CYTOSOLIC PHOSPHOLIPASE A(2) AND CYCLOOXYGENASE-2 MEDIATE RELEASE AND METABOLISM OF ARACHIDONIC-ACID IN TUMOR NECROSIS FACTOR-ALPHA-PRIMED CULTURED INTESTINAL EPITHELIAL-CELLS (INT-407)

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