Direct interactions with HDL promote regulatory T cells survival

摘要 调节性T细胞（Treg）控制先天性和适应性免疫反应，对抑制免疫反应至关重要。 加剧了炎症过程。值得注意的是，Treg限制血管内皮损伤并防止肺动脉高压。 高血压在人类队列和动物模型中的作用。Treg在几种代谢中也出现功能障碍。 疾病，包括肥胖症及其糖尿病并发症。有趣的是，Treg最近被证明可以介导 它们的生存通过不同的代谢途径比效应T细胞，更依赖于脂肪酸氧化，而不是 糖酵解产生能量。Treg摄取外部来源的脂肪酸以支持这些高脂肪酸摄取率。 酸氧化，但涉及的分子和途径尚不清楚。因此， Treg和脂质之间的相互作用将为Treg生物学提供新的见解。 高密度脂蛋白具有抗炎特性，这可能至少部分地由一种脂蛋白介导。 HDL对Treg的影响例如，向LDLR-/-小鼠腹膜内注射HDL增加了脾脏Treg 道理此外，我们最近发现，在接受他汀类药物治疗的正常胆固醇血症成人中，Treg频率 与高密度脂蛋白胆固醇（HDL-c）水平呈正相关，但与LDL-c或甘油三酯水平无关。虽然 这些数据有力地表明，HDL-C促进Treg的积累，潜在的机制尚不清楚。在 特别是，尚不清楚HDL是否直接或间接地对Treg稳态发挥作用。 我们的初步研究表明，HDL直接与Treg相互作用的假设，这增强了他们的免疫功能。 通过增加代谢活动存活。事实上，我们表明，在体外培养纯化的人Treg HDL而不是LDL显著改善了Treg存活。相比之下，HDL并不影响 记忆和幼稚的CD 4 + T细胞。支持HDL对Treg的直接影响，我们发现Treg结合，然后 内化，HDL显着高于他们的天真和记忆同行。显著增加 与其他CD 4 + T细胞亚群相比，Treg上清道夫受体B类（SR-BI/II）的表达 似乎对这种优先摄取至关重要，因为阻断性抗SR-BI/II Ab消除了HDL促存活作用。 效果从机制上讲，我们发现HDL摄取增加了Treg代谢，特别是Treg线粒体 活性，并且阻断脂肪酸氧化也消除了HDL促存活作用。 然而，在知识方面仍然存在重大差距。值得注意的是，通过调节性T细胞和调节性T细胞参与HDL内化的途径， HDL促进代谢活性增加的分子机制仍然知之甚少。是 也没有确定HDL相互作用是否可以改变Treg功能。最后，我们不知道 HDL组分对于Treg存活是可操作的，尽管我们的初步数据将apoA-I鉴定为调节性调节因子。 主要候选人 在本提案中，我们将通过两个目标来解决这些知识差距。在SP. Aim 1中，我们将（1）研究 SR-BI/II介导的途径在HDL内化中的作用;（2）破译 HDL促进Treg存活;和（3）确定HDL相互作用是否改变Treg功能。在Sp. Aim 2，我们将鉴定对Treg存活起作用的HDL组分。我们将使用2个互补 方法，首先使用重建的apoA-I HDL颗粒测试apoA-I在增强Treg存活中的作用 或者相反，apoA-I缺乏颗粒，然后使用蛋白质组学来鉴定介导 对Treg的影响

Abstract Regulatory T cells (Treg) control both innate and adaptive immune responses and are essential to curb exacerbated inflammatory processes. Notably, Treg limit vascular endothelial injury and prevent pulmonary hypertension in human cohorts and animal models. Treg also appear dysfunctional in several metabolic diseases, including obesity and its diabetic complications. Interestingly, Treg were recently shown to mediate their survival through distinct metabolic pathways than effector T cells, relying more on fatty acid oxidation than glycolysis for energy generation. Treg take up externally derived fatty acids to support these high rates of fatty acid oxidation, but the involved molecules and pathways involved are not known. Thus understanding the interaction between Treg and lipids would provide novel insight into Treg biology. High-density lipoproteins have anti-inflammatory properties, which could be at least partially mediated by an effect of HDL on Treg. For example, intra-peritoneal injection of HDL into LDLR-/- mice increased splenic Treg counts. In addition, we recently showed in normocholesterolemic adults treated with statins that Treg frequency positively correlated with HDL cholesterol (HDL-c) levels, but not with those of LDL-c or triglycerides. Although these data strongly suggest that HDL-c promote Treg accrual, underlying mechanisms remain unclear. In particular, it is not clear whether HDL exert their effects on Treg homeostasis directly or indirectly. Our preliminary studies suggest the hypothesis that HDL interact directly with Treg, which enhances their survival through increased metabolic activity. Indeed, we showed that in vitro incubation of purified human Treg with HDL, but not LDL, significantly improved Treg survival. In contrast, HDL did not affect the survival of memory and naïve CD4+ T cells. Supporting a direct effect of HDL on Treg, we found that Treg bind, and then internalize, HDL significantly more than their naïve and memory counterparts. Significantly increased expression of the Scavenger Receptor class B (SR-BI/II) on Treg compared to other CD4+ T cell subsets appeared critical for this preferential uptake, as a blocking anti-SR-BI/II Ab abolished the HDL pro-survival effect. Mechanistically, we found that HDL uptake increased Treg metabolism, notably Treg mitochondrial activity, and that blocking fatty acid oxidation also abolished the HDL pro-survival effect. However, key gaps in knowledge remain. Notably, the pathways involved in HDL internalization by Treg and the molecular mechanisms by which HDL promote increased metabolic activity remain poorly understood. It is also not established whether HDL interactions may modify Treg functionality. Finally, we do not know which HDL component(s) is/are operational for Treg survival, although our preliminary data identified apoA-I as a prime candidate. In this proposal, we will address these gaps in knowledge through 2 Aims. In Sp. Aim 1, we will (1) study the role of the SR-BI/II-mediated pathway in HDL internalization; (2) decipher the molecular mechanisms by which HDL promote Treg survival; and (3) determine whether HDL interactions modify Treg functionality. In Sp. Aim 2, we will identify the HDL component(s) that is/are operational for Treg survival. We will use 2 complementary approaches, first testing the role of apoA-I in enhanced Treg survival, using reconstituted apoA-I HDL particles or conversely, apoA-I devoid particles, and then using proteomics to identify the HDL components that mediate their effect on Treg.