Expression of DP2 (CRTh2), a Prostaglandin D2 Receptor, in Human Mast Cells

Abstract

PGD2 has long been implicated in allergic diseases. Recent cloning of a second PGD2 receptor, DP2 (also known as CRTh2), led to a greater understanding of the physiological and pathophysiological implications of PGD2. PGD2 signaling through DP1 and DP2 mediates different and often opposite effects in many cell types of the immune system. Although mast cells (MC) are the largest source of PGD2 in the body, there is little information about their potential expression of DP2 and its functional significance. In this study, we show that tissue MC in human nasal polyps express DP2 protein, and that human MC lines and primary cultured human MC express mRNA as well as protein of DP2. By immunohistochemistry, we detected that 34% of MC in human nasal polyps expressed DP2. In addition, flow cytometry showed that 87% of the LAD2 human MC line and 98% of primary cultured human MC contained intracellular DP2. However, we could not detect surface expression of DP2 on human MC by single cell analysis using imaging flow cytometry. Blocking of endogenous PGD2 production with aspirin did not induce surface expression of DP2 in human MC. Two DP2 selective agonists, DK-PGD2 and 15R-15-methyl PGD2 induced dose-dependent intracellular calcium mobilization that was abrogated by pertussis toxin, but not by three DP2 selective antagonists. MC mediator release including degranulation was not affected by DP2 selective agonists. Thus, human MC express DP2 intracellularly rather than on their surface, and the function of DP2 in human MC is different than in other immune cells such as Th2 cells, eosinophils and basophils where it is expressed on the cell surface and induces Th2 cytokine and/or granule associated mediator release. Further studies to elucidate the role of intracellular DP2 in human MC may expand our understanding of this molecule and provide novel therapeutic opportunities.

Non‐IgE mediated mast cell activation

“…PGD 2 also reduced responses to systemic or passive anaphylaxis supporting an important role of this lipid mediator and DP1 in MC function. Human MC and MC lines were shown to express DP2, however, the GPCR was observed mostly intracellularly . In agreement functional studies showed that they were unresponsive to stimulation with agonists.…”

Changing the threshold—Signals and mechanisms of mast cell priming

“…Whether the enhanced PGD 2 release following activation of human skin mast cells with IgE/antigen and SCF occurs through a similar mechanism is not known. PGD 2 is a ligand for CRTh2, a receptor expressed on most of the cells important for the pathogenesis of allergic diseases such as Th2 CD4 + lymphocytes, eosinophils and basophils, ILC2 cells, and mast cells …”

Neuroendocrine cells derived chemokine vasoactive intestinal polypeptide (VIP) in allergic diseases

“…In human nasal polyps, 34% of mast cell express CRTH2 receptor. Additionally, 87% of LAD2 human mast cell line and 98% of primary cultured human mast cell showed expression of intracellular CRTH2 [61]. The expression of CRTH2 receptor has also been noticed on basophils that may be responsible for chemotaxis of these cells at the inflammatory site [41, 62].…”