神经源性丝氨酸蛋白酶抑制剂对大鼠小胶质细胞丝裂原活化蛋白激酶和核转录因子-κB信号通路的作用

Effects of neuroserpin on the activation of mitogen-activated protein kinase and nuclear factor-κB signaling pathway of microglias in rats

目的观察小胶质细胞(MG)在缺氧、缺糖(OGD)模型或组织型纤溶酶原激活剂(tPA)干预下被激活的主要信号通路,探讨神经源性丝氨酸蛋白酶抑制剂(NSP)抑制MG进而产生神经保护作用的可能机制。方法体外原代培养大鼠皮层MG并鉴定,建立OGD模型。将MG随机分为正常组、tPA组(经终浓度为0.05μg/μL的tPA干预24h)、OGD 3h组(经OGD模型干预3h)、NSP+tPA组(经终浓度为0.025μg/μL的NSP预处理0.5h后,再以终浓度为0.05μg/μL的tPA干预24h)和NSP+OGD 3h组(经终浓度为0.025μg/μL的NSP预处理0.5h后,再经OGD模型干预3h)。采用免疫荧光双标染色法检测各干预组丝裂原活化蛋白激酶(MAPK)通路磷酸化蛋白的表达情况和核转录因子(NF)-κB的核移位情况。采用免疫印迹法检测各组MAPK通路磷酸化蛋白表达量的变化。结果 MG纯度鉴定结果显示纯度>95%,OGD模型建立成功。免疫组织化学法检测结果显示,MAPK途径的磷酸化细胞外信号调节激酶(pERK)1/2、磷酸化p38(pp38)在正常组MG均有少量表达,且在tPA组和OGD 3h组的表达均显著升高;MAPK途径的磷酸化c-Jun氨基末端激酶(pJNK)在正常组MG有表达,但在tPA组和OGD 3h组的表达无明显变化。Western免疫印迹法检测结果显示,干预组(tPA组和OGD 3h组)pERK1/2、pp38和pJNK的表达量均较正常组显著升高(P值均<0.05)。NSP预处理组(NSP+tPA组和NSP+OGD 3h组)pERK1/2、pp38和pJNK的表达量均较干预组显著降低(P值均<0.05)。免疫荧光双标染色法检测结果显示,正常组MG中可见NF-κB(P65)蛋白主要表达于细胞质,细胞胞突显示清晰。tPA组和OGD 3h组MG中NF-κB发生明显的核移位现象,主要表达于细胞核,且细胞缺少胞突。NSP+tPA组和NSP+OGD 3h组MG中NF-κB的核移位现象明显减轻。结论大鼠肉瘤(Ras)/细胞外信号调节激酶(ERK)、c-Jun-氨基末端激酶(JNK)/应激活化蛋白激酶(SAPK)和p38通路对于MG在tPA和OGD干预下的激活均起作用,其中ERK1/2和p38发挥更重要的作用。tPA和OGD干预MG后,NF-κB发生明显的核移位,此通路被激活,经NSP预处理后,各条信号通路均被不同程度抑制。

[Abstract] Objective To study the signal transduction of microglia interfered with oxygen-glucose deprivation （OGD~ and tissue plasminogen activator （tPA）, and to investigate the protective effects of neuroserpin （NSP） by inhibiting the activity of microglia. Methods Cortical rnicroglia was obtained by primary culture and OGD model was established in rats. The cells were randomly divided into five groups： normal group, tPA group （microglias treated with 0.05μg/μL tPA for 24 h）, OGD 3 h group, NSP＋ tPA group （microglias pretreated with 0. 025μg/μL NSP for 0.5 h and then with 0.05μg/μL tPA for 24 h） and NSP ＋ OGD 3 h group. Expression of mitogen-activated protein kinase （MAPK） was identified by immunocytochemistry staining and was determined by Western-blot. The activation of nuclear factor （NF-κB） was determined by immunofluoence double label method. Results The purity of microglia was higher than 95% and OGD model was successfully established. Immunofluoence double label method showed that a small quantity of phospho-extracellular regulated protein kinases （pERK1/2） and phosphor-p38 （pp38） was found in normal microglias and the levels of pERK1/2 and pp38 increased obviously in tPA and OGD 3 h groups. There were high expressions of phosphor-c-Jun NHz-terminal kinase （pJNK） both in normal microglias and the cells stimulated by tPA or OGD 3 h. Western blot showed that the expressions of pERK1/2, pP38 and pJNK in the cells stimulated by tPA or OGD 3 h were higher than those in the normal microglias （all P〈0.05） the expressions of pERK1/2, pP38 and pJNK in NSP pretreatment groups （NSP ＋ tPA group and NSP-t-OGD 3 h group） were significantly lower than those in tPA group and OGD 3 h group （all P〈0.05）. The immunofluoence double label method showed that NF-κB was mainly found in cytoplasm of normal microglias and the cell process was clears NF-κB was found mainly in nucleus in tPA group and OGD 3 h group, with nucleus displacement and decreased cell process after pretreatment with NSP, the nucleus displacement was obviously decreased. Conclusions tPA and OGD can activate ERK1/2 pathway, p38 pathway and JNK pathway of microglias. And ERK1/2 pathway and p38 pathway play more important roles. TPA and OGD can also activate NF-κB. NSP can inhibit these signal transduction by inhibiting tPA.