Functional expression of the P2Y 14 receptor in human neutrophils

Abstract

Previous studies using quantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis have shown that the P2Y 14 receptor is expressed at high levels in human neutrophils. Therefore the primary aim of this study was to determine whether the P2Y 14 receptor is functionally expressed in human neutrophils. In agreement with previous studies RT-PCR analysis detected the expression of P2Y 14 receptor mRNA in human neutrophils. UDP-glucose (IC 50 = 1 μM) induced a small but significant inhibition ( circa 30%) of forskolin-stimulated cAMP accumulation suggesting functional coupling of endogenously expressed P2Y 14 receptors to the inhibition of adenylyl cyclase activity in human neutrophils. In contrast, the other putative P2Y 14 receptor agonists UDP-galactose and UDP-glucuronic acid (at concentrations up to 100 μM) had no significant effect, whereas 100 μM UDP- N-acetylglucosamine-induced a small but significant inhibition of forskolin-stimulated cAMP accumulation (20% inhibition). UDP-galactose, UDP-glucuronic acid and UDP- N-acetylglucosamine behaved as partial agonists by blocking UDP-glucose mediated inhibition of forskolin-induced cAMP accumulation. Treatment of neutrophils with pertussis toxin (G i/o blocker) abolished the inhibitory effects of UDP-glucose on forskolin-stimulated cAMP accumulation. UDP-glucose (100 μM) also induced a modest increase in extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, whereas the other sugar nucleotides had no effect on ERK1/2 activation. Finally, UDP-glucose and related sugar nucleotides had no significant effect on N-formyl-methionyl-leucyl-phenylalanine-induced elastase release from neutrophils. In summary, although we have shown that the P2Y 14 receptor is functionally expressed in human neutrophils (coupling to inhibition of forskolin-induced cAMP and ERK1/2 activation) it does not modulate neutrophil degranulation (assessed by monitoring elastase release). Clearly further studies are required in order to establish the functional role of the P2Y 14 receptor expressed in human neutrophils.