Attenuating Ischemia/Reperfusion-Induced Cardiomyocyte Apoptosis by Increasing the Expression of DJ-1 in Diabetic Rats

Diabetes is associated with cardiovascular disease, and ischemia/reperfusion (I/R) injuries are increased after myocardial infarction. Cardiomyocyte apoptosis is an important pathologic basis for I/R injuries. The PI3K/AKT signaling pathway can up-regulate Bcl-2 expression, reduce apoptosis, and protect against I/R injuries. The phosphatase and tensin homologue deleted on chromosome ten (PTEN) can negatively regulate the PI3K/AKT signaling pathway, and DJ-1 is an important negative regulator of PTEN. In this study, the model for diabetic rats was established by intraperitoneal injection of streptozotocin (STZ) based on the diabetic model, the myocardial I/R model was established to investigate the regulatory effect of the DJ-1-PTEN-PI3K/AKT/Bcl-2 signaling pathway on myocardial I/R injuries in diabetic rats. Rats were divided into the following 4 groups: normal sham operation group (NS); normal ischemia-reperfusion group (NIR); diabetic sham operation group (DMS): and diabetic ischemia-reperfusion group (DMIR). The expression of DJ-1, PTEN, p-AKT and Bcl-2 in the myocardial tissue of the four groups was detected, and the myocardial infarct size and cardiomyocyte apoptosis rate were compared. The cardiomyocytes of normal and diabetic rats were isolated and cultured in vitro. After culturing in an ischemic and hypoxic environment for 12 h, the cardiomyocytes were treated for 12 h with re-oxygenation to simulate in vivo I/R models. At the same time, conventional cultured rat cardiomyocytes as the controls the expressions of DJ-1, PTEN, p-AKT and Bcl-2 were detected and apoptosis was detected by flow cytometry. The cardiomyocytes of diabetic rats were divided into the following five transfection and treatment groups: control group; pIRES2-blank group; pIRES2-DJ-1 group; PTEN blocker SF1670 treatment group; and pIRES2-DJ-1 +SF1670 treatment group, subjected to I/R treatment. The expressions of DJ-1, PTEN, p-AKT and Bcl-2 were detected and apoptosis was detected by flow cytometry. Compared with the sham group, I/R treatment significantly down-regulated DJ-1, p-AKT, and Bcl-2 expression and up-regulated the expression of PTEN, the myocardial infarct size and the apoptosis rate of cardiomyocytes significantly increased (all P < 0.05). (all P < 0.05). The degree of change of the expressions of DJ-1, PTEN, p-AKT, and Bcl-2, also the degree of the myocardial infarction and the cardiomyocyte apoptosis in the myocardial tissues in diabetic rats were significantly higher than normal control rat (all P < 0.05). I/R treatment decreased DJ-1, p-AKT, and Bcl-2 expression and significantly increased PTEN expression and apoptosis in rat cardiomyocytes cultured in vitro, of which the number of apoptotic cardiomyocytes in diabetic rats was increased. The transfection of pIRES2-DJ-1 significantly up-regulated DJ-1, p-AKT, and Bcl-2 expression in cardiomyocytes of diabetic rats and significantly decreased PTEN expression and apoptosis. SF1670 treatment significantly up-regulated p-AKT and Bcl-2 expression and decreased apoptosis by I/R treatment. Down-regulation of DJ-1 expression was shown to be associated with increased susceptibility to I/R injury of myocardial tissues and cardiomyocytes in diabetic rats. Down-regulation of DJ-1 expression may be mediated by up-regulation of PTEN expression, inhibition of PI3K/AKT activity, and the expression of anti-apoptotic factor Bcl-2, thereby increasing the apoptosis of cardiomyocytes under I/R conditions.