P2X7 Receptor-Dependent Intestinal Afferent Hypersensitivity in a Mouse Model of Postinfectious Irritable Bowel Syndrome

The ATP-gated P2X(7) receptor (P2X(7)R) was shown to be an important mediator of inflammation and inflammatory pain through its regulation of IL-1 beta processing and release. Trichinella spiralis-infected mice develop a postinflammatory visceral hypersensitivity that is reminiscent of the clinical features associated with postinfectious irritable bowel syndrome. In this study, we used P2X(7)R knockout mice (P2X(7)R(-/-)) to investigate the role of P2X(7)R activation in the in vivo production of IL-1 beta and the development of postinflammatory visceral hypersensitivity in the T. spiralis-infected mouse. During acute nematode infection, IL-1 beta-containing cells and P2X(7)R expression were increased in the jejunum of wild-type (WT) mice. Peritoneal and serum IL-1 beta levels were also increased, which was indicative of elevated IL-1 beta release. However, in the P2X(7)R(-/-) animals, we found that infection had no effect upon intracellular, plasma, or peritoneal IL-1 beta levels. Conversely, infection augmented peritoneal TNF-alpha levels in both WT and P2X(7)R(-/-) animals. Infection was also associated with a P2X(7)R-dependent increase in extracellular peritoneal lactate dehydrogenase, and it triggered immunological changes in both strains. Jejunal afferent fiber mechanosensitivity was assessed in uninfected and postinfected WT and P2X(7)R(-/-) animals. Postinfected WT animals developed an augmented afferent fiber response to mechanical stimuli; however, this did not develop in postinfected P2X(7)R(-/-) animals. Therefore, our results demonstrated that P2X(7)Rs play a pivotal role in intestinal inflammation and are a trigger for the development of visceral hypersensitivity. The Journal of Immunology, 2011, 187: 1467-1474.