TY - JOUR T1 - Evidence for a Second Receptor for Prostacyclin on Human Airway Epithelial Cells that Mediates Inhibition of CXCL9 and CXCL10 Release JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.110.069674 SP - mol.110.069674 AU - Sylvia M Wilson AU - Neil A Sheddan AU - Robert Newton AU - Mark Giembycz Y1 - 2010/01/01 UR - http://molpharm.aspetjournals.org/content/early/2010/12/20/mol.110.069674.abstract N2 - Herein we provide evidence for the co-expression of two, distinct, prostacyclin (PGI2) receptors (IP) on BEAS-2B human airway epithelial cells. IP-receptor heterogeneity initially was suggested by the finding that the rank orders of potency of PGI2 and three structurally-similar analogs (taprostene, iloprost, 15-deoxy-TIC) for the inhibition of chemokine (CXCL9 and CXCL10) release and for transcriptional activation/augmentation of CRE and GRE luciferase reporters were distinct. Indeed, PGI2, taprostene and iloprost activated both reporters whereas 15-deoxy-TIC was inert. Conversely, 15-deoxy-TIC, PGI2 and taprostene (but not iloprost) suppressed chemokine release. Further experiments established that iloprost did not antagonize the inhibitory effect taprostene or 15-deoxy-TIC on chemokine output. Similarly, 15-deoxy-TIC failed to antagonize taprostene- and iloprost-induced reporter transactivation. Thus, iloprost- and 15-deoxy-TIC-induced responses were apparently mediated via pharmacologically-distinct receptors. In HEK-293 cells over-expressing the hrIP-receptor, 15-deoxy-TIC was considerably (>10,000-fold) less potent than iloprost and taprostene in promoting cAMP accumulation, yet in BEAS-2B cells these analogs were equipotent. IP-Receptor heterogeneity was also supported by the finding that the affinity of the IP-receptor antagonist, RO3244794, for the receptor mediating inhibition of chemokine release was approximately 10-fold lower than for the receptor mediating both transcriptional outputs. Finally, siRNAs directed against the IP-receptor gene, PTGIR, failed to block the suppression of chemokine output induced by taprostene and 15-deoxy-TIC, whereas taprostene- and iloprost-induced transcriptional responses were markedly attenuated. Collectively, these results indicate that PGI2, taprostene and 15-deoxy-TIC suppress chemokine release from BEAS-2B cells by interacting with a novel IP-receptor, which we denote here as the "IP2"-subtype. ER -