Roles of Rho/Rock signaling pathway in silica-induced epithelial-mesenchymal transition in human bronchial epithelial cells.

OBJECTIVE: To investigate the roles of Rho/Rock signaling pathway in silica-induced Epithelial-mesenchymal transition (EMT) in human bronchial epithelial cells (BEC) in vitro. METHODS: Human BEC were incubated with silica with various concentrations for indicated times. Cell viability was assayed by MTT test. Morphologic Changes were observed by microscope. Mesenchymal marker α-smooth muscle actin (α-SMA), vimentin (Vim), and epithelial marker E-cadherin (E-cad) were analyzed by Western Blot. The pull-down assay was used to measure Rho activity. In the prevention experiments, the specific inhibitor for Rho effector ROCK (Y27632) was used to inhibit the activity of Rho. RESULTS: Human BEC stimulated with silica were converted from a "cobblestone" epithelial structure into an elongated fibroblast-like shape structure. Incubation of human BEC with silica induced de novo expression of α-SMA and Vim, and loss of E-cad. Also, silica treatment resulted in Rho activation in human BEC. Y27632 up-regulated the E-cad expression but attenuated α-SMA and Vim expression in silica-stimulated cells. CONCLUSION: The activation of Rho/ROCK signaling pathways is most likely involved in Silica-induced EMT in human bronchial epithelial cells.