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Ni H, Grandi E. Computational Modeling of Cardiac Electrophysiology. Methods Mol Biol 2024; 2735:63-103. [PMID: 38038844 DOI: 10.1007/978-1-0716-3527-8_5] [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] [Indexed: 12/02/2023]
Abstract
Mathematical modeling and simulation are well-established and powerful tools to integrate experimental data of individual components of cardiac electrophysiology, excitation-contraction coupling, and regulatory signaling pathways, to gain quantitative and mechanistic insight into pathophysiological processes and guide therapeutic strategies. Here, we briefly describe the processes governing cardiac myocyte electrophysiology and Ca2+ handling and their regulation, as well as action potential propagation in tissue. We discuss the models and methods used to describe these phenomena, including procedures for model parameterization and validation, in addition to protocols for model interrogation and analysis and techniques that account for phenotypic variability and parameter uncertainty. Our objective is to provide a summary of basic concepts and approaches as a resource for scientists training in this discipline and for all researchers aiming to gain an understanding of cardiac modeling studies.
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Affiliation(s)
- Haibo Ni
- Department of Pharmacology, University of California, Davis, CA, USA.
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, CA, USA.
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2
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Kang PW, Woodbury L, Angsutararux P, Sambare N, Shi J, Marras M, Abella C, Bedi A, Zinn D, Cui J, Silva JR. Arrhythmia-associated calmodulin variants interact with KCNQ1 to confer aberrant membrane trafficking and function. PNAS NEXUS 2023; 2:pgad335. [PMID: 37965565 PMCID: PMC10642763 DOI: 10.1093/pnasnexus/pgad335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 10/04/2023] [Indexed: 11/16/2023]
Abstract
Missense variants in calmodulin (CaM) predispose patients to arrhythmias associated with high mortality rates ("calmodulinopathy"). As CaM regulates many key cardiac ion channels, an understanding of disease mechanism associated with CaM variant arrhythmias requires elucidating individual CaM variant effects on distinct channels. One key CaM regulatory target is the KCNQ1 (KV7.1) voltage-gated potassium channel that carries the IKs current. Yet, relatively little is known as to how CaM variants interact with KCNQ1 or affect its function. Here, we take a multipronged approach employing a live-cell fluorescence resonance energy transfer binding assay, fluorescence trafficking assay, and functional electrophysiology to characterize >10 arrhythmia-associated CaM variants for effect on KCNQ1 CaM binding, membrane trafficking, and channel function. We identify one variant (G114W) that exhibits severely weakened binding to KCNQ1 but find that most other CaM variants interact with similar binding affinity to KCNQ1 when compared with CaM wild-type over physiological Ca2+ ranges. We further identify several CaM variants that affect KCNQ1 and IKs membrane trafficking and/or baseline current activation kinetics, thereby delineating KCNQ1 dysfunction in calmodulinopathy. Lastly, we identify CaM variants with no effect on KCNQ1 function. This study provides extensive functional data that reveal how CaM variants contribute to creating a proarrhythmic substrate by causing abnormal KCNQ1 membrane trafficking and current conduction. We find that CaM variant regulation of KCNQ1 is not uniform with effects varying from benign to significant loss of function, suggesting how CaM variants predispose patients to arrhythmia via the dysregulation of multiple cardiac ion channels. Classification: Biological, Health, and Medical Sciences, Physiology.
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Affiliation(s)
- Po wei Kang
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Lucy Woodbury
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Paweorn Angsutararux
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Namit Sambare
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Jingyi Shi
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Martina Marras
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Carlota Abella
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Anish Bedi
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - DeShawn Zinn
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Jianmin Cui
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Jonathan R Silva
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
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Ni H, Morotti S, Zhang X, Dobrev D, Grandi E. Integrative human atrial modelling unravels interactive protein kinase A and Ca2+/calmodulin-dependent protein kinase II signalling as key determinants of atrial arrhythmogenesis. Cardiovasc Res 2023; 119:2294-2311. [PMID: 37523735 PMCID: PMC11318383 DOI: 10.1093/cvr/cvad118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 05/18/2023] [Accepted: 06/05/2023] [Indexed: 08/02/2023] Open
Abstract
AIMS Atrial fibrillation (AF), the most prevalent clinical arrhythmia, is associated with atrial remodelling manifesting as acute and chronic alterations in expression, function, and regulation of atrial electrophysiological and Ca2+-handling processes. These AF-induced modifications crosstalk and propagate across spatial scales creating a complex pathophysiological network, which renders AF resistant to existing pharmacotherapies that predominantly target transmembrane ion channels. Developing innovative therapeutic strategies requires a systems approach to disentangle quantitatively the pro-arrhythmic contributions of individual AF-induced alterations. METHODS AND RESULTS Here, we built a novel computational framework for simulating electrophysiology and Ca2+-handling in human atrial cardiomyocytes and tissues, and their regulation by key upstream signalling pathways [i.e. protein kinase A (PKA), and Ca2+/calmodulin-dependent protein kinase II (CaMKII)] involved in AF-pathogenesis. Populations of atrial cardiomyocyte models were constructed to determine the influence of subcellular ionic processes, signalling components, and regulatory networks on atrial arrhythmogenesis. Our results reveal a novel synergistic crosstalk between PKA and CaMKII that promotes atrial cardiomyocyte electrical instability and arrhythmogenic triggered activity. Simulations of heterogeneous tissue demonstrate that this cellular triggered activity is further amplified by CaMKII- and PKA-dependent alterations of tissue properties, further exacerbating atrial arrhythmogenesis. CONCLUSIONS Our analysis reveals potential mechanisms by which the stress-associated adaptive changes turn into maladaptive pro-arrhythmic triggers at the cellular and tissue levels and identifies potential anti-AF targets. Collectively, our integrative approach is powerful and instrumental to assemble and reconcile existing knowledge into a systems network for identifying novel anti-AF targets and innovative approaches moving beyond the traditional ion channel-based strategy.
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Affiliation(s)
- Haibo Ni
- Department of Pharmacology, University of California Davis,
451 Health Sciences Drive, Davis, CA 95616, USA
| | - Stefano Morotti
- Department of Pharmacology, University of California Davis,
451 Health Sciences Drive, Davis, CA 95616, USA
| | - Xianwei Zhang
- Department of Pharmacology, University of California Davis,
451 Health Sciences Drive, Davis, CA 95616, USA
| | - Dobromir Dobrev
- Institute of Pharmacology, Faculty of Medicine, University
Duisburg-Essen, Essen, Germany
- Department of Medicine and Research Center, Montreal Heart Institute and
Université de Montréal, Montréal, Canada
- Department of Molecular Physiology and Biophysics, Baylor College of
Medicine, Houston, TX, USA
| | - Eleonora Grandi
- Department of Pharmacology, University of California Davis,
451 Health Sciences Drive, Davis, CA 95616, USA
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McCormick L, Wadmore K, Milburn A, Gupta N, Morris R, Held M, Prakash O, Carr J, Barrett‐Jolley R, Dart C, Helassa N. Long QT syndrome-associated calmodulin variants disrupt the activity of the slowly activating delayed rectifier potassium channel. J Physiol 2023; 601:3739-3764. [PMID: 37428651 PMCID: PMC10952621 DOI: 10.1113/jp284994] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 06/21/2023] [Indexed: 07/12/2023] Open
Abstract
Calmodulin (CaM) is a highly conserved mediator of calcium (Ca2+ )-dependent signalling and modulates various cardiac ion channels. Genotyping has revealed several CaM mutations associated with long QT syndrome (LQTS). LQTS patients display prolonged ventricular recovery times (QT interval), increasing their risk of incurring life-threatening arrhythmic events. Loss-of-function mutations to Kv7.1 (which drives the slow delayed rectifier potassium current, IKs, a key ventricular repolarising current) are the largest contributor to congenital LQTS (>50% of cases). CaM modulates Kv7.1 to produce a Ca2+ -sensitive IKs, but little is known about the consequences of LQTS-associated CaM mutations on Kv7.1 function. Here, we present novel data characterising the biophysical and modulatory properties of three LQTS-associated CaM variants (D95V, N97I and D131H). We showed that mutations induced structural alterations in CaM and reduced affinity for Kv7.1, when compared with wild-type (WT). Using HEK293T cells expressing Kv7.1 channel subunits (KCNQ1/KCNE1) and patch-clamp electrophysiology, we demonstrated that LQTS-associated CaM variants reduced current density at systolic Ca2+ concentrations (1 μm), revealing a direct QT-prolonging modulatory effect. Our data highlight for the first time that LQTS-associated perturbations to CaM's structure impede complex formation with Kv7.1 and subsequently result in reduced IKs. This provides a novel mechanistic insight into how the perturbed structure-function relationship of CaM variants contributes to the LQTS phenotype. KEY POINTS: Calmodulin (CaM) is a ubiquitous, highly conserved calcium (Ca2+ ) sensor playing a key role in cardiac muscle contraction. Genotyping has revealed several CaM mutations associated with long QT syndrome (LQTS), a life-threatening cardiac arrhythmia syndrome. LQTS-associated CaM variants (D95V, N97I and D131H) induced structural alterations, altered binding to Kv7.1 and reduced IKs. Our data provide a novel mechanistic insight into how the perturbed structure-function relationship of CaM variants contributes to the LQTS phenotype.
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Affiliation(s)
- Liam McCormick
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
- Manchester Centre for Genomic Medicine, North West Genomic Laboratory HubSaint Mary's HospitalManchesterUK
| | - Kirsty Wadmore
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Amy Milburn
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Nitika Gupta
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Rachael Morris
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Marie Held
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Ohm Prakash
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Joseph Carr
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Richard Barrett‐Jolley
- Department of Musculoskeletal and Ageing Science, Institute of Life Course and Medical Sciences, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Caroline Dart
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Nordine Helassa
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
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Verkerk AO, Wilders R. Human Sinoatrial Node Pacemaker Activity: Role of the Slow Component of the Delayed Rectifier K + Current, I Ks. Int J Mol Sci 2023; 24:7264. [PMID: 37108427 PMCID: PMC10138838 DOI: 10.3390/ijms24087264] [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: 03/22/2023] [Revised: 04/07/2023] [Accepted: 04/11/2023] [Indexed: 04/29/2023] Open
Abstract
The pacemaker activity of the sinoatrial node (SAN) has been studied extensively in animal species but is virtually unexplored in humans. Here we assess the role of the slowly activating component of the delayed rectifier K+ current (IKs) in human SAN pacemaker activity and its dependence on heart rate and β-adrenergic stimulation. HEK-293 cells were transiently transfected with wild-type KCNQ1 and KCNE1 cDNA, encoding the α- and β-subunits of the IKs channel, respectively. KCNQ1/KCNE1 currents were recorded both during a traditional voltage clamp and during an action potential (AP) clamp with human SAN-like APs. Forskolin (10 µmol/L) was used to increase the intracellular cAMP level, thus mimicking β-adrenergic stimulation. The experimentally observed effects were evaluated in the Fabbri-Severi computer model of an isolated human SAN cell. Transfected HEK-293 cells displayed large IKs-like outward currents in response to depolarizing voltage clamp steps. Forskolin significantly increased the current density and significantly shifted the half-maximal activation voltage towards more negative potentials. Furthermore, forskolin significantly accelerated activation without affecting the rate of deactivation. During an AP clamp, the KCNQ1/KCNE1 current was substantial during the AP phase, but relatively small during diastolic depolarization. In the presence of forskolin, the KCNQ1/KCNE1 current during both the AP phase and diastolic depolarization increased, resulting in a clearly active KCNQ1/KCNE1 current during diastolic depolarization, particularly at shorter cycle lengths. Computer simulations demonstrated that IKs reduces the intrinsic beating rate through its slowing effect on diastolic depolarization at all levels of autonomic tone and that gain-of-function mutations in KCNQ1 may exert a marked bradycardic effect during vagal tone. In conclusion, IKs is active during human SAN pacemaker activity and has a strong dependence on heart rate and cAMP level, with a prominent role at all levels of autonomic tone.
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Affiliation(s)
- Arie O. Verkerk
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands;
- Department of Experimental Cardiology, Heart Center, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands
| | - Ronald Wilders
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands;
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Kursanov A, Balakina-Vikulova NA, Solovyova O, Panfilov A, Katsnelson LB. In silico analysis of the contribution of cardiomyocyte-fibroblast electromechanical interaction to the arrhythmia. Front Physiol 2023; 14:1123609. [PMID: 36969594 PMCID: PMC10036780 DOI: 10.3389/fphys.2023.1123609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 02/27/2023] [Indexed: 03/12/2023] Open
Abstract
Although fibroblasts are about 5–10 times smaller than cardiomyocytes, their number in the ventricle is about twice that of cardiomyocytes. The high density of fibroblasts in myocardial tissue leads to a noticeable effect of their electromechanical interaction with cardiomyocytes on the electrical and mechanical functions of the latter. Our work focuses on the analysis of the mechanisms of spontaneous electrical and mechanical activity of the fibroblast-coupled cardiomyocyte during its calcium overload, which occurs in a variety of pathologies, including acute ischemia. For this study, we developed a mathematical model of the electromechanical interaction between cardiomyocyte and fibroblasts and used it to simulate the impact of overloading cardiomyocytes. In contrast to modeling only the electrical interaction between cardiomyocyte and fibroblasts, the following new features emerge in simulations with the model that accounts for both electrical and mechanical coupling and mechano-electrical feedback loops in the interacting cells. First, the activity of mechanosensitive ion channels in the coupled fibroblasts depolarizes their resting potential. Second, this additional depolarization increases the resting potential of the coupled myocyte, thus augmenting its susceptibility to triggered activity. The triggered activity associated with the cardiomyocyte calcium overload manifests itself in the model either as early afterdepolarizations or as extrasystoles, i.e., extra action potentials and extra contractions. Analysis of the model simulations showed that mechanics contribute significantly to the proarrhythmic effects in the cardiomyocyte overloaded with calcium and coupled with fibroblasts, and that mechano-electrical feedback loops in both the cardiomyocyte and fibroblasts play a key role in this phenomenon.
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Affiliation(s)
- Alexander Kursanov
- Institute of Immunology and Physiology of the Ural Branch of the Russian Academy of Sciences, Ekaterinburg, Russia
- Laboratory of Mathematical Modeling in Physiology and Medicine Based on Supercomputers, Ural Federal University, Ekaterinburg, Russia
| | - Nathalie A. Balakina-Vikulova
- Institute of Immunology and Physiology of the Ural Branch of the Russian Academy of Sciences, Ekaterinburg, Russia
- Laboratory of Mathematical Modeling in Physiology and Medicine Based on Supercomputers, Ural Federal University, Ekaterinburg, Russia
| | - Olga Solovyova
- Institute of Immunology and Physiology of the Ural Branch of the Russian Academy of Sciences, Ekaterinburg, Russia
- Laboratory of Mathematical Modeling in Physiology and Medicine Based on Supercomputers, Ural Federal University, Ekaterinburg, Russia
| | - Alexander Panfilov
- Laboratory of Mathematical Modeling in Physiology and Medicine Based on Supercomputers, 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
- Laboratory of Mathematical Modeling in Physiology and Medicine Based on Supercomputers, Ural Federal University, Ekaterinburg, Russia
- *Correspondence: Leonid B. Katsnelson,
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7
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Kang PW, Woodbury L, Angsutararux P, Sambare N, Shi J, Marras M, Abella C, Bedi A, Zinn D, Cui J, Silva JR. Arrhythmia-associated Calmodulin Variants Interact with KCNQ1 to Confer Aberrant Membrane Trafficking and Function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.28.526031. [PMID: 36747728 PMCID: PMC9900995 DOI: 10.1101/2023.01.28.526031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Rationale Missense variants in calmodulin (CaM) predispose patients to arrhythmias associated with high mortality rates. As CaM regulates several key cardiac ion channels, a mechanistic understanding of CaM variant-associated arrhythmias requires elucidating individual CaM variant effect on distinct channels. One key CaM regulatory target is the KCNQ1 (K V 7.1) voltage-gated potassium channel that underlie the I Ks current. Yet, relatively little is known as to how CaM variants interact with KCNQ1 or affect its function. Objective To observe how arrhythmia-associated CaM variants affect binding to KCNQ1, channel membrane trafficking, and KCNQ1 function. Methods and Results We combine a live-cell FRET binding assay, fluorescence trafficking assay, and functional electrophysiology to characterize >10 arrhythmia-associated CaM variants effect on KCNQ1. We identify one variant (G114W) that exhibits severely weakened binding to KCNQ1 but find that most other CaM variants interact with similar binding affinity to KCNQ1 when compared to CaM wild-type over physiological Ca 2+ ranges. We further identify several CaM variants that affect KCNQ1 and I Ks membrane trafficking and/or baseline current activation kinetics, thereby contextualizing KCNQ1 dysfunction in calmodulinopathy. Lastly, we delineate CaM variants with no effect on KCNQ1 function. Conclusions This study provides comprehensive functional data that reveal how CaM variants contribute to creating a pro-arrhythmic substrate by causing abnormal KCNQ1 membrane trafficking and current conduction. We find that CaM variant regulation of KCNQ1 is not uniform with effects varying from benign to significant loss of function. This study provides a new approach to collecting details of CaM binding that are key for understanding how CaM variants predispose patients to arrhythmia via the dysregulation of multiple cardiac ion channels.
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Electro-anatomical computational cardiology in humans and experimental animal models. TRANSLATIONAL RESEARCH IN ANATOMY 2022. [DOI: 10.1016/j.tria.2022.100162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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9
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Lyu Y, Thai PN, Ren L, Timofeyev V, Jian Z, Park S, Ginsburg KS, Overton J, Bossuyt J, Bers DM, Yamoah EN, Chen-Izu Y, Chiamvimonvat N, Zhang XD. Beat-to-beat dynamic regulation of intracellular pH in cardiomyocytes. iScience 2022; 25:103624. [PMID: 35005560 PMCID: PMC8718820 DOI: 10.1016/j.isci.2021.103624] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 11/10/2021] [Accepted: 12/10/2021] [Indexed: 11/20/2022] Open
Abstract
The mammalian heart beats incessantly with rhythmic mechanical activities generating acids that need to be buffered to maintain a stable intracellular pH (pHi) for normal cardiac function. Even though spatial pHi non-uniformity in cardiomyocytes has been documented, it remains unknown how pHi is regulated to match the dynamic cardiac contractions. Here, we demonstrated beat-to-beat intracellular acidification, termed pHi transients, in synchrony with cardiomyocyte contractions. The pHi transients are regulated by pacing rate, Cl-/HCO3 - transporters, pHi buffering capacity, and β-adrenergic signaling. Mitochondrial electron-transport chain inhibition attenuates the pHi transients, implicating mitochondrial activity in sculpting the pHi regulation. The pHi transients provide dynamic alterations of H+ transport required for ATP synthesis, and a decrease in pHi may serve as a negative feedback to cardiac contractions. Current findings dovetail with the prevailing three known dynamic systems, namely electrical, Ca2+, and mechanical systems, and may reveal broader features of pHi handling in excitable cells.
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Affiliation(s)
- Yankun Lyu
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Phung N. Thai
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Lu Ren
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Valeriy Timofeyev
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Zhong Jian
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Seojin Park
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV 89557, USA
| | - Kenneth S. Ginsburg
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - James Overton
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Julie Bossuyt
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Donald M. Bers
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Ebenezer N. Yamoah
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV 89557, USA
| | - Ye Chen-Izu
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
- Department of Biomedical Engineering, University of California, Davis, Davis, CA 95616, USA
| | - Nipavan Chiamvimonvat
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
- Department of Veterans Affairs, Northern California Health Care System, Mather, CA 95655, USA
| | - Xiao-Dong Zhang
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
- Department of Veterans Affairs, Northern California Health Care System, Mather, CA 95655, USA
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10
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Simon M, Ko CY, Rebbeck RT, Baidar S, Cornea RL, Bers DM. CaMKIIδ post-translational modifications increase affinity for calmodulin inside cardiac ventricular myocytes. J Mol Cell Cardiol 2021; 161:53-61. [PMID: 34371035 PMCID: PMC8716136 DOI: 10.1016/j.yjmcc.2021.08.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Revised: 07/30/2021] [Accepted: 08/02/2021] [Indexed: 11/18/2022]
Abstract
Persistent over-activation of CaMKII (Calcium/Calmodulin-dependent protein Kinase II) in the heart is implicated in arrhythmias, heart failure, pathological remodeling, and other cardiovascular diseases. Several post-translational modifications (PTMs)-including autophosphorylation, oxidation, S-nitrosylation, and O-GlcNAcylation-have been shown to trap CaMKII in an autonomously active state. The molecular mechanisms by which these PTMs regulate calmodulin (CaM) binding to CaMKIIδ-the primary cardiac isoform-has not been well-studied particularly in its native myocyte environment. Typically, CaMKII activates upon Ca-CaM binding during locally elevated [Ca]free and deactivates upon Ca-CaM dissociation when [Ca]free returns to basal levels. To assess the effects of CaMKIIδ PTMs on CaM binding, we developed a novel FRET (Förster resonance energy transfer) approach to directly measure CaM binding to and dissociation from CaMKIIδ in live cardiac myocytes. We demonstrate that autophosphorylation of CaMKIIδ increases affinity for CaM in its native environment and that this increase is dependent on [Ca]free. This leads to a 3-fold slowing of CaM dissociation from CaMKIIδ (time constant slows from ~0.5 to 1.5 s) when [Ca]free is reduced with physiological kinetics. Moreover, oxidation further slows CaM dissociation from CaMKIIδ T287D (phosphomimetic) upon rapid [Ca]free chelation and increases FRET between CaM and CaMKIIδ T287A (phosphoresistant). The CaM dissociation kinetics-measured here in myocytes-are similar to the interval between heartbeats, and integrative memory would be expected as a function of heart rate. Furthermore, the PTM-induced slowing of dissociation between beats would greatly promote persistent CaMKIIδ activity in the heart. Together, these findings suggest a significant role of PTM-induced changes in CaMKIIδ affinity for CaM and memory under physiological and pathophysiological processes in the heart.
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Affiliation(s)
- Mitchell Simon
- Department of Pharmacology, University of California, Davis, CA, USA
| | - Christopher Y Ko
- Department of Pharmacology, University of California, Davis, CA, USA
| | - Robyn T Rebbeck
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Sonya Baidar
- Department of Pharmacology, University of California, Davis, CA, USA
| | - Razvan L Cornea
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, CA, USA.
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11
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Morotti S, Liu C, Hegyi B, Ni H, Fogli Iseppe A, Wang L, Pritoni M, Ripplinger CM, Bers DM, Edwards AG, Grandi E. Quantitative cross-species translators of cardiac myocyte electrophysiology: Model training, experimental validation, and applications. SCIENCE ADVANCES 2021; 7:eabg0927. [PMID: 34788089 PMCID: PMC8598003 DOI: 10.1126/sciadv.abg0927] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 09/28/2021] [Indexed: 05/13/2023]
Abstract
Animal experimentation is key in the evaluation of cardiac efficacy and safety of novel therapeutic compounds. However, interspecies differences in the mechanisms regulating excitation-contraction coupling can limit the translation of experimental findings from animal models to human physiology and undermine the assessment of drugs’ efficacy and safety. Here, we built a suite of translators for quantitatively mapping electrophysiological responses in ventricular myocytes across species. We trained these statistical operators using a broad dataset obtained by simulating populations of our biophysically detailed computational models of action potential and Ca2+ transient in mouse, rabbit, and human. We then tested our translators against experimental data describing the response to stimuli, such as ion channel block, change in beating rate, and β-adrenergic challenge. We demonstrate that this approach is well suited to predicting the effects of perturbations across different species or experimental conditions and suggest its integration into mechanistic studies and drug development pipelines.
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Affiliation(s)
- Stefano Morotti
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
| | - Caroline Liu
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
| | - Bence Hegyi
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
| | - Haibo Ni
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
| | - Alex Fogli Iseppe
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
| | - Lianguo Wang
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
| | - Marco Pritoni
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | | | - Donald M. Bers
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
| | - Andrew G. Edwards
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
| | - Eleonora Grandi
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
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12
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Hawthorne RN, Blazeski A, Lowenthal J, Kannan S, Teuben R, DiSilvestre D, Morrissette-McAlmon J, Saffitz JE, Boheler KR, James CA, Chelko SP, Tomaselli G, Tung L. Altered Electrical, Biomolecular, and Immunologic Phenotypes in a Novel Patient-Derived Stem Cell Model of Desmoglein-2 Mutant ARVC. J Clin Med 2021; 10:jcm10143061. [PMID: 34300226 PMCID: PMC8306340 DOI: 10.3390/jcm10143061] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 07/05/2021] [Accepted: 07/08/2021] [Indexed: 12/27/2022] Open
Abstract
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a progressive heart condition which causes fibro-fatty myocardial scarring, ventricular arrhythmias, and sudden cardiac death. Most cases of ARVC can be linked to pathogenic mutations in the cardiac desmosome, but the pathophysiology is not well understood, particularly in early phases when arrhythmias can develop prior to structural changes. Here, we created a novel human induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) model of ARVC from a patient with a c.2358delA variant in desmoglein-2 (DSG2). These DSG2-mutant (DSG2Mut) hiPSC-CMs were compared against two wildtype hiPSC-CM lines via immunostaining, RT-qPCR, Western blot, RNA-Seq, cytokine expression and optical mapping. Mutant cells expressed reduced DSG2 mRNA and had altered localization of desmoglein-2 protein alongside thinner, more disorganized myofibrils. No major changes in other desmosomal proteins were noted. There was increased pro-inflammatory cytokine expression that may be linked to canonical and non-canonical NFκB signaling. Action potentials in DSG2Mut CMs were shorter with increased upstroke heterogeneity, while time-to-peak calcium and calcium decay rate were reduced. These were accompanied by changes in ion channel and calcium handling gene expression. Lastly, suppressing DSG2 in control lines via siRNA allowed partial recapitulation of electrical anomalies noted in DSG2Mut cells. In conclusion, the aberrant cytoskeletal organization, cytokine expression, and electrophysiology found DSG2Mut hiPSC-CMs could underlie early mechanisms of disease manifestation in ARVC patients.
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Affiliation(s)
- Robert N. Hawthorne
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (R.N.H.); (A.B.); (J.L.); (S.K.); (R.T.); (J.M.-M.); (K.R.B.)
- Medical Scientist Training Program, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Adriana Blazeski
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (R.N.H.); (A.B.); (J.L.); (S.K.); (R.T.); (J.M.-M.); (K.R.B.)
| | - Justin Lowenthal
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (R.N.H.); (A.B.); (J.L.); (S.K.); (R.T.); (J.M.-M.); (K.R.B.)
- Medical Scientist Training Program, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Suraj Kannan
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (R.N.H.); (A.B.); (J.L.); (S.K.); (R.T.); (J.M.-M.); (K.R.B.)
- Medical Scientist Training Program, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Roald Teuben
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (R.N.H.); (A.B.); (J.L.); (S.K.); (R.T.); (J.M.-M.); (K.R.B.)
| | - Deborah DiSilvestre
- Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (D.D.); (C.A.J.)
| | - Justin Morrissette-McAlmon
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (R.N.H.); (A.B.); (J.L.); (S.K.); (R.T.); (J.M.-M.); (K.R.B.)
| | - Jeffrey E. Saffitz
- Department of Pathology, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA;
| | - Kenneth R. Boheler
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (R.N.H.); (A.B.); (J.L.); (S.K.); (R.T.); (J.M.-M.); (K.R.B.)
- Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (D.D.); (C.A.J.)
| | - Cynthia A. James
- Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (D.D.); (C.A.J.)
| | - Stephen P. Chelko
- Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (D.D.); (C.A.J.)
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA
- Correspondence: (S.P.C.); (G.T.); (L.T.); Tel.: +1-850-644-2215 (S.P.C.); +1-718-430-2801 (G.T.); +1-410-955-9603 (L.T.)
| | - Gordon Tomaselli
- Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (D.D.); (C.A.J.)
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Correspondence: (S.P.C.); (G.T.); (L.T.); Tel.: +1-850-644-2215 (S.P.C.); +1-718-430-2801 (G.T.); +1-410-955-9603 (L.T.)
| | - Leslie Tung
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (R.N.H.); (A.B.); (J.L.); (S.K.); (R.T.); (J.M.-M.); (K.R.B.)
- Correspondence: (S.P.C.); (G.T.); (L.T.); Tel.: +1-850-644-2215 (S.P.C.); +1-718-430-2801 (G.T.); +1-410-955-9603 (L.T.)
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13
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Ion current profiles in canine ventricular myocytes obtained by the "onion peeling" technique. J Mol Cell Cardiol 2021; 158:153-162. [PMID: 34089737 DOI: 10.1016/j.yjmcc.2021.05.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 05/05/2021] [Accepted: 05/21/2021] [Indexed: 02/07/2023]
Abstract
The profiles of ion currents during the cardiac action potential can be visualized by the action potential voltage clamp technique. To obtain multiple ion current data from the same cell, the "onion peeling" technique, based on sequential pharmacological dissection of ion currents, has to be applied. Combination of the two methods allows recording of several ion current profiles from the same myocyte under largely physiological conditions. Using this approach, we have studied the densities and integrals of the major cardiac inward (ICa, INCX, INa-late) and outward (IKr, IKs, IK1) currents in canine ventricular cells and studied the correlation between them. For this purpose, canine ventricular cardiomyocytes were chosen because their electrophysiological properties are similar to those of human ones. Significant positive correlation was observed between the density and integral of ICa and IKr, and positive correlation was found also between the integral of ICa and INCX. No further correlations were detected. The Ca2+-sensitivity of K+ currents was studied by comparing their parameters in the case of normal calcium homeostasis and following blockade of ICa. Out of the three K+ currents studied, only IKs was Ca2+-sensitive. The density and integral of IKs was significantly greater, while its time-to-peak value was shorter at normal Ca2+ cycling than following ICa blockade. No differences were detected for IKr or IK1 in this regard. Present results indicate that the positive correlation between ICa and IKr prominently contribute to the balance between inward and outward fluxes during the action potential plateau in canine myocytes. The results also suggest that the profiles of cardiac ion currents have to be studied under physiological conditions, since their behavior may strongly be influenced by the intracellular Ca2+ homeostasis and the applied membrane potential protocol.
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14
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Kabakov AY, Sengun E, Lu Y, Roder K, Bronk P, Baggett B, Turan NN, Moshal KS, Koren G. Three-Week-Old Rabbit Ventricular Cardiomyocytes as a Novel System to Study Cardiac Excitation and EC Coupling. Front Physiol 2021; 12:672360. [PMID: 34867432 PMCID: PMC8637404 DOI: 10.3389/fphys.2021.672360] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 10/06/2021] [Indexed: 01/14/2023] Open
Abstract
Cardiac arrhythmias significantly contribute to cardiovascular morbidity and mortality. The rabbit heart serves as an accepted model system for studying cardiac cell excitation and arrhythmogenicity. Accordingly, primary cultures of adult rabbit ventricular cardiomyocytes serve as a preferable model to study molecular mechanisms of human cardiac excitation. However, the use of adult rabbit cardiomyocytes is often regarded as excessively costly. Therefore, we developed and characterized a novel low-cost rabbit cardiomyocyte model, namely, 3-week-old ventricular cardiomyocytes (3wRbCMs). Ventricular myocytes were isolated from whole ventricles of 3-week-old New Zealand White rabbits of both sexes by standard enzymatic techniques. Using wheat germ agglutinin, we found a clear T-tubule structure in acutely isolated 3wRbCMs. Cells were adenovirally infected (multiplicity of infection of 10) to express Green Fluorescent Protein (GFP) and cultured for 48 h. The cells showed action potential duration (APD90 = 253 ± 24 ms) and calcium transients similar to adult rabbit cardiomyocytes. Freshly isolated and 48-h-old-cultured cells expressed critical ion channel proteins: calcium voltage-gated channel subunit alpha1 C (Cavα1c), sodium voltage-gated channel alpha subunit 5 (Nav1.5), potassium voltage-gated channel subfamily D member 3 (Kv4.3), and subfamily A member 4 (Kv1.4), and also subfamily H member 2 (RERG. Kv11.1), KvLQT1 (K7.1) protein and inward-rectifier potassium channel (Kir2.1). The cells displayed an appropriate electrophysiological phenotype, including fast sodium current (I Na), transient outward potassium current (I to), L-type calcium channel peak current (I Ca,L), rapid and slow components of the delayed rectifier potassium current (I Kr and I Ks), and inward rectifier (I K1). Although expression of the channel proteins and some currents decreased during the 48 h of culturing, we conclude that 3wRbCMs are a new, low-cost alternative to the adult-rabbit-cardiomyocytes system, which allows the investigation of molecular mechanisms of cardiac excitation on morphological, biochemical, genetic, physiological, and biophysical levels.
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Affiliation(s)
- Anatoli Y Kabakov
- Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI, United States
| | - Elif Sengun
- Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI, United States.,Department of Pharmacology, Institute of Graduate Studies in Health Sciences, Istanbul University, Istanbul, Türkiye
| | - Yichun Lu
- Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI, United States
| | - Karim Roder
- Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI, United States
| | - Peter Bronk
- Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI, United States
| | - Brett Baggett
- Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI, United States
| | - Nilüfer N Turan
- Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI, United States
| | - Karni S Moshal
- Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI, United States
| | - Gideon Koren
- Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI, United States
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15
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Kang PW, Westerlund AM, Shi J, White KM, Dou AK, Cui AH, Silva JR, Delemotte L, Cui J. Calmodulin acts as a state-dependent switch to control a cardiac potassium channel opening. SCIENCE ADVANCES 2020; 6:6/50/eabd6798. [PMID: 33310856 PMCID: PMC7732179 DOI: 10.1126/sciadv.abd6798] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 10/27/2020] [Indexed: 05/09/2023]
Abstract
Calmodulin (CaM) and phosphatidylinositol 4,5-bisphosphate (PIP2) are potent regulators of the voltage-gated potassium channel KCNQ1 (KV7.1), which conducts the cardiac I Ks current. Although cryo-electron microscopy structures revealed intricate interactions between the KCNQ1 voltage-sensing domain (VSD), CaM, and PIP2, the functional consequences of these interactions remain unknown. Here, we show that CaM-VSD interactions act as a state-dependent switch to control KCNQ1 pore opening. Combined electrophysiology and molecular dynamics network analysis suggest that VSD transition into the fully activated state allows PIP2 to compete with CaM for binding to VSD. This leads to conformational changes that alter VSD-pore coupling to stabilize open states. We identify a motif in the KCNQ1 cytosolic domain, which works downstream of CaM-VSD interactions to facilitate the conformational change. Our findings suggest a gating mechanism that integrates PIP2 and CaM in KCNQ1 voltage-dependent activation, yielding insights into how KCNQ1 gains the phenotypes critical for its physiological function.
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Affiliation(s)
- Po Wei Kang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Annie M Westerlund
- Department of Applied Physics, KTH Royal Institute of Technology, Science for Life Laboratory, Stockholm, Sweden
| | - Jingyi Shi
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Kelli McFarland White
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Alex K Dou
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Amy H Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Jonathan R Silva
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Lucie Delemotte
- Department of Applied Physics, KTH Royal Institute of Technology, Science for Life Laboratory, Stockholm, Sweden.
| | - Jianmin Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA.
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16
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Varró A, Tomek J, Nagy N, Virág L, Passini E, Rodriguez B, Baczkó I. Cardiac transmembrane ion channels and action potentials: cellular physiology and arrhythmogenic behavior. Physiol Rev 2020; 101:1083-1176. [PMID: 33118864 DOI: 10.1152/physrev.00024.2019] [Citation(s) in RCA: 86] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Cardiac arrhythmias are among the leading causes of mortality. They often arise from alterations in the electrophysiological properties of cardiac cells and their underlying ionic mechanisms. It is therefore critical to further unravel the pathophysiology of the ionic basis of human cardiac electrophysiology in health and disease. In the first part of this review, current knowledge on the differences in ion channel expression and properties of the ionic processes that determine the morphology and properties of cardiac action potentials and calcium dynamics from cardiomyocytes in different regions of the heart are described. Then the cellular mechanisms promoting arrhythmias in congenital or acquired conditions of ion channel function (electrical remodeling) are discussed. The focus is on human-relevant findings obtained with clinical, experimental, and computational studies, given that interspecies differences make the extrapolation from animal experiments to human clinical settings difficult. Deepening the understanding of the diverse pathophysiology of human cellular electrophysiology will help in developing novel and effective antiarrhythmic strategies for specific subpopulations and disease conditions.
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Affiliation(s)
- András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - Jakub Tomek
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Elisa Passini
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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17
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Osadchii OE. Antiarrhythmic drug effects on premature beats are partly determined by prior cardiac activation frequency in perfused guinea-pig heart. Exp Physiol 2020; 105:819-830. [PMID: 32175633 DOI: 10.1113/ep088165] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 03/13/2020] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Can antiarrhythmic drug effects on repolarization, conduction time and excitation wavelength in premature beats be determined by prior cardiac activation frequency? What is the main finding and its importance? In premature beats induced after a series of cardiac activations at a slow rate, antiarrhythmics prolong repolarization but evoke little or no conduction delay, thus increasing the excitation wavelength, which indicates an antiarrhythmic effect. Fast prior activation rate attenuates prolongation of repolarization, while amplifying the conduction delay induced by drugs, which translates into the reduced excitation wavelength, indicating proarrhythmia. These findings suggest that a sudden increase in heart rate can shape adverse pharmacological profiles in patients with ventricular ectopy. ABSTRACT Antiarrhythmic drugs used to treat atrial fibrillation can occasionally induce ventricular tachyarrhythmia, which is typically precipitated by a premature ectopic beat through a mechanism related, in part, to the shortening of the excitation wavelength (EW). The arrhythmia is likely to occur when a drug induces a reduction, rather than an increase, in the EW of ectopic beats. In this study, I examined whether the arrhythmic drug profile is shaped by the increased cardiac activation rate before ectopic excitation. Ventricular monophasic action potential durations, conduction times and EW values were assessed during programmed stimulations applied at long (S1 -S1 [basic drive cycle length] = 550 ms) and short (S1 -S1 = 200 ms) cycle lengths in perfused guinea-pig hearts. The premature activations were induced with extrastimulus application immediately upon termination of the refractory period. With dofetilide, a class III antiarrhythmic agent, a prolongation in action potential duration and the resulting increase in the EW obtained at S1 -S1 = 550 ms were significantly attenuated at S1 -S1 = 200 ms, in both the regular (S1 ) and the premature (S2 ) beats. With class I antiarrhythmic agents (quinidine, procainamide and flecainide), fast S1 -S1 pacing was found to attenuate the drug-induced increase in action potential duration, while amplifying drug-induced conduction slowing, in both S1 and S2 beats. As a result, although the EW was increased (quinidine and procainamide) or not changed (flecainide) at the long S1 -S1 intervals, it was invariably reduced by these agents at the short S1 -S1 intervals. These findings indicate that the increased heart rate before ectopic activation shapes the arrhythmic profiles by facilitating drug-induced EW reduction.
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Affiliation(s)
- Oleg E Osadchii
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen N, Denmark.,Department of Health Science and Technology, University of Aalborg, Aalborg, Denmark
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18
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Cardiomyocyte calcium handling in health and disease: Insights from in vitro and in silico studies. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 157:54-75. [PMID: 32188566 DOI: 10.1016/j.pbiomolbio.2020.02.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 12/31/2019] [Accepted: 02/29/2020] [Indexed: 02/07/2023]
Abstract
Calcium (Ca2+) plays a central role in cardiomyocyte excitation-contraction coupling. To ensure an optimal electrical impulse propagation and cardiac contraction, Ca2+ levels are regulated by a variety of Ca2+-handling proteins. In turn, Ca2+ modulates numerous electrophysiological processes. Accordingly, Ca2+-handling abnormalities can promote cardiac arrhythmias via various mechanisms, including the promotion of afterdepolarizations, ion-channel modulation and structural remodeling. In the last 30 years, significant improvements have been made in the computational modeling of cardiomyocyte Ca2+ handling under physiological and pathological conditions. However, numerous questions involving the Ca2+-dependent regulation of different macromolecular complexes, cross-talk between Ca2+-dependent regulatory pathways operating over a wide range of time scales, and bidirectional interactions between electrophysiology and mechanics remain to be addressed by in vitro and in silico studies. A better understanding of disease-specific Ca2+-dependent proarrhythmic mechanisms may facilitate the development of improved therapeutic strategies. In this review, we describe the fundamental mechanisms of cardiomyocyte Ca2+ handling in health and disease, and provide an overview of currently available computational models for cardiomyocyte Ca2+ handling. Finally, we discuss important uncertainties and open questions about cardiomyocyte Ca2+ handling and highlight how synergy between in vitro and in silico studies may help to answer several of these issues.
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19
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Varshneya M, Devenyi RA, Sobie EA. Slow Delayed Rectifier Current Protects Ventricular Myocytes From Arrhythmic Dynamics Across Multiple Species: A Computational Study. Circ Arrhythm Electrophysiol 2019; 11:e006558. [PMID: 30354408 DOI: 10.1161/circep.118.006558] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
BACKGROUND The slow and rapid delayed rectifier K+ currents (IKs and IKr, respectively) are responsible for repolarizing the ventricular action potential (AP) and preventing abnormally long APs that may lead to arrhythmias. Although differences in biophysical properties of the 2 currents have been carefully documented, the respective physiological roles of IKr and IKs are less established. In this study, we sought to understand the individual roles of these currents and quantify how effectively each stabilizes the AP and protects cells against arrhythmias across multiple species. METHODS We compared 10 mathematical models describing ventricular myocytes from human, rabbit, dog, and guinea pig. We examined variability within heterogeneous cell populations, tested the susceptibility of cells to proarrhythmic behavior, and studied how IKs and IKr responded to changes in the AP. RESULTS We found that (1) models with higher baseline IKs exhibited less cell-to-cell variability in AP duration; (2) models with higher baseline IKs were less susceptible to early afterdepolarizations induced by depolarizing perturbations; (3) as AP duration is lengthened, IKs increases more profoundly than IKr, thereby providing negative feedback that resists excessive AP prolongation; and (4) the increase in IKs that occurs during β-adrenergic stimulation is critical for protecting cardiac myocytes from early afterdepolarizations under these conditions. CONCLUSIONS Slow delayed rectifier current is uniformly protective across a variety of cell types. These results suggest that IKs enhancement could potentially be an effective antiarrhythmic strategy.
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Affiliation(s)
- Meera Varshneya
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (M.V., R.A.D., E.A.S.)
| | - Ryan A Devenyi
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (M.V., R.A.D., E.A.S.)
| | - Eric A Sobie
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY (M.V., R.A.D., E.A.S.)
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20
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Wang L, Morotti S, Tapa S, Francis Stuart SD, Jiang Y, Wang Z, Myles RC, Brack KE, Ng GA, Bers DM, Grandi E, Ripplinger CM. Different paths, same destination: divergent action potential responses produce conserved cardiac fight-or-flight response in mouse and rabbit hearts. J Physiol 2019; 597:3867-3883. [PMID: 31215643 DOI: 10.1113/jp278016] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 06/17/2019] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS Cardiac electrophysiology and Ca2+ handling change rapidly during the fight-or-flight response to meet physiological demands. Despite dramatic differences in cardiac electrophysiology, the cardiac fight-or-flight response is highly conserved across species. In this study, we performed physiological sympathetic nerve stimulation (SNS) while optically mapping cardiac action potentials and intracellular Ca2+ transients in innervated mouse and rabbit hearts. Despite similar heart rate and Ca2+ handling responses between mouse and rabbit hearts, we found notable species differences in spatio-temporal repolarization dynamics during SNS. Species-specific computational models revealed that these electrophysiological differences allowed for enhanced Ca2+ handling (i.e. enhanced inotropy) in each species, suggesting that electrophysiological responses are fine-tuned across species to produce optimal cardiac fight-or-flight responses. ABSTRACT Sympathetic activation of the heart results in positive chronotropy and inotropy, which together rapidly increase cardiac output. The precise mechanisms that produce the electrophysiological and Ca2+ handling changes underlying chronotropic and inotropic responses have been studied in detail in isolated cardiac myocytes. However, few studies have examined the dynamic effects of physiological sympathetic nerve activation on cardiac action potentials (APs) and intracellular Ca2+ transients (CaTs) in the intact heart. Here, we performed bilateral sympathetic nerve stimulation (SNS) in fully innervated, Langendorff-perfused rabbit and mouse hearts. Dual optical mapping with voltage- and Ca2+ -sensitive dyes allowed for analysis of spatio-temporal AP and CaT dynamics. The rabbit heart responded to SNS with a monotonic increase in heart rate (HR), monotonic decreases in AP and CaT duration (APD, CaTD), and a monotonic increase in CaT amplitude. The mouse heart had similar HR and CaT responses; however, a pronounced biphasic APD response occurred, with initial prolongation (50.9 ± 5.1 ms at t = 0 s vs. 60.6 ± 4.1 ms at t = 15 s, P < 0.05) followed by shortening (46.5 ± 9.1 ms at t = 60 s, P = NS vs. t = 0). We determined the biphasic APD response in mouse was partly due to dynamic changes in HR during SNS and was exacerbated by β-adrenergic activation. Simulations with species-specific cardiac models revealed that transient APD prolongation in mouse allowed for greater and more rapid CaT responses, suggesting more rapid increases in contractility; conversely, the rabbit heart requires APD shortening to produce optimal inotropic responses. Thus, while the cardiac fight-or-flight response is highly conserved between species, the underlying mechanisms orchestrating these effects differ significantly.
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Affiliation(s)
- Lianguo Wang
- Department of Pharmacology, School of Medicine, University of California, Davis, USA
| | - Stefano Morotti
- Department of Pharmacology, School of Medicine, University of California, Davis, USA
| | - Srinivas Tapa
- Department of Pharmacology, School of Medicine, University of California, Davis, USA
| | | | - Yanyan Jiang
- Department of Pharmacology, School of Medicine, University of California, Davis, USA
| | - Zhen Wang
- Department of Pharmacology, School of Medicine, University of California, Davis, USA
| | - Rachel C Myles
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, Glasgow, UK
| | - Kieran E Brack
- Department of Cardiovascular Sciences, University of Leicester, NIHR Leicester Biomedical Research Centre, Leicester, UK
| | - G André Ng
- Department of Cardiovascular Sciences, University of Leicester, NIHR Leicester Biomedical Research Centre, Leicester, UK
| | - Donald M Bers
- Department of Pharmacology, School of Medicine, University of California, Davis, USA
| | - Eleonora Grandi
- Department of Pharmacology, School of Medicine, University of California, Davis, USA
| | - Crystal M Ripplinger
- Department of Pharmacology, School of Medicine, University of California, Davis, USA
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21
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Grandi E, Ripplinger CM. Antiarrhythmic mechanisms of beta blocker therapy. Pharmacol Res 2019; 146:104274. [PMID: 31100336 DOI: 10.1016/j.phrs.2019.104274] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Revised: 05/04/2019] [Accepted: 05/13/2019] [Indexed: 02/07/2023]
Abstract
Sympathetic activity plays an important role in modulation of cardiac rhythm. Indeed, while exerting positive tropic effects in response to physiologic and pathologic stressors, β-adrenergic stimulation influences cardiac electrophysiology and can lead to disturbances of the heart rhythm and potentially lethal arrhythmias, particularly in pathological settings. For this reason, β-blockers are widely utilized clinically as antiarrhythmics. In this review, the molecular mechanisms of β-adrenergic action in the heart, the cellular and tissue level cardiac responses to β-adrenergic stimulation, and the clinical use of β-blockers as antiarrhythmic agents are reviewed. We emphasize the complex interaction between cardiomyocyte signaling, contraction, and electrophysiology occurring over multiple time- and spatial-scales during pathophysiological responses to β-adrenergic stimulation. An integrated understanding of this complex system is essential for optimizing therapies aimed at preventing arrhythmias.
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Affiliation(s)
- Eleonora Grandi
- Department of Pharmacology, University of California Davis, United States.
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22
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Policarová M, Novotný T, Bébarová M. Impaired Adrenergic/Protein Kinase A Response of Slow Delayed Rectifier Potassium Channels as a Long QT Syndrome Motif: Importance and Unknowns. Can J Cardiol 2019; 35:511-522. [DOI: 10.1016/j.cjca.2018.11.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 11/20/2018] [Accepted: 11/20/2018] [Indexed: 12/29/2022] Open
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23
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Hegyi B, Morotti S, Liu C, Ginsburg KS, Bossuyt J, Belardinelli L, Izu LT, Chen-Izu Y, Bányász T, Grandi E, Bers DM. Enhanced Depolarization Drive in Failing Rabbit Ventricular Myocytes: Calcium-Dependent and β-Adrenergic Effects on Late Sodium, L-Type Calcium, and Sodium-Calcium Exchange Currents. Circ Arrhythm Electrophysiol 2019; 12:e007061. [PMID: 30879336 PMCID: PMC6720130 DOI: 10.1161/circep.118.007061] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Heart failure (HF) is characterized by electrophysiological remodeling resulting in increased risk of cardiac arrhythmias. Previous reports suggest that elevated inward ionic currents in HF promote action potential (AP) prolongation, increased short-term variability of AP repolarization, and delayed afterdepolarizations. However, the underlying changes in late Na+ current (INaL), L-type Ca2+ current, and NCX (Na+/Ca2+ exchanger) current are often measured in nonphysiological conditions (square-pulse voltage clamp, slow pacing rates, exogenous Ca2+ buffers). METHODS We measured the major inward currents and their Ca2+- and β-adrenergic dependence under physiological AP clamp in rabbit ventricular myocytes in chronic pressure/volume overload-induced HF (versus age-matched control). RESULTS AP duration and short-term variability of AP repolarization were increased in HF, and importantly, inhibition of INaL decreased both parameters to the control level. INaL was slightly increased in HF versus control even when intracellular Ca2+ was strongly buffered. But under physiological AP clamp with normal Ca2+ cycling, INaL was markedly upregulated in HF versus control (dependent largely on CaMKII [Ca2+/calmodulin-dependent protein kinase II] activity). β-Adrenergic stimulation (often elevated in HF) further enhanced INaL. L-type Ca2+ current was decreased in HF when Ca2+ was buffered, but CaMKII-mediated Ca2+-dependent facilitation upregulated physiological L-type Ca2+ current to the control level. Furthermore, L-type Ca2+ current response to β-adrenergic stimulation was significantly attenuated in HF. Inward NCX current was upregulated at phase 3 of AP in HF when assessed by combining experimental data and computational modeling. CONCLUSIONS Our results suggest that CaMKII-dependent upregulation of INaL in HF significantly contributes to AP prolongation and increased short-term variability of AP repolarization, which may lead to increased arrhythmia propensity, and is further exacerbated by adrenergic stress.
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Affiliation(s)
- Bence Hegyi
- Department of Pharmacology, University of California Davis, Davis
| | - Stefano Morotti
- Department of Pharmacology, University of California Davis, Davis
| | - Caroline Liu
- Department of Pharmacology, University of California Davis, Davis
| | | | - Julie Bossuyt
- Department of Pharmacology, University of California Davis, Davis
| | | | - Leighton T. Izu
- Department of Pharmacology, University of California Davis, Davis
| | - Ye Chen-Izu
- Department of Pharmacology, University of California Davis, Davis
- Department of Biomedical Engineering, University of California Davis, Davis
- Department of Internal Medicine/Cardiology, University of California Davis, Davis
| | - Tamás Bányász
- Department of Pharmacology, University of California Davis, Davis
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Eleonora Grandi
- Department of Pharmacology, University of California Davis, Davis
| | - Donald M. Bers
- Department of Pharmacology, University of California Davis, Davis
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24
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Osadchii OE. Effects of antiarrhythmics on the electrical restitution in perfused guinea-pig heart are critically determined by the applied cardiac pacing protocol. Exp Physiol 2019; 104:490-504. [PMID: 30758086 DOI: 10.1113/ep087531] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 02/12/2019] [Indexed: 01/11/2023]
Abstract
NEW FINDINGS What is the central question of this study? Are modifications in the restitution of ventricular action potential duration induced by antiarrhythmic drugs the same when assessed with premature extrastimulus application at variable coupling intervals (the standard stimulation protocol) and with steady state pacing at variable rates (the dynamic stimulation protocol)? What is the main finding and its importance? With class I and class III antiarrhythmics, the effects on electrical restitution determined with the standard stimulation protocol dissociate from those obtained during dynamic pacing. These findings indicate a limited value of the electrical restitution assessments based on extrasystolic stimulations alone, as performed in the clinical studies, in estimating the outcomes of antiarrhythmic drug therapies. ABSTRACT A steep slope of the ventricular action potential duration (APD) to diastolic interval (DI) relationships (the electrical restitution) can precipitate tachyarrhythmia, whereas a flattened slope is antiarrhythmic. The derangements in APD restitution responsible for transition of tachycardia to ventricular fibrillation can be assessed with cardiac pacing at progressively increasing rates (the dynamic stimulation protocol). Nevertheless, this method is not used clinically owing to the risk of inducing myocardial ischaemia. Instead, the restitution kinetics is determined with a premature extrastimulus application at variable coupling intervals (the standard stimulation protocol). Whether the two protocols are equivalent in estimating antiarrhythmic drug effects is uncertain. In this study, dofetilide and quinidine, the agents blocking repolarizing K+ currents, increased epicardial APD in perfused guinea-pig hearts, with effects being greater at long vs. short DIs. These changes were more pronounced during dynamic pacing compared to premature extrastimulations. Accordingly, although both agents markedly steepened the dynamic restitution, there was only a marginal increase in the standard restitution slope with dofetilide, and no effect with quinidine. Lidocaine and mexiletine, selective Na+ channel blockers, prolonged the effective refractory period without changing APD, and increased the minimum DI that enabled ventricular capture during extrastimulations. No change in the minimum DI was noted during dynamic pacing. Consequently, although lidocaine and mexiletine reduced the standard restitution slope, they failed to flatten the dynamic restitution. Overall, these findings imply a limited value of the electrical restitution assessments with premature extrastimulations alone in discriminating arrhythmic vs. antiarrhythmic changes during drug therapies.
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Affiliation(s)
- Oleg E Osadchii
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen N, Denmark.,Department of Health Science and Technology, University of Aalborg, Fredrik Bajers Vej 7E, 9220, Aalborg, Denmark
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25
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Xu J, Rudy Y. Effects of β-subunit on gating of a potassium ion channel: Molecular simulations of cardiac IKs activation. J Mol Cell Cardiol 2018; 124:35-44. [PMID: 30292722 PMCID: PMC6265052 DOI: 10.1016/j.yjmcc.2018.10.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 08/28/2018] [Accepted: 10/02/2018] [Indexed: 01/19/2023]
Abstract
Dynamic conformational changes of ion channel proteins during activation gating determine their function as carriers of current. The relationship between these molecular movements and channel function over the physiological timescale of the action potential (AP) has not been fully established due to limitations of existing techniques. We constructed a library of possible cardiac IKs protein conformations and applied a combination of protein segmentation and energy linearization to study this relationship computationally. Simulations reproduced the effects of the beta-subunit (KCNE1) on the alpha-subunit (KCNQ1) dynamics and function, observed in experiments. Mechanistically, KCNE1 increased the probability of "visiting" conducting pore conformations on activation trajectories, thereby increasing IKs current. KCNE1 slowed IKs activation by impeding the voltage sensor (VS) movement and reducing its coupling to pore opening. Conformational changes along activation trajectories determined that the S4-S5 linker (S4S5L) plays an important role in these modulatory effects by KCNE1. Integration of these molecular structure-based IKs dynamics into a model of human cardiac ventricular myocyte, revealed that KCNQ1-KCNE1 interaction is essential for normal AP repolarization.
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Affiliation(s)
- Jiajing Xu
- Department of Biomedical Engineering, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO 63130, United States
| | - Yoram Rudy
- Department of Biomedical Engineering, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO 63130, United States; Department of Cell Biology and Physiology, Washington University, School of Medicine, St. Louis, MO 63110, United States; Department of Medicine, Washington University, School of Medicine, St. Louis, MO 63110, United States.
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26
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Chen M, Yin D, Guo S, Xu DZ, Wang Z, Chen Z, Rubart-von der Lohe M, Lin SF, Everett Iv TH, Weiss JN, Chen PS. Sex-specific activation of SK current by isoproterenol facilitates action potential triangulation and arrhythmogenesis in rabbit ventricles. J Physiol 2018; 596:4299-4322. [PMID: 29917243 DOI: 10.1113/jp275681] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 06/11/2018] [Indexed: 01/09/2023] Open
Abstract
KEY POINTS It is unknown if a sex difference exists in cardiac apamin-sensitive small conductance Ca2+ -activated K+ (SK) current (IKAS ). There is no sex difference in IKAS in the basal condition. However, there is larger IKAS in female rabbit ventricles than in male during isoproterenol infusion. IKAS activation by isoproterenol leads to action potential triangulation in females, indicating its abundant activation at early phases of repolarization. IKAS activation in females induces negative Ca2+ -voltage coupling and promotes electromechanically discordant phase 2 repolarization alternans. IKAS is important in the mechanisms of ventricular fibrillation in females during sympathetic stimulation. ABSTRACT Sex has a large influence on cardiac electrophysiological properties. Whether sex differences exist in apamin-sensitive small conductance Ca2+ -activated K+ (SK) current (IKAS ) remains unknown. We performed optical mapping, transmembrane potential, patch clamp, western blot and immunostaining in 62 normal rabbit ventricles, including 32 females and 30 males. IKAS blockade by apamin only minimally prolonged action potential (AP) duration (APD) in the basal condition for both sexes, but significantly prolonged APD in the presence of isoproterenol in females. Apamin prolonged APD at the level of 25% repolarization (APD25 ) more prominently than APD at the level of 80% repolarization (APD80 ), consequently reversing isoproterenol-induced AP triangulation in females. In comparison, apamin prolonged APD to a significantly lesser extent in males and failed to restore the AP plateau during isoproterenol infusion. IKAS in males did not respond to the L-type calcium current agonist BayK8644, but was amplified by the casein kinase 2 (CK2) inhibitor 4,5,6,7-tetrabromobenzotriazole. In addition, whole-cell outward IKAS densities in ventricular cardiomyocytes were significantly larger in females than in males. SK channel subtype 2 (SK2) protein expression was higher and the CK2/SK2 ratio was lower in females than in males. IKAS activation in females induced negative intracellular Ca2+ -voltage coupling, promoted electromechanically discordant phase 2 repolarization alternans and facilitated ventricular fibrillation (VF). Apamin eliminated the negative Ca2+ -voltage coupling, attenuated alternans and reduced VF inducibility, phase singularities and dominant frequencies in females, but not in males. We conclude that β-adrenergic stimulation activates ventricular IKAS in females to a much greater extent than in males. IKAS activation plays an important role in ventricular arrhythmogenesis in females during sympathetic stimulation.
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Affiliation(s)
- Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shuai Guo
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Dong-Zhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Cardiovascular Division, Institute of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Zhuo Wang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Michael Rubart-von der Lohe
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan
| | - Thomas H Everett Iv
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - James N Weiss
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, CA, USA
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
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27
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Jones DC, Gong JQX, Sobie EA. A privileged role for neuronal Na + channels in regulating ventricular [Ca 2+] and arrhythmias. J Gen Physiol 2018; 150:901-905. [PMID: 29899058 PMCID: PMC6028496 DOI: 10.1085/jgp.201812120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Jones et al. provide commentary on the intricate crosstalk between ion transporters that goes awry in long QT arrhythmia.
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Affiliation(s)
- DeAnalisa C Jones
- Department of Pharmacological Sciences, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Jingqi Q X Gong
- Department of Pharmacological Sciences, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Eric A Sobie
- Department of Pharmacological Sciences, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
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28
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Hegyi B, Bossuyt J, Ginsburg KS, Mendoza LM, Talken L, Ferrier WT, Pogwizd SM, Izu LT, Chen-Izu Y, Bers DM. Altered Repolarization Reserve in Failing Rabbit Ventricular Myocytes: Calcium and β-Adrenergic Effects on Delayed- and Inward-Rectifier Potassium Currents. Circ Arrhythm Electrophysiol 2018; 11:e005852. [PMID: 29437761 PMCID: PMC5813707 DOI: 10.1161/circep.117.005852] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Accepted: 12/11/2017] [Indexed: 12/25/2022]
Abstract
BACKGROUND Electrophysiological remodeling and increased susceptibility for cardiac arrhythmias are hallmarks of heart failure (HF). Ventricular action potential duration (APD) is typically prolonged in HF, with reduced repolarization reserve. However, underlying K+ current changes are often measured in nonphysiological conditions (voltage clamp, low pacing rates, cytosolic Ca2+ buffers). METHODS AND RESULTS We measured the major K+ currents (IKr, IKs, and IK1) and their Ca2+- and β-adrenergic dependence in rabbit ventricular myocytes in chronic pressure/volume overload-induced HF (versus age-matched controls). APD was significantly prolonged only at lower pacing rates (0.2-1 Hz) in HF under physiological ionic conditions and temperature. However, when cytosolic Ca2+ was buffered, APD prolongation in HF was also significant at higher pacing rates. Beat-to-beat variability of APD was also significantly increased in HF. Both IKr and IKs were significantly upregulated in HF under action potential clamp, but only when cytosolic Ca2+ was not buffered. CaMKII (Ca2+/calmodulin-dependent protein kinase II) inhibition abolished IKs upregulation in HF, but it did not affect IKr. IKs response to β-adrenergic stimulation was also significantly diminished in HF. IK1 was also decreased in HF regardless of Ca2+ buffering, CaMKII inhibition, or β-adrenergic stimulation. CONCLUSIONS At baseline Ca2+-dependent upregulation of IKr and IKs in HF counterbalances the reduced IK1, maintaining repolarization reserve (especially at higher heart rates) in physiological conditions, unlike conditions of strong cytosolic Ca2+ buffering. However, under β-adrenergic stimulation, reduced IKs responsiveness severely limits integrated repolarizing K+ current and repolarization reserve in HF. This would increase arrhythmia propensity in HF, especially during adrenergic stress.
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Affiliation(s)
- Bence Hegyi
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Julie Bossuyt
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Kenneth S Ginsburg
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Lynette M Mendoza
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Linda Talken
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - William T Ferrier
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Steven M Pogwizd
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Leighton T Izu
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Ye Chen-Izu
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Donald M Bers
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.).
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29
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Piccini I, Fehrmann E, Frank S, Müller FU, Greber B, Seebohm G. Adrenergic Stress Protection of Human iPS Cell-Derived Cardiomyocytes by Fast K v7.1 Recycling. Front Physiol 2017; 8:705. [PMID: 28959214 PMCID: PMC5603700 DOI: 10.3389/fphys.2017.00705] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 08/31/2017] [Indexed: 01/09/2023] Open
Abstract
The fight-or-flight response (FFR), a physiological acute stress reaction, involves positive chronotropic and inotropic effects on heart muscle cells mediated through β-adrenoceptor activation. Increased systolic calcium is required to enable stronger heart contractions whereas elevated potassium currents are to limit the duration of the action potentials and prevent arrhythmia. The latter effect is accomplished by an increased functional activity of the Kv7.1 channel encoded by KCNQ1. Current knowledge, however, does not sufficiently explain the full extent of rapid Kv7.1 activation and may hence be incomplete. Using inducible genetic KCNQ1 complementation in KCNQ1-deficient human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), we here reinvestigate the functional role of Kv7.1 in adapting human CMs to adrenergic stress. Under baseline conditions, Kv7.1 was barely detectable at the plasma membrane of hiPSC-CMs, yet it fully protected these from adrenergic stress-induced beat-to-beat variability of repolarization and torsade des pointes-like arrhythmia. Furthermore, isoprenaline treatment increased field potential durations specifically in KCNQ1-deficient CMs to cause these adverse macroscopic effects. Mechanistically, we find that the protective action by Kv7.1 resides in a rapid translocation of channel proteins from intracellular stores to the plasma membrane, induced by adrenergic signaling. Gene silencing experiments targeting RAB GTPases, mediators of intracellular vesicle trafficking, showed that fast Kv7.1 recycling under acute stress conditions is RAB4A-dependent.Our data reveal a key mechanism underlying the rapid adaptation of human cardiomyocytes to adrenergic stress. These findings moreover aid to the understanding of disease pathology in long QT syndrome and bear important implications for safety pharmacological screening.
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Affiliation(s)
- Ilaria Piccini
- Department of Cardiovascular Medicine, Institute of Genetics of Heart Diseases, University of Münster Medical SchoolMünster, Germany.,Human Stem Cell Pluripotency Laboratory, Max Planck Institute for Molecular BiomedicineMünster, Germany
| | - Edda Fehrmann
- Institute of Pharmacology and Toxicology, University of MünsterMünster, Germany
| | - Stefan Frank
- Human Stem Cell Pluripotency Laboratory, Max Planck Institute for Molecular BiomedicineMünster, Germany.,Chemical Genomics Centre of the Max Planck SocietyDortmund, Germany
| | - Frank U Müller
- Institute of Pharmacology and Toxicology, University of MünsterMünster, Germany
| | - Boris Greber
- Human Stem Cell Pluripotency Laboratory, Max Planck Institute for Molecular BiomedicineMünster, Germany.,Chemical Genomics Centre of the Max Planck SocietyDortmund, Germany
| | - Guiscard Seebohm
- Department of Cardiovascular Medicine, Institute of Genetics of Heart Diseases, University of Münster Medical SchoolMünster, Germany
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30
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Orosz A, Baczkó I, Nyiraty S, Körei AE, Putz Z, Takács R, Nemes A, Várkonyi TT, Balogh L, Ábrahám G, Kempler P, Papp JG, Varró A, Lengyel C. Increased Short-Term Beat-to-Beat QT Interval Variability in Patients with Impaired Glucose Tolerance. Front Endocrinol (Lausanne) 2017; 8:129. [PMID: 28659867 PMCID: PMC5468431 DOI: 10.3389/fendo.2017.00129] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 05/29/2017] [Indexed: 01/02/2023] Open
Abstract
Prediabetic states and diabetes are important risk factors for cardiovascular morbidity and mortality. Determination of short-term QT interval variability (STVQT) is a non-invasive method for assessment of proarrhythmic risk. The aim of the study was to evaluate the STVQT in patients with impaired glucose tolerance (IGT). 18 IGT patients [age: 63 ± 11 years, body mass index (BMI): 31 ± 6 kg/m2, fasting glucose: 6.0 ± 0.4 mmol/l, 120 min postload glucose: 9.0 ± 1.0 mmol/l, hemoglobin A1c (HbA1c): 5.9 ± 0.4%; mean ± SD] and 18 healthy controls (age: 56 ± 9 years, BMI: 27 ± 5 kg/m2, fasting glucose: 5.2 ± 0.4 mmol/l, 120 min postload glucose: 5.5 ± 1.3 mmol/l, HbA1c: 5.4 ± 0.3%) were enrolled into the study. ECGs were recorded, processed, and analyzed off-line. The RR and QT intervals were expressed as the average of 30 consecutive beats, the temporal instability of beat-to-beat repolarization was characterized by calculating STVQT as follows: STVQT = Σ|QTn + 1 - QTn| (30x√2)-1. Autonomic function was assessed by means of standard cardiovascular reflex tests. There were no differences between IGT and control groups in QT (411 ± 43 vs 402 ± 39 ms) and QTc (431 ± 25 vs 424 ± 19 ms) intervals or QT dispersion (44 ± 13 vs 42 ± 17 ms). However, STVQT was significantly higher in IGT patients (5.0 ± 0.7 vs 3.7 ± 0.7, P < 0.0001). The elevated temporal STVQT in patients with IGT may be an early indicator of increased instability of cardiac repolarization during prediabetic conditions.
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Affiliation(s)
- Andrea Orosz
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Szabolcs Nyiraty
- First Department of Medicine, University of Szeged, Szeged, Hungary
| | - Anna E. Körei
- First Department of Medicine, Semmelweis University, Budapest, Hungary
| | - Zsuzsanna Putz
- First Department of Medicine, Semmelweis University, Budapest, Hungary
| | - Róbert Takács
- First Department of Medicine, University of Szeged, Szeged, Hungary
| | - Attila Nemes
- Second Department of Medicine and Cardiology Centre, University of Szeged, Szeged, Hungary
| | | | - László Balogh
- Juhász Gyula Faculty of Education, Institute of Physical Education and Sport Science, University of Szeged, Szeged, Hungary
| | - György Ábrahám
- First Department of Medicine, University of Szeged, Szeged, Hungary
| | - Péter Kempler
- First Department of Medicine, Semmelweis University, Budapest, Hungary
| | - Julius Gy. Papp
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
- MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - Csaba Lengyel
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
- First Department of Medicine, University of Szeged, Szeged, Hungary
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Grandi E. Size matters, proportion too: coupling of experiments and theory reveals relative roles of K + channels in action potential stability. J Physiol 2017; 595:2319-2320. [PMID: 28004403 DOI: 10.1113/jp273665] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- Eleonora Grandi
- Department of Pharmacology, University of California Davis, Davis, CA, USA
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32
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Hill AP. Boosting the reserves: additive regulation of cardiac repolarisation. J Physiol 2017; 595:2269-2270. [PMID: 28094454 DOI: 10.1113/jp273940] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Adam P Hill
- Computational Cardiology, Victor Chang Cardiac Research Institute, Sydney, NSW, 2226, Australia
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Affiliation(s)
- Donald M Bers
- Department of Pharmacology, University of California, Davis, CA, USA
| | - Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, CA, USA
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