Increased Activity and Expression of Inducible Nitric Oxide Synthase in Human Duodenal Enterocytes from Patients with Celiac Disease by

Background & Aims: The activity of nitric oxide synthase was assayed in enterocytes isolated from human duodenal biopsies to determine its role in celiac disease. Patients were categorized into those with irritable bowel syndrome, iron deficiency anemia, B12/folate deficiency and treated and untreated celiac disease. Methods & Results: Enterocytes isolated from all groups showed 1400W-inhibitable, Caindependent nitric oxide synthase activity with a pH and temperature optimum of 9.4 and 37C respectively. Western blotting showed that enterocytes expressed the inducible nitric oxide synthase protein and proteins with nitrated tyrosine residues, the latter being indicative of nitric oxide-driven peroxynitrite and/or free radical damage. Endothelial nitric oxide synthase was seen only in the lamina propria. Patients with celiac disease had higher nitric oxide synthase activity than other patient groups. Treatment of the condition led to a fall in activity. Enzyme-linked immunosorbent assay demonstrated cyclic guanosine monophosphate (cGMP) production by the enterocyte fraction but cGMP levels did not correlate with NOS activity. Conclusion: These results suggest that inducible nitric oxide synthase is constitutively expressed in human duodenal enterocytes, is increased in patients with untreated celiac disease and is partially corrected when such patients are treated. We found no evidence to support a role for nitric oxide in the formation of cGMP within the small intestine. Furthermore we were unable to demonstrate a role for peroxynitrite/free radical damage in the pathophysiology of celiac disease.