Differentiation and fate of monocytes in atherosclerosis

动脉粥样硬化是弹性动脉和肌肉动脉的慢性炎症性疾病。在动脉粥样硬化发病早期，聚集的氧化脂蛋白颗粒附着在受影响动脉内皮下基质中的蛋白质上。单核细胞（Me）穿过覆盖的内皮细胞，与这些基质结合的脂蛋白颗粒接触，吞噬它们，最终吸收大量脂质，发展成脂质充血的巨噬细胞（Mf）衍生的泡沫细胞。泡沫细胞在病变处积聚，分泌促炎细胞因子，刺激Me进一步流入。当Me进入炎症部位时，许多细胞分化成树突状细胞（DC），它们携带抗原并在几天内离开组织，将抗原呈递给引流淋巴结中的T细胞。其余的分化为Mf，可以在组织中存活数月或数年。我们假设单核细胞与动脉壁细胞外基质中聚集的脂蛋白和环境中的炎症细胞因子的相互作用影响了单核细胞的分化和命运。项目2将确定与基质结合脂蛋白的相互作用是否会抑制单核细胞迁移。与这些研究人员合作，我们将确定动脉粥样硬化环境是否会使Me分化为流动性较差的Mf和/或抑制Me、Mf和DC的运动，从而使它们在动脉粥样硬化环境中停留更长时间，促进它们对聚集的氧化脂蛋白的吸收并发育成泡沫细胞。通过与人内皮细胞的体外共培养模型，可以预测Me、Mf和DC在体内的行为和运输，我们发现了Mf积聚脂质并呈现泡沫细胞表型的条件。我们将确定这种情况的发生是否因为Me与基质中聚集的脂蛋白的相互作用使其分化为久坐的Mf，或者这是否会降低DC的流动性从而使它们无法离开（目的1）。我们将确定这是否被Me与IL-lb和TNFa的相互作用所模仿，后者通过分泌鞘磷脂酶刺激基质中脂蛋白的聚集（目的2）。我们将确定在动脉粥样硬化病变中发现的IL-6是否通过以牺牲DC为代价将Me分化为Mf来促进泡沫细胞的发育（Aim 3）。我们将确定促进反向胆固醇运输或阻断细胞因子或其受体的作用的药物是否能逆转这些现象。

Atherosclerosis is a chronic inflammatory disease of elastic and muscular arteries. Early in the pathogenesis of atherosclerosis, aggregated, oxidized lipoprotein particles become attached to proteins in the subendothelial matrix of the affected arteries. Monocytes (Me) that traverse the overlying endothelium come into contact with these matrixbound lipoprotein particles, engulf them, and eventually take up large amounts of lipid, developing into lipid-engorged macrophage (Mf)-derived foam cells. Foam cells accumulate in the lesion, secreting pro-inflammatory cytokines that stimulate further Me influx. When Me enter a site of inflammation, many differentiate into dendritic cells (DC) that pick up antigen and leave the tissue within days to present the antigen to T cells in draining lymph nodes. The remainder differentiate into Mf, which can remain in the tissues for months or years. We hypothesize that interaction of monocytes with aggregated lipoproteins in the extracellular matrix of the arterial wall and with inflammatory cytokines in the environment affect the differentiation and fate of monocytes. Project 2 will determine whether interaction with matrix bound lipoproteins inhibits monocyte migration. Working with these investigators, we will determine whether the atherogenic environment skews the differentiation of Me into less mobile Mf and/or inhibits movement of Me, Mf, and DC so that they remain in the atherogenic environment longer, promoting their uptake of aggregated, oxidized lipoproteins and development into foam cells. Using an in vitro co-culture model with human endothelial cells that has been predictive of Me, Mf, and DC behavior and trafficking in vivo, we have found conditions under which Mf accumulate lipid and take on the phenotype of foam cells. We will determine whether this occurs because interaction of Me with aggregated lipoproteins in the matrix skew their differentiation into sedentary Mf or whether this decreases mobility of DC so they cannot leave (Aim 1). We will determine whether this is mimicked by Me interactions with IL-lb and TNFa, which stimulate the aggregation of lipoproteins in the matrix via secreted sphingomyelinase (Aim 2). We will determine whether IL-6, which has been found in atherosclerotic lesions, promotes the development of foam cells by skewing the differentiation of Me into Mf at the expense of DC (Aim 3). We will determine if agents that promote reverse cholesterol transport or block the actions of the cytokines or their receptors reverse these phenomena.