Abstract: Objective To investigate the effect of neutralizing interleukin-17 (IL-17) on the expressions of collagen
and apoptosis-related factors in model mice with idiopathic pulmonary fibrosis induced by bleomycin. Methods Thirtytwo male C57BL/6 mice were randomly divided into normal control group, model group, neutralizing antibody group and
antibody control group. The mouse model of idiopathic pulmonary fibrosis was induced by intratracheal infusion of bleomycin (BLM, 5 U/kg). Mice in the neutralizing antibody group and the antibody control group were injected with IL-17 monoclonal antibody or isotype control antibody through the caudal vein every 4 days from the day 3 after BLM instillation, and the
model group and the normal control group were given the same amount of normal saline. At the day 28, all mice were
euthanized, the lung fibrosis degree was assessed by Masson staining. The mRNA contents of collagen typeⅠand type Ⅲ in lung tissues were determined by real-time fluorescent quantitative PCR, and the expression levels of Cleaved-cysteinasparate protease (Cleaved-caspase)-3 and Cleaved-caspase-9 were detected by Western blot assay. Results Compared with the model group, the degree of pulmonary fibrosis was significantly declined in the neutralizing antibody group (P＜0.01), the mRNA expressions of collagen typeⅠand type Ⅲ were obviously decreased (P＜0.01), and the protein expressions of Cleaved-caspase-3 and Cleaved-caspase-9 were markedly reduced (P＜0.01), but there were no significant differences in these data between model group and the antibody control group. Conclusion Neutralizing endogenous IL-17 may improve pulmonary fibrosis by regulating the expressions of Cleaved-caspase-3 and Cleaved-caspase-9 proteins.

Key words: interleukin-17, apoptosis, idiopathic pulmonary fibrosis, cystein-asparate protease, collagen type Ⅰ,
collagen type Ⅲ, bleomycin