HMOX1 and pulmonary fibrosis: Based on its antioxidative property of Nrf2/Bach1 in oxidative stress regulation, PFD was used to intervene mouse lung fibroblasts (MLF) induced by TGF-β1 and mice with pulmonary fibrosis induced by BLM in order to observe the influences of the drug on expressions of Nrf2/Bach1 and the downstream antioxidant factors, Ho-1 and Gpx1.