Biopharmaceutical Research on Prostaglandin Receptors

(1)前列腺素受体EPS的信号通路：EP3与Gi活性偶联，抑制腺苷酸环化酶。EP3有多种异构体，它们的c端结构和激动剂依赖性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增强了其他受体刺激的Gs活性。EP3受体对Gs的超激活不受百日咳毒素处理的影响，提示这种超激活不是由gi介导的。无论EP3受体的c端结构如何，在任何类型的小鼠EPS受体亚型中都观察到Gs依赖于EP3激动剂的超激活。这种EP3信号可能反映了PGE2生理功能的某些方面，如痛觉。(2)利用各受体亚型缺乏小鼠阐明PGE2的生理作用：我们发现EP2缺乏在Apc KO小鼠中减少了肠息肉的形成数量和大小。我们还发现野生型小鼠肠息肉中COX-2、EP2和VEGF表达加快，而EP2和Ape双敲除小鼠肠息肉中COX-2和VEGF表达微弱，提示COX-2和EP2之间存在正反馈调节。我们将dextransulfate （DSS）诱导的结肠炎模型引入ep缺陷小鼠。结果，只有ep4缺陷小鼠在3%DSS处理后出现严重结肠炎，而野生型小鼠没有明显的结肠炎。EP4已被证明能促进上皮细胞再生并抑制白细胞和淋巴细胞的活化。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，对花生四烯酯诱导的血栓栓塞的易感性降低。EPS似乎通过增加细胞内Ca2+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.