Activity of inducible and neuronal nitric oxide synthases in colonic mucosa predicts progression of ulcerative colitis

OBJECTIVE: The present study analyzes inducible and neuronal nitric oxide synthase activity and expression in colonic mucosa of patients with ulcerative colitis, and correlates them with the progression of disease extent. METHODS: Thirty patients with ulcerative colitis were included. Synthases; activity and expression were analyzed both in inflamed and noninflamed mucosa. After 2 yr, disease extent was determined and compared with extent at inclusion. RESULTS: Ca2+-independent activity, expressed as median with (interquartile range), in inflamed mucosa was higher than in noninflamed and control mucosa (102 (165-66), 24 (50-3), 1 (2.5-0.1) pmol.min(-1) mg prot(-1), respectively, p < 0.005), whereas Ca2+-dependent activity was significantly lower in inflamed than in noninflamed and control mucosa. Western blot analysis identified inducible and neuronal isoforms and confirmed these differences. Patients with more extended disease after 2 yr had higher levels of Ca2+-independent activity in noninflamed mucosa at inclusion and lower levels of Ca2+-dependent activity than patients with persistence of similar extent of inflammation (50 (78-29) vs 8 (30-0.1), p < 0.005; 51 (100-36) vs 150 (156-106), p < 0.05, respectively). Values of Ca2+-independent activity in noninflamed mucosa greater than 30 pmol . min(-1) mg prot(-1) showed 80% sensitivity and 87.5% specificity in the detection of patients with subsequent progression of disease extent, whereas values of Ca2+-dependent activity in noninflamed mucosa greater than 125 pmol . min(-1) mg prot(-1) showed 75% sensitivity and 80% specificity in the detection of patients with stability of disease extent. A ratio of Ca2+-independent/Ca2+-dependent activities over 0.29 showed 90% sensitivity and 87.5% specificity in the detection of patients with subsequent progression of extent. CONCLUSIONS: Our results show an up-regulation of inducible nitric oxide synthase and a down-regulation of neuronal isoform not only in inflamed mucosa but also in apparently healthy mucosa of patients with ulcerative colitis. The values of activity of both isoforms in apparently healthy mucosa could predict the disease extent after 2 yr follow-up.