Effects of vitamins E, C and catalase on bromobenzene- and hydrogen peroxide-induced intracellular oxidation and DNA single-strand breakage in Hep G2 cells.
OBJECTIVE
Water-soluble vitamin E (Trolox C), ascorbic acid and catalase were shown in our previous study to protect isolated rat hepatocytes against bromobenzene-induced toxicity.


METHODS
In order to study the mechanisms of this protection and the pathogenesis of bromobenzene-induced hepatocellular injury, a fluorometric assay for the investigation of intracellular oxidation, indicated by conversion of dichlorofluorescein diacetate to dichlorofluorescein, was used. Single-strand DNA breakage was also evaluated in Hep G2 cells by a radio-labelling method.


RESULTS
Bromobenzene (2.4 and 4.8 mM) induced a significant increase in dichlorofluorescein fluorescence intensity compared to the controls. Trolox C, ascorbic acid or catalase significantly inhibited bromobenzene-induced enhancement of fluorescence intensity (p<0.05-0.001), as well as reduced auto-intracellular oxidation in untreated Hep G2 cells. Hydrogen peroxide (H2O2) evoked a dose-dependent increase in dichlorofluorescein fluorescence intensity in Hep G2 cells, and the effect was completely blocked by Trolox C (2.0 mM) and catalase (4800 unit/ml). Bromobenzene caused significant single-strand DNA breakage in Hep G2 cells during 2 h suspension incubation and 24 h primary incubation. H2O2 (400 microM) led to marked single-strand DNA breakage in 20 min, and the effect was attenuated by Trolox C.


CONCLUSIONS
Metabolism of bromobenzene in Hep G2 cells induces production of H2O2, indicated by enhancement of dichlorofluorescein fluorescence intensity, or other free radicals, which leads to single-strand DNA breakage in the cells. Vitamins E and C and catalase display strong intracellular antioxidative effects. Vitamin E could partially inhibit H2O2-induced single-strand DNA breakage in the cells.
Wu
J
J
Department of Histology and Cell Biology, Umea University, Sweden.
Karlsson
K
K
Danielsson
A
A
D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology*; D001969:Bromobenzenes / Q000633:toxicity; D002374:Catalase / Q000494:pharmacology*; D002478:Cells, Cultured; D002839:Chromans / Q000494:pharmacology; D004249:DNA Damage / Q000187:drug effects*; D004277:DNA, Single-Stranded / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005452:Fluoresceins; D005453:Fluorescence; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D016877:Oxidants / Q000633:toxicity; D010084:Oxidation-Reduction / Q000187:drug effects; D014810:Vitamin E / Q000494:pharmacology*
D000975:Antioxidants; D001969:Bromobenzenes; D002839:Chromans; D004277:DNA, Single-Stranded; D005452:Fluoresceins; D016877:Oxidants; D014810:Vitamin E; C029569:diacetyldichlorofluorescein; D006861:Hydrogen Peroxide; C032036:bromobenzene; D002374:Catalase; D001205:Ascorbic Acid; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid