Background: Circadian clock has been closely related to the development of diabetes mellitus and cardiovascular disease; the disruption of circadian clock exacerbates myocardial ischemia/reperfusion injury (MI/RI). HDAC3 is a key component of the circadian negative feedback loop by recruitmenting the expression pattern of circadian nuclear receptor Rev-erbα, then to maintain the stability of circadian gene such as BMAL1. In this research, we explored the mechanism of HDAC3-orchestrated Rev-erbα/BMAL1 pathway in increasing MI/RI vulnerability of diabetes, and its relationship with mitophagy.
Methods and results: Streptozocin (STZ) was used to establish type 1 diabetes by intraperitoneal injection. After 8 weeks, the diabetic and non-diabetic rats were exposed to MI/RI by ligating the left anterior descending coronary artery (LDA) for 30 minutes and reperfusion for 120 minutes at four time points of zeitgeber (ZT) 0, 6, 12 and 18. Circadian clock gene oscillations were rapidly attenuated in diabetic I/RI hearts, versus sham and/or the non-diabetic I/RI hearts, in accord with circadian mitophagy. By utilizing AAV-HDAC3 to knockdown HDAC3 expression, HDAC3 deficiency significantly attenuated diabetic MI/RI associated with increased autophagy activation. In vitro experiments, primary cardiomyocytes with or without HDAC3 siRNA and Rev-erbα siRNA exposed to hypoxia/reoxygenation (H/R). The expression of HDAC3 and Rev-erbα in cardiomyocytes was increased under high glucose condition with decreased BMAL1 expression and autophagy level. After H/R stimulation, the cell injury was obviously increased with upregulated HDAC3 and Rev-erbα expression and decreased BMAL1 level. Moreover, high glucose aggravated H/R injury compared with low glucose by reducing autophagy level, increasing the levels of HDAC3 and Rev-erbα and down-regulating BMAL1 expression. HDAC3 and Rev-erbα siRNA can alleviate high glucose and H/R-induced injury by up-regulating BMAL1 expression and mitophagy levels.
Conclusion: These findings suggest that in diabetic rat MI/RI , the circadian clocks were rapidly impaired then to inhibit mitophagy; cardiac-targeted manipulation of HDAC3-orchestrated Rev-erbα/BMAL1 pathway may be the mechanism of the decreased toleration to ischemia with a circadian dependent variability.