Objective To investigate cerebral ischemia-induced upregulation of matrix metalloproteinase ( MMP)-9 function in rat hippocampus and its underlying mechanisms. Methods ①Total of 20 SD rats were divided randomly into model group (n = 15) and sham group(n =5) , the model group was established forebrain ischemia model by using four artery occluding method(the reperfusion was 6,12 and 24hs) , the sham group was treated as above, only the arteries were not occluded;the two groups were both killed and the brain tissues were obtained, immunoblotting assay was employed to observe the activation of extracellular signal-regulated kinase ( ERK ) , phosphorylated F.RK ( p- ERK) and prozymogen (pro)-MMP-9, the most significant reperfusion time pot of expression was chosen and used in the follow experiment. ② Total of 30 SD rats were divided randomly into ketamine group(n=5) , U0126 group(n=5), celiac solvent group(n =5) , ventricle solvent group(n =5) and sham group(n = 10) ,the former four groups were all made forebrain ischemia model as above, and 30 mg/kg ketamine and 0.5μg/2μL-U0126, equal normal saline were given respectively 30 mins before the obstruction, the sham group was treated as above, then the 3 indices were detected as above. Results The level of p-ERK and pro-MMP-9 protein exhibited a significant elevation in response to reperfusion in hippocampus after ischemia ( P < 0.05 ) , and reached the peak at 24 h; the level of p- ERK and pro-MMP-9 protein in ketamine group were both significantly higher than those in celiac solvent group( P < 0.05 ) , the level of pro-MMP-9 protein in U0126 group was significantly higher than that in ventricle solvent group(P<0.05). Conclusion Cerebral ischemia-reperfusion can induce MMP-9 gene expression and protein increase dependent on ERK pathway, the enhancement of calcium signal and its ERK cascade play im portant role in the mechanism; this can provide new ways for the treatment of the cerabral ischemia injury.%目的 研究脑缺血诱导的海马神经基质金属蛋白酶(MMP)-9表达变化及其相关分子调节机制.方法 ①取雄性SD大鼠20只随机分为模型组15只和假手术组5只,模型组采用四动脉阻断法建立前脑缺血模型(再灌注时间分别为6、12、24h),假手术组手术步骤同上、但不阻断动脉；两组均断头取脑,采用电泳和免疫印迹法检测胞外信号调节激酶(ERK)、磷酸化(p)-ERK、前酶原(pro)-MMP-9蛋白表达,选择表达最显著的再灌注时间点用于下述实验的模型制备.②取30只SD大鼠随机分为氯胺酮组、U0126组、腹腔溶剂组、脑室溶剂组各5只和假手术组10只,前四组均采用上述方法建立前脑缺血模型,在动脉阻断前30 min氯胺酮组腹腔注射氯胺酮50 mg/kg,U0126组用微量注射器通过单侧脑室注射U0126(0.5 μg/2 μL),腹腔溶剂维和脑室溶剂组分别经腹腔和脑室注射等量生理盐水,假手术组处理同上,各组处理完毕后均同上检测三种蛋白表达.结果 前脑缺血再灌注后p-ERK和pro-MMP-9蛋白水平持续上调(P＜0.05),且24 h最高；氯胺酮组p-ERK和pro-MMP-9蛋白水平显著高于腹腔溶剂组(P＜0.05),U0126组pro-MMP-9蛋白表达显著高于脑室溶剂组(P＜0.05).结论 脑缺血可诱导海马脑区pro-MMP-9基因表达和ERK活性上调,胞内N-甲基-D-门冬氨酸(NMDA)受体介导的钙信号增强及其激活的ERK级联是其重要机制；此为缺血后脑损伤的临床治疗提供了新的思路.
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