新的血管活性肽salusinβ对血管平滑肌细胞PPARγ表达的影响及调控机制研究

Recently, salusinβ, a new bioactive peptide may contributes to the pathogenesis of atherosclerosis, restenosis and related cardiovascular diseases. The proliferation of vascular smooth muscle cells (VSMCs) is an important pathogenetic factor of vascular disorders such as atherosclerosis and restenosis. It has been confirmed that salusinβ potently stimulates the proliferation of quiescent VSMCs. Peroxisome proliferator activated receptor-γ (PPARγ) is an important transcription factor which has an anti-proliferative effect on VSMCs. The result of our pilot experiment showed that salusinβ could directly inhibit PPARγ expression in VSMCs. The aim of the present study is to examine the effect of salusinβ on PPARγ gene expression and elucidate the underlying mechanisms in VSMCs by using gene silencing, transient transfection approach, western blotting analysis, real-time PCR and chromatin immunoprecipitation assays. Based on the fact that MAPKs（ERK1/2、JNK、p38MAPK）and PI3K/Akt are the major kinases responsible for cell proliferation, and NCoR, SMRT and HDACs are major corepressors for PPARγ, underlying mechanisms will be focused on the effect of salusin β - activated signaling pathways on corepressors for PPARγ, and the relationship with the gene expression of PPARγ. These ?ndings will provide the molecular basis for our understanding of the salusinβ and its impact on cardiovascular diseases, which will be a therapeutic target for the prevention of atherosclerotic cardiovascular diseases.

研究表明新的血管活性肽salusinβ与动脉粥样硬化、血管再狭窄等心血管疾病的病理过程密切相关。血管平滑肌细胞（VSMCs）增殖是此类疾病的共同病理基础。具有致动脉粥样硬化作用的salusinβ能显著刺激VSMCs增殖。已发现PPARγ为抑制VSMCs增殖的重要转录因子。我们前期实验结果表明salusinβ抑制VSMCs中PPARγ表达。本项目旨在初步实验基础上，利用基因沉默、转染、蛋白印迹、PCR及染色质免疫共沉淀等技术揭示salusinβ对VSMCs中PPARγ表达的影响及其调控机制。而调控机制的研究基于VSMCs 主要增殖信号途径MAPKs、PI3K/Akt以及PPARγ核辅助抑制因子NCoR、SMRT、 HDACs，揭示salusin β所激活的增殖信号途径对核辅助抑制因子表达的影响，以及与PPARγ表达的关系。从而为salusinβ作为心血管疾病治疗的一个新的靶点提供分子基础。

研究表明新的血管活性肽salusin β具有致动脉粥样硬化作用。在参与动脉粥样硬化调节的诸多分子中PPARγ的作用十分引人注目。PPARγ通过参与调节炎症、调控血管平滑肌细胞（VSMCs）的增殖、泡沫细胞的形成等多个方面影响动脉粥样硬化的发生和发展。本研究旨在揭示salusin β对PPARγ的调控作用及相关分子机制。我们的研究结果表明salusin β能显著刺激VSMCs增殖，促进细胞周期进程和致炎作用。salusin β在蛋白、mRNA和基因启动子水平抑制PPARγ的表达。且salusin-β对VSMCs促增殖和致炎作用与salusin β抑制PPARγ表达相关。结果显示在VSMCs中salusin-β能激活ERK1/2、JNK、p38、AKT和IκBα信号通路，但对PPARγ抑制作用仅与IκBα信号通路相关。进一步研究表明， NF-κB p50 或 p65并未介导salusin β对PPARγ的抑制作用。Salusin β能诱导HDAC3核转位，沉默HDAC3基因能阻止salusin β对PPARγ的抑制作用。Salusin β诱导HDAC3核转位能显著被IκBα 抑制剂BAY 11-7085扭转。IκBα-HDAC3复合体存在于VSMCs包浆中，但给予salusin β后IκBα-HDAC3复合体消失。以上研究结果表明IκBα-HDAC3信号通路介导了salusin β对PPARγ表达的抑制作用。本项目研究表明在VSMCs中salusin β能显著抑制重要转录因子PPARγ表达，并揭示了其中相关的分子机制，为salusin β成为心血管疾病治疗的一个新的靶点提供分子基础。