Role of apoE in HDL-mediated enhanced survival of human regulatory T-cells

摘要 调节性T细胞（Tcells）介导抗炎功能，并且与自身免疫性疾病最相关。 免疫和自身免疫性疾病。然而，考虑到亚临床或持续低水平的潜在作用， 炎症在代谢和心血管疾病中的作用，最近的注意力集中在 在控制这些病理中的促炎性环境中的TdR。效应器记忆是效应器记忆的子集 是最具抑制性的，但也是最短暂的。我们做了一个惊人的观察- 高密度脂蛋白（HDL），而不是其他脂蛋白，显著改善Treg存活。这些调查结果提供了 我们发现高密度脂蛋白胆固醇和调节性T细胞丰度之间正相关的解释。我们 初步数据显示HDL优先结合Treg记忆亚群并被其内化，特别是通过 效应子记忆T细胞，通过减少效应子半胱天冬酶激活来促进其存活。机械地，我们 新的数据还表明这种HDL促存活作用可能通过激活AKT信号通路而发生， 这导致增强的从头脂肪酸合成和降低的线粒体氧化应激。由于HDL 是一个家族的相关颗粒与复杂的混合物的脂质和蛋白质，我们开始探索， 亚种或组分刺激Treg存活。我们发现，促生存效应是由 HDL蛋白组分，特别是相对次要的HDL蛋白组分，载脂蛋白（APO）E， 和/或共存在于含APOE的HDL上的其它蛋白质。相比之下，主要的HDL支架蛋白， APOA家族没有发挥重要作用。我们的总体假设是富含APOE的HDL特异性地与 与TdR一起触发限制半胱天冬酶依赖性细胞凋亡的途径。目的1将确定细胞内 参与HDL介导的Treg存活的信号传导途径，特别是参与HDL结合的受体， 通过记忆T细胞的内化和HDL促进Treg存活的机制。我们还将 确定HDL对Treg抑制的影响。目的2将确定特定的HDL亚种和蛋白质 促进Treg存活的成分。我们还将进行缺失和定点突变 实验，以确定关键区域（S）的载脂蛋白E，告知探索合成肽，可以模拟 APOE对记忆的促生存作用目的3将评估富含APOE的HDL在Treg中的参与。 体内存活率。我们将利用辛辛那提儿童糖尿病和肥胖中心的队列研究， Treg亚群的绝对数量、其功能特征和HDL亚种之间的关联， 在减肥手术前后。在手术前后收集的HDL亚种的能力， 将研究促进记忆和效应记忆Treg存活。通过识别特定的细胞通路， 负责Treg存活效应的特定脂蛋白种类，我们将开辟新的途径， 治疗性干预旨在调节自身免疫和慢性代谢性疾病宿主中的Treg功能 疾病

Abstract Regulatory T cells (Tregs) mediate anti-inflammatory functions and have been most associated with self- immunity and autoimmune diseases. However, given the underlying role of subclinical or persistent low-level inflammation in metabolic and cardiovascular diseases, attention has recently focused on the potential role of Tregs in controlling the proinflammatory milieu in these pathologies. A subset of Tregs, the effector memory Tregs, are the most suppressive, but are also the most transient. We made the striking observation that high- density lipoproteins (HDL), but not other lipoproteins, significantly improved Treg survival. These findings offer an explanation for the positive correlation we found between HDL cholesterol and Treg abundance. Our preliminary data show that HDL preferentially bind and are internalized by Treg memory subsets, particularly by effector memory Tregs, promoting their survival by reducing effector caspase activation. Mechanistically, our new data also suggest that this HDL pro-survival effect may occur via activation of the AKT signaling pathway, which results in enhanced de novo fatty acid synthesis and reduced mitochondrial oxidative stress. Since HDL is a family of related particles with complex mixtures of lipids and proteins, we started exploring which HDL subspecies or components stimulate Treg survival. We found that the pro-survival effect was mediated by the HDL protein component, and particularly the relatively minor HDL protein constituent, apolipoprotein (APO)E, and/or other proteins that co-reside on APOE-containing HDL. In contrast, the major HDL scaffold proteins from the APOA family did not play a major role. Our overarching hypothesis is that APOE-rich HDL specifically interact with Tregs to trigger pathways that limit caspase-dependent apoptosis. Aim 1 will identify the intracellular signaling pathways involved in HDL-mediated survival of Treg, notably the receptor(s) involved in HDL binding/ internalization by memory Tregs and the mechanisms by which HDL promote Treg survival. We will also determine the effect of HDL on Treg suppression. Aim 2 will identify specific HDL subspecies and protein components that promote Treg survival. We will also perform deletional and site-directed mutagenesis experiments to identify the critical region(s) of APOE, to inform explorations of synthetic peptides that can mimic APOE’s pro-survival effects on memory Tregs. Aim 3 will assess the involvement of APOE-rich HDL in Treg survival in vivo. We will leverage the Cincinnati Pediatric Diabetes and Obesity Center cohort and probe the association between absolute numbers of Treg subsets, their functional characteristics, and HDL subspecies, before and after weight reduction surgery. The ability of HDL subspecies collected before and after surgery to promote memory and effector memory Treg survival will be studied. By identifying specific cellular pathways and specific lipoprotein species responsible for the Treg survival effects, we will open new avenues for potential therapeutic intervention aimed at modulating Treg function in a host of auto-immune and chronic metabolic diseases.