Relationship between ERK1/2 and STAT3 signaling pathways involving in cardioprotection induced by diazoxide postconditioning in rats

Abstract

Objective To evaluate the relationship between extracelluar signal-regulated protein kinase 1/2 (ERK1/2) and signal transducer and activator of transcription 3 (STAT3) signaling pathways involving in cardioprotection induced by diazoxide postconditioning in rats. Methods Sixty adult male Sprague-Dawley rats, aged 3 months, weighing 240-260 g, were randomly divided into 5 groups (n=12 each) using a random number table: sham operation group (SH group) , ischemia-reperfusion (I/R) group, diazoxide postconditioning group (D group) , ERK1/2 inhibitor U0126 group (U group) , and STAT3 inhibitor Stattic group (St group) . Myocardial I/R was produced by occlusion of anterior descending branch of the coronary artery followed by 120 min reperfusionIn I/R and D groups, 0.4% dimethyl sulfoxide 1 ml and 7 mg/kg diazoxide (in 1 ml of 0.4% dimethyl sulfoxide) was injected through the femoral vein at the onset of reperfusionIn U and St groups, U0126 100 μg/kg and Stattic 500 μg/kg were injected through the femoral vein at 10 min before reperfusion, and the other procedures were similar to those previously described in group DAt 120 min of reperfusion, the rats were sacrificed, and myocardial specimens were obtained from the left ventricle for determination of myocardial infarct size, cell apoptosis, and ERK1, ERK2 and STAT3 mRNA expression (real-time PCR) , and phosphorylated ERK1/2 (p-ERK1/2) and phosphorylated STAT3 (p-STAT3) (using Western blot) . Apoptosis index (AI) was calculated. Results Compared with group S, the myocardial infarct size and AI were significantly increased, and the expression of ERK1, ERK2 and STAT3 mRNA, p-ERK1/2 and p-STAT3 was down-regulated in group I/R.Compared with group I/R, the myocardial infarct size and AI were significantly decreased, and the expression of ERK1, ERK2 and STAT3 mRNA, p-ERK1/2 and p-STAT3 was up-regulated in group D. Compared with group D, the myocardial infarct size and AI were significantly increased in U and S groups, the expression of ERK1, ERK2 and STAT3 mRNA, p-ERK1/2 and p-STAT3 was down-regulated in group U, and the expression of STAT3 mRNA and p-STAT3 was down-regulated, and no significant change was found in ERK1 and ERK2 mRNA and p-ERK1/2 expression in group S. Conclusion STAT3 signaling pathway is located downstream of ERK1/2 signaling pathway in the mechanism by which diazoxide postconditioning reduces myocardial I/R injury in rats Key words: Extracellular signal-regulated MAP kinases; STAT3 transcription factor; Diazoxide; Ischemia postconditioning; Myocardial reperfusion injury