Selective modulation of chemokinesis, degranulation, and apoptosis in eosinophils through the PGD2 receptors CRTH2 and DP

Background: PGD(2) is the major prostanoid released by mast cells during an allergic response. Its role in the allergic response, however, remains unclear. Objective: Because the accumulation of eosinophils is a feature of allergic reactions, we investigated the role of PGD(2) in the modulation of eosinophil function. Methods: Circulating human eosinophils were isolated and challenged with PGD(2). The effects of PGD(2) on various eosinophil functions were then analyzed. Results: PGD(2) binds with high affinity preferentially to 2 receptors, DP and chemoattractant receptor-homologous molecule expressed on T(H)2 cells (CRTH2). We show that both DP and CRTH2 are detectable on circulating eosinophils. We demonstrate that PGD(2) (1-10 nmol/L) induces a rapid change in human eosinophil morphology and an increase in chemokinesis and promotes eosinophil degranulation. These effects are induced by the CRTH2-selective agonist 13-14-dihydro-15-keto-PGD(2) (DK-PGD(2)) but not by the DP-selective agonist BW245C. These results suggest a role for CRTH2 in the modulation of eosinophil movement and in triggering the release of cytotoxic proteins. Finally, we demonstrate that BW245C, but not DK-PGD(2), can delay the onset of apoptosis in cultured eosinophils, presumably through interaction with DP. Conclusion: These data support the hypothesis that PGD(2) controls eosinophil functions through 2 pharmacologically distinct receptors with independent functions. Blockade of PGD(2)-mediated effects on human eosinophils may reduce the damage caused by these cells during an allergic response, but inhibition of both receptors may be required.