Expression of inducible and endothelial nitric oxide synthases in pouchitis

To study the induction of nitric oxide synthase (NOS) in different forms of pouchitis, we divided patients in five groups: 1) ulcerative colitis, no pouch; 2) no-pouchitis; 3) chronic asymptomatic pouchitis; 4) chronic active pouchitis; and 5) acute pouchitis. Ileal biopsies were scored for NOS-2 (inducible) and NOS-3 (endothelial) immunoreactivity and acute inflammation. In group 1, most specimens lacked NOS-2 immunoreactivity. In group 2, some specimens showed NOS-2 immunoreactive epithelium. In group 3, areas of NOS-2-immunoreactive epithelium were consistently observed in most specimens. In groups 4 and 5, most specimens showed moderate-to-extensive epithelial NOS-2 staining. NOS-2 immunoreactivity scores of groups 1-5 were 0.25 +/- 0.16, 0.67 +/- 0.19, 1.19 +/- 0.40, 2.0 +/- 0.23, and 2.18 +/- 0.12, respectively. Corresponding acute inflammation scores were 0, 0.53 + 0.17, 1.00 +/- 0.33, 1.80 +/- 0.20, and 1.64 +/- 0.15. NOS-2 score correlated with acute inflammation score (p < 0.0001), indicating that NOS-2 induction correlates with both the clinical degree of pouchitis and the severity of acute inflammation. NOS-3 immunoreactivity increased in all pouchitis groups.