Regulation of purinergic signaling by prostaglandin E2 in murine macrophages

Extracellular nucleotides are primary signals for tissue injury, acting together with various chemical mediators Such as prostanoids at the Inflammatory site. We investigated whether prostaglandin E-2 (PGE(2)) affects purinergic signaling in murine J774 macrophages. J774 cells expressed four different purinoceptor mRNAs: the ionotropic P2X(4) and P2X(7) receptors and G-protein-coupled P2Y(2) and P2Y(6) receptors. Functional responses mediated by these purinoceptor subtypes were confirmed by measurement of intracellular Ca2+ concentration ([Ca2+](i)) in fura-2-loaded cells. Thus, low concentrations (10 mu M) of ATP (P2Y(2) agonist) and UDP (P2Y(6) agonist) evoked Ca2+ transient in a phospholipase C (PLC)-dependent manner, whereas the P2X(7) agonist benzoylbenzoyl-ATP (BzATP, 500 mu M) caused a sustained rise in [Ca2+](i). Furthermore, ivermectin, an activator of the P2X(4)-receptor channel, enhanced the ATP-induced [Ca2+](i) elevation. PGE(2) inhibited ATP- and UDP-induced [Ca2+](i) elevation, without affecting the BzATP-induced sustained [Ca2+](i) elevation. Stimulation or J774 cells by UDP or BzATP increased the production of macrophage inflammatory peptide-alpha (MIP-alpha). PGE(2) abolished the UDP-induced MIP-alpha production, but not the BzATP-induced one. These results demonstrate that purinergic signalings in macrophages were regulated by PGE(2) in a subtype-specific manner. The different inhibitory effects oil distinct purinoceptor functions may be related to the anti-inflammatory property of PGE(2).