to discuss the possible mechanism of Ac-SDKP to delay the development of pulmonary fibrosis in the internal and external pulmonary fibrosis model.

In vivo experiment: 24 healthy male C57BL/6 mice were randomly divided into control group (n=8), pulmonary fibrosis model group (n=8), pulmonary fibrosis+Ac-SDKP treatment group (n=8). A model of pulmonary fibrosis was established by using the endotracheal injection of boliomycin (5 mg/kg). Pulmonary fibrosis after building + Ac-SDKP treatment group mice abdominal cavity into Ac-SDKP trace injection pump (Ac-SDKP 800 μg·kg^-1·d^-1, ice acetic acid 0.1 mol/L, captopril 100 mg·kg^-1·d^-1), continued intervention 21 d. The mice of control group and pulmonary fibrosis model group were executed on the 21st day of the completion of the mold, the mice of pulmonary fibrosis+Ac-SDKP treatment group were executed after intervention 21 d, and the lung tissue was observed to observe its pathological changes. The determination of the content of hydroxyprosine in accordance with the experimental formulae; TUNEL method to measure apoptosis of alveolar epithelial cells; The Western-blot, immunohistochemical method detects the expression levels of GRP78, CHOP protein, and mRNA. In vitro experiments: cultured A549 cells, which collect cells after TGF-β intervention 24 h, and RT-PCR for the expression of Grp78 and CHOP mRNA. For the normal distribution data, the variance analysis was used to compare the differences between groups, and the SNK-q test was used to compare the differences between two groups; for the non normal distribution data, kruskal-Wallis H test was used to compare the differences between groups.

(1) General observation: the control mice had a smooth surface and smooth surface, and no nodules were formed. Pulmonary fibrosis model group lung tissue surface and shard visible in small nodules; Pulmonary fibrosis+Ac-SDKP treatment group of lung tissues also have small nodules on the surface, but they are rare in the pulmonary fibrosis model. (2) HE and Masson dyeing: a significant fibrosis change in the pulmonary fibrosis model group, pulmonary fibrosis, and Ac-SDKP treatment group were reduced in pulmonary fibrosis. (3) Hydroxyproline content: hydroxyproline content differences between the three groups was statistically significant (H=20.490, P<0.01), among them, pulmonary fibrosis, pulmonary fibrosis model group+Ac-SDKP treatment group is significantly higher than control group (q=0.517, 0.167, P<0.05), pulmonary fibrosis+Ac-SDKP treatment group significantly lower than the pulmonary fibrosis model group (q=0.351, P<0.05). (4) The alveolar epithelial cell apoptosis: the rate was statistically significant difference between the 3 groups (F=57.720, P<0.01), among them, the pulmonary fibrosis model group and pulmonary fibrosis model group+Ac-SDKP group is significantly higher than the control group (q=8.471, 3.639, P<0.01), pulmonary fibrosis+Ac-SDKP group was lower than that in group pulmonary fibrosis model (q=4.832, P<0.01). (5) CHOP and Grp78 protein level expression: the pulmonary fibrosis model group and pulmonary fibrosis+Ac-SDKP treatment group significantly increased than the control group (q=22.630, 8.921, and 138.812, 41.233, P<0.05), the pulmonary fibrosis+Ac-SDKP treatment group significantly decreased in the pulmonary fibrosis group (q=13.711, 97.583, P<0.05). (6) CHOP and Grp78 mRNA expression: TGF-β intervention group significantly increased than the control group (q=8.791, 7.782, P<0.05), TGF-β+Ac-SDKP intervention group significantly increased than the Ac-SDKP intervention group (q=4.399, 5.561, P<0.05).

Ac-SDKP may play a role in the anti-pulmonary fibrosis by suppressing the internal network stress to slow the apoptosis of alveolar epithelial cells.