FORMATION OF 8-NITROGUANINE BY THE REACTION OF GUANINE WITH PEROXYNITRITE IN-VITRO

Nitric oxide and superoxide anion, both formed in inflamed tissues, re act rapidly to form the peroxynitrite anion (ONOO-), a strong oxidant which can initiate reactions characteristic of hydroxyl radical (HO.), nitronium ion (NO2+) and nitrogen dioxide radical (NO2.). Peroxynitri te, therefore, may cause DNA or tissue damage, contributing to the mul tistage carcinogenesis process. We have studied reactions of various b ases, nucleosides or deoxynucleosides with peroxynitrite in vitro. Gua nine reacted rapidly with peroxynitrite under physiological conditions and formed several substances, two of which were yellow, a characteri stic of nitro and nitroso compounds. On the basis of chromatographic a nd spectral evidence we identified the major compound (which accounts for similar to 80% of all compounds formed) as 8-nitroguanine. Its for mation was maximal at similar to pH 8 and increased dose-dependently w ith peroxynitrite concentration, but was not dependent on guanine conc entration. The presence of ferric ions, which has been shown to cataly se nitration of tyrosine, did not affect nitration of guanine. 8-Nitro guanine could act as a specific marker for DNA damage induced by perox ynitrite in inflamed tissues.