The Bacteroides fragilis toxin fragilysin disrupts the paracellular barrier of epithelial cells
The Bacteroides fragilis toxin fragilysin disrupts the paracellular barrier of epithelial cells
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DOI：
10.1128/iai.65.4.1431-1439.1997
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发表时间：
1997-04-01
影响因子：
3.1
通讯作者：
Wilkins, TD
中科院分区：
文献类型：
--
作者：
Obiso, RJ;Azghani, AO;Wilkins, TD
脆弱拟杆菌是大多数哺乳动物正常结肠微生物区系的成员，并且是最常见的从人类临床标本分离的厌氧菌。一些菌株产生一种毒素（脆裂素，一种锌金属蛋白酶），可能是家畜和人类腹泻病的原因。我们实验室的研究证实，这种毒素的蛋白水解活性是体内观察到的液体分泌和组织损伤的原因。在这项研究中，我们研究了脆弱溶素对上皮细胞的细胞旁屏障的影响。研究人员认为，由于这种毒素迅速使HT-29细胞中毒，它可能被内化。然而，我们不能通过使用受体介导的内吞作用的抑制剂来防止细胞变圆，这表明毒素可能在细胞外起作用。基于这些观察，我们研究了高纯度B的影响。fragilis fragilysin对培养的上皮细胞屏障功能的影响。脆性溶素迅速增加上皮细胞的细胞旁屏障对离子（单层电阻降低）和大分子（单层甘露醇通量增加）的渗透性。我们测试了人类结肠细胞系以及来自肺和肾的细胞系;人类结肠细胞系最敏感，但所有三种细胞系都以相同的方式受到影响。我们的研究表明，B. fragilis fragilysin可能通过降解紧密连接蛋白如ZO-1改变上皮衬里的屏障功能。蛋白水解活性是引起这种效应所必需的。毒素的作用被认为是有限的肠道，然而，我们的研究表明，脆溶素也可能有助于B的发病机制。脆弱性肠外感染。
Bacteroides fragilis is a member of the normal colonic microflora of most mammals and is the most commonly isolated anaerobe from human clinical specimens. Some strains produce a toxin (fragilysin, a zinc-metalloproteinase) implicated as a cause of diarrheal disease in farm animals and humans. Studies in our laboratory confirm that the proteolytic activity of this toxin is responsible for the fluid secretion and tissue damage observed in vivo. In this study, we investigated the effects of fragilysin on the paracellular barrier of epithelial cells. Researchers suggest that, since the toxin rapidly intoxicates HT-29 cells, it may be internalized. However, we could not prevent cell rounding by using inhibitors of receptor-mediated endocytosis, which indicates that the toxin may act outside the cell. Based on these observations, we studied the effects of the highly purified B. fragilis fragilysin on the barrier function of cultured epithelial cells. Fragilysin rapidly increased the permeability of the paracellular barrier of epithelial cells to ions (decrease in electrical resistance across monolayers) and to larger molecules (increase in mannitol flux across monolayers). We tested a human colon cell line and cell lines from the lung and the kidney; the human colon cell line was most sensitive, but all three were affected in the same manner. Our studies show that B. fragilis fragilysin alters the barrier function of the epithelial lining, possibly by degrading the tight junction proteins, such as ZO-1. The proteolytic activity is required to cause this effect. The toxin's action has been assumed to be limited to the intestine; however, our studies show that fragilysin could also contribute to the pathogenesis of B. fragilis in extraintestinal infections.