Patten Daniel A, Hussein Enas, Davies Scott P, Humphreys Paul N, Collett Andrew
Department of Chemical and Biological Sciences, University of Huddersfield, Huddersfield, UK.
Centre for Liver Research, Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK.
Microbiology (Reading). 2017 May;163(5):702-711. doi: 10.1099/mic.0.000468. Epub 2017 May 22.
Under normal physiological conditions, the intestinal immunity remains largely hyporesponsive to the commensal microbiota, yet also retains the inherent ability to rapidly respond to pathogenic antigens. However, immunomodulatory activities of extracellular products from commensal bacteria have been little studied, with previous investigations generally utilizing the live bacterium to study microbiota-epithelial interactions. In this study, we demonstrate that extracellular products of a commensal bacterium, Escherichia coli C25, elicit a moderate release of proinflammatory IL-8 and stimulate transcriptional up-regulation of Toll-like receptors (TLRs) in intestinal epithelial cell lines HT29-19A and Caco-2. Additionally, we show that removal of outer membrane vesicles (OMVs) reduces the proinflammatory effect of secreted products from E. coli C25. Furthermore, we show that isolated OMVs have a dose-dependent proinflammatory effect on intestinal epithelial cells (IECs). Interestingly, a relatively high concentration (40 µg ml-1 protein) of OMVs had no significant regulatory effects on TLR mRNA expression in both cell lines. Finally, we also demonstrate that pre-incubation with E. coli C25-derived OMVs subsequently inhibited the internalization of the bacterium itself in both cell lines. Taken together, our results suggest that commensal-derived extracellular products, in particular OMVs, could significantly contribute to intestinal homeostasis. We also demonstrate a unique interaction between commensal-derived OMVs and host cells.
在正常生理条件下，肠道免疫系统对共生微生物群大多保持低反应性，但仍保留对病原性抗原快速反应的固有能力。然而，共生细菌胞外产物的免疫调节活性鲜有研究，以往的研究通常利用活细菌来研究微生物群与上皮细胞的相互作用。在本研究中，我们证明共生细菌大肠杆菌C25的胞外产物可引起促炎细胞因子IL-8的适度释放，并刺激肠道上皮细胞系HT29-19A和Caco-2中Toll样受体（TLRs）的转录上调。此外，我们发现去除外膜囊泡（OMVs）可降低大肠杆菌C25分泌产物的促炎作用。此外，我们还表明，分离出的OMVs对肠道上皮细胞（IECs）具有剂量依赖性的促炎作用。有趣的是，相对高浓度（40μg ml-1蛋白质）的OMVs对两种细胞系中TLR mRNA表达均无显著调节作用。最后，我们还证明，用大肠杆菌C25来源的OMVs预孵育随后会抑制两种细胞系中细菌本身的内化。综上所述，我们的结果表明，共生来源的胞外产物，特别是OMVs，可能对肠道稳态有显著贡献。我们还证明了共生来源的OMVs与宿主细胞之间存在独特的相互作用。
