The functional and structural integrity of the endothelium is essential for vascular homeostasis. Loss of barrier function in quiescent and migratory capacity in proliferative endothelium causes exuberant vascular permeability, a cardinal feature of many inflammatory diseases including acute lung injury (ALI). However, the signals governing these fundamental endothelial cell (EC) functions are poorly understood. Here, we identify mechanistic target of rapamycin (MTOR) as an important link in preserving the barrier integrity and migratory/angiogenic responses in EC and preventing lung vascular injury and mortality in mice. Knockdown of MTOR in EC altered cell morphology, impaired proliferation and migration, and increased endocytosis of cell surface vascular endothelial (VE)-cadherin leading to disrupted barrier function. MTOR-depleted EC also exhibited reduced VE-cadherin and vascular endothelial growth factor receptor-2 (VEGFR2) levels mediated in part by autophagy. Similarly, lungs from mice with EC-specific MTOR deficiency displayed spontaneous vascular leakage marked by decreased VE-cadherin and VEGFR2 levels, indicating that MTOR deficiency in EC is sufficient to disrupt lung vascular integrity and may be a key pathogenic mechanism of ALI. Indeed, MTOR as well as VEGFR2 and VE-cadherin levels were markedly reduced in injured mouse lungs or EC. Importantly, EC-targeted gene transfer of MTOR cDNA, either prophylactically or therapeutically, mitigated inflammatory lung injury, and improved lung function and survival in mouse models of ALI. These findings reveal an essential role of MTOR in maintaining EC function, identify loss of endothelial MTOR as a key mechanism of lung vascular injury, and show the therapeutic potential of EC-targeted MTOR expression in combating ALI and mortality in mice.

中文翻译：

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MTOR 维持内皮细胞完整性以限制肺血管损伤


内皮的功能和结构完整性对于血管稳态至关重要。增生性内皮细胞静止和迁移能力屏障功能的丧失导致血管通透性旺盛，这是包括急性肺损伤 （ALI） 在内的许多炎症性疾病的主要特征。然而，控制这些基本内皮细胞 （EC） 功能的信号知之甚少。在这里，我们确定了雷帕霉素 （MTOR） 的机制靶标是保持 EC 中屏障完整性和迁移/血管生成反应以及预防小鼠肺血管损伤和死亡的重要环节。EC 中 MTOR 的敲除改变了细胞形态，损害了增殖和迁移，并增加了细胞表面血管内皮 （VE） -钙粘蛋白的内吞作用，导致屏障功能中断。MTOR 耗尽的 EC 还表现出部分由自噬介导的 VE-钙粘蛋白和血管内皮生长因子受体 2 （VEGFR2） 水平降低。同样，EC 特异性 MTOR 缺陷小鼠的肺表现出自发性血管渗漏，其特征是 VE-钙粘蛋白和 VEGFR2 水平降低，表明 EC 中的 MTOR 缺陷足以破坏肺血管完整性，可能是 ALI 的关键致病机制。事实上，在受伤的小鼠肺或 EC 中，MTOR 以及 VEGFR2 和 VE-钙粘蛋白水平显着降低。重要的是，MTOR cDNA 的 EC 靶向基因转移，无论是预防性的还是治疗性的，都减轻了炎症性肺损伤，并改善了 ALI 小鼠模型的肺功能和存活率。 这些发现揭示了 MTOR 在维持 EC 功能中的重要作用，确定了内皮 MTOR 的缺失是肺血管损伤的关键机制，并显示了 EC 靶向 MTOR 表达在对抗小鼠 ALI 和死亡率方面的治疗潜力。