OBJECTIVE: To investigate the effect of Danggui Buxue Tang(DBT), a decoction from Traditional Chinese Medicine, on bleomycin-induced pulmonary fibrosis in rats, and to propose the possible underlying mechanism.METHODS: Forty male Sprague-Dawley rats were randomly divided into sham group, model group,prednisone group and DBT group. Pulmonary fibrosis rat model was established by intratracheal injection with bleomycin. Body weight and lung index were monitored. Histopathologic examination and collagen deposition were determined using Hematoxylin and eosin(HE) and Masson's trichrome staining. Immunohistochemistry staining was applied to observe the expression of alpha-smooth muscle actin(α-SMA). m RNA expression of α-SMA,collagen Ⅰ and collagen Ⅲ were measured by realtime fluorescence quantitative PCR(RT-q PCR). Inflammatory cytokines, including tumor necrosis factor alpha(TNF-α), interleukin-6(IL-6) and IL-1β in serum were detected by Enzyme-linked immunosorbent assay. Alkali hydrolysis method was conducted to investigate the content of hydroxyproline(HYP). Transforming growth factor-β1(TGF-β1),Smad3 and plasminogen activator inhibitor-1(PAI-1) protein level were examined by Western blot assay.RESULTS: DBT significantly reduced the severity of bleomycin-induced pulmonary fibrosis and inflammation as indicated by minimizing the lost of weight, and by lowering the levels of lung index, inflammation score, Ashcroft score, collagen volume fraction(%), HYP, α-SMA, collagen Ⅰ, collagen Ⅲ,TNF-α, IL-6, IL-1β, TGF-β1, Smad3 and PAI-1, consistent with the effect of prednisone.CONCLUSION: Our findings suggest that DBT is able to ameliorate the pulmonary fibrosis, the possible mechanism may involve inhibition of pulmonary inflammation and collagen deposition, possibly via suppressing TGF-β1/Smad3/PAI-1 signaling pathway.