Wells C L, Jechorek R P, Olmsted S B, Erlandsen S L
Department of Laboratory Medicine & Pathology, University of Minnesota, Minneapolis 55455.
Circ Shock. 1993 Aug;40(4):276-88.
Bacterial lipopolysaccharide (LPS) has been speculated to facilitate bacterial translocation by a mechanism involving physical disruption of the gut mucosal barrier. Polarized, cultured intestinal epithelial cells (Caco-2 cells) were used to study the effect of LPS on enterocyte structure, viability, and susceptibility to bacterial invasion. Varying concentrations of biologically active LPS were incubated with enterocytes for 1 and 16 hr. LPS had no noticeable effect on enterocyte viability or morphology, as measured by uptake of vital dyes, by distribution of cytoskeletal filamentous actin, and by visualization of subcellular ultrastructure. Transepithelial electrical resistance was similar in enterocyte cultures incubated with LPS for 1 hr, but there was a noticeable decrease after 16 hr, indicating a loss of epithelial integrity after prolonged exposure to LPS. The effect of LPS on bacterial uptake was studied using six strains of enteric bacteria with varying abilities to invade Caco-2 cells: Listeria monocytogenes, Salmonella typhimurium, Proteus mirabilis, Escherichia coli (2 strains), and Enterococcus faecalis. Electron microscopy showed enteric bacteria in intimate association with enterocyte apical microvilli, and internalized bacteria were consistently observed within cytoplasmic, membrane-bound vacuoles. Following a 1-hr incubation of individual strains of enteric bacteria with Caco-2 cells, numbers of viable intracellular bacteria varied significantly between individual bacterial strains, but numbers of intracellular bacteria were similar for each strain incubated with enterocytes exposed to 0, 10, and 100 micrograms LPS for 1 and 16 hr. Thus, although prolonged exposure to LPS might have some effect on enterocyte culture integrity (as measured by decreased electrical resistance), LPS had no discernible effect on enterocyte structure, viability, and susceptibility to bacterial invasion. These results suggested that LPS-induced bacterial translocation might not involve loss of epithelial viability, or facilitated entry of bacteria into intestinal epithelial cells.
细菌脂多糖（LPS）被推测可通过一种涉及肠道黏膜屏障物理破坏的机制促进细菌移位。使用极化的培养肠上皮细胞（Caco-2细胞）来研究LPS对肠上皮细胞结构、活力以及对细菌侵袭易感性的影响。将不同浓度的生物活性LPS与肠上皮细胞孵育1小时和16小时。通过摄取活性染料、细胞骨架丝状肌动蛋白的分布以及亚细胞超微结构的可视化来测量，LPS对肠上皮细胞活力或形态没有明显影响。在与LPS孵育1小时的肠上皮细胞培养物中，跨上皮电阻相似，但16小时后有明显下降，表明长时间暴露于LPS后上皮完整性丧失。使用六种侵袭Caco-2细胞能力不同的肠道细菌菌株研究LPS对细菌摄取的影响：单核细胞增生李斯特菌、鼠伤寒沙门氏菌、奇异变形杆菌、大肠杆菌（两株）和粪肠球菌。电子显微镜显示肠道细菌与肠上皮细胞顶端微绒毛紧密相连，并且在细胞质膜结合的液泡内始终观察到内化细菌。将各肠道细菌菌株与Caco-2细胞孵育1小时后，各细菌菌株的活细胞内细菌数量差异显著，但对于与暴露于0、10和100微克LPS 1小时和16小时的肠上皮细胞一起孵育的每种菌株，细胞内细菌数量相似。因此，尽管长时间暴露于LPS可能对肠上皮细胞培养完整性有一些影响（通过电阻降低来衡量），但LPS对肠上皮细胞结构、活力以及对细菌侵袭的易感性没有明显影响。这些结果表明，LPS诱导的细菌移位可能不涉及上皮活力丧失，也不涉及细菌进入肠道上皮细胞的促进作用。
