Pharmacological effects mediated by UDP-glucose that are independent of P2Y14 receptor expression.

In transfected cells, the P2Y14 receptor reportedly couples to pertussis toxin-sensitive G(i/o)-proteins. However, the functional coupling of endogenously expressed P2Y14 receptors to the inhibition of adenylyl cyclase activity has not been reported. Therefore, the primary aim of this study was to investigate the effects of uridine 5'-diphosphoglucose (UDP-glucose) on forskolin-stimulated cyclic AMP (cAMP) accumulation in two cell lines that reportedly express P2Y14 receptor mRNA, namely human neuroblastoma SH-SY5Y cells and human astrocytoma U373 MG cells. In U373 MG cells, UDP-glucose inhibited forskolin-stimulated cAMP accumulation in a concentration-dependent manner (pEC50=4.5 +/- 0.3). Furthermore, treatment with pertussis toxin abolished the inhibitory effects of UDP-glucose on forskolin-stimulated cAMP accumulation in U373 MG cells. In SH-SY5Y cells, UDP-glucose had no significant effect on forskolin-stimulated cAMP accumulation. To confirm the expression of P2Y14 receptor mRNA in U373 MG and SH-SY5Y cells, we performed reverse transcriptase polymerase chain reaction (RT-PCR) analysis. However, RT-PCR did not detect the expression of P2Y14 receptor mRNA in SH-SY5Y cells or surprisingly in U373 MG cells. In conclusion, we have shown that although UDP-glucose inhibits forskolin-stimulated cAMP accumulation in human U373 MG astrocytoma cells, we did not detect P2Y14 receptor mRNA in these cells. These results would suggest that the effects of UDP-glucose in U373 MG cells are independent of P2Y14 receptor expression. Thus, results obtained with UDP-glucose should be interpreted with caution, since they clearly may not necessarily reflect the involvement of the P2Y14 receptor.