Yuan Hung1,2, Yao-Chang Chen3, Shih-Yu Huang4,5, Yen-Yu Lu4,6, Yung-Kuo Lin7,8, Yu-Hsun Kao9,10, Wei-Shiang Lin1,3, Shih-Ann Chen11,12, Yi-Jen Chen7,10. 1. Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan. 2. Division of Cardiology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan. 3. Department of Biomedical Engineering, National Defense Medical Center, Taipei, Taiwan. 4. School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan. 5. Division of Cardiac Electrophysiology, Cardiovascular Center, Cathay General Hospital, Taipei, Taiwan. 6. Division of Cardiology, Department of Internal Medicine, Sijhih Cathay General Hospital, New Taipei City, Taiwan. 7. Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan. 8. Division of Cardiology, Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan. 9. Department of Medical Education and Research, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan. 10. Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan. 11. School of Medicine, National Yang-Ming University, Taipei, Taiwan. 12. Division of Cardiology and Cardiovascular Research Center, Veterans General Hospital-Taipei, Taipei, Taiwan.
Abstract
AIMS: Klotho, a potential antiageing protein has remarkable cardiovascular effects, which is lower in the patients with chronic kidney disease (CKD). Chronic kidney disease increases the risk of atrial fibrillation, majorly triggered by pulmonary vein (PV) arrhythmogenesis. This study investigated whether klotho protein can modulate PV electrical activity and the underlying potential mechanisms. METHODS AND RESULTS: A conventional microelectrode and whole-cell patch clamp were used to investigate the action potentials and ionic currents in isolated rabbit PV tissue preparations and single cardiomyocytes before and after klotho administration. Phosphoinositide 3-kinase (PI3K)/Akt signalling was studied using western blotting. Klotho significantly reduced PV spontaneous beating rates in PV tissue preparations at 1.0 and 3.0 ng/mL (but not at 0.1 and 0.3 ng/mL). In the presence of the Akt inhibitor (10 µM), klotho (1.0 and 3.0 ng/mL) did not change PV electrical activities. Klotho (1.0 ng/mL) significantly decreased the late sodium current (INa-Late) and L-type calcium current (ICa-L), similar to the Akt inhibitor (10 µM). Western blots demonstrated that klotho (1.0 ng/mL)-treated PV cardiomyocytes had less phosphorylation of Akt (Ser473) compared with klotho-untreated cardiomyocytes. Compared with control PVs, klotho at relatively lower concentrations (0.1 and 0.3 ng/mL) significantly reduced beating rates and decreased the amplitudes of delay afterdepolarizations in CKD PVs. CONCLUSION: Klotho modulated PV electrical activity by inhibiting PI3K/Akt signalling, which may provide a novel insight into CKD-induced arrhythmogenesis. Published on behalf of the European Society of Cardiology. All rights reserved.
AIMS: Klotho, a potential antiageing protein has remarkable cardiovascular effects, which is lower in the patients with chronic kidney disease (CKD). Chronic kidney disease increases the risk of atrial fibrillation, majorly triggered by pulmonary vein (PV) arrhythmogenesis. This study investigated whether klotho protein can modulate PV electrical activity and the underlying potential mechanisms. METHODS AND RESULTS: A conventional microelectrode and whole-cell patch clamp were used to investigate the action potentials and ionic currents in isolated rabbit PV tissue preparations and single cardiomyocytes before and after klotho administration. Phosphoinositide 3-kinase (PI3K)/Akt signalling was studied using western blotting. Klotho significantly reduced PV spontaneous beating rates in PV tissue preparations at 1.0 and 3.0 ng/mL (but not at 0.1 and 0.3 ng/mL). In the presence of the Akt inhibitor (10 µM), klotho (1.0 and 3.0 ng/mL) did not change PV electrical activities. Klotho (1.0 ng/mL) significantly decreased the late sodium current (INa-Late) and L-type calcium current (ICa-L), similar to the Akt inhibitor (10 µM). Western blots demonstrated that klotho (1.0 ng/mL)-treated PV cardiomyocytes had less phosphorylation of Akt (Ser473) compared with klotho-untreated cardiomyocytes. Compared with control PVs, klotho at relatively lower concentrations (0.1 and 0.3 ng/mL) significantly reduced beating rates and decreased the amplitudes of delay afterdepolarizations in CKD PVs. CONCLUSION:Klotho modulated PV electrical activity by inhibiting PI3K/Akt signalling, which may provide a novel insight into CKD-induced arrhythmogenesis. Published on behalf of the European Society of Cardiology. All rights reserved.