Co-operative signalling through DP1 and DP2 prostanoid receptors is required to enhance leukotriene C4 synthesis induced by prostaglandin D2 in eosinophils

BACKGROUND AND PURPOSE Prostaglandin (PG) D-2 has emerged as a key mediator of allergic inflammatory pathologies and, particularly, PGD(2) induces leukotriene (LT) C-4 secretion from eosinophils. Here, we have characterized how PGD2 signals to induce LTC4 synthesis in eosinophils. EXPERIMENTAL APPROACH Antagonists and agonists of DP1 and DP2 prostanoid receptors were used in a model of PGD(2)-induced eosinophilic inflammation in vivo and with PGD(2)-stimulated human eosinophils in vitro, to identify PGD(2) receptor(s) mediating LTC4 secretion. The signalling pathways involved were also investigated. KEY RESULTS In vivo and in vitro assays with receptor antagonists showed that PGD(2)-triggered cysteinyl-LT (cysLT) secretion depends on the activation of both DP1 and DP2 receptors. DP1 and DP2 receptor agonists elicited cysLTs production only after simultaneous activation of both receptors. In eosinophils, LTC4 synthesis, but not LTC4 transport/ export, was activated by PGD(2) receptor stimulation, and lipid bodies (lipid droplets) were the intracellular compartments of DP1/DP2 receptor-driven LTC4 synthesis. Although not sufficient to trigger LTC4 synthesis by itself, DP1 receptor activation, signalling through protein kinase A, did activate the biogenesis of eosinophil lipid bodies, a process crucial for PGD(2)-induced LTC4 synthesis. Similarly, concurrent DP2 receptor activation used Pertussis toxin-sensitive and calcium-dependent signalling pathways to achieve effective PGD(2)-induced LTC4 synthesis. CONCLUSIONS AND IMPLICATIONS Based on pivotal roles of cysLTs in allergic inflammatory pathogenesis and the collaborative interaction between PGD(2) receptors described here, our data suggest that both DP1 and DP2 receptor antagonists might be attractive candidates for anti-allergic therapies.