脑缺血预处理对脑缺血再灌注大鼠血脑屏障通透性和基质金属蛋白酶-9表达的影响

目的 探讨脑缺血预处理(ischemic preconditioning,IP)对脑缺血再灌注大鼠血脑屏障通透性和基质金属蛋白酶-9(matrix metalloproteinase-9,MMP-9)表达的影响.方法 154只Wistar大鼠随机分为假手术组(14只)、非缺血预处理(non-ischemic preconditioning,NIP)组(70只)和IP组(70只),后两组再随机分为5个亚组,每组14只.线栓法建立大脑中动脉闭塞模型,缺血预处理10 min,分别在IP后1、3、7、14和21 d进行再次缺血2 h再灌注22 h.采用2,3,5-氯化三苯基四氮唑(2,3,5-triphenyltetrazolium chloride,TTC)染色测定脑梗死体积,通过测定渗出血管外的伊文思蓝(Evans blue,EB)含量评价血脑屏障通透性,采用于湿重法评价脑水肿程度,免疫组化染色和原位杂交法检测MMP-9蛋白和mRNA表达.结果 与NIP组相应亚组比较,IP组缺血预处理1、3和7 d亚组神经功能缺损评分显著降低,脑梗死体积显著缩小,EB含量和脑水含量显著降低,MMP-9蛋白和mRNA表达均显著下调(P＜0.05或P＜0.01).IP组1、3和7 d亚组梗死体积和MMP-9 mRNA表达较IP组14 d和21 d亚组显著缩小或下调,3 d和7 d亚组EB含量、脑水含量和MMP-9蛋白表达较其他亚组显著降低,其中以3 d亚组降低最显著(P＜0.05).结论 缺血预处理诱导的血脑屏障通透性改变和MMP-9表达下调在脑缺血耐受中发挥着重要作用.

Effects of ischemic preconditioning on blood-brain barrier permeability and matrix metalloproteinase-9 expression after cerebral ischemia-reperfusion in rats

Objective To investigate the effects of ischemic preconditioning (IP) on blood-brain barrier permeability and matrix metalloproteinase-9 expression after cerebral ischemia reperfusion in rats.Methods A total of 154 Wistar rats were randomly divided into sham operation (n = 14),non-ischemic preconditioning (NIP,n = 70),and IP (n = 70) group.The latter two groups were redivided into 5 subgroups (n = 14 in each subgroup).A middle cerebral artery occlusion model was induced by intraluminal suture method.After 10 minutes IP,re-ischemia for 2 hours and reperfusion for 22 hours were performed at day 1,3,7,14,and 21,respectively.The infarct volume was detected using 2,3,5-triphenyltetrazolium chloride (TTC)staining.The BBB permeability were evaluated by measuring the content of the extravascular exudation of Evan's blue (EB).The degree of cerebral edema was evaluated using the wet-dry weight method.MMP-9 protein and mRNA expression were detected by immunohistochemical staining and in situ hybridization.Results Compared to the corresponding subgroups in the NIP group,the neurological deficit scores,infarct volume,EB content,and brain water content were decreased significantly,and MMP-9 protein and mRNA expression were down-regulated significantly in the day 1,3,and 7 subgroups in the IP group (P ＜ 0.05 or P ＜ 0.01 ).The infarct volume and MMP-9 mRNA expression of the day 1,3,7 subgroups in the IP group were more significantly reduced or down-regulated than those of the day 14 and21 subgroups in the IP group.The EB content,brain water content,and MMP-9 protein expression of the day 3 and 7 subgroups were more significantly lower than those in other subgroups.Among them,they were decreased most significantly in the day 3 subgroup (P ＜ 0.05).Conclusions The changes of IP-induced BBB permeability and the down-regulated MMP-9 expression may play important roles in cerebral ischemic tolerance.