Impact of dysbiotic and symbiotic catabolism of luminal amino acids on intestinal epithelial barrier function and inflammation

在美国，超过300万成年人患有炎症性肠病（IBD），其包括克罗恩病（Crohn's disease）。 疾病（CD）和溃疡性结肠炎（UC）。IBD的特征在于肠道微生物群失调，上皮细胞受损， 屏障功能、慢性肠道炎症和粘膜细胞因子增加。上皮屏障功能是 由一系列细胞间连接调节，包括紧密连接（TJ）、粘附连接和 桥粒关键上皮屏障的破坏允许腔内容物进入免疫学上的 特权区室，从而有助于IBD发病机制。肠道微生物群引起的 粘膜炎症扰乱细胞间连接和上皮细胞的稳态特性，从而导致 受损的上皮屏障然而，我们对神经刺激的分子基础的了解 细胞间连接蛋白的功能，上皮细胞的稳态和受损上皮细胞的恢复 肠道炎症期间的屏障非常有限。因此，本提案的总体目标是确定 特定的肠道细菌和细菌代谢产物调节肠道功能的机制 细胞间连接蛋白，并保护免受上皮屏障损害和损伤。我们的初步数据 确定共生的单形拟杆菌主要分解代谢精氨酸产生多胺 亚精胺，促进健康的屏障。与此相反，生态失调的变形菌E.大肠杆菌占优势 分解代谢赖氨酸以合成多胺尸胺，其损害肠道通透性。细菌多胺是 调节多种细胞过程的脂肪胺。根据我们的初步数据，我们假设， 微生物多胺通过激活TRPV和调节TJ SUMO化来调节上皮屏障功能， 肠上皮屏障中的紧密连接蛋白和ZO蛋白的翻译后修饰。多胺可以激活 瞬时受体电位受体（TRPVs）调节细胞功能。在目标1中，我们将剖析 共生多胺激活TRPV1和生态失调的尸胺诱导TRPV3介导的TJ调节 流程.在目标2中，我们将阐明微生物多胺驱动的TJ蛋白SUMO化， 扰动屏障功能。最后，在目标3中，我们将确定小分子和管腔的影响。 代谢物，其抑制生态失调的肠道细菌的尸胺合成酶，从而抑制 肠道炎症该项目在概念和技术上都具有创新性。它将利用创造性的 Trpv1和Trpv3基因敲除小鼠的用途以及新的病原体特异性抗菌剂。调查 肠道细菌产生的多胺对上皮TRPV和TJ SUMO化途径的影响是新的。 这些研究的完成将为肠上皮屏障的分子基础提供清晰的见解 氨基酸催化剂的调节，并产生了新的思路和开发原理的证明 微生物代谢产物开发IBD和其他胃肠道疾病的治疗方法， NIDDK研究优先。

Over 3 million adults in the U.S. suffer from inflammatory bowel diseases (IBD), which encompasses Crohn’s disease (CD) and ulcerative colitis (UC). IBD is characterized by dysbiotic gut microbiota, compromised epithelial barrier function, chronic intestinal inflammation, and increased mucosal cytokines. Epithelial barrier function is regulated by a series of intercellular junctions that encompass the tight junction (TJ), adherens junction, and desmosomes. Disruption of the critical epithelial barrier allows access of luminal contents to immunologically privileged compartments, thereby contributing to IBD pathogenesis. The dysbiotic gut microbiota-induced mucosal inflammation perturbs intercellular junctions and epithelial homeostatic properties, thereby resulting in a compromised epithelial barrier. However, our knowledge of the molecular basis of commensal-stimulated intercellular junction proteins’ function, epithelial homeostasis, and restoration of the compromised epithelial barrier during intestinal inflammation is very limited. Thus, the overall goals of this proposal are to identify mechanisms by which specific commensal bacteria and bacterial metabolic products regulate functions of intercellular junction proteins, and protect from epithelial barrier compromise and injury. Our preliminary data determined that the symbiotic Bacteroides uniformis predominantly catabolizes arginine to produce polyamine spermidine, which promotes a healthy barrier. In contrast, dysbiotic Proteobacterial species E. coli predominantly catabolizes lysine to synthesize polyamine cadaverine, which impairs gut permeability. Bacterial polyamines are aliphatic amines that regulate multiple cellular processes. Based on our preliminary data, we hypothesize that microbial polyamines regulate epithelial barrier functions by activating TRPV and regulating TJ SUMOylation, a post-translational modification of claudin and ZO proteins in the gut epithelial barrier. Polyamines can activate Transient Receptor Potential Receptors (TRPVs) to regulate cellular functions. In Aim 1, we will dissect the symbiotic polyamine-activated TRPV1 and dysbiotic cadaverine-elicited TRPV3-mediated TJ regulatory processes. In Aim 2, we will elucidate microbial polyamine-driven SUMOylation of TJ proteins eventuating in the perturbed barrier function. Finally, in Aim 3, we will determine the impact of small molecules and luminal metabolites, which inhibit cadaverine synthesizing enzymes of the dysbiotic gut bacteria and thereby dampen intestinal inflammation. This project is both conceptually and technically innovative. It will employ the creative use of Trpv1 and Trpv3 knockout mice and a novel pathogen-specific antibacterial agent. The investigation of the effects of gut bacterially produced polyamines on epithelial TRPV and TJ SUMOylation approach is novel. Completion of these studies will provide clear insights into the molecular basis of intestinal epithelial barrier regulation by commensals’ amino acid catabolism and engender new ideas and proof-of-principle of exploiting commensal bacterial metabolites to develop therapeutics for IBD and other gastrointestinal diseases, a high NIDDK research priority.