Objective To investigate the effect of mTOR signaling pathway on bleomycin-induced pulmonary fibrosis.Methods 30 healthy male C57BL/6 mice aged 6～8 weeks were fed for 1 week and divided into control group(NC group,n=5),bleomycin group(BLM group,n=5),and rapamycin+bleomycin group(Rapa+BLM group,n=5).Mice were euthanized by cervical dislocation at 7 and 28 days,and lung tissues were collected.HE staining was used to observe inflammatory infiltration in lung tissue,and Masson's staining was used to assess the severity of lung fibrosis.Western blot and qPCR were used to detect the expression levels of collagen Ⅰ,collagen Ⅲ and α-SMA to evaluate the degree of lung fibrosis.Western blot was used to detect the expression of mTOR,P70S6K and their phosphorylation levels in each group.Results Compared with the NC group,the BLM group showed thickened alveolar septa,obvious inflammatory changes,and collagen deposition.The protein expression of Collagen Ⅰ,Collagen Ⅲ,and α-SMA were significantly increased(P<0.01),with increased mRNA expression of Collagen Ⅰ,Collagen Ⅲ,and α-SMA(P<0.05),and elevated p-mTOR and p-p70S6K expression(P<0.05).Compared with the BLM group,the Rapa+BLM group showed improved lung tissue structure,reduced inflammation and collagen deposition,a downward trend in Collagen Ⅰ,Collagen Ⅲ,and α-SMA protein expression(P>0.05),a downward trend in Collagen Ⅰ mRNA(P>0.05),and decreased Collagen Ⅲ and α-SMA mRNA expression(P<0.05).Conclusion Abnormal mTOR activation was observed in bleomycin-induced pulmonary fibrosis;inhibiting mTOR signaling pathway activation can effectively alleviate the formation of pulmonary fibrosis.