Department of Inflammation & Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
Department of Inflammation & Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
Matrix Biol. 2024 Nov;133:116-133. doi: 10.1016/j.matbio.2024.08.007. Epub 2024 Aug 24.
BACKGROUND: Metabolic syndrome and diabetes in obese individuals are strong risk factors for development of inflammatory bowel disease (IBD) and colorectal cancer. The pathogenic mechanisms of low-grade metabolic inflammation, including chronic hyperglycemic stress, in disrupting gut homeostasis are poorly understood. In this study, we sought to understand the impact of a hyperglycemic environment on intestinal barrier integrity and the protective effects of small molecular weight (35 kDa) hyaluronan on epithelial barrier function. METHODS: Intestinal organoids derived from mouse colon were grown in normal glucose media (5 mM) or high glucose media (25 mM) to study the impact of hyperglycemic stress on the intestinal barrier. Additionally, organoids were pretreated with 35 kDa hyaluronan (HA35) to investigate the effect of hyaluronan on epithelial barrier under high glucose stress. Immunoblotting as well as confocal imaging was used to understand changes in barrier proteins, quantitative as well as spatial distribution, respectively. Alterations in barrier function were measured using trans-epithelial electrical resistance and fluorescein isothiocyanate flux assays. Untargeted proteomics analysis was performed to elucidate mechanisms by which HA35 exerts a protective effect on the barrier. Intestinal organoids derived from receptor knockout mice specific to various HA receptors were utilized to understand the role of HA receptors in barrier protection under high glucose conditions. RESULTS: We found that high glucose stress decreased the protein expression as well as spatial distribution of two key barrier proteins, zona occludens-1 (ZO-1) and occludin. HA35 prevented the degradation or loss of ZO-1 and maintained the spatial distribution of both ZO-1 and occludin under hyperglycemic stress. Functionally, we also observed a protective effect of HA35 on the epithelial barrier under high glucose conditions. We found that HA receptor, layilin, was involved in preventing barrier protein loss (ZO-1) as well as maintaining spatial distribution of ZO-1 and occludin. Additionally, proteomics analysis showed that cell death and survival was the primary pathway upregulated in organoids treated with HA35 under high glucose stress. We found that XIAP associated factor 1 (Xaf1) was modulated by HA35 thereby regulating apoptotic cell death in the intestinal organoid system. Finally, we observed that spatial organization of both focal adhesion kinase (FAK) as well as F-actin was mediated by HA35 via layilin. CONCLUSION: Our results highlight the impact of hyperglycemic stress on the intestinal barrier function. This is of clinical relevance, as impaired barrier function has been observed in individuals with metabolic syndrome. Additionally, we demonstrate barrier protective effects of HA35 through its receptor layilin and modulation of cellular apoptosis under high glucose stress.
背景:肥胖个体中的代谢综合征和糖尿病是炎症性肠病(IBD)和结直肠癌发展的强烈危险因素。包括慢性高血糖应激在内的低度代谢炎症的发病机制,在破坏肠道内稳态方面仍知之甚少。在这项研究中,我们试图了解高血糖环境对肠道屏障完整性的影响,以及小分子(35 kDa)透明质酸对上皮屏障功能的保护作用。
方法:从小鼠结肠中分离出的肠类器官在正常葡萄糖培养基(5 mM)或高葡萄糖培养基(25 mM)中生长,以研究高血糖应激对肠道屏障的影响。此外,用 35 kDa 透明质酸(HA35)预处理类器官,以研究高糖应激下透明质酸对上皮屏障的影响。使用免疫印迹和共聚焦成像分别了解屏障蛋白的变化,以及定量和空间分布。通过跨上皮电阻和荧光素异硫氰酸酯通量测定来测量屏障功能的改变。进行非靶向蛋白质组学分析以阐明 HA35 发挥屏障保护作用的机制。利用针对各种 HA 受体的受体敲除小鼠来源的肠类器官,了解 HA 受体在高糖条件下对屏障保护的作用。
结果:我们发现高糖应激降低了两种关键屏障蛋白,即紧密连接蛋白-1(ZO-1)和闭合蛋白的蛋白表达和空间分布。HA35 可防止 ZO-1 的降解或丢失,并在高糖应激下维持 ZO-1 和闭合蛋白的空间分布。功能上,我们还观察到 HA35 在高糖条件下对上皮屏障具有保护作用。我们发现,透明质酸受体层粘连蛋白参与防止屏障蛋白丢失(ZO-1)以及维持 ZO-1 和闭合蛋白的空间分布。此外,蛋白质组学分析显示,在高糖应激下用 HA35 处理的类器官中,细胞死亡和存活是上调的主要途径。我们发现 XIAP 相关因子 1(Xaf1)被 HA35 调节,从而调节肠道类器官系统中的细胞凋亡。最后,我们观察到粘着斑激酶(FAK)和 F-肌动蛋白的空间组织均通过层粘连蛋白被 HA35 介导。
结论:我们的结果强调了高血糖应激对肠道屏障功能的影响。这具有临床相关性,因为代谢综合征患者中观察到了受损的屏障功能。此外,我们通过层粘连蛋白介导的透明质酸受体展示了 HA35 在高糖应激下的屏障保护作用及其对细胞凋亡的调节。
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