Abstract: Objective To investigate the developing expression of Rho associated kinase-1(Rock-1) and its relation to epithelial-mesenchymal transition in bleomycin-induced pulmonary fibrosis in mice. Methods Sixty mice were randomly divided into three groups, control group(EM>n/EM>=20)(normal saline),experimental group (EM>n/EM>=20)( blemycin-injected 5mg/kg,intratracheal injection) and treated group (EM>n/EM>=20)(dexamethason-injected 5mg/kg every day, intraperitoneal injection). On day 3,7,14 and 28 after treatment, lung tissue was stained with HE method.Lung hydroxyproline (HYP) content was evaluated. Immunohistochemistry was used to detect the expression of alpha-smooth muscle actin (α-SMA) and E-cadherin(E-cad). Western blotting was used to detect the expression of Rock-1. Results In experimental group, dynamic changes from alveolitis to pulmonary fibrosis could be observed in the slices by pathological method. Collagen deposition increased evidently on day 3, and peaked on day 28. Lung hydroxyproline (HYP) content increased gradually. Compared to those in the control group, the protein level of α-SMA increased significantly in the model group and treated group, while the protein level of E-cadherin decreased significantly. The expressions of Rock-1 protein in lung tissues in experimental group were higher than those in the control group(EM>P/EM>< 0.05),which increased from the third day, and peaked on the 14th day, then decreased on the 28th day. While the protein level of Rock-1 in treated group decreased significantly. Conclusion The expression of Rock-1 is positively correlated with not only the degree of pulmonary fibrosis but also the level of α-SMA and E-Cad, which probably suggests that Rock-1 is a promoter to pulmonary fibrosis via the induction of epithelial-mesenchymal

Key words: Rho associated kinase, Pulmonary fibrosis, Bleomycin, Immunohistochemistry, Western blotting, Mouse