Role of class I histone deacetylase in myocardial ischemia-reperfusion injury in diabetic rats and the relationship with AMPK/mTOR signaling pathway

Objective To evaluate the role of class Ⅰ histone deacetylase (HDAC) in myocardial ischemia-reperfusion (I/R) injury in diabetic rats and the relationship with adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway. Methods SPF healthy adult male Sprague-Dawley rats, weighing 210-220 g, were used in this study.Type I diabetes mellitus was induced by single intraperitoneal injection of streptozotocin dissolved in citrate buffer 60 mg/kg, and 8 weeks later the rats with type I diabetes mellitus were used for experiment.Forty-eight diabetic rats were divided into 4 groups (n=12 each) by using a random number table method: sham operation group (group S), myocardial I/R group (group I/R), myocardial I/R plus class I HDAC inhibitor MS-275 group (group I/R+ MS) and myocardial I/R plus MS-275 plus AMPK inhibitor Compound C group (group I/R+ MS+ CC). Myocardial I/R was induced by ligation of the left anterior descending branch of the coronary artery for 45 min followed by 180 min of reperfusion in anesthetized rats.In group I/R+ MS, MS-275 10 mg/kg was intraperitoneally injected once a day for 7 consecutive days, and myocardial I/R was produced after the end of administration.AMPK inhibitor Compound C 0.5 mg/kg was intravenously injected at 30 min before ischemia in group I/R+ MS+ CC.Six rats were sacrificed at the end of reperfusion for determination of myocardial infarct size.Another 6 rats were selected at the end of reperfusion and sacrificed for determination of the level of creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) in serum (by enzyme-linked immunosorbent assay), expression of AMPK, phosphorylated AMPK (p-AMPK), mTOR, phosphorylated mTOR (p-mTOR), ubiquitin-binding protein P62 (P62), microtubule-associated protein 1 light chain 3 Ⅰ (LC3 Ⅰ) and LC3Ⅱ in myocardial tissues (by Western blot). The ratios of p-AMPK/AMPK, p-mTOR/mTOR and LC3Ⅱ/Ⅰ were calculated. Results Compared with group S, the myocardial infarct size and levels of serum CK-MB and LDH were significantly increased in I/R, I/R+ MS and I/R+ M+ CC groups, the ratios of p-AMPK/AMPK and LC3Ⅱ/Ⅰ were significantly increased, p-mTOR/mTOR ratio was decreased, and P62 expression was down-regulated in group I/R+ MS (P 0.05). Compared with group I/R, the myocardial infarct size and levels of serum CK-MB and LDH were significantly decreased, the ratios of p-AMPK/AMPK and LC3Ⅱ/Ⅰ were increased, p-mTOR/mTOR ratio was decreased, and P62 expression was down-regulated in group I/R+ MS (P 0.05). Compared with group I/R+ MS, the myocardial infarct size and levels of serum CK-MB and LDH were significantly increased, the ratios of p-AMPK/AMPK and LC3Ⅱ/Ⅰ were decreased, p-mTOR/mTOR ratio was increased, and P62 expression was up-regulated in group I/R+ M+ CC (P<0.05). Conclusion Class Ⅰ HDAC is involved in myocardial I/R injury through enhancing AMPK/mTOR signaling pathway-regulated level of autophagy in diabetic rats. Key words: Histone deacetylase; Autophagy; Diabetes mellitus; Myocardial reperfusion injury; Protein-serine-threonine kinases; Receptor-interacting protein serine-threonine kinases