Attenuation of tert-Butyl Hydroperoxide (t-BHP)-Induced Oxidative Damage in HepG2 Cells by Tangeretin: Relevance of the Nrf2–ARE and MAPK Signaling Pathways

The current study evaluates the protective effects of tangeretin, a representative polymethoxyflavone (PMF) mainly isolated from the peels of citrus fruits, against tert-butyl hydroperoxide (t-BHP)-induced oxidative damage in HepG2 cells and the potential mechanisms of this protection. Tangeretin suppressed t-BHP-induced oxidative damage, as evaluated by cell viability, reactive-oxygen-species (ROS) levels, lactate dehydrogenase (LDH) leakage and glutathione (GSH) levels. Further mechanistic studies showed that tangeretin up-regulated the expression of heme oxygenase 1 (HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1). Moreover, tangeretin induced antioxidant-responsive-element (ARE)-dependent luciferase activation, nuclear factor (erythroid-derived 2)-like 2 (Nrf2) nuclear translocation, and mitogen-activated-protein-kinase (MAPK) phosphorylation. Results in the study indicate that the protective effects of tangeretin may be at least partly due to its capacity to up-regulate the antioxidant enzymes NQO1...