SMAD3 and idiopathic pulmonary fibrosis: In this study, we demonstrated that pirfenidone treatment at concentrations of 50μM (~9.2 μg/ml) reduced the TGF-β1-induced SMAD3 nuclear accumulation in ATII cells from healthy donors and primary lung fibroblasts from IPF patients, as well as, the SBE DNA activation in A549 cells.