Cytosolic Phospholipase A2and Cyclooxygenase-2 Mediate Release and Metabolism of Arachidonic Acid in Tumor Necrosis Factor-α-Primed Cultured Intestinal Epithelial Cells (INT 407)

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Abstract
Background: We have recently reported that tumor necrosis factor-α (TNF-α), a pro-inflammatory cytokine that has been suggested to play a role in the pathogenesis of inflammatory bowel disease, potentiates phospholipase A2 (PLA2)-stimulated arachidonic acid (AA) release and prostaglandin E2(PGE2) formation in cultured intestinal epithelial cells (INT 407). The aim of the present study was to investigate which particular isoforms of PLA2 and cyclooxygenase (COX) are involved in these processes. Methods: Cells were labeled with 14C-AA or 14C-oleic acid, and the amounts of released fatty acid and PGE2 were analyzed by thin-layer chromatography. mRNA was analyzed by reverse transcription and polymerase chain reaction. Results: The cells contained mainly mRNA for cytosolic PLA2 (cPLA2) and only trace amounts of mRNA for group I and II PLA2. TNF-α potentiated the release of 14C-AA but not of 14C-oleic acid. The TNF-α-potentiated PGE2 release was reduced after inhibition of cellular COX activity or mRNA synthesis. TNF-α increased the amounts of mRNA for COX-2 but not for COX-1. Conclusions: The results point to the possibility that TNF-α may modulate the intestinal mucosal content of biologically active AA metabolites by priming cPLA2- and COX-2-mediated processes in the epithelial cells.