Intestinal Inflammation Increases the Expression of the P2Y6 Receptor on Epithelial Cells and the Release of CXC Chemokine Ligand 8 by UDP

Abstract

Epithelial cells participate in the immune response of the intestinal mucosa. Extracellular nucleotides have been recognized as inflammatory molecules. We investigated the role of extracellular nucleotides and their associated P2Y receptors in the secretion of cytokines by epithelial cells. The effect of intestinal inflammation on P2Y6 receptor expression was determined by PCR in the mouse, rat, and human. Localization of the P2Y6 receptor was determined by immunofluorescence microscopy in the colon of normal and dextran sulfate sodium-treated mice. The effect of P2Y6 activation by UDP on cytokine expression and release by epithelial cells was determined using a combination of Western blots, luciferase assays, RT-PCR, cytokine Ab arrays, and ELISA. Inflammation up-regulates P2Y2 as well as P2Y6 receptor expression in the mucosa of the colon of colitic mice. In vitro, we demonstrated that UDP could be released by Caco-2/15 cells. We have confirmed the increased expression of P2Y6 by challenging intestinal epithelial cell-6 and Caco-2/15 cells with TNF-α and IFN-γ and showing that stimulation of epithelial cells by UDP results in an increased expression and release of CXCL8 by an ERK1/2-dependent mechanism. The increase in CXCL8 expression was associated with a transcriptional activation by the P2Y6 receptor. This study is the first report demonstrating the implication of P2Y receptors in the inflammatory response of intestinal epithelial cells. We show for the first time that P2Y6, as well as P2Y2, expression is increased by the stress associated with intestinal inflammation. These results demonstrate the emergence of extracellular nucleotide signaling in the orchestration of intestinal inflammation.

Concomitant activation of P2Y2 and P2Y6 receptors on monocytes is required for TLR1/2‐induced neutrophil migration by regulating IL‐8 secretion

“…As IL-8 secreted by a variety of inflammatory cells including monocytes has been implicated in a number of inflammatory/infectious diseases, such as rheumatoid arthritis [33], inflammatory bowel disease [34], psoriasis [35,36], palmoplantar pustulosis [37,38], asthma and chronic obstructive pulmonary disease [39], targeting P2Y 2 and/or P2Y 6 receptors may reveal as novel therapeutic approaches to fight these diseases. These data are also in agreement with a new concept proposing that extracellular nucleotides serve as endogenous danger-signaling molecules called alarmins that are rapidly released in stress conditions and resolve the innate immune response [40].…”

The touching story of purinergic signaling in epithelial and endothelial cells

“…This was confirmed in vivo, as LPS-induced vascular inflammation was attenuated in P2Y6 −/− mice [122]. A similar response has been demonstrated in intestinal inflammation [123]. It is noteworthy that one of the most highly expressed P2Y receptors of endothelial cells is the P2Y11 receptor, which has no known function in regulation of vessel patency, but might be involved in the inflammatory response of this tissue.…”

Pharmacological characterization of uracil nucleotide-preferring P2Y receptors modulating intestinal motility: a study on mouse ileum

“…Large amounts of extracellular nucleotides are rapidly released into the extracellular environment at the site of inflammation [41], and P2Y 6 receptors have been reported to be upregulated in the context of inflammatory insult in a mouse colon [42].…”