PGC-1α转基因兔抗动脉粥样硬化机制中miRNA调控作用的研究

MicroRNAs (miRNAs) are small noncoding RNAs post-transcripionally control gene expression in many pathogenic and physiological processes. In our previous study, the nuclear hormone receptor peroxisome proliferator-activated receptor-gamma (PPARγ) coactivator-1alpha (PGC-1α), which is a transcriptional co-activator involved in the regulation of cellular energy metabolism, showed atheroprotective effect. Recently, the transgenic rabbit which specifically express high level of PGC-1α in vascular smooth muscles has been successfully constructed. Consist with our expectation, this transgenic rabbit is resistant to high fat induced atherosclerotic lesion formation. By testing human atherosclerotic lesion, we surprisingly found that the expression of PGC-1α was increased, however, the protein level of PGC-1α was down-regulated, suggesting that miRNAs may involve in this process in terms of their function of posttranscriptional gene regulation. According to our plan, first, we are going to predict the miRNAs which may participate this process by microarray and bioinformatics analysis; secondly, the predicted miRNAs will be used on endothelial and vascular smooth muscle cells to identify whether they regulate the protein level of PGC-1α or not; last but not least, the confirmed miRNAs will be tested on PGC-1α transgenic rabbit to further investigate their function in atherosclerotic process. Here, we aim to identify miRNAs which could regulate PGC-1α in post-transcriptional level and this may comprise a promising strategy to combat atherosclerosis.

微小RNA（miRNA）是一种小的非编码RNA，它通过转录后修饰在多种病理生理过程中调控相关基因的表达。近期研究在细胞水平证明，转录共激活因子 PGC-1α具有抗动脉粥样硬化的作用。最近我们已基本成功构建了在血管平滑肌细胞中特异性表达高水平 PGC-1α的转基因兔子，该种转基因兔能够显著抵抗高脂诱导的动脉粥样硬化斑块形成。通过对人动脉硬化手术样本检测，我们发现 PGC-1α的mRNA升高，而蛋白表达却明显降低，基于miRNA对基因广泛的转录后调控作用，我们预测他们很可能参与了此过程。首先，我们将使用生物芯片以及生物信息方法预测可能参与这一过程的miRNA；第二，检测筛选出的miRNA是否能在细胞水平调控的PGC-1α的表达；第三，在转基因兔中验证miRNA对 PGC-1α抗动脉粥样硬化功能的影响。我们希望通过筛选转录后水平上调节 PGC-1α的miRNA对动脉粥样硬化的防治提供新的策略。

转录共激活因子PGC-1α作为线粒体功能的重要调控基因，分布于全身组织并参与多种生理过程及病理进程。迄今为止，大部分针对PGC-1α的研究尚集中在肝脏，骨骼肌，褐色脂肪及心肌等能量代谢最为旺盛的组织器官。根据我们的前期实验结果，为了阐明在动脉粥样硬化的发生发展过程中PGC-1α的作用，我们构建了血管特异性高表达PGC-1α的转基因兔，并结合收集的动脉粥样硬化病人的样本研究其可能的调控机制。在本项目中，我们证明在动脉粥样硬化过程中，血管中PGC-1α蛋白的表达显著降低，而在家兔血管中高表达PGC-1α能够有效抵抗高脂诱导的动脉粥样硬化斑块的形成。进一步研究发现，在该病理条件下，miR-19b和miR-221/222通过在内皮层直接下调PGC-1α蛋白的表达，影响线粒体的数量及功能，导致内皮细胞内ROS的累积以及细胞凋亡促进局部炎症反应，最终造成动脉粥样硬化的发生发展。该研究从转录水平和转录后调控水平进一步揭示了动脉粥样硬化的发生发展机制，为其预防和治疗提供新的理论依据和药物靶点。