Cysteinyl Leukotrienes and Extracellular Nucleotides Mediate the Cross-talk between Platelets and Mast cells in Allergic Inflammation

Mast cells are responsible for allergic reactions by releasing a variety of mediators such as prostaglandin D2 (PGD2) and Cysteinyl leukotrienes (CysLTs). There is accumulating evidence that platelets interact with other immune cells to boost proinflammatory responses in severe asthma and Aspirin Exacerbated Respiratory Disease (AERD). However, potential cross-talk between platelets and mast cells in allergic inflammation remains unexplored. We developed a co-culture system of IL-33 stimulated mouse bone marrow-derived mast cells (BMMCs) and mouse platelets, and examined the cross-talk between mast cells and platelets using specific receptor antagonists and mast cell-specific ST2 knock-out mice. The supernatants from IL-33-stimulated BMMCs or leukotriene C4 (LTC4)-treated platelets were used to identify key mediators from the respective cells. The presence of platelets dose-dependently potentiated IL-33-induced mast cell PGD2 release. This potentiation was completely blocked in mast cell-specific ST2 KO BMMCs or CysLT2-specific antagonist-treated cells. CysLTs were detected in the supernatant of BMMCs stimulated with IL-33, and activated platelets. The cell-free supernatant from LTC4-stimulated platelets, but not LTC4 itself, drove PGD2 release from BMMCs. The platelet-derived activity resisted heat inactivation and proteinase K, suggesting that extracellular protein is not involved in this event. LTC4 potently induced release of both ATP and ADP by platelets. Nonselective antagonists of purinergic (P2Y) receptors for nucleotides significantly blocked the production of PGD2 by BMMCs stimulated by platelet supernatants, and receptor-selective antagonists implicated both P2Y1 and P2Y13 receptors. Mast cell-derived CysLTs and platelet-derived extracellular nucleotides were identified as key mediators in the platelet-mast cell circuit in allergic inflammation.