HMOX1 and pulmonary fibrosis: Celastrol also enhanced the antioxidant defense system and provided protection against bleomycin-induced pulmonary fibrosis in rats by inhibiting antioxidant enzymes such as heme oxygenase-1 (HO-1), glutathione S-transferase, and NADPH: quinine oxidoreductase restored via the Nrf2 pathway [114].