title: 2- and 4-Aminobiphenyls induce oxidative DNA damage in human hepatoma (Hep G2) cells via different mechanisms.
abstract: 4-Aminobiphenyl (4-ABP) and its analogue, 2-aminobiphenyl (2-ABP), were examined for their ability to induce oxidative DNA damage in Hep G2 cells. Using the alkaline comet assay, we showed that 2-ABP and 4-ABP (25-200 microM) were able to induce the DNA damage in Hep G2 cells. With both compounds, formation of intracellular reactive oxygen species (ROS) was detected using flow cytometry analysis. Post-treatment of 2-ABP and 4-ABP-treated cells by endonuclease III (Endo III) or formamidopyrimidine-DNA glycosylase (Fpg) to determine the formation of oxidized pyrimidines or oxidized purines showed a significant increase of the extent of DNA migration. This indicated that oxidative DNA damage occurs in Hep G2 cells after exposure to 2-ABP and 4-ABP. This assumption was further substantiated by the fact that the spin traps, 5,5-dimethyl-pyrroline-N-oxide (DMPO) and N-tert-butyl-alpha-phenylnitrone (PBN), decreased DNA damage significantly. Furthermore, addition of the catalase (100 U/ml) caused a decrease in the DNA damage induced by 2-ABP or 4-ABP, indicating that H(2)O(2) is involved in ABP-induced DNA damage. Pre-incubation of the cells with the iron chelator desferrioxamine (DFO) (1mM) and with the copper chelator neocupronine (NC) (100 microM) also decreased DNA damage in cells treated with 200 microM 2-ABP or 200 microM 4-ABP, while the calcium chelator {1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester}(BAPTA/AM) (10 microM) decreased only DNA strand breaks in cells exposed to 4-ABP. This suggested that ions are involved in the formation of DNA strand breaks. Using RT-PCR and Western blotting, lower inhibition of the expression of the OGG1 gene and of the OGG1 protein was observed in cells treated with 4-ABP, and 2-ABP-treated cells showed a marked reduction in the expression of OGG1 gene and OGG1 protein. Taken together, our finding indicated the mechanisms of induced oxidative DNA damage in Hep G2 cell by 2-ABP and 4-ABP are different, although both tested compounds are isomers.
authors.affiliation: Institute of Medicine, China Medical University, Taichung, Taiwan.
authors.forename: Shu Chi
authors.initials: SC
authors.lastname: Wang
authors.forename: Jing-Gung
authors.initials: JG
authors.lastname: Chung
authors.forename: Ching-Hsein
authors.initials: CH
authors.lastname: Chen
authors.forename: Ssu-Ching
authors.initials: SC
authors.lastname: Chen
mesh_terms: D000611:Aminobiphenyl Compounds / Q000633:toxicity*; D015153:Blotting, Western; D002273:Carcinogens / Q000633:toxicity; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology; D002374:Catalase / Q000378:metabolism; D045744:Cell Line, Tumor; D020552:Comet Assay; D004249:DNA Damage; D045647:DNA Glycosylases / Q000235:genetics; D004260:DNA Repair; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology; D008670:Metals / Q000378:metabolism; D010084:Oxidation-Reduction; D012333:RNA, Messenger / Q000235:genetics; D017382:Reactive Oxygen Species; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013113:Spin Labels
chemical_list: D000611:Aminobiphenyl Compounds; D002273:Carcinogens; D008670:Metals; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D013113:Spin Labels; C006757:4-biphenylamine; C014970:2-aminodiphenyl; D002374:Catalase; D045647:DNA Glycosylases; C479058:oxoguanine glycosylase 1, human