Analyses of 8-Methyldeoxyadenosine and 8-Methyldeoxyguanosine as Markers of Free Radical-mediated DNA Methylation in Mouse

Abstract

To examine whether methyl radical-induced DNA damage occurs in vivo, cumene hydroperoxide (CuOOH) and methionine sulfoxide (MetO) were administered to mice as methyl radical generators, and 8-methyldeoxyadenosine (m⁸dA) and 8-methyldeoxyguanosine (m⁸dG) in the tissue DNA were analyzed by the LC/MS/MS method. After mouse skin was treated with CuOOH and Fe²⁺, both m⁸dA and m⁸dG were detected in the epidermal DNA. m⁸dA formation was also detected in the liver DNA from MetO-treated, non-alcoholic steatohepatitis (NASH) mice. Since 5-methyldeoxycytidine, m⁸dA, and m⁸dG are formed in DNA by methyl radicals, these results support our hypothesis that de novo DNA methylation at the cytosine C-5 position is triggered by a free radical mechanism and may initiate epigenetic changes.