Oxidative damage of DNA induced by methylglyoxal in vitro.

Methylglyoxal is an endogenous metabolic by-product of glycolysis and has genotoxic effects. Previous studies suggested that the reaction of methylglyoxal with amino acid leads to the production of free radicals. In this study, oxidative damage of DNA by the reaction of methylglyoxal with amino acid was investigated. When plasmid DNA was incubated with methylglyoxal and lysine, DNA strand was cleaved. Cu(2+) enhanced DNA strand breakage induced by the reaction of methylglyoxal with lysine. The formation of superoxide anion was detected during the glycation reaction of methylglyoxal with lysine. Radical scavengers, catalase, and copper chelators inhibited the DNA breakage. The deoxyribose assay showed that hydroxyl radicals were generated during the reaction of methylglyoxal with lysine in the presence of Cu(2+). The generation of hydroxyl radicals was inhibited by radical scavenger, catalase, and copper chelator. These results suggest that superoxide anion and H2O2 may generate from the glycation reaction of methylglyoxal with lysine and then Cu(2+) likely participates in a Fenton's type reaction to produce hydroxyl radicals, which may cause DNA cleavage. This mechanism may be linked to several diverse biological processes including mutagenesis, aging, carcinogenesis, and diabetic complications.