8-Arylguanine adducts from arenediazonium ions and DNA

Arenediazonium ions (ArN₂⁺) are genotoxic though the source of their genotoxicity is unknown. The present studies were undertaken to determine if reductive decomposition of ArN₂⁺ to aryl radicals (Ar ^.) in the presence of calf thymus DNA (ctDNA) or in cells results in the formation of DNA adducts. We found that when arenediazonium ions of the general structure p-X-ArN₂⁺ (X = CH₃, CH₂OCH₃, CH₂OH) are allowed to react with ctDNA or incubated with cells under conditions that produce p-X-Ar ^., DNA adducts are formed with guanine. The structure of the adduct is the C⁸-substitution product derived from guanine and p-X-Ar ^.. Formation of p-X-Ar ^. was determined by ESR spin-trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The extent of C⁸-arylguanine adduction was measured by high performance liquid chromatography (HPLC) analysis of the DNA hydrosylate and comparison with authentic synthetic standards. The C⁸-arylguanine adducts observed to form may be important in regard to the genotoxicity of ArN₂⁺, though other DNA adducts such as the N⁶-triazene of adenine or C⁸-aryladenine adducts can form. Finally, though the formation of C⁸-arylguanine adducts from arenediazonium ions has been proposed, this is the first report demonstrating their formation in DNA.