NITROTYROSINE FORMATION, APOPTOSIS, AND OXIDATIVE DAMAGE - RELATIONSHIPS TO NITRIC-OXIDE PRODUCTION IN SJL MICE BEARING THE RCSX TUMOR

In SJL mice, growth of RcsX lymphoma cells results in activation of ma crophages in the spleen and lymph nodes to produce high levels of NO r adical (NO.). We used this experimental model system to study the toxi cology of NO. in vivo. To characterize spatial relationships between s ites of NO. production and tissue damage, immunohistochemical techniqu es were developed for simultaneous detection of inducible NO. synthase (iNOS), 3-nitrotyrosine, and apoptosis in spleen and lymph nodes of t umor-bearing animals. Elevated expression of iNOS, presumed to reflect increased NO. production, was associated with a significant increase in frequency of apoptotic nuclei, Both apoptotic nuclei and 3-nitrotyr osine staining were found in cells juxtaposed to iNOS-expressing (i.e. , NO.-producing) macrophages and also within the macrophages themselve s. To assess the extent of DNA damage associated with the response, 8- oxoguanine levels were quantified in DNA extracted from spleens of tum or-bearing mice, No increase in levels of this marker of oxidative DNA damage was found in tissues in which apoptosis and 3-nitrotyrosine le vels were highly elevated within specific subsets of cells. Collective ly, our results indicate that under the pathophysiological conditions existing in the RcsX tumor-bearing SJL mouse, cellular damage caused b y NO. and/or other reactive species produced by activated macrophages is highly localized within cells in close proximity to the activated m acrophages.