人参皂甙Rb1阻止大鼠局灶性脑缺血细胞凋亡和诱导NAIP表达

人参皂甙Rb1(GRb1)是人参中一个最重要的有效成分(人参属五加科中一属),能减少大鼠暂时性脑缺血梗塞面积和改善神经功能缺失症状,这种神经保护作用的机制不完全清楚。本实验研究GRb1的神经保护作用是否与防止神经元凋亡和调控神经元凋亡抑制蛋白(NAIP)的表达有关。通过阻塞大鼠大脑中动脉建立局灶性脑缺血模型,再灌注开始后立即给予腹腔注射GRb1(40mg/kg)。具有神经功能缺失的大鼠被随机分成2组:缺血组和GRb1组,每个组根据再灌注时间(3h,12h,1d,2d,3d,5d,10d,n=4/每时间点)分为亚组。正常大鼠和假手术组做为对照组。TUNEL标记分析凋亡细胞,用免疫组织化学的方法检测NAIP的表达。结果显示再灌注3h凋亡细胞数量开始升高,24h达高峰,后下降,但再灌注10d的凋亡细胞数量显著高于对照组(P<0.01)。与缺血组相比,GRb1各亚组的凋亡细胞数减少,但再灌注12h至3d,其差异具有统计学意义。在对照组,NAIP弱或阴性的免疫反应广泛出现在脑实质神经元。再灌注3h,NAIP阳性细胞增加,12h时达高峰,后下降。再灌注5d,NAIP阳性细胞数量比对照组少(P<0.05)。NAIP阳性神经元出现缺血性改变如扇形或三角形,纹状体星形胶质细胞强表达NAIP。在GRb1组,NAIP阳性细胞数量从再灌注12h到10d,显著高于缺血组。本实验结果提示大鼠局灶性脑缺血时,GRb1能减少细胞凋亡,其机制可能与增加NAIP的表达有关。

GINSENOSIDE Rb1 PREVENTS APOPTOSIS AND INDUCES NAIP EXPRESSION IN RATS SUBJECTED TO FOCAL CEREBRAL ISCHEMIA

Previous experiments has shown that Ginsenoside Rb1(GRb1),which is one of the most important active ingredients in ginseng(Panax ginseng C.A.Meyer),reduced infarct and neurologic deficit followed by the transient cerebral ischemia in rats.The mechanism of this neuroprotective function is unclear.In this study,we tested whether the neuroprotective effect of GRb1 is achieved through preventing the neuronal apoptosis and modulating expression of neuronal apoptosis inhibitory protein(NAIP).Focal cerebral ischemia was induced by the middle cerebral artery occlusion(MCAO)in Wistar rats.GRb1(40 mg/kg,i.p.)was administered immediately after the onset of reperfusion.The rats with neurological deficits were randomly divided into 2 groups:the ischemia and the GRb1 group.Each group was again divided into subgroups according to the various reperfusion time(3 h,12 h,1,2,3,5,10 days,n=4 per time point).Apoptotic cells were analyzed using TUNEL.Immunohistochemical method was used to assess expression of NAIP.This results showed that the number of apoptotic cells elevated at 3 h of reperfusion,and peaked at 24 h,then declined,but the number of apoptotic cells at 10 d after ischemia was significantly more than those of control groups(P<0.01).Compared with ischemia group,the apoptotic cells decreased at all subgroups of GRb1;however,the significant differences were only found from 12 h to 3 d of reperfusion.In normal and sham groups,NAIP weak immunostaining was diffusely present in the neurons of parenchyma.The number of NAIP-positive cells started to increase in ischemic regions at 3 h after ischemia,peaked at 12 h and declined up to 5 d of reperfusion.At 5 d after ischemia,the number of NAIP-positive cells was less than that of control group(P<0.05).A few astrocytes strongly expressed NAIP in the ischemic area.In the GRb1 group,the number of NAIP-positive cells from 12 h to 10 d after ischemia was evidently higher than in the ischemia group.Thus,these results suggest that GRb1 has potential ability to prevent apoptosis,the mechanism of which is related to induce expression of NAIP.