In order to clarify the functional role of ionotropic purinergic (P2X) receptors in pancreatic β-cells, we examined the effect of several P2 receptor agonists and antagonists on insulin secretion by mouse pancreatic islets, mouse Beta-TC6 cell proliferation and survival of dispersed islet cells in culture. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed the expression of mRNAs of P2X4 receptor in mouse islets and P2X1, P2X2, P2X3, P2X4, P2X5 and P2X7 receptors in Beta-TC6 cells. The presence of P2X4 receptor proteins in islets and Beta-TC6 cells was confirmed by immunofluorescent staining and Western blot analysis. We have previously found that the functional P2Y1 receptor but not P2Y2 and P2Y4 receptors was present in islets. In this study we found that a nonspecific P2 receptor agonist, ATP (1 µM) stimulated insulin secretion by islets in the presence of high glucose (20 mM) in culture. The effect of ATP was partially inhibited by a P2 receptor antagonist PPADS as well as a P2Y1 receptor antagonist MRS2179. In addition, a P2X4 receptor potentiator ivermectin per se augmented glucose-induced insulin secretion and slightly potentiated the effect of ATP. These results suggested the involvement of P2Y1and P2X receptors. We also found that ATP inhibited proliferation of Beta-TC6 cells in a concentration-dependent manner during 72 h culture. The inhibitory effect of ATP was completely reversed by PPADS and partially by treating cells with small interfering RNA targeted for P2X4 receptor mRNA. Furthermore, we found that the phosphorylation of the extracellular signal-regulated kinase 1 and 2 (ERK1/2) was suppressed by treatment with ATP in Beta-TC6 cells. In addition, we found that ATP reduced the cell viability and DNA synthesis of islet cells in culture. The effect of ATP on the cell viability was blocked by PPADS or MRS2179. These results suggested that P2X receptors as well as the P2Y1 receptor played a role in the modulation of insulin secretion, proliferation and cell viability in mouse pancreatic β-cells.

Keywords:
ATP, P2X receptor, Insulin secretion, Pancreatic β-cells, Proliferation
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© 2011 S. Karger AG, Basel
2011
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