Bacterial induction of inducible nitric oxide synthase in cultured human intestinal epithelial cells.
OBJECTIVE
Enterocytes play a major role in the mucosa as a source of proinflammatory cytokines and cytotoxins. We tested the hypothesis that bacteria induce expression of the inducible nitric oxide synthase (iNOS) in cultured human enterocytes.


METHODS
DLD-1 and Caco-2BBe cell monolayers exposed to Salmonella dublin were analyzed for iNOS up-regulation and nitric oxide production (NOx) in the presence of various proinflammatory cytokines.


RESULTS
S. dublin augmented NOx in interferon gamma (IFN-gamma)-primed cells but had no independent effect on iNOS expression. S. dublin-induced NOx was not mediated by endotoxin and was augmented by an enteroinvasive phenotype. In DLD-1 cells, S. dublin-mediated NOx was blocked by inhibitors of nuclear factor kappa B (NF-kappa B) and tyrosine kinase activation and was steroid resistant. Cis-acting elements in the human iNOS promoter responsive to endotoxin and S. dublin stimulation of IFN-gamma-treated DLD-1 cells were identified between 10.9 and 8.7 kilobases upstream of the transcription initiation site.


CONCLUSIONS
S. dublin alters the regulation of iNOS messenger RNA in IFN-gamma-treated intestinal epithelial cells via a steroid-resistant pathway involving NF-kappa B and tyrosine kinase activity. Because bacterial interaction with cytokine-primed epithelial cells induces the synthesis of NO, an endogenous antimicrobial agent, these findings may have implications for the regulation of mucosal immunity.
Salzman
A L
AL
Division of Critical Care, Children's Hospital Medical Center, Cincinnati, Ohio, USA. als@chmcc.org
Eaves-Pyles
T
T
Linn
S C
SC
Denenberg
A G
AG
Szabó
C
C
D002460:Cell Line; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000201:enzymology* / Q000382:microbiology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D012475:Salmonella; D012480:Salmonella Infections / Q000201:enzymology*
D008070:Lipopolysaccharides; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase