For many diseases, mediation of pathogenesis by
nitric oxide (NO) has been suggested. In this study, we explored NO-induced viral pathogenesis with a focus on
nucleic acid damage as evidenced by
8-nitroguanosine formation in vivo. Wild-type mice and littermate mice deficient in inducible
NO synthase (iNOS) were infected with
influenza or Sendai virus. Formation of
8-nitroguanosine in virus-infected lungs was assessed immunohistochemically with an antibody specific for
8-nitroguanosine. Extensive nitration of
RNA either treated with
peroxynitrite or obtained from cultured RAW 264 cells expressing iNOS was readily detected by this antibody. Strong
8-nitroguanosine immunostaining was evident primarily in the cytosol of bronchial and bronchiolar epithelial cells of virus-infected wild-type mice but not iNOS-deficient mice. This staining colocalized with iNOS immunostaining in the lung. 8- Nitroguanosine staining disappeared after addition of exogenous authentic
8-nitroguanosine during the antibody reaction and after pretreatment of tissues with
sodium hydrosulfite, which reduces
8-nitroguanosine to
8-aminoguanosine. NO was generated in excess in lungs of wild-type mice but was eliminated in iNOS-deficient mice after
virus infection; this result also correlated well with formation of
8-nitroguanosine and
3-nitrotyrosine. One consequence of the lack of iNOS expression was marked improvement in histopathological changes in the lung and the lethality of the
infection without effects on
cytokine responses and viral clearance. It is intriguing that
8-nitroguanosine markedly stimulated
superoxide generation from
cytochrome P450 reductase and iNOS in vitro. The present data constitute a demonstration of
8-nitroguanosine formation in vivo and suggest a potential role for NO-induced nitrative stress in viral pathogenesis.