Leukotriene E4-induced pulmonary inflammation is mediated by the P2Y12 receptor

Of the potent lipid inflammatory mediators comprising the cysteinyl leukotrienes (LTs; LTC4, LTD4, and LTE4), only LTE4 is stable and abundant in vivo. Although LTE4 shows negligible activity at the type 1 and 2 receptors for cys-LTs (CysLT(1)R and CysLT(2)R), it is a powerful inducer of mucosal eosinophilia and airway hyperresponsiveness in humans with asthma. We show that the adenosine diphosphate (ADP)-reactive purinergic (P2Y(12)) receptor is required for LTE4-mediated pulmonary inflammation. P2Y(12) receptor expression permits LTE4-induced activation of extracellular signal-regulated kinase in Chinese hamster ovary cells and permits chemokine and prostaglandin D-2 production by LAD2 cells, a human mast cell line. P2Y(12) receptor expression by LAD2 cells is required for competition between radiolabeled ADP and unlabeled LTE4 but not for direct binding of LTE4, suggesting that P2Y(12) complexes with another receptor to recognize LTE4. Administration of LTE4 to the airways of sensitized mice potentiates eosinophilia, goblet cell metaplasia, and expression of interleukin-13 in response to low-dose aerosolized allergen. These responses persist in mice lacking both CysLT(1)R and CysLT(2)R but not in mice lacking P2Y(12) receptors. The effects of LTE4 on P2Y(12) in the airway were abrogated by platelet depletion. Thus, the P2Y(12) receptor is required for proinflammatory actions of the stable abundant mediator LTE4 and is a novel potential therapeutic target for asthma.