Division of Gastroenterology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.
Am J Pathol. 2010 Jan;176(1):158-67. doi: 10.2353/ajpath.2010.090548. Epub 2009 Dec 11.
In inflammatory bowel disease (IBD), aberrant activation of innate and adaptive immune responses enhances mucosal permeability through mechanisms not completely understood. To examine the role of epithelial nuclear factor (NF-kappaB) in IBD-induced enhanced permeability, epithelial-specific IkappaBalpha mutant (NF-kappaB super repressor) transgenic (TG) mice were generated. NF-kB activation was inhibited in TG mice, relative to wild-type mice, following T cell-mediated immune cell activation using an anti-CD3 monoclonal antibody. Furthermore, epithelial NF-kappaB super repressor protein inhibited diarrhea and blocked changes in transepithelial resistance and transmucosal flux of alexa350 (0.35 kDa) and dextran3000 (3 kDa). In vivo perfusion loop studies in TG mice revealed reversed net water secretion and reduced lumenal flux of different molecular probes (bovine serum albumin, alexa350, and dextran3000). Cell-imaging and immunoblotting of low-density, detergent-insoluble membrane fractions confirmed that tight junction proteins (occludin, claudin-1 and zona occludens-1) are internalized through an NF-kappaB-dependent pathway. Taken together, these data suggest that IBD-associated diarrhea results from NF-kappaB-mediated tight junction protein internalization and increased paracellular permeability. Thus, reduction of epithelial NF-kappaB activation in IBD may repair defects in epithelial barrier function, reduce diarrhea, and limit protein (eg, serum albumin) losses. Epithelial NF-kappaB activation induced by mucosal T cells, therefore, actively plays a role in opening paracellular spaces to promote transmucosal fluid effux into the intestinal lumen.
在炎症性肠病(IBD)中,先天和适应性免疫反应的异常激活通过尚未完全理解的机制增强了黏膜通透性。为了研究上皮核因子(NF-κB)在 IBD 诱导的通透性增强中的作用,生成了上皮特异性 IkappaBalpha 突变体(NF-κB 超级抑制剂)转基因(TG)小鼠。与野生型小鼠相比,在用抗 CD3 单克隆抗体介导的免疫细胞激活后,TG 小鼠中的 NF-κB 激活受到抑制。此外,上皮 NF-κB 超级抑制剂蛋白抑制腹泻,并阻止了跨上皮电阻和 Alexa350(0.35 kDa)和右旋糖酐 3000(3 kDa)的跨粘膜通量的变化。在 TG 小鼠的体内灌注环研究中,发现净水分泌逆转和不同分子探针(牛血清白蛋白、Alexa350 和右旋糖酐 3000)的腔内腔通量减少。低密度、去垢剂不可溶膜部分的细胞成像和免疫印迹证实,紧密连接蛋白(occludin、claudin-1 和 zona occludens-1)通过 NF-κB 依赖性途径内化。总之,这些数据表明,IBD 相关的腹泻是由 NF-κB 介导的紧密连接蛋白内化和增加的细胞旁通透性引起的。因此,在 IBD 中减少上皮 NF-κB 激活可能会修复上皮屏障功能的缺陷,减少腹泻,并限制蛋白质(例如血清白蛋白)的损失。因此,黏膜 T 细胞诱导的上皮 NF-κB 激活积极发挥作用,打开细胞旁间隙,促进跨粘膜液体流出肠腔。