局部亚低温对大鼠局灶性脑缺血再灌注后XIAP和Caspase-9表达的影响

Effect of mild hypothermia at focal side on changes of X-linked inhibitor of apoptosis protein and Caspase-9 in rats after focal cerebral ischemia and reperfusion

目的观察病变侧亚低温对大鼠局灶性脑缺血再灌注后X染色体连锁的凋亡抑制蛋白(X-linked inhibitorof apoptosis protein,XIAP)和半胱天冬蛋白酶-9(Caspase-9)表达的影响,研究亚低温的脑保护机制。方法用线栓法制作大鼠大脑中动脉闭塞(MCAO)局灶脑缺血再灌注模型,随机分为正常组、假手术组、常温缺血组和亚低温缺血组,后两组又再分别分为缺血2 h再灌注3 h6、h1、2 h2、4 h、72 h、7 d组,亚低温组于缺血后30 min内实施病灶侧脑亚低温并持续4 h。处死前进行神经功能缺陷评分,HE染色观察组织病理变化,免疫组化检测XIAP和Caspase-9的表达。结果神经功能缺陷评分,亚低温组大鼠各时间点均明显低于常温组(P<0.05)。XIAP表达在常温缺血2 h再灌注3 h表达开始增加,随着时间延长而表达逐渐增强,至再灌注24 h达高峰,与常温组比,亚低温组在3 h、6 h表达差异不明显,其它时间点增加明显(P<0.05)。Caspase-9表达也是在常温缺血2 h再灌注3 h表达开始增加,随着时间延长而表达逐渐增强,至再灌注24 h达高峰,亚低温组则在72 h达到高峰,与常温组比,亚低温组在3 h表达差异不明显,6 h1、2 h2、4 h明显减少(P<0.05),72 h7、d明显增加(P<0.05)。结论提示亚低温能促进XIAP表达,降低Caspase-9表达,从而减少神经元凋亡,其机制可能与促进蛋白合成有关。

Objective To observe the effect of local mild hypothennia on expression of X-linked inhibitor of apoptosis protein （XIAP） and Caspase-9 after rat focal cerebral ischemia reperfusion and to study the mecha- nism of neuroprotection by mild hypothennia. Methods The middle cerebral artery occlusision （MCAO）and reperfusion rat model were prepared by modified thread embolism. The rats were randomly divided into normal, sham-operated, normothennia and mild hypothennia group. The latter 2 groups respectively were further divided into 6 subgroups according to reperfusion interval such as 3,6, 12,24,72 h and 7 days. Mild hypothennia at fo- cal side were performed in 30 min after ischemia for 4 h. Neural functional defect evaluation wag conducted before deatho Pathological changes were observed with hematoxylin and eosin dye. The expressions of XIAP and Caspase-9 were assessed by immunohistochemical method. Results Assessment of neural functional defect in the mild hypothennia group was significantly lower than that in the normothermia group （ P 〈 0.05）. The expression of XIAP began to increase after reperfusion for 3 h, and peaked at 24 h of reperfusion. Compared with normothennia group,the expression of XIAP markedly increased at 12,24,72 h in mild hypothennia group （P 〈 0.05）. The expression of Caspase-9 was the same tendency expression of XIAP in, normothennia group, but the peak delayed at 72 h in hypothermia group. Compared with normothermia group, The expression of Caspase- 9 markedly decreased at 6,12,24 h, and increased at 72 h and 7 days in hypothermia ischemia group （ P 〈 0.05）. Conclusion Mild hypothermia might increase expression of XIAP by interfere with protein synthesis and decrease expression of Caspase-9, then attenuate neuronal apoptosis.