MUTAGENICITY OF P-AMINOPHENOL IN ESCHERICHIA-COLI WP2UVRA PKM101 AND ITS RELEVANCE TO OXIDATIVE DNA-DAMAGE/

It was recently reported that p-aminophenol (p-AP) induces DNA cleavag e in mouse lymphoma cells, CHO cells and human lymphoblastoid cells. T he mutagenicity of p-AP has not, however, been detected by reverse mut ation assays. The purpose of this study was to assess the mutagenicity of p-AP by reverse mutation assay using Escherichia coli WP2 uvrA/pKM 101, which has a spectrum for detecting mutations different from those of other strains in the family with an AT base pair at the mutation s ite and has higher sensitivity to certain oxidative mutagens as compar ed to other strains. We found that p-AP was mutagenic to E. coli WP2uv rA/pKM101. The mutagenic activity of this compound was suppressed with the addition of dimethylsulfoxide or catalase, suggesting the involve ment of active oxygen species in the mutagenic process induced by p-AP . To further elucidate the underlying mechanism, pie used isolated DNA for the following experiments. It was revealed, by gel electrophoreti c analysis, that p-AP induced DNA cleavage in the presence of Fe(III). However, p-AP alone did not induce this cleavage. Formation of 8-oxo- 7,8-dihydro-2'-deoxyguanosine by p-AP in calf thymus DNA was also dete cted in the presence of Fe(III) by HPLC with an electrochemical detect or. ESR-spin trapping experiments using DMPO detected the production o f hydroxyl radical ((OH)-O-.) in the solution of p-AP with Fe(III). Bo th p-AP mediated DNA damages and (OH)-O-. production by p-AP in the pr esence of Fe(III) were completely inhibited by (OH)-O-. scavengers (et hanol, mannitol, sodium formate, dimethylsulfoxide) and catalase. Thes e results suggest that (OH)-O-. derived from the reaction between H2O2 and Fe(III) (Fenton reaction) participates in the oxidative DNA damag e. Accordingly, the same mechanism might be working in E. coli WP2uvrA /pKM101 during induction of the mutation by p-AP. (C) 1998 Elsevier Sc ience B.V. All rights reserved.