METABOLIC CONTROL OF EPITHELIAL AUTOPHAGY DURING INFLAMMATION

 描述（由申请人提供）：胃肠上皮包括对抗无所不在的管腔抗原的主要细胞屏障，并作为微生物病原体和肠道生物体的先天免疫传感器积极参与。因此，肠上皮细胞定义了宿主-微生物群相互作用和肠内稳态的中心界面。基于它们与缺氧肠腔的并置，肠上皮细胞在低氧张力微环境中生理性地发挥功能，并且表现出独特的适应性氧合特征。在与炎性肠病（IBD）相关的活动性炎症中，粘膜代谢发生深刻改变，导致营养和氧气耗尽或缺氧。哺乳动物细胞中缺氧引起的适应性转录程序主要通过缺氧诱导因子（HIF）复合物介导。HIF在协调上皮基因调控中的保护作用已经被确定，转录反应被整合以特异性地支持屏障功能和对缺氧微环境的适应。HIF靶位点的全基因组分析突出了与宿主-微生物代谢轴有关的两种新的低氧调节途径：促进时空ATP缓冲和屏障能量学的肌酸激酶穿梭和选择性自噬。自噬是一种高度保守的分解代谢途径，协调细胞和生物体对代谢应激和感染的反应的各个方面，最近被认为在消除侵入性细菌（xenophagy）中起关键作用。重要的是，上皮细胞自噬途径在IBD中失调。虽然重大的努力集中在核心自噬成分的鉴定，上皮细胞自噬在转录水平上的调节是很差的特点。特别是，很少有人知道关于典型的自噬基因反应的协调，以及这些如何调节胞内病原体的异噬捕获。损伤线粒体的选择性自噬（mitophagy）和感染性疾病之间的基本联系最近已经建立，线粒体能量学已被证明显着影响小鼠结肠炎的临床过程。我们正在进行的研究已经鉴定了一组线粒体吞噬（BNIP 3L）和异源吞噬（NOD 2）基因，其由上皮中的缺氧和HIF稳定化诱导。初步研究表明，在低氧条件下，入侵性细菌以HIF依赖性方式被食异作用有效靶向。上皮HIF缺陷小鼠在急性细菌攻击后表现出增加的细菌传播和疾病活性。此外，增强HIF介导的肌酸代谢和上皮生物能量学证明在小鼠肠道炎症模型中具有保护作用。基于这些观察结果，我们假设上皮HIF途径以细胞自主的方式收敛，以协调线粒体和代谢稳态与侵入性微生物检测。

 DESCRIPTION (provided by applicant): The gastrointestinal epithelium comprises the primary cellular barrier against omnipresent luminal antigens, and actively participates as an innate immune sensor of microbial pathogens and commensal organisms. As such, intestinal epithelia define the central interface for host-microbiota interactions and intestinal homeostasis. Based on their juxtaposition to the anoxic gut lumen, intestinal epithelial cells function physiologicall in a low- oxygen-tension microenvironment, and exhibit a uniquely adaptive oxygenation profile. In active inflammation associated with inflammatory bowel disease (IBD), mucosal metabolism is profoundly altered, resulting in nutrient and oxygen depletion or hypoxia. Adaptive transcriptional programs elicited by oxygen deprivation in mammalian cells are mediated primarily through the hypoxia-inducible factor (HIF) complex. A protective role for HIF in orchestrating epithelial gene regulation has been identified, with transcriptional responses integrated to specifically support barrier function and adaptations to the hypoxic microenvironment. Genome-wide profiling of HIF target loci highlighted two novel hypoxia-regulated pathways implicated in the host-microbial metabolic axis: the creatine kinase shuttle that promotes spatiotemporal ATP buffering and barrier energetics, and selective autophagy. Autophagy, a highly conserved catabolic pathway, coordinates diverse aspects of cellular and organismal responses to metabolic stressors and infection and has recently been ascribed a key role in the elimination of invasive bacteria (xenophagy). Importantly, epithelial autophagic pathways are dysregulated in IBD. While significant efforts have focused on identification of core autophagy components, regulation of epithelial autophagy at the transcriptional level is poorly characterized. In particular, little is known regarding the coordination of canonical autophagy gene responses and how these modulate xenophagic capture of intracellular pathogens. A fundamental link between selective autophagy of damaged mitochondria (mitophagy) and infectious disease has recently been established, and mitochondrial energetics have been shown to significantly influence the clinical course of murine colitis. Our ongoing studies have identified a cohort of both mitophagic (BNIP3L) and xenophagic (NOD2) genes that are induced by hypoxia and HIF- stabilization in epithelia. Preliminary work has revealed that invasive bacteria are effectively targeted by xenophagy under hypoxic conditions in a HIF-dependent manner. Epithelial HIF-deficient mice demonstrate increased bacterial dissemination and disease activity following acute bacterial challenge. Moreover, augmentation of HIF-mediated creatine metabolism and epithelial bioenergetics proved protective in mouse models of intestinal inflammation. Based on these observations, we hypothesize that epithelial HIF pathways converge in a cell autonomous manner to coordinate mitochondrial and metabolic homeostasis with invasive microbe detection.