In addition, we found that Nrf2 mediates the inhibitory effect of protodioscin on the TGF-β/Smad pathway (Additional file 2: Fig. S3). Thus, Nrf2 mediates the anti-oxidative stress and anti-pulmonary fibrosis effects of protodioscin. The gene discussed is TGFB1; the disease is pulmonary fibrosis.