EGFR信号通路在SiO2诱导肺上皮细胞间质转化中的作用机制

目的：在二氧化硅（SiO2）刺激下可引起肺部一系列的炎症反应及其伴随相关的成纤维细胞增殖，然而EGFR信号通路可维持细胞增殖、分化和凋亡的平衡，因此，我们可以设想EGFR信号通路是否在肺纤维化的发生发展中起到重要的作用。本实验探讨SiO2是否能诱导人肺上皮细胞（A549）发生上皮间质转化，并且研究EGFR信号通路在矽肺纤维化中的作用机制。方法：以A549为研究对象，用0（对照组）、50、100、200μg／mlSiO2孵育A549，作用48h后于倒置显微镜观察细胞形态学改变，并收集不同时段细胞，采用实时荧光定量PCR（RT-PCR）检测E-钙黏蛋白（E-cadherin）和α-平滑肌肌动蛋白（α-SMA）mRNA表达变化，细胞免疫荧光方法检测E-cadllerin、α-SMA及信号转导蛋白EGFR表达的变化。结果：倒置显微镜观察A549经SiO2处理后细胞形态由鹅卵石状转变为纺锤型或梭型，形态似成纤维细胞，随着SiO2浓度的升高，E-cadmRNA和蛋白表达逐渐下调，在200μg／ml组表达最低，α-SMAmRNA和蛋白表达逐渐上调，200μg／ml组α-SMA表达最高；EGFR蛋白表达上调；50、100、200μg／ml与对照组的差异具有统计学学意义（P〈0．05）。结论：SiO2可诱导肺上皮细胞向间质细胞转化，其机制可能与EGFR信号通路有关。

Roles of EGFR Signaling Pathway in Silica-induced Epithelial-mesenchymal Transition in Human A549 cells

Objective： Silica exposure results in an initially acute lung inflammatory response followed by the proliferation of fibroblasts. The epidermal growth factor receptor （EGF-R） signaling pathway maintains a balance between cell proliferation, differentiation and apoptosis, and thus it is imagined that EGF-R signaling pathways play an important role in the development and progression of Pulmonary fibrosis. To investigate silica-induced Epithelial-mesenehymal transition （EMT） in human A549 cells and the roles of EGFR signaling pathway in silica-induced EMT in Human A549 cells in vitro. Methods： A549 cells were cultured and stimulated with indicated doses of silica （0, 50, 100, 200 ug/ml）. The cells morphology changes were observed under phase-constrast microscope. In addition, The mRNA level of E-cadherin and a-SMA were also evaluated by Real-time PCR（qRT-PCR）. The protein level of E-cadherin, a-SMA and EGFR were assessed by immunnoflurescence staining. Results： The data showed that silica-induced A549 cells with epithelial cell characteristics to undergo EMT in a dose-dependent manner. After exposure to silica, A549 cells induced EMT characterized by cells morphological changes, such as displayed a spindle-shape, fibroblast-like morphology. Compared with the control, the expression of E-cad mRNA and protein in silica-induced A549 cells was significantly down-regulated; The expression of a-SMA mRNA and protein in silica-induced A549 cells was significantly up-regulated. Compared with the control group, the activation of EGFR was obvious in silica-stimulated A549 cells （P〈0.05）. Conelusiun： Silica might induce EMT in human A549 cells indirectly, and the mechanism is most likely associated with the activation of EGFR signaling pathway.