Effect of mild hypothermia on expression of HSP70 and cell apoptosis after the cerebral ischemia-reperfusion injury in rats

[Objective]To observe the effect of mild hypothermia on expression of heat shock protein 70(HSP70) after focal cerebral ischemia and reperfusion injury in rats,and to explore the protection mechanism for neuron of mild hypothermia.[Methods]The rats were randomly divided into normal group,sham-operation group,normothermia ischemia/reperfusion group and hypothermia ischemia/reperfusion group.The focal cerebral ischemia/reperfusion models of rats were induced by line bolt.After ischemia for 2 hours,reperfusion at middle cerebral artery was performed for 3,6,12,24,72 h and 7 d,then the rats were killed.Sub-hypothermia at focal side was performed 30 min after ischemia for 4 h.Pathological changes were observed under microscope.The expression of HSP70 was detected with immunohistochemistry.The apoptosis was detected with TUNEL.[Results]No obvious pathological changes were observed in normal group and sham-operation group.There were obvious infarction region with lots of neuron necrosis in normothermia ischemia/reperfusion group,but no obvious infarction region with neuron necrosis in hypothermia ischemia/ reperfusion group.No or little expressions of HSP70 were detected in normal group and sham-operation group.High expressions of HSP70 were detected in normothermia ischemia/reperfusion group.The expressions of HSP70 in hypothermia ischemia/reperfusion group were lower obviously than that in normothermia ischemia/reperfusion group at corresponding time spots(P0.05).The apoptotic cells increased gradually with the elongation of reperfusion time and reached the peak till the 72 h.The apoptotic cells in hypothermia ischemia/reperfusion group were fewer than those in normothermia ischemia/reperfusion group(P0.05).[Conclusion]Mild hypothermia can protect neurons at the cerebral ischemia-reperfusion injury in rats by inhibiting neuron apoptosis and reducing the protective expression of HSP70.