Functions of Nonclassical Monocytes in the Vasculature

 描述(申请人提供)：传统上，单核细胞被认为是简单的、不活跃的巨噬细胞前体。然而，在发现血液单核细胞包含几个群体后，单核细胞在血管系统中具有重要的独立功能变得清晰起来。非经典的巡逻单核细胞亚群(小鼠的CX3CR1HighLy6C-和人类的CX3CR1HighCD14dimCD16+)不同于经典的单核细胞亚群(小鼠的CCR2HighLy6C+和人类的CCR2HighCD14+CD16-)，并显示出在动态平衡和炎症条件下主动巡逻血管内皮细胞的独特能力。尽管经典单核细胞可以分化为巨噬细胞，但非经典单核细胞是否经历这种分化尚不清楚。最近，我们发现循环中的非经典单核细胞吞噬血管内肿瘤细胞，从而定义了这些单核细胞的一种新的具有生物学意义的血管内功能。我们假设，循环中的非经典单核细胞的一个关键功能是检测和摧毁循环中转移的肿瘤细胞。我们发现核受体Nr4a1是非经典单核细胞发育所必需的转录因子。我们最近发现，缺乏非经典单核细胞的Nr4a1缺陷小鼠体内肿瘤种植增加，非常重要的是，仅将非经典单核细胞转移回这些Nr4a1缺陷小鼠以恢复其血液中正常水平的巡逻单核细胞可防止肿瘤的发展。重要的是，非经典单核细胞的这种功能在肿瘤细胞渗透到循环中的几个小时内发生得相当快。我们有两个特定的目标来测试我们的假设特定的目标1将测试非经典单核细胞指导循环中的肿瘤细胞杀伤的假设，并将确定这一过程如何发生的机制。我们将测试Ly6C-非经典单核细胞是直接杀伤肿瘤细胞，还是招募其他先天免疫细胞进行杀伤。我们将确定非经典单核细胞如何识别肿瘤细胞的受体机制。特定目标2将测试循环中增加非经典单核细胞数量是否可以防止体内转移。Nr4a1激动剂Cytosporone B增加了小鼠循环中的非经典单核细胞数量。我们将给野生型小鼠注射胞孢素B以增加循环中非经典单核细胞的数量，并将询问直接靶向单核细胞中的Nr4a1和增加循环中的非经典单核细胞数量是否可以防止肿瘤细胞的转移。我们还将测试CD14dim单核细胞--相当于Ly6C-非经典单核细胞的人类单核细胞功能--是否可以在体内摄取循环中的肿瘤细胞。这些研究将为血管系统中的非经典单核细胞定义一个至关重要的稳态功能。

 DESCRIPTION (provided by applicant): Traditionally, monocytes have been viewed as simple, inactive precursors of macrophages. However, after discoveries that blood monocytes encompass several populations, it became clear that monocytes have important independent functions within the vasculature. Nonclassical patrolling monocyte subsets (CX3CR1highLy6C- in mouse and CX3CR1highCD14dimCD16+ in humans) are distinct from the classical monocyte subsets (CCR2highLy6C+ in mouse, and CCR2highCD14+CD16- in humans) and exhibit a unique ability to actively patrol the vascular endothelium under both homeostatic and inflammatory conditions. Although classical monocytes can differentiate into macrophages, it is unclear that nonclassical monocytes undergo this differentiation. Recently, we have found that nonclassical monocytes in circulation phagocytose intravascular tumor cells, thus defining a new and biologically important intravascular function of these monocytes. We hypothesize that a critical function of nonclassical monocytes in circulation is to detect and destroy metastasizing tumor cells in circulation. We discovered that the nuclear receptor Nr4a1 is an essential transcription factor required for the development of nonclassical monocytes. We recently found that Nr4a1-deficient mice that lack nonclassical monocytes have increased tumor seeding in vivo, and very importantly, that transfer of only nonclassical monocytes back into these Nr4a1-deficient mice to restore normal levels of patrolling monocytes in their blood prevents tumor development. Importantly, this function of nonclassical monocytes occurs quite rapidly, within hours of tumor cell infiltration into circulation. We have two specific aims to test our hypothesis Specific Aim 1 will test the hypothesis that nonclassical monocytes direct the killing of tumor cells in circulation and will identify mechanisms for how this occurs. We will test whether Ly6C- nonclassical monocytes kill tumor cells directly or whether they recruit other innate immune cells for killing. We will identify receptor mechanisms for how nonclassical monocytes recognize tumor cells. Specific Aim 2 will test whether increasing nonclassical monocyte numbers in circulation prevents metastasis in vivo. The Nr4a1 agonist Cytosporone B increases nonclassical monocyte numbers in circulation in mice. We will administer Cytosporone B into wild-type mice to increase circulating nonclassical monocyte numbers and will ask whether directly targeting Nr4a1 in monocytes and increasing nonclassical monocyte numbers in circulation prevent tumor cell metastasis. We will also test whether CD14dim monocytes, the human monocyte functional equivalent to Ly6C- nonclassical monocytes, can ingest circulating tumor cells in vivo. These studies will define a critically important homeostatic function for nonclassical monocytes in the vasculature.