Li E, Stenson W F, Kunz-Jenkins C, Swanson P E, Duncan R, Stanley S L
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Infect Immun. 1994 Nov;62(11):5112-9. doi: 10.1128/iai.62.11.5112-5119.1994.
To model the initial pathogenic effects of Entamoeba histolytica trophozoites on intestinal epithelial cells, the interactions of E. histolytica HM1-IMSS trophozoites with polarized human intestinal Caco-2 cell monolayers grown on permeabilized filters were examined. Trophozoites, when incubated with the apical surface of the monolayers at 37 degrees C, induced a rapid decrease in transepithelial resistance over 15 to 60 min. The transmonolayer resistance response was not associated with changes in short-circuit current but was associated with an increase in mannitol flux, suggesting that the drop in resistance reflected a nonselective increase in epithelial permeability rather than stimulation of electrogenic ion transport. This response preceded the earliest detection of morphologic disruption of monolayer integrity by light or electron microscopy. Apical injury to the monolayer was detected by ultrastructural studies which revealed a loss of brush border in regions of contact between epithelial cells and amebas and by chromium release assays where a small increase in the apical release of 51Cr from the monolayer (6% over background) was observed. The transmonolayer resistance response was inhibited when the temperature was reduced to 4 degrees C and by addition of cytochalasin D (1 microgram/ml) to the medium at concentrations that did not directly affect transmonolayer resistance. Application of amebic lysates or medium conditioned by coincubation of amebas with Caco-2 monolayers failed to lower transmonolayer resistance, suggesting that this effect was not mediated by soluble amebic cytotoxins. Polarized Caco-2 monolayers grown on permeable filters provide a useful model for studying the initial interactions of E. histolytica trophozoites with intestinal epithelial cells.
为模拟溶组织内阿米巴滋养体对肠道上皮细胞的初始致病作用，研究了溶组织内阿米巴HM1-IMSS滋养体与在通透滤器上生长的极化人肠道Caco-2细胞单层之间的相互作用。将滋养体与单层细胞的顶端表面在37℃孵育时，跨上皮电阻在15至60分钟内迅速下降。跨单层电阻反应与短路电流的变化无关，但与甘露醇通量的增加有关，这表明电阻下降反映了上皮通透性的非选择性增加，而非电生性离子转运的刺激。这种反应先于通过光学或电子显微镜最早检测到的单层完整性形态破坏。通过超微结构研究检测到单层的顶端损伤，该研究显示上皮细胞与阿米巴接触区域的刷状缘丧失，并且通过铬释放试验观察到单层顶端51Cr释放略有增加（比背景高6%）。当温度降至4℃以及在不直接影响跨单层电阻的浓度下向培养基中添加细胞松弛素D（1微克/毫升）时，跨单层电阻反应受到抑制。应用阿米巴裂解物或由阿米巴与Caco-2单层共同孵育条件化的培养基未能降低跨单层电阻，这表明这种作用不是由可溶性阿米巴细胞毒素介导的。在可渗透滤器上生长的极化Caco-2单层为研究溶组织内阿米巴滋养体与肠道上皮细胞的初始相互作用提供了一个有用的模型。
