Neurtophil Homeostasis and Lung Sequestration

描述(申请人提供)：炎症反应中性粒细胞从骨髓中的释放仍然知之甚少。包括成人呼吸窘迫综合征(ARDS)在内的许多中性粒细胞依赖型肺部疾病的特征是未成熟的中性粒细胞从骨髓释放到循环中。我们建议检验相关假说，以探索中性粒细胞释放对肺部炎症反应的基本机制。利用上一批赠款期间开发的新的体外骨髓培养系统，条件永生化和捕获特定发育阶段的新方法，体外骨髓显微镜和体内中性粒细胞在小鼠体内的运输，我们将(1)确定A4？1黏附状态的变化调节中性粒细胞在体内稳态期间从骨髓释放的机制，因为我们假设通过A4？1的黏附抑制中性粒细胞亚群的释放，(2)确定炎症期间A4？1的黏附状态调节中性粒细胞从骨髓释放的机制，假设通过A4？1调节黏附对于加速释放不成熟的细胞是必要的，这些细胞必须在CXCR2配体的影响下迁移到血管系统。(3)验证炎症过程中中性粒细胞的释放需要CXCL12/CXCR4、CXCL5/CXCR2和S1P/S1P受体(S)协同作用的假设，假设通过CXCR2作用的CXCL5下调CXCR4信号允许细胞释放，而S1P促进CXCR2配体(如CXCL5)诱导的血管迁移。这些研究应该揭示中性粒细胞在肺部炎症反应中释放的调节机制，并为不仅提高宿主防御能力，而且将组织损伤降至最低提供新的靶点。

DESCRIPTION (provided by applicant): The release of neutrophils from the marrow in response to inflammation remain poorly understood. A number of neutrophil-dependent lung disorders, including the Adult Respiratory Distress Syndrome (ARDS) are characterized by release of immature neutrophils from marrow into the circulation. We propose to test interrelated hypotheses that explore fundamental mechanisms of neutrophil release in response to lung inflammation. Using a novel in vitro marrow culture system developed in the previous grant period, new approaches to conditional immortalization and capture of specific developmental stages, in vitro microscopy of marrow and in vivo trafficking of neutrophils in the mouse, we will (1) Determine the mechanisms by which alterations in adhesive state of a4¿1 regulates release of neutrophils from marrow during homeostasis, as we hypothesize that adhesion through a4¿1 restrains release of a subset of neutrophils primed for release, (2) Determine the mechanisms by which the adhesive state of a4¿1 regulates release of neutrophils from marrow during inflammation, hypothesizing that regulation of adhesion through a4¿1 is necessary for accelerated release of less-mature cells that must migrate to the vasculature under the influence of CXCR2 ligands. (3) Test the hypothesis that release of neutrophils during inflammation requires the coordinated action of CXCL12/CXCR4, CXCL5/CXCR2, and S1P/S1P receptor(s), with the hypothesis that down-regulation of signaling through CXCR4 by CXCL5 acting through CXCR2 permits release of cells, while S1P enhances migration towards the vasculature induced by CXCR2 ligands such as CXCL5. These studies should reveal mechanisms by which the release of neutrophils in response to an inflammatory response in the lung is regulated, and provide new targets for not only improving host defense, but also minimizing tissue injury.