Background: Active colitis in patients with inflammatory bowel disease is associated with mucosal vasodilation, increased intestinal permeability and abnormal colonic motility. Nitric oxide is a messenger molecule with many functions, including regulation of local blood flow, vasomotor tone, and inflammation. Increased nitric oxide production and inducible nitric oxide synthase activity have been demonstrated in experimental models of colitis. This study was designed to determine the relationship between nitric oxide production and colonic inflammation in children with active colitis and in control subjects and whether expression of inducible nitric oxide synthase protein is demonstrable in the intestinal epithelium of these patients.
Methods: Nitrate + nitrite were measured in urine, stool, and plasma using the Griess assay. Expression of inducible nitric oxide synthase protein in intestinal tissue was determined by immunohistochemical localization.
Results: Urinary nitrate + nitrite levels were not significantly different in patients and control subjects. In contrast, stool and plasma nitrate + nitrite concentrations were significantly higher in children with inflammatory bowel disease compared with levels in control children (stool: 162.4 +/- 31.0 mumol/l versus 77.2 +/- 22.1 mumol/l; plasma: 65.2 +/- 9.9 mumol/l versus 38.1 +/- 6.6 mumol/L; p < 0.05). Stool nitrate + nitrite levels significantly correlated with plasma values. Immunohistochemical staining of colonic tissue from children with inflammatory bowel disease demonstrated inducible nitric oxide synthase protein located exclusively in epithelial cells.
Conclusion: Increased nitric oxide production and enhanced intestinal epithelial cell expression of inducible nitric oxide synthase protein are associated with active colonic inflammation.