Formation of a substituted 1,N-6-etheno-2 '-deoxyadenosine adduct by lipidhydroperoxide-mediated generation of 4-oxo-2-nonenal

Analysis of the reaction between 2'-deoxyadenosine and 13-hydroperoxylinole ic acid by liquid chromatography/constant neutral loss mass spectrometry re vealed the presence of two major products (adducts A and B). Adduct A was s hown to be a mixture of two isomers (A(1) and A(2)) that each decomposed wi th the loss of water to form adduct B. The mass spectral characteristics of adduct B were consistent with the substituted 1,N-6-etheno-2'-deoxyadensoi ne adduct 1 "-[3-(2'-deoxy-beta-D-erythro- pentafuranosyl)-3H-imidazo[2,1-i ]purin-7-yl]heptan-2 "-one. Adducts A(1), A(2), and B were formed when 2'-d eoxyadenosine was treated with synthetic 4-oxo-2-nonenal, which suggested t hat it was formed by the breakdown of 13-hydroperoxylinoleic acid. A substa ntial increase in the rate of formation of adducts A(1), A(2), and B was ob served when 13-hydroperoxylinoleic acid and 2'-deoxyadenosine were incubate d in the presence of Fe-II. Thus, 4-oxo-2-nonenal was most likely formed by a homolytic process. Although adducts A(1), A(2), and B were formed in the reaction between 4-hydroxy-2-nonenal and 2'-deoxyadenosine, a number of ad ditional products were observed. This suggested that 4-hydroxy-2-nonenal wa s not a precursor in the formation of 4-oxo-2-nonenal from 13-hydroperoxyli noleic acid. This study has provided additional evidence which shows that 4 -oxo-2-nonenal is a major product of lipid peroxidation and that it reacts efficiently with DNA to form substituted etheno adducts.