Endothelial Cell Deubiquitinase A20 Signals Repair of Lung Vascular Injury

 描述（由申请人提供）：急性肺损伤（ALI）是一种复杂的炎性疾病，与肺血管通透性增加、富含蛋白质的水肿液形成以及肺组织和空气中炎性细胞浸润相关。肺血管内皮粘附连接（AJs）的重组是急性炎症性肺损伤（ALI）的重要因素。血管内皮（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AJs重组的信号转导机制知之甚少。我们已经在内皮细胞（EC）限制性A20（Tnfaip 3）敲除（A20ΔEC）小鼠的遗传模型中确定了A20的泛素编辑功能在调节AJs的VE-钙粘蛋白和VE-PTP表达中的新作用。我们进行了以下关键观察（支持性数据）：（i）A20ΔEC小鼠显示AJs处VE-钙粘蛋白和VE-PTP的表达显著降低;（ii）内毒素激发后A20ΔEC小鼠AJs处VE-钙粘蛋白和VE-PTP的表达未恢复;（iii）内毒素激发后A20 ΔEC小鼠显示持续的脯氨酰羟化酶2（PHD 2）表达和缺陷的HIF 2 α表达。基于这些新的观察结果，在目标1中，我们将检验以下假设：肺EC中TLR 4信号传导下游的A20表达促进VE-钙粘蛋白在AJs的隔离，因此是稳定内皮屏障和促进肺损伤消退的中心反馈机制。在目的2中，我们将检验以下假设：EC表达的A20通过下调PHD 2以稳定HIF 2 α并转录调节VE-PTP表达以加强AJs的VE-钙粘蛋白功能，在炎性肺损伤中起到促消退作用。随着对肺内皮细胞中A20功能的信号传导机制的更好理解，我们将能够确定可以靶向A20功能的治疗策略， 从而恢复内皮屏障完整性以解决炎性肺损伤。

 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.