Δ12-Prostaglandin J2, a Plasma Metabolite of Prostaglandin D2, Causes Eosinophil Mobilization from the Bone Marrow and Primes Eosinophils for Chemotaxis

Abstract

PGD2, 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, PGD2 is rapidly transformed into its major metabolite Δ12-PGJ2, the effect of which on eosinophil migration has not yet been characterized. In this study we found that Δ12-PGJ2 was a highly effective chemoattractant and inducer of respiratory burst in human eosinophils, with the same efficacy as PGD2, PGJ2, or 15-deoxy-Δ12,14-PGJ2. Moreover, pretreatment of eosinophils with Δ12-PGJ2 markedly enhanced the chemotactic response to eotaxin, and in this respect Δ12-PGJ2 was more effective than PGD2. Δ12-PGJ2-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 Δ12-PGJ2 signaled through the same receptor, CRTH2, as PGD2. Finally, Δ12-PGJ2 was able to mobilize mature eosinophils from the bone marrow of the guinea pig isolated perfused hind limb. Given that Δ12-PGJ2 is present in the systemic circulation at relevant levels, a role for this PGD2 metabolite in eosinophil release from the bone marrow and in driving eosinophil recruitment to sites of inflammation appears conceivable.

Hierarchy of eosinophil chemoattractants: role of p38 mitogen‐activated protein kinase

“…To determine how exposure of eosinophils to a chemoattractant alters their responsiveness to a second chemoattractant, we mixed purified eosinophils with a first chemoattractant, applied them to the top wells of a microBoyden chamber and allowed them to migrate towards a second chemoattractant in the bottom wells. The concentrations of eotaxin (3 nM), 5-oxo-ETE (10 nM) and PGD 2 (30 nM) in the bottom wells were selected from previous experiments, because they were approximately equieffective and gave 25-35% of the maximal chemotactic response [10,24,27]. When present in the top wells, PGD 2 concentration-dependently augmented the migration of eosinophils toward eotaxin (Fig.…”

“…Blood was sampled from healthy volunteers according to a protocol approved by the Ethics Committee of the Medical University of Graz and processed as described previously [10]. Buffy coats and platelet-rich plasma were obtained by centrifugation of whole blood at 300 Â g for 20 min.…”

“…The chambers were incubated at 37 C in a humidified CO 2 incubator for 1 h, and the membrane carefully removed. Cells that had migrated to the lower chamber were enumerated by a FACSCalibur flow cytometer (Becton Dickinson) counting for 30 s, and contaminating cells were gated out by side scatter and autofluorescence as previously described [10]. Basophil chemotaxis was determined as described above using peripheral blood mononuclear cells, and migrated basophils were enumerated by flow cytometry as CD123 + /HLA-DR -cells [24].…”

“…Shape change responses of eosinophils and neutrophils were assayed in whole blood, washed leukocyte preparations, or buffy coats suspended in platelet-rich plasma, platelet-poor plasma or assay buffer without Ca 2+ /Mg 2+ , as described previously [10]. Aliquots (90 lL) of cells were stimulated with 10 lL agonists for 4 min at 37 C, transferred to ice and fixed with 250 lL of fixative solution followed by NH 4 Cl-induced lysis of red blood cells.…”

“…Prostaglandin (PG) D 2 , a major mast cell mediator released during the allergic response [7] might be of particular importance, since PGD 2 is capable of inducing the chemotaxis of eosinophils, basophils and Th2-type T cells via a novel receptor, chemoattractant receptorhomologous molecule expressed on TH2 cells (CRTH2) [8,9]. Besides chemotaxis, we have shown that activation of CRTH2 also causes eosinophil respiratory burst and the release of eosinophils from the bone marrow [10]. In vivo, PGD 2 can induce pulmonary eosinophilia [11], and a significant contribution of PGD 2 to the late phase allergic reaction is suggested by enhanced eosinophilic lung inflammation and cytokine release in transgenic mice overexpressing PGD 2 synthase [12].…”