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Dowrick JM, Taberner AJ, Han JC, Tran K. Methods for assessing cardiac myofilament calcium sensitivity. Front Physiol 2023; 14:1323768. [PMID: 38116581 PMCID: PMC10728676 DOI: 10.3389/fphys.2023.1323768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 11/23/2023] [Indexed: 12/21/2023] Open
Abstract
Myofilament calcium (Ca2+) sensitivity is one of several mechanisms by which force production of cardiac muscle is modulated to meet the ever-changing demands placed on the heart. Compromised Ca2+ sensitivity is associated with pathologies, which makes it a parameter of interest for researchers. Ca2+ Sensitivity is the ratio of the association and dissociation rates between troponin C (TnC) and Ca2+. As it is not currently possible to measure these rates in tissue preparations directly, methods have been developed to infer myofilament sensitivity, typically using some combination of force and Ca2+ measurements. The current gold-standard approach constructs a steady-state force-Ca2+ relation by exposing permeabilised muscle samples to a range of Ca2+ concentrations and uses the half-maximal concentration as a proxy for sensitivity. While a valuable method for steady-state investigations, the permeabilisation process makes the method unsuitable when examining dynamic, i.e., twitch-to-twitch, changes in myofilament sensitivity. The ability of the heart to transiently adapt to changes in load is an important consideration when evaluating the impact of disease states. Alternative methods have been proffered, including force-Ca2+ phase loops, potassium contracture, hybrid experimental-modelling and conformation-based fluorophore approaches. This review provides an overview of the mechanisms underlying myofilament Ca2+ sensitivity, summarises existing methods, and explores, with modelling, whether any of them are suited to investigating dynamic changes in sensitivity. We conclude that a method that equips researchers to investigate the transient change of myofilament Ca2+ sensitivity is still needed. We propose that such a method will involve simultaneous measurements of cytosolic Ca2+ and TnC activation in actively twitching muscle and a biophysical model to interpret these data.
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Affiliation(s)
- Jarrah M. Dowrick
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Andrew J. Taberner
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Department of Engineering Science and Biomedical Engineering, University of Auckland, Auckland, New Zealand
| | - June-Chiew Han
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Kenneth Tran
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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Lookin O, Khokhlova A, Myachina T, Butova X, Cazorla O, de Tombe P. Contractile State Dependent Sarcomere Length Variability in Isolated Guinea-Pig Cardiomyocytes. Front Physiol 2022; 13:857471. [PMID: 35444559 PMCID: PMC9013801 DOI: 10.3389/fphys.2022.857471] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 03/11/2022] [Indexed: 11/13/2022] Open
Abstract
Cardiomyocytes contract keeping their sarcomere length (SL) close to optimal values for force generation. Transmural heterogeneity in SL across the ventricular wall coordinates the contractility of the whole-ventricle. SL heterogeneity (variability) exists not only at the tissue (macroscale) level, but also presents at the level of a single cardiomyocyte (microscale level). However, transmural differences in intracellular SL variability and its possible dependence on the state of contraction (e.g. end-diastole or end-systole) have not been previously reported. In the present study, we studied three aspects of sarcomere-to-sarcomere variability in intact cardiomyocytes isolated from the left ventricle of healthy guinea-pig: 1) transmural differences in SL distribution between subepi- (EPI) and subendocardial (ENDO) cardiomyocytes; 2) the dependence of intracellular variability in SL upon the state of contraction; 3) local differences in SL variability, comparing SL distributions between central and peripheral regions within the cardiomyocyte. To characterize the intracellular variability of SL, we used different normality tests for the assessment of SL distributions, as well as nonparametric coefficients to quantify the variability. We found that individual SL values in the end-systolic state of contraction followed a normal distribution to a lesser extent as compared to the end-diastolic state of contraction (∼1.3-fold and ∼1.6-fold in ENDO and EPI, respectively). The relative and absolute coefficients of sarcomere-to-sarcomere variability in end-systolic SL were significantly greater (∼1.3-fold) as compared to end-diastolic SL. This was independent of both the transmural region across the left ventricle and the intracellular region within the cardiomyocyte. We conclude that the intracellular variability in SL, which exists in normal intact guinea-pig cardiomyocytes, is affected by the contractile state of the myocyte. This phenomenon may play a role in inter-sarcomere communication in the beating heart.
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Affiliation(s)
- Oleg Lookin
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
- *Correspondence: Oleg Lookin,
| | - Anastasia Khokhlova
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
| | - Tatiana Myachina
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
| | - Xenia Butova
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
| | - Olivier Cazorla
- Laboratoire “Physiologie et Médecine Expérimentale du Coeur et des Muscles”, Phymedexp, INSERM—CNRS - Montpellier University, Montpellier, France
| | - Pieter de Tombe
- Laboratoire “Physiologie et Médecine Expérimentale du Coeur et des Muscles”, Phymedexp, INSERM—CNRS - Montpellier University, Montpellier, France
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, United States
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Kabanov D, Klimovic S, Rotrekl V, Pesl M, Pribyl J. Atomic Force Spectroscopy is a promising tool to study contractile properties of cardiac cells. Micron 2021; 155:103199. [DOI: 10.1016/j.micron.2021.103199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 11/15/2021] [Accepted: 12/15/2021] [Indexed: 10/19/2022]
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S Beserra S, Roman-Campos D. Impact of pacing frequency in amiodarone interaction with cardiomyocytes near physiological temperature in health and disease conditions. Basic Clin Pharmacol Toxicol 2020; 128:615-620. [PMID: 33124101 DOI: 10.1111/bcpt.13527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 10/21/2020] [Accepted: 10/26/2020] [Indexed: 11/29/2022]
Abstract
Long QT syndrome type 3 (LQT-3) is a disease related to abnormal cardiac sodium channel function (Nav 1.5), usually due to augmented late sodium current (INaL ), and may lead to ventricular fibrillation. Amiodarone is approved for ventricular fibrillation. Thus, we investigated whether pacing frequency impacts the ability of amiodarone to reverse the arrhythmic phenotype observed in LQT-3. Anemone neurotoxin 2 (ATX-II, here named only ATX) was used to enhance INaL in mice left ventricular myocytes (LVM). A video detector system monitored sarcomere shortening. At 1 Hz, amiodarone attenuated sarcomere shortening only at 10 µmol/L; at 3 and 5 Hz, 0.1 and 1 µmol/L amiodarone also reduced sarcomere shortening. However, no effect of amiodarone was observed on time to 50% of sarcomere contraction and relaxation. In LVM exposed to ATX (10 nmol/L), an arrhythmic phenotype was observed, and it was more severe when cells were paced at 1 Hz. Amiodarone failed to reverse the ATX induced phenotype at different pacing frequencies. Thus, our results suggest that amiodarone's ability to reverse arrhythmias induced by augmentation of INaL is limited. These findings suggest further experimentation will be required to clarify whether a clinical effect can be ascribed to an effect of amiodarone on other ion channels in LQT-3.
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Affiliation(s)
- Samuel S Beserra
- Laboratory of CardioBiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Danilo Roman-Campos
- Laboratory of CardioBiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Sao Paulo, Brazil
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Nollet EE, Manders EM, Goebel M, Jansen V, Brockmann C, Osinga J, van der Velden J, Helmes M, Kuster DWD. Large-Scale Contractility Measurements Reveal Large Atrioventricular and Subtle Interventricular Differences in Cultured Unloaded Rat Cardiomyocytes. Front Physiol 2020; 11:815. [PMID: 32848817 PMCID: PMC7396550 DOI: 10.3389/fphys.2020.00815] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 06/18/2020] [Indexed: 01/22/2023] Open
Abstract
The chambers of the heart fulfill different hemodynamic functions, which are reflected in their structural and contractile properties. While the atria are highly elastic to allow filling from the venous system, the ventricles need to be able to produce sufficiently high pressures to eject blood into the circulation. The right ventricle (RV) pumps into the low pressure pulmonary circulation, while the left ventricle (LV) needs to overcome the high pressure of the systemic circulation. It is incompletely understood whether these differences can be explained by the contractile differences at the level of the individual cardiomyocytes of the chambers. We addressed this by isolating cardiomyocytes from atria, RV, LV, and interventricular septum (IVS) of five healthy wild-type rats. Using a high-throughput contractility set-up, we measured contractile function of 2,043 cells after overnight culture. Compared to ventricular cardiomyocytes, atrial cells showed a twofold lower contraction amplitude and 1.4- to 1.7-fold slower kinetics of contraction and relaxation. The interventricular differences in contractile function were much smaller; RV cells displayed 12–13% less fractional shortening and 5–9% slower contraction and 3–15% slower relaxation kinetics relative to their LV and IVS counterparts. Aided by a large dataset, we established relationships between contractile parameters and found contraction velocity, fractional shortening and relaxation velocity to be highly correlated. In conclusion, our findings are in line with contractile differences observed at the atrioventricular level, but can only partly explain the interventricular differences that exist at the organ level.
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Affiliation(s)
- Edgar E Nollet
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | | | - Max Goebel
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Valentijn Jansen
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Cord Brockmann
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Jorrit Osinga
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Jolanda van der Velden
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Michiel Helmes
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands.,CytoCypher BV, Wageningen, Netherlands
| | - Diederik W D Kuster
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
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Czeiszperger TL, Wang MP, Chung CS. Membrane stabilizer Poloxamer 188 improves yield of primary isolated rat cardiomyocytes without impairing function. Physiol Rep 2020; 8:e14382. [PMID: 32109347 PMCID: PMC7048379 DOI: 10.14814/phy2.14382] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 02/05/2020] [Accepted: 02/05/2020] [Indexed: 12/23/2022] Open
Abstract
Intact cardiomyocytes are used to investigate cardiac contractility and evaluate the efficacy of new therapeutic compounds. Primary enzymatic isolation of adult rodent cardiomyocytes has limitations, including low cardiomyocyte survival, which is likely due to ischemic conditions and/or membrane damage. The addition of Poloxamer 188 (P188) has been used to reduce ischemia- and membrane-related damage in ischemia-reperfusion and muscular dystrophy studies. P188 stabilizes membranes, reducing cell death. Cardiomyocytes were isolated from rats, under three conditions: (1) using standard isolation solutions, (2) with P188 added during cannulation (ischemic event), and (3) with P188 added during cannulation, enzymatic digestion, and trituration. Cell survival was assessed by quantifying the number of rod-shaped versus contracted cells on the day of isolation and up to 3 days post-isolation. Adding P188 only during cannulation yielded improved survival on the day of isolation. Little difference in survival was seen among the three conditions in the days post-isolation. Cardiomyocyte function was assessed by measuring calcium transients and unloaded sarcomere lengths for up to 2 days post-isolation. P188 did not consistently alter calcium handling or sarcomere shortening in the isolated cardiomyocytes. We conclude that the addition of P188 to the cannulation (e.g., wash) of the isolated heart may improve initial survival of cardiomyocytes upon primary enzymatic isolation.
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Khokhlova A, Balakina-Vikulova N, Katsnelson L, Iribe G, Solovyova O. Transmural cellular heterogeneity in myocardial electromechanics. J Physiol Sci 2018; 68:387-413. [PMID: 28573594 PMCID: PMC10717105 DOI: 10.1007/s12576-017-0541-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 04/24/2017] [Indexed: 12/22/2022]
Abstract
Myocardial heterogeneity is an attribute of the normal heart. We have developed integrative models of cardiomyocytes from the subendocardial (ENDO) and subepicardial (EPI) ventricular regions that take into account experimental data on specific regional features of intracellular electromechanical coupling in the guinea pig heart. The models adequately simulate experimental data on the differences in the action potential and contraction between the ENDO and EPI cells. The modeling results predict that heterogeneity in the parameters of calcium handling and myofilament mechanics in isolated ENDO and EPI cardiomyocytes are essential to produce the differences in Ca2+ transients and contraction profiles via cooperative mechanisms of mechano-calcium-electric feedback and may further slightly modulate transmural differences in the electrical properties between the cells. Simulation results predict that ENDO cells have greater sensitivity to changes in the mechanical load than EPI cells. These data are important for understanding the behavior of cardiomyocytes in the intact heart.
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Affiliation(s)
- Anastasia Khokhlova
- Ural Federal University, Ekaterinburg, Russia.
- Institute of Immunology and Physiology, Russian Academy of Sciences, 106 Pervomayskaya, Ekaterinburg, 620049, Russia.
| | - Nathalie Balakina-Vikulova
- Ural Federal University, Ekaterinburg, Russia
- Institute of Immunology and Physiology, Russian Academy of Sciences, 106 Pervomayskaya, Ekaterinburg, 620049, Russia
| | - Leonid Katsnelson
- Ural Federal University, Ekaterinburg, Russia
- Institute of Immunology and Physiology, Russian Academy of Sciences, 106 Pervomayskaya, Ekaterinburg, 620049, Russia
| | - Gentaro Iribe
- Okayama University, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama, 700-8558, Japan
| | - Olga Solovyova
- Ural Federal University, Ekaterinburg, Russia
- Institute of Immunology and Physiology, Russian Academy of Sciences, 106 Pervomayskaya, Ekaterinburg, 620049, Russia
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Voltage dependence of the Ca 2+ transient in endocardial and epicardial myocytes from the left ventricle of Goto-Kakizaki type 2 diabetic rats. Mol Cell Biochem 2018; 446:25-33. [PMID: 29318456 DOI: 10.1007/s11010-018-3269-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 01/04/2018] [Indexed: 01/09/2023]
Abstract
Diabetes mellitus is a major global health disorder and, currently, over 450 million people have diabetes with 90% suffering from type 2 diabetes. Left untreated, diabetes may lead to cardiovascular diseases which are a leading cause of death in diabetic patients. Calcium is the trigger and regulator of cardiac muscle contraction and derangement in cellular Ca2+ homeostasis, which can result in heart failure and sudden cardiac death. It is of paramount importance to investigate the regional involvement of Ca2+ in diabetes-induced cardiomyopathy. Therefore, the aim of this study was to investigate the voltage dependence of the Ca2+ transients in endocardial (ENDO) and epicardial (EPI) myocytes from the left ventricle of the Goto-Kakizaki (GK) rats, an experimental model of type 2 diabetes mellitus. Simultaneous measurement of L-type Ca2+ currents and Ca2+ transients was performed by whole-cell patch clamp techniques. GK rats displayed significantly increased heart weight, heart weight/body weight ratio, and non-fasting and fasting blood glucose compared to controls (CON). Although the voltage dependence of L-type Ca2+ current was unaltered, the voltage dependence of the Ca2+ transients was reduced to similar extents in EPI-GK and ENDO-GK compared to EPI-CON and ENDO-CON myocytes. TPK L-type Ca2+ current and Ca2+ transient were unaltered. THALF decay of L-type Ca2+ current was unaltered; however, THALF decay of the Ca2+ transient was shortened in ENDO and EPI myocytes from GK compared to CON rat hearts. In conclusion, the amplitude of L-type Ca2+ current was unaltered; however, the voltage dependence of the Ca2+ transient was reduced to similar extents in EPI and ENDO myocytes from GK rats compared to their respective controls, suggesting the possibility of dysfunctional sarcoplasmic reticulum Ca2+ transport in the GK diabetic rat hearts.
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Khokhlova A, Iribe G, Katsnelson L, Naruse K, Solovyova O. The effects of load on transmural differences in contraction of isolated mouse ventricular cardiomyocytes. J Mol Cell Cardiol 2017; 114:276-287. [PMID: 29217431 DOI: 10.1016/j.yjmcc.2017.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 12/01/2017] [Indexed: 12/31/2022]
Abstract
Mechanical properties of cardiomyocytes from different transmural regions are heterogeneous in the left ventricular wall. The cardiomyocyte mechanical environment affects this heterogeneity because of mechano-electric feedback mechanisms. In the present study, we investigated the effects of the mechanical load (preload and afterload) on transmural differences in contraction of subendocardial (ENDO) and subepicardial (EPI) single cells isolated from the murine left ventricle. Various preloads imposed via axial stretch and afterloads (unloaded and heavy loaded conditions) were applied to the cells using carbon fiber techniques for single myocytes. To simulate experimentally obtained results and to predict mechanisms underlying the cellular response to change in load, our mathematical models of the ENDO and EPI cells were used. Our major findings are the following. Our results show that ENDO and EPI cardiomyocytes have different mechanical responses to changes in preload to the cells. Under auxotonic contractions at low preload (unstretched cells), time to peak contraction (Tmax) and the time constant of [Ca2+]i transient decay were significantly longer in ENDO cells than in EPI cells. An increase in preload (stretched cells) prolonged Tmax in both cell types; however, the prolongation was greater in EPI cells, resulting in a decrease in the transmural gradient in Tmax at high preload. Comparing unloaded and heavy loaded (isometric) contractions of the cells we found that transmural gradient in the time course of contraction is independent of the loading conditions. Our mathematical cell models were able to reproduce the experimental results on the distinct cellular responses to changes in the mechanical load when we accounted for an ENDO/EPI difference in the parameters of cooperativity of calcium activation of myofilaments.
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Affiliation(s)
- Anastasia Khokhlova
- Ural Federal University, Mira 19, 620002 Ekaterinburg, Russia; Institute of Immunology and Physiology, Russian Academy of Sciences, Pervomajskaya 106, 620049 Ekaterinburg, Russia.
| | - Gentaro Iribe
- Okayama University, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Shikata cho 2-5-1, 1700-8558 Okayama, Japan
| | - Leonid Katsnelson
- Ural Federal University, Mira 19, 620002 Ekaterinburg, Russia; Institute of Immunology and Physiology, Russian Academy of Sciences, Pervomajskaya 106, 620049 Ekaterinburg, Russia
| | - Keiji Naruse
- Okayama University, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Shikata cho 2-5-1, 1700-8558 Okayama, Japan
| | - Olga Solovyova
- Ural Federal University, Mira 19, 620002 Ekaterinburg, Russia; Institute of Immunology and Physiology, Russian Academy of Sciences, Pervomajskaya 106, 620049 Ekaterinburg, Russia; Institute of Mathematics and Mechanics, Russian Academy of Sciences, Kovalevskaya 16, 620990 Ekaterinburg, Russia
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Khokhlova A, Iribe G, Yamaguchi Y, Naruse K, Solovyova O. Effects of simulated ischemia on the transmural differences in the Frank-Starling relationship in isolated mouse ventricular cardiomyocytes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 130:323-332. [PMID: 28571718 DOI: 10.1016/j.pbiomolbio.2017.05.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 05/25/2017] [Accepted: 05/26/2017] [Indexed: 12/26/2022]
Abstract
The electrical and mechanical functions of cardiomyocytes differ in relation to the spatial locations of cells in the ventricular wall. This physiological heterogeneity may change under pathophysiological conditions, providing substrates for arrhythmia and contractile dysfunctions. Previous studies have reported distinctions in the electrophysiological and mechanical responses to ischemia of unloaded subendocardial (ENDO) and subepicardial (EPI) single cardiomyocytes. In this paper, we briefly recapitulated the available experimental data on the ischemia effects on the transmural cellular gradient in the heart ventricles and for the first time evaluated the preload-dependent changes in passive and active forces in ENDO and EPI cardiomyocytes isolated from mouse hearts subjected to simulated ischemia. Combining the results obtained in mechanically loaded contracting cardiomyocytes with data from previous studies, we showed that left ventricular ENDO and EPI cardiomyocytes are different in their mechanical responses to metabolic inhibition. Simulated ischemia showed opposite effects on the stiffness of ENDO and EPI cells and greatly prolonged the time course of contraction in EPI cells than in ENDO cells, thereby changing the normal transmural gradient in the cellular mechanics.
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Affiliation(s)
- Anastasia Khokhlova
- Ural Federal University, 620002, Mira 19, Ekaterinburg, Russia; Institute of Immunology and Physiology, Russian Academy of Sciences, 620049, Pervomajskaya 106, Ekaterinburg, Russia.
| | - Gentaro Iribe
- Okayama University, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 1700-8558, Shikata Cho 2-5-1, Okayama, Japan
| | - Yohei Yamaguchi
- Okayama University, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 1700-8558, Shikata Cho 2-5-1, Okayama, Japan
| | - Keiji Naruse
- Okayama University, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 1700-8558, Shikata Cho 2-5-1, Okayama, Japan
| | - Olga Solovyova
- Ural Federal University, 620002, Mira 19, Ekaterinburg, Russia; Institute of Immunology and Physiology, Russian Academy of Sciences, 620049, Pervomajskaya 106, Ekaterinburg, Russia
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Chung CS, Hoopes CW, Campbell KS. Myocardial relaxation is accelerated by fast stretch, not reduced afterload. J Mol Cell Cardiol 2017; 103:65-73. [PMID: 28087265 DOI: 10.1016/j.yjmcc.2017.01.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 01/08/2017] [Accepted: 01/09/2017] [Indexed: 12/19/2022]
Abstract
Fast relaxation of cross-bridge generated force in the myocardium facilitates efficient diastolic function. Recently published research studying mechanisms that modulate the relaxation rate has focused on molecular factors. Mechanical factors have received less attention since the 1980s when seminal work established the theory that reducing afterload accelerates the relaxation rate. Clinical trials using afterload reducing drugs, partially based on this theory, have thus far failed to improve outcomes for patients with diastolic dysfunction. Therefore, we reevaluated the protocols that suggest reducing afterload accelerates the relaxation rate and identified that myocardial relengthening was a potential confounding factor. We hypothesized that the speed of myocardial relengthening at end systole (end systolic strain rate), and not afterload, modulates relaxation rate and tested this hypothesis using electrically-stimulated trabeculae from mice, rats, and humans. We used load-clamp techniques to vary afterload and end systolic strain rate independently. Our data show that the rate of relaxation increases monotonically with end systolic strain rate but is not altered by afterload. Computer simulations mimic this behavior and suggest that fast relengthening quickens relaxation by accelerating the detachment of cross-bridges. The relationship between relaxation rate and strain rate is novel and upends the prevailing theory that afterload modifies relaxation. In conclusion, myocardial relaxation is mechanically modified by the rate of stretch at end systole. The rate of myocardial relengthening at end systole may be a new diagnostic indicator or target for treatment of diastolic dysfunction.
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Affiliation(s)
- Charles S Chung
- Department of Physiology, Wayne State University, Detroit, MI, USA; Department of Physiology, University of Kentucky, Lexington, KY, USA.
| | - Charles W Hoopes
- Department of Surgery, University of Kentucky, Lexington, KY, USA
| | - Kenneth S Campbell
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Division of Cardiovascular Medicine, University of Kentucky, Lexington, KY, USA
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Haque MZ, McIntosh VJ, Abou Samra AB, Mohammad RM, Lasley RD. Cholesterol Depletion Alters Cardiomyocyte Subcellular Signaling and Increases Contractility. PLoS One 2016; 11:e0154151. [PMID: 27441649 PMCID: PMC4956108 DOI: 10.1371/journal.pone.0154151] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 04/09/2016] [Indexed: 01/14/2023] Open
Abstract
Membrane cholesterol levels play an important factor in regulating cell function. Sarcolemmal cholesterol is concentrated in lipid rafts and caveolae, which are flask-shaped invaginations of the plasma membrane. The scaffolding protein caveolin permits the enrichment of cholesterol in caveolae, and caveolin interactions with numerous proteins regulate their function. The purpose of this study was to determine whether acute reductions in cardiomyocyte cholesterol levels alter subcellular protein kinase activation, intracellular Ca2+ and contractility. Methods: Ventricular myocytes, isolated from adult Sprague Dawley rats, were treated with the cholesterol reducing agent methyl-β-cyclodextrin (MβCD, 5 mM, 1 hr, room temperature). Total cellular cholesterol levels, caveolin-3 localization, subcellular, ERK and p38 mitogen activated protein kinase (MAPK) signaling, contractility, and [Ca2+]i were assessed. Results: Treatment with MβCD reduced cholesterol levels by ~45 and shifted caveolin-3 from cytoskeleton and triton-insoluble fractions to the triton-soluble fraction, and increased ERK isoform phosphorylation in cytoskeletal, cytosolic, triton-soluble and triton-insoluble membrane fractions without altering their subcellular distributions. In contrast the primary effect of MβCD was on p38 subcellular distribution of p38α with little effect on p38 phosphorylation. Cholesterol depletion increased cardiomyocyte twitch amplitude and the rates of shortening and relaxation in conjunction with increased diastolic and systolic [Ca2+]i. Conclusions: These results indicate that acute reductions in membrane cholesterol levels differentially modulate basal cardiomyocyte subcellular MAPK signaling, as well as increasing [Ca2+]i and contractility.
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Affiliation(s)
- Mohammed Z. Haque
- Interim Translational Research Institute, Department of Internal Medicine, Academic Health System, Hamad Medical Corporation, Doha, Qatar
- Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital, 2799 West Grand Blvd., Detroit, MI 48202, United States of America
- * E-mail:
| | - Victoria J. McIntosh
- Department of Physiology, Wayne State University School of Medicine, 1104 Elliman Bldg., 421 East Canfield, Detroit, MI 48201, United States of America
| | - Abdul B. Abou Samra
- Interim Translational Research Institute, Department of Internal Medicine, Academic Health System, Hamad Medical Corporation, Doha, Qatar
| | - Ramzi M. Mohammad
- Interim Translational Research Institute, Department of Internal Medicine, Academic Health System, Hamad Medical Corporation, Doha, Qatar
| | - Robert D. Lasley
- Department of Physiology, Wayne State University School of Medicine, 1104 Elliman Bldg., 421 East Canfield, Detroit, MI 48201, United States of America
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Chung CS, Mechas C, Campbell KS. Myocyte contractility can be maintained by storing cells with the myosin ATPase inhibitor 2,3 butanedione monoxime. Physiol Rep 2015; 3:3/6/e12445. [PMID: 26116551 PMCID: PMC4522161 DOI: 10.14814/phy2.12445] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Isolated intact myocytes can be used to investigate contractile mechanisms and to screen new therapeutic compounds. These experiments typically require euthanizing an animal and isolating fresh cells each day or analyzing cultured myocytes, which quickly lose their rod-shaped morphology. Recent data suggest that the viability of canine myocytes can be prolonged using low temperature and N-benzyl-p-toluene sulfonamide (an inhibitor of skeletal myosin ATPase). We performed similar studies in rat myocytes in order to test whether the cardiac myosin ATPase inhibitors 2,3-Butanedione monoxime (BDM) and blebbistatin help to maintain cell-level function over multiple days. Myocytes were isolated from rats and separated into batches that were stored at 4°C in a HEPES-buffered solution that contained 0.5 mmol L(-1) Ca(2+) and (1) no myosin ATPase inhibitors; (2) 10 mmol L(-1) BDM; or (3) 3 μmol L(-1) blebbistatin. Functional viability of myocytes was assessed up to 3 days after the isolation by measuring calcium transients and unloaded shortening profiles induced by electrical stimuli in inhibitor-free Tyrode's solution. Cells stored without myosin ATPase inhibitors had altered morphology (fewer rod-shaped cells, shorter diastolic sarcomere lengths, and membrane blebbing) and were not viable for contractile assays after 24 h. Cells stored in BDM maintained morphology and contractile function for 48 h. Storage in blebbistatin maintained cell morphology for 72 h but inhibited contractility. These data show that storing cells with myosin ATPase inhibitors can extend the viability of myocytes that will be used for functional assays. This may help to refine and reduce the use of animals in experiments.
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Affiliation(s)
- Charles S Chung
- Department of Physiology and Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
| | - Charles Mechas
- Department of Physiology and Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
| | - Kenneth S Campbell
- Department of Physiology and Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
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Exposure to phthalates affects calcium handling and intercellular connectivity of human stem cell-derived cardiomyocytes. PLoS One 2015; 10:e0121927. [PMID: 25799571 PMCID: PMC4370601 DOI: 10.1371/journal.pone.0121927] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 02/14/2015] [Indexed: 12/25/2022] Open
Abstract
Background The pervasive nature of plastics has raised concerns about the impact of continuous exposure to plastic additives on human health. Of particular concern is the use of phthalates in the production of flexible polyvinyl chloride (PVC) products. Di-2-ethylhexyl-phthalate (DEHP) is a commonly used phthalate ester plasticizer that imparts flexibility and elasticity to PVC products. Recent epidemiological studies have reported correlations between urinary phthalate concentrations and cardiovascular disease, including an increased risk of high blood pressure and coronary risk. Yet, there is little direct evidence linking phthalate exposure to adverse effects in human cells, including cardiomyocytes. Methods and Results The effect of DEHP on calcium handling was examined using monolayers of gCAMP3 human embryonic stem cell-derived cardiomyocytes, which contain an endogenous calcium sensor. Cardiomyocytes were exposed to DEHP (5 – 50 μg/mL), and calcium transients were recorded using a Zeiss confocal imaging system. DEHP exposure (24 – 72 hr) had a negative chronotropic and inotropic effect on cardiomyocytes, increased the minimum threshold voltage required for external pacing, and modified connexin-43 expression. Application of Wy-14,643 (100 μM), an agonist for the peroxisome proliferator-activated receptor alpha, did not replicate DEHP’s effects on calcium transient morphology or spontaneous beating rate. Conclusions Phthalates can affect the normal physiology of human cardiomyocytes, including DEHP elicited perturbations in cardiac calcium handling and intercellular connectivity. Our findings call for additional studies to clarify the extent by which phthalate exposure can alter cardiac function, particularly in vulnerable patient populations who are at risk for high phthalate exposure.
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