脑缺血预处理后Caspase-8蛋白的表达与神经元的保护作用

Caspase-8 protein expression and protective effects on neurons following ischemic preconditioning

目的:探讨脑缺血预处理后凋亡相关基因Caspase-8蛋白表达与神经元保护作用的关系。方法:雄性Wistar大鼠70只,随机分为对照组(10只)、预处理组(10只)、缺血预处理组(25只)和缺血组(25只)。四血管阻断法复制全脑缺血模型,尼氏和TUNEL染色法观察脑皮质及海马CA1区神经元数和凋亡细胞数,免疫组化方法检测Caspase-8蛋白在缺血预处理后表达变化情况。结果:①缺血7d时,缺血预处理组皮质及海马CA1区神经元数无显著变化犤(268±8.5)个/视野犦,缺血组神经元数则显著减少犤(135.0±5.6)个/视野犦。②缺血预处理组Caspase-8蛋白缺血12h表达升高犤(125.6±9.0)个/视野犦,24h达高峰犤(167.0±8.1)个/视野犦;缺血组caspase-8蛋白缺血6h表达升高犤(154.2±18.4)个/视野犦,12h达高峰犤(222.8±17.1)个/视野犦;各对应时点缺血组Caspase-8蛋白阳性表达细胞较缺血预处理组明显增多。③缺血预处理组和缺血组均在缺血12h皮质及海马CA1区凋亡细胞数开始增多犤(15.5±2.1),(39.8±3.9)个/视野犦,缺血48h凋亡细胞数达高峰犤(68.3±13.6),(328.4±24.0)个/视野犦,但缺血组凋亡细胞数较缺血预处理组显著增多。结论:全脑缺血可能通过诱导Caspase-8蛋白的表达增多,启动细胞凋亡,导致缺血后神经元凋亡的发生。

AIM: To study the relationship between the Caspase-8 protein expressions related with apoptosis and the protective roles in neurons after ischemic-preconditioning. METHODS:Seventy male Wistar rats were randomly divided into control group(n=10),pretreatment group(n=10), ischemic pretreatment group(n=25) and ischemic group(n=25).Four-vessel occlusion method was used to replicate animal models of global cerebral ischemia.Nissle staining and Terminal deoxynucleotidyl transferase(TDT)-mediated dUTP nick end-labeling(TNNEL) were used to observe the amounts of neurons and apoptotic cells in cerebral cortex and hippocampal CA1 region. Immunohistochemistry was used to detect the variation of Caspase-8 protein expressions after global cerebral ischemia. RESULTS:Seven days after global cerebral ischemia,the amount of neurons in the cortex and hippocampal CA1 region of ischemic pretreatment group[(268±8.5) per visual field] had insignificant changes,but that of the ischemic group[(135.0±5.6) per visual field] decreased significantly.The expression of Caspase-8 protein in the ischemic pretreatment began to increase at 12 hours after global cerebral ischemia[(125.6±9.0) per visual field],and reached the peak value after 12 hours[(167.0±8.1) per visual field];In the ischemic group, the amount of Caspase-8 protein-positive cells began to increase at 6 hours[(154.2±18.4) per visual field],and reached the peak at 12 hours[(222.8±17.1) per visual field],which increased significantly at different corresponding time point in comparison with that in the ischemic pretreatment group. The amounts of apoptotic cells in the cortex and hippocampal CA1 region began to increase in the ischemic pretreatment and ischemic group 12 hours after ischemia[(15.5±2.1) per visual field and(39.8±3.9) per visual field respectively], and reach the peak at 48 hours[(68.3±13.6) per visual field and(328.4±24.0) per visual field respectively],but the quality of apoptotic cells in the ischemic group was much more than that in the ischemic pretreatment group at different corresponding time. CONCLUSION: Global cerebral ischemia may increase the expressions of Caspase-8 proteins to start up cell apoptosis and induce the apoptosis of neurons after ischemia.Ischemic preconditioning can delay and reduce the expression of Caspase-8 proteins, and decrease the occurrence of cell apoptosis,which may be one of the neuroprotective mechanisms.