Effect of mild hypothermia at focal side on changes of HIF-1αand Bcl-2 protein in rats after focal cerebral ischemia and reperfusion

Objective To observe the effect of local mild hypothermia on expression of HIF-1α and Bcl-2 protein after focal cerebral ischemia and reperfusion injury.Methods The rats were randomly divided into normal group,sham-operation group,normothermia ischemia group and mild hypothermia ischemia group.The focal cerebral ischemia models of rats were achieved by modified thread embolism.After ischemia for 2 hours and reperfusion at middle cerebral artery for 3h,6h,12h,24h,72h and 7d,the rats were killed.Neural functional defect evaluation was conducted before death.Mild hypothermia at focal side was performed 30min after 4h ischemia.Pathological changes were observed with hematoxylin and eosin staining.The expression of HIF-1αand bcl-2 was detected with immunohistochemical method.Results (1)Assessment of neural functional defect:It was significantly lower in the mild hypothermia ischemic group than that in the normal ischemic group(P0.05).(2)HIF-1α expression:The expression increased at 3h after reperfusion,reached peak at 24h,and then fell down.There was no difference between sub-hypothermia ischemia group and normothermia ischemia group at each time point(P0.05).(3)Bcl-2 expression:The expression increased at 3h after reperfusion,and still increased gradually with the prolongation of reperfusion time(P0.05).Till 6h it reached the peak,and then decreased.The expression in the sub-hypothermia ischemia group at each time point was higher markedly than that in the normothermia ischemia group(P0.05).Conclusion HIF-1α in early cerebral ischemia play an important role in protection.Bcl-2 could restrain apoptosis.Mild Hypothermia could increase expression of Bcl-2,markedly alleviate pathological change resulted from ischemia and prevent dramatically apoptosis and execute curative effect for ischemic damage.