Role of nitrite on nitration of 2′-deoxyguanosine by nitryl chloride

Nitryl chloride and peroxynitrite are reactive nitrogen species generated by activated phagocytes against invading pathogens during infections and inflammation. In our previous report, formation of 8-nitroxanthine and 8-nitroguanine was observed in reaction of 2'-deoxyguanosine or calf thymus DNA with nitryl chloride generated by mixing hypochlorous acid (HOCl) with nitrite (NO2-). The present study investigates factors controlling the yields of 8-nitroxanthine and 8-nitroguanine formation in nitration of 2'-deoxyguanosine by nitryl chloride. We found that the yields of 8-nitroxanthine and 8-nitroguanine in reaction of 2'-deoxyguanosine with nitryl chloride were highly dependent on the ratio of NO2- versus HOCl concentration. The yields of 8-nitroxanthine and 8-nitroguanine reached a plateau when the ratio of NO2- versus HOCl concentration was higher than 2. A possible mechanism was postulated to explain this observation. While 8-nitroguanine is not stable in the presence of peroxynitrite, 8-nitroxanthine is sensitive to HOCl. The stability of these two nitrated adducts might be a factor on their final yields in this reaction. Since HOCl is produced by neutrophils at sites of inflammation where the level of NO2- is elevated, it is conceivable that nitryl chloride contributes to DNA base nitration in vivo, forming 8-nitroxanthine and 8-nitroguanine.