A negative regulator of delayed prostaglandin D2 production in mouse mast cells

We have previously shown that maturation of mouse bone marrow-derived mast cells (BMMCs) into connective tissue mast cells (CTMCs) upon coculture with fibroblasts in the presence of stem cell factor (kit ligand) is accompanied by marked induction of a panel of genes, one of which was identified as NLRP3. Here we report that NLRP3 acts as a novel negative regulator of delayed prostaglandin (PG) D2 production in BMMCs. We found that, apart from its cell maturation-associated induction, NLRP3 expression was markedly induced in BMMCs several hours after FcɛRI crosslinking or cytokine stimulation. Ectopic expression of NLRP3 in BMMCs resulted in marked attenuation of cyclooxygenase (COX)-2-dependent delayed PGD2 generation, whereas it had no effects on other effector functions, including degranulation, COX-1-dependent immediate PGD2 generation and cytokine/chemokine expression. The suppression of delayed PGD2 generation by NLRP3 was preceded by a transient decrease of NF-κB activation and a marked reduction in the expression of COX-2, but not that of cytosolic phospholipase A2 α (cPLA2α), COX-1 and hematopoietic PGD2 synthase. Moreover, in CTMC-like differentiated cells in which endogenous NLRP3 expression was induced, cytokine-stimulated induction of COX-2 and attendant delayed PGD2 generation were markedly reduced. Our results suggest that, in mouse mast cells, NLRP3 counter-regulates COX-2-dependent sustained production of PGD2, a prostanoid that exhibits both pro- and anti-allergic effects, thereby potentially influencing the duration of allergic and other mast cell-associated inflammatory diseases.