Millar Michelle Warren, Najar Rauf A, Slavin Spencer A, Shadab Mohammad, Tahir Imran, Mahamed Zahra, Lin Xin, Abe Jun-Ichi, Wright Terry W, Dean David A, Fazal Fabeha, Rahman Arshad
Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA.
Department of Cardiology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
J Biol Chem. 2024 Dec;300(12):107952. doi: 10.1016/j.jbc.2024.107952. Epub 2024 Nov 6.
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 complementary DNA, 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.
内皮细胞的功能和结构完整性对于血管稳态至关重要。静止内皮细胞屏障功能的丧失以及增殖内皮细胞迁移能力的丧失会导致血管通透性亢进，这是包括急性肺损伤（ALI）在内的许多炎症性疾病的一个主要特征。然而，调控这些内皮细胞基本功能的信号却知之甚少。在此，我们确定雷帕霉素的机制性靶点（MTOR）是维持内皮细胞屏障完整性、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。内皮细胞中MTOR的敲低改变了细胞形态，损害了增殖和迁移能力，并增加了细胞表面血管内皮（VE）-钙黏蛋白的内吞作用，导致屏障功能破坏。MTOR缺失的内皮细胞还表现出部分由自噬介导的VE-钙黏蛋白和血管内皮生长因子受体2（VEGFR2）水平降低。同样，具有内皮细胞特异性MTOR缺陷的小鼠肺脏表现出自发性血管渗漏，其特征是VE-钙黏蛋白和VEGFR2水平降低，这表明内皮细胞中的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，在受伤的小鼠肺脏或内皮细胞中，MTOR以及VEGFR2和VE-钙黏蛋白水平均显著降低。重要的是，无论是预防性还是治疗性地进行内皮细胞靶向的MTOR互补DNA基因转移，均可减轻炎症性肺损伤，并改善ALI小鼠模型的肺功能和存活率。这些发现揭示了MTOR在维持内皮细胞功能中的重要作用，确定内皮MTOR的缺失是肺血管损伤的关键机制，并显示了内皮细胞靶向MTOR表达在对抗小鼠ALI和死亡率方面的治疗潜力。
