基于HIF-1α对肠上皮细胞自噬的调控探讨短链脂肪酸治疗IBD的作用及机理

The autophagy pathway has been increasingly recognized as an important mechanism for regulating homeostasis of gut microbiota and host defense. The discovery of molecular mechanism for autophagy has provided exciting advances in our understanding of inflammatory bowel disease treatment. Our preliminary data showed that hypoxia-inducible factor-1α (HIF-1α) could induce autophagy and autophagy-related proteins. Absence of intestinal epithelial HIF-1α affects microbial assemblage and increases susceptibility to dextran sulfate sodium-induced colitis. Recent study revealed that microbiota-derived short-chain fatty acids (SCFA) promote intestinal epithelial O2 consumption to the extent that HIF is stabilized and the expression of barrier-protective HIF target genes. Therefore, we hypothesize that the intestinal epithelial HIF-1α is a target of SCFA through its actions on the autophagy, thus determining states of host defense and microbial assembly. In this study, we would like to confirm the above mentioned hypothesis by using technology of HIF-1α-knockout mice and hypoxic cell model, and test whether SCFA upregulates the autophagy-related proteins through HIF-1α. These findings provide profound insight for the development of therapies to treat IBD.

肠上皮细胞自噬功能的维持是肠屏障发挥功能、肠道菌群平衡的保障。探讨维持自噬功能的分子机制可为治疗肠炎提供新依据。我们前期发现缺氧诱导因子-1α (hypoxia-inducible factor-1α, HIF-1α)可诱导肠上皮细胞自噬相关蛋白高表达，促进自噬小体形成。肠上皮细胞特异性敲除HIF-1α后肠道炎症明显加重，肠道菌群紊乱。新近研究表明，益生菌代谢产物短链脂肪酸（short-chain fatty acids, SCFA）是从肠腔激活HIF-1α的理想分子。因此我们假设：肠炎条件下口饲SCFA可以刺激HIF-1α，从而增强自噬，维持肠屏障稳态。本研究拟采用体内外研究模型，通过SCFA口饲、缺氧、自噬抑制等手段，利用细胞和动物模型，阐明SCFA通过激活HIF-1α对自噬产生调控，为SCFA治疗肠炎提供理论依据。

炎症性肠病（Inflammatory Bowel Disease, IBD）是一类病因不明的累及肠道的慢性非特异性疾病，包括克罗恩病(Crohns disease ，CD)和溃疡性结肠炎(ulcerative colitis，UC)。近年来，越来越多的研究表明，肠屏障在IBD的发生发展中起着关键作用。肠屏障是指分隔肠道微环境与肠腔之间的分界线，主要由肠上皮细胞（IEC）及上皮间淋巴细胞（IELs）构成。缺氧诱导因子-1α（Hypoxia-inducible factor 1α，HIF-1α）是胞内低氧条件下可对多种基因进行调控的转录因子，使细胞适应低氧环境。更有趣的是，肠道的“生理性缺氧”可以诱导肠道自噬，从而防止病原菌入侵。因此，我们推测HIF-1α与自噬密切相关。.新近研究表明，益生菌代谢产物短链脂肪酸（short-chain fatty acids, SCFA）是从肠腔激活HIF-1α的理想分子。本研究构建肠上皮细胞特异性敲出HIF-1α小鼠（HIF-1α∆IEC小鼠），探讨肠上皮来源的HIF-1α在小鼠结肠炎中的作用，发现HIF-1α在小鼠肠道稳态维持中扮演着重要作用，小鼠肠道上皮缺乏HIF-1α，会影响其肠道微生态平衡，并且增加肠道对损伤敏感性。SCFA丁酸可以通过稳定肠道上皮HIF-1α诱导小鼠肠道发生自噬从而缓解小鼠结肠炎。同时，通过构建葡聚糖硫酸钠（DSS）诱导的肠炎模型，分离纯化IELs并采取高通量测序及生物信息学分析，研究炎性肠病中的IELs的mRNA及lncRNA变化规律，并筛选了可能的干预靶点。我们还研究了肠道真菌在内毒素诱导败血症发病机制中的保护作用，发现肠道真菌通过抑制GSDMD裂解保护小鼠免受LPS诱导的败血症。以上研究不仅能够完善肠道稳态调控的分子机制，也将为临床结肠炎等疾病的治疗提供理论依据和新策略。

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