Dysregulated gut-microbe CD4 T cell interactions with Aging

摘要 生理性衰老与一种低级别的慢性炎症状态有关，这种状态与许多 老年合并症。虽然可能有多个因素导致了这种“炎症”表型，但 最近的一些动物模型研究表明，肠道内稳态的破坏是一个关键因素。我们 确定了指示肠道上皮屏障损伤和肠道微生物的人类血浆生物标志物 移位随着年龄的增长而增加，并与全身免疫激活的标志物相关，从而表明 与年龄相关的人体肠道平衡失调与炎症有关。先前的研究表明， 随着年龄的增长，粪便微生物群会发生变化或“反生性”，肠道共生菌的数量会增加 引起炎症(病原体)和免疫调节细菌代谢物的减少(例如短小的 链脂肪酸，丁酸盐)。肠道CD4T细胞是肠道粘膜中最大的T细胞群，在肠道疾病中发挥着重要作用 通过防止肠道病原体或转移微生物来维持动态平衡。我们证明了这一点 人肠道固有层(LP)CD_4~+T细胞活化，产生炎性细胞因子(IL-17、干扰素γ)， 并在体外暴露于肠道致病菌后增殖。我们现在有了初步数据 证明丁酸盐抑制这些细菌驱动的炎症反应，并诱导表达 如PD1和IL-10等调节分子。在试验性的体外研究中，我们表明年龄较大与 产生IL-17的T辅助细胞(Th)的聚集，特别是那些共同产生干扰素γ的细胞，这是一种已知的 炎症性亚群。此外，年龄较大的LP CD4T细胞表达的协同抑制水平明显较低 免疫检查点PD1和CTLA4比年轻的LP、CD4T细胞和更高水平的抗凋亡细胞Bcl2。 这一发现是违反直觉的，因为PD1和CTLA4的表达增加与疲劳有关 外周血T细胞的数量。我们最重要的假设是年龄相关的内在免疫 肠道CD4T细胞与PRO结合的调节失调(低共抑制免疫检查点表达) 炎症性(高致病力、低丁酸率)肠道生物失调将导致炎症性Th17的扩张 细胞。为了探索与年龄相关的肠道CD4T细胞/微生物的相互作用，我们提出了两个目标，将利用EX 活体人结肠LP单核细胞模型研究衰老对肠道微生物群CD4的影响 T细胞的相互作用。在目标1中，我们将确定不同的结肠Th细胞是否差异表达a 调节失调的衰老免疫表型，并确定与此相关的相应转录组谱 表型。在目标2中，我们将评估衰老对结肠Th亚群免疫功能的影响 对结肠微生物组相关的免疫刺激和免疫调节因子。这些研究将提供 年龄相关背景下年龄对肠道CD4T细胞免疫影响的急需信息 生物失调。所获得的洞察力将支持未来在老年人口中旨在探索这一贡献的研究 从肠道炎症到全身性炎症和并存的特定途径。

ABSTRACT Physiological aging is associated with a low grade chronic inflammatory state which has been link to numerous geriatric comorbid conditions. While there are likely multiple contributors to this “inflammaging” phenotype, a number of recent animal model studies have implicated a breakdown in gut homeostasis as a key factor. We established that human plasma biomarkers indicative of gut epithelial barrier damage and gut microbial translocation increased with age and correlated with markers of systemic immune activation thus showing that age-related disruption of human gut homeostasis is linked to inflammaging. Prior studies have shown that the fecal microbiome is altered or “dysbiotic” with age, with an increase in enteric commensal bacteria capable of inducing inflammation (pathobionts) and a decrease in immune regulatory bacterial metabolites (e.g. the short chain fatty acid, butyrate). Gut CD4 T cells are the largest gut mucosal T cell population and play a vital role in maintaining homeostasis by protecting against gut pathogens or translocating microbes. We demonstrated that human gut lamina propria (LP) CD4+ T cells become activated, produce inflammatory cytokines (IL-17, IFNγ), and proliferate upon exposure to enteric pathobiont bacteria in vitro. We now have preliminary data demonstrating that butyrate inhibits these bacteria-driven inflammatory responses and induces expression of regulatory molecules such as PD1 and IL-10. In pilot ex vivo studies we show that older age is associated with an accumulation of IL-17-producing T helper (Th) cells (Th17), especially those that co-produce IFNγ, a known inflammatory subset. Furthermore, older LP CD4 T cells expressed significantly lower levels of the co-inhibitory immune checkpoints PD1 and CTLA4 than younger LP CD4 T cells and higher levels of anti-apoptotic Bcl-2. This finding is counterintuitive as increased expression of PD1 and CTLA4 have been associated with exhaustion of peripheral blood T cells. Our overarching hypothesis is that age-associated intrinsic immune dysregulation (low co-inhibitory immune checkpoint expression) of gut CD4 T cells combined with pro- inflammatory (high pathobiont, low butyrate) gut dysbiosis will result in expansion of inflammatory Th17 cells. To explore age-associated gut CD4 T cell/microbe interactions, we propose 2 aims that will utilize an ex vivo human colon LP mononuclear cell model to gain insights into the effects of aging on microbiome-gut CD4 T cells interactions. In Aim 1, we will determine whether distinct colonic Th cells differentially express a dysregulated aging immune phenotype and identify a corresponding transcriptomics profile linked to this phenotype. In Aim 2 we will evaluate the impact of aging on immune function of colonic Th subsets in response to colonic microbiome-associated immune-stimulatory and immune-regulatory factors. These studies will provide critically needed information on the impact of age on gut CD4 T cell immunity in the setting of age-associated dysbiosis. The insights gained will support future studies in older populations designed to probe the contribution of specific pathways of gut inflammation to systemic inflammation and comorbidities.