Nrf2 and its downstream target NAD(P)H: quinine oxidoreductase 1 (NQO1) and heme oxygenase-1 (HO-1) expression, the nuclear translocation of Nrf2, and the binding ability of Nrf2 and antioxidant response element

Triptolide (TP), a diterpenoid epoxide, is the major active component of the Tripterygium wilfordii Hook f., which has been widely used in Chinese medicine to treat autoimmune diseases, such as rheumatoid arthritis and lupus erythematosus. TP has been reported to have activities against mouse models of cancer, renal fi brosis and polycystic kidney disease. It has exhibited many pharmacological activit ies, including immune modulation, antiinflammatory, proapoptotic and antiproliferative activities. Thus, TP has also risen to wide acceptance in the medical research in the West. Several putative target proteins of TP have been reported, including polycystin-2, ADAM10, DCTPP1, TAB1, and XPB. However, the toxicity of TP limits its therapeutic potential. It has a narrow margin between the therapeutic and toxic doses and could cause severe injury to the circulatory, digestive, reproductive and urogenital systems.