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Dewan S, Witayavanitkul N, Kumar M, Mayer BJ, Betancourt L, Cazorla O, de Tombe PP. Depressed myocardial cross-bridge cycling kinetics in a female guinea pig model of diastolic heart failure. J Gen Physiol 2023; 155:e202213288. [PMID: 37102986 PMCID: PMC10140646 DOI: 10.1085/jgp.202213288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 02/10/2023] [Accepted: 04/17/2023] [Indexed: 04/28/2023] Open
Abstract
Cardiac hypertrophy is associated with diastolic heart failure (DHF), a syndrome in which systolic function is preserved but cardiac filling dynamics are depressed. The molecular mechanisms underlying DHF and the potential role of altered cross-bridge cycling are poorly understood. Accordingly, chronic pressure overload was induced by surgically banding the thoracic ascending aorta (AOB) in ∼400 g female Dunkin Hartley guinea pigs (AOB); Sham-operated age-matched animals served as controls. Guinea pigs were chosen to avoid the confounding impacts of altered myosin heavy chain (MHC) isoform expression seen in other small rodent models. In vivo cardiac function was assessed by echocardiography; cardiac hypertrophy was confirmed by morphometric analysis. AOB resulted in left ventricle (LV) hypertrophy and compromised diastolic function with normal systolic function. Biochemical analysis revealed exclusive expression of β-MHC isoform in both sham control and AOB LVs. Myofilament function was assessed in skinned multicellular preparations, skinned single myocyte fragments, and single myofibrils prepared from frozen (liquid N2) LVs. The rates of force-dependent ATP consumption (tension-cost) and force redevelopment (Ktr), as well as myofibril relaxation time (Timelin) were significantly blunted in AOB, indicating reduced cross-bridge cycling kinetics. Maximum Ca2+ activated force development was significantly reduced in AOB myocytes, while no change in myofilament Ca2+ sensitivity was observed. Our results indicate blunted cross-bridge cycle in a β-MHC small animal DHF model. Reduced cross-bridge cycling kinetics may contribute, at least in part, to the development of DHF in larger mammals, including humans.
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Affiliation(s)
- Sukriti Dewan
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
| | - Namthip Witayavanitkul
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
| | - Mohit Kumar
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
| | - Beth J Mayer
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
| | - Lauren Betancourt
- Phymedexp INSERM, CNRS, University of Montpellier , Montpellier, France
| | - Olivier Cazorla
- Phymedexp INSERM, CNRS, University of Montpellier , Montpellier, France
| | - Pieter P de Tombe
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
- Phymedexp INSERM, CNRS, University of Montpellier , Montpellier, France
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2
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Kimmig F, Caruel M, Chapelle D. Varying thin filament activation in the framework of the Huxley'57 model. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2022; 38:e3655. [PMID: 36210493 DOI: 10.1002/cnm.3655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 04/29/2022] [Accepted: 09/24/2022] [Indexed: 06/16/2023]
Abstract
Muscle contraction is triggered by the activation of the actin sites of the thin filament by calcium ions. It results that the thin filament activation level varies over time. Moreover, this activation process is also used as a regulation mechanism of the developed force. Our objective is to build a model of varying actin site activation level within the classical Huxley'57 two-state framework. This new model is obtained as an enhancement of a previously proposed formulation of the varying thick filament activation within the same framework. We assume that the state of an actin site depends on whether it is activated and whether it forms a cross-bridge with the associated myosin head, which results in four possible states. The transitions between the actin site states are controlled by the global actin sites activation level and the dynamics of these transitions is coupled with the attachment-detachment process. A preliminary calibration of the model with experimental twitch contraction data obtained at varying sarcomere lengths is performed.
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Affiliation(s)
- François Kimmig
- LMS, École Polytechnique, CNRS, Institut Polytechnique de Paris, Palaiseau, France
- Inria, Palaiseau, France
| | - Matthieu Caruel
- CNRS, UMR 8208, MSME, Univ Paris Est Creteil, Univ Gustave Eiffel, Créteil, France
| | - Dominique Chapelle
- LMS, École Polytechnique, CNRS, Institut Polytechnique de Paris, Palaiseau, France
- Inria, Palaiseau, France
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3
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Papadaki M, Kampaengsri T, Barrick SK, Campbell SG, von Lewinski D, Rainer PP, Harris SP, Greenberg MJ, Kirk JA. Myofilament glycation in diabetes reduces contractility by inhibiting tropomyosin movement, is rescued by cMyBPC domains. J Mol Cell Cardiol 2022; 162:1-9. [PMID: 34487755 PMCID: PMC8766917 DOI: 10.1016/j.yjmcc.2021.08.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 07/21/2021] [Accepted: 08/19/2021] [Indexed: 01/17/2023]
Abstract
Diabetes doubles the risk of developing heart failure (HF). As the prevalence of diabetes grows, so will HF unless the mechanisms connecting these diseases can be identified. Methylglyoxal (MG) is a glycolysis by-product that forms irreversible modifications on lysine and arginine, called glycation. We previously found that myofilament MG glycation causes sarcomere contractile dysfunction and is increased in patients with diabetes and HF. The aim of this study was to discover the molecular mechanisms by which MG glycation of myofilament proteins cause sarcomere dysfunction and to identify therapeutic avenues to compensate. In humans with type 2 diabetes without HF, we found increased glycation of sarcomeric actin compared to non-diabetics and it correlated with decreased calcium sensitivity. Depressed calcium sensitivity is pathogenic for HF, therefore myofilament glycation represents a promising therapeutic target to inhibit the development of HF in diabetics. To identify possible therapeutic targets, we further defined the molecular actions of myofilament glycation. Skinned myocytes exposed to 100 μM MG exhibited decreased calcium sensitivity, maximal calcium-activated force, and crossbridge kinetics. Replicating MG's functional affects using a computer simulation of sarcomere function predicted simultaneous decreases in tropomyosin's blocked-to-closed rate transition and crossbridge duty cycle were consistent with all experimental findings. Stopped-flow experiments and ATPase activity confirmed MG decreased the blocked-to-closed transition rate. Currently, no therapeutics target tropomyosin, so as proof-of-principal, we used a n-terminal peptide of myosin-binding protein C, previously shown to alter tropomyosin's position on actin. C0C2 completely rescued MG-induced calcium desensitization, suggesting a possible treatment for diabetic HF.
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Affiliation(s)
- Maria Papadaki
- Department of Cell and Molecular Physiology, Loyola University of Chicago, Maywood, Illinois, USA
| | - Theerachat Kampaengsri
- Department of Cell and Molecular Physiology, Loyola University of Chicago, Maywood, Illinois, USA
| | - Samantha K. Barrick
- Department of Biochemistry and Molecular Biophysics, Washington University in St Louis, St Louis, Missouri, USA
| | - Stuart G. Campbell
- Department of Bioengineering, Yale University, New Haven, Connecticut, USA
| | | | - Peter P. Rainer
- Division of Cardiology, Medical University of Graz, Graz, Austria
| | - Samantha P. Harris
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA
| | - Michael J. Greenberg
- Department of Biochemistry and Molecular Biophysics, Washington University in St Louis, St Louis, Missouri, USA
| | - Jonathan A. Kirk
- Department of Cell and Molecular Physiology, Loyola University of Chicago, Maywood, Illinois, USA,Corresponding Author: Jonathan A. Kirk, Ph.D., Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Center for Translational Research and Education, Room 522, 2160 S. First Ave., Maywood, IL 60153, Ph: 708-216-6348,
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4
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Solís C, Solaro RJ. Novel insights into sarcomere regulatory systems control of cardiac thin filament activation. J Gen Physiol 2021; 153:211903. [PMID: 33740037 PMCID: PMC7988513 DOI: 10.1085/jgp.202012777] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 02/23/2021] [Indexed: 12/11/2022] Open
Abstract
Our review focuses on sarcomere regulatory mechanisms with a discussion of cardiac-specific modifications to the three-state model of thin filament activation from a blocked to closed to open state. We discuss modulation of these thin filament transitions by Ca2+, by crossbridge interactions, and by thick filament–associated proteins, cardiac myosin–binding protein C (cMyBP-C), cardiac regulatory light chain (cRLC), and titin. Emerging evidence supports the idea that the cooperative activation of the thin filaments despite a single Ca2+ triggering regulatory site on troponin C (cTnC) cannot be considered in isolation of other functional domains of the sarcomere. We discuss long- and short-range interactions among these domains with the regulatory units of thin filaments, including proteins at the barbed end at the Z-disc and the pointed end near the M-band. Important to these discussions is the ever-increasing understanding of the role of cMyBP-C, cRLC, and titin filaments. Detailed knowledge of these control processes is critical to the understanding of mechanisms sustaining physiological cardiac state with varying hemodynamic load, to better defining genetic and acquired cardiac disorders, and to developing targets for therapies at the level of the sarcomeres.
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Affiliation(s)
- Christopher Solís
- University of Illinois at Chicago, College of Medicine, Department of Physiology and Biophysics and Center for Cardiovascular Research, Chicago, IL
| | - R John Solaro
- University of Illinois at Chicago, College of Medicine, Department of Physiology and Biophysics and Center for Cardiovascular Research, Chicago, IL
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5
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Douglas CM, Hesketh SJ, Esser KA. Time of Day and Muscle Strength: A Circadian Output? Physiology (Bethesda) 2021; 36:44-51. [PMID: 33325817 PMCID: PMC8425416 DOI: 10.1152/physiol.00030.2020] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/11/2020] [Accepted: 10/12/2020] [Indexed: 11/22/2022] Open
Abstract
For more than 20 years, physiologists have observed a morning-to-evening increase in human muscle strength. Recent data suggest that time-of-day differences are the result of intrinsic, nonneural, muscle factors. We evaluate circadian clock data sets from human and mouse circadian studies and highlight possible mechanisms through which the muscle circadian clock may contribute to time-of-day muscle strength outcomes.
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Affiliation(s)
- Collin M Douglas
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FloridaMyology Institute, University of Florida, Gainesville, Florida
| | - Stuart J Hesketh
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FloridaMyology Institute, University of Florida, Gainesville, Florida
| | - Karyn A Esser
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FloridaMyology Institute, University of Florida, Gainesville, Florida
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6
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Vikhorev PG, Vikhoreva NN, Yeung W, Li A, Lal S, dos Remedios CG, Blair CA, Guglin M, Campbell KS, Yacoub MH, de Tombe P, Marston SB. Titin-truncating mutations associated with dilated cardiomyopathy alter length-dependent activation and its modulation via phosphorylation. Cardiovasc Res 2020; 118:241-253. [PMID: 33135063 PMCID: PMC8752363 DOI: 10.1093/cvr/cvaa316] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 10/20/2020] [Indexed: 12/18/2022] Open
Abstract
Abstract
Aims
Dilated cardiomyopathy (DCM) is associated with mutations in many genes encoding sarcomere proteins. Truncating mutations in the titin gene TTN are the most frequent. Proteomic and functional characterizations are required to elucidate the origin of the disease and the pathogenic mechanisms of TTN-truncating variants.
Methods and results
We isolated myofibrils from DCM hearts carrying truncating TTN mutations and measured the Ca2+ sensitivity of force and its length dependence. Simultaneous measurement of force and adenosine triphosphate (ATP) consumption in skinned cardiomyocytes was also performed. Phosphorylation levels of troponin I (TnI) and myosin binding protein-C (MyBP-C) were manipulated using protein kinase A and λ phosphatase. mRNA sequencing was employed to overview gene expression profiles. We found that Ca2+ sensitivity of myofibrils carrying TTN mutations was significantly higher than in myofibrils from donor hearts. The length dependence of the Ca2+ sensitivity was absent in DCM myofibrils with TTN-truncating variants. No significant difference was found in the expression level of TTN mRNA between the DCM and donor groups. TTN exon usage and splicing were also similar. However, we identified down-regulation of genes encoding Z-disk proteins, while the atrial-specific regulatory myosin light chain gene, MYL7, was up-regulated in DCM patients with TTN-truncating variants.
Conclusion
Titin-truncating mutations lead to decreased length-dependent activation and increased elasticity of myofibrils. Phosphorylation levels of TnI and MyBP-C seen in the left ventricles are essential for the length-dependent changes in Ca2+ sensitivity in healthy donors, but they are reduced in DCM patients with TTN-truncating variants. A decrease in expression of Z-disk proteins may explain the observed decrease in myofibril passive stiffness and length-dependent activation.
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Affiliation(s)
- Petr G Vikhorev
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Natalia N Vikhoreva
- Heart Science Centre, Magdi Yacoub Institute, Harefield Hospital, London UB9 6JH, UK
| | - WaiChun Yeung
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Amy Li
- Department of Pharmacy and Biomedical Sciences, La Trobe University, Bendigo, VIC 3550, Australia
| | - Sean Lal
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW 2006, Australia
| | - Cristobal G dos Remedios
- Division of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia
| | - Cheavar A Blair
- Division of Cardiovascular Medicine, Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Maya Guglin
- Division of Cardiovascular Medicine, Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Kenneth S Campbell
- Division of Cardiovascular Medicine, Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Magdi H Yacoub
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Pieter de Tombe
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
- Heart Science Centre, Magdi Yacoub Institute, Harefield Hospital, London UB9 6JH, UK
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, USA
| | - Steven B Marston
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
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7
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Nollet EE, Manders EM, Goebel M, Jansen V, Brockmann C, Osinga J, van der Velden J, Helmes M, Kuster DWD. Large-Scale Contractility Measurements Reveal Large Atrioventricular and Subtle Interventricular Differences in Cultured Unloaded Rat Cardiomyocytes. Front Physiol 2020; 11:815. [PMID: 32848817 PMCID: PMC7396550 DOI: 10.3389/fphys.2020.00815] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 06/18/2020] [Indexed: 01/22/2023] Open
Abstract
The chambers of the heart fulfill different hemodynamic functions, which are reflected in their structural and contractile properties. While the atria are highly elastic to allow filling from the venous system, the ventricles need to be able to produce sufficiently high pressures to eject blood into the circulation. The right ventricle (RV) pumps into the low pressure pulmonary circulation, while the left ventricle (LV) needs to overcome the high pressure of the systemic circulation. It is incompletely understood whether these differences can be explained by the contractile differences at the level of the individual cardiomyocytes of the chambers. We addressed this by isolating cardiomyocytes from atria, RV, LV, and interventricular septum (IVS) of five healthy wild-type rats. Using a high-throughput contractility set-up, we measured contractile function of 2,043 cells after overnight culture. Compared to ventricular cardiomyocytes, atrial cells showed a twofold lower contraction amplitude and 1.4- to 1.7-fold slower kinetics of contraction and relaxation. The interventricular differences in contractile function were much smaller; RV cells displayed 12–13% less fractional shortening and 5–9% slower contraction and 3–15% slower relaxation kinetics relative to their LV and IVS counterparts. Aided by a large dataset, we established relationships between contractile parameters and found contraction velocity, fractional shortening and relaxation velocity to be highly correlated. In conclusion, our findings are in line with contractile differences observed at the atrioventricular level, but can only partly explain the interventricular differences that exist at the organ level.
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Affiliation(s)
- Edgar E Nollet
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | | | - Max Goebel
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Valentijn Jansen
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Cord Brockmann
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Jorrit Osinga
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Jolanda van der Velden
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Michiel Helmes
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands.,CytoCypher BV, Wageningen, Netherlands
| | - Diederik W D Kuster
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
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8
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Kimmig F, Caruel M. Hierarchical modeling of force generation in cardiac muscle. Biomech Model Mechanobiol 2020; 19:2567-2601. [PMID: 32681201 DOI: 10.1007/s10237-020-01357-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Accepted: 06/10/2020] [Indexed: 11/25/2022]
Abstract
Performing physiologically relevant simulations of the beating heart in clinical context requires to develop detailed models of the microscale force generation process. These models, however, may reveal difficult to implement in practice due to their high computational costs and complex calibration. We propose a hierarchy of three interconnected muscle contraction models-from the more refined to the more simplified-that are rigorously and systematically related to each other, offering a way to select, for a specific application, the model that yields a good trade-off between physiological fidelity, computational cost and calibration complexity. The three model families are compared to the same set of experimental data to systematically assess what physiological indicators can be reproduced or not and how these indicators constrain the model parameters. Finally, we discuss the applicability of these models for heart simulation.
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Affiliation(s)
- François Kimmig
- LMS, CNRS, École polytechnique, Institut Polytechnique de Paris, Paris, France.
- Inria, Inria Saclay-Ile-de-France, Palaiseau, France.
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9
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Mann CK, Lee LC, Campbell KS, Wenk JF. Force-dependent recruitment from myosin OFF-state increases end-systolic pressure-volume relationship in left ventricle. Biomech Model Mechanobiol 2020; 19:2683-2692. [PMID: 32346808 DOI: 10.1007/s10237-020-01331-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 04/16/2020] [Indexed: 11/24/2022]
Abstract
Finite element (FE) modeling is becoming increasingly prevalent in the world of cardiac mechanics; however, many existing FE models are phenomenological and thus do not capture cellular-level mechanics. This work implements a cellular-level contraction scheme into an existing nonlinear FE code to model ventricular contraction. Specifically, this contraction model incorporates three myosin states: OFF-, ON-, and an attached force-generating state. It has been speculated that force-dependent transitions from the OFF- to ON-state may contribute to length-dependent activation at the cellular level. The current work investigates the contribution of force-dependent recruitment out of the OFF-state to ventricular-level function, specifically the Frank-Starling relationship, as seen through the end-systolic pressure-volume relationship (ESPVR). Five FE models were constructed using geometries of rat left ventricles obtained via cardiac magnetic resonance imaging. FE simulations were conducted to optimize parameters for the cellular contraction model such that the differences between FE predicted ventricular pressures for the models and experimentally measured pressures were minimized. The models were further validated by comparing FE predicted end-systolic strain to experimentally measured strain. Simulations mimicking vena cava occlusion generated descending pressure volume loops from which ESPVRs were calculated. In simulations with the inclusion of the OFF-state, using a force-dependent transition to the ON-state, the ESPVR calculated was steeper than in simulations excluding the OFF-state. Furthermore, the ESPVR was also steeper when compared to models that included the OFF-state without a force-dependent transition. This suggests that the force-dependent recruitment of thick filament heads from the OFF-state at the cellular level contributes to the Frank-Starling relationship observed at the organ level.
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Affiliation(s)
- Charles K Mann
- Department of Mechanical Engineering, University of Kentucky, 269 Ralph G. Anderson Building, Lexington, KY, 40506-0503, USA
| | - Lik Chuan Lee
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, USA
| | - Kenneth S Campbell
- Division of Cardiovascular Medicine, Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Jonathan F Wenk
- Department of Mechanical Engineering, University of Kentucky, 269 Ralph G. Anderson Building, Lexington, KY, 40506-0503, USA. .,Department of Surgery, University of Kentucky, Lexington, KY, USA.
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10
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The relation between sarcomere energetics and the rate of isometric tension relaxation in healthy and diseased cardiac muscle. J Muscle Res Cell Motil 2019; 42:47-57. [PMID: 31745760 PMCID: PMC7932984 DOI: 10.1007/s10974-019-09566-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 11/13/2019] [Indexed: 12/24/2022]
Abstract
Full muscle relaxation happens when [Ca2+] falls below the threshold for force activation. Several experimental models, from whole muscle organs and intact muscle down to skinned fibers, have been used to explore the cascade of kinetic events leading to mechanical relaxation. The use of single myofibrils together with fast solution switching techniques, has provided new information about the role of cross-bridge (CB) dissociation in the time course of isometric force decay. Myofibril’s relaxation is biphasic starting with a slow seemingly linear phase, with a rate constant, slow kREL, followed by a fast mono-exponential phase. Sarcomeres remain isometric during the slow force decay that reflects CB detachment under isometric conditions while the final fast relaxation phase begins with a sudden give of few sarcomeres and is then dominated by intersarcomere dynamics. Based on a simple two-state model of the CB cycle, myofibril slow kREL represents the apparent forward rate with which CBs leave force generating states (gapp) under isometric conditions and correlates with the energy cost of tension generation (ATPase/tension ratio); in short slow kREL ~ gapp ~ tension cost. The validation of this relationship is obtained by simultaneously measuring maximal isometric force and ATP consumption in skinned myocardial strips that provide an unambiguous determination of the relation between contractile and energetic properties of the sarcomere. Thus, combining kinetic experiments in isolated myofibrils and mechanical and energetic measurements in multicellular cardiac strips, we are able to provide direct evidence for a positive linear correlation between myofibril isometric relaxation kinetics (slow kREL) and the energy cost of force production both measured in preparations from the same cardiac sample. This correlation remains true among different types of muscles with different ATPase activities and also when CB kinetics are altered by cardiomyopathy-related mutations. Sarcomeric mutations associated to hypertrophic cardiomyopathy (HCM), a primary cardiac disorder caused by mutations in genes encoding sarcomeric proteins, have been often found to accelerate CB turnover rate and increase the energy cost of myocardial contraction. Here we review data showing that faster CB detachment results in a proportional increase in the energetic cost of tension generation in heart samples from both HCM patients and mouse models of the disease.
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11
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Ding Y, Dvornikov AV, Ma X, Zhang H, Wang Y, Lowerison M, Packard RR, Wang L, Chen J, Zhang Y, Hsiai T, Lin X, Xu X. Haploinsufficiency of mechanistic target of rapamycin ameliorates bag3 cardiomyopathy in adult zebrafish. Dis Model Mech 2019; 12:dmm040154. [PMID: 31492659 PMCID: PMC6826022 DOI: 10.1242/dmm.040154] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 08/28/2019] [Indexed: 12/14/2022] Open
Abstract
The adult zebrafish is an emerging vertebrate model for studying human cardiomyopathies; however, whether the simple zebrafish heart can model different subtypes of cardiomyopathies, such as dilated cardiomyopathy (DCM), remains elusive. Here, we generated and characterized an inherited DCM model in adult zebrafish and used this model to search for therapeutic strategies. We employed transcription activator-like effector nuclease (TALEN) genome editing technology to generate frame-shift mutants for the zebrafish ortholog of human BCL2-associated athanogene 3 (BAG3), an established DCM-causative gene. As in mammals, the zebrafish bag3 homozygous mutant (bag3e2/e2 ) exhibited aberrant proteostasis, as indicated by impaired autophagy flux and elevated ubiquitinated protein aggregation. Through comprehensive phenotyping analysis of the mutant, we identified phenotypic traits that resembled DCM phenotypes in mammals, including cardiac chamber enlargement, reduced ejection fraction characterized by increased end-systolic volume/body weight (ESV/BW), and reduced contractile myofibril activation kinetics. Nonbiased transcriptome analysis identified the hyperactivation of the mechanistic target of rapamycin (mTOR) signaling in bag3e2/e2 mutant hearts. Further genetic studies showed that mtorxu015/+ , an mTOR haploinsufficiency mutant, repaired abnormal proteostasis, improved cardiac function and rescued the survival of the bag3e2/e2 mutant. This study established the bag3e2/e2 mutant as a DCM model in adult zebrafish and suggested mtor as a candidate therapeutic target gene for BAG3 cardiomyopathy.
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Affiliation(s)
- Yonghe Ding
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | - Alexey V Dvornikov
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | - Xiao Ma
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN 55905, USA
- Center for Clinical and Translational Science, Mayo Clinic, Rochester, MN 55905, USA
- Mayo Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN 55905, USA
| | - Hong Zhang
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN 55905, USA
- Clinical Center for Gene Diagnosis and Therapy, the Second Xiangya Hospital of Central South University, Changsha, China 410011
| | - Yong Wang
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN 55905, USA
- Institute of Life Science, Beijing University of Chinese Medicine, Beijing, China 100029
| | | | - Rene R Packard
- School of Medicine, University of California Los Angeles, Los Angeles, CA 90073, USA
| | - Lei Wang
- Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Jun Chen
- Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN 55905, USA
| | - Yuji Zhang
- Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Tzung Hsiai
- School of Medicine, University of California Los Angeles, Los Angeles, CA 90073, USA
| | - Xueying Lin
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | - Xiaolei Xu
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN 55905, USA
- Center for Clinical and Translational Science, Mayo Clinic, Rochester, MN 55905, USA
- Mayo Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN 55905, USA
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12
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Dvornikov AV, Wang M, Yang J, Zhu P, Le T, Lin X, Cao H, Xu X. Phenotyping an adult zebrafish lamp2 cardiomyopathy model identifies mTOR inhibition as a candidate therapy. J Mol Cell Cardiol 2019; 133:199-208. [PMID: 31228518 PMCID: PMC6705397 DOI: 10.1016/j.yjmcc.2019.06.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 05/31/2019] [Accepted: 06/18/2019] [Indexed: 12/23/2022]
Abstract
Adult zebrafish is an emerging vertebrate model for studying genetic basis of cardiomyopathies; but whether the simple fish heart can model essential features of hypertrophic cardiomyopathy (HCM) remained unknown. Here, we report a comprehensive phenotyping of a lamp2 knockout (KO) mutant. LAMP2 encodes a lysosomal protein and is a causative gene of Danon disease that is characterized by HCM and massive autophagic vacuoles accumulation in the tissues. There is no effective therapy yet to treat this most lethal cardiomyopathy in the young. First, we did find the autophagic vacuoles accumulation in cardiac tissues from lamp2 KO. Next, through employing a set of emerging phenotyping tools, we revealed heart failure phenotypes in the lamp2 KO mutants, including decreased ventricular ejection fraction, reduced physical exercise capacity, blunted β-adrenergic contractile response, and enlarged atrium. We also noted changes of the following indices suggesting cardiac hypertrophic remodeling in lamp2 KO: a rounded heart shape, increased end-systolic ventricular volume and density of ventricular myocardium, elevated actomyosin activation kinetics together with increased maximal isometric tension at the level of cardiac myofibrils. Lastly, we assessed the function of lysosomal-localized mTOR on the lamp2-associated Danon disease. We found that haploinsufficiency of mtor was able to normalize some characteristics of the lamp2 KO, including ejection fraction, β-adrenergic response, and the actomyosin activation kinetics. In summary, we demonstrate the feasibility of modeling the inherited HCM in the adult zebrafish, which can be used to develop potential therapies.
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Affiliation(s)
- Alexey V Dvornikov
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Mingmin Wang
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA; Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Jingchun Yang
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Ping Zhu
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Tai Le
- Department of Electrical Engineering and Computer Science, University of California Irvine, CA, USA
| | - Xueying Lin
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Hung Cao
- Department of Electrical Engineering and Computer Science, University of California Irvine, CA, USA; Department of Biomedical Engineering, University of California Irvine, CA, USA
| | - Xiaolei Xu
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA.
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13
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MyoRobot 2.0: An advanced biomechatronics platform for automated, environmentally controlled skeletal muscle single fiber biomechanics assessment employing inbuilt real-time optical imaging. Biosens Bioelectron 2019; 138:111284. [DOI: 10.1016/j.bios.2019.04.052] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 04/24/2019] [Indexed: 11/23/2022]
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14
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Ishii S, Oyama K, Arai T, Itoh H, Shintani SA, Suzuki M, Kobirumaki-Shimozawa F, Terui T, Fukuda N, Ishiwata S. Microscopic heat pulses activate cardiac thin filaments. J Gen Physiol 2019; 151:860-869. [PMID: 31010810 PMCID: PMC6572001 DOI: 10.1085/jgp.201812243] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 02/20/2019] [Accepted: 03/31/2019] [Indexed: 11/30/2022] Open
Abstract
During the excitation-contraction coupling of the heart, sarcomeres are activated via thin filament structural changes (i.e., from the "off" state to the "on" state) in response to a release of Ca2+ from the sarcoplasmic reticulum. This process involves chemical reactions that are highly dependent on ambient temperature; for example, catalytic activity of the actomyosin ATPase rises with increasing temperature. Here, we investigate the effects of rapid heating by focused infrared (IR) laser irradiation on the sliding of thin filaments reconstituted with human α-tropomyosin and bovine ventricular troponin in an in vitro motility assay. We perform high-precision analyses measuring temperature by the fluorescence intensity of rhodamine-phalloidin-labeled F-actin coupled with a fluorescent thermosensor sheet containing the temperature-sensitive dye Europium (III) thenoyltrifluoroacetonate trihydrate. This approach enables a shift in temperature from 25°C to ∼46°C within 0.2 s. We find that in the absence of Ca2+ and presence of ATP, IR laser irradiation elicits sliding movements of reconstituted thin filaments with a sliding velocity that increases as a function of temperature. The heating-induced acceleration of thin filament sliding likewise occurs in the presence of Ca2+ and ATP; however, the temperature dependence is more than twofold less pronounced. These findings could indicate that in the mammalian heart, the on-off equilibrium of the cardiac thin filament state is partially shifted toward the on state in diastole at physiological body temperature, enabling rapid and efficient myocardial dynamics in systole.
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Affiliation(s)
- Shuya Ishii
- Department of Physics, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
| | - Kotaro Oyama
- Department of Physics, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, Gunma, Japan
- PRESTO, Japan Science and Technology Agency, Saitama, Japan
| | - Tomomi Arai
- Department of Physics, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan
| | - Hideki Itoh
- Department of Physics, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
- Epithelial Biology Laboratory, Institute of Medical Biology, Agency for Science, Technology and Research, Singapore, Singapore
| | | | - Madoka Suzuki
- PRESTO, Japan Science and Technology Agency, Saitama, Japan
- Institute for Protein Research, Osaka University, Osaka, Japan
| | | | - Takako Terui
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan
- Department of Anesthesiology, The Jikei University School of Medicine, Tokyo, Japan
| | - Norio Fukuda
- Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan
| | - Shin'ichi Ishiwata
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo, Japan
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15
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Reda SM, Gollapudi SK, Chandra M. Developmental increase in β-MHC enhances sarcomere length-dependent activation in the myocardium. J Gen Physiol 2019; 151:635-644. [PMID: 30602626 PMCID: PMC6504293 DOI: 10.1085/jgp.201812183] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 10/08/2018] [Accepted: 11/29/2018] [Indexed: 01/10/2023] Open
Abstract
The expression of β-myosin heavy chain (β-MHC) in the guinea pig heart increases during postnatal development. Reda et al. show that this increase in β-MHC enhances length-mediated increases in myofilament Ca2+ sensitivity and sarcomere length–dependent changes in contractile function. Shifts in myosin heavy chain (MHC) isoforms in cardiac myocytes have been shown to alter cardiac muscle function not only in healthy developing hearts but also in diseased hearts. In guinea pig hearts, there is a large age-dependent shift in MHC isoforms from 80% α-MHC/20% β-MHC at 3 wk to 14% α-MHC/86% β-MHC at 11 wk. Because kinetic differences in α- and β-MHC cross-bridges (XBs) are known to impart different cooperative effects on thin filaments, we hypothesize here that differences in α- and β-MHC expression in guinea pig cardiac muscle impact sarcomere length (SL)–dependent contractile function. We therefore measure steady state and dynamic contractile parameters in detergent-skinned cardiac muscle preparations isolated from the left ventricles of young (3 wk old) or adult (11 wk old) guinea pigs at two different SLs: short (1.9 µm) and long (2.3 µm). Our data show that SL-dependent effects on contractile parameters are augmented in adult guinea pig cardiac muscle preparations. Notably, the SL-mediated increase in myofilament Ca2+ sensitivity (ΔpCa50) is twofold greater in adult guinea pig muscle preparations (ΔpCa50 being 0.11 units in adult preparations but only 0.05 units in young preparations). Furthermore, adult guinea pig cardiac muscle preparations display greater SL-dependent changes than young muscle preparations in (1) the magnitude of length-mediated increase in the recruitment of new force-bearing XBs, (2) XB detachment rate, (3) XB strain-mediated effects on other force-bearing XBs, and (4) the rate constant of force redevelopment. Our findings suggest that increased β-MHC expression enhances length-dependent activation in the adult guinea pig cardiac myocardium.
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Affiliation(s)
- Sherif M Reda
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
| | - Sampath K Gollapudi
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
| | - Murali Chandra
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
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16
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Kieu TT, Awinda PO, Tanner BCW. Omecamtiv Mecarbil Slows Myosin Kinetics in Skinned Rat Myocardium at Physiological Temperature. Biophys J 2019; 116:2149-2160. [PMID: 31103235 DOI: 10.1016/j.bpj.2019.04.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 04/10/2019] [Accepted: 04/15/2019] [Indexed: 12/15/2022] Open
Abstract
Heart failure is a life-threatening condition that occurs when the heart muscle becomes weakened and cannot adequately circulate blood and nutrients around the body. Omecamtiv mecarbil (OM) is a compound that has been developed to treat systolic heart failure via targeting the cardiac myosin heavy chain to increase myocardial contractility. Biophysical and biochemical studies have found that OM increases calcium (Ca2+) sensitivity of contraction by prolonging the myosin working stroke and increasing the actin-myosin cross-bridge duty ratio. Most in vitro studies probing the effects of OM on cross-bridge kinetics and muscle force production have been conducted at subphysiological temperature, even though temperature plays a critical role in enzyme activity and cross-bridge function. Herein, we used skinned, ventricular papillary muscle strips from rats to investigate the effects of [OM] on Ca2+-activated force production, cross-bridge kinetics, and myocardial viscoelasticity at physiological temperature (37°C). We find that OM only increases myocardial contractility at submaximal Ca2+ activation levels and not maximal Ca2+ activation levels. As [OM] increased, the kinetic rate constants for cross-bridge recruitment and detachment slowed for both submaximal and maximal Ca2+-activated conditions. These findings support a mechanism by which OM increases cardiac contractility at physiological temperature via increasing cross-bridge contributions to thin-filament activation as cross-bridge kinetics slow and the duration of cross-bridge attachment increases. Thus, force only increases at submaximal Ca2+ activation due to cooperative recruitment of neighboring cross-bridges, because thin-filament activation is not already saturated. In contrast, OM does not increase myocardial force production for maximal Ca2+-activated conditions at physiological temperature because cooperative activation of thin filaments may already be saturated.
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Affiliation(s)
- Thinh T Kieu
- Department of Integrative Physiology and Neuroscience
| | | | - Bertrand C W Tanner
- Department of Integrative Physiology and Neuroscience; Washington Center for Muscle Biology, Washington State University, Pullman, Washington.
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17
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Mamidi R, Li J, Doh CY, Holmes JB, Stelzer JE. Lost in translation: Interpreting cardiac muscle mechanics data in clinical practice. Arch Biochem Biophys 2019; 662:213-218. [PMID: 30576628 PMCID: PMC6345594 DOI: 10.1016/j.abb.2018.12.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 10/25/2018] [Accepted: 12/17/2018] [Indexed: 01/10/2023]
Abstract
Current inotropic therapies improve systolic function in heart failure patients but also elicit undesirable side effects such as arrhythmias and increased intracellular Ca2+ transients. In order to maintain myocyte Ca2+ homeostasis, the increased cytosolic Ca2+ needs to be actively transported back to sarcoplasmic reticulum leading to depleted ATP reserves. Thus, an emerging approach is to design sarcomere-based treatments to correct impaired contractility via a direct and allosteric modulation of myosin's intrinsic force-generating behavior -a concept that potentially avoids the "off-target" effects. To achieve this goal, various biophysical approaches are utilized to investigate the mechanistic impact of sarcomeric modulators but information derived from diverse approaches is not fully integrated into therapeutic applications. This is in part due to the lack of information that provides a coherent connecting link between biophysical data to in vivo function. Hence, our ability to clearly discern the drug-mediated impact on whole-heart function is diminished. Reducing this translational barrier can significantly accelerate clinical progress related to sarcomere-based therapies by optimizing drug-dosing and treatment duration protocols based on information obtained from biophysical studies. Therefore, we attempt to link biophysical mechanical measurements obtained in isolated cardiac muscle and in vivo contractile function.
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Affiliation(s)
- Ranganath Mamidi
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Jiayang Li
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Chang Yoon Doh
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Joshua B Holmes
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Julian E Stelzer
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA.
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18
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Dvornikov AV, de Tombe PP, Xu X. Phenotyping cardiomyopathy in adult zebrafish. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2018; 138:116-125. [PMID: 29884423 PMCID: PMC6269218 DOI: 10.1016/j.pbiomolbio.2018.05.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2018] [Revised: 04/26/2018] [Accepted: 05/29/2018] [Indexed: 12/21/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is usually manifested by increased myofilament Ca2+ sensitivity, excessive contractility, and impaired relaxation. In contrast, dilated cardiomyopathy (DCM) originates from insufficient sarcomere contractility and reduced cardiac pump function, subsequently resulting in heart failure. The zebrafish has emerged as a new model of human cardiomyopathy with high-throughput screening, which will facilitate the discovery of novel genetic factors and the development of new therapies. Given the small hearts of zebrafish, better phenotyping tools are needed to discern different types of cardiomyopathy, such as HCM and DCM. This article reviews the existing models of cardiomyopathy, available morphologic and functional methods, and current understanding of the different types of cardiomyopathy in adult zebrafish.
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Affiliation(s)
- Alexey V Dvornikov
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA.
| | - Pieter P de Tombe
- University of Illinois at Chicago, Department of Physiology and Biophysics, Chicago, IL, USA; Magdi Yacoub Institute, Cardiac Biophysics Division, Harefield, UK; Imperial College, Heart and Lung Institute, London, UK; Freiburg University, Institute for Experimental Cardiovascular Medicine, Germany
| | - Xiaolei Xu
- Department of Biochemistry and Molecular Biology, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA.
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19
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Muangkram Y, Noma A, Amano A. A new myofilament contraction model with ATP consumption for ventricular cell model. J Physiol Sci 2018; 68:541-554. [PMID: 28770433 PMCID: PMC10717283 DOI: 10.1007/s12576-017-0560-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Accepted: 07/14/2017] [Indexed: 01/14/2023]
Abstract
A new contraction model of cardiac muscle was developed by combining previously described biochemical and biophysical models. The biochemical component of the new contraction model represents events in the presence of Ca2+-crossbridge attachment and power stroke following inorganic phosphate release, detachment evoked by the replacement of ADP by ATP, ATP hydrolysis, and recovery stroke. The biophysical component focuses on Ca2+ activation and force (F b) development assuming an equivalent crossbridge. The new model faithfully incorporates the major characteristics of the biochemical and biophysical models, such as F b activation by transient Ca2+ ([Ca2+]-F b), [Ca2+]-ATP hydrolysis relations, sarcomere length-F b, and F b recovery after jumps in length under the isometric mode and upon sarcomere shortening after a rapid release of mechanical load under the isotonic mode together with the load-velocity relationship. ATP consumption was obtained for all responses. When incorporated in a ventricular cell model, the contraction model was found to share approximately 60% of the total ATP usage in the cell model.
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Affiliation(s)
- Yuttamol Muangkram
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan
| | - Akinori Noma
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan
| | - Akira Amano
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan.
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20
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Zhang X, Liu ZQ, Campbell KS, Wenk JF. Evaluation of a Novel Finite Element Model of Active Contraction in the Heart. Front Physiol 2018; 9:425. [PMID: 29740338 PMCID: PMC5924776 DOI: 10.3389/fphys.2018.00425] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 04/05/2018] [Indexed: 12/22/2022] Open
Abstract
Finite element (FE) modeling is becoming a widely used approach for the investigation of global heart function. In the present study, a novel model of cellular-level systolic contraction, which includes both length- and velocity-dependence, was implemented into a 3D non-linear FE code. To validate this new FE implementation, an optimization procedure was used to determine the contractile parameters, associated with sarcomeric function, by comparing FE-predicted pressure and strain to experimental measures collected with magnetic resonance imaging and catheterization in the ventricles of five healthy rats. The pressure-volume relationship generated by the FE models matched well with the experimental data. Additionally, the regional distribution of end-systolic strains and circumferential-longitudinal shear angle exhibited good agreement with experimental results overall, with the main deviation occurring in the septal region. Moreover, the FE model predicted a heterogeneous distribution of sarcomere re-lengthening after ventricular ejection, which is consistent with previous in vivo studies. In conclusion, the new FE active contraction model was able to predict the global performance and regional mechanical behaviors of the LV during the entire cardiac cycle. By including more accurate cellular-level mechanisms, this model could provide a better representation of the LV and enhance cardiac research related to both systolic and diastolic dysfunction.
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Affiliation(s)
- Xiaoyan Zhang
- Department of Mechanical Engineering, University of Kentucky, Lexington, KY, United States
| | - Zhan-Qiu Liu
- Department of Mechanical Engineering, University of Kentucky, Lexington, KY, United States
| | - Kenneth S Campbell
- Department of Physiology, University of Kentucky, Lexington, KY, United States
| | - Jonathan F Wenk
- Department of Mechanical Engineering, University of Kentucky, Lexington, KY, United States.,Department of Surgery, University of Kentucky, Lexington, KY, United States
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21
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Kristensen AM, Nielsen OB, Overgaard K. Effects of manipulating tetanic calcium on the curvature of the force-velocity relationship in isolated rat soleus muscles. Acta Physiol (Oxf) 2018; 222. [PMID: 28972685 DOI: 10.1111/apha.12977] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 09/25/2017] [Accepted: 09/25/2017] [Indexed: 01/03/2023]
Abstract
AIM In dynamically contracting muscles, increased curvature of the force-velocity relationship contributes to the loss of power during fatigue. It has been proposed that fatigue-induced reduction in [Ca++ ]i causes this increased curvature. However, earlier studies on single fibres have been conducted at low temperatures. Here, we investigated the hypothesis that curvature is increased by reductions in tetanic [Ca++ ]i in isolated skeletal muscle at near-physiological temperatures. METHODS Rat soleus muscles were stimulated at 60 Hz in standard Krebs-Ringer buffer, and contraction force and velocity were measured. Tetanic [Ca++ ]i was in some experiments either lowered by addition of 10 μmol/L dantrolene or use of submaximal stimulation (30 Hz) or increased by addition of 2 mmol/L caffeine. Force-velocity curves were constructed by fitting shortening velocity at different loading forces to the Hill equation. Curvature was determined as the ratio a/F0 with increased curvature reflecting decreased a/F0 . RESULTS Compared to control levels, lowering tetanic [Ca++ ]i with dantrolene or reduced stimulation frequency decreased the curvature slightly as judged from increase in a/F0 of 13 ± 1% (P = < .001) and 20 ± 2% (P = < .001) respectively. In contrast, increasing tetanic [Ca++ ]i with caffeine increased the curvature (a/F0 decreased by 17 ± 1%; P = < .001). CONCLUSION Contrary to our hypothesis, interventions that reduced tetanic [Ca++ ]i caused a decrease in curvature, while increasing tetanic [Ca++ ]i increased the curvature. These results reject a simple causal relation between [Ca++ ]i and curvature of the force-velocity relation during fatigue.
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Affiliation(s)
- A. M. Kristensen
- Department of Public Health; Aarhus University; Aarhus C Denmark
| | - O. B. Nielsen
- Department of Biomedicine; Aarhus University; Aarhus C Denmark
| | - K. Overgaard
- Department of Public Health; Aarhus University; Aarhus C Denmark
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22
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Irving M. Regulation of Contraction by the Thick Filaments in Skeletal Muscle. Biophys J 2017; 113:2579-2594. [PMID: 29262355 PMCID: PMC5770512 DOI: 10.1016/j.bpj.2017.09.037] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 09/27/2017] [Accepted: 09/29/2017] [Indexed: 11/23/2022] Open
Abstract
Contraction of skeletal muscle cells is initiated by a well-known signaling pathway. An action potential in a motor nerve triggers an action potential in a muscle cell membrane, a transient increase of intracellular calcium concentration, binding of calcium to troponin in the actin-containing thin filaments, and a structural change in the thin filaments that allows myosin motors from the thick filaments to bind to actin and generate force. This calcium/thin filament mediated pathway provides the "START" signal for contraction, but it is argued that the functional response of the muscle cell, including the speed of its contraction and relaxation, adaptation to the external load, and the metabolic cost of contraction is largely determined by additional mechanisms. This review considers the role of the thick filaments in those mechanisms, and puts forward a paradigm for the control of contraction in skeletal muscle in which both the thick and thin filaments have a regulatory function. The OFF state of the thick filament is characterized by helical packing of most of the myosin head or motor domains on the thick filament surface in a conformation that makes them unavailable for actin binding or ATP hydrolysis, although a small fraction of the myosin heads are constitutively ON. The availability of the majority fraction of the myosin heads for contraction is controlled in part by the external load on the muscle, so that these heads only attach to actin and hydrolyze ATP when they are required. This phenomenon seems to be the major determinant of the well-known force-velocity relationship of muscle, and controls the metabolic cost of contraction. The regulatory state of the thick filament also seems to control the dynamics of both muscle activation and relaxation.
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Affiliation(s)
- Malcolm Irving
- Randall Centre for Cell and Molecular Biophysics and BHF Centre of Research Excellence, King's College London, London, United Kingdom.
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23
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Milani-Nejad N, Chung JH, Canan BD, Fedorov VV, Whitson BA, Kilic A, Mohler PJ, Janssen PML. Increased cross-bridge recruitment contributes to transient increase in force generation beyond maximal capacity in human myocardium. J Mol Cell Cardiol 2017; 114:116-123. [PMID: 29141185 DOI: 10.1016/j.yjmcc.2017.11.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 10/25/2017] [Accepted: 11/10/2017] [Indexed: 11/17/2022]
Abstract
Cross-bridge attachment allows force generation to occur, and rate of tension redevelopment (ktr) is a commonly used index of cross-bridge cycling rate. Tension overshoots have been observed briefly after a slack-restretch ktr maneuver in various species of animal models and humans. In this study, we set out to determine the properties of these overshoots and their possible underlying mechanism. Utilizing human cardiac trabeculae, we have found that tension overshoots are temperature-dependent and that they do not occur at resting states. In addition, we have found that myosin cross-bridge cycle is vital to these overshoots as inhibition of the cycle results in the blunting of the overshoots and the magnitude of the overshoots are dependent on the level of myofilament activation. Lastly, we show that the number of cross-bridges transiently increase during tension overshoots. These findings lead us to conclude that tension overshoots are likely due to a transient enhancement of the recruitment of myosin heads into the cross-bridge cycling, regulated by the myocardium, and with potential physiological significance in determining cardiac output. NEWS AND NOTEWORTHY We show that isolated human myocardium is capable of transiently increasing its maximal force generation capability by increasing cross-bridge recruitment following slack-restretch maneuver. This process can potentially have important implications and significance in cardiac contraction in vivo.
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Affiliation(s)
- Nima Milani-Nejad
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA; Medical Scientist Training Program and Biomedical Sciences Graduate Program, The Ohio State University Wexner Medical Center, USA
| | - Jae-Hoon Chung
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA; Medical Scientist Training Program and Biomedical Sciences Graduate Program, The Ohio State University Wexner Medical Center, USA
| | - Benjamin D Canan
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA
| | - Vadim V Fedorov
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA
| | - Bryan A Whitson
- Department of Surgery, Division of Cardiac Surgery, The Ohio State University Wexner Medical Center, USA
| | - Ahmet Kilic
- Department of Surgery, Division of Cardiac Surgery, The Ohio State University Wexner Medical Center, USA
| | - Peter J Mohler
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA; Department of Internal Medicine, The Ohio State University Wexner Medical Center, USA
| | - Paul M L Janssen
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA; Department of Internal Medicine, The Ohio State University Wexner Medical Center, USA.
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24
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Kinetic coupling of phosphate release, force generation and rate-limiting steps in the cross-bridge cycle. J Muscle Res Cell Motil 2017; 38:275-289. [PMID: 28918606 DOI: 10.1007/s10974-017-9482-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 09/12/2017] [Indexed: 10/18/2022]
Abstract
A basic goal in muscle research is to understand how the cyclic ATPase activity of cross-bridges is converted into mechanical force. A direct approach to study the chemo-mechanical coupling between Pi release and the force-generating step is provided by the kinetics of force response induced by a rapid change in [Pi]. Classical studies on fibres using caged-Pi discovered that rapid increases in [Pi] induce fast force decays dependent on final [Pi] whose kinetics were interpreted to probe a fast force-generating step prior to Pi release. However, this hypothesis was called into question by studies on skeletal and cardiac myofibrils subjected to Pi jumps in both directions (increases and decreases in [Pi]) which revealed that rapid decreases in [Pi] trigger force rises with slow kinetics, similar to those of calcium-induced force development and mechanically-induced force redevelopment at the same [Pi]. A possible explanation for this discrepancy came from imaging of individual sarcomeres in cardiac myofibrils, showing that the fast force decay upon increase in [Pi] results from so-called sarcomere 'give'. The slow force rise upon decrease in [Pi] was found to better reflect overall sarcomeres cross-bridge kinetics and its [Pi] dependence, suggesting that the force generation coupled to Pi release cannot be separated from the rate-limiting transition. The reasons for the different conclusions achieved in fibre and myofibril studies are re-examined as the recent findings on cardiac myofibrils have fundamental consequences for the coupling between Pi release, rate-limiting steps and force generation. The implications from Pi-induced force kinetics of myofibrils are discussed in combination with historical and recent models of the cross-bridge cycle.
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25
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Ait-Mou Y, Zhang M, Martin JL, Greaser ML, de Tombe PP. Impact of titin strain on the cardiac slow force response. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017. [PMID: 28648628 DOI: 10.1016/j.pbiomolbio.2017.06.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Stretch of myocardium, such as occurs upon increased filling of the cardiac chamber, induces two distinct responses: an immediate increase in twitch force followed by a slower increase in twitch force that develops over the course of several minutes. The immediate response is due, in part, to modulation of myofilament Ca2+ sensitivity by sarcomere length (SL). The slowly developing force response, termed the Slow Force Response (SFR), is caused by a slowly developing increase in intracellular Ca2+ upon sustained stretch. A blunted immediate force response was recently reported for myocardium isolated from homozygous giant titin mutant rats (HM) compared to muscle from wild-type littermates (WT). Here, we examined the impact of titin isoform on the SFR. Right ventricular trabeculae were isolated and mounted in an experimental chamber. SL was measured by laser diffraction. The SFR was recorded in response to a 0.2 μm SL stretch in the presence of [Ca2+]o = 0.4 mM, a bathing concentration reflecting ∼50% of maximum twitch force development at 25 °C. Presence of the giant titin isoform (HM) was associated with a significant reduction in diastolic passive force upon stretch, and ∼50% reduction of the magnitude of the SFR; the rate of SFR development was unaffected. The sustained SL stretch was identical in both muscle groups. Therefore, our data suggest that cytoskeletal strain may underlie directly the cellular mechanisms that lead to the increased intracellular [Ca2+]i that causes the SFR, possibly by involving cardiac myocyte integrin signaling pathways.
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Affiliation(s)
- Younss Ait-Mou
- Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine, 2160 South First Ave, Maywood, IL 60153, United States
| | - Mengjie Zhang
- Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine, 2160 South First Ave, Maywood, IL 60153, United States
| | - Jody L Martin
- Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine, 2160 South First Ave, Maywood, IL 60153, United States
| | - Marion L Greaser
- Department of Animal Sciences, Muscle Biology Laboratory, University of Wisconsin - Madison, 1450 Linden Drive, Madison, WI 53706, United States
| | - Pieter P de Tombe
- Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine, 2160 South First Ave, Maywood, IL 60153, United States.
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26
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Land S, Park-Holohan SJ, Smith NP, Dos Remedios CG, Kentish JC, Niederer SA. A model of cardiac contraction based on novel measurements of tension development in human cardiomyocytes. J Mol Cell Cardiol 2017; 106:68-83. [PMID: 28392437 DOI: 10.1016/j.yjmcc.2017.03.008] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 01/12/2017] [Accepted: 03/31/2017] [Indexed: 11/18/2022]
Abstract
Experimental data from human cardiac myocytes at body temperature is crucial for a quantitative understanding of clinically relevant cardiac function and development of whole-organ computational models. However, such experimental data is currently very limited. Specifically, important measurements to characterize changes in tension development in human cardiomyocytes that occur with perturbations in cell length are not available. To address this deficiency, in this study we present an experimental data set collected from skinned human cardiac myocytes, including the passive and viscoelastic properties of isolated myocytes, the steady-state force calcium relationship at different sarcomere lengths, and changes in tension following a rapid increase or decrease in length, and after constant velocity shortening. This data set is, to our knowledge, the first characterization of length and velocity-dependence of tension generation in human skinned cardiac myocytes at body temperature. We use this data to develop a computational model of contraction and passive viscoelasticity in human myocytes. Our model includes troponin C kinetics, tropomyosin kinetics, a three-state crossbridge model that accounts for the distortion of crossbridges, and the cellular viscoelastic response. Each component is parametrized using our experimental data collected in human cardiomyocytes at body temperature. Furthermore we are able to confirm that properties of length-dependent activation at 37°C are similar to other species, with a shift in calcium sensitivity and increase in maximum tension. We revise our model of tension generation in the skinned isolated myocyte to replicate reported tension traces generated in intact muscle during isometric tension, to provide a model of human tension generation for multi-scale simulations. This process requires changes to calcium sensitivity, cooperativity, and crossbridge transition rates. We apply this model within multi-scale simulations of biventricular cardiac function and further refine the parametrization within the whole organ context, based on obtaining a healthy ejection fraction. This process reveals that crossbridge cycling rates differ between skinned myocytes and intact myocytes.
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Affiliation(s)
- Sander Land
- Department of Biomedical Engineering, King's College London, UK.
| | - So-Jin Park-Holohan
- Cardiovascular Division, King's College London British Heart Foundation Centre of Research Excellence, UK
| | - Nicolas P Smith
- Department of Engineering Science, University of Auckland, New Zealand
| | | | - Jonathan C Kentish
- Cardiovascular Division, King's College London British Heart Foundation Centre of Research Excellence, UK
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27
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Dewan S, McCabe KJ, Regnier M, McCulloch AD. Insights and Challenges of Multi-Scale Modeling of Sarcomere Mechanics in cTn and Tm DCM Mutants-Genotype to Cellular Phenotype. Front Physiol 2017; 8:151. [PMID: 28352236 PMCID: PMC5348544 DOI: 10.3389/fphys.2017.00151] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 02/24/2017] [Indexed: 01/18/2023] Open
Abstract
Dilated Cardiomyopathy (DCM) is a leading cause of sudden cardiac death characterized by impaired pump function and dilatation of cardiac ventricles. In this review we discuss various in silico approaches to elucidating the mechanisms of genetic mutations leading to DCM. The approaches covered in this review focus on bridging the spatial and temporal gaps that exist between molecular and cellular processes. Mutations in sarcomeric regulatory thin filament proteins such as the troponin complex (cTn) and Tropomyosin (Tm) have been associated with DCM. Despite the experimentally-observed myofilament measures of contractility in the case of these mutations, the mechanisms by which the underlying molecular changes and protein interactions scale up to organ failure by these mutations remains elusive. The review highlights multi-scale modeling approaches and their applicability to study the effects of sarcomeric gene mutations in-silico. We discuss some of the insights that can be gained from computational models of cardiac biomechanics when scaling from molecular states to cellular level.
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Affiliation(s)
- Sukriti Dewan
- Departments of Bioengineering and Medicine, University of California San Diego, La Jolla, CA, USA
| | - Kimberly J McCabe
- Departments of Bioengineering and Medicine, University of California San Diego, La Jolla, CA, USA
| | - Michael Regnier
- Departments of Bioengineering and Medicine, University of Washington Seattle, WA, USA
| | - Andrew D McCulloch
- Departments of Bioengineering and Medicine, University of California San Diego, La Jolla, CA, USA
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28
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A simple model of cardiac muscle for multiscale simulation: Passive mechanics, crossbridge kinetics and calcium regulation. J Theor Biol 2017; 420:105-116. [PMID: 28223172 DOI: 10.1016/j.jtbi.2017.02.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 02/09/2017] [Accepted: 02/16/2017] [Indexed: 11/22/2022]
Abstract
A simple model of cardiac muscle was designed for multiscale simulation of heart mechanics. Relaxed cardiac muscle was described as a transversally isotropic hyperelastic material. Active tension caused by actin-myosin crossbridges depends on the ensemble averaged strain of myosin heads bound to actin. Calcium activation was modeled by Ca2+ binding to troponin-C. To account for the dependence of troponin affinity for Ca2+ on myosin heads strongly bound to actin, the kinetics of troponin binding to Ca2+ in the overlap zone of the thin and thick filaments and outside it were separated. The changes in the length of these zones during muscle shortening or lengthening were accounted for explicitly. Simplified version of the model contains only 5 ordinary differential equations (ODE). Model parameters were estimated from a limited set of experiments with skeletal and cardiac muscle. Simulations have shown that model reproduces qualitatively a number of experimental observations: steady-state force-velocity and stiffness-velocity relations; mechanical responses to step changes in muscle length or load; steep Ca2+-tension relationship and its dependence on sarcomere length tension (the Frank-Starling mechanism); tension, shortening and Ca2+-transients in twitch isometric and isotonic contractions, tension development and redevelopment upon fast change in Ca2+ concentration or muscle release followed by re-stretch. We believe that the model can be effectively used for modeling contraction and relaxation of the heart.
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29
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Karam CN, Warren CM, Henze M, Banke NH, Lewandowski ED, Solaro RJ. Peroxisome proliferator-activated receptor-α expression induces alterations in cardiac myofilaments in a pressure-overload model of hypertrophy. Am J Physiol Heart Circ Physiol 2017; 312:H681-H690. [PMID: 28130336 DOI: 10.1152/ajpheart.00469.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 01/04/2017] [Accepted: 01/17/2017] [Indexed: 01/22/2023]
Abstract
Although alterations in fatty acid (FA) metabolism have been shown to have a negative impact on contractility of the hypertrophied heart, the targets of action remain elusive. In this study we compared the function of skinned fiber bundles from transgenic (Tg) mice that overexpress a relatively low level of the peroxisome proliferator-activated receptor α (PPARα), and nontransgenic (NTg) littermates. The mice (NTg-T and Tg-T) were stressed by transverse aortic constriction (TAC) and compared with shams (NTg-S and Tg-S). There was an approximate 4-fold increase in PPARα expression in Tg-S compared with NTg-S, but Tg-T hearts showed the same PPARα expression as NTg-T. Expression of PPARα did not alter the hypertrophic response to TAC but did reduce ejection fraction (EF) in Tg-T hearts compared with other groups. The rate of actomyosin ATP hydrolysis was significantly higher in Tg-S skinned fiber bundles compared with all other groups. Tg-T hearts showed an increase in phosphorylation of specific sites on cardiac myosin binding protein-C (cMyBP-C) and β-myosin heavy chain isoform. These results advance our understanding of potential signaling to the myofilaments induced by altered FA metabolism under normal and pathological states. We demonstrate that chronic and transient PPARα activation during pathological stress alters myofilament response to Ca2+ through a mechanism that is possibly mediated by MyBP-C phosphorylation and myosin heavy chain isoforms.NEW & NOTEWORTHY Data presented here demonstrate novel signaling to sarcomeric proteins by chronic alterations in fatty acid metabolism induced by PPARα. The mechanism involves modifications of key myofilament regulatory proteins modifying cross-bridge dynamics with differential effects in controls and hearts stressed by pressure overload.
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Affiliation(s)
- Chehade N Karam
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and
| | - Chad M Warren
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and
| | - Marcus Henze
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and
| | - Natasha H Banke
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and
| | - E Douglas Lewandowski
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and.,Sanford Burnham Presbyterian Medical Discovery Institute, Orlando, Florida
| | - R John Solaro
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois; and
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30
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Gollapudi SK, Chandra M. Dilated Cardiomyopathy Mutation (R134W) in Mouse Cardiac Troponin T Induces Greater Contractile Deficits against α-Myosin Heavy Chain than against β-Myosin Heavy Chain. Front Physiol 2016; 7:443. [PMID: 27757084 PMCID: PMC5047882 DOI: 10.3389/fphys.2016.00443] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 09/20/2016] [Indexed: 11/13/2022] Open
Abstract
Many studies have demonstrated that depressed myofilament Ca2+ sensitivity is common to dilated cardiomyopathy (DCM) in humans. However, it remains unclear whether a single determinant-such as myofilament Ca2+ sensitivity-is sufficient to characterize all cases of DCM because the severity of disease varies widely with a given mutation. Because dynamic features dominate in the heart muscle, alterations in dynamic contractile parameters may offer better insight on the molecular mechanisms that underlie disparate effects of DCM mutations on cardiac phenotypes. Dynamic features are dominated by myofilament cooperativity that stem from different sources. One such source is the strong tropomyosin binding region in troponin T (TnT), which is known to modulate crossbridge (XB) recruitment dynamics in a myosin heavy chain (MHC)-dependent manner. Therefore, we hypothesized that the effects of DCM-linked mutations in TnT on contractile dynamics would be differently modulated by α- and β-MHC. After reconstitution with the mouse TnT equivalent (TnTR134W) of the human DCM mutation (R131W), we measured dynamic contractile parameters in detergent-skinned cardiac muscle fiber bundles from normal (α-MHC) and transgenic mice (β-MHC). TnTR134W significantly attenuated the rate constants of tension redevelopment, XB recruitment dynamics, XB distortion dynamics, and the magnitude of length-mediated XB recruitment only in α-MHC fiber bundles. TnTR134W decreased myofilament Ca2+ sensitivity to a greater extent in α-MHC (0.14 pCa units) than in β-MHC fiber bundles (0.08 pCa units). Thus, our data demonstrate that TnTR134W induces a more severe DCM-like contractile phenotype against α-MHC than against β-MHC background.
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Affiliation(s)
- Sampath K Gollapudi
- Department of Integrative Physiology and Neuroscience, Washington State University Pullman, WA, USA
| | - Murali Chandra
- Department of Integrative Physiology and Neuroscience, Washington State University Pullman, WA, USA
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31
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Dewan S, McCabe KJ, Regnier M, McCulloch AD, Lindert S. Molecular Effects of cTnC DCM Mutations on Calcium Sensitivity and Myofilament Activation-An Integrated Multiscale Modeling Study. J Phys Chem B 2016; 120:8264-75. [PMID: 27133568 PMCID: PMC5001916 DOI: 10.1021/acs.jpcb.6b01950] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mutations in cardiac troponin C (D75Y, E59D, and G159D), a key regulatory protein of myofilament contraction, have been associated with dilated cardiomyopathy (DCM). Despite reports of altered myofilament function in these mutants, the underlying molecular alterations caused by these mutations remain elusive. Here we investigate in silico the intramolecular mechanisms by which these mutations affect myofilament contraction. On the basis of the location of cardiac troponin C (cTnC) mutations, we tested the hypothesis that intramolecular effects can explain the altered myofilament calcium sensitivity of force development for D75Y and E59D cTnC, whereas altered cardiac troponin C-troponin I (cTnC-cTnI) interaction contributes to the reported contractile effects of the G159D mutation. We employed a multiscale approach combining molecular dynamics (MD) and Brownian dynamics (BD) simulations to estimate cTnC calcium association and hydrophobic patch opening. We then integrated these parameters into a Markov model of myofilament activation to compute the steady-state force-pCa relationship. The analysis showed that myofilament calcium sensitivity with D75Y and E59D can be explained by changes in calcium binding affinity of cTnC and the rate of hydrophobic patch opening, if a partial cTnC interhelical opening angle (110°) is sufficient for cTnI switch peptide association to cTnC. In contrast, interactions between cTnC and cTnI within the cardiac troponin complex must also be accounted for to explain contractile alterations due to G159D. In conclusion, this is the first multiscale in silico study to elucidate how direct molecular effects of genetic mutations in cTnC translate to altered myofilament contractile function.
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Affiliation(s)
- Sukriti Dewan
- Department of Bioengineering, University of California at San Diego, La Jolla, CA, 92093
| | - Kimberly J. McCabe
- Department of Bioengineering, University of California at San Diego, La Jolla, CA, 92093
| | - Michael Regnier
- Dept. of Bioengineering, University of Washington, Seattle, WA 98195
- Center for Cardiovascular Biology, University of Washington, Seattle, WA 98109
| | - Andrew D. McCulloch
- Department of Bioengineering, University of California at San Diego, La Jolla, CA, 92093
| | - Steffen Lindert
- Department of Chemistry & Biochemistry, Ohio State University, Columbus, OH, 43210
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32
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Dvornikov AV, Smolin N, Zhang M, Martin JL, Robia SL, de Tombe PP. Restrictive Cardiomyopathy Troponin I R145W Mutation Does Not Perturb Myofilament Length-dependent Activation in Human Cardiac Sarcomeres. J Biol Chem 2016; 291:21817-21828. [PMID: 27557662 DOI: 10.1074/jbc.m116.746172] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 08/23/2016] [Indexed: 02/05/2023] Open
Abstract
The cardiac troponin I (cTnI) R145W mutation is associated with restrictive cardiomyopathy (RCM). Recent evidence suggests that this mutation induces perturbed myofilament length-dependent activation (LDA) under conditions of maximal protein kinase A (PKA) stimulation. Some cardiac disease-causing mutations, however, have been associated with a blunted response to PKA-mediated phosphorylation; whether this includes LDA is unknown. Endogenous troponin was exchanged in isolated skinned human myocardium for recombinant troponin containing either cTnI R145W, PKA/PKC phosphomimetic charge mutations (S23D/S24D and T143E), or various combinations thereof. Myofilament Ca2+ sensitivity of force, tension cost, LDA, and single myofibril activation/relaxation parameters were measured. Our results show that both R145W and T143E uncouple the impact of S23D/S24D phosphomimetic on myofilament function, including LDA. Molecular dynamics simulations revealed a marked reduction in interactions between helix C of cTnC (residues 56, 59, and 63), and cTnI (residue 145) in the presence of either cTnI RCM mutation or cTnI PKC phosphomimetic. These results suggest that the RCM-associated cTnI R145W mutation induces a permanent structural state that is similar to, but more extensive than, that induced by PKC-mediated phosphorylation of cTnI Thr-143. We suggest that this structural conformational change induces an increase in myofilament Ca2+ sensitivity and, moreover, uncoupling from the impact of phosphorylation of cTnI mediated by PKA at the Ser-23/Ser-24 target sites. The R145W RCM mutation by itself, however, does not impact LDA. These perturbed biophysical and biochemical myofilament properties are likely to significantly contribute to the diastolic cardiac pump dysfunction that is seen in patients suffering from a restrictive cardiomyopathy that is associated with the cTnI R145W mutation.
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Affiliation(s)
- Alexey V Dvornikov
- From the Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois 60153
| | - Nikolai Smolin
- From the Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois 60153
| | - Mengjie Zhang
- From the Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois 60153
| | - Jody L Martin
- From the Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois 60153
| | - Seth L Robia
- From the Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois 60153
| | - Pieter P de Tombe
- From the Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois 60153
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33
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Toepfer CN, West TG, Ferenczi MA. Revisiting Frank-Starling: regulatory light chain phosphorylation alters the rate of force redevelopment (ktr ) in a length-dependent fashion. J Physiol 2016; 594:5237-54. [PMID: 27291932 PMCID: PMC5023691 DOI: 10.1113/jp272441] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 06/01/2016] [Indexed: 11/24/2022] Open
Abstract
Key points Regulatory light chain (RLC) phosphorylation has been shown to alter the ability of muscle to produce force and power during shortening and to alter the rate of force redevelopment (ktr) at submaximal [Ca2+]. Increasing RLC phosphorylation ∼50% from the in vivo level in maximally [Ca2+]‐activated cardiac trabecula accelerates ktr. Decreasing RLC phosphorylation to ∼70% of the in vivo control level slows ktr and reduces force generation. ktr is dependent on sarcomere length in the physiological range 1.85–1.94 μm and RLC phosphorylation modulates this response. We demonstrate that Frank–Starling is evident at maximal [Ca2+] activation and therefore does not necessarily require length‐dependent change in [Ca2+]‐sensitivity of thin filament activation. The stretch response is modulated by changes in RLC phosphorylation, pinpointing RLC phosphorylation as a modulator of the Frank–Starling law in the heart. These data provide an explanation for slowed systolic function in the intact heart in response to RLC phosphorylation reduction.
Abstract Force and power in cardiac muscle have a known dependence on phosphorylation of the myosin‐associated regulatory light chain (RLC). We explore the effect of RLC phosphorylation on the ability of cardiac preparations to redevelop force (ktr) in maximally activating [Ca2+]. Activation was achieved by rapidly increasing the temperature (temperature‐jump of 0.5–20ºC) of permeabilized trabeculae over a physiological range of sarcomere lengths (1.85–1.94 μm). The trabeculae were subjected to shortening ramps over a range of velocities and the extent of RLC phosphorylation was varied. The latter was achieved using an RLC‐exchange technique, which avoids changes in the phosphorylation level of other proteins. The results show that increasing RLC phosphorylation by 50% accelerates ktr by ∼50%, irrespective of the sarcomere length, whereas decreasing phosphorylation by 30% slows ktr by ∼50%, relative to the ktr obtained for in vivo phosphorylation. Clearly, phosphorylation affects the magnitude of ktr following step shortening or ramp shortening. Using a two‐state model, we explore the effect of RLC phosphorylation on the kinetics of force development, which proposes that phosphorylation affects the kinetics of both attachment and detachment of cross‐bridges. In summary, RLC phosphorylation affects the rate and extent of force redevelopment. These findings were obtained in maximally activated muscle at saturating [Ca2+] and are not explained by changes in the Ca2+‐sensitivity of acto‐myosin interactions. The length‐dependence of the rate of force redevelopment, together with the modulation by the state of RLC phosphorylation, suggests that these effects play a role in the Frank–Starling law of the heart. Regulatory light chain (RLC) phosphorylation has been shown to alter the ability of muscle to produce force and power during shortening and to alter the rate of force redevelopment (ktr) at submaximal [Ca2+]. Increasing RLC phosphorylation ∼50% from the in vivo level in maximally [Ca2+]‐activated cardiac trabecula accelerates ktr. Decreasing RLC phosphorylation to ∼70% of the in vivo control level slows ktr and reduces force generation. ktr is dependent on sarcomere length in the physiological range 1.85–1.94 μm and RLC phosphorylation modulates this response. We demonstrate that Frank–Starling is evident at maximal [Ca2+] activation and therefore does not necessarily require length‐dependent change in [Ca2+]‐sensitivity of thin filament activation. The stretch response is modulated by changes in RLC phosphorylation, pinpointing RLC phosphorylation as a modulator of the Frank–Starling law in the heart. These data provide an explanation for slowed systolic function in the intact heart in response to RLC phosphorylation reduction.
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Affiliation(s)
- Christopher N Toepfer
- Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London, UK. .,Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, MD, USA.
| | - Timothy G West
- Structure & Motion Laboratory, Royal Veterinary College London, North Mymms, UK
| | - Michael A Ferenczi
- Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London, UK.,Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
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34
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Tewari SG, Bugenhagen SM, Palmer BM, Beard DA. Dynamics of cross-bridge cycling, ATP hydrolysis, force generation, and deformation in cardiac muscle. J Mol Cell Cardiol 2016; 96:11-25. [PMID: 25681584 PMCID: PMC4532654 DOI: 10.1016/j.yjmcc.2015.02.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 01/29/2015] [Accepted: 02/04/2015] [Indexed: 11/27/2022]
Abstract
Despite extensive study over the past six decades the coupling of chemical reaction and mechanical processes in muscle dynamics is not well understood. We lack a theoretical description of how chemical processes (metabolite binding, ATP hydrolysis) influence and are influenced by mechanical processes (deformation and force generation). To address this need, a mathematical model of the muscle cross-bridge (XB) cycle based on Huxley's sliding filament theory is developed that explicitly accounts for the chemical transformation events and the influence of strain on state transitions. The model is identified based on elastic and viscous moduli data from mouse and rat myocardial strips over a range of perturbation frequencies, and MgATP and inorganic phosphate (Pi) concentrations. Simulations of the identified model reproduce the observed effects of MgATP and MgADP on the rate of force development. Furthermore, simulations reveal that the rate of force re-development measured in slack-restretch experiments is not directly proportional to the rate of XB cycling. For these experiments, the model predicts that the observed increase in the rate of force generation with increased Pi concentration is due to inhibition of cycle turnover by Pi. Finally, the model captures the observed phenomena of force yielding suggesting that it is a result of rapid detachment of stretched attached myosin heads.
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Affiliation(s)
- Shivendra G Tewari
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Scott M Bugenhagen
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Bradley M Palmer
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA
| | - Daniel A Beard
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA.
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35
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Birch CL, Behunin SM, Lopez-Pier MA, Danilo C, Lipovka Y, Saripalli C, Granzier H, Konhilas JP. Sex dimorphisms of crossbridge cycling kinetics in transgenic hypertrophic cardiomyopathy mice. Am J Physiol Heart Circ Physiol 2016; 311:H125-36. [PMID: 27199124 DOI: 10.1152/ajpheart.00592.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 05/03/2016] [Indexed: 11/22/2022]
Abstract
Familial hypertrophic cardiomyopathy (HCM) is a disease of the sarcomere and may lead to hypertrophic, dilated, restrictive, and/or arrhythmogenic cardiomyopathy, congestive heart failure, or sudden cardiac death. We hypothesized that hearts from transgenic HCM mice harboring a mutant myosin heavy chain increase the energetic cost of contraction in a sex-specific manner. To do this, we assessed Ca(2+) sensitivity of tension and crossbridge kinetics in demembranated cardiac trabeculas from male and female wild-type (WT) and HCM hearts at an early time point (2 mo of age). We found a significant effect of sex on Ca(2+) sensitivity such that male, but not female, HCM mice displayed a decrease in Ca(2+) sensitivity compared with WT counterparts. The HCM transgene and sex significantly impacted the rate of force redevelopment by a rapid release-restretch protocol and tension cost by the ATPase-tension relationship. In each of these measures, HCM male trabeculas displayed a gain-of-function when compared with WT counterparts. In addition, cardiac remodeling measured by echocardiography, histology, morphometry, and posttranslational modifications demonstrated sex- and HCM-specific effects. In conclusion, female and male HCM mice display sex dimorphic crossbridge kinetics accompanied by sex- and HCM-dependent cardiac remodeling at the morphometric, histological, and cellular level.
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Affiliation(s)
- Camille L Birch
- Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona; Department of Biomedical Engineering, University of Arizona, Tucson, Arizona
| | - Samantha M Behunin
- Department of Physiology, University of Arizona, Tucson, Arizona; Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona
| | - Marissa A Lopez-Pier
- Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona; Department of Biomedical Engineering, University of Arizona, Tucson, Arizona
| | - Christiane Danilo
- Department of Physiology, University of Arizona, Tucson, Arizona; Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona
| | - Yulia Lipovka
- Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona; Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona; and
| | - Chandra Saripalli
- Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona; Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
| | - Henk Granzier
- Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona; Department of Cellular and Molecular Medicine, University of Arizona, Tucson, Arizona
| | - John P Konhilas
- Department of Physiology, University of Arizona, Tucson, Arizona; Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, Arizona;
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Tewari SG, Bugenhagen SM, Vinnakota KC, Rice JJ, Janssen PML, Beard DA. Influence of metabolic dysfunction on cardiac mechanics in decompensated hypertrophy and heart failure. J Mol Cell Cardiol 2016; 94:162-175. [PMID: 27085901 DOI: 10.1016/j.yjmcc.2016.04.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 03/28/2016] [Accepted: 04/07/2016] [Indexed: 01/10/2023]
Abstract
Alterations in energetic state of the myocardium are associated with decompensated heart failure in humans and in animal models. However, the functional consequences of the observed changes in energetic state on mechanical function are not known. The primary aim of the study was to quantify mechanical/energetic coupling in the heart and to determine if energetic dysfunction can contribute to mechanical failure. A secondary aim was to apply a quantitative systems pharmacology analysis to investigate the effects of drugs that target cross-bridge cycling kinetics in heart failure-associated energetic dysfunction. Herein, a model of metabolite- and calcium-dependent myocardial mechanics was developed from calcium concentration and tension time courses in rat cardiac muscle obtained at different lengths and stimulation frequencies. The muscle dynamics model accounting for the effect of metabolites was integrated into a model of the cardiac ventricles to simulate pressure-volume dynamics in the heart. This cardiac model was integrated into a simple model of the circulation to investigate the effects of metabolic state on whole-body function. Simulations predict that reductions in metabolite pools observed in canine models of heart failure can cause systolic dysfunction, blood volume expansion, venous congestion, and ventricular dilation. Simulations also predict that myosin-activating drugs may partially counteract the effects of energetic state on cross-bridge mechanics in heart failure while increasing myocardial oxygen consumption. Our model analysis demonstrates how metabolic changes observed in heart failure are alone sufficient to cause systolic dysfunction and whole-body heart failure symptoms.
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Affiliation(s)
- Shivendra G Tewari
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, United States
| | - Scott M Bugenhagen
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd, Milwaukee, WI 53226, United States
| | - Kalyan C Vinnakota
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, United States
| | - J Jeremy Rice
- Functional Genomics and Systems Biology Group, IBM T.J. Watson Research Center, New York, United States
| | - Paul M L Janssen
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH 43210, United States
| | - Daniel A Beard
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, United States.
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Michael JJ, Chandra M. Interplay Between the Effects of Dilated Cardiomyopathy Mutation (R206L) and the Protein Kinase C Phosphomimic (T204E) of Rat Cardiac Troponin T Are Differently Modulated by α- and β-Myosin Heavy Chain Isoforms. J Am Heart Assoc 2016; 5:e002777. [PMID: 27001966 PMCID: PMC4943253 DOI: 10.1161/jaha.115.002777] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background We hypothesized that the functional effects of R206L—a rat analog of the dilated cardiomyopathy (DCM) mutation R205L in human cardiac troponin T (TnT)—were differently modulated by myosin heavy chain (MHC) isoforms and T204E, a protein kinase C (PKC) phosphomimic of TnT. Our hypothesis was based on two observations: (1) α‐ and β‐MHC differentially influence the functional effects of TnT; and (2) PKC isoforms capable of phosphorylating TnT are upregulated in failing human hearts. Methods and Results We generated 4 recombinant TnT variants: wild type; R206L; T204E; and R206L+T204E. Functional effects of the TnT variants were tested in cardiac muscle fibers (minimum 14 per group) from normal (α‐MHC) and propylthiouracil‐treated rats (β‐MHC) using steady‐state and dynamic contractile measurements. Notably, in α‐MHC fibers, Ca2+‐activated maximal tension was attenuated by R206L (≈32%), T204E (≈63%), and R206L+T204E (≈64%). In β‐MHC fibers, maximal tension was unaffected by R206L, but was attenuated by T204E (≈33%) and R206L+T204E (≈40%). Thus, β‐MHC differentially counteracted the attenuating effects of the TnT variants on tension. However, in β‐MHC fibers, R206L+T204E attenuated tension to a greater extent when compared to T204E alone. In β‐MHC fibers, R206L+T204E attenuated the magnitude of the length‐mediated recruitment of new cross‐bridges (≈28%), suggesting that the Frank‐Starling mechanism was impaired. Conclusions Our findings are the first (to our knowledge) to demonstrate that the functional effects of a DCM‐linked TnT mutation are not only modulated by MHC isoforms, but also by the pathology‐associated post‐translational modifications of TnT.
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Affiliation(s)
- John Jeshurun Michael
- Department of Integrative Physiology and Neuroscience Washington State University, Pullman, WA
| | - Murali Chandra
- Department of Integrative Physiology and Neuroscience Washington State University, Pullman, WA
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Gollapudi SK, Chandra M. The effect of cardiomyopathy mutation (R97L) in mouse cardiac troponin T on the muscle length-mediated recruitment of crossbridges is modified divergently by α- and β-myosin heavy chain. Arch Biochem Biophys 2016; 601:105-12. [PMID: 26792537 DOI: 10.1016/j.abb.2016.01.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2015] [Revised: 12/28/2015] [Accepted: 01/08/2016] [Indexed: 01/19/2023]
Abstract
Hypertrophic cardiomyopathy mutations in cardiac troponin T (TnT) lead to sudden cardiac death. Augmented myofilament Ca(2+) sensitivity is a common feature in TnT mutants, but such observations fail to provide a rational explanation for severe cardiac phenotypes. To better understand the mutation-induced effect on the cardiac phenotype, it is imperative to determine the effects on dynamic contractile features such as the muscle length (ML)-mediated activation against α- and β-myosin heavy chain (MHC) isoforms. α- and β-MHC are not only differentially expressed in rodent and human hearts, but they also modify ML-mediated activation differently. Mouse analog of human TnTR94L (TnTR97L) or wild-type TnT was reconstituted into de-membranated muscle fibers from normal (α-MHC) and transgenic (β-MHC) mouse hearts. TnTR97L augmented myofilament Ca(2+) sensitivity by a similar amount in α- and β-MHC fibers. However, TnTR97L augmented the negative impact of strained crossbridges on other crossbridges (γ) by 22% in α-MHC fibers, but attenuated γ by 21% in β-MHC fibers. TnTR97L decreased the magnitude of ML-mediated recruitment of crossbridges (ER) by 37% in α-MHC fibers, but increased ER by 35% in β-MHC fibers. We provide a mechanistic basis for the TnTR97L-induced effects in α- and β-MHC fibers and discuss the relevance to human hearts.
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Affiliation(s)
- Sampath K Gollapudi
- Department of Integrative Physiology and Neuroscience (IPN), Washington State University, Pullman, WA, USA
| | - Murali Chandra
- Department of Integrative Physiology and Neuroscience (IPN), Washington State University, Pullman, WA, USA.
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39
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Amiad Pavlov D, Landesberg A. The cross-bridge dynamics is determined by two length-independent kinetics: Implications on muscle economy and Frank–Starling Law. J Mol Cell Cardiol 2016; 90:94-101. [DOI: 10.1016/j.yjmcc.2015.11.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 10/19/2015] [Accepted: 11/04/2015] [Indexed: 11/16/2022]
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40
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Milani-Nejad N, Canan BD, Elnakish MT, Davis JP, Chung JH, Fedorov VV, Binkley PF, Higgins RSD, Kilic A, Mohler PJ, Janssen PML. The Frank-Starling mechanism involves deceleration of cross-bridge kinetics and is preserved in failing human right ventricular myocardium. Am J Physiol Heart Circ Physiol 2015; 309:H2077-86. [PMID: 26453335 DOI: 10.1152/ajpheart.00685.2015] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 10/05/2015] [Indexed: 01/08/2023]
Abstract
Cross-bridge cycling rate is an important determinant of cardiac output, and its alteration can potentially contribute to reduced output in heart failure patients. Additionally, animal studies suggest that this rate can be regulated by muscle length. The purpose of this study was to investigate cross-bridge cycling rate and its regulation by muscle length under near-physiological conditions in intact right ventricular muscles of nonfailing and failing human hearts. We acquired freshly explanted nonfailing (n = 9) and failing (n = 10) human hearts. All experiments were performed on intact right ventricular cardiac trabeculae (n = 40) at physiological temperature and near the normal heart rate range. The failing myocardium showed the typical heart failure phenotype: a negative force-frequency relationship and β-adrenergic desensitization (P < 0.05), indicating the expected pathological myocardium in the right ventricles. We found that there exists a length-dependent regulation of cross-bridge cycling kinetics in human myocardium. Decreasing muscle length accelerated the rate of cross-bridge reattachment (ktr) in both nonfailing and failing myocardium (P < 0.05) equally; there were no major differences between nonfailing and failing myocardium at each respective length (P > 0.05), indicating that this regulatory mechanism is preserved in heart failure. Length-dependent assessment of twitch kinetics mirrored these findings; normalized dF/dt slowed down with increasing length of the muscle and was virtually identical in diseased tissue. This study shows for the first time that muscle length regulates cross-bridge kinetics in human myocardium under near-physiological conditions and that those kinetics are preserved in the right ventricular tissues of heart failure patients.
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Affiliation(s)
- Nima Milani-Nejad
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio; Medical Scientist Training Program and Biomedical Sciences Graduate Program, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Benjamin D Canan
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Mohammad T Elnakish
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio; Department of Pharmacology and Toxicology, Faculty of Pharmacy, Helwan University, Cairo, Egypt
| | - Jonathan P Davis
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Jae-Hoon Chung
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio; Medical Scientist Training Program and Biomedical Sciences Graduate Program, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Vadim V Fedorov
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Philip F Binkley
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio; Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio; and
| | - Robert S D Higgins
- Division of Cardiac Surgery, Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Ahmet Kilic
- Division of Cardiac Surgery, Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Peter J Mohler
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio; Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio; and
| | - Paul M L Janssen
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio; Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio; and
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41
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Chandra V, Gollapudi SK, Chandra M. Rat cardiac troponin T mutation (F72L)-mediated impact on thin filament cooperativity is divergently modulated by α- and β-myosin heavy chain isoforms. Am J Physiol Heart Circ Physiol 2015; 309:H1260-70. [PMID: 26342069 DOI: 10.1152/ajpheart.00519.2015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 08/31/2015] [Indexed: 11/22/2022]
Abstract
The primary causal link between disparate effects of human hypertrophic cardiomyopathy (HCM)-related mutations in troponin T (TnT) and α- and β-myosin heavy chain (MHC) isoforms on cardiac contractile phenotype remains poorly understood. Given the divergent impact of α- and β-MHC on the NH2-terminal extension (44-73 residues) of TnT, we tested if the effects of the HCM-linked mutation (TnTF70L) were differentially altered by α- and β-MHC. We hypothesized that the emergence of divergent thin filament cooperativity would lead to contrasting effects of TnTF70L on contractile function in the presence of α- and β-MHC. The rat TnT analog of the human F70L mutation (TnTF72L) or the wild-type rat TnT (TnTWT) was reconstituted into demembranated muscle fibers from normal (α-MHC) and propylthiouracil-treated (β-MHC) rat hearts to measure steady-state and dynamic contractile function. TnTF72L-mediated effects on tension, myofilament Ca(2+) sensitivity, myofilament cooperativity, rate constants of cross-bridge (XB) recruitment dynamics, and force redevelopment were divergently modulated by α- and β-MHC. TnTF72L increased the rate of XB distortion dynamics by 49% in α-MHC fibers but had no effect in β-MHC fibers; these observations suggest that TnTF72L augmented XB detachment kinetics in α-MHC, but not β-MHC, fibers. TnTF72L increased the negative impact of strained XBs on the force-bearing XBs by 39% in α-MHC fibers but had no effect in β-MHC fibers. Therefore, TnTF72L leads to contractile changes that are linked to dilated cardiomyopathy in the presence of α-MHC. On the other hand, TnTF72L leads to contractile changes that are linked to HCM in the presence of β-MHC.
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Affiliation(s)
- Vikram Chandra
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, Washington
| | - Sampath K Gollapudi
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, Washington
| | - Murali Chandra
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, Washington
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42
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Irie T, Sips PY, Kai S, Kida K, Ikeda K, Hirai S, Moazzami K, Jiramongkolchai P, Bloch DB, Doulias PT, Armoundas AA, Kaneki M, Ischiropoulos H, Kranias E, Bloch KD, Stamler JS, Ichinose F. S-Nitrosylation of Calcium-Handling Proteins in Cardiac Adrenergic Signaling and Hypertrophy. Circ Res 2015; 117:793-803. [PMID: 26259881 DOI: 10.1161/circresaha.115.307157] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 08/10/2015] [Indexed: 01/08/2023]
Abstract
RATIONALE The regulation of calcium (Ca(2+)) homeostasis by β-adrenergic receptor (βAR) activation provides the essential underpinnings of sympathetic regulation of myocardial function, as well as a basis for understanding molecular events that result in hypertrophic signaling and heart failure. Sympathetic stimulation of the βAR not only induces protein phosphorylation but also activates nitric oxide-dependent signaling, which modulates cardiac contractility. Nonetheless, the role of nitric oxide in βAR-dependent regulation of Ca(2+) handling has not yet been explicated fully. OBJECTIVE To elucidate the role of protein S-nitrosylation, a major transducer of nitric oxide bioactivity, on βAR-dependent alterations in cardiomyocyte Ca(2+) handling and hypertrophy. METHODS AND RESULTS Using transgenic mice to titrate the levels of protein S-nitrosylation, we uncovered major roles for protein S-nitrosylation, in general, and for phospholamban and cardiac troponin C S-nitrosylation, in particular, in βAR-dependent regulation of Ca(2+) homeostasis. Notably, S-nitrosylation of phospholamban consequent upon βAR stimulation is necessary for the inhibitory pentamerization of phospholamban, which activates sarcoplasmic reticulum Ca(2+)-ATPase and increases cytosolic Ca(2+) transients. Coincident S-nitrosylation of cardiac troponin C decreases myocardial sensitivity to Ca(2+). During chronic adrenergic stimulation, global reductions in cellular S-nitrosylation mitigate hypertrophic signaling resulting from Ca(2+) overload. CONCLUSIONS S-Nitrosylation operates in concert with phosphorylation to regulate many cardiac Ca(2+)-handling proteins, including phospholamban and cardiac troponin C, thereby playing an essential and previously unrecognized role in cardiac Ca(2+) homeostasis. Manipulation of the S-nitrosylation level may prove therapeutic in heart failure.
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Affiliation(s)
- Tomoya Irie
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Patrick Y Sips
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Shinichi Kai
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Kotaro Kida
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Kohei Ikeda
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Shuichi Hirai
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Kasra Moazzami
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Pawina Jiramongkolchai
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Donald B Bloch
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Paschalis-Thomas Doulias
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Antonis A Armoundas
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Masao Kaneki
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Harry Ischiropoulos
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Evangelia Kranias
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Kenneth D Bloch
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Jonathan S Stamler
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.)
| | - Fumito Ichinose
- From the Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine (T.I., P.Y.S., S.K., K.K., K.I., S.H., P.J., D.B.B., M.K., K.D.B., F.I.), Cardiovascular Research Center, Division of Cardiology, Department of Medicine (K.M., A.A.A., K.D.B.), and Division of Rheumatology Allergy and Immunology, Department of Medicine (D.B.B.), Massachusetts General Hospital and Harvard Medical School, Boston; Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA (P.Y.S.); Children's Hospital of Philadelphia Research Institute, Department of Pediatrics and Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine at the University of Pennsylvania (P.-T.D., H.I.); Department of Research, Shriners Hospitals for Children (M.K.) and Department of Pharmacology (E.K.), University of Cincinnati College of Medicine, OH; and Institute for Transformative Molecular Medicine, Case Western Reserve University, Harrington Discovery Institute University Hospitals, Cleveland, OH (J.S.S.).
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43
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Witjas-Paalberends ER, Ferrara C, Scellini B, Piroddi N, Montag J, Tesi C, Stienen GJM, Michels M, Ho CY, Kraft T, Poggesi C, van der Velden J. Faster cross-bridge detachment and increased tension cost in human hypertrophic cardiomyopathy with the R403Q MYH7 mutation. J Physiol 2014; 592:3257-72. [PMID: 24928957 DOI: 10.1113/jphysiol.2014.274571] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The first mutation associated with hypertrophic cardiomyopathy (HCM) is the R403Q mutation in the gene encoding β-myosin heavy chain (β-MyHC). R403Q locates in the globular head of myosin (S1), responsible for interaction with actin, and thus motor function of myosin. Increased cross-bridge relaxation kinetics caused by the R403Q mutation might underlie increased energetic cost of tension generation; however, direct evidence is absent. Here we studied to what extent cross-bridge kinetics and energetics are related in single cardiac myofibrils and multicellular cardiac muscle strips of three HCM patients with the R403Q mutation and nine sarcomere mutation-negative HCM patients (HCMsmn). Expression of R403Q was on average 41 ± 4% of total MYH7 mRNA. Cross-bridge slow relaxation kinetics in single R403Q myofibrils was significantly higher (P < 0.0001) than in HCMsmn myofibrils (0.47 ± 0.02 and 0.30 ± 0.02 s(-1), respectively). Moreover, compared to HCMsmn, tension cost was significantly higher in the muscle strips of the three R403Q patients (2.93 ± 0.25 and 1.78 ± 0.10 μmol l(-1) s(-1) kN(-1) m(-2), respectively) which showed a positive linear correlation with relaxation kinetics in the corresponding myofibril preparations. This correlation suggests that faster cross-bridge relaxation kinetics results in an increase in energetic cost of tension generation in human HCM with the R403Q mutation compared to HCMsmn. Therefore, increased tension cost might contribute to HCM disease in patients carrying the R403Q mutation.
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Affiliation(s)
| | - Claudia Ferrara
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Beatrice Scellini
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Nicoletta Piroddi
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Judith Montag
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Chiara Tesi
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Ger J M Stienen
- Department of Physiology, VU University Medical Centre, Amsterdam, The Netherlands Department of Physics and Astronomy, VU University, Amsterdam, The Netherlands
| | - Michelle Michels
- Thorax Centre, Cardiology, Erasmus Medical Centre, Rotterdam, The Netherlands
| | - Carolyn Y Ho
- Brigham and Women's Hospital, Cardiology, Boston, USA
| | - Theresia Kraft
- Institute of Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Corrado Poggesi
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Jolanda van der Velden
- Department of Physiology, VU University Medical Centre, Amsterdam, The Netherlands ICIN-Netherlands Heart Institute, Utrecht, The Netherlands
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44
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Instability in the central region of tropomyosin modulates the function of its overlapping ends. Biophys J 2014; 105:2104-13. [PMID: 24209855 DOI: 10.1016/j.bpj.2013.09.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 08/20/2013] [Accepted: 09/17/2013] [Indexed: 12/14/2022] Open
Abstract
The causal link between disparate tropomyosin (Tm) functions and the structural instability in Tm is unknown. To test the hypothesis that the structural instability in the central region of Tm modulates the function of the overlapping ends of contiguous Tm dimers, we used transgenic mice (Tm(DM)) that expressed a mutant α-Tm in the heart; S229E and H276N substitutions induce structural instability in the central region and the overlapping ends of Tm, respectively. In addition, two mouse cardiac troponin T mutants (TnT(1-44Δ) and TnT(45-74Δ)) that have a divergent effect on the overlapping ends of Tm were employed. The S229E-induced instability in the central region of Tm(DM) altered the overlapping ends of Tm(DM), thereby it negated the attenuating effect of H276N on Ca(2+)-activated maximal tension. The rate of cross-bridge detachment (g) decreased in Tm(DM)+TnT(WT) and Tm(H276N)+TnT(WT) fibers but increased in Tm(DM)+TnT(45-74Δ) fibers; however, TnT(45-74Δ) did not alter g, demonstrating that S229E in Tm(DM) had divergent effects on g. The S229E substitution in Tm(DM) ablated the H276N-induced desensitization of myofilament Ca(2+) sensitivity in Tm(DM)+TnT(1-44Δ) fibers. To our knowledge, novel findings from this study show that the structural instability in the central region of Tm modifies cardiac contractile function via its effect on the overlapping ends of contiguous Tm.
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45
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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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46
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van Dijk SJ, Boontje NM, Heymans MW, Ten Cate FJ, Michels M, Dos Remedios C, Dooijes D, van Slegtenhorst MA, van der Velden J, Stienen GJM. Preserved cross-bridge kinetics in human hypertrophic cardiomyopathy patients with MYBPC3 mutations. Pflugers Arch 2013; 466:1619-33. [PMID: 24186209 DOI: 10.1007/s00424-013-1391-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 10/04/2013] [Accepted: 10/19/2013] [Indexed: 12/23/2022]
Abstract
Mutations in the MYBPC3 gene, encoding cardiac myosin binding protein C (cMyBP-C) are frequent causes of hypertrophic cardiomyopathy (HCM). Previously, we have presented evidence for reduced cMyBP-C expression (haploinsufficiency), in patients with a truncation mutation in MYBPC3. In mice, lacking cMyBP-C cross-bridge kinetics was accelerated. In this study, we investigated whether cross-bridge kinetics was altered in myectomy samples from HCM patients harboring heterozygous MYBPC3 mutations (MYBPC3mut). Isometric force and the rate of force redevelopment (k tr) at different activating Ca(2+) concentrations were measured in mechanically isolated Triton-permeabilized cardiomyocytes from MYBPC3mut (n = 18) and donor (n = 7) tissue. Furthermore, the stretch activation response of cardiomyocytes was measured in tissue from eight MYBPC3mut patients and five donors to assess the rate of initial force relaxation (k 1) and the rate and magnitude of the transient increase in force (k 2 and P 3, respectively) after a rapid stretch. Maximal force development of the cardiomyocytes was reduced in MYBPC3mut (24.5 ± 2.3 kN/m(2)) compared to donor (34.9 ± 1.6 kN/m(2)). The rates of force redevelopment in MYBPC3mut and donor over a range of Ca(2+) concentrations were similar (k tr at maximal activation: 0.63 ± 0.03 and 0.75 ± 0.09 s(-1), respectively). Moreover, the stretch activation parameters did not differ significantly between MYBPC3mut and donor (k 1: 8.5±0.5 and 8.8 ± 0.4 s(-1); k 2: 0.77 ± 0.06 and 0.74 ± 0.09 s(-1); P 3: 0.08 ± 0.01 and 0.09 ± 0.01, respectively). Incubation with protein kinase A accelerated k 1 in MYBPC3mut and donor to a similar extent. Our experiments indicate that, at the cMyBP-C expression levels in this patient group (63 ± 6 % relative to donors), cross-bridge kinetics are preserved and that the depressed maximal force development is not explained by perturbation of cross-bridge kinetics.
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Affiliation(s)
- Sabine J van Dijk
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands
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47
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Milani-Nejad N, Xu Y, Davis JP, Campbell KS, Janssen PML. Effect of muscle length on cross-bridge kinetics in intact cardiac trabeculae at body temperature. ACTA ACUST UNITED AC 2013; 141:133-9. [PMID: 23277479 PMCID: PMC3536524 DOI: 10.1085/jgp.201210894] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Dynamic force generation in cardiac muscle, which determines cardiac pumping activity, depends on both the number of sarcomeric cross-bridges and on their cycling kinetics. The Frank–Starling mechanism dictates that cardiac force development increases with increasing cardiac muscle length (corresponding to increased ventricular volume). It is, however, unclear to what extent this increase in cardiac muscle length affects the rate of cross-bridge cycling. Previous studies using permeabilized cardiac preparations, sub-physiological temperatures, or both have obtained conflicting results. Here, we developed a protocol that allowed us to reliably and reproducibly measure the rate of tension redevelopment (ktr; which depends on the rate of cross-bridge cycling) in intact trabeculae at body temperature. Using K+ contractures to induce a tonic level of force, we showed the ktr was slower in rabbit muscle (which contains predominantly β myosin) than in rat muscle (which contains predominantly α myosin). Analyses of ktr in rat muscle at optimal length (Lopt) and 90% of optimal length (L90) revealed that ktr was significantly slower at Lopt (27.7 ± 3.3 and 27.8 ± 3.0 s−1 in duplicate analyses) than at L90 (45.1 ± 7.6 and 47.5 ± 9.2 s−1). We therefore show that ktr can be measured in intact rat and rabbit cardiac trabeculae, and that the ktr decreases when muscles are stretched to their optimal length under near-physiological conditions, indicating that the Frank–Starling mechanism not only increases force but also affects cross-bridge cycling kinetics.
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Affiliation(s)
- Nima Milani-Nejad
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH 43210, USA
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48
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Weise LD, Panfilov AV. A discrete electromechanical model for human cardiac tissue: effects of stretch-activated currents and stretch conditions on restitution properties and spiral wave dynamics. PLoS One 2013; 8:e59317. [PMID: 23527160 PMCID: PMC3602082 DOI: 10.1371/journal.pone.0059317] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Accepted: 02/13/2013] [Indexed: 11/24/2022] Open
Abstract
We introduce an electromechanical model for human cardiac tissue which couples a biophysical model of cardiac excitation (Tusscher, Noble, Noble, Panfilov, 2006) and tension development (adjusted Niederer, Hunter, Smith, 2006 model) with a discrete elastic mass-lattice model. The equations for the excitation processes are solved with a finite difference approach, and the equations of the mass-lattice model are solved using Verlet integration. This allows the coupled problem to be solved with high numerical resolution. Passive mechanical properties of the mass-lattice model are described by a generalized Hooke's law for finite deformations (Seth material). Active mechanical contraction is initiated by changes of the intracellular calcium concentration, which is a variable of the electrical model. Mechanical deformation feeds back on the electrophysiology via stretch-activated ion channels whose conductivity is controlled by the local stretch of the medium. We apply the model to study how stretch-activated currents affect the action potential shape, restitution properties, and dynamics of spiral waves, under constant stretch, and dynamic stretch caused by active mechanical contraction. We find that stretch conditions substantially affect these properties via stretch-activated currents. In constantly stretched medium, we observe a substantial decrease in conduction velocity, and an increase of action potential duration; whereas, with dynamic stretch, action potential duration is increased only slightly, and the conduction velocity restitution curve becomes biphasic. Moreover, in constantly stretched medium, we find an increase of the core size and period of a spiral wave, but no change in rotation dynamics; in contrast, in the dynamically stretching medium, we observe spiral drift. Our results may be important to understand how altered stretch conditions affect the heart's functioning.
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Affiliation(s)
- Louis D Weise
- Department of Theoretical Biology, Utrecht University, Utrecht, The Netherlands.
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49
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Joumaa V, Herzog W. Energy cost of force production is reduced after active stretch in skinned muscle fibres. J Biomech 2013; 46:1135-9. [PMID: 23422864 DOI: 10.1016/j.jbiomech.2013.01.008] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 01/08/2013] [Accepted: 01/13/2013] [Indexed: 10/27/2022]
Abstract
Residual force enhancement has been observed consistently in skeletal muscles. Despite an abundance of experimental observations, there has been no information about the metabolic cost of the force observed after stretch. Our aim was to investigate the energy cost of force production after active stretch in skinned fibres isolated from rabbit psoas muscle, by quantifying the ATPase activity using an enzyme-coupled assay. Fibres were actively stretched from an average sarcomere length of 2.4 μm to average sarcomere lengths of 2.8 and 3.2 μm. Purely isometric reference contractions were performed at average sarcomere lengths of 2.8 and 3.2 μm. Simultaneously with the force measurements, the ATP cost per unit of force produced was measured during the last 40s of isometric contraction. Results showed that ATPase activity per unit of force was reduced by 17.2±4.1% in the isometric contractions after active stretch, compared to the purely isometric contraction at the corresponding lengths for both stretch magnitudes. Fibres stretched to an average sarcomere length of 3.2 μm showed a higher reduction in ATPase activity per unit of force compared to fibres stretched to an average sarcomere length of 2.8 μm (20.7±4.4 versus 12.4±3.2% respectively). Passive force enhancement was observed in all fibres and was correlated with the decrease in ATPase activity. No difference in stiffness was observed between reference and active stretch contractions. These results suggest that skeletal muscles become more efficient after stretch, either by increasing the amount of force produced per cross bridge or by engaging a passive element.
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Affiliation(s)
- V Joumaa
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Alta., Canada, T2N 1N4
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50
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de Tombe PP, ter Keurs HE. The velocity of cardiac sarcomere shortening: mechanisms and implications. J Muscle Res Cell Motil 2012; 33:431-7. [PMID: 22752243 PMCID: PMC3568939 DOI: 10.1007/s10974-012-9310-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Accepted: 06/11/2012] [Indexed: 10/28/2022]
Abstract
A classical paper published by Michael Barany almost 50 years ago demonstrated a tight correlation between the mechanical parameter of maximal velocity of shortening and the biochemical parameter of myosin ATPase activity in a wide spectrum of species. Here, we review the determinants of muscle dynamics by mechanical load and the relation between sarcomere shortening velocity and cross-bridge dynamics in rat myocardium containing a range of fast and slow myosin. Observations from molecular level to mechanics of the intact human heart suggest that cardiac actin-myosin kinetic properties are matched so as to optimize myocardial strain rate and allow for the maximum rate of hydraulic energy output observed during ejection in the whole ventricle.
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Affiliation(s)
- Pieter P. de Tombe
- Department of Cell and Molecular Physiology, Loyola University School of Medicine, 2160 South First Avenue, Maywood, IL 60153, USA
| | - Henk E.D.J. ter Keurs
- Department of Physiology/Biophysics, University of Calgary, 3280 Hospital Drive, NW, Calgary, Alberta, T2N 4Z6, Canada
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