title: Potent protective effect of isoimperatorin against aflatoxin B1-inducible cytotoxicity in H4IIE cells: bifunctional effects on glutathione S-transferase and CYP1A.
abstract: Typically chemopreventive agents either induce phase II detoxifying enzymes or inhibit the cytochrome P450 enzymes (CYPs) that are required for the metabolism of carcinogens. In this study, we isolated a coumarin compound, isoimperatorin from Poncirus trifoliata Raf., and studied its protective effects against aflatoxin B1 (AFB1)-induced cytotoxicity in H4IIE cells. Isoimperatorin (>0.3 microM) significantly inhibited the cytotoxic effect of AFB1. CDNB [1-chloro-2,4-dinitrobenzene; glutathine S-transferase (GST) subtype-non-specific] and NBD (7-chloro-4-nitrobenzo-2-oxa-1,3-diazole; GSTalpha type-specific) assays revealed that isoimperatorin (0.3-3 microM) increased GST activity in a concentration-dependent manner. Western blot analyses using subtype-specific antibodies confirmed that GSTalpha protein, but not GSTmu or GSTpi, was induced in cells treated with isoimperatorin. Reporter gene analysis using an antioxidant response element (ARE) containing construct and subcellular fractionation assays revealed that GSTalpha induction by isoimperatorin is associated with Nrf2/ARE activation. Moreover, ethoxyresorufin-O-deethylase assays showed that isoimperatorin (2 microM) completely inhibited 3-methylchoranthrene-inducible CYP1A activity. These results indicate that isoimperatorin from Poncirus trifoliata Raf. possesses a potent hepatoprotective effect against AFB1, presumably through the induction of GSTalpha and the direct inhibition of CYP1A, and suggest that isoimperatorin should be considered a potential chemopreventive.
authors.affiliation: College of Pharmacy, Chosun University Seosuk-dong, Dong-gu, Gwangju 501-759, South Korea.
authors.forename: Yuba Raj
authors.initials: YR
authors.lastname: Pokharel
authors.forename: Eun Hee
authors.initials: EH
authors.lastname: Han
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Soo Jin
authors.initials: SJ
authors.lastname: Oh
authors.forename: Sang Kyum
authors.initials: SK
authors.lastname: Kim
authors.forename: Eun-Rhan
authors.initials: ER
authors.lastname: Woo
authors.forename: Hye Gwang
authors.initials: HG
authors.lastname: Jeong
authors.forename: Keon Wook
authors.initials: KW
authors.lastname: Kang
mesh_terms: D016604:Aflatoxin B1 / Q000633:toxicity*; D000818:Animals; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects*; D019363:Cytochrome P-450 CYP1A1 / Q000187:drug effects / Q000378:metabolism*; D004365:Drugs, Chinese Herbal; D011564:Furocoumarins / Q000494:pharmacology*; D005982:Glutathione Transferase / Q000187:drug effects / Q000378:metabolism*; D008113:Liver Neoplasms; D051381:Rats
chemical_list: D004365:Drugs, Chinese Herbal; D011564:Furocoumarins; C055542:isoimperatorin; D016604:Aflatoxin B1; D019363:Cytochrome P-450 CYP1A1; D005982:Glutathione Transferase