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Abstract
The immediate-early cyclooxygenase-2 (COX-2) gene encodes an inducible prostaglandin synthase enzyme which is implicated in inflammatory and proliferative diseases. COX-2 is highly induced during cell activation by various factors, including mitogens, hormones and cytokines. Since pro-inflammatory cytokine IL-1β has been shown to induce prostaglandin E^sub 2^ (PGE^sub 2^) release in human gingival fibroblasts (HGF), here we analyzed the effect of IL-1β on the expression of COX-2 and the activation of NFκB in HGF. Northern hybridization analysis revealed that IL-1β (200 pg/ml) increased the expression of COX-2 mRNA in HGF. The effect of IL-1β was abrogated by herbimycin A, a protein tyrosine kinase inhibitor, and enhanced by orthovanadate, a protein tyrosine phosphatase inhibitor. IL-1β-induced PGE^sub 2^ release was blocked by the tyrosine kinase inhibitor and increased by the tyrosine phosphatase inhibitor. The results of transient transfection assays using chimeric constructs of the human COX-2 promoter (nt -1432 ~ +59) ligated to a luciferase reporter gene indicated that IL-1β stimulated the transcriptional activity ~ 1.5-fold. Gel mobility shift assays with a radiolabelled COX-2-NFκB oligonucleotide (nts -223 to -214) revealed an increase in the binding of nuclear proteins from IL-1β-stimulated HGF. This increase of DNA-protein complex formation induced by IL-1β was blocked by herbimycin A and another tyrosine kinase inhibitor, genistein. These results suggest that NFκB is an important transcription factor for IL-1β-induced COX-2 gene expression, and is involved in inducing COX-2 gene transcription through tyrosine phosphorylation in HGF.[PUBLICATION ABSTRACT]