Box-siRNA预先给药对大鼠脑缺血再灌注损伤的作用

Effect of Bax-siRNA pretreatment on brain against ischemia-reperfusion injury in rats

目的探讨B细胞淋巴瘤相关X蛋白基因-双链RNA(Bax-siRNA)对大鼠脑缺血再灌注损伤的作用。方法SD大鼠66只,体重290～310 g,随机分成3组：假手术组(S组,n=6)、局灶性脑缺血再灌注组(C组,n=30)、局灶性脑缺血再灌注+Bax-siRNA组(B组,n=30)。C组、B组行大脑中动脉阻断,阻断1h再开放,制备大鼠局灶性脑缺血再灌注模型,B组在缺血前即刻、16、24 h水压法尾静脉注射Bax-siRNA 2．5 mg／kg(用PBS稀释至10ml),C组给予等量PBS,S组只作切口,不作缺血再灌注。B组、C组分别于再灌注1、5、11、23、47 h各处死6只大鼠,S组实验后23 h处死大鼠,断头取脑,计算脑梗塞体积比,用RT-PCR法测定脑缺血半影区Bax mRNA表达水平。结果B组、C组再灌注11 h时脑梗塞体积比达到高峰,再灌注23 h时B组、C组脑梗塞体积比均高于S组(P＜0．01)；与C组比较,B组脑梗塞体积比缩小(P＜0．05)。S组和B组Bax mRNA无表达,C组再灌注23 h时Bax mRNA表达强于S组。结论Bax-siRNA预先给药可减轻大鼠脑缺血再灌注损伤。

Objective To investigate the protective effect of Bax-siRNA pretreatment on the brain against ischemia-reporfusion injury.Methods Sixty-six male SD rats weighing 290-310 g were randomly divided into 3 groups： group Ⅰ sham operation （ n = 6） ; group Ⅱ middle cerebral artery occlusion （MCAO） （ n = 30） and group Ⅲ Bax-siRNA ＋ MCAO （ n = 30）. In group Ⅱ and Ⅲ the animals were anesthetized with intraperitoneal 10% chloral hydrate 350 mg·kg^-1 . Right common carotid artery was exposed and a nylon thread （diameter 0.25 mm） with rounded tip was inserted into internal carotid artery and threaded cranially until resistance was felt. Successful MCAO was confirmed by ipsilateral Homer＇s syndrome and contralateral hemiplegia. MCAO was maintained for lh and the nylon thread was withdrawn to allow reperfusion. In group Ⅰ the internal carotid artery was exposed but no MCAOwas performed. In group m Bax-siRNA solution （2.5 mg· kg^-1） was given i.v. at 24 h, 16 h and immediately before MCAO, while in group Ⅱ PBS solution was given instead of Bax-siRNA solution. In group Ⅱ and Ⅲ the animals were killed at 1, 5, 11, 23 and 47 h after reperfusion was started （ n = 6 at each time point） while in group Ⅰ at 23 h after sham operation. Brains were immediately removed and sliced. The infarct size was estimated by using Kontron IBAS 2.5 image auto-analysis system. The Bax mRNA expression was measured by RT-PCR. Results The infarct size was significantly smaller in group m than in group Ⅱ at 1, 5, 11, 23 and 47 h. No expression of Bax mRNA was detected in the brain in group Ⅰ and m .Conclusion Bax-siRNA pretreatment can protect the brain from I/R injury to some extent.