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Kambayashi R, Goto A, Takahara A, Saito H, Izumi-Nakaseko H, Takei Y, Akie Y, Hori M, Sugiyama A. Characterization of remodeling processes in the atria of atrioventricular block dogs: Utility as an early-stage atrial fibrillation model. J Pharmacol Sci 2024; 156:19-29. [PMID: 39068031 DOI: 10.1016/j.jphs.2024.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 06/08/2024] [Accepted: 06/26/2024] [Indexed: 07/30/2024] Open
Abstract
To characterize utility of atrioventricular block (AVB) dogs as atrial fibrillation (AF) model, we studied remodeling processes occurring in their atria in acute (<2 weeks) and chronic (>4 weeks) phases. Fifty beagle dogs were used. Holter electrocardiogram demonstrated that paroxysmal AF occurred immediately after the production of AVB, of which duration tended to be prolonged in chronic phase. Electrophysiological analysis showed that inter-atrial conduction time and duration of burst pacing-induced AF increased in the chronic phase compared with those in the acute phase, but that atrial effective refractory period was hardly altered. Echocardiographic study revealed that diameters of left atrium, right pulmonary vein and inferior vena cava increased similarly in the acute and chronic phases. Histological evaluation indicated that hypertrophy and fibrosis in atrial tissue increased in the chronic phase. Electropharmacological characterization showed that i.v. pilsicainide effectively suppressed burst pacing-induced AF with increasing atrial conduction time and refractoriness of AVB dogs in chronic phase, but that i.v. amiodarone did not exert such electrophysiological effects. Taken together, AVB dogs in chronic phase appear to possess such pathophysiology as developed in the atria of early-stage AF patients, and therefore they can be used to evaluate drug candidates against early-stage AF.
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Affiliation(s)
- Ryuichi Kambayashi
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan
| | - Ai Goto
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan
| | - Akira Takahara
- Department of Pharmacology and Therapeutics, Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi-shi, Chiba 274-8510, Japan
| | - Hiroyuki Saito
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan; CMIC Bioresearch Center, CMIC Pharma Science Co., Ltd., 10221 Kobuchisawa, Hokuto, Yamanashi 408-0044, Japan
| | - Hiroko Izumi-Nakaseko
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan
| | - Yoshinori Takei
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan
| | - Yasuki Akie
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan; CMIC Bioresearch Center, CMIC Pharma Science Co., Ltd., 10221 Kobuchisawa, Hokuto, Yamanashi 408-0044, Japan
| | - Masaaki Hori
- Department of Radiology, Faculty of Medicine, Toho University, 6-11-1 Omori-nishi, Ota-ku, Tokyo 143-8541, Japan
| | - Atsushi Sugiyama
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan; Yamanashi Research Center of Clinical Pharmacology, 73-5 Hatta, Fuefuki, Yamanashi 406-0023, Japan; Organization for the Promotion of Research and Social Collaboration, University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi 400-8510, Japan.
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2
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Kamkin AG, Mitrokhin VM, Kamkina OV, Kazansky VE, Rodina AS, Zolotareva AD, Zolotarev VI, Sutyagin PV, Mladenov MI, Shenkman BS, Kalashnikov VE, Orlov OI. Simulated Microgravity Changes the Number of Mechanically Gated and Mechanosensitive Ion Channels Genes Transcripts in Rat Ventricular Cardiomyocytes. DOKL BIOCHEM BIOPHYS 2023; 512:251-255. [PMID: 38093125 DOI: 10.1134/s1607672923700369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 06/03/2023] [Accepted: 06/05/2023] [Indexed: 12/18/2023]
Abstract
The mechanoelectrical feedback in the heart is based on the work of mechanically gated (MGCs) and mechanosensitive (MSCs) channels. Since microgravity alters the heart's morphological and physiological properties, we hypothesized that the expression of both MGCs and MSCs would be affected. We employed RNA transcriptome sequencing to investigate changes in the gene transcript levels of MGCs and MSCs in isolated rat ventricular cardiomyocytes under control conditions and in a simulated microgravity environment. For the first time, our findings demonstrated that simulated microgravity induces alterations in the gene transcript levels of specific MGCs, such as TRPM7, TRPV2, TRPP1, TRPP2, Piezo1, TMEM63A, TMEM36B, and known MSCs, including K2P2.1, K2P3.1, Kir6.1, Kir6.2, NaV1.5, CaV1.2, KV7.1. However, other voltage-gated channels and channels lacking a voltage sensor remained unaffected. These findings suggest that the altered expression of MGCs and MSCs could lead to changes in the net currents across the membrane, ultimately impacting the heart's function.
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Affiliation(s)
- A G Kamkin
- Pirogov Russian National Research Medical University, Moscow, Russia.
| | - V M Mitrokhin
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - O V Kamkina
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - V E Kazansky
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - A S Rodina
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - A D Zolotareva
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - V I Zolotarev
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - P V Sutyagin
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - M I Mladenov
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - B S Shenkman
- State Scientific Center of Russian Federation Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
| | - V E Kalashnikov
- State Scientific Center of Russian Federation Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
| | - O I Orlov
- State Scientific Center of Russian Federation Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
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3
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Gwanyanya A, Andriulė I, Istrate BM, Easmin F, Mubagwa K, Mačianskienė R. Modulation of the Cardiac Myocyte Action Potential by the Magnesium-Sensitive TRPM6 and TRPM7-like Current. Int J Mol Sci 2021; 22:ijms22168744. [PMID: 34445449 PMCID: PMC8395930 DOI: 10.3390/ijms22168744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/04/2021] [Accepted: 08/12/2021] [Indexed: 01/08/2023] Open
Abstract
The cardiac Mg2+-sensitive, TRPM6, and TRPM7-like channels remain undefined, especially with the uncertainty regarding TRPM6 expression in cardiomyocytes. Additionally, their contribution to the cardiac action potential (AP) profile is unclear. Immunofluorescence assays showed the expression of the TRPM6 and TRPM7 proteins in isolated pig atrial and ventricular cardiomyocytes, of which the expression was modulated by incubation in extracellular divalent cation-free conditions. In patch clamp studies of cells dialyzed with solutions containing zero intracellular Mg2+ concentration ([Mg2+]i) to activate the Mg2+-sensitive channels, raising extracellular [Mg2+] ([Mg2+]o) from the 0.9-mM baseline to 7.2 mM prolonged the AP duration (APD). In contrast, no such effect was observed in cells dialyzed with physiological [Mg2+]i. Under voltage clamp, in cells dialyzed with zero [Mg2+]i, depolarizing ramps induced an outward-rectifying current, which was suppressed by raising [Mg2+]o and was absent in cells dialyzed with physiological [Mg2+]i. In cells dialyzed with physiological [Mg2+]i, raising [Mg2+]o decreased the L-type Ca2+ current and the total delayed-rectifier current but had no effect on the APD. These results suggest a co-expression of the TRPM6 and TRPM7 proteins in cardiomyocytes, which are therefore the molecular candidates for the native cardiac Mg2+-sensitive channels, and also suggest that the cardiac Mg2+-sensitive current shortens the APD, with potential implications in arrhythmogenesis.
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Affiliation(s)
- Asfree Gwanyanya
- Department of Cardiovascular Sciences, KU Leuven, 3000 Leuven, Belgium; (A.G.); (B.M.I.); (F.E.); (K.M.)
- Department of Human Biology, University of Cape Town, Cape Town 7925, South Africa
| | - Inga Andriulė
- Institute of Cardiology, Lithuanian University of Health Sciences, 50103 Kaunas, Lithuania;
| | - Bogdan M. Istrate
- Department of Cardiovascular Sciences, KU Leuven, 3000 Leuven, Belgium; (A.G.); (B.M.I.); (F.E.); (K.M.)
| | - Farjana Easmin
- Department of Cardiovascular Sciences, KU Leuven, 3000 Leuven, Belgium; (A.G.); (B.M.I.); (F.E.); (K.M.)
| | - Kanigula Mubagwa
- Department of Cardiovascular Sciences, KU Leuven, 3000 Leuven, Belgium; (A.G.); (B.M.I.); (F.E.); (K.M.)
- Department of Basic Sciences, Faculty of Medicine, Université Catholique de Bukavu, Bukavu, Congo
| | - Regina Mačianskienė
- Institute of Cardiology, Lithuanian University of Health Sciences, 50103 Kaunas, Lithuania;
- Correspondence:
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Electro-Mechanical Whole-Heart Digital Twins: A Fully Coupled Multi-Physics Approach. MATHEMATICS 2021. [DOI: 10.3390/math9111247] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mathematical models of the human heart are evolving to become a cornerstone of precision medicine and support clinical decision making by providing a powerful tool to understand the mechanisms underlying pathophysiological conditions. In this study, we present a detailed mathematical description of a fully coupled multi-scale model of the human heart, including electrophysiology, mechanics, and a closed-loop model of circulation. State-of-the-art models based on human physiology are used to describe membrane kinetics, excitation-contraction coupling and active tension generation in the atria and the ventricles. Furthermore, we highlight ways to adapt this framework to patient specific measurements to build digital twins. The validity of the model is demonstrated through simulations on a personalized whole heart geometry based on magnetic resonance imaging data of a healthy volunteer. Additionally, the fully coupled model was employed to evaluate the effects of a typical atrial ablation scar on the cardiovascular system. With this work, we provide an adaptable multi-scale model that allows a comprehensive personalization from ion channels to the organ level enabling digital twin modeling.
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5
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Joshi V, Strege PR, Farrugia G, Beyder A. Mechanotransduction in gastrointestinal smooth muscle cells: role of mechanosensitive ion channels. Am J Physiol Gastrointest Liver Physiol 2021; 320:G897-G906. [PMID: 33729004 PMCID: PMC8202201 DOI: 10.1152/ajpgi.00481.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Mechanosensation, the ability to properly sense mechanical stimuli and transduce them into physiologic responses, is an essential determinant of gastrointestinal (GI) function. Abnormalities in this process result in highly prevalent GI functional and motility disorders. In the GI tract, several cell types sense mechanical forces and transduce them into electrical signals, which elicit specific cellular responses. Some mechanosensitive cells like sensory neurons act as specialized mechanosensitive cells that detect forces and transduce signals into tissue-level physiological reactions. Nonspecialized mechanosensitive cells like smooth muscle cells (SMCs) adjust their function in response to forces. Mechanosensitive cells use various mechanoreceptors and mechanotransducers. Mechanoreceptors detect and convert force into electrical and biochemical signals, and mechanotransducers amplify and direct mechanoreceptor responses. Mechanoreceptors and mechanotransducers include ion channels, specialized cytoskeletal proteins, cell junction molecules, and G protein-coupled receptors. SMCs are particularly important due to their role as final effectors for motor function. Myogenic reflex-the ability of smooth muscle to contract in response to stretch rapidly-is a critical smooth muscle function. Such rapid mechanotransduction responses rely on mechano-gated and mechanosensitive ion channels, which alter their ion pores' opening in response to force, allowing fast electrical and Ca2+ responses. Although GI SMCs express a variety of such ion channels, their identities remain unknown. Recent advancements in electrophysiological, genetic, in vivo imaging, and multi-omic technologies broaden our understanding of how SMC mechano-gated and mechanosensitive ion channels regulate GI functions. This review discusses GI SMC mechanosensitivity's current developments with a particular emphasis on mechano-gated and mechanosensitive ion channels.
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Affiliation(s)
- Vikram Joshi
- 1Division of Gastroenterology & Hepatology, Enteric NeuroScience Program (ENSP), Mayo Clinic, Rochester, Minnesota
| | - Peter R. Strege
- 1Division of Gastroenterology & Hepatology, Enteric NeuroScience Program (ENSP), Mayo Clinic, Rochester, Minnesota
| | - Gianrico Farrugia
- 1Division of Gastroenterology & Hepatology, Enteric NeuroScience Program (ENSP), Mayo Clinic, Rochester, Minnesota,2Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Arthur Beyder
- 1Division of Gastroenterology & Hepatology, Enteric NeuroScience Program (ENSP), Mayo Clinic, Rochester, Minnesota,2Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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6
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Quinn TA, Kohl P. Cardiac Mechano-Electric Coupling: Acute Effects of Mechanical Stimulation on Heart Rate and Rhythm. Physiol Rev 2020; 101:37-92. [PMID: 32380895 DOI: 10.1152/physrev.00036.2019] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The heart is vital for biological function in almost all chordates, including humans. It beats continually throughout our life, supplying the body with oxygen and nutrients while removing waste products. If it stops, so does life. The heartbeat involves precise coordination of the activity of billions of individual cells, as well as their swift and well-coordinated adaption to changes in physiological demand. Much of the vital control of cardiac function occurs at the level of individual cardiac muscle cells, including acute beat-by-beat feedback from the local mechanical environment to electrical activity (as opposed to longer term changes in gene expression and functional or structural remodeling). This process is known as mechano-electric coupling (MEC). In the current review, we present evidence for, and implications of, MEC in health and disease in human; summarize our understanding of MEC effects gained from whole animal, organ, tissue, and cell studies; identify potential molecular mediators of MEC responses; and demonstrate the power of computational modeling in developing a more comprehensive understanding of ‟what makes the heart tick.ˮ.
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Affiliation(s)
- T Alexander Quinn
- Department of Physiology and Biophysics and School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; Institute for Experimental Cardiovascular Medicine, University Heart Centre Freiburg/Bad Krozingen, Medical Faculty of the University of Freiburg, Freiburg, Germany; and CIBSS-Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Peter Kohl
- Department of Physiology and Biophysics and School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; Institute for Experimental Cardiovascular Medicine, University Heart Centre Freiburg/Bad Krozingen, Medical Faculty of the University of Freiburg, Freiburg, Germany; and CIBSS-Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
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7
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Balakina-Vikulova NA, Panfilov A, Solovyova O, Katsnelson LB. Mechano-calcium and mechano-electric feedbacks in the human cardiomyocyte analyzed in a mathematical model. J Physiol Sci 2020; 70:12. [PMID: 32070290 PMCID: PMC7028825 DOI: 10.1186/s12576-020-00741-6] [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: 10/21/2019] [Accepted: 02/04/2020] [Indexed: 12/11/2022]
Abstract
Experiments on animal hearts (rat, rabbit, guinea pig, etc.) have demonstrated that mechano-calcium feedback (MCF) and mechano-electric feedback (MEF) are very important for myocardial self-regulation because they adjust the cardiomyocyte contractile function to various mechanical loads and to mechanical interactions between heterogeneous myocardial segments in the ventricle walls. In in vitro experiments on these animals, MCF and MEF manifested themselves in several basic classical phenomena (e.g., load dependence, length dependence of isometric twitches, etc.), and in the respective responses of calcium transients and action potentials. However, it is extremely difficult to study simultaneously the electrical, calcium, and mechanical activities of the human heart muscle in vitro. Mathematical modeling is a useful tool for exploring these phenomena. We have developed a novel model to describe electromechanical coupling and mechano-electric feedbacks in the human cardiomyocyte. It combines the ‘ten Tusscher–Panfilov’ electrophysiological model of the human cardiomyocyte with our module of myocardium mechanical activity taken from the ‘Ekaterinburg–Oxford’ model and adjusted to human data. Using it, we simulated isometric and afterloaded twitches and effects of MCF and MEF on excitation–contraction coupling. MCF and MEF were found to affect significantly the duration of the calcium transient and action potential in the human cardiomyocyte model in response to both smaller afterloads as compared to bigger ones and various mechanical interventions applied during isometric and afterloaded twitches.
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Affiliation(s)
- Nathalie A Balakina-Vikulova
- Institute of Immunology and Physiology of the Ural Branch of the Russian Academy of Sciences, Ekaterinburg, Russia. .,Ural Federal University, Ekaterinburg, Russia.
| | - Alexander Panfilov
- Ural Federal University, Ekaterinburg, Russia.,Ghent University, Ghent, Belgium
| | - Olga Solovyova
- Institute of Immunology and Physiology of the Ural Branch of the Russian Academy of Sciences, Ekaterinburg, Russia.,Ural Federal University, Ekaterinburg, Russia
| | - Leonid B Katsnelson
- Institute of Immunology and Physiology of the Ural Branch of the Russian Academy of Sciences, Ekaterinburg, Russia.,Ural Federal University, Ekaterinburg, Russia
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8
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Spreckelsen F, Luther S, Parlitz U. Synchronization of viscoelastically coupled excitable oscillators. Phys Rev E 2019; 100:032214. [PMID: 31640069 DOI: 10.1103/physreve.100.032214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Indexed: 11/07/2022]
Abstract
Viscoelastically coupled excitable oscillators are used to model individually beating spatially separated cardiomyocytes surrounded by an extracellular matrix (ECM). We investigate how mechanical coupling via the ECM can synchronize two such oscillators with excitation contraction coupling and electromechanical feedback and how this synchronization depends on the rheological properties of the ECM. Extending our study to a linear chain of coupled oscillators we find a transition to synchronization as the ECM becomes stiffer. In the case of purely elastic coupling we observe antiphase chimera states.
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Affiliation(s)
- Florian Spreckelsen
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, D-37077 Göttingen, Germany.,University of Göttingen, Institute for the Dynamics of Complex Systems, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Göttingen, Robert-Koch-Straße 42a, D-37075 Göttingen, Germany
| | - Stefan Luther
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, D-37077 Göttingen, Germany.,University of Göttingen, Institute for the Dynamics of Complex Systems, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Göttingen, Robert-Koch-Straße 42a, D-37075 Göttingen, Germany.,University Medical Center Göttingen (UMG), Institute of Pharmacology and Toxicology, Robert-Koch-Straße 40, D-37075 Göttingen, Germany
| | - Ulrich Parlitz
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, D-37077 Göttingen, Germany.,University of Göttingen, Institute for the Dynamics of Complex Systems, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Göttingen, Robert-Koch-Straße 42a, D-37075 Göttingen, Germany
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9
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Hazim A, Belhamadia Y, Dubljevic S. Effects of mechano-electrical feedback on the onset of alternans: A computational study. CHAOS (WOODBURY, N.Y.) 2019; 29:063126. [PMID: 31266317 DOI: 10.1063/1.5095778] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 06/05/2019] [Indexed: 06/09/2023]
Abstract
Cardiac alternans is a heart rhythm instability that is associated with cardiac arrhythmias and may lead to sudden cardiac death. The onset of this instability, which is linked to period-doubling bifurcation and may be a route to chaos, is of particular interest. Mechano-electric feedback depicts the effects of tissue deformation on cardiac excitation. The main effect of mechano-electric feedback is delivered via the so-called stretch-activated ion channels and is caused by stretch-activated currents. Mechano-electric feedback, which is believed to have proarrhythmic and antiarrhythmic effects on cardiac electrophysiology, affects the action potential duration in a manner dependent on cycle length, but the mechanisms by which this occurs remain to be elucidated. In this study, a biophysically detailed electromechanical model of cardiac tissue is employed to show how a stretch-activated current can affect the action potential duration at cellular and tissue levels, illustrating its effects on the onset of alternans. Also, using a two-dimensional iterated map that incorporates stretch-activated current effects, we apply linear stability analysis to study the stability of the bifurcation. We show that alternans bifurcation can be prevented depending on the strength of the stretch-activated current.
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Affiliation(s)
- Azzam Hazim
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta T6G 2V2, Canada
| | - Youssef Belhamadia
- Department of Mathematics and Statistics, American University of Sharjah, Sharjah, United Arab Emirates
| | - Stevan Dubljevic
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada
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10
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Dowrick JM, Tran K, Loiselle DS, Nielsen PMF, Taberner AJ, Han J, Ward M. The slow force response to stretch: Controversy and contradictions. Acta Physiol (Oxf) 2019; 226:e13250. [PMID: 30614655 DOI: 10.1111/apha.13250] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 12/20/2018] [Accepted: 01/02/2019] [Indexed: 12/19/2022]
Abstract
When exposed to an abrupt stretch, cardiac muscle exhibits biphasic active force enhancement. The initial, instantaneous, force enhancement is well explained by the Frank-Starling mechanism. However, the cellular mechanisms associated with the second, slower phase remain contentious. This review explores hypotheses regarding this "slow force response" with the intention of clarifying some apparent contradictions in the literature. The review is partitioned into three sections. The first section considers pathways that modify the intracellular calcium handling to address the role of the sarcoplasmic reticulum in the mechanism underlying the slow force response. The second section focuses on extracellular calcium fluxes and explores the identity and contribution of the stretch-activated, non-specific, cation channels as well as signalling cascades associated with G-protein coupled receptors. The final section introduces promising candidates for the mechanosensor(s) responsible for detecting the stretch perturbation.
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Affiliation(s)
- Jarrah M. Dowrick
- Auckland Bioengineering Institute University of Auckland Auckland New Zealand
| | - Kenneth Tran
- Auckland Bioengineering Institute University of Auckland Auckland New Zealand
| | - Denis S. Loiselle
- Auckland Bioengineering Institute University of Auckland Auckland New Zealand
- Department of Physiology University of Auckland Auckland New Zealand
| | - Poul M. F. Nielsen
- Auckland Bioengineering Institute University of Auckland Auckland New Zealand
- Department of Engineering Science University of Auckland Auckland New Zealand
| | - Andrew J. Taberner
- Auckland Bioengineering Institute University of Auckland Auckland New Zealand
- Department of Engineering Science University of Auckland Auckland New Zealand
| | - June‐Chiew Han
- Auckland Bioengineering Institute University of Auckland Auckland New Zealand
| | - Marie‐Louise Ward
- Department of Physiology University of Auckland Auckland New Zealand
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11
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Kim JC, Son MJ, Woo SH. Regulation of cardiac calcium by mechanotransduction: Role of mitochondria. Arch Biochem Biophys 2018; 659:33-41. [DOI: 10.1016/j.abb.2018.09.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 09/28/2018] [Indexed: 12/27/2022]
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12
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Zhang H, Walcott GP, Rogers JM. Effects of gadolinium on cardiac mechanosensitivity in whole isolated swine hearts. Sci Rep 2018; 8:10506. [PMID: 30002391 PMCID: PMC6043572 DOI: 10.1038/s41598-018-28743-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 06/28/2018] [Indexed: 12/13/2022] Open
Abstract
Mechanical stimulation can elicit electrical activation of the heart. This mechanosensitivity can start life-threatening arrhythmias (commotio cordis) or terminate them (precordial thump). Mechanosensitivity may also be involved in arrhythmogenesis in other settings. Stretch-activated ion channels (SACs) are thought to be important in mechanosensitivity and a number of agents that block them have been identified. Such agents could potentially be used as tools in experimental investigation of mechanosensitivity. However, studies using them in intact-heart preparations have yielded inconsistent results. In the present study, we used isolated, perfused hearts from 25-35 kg pigs and a computer-controlled device that repeatably delivered focal mechanical stimuli. The concentration-dependent ability of the SAC blocker gadolinium to suppress mechanical activation was assessed by the success rate of mechanical stimulation and by the delay between successful mechanical stimulation and electrical activation. In six hearts, perfusate was recirculated. In an additional six hearts, perfusate was not recirculated to prevent gadolinium from forming complexes with metabolic waste and possibly precipitating. Gadolinium did not suppress mechanically-induced activation. Although gadolinium has been shown to be an effective SAC blocker in isolated cells, using it to probe the role of mechanical stimulation in whole heart preparations should be done with great caution.
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Affiliation(s)
- Hanyu Zhang
- University of Alabama at Birmingham, Department of Biomedical Engineering, Birmingham, 35294, United States of America
| | - Gregory P Walcott
- University of Alabama at Birmingham, Division of Cardiovascular Disease, Department of Medicine, Birmingham, 35294, United States of America
| | - Jack M Rogers
- University of Alabama at Birmingham, Department of Biomedical Engineering, Birmingham, 35294, United States of America.
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13
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Satriano A, Vigmond EJ, Schwartzman DS, Di Martino ES. Mechano-electric finite element model of the left atrium. Comput Biol Med 2018. [PMID: 29529527 DOI: 10.1016/j.compbiomed.2018.02.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Mechanical stretch plays a major role in modulating atrial function, being responsible for beat-by-beat responses to changes in chamber preload, enabling a prompt regulation of cardiac function. Mechano-electric coupling (MEC) operates through many mechanisms and has many targets, making it experimentally difficult to isolate causes and effects especially under sinus conditions where effects are more transient and subtle. Therefore, modelling is a powerful tool to help understand the role of MEC with respect to the atrial electromechanical interaction. We propose a cellular-based computational model of the left atrium that includes a strongly coupled MEC component and mitral flow component to account for correct pressure generation in the atrial chamber as a consequence of blood volume and contraction. The method was applied to a healthy porcine left atrium. Results of the strongly coupled simulation show that strains are higher in the areas adjacent to the mitral annulus, the rim of the appendage, around the pulmonary venous trunks and at the location of the Bachmann's bundle, approximately between the mitral annulus and the region where the venous tissue transitions into atrial. These are regions where arrhythmias are likely to originate. The role of stretch-activated channels was very small for sinus rhythm for the single cardiac beat simulation, although tension development was very sensitive to stretch. The method could be applied to investigate potential therapeutic interventions acting on the mechano-electrical properties of the left atrium.
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Affiliation(s)
- Alessandro Satriano
- Stephenson Cardiac Imaging Centre, The University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4, Canada
| | - Edward J Vigmond
- Department of Electrical and Computer Engineering, University of Calgary, 2500 University Dr NW, Calgary, Alberta T2N 1N4, Canada; LIRYC, Electrophysiology and Heart Modelling Institute, PTIB-Hopital Xavier Arnozan, Avenue Haut-Lévèque, Pessac, 33600, France; IMB, University of Bordeaux, 351 Cours de la Liberation, Talence, 33405, France
| | - David S Schwartzman
- Heart and Vascular Institute, University of Pittsburgh, UPMC Presbyterian, B535, Pittsburgh, PA 15213 2582, United States
| | - Elena S Di Martino
- Department of Civil Engineering, Libin Cardiovascular Institute of Alberta and Centre for Bioengineering Research and Education, The University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4, Canada.
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14
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Shim AL, Mitrokhin VM, Kazanski VE, Mladenov MI, Kamkin AG. Discrete Stretch Eliminates Electrophysiological Dose-Dependent Effects of Nitric Oxide Donor SNAP in Rat Atrium. Bull Exp Biol Med 2017; 163:705-709. [PMID: 29063314 DOI: 10.1007/s10517-017-3885-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Indexed: 02/02/2023]
Abstract
Depolarization of cardiomyocytes triggered by stretch and activation of mechanically gated ion channels can lead to serious arrhythmias. However, stretch-induced signaling activating these channels remain little studied. This study tested the hypothesis on implication of NO in shaping the electrical abnormalities provoked by stretch of the right atrial myocardium in rat via a mechanism engaging a signaling cascade, where NO plays a significant role. This approach showed that in isolated right atrial preparation, NO donor SNAP induces the electrical abnormalities similar to those provoked by stretch, and the latter results from activation of NO synthase.
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Affiliation(s)
- A L Shim
- Department of Physiology, N. I. Pirogov Russian National Research Medical University, Ministry of Health of the Russian Federation, Moscow, Russia
| | - V M Mitrokhin
- Department of Physiology, N. I. Pirogov Russian National Research Medical University, Ministry of Health of the Russian Federation, Moscow, Russia.
| | - V E Kazanski
- Department of Physiology, N. I. Pirogov Russian National Research Medical University, Ministry of Health of the Russian Federation, Moscow, Russia
| | - M I Mladenov
- Department of Physiology, N. I. Pirogov Russian National Research Medical University, Ministry of Health of the Russian Federation, Moscow, Russia
| | - A G Kamkin
- Department of Physiology, N. I. Pirogov Russian National Research Medical University, Ministry of Health of the Russian Federation, Moscow, Russia
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15
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Kim JC, Son MJ, Wang J, Woo SH. Regulation of cardiac Ca 2+ and ion channels by shear mechanotransduction. Arch Pharm Res 2017; 40:783-795. [PMID: 28702845 DOI: 10.1007/s12272-017-0929-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Accepted: 07/06/2017] [Indexed: 11/25/2022]
Abstract
Cardiac contraction is controlled by a Ca2+ signaling sequence that includes L-type Ca2+ current-gated opening of Ca2+ release channels (ryanodine receptors) in the sarcoplasmic reticulum (SR). Local Ca2+ signaling in the atrium differs from that in the ventricle because atrial myocytes lack transverse tubules and have more abundant corbular SR. Myocardium is subjected to a variety of forces with each contraction, such as stretch, shear stress, and afterload, and adapts to those mechanical stresses. These mechanical stimuli increase in heart failure, hypertension, and valvular heart diseases that are clinically implicated in atrial fibrillation and stroke. In the present review, we describe distinct responses of atrial and ventricular myocytes to shear stress and compare them with other mechanical responses in the context of local and global Ca2+ signaling and ion channel regulation. Recent evidence suggests that shear mechanotransduction in cardiac myocytes involves activation of gap junction hemichannels, purinergic signaling, and generation of mitochondrial reactive oxygen species. Significant alterations in Ca2+ signaling and ionic currents by shear stress may be implicated in the pathogenesis of cardiac arrhythmia and failure.
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Affiliation(s)
- Joon-Chul Kim
- College of Pharmacy, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon, 305-764, South Korea
| | - Min-Jeong Son
- College of Pharmacy, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon, 305-764, South Korea
| | - Jun Wang
- College of Pharmacy, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon, 305-764, South Korea
| | - Sun-Hee Woo
- College of Pharmacy, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon, 305-764, South Korea.
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16
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Schönleitner P, Schotten U, Antoons G. Mechanosensitivity of microdomain calcium signalling in the heart. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017. [PMID: 28648626 DOI: 10.1016/j.pbiomolbio.2017.06.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In cardiac myocytes, calcium (Ca2+) signalling is tightly controlled in dedicated microdomains. At the dyad, i.e. the narrow cleft between t-tubules and junctional sarcoplasmic reticulum (SR), many signalling pathways combine to control Ca2+-induced Ca2+ release during contraction. Local Ca2+ gradients also exist in regions where SR and mitochondria are in close contact to regulate energetic demands. Loss of microdomain structures, or dysregulation of local Ca2+ fluxes in cardiac disease, is often associated with oxidative stress, contractile dysfunction and arrhythmias. Ca2+ signalling at these microdomains is highly mechanosensitive. Recent work has demonstrated that increasing mechanical load triggers rapid local Ca2+ releases that are not reflected by changes in global Ca2+. Key mechanisms involve rapid mechanotransduction with reactive oxygen species or nitric oxide as primary signalling molecules targeting SR or mitochondria microdomains depending on the nature of the mechanical stimulus. This review summarizes the most recent insights in rapid Ca2+ microdomain mechanosensitivity and re-evaluates its (patho)physiological significance in the context of historical data on the macroscopic role of Ca2+ in acute force adaptation and mechanically-induced arrhythmias. We distinguish between preload and afterload mediated effects on local Ca2+ release, and highlight differences between atrial and ventricular myocytes. Finally, we provide an outlook for further investigation in chronic models of abnormal mechanics (eg post-myocardial infarction, atrial fibrillation), to identify the clinical significance of disturbed Ca2+ mechanosensitivity for arrhythmogenesis.
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Affiliation(s)
- Patrick Schönleitner
- Dept of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, The Netherlands
| | - Uli Schotten
- Dept of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, The Netherlands
| | - Gudrun Antoons
- Dept of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, The Netherlands.
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17
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Hariyanto H, Yahya CQ, Wibowo P, Tampubolon OE. A tale of the broken heart: peripartum cardiomyopathy, a case report. MEDICAL JOURNAL OF INDONESIA 2016. [DOI: 10.13181/mji.v25i1.1278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Progressive dyspnea following childbirth warrants a prompt suspicion into the diagnosis of peripartum cardiomyopathy, PPCM. Pump failure causes an inadequate cardiac output which ultimately contributes to PPCM high mortality rate; however early airway control, vigilant fluid balance and vasoactive support will substantially reduce the incidence of patients falling into decompensated heart failure. More importantly, it is imperative that these patients are cared in a setting where continuous hemodynamic monitoring is available. This case report serves as a reminder not to focus end-point therapy solely on blood pressure readings, but to observe signs and symptoms of hypoperfusion such as cold clammy skin, cool extremities, decreased urine output and mental status.
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18
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Son MJ, Kim JC, Kim SW, Chidipi B, Muniyandi J, Singh TD, So I, Subedi KP, Woo SH. Shear stress activates monovalent cation channel transient receptor potential melastatin subfamily 4 in rat atrial myocytes via type 2 inositol 1,4,5-trisphosphate receptors and Ca(2+) release. J Physiol 2016; 594:2985-3004. [PMID: 26751048 DOI: 10.1113/jp270887] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 01/06/2016] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS During each contraction and haemodynamic disturbance, cardiac myocytes are subjected to fluid shear stress as a result of blood flow and the relative movement of sheets of myocytes. The present study aimed to characterize the shear stress-sensitive membrane current in atrial myocytes using the whole-cell patch clamp technique, combined with pressurized fluid flow, as well as pharmacological and genetic interventions of specific proteins. The data obtained suggest that shear stress indirectly activates the monovalent cation current carried by transient receptor potential melastatin subfamily 4 channels via type 2 inositol 1,4,5-trisphosphate receptor-mediated Ca(2+) release in subsarcolemmal domains of atrial myocytes. Ca(2+) -mediated interactions between these two proteins under shear stress may be an important mechanism by which atrial cells measure mechanical stress and translate it to alter their excitability. ABSTRACT Atrial myocytes are subjected to shear stress during the cardiac cycle under physiological or pathological conditions. The ionic currents regulated by shear stress remain poorly understood. We report the characteristics, molecular identity and activation mechanism of the shear stress-sensitive current (Ishear ) in rat atrial myocytes. A shear stress of ∼16 dyn cm(-2) was applied to single myocytes using a pressurized microflow system, and the current was measured by whole-cell patch clamp. In symmetrical CsCl solutions with minimal concentrations of internal EGTA, Ishear showed an outwardly rectifying current-voltage relationship (reversal at -2 mV). The current was conducted primarily (∼80%) by monovalent cations but not Ca(2+) . It was suppressed by intracellular Ca(2+) buffering at a fixed physiological level, inhibitors of transient receptor potential melastatin subfamily 4 (TRPM4), intracellular introduction of TRPM4 antibodies or knockdown of TRPM4 expression, suggesting that TRPM4 carries most of this current. A notable reduction in Ishear occurred upon inhibition of Ca(2+) release through the ryanodine receptors or inositol 1,4,5-trisphosphate receptors (IP3 R) and upon depletion of sarcoplasmic reticulum Ca(2+) . In type 2 IP3 R (IP3 R2) knockout atrial myocytes, Ishear was 10-20% of that in wild-type myocytes. Immunocytochemistry and proximity ligation assays revealed that TRPM4 and IP3 R2 were expressed at peripheral sites with co-localization, although they are not localized within 40 nm. Peripheral localization of TRPM4 was intact in IP3 R2 knockout cells. The data obtained in the present study suggest that shear stress activates TRPM4 current by triggering Ca(2+) release from the IP3 R2 in the peripheral domains of atrial myocytes.
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Affiliation(s)
- Min-Jeong Son
- Laboratory of Physiology, College of Pharmacy, Chungnam National University, Yuseong-gu, Daejeon, South Korea
| | - Joon-Chul Kim
- Laboratory of Physiology, College of Pharmacy, Chungnam National University, Yuseong-gu, Daejeon, South Korea
| | - Sung Woo Kim
- Laboratory of Physiology, College of Pharmacy, Chungnam National University, Yuseong-gu, Daejeon, South Korea
| | - Bojjibabu Chidipi
- Laboratory of Physiology, College of Pharmacy, Chungnam National University, Yuseong-gu, Daejeon, South Korea
| | - Jeyaraj Muniyandi
- Laboratory of Physiology, College of Pharmacy, Chungnam National University, Yuseong-gu, Daejeon, South Korea
| | - Thoudam Debraj Singh
- Laboratory of Physiology, College of Pharmacy, Chungnam National University, Yuseong-gu, Daejeon, South Korea
| | - Insuk So
- Department of Physiology, College of Medicine, Seoul National University, Seoul, South Korea
| | - Krishna P Subedi
- Laboratory of Physiology, College of Pharmacy, Chungnam National University, Yuseong-gu, Daejeon, South Korea.,Secretory Physiology Section, Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, NIH, Bethesda, MD, USA
| | - Sun-Hee Woo
- Laboratory of Physiology, College of Pharmacy, Chungnam National University, Yuseong-gu, Daejeon, South Korea
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19
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Kim JC, Woo SH. Shear stress induces a longitudinal Ca(2+) wave via autocrine activation of P2Y1 purinergic signalling in rat atrial myocytes. J Physiol 2015; 593:5091-109. [PMID: 26377030 DOI: 10.1113/jp271016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Accepted: 09/11/2015] [Indexed: 12/25/2022] Open
Abstract
Atrial myocytes are exposed to shear stress during the cardiac cycle and haemodynamic disturbance. In response, they generate a longitudinally propagating global Ca(2+) wave. Here, we investigated the cellular mechanisms underlying the shear stress-mediated Ca(2+) wave, using two-dimensional confocal Ca(2+) imaging combined with a pressurized microflow system in single rat atrial myocytes. Shear stress of ∼16 dyn cm(-2) for 8 s induced ∼1.2 aperiodic longitudinal Ca(2+) waves (∼79 μm s(-1)) with a delay of 0.2-3 s. Pharmacological blockade of ryanodine receptors (RyRs) or inositol 1,4,5-trisphosphate receptors (IP3 Rs) abolished shear stress-induced Ca(2+) wave generation. Furthermore, in atrial myocytes from type 2 IP3R (IP3R2) knock-out mice, shear stress failed to induce longitudinal Ca(2+) waves. The phospholipase C (PLC) inhibitor U73122, but not its inactive analogue U73343, abolished the shear-induced longitudinal Ca(2+) wave. However, pretreating atrial cells with blockers for stretch-activated channels, Na(+)-Ca(2+) exchanger, transient receptor potential melastatin subfamily 4, or nicotinamide adenine dinucleotide phosphate oxidase did not suppress wave generation under shear stress. The P2 purinoceptor inhibitor suramin, and the potent P2Y1 receptor antagonist MRS 2179, both suppressed the Ca(2+) wave, whereas the P2X receptor antagonist, iso-PPADS, did not alter it. Suppression of gap junction hemichannels permeable to ATP or extracellular application of ATP-metabolizing apyrase inhibited the wave. Removal of external Ca(2+) to enhance hemichannel opening facilitated the wave generation. Our data suggest that longitudinally propagating, regenerative Ca(2+) release through RyRs is triggered by P2Y1-PLC-IP3R2 signalling that is activated by gap junction hemichannel-mediated ATP release in atrial myocytes under shear stress.
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Affiliation(s)
- Joon-Chul Kim
- Laboratory of Physiology, College of Pharmacy, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon, 305-764, South Korea
| | - Sun-Hee Woo
- Laboratory of Physiology, College of Pharmacy, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon, 305-764, South Korea
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20
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Burnstock G, Pelleg A. Cardiac purinergic signalling in health and disease. Purinergic Signal 2015; 11:1-46. [PMID: 25527177 PMCID: PMC4336308 DOI: 10.1007/s11302-014-9436-1] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 11/25/2014] [Indexed: 01/09/2023] Open
Abstract
This review is a historical account about purinergic signalling in the heart, for readers to see how ideas and understanding have changed as new experimental results were published. Initially, the focus is on the nervous control of the heart by ATP as a cotransmitter in sympathetic, parasympathetic, and sensory nerves, as well as in intracardiac neurons. Control of the heart by centers in the brain and vagal cardiovascular reflexes involving purines are also discussed. The actions of adenine nucleotides and nucleosides on cardiomyocytes, atrioventricular and sinoatrial nodes, cardiac fibroblasts, and coronary blood vessels are described. Cardiac release and degradation of ATP are also described. Finally, the involvement of purinergic signalling and its therapeutic potential in cardiac pathophysiology is reviewed, including acute and chronic heart failure, ischemia, infarction, arrhythmias, cardiomyopathy, syncope, hypertrophy, coronary artery disease, angina, diabetic cardiomyopathy, as well as heart transplantation and coronary bypass grafts.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF, UK,
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21
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Living cardiac tissue slices: an organotypic pseudo two-dimensional model for cardiac biophysics research. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 115:314-27. [PMID: 25124067 DOI: 10.1016/j.pbiomolbio.2014.08.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 08/02/2014] [Indexed: 11/24/2022]
Abstract
Living cardiac tissue slices, a pseudo two-dimensional (2D) preparation, have received less attention than isolated single cells, cell cultures, or Langendorff-perfused hearts in cardiac biophysics research. This is, in part, due to difficulties associated with sectioning cardiac tissue to obtain live slices. With moderate complexity, native cell-types, and well-preserved cell-cell electrical and mechanical interconnections, cardiac tissue slices have several advantages for studying cardiac electrophysiology. The trans-membrane potential (Vm) has, thus far, mainly been explored using multi-electrode arrays. Here, we combine tissue slices with optical mapping to monitor Vm and intracellular Ca(2+) concentration ([Ca(2+)]i). This combination opens up the possibility of studying the effects of experimental interventions upon action potential (AP) and calcium transient (CaT) dynamics in 2D, and with relatively high spatio-temporal resolution. As an intervention, we conducted proof-of-principle application of stretch. Mechanical stimulation of cardiac preparations is well-established for membrane patches, single cells and whole heart preparations. For cardiac tissue slices, it is possible to apply stretch perpendicular or parallel to the dominant orientation of cells, while keeping the preparation in a constant focal plane for fluorescent imaging of in-slice functional dynamics. Slice-to-slice comparison furthermore allows one to assess transmural differences in ventricular tissue responses to mechanical challenges. We developed and tested application of axial stretch to cardiac tissue slices, using a manually-controlled stretching device, and recorded Vm and [Ca(2+)]i by optical mapping before, during, and after application of stretch. Living cardiac tissue slices, exposed to axial stretch, show an initial shortening in both AP and CaT duration upon stretch application, followed in most cases by a gradual prolongation of AP and CaT duration during stretch maintained for up to 50 min. After release of sustained stretch, AP duration (APD) and CaT duration reverted to shorter values. Living cardiac tissue slices are a promising experimental model for the study of cardiac mechano-electric interactions. The methodology described here can be refined to achieve more accurate control over stretch amplitude and timing (e.g. using a computer-controlled motorised stage, or by synchronising electrical and mechanical events) and through monitoring of regional tissue deformation (e.g. by adding motion tracking).
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22
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Shear stress triggers insertion of voltage-gated potassium channels from intracellular compartments in atrial myocytes. Proc Natl Acad Sci U S A 2013; 110:E3955-64. [PMID: 24065831 DOI: 10.1073/pnas.1309896110] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Atrial myocytes are continuously exposed to mechanical forces including shear stress. However, in atrial myocytes, the effects of shear stress are poorly understood, particularly with respect to its effect on ion channel function. Here, we report that shear stress activated a large outward current from rat atrial myocytes, with a parallel decrease in action potential duration. The main ion channel underlying the increase in current was found to be Kv1.5, the recruitment of which could be directly observed by total internal reflection fluorescence microscopy, in response to shear stress. The effect was primarily attributable to recruitment of intracellular pools of Kv1.5 to the sarcolemma, as the response was prevented by the SNARE protein inhibitor N-ethylmaleimide and the calcium chelator BAPTA. The process required integrin signaling through focal adhesion kinase and relied on an intact microtubule system. Furthermore, in a rat model of chronic hemodynamic overload, myocytes showed an increase in basal current despite a decrease in Kv1.5 protein expression, with a reduced response to shear stress. Additionally, integrin beta1d expression and focal adhesion kinase activation were increased in this model. This data suggests that, under conditions of chronically increased mechanical stress, the integrin signaling pathway is overactivated, leading to increased functional Kv1.5 at the membrane and reducing the capacity of cells to further respond to mechanical challenge. Thus, pools of Kv1.5 may comprise an inducible reservoir that can facilitate the repolarization of the atrium under conditions of excessive mechanical stress.
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23
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Sharma PS, Callans DJ. Treatment Considerations for a Dual Epidemic of Atrial Fibrillation and Heart Failure. J Atr Fibrillation 2013; 6:740. [PMID: 28496869 PMCID: PMC5153227 DOI: 10.4022/jafib.740] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 04/20/2013] [Accepted: 04/21/2013] [Indexed: 06/07/2023]
Abstract
Atrial fibrillation (AF) and heart failure (HF) have emerged as major cardiovascular epidemics in developed nations over the past decade. They share similar risk factors, seem to mutually accelerate progression and are associated with increased morbidity and mortality. Their relationship involves complex hemodynamic, neuro-hormonal, inflammatory and electrophysiologic mechanisms, which go beyond just mutual risk factors. This review focuses on updates in AF and HF with a hope of better understanding this relationship and the management of this complex duo.
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Affiliation(s)
- Parikshit S Sharma
- Dr. Sharma- Cardiology Fellow, Wright Center for Graduate Medical Education, Scranton, PA; Associate Professor of Medicine, The Commonwealth Medical College, Scranton, PA.Dr. Callans- Professor of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA
| | - David J Callans
- Dr. Sharma- Cardiology Fellow, Wright Center for Graduate Medical Education, Scranton, PA; Associate Professor of Medicine, The Commonwealth Medical College, Scranton, PA.Dr. Callans- Professor of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA
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24
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TNF-α provokes electrical abnormalities in rat atrial myocardium via a NO-dependent mechanism. Pflugers Arch 2013; 465:1741-52. [DOI: 10.1007/s00424-013-1320-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 06/09/2013] [Accepted: 06/22/2013] [Indexed: 01/06/2023]
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25
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Weise LD, Panfilov AV. A discrete electromechanical model for human cardiac tissue: effects of stretch-activated currents and stretch conditions on restitution properties and spiral wave dynamics. PLoS One 2013; 8:e59317. [PMID: 23527160 PMCID: PMC3602082 DOI: 10.1371/journal.pone.0059317] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Accepted: 02/13/2013] [Indexed: 11/24/2022] Open
Abstract
We introduce an electromechanical model for human cardiac tissue which couples a biophysical model of cardiac excitation (Tusscher, Noble, Noble, Panfilov, 2006) and tension development (adjusted Niederer, Hunter, Smith, 2006 model) with a discrete elastic mass-lattice model. The equations for the excitation processes are solved with a finite difference approach, and the equations of the mass-lattice model are solved using Verlet integration. This allows the coupled problem to be solved with high numerical resolution. Passive mechanical properties of the mass-lattice model are described by a generalized Hooke's law for finite deformations (Seth material). Active mechanical contraction is initiated by changes of the intracellular calcium concentration, which is a variable of the electrical model. Mechanical deformation feeds back on the electrophysiology via stretch-activated ion channels whose conductivity is controlled by the local stretch of the medium. We apply the model to study how stretch-activated currents affect the action potential shape, restitution properties, and dynamics of spiral waves, under constant stretch, and dynamic stretch caused by active mechanical contraction. We find that stretch conditions substantially affect these properties via stretch-activated currents. In constantly stretched medium, we observe a substantial decrease in conduction velocity, and an increase of action potential duration; whereas, with dynamic stretch, action potential duration is increased only slightly, and the conduction velocity restitution curve becomes biphasic. Moreover, in constantly stretched medium, we find an increase of the core size and period of a spiral wave, but no change in rotation dynamics; in contrast, in the dynamically stretching medium, we observe spiral drift. Our results may be important to understand how altered stretch conditions affect the heart's functioning.
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Affiliation(s)
- Louis D Weise
- Department of Theoretical Biology, Utrecht University, Utrecht, The Netherlands.
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26
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Dössel O, Krueger MW, Weber FM, Wilhelms M, Seemann G. Computational modeling of the human atrial anatomy and electrophysiology. Med Biol Eng Comput 2012; 50:773-99. [PMID: 22718317 DOI: 10.1007/s11517-012-0924-6] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 05/21/2012] [Indexed: 01/08/2023]
Abstract
This review article gives a comprehensive survey of the progress made in computational modeling of the human atria during the last 10 years. Modeling the anatomy has emerged from simple "peanut"-like structures to very detailed models including atrial wall and fiber direction. Electrophysiological models started with just two cellular models in 1998. Today, five models exist considering e.g. details of intracellular compartments and atrial heterogeneity. On the pathological side, modeling atrial remodeling and fibrotic tissue are the other important aspects. The bridge to data that are measured in the catheter laboratory and on the body surface (ECG) is under construction. Every measurement can be used either for model personalization or for validation. Potential clinical applications are briefly outlined and future research perspectives are suggested.
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Affiliation(s)
- Olaf Dössel
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology, Karlsruhe, Germany.
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27
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Tanimoto S, Sugiyama Y, Takahashi T, Ishizuka T, Yawo H. Involvement of glutamate 97 in ion influx through photo-activated channelrhodopsin-2. Neurosci Res 2012; 75:13-22. [PMID: 22664343 DOI: 10.1016/j.neures.2012.05.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 05/17/2012] [Accepted: 05/18/2012] [Indexed: 10/28/2022]
Abstract
The light absorption of a channelrhodopsin-2 (ChR2) is followed by conformational changes to the molecule, which allows the channel structure to become permeable to cations. Previously, a single point mutation in ChR2, which replaces glutamate residue 97 with a nonpolar alanine (E97A), was found to attenuate the photocurrent, suggesting that the E97 residue is involved in ion flux regulation. Here, the significance of E97 and its counterpart ChR1 (E136) were extensively studied by mutagenesis, whereby we replaced these glutamates with aspartate (D), glutamine (Q) or arginine (R). We found that the charge at this position strongly influences ion permeation and that the photocurrents were attenuated in the order of ChR2>E97D≈E97Q>E97R. We observed similar results with our chimeric/synthetic/artificial construct, ChR-wide receiver (ChRWR), which contains the first to fifth transmembrane helices of ChR1. The E-to-Q or E-to-R mutations, but not the E-to-D mutation, strongly retarded the sensitivity to the Gd(3+)-dependent blocking of the ChR1 or ChR2 channels. Our results suggest that the glutamate residue at this position lies in the outer pore, where it interacts with a cation to facilitate dehydration, and that this residue is the primary binding target of Gd(3+).
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Affiliation(s)
- Saki Tanimoto
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences and JST, CREST, Sendai 980-8577, Japan
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28
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Shklyar TF, Dinislamova OA, Safronov AP, Blyakhman FA. Effect of cytoskeletal elastic properties on the mechanoelectrical transduction in excitable cells. J Biomech 2012; 45:1444-9. [DOI: 10.1016/j.jbiomech.2012.02.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 01/14/2012] [Accepted: 02/16/2012] [Indexed: 11/25/2022]
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29
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Caldwell JC, Mamas MA. Heart failure, diastolic dysfunction and atrial fibrillation; mechanistic insight of a complex inter-relationship. Heart Fail Rev 2012; 17:27-33. [PMID: 21103928 DOI: 10.1007/s10741-010-9204-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Atrial fibrillation (AF) and heart failure (HF) commonly coexist, and their co-presence is associated with adverse outcomes relating to thromboembolic events, HF progression, hospitalisation and death. Diastolic dysfunction (DD) is also frequently present in patients with HF and is an independent predictor of hospitalisation and mortality. The presence of DD is a strong predictor of incident AF in patients with HF. In this review, we provide mechanistic insight into pathophysiological processes that frequently promote the occurrence of AF, HF and DD and outline the yin-yang relationship between AF, DD and HF. More recently, invasive studies have also shown that asymptomatic paroxysmal atrial fibrillation (PAF) is a common phenomenon in HF patients. We examine complex inter-relationships between PAF, HF and DD and speculate upon the possible clinical influence of undiagnosed PAF in HF patients.
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Affiliation(s)
- J C Caldwell
- Manchester Heart Centre, Manchester Royal Infirmary, Biomedical Research Centre, Manchester, UK.
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Weise LD, Panfilov AV. New mechanism of spiral wave initiation in a reaction-diffusion-mechanics system. PLoS One 2011; 6:e27264. [PMID: 22114667 PMCID: PMC3215707 DOI: 10.1371/journal.pone.0027264] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2011] [Accepted: 10/12/2011] [Indexed: 11/21/2022] Open
Abstract
Spiral wave initiation in the heart muscle is a mechanism for the onset of dangerous cardiac arrhythmias. A standard protocol for spiral wave initiation is the application of a stimulus in the refractory tail of a propagating excitation wave, a region that we call the “classical vulnerable zone.” Previous studies of vulnerability to spiral wave initiation did not take the influence of deformation into account, which has been shown to have a substantial effect on the excitation process of cardiomyocytes via the mechano-electrical feedback phenomenon. In this work we study the effect of deformation on the vulnerability of excitable media in a discrete reaction-diffusion-mechanics (dRDM) model. The dRDM model combines FitzHugh-Nagumo type equations for cardiac excitation with a discrete mechanical description of a finite-elastic isotropic material (Seth material) to model cardiac excitation-contraction coupling and stretch activated depolarizing current. We show that deformation alters the “classical,” and forms a new vulnerable zone at longer coupling intervals. This mechanically caused vulnerable zone results in a new mechanism of spiral wave initiation, where unidirectional conduction block and rotation directions of the consequently initiated spiral waves are opposite compared to the mechanism of spiral wave initiation due to the “classical vulnerable zone.” We show that this new mechanism of spiral wave initiation can naturally occur in situations that involve wave fronts with curvature, and discuss its relation to supernormal excitability of cardiac tissue. The concept of mechanically induced vulnerability may lead to a better understanding about the onset of dangerous heart arrhythmias via mechano-electrical feedback.
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Affiliation(s)
- Louis D Weise
- Department of Theoretical Biology, Utrecht University, Utrecht, The Netherlands.
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Abstract
The heart exhibits remarkable adaptive responses to a wide array of genetic and extrinsic factors to maintain contractile function. When compensatory responses are not sustainable, cardiac dysfunction occurs, leading to cardiomyopathy. The many forms of cardiomyopathy exhibit a set of overlapping phenotypes reflecting the limited range of compensatory responses that the heart can use. These include cardiac hypertrophy, induction of genes normally expressed during development, fibrotic deposits that replace necrotic and apoptotic cardiomyocytes, and metabolic disturbances. The compensatory responses are mediated by signaling pathways that initially serve to maintain normal contractility; however, persistent activation of these pathways leads to cardiac dysfunction. Current research focuses on ways to target these specific pathways therapeutically.
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Affiliation(s)
- Pamela A Harvey
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado at Boulder, USA
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A discrete model to study reaction-diffusion-mechanics systems. PLoS One 2011; 6:e21934. [PMID: 21804911 PMCID: PMC3133613 DOI: 10.1371/journal.pone.0021934] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 06/10/2011] [Indexed: 11/28/2022] Open
Abstract
This article introduces a discrete reaction-diffusion-mechanics (dRDM) model to study the effects of deformation on reaction-diffusion (RD) processes. The dRDM framework employs a FitzHugh-Nagumo type RD model coupled to a mass-lattice model, that undergoes finite deformations. The dRDM model describes a material whose elastic properties are described by a generalized Hooke's law for finite deformations (Seth material). Numerically, the dRDM approach combines a finite difference approach for the RD equations with a Verlet integration scheme for the equations of the mass-lattice system. Using this framework results were reproduced on self-organized pacemaking activity that have been previously found with a continuous RD mechanics model. Mechanisms that determine the period of pacemakers and its dependency on the medium size are identified. Finally it is shown how the drift direction of pacemakers in RDM systems is related to the spatial distribution of deformation and curvature effects.
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RAVELLI FLAVIA, MASÈ MICHELA, DEL GRECO MAURIZIO, MARINI MASSIMILIANO, DISERTORI MARCELLO. Acute Atrial Dilatation Slows Conduction and Increases AF Vulnerability in the Human Atrium. J Cardiovasc Electrophysiol 2010; 22:394-401. [DOI: 10.1111/j.1540-8167.2010.01939.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Tashiro M, Inoue H, Konishi M. KB-R7943 inhibits Na+-dependent Mg2+ efflux in rat ventricular myocytes. J Physiol Sci 2010; 60:415-24. [PMID: 20862573 PMCID: PMC10717662 DOI: 10.1007/s12576-010-0113-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Accepted: 08/26/2010] [Indexed: 11/29/2022]
Abstract
Na(+)-dependent Mg(2+) efflux activity was studied with the fluorescent Mg(2+) indicator furaptra in the presence of various potential antagonists known to inhibit other transporters and channels. Among the compounds tested, KB-R7943, an inhibitor of Na(+)/Ca(2+) exchange, most potently inhibited the Na(+)/Mg(2+) exchange with half inhibitory concentrations (IC(50)) of 21 μM: (25°C) and 16 μM: (35°C). These IC(50) values were a factor of three to four lower than those of imipramine, a widely used inhibitor of Na(+)/Mg(2+) exchange. Apart from the inhibitory effect on Na(+)/Mg(2+) exchange, relatively high concentrations of KB-R7943 (100 μM: at 25°C and ≥20 μM: at 35°C), in combination with prolonged UV-illumination, caused cell shortening, probably because of the phototoxicity of the compound and the formation of rigor crossbridges. We conclude that KB-R7943 may be a useful tool to study cellular Mg(2+) homeostasis if care is taken to minimize its phototoxicity.
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Affiliation(s)
- Michiko Tashiro
- Department of Physiology, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo, 160-8402 Japan
| | - Hana Inoue
- Department of Physiology, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo, 160-8402 Japan
| | - Masato Konishi
- Department of Physiology, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo, 160-8402 Japan
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Chorro FJ, Trapero I, Such-Miquel L, Pelechano F, Mainar L, Cánoves J, Tormos Á, Alberola A, Hove-Madsen L, Cinca J, Such L. Pharmacological modifications of the stretch-induced effects on ventricular fibrillation in perfused rabbit hearts. Am J Physiol Heart Circ Physiol 2009; 297:H1860-9. [DOI: 10.1152/ajpheart.00144.2009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Stretch induces modifications in myocardial electrical and mechanical activity. Besides the effects of substances that block the stretch-activated channels, other substances could modulate the effects of stretch through different mechanisms that affect Ca2+ handling by myocytes. Thirty-six Langendorff-perfused rabbit hearts were used to analyze the effects of the Na+/Ca2+ exchanger blocker KB-R7943, propranolol, and the adenosine A2 receptor antagonist SCH-58261 on the acceleration of ventricular fibrillation (VF) produced by acute myocardial stretching. VF recordings were obtained with two epicardial multiple electrodes before, during, and after local stretching in four experimental series: control ( n = 9), KB-R7943 (1 μM, n = 9), propranolol (1 μM, n = 9), and SCH-58261 (1 μM, n = 9). Both the Na+/Ca2+ exchanger blocker KB-R7943 and propranolol induced a significant reduction ( P < 0.001 and P < 0.05, respectively) in the dominant frequency increments produced by stretching with respect to the control and SCH-58261 series (control = 49.9%, SCH-58261 = 52.1%, KB-R7943 = 9.5%, and propranolol = 12.5%). The median of the activation intervals, the functional refractory period, and the wavelength of the activation process during VF decreased significantly under stretch in the control and SCH-58261 series, whereas no significant variations were observed in the propranolol and KB-R7943 series, with the exception of a slight but significant decrease in the median of the fibrillation intervals in the KB-R7943 series. KB-R7943 and propranolol induced a significant reduction in the activation maps complexity increment produced by stretch with respect to the control and SCH-58261 series. In conclusion, the electrophysiological effects responsible for stretch-induced VF acceleration in the rabbit heart are reduced by the Na+/Ca2+ exchanger blocker KB-R7943 and by propranolol but not by the adenosine A2 receptor antagonist SCH-58261.
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Affiliation(s)
- Francisco J. Chorro
- Service of Cardiology, Valencia University Clinic Hospital, Valencia
- Departments of 2Medicine,
| | | | | | | | - Luis Mainar
- Service of Cardiology, Valencia University Clinic Hospital, Valencia
| | - Joaquín Cánoves
- Service of Cardiology, Valencia University Clinic Hospital, Valencia
| | - Álvaro Tormos
- Department of Electronics, Valencia Polytechnic University, Valencia; and
| | | | - Leif Hove-Madsen
- Cardiology Department, Santa Creu i Sant Pau Hospital, Barcelona, Spain
| | - Juan Cinca
- Cardiology Department, Santa Creu i Sant Pau Hospital, Barcelona, Spain
| | - Luis Such
- Physiology, Valencia University, Valencia
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Qi J, Xiao J, Zhang Y, Li J, Liu Y, Li P, Liang L, Jiang B, Wen W, Zhao C, Liang D, Liu Y, Chen YH. Effects of Potassium Channel Blockers on Changes in Refractoriness of Atrial Cardiomyocytes Induced by Stretch. Exp Biol Med (Maywood) 2009; 234:779-84. [PMID: 19429854 DOI: 10.3181/0902-rm-45] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Shortening of the effective refractory period (ERP) is regarded as one of the key mechanisms of atrial fibrillation (AF). Stretch is an important predisposing factor in the pathogenesis of AF. However, effective methods to counteract alteration of ERP induced by stretch still need to be explored. Although potassium channels play important roles in cardiac repolarization and refractoriness, the effects of potassium channel blockers on the alteration of repolarization and refractoriness induced by stretch are still unknown. Action potential duration (APD) and ERP were recorded using the standard intracellular microelectrode technique in the left atrial appendage cardiomyocytes of guinea pigs. Stretch accelerated repolarization of atrial cardiomyocytes and also shortened the ERP ( P < 0.05). Dofetilide, a rapid delayed rectifying potassium ion channel (IKr) blocker; 4-AP, a transient outward potassium ion channel (Ito) blocker; and BaCl2, an inward rectifying potassium ion channel (IK1) blocker could counteract the shortening of APD and ERP ( P < 0.01). Glibenclamide, an ATP-sensitive potassium ion channel (IKATP) blocker; 293-B, a slow delayed rectifying potassium channel (IKs) blocker; and DPO-1, an ultra-rapid delayed rectifying potassium ion channel (IKur) blocker all had no effect on APD and ERP ( P > 0.05). Stretch could accelerate repolarization of atrial cardiomyocytes and shorten their ERP, and the Ito, IKr, and IK1 blockers could counteract the effects of stretch.
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Affiliation(s)
- Jie Qi
- Department of Cardiology, Tongji Hospital, Tongji University School of Medicine, 200065 Shanghai, China
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Inoue R, Jian Z, Kawarabayashi Y. Mechanosensitive TRP channels in cardiovascular pathophysiology. Pharmacol Ther 2009; 123:371-85. [PMID: 19501617 DOI: 10.1016/j.pharmthera.2009.05.009] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Accepted: 05/14/2009] [Indexed: 12/22/2022]
Abstract
Transient receptor potential (TRP) proteins constitute a large non-voltage-gated cation channel superfamily, activated polymodally by various physicochemical stimuli, and are implicated in a variety of cellular functions. Known activators for TRP include not only chemical stimuli such as receptor stimulation, increased acidity and pungent/cooling agents, but temperature change and various forms of mechanical stimuli such as osmotic stress, membrane stretch, and shear force. Recent investigations have revealed that at least ten mammalian TRPs exhibit mechanosensitivity (TRPC1, 5, 6; TRPV1, 2, 4; TRPM3, 7; TRPA1; TRPP2), but the mechanisms underlying it appear considerably divergent and complex. The proposed mechanisms are associated with lipid bilayer mechanics, specialized force-transducing structures, biochemical reactions, membrane trafficking and transcriptional regulation. Many of mechanosensitive (MS)-TRP channel likely undergo multiple regulations via these mechanisms. In the cardiovascular system in which hemodynamic forces constantly operate, the impact of mechanical stress may be particularly significant. Extensive morphological and functional studies have indicated that several MS-TRP channels are expressed in cardiac muscle, vascular smooth muscle, endothelium and vasosensory neurons, each differentially contributing to cardiovascular (CV) functions. To further complexity, the recent evidence suggests that mechanical stress may synergize with neurohormonal mechanisms thereby amplifying otherwise marginal responses. Furthermore, the currently available data suggest that MS-TRP channels may be involved in CV pathophysiology such as cardiac arrhythmia, cardiac hypertrophy/myopathy, hypertension and aneurysms. This review will overview currently known mechanisms for mechanical activation/modulation of TRPs and possible connections of MS-TRP channels to CV disorders.
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Affiliation(s)
- Ryuji Inoue
- Department of Physiology, Graduate School of Medical Sciences, Fukuoka University, Nanakuma 7-45-1, Jonan-ku, Fukuoka 814-0180, Japan.
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Formigli L, Sassoli C, Squecco R, Bini F, Martinesi M, Chellini F, Luciani G, Sbrana F, Zecchi-Orlandini S, Francini F, Meacci E. Regulation of transient receptor potential canonical channel 1 (TRPC1) by sphingosine 1-phosphate in C2C12 myoblasts and its relevance for a role of mechanotransduction in skeletal muscle differentiation. J Cell Sci 2009; 122:1322-33. [DOI: 10.1242/jcs.035402] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Transient receptor potential canonical (TRPC) channels provide cation and Ca2+ entry pathways, which have important regulatory roles in many physio-pathological processes, including muscle dystrophy. However, the mechanisms of activation of these channels remain poorly understood. Using siRNA, we provide the first experimental evidence that TRPC channel 1 (TRPC1), besides acting as a store-operated channel, represents an essential component of stretch-activated channels in C2C12 skeletal myoblasts, as assayed by whole-cell patch-clamp and atomic force microscopic pulling. The channel's activity and stretch-induced Ca2+ influx were modulated by sphingosine 1-phosphate (S1P), a bioactive lipid involved in satellite cell biology and tissue regeneration. We also found that TRPC1 was functionally assembled in lipid rafts, as shown by the fact that cholesterol depletion resulted in the reduction of transmembrane ion current and conductance. Association between TRPC1 and lipid rafts was increased by formation of stress fibres, which was elicited by S1P and abolished by treatment with the actin-disrupting dihydrocytochalasin B, suggesting a role for cytoskeleton in TRPC1 membrane recruitment. Moreover, TRPC1 expression was significantly upregulated during myogenesis, especially in the presence of S1P, implicating a crucial role for TRPC1 in myoblast differentiation. Collectively, these findings may offer new tools for understanding the role of TRPC1 and sphingolipid signalling in skeletal muscle regeneration and provide new therapeutic approaches for skeletal muscle disorders.
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Affiliation(s)
- Lucia Formigli
- Department of Anatomy, Histology and Forensic Medicine, University of Florence, Florence, Italy
- Interuniversity Institute of Miology (IIM), University of Florence, Florence, Italy
| | - Chiara Sassoli
- Department of Anatomy, Histology and Forensic Medicine, University of Florence, Florence, Italy
- Interuniversity Institute of Miology (IIM), University of Florence, Florence, Italy
| | - Roberta Squecco
- Department of Physiological Sciences, University of Florence, Florence, Italy
- Interuniversity Institute of Miology (IIM), University of Florence, Florence, Italy
| | - Francesca Bini
- Department of Biochemical Sciences, University of Florence, Florence, Italy
| | - Maria Martinesi
- Department of Biochemical Sciences, University of Florence, Florence, Italy
| | - Flaminia Chellini
- Department of Anatomy, Histology and Forensic Medicine, University of Florence, Florence, Italy
| | - Giorgia Luciani
- Department of Physiological Sciences, University of Florence, Florence, Italy
| | - Francesca Sbrana
- C.S.D.C. Department of Physics, University of Florence, Florence, Italy
| | - Sandra Zecchi-Orlandini
- Department of Anatomy, Histology and Forensic Medicine, University of Florence, Florence, Italy
- Interuniversity Institute of Miology (IIM), University of Florence, Florence, Italy
| | - Fabio Francini
- Department of Physiological Sciences, University of Florence, Florence, Italy
- Interuniversity Institute of Miology (IIM), University of Florence, Florence, Italy
| | - Elisabetta Meacci
- Department of Biochemical Sciences, University of Florence, Florence, Italy
- Interuniversity Institute of Miology (IIM), University of Florence, Florence, Italy
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Zhang YH, Dingle L, Hall R, Casadei B. The role of nitric oxide and reactive oxygen species in the positive inotropic response to mechanical stretch in the mammalian myocardium. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:811-7. [PMID: 19361482 PMCID: PMC2791851 DOI: 10.1016/j.bbabio.2009.03.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Revised: 03/28/2009] [Accepted: 03/31/2009] [Indexed: 11/13/2022]
Abstract
The endothelial nitric oxide synthase (eNOS) has been implicated in the rapid (Frank–Starling) and slow (Anrep) cardiac response to stretch. Our work and that of others have demonstrated that a neuronal nitric oxide synthase (nNOS) localized to the myocardium plays an important role in the regulation of cardiac function and calcium handling. However, the effect of nNOS on the myocardial response to stretch has yet to be investigated. Recent evidence suggests that the stretch-induced release of angiotensin II (Ang II) and endothelin 1 (ET-1) stimulates myocardial superoxide production from NADPH oxidases which, in turn, contributes to the Anrep effect. nNOS has also been shown to regulate the production of myocardial superoxide, suggesting that this isoform may influence the cardiac response to stretch or ET-1 by altering the NO-redox balance in the myocardium. Here we show that the increase in left ventricular (LV) myocyte shortening in response to the application of ET-1 (10 nM, 5 min) did not differ between nNOS−/− mice and their wild type littermates (nNOS+/+). Pre-incubating LV myocytes with the NADPH oxidase inhibitor, apocynin (100 μM, 30 min), reduced cell shortening in nNOS−/− myocytes only but prevented the positive inotropic effects of ET-1 in both groups. Superoxide production (O2−) was enhanced in nNOS−/− myocytes compared to nNOS+/+; however, this difference was abolished by pre-incubation with apocynin. There was no detectable increase in O2− production in ET-1 pre-treated LV myocytes. Inhibition of protein kinase C (chelerythrine, 1 μM) did not affect cell shortening in either group, however, protein kinase A inhibitor, PKI (2 μM), significantly reduced the positive inotropic effects of ET-1 in both nNOS+/+ and nNOS−/− myocytes. Taken together, our findings show that the positive inotropic effect of ET-1 in murine LV myocytes is independent of nNOS but requires NADPH oxidases and protein kinase A (PKA)-dependent signaling. These results may further our understanding of the signaling pathways involved in the myocardial inotropic response to stretch.
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Affiliation(s)
- Yin Hua Zhang
- Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK.
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Wang Y, Joyner RW, Wagner MB, Cheng J, Lai D, Crawford BH. Stretch-activated channel activation promotes early afterdepolarizations in rat ventricular myocytes under oxidative stress. Am J Physiol Heart Circ Physiol 2009; 296:H1227-35. [PMID: 19286952 DOI: 10.1152/ajpheart.00808.2008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Mechanical stretch and oxidative stress have been shown to prolong action potential duration (APD) and produce early afterdepolarizations (EADs). Here, we developed a simulation model to study the role of stretch-activated channel (SAC) currents in triggering EADs in ventricular myocytes under oxidative stress. We adapted our coupling clamp circuit so that a model ionic current representing the actual SAC current was injected into ventricular myocytes and added as a real-time current. This current was calculated as I(SAC) = G(SAC) * (V(m) - E(SAC)), where G(SAC) is the stretch-activated conductance, V(m) is the membrane potential, and E(SAC) is the reversal potential. In rat ventricular myocytes, application of G(SAC) did not produce sustained automaticity or EADs, although turn-on of G(SAC) did produce some transient automaticity at high levels of G(SAC). Exposure of myocytes to 100 microM H(2)O(2) induced significant APD prolongation and increase in intracellular Ca(2+) load and transient, but no EAD or sustained automaticity was generated in the absence of G(SAC). However, the combination of G(SAC) and H(2)O(2) consistently produced EADs at lower levels of G(SAC) (2.6 +/- 0.4 nS, n = 14, P < 0.05). Pacing myocytes at a faster rate further prolonged APD and promoted the development of EADs. SAC activation plays an important role in facilitating the development of EADs in ventricular myocytes under acute oxidative stress. This mechanism may contribute to the increased propensity to lethal ventricular arrhythmias seen in cardiomyopathies, where the myocardium stretch and oxidative stress generally coexist.
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Affiliation(s)
- Yanggan Wang
- Dept. of Pediatrics, Emory Univ., 2015 Uppergate Dr., Rm. 364, Atlanta, GA 30322, USA.
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Vassort G, Alvarez J. Transient receptor potential: a large family of new channels of which several are involved in cardiac arrhythmiaThis article is one of a selection of papers from the NATO Advanced Research Workshop on Translational Knowledge for Heart Health (published in part 1 of a 2-part Special Issue). Can J Physiol Pharmacol 2009; 87:100-7. [DOI: 10.1139/y08-112] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The transient receptor potential (TRP) family of ion channels comprises more than 50 cation-permeable channels expressed throughout the animal kingdom. TRPs can be grouped into 7 main subfamilies according to structural homology: the TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), TRPA (ankyrin), and TRPN (NO mechanopotential). During the past 20 years, the cloning and characterization after reexpression of most members of these cation channels have led to a plethora of data and more recently to some understanding of their roles in various cells and tissues. Specifically in the heart, TRPs are known to be involved in various diseases, including hypertrophy, heart failure, and arrhythmia. The later part of this review focuses on the potential contribution of TRPs to cardiac rhythm and their potential proarrhythmic effects. Furthermore, several neurotransmitters that activate the formation of diacylglycerol could modulate cardiac rhythm or, like ATP, induce arrhythmia.
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Affiliation(s)
- Guy Vassort
- INSERM U-637 Physiopathologie cardiovasculaire, CHU Arnaud de Villeneuve, Montpellier Cedex 05, 34295 France
- Laboratorio de Electrofisiologia, Instituto de Cardiologia, La Habana 10400, Cuba
| | - Julio Alvarez
- INSERM U-637 Physiopathologie cardiovasculaire, CHU Arnaud de Villeneuve, Montpellier Cedex 05, 34295 France
- Laboratorio de Electrofisiologia, Instituto de Cardiologia, La Habana 10400, Cuba
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Youm JB, Leem CH, Zhang YH, Kim N, Han J, Earm YE. Modeling of arrhythmogenic automaticity induced by stretch in rat atrial myocytes. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2008; 12:267-74. [PMID: 19967066 DOI: 10.4196/kjpp.2008.12.5.267] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Since first discovered in chick skeletal muscles, stretch-activated channels (SACs) have been proposed as a probable mechano-transducer of the mechanical stimulus at the cellular level. Channel properties have been studied in both the single-channel and the whole-cell level. There is growing evidence to indicate that major stretch-induced changes in electrical activity are mediated by activation of these channels. We aimed to investigate the mechanism of stretch-induced automaticity by exploiting a recent mathematical model of rat atrial myocytes which had been established to reproduce cellular activities such as the action potential, Ca(2+) transients, and contractile force. The incorporation of SACs into the mathematical model, based on experimental results, successfully reproduced the repetitive firing of spontaneous action potentials by stretch. The induced automaticity was composed of two phases. The early phase was driven by increased background conductance of voltage-gated Na(+) channel, whereas the later phase was driven by the reverse-mode operation of Na(+)/Ca(2+) exchange current secondary to the accumulation of Na(+) and Ca(2+) through SACs. These results of simulation successfully demonstrate how the SACs can induce automaticity in a single atrial myocyte which may act as a focus to initiate and maintain atrial fibrillation in concert with other arrhythmogenic changes in the heart.
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Affiliation(s)
- Jae Boum Youm
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology and Biophysics, College of Medicine, Inje University, Busan 614-735, Korea
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Stretch-activated non-selective cation channel: A causal link between mechanical stretch and atrial natriuretic peptide secretion. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 98:1-9. [DOI: 10.1016/j.pbiomolbio.2008.05.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Bai GY, Yuan K, Park WH, Kim SZ, Kim SH. Attenuation of hypoosmotic stress-induced ANP secretion via I(Cl,swell) in renal hypertensive rat atria. Peptides 2008; 29:1566-74. [PMID: 18582990 DOI: 10.1016/j.peptides.2008.05.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Revised: 05/13/2008] [Accepted: 05/13/2008] [Indexed: 10/22/2022]
Abstract
Cardiac hypertrophy, an adaptive process to an increased hemodynamic overload, includes not only an increase in cell size but also qualitative changes in constituent proteins. Although swelling-activated chloride channels (I(Cl,swell)) chronically activate in hypertrophied atrial myocytes, the role of I(Cl,swell) in regulation of atrial natriuretic peptide (ANP) release is poorly understood. We investigated the effects of I(Cl,swell) on ANP release and contractility and its modification in hypertrophied rat atria. To stimulate I(Cl,swell), hypoosmotic HEPES buffered solution (0.8T, 0.7T and 0.6T) was perfused into isolated perfused beating atria. The hypoosmotic HEPES buffered solution increased ANP release as compared to isoosmotic buffered solution (1T) in an osmolarity-reduction dependent manner. Atrial contractility and extracellular fluid translocation did not change. Exposure to hypoosmotic buffer (0.8T) containing low chloride (8mM), tamoxifen or diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) significantly attenuated hypoosmolarity-induced ANP release. The pretreatment with genistein, okdaic acid, U73122, GF109203x, and staurosporine attenuated hypoosmolarity-induced ANP release whereas orthovanadate augmented it significantly. In hypertrophied atria from renal hypertensive rats, hypoosmolarity-induced ANP release was markedly attenuated and DIDS-induced decrease in ANP release and negative inotropy were augmented as compared to sham-operated rat atria. Therefore, we suggest that I(Cl,swell) may partly participate hypoosmolarity-induced ANP release through protein tyrosine kinase and phospholipase C-protein kinase C pathway. The modification of responses of ANP release to hypoosmolarity and DIDS in hypertrophied atria may relate to changes in I(Cl,swell) activity by persistent high blood pressure.
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Affiliation(s)
- Guang Yi Bai
- Department of Physiology, Medical School, Institute for Medical Sciences, 2-20 Keum-Am-Dong-San, Chonbuk National University, Jeonju 561-180, Republic of Korea
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Sbrana F, Sassoli C, Meacci E, Nosi D, Squecco R, Paternostro F, Tiribilli B, Zecchi-Orlandini S, Francini F, Formigli L. Role for stress fiber contraction in surface tension development and stretch-activated channel regulation in C2C12 myoblasts. Am J Physiol Cell Physiol 2008; 295:C160-72. [DOI: 10.1152/ajpcell.00014.2008] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Membrane-cytoskeleton interaction regulates transmembrane currents through stretch-activated channels (SACs); however, the mechanisms involved have not been tested in living cells. We combined atomic force microscopy, confocal immunofluorescence, and patch-clamp analysis to show that stress fibers (SFs) in C2C12 myoblasts behave as cables that, tensed by myosin II motor, activate SACs by modifying the topography and the viscoelastic (Young's modulus and hysteresis) and electrical passive (membrane capacitance, Cm) properties of the cell surface. Stimulation with sphingosine 1-phosphate to elicit SF formation, the inhibition of Rho-dependent SF formation by Y-27632 and of myosin II-driven SF contraction by blebbistatin, showed that not SF polymerization alone but the generation of tensional forces by SF contraction were involved in the stiffness response of the cell surface. Notably, this event was associated with a significant reduction in the amplitude of the cytoskeleton-mediated corrugations in the cell surface topography, suggesting a contribution of SF contraction to plasma membrane stretching. Moreover, Cm, used as an index of cell surface area, showed a linear inverse relationship with cell stiffness, indicating participation of the actin cytoskeleton in plasma membrane remodeling and the ability of SF formation to cause internalization of plasma membrane patches to reduce Cm and increase membrane tension. SF contraction also increased hysteresis. Together, these data provide the first experimental evidence for a crucial role of SF contraction in SAC activation. The related changes in cell viscosity may prevent SAC from abnormal activation.
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Nishimura S, Seo K, Nagasaki M, Hosoya Y, Yamashita H, Fujita H, Nagai R, Sugiura S. Responses of single-ventricular myocytes to dynamic axial stretching. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 97:282-97. [DOI: 10.1016/j.pbiomolbio.2008.02.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Stretch-activated channels in the heart: Contributions to length-dependence and to cardiomyopathy. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 97:232-49. [DOI: 10.1016/j.pbiomolbio.2008.02.009] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Han JH, Bai GY, Park JH, Yuan K, Park WH, Kim SZ, Kim SH. Regulation of stretch-activated ANP secretion by chloride channels. Peptides 2008; 29:613-21. [PMID: 18226426 DOI: 10.1016/j.peptides.2007.12.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2007] [Revised: 11/30/2007] [Accepted: 12/04/2007] [Indexed: 11/23/2022]
Abstract
This study was aimed to define roles of stretch-activated ion channels (SACs), especially Cl(-) channels, in regulation of atrial natriuretic peptide (ANP) secretion using isolated perfused beating atria. The volume load was achieved by elevating height of outflow catheter connected to isolated rat atria and the pressure load was achieved by decreasing diameter of outflow catheter. Both methods increased atrial contractility similarly although volume load was different (736microl for volume load vs. 129microl for pressure load). Atrial stretch by volume load markedly increased ECF translocation and ANP secretion but the pressure load slightly increased. The ANP secretion was positively correlated to workload generated by volume or pressure load. Treatment of atria with gadolinium, a blocker for SACs, attenuated the ECF translocation and the ANP secretion induced by volume load. A blocker for Ca2+-activated Cl(-) channel, niflumic acid (NFA), accentuated the ANP secretion induced by volume load whereas a blocker for swelling-activated Cl(-) channel, diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS), attenuated the ANP secretion. The ANP secretion of hypertrophied atria by volume load was markedly reduced and the augmented effect of NFA on volume load-induced ANP secretion was not observed. These results indicate that Cl(-) channels may differently regulate stretch-activated ANP secretion.
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Affiliation(s)
- Jeong Hee Han
- 2-20 Keum-Am-Dong-San, Department of Physiology, Institute for Medical Sciences, Chonbuk National University Medical School, Jeonju 561-180, Republic of Korea
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McNary TG, Sohn K, Taccardi B, Sachse FB. Experimental and computational studies of strain-conduction velocity relationships in cardiac tissue. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 97:383-400. [PMID: 18406453 DOI: 10.1016/j.pbiomolbio.2008.02.023] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Velocity of electrical conduction in cardiac tissue is a function of mechanical strain. Although strain-modulated velocity is a well established finding in experimental cardiology, its underlying mechanisms are not well understood. In this work, we summarized potential factors contributing to strain-velocity relationships and reviewed related experimental and computational studies. We presented results from our experimental studies on rabbit papillary muscle, which supported a biphasic relationship of strain and velocity under uni-axial straining conditions. In the low strain range, the strain-velocity relationship was positive. Conduction velocity peaked with 0.59 m/s at 100% strain corresponding to maximal force development. In the high strain range, the relationship was negative. Conduction was reversibly blocked at 118+/-1.8% strain. Reversible block occurred also in the presence of streptomycin. Furthermore, our studies revealed a moderate hysteresis of conduction velocity, which was reduced by streptomycin. We reconstructed several features of the strain-velocity relationship in a computational study with a myocyte strand. The modeling included strain-modulation of intracellular conductivity and stretch-activated cation non-selective ion channels. The computational study supported our hypotheses, that the positive strain-velocity relationship at low strain is caused by strain-modulation of intracellular conductivity and the negative relationship at high strain results from activity of stretch-activated channels. Conduction block was not reconstructed in our computational studies. We concluded this work by sketching a hypothesis for strain-modulation of conduction and conduction block in papillary muscle. We suggest that this hypothesis can also explain uni-axially measured strain-conduction velocity relationships in other types of cardiac tissue, but apparently necessitates adjustments to reconstruct pressure or volume related changes of velocity in atria and ventricles.
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Affiliation(s)
- T G McNary
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA
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Seol CA, Kim WT, Ha JM, Choe H, Jang YJ, Youm JB, Earm YE, Leem CH. Stretch-activated currents in cardiomyocytes isolated from rabbit pulmonary veins. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 97:217-31. [PMID: 18353429 DOI: 10.1016/j.pbiomolbio.2008.02.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Evidence is growing of a relationship between atrial dilation and atrial fibrillation (AF), the most prevalent type of arrhythmia. Pulmonary veins, which are important ectopic foci for provoking AF, are of increasing interest in relation to the early development of AF. Here, using single cardiomyocytes isolated from rabbit pulmonary veins, we characterised the stretch-activated currents induced by swelling and axial mechanical stretching. Swelling induced both a stretch-activated nonselective cationic current (NSC) and a Cl(-) current. The swelling-induced Cl(-) current (I Cl,swell) was inhibited by DIDS, whereas the swelling-induced NSC (I NSC,swell) was inhibited by Gd3+. The cationic selectivity of the I NSC,swell was K+ >Cs+ >Na+ >Li+, whilst the PK/PNa, PCs/PNa, and PLi/PNa permeability ratios were 2.84, 1.86, and 0.85, respectively. Activation of the I NSC,swell was faster than that of the I Cl,swell. Given a high K+ concentration in the bath solution, the I NSC,swell showed limited amplitude (<-70 mV). Mechanical stretching induced an immediate Gd3+- and streptomycin-sensitive NSC (I NSC,stretch) that was permeable to Na+, K+, Cs+ and NMDG. Persistent stretching activated a DIDS-sensitive current (I Cl,stretch). The I NSC,stretch, but not the I NSC,swell, was completely blocked by 400 microM streptomycin; therefore, the two currents may not be associated with the same channel. In addition, the type of current induced may depend on the type of stretching. Thus, stretch-induced anionic and cationic currents are functionally present in the cardiomyocytes of the main pulmonary veins of rabbits, and they may have pathophysiological roles in the development of AF under stretched conditions.
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Affiliation(s)
- Chang Ahn Seol
- Department of Physiology, University of Ulsan College of Medicine, 388-1 Poongnap-Dong Songpa-Ku, Seoul, Republic of Korea
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