IgE-dependent activation of cytokine-primed mouse cultured mast cells induces a delayed phase of prostaglandin D₂ generation via prostaglandin endoperoxide synthase-2

Mouse hone marrow-derived mast cells (BMMC) developed with IL-3 generate prostaglandin D₂ (PGD₂) through the utilization of prostaglandin endoperoxide synthase (PGHS)-1 within several minutes of cross-linking the high affinity Fc receptor for IgE (FcεRI) by hapten-specific IgE and Ag. We now report that this immediate generation of PGD₂ is followed by a 15-fold induction of steady-state transcripts for PGHS-2, with a maximum at 30 min, accompanied by transient expression of PGHS-2 protein. When BMMC were pretreated with c-kit ligand (KL) in combination with IL-10 for 2 h, sensitized with IgE, and activated with Ag, their expression of steady-state transcripts for PGHS-2 increased 111-fold and their expression of PGHS-2 protein was markedly enhanced, with maximal expression at 1 h and 5 h, respectively, after activation. These events were accompanied by PGD₂ generation from 1 to 10 h after activation that accounted for approximately 50% of total PGD₂ generation. The expression of PGHS-1 protein did not change during this period. The optimal priming interval for the effect of KL plus IL-10 on the IgE-dependent induction of PGHS-2 was 2 h, at which time only this particular cytokine combination acted synergistically with activation by IgE and Ag. In contrast, at 2 days the accessory cytokines that could provide priming with KL included IL-3 and IL-9 in addition to IL-10. Dexamethasone, which inhibited the expression of PGHS-2 but not PGHS-1, and NS-398, a selective inhibitor of PGHS-2, each suppressed the delayed phase but not the immediate phase of PGD₂ generation. Conversely, valeryl salicylate, a selective inhibitor of PGHS-1, suppressed the immediate but not the delayed phase of PGD₂ generation after cell priming and IgE-dependent activation.