Cyclooxygenase-2 downregulates inducible nitric oxide synthase in rat intestinal epithelial cells

O. Kobayashi, H. Miwa, S. Watanabe, M. Tsujii, R. N. Dubois, N. Sato

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

Cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression has been demonstrated in inflamed intestinal mucosa. Although regulation of COX-2 and iNOS expression has been studied extensively, the interplay between these two enzymes remains unclear. Because they play crucial roles in inflammation and/or carcinogenesis, we investigated whether COX-2 regulates iNOS expression and evaluated the effects of COX-2 inhibitor and arachidonic acid (AA) on iNOS induction. The COX-2 gene coding region was stably transfected into rat intestinal epithelial cells (RIE sense cells). After interferon-γ (IFN-γ) and lipopolysaccharide (LPS) administration, iNOS and COX-2 expression was evaluated by Western blotting. PGE2 was measured by the enzyme immunoassay (EIA) method. Expression of IFN response factor-1, phosphorylated extracellular signal-related kinase-1 and -2, and Iκ-Bα was evaluated. Activator protein-1 and nuclear factor-KB (NF-κB) were examined by gel mobility shift assay; a supershift assay was performed to identify the NF-κB complex components. JTE-522 or AA was added before IFN-γ and LPS administration, and effects on iNOS and PGE2 induction were evaluated by Western blotting or EIA. iNOS protein and mRNA expression was inhibited in RIE sense cells. Although NF-κB activation was suppressed and Iκ-Ba protein was more stable, respectively, in RIE sense cells, no difference was noted in other transcription factors. JTE-522 increased iNOS protein expression in RIE cells. We conclude that COX-2 suppressed iNOS expression in RIE cells through suppression of NF-κB by stabilizing Iκ-Bα.

Original languageEnglish (US)
Pages (from-to)G688-G696
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume281
Issue number3 44-3
DOIs
StatePublished - 2001
Externally publishedYes

Keywords

  • Activator protein-1
  • Cyclooxygenase-2 inhibitor
  • Extracellular signal-related kinase-1
  • Extracellular signal-related kinase-2
  • Interferon response factor-1
  • Iκ-Ba
  • Nuclear factor-κB

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

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