两次线栓法构建脑缺血耐受模型大鼠血脑屏障通透性改变与基质金属蛋白酶9的表达☆

背景：诸多研究证实，短暂性脑缺血预处理可诱导脑缺血耐受。然而，脑缺血耐受的内源性保护机制尚未明确。 目的：观察脑缺血预处理诱导脑缺血耐受大鼠再灌注不同时间窗血脑屏障通透性改变及基质金属蛋白酶9表达的变化。 方法：将Wistar大鼠随机分为3组，缺血预处理组采用线栓法阻塞大脑中动脉10 min建立局灶性缺血预处理模型，分别在缺血预处理后1，3，7，14，21 d进行再次缺血2 h；模型组不进行缺血预处理，假手术组不阻塞血管。于再灌注22 h进行神经功能检测，采用TTC染色测定脑梗死体积，通过测定渗出血管外的伊文思蓝含量来评价血脑屏障通透性的变化，免疫组织化学和原位杂交法检测基质金属蛋白酶9蛋白及mRNA的表达。 结果与结论：与模型组比较，缺血预处理组1，3，7 d亚组的神经功能评分、脑梗死体积、血脑屏障通透性、脑含水量以及基质金属蛋白酶9蛋白和mRNA表达均明显减小/降低(P < 0.05或P < 0.01)，其中以3 d亚组降低最为明显。提示缺血预处理诱导了脑缺血耐受，预缺血诱导的血脑屏障通透性改变以及基质金属蛋白酶9表达减低在脑缺血耐受中发挥重要作用。

Change of blood-brain barrier permeability and matrix metalloproteinase-9 expression in a rat model of cerebral ischemic tolerance constructed by twice suture method

BACKGROUND: Numerous studies have shown that, transient ischemic preconditioning (IP) induces cerebral ischemic tolerance. However, the underlying mechanisms of endogenous protection following IP remain unclear. OBJECTIVE: To investigate the changes of blood-brain barrier permeability and matrix metalloproteinase-9 expression in a rat model of IP-induced cerebral ischemic tolerance at varying time points following focal ischemia/reperfusion. METHODS: Wistar rats were randomly assigned to three groups: sham-surgery (n = 14), model (n = 70), and IP (n = 70). For IP group, the rats were given middle cerebral artery occlusion for 10 minutes to establish focal IP models. At 1, 3, 7, 14, and 21 days after IP, rat models were again subjected to ischemia for 2 hours. IP was not given to the model group. Sham-surgery group did not received middle cerebral artery occlusion. Neurological functions were determined at 22 hours following reperfusion. Cerebral infarct volume was measured with TTC staining. Change of blood-brain barrier permeability was evaluated by measuring the content of Evans blue. Matrix metalloproteinase-9 protein and mRNA expressions were determined by immunohistochemical staining and in situ hybridization, respectively. RESULTS AND CONCLUSION: Compared with the model group, the neurological deficit scores, infarct volume, blood-brain barrier permeability, ischemic brain edema, matrix metalloproteinase-9 protein and mRNA expression were significantly decreased or attenuated at 1, 3, 7 days of IP group (P < 0.05 or P < 0.01), these changes were apparent at 3 days. IP induced cerebral ischemic tolerance, the altered blood-brain barrier permeability and the decreased matrix metalloproteinase-9 expression induced by IP might contribute to brain ischemic tolerance.