The Expression Of 5-lipoxygenase And The Activation And Cytotoxicity Of 4-Aminobiphenyl In Human Bronchial Epithelial Cell

[Objectives] The effects of 4-aminobiphenyl to 5-lipoxygenase protein expression and cytotoxicity and DNA damage were been investigated in HBE cells, with the experiment that can affirm the co-oxidation of 4-aminobiphenyl mediated by SLO in the vitro-enzymic system, in order to approach the metabolism of xenobiotic by 5-LOX and provide further proof that lipoxygenase is the alternative pathway for the oxidation of xenobiotics mediated by cytochrome P450.[Methods] Enzymic experiment: In vitro suitable reaction conditions soybean lipoxygenase (SLO), substrate (4-aminobiphenyl) and other component react in the enzymic system, and followed by detecting the reaction product in the reaction medium by spectrophotometry. The oxidative rate of 4-aminobiphenyl catalyzed by SLO and the inhibition ratio of the NDGA for the oxidation are calculated, respectively.Cellular experiment: The effect of 4-aminobiphenyl on cell survival rate were assessed by reductions of tetrazolium dye(MTT) in cultured HBE cells. After HBE cells exposure to different concentrations of 4-aminobiphenyl for 24 hours, the protein expressions of 5-lipoxygenase in the cells are tested by western-blot, and the DNA damages by the single cell gel electrophoresis. At last, the effect of the specific inhibitor of 5-lipoxygenase(AA-861) on 5-lipoxygenase protein expression and DNA damage in the cells are detected.[Results] SLO can catalyze the co-oxidation of 4-aminobiphenyl to generate 4,4'-azobis(biphenyl)in the presence of hydrogen peroxide. NDGA can inhibit the oxidation of 4-aminobiphenyl by SLO, which appears to concentration-dependent manner in special range. 4-aminobiphenyl can induce 5-lipoxygenase protein expression, but AA-861 can not in HBE. 4-aminobiphenyl causes toxic action and DNA damage in HBE, which can significantly inhibit by AA-861 and naproxen.[Conclusions] In the presence of hydrogen peroxide, SLO can mediate 4-aminobiphenyl co-oxidation, which can be inhibited by NDGA. 5-LOX protein expression in HBE can be regulated by 4-aminobiphenyl, and specific inhibitor of 5-LOX (AA-861) has no obvious effect on the expression. The co-oxidate of 4-aminobiphenyl by 5-LOX turns into electrophiles that covalently bind to DNA and induce DNA damage, which can be significantly inhibited by AA-861.