Time course of nitric oxide synthase generation after gluten exposure in the rectal mucosa of gluten-sensitive patients

Background: Nitric oxide is thought to play an important role in modulating chronic inflammatory responses as well as in immune-mediated inflammation. We reproduced a gluten-mediated mucosal response in the rectum of celiac a nd control subjects in order to determine the role of inducible and constit utive nitric oxide synthases in the pathogenesis of this process. Material: Nine patients with confirmed celiac disease and five healthy controls unde rwent a long-term rectal gluten challenge (48 h) after an enema of 6 g of c rude gluten, and constitutive and inducible nitric oxide synthase activity were determined in rectal biopsies. The histological localization of induci ble nitric oxide synthase was determined by immunohistochemistry. Results: Activity of bath isoforms of nitric oxide synthase in control subjects did not change significantly after gluten instillation. In celiac patients, con stitutive nitric oxide synthase on rectal mucosa also showed no significant changes after challenge with gluten. Inducible nitric oxide synthase isofo rm exhibited a modest increase 4h after gluten instillation in celiac patie nts (mean increase 35% compared with baseline levels) but, 8 h after challe nge, generation of iNO synthase was significantly higher: 54% more than pre -challenge production (P < 0.05) and higher than control values (P < 0.05). Inducible nitric oxide synthase staining was mostly localized in mononucle ar cells of the epithelium and the lamina propria. After gluten instillatio n, the enhanced staining was mainly localized in subepithelial areas of the lamina propria. Conclusion: Our data suggest a role for nitric oxide, gene rated by inducible nitric oxide synthase, in the process of rectal mucosa i njury by local gluten instillation in sensitized patients. We could not, ho wever, determine if the role of nitric oxide in the ensuing injury of this gluten-induced immune inflammation model is a protective one, or merely a b y-product generated by the activation of the inflammation cells.