Lexington, Kentucky
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23
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Posttranslational modifications of cardiac troponin T: An overview. J Mol Cell Cardiol 2013; 63:47-56. [DOI: 10.1016/j.yjmcc.2013.07.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 06/18/2013] [Accepted: 07/08/2013] [Indexed: 12/22/2022]
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24
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McKee LA, Chen H, Regan JA, Behunin SM, Walker JW, Walker JS, Konhilas JP. Sexually dimorphic myofilament function and cardiac troponin I phosphospecies distribution in hypertrophic cardiomyopathy mice. Arch Biochem Biophys 2013; 535:39-48. [PMID: 23352598 PMCID: PMC3640654 DOI: 10.1016/j.abb.2012.12.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 12/12/2012] [Accepted: 12/14/2012] [Indexed: 11/16/2022]
Abstract
The pathological progression of hypertrophic cardiomyopathy (HCM) is sexually dimorphic such that male HCM mice develop phenotypic indicators of cardiac disease well before female HCM mice. Here, we hypothesized that alterations in myofilament function underlies, in part, this sex dimorphism in HCM disease development. Firstly, 10-12month female HCM (harboring a mutant [R403Q] myosin heavy chain) mice presented with proportionately larger hearts than male HCM mice. Next, we determined Ca(2+)-sensitive tension development in demembranated cardiac trabeculae excised from 10-12month female and male HCM mice. Whereas HCM did not impact Ca(2+)-sensitive tension development in male trabeculae, female HCM trabeculae were more sensitive to Ca(2+) than wild-type (WT) counterparts and both WT and HCM males. We hypothesized that the underlying cause of this sex difference in Ca(2+)-sensitive tension development was due to changes in Ca(2+) handling and sarcomeric proteins, including expression of SR Ca(2+) ATPase (2a) (SERCA2a), β-myosin heavy chain (β-MyHC) and post-translational modifications of myofilament proteins. Female HCM hearts showed an elevation of SERCA2a and β-MyHC protein whereas male HCM hearts showed a similar elevation of β-MyHC protein but a reduced level of cardiac troponin T (cTnT) phosphorylation. We also measured the distribution of cardiac troponin I (cTnI) phosphospecies using phosphate-affinity SDS-PAGE. The distribution of cTnI phosphospecies depended on sex and HCM. In conclusion, female and male HCM mice display sex dimorphic myofilament function that is accompanied by a sex- and HCM-dependent distribution of sarcomeric proteins and cTnI phosphospecies.
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Affiliation(s)
- Laurel A.K. McKee
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
| | - Hao Chen
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
| | - Jessica A. Regan
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
| | - Samantha M. Behunin
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
| | - Jeffery W. Walker
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
| | - John S. Walker
- University of Colorado Denver, Department of Medicine/Cardiology, Aurora, CO 80045, USA
| | - John P. Konhilas
- Department of Physiology, Sarver Molecular Cardiovascular Research Program, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ 85724, USA
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25
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Chu C, Thai K, Park KW, Wang P, Makwana O, Lovett DH, Simpson PC, Baker AJ. Intraventricular and interventricular cellular heterogeneity of inotropic responses to α(1)-adrenergic stimulation. Am J Physiol Heart Circ Physiol 2013; 304:H946-53. [PMID: 23355341 DOI: 10.1152/ajpheart.00822.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
α1-Adrenergic receptors (α1-ARs) elicit a negative inotropic effect (NIE) in the mouse right ventricular (RV) myocardium but a positive inotropic effect (PIE) in the left ventricular (LV) myocardium. Effects on myofilament Ca(2+) sensitivity play a role, but effects on Ca(2+) handling could also contribute. We monitored the effects of α1-AR stimulation on contraction and Ca(2+) transients using single myocytes isolated from the RV or LV. Interestingly, for both the RV and LV, we found heterogeneous myocyte inotropic responses. α1-ARs mediated either a PIE or NIE, although RV myocytes had a greater proportion of cells manifesting a NIE (68%) compared with LV myocytes (36%). Stimulation of a single α1-AR subtype (α1A-ARs) with a subtype-selective agonist also elicited heterogeneous inotropic responses, suggesting that the heterogeneity arose from events downstream of the α1A-AR subtype. For RV and LV myocytes, an α1-AR-mediated PIE was associated with an increased Ca(2+) transient and a NIE was associated with a decreased Ca(2+) transient, suggesting a key role for Ca(2+) handling. For RV and LV myocytes, α1-AR-mediated decreases in the Ca(2+) transient were associated with increased Ca(2+) export from the cell and decreased Ca(2+) content of the sarcoplasmic reticulum. In contrast, for myocytes with α1-AR-induced increased Ca(2+) transients, sarcoplasmic reticulum Ca(2+) content was not increased, suggesting that other mechanisms contributed to the increased Ca(2+) transients. This study demonstrates the marked heterogeneity of LV and RV cellular inotropic responses to stimulation of α1-ARs and reveals a new aspect of biological heterogeneity among myocytes in the regulation of contraction.
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Affiliation(s)
- Charles Chu
- Veterans Affairs Medical Center, San Francisco, CA 94121, USA
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26
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Kindo M, Gerelli S, Bouitbir J, Charles AL, Zoll J, Hoang Minh T, Monassier L, Favret F, Piquard F, Geny B. Pressure overload-induced mild cardiac hypertrophy reduces left ventricular transmural differences in mitochondrial respiratory chain activity and increases oxidative stress. Front Physiol 2012; 3:332. [PMID: 22934079 PMCID: PMC3428974 DOI: 10.3389/fphys.2012.00332] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 07/29/2012] [Indexed: 12/31/2022] Open
Abstract
Objective: Increased mechanical stress and contractility characterizes normal left ventricular (LV) subendocardium (Endo) but whether Endo mitochondrial respiratory chain complex activities is reduced as compared to subepicardium (Epi) and whether pressure overload-induced LV hypertrophy (LVH) might modulate transmural gradients through increased reactive oxygen species (ROS) production is unknown. Methods: LVH was induced by 6 weeks abdominal aortic banding and cardiac structure and function were determined with echocardiography and catheterization in sham-operated and LVH rats (n = 10 for each group). Mitochondrial respiration rates, coupling, content and ROS production were measured in LV Endo and Epi, using saponin-permeabilized fibers, Amplex Red fluorescence and citrate synthase activity. Results: In sham, a transmural respiratory gradient was observed with decreases in endo maximal oxidative capacity (−36.7%, P < 0.01) and complex IV activity (−57.4%, P < 0.05). Mitochondrial hydrogen peroxide (H2O2) production was similar in both LV layers. Aortic banding induced mild LVH (+31.7% LV mass), associated with normal LV fractional shortening and end diastolic pressure. LVH reduced maximal oxidative capacity (−23.6 and −33.3%), increased mitochondrial H2O2 production (+86.9 and +73.1%), free radical leak (+27.2% and +36.3%) and citrate synthase activity (+27.2% and +36.3%) in Endo and Epi, respectively. Transmural mitochondrial respiratory chain complex IV activity was reduced in LVH (−57.4 vs. −12.2%; P = 0.02). Conclusions: Endo mitochondrial respiratory chain complexes activities are reduced compared to LV Epi. Mild LVH impairs mitochondrial oxidative capacity, increases oxidative stress and reduces transmural complex IV activity. Further studies will be helpful to determine whether reduced LV transmural gradient in mitochondrial respiration might be a new marker of a transition from uncomplicated toward complicated LVH.
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Affiliation(s)
- Michel Kindo
- Service de Chirurgie Cardiovasculaire, Pôle d'activité médico-chirurgicale Cardiovasculaire, Hôpitaux Universitaires, CHRU Strasbourg Strasbourg, France
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