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.