CCR2 in Atherosclerosis and Monocyte Trafficking

描述（由申请人提供）：单核细胞来源的巨噬细胞，脂肪条纹病变中脂质泡沫细胞的前体，在动脉粥样硬化的发生中至关重要。在早期资助期间，我们发现并克隆了CCR2，一种调节单核细胞向MCP-1迁移的趋化因子受体，并表明CCR2-/-小鼠在小鼠动脉粥样硬化模型中受到保护。在过去的资助期内，最近的研究揭示了循环血液单核细胞之间的相当大的异质性，以及CCR2在单核细胞从骨髓到血液的输出中起关键作用。基于这一科学进展，我们提出了三个相互关联的具体目标，以确定CCR2及其趋化因子配体在单核细胞从骨髓迁移到血液并进而迁移到动脉粥样硬化病变中的作用，以及在现有病变中的巨噬细胞激活中的作用。我们的工作模型是CCR2是介导“炎症”单核细胞亚群从骨髓血管生态位迁移到发展为动脉粥样硬化病变的关键受体。特异性目标1将定义ccr2依赖性单核细胞从骨髓中输出的机制。使用新型CCR2- rfp敲入小鼠和MCP-1/MCP-3 lac-Z报告小鼠，我们将验证CCR2介导单核细胞和单核祖细胞从骨髓成骨细胞生态位到血管生态位的选择性运动并释放到外周血中的假设。特异性目标2将确定募集到动脉粥样硬化病变的单核细胞群和指导这种运输的趋化因子受体。利用CCR2-RFP小鼠和骨髓单核细胞亚群的过继转移，我们将验证ccr2表达细胞被选择性募集到动脉粥样硬化病变的假设。特异性目的3将确定CCR2的药物阻断是否促进病变消退或降低病变巨噬细胞金属蛋白酶或组织蛋白酶的活性。利用新型人类CCR2敲入小鼠和蛋白酶特异性荧光“信标”的近红外成像，我们将确定有效的CCR2拮抗剂是否能降低病变内巨噬细胞的炎症潜力。这些研究的完成将加深我们对趋化因子在单核细胞稳态中的作用以及巨噬细胞激活在动脉粥样硬化斑块不稳定中的重要性的理解。

DESCRIPTION (provided by applicant): Monocyte-derived macrophages, the precursors of the lipid-laden foam cells in fatty-streak lesions, are critically important in the initiation of atherosclerosis. During earlier funding periods, we discovered and cloned CCR2, the chemokine receptor that regulates monocyte migration to MCP-1, and showed that CCR2-/- mice are protected in murine models of atherosclerosis. Recent studies during the past funding period revealed considerable heterogeneity among circulating blood monocytes and a pivotal role for CCR2 in monocyte egress from the bone marrow to the blood. Building on this scientific progress, we propose three interrelated specific aims to define the role of CCR2 and its chemokine ligands both in the the migration of monocytes from the bone marrow to the blood and thence to atherosclerotic lesions, and in the activation of macrophages within existing lesions. Our working model is that CCR2 is the key receptor in mediating the migration of a subpopulation of "inflammatory" monocytes from the vascular niche of the bone marrow to developing atherosclerotic lesions. Specific Aim 1 will define the mechanism(s) for CCR2-dependent monocyte egress from the bone marrow. Using novel CCR2-RFP knock-in mice and MCP-1/MCP-3 lac-Z reporter mice, we will test the hypothesis that CCR2 mediates selective movement of monocytes and monocyte progenitor cells from the bone marrow osteoblastic niche to the vascular niche for release into the peripheral blood. Specific Aim 2 will identify the monocyte population(s) recruited to atherosclerotic lesions and the chemokine receptors that direct this trafficking. Using CCR2-RFP mice and adoptive transfer of subpopulations of bone marrow monocytes, we will test the hypothesis that CCR2-expressing cells are selectively recruited to developing atherosclerotic lesions. Specific Aim 3 will determine if pharmacological blockade of CCR2 facilitates lesion regression or reduces the activity of lesional macrophage metalloproteinases or cathepsins. Using novel human CCR2 knock-in mice and near-infrared imaging of protease-specific fluorescent "beacons," we will determine if potent CCR2 antagonists reduce the inflammatory potential of macrophages within lesions. Completion of these studies will deepen our understanding of the role of chemokines in monocyte homeostasis and the importance of macrophage activation in atherosclerotic plaque instability.