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Saad NS, Mashali MA, Repas SJ, Janssen PML. Altering Calcium Sensitivity in Heart Failure: A Crossroads of Disease Etiology and Therapeutic Innovation. Int J Mol Sci 2023; 24:17577. [PMID: 38139404 PMCID: PMC10744146 DOI: 10.3390/ijms242417577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 12/14/2023] [Accepted: 12/15/2023] [Indexed: 12/24/2023] Open
Abstract
Heart failure (HF) presents a significant clinical challenge, with current treatments mainly easing symptoms without stopping disease progression. The targeting of calcium (Ca2+) regulation is emerging as a key area for innovative HF treatments that could significantly alter disease outcomes and enhance cardiac function. In this review, we aim to explore the implications of altered Ca2+ sensitivity, a key determinant of cardiac muscle force, in HF, including its roles during systole and diastole and its association with different HF types-HF with preserved and reduced ejection fraction (HFpEF and HFrEF, respectively). We further highlight the role of the two rate constants kon (Ca2+ binding to Troponin C) and koff (its dissociation) to fully comprehend how changes in Ca2+ sensitivity impact heart function. Additionally, we examine how increased Ca2+ sensitivity, while boosting systolic function, also presents diastolic risks, potentially leading to arrhythmias and sudden cardiac death. This suggests that strategies aimed at moderating myofilament Ca2+ sensitivity could revolutionize anti-arrhythmic approaches, reshaping the HF treatment landscape. In conclusion, we emphasize the need for precision in therapeutic approaches targeting Ca2+ sensitivity and call for comprehensive research into the complex interactions between Ca2+ regulation, myofilament sensitivity, and their clinical manifestations in HF.
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Affiliation(s)
- Nancy S. Saad
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH 43210, USA;
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Helwan University, Cairo 11795, Egypt
| | - Mohammed A. Mashali
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH 43210, USA;
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
- Department of Surgery, Faculty of Veterinary Medicine, Damanhour University, Damanhour 22514, Egypt
| | - Steven J. Repas
- Department of Emergency Medicine, Wright State University Boonshoft School of Medicine, Dayton, OH 45324, USA;
| | - Paul M. L. Janssen
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH 43210, USA;
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
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2
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Bishop SP, Zhang J, Ye L. Cardiomyocyte Proliferation from Fetal- to Adult- and from Normal- to Hypertrophy and Failing Hearts. Biology 2022; 11:880. [PMID: 35741401 PMCID: PMC9220194 DOI: 10.3390/biology11060880] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Revised: 05/26/2022] [Accepted: 06/02/2022] [Indexed: 11/20/2022]
Abstract
Simple Summary Death from injury to the heart from a variety of causes remains a major cause of mortality worldwide. The cardiomyocyte, the major contracting cell of the heart, is responsible for pumping blood to the rest of the body. During fetal development, these immature cardiomyocytes are small and rapidly divide to complete development of the heart by birth when they develop structural and functional characteristics of mature cells which prevent further division. All further growth of the heart after birth is due to an increase in the size of cardiomyocytes, hypertrophy. Following the loss of functional cardiomyocytes due to coronary artery occlusion or other causes, the heart is unable to replace the lost cells. One of the significant research goals has been to induce adult cardiomyocytes to reactivate the cell cycle and repair cardiac injury. This review explores the developmental, structural, and functional changes of the growing cardiomyocyte, and particularly the sarcomere, responsible for force generation, from the early fetal period of reproductive cell growth through the neonatal period and on to adulthood, as well as during pathological response to different forms of myocardial diseases or injury. Multiple issues relative to cardiomyocyte cell-cycle regulation in normal or diseased conditions are discussed. Abstract The cardiomyocyte undergoes dramatic changes in structure, metabolism, and function from the early fetal stage of hyperplastic cell growth, through birth and the conversion to hypertrophic cell growth, continuing to the adult stage and responding to various forms of stress on the myocardium, often leading to myocardial failure. The fetal cell with incompletely formed sarcomeres and other cellular and extracellular components is actively undergoing mitosis, organelle dispersion, and formation of daughter cells. In the first few days of neonatal life, the heart is able to repair fully from injury, but not after conversion to hypertrophic growth. Structural and metabolic changes occur following conversion to hypertrophic growth which forms a barrier to further cardiomyocyte division, though interstitial components continue dividing to keep pace with cardiac growth. Both intra- and extracellular structural changes occur in the stressed myocardium which together with hemodynamic alterations lead to metabolic and functional alterations of myocardial failure. This review probes some of the questions regarding conditions that regulate normal and pathologic growth of the heart.
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Santini L, Coppini R, Cerbai E. Ion Channel Impairment and Myofilament Ca 2+ Sensitization: Two Parallel Mechanisms Underlying Arrhythmogenesis in Hypertrophic Cardiomyopathy. Cells 2021; 10:2789. [PMID: 34685769 DOI: 10.3390/cells10102789] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 10/07/2021] [Accepted: 10/13/2021] [Indexed: 11/17/2022] Open
Abstract
Life-threatening ventricular arrhythmias are the main clinical burden in patients with hypertrophic cardiomyopathy (HCM), and frequently occur in young patients with mild structural disease. While massive hypertrophy, fibrosis and microvascular ischemia are the main mechanisms underlying sustained reentry-based ventricular arrhythmias in advanced HCM, cardiomyocyte-based functional arrhythmogenic mechanisms are likely prevalent at earlier stages of the disease. In this review, we will describe studies conducted in human surgical samples from HCM patients, transgenic animal models and human cultured cell lines derived from induced pluripotent stem cells. Current pieces of evidence concur to attribute the increased risk of ventricular arrhythmias in early HCM to different cellular mechanisms. The increase of late sodium current and L-type calcium current is an early observation in HCM, which follows post-translation channel modifications and increases the occurrence of early and delayed afterdepolarizations. Increased myofilament Ca2+ sensitivity, commonly observed in HCM, may promote afterdepolarizations and reentry arrhythmias with direct mechanisms. Decrease of K+-currents due to transcriptional regulation occurs in the advanced disease and contributes to reducing the repolarization-reserve and increasing the early afterdepolarizations (EADs). The presented evidence supports the idea that patients with early-stage HCM should be considered and managed as subjects with an acquired channelopathy rather than with a structural cardiac disease.
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Kanavy DM, McNulty SM, Jairath MK, Brnich SE, Bizon C, Powell BC, Berg JS. Comparative analysis of functional assay evidence use by ClinGen Variant Curation Expert Panels. Genome Med 2019; 11:77. [PMID: 31783775 PMCID: PMC6884856 DOI: 10.1186/s13073-019-0683-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 11/05/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The 2015 American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP) guidelines for clinical sequence variant interpretation state that "well-established" functional studies can be used as evidence in variant classification. These guidelines articulated key attributes of functional data, including that assays should reflect the biological environment and be analytically sound; however, details of how to evaluate these attributes were left to expert judgment. The Clinical Genome Resource (ClinGen) designates Variant Curation Expert Panels (VCEPs) in specific disease areas to make gene-centric specifications to the ACMG/AMP guidelines, including more specific definitions of appropriate functional assays. We set out to evaluate the existing VCEP guidelines for functional assays. METHODS We evaluated the functional criteria (PS3/BS3) of six VCEPs (CDH1, Hearing Loss, Inherited Cardiomyopathy-MYH7, PAH, PTEN, RASopathy). We then established criteria for evaluating functional studies based on disease mechanism, general class of assay, and the characteristics of specific assay instances described in the primary literature. Using these criteria, we extensively curated assay instances cited by each VCEP in their pilot variant classification to analyze VCEP recommendations and their use in the interpretation of functional studies. RESULTS Unsurprisingly, our analysis highlighted the breadth of VCEP-approved assays, reflecting the diversity of disease mechanisms among VCEPs. We also noted substantial variability between VCEPs in the method used to select these assays and in the approach used to specify strength modifications, as well as differences in suggested validation parameters. Importantly, we observed discrepancies between the parameters VCEPs specified as required for approved assay instances and the fulfillment of these requirements in the individual assays cited in pilot variant interpretation. CONCLUSIONS Interpretation of the intricacies of functional assays often requires expert-level knowledge of the gene and disease, and current VCEP recommendations for functional assay evidence are a useful tool to improve the accessibility of functional data by providing a starting point for curators to identify approved functional assays and key metrics. However, our analysis suggests that further guidance is needed to standardize this process and ensure consistency in the application of functional evidence.
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Affiliation(s)
- Dona M Kanavy
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Shannon M McNulty
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Meera K Jairath
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Sarah E Brnich
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Chris Bizon
- Renaissance Computing Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Bradford C Powell
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Jonathan S Berg
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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5
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Wijnker PJM, Sequeira V, Kuster DWD, Velden JVD. Hypertrophic Cardiomyopathy: A Vicious Cycle Triggered by Sarcomere Mutations and Secondary Disease Hits. Antioxid Redox Signal 2019; 31:318-358. [PMID: 29490477 PMCID: PMC6602117 DOI: 10.1089/ars.2017.7236] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Significance: Hypertrophic cardiomyopathy (HCM) is a cardiac genetic disease characterized by left ventricular hypertrophy, diastolic dysfunction, and myocardial disarray. Disease onset occurs between 20 and 50 years of age, thus affecting patients in the prime of their life. HCM is caused by mutations in sarcomere proteins, the contractile building blocks of the heart. Despite increased knowledge of causal mutations, the exact path from genetic defect leading to cardiomyopathy is complex and involves additional disease hits. Recent Advances: Laboratory-based studies indicate that HCM development not only depends on the primary sarcomere impairment caused by the mutation but also on secondary disease-related alterations in the heart. Here we propose a vicious mutation-induced disease cycle, in which a mutation-induced energy depletion alters cellular metabolism with increased mitochondrial work, which triggers secondary disease modifiers that will worsen disease and ultimately lead to end-stage HCM. Critical Issues: Evidence shows excessive cellular reactive oxygen species (ROS) in HCM patients and HCM animal models. Oxidative stress markers are increased in the heart (oxidized proteins, DNA, and lipids) and serum of HCM patients. In addition, increased mitochondrial ROS production and changes in endogenous antioxidants are reported in HCM. Mutant sarcomeric protein may drive excessive levels of cardiac ROS via changes in cardiac efficiency and metabolism, mitochondrial activation and/or dysfunction, impaired protein quality control, and microvascular dysfunction. Future Directions: Interventions restoring metabolism, mitochondrial function, and improved ROS balance may be promising therapeutic approaches. We discuss the effects of current HCM pharmacological therapies and potential future therapies to prevent and reverse HCM. Antioxid. Redox Signal. 31, 318-358.
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Affiliation(s)
- Paul J M Wijnker
- 1 Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, The Netherlands
| | - Vasco Sequeira
- 1 Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, The Netherlands
| | - Diederik W D Kuster
- 1 Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, The Netherlands
| | - Jolanda van der Velden
- 1 Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, The Netherlands.,2 Netherlands Heart Institute, Utrecht, The Netherlands
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Sequeira V, Bertero E, Maack C. Energetic drain driving hypertrophic cardiomyopathy. FEBS Lett 2019; 593:1616-1626. [PMID: 31209876 DOI: 10.1002/1873-3468.13496] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 06/07/2019] [Accepted: 06/13/2019] [Indexed: 01/09/2023]
Abstract
Hypertrophic cardiomyopathy (HCM) is the most common form of hereditary cardiomyopathy and is mainly caused by mutations of genes encoding cardiac sarcomeric proteins. HCM is characterized by hypertrophy of the left ventricle, frequently involving the septum, that is not explained solely by loading conditions. HCM has a heterogeneous clinical profile, but diastolic dysfunction and ventricular arrhythmias represent two dominant features of the disease. Preclinical evidence indicates that the enhanced Calcium (Ca2+ ) sensitivity of the myofilaments plays a key role in the pathophysiology of HCM. Notably, this is not always a direct consequence of sarcomeric mutations, but can also result from secondary mutation-driven alterations. Here, we review experimental and clinical evidence indicating that increased myofilament Ca2+ sensitivity lies upstream of numerous cellular derangements which potentially contribute to the progression of HCM toward heart failure and sudden cardiac death.
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Affiliation(s)
- Vasco Sequeira
- Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Germany
| | - Edoardo Bertero
- Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Germany
| | - Christoph Maack
- Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Germany
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Ishii S, Suzuki M, Ishiwata S, Kawai M. Functional significance of HCM mutants of tropomyosin, V95A and D175N, studied with in vitro motility assays. Biophys Physicobiol 2019; 16:28-40. [PMID: 30923661 PMCID: PMC6435021 DOI: 10.2142/biophysico.16.0_28] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 12/18/2018] [Indexed: 12/21/2022] Open
Abstract
The majority of hypertrophic cardiomyopathy (HCM) is caused by mutations in sarcomere proteins. We examined tropomyosin (Tpm)’s HCM mutants in humans, V95A and D175N, with in vitro motility assay using optical tweezers to evaluate the effects of the Tpm mutations on the actomyosin interaction at the single molecular level. Thin filaments were reconstituted using these Tpm mutants, and their sliding velocity and force were measured at varying Ca2+ concentrations. Our results indicate that the sliding velocity at pCa ≥8.0 was significantly increased in mutants, which is expected to cause a diastolic problem. The velocity that can be activated by Ca2+ decreased significantly in mutants causing a systolic problem. With sliding force, Ca2+ activatable force decreased in V95A and increased in D175N, which may cause a systolic problem. Our results further demonstrate that the duty ratio determined at the steady state of force generation in saturating [Ca2+] decreased in V95A and increased in D175N. The Ca2+ sensitivity and cooperativity were not significantly affected by the mutations. These results suggest that the two mutants modulate molecular processes of the actomyosin interaction differently, but to result in the same pathology known as HCM.
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Affiliation(s)
- Shuya Ishii
- Department of Physics, Faculty of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Madoka Suzuki
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan.,PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Shin'ichi Ishiwata
- Department of Physics, Faculty of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Masataka Kawai
- Department of Anatomy and Cell Biology, College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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Cohn R, Thakar K, Lowe A, Ladha FA, Pettinato AM, Romano R, Meredith E, Chen YS, Atamanuk K, Huey BD, Hinson JT. A Contraction Stress Model of Hypertrophic Cardiomyopathy due to Sarcomere Mutations. Stem Cell Reports 2018; 12:71-83. [PMID: 30554920 PMCID: PMC6335568 DOI: 10.1016/j.stemcr.2018.11.015] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 11/18/2018] [Accepted: 11/19/2018] [Indexed: 12/14/2022] Open
Abstract
Thick-filament sarcomere mutations are a common cause of hypertrophic cardiomyopathy (HCM), a disorder of heart muscle thickening associated with sudden cardiac death and heart failure, with unclear mechanisms. We engineered four isogenic induced pluripotent stem cell (iPSC) models of β-myosin heavy chain and myosin-binding protein C3 mutations, and studied iPSC-derived cardiomyocytes in cardiac microtissue assays that resemble cardiac architecture and biomechanics. All HCM mutations resulted in hypercontractility with prolonged relaxation kinetics in proportion to mutation pathogenicity, but not changes in calcium handling. RNA sequencing and expression studies of HCM models identified p53 activation, oxidative stress, and cytotoxicity induced by metabolic stress that can be reversed by p53 genetic ablation. Our findings implicate hypercontractility as a direct consequence of thick-filament mutations, irrespective of mutation localization, and the p53 pathway as a molecular marker of contraction stress and candidate therapeutic target for HCM patients.
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Affiliation(s)
- Rachel Cohn
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Drive, Farmington, CT 06032, USA
| | - Ketan Thakar
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Drive, Farmington, CT 06032, USA
| | - Andre Lowe
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Drive, Farmington, CT 06032, USA
| | - Feria A Ladha
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Drive, Farmington, CT 06032, USA; University of Connecticut School of Medicine, 263 Farmington Avenue, Farmington, CT 06032, USA
| | - Anthony M Pettinato
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Drive, Farmington, CT 06032, USA; University of Connecticut School of Medicine, 263 Farmington Avenue, Farmington, CT 06032, USA
| | - Robert Romano
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Drive, Farmington, CT 06032, USA; University of Connecticut School of Medicine, 263 Farmington Avenue, Farmington, CT 06032, USA
| | - Emily Meredith
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Drive, Farmington, CT 06032, USA; University of Connecticut School of Medicine, 263 Farmington Avenue, Farmington, CT 06032, USA
| | - Yu-Sheng Chen
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Drive, Farmington, CT 06032, USA
| | - Katherine Atamanuk
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA
| | - Bryan D Huey
- Department of Materials Science and Engineering, University of Connecticut, Storrs, CT 06269, USA
| | - J Travis Hinson
- The Jackson Laboratory for Genomic Medicine, 10 Discovery Drive, Farmington, CT 06032, USA; University of Connecticut School of Medicine, 263 Farmington Avenue, Farmington, CT 06032, USA.
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Cabassi A, Miragoli M. Altered Mitochondrial Metabolism and Mechanosensation in the Failing Heart: Focus on Intracellular Calcium Signaling. Int J Mol Sci 2017; 18:E1487. [PMID: 28698526 DOI: 10.3390/ijms18071487] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 06/28/2017] [Accepted: 07/04/2017] [Indexed: 12/26/2022] Open
Abstract
The heart consists of millions of cells, namely cardiomyocytes, which are highly organized in terms of structure and function, at both macroscale and microscale levels. Such meticulous organization is imperative for assuring the physiological pump-function of the heart. One of the key players for the electrical and mechanical synchronization and contraction is the calcium ion via the well-known calcium-induced calcium release process. In cardiovascular diseases, the structural organization is lost, resulting in morphological, electrical, and metabolic remodeling owing the imbalance of the calcium handling and promoting heart failure and arrhythmias. Recently, attention has been focused on the role of mitochondria, which seem to jeopardize these events by misbalancing the calcium processes. In this review, we highlight our recent findings, especially the role of mitochondria (dys)function in failing cardiomyocytes with respect to the calcium machinery.
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10
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Chung JH, Biesiadecki BJ, Ziolo MT, Davis JP, Janssen PML. Myofilament Calcium Sensitivity: Role in Regulation of In vivo Cardiac Contraction and Relaxation. Front Physiol 2016; 7:562. [PMID: 28018228 PMCID: PMC5159616 DOI: 10.3389/fphys.2016.00562] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 11/07/2016] [Indexed: 11/13/2022] Open
Abstract
Myofilament calcium sensitivity is an often-used indicator of cardiac muscle function, often assessed in disease states such as hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). While assessment of calcium sensitivity provides important insights into the mechanical force-generating capability of a muscle at steady-state, the dynamic behavior of the muscle cannot be sufficiently assessed with a force-pCa curve alone. The equilibrium dissociation constant (Kd) of the force-pCa curve depends on the ratio of the apparent calcium association rate constant (kon) and apparent calcium dissociation rate constant (koff) of calcium on TnC and as a stand-alone parameter cannot provide an accurate description of the dynamic contraction and relaxation behavior without the additional quantification of kon or koff, or actually measuring dynamic twitch kinetic parameters in an intact muscle. In this review, we examine the effect of length, frequency, and beta-adrenergic stimulation on myofilament calcium sensitivity and dynamic contraction in the myocardium, the effect of membrane permeabilization/mechanical- or chemical skinning on calcium sensitivity, and the dynamic consequences of various myofilament protein mutations with potential implications in contractile and relaxation behavior.
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Affiliation(s)
- Jae-Hoon Chung
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical CenterColumbus, OH, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical CenterColumbus, OH, USA; Medical Scientist Training Program and Biomedical Sciences Graduate Program, The Ohio State University Wexner Medical CenterColumbus, OH, USA
| | - Brandon J Biesiadecki
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical CenterColumbus, OH, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical CenterColumbus, OH, USA
| | - Mark T Ziolo
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical CenterColumbus, OH, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical CenterColumbus, OH, USA
| | - Jonathan P Davis
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical CenterColumbus, OH, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical CenterColumbus, OH, USA
| | - Paul M L Janssen
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical CenterColumbus, OH, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical CenterColumbus, OH, USA; Department of Internal Medicine, The Ohio State University Wexner Medical CenterColumbus, OH, USA
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11
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Miragoli M, Sanchez-Alonso JL, Bhargava A, Wright PT, Sikkel M, Schobesberger S, Diakonov I, Novak P, Castaldi A, Cattaneo P, Lyon AR, Lab MJ, Gorelik J. Microtubule-Dependent Mitochondria Alignment Regulates Calcium Release in Response to Nanomechanical Stimulus in Heart Myocytes. Cell Rep 2015; 14:140-151. [PMID: 26725114 PMCID: PMC4983655 DOI: 10.1016/j.celrep.2015.12.014] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 09/07/2015] [Accepted: 11/23/2015] [Indexed: 12/01/2022] Open
Abstract
Arrhythmogenesis during heart failure is a major clinical problem. Regional electrical gradients produce arrhythmias, and cellular ionic transmembrane gradients are its originators. We investigated whether the nanoscale mechanosensitive properties of cardiomyocytes from failing hearts have a bearing upon the initiation of abnormal electrical activity. Hydrojets through a nanopipette indent specific locations on the sarcolemma and initiate intracellular calcium release in both healthy and heart failure cardiomyocytes, as well as in human failing cardiomyocytes. In healthy cells, calcium is locally confined, whereas in failing cardiomyocytes, calcium propagates. Heart failure progressively stiffens the membrane and displaces sub-sarcolemmal mitochondria. Colchicine in healthy cells mimics the failing condition by stiffening the cells, disrupting microtubules, shifting mitochondria, and causing calcium release. Uncoupling the mitochondrial proton gradient abolished calcium initiation in both failing and colchicine-treated cells. We propose the disruption of microtubule-dependent mitochondrial mechanosensor microdomains as a mechanism for abnormal calcium release in failing heart. Nanomechanical pressure application changes mechanosensitivity in failing heart cells Microtubular network disorganization mediates the change in mechanosensitivity Mitochondria are displaced from their original location and trigger calcium release Uncoupling the mitochondrial proton gradient completely abolishes the phenomena
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Affiliation(s)
- Michele Miragoli
- National Heart and Lung Institute, Imperial College London, 4th floor, Imperial Centre for Translational and Experimental Medicine, Hammersmith Campus Du Cane Road, London W12 0NN, UK; Humanitas Clinical and Research Center, via Manzoni 56, Rozzano, 20090 Milan, Italy; Center of Excellence for Toxicological Research, INAIL exISPESL, University of Parma, via Gramsci 14, 43126 Parma, Italy.
| | - Jose L Sanchez-Alonso
- National Heart and Lung Institute, Imperial College London, 4th floor, Imperial Centre for Translational and Experimental Medicine, Hammersmith Campus Du Cane Road, London W12 0NN, UK
| | - Anamika Bhargava
- National Heart and Lung Institute, Imperial College London, 4th floor, Imperial Centre for Translational and Experimental Medicine, Hammersmith Campus Du Cane Road, London W12 0NN, UK; Department of Biotechnology, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram, 502205 Telangana, India
| | - Peter T Wright
- National Heart and Lung Institute, Imperial College London, 4th floor, Imperial Centre for Translational and Experimental Medicine, Hammersmith Campus Du Cane Road, London W12 0NN, UK
| | - Markus Sikkel
- National Heart and Lung Institute, Imperial College London, 4th floor, Imperial Centre for Translational and Experimental Medicine, Hammersmith Campus Du Cane Road, London W12 0NN, UK
| | - Sophie Schobesberger
- National Heart and Lung Institute, Imperial College London, 4th floor, Imperial Centre for Translational and Experimental Medicine, Hammersmith Campus Du Cane Road, London W12 0NN, UK
| | - Ivan Diakonov
- National Heart and Lung Institute, Imperial College London, 4th floor, Imperial Centre for Translational and Experimental Medicine, Hammersmith Campus Du Cane Road, London W12 0NN, UK
| | - Pavel Novak
- National Heart and Lung Institute, Imperial College London, 4th floor, Imperial Centre for Translational and Experimental Medicine, Hammersmith Campus Du Cane Road, London W12 0NN, UK; School of Engineering and Materials Science, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
| | - Alessandra Castaldi
- Humanitas Clinical and Research Center, via Manzoni 56, Rozzano, 20090 Milan, Italy
| | - Paola Cattaneo
- Humanitas Clinical and Research Center, via Manzoni 56, Rozzano, 20090 Milan, Italy
| | - Alexander R Lyon
- National Heart and Lung Institute, Imperial College London, 4th floor, Imperial Centre for Translational and Experimental Medicine, Hammersmith Campus Du Cane Road, London W12 0NN, UK; NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London SW36NP, UK
| | - Max J Lab
- National Heart and Lung Institute, Imperial College London, 4th floor, Imperial Centre for Translational and Experimental Medicine, Hammersmith Campus Du Cane Road, London W12 0NN, UK.
| | - Julia Gorelik
- National Heart and Lung Institute, Imperial College London, 4th floor, Imperial Centre for Translational and Experimental Medicine, Hammersmith Campus Du Cane Road, London W12 0NN, UK.
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Tanaka A, Yuasa S, Mearini G, Egashira T, Seki T, Kodaira M, Kusumoto D, Kuroda Y, Okata S, Suzuki T, Inohara T, Arimura T, Makino S, Kimura K, Kimura A, Furukawa T, Carrier L, Node K, Fukuda K. Endothelin-1 induces myofibrillar disarray and contractile vector variability in hypertrophic cardiomyopathy-induced pluripotent stem cell-derived cardiomyocytes. J Am Heart Assoc 2014; 3:e001263. [PMID: 25389285 PMCID: PMC4338713 DOI: 10.1161/jaha.114.001263] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BACKGROUND Despite the accumulating genetic and molecular investigations into hypertrophic cardiomyopathy (HCM), it remains unclear how this condition develops and worsens pathologically and clinically in terms of the genetic-environmental interactions. Establishing a human disease model for HCM would help to elucidate these disease mechanisms; however, cardiomyocytes from patients are not easily obtained for basic research. Patient-specific induced pluripotent stem cells (iPSCs) potentially hold much promise for deciphering the pathogenesis of HCM. The purpose of this study is to elucidate the interactions between genetic backgrounds and environmental factors involved in the disease progression of HCM. METHODS AND RESULTS We generated iPSCs from 3 patients with HCM and 3 healthy control subjects, and cardiomyocytes were differentiated. The HCM pathological phenotypes were characterized based on morphological properties and high-speed video imaging. The differences between control and HCM iPSC-derived cardiomyocytes were mild under baseline conditions in pathological features. To identify candidate disease-promoting environmental factors, the cardiomyocytes were stimulated by several cardiomyocyte hypertrophy-promoting factors. Interestingly, endothelin-1 strongly induced pathological phenotypes such as cardiomyocyte hypertrophy and intracellular myofibrillar disarray in the HCM iPSC-derived cardiomyocytes. We then reproduced these phenotypes in neonatal cardiomyocytes from the heterozygous Mybpc3-targeted knock in mice. High-speed video imaging with motion vector prediction depicted physiological contractile dynamics in the iPSC-derived cardiomyocytes, which revealed that self-beating HCM iPSC-derived single cardiomyocytes stimulated by endothelin-1 showed variable contractile directions. CONCLUSIONS Interactions between the patient's genetic backgrounds and the environmental factor endothelin-1 promote the HCM pathological phenotype and contractile variability in the HCM iPSC-derived cardiomyocytes.
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Affiliation(s)
- Atsushi Tanaka
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.) Department of Cardiovascular Medicine, Saga University, Saga, Japan (A.T., K.N.)
| | - Shinsuke Yuasa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.)
| | - Giulia Mearini
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany (G.M., L.C.) DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Germany (G.M., L.C.)
| | - Toru Egashira
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.)
| | - Tomohisa Seki
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.)
| | - Masaki Kodaira
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.)
| | - Dai Kusumoto
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.)
| | - Yusuke Kuroda
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.)
| | - Shinichiro Okata
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.) Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan (S.O., T.F.)
| | - Tomoyuki Suzuki
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.)
| | - Taku Inohara
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.)
| | - Takuro Arimura
- Department of Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan (T.A., A.K.)
| | - Shinji Makino
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.)
| | - Kensuke Kimura
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.)
| | - Akinori Kimura
- Department of Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan (T.A., A.K.)
| | - Tetsushi Furukawa
- Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan (S.O., T.F.)
| | - Lucie Carrier
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany (G.M., L.C.) DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Germany (G.M., L.C.)
| | - Koichi Node
- Department of Cardiovascular Medicine, Saga University, Saga, Japan (A.T., K.N.)
| | - Keiichi Fukuda
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan (A.T., S.Y., T.E., T.S., M.K., D.K., Y.K., S.O., T.S., T.I., S.M., K.K., K.F.)
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13
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Abstract
Stem cell differentiation into a variety of lineages is known to involve signaling from the extracellular niche, including from the physical properties of that environment. What regulates stem cell responses to these cues is there ability to activate different mechanotransductive pathways. Here, we will review the structures and pathways that regulate stem cell commitment to a cardiomyocyte lineage, specifically examining proteins within muscle sarcomeres, costameres, and intercalated discs. Proteins within these structures stretch, inducing a change in their phosphorylated state or in their localization to initiate different signals. We will also put these changes in the context of stem cell differentiation into cardiomyocytes, their subsequent formation of the chambered heart, and explore negative signaling that occurs during disease.
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Affiliation(s)
- Gaurav Kaushik
- Department of Bioengineering, University of California, San Diego, La Jolla, California, USA
| | - Adam J Engler
- Department of Bioengineering, University of California, San Diego, La Jolla, California, USA
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14
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Chuan P, Sivaramakrishnan S, Ashley EA, Spudich JA. Cell-intrinsic functional effects of the α-cardiac myosin Arg-403-Gln mutation in familial hypertrophic cardiomyopathy. Biophys J 2012; 102:2782-90. [PMID: 22735528 DOI: 10.1016/j.bpj.2012.04.049] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Revised: 04/02/2012] [Accepted: 04/13/2012] [Indexed: 01/27/2023] Open
Abstract
Human familial hypertrophic cardiomyopathy is the most common Mendelian cardiovascular disease worldwide. Among the most severe presentations of the disease are those in families heterozygous for the mutation R403Q in β-cardiac myosin. Mice heterozygous for this mutation in the α-cardiac myosin isoform display typical familial hypertrophic cardiomyopathy pathology. Here, we study cardiomyocytes from heterozygous 403/+ mice. The effects of the R403Q mutation on force-generating capabilities and dynamics of cardiomyocytes were investigated using a dual carbon nanofiber technique to measure single-cell parameters. We demonstrate the Frank-Starling effect at the single cardiomyocyte level by showing that cell stretch causes an increase in amplitude of contraction. Mutant 403/+ cardiomyocytes exhibit higher end-diastolic and end-systolic stiffness than +/+ cardiomyocytes, whereas active force generation capabilities remain unchanged. Additionally, 403/+ cardiomyocytes show slowed relaxation dynamics. These phenotypes are consistent with increased end-diastolic and end-systolic chamber elastance, as well as diastolic dysfunction seen at the level of the whole heart. Our results show that these functional effects of the R403Q mutation are cell-intrinsic, a property that may be a general phenomenon in familial hypertrophic cardiomyopathy.
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Affiliation(s)
- Peiying Chuan
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California, USA
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15
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Bai F, Weis A, Takeda AK, Chase PB, Kawai M. Enhanced active cross-bridges during diastole: molecular pathogenesis of tropomyosin's HCM mutations. Biophys J 2011; 100:1014-23. [PMID: 21320446 DOI: 10.1016/j.bpj.2011.01.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Revised: 12/22/2010] [Accepted: 01/03/2011] [Indexed: 11/28/2022] Open
Abstract
Three HCM-causing tropomyosin (Tm) mutants (V95A, D175N, and E180G) were examined using the thin-filament extraction and reconstitution technique. The effects of Ca(2+), ATP, phosphate, and ADP concentrations on cross-bridge kinetics in myocardium reconstituted with each of these mutants were studied at 25°C, and compared to wild-type (WT) Tm at physiological ionic strength (200 mM). All three mutants showed significantly higher (2-3.5 fold) low Ca(2+) tension (T(LC)) and stiffness than WT at pCa 8.0. High Ca(2+) tension (T(HC)) was significantly higher for E180G than that for WT, whereas T(HC) of V95A and D175N was similar to WT; high Ca(2+) stiffness (Y(HC)) had the same trend. The Ca(2+) sensitivity of isometric force was significantly greater for V95A and E180G than for WT, whereas that of D175N remained the same as for WT; for all mutants, cooperativity was lower than for WT. Nine kinetic constants and the cross-bridge distribution were deduced using sinusoidal analysis. The number of force-generating cross bridges was similar among the D175N, E180G, and WT Tm forms, but it was significantly larger in the case of V95A than WT. We conclude that the increased number of actively cycling cross bridges at pCa 8 is the major cause of Tm mutation-related HCM pathogenesis, which may result in diastolic dysfunction. Decreased contractility (T(act)) in V95A and D175N may further contribute to the severity of myocyte hypertrophy and related prognosis of the disease.
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Affiliation(s)
- Fan Bai
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa, USA
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16
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Davis J, Metzger JM. Combinatorial effects of double cardiomyopathy mutant alleles in rodent myocytes: a predictive cellular model of myofilament dysregulation in disease. PLoS One 2010; 5:e9140. [PMID: 20161772 PMCID: PMC2818843 DOI: 10.1371/journal.pone.0009140] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Accepted: 01/19/2010] [Indexed: 12/05/2022] Open
Abstract
Inherited cardiomyopathy (CM) represents a diverse group of cardiac muscle diseases that present with a broad spectrum of symptoms ranging from benign to highly malignant. Contributing to this genetic complexity and clinical heterogeneity is the emergence of a cohort of patients that are double or compound heterozygotes who have inherited two different CM mutant alleles in the same or different sarcomeric gene. These patients typically have early disease onset with worse clinical outcomes. Little experimental attention has been directed towards elucidating the physiologic basis of double CM mutations at the cellular-molecular level. Here, dual gene transfer to isolated adult rat cardiac myocytes was used to determine the primary effects of co-expressing two different CM-linked mutant proteins on intact cardiac myocyte contractile physiology. Dual expression of two CM mutants, that alone moderately increase myofilament activation, tropomyosin mutant A63V and cardiac troponin mutant R146G, were shown to additively slow myocyte relaxation beyond either mutant studied in isolation. These results were qualitatively similar to a combination of moderate and strong activating CM mutant alleles alphaTmA63V and cTnI R193H, which approached a functional threshold. Interestingly, a combination of a CM myofilament deactivating mutant, troponin C G159D, together with an activating mutant, cTnIR193H, produced a hybrid phenotype that blunted the strong activating phenotype of cTnIR193H alone. This is evidence of neutralizing effects of activating/deactivating mutant alleles in combination. Taken together, this combinatorial mutant allele functional analysis lends molecular insight into disease severity and forms the foundation for a predictive model to deconstruct the myriad of possible CM double mutations in presenting patients.
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Affiliation(s)
- Jennifer Davis
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Joseph M. Metzger
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, Minnesota, United States of America
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17
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Pacak CA, Sakai Y, Thattaliyath BD, Mah CS, Byrne BJ. Tissue specific promoters improve specificity of AAV9 mediated transgene expression following intra-vascular gene delivery in neonatal mice. Genet Vaccines Ther 2008; 6:13. [PMID: 18811960 PMCID: PMC2557000 DOI: 10.1186/1479-0556-6-13] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2008] [Accepted: 09/23/2008] [Indexed: 01/11/2023]
Abstract
The AAV9 capsid displays a high natural affinity for the heart following a single intravenous (IV) administration in both newborn and adult mice. It also results in substantial albeit relatively lower expression levels in many other tissues. To increase the overall safety of this gene delivery method we sought to identify which one of a group of promoters is able to confer the highest level of cardiac specific expression and concurrently, which is able to provide a broad biodistribution of expression across both cardiac and skeletal muscle. The in vivo behavior of five different promoters was compared: CMV, desmin (Des), alpha-myosin heavy chain (α-MHC), myosin light chain 2 (MLC-2) and cardiac troponin C (cTnC). Following IV administration to newborn mice, LacZ expression was measured by enzyme activity assays. Results showed that rAAV2/9-mediated gene delivery using the α-MHC promoter is effective for focal transgene expression in the heart and the Des promoter is highly suitable for achieving gene expression in cardiac and skeletal muscle following systemic vector administration. Importantly, these promoters provide an added layer of control over transgene activity following systemic gene delivery.
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Affiliation(s)
- Christina A Pacak
- Powell Gene Therapy Center, College of Medicine, University of Florida, 1600 SW Archer Road, Gainesville, FL 32610-0266, USA
| | - Yoshihisa Sakai
- Powell Gene Therapy Center, College of Medicine, University of Florida, 1600 SW Archer Road, Gainesville, FL 32610-0266, USA
| | - Bijoy D Thattaliyath
- Powell Gene Therapy Center, College of Medicine, University of Florida, 1600 SW Archer Road, Gainesville, FL 32610-0266, USA
| | - Cathryn S Mah
- Powell Gene Therapy Center, College of Medicine, University of Florida, 1600 SW Archer Road, Gainesville, FL 32610-0266, USA
| | - Barry J Byrne
- Powell Gene Therapy Center, College of Medicine, University of Florida, 1600 SW Archer Road, Gainesville, FL 32610-0266, USA
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18
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Palmer BM, Wang Y, Teekakirikul P, Hinson JT, Fatkin D, Strouse S, Vanburen P, Seidman CE, Seidman JG, Maughan DW. Myofilament mechanical performance is enhanced by R403Q myosin in mouse myocardium independent of sex. Am J Physiol Heart Circ Physiol 2008; 294:H1939-47. [PMID: 18281382 DOI: 10.1152/ajpheart.00644.2007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Male but not female mice carrying a single R403Q missense allele for cardiac alpha-myosin heavy chain (M-alphaMHC(R403Q/+) and F-alphaMHC(R403Q/+), respectively) develop significant hypertrophic cardiomyopathy (HCM) compared with male and female wild-type mice (M-alphaMHC(+/+) and F-alphaMHC(+/+), respectively) after approximately 30 wk of age. We tested the hypothesis that myofilament mechanical performance differs between M-alphaMHC(R403Q/+) and F-alphaMHC(R403Q/+) at younger ages (10-20 wk) and could account for sex differences in HCM development. The sensitivity of chemically skinned myocardial strips to Ca(2+) activation (pCa(50)) was significantly (P < 0.05) enhanced in male mice independent of genotype (M-alphaMHC(R403Q/+): 5.70 +/- 0.06, M-alphaMHC(+/+): 5.63 +/- 0.05, F-alphaMHC(R403Q/+): 5.57 +/- 0.03, F-alphaMHC(+/+): 5.54 +/- 0.04) by two-way ANOVA, whereas maximum developed tension was significantly enhanced in alpha-MHC(R403Q/+) independent of sex (M-alphaMHC(R403Q/+): 29.3 +/- 2.3, M-alphaMHC(+/+): 26.0 +/- 1.4, F-alphaMHC(R403Q/+): 30.2 +/- 2.1, F-alphaMHC(+/+): 26.2 +/- 1.2 mN/mm(2)). The frequency of maximum work generated by sinusoidal length perturbation was significantly higher in alphaMHC(R403Q/+) mice than in sex-matched controls (M-alphaMHC(R403Q/+): 2.26 +/- 0.47, M-alphaMHC(+/+): 1.29 +/- 0.18, F-alphaMHC(R403Q/+): 3.21 +/- 0.33, F-alphaMHC(+/+): 2.52 +/- 0.36 Hz). Unloaded shortening velocity was significantly enhanced in alphaMHC(R403Q/+) and in female mice (M-alphaMHC(R403Q/+): 2.26 +/- 0.47, M-alphaMHC(+/+): 1.29 +/- 0.18, F-alphaMHC(R403Q/+): 3.21 +/- 0.33, F-alphaMHC(+/+): 2.52 +/- 0.36 muscle lengths/s), and normalized mechanical power, calculated from the tension-velocity relationship, was significantly enhanced in alphaMHC(R403Q/+) independent of sex (M-alphaMHC(R403Q/+): 60 +/- 2 10(-3), M-alphaMHC(+/+): 37 +/- 3 10(-3), F-alphaMHC(R403Q/+): 57 +/- 3 10(-3), F-alphaMHC(+/+) 25 +/- 3 10(-3) muscle lengths/s x normalized tension). We did not find a statistically significant sex x mutation interaction for any measure of myofilament performance. Therefore, sarcomeric incorporation of the R403Q myosin similarly enhanced left ventricular myofilament mechanical performance in both male and female mice. The sex-dependent development of HCM due to the R403Q myosin may then be inhibited by female sex hormones, which may additionally underlie the observed sex differences for pCa(50) and unloaded shortening velocity.
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Affiliation(s)
- Bradley M Palmer
- Dept. of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA.
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19
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Volkmann N, Lui H, Hazelwood L, Trybus KM, Lowey S, Hanein D. The R403Q myosin mutation implicated in familial hypertrophic cardiomyopathy causes disorder at the actomyosin interface. PLoS One 2007; 2:e1123. [PMID: 17987111 PMCID: PMC2040505 DOI: 10.1371/journal.pone.0001123] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Accepted: 10/04/2007] [Indexed: 11/29/2022] Open
Abstract
Background Mutations in virtually all of the proteins comprising the cardiac muscle sarcomere have been implicated in causing Familial Hypertrophic Cardiomyopathy (FHC). Mutations in the β-myosin heavy chain (MHC) remain among the most common causes of FHC, with the widely studied R403Q mutation resulting in an especially severe clinical prognosis. In vitro functional studies of cardiac myosin containing the R403Q mutation have revealed significant changes in enzymatic and mechanical properties compared to wild-type myosin. It has been proposed that these molecular changes must trigger events that ultimately lead to the clinical phenotype. Principal Findings Here we examine the structural consequences of the R403Q mutation in a recombinant smooth muscle myosin subfragment (S1), whose kinetic features have much in common with slow β-MHC. We obtained three-dimensional reconstructions of wild-type and R403Q smooth muscle S1 bound to actin filaments in the presence (ADP) and absence (apo) of nucleotide by electron cryomicroscopy and image analysis. We observed that the mutant S1 was attached to actin at highly variable angles compared to wild-type reconstructions, suggesting a severe disruption of the actin-myosin interaction at the interface. Significance These results provide structural evidence that disarray at the molecular level may be linked to the histopathological myocyte disarray characteristic of the diseased state.
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Affiliation(s)
- Niels Volkmann
- Burnham Institute for Medical Research, La Jolla, California, United States of America
| | - HongJun Lui
- Burnham Institute for Medical Research, La Jolla, California, United States of America
| | - Larnele Hazelwood
- Burnham Institute for Medical Research, La Jolla, California, United States of America
| | - Kathleen M. Trybus
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont, United States of America
| | - Susan Lowey
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont, United States of America
- * To whom correspondence should be addressed. E-mail: (SL); (DH)
| | - Dorit Hanein
- Burnham Institute for Medical Research, La Jolla, California, United States of America
- * To whom correspondence should be addressed. E-mail: (SL); (DH)
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20
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Davis J, Wen H, Edwards T, Metzger JM. Thin Filament Disinhibition by Restrictive Cardiomyopathy Mutant R193H Troponin I Induces Ca
2+
-Independent Mechanical Tone and Acute Myocyte Remodeling. Circ Res 2007; 100:1494-502. [PMID: 17463320 DOI: 10.1161/01.res.0000268412.34364.50] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Inherited restrictive cardiomyopathy (RCM) is a debilitating disease characterized by a stiff heart with impaired ventricular relaxation. Mutations in cardiac troponin I (cTnI) were identified as causal for RCM. Acute genetic engineering of adult cardiac myocytes was used to identify primary structure/function effects of mutant cTnI. Studies focused on R193H cTnI owing to the poor prognosis of this allele. Compared with wild-type cTnI, R193H mutant cTnI more effectively incorporated into the sarcomere, where it exerted dose-dependent effects on basal and dynamic contractile function. Under loaded conditions, permeabilized myocyte Ca
2+
sensitivity of tension was increased, whereas the passive tension–extension relationship was not altered by R193H cTnI. Normal rod-shaped myocyte morphology acutely transitioned to a “short-squat” phenotype in concert with progressive stoichiometric incorporation of R193H in the absence of altered diastolic Ca
2+
. The specific myosin inhibitor blebbistatin fully blocked this transition. Heightened Ca
2+
buffering by the R193H myofilaments, and not alterations in Ca
2+
handling by the sarcoplasmic reticulum, slowed the decay rate of the Ca
2+
transient. Incomplete mechanical relaxation conferred by R193H was exacerbated at increasing pacing frequencies independent of elevated diastolic Ca
2+
. R193H cTnI–dependent mechanical tone caused acute remodeling to a quasicontracted state not elicited by other Ca
2+
-sensitizing proteins and is a direct correlate of the stiff heart characteristic of RCM in vivo. These results point toward targets downstream of Ca
2+
handling, notably thin filament regulation and actin–myosin interaction, in designing therapeutic strategies to redress the primary cell morphological and mechanical underpinnings of RCM.
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Affiliation(s)
- Jennifer Davis
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
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21
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Linz P, Amann K, Freisinger W, Ditting T, Hilgers KF, Veelken R. Sensory neurons with afferents from hind limbs: enhanced sensitivity in secondary hypertension. Hypertension 2006; 47:527-31. [PMID: 16401763 DOI: 10.1161/01.hyp.0000199984.78039.36] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Sensory nerve fibers from the dorsal root ganglia (DRG) may contribute to the regulation of peripheral vascular resistance. Axons of DRG neurons of the lower thoracic cord project mainly to resistance vessels in the lower limbs, likely opposing the vasoconstrictor effects of the sympathetic activity. This mechanism might be of importance in hypertension with increased sympathetic activity. We tested the hypothesis that sensory neurons of the DRG in the lower thoracic cord show an altered sensitivity to mechanical stimuli in hypertension. Neurons from DRG (T11 to L1) of rats with hypertension (2 kidney-1 clip hypertensive rats and 5 of 6 nephrectomized rats) were cultured on coverslips. Current time relationships were established with whole-cell patch recordings. Cells were characterized under control conditions and after exposure to hypoosmotic solutions to induce mechanical stress. Neurons with projections to the kidney were studied for comparison. The hypoosmotic extracellular medium induced a significant change in conductance of the cells in all of the groups of rats. In hypertensive rats, responses of cells with hindlimb axons were significantly different from controls: (2 kidney-1 clip hypertensives: delta-351+/-52 pA and 5 of 6 nephrectomized rats: delta-372+/-43 pA versus controls: delta-190+/-25 pA; P<0.05). Responses of DRG cells with renal afferents to mechanical stress were unaffected. Neurons from DRG in the lower thoracic cord with projections to the lower limbs exhibited an increased sensitivity to mechanical stress. We speculate that this observation may indicate an increased activity of these neurons, their axons, and neurotransmitters in the control of resistance vessels in hypertension.
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Affiliation(s)
- Peter Linz
- Department of Internal Medicine 4/Nephrology and Hypertension, University of Erlangen-Nürnberg, Erlangen, Germany
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22
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Palmer BM, Fishbaugher DE, Schmitt JP, Wang Y, Alpert NR, Seidman CE, Seidman JG, VanBuren P, Maughan DW. Differential cross-bridge kinetics of FHC myosin mutations R403Q and R453C in heterozygous mouse myocardium. Am J Physiol Heart Circ Physiol 2004; 287:H91-9. [PMID: 15001446 DOI: 10.1152/ajpheart.01015.2003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The kinetic effects of the cardiac myosin point mutations R403Q and R453C, which underlie lethal forms of familial hypertrophic cardiomyopathy (FHC), were assessed using isolated myosin and skinned strips taken from heterozygous (R403Q/+ and R453C/+) male mouse hearts. Compared with wild-type (WT) mice, actin-activated ATPase was increased by 38% in R403Q/+ and reduced by 45% in R453C/+, maximal velocity of regulated thin filament ( VRTF) in the in vitro motility assay was increased by 8% in R403Q/+ and was not different in R453C/+, myosin concentration at half-maximal VRTF was reduced by 30% in R403Q/+ and not different in R453C/+, and the characteristic frequency for oscillatory work production ( b frequency), determined by sinusoidal analysis in the skinned strip at maximal calcium activation, was 27% lower in R403Q/+ and 18% higher in R453C/+. The calcium sensitivity for isometric tension in the skinned strip was not different in R403Q/+ (pCa50 5.64 ± 0.02) and significantly enhanced in R453C/+ (5.82 ± 0.03) compared with WT (5.58 ± 0.02). We conclude that isolated myosin and skinned strips of R403Q/+ and R453C/+ myocardium show marked differences in cross-bridge kinetic parameters and in calcium sensitivity of force production that indicate different functional roles associated with the location of each point mutation at the molecular level.
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Affiliation(s)
- Bradley M Palmer
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA.
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23
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Olsson MC, Palmer BM, Stauffer BL, Leinwand LA, Moore RL. Morphological and functional alterations in ventricular myocytes from male transgenic mice with hypertrophic cardiomyopathy. Circ Res 2003; 94:201-7. [PMID: 14670849 DOI: 10.1161/01.res.0000111521.40760.18] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Familial hypertrophic cardiomyopathy (FHC) is a human genetic disorder caused by mutations in sarcomeric proteins. It is generally characterized by cardiac hypertrophy, fibrosis, and myocyte disarray. A transgenic mouse model of FHC with mutations in the actin-binding domain of the alpha-myosin heavy chain (MyHC) gene displays many phenotypes similar to human FHC. At 4 months, male transgenic (TG) mice present with concentric cardiac hypertrophy that progresses to dilation with age. Accompanying this latter morphological change is systolic and diastolic dysfunction. Left ventricular (LV) myocytes from male TG and wild-type (WT) littermates at 5 and 12 months of age were isolated and used for morphological and functional studies. Myocytes from 5- and 12-month-old TG animals had shorter sarcomere lengths compared with WT. This sarcomere length difference was abolished in the presence of 2,3-butanedione monoxime, suggesting that the basal level of contractile element activation was increased in TG myocytes. Myocytes from 12-month-old TG mice were significantly longer than those from age-matched WT controls, and TG myocytes exhibited Z-band disorganization. When cells were paced at 0.5 Hz, TG myocyte relengthening and the fall in intracellular [Ca2+] were slowed when compared with cells from age-matched WT controls. Moreover, an increased amount of beta-myosin heavy chain protein was found in hearts from TG compared with WT. Thus, myocytes from the alpha-MyHC TG mouse model display many morphological and functional abnormalities that may help explain the LV dysfunction seen in this TG mouse model of FHC.
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MESH Headings
- Age Factors
- Amino Acid Substitution
- Animals
- Calcium/metabolism
- Cardiomyopathy, Hypertrophic, Familial/pathology
- Cardiomyopathy, Hypertrophic, Familial/physiopathology
- Diacetyl/analogs & derivatives
- Diacetyl/pharmacology
- Diastole
- Gene Expression
- Heart Ventricles/cytology
- Male
- Mice
- Mice, Transgenic
- Microscopy, Electron
- Models, Animal
- Mutation, Missense
- Myocardial Contraction
- Myocytes, Cardiac/physiology
- Myocytes, Cardiac/ultrastructure
- Myosin Heavy Chains/genetics
- Phenotype
- Protein Isoforms/biosynthesis
- Protein Isoforms/genetics
- Sarcomeres/ultrastructure
- Systole
- Ventricular Dysfunction, Left/pathology
- Ventricular Dysfunction, Left/physiopathology
- Ventricular Myosins/biosynthesis
- Ventricular Myosins/genetics
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Affiliation(s)
- M Charlotte Olsson
- Department of Integrative Physiology, University of Colorado, Boulder, Colo 80309-0354, USA
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24
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Abstract
A new system for studying mechanical activity of freshly isolated cardiac myocytes from up to four experimental groups simultaneously is described. Suspensions of cardiac myocytes isolated from adult rat hearts were drawn into microhematocrit capillary tubes, which were then mounted in parallel fashion between two four-channel tubing manifolds placed on the movable stage of an inverted microscope. Within a few minutes, cells settled and attached to the bottom of the tubes and then could be superfused with various test solutions. The system allowed for electrical field stimulation, rapid changes in bathing solutions, control of temperature, and simulation of ischemia and reperfusion with measurements of the effects of such interventions on both populations of cells (low power survey) and individual myocytes (high power). Myocyte responses to these various interventions are described. The primary advantage of this system is the ability to conduct experiments on cardiac myocytes isolated concurrently from multiple experimental groups at the same time and under identical conditions.
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Affiliation(s)
- Lois Jane Heller
- Department of Physiology, School of Medicine, University of Minnesota-Duluth, 1035 University Drive, Duluth, MN 55812, USA.
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25
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Semsarian C, Ahmad I, Giewat M, Georgakopoulos D, Schmitt JP, McConnell BK, Reiken S, Mende U, Marks AR, Kass DA, Seidman CE, Seidman JG. The L-type calcium channel inhibitor diltiazem prevents cardiomyopathy in a mouse model. J Clin Invest 2002; 109:1013-20. [PMID: 11956238 PMCID: PMC150949 DOI: 10.1172/jci14677] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Dominant mutations in sarcomere protein genes cause hypertrophic cardiomyopathy, an inherited human disorder with increased ventricular wall thickness, myocyte hypertrophy, and disarray. To understand the early consequences of mutant sarcomere proteins, we have studied mice (designated alphaMHC(403/+)) bearing an Arg403Gln missense mutation in the alpha cardiac myosin heavy chain. We demonstrate that Ca(2+) is reduced in the sarcoplasmic reticulum of alphaMHC(403/+) mice, and levels of the sarcoplasmic reticulum Ca(2+)-binding protein calsequestrin are diminished in advance of changes in cardiac histology or morphology. Further evidence for dysregulation of sarcoplasmic reticulum Ca(2+) in these animals is seen in their decreased expression of the ryanodine receptor Ca(2+)-release channel and its associated membrane proteins and in an increase in ryanodine receptor phosphorylation. Early administration of the L-type Ca(2+) channel inhibitor diltiazem restores normal levels of these sarcoplasmic reticular proteins and prevents the development of pathology in alphaMHC(403/+) mice. We conclude that disruption of sarcoplasmic reticulum Ca(2+) homeostasis is an important early event in the pathogenesis of this disorder and suggest that the use of Ca(2+) channel blockers in advance of established clinical disease could prevent hypertrophic cardiomyopathy caused by sarcomere protein gene mutations.
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MESH Headings
- Animals
- Calcium/metabolism
- Calcium Channel Blockers/pharmacology
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/metabolism
- Calsequestrin/metabolism
- Cardiomyopathy, Hypertrophic, Familial/genetics
- Cardiomyopathy, Hypertrophic, Familial/metabolism
- Cardiomyopathy, Hypertrophic, Familial/pathology
- Cardiomyopathy, Hypertrophic, Familial/prevention & control
- Diltiazem/pharmacology
- Disease Models, Animal
- Humans
- Mice
- Mice, Mutant Strains
- Mutation, Missense
- Myocardium/pathology
- Myosin Heavy Chains/genetics
- Ventricular Myosins/genetics
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Affiliation(s)
- Christopher Semsarian
- Department of Genetics, Howard Hughes Medical Institute and Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
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26
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Hardt SE, Geng YJ, Montagne O, Asai K, Hong C, Yang GP, Bishop SP, Kim SJ, Vatner DE, Seidman CE, Seidman JG, Homcy CJ, Vatner SF. Accelerated cardiomyopathy in mice with overexpression of cardiac G(s)alpha and a missense mutation in the alpha-myosin heavy chain. Circulation 2002; 105:614-20. [PMID: 11827928 DOI: 10.1161/hc0502.103012] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND To understand further the pathogenesis of familial hypertrophic cardiomyopathy, we determined how the cardiomyopathy induced by an Arg403-->Gln missense mutation in the alpha-myosin heavy chain (403) is affected by chronically enhancing sympathetic drive by mating the mice with those overexpressing G(s)alpha (G(s)alpha x403). METHODS AND RESULTS Heart rate in 3-month-old conscious mice was elevated similarly (P<0.05) in mice overexpressing G(s)alpha (G(s)alpha mice; 746 +/- 14 bpm) and G(s)alpha x403 mice (718+/- 19 bpm) compared with littermate wild-type mice (WT; 623+/- 18 bpm) and 403 mice (594+/- 16 bpm). Left ventricular ejection fraction (LVEF), as determined by echocardiography, was enhanced in G(s)alpha x403 mice (88+/- 1%, P<0.001) compared with WT (69+/- 1%), 403 (75+/- 1%), and G(s)alpha (69 +/- 2%) mice. Isolated cardiomyocytes from G(s)alpha x403 mice also exhibited higher (P<0.001) baseline percent contraction (11.9+/- 0.5%) than WT (7.0+/- 0.5%), 403 (5.5+/- 0.5%), and G(s)alpha (7.8+/- 0.3%) cardiomyocytes. Relaxation of myocytes was impaired in 403 mice compared with WT but enhanced in G(s)alpha and normalized in G(s)alpha x403 mice. This was also observed in vivo. In vivo isoproterenol (0.1 microgram . kg(-1) . min(-1)) increased LVEF to maximal levels in G(s)alpha x403 and G(s)alpha, whereas in 403, the response was attenuated compared with WT. At 10 months of age, G(s)alpha x403 had significantly depressed LVEF (57 +/- 4%). Histopathological examination demonstrated that myocyte hypertrophy and fibrosis were already present in young G(s)alpha x403 mice and that old animals had severe cardiomyopathy. By 15 months of age, the survival of G(s)alpha x403 was 0% compared with 100% for WT, 71% for G(s)alpha, and 100% for 403 mice (P<0.05). CONCLUSIONS These results show that the cardiomyopathy developed by G(s)alpha x403 mice is synergistic rather than additive, most likely owing to the elevated baseline function combined with enhanced responsiveness to sympathetic stimulation.
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MESH Headings
- Animals
- Body Weight
- Cardiomyopathy, Hypertrophic, Familial/genetics
- Cardiomyopathy, Hypertrophic, Familial/metabolism
- Cardiomyopathy, Hypertrophic, Familial/pathology
- Cell Separation
- Crosses, Genetic
- Disease Models, Animal
- Disease Progression
- Echocardiography
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- GTP-Binding Protein alpha Subunits, Gs/genetics
- GTP-Binding Protein alpha Subunits, Gs/metabolism
- Heart Rate/genetics
- In Vitro Techniques
- Mice
- Mice, Transgenic
- Mutation, Missense
- Myocardial Contraction/genetics
- Myocardium/metabolism
- Myocardium/pathology
- Myosin Heavy Chains/genetics
- Myosin Heavy Chains/metabolism
- Organ Size
- Stroke Volume/genetics
- Survival Rate
- Ventricular Function, Left/genetics
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Affiliation(s)
- Stefan E Hardt
- Cardiovascular Research Institute, Department of Cell Biology, University of Medicine and Dentistry New Jersey, New Jersey Medical School, Newark, USA
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27
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Abstract
There is increasing evidence that nitric oxide (NO) produced by inducible NO synthase (iNOS) plays a key role in cadioprotection during the "second window of protection" (SWOP). The goals of this study were to determine 1) whether a transient ischemic episode [10-min coronary artery occlusion (CAO), followed by full reperfusion] enhances NOS function in cardiac myocytes, 2) which specific NOS isoform is responsible for the enhanced NOS function in myocytes, and 3) to localize iNOS expression during SWOP. To address these questions, 10 dogs were instrumented to measure aortic and left ventricular pressures and wall thickness. At 1-2 wk after recovery, myocardial ischemia was induced regionally by a 10-min left circumflex CAO. After 24-h reperfusion, cardiac myocytes were isolated from the previously ischemic and nonischemic regions (n = 6). Myocyte contractile function was assessed using a video motion detector at 1 Hz (35 +/- 2 degrees C). At baseline, myocyte contractile function (% contraction) was similar in the two regions (ischemic 7.8 +/- 0.5% vs. nonischemic 7.8 +/- 0.2%). L-Arginine (1 mM) significantly reduced (P < 0.05) myocyte contraction in the ischemic (-34 +/- 3%, P < 0.05) but not (-7 +/- 4%) nonischemic regions; these responses were abolished by N(G)-nitro-L-arginine (1 mM), a nonspecific NOS inhibitor, as well as 2-amino-5,6-dihydro-6-methy-4H-1,3,thiazine (1 mM), a specific iNOS inhibitor. Immunohistochemistry also revealed enhanced iNOS expression in the myocardium and in particular the interstitial spaces in the ischemic zone. These results indicate that a brief ischemic episode upregulates iNOS function in myocytes as well as in the interstitial space between blood vessels and myocytes, strategically where it can regulate both vascular and myocyte function during the SWOP.
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Affiliation(s)
- Song-Jung Kim
- Cardiovascular Research Institute and Department of Medicine, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark 07103, USA.
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28
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Abstract
Cardiomyopathies are diseases of heart muscle that may result from a diverse array of conditions that damage the heart and other organs and impair myocardial function, including infection, ischemia, and toxins. However, they may also occur as primary diseases restricted to striated muscle. Over the past decade, the importance of inherited gene defects in the pathogenesis of primary cardiomyopathies has been recognized, with mutations in some 18 genes having been identified as causing hypertrophic cardiomyopathy (HCM) and/or dilated cardiomyopathy (DCM). Defining the role of these genes in cardiac function and the mechanisms by which mutations in these genes lead to hypertrophy, dilation, and contractile failure are major goals of ongoing research. Pathophysiological mechanisms that have been implicated in HCM and DCM include the following: defective force generation, due to mutations in sarcomeric protein genes; defective force transmission, due to mutations in cytoskeletal protein genes; myocardial energy deficits, due to mutations in ATP regulatory protein genes; and abnormal Ca2+ homeostasis, due to altered availability of Ca2+ and altered myofibrillar Ca2+ sensitivity. Improved understanding that will result from these studies should ultimately lead to new approaches for the diagnosis, prognostic stratification, and treatment of patients with heart failure.
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Affiliation(s)
- Diane Fatkin
- Molecular Cardiology Unit, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia.
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29
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Abstract
Hypertrophic cardiomyopathy (HCM), a relatively common disease, is diagnosed clinically by unexplained cardiac hypertrophy and pathologically by myocyte hypertrophy, disarray, and interstitial fibrosis. HCM is the most common cause of sudden cardiac death (SCD) in the young and a major cause of morbidity and mortality in elderly. Hypertrophy and fibrosis are the major determinants of morbidity and SCD. More than 100 mutations in nine genes, all encoding sarcomeric proteins have been identified in patients with HCM, which had led to the notion that HCM is a disease of contractile sarcomeric proteins. The beta -myosin heavy chain (MyHC), cardiac troponin T (cTnT) and myosin binding protein-C (MyBP-C) are the most common genes accounting for approximately 2/3 of all HCM cases. Genotype-phenotype correlation studies suggest that mutations in the beta -MyHC gene are associated with more extensive hypertrophy and a higher risk of SCD as compared to mutations in genes coding for other sarcomeric proteins, such as MyBP-C and cTnT. The prognostic significance of mutations is related to their hypertrophic expressivity and penetrance, with the exception of those in the cTnT, which are associated with mild hypertrophic response and a high incidence of SCD. However, there is a significant variability and factors, such as modifier genes and probably the environmental factors affect the phenotypic expression of HCM. The molecular pathogenesis of HCM is not completely understood. In vitro and in vivo studies suggest that mutations impart a diverse array of functional defects including reduced ATPase activity of myosin, acto-myosin interaction, cross-bridging kinetics, myocyte contractility, and altered Ca2+ sensitivity. Hypertrophy and other clinical and pathological phenotypes are considered compensatory phenotypes secondary to functional defects. In summary, the molecular genetic basis of HCM has been identified, which affords the opportunity to delineate its pathogenesis. Understanding the pathogenesis of HCM could provide for genetic based diagnosis, risk stratification, treatment and prevention of cardiac phenotypes.
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Affiliation(s)
- A J Marian
- Section of Cardiology, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA.
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30
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Fatkin D, McConnell BK, Mudd JO, Semsarian C, Moskowitz IG, Schoen FJ, Giewat M, Seidman CE, Seidman JG. An abnormal Ca(2+) response in mutant sarcomere protein-mediated familial hypertrophic cardiomyopathy. J Clin Invest 2000; 106:1351-9. [PMID: 11104788 PMCID: PMC381468 DOI: 10.1172/jci11093] [Citation(s) in RCA: 169] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Dominant-negative sarcomere protein gene mutations cause familial hypertrophic cardiomyopathy (FHC), a disease characterized by left-ventricular hypertrophy, angina, and dyspnea that can result in sudden death. We report here that a murine model of FHC bearing a cardiac myosin heavy-chain gene missense mutation (alphaMHC(403/+)), when treated with calcineurin inhibitors or a K(+)-channel agonist, developed accentuated hypertrophy, worsened histopathology, and was at risk for early death. Despite distinct pharmacologic targets, each agent augmented diastolic Ca(2+) concentrations in wild-type cardiac myocytes; alphaMHC(403/+) myocytes failed to respond. Pretreatment with a Ca(2+)-channel antagonist abrogated diastolic Ca(2+) changes in wild-type myocytes and prevented the exaggerated hypertrophic response of treated alphaMHC(403/+) mice. We conclude that FHC-causing sarcomere protein gene mutations cause abnormal Ca(2+) responses that initiate a hypertrophic response. These data define an important Ca(2+)-dependent step in the pathway by which mutant sarcomere proteins trigger myocyte growth and remodel the heart, provide definitive evidence that environment influences progression of FHC, and suggest a rational therapeutic approach to this prevalent human disease.
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Affiliation(s)
- D Fatkin
- Department of Genetics, Harvard Medical School and Howard Hughes Medical Institute, Boston, Massachusetts, USA
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31
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Nagueh SF, Kopelen HA, Lim DS, Zoghbi WA, Quiñones MA, Roberts R, Marian AJ. Tissue Doppler imaging consistently detects myocardial contraction and relaxation abnormalities, irrespective of cardiac hypertrophy, in a transgenic rabbit model of human hypertrophic cardiomyopathy. Circulation 2000; 102:1346-50. [PMID: 10993850 PMCID: PMC2907266 DOI: 10.1161/01.cir.102.12.1346] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Hypertrophic cardiomyopathy (HCM) is diagnosed clinically by the presence of left ventricular hypertrophy (LVH). However, LVH is absent in a significant number of genotype-positive patients. Because myocyte dysfunction and disarray are the primary abnormalities in HCM, we reasoned that tissue Doppler imaging could identify contraction and relaxation abnormalities, irrespective of hypertrophy, in a transgenic rabbit model of human HCM. METHODS AND RESULTS M-mode, 2D, Doppler echocardiography and tissue Doppler imaging were performed in nontransgenic (n=24), wild-type beta-myosin heavy chain-arginine(403) (n=14), and mutant beta-myosin heavy chain-glutamic acid(403) (n=24) transgenic rabbits. Mean septal thicknesses were 2.0+/-0.3, 2.0+/-0.25, and 2.75+/-0.3 mm in the 3 groups, respectively (P:=0.001). LVH was absent in 9 of the 24 mutant rabbits. Left ventricular dimensions, systolic function, heart rate, mitral inflow velocities, and time intervals were similar in the groups. However, the difference between atrial reversal and transmitral A wave duration was increased in the mutant rabbits (P:<0.001). More importantly, systolic and early diastolic tissue Doppler velocities were significantly lower in all mutant rabbits (7.45+/-2.2 versus 10.8+/-2.3 cm/s in nontransgenic and 9. 0+/-0.76 cm/s in wild-type; P:<0.001), including the 9 without LVH. A systolic velocity <8.5 cm/s had an 86% sensitivity and 100% specificity in identifying the mutant transgenic rabbits. CONCLUSIONS Myocardial contraction and relaxation were reduced in the mutant beta-myosin heavy chain-glutamic acid(403) transgenic rabbit model of human HCM, irrespective of the presence or absence of LVH. In addition, tissue Doppler imaging is more sensitive than conventional echocardiography for HCM screening.
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Affiliation(s)
- S F Nagueh
- Section of Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA.
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32
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Affiliation(s)
- G Shah
- Section of Cardiology, Baylor College of Medicine, Houston, Tex 77030, USA
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33
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Marian AJ, Wu Y, Lim DS, McCluggage M, Youker K, Yu QT, Brugada R, DeMayo F, Quinones M, Roberts R. A transgenic rabbit model for human hypertrophic cardiomyopathy. J Clin Invest 1999; 104:1683-92. [PMID: 10606622 PMCID: PMC409884 DOI: 10.1172/jci7956] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/1999] [Accepted: 10/29/1999] [Indexed: 01/19/2023] Open
Abstract
Certain mutations in genes for sarcomeric proteins cause hypertrophic cardiomyopathy (HCM). We have developed a transgenic rabbit model for HCM caused by a common point mutation in the beta-myosin heavy chain (MyHC) gene, R400Q. Wild-type and mutant human beta-MyHC cDNAs were cloned 3' to a 7-kb murine beta-MyHC promoter. We injected purified transgenes into fertilized zygotes to generate two lines each of the wild-type and mutant transgenic rabbits. Expression of transgene mRNA and protein were confirmed by Northern blotting and 2-dimensional gel electrophoresis followed by immunoblotting, respectively. Animals carrying the mutant transgene showed substantial myocyte disarray and a 3-fold increase in interstitial collagen expression in their myocardia. Mean septal thicknesses were comparable between rabbits carrying the wild type transgene and their nontransgenic littermates (NLMs) but were significantly increased in the mutant transgenic animals. Posterior wall thickness and left ventricular mass were also increased, but dimensions and systolic function were normal. Premature death was more common in mutant than in wild-type transgenic rabbits or in NLMs. Thus, cardiac expression of beta-MyHC-Q(403) in transgenic rabbits induced hypertrophy, myocyte and myofibrillar disarray, interstitial fibrosis, and premature death, phenotypes observed in humans patients with HCM due to beta-MyHC-Q(403).
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Affiliation(s)
- A J Marian
- Section of Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.
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34
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Kim SJ, Yatani A, Vatner DE, Yamamoto S, Ishikawa Y, Wagner TE, Shannon RP, Kim YK, Takagi G, Asai K, Homcy CJ, Vatner SF. Differential regulation of inotropy and lusitropy in overexpressed Gsalpha myocytes through cAMP and Ca2+ channel pathways. J Clin Invest 1999; 103:1089-97. [PMID: 10194482 PMCID: PMC408254 DOI: 10.1172/jci4848] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We investigated the mechanisms responsible for altered contractile and relaxation function in overexpressed Gsalpha myocytes. Although baseline contractile function (percent contraction) in Gsalpha mice was similar to that of wild-type (WT) mice, left ventricular myocyte contraction, fura-2 Ca2+transients, and Ca2+ channel currents (ICa) were greater in Gsalpha mice in response to 10(-8) M isoproterenol (ISO) compared with WT mice. The late phase of relaxation of the isolated myocytes and fura-2 Ca2+ transients was accelerated at baseline in Gsalpha but did not increase further with ISO. In vivo measurements using echocardiography also demonstrated enhanced relaxation at baseline in Gsalpha mice. Forskolin and CaCl2 increased contraction similarly in WT and Gsalpha mice. Rp-cAMP, an inhibitor of protein kinase, blocked the increases in contractile response and Ca2+ currents to ISO in WT and to forskolin in both WT and Gsalpha. It also blocked the accelerated relaxation in Gsalpha at baseline but not the contractile response to ISO in Gsalpha myocytes. Baseline measurements of cAMP and phospholambation phosphorylation were enhanced in Gsalpha compared with WT. These data indicate that overexpression of Gsalpha accelerates relaxation at end diastolic but does not affect baseline systolic function in isolated myocytes. However, the enhanced responses to sympathetic stimulation partly reflect increased Ca2+ channel activity; i.e the cellular mechanisms mediating these effects appear to involve a cAMP-independent as well as a cAMP-dependent pathway.
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Affiliation(s)
- S J Kim
- Cardiovascular and Pulmonary Research Institute, Allegheny University of the Health Sciences, Pittsburgh, Pennsylvania 15212, USA
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