Inflammatory Angiogenesis in the Lung

 描述(申请人提供)：有缺陷的肺微血管分支是支气管肺发育不良(BPD)的标志，这是一种在早产儿中发展起来的肺部疾病。尽管临床研究证实脓毒症是BPD的主要危险因素，但脓毒症促进肺血管重构的机制仍然知之甚少。我们实验室以前的工作表明，脓毒症期间释放的细菌配体，如脂多糖(LPS)，会引起内皮免疫激活；从“静止”的内皮表型转变为“炎症”的内皮表型。这项应用的首要目标是了解脓毒症诱导的肺内皮细胞免疫激活促进炎症和发育中肺血管生成改变的机制。正在进行的研究表明，NADPH氧化酶2(NOX2)是一种属于NOX家族的氧化还原酶，它调节内毒素诱导的肺内皮细胞免疫激活。NOX2介导的内皮激活通过诱导细胞间黏附分子-1(ICAM-1)和细胞因子的表达而促进肺炎症。此外，NOX2还调节脓毒症诱导的肺血管生成素-2(ANGPT2)的表达，从而刺激血管生成。有趣的是，在我们的脓毒症小鼠模型中，NOX2-/-小鼠的肺内皮细胞激活和炎症受到抑制。这些初步数据支持内皮NOX2在调节脓毒症诱导的肺促炎症血管生成信号中的关键作用，这一点在AIM 1中进行了研究。脂多糖介导的ANGPT2信号通过其受体TIE2在人肺内皮细胞中介导自分泌血管生成。此外，ANGPT2信号通过TIE2在体外诱导顶端细胞内皮细胞规范标记如Delta-like 4(DLL4)优先于茎细胞规范标记Jagge-1(JAG1)的表达。在新生小鼠中，败血症强烈地诱导肺组织表达DLL4和KDR(血管内皮生长因子受体)。此外，败血症还会在发育中的视网膜中编程异常的血管生成。这些数据为ANGPT2调节败血症诱导的新生肺血管生成的机制提供了新的见解；这也是我们在AIM 2中研究的重点。鉴于这些初步结果，我们假设“内皮NOX2调节败血症诱导的肺部炎症和ANGPT2的表达，从而通过调节DLL4-Notch尖端与柄细胞的发育来指导新生儿肺内血管生成的改变”。这一假说将在以下特定目的的实验中得到解决：1)研究内皮细胞NOX2是否调节脓毒症时肺内皮细胞的免疫激活和炎症；以及2)确定脓毒症诱导的ANGPT2在DLL4-Notch介导的肺血管生成中的作用。我们预计，拟议的研究将确定内皮细胞NOX2和ANGPT2是调节败血症诱导的炎症和新生儿肺内血管生成变化的关键分子。我们对内皮NOX2信号，ANGPT2导向的血管生成的理解也有望取得重大进展，这将为未来减少早产儿BPD负担的治疗策略提供参考。

 DESCRIPTION (provided by applicant): Defective lung microvascular arborization is a hallmark of bronchopulmonary dysplasia (BPD), a lung disease that develops in premature infants. Although clinical studies identify sepsis as a major risk-factor for BPD the mechanisms by which sepsis contributes to pulmonary vascular remodeling remain poorly understood. Prior work from our laboratory indicate that bacterial ligands like lipopolysaccharide (LPS) released during sepsis cause endothelial immune activation; a switch from a "quiescent" to an "inflammatory" endothelial phenotype. The overarching goal of this application is to understand the mechanisms by which sepsis-induced pulmonary endothelial immune activation contributes to inflammation and altered angiogenesis in the developing lung. Ongoing studies suggest that NADPH oxidase 2 (NOX2), an oxidoreductase enzyme belonging to the NOX family regulates LPS-induced lung endothelial immune activation. NOX2-mediated endothelial activation promotes lung inflammation by inducing intercellular adhesion molecule-1 (ICAM-1) and cytokine expression. Further, NOX2 also regulates sepsis-induced lung Angiopoietin-2 (ANGPT2) expression, which stimulates angiogenesis. Interestingly, in our mouse model of sepsis lung endothelial activation and inflammation are suppressed in NOX2-/- mice. These pilot data support a key role for endothelial NOX2 in regulating sepsis- induced lung pro-inflammatory angiogenic signaling, which is examined in Aim 1. LPS-mediated ANGPT2 signaling mediates autocrine angiogenesis through its receptor TIE2 in human lung endothelial cells. Further, ANGPT2 signaling through TIE2 induces expression of tip cell endothelial specification markers such as Delta- Like 4 (DLL4) preferentially over stalk cell specification markers like Jagged-1 (JAG1) in vitro. In neonatal mice sepsis robustly induces lung expression of DLL4 and KDR (VEGF receptor). Further, sepsis also programs aberrant angiogenesis in the developing retina. These data provide new insights into the mechanisms by which ANGPT2 regulates sepsis-induced angiogenesis in the neonatal lung; the focus of our studies in Aim 2. Given these preliminary results, we hypothesize that "endothelial NOX2 regulates sepsis-induced lung inflammation and ANGPT2 expression, which directs altered angiogenesis in the neonatal lung by modulating the DLL4-Notch tip vs. stalk cell development ". This hypothesis will be addressed in the experiments of the following Specific Aims: 1) Investigate whether endothelial NOX2 regulates lung endothelial immune activation and inflammation in sepsis; and 2) Determine the role of sepsis-induced ANGPT2 on DLL4-Notch directed lung angiogenesis. We expect that proposed studies will identify endothelial NOX2 and ANGPT2 as key molecular players regulating sepsis-induced inflammation and altered angiogenesis in the neonatal lung. Significant gains in our understanding of endothelial NOX2 signaling, ANGPT2-directed angiogenesis are also anticipated, which will inform future therapeutic strategies to decrease BPD burden in premature infants.