Bifidobacterium bifidum modulation of intestinal barrier and intestinal inflammation

 描述(申请人提供)：肠道上皮紧密连接(TJ)屏障缺陷是炎症性肠病(IBD)和其他肠道炎症条件的关键致病因素。漏水的TJ屏障可以增加肠道内细菌抗原的渗透，从而引发炎症反应。先前的研究表明，在IBD动物模型和人类IBD模型中，肠道TJ屏障的收紧(或重新收紧)可以防止肠道炎症的发展。然而，目前还没有可用的治疗药物来靶向肠道TJ屏障。在医疗方面也有一个重要的差距 关于可靶向诱导肠道TJ屏障治疗性收紧的细胞内过程的知识。在这项拨款申请中，我们打算1)推出一项新的 以肠道TJ屏障为靶点的治疗剂，可迅速推进临床 用法；以及2)确定可靶向诱导肠道TJ屏障收紧的细胞内机制。在我们的初步研究中，我们测试了一些商业上广泛可用的益生菌物种/菌株，以鉴定单一菌株双歧双歧杆菌VIII-21(BB)，该菌株可显著增强肠道TJ屏障，并在IBD动物模型中具有治疗效果。本应用的总体目标是研究BB对肠道TJ屏障的增强作用，并确定BB在IBD动物模型中的治疗效果。基于我们令人信服的初步数据，我们提出了一个新的假设，即BB通过增强和保护肠道TJ屏障来预防肠道炎症的发展；BB增强和保护肠道TJ屏障是通过Nod1信号转导途径激活occludin基因和抑制肌球蛋白轻链激酶(MLCK)基因来介导的。在这项拨款申请中，我们还挑战了两个成熟的科学范式：1)Nod1是细胞质模式识别受体；2)Nod1的主要细胞靶点是激活NF-κB。我们还假设，BB可以通过Nod1/PPAR-γ介导的抑制(而不是激活)NF-κB和MLCK基因的抑制(而不是激活)来对抗促炎细胞因子诱导的肠道TJ通透性增加。提出了四个相互关联的具体目标来解决上述假设：1)阐明PRRs在BB诱导的肠上皮TJ屏障增强中的作用；2)阐明BB调节肠TJ屏障的分子机制；3)阐明BB对抗促炎细胞因子诱导的肠TJ通透性增加的保护机制；以及4)BB在IBD动物模型中的治疗作用。拟议研究的成功完成将有助于弥合科学知识方面的重要差距，并提供关键的临床前数据，以支持计划中的未来临床研究。

 DESCRIPTION (provided by applicant): Defective intestinal epithelial tight junction (TJ) barrier is a key pathogenic factor of inflammatory bowel disease (IBD) and other inflammatory conditions of the gut. A leaky TJ barrier allows increased intestinal permeation of bacterial antigens that induce inflammatory response. Previous studies have shown that tightening (or re-tightening) of the intestinal TJ barrier prevents the development of intestinal inflammation in both animal models of IBD and in human IBD. However, there are no currently available therapeutic agents that target the intestinal TJ barrier. There is also an important gap in medical knowledge regarding the intracellular processes that can be targeted to induce therapeutic tightening of the intestinal TJ barrier. In this grant application, we intend to 1) introduce a new therapeutic agent that targets the intestinal TJ barrier which can be rapidly advanced for clinical usage; and 2) identify intracellular mechanisms that can be targeted to induce tightening of the intestinal TJ barrier. In our preliminary studies, we tested number of probiotic species/strains that are widely available commercially to identify a single strain, Bifidobacterium bifidum VIII-21 (BB), which causes a marked enhancement in intestinal TJ barrier and has therapeutic efficacy in animal models of IBD. The over-arching goals of this application are to investigate the intestinal TJ barrier augmenting effects of BB and to determine the therapeutic efficacy of BB in animal models of IBD. Based on our compelling preliminary data, we advance a novel hypothesis that BB protects against the development of intestinal inflammation by enhancing and preserving the intestinal TJ barrier; and that BB enhancement and protection of intestinal TJ barrier is mediated by Nod1 signal-transduction pathway activation of occludin gene and suppression of myosin light chain kinase (MLCK) gene. In this grant application, we also challenge 2 well-established scientific paradigms: 1) that Nod1 is a cytoplasmic pattern recognition receptor (PRR); and 2) that the primary cellular target of Nod1 is the activation of NF-κB. We also hypothesize that BB protects against pro-inflammatory cytokine-induced increase in intestinal TJ permeability by Nod1/PPAR- γ mediated suppression (not activation) of NF-κB and MLCK gene. Four inter-linked specific aims are proposed to address above hypotheses: 1) to delineate the role of PRRs in BB-induced augmentation of intestinal epithelial TJ barrier; 2) to delineate the molecular mechanism of BB modulation of intestinal TJ barrier; 3) to delineate the protective mechanism of BB against of pro-inflammatory cytokine-induced increase in intestinal TJ permeability; and 4) to delineate the therapeutic efficacy of BB in anima models of IBD. The successful completion of the proposed studies will help bridge the important gap in scientific knowledge and provide crucial pre-clinical data to support the planned future clinical studies.