NTPDase8 protects mice from intestinal inflammation by limiting P2Y₆ receptor activation: identification of a new pathway of inflammation for the potential treatment of IBD.

Abstract

Nucleotides are danger signals that activate inflammatory responses via binding P2 receptors. The nucleoside triphosphate diphosphohydrolase-8 (NTPDase8) is an ectonucleotidase that hydrolyses P2 receptor ligands. We investigated the role of NTPDase8 in intestinal inflammation. We generated NTPDase8-deficient (<i>Entpd8</i>^-/-) mice to define the role of NTPDase8 in the dextran sodium sulfate (DSS) colitis model. To assess inflammation, colons were collected and analysed by histopathology, reverse transcriptase-quantitative real-time PCR (RT-qPCR) and immunohistochemistry. P2 receptor expression was analysed by RT-qPCR on primary intestinal epithelium and NTPDase8 activity by histochemistry. The role of intestinal P2Y₆ receptors was assessed by bone marrow transplantation experiments and with a P2Y₆ receptor antagonist. NTPDase8 is the dominant enzyme responsible for the hydrolysis of nucleotides in the lumen of the colon. Compared with wild-type (WT) control mice, the colon of <i>Entpd8</i>^-/- mice treated with DSS displayed significantly more histological damage, immune cell infiltration, apoptosis and increased expression of several proinflammatory cytokines. P2Y₆ was the dominant P2Y receptor expressed at the mRNA level by the colonic epithelia. Irradiated <i>P2ry6</i>^-/- mice transplanted with WT bone marrow were fully protected from DSS-induced intestinal inflammation. In agreement, the daily intrarectal injection of a P2Y₆ antagonist protected mice from DSS-induced intestinal inflammation in a dose-dependent manner. Finally, human intestinal epithelial cells express NTPDase8 and P2Y₆ similarly as in mice. NTPDase8 protects the intestine from inflammation most probably by limiting the activation of P2Y₆ receptors in colonic epithelial cells. This may provide a novel therapeutic strategy for the treatment of inflammatory bowel disease.