title: Mediation of 8-hydroxy-guanine formation in DNA by thiazin dyes plus light.
abstract: We have discovered that methylene blue plus light mediates the formation of 8-OHdG in DNA. Methylene blue is one of several thiazin dyes and we report here that the other thiazin dyes tested, in combination with white light, are effective in mediating 8-OHdG formation in DNA. The effectiveness of light plus the thiazin dyes in forming 8-OHdG in DNA were as follows: methylene blue greater than azure B greater than azure A greater than toluidine blue greater than thionin. Two other compounds tested; riboflavin and fuschin acid, in combination with light, caused formation of very little, if any, 8-OHdG in DNA. Thiazin dye mediated formation of 8-OHdG in DNA was not inhibited by the spin trap alpha-phenyl-t-butyl nitrone, which supports our previous observations that oxygen free radical scavengers did not inhibit methylene blue plus light mediated 8-OHdG formation in DNA. Ascorbate addition to methylene blue plus DNA, in the absence of light, was ineffective in mediating 8-OHdG formation in DNA.
authors.affiliation: Molecular Toxicology Research Group, Oklahoma Medical Research Foundation, Oklahoma City 73104.
authors.forename: R A
authors.initials: RA
authors.lastname: Floyd
authors.forename: M S
authors.initials: MS
authors.lastname: West
authors.forename: K L
authors.initials: KL
authors.lastname: Eneff
authors.forename: J E
authors.initials: JE
authors.lastname: Schneider
mesh_terms: D000818:Animals; D001399:Azure Stains; D001578:Benzopyrans; D002417:Cattle; D004396:Coloring Agents; D003497:Cyclic N-Oxides; D004247:DNA; D005609:Free Radicals; D006147:Guanine / Q000031:analogs & derivatives*; D008027:Light; D008751:Methylene Blue; D009589:Nitrogen Oxides; D010640:Phenothiazines; D012256:Riboflavin; D014048:Tolonium Chloride
chemical_list: D001399:Azure Stains; D001578:Benzopyrans; D004396:Coloring Agents; D003497:Cyclic N-Oxides; D005609:Free Radicals; D009589:Nitrogen Oxides; D010640:Phenothiazines; C100026:fuscin; D014048:Tolonium Chloride; C029217:phenyl-N-tert-butylnitrone; C024829:8-hydroxyguanine; D006147:Guanine; D004247:DNA; D008751:Methylene Blue; D012256:Riboflavin