Bexarotene靶向睾丸孤核受体4治疗库欣病的分子机制研究

Cushing’s disease (CD) represents one kind of rare diseases which seriously affect the life quality of patients. Its treatment depends mainly on surgery and drug efficacy is very poor, thus it is a big threat to patients who can not undergo surgery. The testicular nuclear receptor 4 (TR4) was identified to be a new target for treatment of CD in recent years, however, TR4 lacks effective inhibitors currently. Our previous study revealed that bexarotene could inhibit TR4 via decreasing the TR4 nuclear localization, and lead to inhibition of its downstream POMC expression and ACTH secretion, indicating its potential roles in treatment of CD. Our study aims to make a comprehensive evaluation of bexarotene for treatment of CD, and to clarify the detailed mechanism of targeted suppression of TR4 by bexarotene via investigating the influence of bexarotene on: (1) the TR4 subcellular distribution mediated by the nuclear localization signal or nuclear export signals; (2) the interaction between TR4 and co-regulators; (3) the affinity of TR4 to its response element. This study will provide theoretical guidance and experimental basis for the application of bexarotene in treatment of CD, and provide guidance for the development of novel CD drugs.

库欣病是严重影响生活质量的罕见病，其治疗主要依赖于手术，药物疗效不佳，故对无法实施手术的患者构成了严重威胁。睾丸孤核受体4（TR4）是近年来发现的库欣病潜在治疗靶点，但目前缺乏有效的TR4抑制剂。前期工作中我们发现抗癌药物bexarotene可能通过减少核定位TR4抑制TR4功能，从而抑制TR4下游POMC表达及ACTH分泌，对库欣病具有潜在的治疗作用。本课题拟在此基础上从分子、细胞及整体动物水平综合评价bexarotene对库欣病的疗效，通过研究bexarotene对：①核定位信号或核输出信号介导的TR4亚细胞分布、②TR4与共调节因子相互作用、③TR4与其应答原件相互结合等的影响，阐明bexarotene靶向调控TR4抑制其功能从而治疗库欣病的具体机制。此项研究的顺利完成将为bexarotene应用于库欣病的治疗奠定理论基础，并为库欣病药物的开发提供新思路。

库欣病是严重影响生活质量的罕见病，其治疗依赖于手术，药物疗效不佳，故对无法实施手术的患者构成了严重威胁。睾丸孤核受体 4（TR4）是近年来发现的库欣病治疗新靶点，但是目前缺乏有效的 TR4 抑制剂。本课题通过建立TR4的活性结构模型，并运用虚拟筛选结合双荧光素酶报告基因测试得到了一种新的TR4抑制剂-bexarotene。研究结果显示Bexarotene可以直接与TR4配体结合域(TR4- LBD)相互作用，引起TR4-LBD二级结构的构象变化。Bexarotene可抑制垂体腺瘤细胞AtT-20生长，前促黑激素(POMC)表达和促肾上腺皮质激素(ACTH)分泌。机制分析表明，bexarotene可通过促进TR4滞留在胞浆，导致TR4与POMC 启动子区TR4响应元件(TR4RE)的结合减少，从而抑制POMC的转录。 裸鼠荷瘤模型的结果显示，口服bexarotene能显著抑制ACTH分泌腺瘤的生长，抑制裸鼠ACTH和皮质酮的分泌，并缓解库欣病所致的肾上腺增大以及腹部脂肪堆积。 本项目研究结果提示bexarotene是一种潜在的库欣病治疗药物。本项目共计发表SCI期刊论文5篇，并获授权国家发明专利1项，参与国际学术交流2次，相关成果在会议做报告发言1次。

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