Role of autophagy in cerebral ischemia-reperfusion injury in diabetic mice: the relationship with HDAC3/Bmal1 signaling pathway

Objective To evaluate the role of autophagy in cerebral ischemia-reperfusion (I/R) injury in diabetic mice and the relationship with histone deacetylase 3 (HDAC3)/Bmal1 signaling pathway. Methods Healthy clean-grade male C57BL/6 mice were used in the study.Diabetes mellitus was induced by intraperitoneal injection of streptozotocin.Thirty-six mice with diabetes mellitus after being fed for 8 weeks were divided into 3 groups (n=12 each) using a random number table method: sham operation group (group S), I/R group and I/R plus HDAC3 inhibitor group (group I/R-H). Cerebral I/R was induced by middle cerebral artery occlusion for 1 h, followed by 24-h reperfusion in anesthetized mice.Specific HDAC3 inhibitor RGFP966 10 mg/kg was subcutaneously injected at 30 min before establishing the model in group I/R-H.Brain tissues were obtained at 24 h of reperfusion for microscopic examination and for determination of cerebral infarct size (by TTC), cell apoptosis (by TUNEL), activities of superoxide dismutase (SOD) and reactive oxygen species (ROS) and malondialdehyde (MDA) content (by colorimetric assay), expression of autophagy-related protein Beclin-1 and LC3B (by immunofluorescence), and expression of HDAC3, Bmal1, GSK-3β and p62 (by Western blot). Apoptosis index (AI) was calculated. Results Compared with group S, the cerebral infarct size was significantly increased, the activities of SOD and ROS and content of MDA in brain tissues were decreased, the expression of Bmal1, p-GSK-3β and HDAC3 was down-regulated, and AI was increased in group I/R (P<0.05). Compared with group I/R, the cerebral infarct size was significantly increased, the activities of SOD and ROS and content of MDA in brain tissues were increased, the expression of Bmal1, p-GSK-3β, Beclin-1 and LC3B was up-regulated, AI was decreased, and the expression of HDAC3 and p62 was down-regulated in group I/R-H (P<0.05). Conclusion HDAC3/Bmal1 signaling pathway exerts endogenous protective effect through activating autophagy and increasing the antioxidant capacity following cerebral I/R in diabetic mice. Key words: HDAC3; Bmal1; Autophagy; Diabetic; Cerebral ischemia reperfusion injury