Characterizing the presence and sensitivity of the P2X7 receptor in different compartments of the gut.

Purinergic signaling has been established as an important feature of inflammation and homeostasis. The expression of a number of P2 receptor subtypes in the gut has been reported. In this study, using a well-known permeabilization method that is assessed by flow cytometry, we show that lymphocytes and macrophages from the mesenteric lymph nodes (MLN) and the peritoneal cavity exhibit different sensitivities to extracellular ATP. Compared with the macrophages, the lymphocytes are more sensitive to ATP in the MLN compartment, whereas in the peritoneal cavity the macrophages are more sensitive to ATP than the lymphocytes. In addition, we have shown that the epithelial cells from the small bowel are more resistant to the ATP effects than the cells from the colon. These cells, however, become susceptible after exposure to IFN-γ. Furthermore, by examining parameters such as pH manipulation, the exposure to divalent cations and the P2X7 antagonist Brilliant Blue G, and the use of cells from P2X7(-/-) mice, we have shown that the P2X7 receptors are the ATP-activated receptors responsible for the permeabilization phenomenon. In addition, using Western blot analysis, we have demonstrated the changes in the P2X7 receptor expression in immune cells isolated from different sites in the gut and in the gut-associated lymphoid tissues. Our findings suggest the existence of the site-specific modulation of P2X7 receptors on epithelial and immune cells, and we define purinergic signaling as a new regulatory element in the control of inflammation and cell fate in the gut and in the gut-associated lymphoid tissues.