Ma Thomas Y, Iwamoto Gary K, Hoa Neil T, Akotia Vimesh, Pedram Ali, Boivin Michel A, Said Hamid M
Department of Internal Medicine, University of New Mexico, Albuquerque, NM 87131-0001, USA.
Am J Physiol Gastrointest Liver Physiol. 2004 Mar;286(3):G367-76. doi: 10.1152/ajpgi.00173.2003.
Crohn's disease (CD) patients have an abnormal increase in intestinal epithelial permeability. The defect in intestinal tight junction (TJ) barrier has been proposed as an important etiologic factor of CD. TNF-alpha increases intestinal TJ permeability. Because TNF-alpha levels are markedly increased in CD, TNF-alpha increase in intestinal TJ permeability could be a contributing factor of intestinal permeability defect in CD. Our purpose was to determine some of the intracellular mechanisms involved in TNF-alpha modulation of intestinal epithelial TJ permeability by using an in vitro intestinal epithelial system consisting of filter-grown Caco-2 monolayers. TNF-alpha produced a concentration- and time-dependent increase in Caco-2 TJ permeability. TNF-alpha-induced increase in Caco-2 TJ permeability correlated with Caco-2 NF-kappa B activation. Inhibition of TNF-alpha-induced NF-kappa B activation by selected NF-kappa B inhibitors, curcumin and triptolide, prevented the increase in Caco-2 TJ permeability, indicating that NF-kappa B activation was required for the TNF-alpha-induced increase in Caco-2 TJ permeability. This increase in Caco-2 TJ permeability was accompanied by down-regulation of zonula occludens (ZO)-1 proteins and alteration in junctional localization of ZO-1 proteins. TNF-alpha modulation of ZO-1 protein expression and junctional localization were also prevented by NF-kappa B inhibitors. TNF-alpha did not induce apoptosis in Caco-2 cells, suggesting that apoptosis was not the mechanism involved in TNF-alpha-induced increase in Caco-2 TJ permeability. These results demonstrate for the first time that TNF-alpha-induced increase in Caco-2 TJ permeability was mediated by NF-kappa B activation. The increase in permeability was associated with NF-kappa B-dependent downregulation of ZO-1 protein expression and alteration in junctional localization.
克罗恩病（CD）患者的肠道上皮通透性异常增加。肠道紧密连接（TJ）屏障缺陷被认为是CD的一个重要病因。肿瘤坏死因子-α（TNF-α）可增加肠道TJ通透性。由于CD患者体内TNF-α水平显著升高，因此TNF-α导致的肠道TJ通透性增加可能是CD患者肠道通透性缺陷的一个促成因素。我们的目的是通过使用由滤膜培养的Caco-2单层细胞组成的体外肠道上皮系统，确定TNF-α调节肠道上皮TJ通透性所涉及的一些细胞内机制。TNF-α使Caco-2 TJ通透性呈浓度和时间依赖性增加。TNF-α诱导的Caco-2 TJ通透性增加与Caco-2核因子-κB（NF-κB）激活相关。选用的NF-κB抑制剂姜黄素和雷公藤内酯醇抑制TNF-α诱导的NF-κB激活，可阻止Caco-2 TJ通透性增加，表明NF-κB激活是TNF-α诱导Caco-2 TJ通透性增加所必需的。Caco-2 TJ通透性的这种增加伴随着闭合蛋白（ZO）-1蛋白的下调以及ZO-1蛋白连接定位的改变。NF-κB抑制剂也可阻止TNF-α对ZO-1蛋白表达和连接定位的调节。TNF-α未诱导Caco-2细胞凋亡，提示凋亡不是TNF-α诱导Caco-2 TJ通透性增加的机制。这些结果首次证明，TNF-α诱导的Caco-2 TJ通透性增加是由NF-κB激活介导的。通透性增加与NF-κB依赖性的ZO-1蛋白表达下调以及连接定位改变有关。
