Interleukin-3 regulates development of the 5-lipoxygenase/leukotriene C₄ synthase pathway in mouse mast cells

To study cytokine regulation of the 5-lipoxygenase (5-LO)/leukotriene (LT) synthase pathway we have developed mouse bone marrow-derived mast cells (BMMC) that minimally express each protein of the pathway by using a novel culture system, lacking interleukin (IL)-3. When mouse bone marrow cells were cultured for 5 weeks with 100 ng/ml c-kit ligand (KL) and 10 units/ml IL-10, a population of >95% mast cells was obtained. These cells generated 8.3 ± 4.5 ng of LTC₄/10⁶ cells and 8.1 ± 2.4 ng of prostaglandin (PG) D₂/10⁶ cells after IgE-dependent activation. When these BMMC were cultured for 2-5 weeks more with 100 units/ml IL-3 in the continued presence of KL and IL-10, the IgE-dependent generation of LTC₄ and PGD₂ increased to 212 ± 36 and 25.5 ± 8.6 ng/10₆ cells, respectively. The dramatic increase in the IgE- dependent generation of LTC₄ in response to IL-3 was accompanied by a concomitant increase in expression of 5-LO and 5-LO-activating protein and preceded the increased expression of cytosolic phospholipase A₂ and LTC₄ synthase. The recognition that IL-3 up-regulates the expression of each protein of the 5-LO pathway for the generation of LTC₄ contrasts with our recent finding that KL up-regulates the expression of cytosolic phospholipase A₂, prostaglandin endoperoxide synthase-1, and hematopoietic PGD₂ synthase and increases the IgE-dependent generation of PGD₂ in BMMC developed from bone marrow with IL-3. Thus, developmentally segregated regulation of the prostanoid and cysteinyl leukotriene pathways in lineage-related committed mast cell progenitors reveals the pleiotropism of this effector cell of allergic inflammation, a cytokine/growth factor basis for preferential expression of pathways of eicosanoid biosynthesis, and the particular role of IL-3 in regulating the expression of the proteins of the 5-LO/LTC₄ synthase pathway.