Prostaglandin E2 Stimulates IL-8 Gene Expression in Human Colonic Epithelial Cells by a Posttranscriptional Mechanism

Abstract

Intestinal mucosal epithelial cells produce IL-8, a neutrophil chemoattractant that contributes to mucosal inflammation in various infectious and inflammatory diseases. However, the mediators involved and the molecular regulation of IL-8 production are poorly understood. As PGE2 is central in gut inflammation and modulates a variety of mucosal epithelial cell functions, we determined whether PGE2 can affect the expression of IL-8. Exogenous PGE2 induced the accumulation of IL-8 mRNA and protein production in a dose- and time-dependent manner in T84 human colonic epithelial cells. Forskolin and dibutyryl cAMP, which increase intracellular cAMP, stimulated IL-8 in a fashion similar to that of PGE2. PGE2 and PGE2 receptor agonists coupling through EP4 receptors elevated intracellular cAMP and up-regulated IL-8 mRNA expression by activating protein kinase A. Unlike PMA, PGE2 and forskolin did not increase IL-8 gene transcription. However, PGE2, forskolin, and PMA enhanced the stability of IL-8 mRNA transcripts, suggesting the involvement of posttranscriptional regulation. Chloramphenicol acetyltransferase reporter gene transfection studies confirmed the presence of a PGE2 responsive cis-element(s) in the IL-8 3' untranslated region. Furthermore, dexamethasone inhibited PGE2-, forskolin-, and dibutyryl cAMP-induced, but not PMA-induced, IL-8 protein production. These results highlight a novel role for PGE2 in up-regulating IL-8 gene expression by colonic epithelial cells, which may contribute to exacerbation of inflammation in the gastrointestinal tract.