Δ12-Prostaglandin J2, a plasma causes eosinophil mobilization metabolite of prostaglandin D2, from the bone marrow and primes eosinophils for chemotaxis

PGD(2), a major mast cell mediator, is a potent eosinophil chemoattractant and is thought to be involved in eosinophil recruitment to sites of allergic inflammation. In plasma, PGD(2) is rapidly transformed into its major metabolite Delta(12)-PGJ(2), the effect of which on eosinophil migration has not yet been characterized. In this study we found that Delta(12)-PGJ(2) was a highly effective chemoattractant and inducer of respiratory burst in human eosinophils, with the same efficacy as PGD(2), PGJ(2), or 15-deoxy-Delta(12,14)-PGJ(2). Moreover, pretreatment of eosinophils with Delta(12)-PGJ(2) markedly enhanced the chemotactic response to eotaxin, and in this respect Delta(12)-PGJ(2) was more effective than PGD(2). Delta(12)-PGJ(2)-induced facilitation of eosinophil migration toward eotaxin was not altered by specific inhibitors of intracellular signaling pathways relevant to the chemotactic response, phosphatidylinositol 3-kinase (LY-294002), mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (U-0126), or p38 mitogen-activated protein kinase (SB-202190). Desensitization studies using calcium flux suggested that Delta(12)-PGJ(2) signaled through the same receptor, CRTH2, as PGD(2). Finally, Delta(12)-PGJ(2) was able to mobilize mature eosinophils from the bone marrow of the guinea pig isolated perfused hind limb. Given that Delta(12)-PGJ(2) is present in the systemic circulation at relevant levels, a role for this PGD(2) metabolite in eosinophil release from the bone marrow and in driving eosinophil recruitment to sites of inflammation appears conceivable.