2548 S. Mark Duffy et al. DOI 10.1002/eji.200738106 Eur. J. Immunol. 2008. 38: 2548–2556 Engagement of the EP2 prostanoid receptor closes 1 the K channel KCa3.1 in human lung mast cells and attenuates their migration S. Mark Duffy, Glenn Cruse, Sarah L. Cockerill, Chris E. Brightling and Peter Bradding The Department of Infection, Immunity and Inﬂammation, Institute for Lung Health, University of Leicester, UK Human lung mast cells (HLMC) express the Ca21-activated K1 channel KCa3.1, which plays a crucial role in their migration to a variety of diverse chemotactic stimuli. KCa3.1 acti- vation is attenuated by the b2-adrenoceptor and the adenosine A2A receptor through a Gs-coupled mechanism independent of cyclic AMP. Prostaglandin E2 promotes degranu- lation and migration of mouse bone marrow-derived mast cells through the Gi-coupled EP3 prostanoid receptor, and induces LTC4 and cytokine secretion from human cord blood- derived mast cells. However, PGE2 binding to the Gs-coupled EP2 receptor on HLMC inhibits their degranulation. We show that EP2 receptor engagement closes KCa3.1 in HLMC. The EP2 receptor-speciﬁc agonist butaprost was more potent than PGE2 in this respect, and the effects of both agonists were reversed by the EP2 receptor antagonist AH6809. Butaprost markedly inhibited HLMC migration induced by chemokine-rich airway smooth muscle- conditioned media. Interestingly, PGE2 alone was chemotactic for HLMC at high concen- trations (1 lM), but was a more potent chemoattractant for HLMC following EP2 receptor blockade. Therefore, the Gs-coupled EP2 receptor closes KCa3.1 in HLMC and atten- uates both chemokine- and PGE2-dependent HLMC migration. EP2 receptor agonists with KCa3.1 modulating function may be useful for the treatment of mast cell-mediated disease. Key words: Chemotaxis Ion channel KCa3.1 Mast cell Prostaglandin E2 Introduction Mast cells are tissue-dwelling cells derived from bone marrow progenitors. They are present in all organs throughout the human body, both at mucosal surfaces and within connective tissues. Mast cells play a major role in tissue homeostasis, host defence and the pathophysiology of many diverse diseases [1]. These include pulmonary ﬁbrosis, rheumatoid disease and atherosclero- sis, but they are most commonly associated with allergic disease due to their activation by allergen [2]. In many diseases mast cells Correspondence: Peter Bradding e-mail: pbradding@hotmail.com re-locate to speciﬁc compartments within tissue. This is typiﬁed in asthma where mast cells migrate into the airway epithelium [3], airway smooth muscle (ASM) [4] and submucosal glands [5]. This places activated mast cells in direct contact with these dysfunc- tional airway elements, allowing the speciﬁc delivery of detri- mental cell–cell signals. Drugs that inhibit this tissue relocation by preventing mast cell migration may prove particularly effective in the treatment of mast cell-mediated disease. Human mast cells express the intermediate conductance Ca21-activated K1 channel KCa3.1, which plays a critical role in their migration to diverse chemotactic stimuli [6], and to a lesser extent in their degranulation [7, 8]. Drugs that directly block this channel or which close it indirectly therefore have potential as novel therapies for mast cell-dependent disease. KCa3.1 in human & 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu