Regulation of nitric oxide production in cultured human T84 intestinal epithelial cells by nuclear factor-kappa B-dependent induction of inducible nitric oxide synthase after exposure to bacterial endotoxin

Background: Intestinal epithelium is consistently in contact with lipopolys accharide (LPS) produced by intraluminal microbes. LPS induces nitric oxide production in many rodent cells, but in human cells it is very differently regulated. Aim: To test the hypothesis that exposure to LPS up-regulates nitric oxide synthesis in human intestinal epithelium. Methods and results: LPS induced nitric oxide synthesis in T84 cells in a t ime- and dose-dependent manner whereas detectable amounts of peroxynitrite were not produced. A novel selective inducible nitric oxide synthase (iNOS) inhibitor 1400 W potently inhibited LPS-induced nitric oxide synthesis in T84 cells while dexamethasone was relatively ineffective. Nitric oxide prod uction was sensitive to cycloheximide, indicating that it was dependent on de novo protein synthesis. Nuclear factor-kappa B (NF-kappa B) inhibitor py rrolidinedithiocarbamate abolished iNOS and nitric oxide production. Nitric oxide synthesis was also suppressed by genistein (tyrosine kinase inhibito r) and PD 98059 (p44/42 MAP kinase inhibitor) but enhanced by SB 203580 (p3 8 MAP kinase inhibitor). Conclusions: Intestinal epithelial cells express iNOS and produce nitric ox ide in a nuclear factor-kappa B-dependent manner when exposed to LPS. The p rocess is regulated by tyrosine kinases, and p44/42 and p38 MAP kinases. Be cause nitric oxide acts as an antimicrobial agent and immune modulator, the se findings are implicated in the regulation of gut mucosal immunity.