SMAD3 and pulmonary fibrosis: Low-dose PTX (0.6 mg/kg) was found to significantly attenuate the histological and biochemical signs of BLM-induced pulmonary fibrosis, including epithelial degeneration, collagen deposition and several fibrogenic cytokines, such as TGF-β1, α-SMA, Smad3 and p-Smad3, supporting that PTX ameliorated pulmonary fibrosis by suppressing TGF-β1 pathway.