Host: The Japanese Pharmacological Society, The Japanese Society of Clinical Pharmacology
Name : WCP2018 (18th World Congress of Basic and Clinical Pharmacology)
Location : Kyoto
Date : July 01, 2018 - July 06, 2018
[Back ground] Mast cells are immune cells playing a central role in type I allergic reactions. A major mechanism for mast cell activation is the interaction of antigen with the IgE-bound FcεRI. This antigen-dependent mast cell response can be enhanced by various humoral factors such as PGE2 and adenosine via activation of G protein-coupled receptor. We have recently demonstrated that extracellular ATP also up-regulated the antigen/IgE-mediated mast cell activation via ligand-gated ion channel P2X4 receptor. In this study, we investigated interactive effects between ionotropic and G protein-coupled receptor signaling on mast cell degranulation, using ATP and PGE2.
[Methods] Bone marrow derived mast cells (BMMCs) are established using bone marrow from wild type and P2X4 receptor deficient C57BL/6 mice. Almost all (> 95%) cells displayed a mast cell phenotype as assessed by the expression of c-Kit and FcεRI using a FACSCantII flow cytometer. Degranulation was evaluated by measuring β-hexosaminidase release.
[Results and discussion] Although ATP or PGE2 alone had little effect on mast cell degranulation, co-stimulation with them caused a marked degranulation. This synergistic response was inhibited by pertussis toxin treatment and EP3 receptor antagonist ONO-AE-240, suggesting an involvement of EP3-Gi protein signaling. On the other hand, ATP-induced response was inhibited by the P2X4 antagonist 5-BDBD, and enhanced by P2X4 positive allosteric modulator ivermectin. In addition, the synergistic effect between ATP and PGE2 on degranulation response was absent in BMMC prepared from P2X4 deficient mice. These results suggest that BMMC can be stimulated by the combination of ATP and PGE2 via stimulation of ionotropic P2X4 and Gi-coupled EP3 receptor, respectively, in an antigen-independent manner. Since extracellular ATP and PGE2 should coexist at the site of inflammation, our results could lead to new therapeutic targets for intervention in mast cell dependent disorders.
