白介素-1 β通过JNK/p38信号-转导通路调控肾系膜细胞表达α-平滑肌肌动蛋白

为探讨细胞内丝裂素原活化蛋白激酶（MAPK）家族各亚类信号转导通路在炎症性细胞因子白介素－1β（IL－1β）对大鼠肾系膜细胞（rMC)表型标志物α-平滑肌肌动蛋白（α－SMA）表达及其分布中的调控作用,以IL－1β（10ng/ml)刺激体外培养的rMC,用电穿孔基因转染及免疫杂交法观察IL－1β对α－SMA基因启动子活性及蛋白表达的作用,并用共聚焦荧光显微镜及透射电镜观察IL－1β刺激前后细胞内α-SMA及微丝的分布变化。通过应用PD98059和SB203580特异阻断ERK和p38通路、共转染显性失活JNKK基因特异阻断JNK通路,观察阻断对IL－1β刺激所致α-SMA表达或启动子活性的影响。结果显示,IL－1β刺激6h可明显上调α－SMA启动子活性,在1－2d内显著促进其蛋白合成;IL－1β刺激24h后,细胞内α-SMA及微丝在细胞核周的分布增加。阻断ERK通路对IL－1β诱导的α-SMA表达无明显影响;阻断JNK及p38通路均可使IL－1β诱导的α－SMA表达明显受抑;阻断p38通路的作用比阻断JNK通路更强,而且对基础状态的α-SMA表达也有抑制作用。上述结果提示,IL－1β可刺激rMC发生表型转化,其表型标志物α－SMA可通过基因转录增强而增加蛋白表达,在细胞内的分布向核周转位积聚。JNK及p38通路是介导IL－1β刺激rMC α-SMA表达的主要信号转导途径,而ERK通路不影响IL－1β的这一作用。

IL-1beta stimulates alpha-smooth muscle actin expression through JNK/p38 signal pathway in cultured rat mesangial cells

To investigate the role of intracellular mitogen activated protein kinase (MAPKs, ERK, JNK and p38) signal pathways in IL-1beta -stimulated alpha-smooth muscle actin (alpha-SMA) expression in rat mesangial cells (rMC), alpha-SMA-promoter gene was transfected into rMC by electro-perforation method and the promoter activity was assayed after IL-1beta (10 ng/ml) stimulation. Protein expression of alpha-SMA was assayed by Western blot. The results were compared between the groups stimulated by IL-1beta with or without PD98059 and SB203580, which are thought to block ERK and p38 pathway, respectively. Dominant-negative-JNKK plasmid was co-transfected in rMC to block JNK pathway. The spatial distribution of alpha-SMA and microfilament-like structure was observed by a confocal laser scanning microscope or an electric microscope. After 6 or 24 h of incubation with IL-1beta, rMC underwent a phenotypic change, which was represented by up-regulation of alpha-SMA promoter activity and protein expression. An increase in alpha-SMA and microfilament-like structure was found around the cell nucleus. Block of JNK and/or p38 pathway greatly inhibited IL-1beta -induced alpha-SMA expression, and the block of p38 pathway also suppressed the basal level of alpha-SMA expression. In contrast, ERK pathway had no influence on the process. It is, therefore, concluded that IL-1beta -stimulated expression of alpha-SMA is due to its protein synthesis and cytoskeleton re-organization in activated rMC. Intracellular signal regulation of alpha-SMA expression seems to be mediated mainly by JNK/p38 pathways, but ERK appears to have no effect on the process.