Engineered nanomaterials (ENMs) have become common in the food industry, which motivates the need to evaluate ENM effects on human health. Gastrointestinal (GI) in vitro models (e.g. Caco-2, Caco-2/HT29-MTX) have been used in nanotoxicology research. However, the human gut environment is composed of both human cells and the gut microbiota. The goal of this study is to increase the complexity of the Caco-2/HT29-MTX in vitro model by co-culturing human cells with the Gram-positive, commensal Lactobacillus rhamnosus or the Gram-negative, opportunistic Escherichia coli; with the hypothesis that the presence of bacteria would ameliorate the effects of exposure to metal oxide nanoparticles (NPs) such as iron oxide (Fe₂O₃), silicone dioxide (SiO₂), titanium dioxide (TiO₂), or zinc oxide (ZnO). To understand this relationship, Caco-2/HT29-MTX cell barriers were acutely co-exposed (4 hours) to bacteria and/or NPs (pristine or in vitro digested). The activity of the brush border membrane (BBM) enzymes intestinal alkaline phosphatase (IAP), aminopeptidase-N (APN), sucrase isomaltase (SI) and the basolateral membrane enzyme (BLM) Na⁺/K⁺ATPase were assessed. Findings show that (i) the human digestion process alters the physicochemical properties of NPs, (ii) large agglomerates of NPs remain entrapped on the apical side of the intestinal barrier, which (iii) affects the activity of BBM enzymes. Interestingly, some NP effects were attenuated in the presence of either bacterial strain. Confocal microscopy detected bacteria–NP interactions, which may impede the NP-intestinal cell contact. These results highlight the importance of improving in vitro models to closely mimic the complexities of the human body.

中文翻译：

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金属氧化物纳米粒子、大肠杆菌和鼠李糖乳杆菌对小肠酶活性的作用

工程纳米材料 (ENM) 在食品行业中已变得很常见，这激发了评估 ENM 对人类健康影响的需求。胃肠道（GI）体外模型（例如Caco-2、Caco-2/HT29-MTX）已用于纳米毒理学研究。然而，人类肠道环境由人类细胞和肠道微生物群组成。本研究的目的是通过将人类细胞与革兰氏阳性共生鼠李糖乳杆菌或革兰氏阴性机会性大肠杆菌共培养来增加 Caco-2/HT29-MTX体外模型的复杂性；假设细菌的存在会改善接触金属氧化物纳米粒子 (NP)（例如氧化铁 (Fe ₂ O ₃ )、二氧化硅 (SiO ₂ )、二氧化钛 (TiO ₂ ) 或氧化锌）的影响。氧化锌）。为了了解这种关系，将 Caco-2/HT29-MTX 细胞屏障急剧地同时暴露于细菌和/或 NP（原始或体外消化的）中（4 小时）。评估刷状缘膜（BBM）酶肠碱性磷酸酶（IAP）、氨肽酶-N（APN）、蔗糖酶异麦芽酶（SI）和基底外侧膜酶（BLM）Na + /K + ATP酶^的活性^。研究结果表明，(i) 人体消化过程改变了 NP 的理化性质，(ii) NP 的大团聚体仍然被截留在肠屏障的顶端，这 (iii) 影响了 BBM 酶的活性。有趣的是，一些 NP 效应在任一菌株存在时都会减弱。共聚焦显微镜检测到细菌与纳米颗粒的相互作用，这可能会阻碍纳米颗粒与肠细胞的接触。这些结果凸显了改进体外模型以密切模拟人体复杂性的重要性。