title: Phenoxyl radical-induced thiol-dependent generation of reactive oxygen species: implications for benzene toxicity.
abstract: Mechanisms of phenoxyl radical-induced generation of oxygen radicals potentially involved in toxicity of benzene were studied. We hypothesized that phenoxyl radical intermediates formed from phenolic metabolites of benzene by oxidative enzymes (e.g., peroxidases, tyrosinase) are able to damage biomolecules via (i) oxidation of low-molecular-weight thiols and protein thiols and (ii) thiol-dependent generation of oxygen radicals and subsequent oxidation of DNA. Phenoxyl radicals were generated by the oxidation of phenol by myeloperoxidase+H2O2, horseradish peroxidase+H2O2, or tyrosinase. The reaction of phenolphenoxyl radicals with GSH and dihydrolipoic acid was studied. Our HPLC measurements showed that both thiols reduced the phenoxyl radical back to phenol. This reaction was accompanied by the formation of thiyl radicals (detected by ESR as 5,5-dimethyl-1-pyrroline-N-oxide/glutathione thiyl radical spin adducts) and of superoxide radicals (measured by their chemiluminescence response in the presence of lucigenin). Hydroxylation of 2'-deoxyguanosine to 8-oxo-7,8-dihydro-2'-deoxyguanosine was demonstrated in the course of the tyrosinase-catalyzed oxidation of phenol in the presence of dihydrolipoic acid and Fe(III)-EDTA. Redox-cycling of phenoxyl radicals by thiols produces oxygen radicals which can be responsible for the oxidative damage of DNA by radical intermediates of benzene metabolism.
authors.affiliation: Department of Environmental and Occupational Health, University of Pittsburgh, Pennsylvania 15238.
authors.forename: D A
authors.initials: DA
authors.lastname: Stoyanovsky
authors.forename: R
authors.initials: R
authors.lastname: Goldman
authors.forename: H G
authors.initials: HG
authors.lastname: Claycamp
authors.forename: V E
authors.initials: VE
authors.lastname: Kagan
mesh_terms: D000166:Acridines / Q000737:chemistry; D001554:Benzene / Q000378:metabolism / Q000633:toxicity*; D002851:Chromatography, High Pressure Liquid; D003497:Cyclic N-Oxides; D004247:DNA / Q000378:metabolism; D003849:Deoxyguanosine / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D005978:Glutathione / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D008163:Luminescent Measurements; D014442:Monophenol Monooxygenase / Q000378:metabolism; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000378:metabolism; D019800:Phenol; D010636:Phenols / Q000378:metabolism / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013113:Spin Labels; D013438:Sulfhydryl Compounds / Q000494:pharmacology*; D013481:Superoxides / Q000032:analysis / Q000378:metabolism; D008063:Thioctic Acid / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D000166:Acridines; D003497:Cyclic N-Oxides; D010636:Phenols; D017382:Reactive Oxygen Species; D013113:Spin Labels; D013438:Sulfhydryl Compounds; D013481:Superoxides; C033472:10,10'-dimethyl-9,9'-biacridinium; C042329:phenoxy radical; D019800:Phenol; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D008063:Thioctic Acid; C015144:dihydrolipoic acid; D004247:DNA; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; D009195:Peroxidase; D014442:Monophenol Monooxygenase; D003849:Deoxyguanosine; D005978:Glutathione; D001554:Benzene