College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, Shaanxi, China.
Department of Animal Engineering, Yangling Vocation and Technical Colleg, Yangling, 712100, Shaanxi, China.
BMC Microbiol. 2020 Aug 27;20(1):268. doi: 10.1186/s12866-020-01953-x.
Probiotic Escherichia coli Nissle 1917 (EcN) has been widely studied for the treatment of intestinal inflammatory diseases and infectious diarrhea, but the mechanisms by which they communicate with the host are not well-known. Outer membrane vesicles (OMVs) are produced by Gram-negative bacteria and deliver microbial molecules to distant target cells in the host, which play a very important role in mediating bacteria-host communication. Here, we aimed to investigate whether EcN-derived OMVs (EcN_OMVs) could mediate immune regulation in macrophages.
In this study, after the characterization of EcN_OMVs using electron microscopy, nanoparticle tracking and proteomic analyses, we demonstrated by confocal fluorescence microscopy that EcN_OMVs could be internalized by RAW 264.7 macrophages. Stimulation with EcN_OMVs at appropriate concentrations promoted proliferation, immune-related enzymatic activities and phagocytic functions of RAW264.7 cells. Moreover, EcN_OMVs induced more anti-inflammatory responses (IL-10) than pro-inflammatory responses (IL-6 and TNF-α) in vitro, and also modulated the production of Th1-polarizing cytokine (IL-12) and Th2-polarizing cytokine (IL-4). Treatments with EcN_OMVs effectively improved the antibacterial activity of RAW 264.7 macrophages.
These findings indicated that EcN_OMVs could modulate the functions of the host immune cells, which will enrich the existing body of knowledge of EVs as an important mechanism for the communication of probiotics with their hosts.
益生菌大肠杆菌 Nissle 1917（EcN）已被广泛研究用于治疗肠道炎症性疾病和感染性腹泻，但它们与宿主相互作用的机制尚不清楚。外膜囊泡（OMVs）由革兰氏阴性菌产生，并将微生物分子递送至宿主中的远处靶细胞，在外膜囊泡在介导细菌-宿主通讯中起着非常重要的作用。在这里，我们旨在研究 EcN 衍生的 OMVs（EcN_OMVs）是否可以调节巨噬细胞的免疫。
在使用电子显微镜、纳米颗粒跟踪和蛋白质组学分析对 EcN_OMVs 进行表征后，我们通过共聚焦荧光显微镜证明 EcN_OMVs 可以被 RAW 264.7 巨噬细胞内化。在适当浓度下刺激 EcN_OMVs 可促进 RAW264.7 细胞的增殖、免疫相关酶活性和吞噬功能。此外，EcN_OMVs 在体外诱导的抗炎反应（IL-10）多于促炎反应（IL-6 和 TNF-α），并且还调节 Th1 极化细胞因子（IL-12）和 Th2 极化细胞因子（IL-4）的产生。用 EcN_OMVs 处理可有效改善 RAW 264.7 巨噬细胞的抗菌活性。
这些发现表明 EcN_OMVs 可以调节宿主免疫细胞的功能，这将丰富 EVs 作为益生菌与其宿主进行通讯的重要机制的现有知识体系。
