Autoregulation of human monocyte-derived dendritic cell maturation and IL-12 production by cyclooxygenase-2-mediated prostanoid production

PG added to cell culture profoundly affect the in vitro maturation and func tion of monocyte-derived dendritic cells (MDC). Because unstimulated monocy tes express cyclooxygenase (COX)-1, and COX-2 when activated, we examined w hether MDC express these enzymes and produce prostanoids that autoregulate maturation and IL-12 production. Immature MDC (I-MDC) and mature MDC expres s COX-1, but, unlike monocytes, both MDC populations constitutively express COX-2, However, COX-2 regulation in both MDC populations differs from mono cytes, as IL-4 does not suppress enzyme expression. COX-2 is functional in MDC as a specific inhibitor, NS-398, significantly reduces PGE, production. I-MDC undergoing maturation with soluble CD40 ligand (sCD40L) increase PGE (2) synthesis, but prostanoid synthesis is switched to COX-1. However, with IFN-gamma present, sCD40L-stimulated PG metabolism is redirected to COX-2, and PGE, synthesis increases severalfold. Endogenous PG production by MDC does not regulate CD40, CD80, CD86, or HLA DR expression; however, it does promote MDC maturation, as NS-398 significantly reduces CD83 expression in I-MDC matured with sCD40L/IFN-gamma. PG produced through COX-2 also autoreg ulate IL-12, but the effects are dependent on the MDC maturation state. Blo cking COX-2 reduces I-MDC secretion of IL-12p40, whereas it increases IL-12 p40 and p70 production by maturing MDC, COX-2-mediated PG production impact s MDC function as maturing these cells in the presence of NS-398 yields MDC that stimulate significantly more IFN-gamma in an allogeneic mixed lymphoc yte response than MDC matured withont this inhibitor. These studies demonst rate that MDC express both COX isoforms constitutively and produce prostano ids, which autoregulate their maturation and function.