Department of Physiology and Pharmacology, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada.
Mol Pharmacol. 2011 Mar;79(3):586-95. doi: 10.1124/mol.110.069674. Epub 2010 Dec 20.
Herein we provide evidence for the coexpression of two distinct prostacyclin (PGI(2)) 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 PGI(2) and three structurally similar analogs [taprostene, iloprost, 15-deoxy-16-(m-tolyl)-17,18,19,20-tetranorisocarbacyclin (15-deoxy-TIC)] for the inhibition of chemokine (CXCL9 and CXCL10) release and for transcriptional activation/augmentation of cAMP response element and glucocorticoid response element luciferase reporters were distinct. Indeed, PGI(2), taprostene, and iloprost activated both reporters whereas 15-deoxy-TIC was inert. Conversely, 15-deoxy-TIC, PGI(2), 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. Likewise, 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 human embryonic kidney 293 cells overexpressing the human recombinant IP receptor receptor, 15-deoxy-TIC was considerably less potent (>10,000-fold) 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 R-3-(4-fluorophenyl)-2-[5-(4-fluorophenyl)-benzofuran-2-yl-methoxycarbonyl-amino] propionic acid (RO3244794) for the receptor mediating inhibition of chemokine release was approximately 10-fold lower than for the receptor mediating both transcriptional outputs. Finally, small interfering RNAs 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 PGI(2), taprostene and 15-deoxy-TIC suppress chemokine release from BEAS-2B cells by interacting with a novel IP receptor that we denote here as the "IP(2)" subtype.
在这里，我们提供了证据表明，在 BEAS-2B 人呼吸道上皮细胞上存在两种不同的前列腺素 I2（PGI2）受体（IP）的共表达。IP 受体的异质性最初是通过发现 PGI2 和三种结构相似的类似物（taprostene、iloprost、15-去氧-16-（m-甲苯基）-17、18、19、20-四去甲环丙基环前列腺素（15-去氧-TIC））对趋化因子（CXCL9 和 CXCL10）释放的抑制作用和对 cAMP 反应元件和糖皮质激素反应元件荧光素酶报告基因的转录激活/增强的效力顺序不同而提出的。事实上，PGI2、taprostene 和 iloprost 都激活了这两个报告基因，而 15-去氧-TIC 则没有活性。相反，15-去氧-TIC、PGI2 和 taprostene（但不是 iloprost）抑制趋化因子释放。进一步的实验表明，iloprost 不能拮抗 taprostene 或 15-去氧-TIC 对趋化因子输出的抑制作用。同样，15-去氧-TIC 不能拮抗 taprostene 和 iloprost 诱导的报告基因转导激活。因此，iloprost 和 15-去氧-TIC 诱导的反应显然是通过药理学上不同的受体介导的。在过表达人重组 IP 受体的人胚肾 293 细胞中，15-去氧-TIC 在促进 cAMP 积累方面的效力比 iloprost 和 taprostene 低 10000 倍以上，但在 BEAS-2B 细胞中，这些类似物具有同等效力。IP 受体的异质性还得到了以下发现的支持：IP 受体拮抗剂 R-3-（4-氟苯基）-2-（5-（4-氟苯基）苯并呋喃-2-基-甲氧羰基-氨基）丙酸（RO3244794）对介导趋化因子释放抑制的受体的亲和力约为对同时介导两种转录输出的受体的亲和力低 10 倍。最后，针对 IP 受体基因（PTGIR）的小干扰 RNA 未能阻断 taprostene 和 15-去氧-TIC 诱导的趋化因子释放抑制，而 taprostene 和 iloprost 诱导的转录反应则明显减弱。总之，这些结果表明，PGI2、taprostene 和 15-去氧-TIC 通过与我们在此称为“IP（2）”亚型的新型 IP 受体相互作用来抑制 BEAS-2B 细胞中趋化因子的释放。
