Prostaglandin E2 release triggered by phagocytosis of latex particles. A distinct association with prostaglandin synthase isozymes in bone marrow macrophages.

Previous studies showed that murine bone marrow-derived macrophages (M phi) induced in vitro by IL-3 express cellular prostaglandin G/H synthase (PGHS)-1 but not PGHS-2. To induce PGHS-2 in this study, the M phi were primed further with IFN-gamma plus LPS. The expression of the PGHS isozymes was determined by cytometric analysis using Abs against PGHS-1 and PGHS-2. The expression of PGHS-2, but not PGHS-1, was dexamethasone-sensitive. To assess PGE2-releasing capacity, the primed M phi were triggered by challenge with calcium ionophore A23187, the protein kinase C (PKC) activator PMA, exogenous arachidonic acid, and 1.1-micron latex bead particles. Our results showed that the primed M phi expressed both isozymes and responded to all challenges used to release a substantial amount of PGE2 (> 10 ng PGE2/10(6) cells/ml), whereas the control unprimed M phi responded to A23187 and arachidonic acid but not to PMA or latex beads to release PGE2. However, the primed M phi did not release PGE2 when triggered with nonphagocytosable particles (> or = 40 microns) or when pretreated with cytochalasin D before they were challenged with 1.1-micron beads. Furthermore, staurosporine, a PKC inhibitor, did not inhibit the PGE2 release triggered by the beads. PMA-triggered PGE2 release by the primed M phi, in sharp contrast, was staurosporine-sensitive but cytochalasin D-resistant. Our data suggest that there are multiple or alternative pathways for triggering PGE2 synthesis and release distinctively associated with two PGH synthase isozymes. It is of special interest that the novel pathway triggered by interiorization of particles is associated with the expression of PGHS-2.