LOX-1在低氧诱导肺动脉高压血管重构中的作用及机制研究

Pulmonary arterial hypertension（PAH）is characterized by hyperproliferation of pulmonary artery smooth muscle cells (PASMCs) within the vascular wall of the resistant pulmonary arteries, leading to vascular lumen occlusion. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), a multifunctional receptor, plays critical roles in multiple signal transduction pathways and is involved in the genesis and development of multiple cardiovascular diseases. However, the role of LOX-1 in vascular remodeling in PAH remains unknown. Our pilot study showed that the expression of LOX-1 mRNA and protein was up-regulated in pulmonary arteries in hypoxia-induced PAH rats, and the LOX-1-neutralizing antibody TS-20 significantly inhibited proliferation of primary cultured PASMCs induced by hypoxia. We will be planning to explore the important/potential role of LOX-1 in mediating the pulmonary vascular remodeling in PAH rats and the proliferation of primary cultured rat PASMCs. Furthermore, we will investigate the underlying mechanisms responsible for the up-regulation of LOX-1 in pulmonary arteries in hypoxia-induced PAH rats (focusing on positive feedback regulation between microRNA let-7g and LOX-1) and the downstream signaling of LOX-1 that LOX-1 promotes vascular remodeling (focusing on LOX-1/Calpain/pElk-1-MRTF-A/SRF/c-fos pathway). This study will contribute to the understanding of the pathogenesis of PAH, and provide new strategies to seek for the new drugs directing at LOX-1 target.

肺动脉高压（PAH）的主要病因是肺血管重构导致肺动脉腔隙狭窄。植物凝集素样氧化性低密度脂蛋白受体-1（LOX-1）是一种多配体受体，介导多种信号通路，在多种心血管疾病的发生与发展中起重要作用。然而，LOX-1是否参与PAH 时肺血管重构尚不清楚。我们的预实验发现，低氧诱导的PAH大鼠肺动脉LOX-1 mRNA和蛋白表达增高；LOX-1中和抗体TS-20能显著抑制低氧诱导的原代肺动脉平滑肌细胞增殖。本项目拟通过在体动物与细胞实验，查明LOX-1在PAH肺血管重构发生过程中的重要作用，在此基础上，在体动物与细胞实验相结合，探讨PAH发病过程中上调LOX-1的机制（miR-let-7g-LOX-1的正反馈调节）以及LOX-1促血管重构的机制（LOX-1/Calpain/pElk-1-MRTF-A/SRF/c-fos信号通路）。本项目将有助于阐明PAH的发病机制，为寻找防治PAH的新靶点奠定基础。

肺动脉高压（PAH）的主要病因是肺小动脉原发病变而导致肺动脉阻力增加，最终可导致患者右心衰竭而死亡。PAH时肺动脉阻力增高的主要原因是肺血管重构导致肺动脉腔隙狭窄，而肺动脉平滑肌细胞（PASMCs）的过度增殖是引起血管重构的关键因素。凝集素样氧化性低密度脂蛋白受体-1（LOX-1）在多种心血管疾病的发生与发展中起重要作用。LOX-1通过氧化应激和促炎机制损伤血管内皮细胞，促进心肌细胞和血管平滑肌细胞增殖从而介导心脏、胸主动脉和肾血管重构。LOX-1在培养的慢性栓塞性肺动脉高压患者PASMCs中表达增加，可能介导C反应蛋白所诱导的PASMCs增殖。但LOX-1在低氧PAH血管重构中的作用及机制目前仍不清楚。因此，本研究拟在低氧诱导的PAH大鼠模型及原代PASMCs模型，探讨LOX-1是否介导低氧诱导PAH肺血管重构，并进一步探讨该作用是否与其促PASMCs增殖有关以及作用机制。.结果发现：（1）低氧诱导PAH大鼠肺动脉显著重构以及肺动脉中LOX-1 mRNA和蛋白表达显著增加。（2）低氧可促进PASMCs增殖，诱导LOX-1表达；LOX-1中和抗体及LOX-1 siRNA可显著抑制低氧引起的PASMCs增殖。（3）低氧诱导PAH大鼠肺动脉和PASMCs中let-7g mRNA表达显著降低，let-7g mimic可显著降低低氧诱导的PASMCs增殖和LOX-1表达上调；抑制LOX-1可显著逆转低氧引起的let-7g 表达下调，LOX-1与let-7g之间存在着反馈调节。（4）低氧引起PASMCs中LOX-1表达上调的上游机制为LOX-1-calpains-PKC-OCT-1-let-7g-LOX-1反馈调节通路。（5）LOX-1介导低氧诱导PASMCs增殖的下游通路可能为LOX-1- ERK1/2-pElk/MRTF-A-SRF-c-fos信号通路。.本项目主要阐明了内源性LOX-1在低氧诱导大鼠PAH时介导肺血管重构的作用和分子机制，将有助于阐明PAH的发病机制，为寻找防治PAH的新靶点奠定实验和理论基础。