Study on the clarification of molecular and pharmacological structure-activity relationships of 5-HT2A antagonists

在几种疾病的病理生理学中已经发现了产生结构性活性G蛋白偶联受体(GPCRs)的突变，这意味着结构性活性受体上的反向激动剂可能有更好的治疗应用。由于5-HT2a和gt；受体参与了多种心血管疾病的调节，5-HT2a和gt；受体的结构性活性突变可能与疾病状态有关。因此，本研究的目的是研究选择性5-羟色胺受体拮抗剂Sarpogrelate及其活性代谢物M-1的反向激动剂活性，并与其他5-羟色胺受体拮抗剂如利坦丝林、酮丝林和赛庚啶的活性进行比较。利用人5-羟色胺受体的结构性活性突变体(C322K)，我们证明了与其他5-羟色胺受体拮抗剂一样，Sarpogrelate通过显著降低基础肌醇磷酸(IP)水平而发挥强大的反向激动剂的作用。然而，Sarpogrelate与其他5-羟色胺受体拮抗剂的反向激动剂活性没有显著差异。与野生型受体相比，突变型受体对5-羟色胺具有较高的亲和力，而对血管紧张素受体的亲和力较低。这些结果表明，稳定5-羟色胺受体的非活性构象可能是其作用机制中的一个关键成分。

Mutations producing constitutively active G-protein coupled receptors (GPCRs) have been found in the pathophysiology of several diseases, implying that inverse agonists at the constitutively active receptors may have preferred therapeutic applications. Because of the involvement of 5-HT_<2A> receptors in mediating many cardiovascular diseases, constitutively active mutants of the 5-HT_<2A> receptor may be responsible for the disease states. Thus, the purpose of the present study was to investigate the inverse agonist activity of sarpogrelate, a selective 5-HT_<2A>-receptor antagonist, and its active metabolite, M-1; and we compared their activities with those of other 5-HT_<2A>-receptor antagonists such as ritanserin, ketanserin, and cyproheptadine. Using a constitutively active mutant (C322K) of the human 5-HT_<2A> receptor, we demonstrated that like other 5-HT_<2A>-receptor antagonists, sarpogrelate acts as a potent inverse agonist by significantly reducing basal inositol phosphate (IP) levels. However, there were no significant differences between sarpogrelate and other 5-HT_<2A>-receptor antagonists for their inverse agonist activity. Compared with the wild type receptor, mutant receptor displayed significantly higher affinity for 5-HT and lower affinity for sarpogrelate. These results indicate that stabilization of the inactive conformation of the 5-HT_<2A> receptor may be a key component of the mechanism of action of sarpogrelate.