Crystal-induced neutrophil activation -: VIII.: Immediate production of prostaglandin E2 mediated by constitutive cyclooxygenase 2 in human neutrophils stimulated by urate crystals

Objective. To evaluate the impact of monosodium urate monohydrate (MSUM) crystals on the synthesis of prostaglandin E-2 (PGE(2)) by human neutrophils, and to examine some of the mechanisms underlying these responses. Methods. The amount of PGE(2) released in the supernatants of stimulated human neutrophils was evaluated by enzyme immunoassay, and expression of cyclooxygenase 2 (COX-2) was monitored by immunoblot on cell lysates, as well as by cytofluorometry of buffy-coat cells. Results. We observed that MSUM crystals rapidly stimulated the synthesis of PGE(2),with levels peaking at 1 hour. This response was decreased by NS-398, a specific inhibitor of COX-2. We also detected a constitutive expression of COX-2 in unstimulated and unprimed neutrophils. This rapid COX-2-dependent PGE(2) accumulation was independent of translation and transcription. We also observed that piceatannol, but not colchicine, blocked the synthesis of PGE(2) stimulated by MSUM crystals. Conclusion. These results show that the interaction of MSUM crystals with human neutrophils stimulates a significant synthesis of PGE(2) mediated by constitutively expressed COX-2. The results of this study emphasize the potential importance of the neutrophil as a source of PGE(2), which may modulate, positively or negatively, the inflammatory response.