BACKGROUND NGF-TrkA is well known to play a key role in propagating and sustaining pruritogenic signals, which form the pathology of chronic pruritus. Inhibition of NGF-TrkA is a known strategy for the treatment of pruritus. In the present paper, we describe the identification, in vitro characterization, structure-activity analysis, and inhibitory evaluation of a novel TrkA inhibitory scaffold exemplified by Cucurbitacins (Cus). METHODS Cus were identified as TrkA inhibitors in a large-scale kinase library screen. To obtain structural models of Cus as TrkA inhibitors, AutoDock was used to explore their binding to TrkA. Furthermore, PC12 cell culture systems have been used to study the effects of Cus and traditional Chinese medicinal plants (Tian Gua Di and bitter gourd leaf) extracts on the kinase activity of TrkA. RESULTS Cus block the phosphorylation of TrkA on several tyrosine sites, including Tyr490, Tyr674/675, and Tyr785, and inhibit downstream Akt and MAPK phosphorylation in response to NGF in PC12 cell model systems. Furthermore, traditional Chinese medicinal plants (Tian Gua Di and bitter gourd leaf) containing Cu extracts were shown to inhibit the phosphorylation of TrkA and Akt. These data reveal mechanisms, at least partly, of the anti-pruritus bioactivity of Cus. CONCLUSION Taken together, with the recent discovery of the important role of TrkA as a therapeutic target, Cus could be the basis for the design of improved TrkA kinase inhibitors, which could someday help treat pruritus.

中文翻译：

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葫芦素的鉴定和表征，葫芦素是一类新的小分子肌球蛋白受体激酶a抑制剂。

背景技术众所周知，NGF-TrkA在传播和维持形成慢性瘙痒病的致病性信号中起关键作用。NGF-TrkA的抑制是治疗瘙痒症的已知策略。在本文中，我们描述了以葫芦素（Cus）为代表的新型TrkA抑制性支架的鉴定，体外表征，结构活性分析和抑制性评价。方法在大规模的激酶文库筛选中，将Cus鉴定为TrkA抑制剂。为了获得Cus作为TrkA抑制剂的结构模型，使用AutoDock探索了它们与TrkA的结合。此外，PC12细胞培养系统已用于研究Cus和中药提取物（天瓜地和苦瓜叶）对TrkA激酶活性的影响。结果Cus阻断了Tyr490，Tyr674 / 675和Tyr785等多个酪氨酸位点上TrkA的磷酸化，并在PC12细胞模型系统中响应NGF抑制了下游Akt和MAPK磷酸化。此外，含有铜提取物的传统中草药植物（天瓜地和苦瓜叶）显示出可抑制TrkA和Akt的磷酸化。这些数据至少部分揭示了Cus的抗瘙痒生物活性的机制。结论结合最近发现的TrkA作为治疗靶标的重要作用，Cus可以作为设计改良TrkA激酶抑制剂的基础，该抑制剂有朝一日可以帮助治疗瘙痒症。并在PC12细胞模型系统中响应NGF抑制下游Akt和MAPK磷酸化。此外，含有铜提取物的传统中草药植物（天瓜地和苦瓜叶）显示出可抑制TrkA和Akt的磷酸化。这些数据至少部分揭示了Cus的抗瘙痒生物活性的机制。结论结合最近发现的TrkA作为治疗靶标的重要作用，Cus可以作为设计改良TrkA激酶抑制剂的基础，该抑制剂有朝一日可以帮助治疗瘙痒症。并在PC12细胞模型系统中响应NGF抑制下游Akt和MAPK磷酸化。此外，含有铜提取物的传统中草药植物（天瓜地和苦瓜叶）显示出可抑制TrkA和Akt的磷酸化。这些数据至少部分揭示了Cus的抗瘙痒生物活性的机制。结论结合最近发现的TrkA作为治疗靶标的重要作用，Cus可以作为设计改良TrkA激酶抑制剂的基础，该抑制剂有朝一日可以帮助治疗瘙痒症。