Effects of Ac-SDKP on bleomycin induced pulmonary fibrosis mice

Abstract

Objective To investigate the effect of Ac-SDKP on reducing lung epithelial mesenchymal transition by inhibiting the endoplasmic reticulum stress in pulmonary fibrosis mice. Methods 24 male C57BL/6 mice of nine weeks old were randomly divided into the following groups: ①control group (group N, n=8). ②fibrosis model group (group M, n=8). Mice were subjected to bleomycin instillation intratracheally in a dose of 5 mg/kg.③fibrosis model group+ Ac-SDKP group (group P, n=8). Same as the group M but Ac-SDKP was administered (800 μg·kg-1·d-1) via a mini-osmotic pump implanted into the abdominal cavity after bleomycin until 21 days.After the formation of the pulmonary fibrosis model, lung tissues were collected for HE staining, masson staining and measuring the content of hydroxyproline (HYP) to evaluate the histological changes of lungs and observe whether the model of pulmonary fibrosis in mice was successful.The expressions of proteins related to endoplasmic reticulum stress GRP78, CHOP, epithelial cell marker E-cadherin and mesenchymal markers Vementin, α-SMA were assessed by immunohistochemistry and Western blot. Results ①Morphological observation: in group N, surface and cut surface of lung tissues were smooth, there was no nodule formation.In group M, there were many visible scattered gray nodules in surface and cut surface of lung tissues.Group P was the same as group M, but the numbers were lesser.②Histopathological examination: on the 21 day, the histopathological findings of fibrosis were induced in group M, which showed that bleomycin induced pulmonary fibrosis in mice model was successful.Compared with group M, fibrosis changes were lesser in group P. ③The level of HYP in group M was significantly upregulated, the content of HYP in group P was lower than that in group M (P<0.05). ④ Immunohistochemistry: compared with group N, the expressions of α-SMA, Vimentin, CHOP and GRP78 were higher in group M, and the expressions of them in group P were between group N and group M (P<0.05). The expression of E-cadherin was lower in group M, and the expression of it in group P was between group N and group M (P<0.05). ⑤Western blot: protein expressions of GRP78, CHOP, Vementin in group M were significantly higher than those in group N, and E-cadherin in group M was lower than that in group N, which in group P were between group M and group N (P<0.05). Conclusions In the process of pulmonary fibrosis, Ac-SDKP plays an important role in alleviating pulmonary fibrosis by reducing endoplasmic reticulum stress and epithelial-mesenchymal transition. Key words: Ac-SDKP; Pulmonary fibrosis; Endoplasmic reticulum stress; Epithelial-mesenchymal transition