Biopharmaceutical Research on Prostaglandin Receptors

(1)前列腺素受体EPS：EP3介导的新的信号转导途径与GI活性、腺苷环化酶抑制有关。EP3有多种不同的异构体，它们的C末端结构和激动剂依赖的GI活性不同。我们发现，在COS-7细胞中表达的EP3受体以激动剂依赖的方式表现出其他受体刺激的Gs活性的增强。百日咳毒素对EP3受体激活Gs的作用不受影响，提示这种激活不是由Gi介导的。在任何类型的小鼠EPS受体亚型中都可以观察到EP3激动剂依赖的Gs的过度激活，而与EP3受体的C-末端结构无关。这种EP3信号可能反映了PGE2生理功能的某些方面，如痛觉。(2)利用每个受体亚型缺陷小鼠阐明PGE2的生理作用：我们发现EP2缺乏在APC KO小鼠的肠息肉形成数量和大小上都有所减少。野生型小鼠肠息肉组织中COX-2、EP2和血管内皮生长因子表达加速，而EP2和APE双基因敲除小鼠肠息肉组织中COX-2和VEGF表达较弱，提示COX-2和EP2之间存在正反馈调节。我们将葡萄糖转硫酸盐(DSS)诱导的结肠炎模型引入EP缺陷小鼠。结果，只有EP4基因缺陷的小鼠在3%的DSS治疗下表现出严重的结肠炎，而在野生型小鼠中没有引起明显的结肠炎。EP4被证明可以促进上皮再生，抑制白细胞和淋巴细胞的激活。我们进一步发现，与野生型小鼠相比，EPS缺陷小鼠的出血倾向增加，对花生四烯酸诱导的血栓栓塞症的易感性降低。EPS可能通过增加细胞内钙离子和/或降低cAMP水平来增强TP诱导的血小板聚集。

(1) The new signal transaction pathway exerted by prostanoid receptor EPS : EP3 has been shown to be coupled to Gi activity, inhibition of adenylate cyclase. EP3 has multiple isoforms that are different in their C-terminal structure and in their agonist-dependent Gi activity. We found that EP3 receptors expressed in COS-7 cells showed augmentation of other receptor-stimulated Gs activity in an agonist-dependent manner. The superactivatipn of Gs by EP3 receptors was not affected by the treatment of pertussis toxin, suggesting that the superactivation is not Gi-mediated. The EP3 agonist-dependent supeactivation of Gs is observed in any type of mouse EPS receptor isoforms, irrespective of C-termnal structure of EP3 receptor. This EP3 signaling may reflect some aspects of the physiological function of PGE2, such as pain sensation.(2) Elucidation of physiological roles of PGE2 by using each receptor subtype-deficient mice : We found that EP2 deficiency attenuated intestinal polyp formation both in number and size in Apc KO mice. We also showed acceleration of COX-2, EP2 and VEGF expression in the intestinal polyps of wild-type mice, but faint expression of COX-2 or VEGF in those of EP2 and Ape double-knockout mice, suggesting that there exists positive feedback regulation between COX-2 and EP2. We introduced dextransulfate (DSS)-induced colitis model into EP-deficient mice. As a result, only EP4-deficient mice showed severe colitis upon 3%DSS treatment that did not induce significant colitisin wild-type mice. EP4 has been shown to promote epithelial regeneration and to inhibit activation ofleukocytes and lymphocytes. We further found that EPS-deficient mice showed increased bleeding tendency and decreased susceptibility to arachidonate-induced thromboembolism compared with wild-type mice. EPS appears to potentiate TP-induced platelet aggregation by increasing intracellular Ca2+ and/or decreasing cAMP level.