P2X7 receptor-dependent tuning of gut epithelialresponses to infection

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Infection and injury of the gut are associated with cell damage and release of molecules such as extracellular adenosine 5′-triphosphate (ATP), which is recognised by the purinergic P2X7 receptor (P2X7R). P2X7R is widely expressed in the gut by antigen-presenting cells (APCs) and epithelial cells, but the role of the P2X7R on epithelial cells is poorly understood. We investigated P2X7R in intestinal epitheliumin vitroandin vivousing two model infections,Toxoplasma gondiiandTrichinella spiralis. Lipopolysaccharide and ATP treatment of intestinal epithelial cells and infection withT. gondii in vitrodid not promote inflammasome-associated interleukin-1β (IL-1β) or IL-18 secretion, but promoted C-C motif chemokine ligand 5 (CCL5), tumour necrosis factor-α and IL-6 production that were significantly reduced when the P2X7R was blocked. Similarly,in vivo, infection with eitherT. spiralis or T. gondiiinduced rapid upregulation of epithelial CCL5 in wild-type (wild-type (WT)) mice that was significantly reduced in P2X7R-/- littermate controls. The effects of reduced epithelial CCL5 were assayed by investigating recruitment of dendritic cells (DCs) to the epithelium. Infection induced a rapid recruitment of CD11c+CD103+ DC subsets into the epithelial layer of WT mice but not P2X7R-/- mice.In vitrochemotaxis assays and bone marrow chimeras demonstrated the importance of epithelial P2X7R in DC recruitment. P2X7R signalling in epithelial cells mediates chemokine responses to promote initiation of host immunity to infection.

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