INTERLEUKIN-4 SUPPRESSES C-KIT LIGAND-INDUCED EXPRESSION OF CYTOSOLIC PHOSPHOLIPASE A(2) AND PROSTAGLANDIN ENDOPEROXIDE SYNTHASE-2 AND THEIR ROLES IN SEPARATE PATHWAYS OF EICOSANOID SYNTHESIS IN MOUSE BONE-MARROW-DERIVED MAST-CELLS

Mouse bone marrow-derived mast cells (BMMCs) developed with interleukin 3 (IL-3) can be stimulated by c-kit ligand (KL) and accessory cytokines over a period of hours for direct delayed prostaglandin (PG) generation or over a period of days to prime for augmented IgE-dependent PG and leukotriene (LT) production, as previously reported. We now report that IL-4 is counterregulatory for each of these distinct KL-dependent responses, BMMCs cultured for 4 days with KL + IL-3 or with KL + IL-10 produced 5- to 7-fold more PGD(2) and approximate to 2-fold more LTC(4) in response to IgE-dependent activation than BMMCs maintained in IL-3 alone. IL-4 inhibited the priming for increased IgE-dependent PGD(2) and LTC(4) production to the level obtained by activation of BMMCs maintained in IL-3 alone with an IC50 of approximate to 0.2 ng/ml, IL-4 inhibited the KL-induced increase in expression of cytosolic phospholipase A(2) (cPLA(2)) but had no effect on the incremental expression of PG endoperoxide synthase 1 (PGHS-1) and hematopoietic PGD(2) synthase or on the continued baseline expression of 5-lipoxygenase, 5-lipoxygenase activating protein, and LTC(4) synthase, BMMCs stimulated by KL + IL-10 for 10 h exhibited a delayed phase of PGD(2) generation, which was dependent on de novo induction of PGHS-2. IL-4 inhibited the induction of PGHS-2 expression and the accompanying cytokine-initiated delayed PGD(2) generation with an IC50 of approximate to 6 ng/ml, IL-4 had no effect on the expression of PGHS-2 and the production of PGD(2) elicited by addition of IL-1 beta to the combination of KL + IL-10. IL-4 had no effect on the immediate phase of eicosanoid synthesis elicited by KL alone or by IgE and antigen in BMMCs maintained in IL-3, Thus, the counterregulatory action of IL-4 on eicosanoid generation is highly selective for the induced incremental expression of cPLA(2) and the de novo expression of PGHS-2, thereby attenuating time-dependent cytokine-regulated responses to stimulation via Fc epsilon receptor I and stimulation via c-kit, respectively.