核受体LXR下调ET-1表达的分子机制及其在抗肺动脉高压中的作用研究

Pulmonary arterial hypertension (PAH) constitutes a heterogeneous group of clinical entities sharing similar pathologies with limited therapeutic options, and endothelin-1 (ET-1) in endothelial cells has been shown to one of the critical factors in the development of PAH. Therefore, manipulating ET-1 expression would be important and effective for treating these diseases. Our group has found that one of the nuclear receptors, liver X receptor (LXR), could significantly decrease the expression of ET-1 in endothelial cells. However, the mechanism underlying the effect remains unclear. Based on our preliminary studies and reports by others, we hypothesize that activation of LXR downregulates ET-1 by suppressing activator protein-1 (AP-1) at levels of mRNA expression, protein expression and transcriptional activities in endothelial cells. This study aims at understanding the mechanism via a series of experiments including site mutation, luciferase activity assay, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation assay (ChIP). Furthermore, we establish a rat model of PAH induced by monocrotatine (MCT)to observe the effect on ET-1 expression and the development of PAH after interfering with LXR－ET-1 signaling pathway. This study provides a solid theoretical support for exploring LXR as a potential molecular target, which may lead to better manipulation of PAH.

肺动脉高压（PAH）是一组治疗途径和治疗药物都十分有限的严重疾患，而血管内皮细胞过度生成的内皮素-1(ET-1)是加剧PAH形成的关键分子，因此有效抑制ET-1的表达对治疗PAH具有重要意义。本课题组前期研究发现核受体家族中的肝X受体（LXR）被激活后可显著下调血管内皮细胞中ET-1的表达，但具体机制不明。结合预实验和文献分析，我们提出LXR下调血管内皮细胞ET-1表达的可能机制是：LXR通过影响转录因子AP-1的表达和转录活性进而下调血管内皮细胞中ET-1的表达。本课题拟采用点突变、报告基因检测、凝胶迁移实验和染色质免疫沉淀等方法深入解析该机制；然后再利用PAH的大鼠模型观察LXR对ET-1表达水平及PAH进程的影响，从而揭示LXR-ET-1通路的抗PAH作用。本研究将为探索以LXR为靶点的、防治PAH的新思路提供有力的理论依据。

肺动脉高压（PAH）是一组治疗途径和治疗药物都十分有限的严重疾患，而血管内皮细胞过度生成的内皮素-1(ET-1)是加剧PAH形成的关键分子，因此有效抑制ET-1的表达对治疗PAH具有重要意义。本课题组前期研究发现核受体家族中的肝X受体（LXR）被激活后可显著下调血管内皮细胞中ET-1的表达，但具体机制不明。本课题采用点突变、报告基因检测、凝胶迁移实验（EMSA）和染色质免疫沉淀（CHIP）等方法深入解析该机制；并用PAH模型观察LXR对ET-1表达水平及PAH组织形态的影响，从而揭示LXR/ET-1通路的抗PAH作用。结果发现：（1）LXR激活可显著降低LPS诱导的C57BL/6J小鼠ET-1血清中蛋白分泌水平；（2）LXR显著抑制人血管内皮细胞中ET-1的mRNA和蛋白表达；（3）LXR通过影响ET-1基因的启动子区域转录因子AP-1/NF-κB的表达和转录活性进而下调血管内皮细胞中ET-1的表达。本研究为探索以LXR 为靶点防治ET-1异常表达所致疾病的新思路提供有力的理论依据。