Endothelial Cell Deubiquitinase A20 Signals Repair of Lung Vascular Injury

 描述(申请人提供)：急性肺损伤(ALI)是一种复杂的炎症性疾病，与肺血管通透性增加，形成富含蛋白质的水肿液，以及肺组织和空隙内的炎细胞渗透有关。肺血管内皮细胞黏附连接(AJs)的重组是急性炎症性肺损伤缓解的关键因素。血管内皮细胞(VE)-钙粘蛋白和相互作用的内皮蛋白酪氨酸磷酸酶(VE-PTP)在AJs的表达对内皮屏障的完整性至关重要。然而，介导内皮细胞AJ重组的信号机制却知之甚少。我们在内皮细胞限制性A20(TnFAIP3)基因敲除小鼠(A20ΔEC)的遗传模型中发现，A20的泛素编辑功能在调节AJs的VE-钙粘蛋白和VE-PTP表达方面具有新的作用。我们做了以下关键观察(支持数据)：(I)A20ΔEC小鼠AJ处VE-钙粘附素和VE-PtP的表达显著降低；(Ii)A20ΔEC小鼠内毒素攻击后AJ的VE-钙粘附素和VE-Ptp表达未恢复；(Iii)A20ΔEC小鼠内毒素攻击后持续表达Pro-2，且HIF2α表达缺陷。基于这些新的观察结果，在目标1中，我们将检验一种假设，即TLR4信号下游的肺内皮细胞中A20的表达促进了VE-钙粘蛋白在AJs的滞留，从而是稳定内皮屏障和促进肺损伤缓解的中枢反馈机制。在目标2中，我们将通过下调PHD2以稳定HIF2α并在转录上调节VE-PTP的表达从而增强AJs的VE-钙粘附素功能，来验证EC表达的A20在炎性肺损伤中起促进消解作用的假设。随着对A20功能在肺内皮细胞中的信号机制的更好的理解，我们将能够确定针对A20功能和 从而恢复内皮屏障的完整性，化解炎症性肺损伤。

 DESCRIPTION (provided by applicant): Acute lung injury (ALI) is a complex inflammatory disease associated with increased lung vascular permeability and formation of protein-rich edema fluid and an infiltration of inflammatory cells in lung tissue and airspace. Reassembly of lung vascular endothelial adherens junctions (AJs) is a critical factor contributing to resolution f acute inflammatory lung injury. Expression of vascular endothelial (VE)-cadherin and the interacting endothelial protein tyrosine phosphatase (VE-PTP) at AJs is vital for endothelial barrier integrity. However, the signaling mechanisms that mediate the reassembly of endothelial AJs are poorly understood. We have identified in a genetic model of endothelial cell (EC)-restricted A20 (Tnfaip3) knockout (A20ΔEC) mice, the novel role of the ubiquitin editing function of A20 in regulating expression of VE-cadherin and VE-PTP at AJs. We made the following key observations (Supporting Data): (i) A20ΔEC mice displayed markedly reduced expression of VE- cadherin and VE-PTP at AJs; (ii) VE-cadherin and VE-PTP expression was not restored at AJs of A20ΔEC mice after endotoxin challenge; (iii) A20ΔEC mice showed persistent prolyl hydroxylase 2 (PHD2) expression and defective HIF2α expression post-endotoxin challenge. Based on these novel observations, in Aim 1, we will test the hypothesis that expression of A20 in lung ECs, downstream of TLR4 signaling, promotes the sequestration of VE-cadherin at AJs, and thus is a central feedback mechanism for stabilizing endothelial barrier and promoting resolution of lung injury. In Aim 2, we will test the hypothesis that EC-expressed A20 serves a pro-resolution function in inflammatory lung injury by down-regulating PHD2 to stabilize HIF2α and transcriptionally regulating VE-PTP expression so as to strengthen VE-cadherin function at AJs. With a better understanding of the signaling mechanisms of A20 function in lung endothelial cells, we will be in a position to identify therapeutic strategies that can target A20 function and thereby restore endothelial barrier integrity to resolve inflammatory lung injury.