Quinol-glutathione conjugate-induced mutation spectra in the supF gene replicated in human AD293 cells and bacterial MBL50 cells

Hydroquinone is a nephrocarcinogen in rats but generally tests negative in standard mutagenicity assays. However, 2,3,5-tris-(glutathion-S-yl)hydroqui none, a potent nephrotoxic metabolite of hydroquinone, and 2-bromo-bis-(glu tathion-S-yl)hydroquinone another cytotoxic quinol-glutathione (GSH) conjug ate, cause extensive single strand breaks in DNA in a manner that is depend ent on the formation of reactive oxygen species. We, therefore, investigate d whether quinol-GSH conjugates have the potential to behave as genotoxican ts. The shuttle vector pSP189, containing the supF gene, was treated with 2 ,3,5-tris-(glutathion-S-yl)hydroquinone and replicated in both human AD293 cells and Escherichia coli MBL50 cells. The mutation frequency increased 4. 6- and 2.6 fold in human AD293 and bacterial MBL50 cells, respectively. Bas e substitutions were the major type of mutations, and they occurred predomi nantly at G:C sites in both cell types. A high frequency of deletions (30%) , including <10- and >10-hp deletions, were observed in AD293-replicated pl asmids. The most common types of mutations in AD293 cells were G:C to A:T t ransitions (33.8%) and G:C to T:A (29.4%) and G:C to C::G (19.1%) transvers ions. In MBL50 cells, the major mutations were G:C to T:A (33.8%) and G:C t o C:G (31.3%) transversions and G:C to A:T transitions (27.5%). The mutatio n spectra were similar to those reported for OH-induced mutations, suggesti ng that . OH generated from polyphenolic-GSH conjugates not only plays a ro le in cytotoxicity but also provides a basis for their mutagenicity and car cinogenicity.