神经生长因子对鼠脑缺血-再灌注损伤的影响

Effects of NGF against cerebral ischemia-reperfusion injury in gerbils

目的探讨神经生长因子(NGF)预先给药对沙土鼠脑缺血-再灌注后神经细胞凋亡的影响。方法沙土鼠54只,随机分为五组:正常对照组(C组,n=6)、缺血-再灌注组(I/R组,n=12)、NGF预先给药低剂量组(L组,n=12)、中剂量组(M组,n=12)、高剂量组(H组,n=12)。除C组外,其余各组在行脑缺血20min后据再灌注至取标本时间的不同随机分为24h和72h两个亚组。采用夹闭沙土鼠双侧颈总动脉后去除动脉夹使血流再通的方法制作脑缺血-再灌注损伤模型,TUNEL法观察缺血-再灌注后大脑皮层凋亡神经细胞,免疫组化法检测Bcl-2、Bax蛋白阳性表达。结果I/R组及NGF预先给药各组的72h亚组沙土鼠大脑皮层神经细胞凋亡指数及Bax蛋白阳性表达均明显高于24h亚组、而Bcl-2蛋白的阳性表达均明显低于24h亚组(P<0.05或P<0.01);I/R组脑皮层细胞凋亡指数及Bax蛋白的阳性细胞指数均明显高于NGF预先给药各组(P<0.05);在NGF预先给药各组中以H组的大脑皮层神经细胞凋亡指数及Bax蛋白阳性表达最低、Bcl-2蛋白阳性表达最高。结论细胞凋亡参与了脑缺血-再灌注损伤的发生发展。不同剂量的NGF预先给药均能明显减轻脑缺血-再灌注后神经细胞凋亡,且随剂量增加细胞凋亡进一步减少;其机制可能与NGF预先给药诱导Bcl-2的表达,同时抑制Bax的表达有关。

Objective To investigate the effect of pretreatment with nerve growth factor（NGF） on apoptosis of neurons following global cerebral ischemia reperfusion （I/R） injury in gerbils. Methods Fifty-four gerbils were randomly divided into five groups of sham operation（C, n=6）, I/R （n=12）,low dose of NGF（L,n=12）,middle dose of NGF（M,n=12） and high dose of NGF（H,n=12）. Groups I/R, L and H were divided into 2 subgroups according to the time from reperfusion to taking specimens, 24-h and 72-h. Global cerebral I/R injury model was induced by occlusion of bilateral carotid arteries. NGF was injected into the lateral ventricle. Neural apoptosis was identified by TUNEL method and the expressions of Bcl-2 and Bax in the cerebral cortex were detected wib immunohischemistry assay. Results The number of apoptotic neurons and the positive expression of Bax protein in the cerebral cortex were increased and the positive expression of Bcl-2 protein was decreased as the duration of reperfusion prolonged in groups I/R, L, M and H, which were significantly more in groups L, M and H than those in group I/R and more in 72-h subgroup than those in 24-h subgroup （P〈0.05 or P〈0.01）. Conclusion The neuronal cell apoptosis is involved in the progress of cerebral I/R injury. The pretreatment with different doses of NGF can significantly decrease the number of apoptotic neuronal cells in the cerebral cortex in a dose-dependent manner, which may be related to inducing Bcl-2 expression and inhibiting Bax expression.