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Kurata Y, Tsumoto K, Hayashi K, Hisatome I, Kuda Y, Tanida M. Multiple Dynamical Mechanisms of Phase-2 Early Afterdepolarizations in a Human Ventricular Myocyte Model: Involvement of Spontaneous SR Ca 2+ Release. Front Physiol 2020; 10:1545. [PMID: 31998140 PMCID: PMC6965073 DOI: 10.3389/fphys.2019.01545] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 12/05/2019] [Indexed: 12/19/2022] Open
Abstract
Early afterdepolarization (EAD) is known to cause lethal ventricular arrhythmias in long QT syndrome (LQTS). In this study, dynamical mechanisms of EAD formation in human ventricular myocytes (HVMs) were investigated using the mathematical model developed by ten Tusscher and Panfilov (Am J Physiol Heart Circ Physiol 291, 2006). We explored how the rapid (IKr) and slow (IKs) components of delayed-rectifier K+ channel currents, L-type Ca2+ channel current (ICa L), Na+/Ca2+ exchanger current (INCX), and intracellular Ca2+ handling via the sarcoplasmic reticulum (SR) contribute to initiation, termination and modulation of phase-2 EADs during pacing in relation to bifurcation phenomena in non-paced model cells. Parameter-dependent dynamical behaviors of the non-paced model cell were determined by calculating stabilities of equilibrium points (EPs) and limit cycles, and bifurcation points to construct bifurcation diagrams. Action potentials (APs) and EADs during pacing were reproduced by numerical simulations for constructing phase diagrams of the paced model cell dynamics. Results are summarized as follows: (1) A modified version of the ten Tusscher-Panfilov model with accelerated ICaL inactivation could reproduce bradycardia-related EADs in LQTS type 2 and β-adrenergic stimulation-induced EADs in LQTS type 1. (2) Two types of EADs with different initiation mechanisms, ICaL reactivation-dependent and spontaneous SR Ca2+ release-mediated EADs, were detected. (3) Termination of EADs (AP repolarization) during pacing depended on the slow activation of IKs. (4) Spontaneous SR Ca2+ releases occurred at higher Ca2+ uptake rates, attributable to the instability of steady-state intracellular Ca2+ concentrations. Dynamical mechanisms of EAD formation and termination in the paced model cell are closely related to stability changes (bifurcations) in dynamical behaviors of the non-paced model cell, but they are model-dependent. Nevertheless, the modified ten Tusscher-Panfilov model would be useful for systematically investigating possible dynamical mechanisms of EAD-related arrhythmias in LQTS.
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Affiliation(s)
- Yasutaka Kurata
- Department of Physiology II, Kanazawa Medical University, Uchinada, Japan
| | - Kunichika Tsumoto
- Department of Physiology II, Kanazawa Medical University, Uchinada, Japan
| | - Kenshi Hayashi
- Department of Cardiovascular and Internal Medicine, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan
| | - Ichiro Hisatome
- Department of Genetic Medicine and Regenerative Therapeutics, Graduate School of Medical Sciences, Tottori University, Yonago, Japan
| | - Yuhichi Kuda
- Department of Physiology II, Kanazawa Medical University, Uchinada, Japan
| | - Mamoru Tanida
- Department of Physiology II, Kanazawa Medical University, Uchinada, Japan
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Onohara T, Hisatome I, Kurata Y, Li P, Notsu T, Morikawa K, Otani N, Yoshida A, Iitsuka K, Kato M, Miake J, Ninomiya H, Higaki K, Shirayoshi Y, Nishihara T, Itoh T, Nakamura Y, Nishimura M. Molecular mechanisms underlying the pilsicainide-induced stabilization of hERG proteins in transfected mammalian cells. J Arrhythm 2017; 33:226-233. [PMID: 28607619 PMCID: PMC5459418 DOI: 10.1016/j.joa.2016.09.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 09/08/2016] [Accepted: 09/13/2016] [Indexed: 11/28/2022] Open
Abstract
Background Pilsicainide, classified as a relatively selective Na+ channel blocker, also has an inhibitory action on the rapidly-activating delayed-rectifier K+ current (IKr) through human ether-a-go-go-related gene (hERG) channels. We studied the effects of chronic exposure to pilsicainide on the expression of wild-type (WT) hERG proteins and WT-hERG channel currents, as well as on the expression of mutant hERG proteins, in a heterologous expression system. Methods HEK293 cells stably expressing WT or mutant hERG proteins were subjected to Western blotting, immunofluorescence microscopy and patch-clamp experiments. Results Acute exposure to pilsicainide at 0.03–10 μM influenced neither the expression of WT-hERG proteins nor WT-hERG channel currents. Chronic treatment with 0.03–10 μM pilsicainide for 48 h, however, increased the expression of WT-hERG proteins and channel currents in a concentration-dependent manner. Chronic treatment with 3 μM pilsicainide for 48 h delayed degradation of WT-hERG proteins and increased the channels expressed on the plasma membrane. A cell membrane-impermeant pilsicainide derivative did not influence the expression of WT-hERG, indicating that pilsicainide stabilized the protein inside the cell. Pilsicainide did not influence phosphorylation of Akt (protein kinase B) or expression of heat shock protein families such as HSF-1, hsp70 and hsp90. E4031, a chemical chaperone for hERG, abolished the pilsicainide effect on hERG. Chronic treatment with pilsicainide could also increase the protein expression of trafficking-defective mutant hERG, G601S and R752W. Conclusions Pilsicainide penetrates the plasma membrane, stabilizes WT-hERG proteins by acting as a chemical chaperone, and enhances WT-hERG channel currents. This mechanism could also be applicable to modulations of certain mutant-hERG proteins.
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Affiliation(s)
- Takeshi Onohara
- Division of Organ Regeneration Surgery, Tottori University Faculty of Medicine, Yonago, Japan
| | - Ichiro Hisatome
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, Nishichou 36-1, Yonago, Japan
| | - Yasutaka Kurata
- Department of Physiology II, Kanazawa Medical University, 1-1 Daigaku, Uchinada-machi, Kahoku-gun, Ishikawa, Japan
| | - Peili Li
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, Nishichou 36-1, Yonago, Japan
| | - Tomomi Notsu
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, Nishichou 36-1, Yonago, Japan
| | - Kumi Morikawa
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, Nishichou 36-1, Yonago, Japan
| | - Naoyuki Otani
- Department of Pharmacology, Dokkyo Medical College, Tochigi, Japan
| | - Akio Yoshida
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, Nishichou 36-1, Yonago, Japan
| | - Kazuhiko Iitsuka
- Division of Cardiovascular Medicine, Department of Molecular Medicine and Therapeutics, Faculty of Medicine, Tottori University, Nishichou 36-1, Yonago, Japan
| | - Masaru Kato
- Division of Cardiovascular Medicine, Department of Molecular Medicine and Therapeutics, Faculty of Medicine, Tottori University, Nishichou 36-1, Yonago, Japan
| | - Junichiro Miake
- Division of Cardiovascular Medicine, Department of Molecular Medicine and Therapeutics, Faculty of Medicine, Tottori University, Nishichou 36-1, Yonago, Japan
| | - Haruaki Ninomiya
- Department of Biological Regulation, Tottori University Faculty of Medicine, Nishichou 36-1, Yonago, Japan
| | - Katsumi Higaki
- Division of Functional Genomics, Research Center for Bioscience and Technology, Tottori University, Nishichou 36-1, Yonago, Japan
| | - Yasuaki Shirayoshi
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, Nishichou 36-1, Yonago, Japan
| | - Takashi Nishihara
- Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan.,Center for Research on Green Sustainable Chemistry, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan
| | - Toshiyuki Itoh
- Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan.,Center for Research on Green Sustainable Chemistry, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan
| | - Yoshinobu Nakamura
- Division of Organ Regeneration Surgery, Tottori University Faculty of Medicine, Yonago, Japan
| | - Motonobu Nishimura
- Division of Organ Regeneration Surgery, Tottori University Faculty of Medicine, Yonago, Japan
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