PEDF-p67LR通路介导内皮细胞连接稳定防治心肌无复流的机制研究

No-reflow is unlikely to be simply consequence of the extent of acute myocardial infarction (AMI), and contributes to inadequate myocardial perfusion of patients who receive recanalization therapy. Maintaining the integrity and function of the microvascular is the key to prevent no-reflow. It was previously believed that PEDF negatively regulated angiogenesis by via inducing endothelial cells apoptosis. But we identified PEDF could preserve microvascular interity and myocardial perfusion, inhibit hypoxia-induced VE-cadherin phosphorylation, and reduce endothelial gaps, suggesting that PEDF could maintain microvascular stability and diminish no-reflow in the early stage after AMI. 67LR is a receptor that mediates the anti-angiogenic activity of PEDF; the phosphorylation of 67LR is involved in cellular migration, proliferation and adhesion. However, we barely know the effect and mechanism about the phosphorylation of 67LR. Our recent data showed that hypoxia increased 67LR phosphorylation, but PEDF could play a role in inhibiting 67LR phosphorylation. On the basis of these findings, we propose the hypothesis that PEDF decreases VE-cadherin phosphorylation via inhibiting 67LR phosphorylation, thereby maintaining endothelial junction, and ultimately diminishes no-reflow and ameliorates myocardial perfusion. This project intends to study the mechanism that PEDF maintains microvascular stability and function via inhibiting 67LR phosphorylation in vitro and in vivo. The success of this project will provide a new insight of the 67LR phosphorylation. And PEDF could be a novel therapeutic target for recanalization after AMI.

急性心梗冠脉再通后发生无复流严重影响预后。稳定内皮连接是维持微血管结构功能，防治无复流的关键。传统观点认为PEDF发挥抑血管作用，但申请人最新研究发现PEDF能维持大鼠心梗早期血管结构并改善灌注；抑制缺氧引起的VE-cadherin磷酸化，维持内皮连接稳定，提示PEDF可作为血管稳定因子减少心肌无复流。67LR是内皮细胞的PEDF受体，介导PEDF抑血管新生。67LR磷酸化可引起内皮迁移。预实验发现缺氧内皮细胞中67LR磷酸化水平增高，PEDF可抑制67LR磷酸化，提示67LR磷酸化水平可能和PEDF稳定血管内皮作用有关。据此提出科学假说：PEDF通过抑制67LR磷酸化下调VE-cadherin磷酸化水平，稳定内皮连接，维持微血管结构功能，减少心肌无复流。本课题拟利用已构建的细胞和动物模型，研究PEDF-p67LR通路介导内皮连接稳定防治心肌无复流的机制，为临床提升冠脉再通效果开辟新途径。

心肌梗死后急性缺血缺氧引起的微血管内皮结构破坏和功能紊乱是造成无复流发生的关键因素。然而，无复流现象严重局限了经皮冠状动脉介入治疗的效果，限制了冠状动脉再通的治疗价值，并导致预后不良。因此，探索开发稳定血管内皮结构和功能的新型药物用于预防和治疗无复流是临床上亟待解决的问题。本项目旨在研究PEDF在减少无复流发生和改善AMI预后方面的药用价值并阐明相关的分子机制。本研究明确了PEDF可显著减少大鼠心梗冠脉再通后心肌无复流的发生；阐明了PEDF通过抑制LR磷酸化下调VE-cadherin位点Ser665磷酸化水平，抑制VE-cadherin的内吞，改善内皮粘附连接的稳定性，维持冠脉微血管结构和功能，进而发挥防治心肌无复流的作用。此外，我们的研究还发现缺氧诱导的LR磷酸化引起LR-TIMAP/PP1c复合物解离，导致内皮细胞VE-cadherin表达降低和内皮通透性的增加，并最终导致无复流的发生。本研究结果将有助于阐明PEDF在急性心梗初期作为血管稳定因子的作用机制，并有望为防治急性心梗冠脉再通后无复流提供新的治疗靶点。