Characterization of Covalent Adducts of Nucleosides and DNA Formed by Reaction with Levuglandin

Enhanced expression of cyclooxygenase-2 (COX-2) is associated with development of several cancers. The product of COX-2, prostaglandin H-2(PGH(2)), call undergo spontaneous rearrangement and nonenzymatic ring cleavage to form the highly reactive levuglandin E-2 (LGE(2)) or D-2 (LGD(2)). Incubation with LGE(2) causes DNA-protein cross-linking In Cultured cells, suggesting that levuglandins can directly react with DNA. We report the identification by liquid chromatography-tandem mass spectrometry of a stable levuglandin-deoxycytidine (LG-dC) adduct that forms upon reaction of levuglandin with DNA. We found that LGE(2) reacted With deoxycytidine, deoxyadenosine, or deoxyguanosine In vitro to form covalent adducts with a dihydroxypyrrolidine structure, as deduced from selective ion fragmentation. For LG-deoxycytidine adducts, the initial dihydroxypyrrolidine structure converted to a pyrrole structure over time. Reaction of LG with DNA yielded a stable LG-dC adduct with a pyrrole structure. These results describe the first structure of levunglandinyl-DNA adducts and provide the tools with which to evaluate the potential for LG-DNA adduct formation in vivo.