Abstract: Objective To study the relationship between cytochrome oxidase P450(CYP450) subtype CYP2E1 and the hepatotoxicity of Polygoni Multiflori Radix(PMR), and screen the toxic components. Methods MTT assay was used to detect the toxic effects of aqueous extract of PMRE on L02 cells treated with CYP2E1 specific inhibitor sodium diethyldithiocarbamate (DDTC), and the toxic effects of PMR and 6 major ingredients 2,3,5,4'-tetrahydroxystilbene-2-O-β-D- glucoside (TSG), emodin-8-O-β-D-glucoside (EG), emodin (EM), gallic acid (GA), physcione (PH) and rhein (RH) on stably transfected HepaRG-shCYP2E1 cells.Then, the effects of PMR combined with CYP2E1 specific inhibitor 4-methylpyrazole (4-MP) on hepatotoxicity were studied in rats. Results CYP2E1 activity was decreased significantly when treated with DDTC, so was cell viability after being treated with PMR combined with DDTC compared with PMR alone(P<0.01). A stably transfected cell line, HepaRG-shCYP2E1,was successfully constructed, and the mRNA expression of CYP2E1 in HepaRG-shCYP2E1 cells decreased by more than 70%. Compared with the control group, the cytotoxic effect of PMR, EM, PH and RH on HepaRG-shCYP2E1 was significantly increased (P<0.01), while TSG and EG showed a decreasing toxicity at certain concentrations(P<0.01). The rat experiment showed that the levels of ALT and AST in PMR combined with CYP2E1 specific inhibitor 4-MP group were significantly increased compared with the control group and the 4-MP group, and the levels of AST in PMR combined with 4-MP group were significantly increased compared with PMR group, indicating that the hepatotoxicity of PMR increased after the inhibition of CYP2E1 in rats. Conclusion The decrease of CYP2E1 activity or expression in rats could increase the hepatotoxicity of PMR. The main cytotoxic components are free anthraquinones including EM, PH and RH.

Key words: CYP2E1, Polygoni Multiflori Radix, hepatotoxicity, free anthraquinones, CYP2E1 specific inhibitor, RNAi, rat