Probiotic Escherichia coli Nissle 1917-derived outer membrane vesicles enhance immunomodulation and antimicrobial activity in RAW264.7 macrophages

Abstract

Background: 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. Results: 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. Conclusions: 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.

Francisella tularensis Outer Membrane Vesicles Participate in the Early Phase of Interaction With Macrophages

“…Most of the studies focused on OMV-host cell interaction have demonstrated the internalization of the vesicles into epithelial cells (Kunsmann et al, 2015;Mondal et al, 2016;Bielaszewska et al, 2017;O'Donoghue et al, 2017;Turner et al, 2018). Only a few studies have provided direct evidence for OMV uptake into macrophages (Pollak et al, 2012;Vanaja et al, 2016;Hu et al, 2020). This might mainly be due to the fact that, as professional phagocytes, macrophages are naturally programmed to engulf and eliminate any foreign particles, and therefore the internalization of OMV is highly assumed.…”

Heterogeneous Populations of Outer Membrane Vesicles Released from Helicobacter Pylori SS1 with Distinct Biological Properties

“…8 a&b and Fig. 9) [77,78] . Similar findings were reported when the response of macrophages towards OMVs derived from…”

An OMV-Based Nanovaccine Confers Safety and Protection against Pathogenic Escherichia coli via Both Humoral and Predominantly Th1 Immune Responses in Poultry

“…This APEC isolate was grown in Luria–Bertani (LB) broth at 37 °C. Native OMVs were isolated and purified from bacterial culture supernatant by a series of centrifugal processes, as described in our previous studies [ 36 , 37 ]. Briefly, the bacteria-free supernatant was collected from the culture medium in the logarithmic phase by centrifugation (12,000× g , 15 min, 4 °C), and filtered through a 0.45-μm membrane (Merck Millipore, Tullagreen, Carrigtwohill, Ireland) followed by ultracentrifugation (150,000× g , 2 h, 4 °C).…”