Wen-Chin Tsai1, Yen-Yu Lu2, Yao-Chang Chen3, Chien-Jung Chang4, Yu-Hsun Kao5, Yung-Kuo Lin6, Yu-Hsin Chen7, Shih-Ann Chen8, Liang-Yo Yang9, Yi-Jen Chen10. 1. Division of Cardiology, Tzu-Chi General Hospital, Hualien, Taiwan. 2. Division of Cardiology, Sijhih Cathay General Hospital, New Taipei City, Taiwan. 3. Department of Biomedical Engineering, National Defense Medical Center, Taipei, Taiwan. 4. Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan. 5. Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan; Department of Medical Education and Research, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan. 6. Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan. 7. Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan; Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan. 8. Division of Cardiology, Veterans General Hospital, Taipei, Taiwan. 9. Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan; Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei, Taiwan; Neuroscience Research Center, Taipei Medical University Hospital, Taipei, Taiwan. Electronic address: yangly@tmu.edu.tw. 10. Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan. Electronic address: a9900112@ms15.hinet.net.
Abstract
BACKGROUND: Sex hormones and calcium (Ca(2+)) regulation play roles in the pathophysiology of ventricular tachycardia from right ventricular outflow tract (RVOT). The purpose of this study was to evaluate whether androgen receptor knockout (ARKO) can increase RVOT arrhythmogenesis through modulating RVOT electrophysiology and Ca(2+) homeostasis. METHODS: Conventional microelectrodes were used to study the action potential (AP) in RVOT tissues prepared from wild type (WT) and ARKO mice (aged 6-10 months) before and after caffeine (1mM), isoproterenol (1 μM), adenosine (10 μM) and flecainide (5 μM) administration. The Fluo-3 fluorescence Ca(2+) imaging with confocal microscopy and western blots were used to investigate intracellular Ca(2+) (Ca(2+)i) transients, Ca(2+) sparks, and the expressions of ionic channel proteins in ARKO and WT RVOT myocytes. RESULTS: We found that ARKO RVOTs (n = 13) had longer AP duration, faster burst firing (5.4 ± 0.7 vs. 3.4 ± 0.7 Hz, P < 0.05), and higher incidence of early afterdepolarizations (82% vs. 8%, P < 0.001) than WT RVOTs (n = 11). Adenosine and flecainide can suppress caffeine- or isoproterenol-induced spontaneous rates and burst firing in WT RVOTs, but not in ARKO RVOTs. ARKO RVOT myocytes had a higher frequency (7.7 ± 2.8 vs. 1.3 ± 0.4 spark/mm/s, P < 0.05) and incidence (89% vs. 47%, P < 0.05) of Ca(2+) sparks, and greater expressions of Cav1.2, NCX, phosphorylated RyR (s2814), phosphorylated phospholamban (Thr17), CAMKII and GRK2 than WT RVOT myocytes. However, ARKO and WT RVOT myocytes exhibit similar Ca(2+)i transients and SR Ca(2+) content, and less expression of calsequestrin. CONCLUSIONS: ARKO changes RVOT electrophysiology and Ca(2+) homeostasis with increased ventricular arrhythmogenesis.
BACKGROUND: Sex hormones and calcium (Ca(2+)) regulation play roles in the pathophysiology of ventricular tachycardia from right ventricular outflow tract (RVOT). The purpose of this study was to evaluate whether androgen receptor knockout (ARKO) can increase RVOT arrhythmogenesis through modulating RVOT electrophysiology and Ca(2+) homeostasis. METHODS: Conventional microelectrodes were used to study the action potential (AP) in RVOT tissues prepared from wild type (WT) and ARKOmice (aged 6-10 months) before and after caffeine (1mM), isoproterenol (1 μM), adenosine (10 μM) and flecainide (5 μM) administration. The Fluo-3 fluorescence Ca(2+) imaging with confocal microscopy and western blots were used to investigate intracellular Ca(2+) (Ca(2+)i) transients, Ca(2+) sparks, and the expressions of ionic channel proteins in ARKO and WT RVOT myocytes. RESULTS: We found that ARKO RVOTs (n = 13) had longer AP duration, faster burst firing (5.4 ± 0.7 vs. 3.4 ± 0.7 Hz, P < 0.05), and higher incidence of early afterdepolarizations (82% vs. 8%, P < 0.001) than WT RVOTs (n = 11). Adenosine and flecainide can suppress caffeine- or isoproterenol-induced spontaneous rates and burst firing in WT RVOTs, but not in ARKO RVOTs. ARKO RVOT myocytes had a higher frequency (7.7 ± 2.8 vs. 1.3 ± 0.4 spark/mm/s, P < 0.05) and incidence (89% vs. 47%, P < 0.05) of Ca(2+) sparks, and greater expressions of Cav1.2, NCX, phosphorylated RyR (s2814), phosphorylated phospholamban (Thr17), CAMKII and GRK2 than WT RVOT myocytes. However, ARKO and WT RVOT myocytes exhibit similar Ca(2+)i transients and SR Ca(2+) content, and less expression of calsequestrin. CONCLUSIONS:ARKO changes RVOT electrophysiology and Ca(2+) homeostasis with increased ventricular arrhythmogenesis.