Effects of DHA on nitrotyrosine formation and iNOS expression. Immunohistochemical and Western blot analysis in the spinal cord section 24 h after SCI. Sections from sham-operated mice did not stain for iNOS (A, see densitometry analysis G), whereas those from SCI-operated mice exhibited staining for iNOS (B, see densitometry analysis G) mainly in various inflammatory cells in the gray matter. Treatment with DHA reduced the degree of staining for iNOS (C, see densitometry analysis G). Moreover, by Western blot analysis we observed high levels of iNOS in the SCI group (H), whereas the DHA treatment group revealed a low expression of iNOS (H). Thus, the tissue sections obtained from SCI mice demonstrate staining for nitrotyrosine mainly localized in inflammatory cells and in Schwann cell nuclei in the white and gray matter (E, see densitometry analysis I). DHA treatment reduced the degree of staining for nitrotyrosine (F, see densitometry analysis I). Conversely, spinal cord from sham-operated mice did not stain for nitrotyrosine (D, see densitometry analysis I). For each SCI group, see the high magnification of the images. (G,I) Densitometry analysis of immunocytochemistry photographs (n = 5 photos from each sample collected from all mice in each experimental group) for iNOS and nitrotyrosine. Data expressed as a percentage of total tissue area. This figure is representative of at least three experiments performed on different experimental days. Data are mean ± SEM of ten mice for each group.*P < 0.01 vs sham; °P < 0.01 vs SCI; ND: not detectable.