Potent protective effect of isoimperatorin against aflatoxin B1-inducible cytotoxicity in H4IIE cells: bifunctional effects on glutathione S-transferase and CYP1A Yuba Raj Pokharel, Eun Hee Han, Ji Young Kim, Soo Jin Oh1, Sang Kyum Kim1, Eun-Rhan Woo, Hye Gwang Jeong* and Keon Wook Kang* College of Pharmacy, Chosun University Seosuk-dong, Dong-gu, Gwangju 501-759, South Korea 1 College of Pharmacy and Research Center for Transgenic Cloned Pigs, Chungnam National University Daejeon, 305-764, South Korea *To whom correspondence should be addressed Email: kwkang@chosun.ac.kr or hgjeong@chosun.ac.kr 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 µM) 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; GST type-specific) assays revealed that isoimperatorin (0.3–3 µM) increased GST activity in a concentration-dependent manner. Western blot analyses using subtype-specific antibodies confirmed that GST protein, but not GSTµ or GST, was induced in cells treated with isoimperatorin. Reporter gene analysis using an antioxidant response element (ARE) containing construct and subcellular fractionation assays revealed that GST induction by isoimperatorin is associated with Nrf2/ARE activation. Moreover, ethoxyresorufin-O-deethylase assays showed that isoimperatorin (2 µM) 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 GST and the direct inhibition of CYP1A, and suggest that isoimperatorin should be considered a potential chemopreventive. Carcinogenesis 2006 27(12):2483-2490; doi:10.1093/carcin/bgl118 Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.