基于RCT途径构建新型PPARγ/LXRα双靶点调血脂药物的研究

Reverse cholesterol transport (RCT) is the main and basic pathway by which excess cholesterol is transported from the macrophages back to the liver for clearance. The reduction of LDL-C level and the function improvement of HDL-C mediated cholesterol efflux and metabolism are expected to prevent lipidosis and atherosclerotic plaque formation, and fundamentally treat the dyslipidemia. According to the latest research advances in lipid homeostasis, co-activation of PPARγ and LXRα should accelerate cholesterol efflux more effectively than either one individually. Herein we innovatively suggest that PPARγ/LXRα dual agonist may be able to accelerate cholesterol efflux from macrophages, which is the rate-determining step of RCT, and enhance the RCT function synergistically via PPARγ-LXRα-ABC pathway. Previous studies from our group found that formononetin undecylenic ether synthesized in our laboratory upregulated PPARγ and LXRα in pre-adipocytes and exhibited obvious effects of lowering total cholesterol. In this research project, novel compounds will be creatively designed by using formononetin undecylenic ether as lead compound and PPARγ/LXRα as dual targets. New lipophilic fused-heterocycle or steroidal skeleton will be built to substitute for formononetin through “scaffold hopping” strategy. Under the guide of diversity-oriented synthesis, active functional groups which help to improve the affinity and selectivity of receptors will be introduced to the linkage part and the hydrophilic end of the target molecules in order to get drug-like compounds with PPARγ/LXRα dual agonism. Their bioactivities of accelerating cholesterol efflux and regulating lipid homeostasis will be evaluated in vitro and vivo. The molecular mechanism of promoting RCT and decreasing hepatic lipidosis via PPARγ/LXRα signaling pathway will also be explored.

胆固醇逆转运（RCT）是机体排出多余胆固醇的基本途径，实现下调LDL-C水平、同时提高HDL-C介导的胆固醇流出与代谢功能，有望从根本上调节血脂平衡，预防动脉粥样硬化斑块形成。依据同时激活PPARγ和LXRα，比激活单靶点更能加快胆固醇流出的脂代谢新进展，本项目提出PPARγ/LXRα双靶点药物的研究思路，基于RCT途径，通过PPARγ-LXRα-ABC信号通路协同作用，加速胆固醇流出与下游代谢，提高RCT功能。课题组前期合成的刺芒柄花素十一烯醚有较好的调血脂活性，对PPARγ和LXRα均有激活作用，在此基础上，针对双靶点，运用“骨架跃迁”的方法构建稠杂环或甾环等亲脂性母核，在连接链或亲水性末端引入能提高双靶点选择性的药效团，设计合成高亲和性双靶点分子，从细胞、动物和分子水平评价生物活性，获得调血脂活性和类药性好、副作用小的先导化合物，并探索通过RCT途径调节血脂、减少肝脂沉积的作用机制。

本项目前期合成的刺芒柄花素十一烯醚（Formononetin undecylenic ether, FUE）有一定调血脂活性，上调PPARγ和LXRα的mRNA表达，但其水溶性较差，且作用机制有待探索。由于胆固醇逆转运（RCT）是人体排出多余胆固醇的主要途径，PPARγ-LXRα-ABC是RCT的重要信号通路。因此，本项目提出PPARγ/LXRα双靶点药物的研究思路，有望通过协同作用提高RCT功能，加速胆固醇流出，抑制肝脂沉积。.本项目开展了以下研究工作并取得重要结果：（1） 以FUE为先导物，辅以CADD，基于PPARγ/LXRα双靶点，设计了兼具PPARγ激动剂和LXRα激动剂结构特征的新型化合物，共设计合成了橙酮、异噁唑、甾体、芳基叔胺等母核共12个系列142个全新结构化合物。（2）构建了双靶点调血脂化合物的活性筛选模型，通过前脂肪细胞3T3-L1、成脂肪细胞增殖抑制活性实验，HepG2细胞和巨噬细胞RAW264.7脂质蓄积抑制活性实验，筛选出甾体母核和芳基叔胺母核的双靶点活性化合物QZY323和B4，它们对RAW264.7细胞、HepG2细胞PPARγ、LXRα具有激活作用，能上调调血脂相关ABC蛋白的mRNA表现出表达的影响，探索了活性化合物通过激活RCT关键信号通路PPAR-LXRα-ABC抑制肝脂沉积、调节血脂的作用机制。（3）跟进药物研发前沿，开展了靶向降解HMGCR的调血脂PROTAC药物的探索性研究。其中，基于洛伐他汀（ lovastatin）和VHL配体VHL231设计的PROTAC 分子21c及其内酯前体分子21b，能诱导HepG2细胞中HMGCR降解。动物实验研究结果显示化合物21b经口服给药途径，在体内与HMGCR 、VHL 形成稳定的三元复合体，进一步代谢产生21c，对高胆固醇小鼠模型表现出良好的HMGCR 降解和调血脂作用。