Induction of cyclo‐oxygenase‐2 expression by methyl arachidonyl fluorophosphonate in murine J774 macrophages: roles of protein kinase C, ERKs and p38 MAPK

Abstract

Methyl arachidonyl fluorophosphonate (MAFP), an inhibitor of phospholipase A₂ (PLA₂), has been widely used to assess the roles of PLA₂ in various cell functions. Here, we report on a novel action of this compound at concentrations similar to those used for PLA₂ inhibition. The murine macrophage J774 released a large amount of prostaglandin E₂ (PGE₂) by MAFP (1–30 μM), which was abolished by indomethacin and NS-398 but not by valeryl salicylate, and results from increased cyclo-oxygenase-2 (COX-2) protein levels and gene expression. This PGE₂ release was blocked by inhibitors of tyrosine kinase (genistein), protein kinase C (PKC) (Ro 31-8220, Go 6976 or LY 379196), mitogen-activated protein kinase kinase (MEK) (PD 098059) or p38 mitogen-activated protein kinase (MAPK) (SB 203580). Consistent with these results, MAFP caused membrane translocation of PKCβI and βII isoforms and activated extracellular signal-regulated kinase (ERK) and p38 MAPK. In accordance with these effects of MAFP, PKC activator phorbol 12-myristate 13-acetate (PMA) increased PGE₂ release and caused activation of PKCβ, ERKs and p38 MAPK. This is the first report that the PLA₂ inhibitor, MAFP, can induce COX-2 gene expression and PGE₂ synthesis via the PKC-, ERK- and p38 MAPK-dependent pathways. Thus, the use of MAFP as a PLA₂ inhibitor should be treated with caution.