Immunohistochemical localization of protein 3-nitrotyrosine and S-nitrosocysteine in a murine model of inhaled nitric oxide therapy

Inhaled nitric oxide (INO) therapy is currently used clinically to selectively dilate the pulmonary vasculature and to help treat persistent pulmonary hypertension and bronchopulmonary dysplasia in the neonate. However, in the presence of oxygen or superoxide, nitric oxide forms potentially harmful reactive nitrogen species. Using an experimental mice model, we examined the effects of concurrent hyperoxia and INO on protein tyrosine nitration and cysteine S-nitrosylation in pulmonary tissue. Data showed enhanced S-nitrotyrosine staining within the airway epithelium and alveolar interstitium of mice lungs treated with hyperoxia, which did not increase significantly with INO administration. Within the alveolar interstitium, 3-nitrotyrosine staining was localized to macrophages. S-Nitrosocysteine staining in airway epithelium was significantly enhanced with INO administration regardless of oxygen content. These data suggest that the formation of protein S-nitrosocysteine is the major protein modification during administration of INO.