Tetrahydrocurcumin and octahydrocurcumin, the primary and final hydrogenated metabolites of curcumin, possess superior hepatic-protective effect against acetaminophen-induced liver injury: Role of CYP2E1 and Keap1-Nrf2 pathway

Acetaminophen (APAP) overdose-induced hepatotoxicity is tightly associated with oxidative stress. Tetrahydrocurcumin (THC) and octahydrocurcumin (OHC), the primary and final hydrogenated metabolites of curcumin (CUR), possess stronger antioxidant activity in vitro. The present study was performed to investigate the potential and mechanism of OHC and THC against APAP-induced hepatotoxicity in parallel to CUR. Our results showed that OHC and THC dose-dependently enhanced liver function (ALT and AST levels) and alleviated histopathological deterioration. Besides, OHC and THC significantly restored the hepatic antioxidant status by miring level of MDA and ROS, and elevated levels of GSH, SOD, CAT and T-AOC. In addition, OHC and THC markedly suppressed the activity and expressions of CYP2E1, and bound to the active sites of CYP2E1. Moreover, OHC and THC activated the Keap1-Nrf2 pathway and enormously enhanced the translational activation of Nrf2-targeted gene (GCLC, GCLM, NQO1 and HO-1) against oxidative stress, via inhibiting the expression of Keap1 and blocking the interaction between Keap1 and Nrf2. Particularly, OHC and THC exerted superior hepatoprotective and antioxidant activities to CUR. In conclusion, OHC and THC possess favorable hepato-protective effect through restoring antioxidant status, inhibiting CYP2E1 and activating Keap1-Nrf2 pathway, which might represent promising antioxidants for the treatment of APAP-induced hepatotoxicity.