Role of beta2 integrins in macrophage retention and egress during inflammation

描述(由申请人提供)：最近的研究表明，慢性低度炎症对许多破坏性疾病的发展至关重要，如动脉粥样硬化、肥胖症和糖尿病。慢性炎症的关键步骤是炎症周围组织中巨噬细胞的聚集，但仍不清楚。这项提案的总体目标是测试b2整合素在炎症部位巨噬细胞滞留和排出中的作用，特别是在动脉粥样硬化和肥胖诱导的糖尿病期间。本工作的目的是评估不同表面密度的相关整合素�M�2和 �D�2具有相似的配体结合特性，但对炎症的发展具有相反的作用，调节炎症组织中巨噬细胞的聚集。核心假设是，整合素�M�2和�D�2在慢性炎症中的相反作用取决于这些整合素在炎症巨噬细胞上的不同表达水平。中等密度的�M�2支持巨噬细胞从炎症组织中流出，而高密度的�D�2则促进巨噬细胞在炎症部位的滞留。在强大的初步数据的指导下，这一假说将通过追求三个具体目标来验证：1.评估�M�2和�D�2在代谢综合征中的作用与炎症部位b2整合素表达水平的相关性。2.探讨�-M-�-2和�-D-�-2在肥胖性糖尿病和动脉粥样硬化形成过程中对M1、M2巨噬细胞体外迁移和体内巨噬细胞转运的影响。3.观察短链�D片段对�D�2介导的脂肪组织巨噬细胞迁移和体内巨噬细胞滞留的影响。在第一个目标下，将研究�M-和�D-缺乏症在代谢综合征发展中的作用。这一数据将被炎症部位�M和�D的表达及其对M1和M2激活的巨噬细胞的调节机制的分析所支持。在目标二下，将使用体外和体内方法评估�D-/-和�M-/-巨噬细胞的迁移。在目标三下，将通过体外黏附和迁移试验以及过继转移的单核细胞体内转运来研究抑制�D介导的巨噬细胞滞留的潜在机制。这些研究的意义在于为慢性炎症的发展提供新的见解，侧重于巨噬细胞滞留的机制，而不是研究巨噬细胞向炎症部位的迁移。这一建议是创新的，因为细胞表面整合素密度对于慢性炎症进展和消退的重要性以前还没有被提出过。因此，巨噬细胞在炎症部位的整合素依赖性滞留假说为慢性炎症性疾病的治疗提供了一种定性的新方法。因此，在动脉粥样硬化或糖尿病期间阻断整合素�D可以防止巨噬细胞在炎症部位聚集，刺激慢性炎症的消退，阻止疾病的进展。

DESCRIPTION (provided by applicant): Recent studies demonstrate the importance of chronic low-grade inflammation for the development of many devastating diseases such as atherosclerosis, obesity and diabetes. The critical, yet still unclear, step of chronic inflammatio is macrophage accumulation in the inflamed peripheral tissue. The overall goal of this proposal is to test the contribution of b2 integrins to the retention and egress of macrophages within the site of inflammation, specifically during atherogenesis and obesity-induced diabetes. The objective of this work is to evaluate how different surface densities of related integrins �M�2 and �D�2, that have similar ligand binding properties, but an opposite effect on the development of inflammation, regulate the accumulation of macrophages in inflamed tissue. The central hypothesis is that the opposing contributions of integrins �M�2 and �D�2 to chronic inflammation depend on the different levels of expression of these integrins on the inflammatory macrophages. While a moderate density of �M�2 supports macrophage egress from inflamed tissue, a high density of �D�2 promotes macrophage retention within the site of inflammation. Guided by strong preliminary data, this hypothesis will be tested by pursuing three Specific Aims: 1. To evaluate the correlation between the contribution of �M�2 and �D�2 to metabolic syndrome and the level of b2 integrins expression at the sites of inflammation. 2. To identify the role of �M�2 and �D�2 in migration of M1 and M2 macrophages in vitro and macrophage trafficking in vivo during obesity-induced diabetes and atherogenesis. 3. To evaluate the effect of short �D segment on �D�2-mediated migration in vitro and macrophage retention in adipose tissue and atherosclerotic lesions in vivo. Under the first aim, the role of �M- and �D-deficiency on the development of metabolic syndrome will be examined. This data will be supported by the analysis of �M and �D expression at the site of inflammation and the mechanism of its regulation on M1- and M2-activated macrophages. Under aim two, the migration of �D-/- and �M-/- macrophages will be evaluated using in vitro and in vivo approaches. Under aim three, the potential mechanism of inhibition of �D-mediated retention of macrophages will be studied using in vitro adhesion and migration assays and in vivo trafficking of adoptively transferred monocytes. The significance of these studies resides in providing new insights on the development of chronic inflammation focusing on the mechanism of macrophage retention, instead of studying macrophage migration to the inflammatory site. This proposal is innovative because the importance of integrin density on the cell surface for the progression and resolution of chronic inflammation has not been previously suggested. Hence, the hypothesis of integrin-dependent retention of macrophages at the site of inflammation proposes a qualitatively new approach for the treatment of chronic inflammatory diseases. Thus, the blocking of integrin �D during atherogenesis or diabetes can prevent macrophage accumulation at the inflammatory site stimulating the resolution of chronic inflammation and thwarting the progression of the disease.