缺血预处理对脑缺血再灌注损伤沙土鼠海马细胞外信号调节激酶和c-jun氨基末端激酶表达的影响

Effects of ischemic preconditioning on the expression of extracellular signal-regulated protein kinase and c-jun N-terminal kinase in hippocampus in a gerbil model of cerebral ischemia-reperfusion injury

目的 探讨缺血预处理(IP)对脑缺血再灌注损伤沙土鼠海马细胞外信号调节激酶(ERK)和c-jun氨基末端激酶(JNK)表达的影响。方法 蒙古沙土鼠,雌雄不拘,随机分为假手术组、预处理对照组(IC组)、预处理缺血组(IP组)及脑缺血再灌注组(IR组),各组根据再灌注15 min、2 h、4h、6 h、1 d、3 d、5 d及7 d又分8个亚组,每亚组6只动物。建立沙土鼠前脑缺血再灌注损伤模型。在预定时间点行开阔法行为学检查、组织形态学检查、TUNEL法海马CA1及CA3区凋亡细胞检测、免疫组织化学SP法测定p-ERK、p-JNK在海马区的变化。结果 与IR组比较,IP组沙土鼠探索活动减弱,海马CA1、CA3区凋亡锥体细胞数量减少,存活神经元数量增加(P<0.01)。各组CA1区p-ERK无表达,IR组海马CA1区p-JNK的表达增强,IP组CA1区p-JNK的表达减弱(P<0.01),CA3区p-ERK的表达增强(P<0.05或0.01)。结论 通过抑制CA1区p-JNK表达和加强CA3区p-ERK表达,IP保护脑缺血再灌注损伤的脑神经元。

Objective To investigate the effects of ischemic preconditioning (IP) on the expression of extracellular signal-regulated protein kinase (ERK) and c-jun N-terminal kinase (JNK) in hippocampus in a gerbil model of ischemia-reperfusion (I/R) injury and the role of ERK and JNK in the mechanism of ischemic cerebral preconditioning. Methods Gerbils of both sexes weighing 50-70kg were randomly divided into 4 groups : ( Ⅰ ) sham operation group; ( Ⅱ ) IP group; (Ⅲ) I/R group and ( Ⅳ ) IP + I/R group. Cerebral ischemia was produced by occlusion of bilateral common carotid arteries and confirmed by isoelectricity on EEG. In sham operation group bilateral common carotid arteries were exposed but not occluded. In IP and I/R groups the animals were subjected to 3 min (IP group) or 5 min (I/R group) cerebral ischemia respectively. In IP + I/R group the animals first underwent 3 min cerebral ischemia followed by 24h reperfusion and then were again subjected to 5 min cerebral ischemia. Open field test was performed to evaluate the behavioral deficit 1,3,5 and 7 days after ischemia. The animals were sacrificed at 15 min, 2, 4, 6h and 1, 3, 5, 7 days after ischemia. The brains were immediately removed for detection of apoptosis (TUNEL) and expression of p-ERK and JNK (immuno-histochemistry) in hippocampal CA1 and CA3 regions and microscopic examination. Results Compared with I/R group the behavioral deficit was significantly decreased and the number of living pyramidal neurons was significantly increased and apoptotic neurons significantly decreased in IP + I/R group. No p-ERK expression was detected in CA1 region in all of the 4 groups but in CA3 region the p-ERK expression was significantly higher in group IP + I/R than in group I/R. The p-JNK expression increased gradually during reperfusion in both CA1 and CA3 regions and was still detectable 7 days after ischemia and was significantly lower in CA1 region in group IP + I/R than in group I/R.Conclusion IP protects hippocampal neurons from I/R injury by inhibiting the expression of p-JNK in CA1 region and enhancing the activity of p-ERK in CA3 region