Changes in expression of DJ-1 protein during myocardial ischemia-reperfusion in diabetic rats

Objective To evaluate the changes in the expression of DJ-1 protein during myocardial ischemia-reperfusion (I/R) in diabetic rats.Methods Fifty male Sprague-Dawley rats,weighing 220-280 g,were used in this study.Type 1 diabetes mellitus was induced by intraperitoneal streptozotocin 65 mg/kg and confirmed by fasting blood glucose ＞ 16.7 mmol/L.Forty animals with type 1 diabetes mellitus were randomly divided into 3 groups:diabetes group (group D,n =10),diabetic sham operation group (group DS,n =15) and diabetic I/R group (group DIR,n =15).Another 10 non-diabetic rats in which citrate buffer 6 ml/kg was injected intraperitoneally were served as control group (group C).Myocardial I/R was produced by occlusion of the anterior descending branch of left coronary artery for 30 min followed by 120 min reperfusion in group I/R.At 120 min of reperfusion,5 rats were sacrificed and myocardial specimens were c(on)tained for determination of infarct size in groups DS and DIR,and 10 rats were sacrificed and myocardial specimens were obtained for microscopic examination and for determination of cell apoptosis,malondialdehyde (MDA) content,superoxide dismutase (SOD) activity and expression of DJ-1 and phosphatase and tensin homologue (PTEN) protein.Apoptotic index (AI) was calculated.Linear correlation between the expression of DJ-1 protein and MDA content,SOD activity,AI and expression of PTEN protein was analyzed.Results Compared with group DS,the myocardial infract size was significantly increased in group DIR (P ＜ 0.05).Compared with group C,MDA content and AI were significantly increased,SOD activity was decreased,the expression of DJ-1 was down-regulated,and the expression of PTEN protein was up-regulated in groups D,DS and DIR (P ＜ 0.05).Compared with groups D and DS,MDA content and AI were significantly increased,SOD activity was decreased,the expression of DJ-1 was down-regulated,and the expression of PTEN protein was up-regulated in group DIR (P ＜ 0.05).There was no significant difference in the parameters mentioned above between groups D and DS (P ＞ 0.05).There was linear correlation between the expression of DJ-1 protein and MDA content,SOD activity,AI and expression of PTEN protein and the correlation coefficients (r) were-0.734,0.593,-0.818,and-0.812 in turn.Conclusion Down-regulation of DJ-1 protein expression is involved in myocardial I/R injury in diabetic rats via decreasing anti-oxidative stress responses and upregulating PTEN protein expression. Key words: Intracellular signaling peptides and proteins;  Myocardial reperfusion injury;  Diabetes mellitus