Expression of NOSII and its role in experimental small bowel ulceration in rats

Background. Overproduction of nitric oxide (NO) has been implicated in the pathogenesis of experimental and clinical inflammatory bowel disease (IBD). Methods. We observed the expression and localization of inducible NO synthase (NOS-II) in small intestinal ulceration induced by indomethacin in rats. The role of NO was investigated by using NO synthase inhibitors. Results. The small intestine was affected by longitudinal ulcers after indomethacin administration and ulceration was associated with distinctive expression of NOS-II protein and mRNA. The amount of its expression was found to correlate with the extent of inflammation. Histologically, both immunohistochemistry and in situ hybridization revealed a similar localization of NOS-II to inflammatory and epithelial cells. The possible amelioration of the inflammation was modulated by aminoguanidine (AG) and NG-nitro-L-arginine methyl ester (L-NAME) treatment for 10 days. Both AG and L-NAME attenuated intestinal myeloperoxidase activity and gross inflammation, only AG was found to decrease intestinal permeability with a significant amelioration of body weight loss. Conclusion. These findings indicate that NO derived mainly from inflammatory cells may play an important role in the pathophysiology of intestinal ulceration and offer the potential for future treatment directed at blocking neutrophils recruitment and NO overproduction in IBD.