Metabolites of the biocide o-phenylphenol generate oxidative DNA lesions in V 79 cells.

Incubation of the o-phenylphenol (OPP) metabolites, o-phenylhydroquinone (PHQ) and o-phenylbenzoquinone (PBQ) with V 79 Chinese hamster cells led to a significant enhancement of the amount of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) in nuclear DNA. With OPP no distinct induction of this lesion could be observed. In addition, PHQ and PBQ were able to generate DNA single-strand breaks (DNA SSB), while OPP failed to induce this lesion. All incubations were performed for 1 h without exogenous metabolic activations and the lowest effective concentration tested was 20 microM. It is concluded that these metabolites may contribute to the carcinogenicity of OPP and sodium o-phenylphenolate (SOPP) observed in rats, by generating reactive oxygen species (ROS) through their redox cycling properties.

Oxidative DNA lesions in V79 cells mediated by pentachlorophenol metabolites.

Incubation of the pentachlorophenol (PCP) metabolites, tetrachloro-p-benzoquinone (chloranil, TCpBQ), tetrachloro-p-hydroquinone (TCpHQ) and tetrachloro-p-benzoquinone (TCoBQ) with V79 Chinese hamster cells led to a significant enhancement of the amount of 8-hydroxydeoxyguanosine (8-OH-dG) in DNA. With PCP itself and the metabolite tetrachloro-o-hydroquinone (TCoHQ) no distinct induction of this lesion could be observed. The average yields of 8-OH-dG were about 2-2.5 times above background levels. In addition, TCpBQ and TCpHQ were able to generate DNA single-strand breaks, while PCP, TCoHQ and TCoBQ failed to induce this lesion. All incubations were performed for 1 h without exogenous metabolic activation and concentrations were 25 microM of the respective agent. It is concluded that these metabolites may contribute to the carcinogenicity of PCP observed in mice, by generating reactive oxygen species (ROS) through their redox cycling properties.

Induction of 8-hydroxy-2-deoxyguanosine and single-strand breaks in DNA of V79 cells by tetrachloro-p-hydroquinone.

The biocide pentachlorophenol (PCP) is in part metabolized, by microsomal enzymes, to tetrachloro-p-hydroquinone (TCHQ), which easily oxidizes to its semiquinone radical. Redox cycling of this compound produces reactive oxygen species (ROS) which ultimately may damage cellular DNA. Here, we report on DNA damage generated by TCHQ in hamster lung fibroblasts (V79 cells) using 8-hydroxy-2-deoxyguanosine (8-OH-dG) as a marker of a major oxidative genetic lesion and measuring the induction of DNA single-strand breaks (DNA SSB) with the aid of the alkaline elution assay. TCHQ was administered to cell cultures in concentrations of 6.25, 12.5, 25, and 50 microM for 1 h. 6.25 and 12.5 microM had no significant effect on both parameters, whereas the higher concentrations resulted in increases of the level of 8-OH-dG (2.3- and 2.0-fold, respectively) and induced DNA SSB. The latter lesion may arise from (i) direct attack of OH., (ii) repair of hydroxylated DNA bases, or (iii) cytotoxic effects. Metabolic transformation of PCP to TCHQ and/or other metabolites with quinoid structures and the subsequent generation of ROS, producing oxidative DNA damage, may play a role in PCP-induced carcinogenicity observed in mice.