亚低温对大鼠脑缺血再灌注损伤后热休克蛋白70表达及细胞凋亡的影响

目的]观察亚低温对大鼠局灶脑缺血再灌注损伤后热休克蛋白70(HSP70)表达的影响,探讨亚低温对脑神经细胞保护作用的机制。方法]将SD大鼠随机分为正常组、假手术组、常温缺血组和亚低温缺血组。应用大脑中动脉线栓法(MCAO)建立大鼠局灶脑缺血再灌注模型,于缺血2 h再灌注,再灌注后3、6、12、24、72 h和7 d处死。其中亚低温组大鼠于缺血后30 min实施病灶侧脑亚低温并持续4 h。采用HE染色观察神经细胞形态学改变,免疫组化法检测脑组织HSP70表达,TUNEL法检测凋亡细胞。结果]正常组及假手术组均未见明显病理改变;常温缺血组梗死灶明显,大量神经元坏死消失;亚低温缺血组未见明显梗死灶,但可见神经元固缩。正常组及假手术组未见或偶见HSP70阳性细胞;常温缺血组HSP70阳性细胞较多;与常温缺血组相比亚低温缺血组在相应时间点均明显减少(P<0.05)。常温缺血组TUNEL阳性细胞数随再灌注时间的延长而逐渐增多,至72 h达高峰;与常温缺血组相比,亚低温缺血组各时间点均明显减少(P<0.05)。结论]亚低温对大鼠缺血再灌注损伤脑有保护作用,通过降低HSP70的表达和减少细胞凋亡可能是其保护机制之一。

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(P<0.05).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(P<0.05).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.