title: Inhibition of aflatoxin B1 genotoxicity in human liver-derived HepG2 cells by kolaviron biflavonoids and molecular mechanisms of action.
abstract: Kolaviron biflavonoids have demonstrated antihepatotoxic activity in animal studies. The present study investigated the possible chemopreventive potential of kolaviron in inhibiting aflatoxin B1 (AFB1) genotoxicity in HepG2 cells. Kolaviron inhibition of AFB1-induced cytotoxicity by clonogenic assay and genotoxicity by [3H]thymidine incorporation in unscheduled DNA synthesis were evaluated, including antioxidant potential of kolaviron determined by its reduction in the intracellular reactive oxygen species level induced by hydrogen peroxide. Induction of AFB1-detoxicating enzymes such as cytochrome P450 3A4 (3A4) and glutathione S-transferases (GSTs) A1-1/ A2-2 (alpha) and M1B (mu) was determined by reverse transcription polymerase chain reaction (RT-PCR) and northern blotting for the messages and western immunoblot analysis for protein. Kolaviron significantly (P < 0.01) and dose-dependently inhibited the cytotoxicity (by 71.6%) and genotoxicity (47.1%) of AFB1 in HepG2 cells. The antioxidant potential of kolaviron compared favourably with values for the standard antioxidant trolox C (53.8% at only 4.5 x 10(-2)-fold kolaviron concentration) but was below that of butylated hydroxyanisole (58.1% at a ninefold kolaviron concentration). It induced about threefold increases in the messages for 3A4 and GSTs alpha and mu, including a twofold increase in GSTalpha protein. Kolaviron may have chemopreventive potential in inhibition of human AFB1 genotoxicity and possibly hepatocarcinogenesis.
authors.affiliation: Department of Biochemistry, College of Medicine, University of Iowa, Iowa City 52242, USA. joseph-nwankwo@uiowa.edu
authors.forename: J O
authors.initials: JO
authors.lastname: Nwankwo
authors.forename: J G
authors.initials: JG
authors.lastname: Tahnteng
authors.forename: G O
authors.initials: GO
authors.lastname: Emerole
mesh_terms: D016604:Aflatoxin B1 / Q000633:toxicity*; D015152:Blotting, Northern; D015153:Blotting, Western; D002083:Butylated Hydroxyanisole / Q000494:pharmacology; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology*; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000166:cytology / Q000187:drug effects; D009153:Mutagens; D010936:Plant Extracts / Q000494:pharmacology; D010946:Plants, Medicinal; D016133:Polymerase Chain Reaction; D013936:Thymidine / Q000378:metabolism
chemical_list: D005419:Flavonoids; D009153:Mutagens; D010936:Plant Extracts; D002083:Butylated Hydroxyanisole; D003577:Cytochrome P-450 Enzyme System; D016604:Aflatoxin B1; D005982:Glutathione Transferase; C045492:kolaviron; D013936:Thymidine