SMAD2 and pulmonary fibrosis: Carotene and TRF were found to inhibit the expressions of TGF-β1, α-SMA, Smad2, and Smad3 in the lung tissues of the BLM-induced rats, but increased the expression of Smad7 protein, indicating that the wonderful anti-pulmonary fibrosis mechanisms of carotene and TRF may be related to the TGF-β/Smad signal pathway.