PO-01-244 BMAL1 REGULATES THE CIRCADIAN RHYTHM OF RYR2 AND CONTRIBUTES TO CIRCADIAN VENTRICULAR ARRHYTHMIA IN CHRONIC HEART FAILURE AFTER MYOCARDIAL INFARCTION

Abstract

Ventricular arrhythmia (VAs) is the major cause of sudden cardiac death in chronic heart failure (CHF) after myocardial infarction (MI), and previous studies have reported that VAs exist circadian oscillation in CHF. Peripheral circadian clock can regulate expression and function of ion channels in cardiomyocytes, which is associated with circadian rhythm of VAs in CHF. However, the regulation of peripheral circadian clock on Ryanodine Receptor 2 (RYR2), a calcium channel on cardiac sarcoplasmic reticulum, remain to be fully understood. We aimed to explore the regulation of peripheral circadian clock on RYR2 and VA events in CHF. CHF was induced by ligation of coronary artery of mice, and RT-PCR were performed to investigate the circadian rhythm of RYR2 in CHF myocardial tissue. Amplitude of calcium transient of ISO-induced cardiomyocytes at different time was measured to study the circadian rhythm of RYR2 function. To confirm the circadian oscillation of VAs, VAs incidences at different time of CHF wild type mice and cardiomyocyte-specific Bmal1 knockout (CKO) mice were investigated by programmed electrical stimulation. Infections of Ad-CLOCK and/or Ad-BMAL1 were applied to overexpress CLOCK, BMAL1 and CLOCK-BMAL1 in cardiomyocytes, and expression of RYR2 was measured by Western blot. Chromatin immunoprecipitation assay (ChIP) and luciferase (LUC) were applied to determine whether CLOCK-BMAL1 transcriptionally regulate RYR2 expression. CLOCK, BMAL1, and RYR2 exhibited notable circadian rhythm in CHF mice (Figure A, P<0.05). Amplitude of calcium transient at CT36 was lower than CT24 (Figure B, P<0.05). Compared to CT36, VAs had higher incidence at CT24(Figure C, P<0.05), and incidences of VAs had no significant difference between CT24 and CT36 in CKO Mice or using Dantrolene, an antagonist of RYR2. Ad-CLOCK and Ad-BMAL1 co-infection resulted in overexpression of RYR2 (Figure D, P<0.05), and BMAL1 bound to the enhancer of RYR2 gene and upregulated RYR2 expression transcriptionally (Figure E). In conclusion, BMAL1, as peripheral circadian clock, could contribute to circadian oscillation of VAs in CHF by regulating the circadian rhythm of RYR2.