title: Activation of Immune and Defense Responses in the Intestinal Mucosa by Outer Membrane Vesicles of Commensal and Probiotic Escherichia coli Strains.
abstract: The influence of microbiota in human health is well-known. Imbalances in microbiome structure have been linked to several diseases. Modulation of microbiota composition through probiotic therapy is an attempt to harness the beneficial effects of commensal microbiota. Although, there is wide knowledge of the responses induced by gut microbiota, the microbial factors that mediate these effects are not well-known. Gram-negative bacteria release outer membrane vesicles (OMVs) as a secretion mechanism of microbial factors, which have an important role in intercellular communication. Here, we investigated whether OMVs from the probiotic Escherichia coli strain Nissle 1917 (EcN) or the commensal E. coli strain ECOR12 trigger immune responses in various cellular models: (i) peripheral blood mononuclear cells (PBMCs) as a model of intestinal barrier disruption, (ii) apical stimulation of Caco-2/PMBCs co-culture as a model of intact intestinal mucosa, and (iii) colonic mucosa explants as an ex vivo model. Stimulations with bacterial lysates were also performed. Whereas, both OMVs and lysates activated expression and secretion of several cytokines and chemokines in PBMCs, only OMVs induced basolateral secretion and mRNA upregulation of these mediators in the co-culture model. We provide evidence that OMVs are internalized in polarized Caco-2 cells. The activated epithelial cells elicit a response in the underlying immunocompetent cells. The OMVs effects were corroborated in the ex vivo model. This experimental study shows that OMVs are an effective strategy used by beneficial gut bacteria to communicate with and modulate host responses, activating signaling events through the intestinal epithelial barrier.
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Institut de Biomedicina de la Universitat de Barcelona, Universitat de Barcelona Barcelona, Spain.
authors.forename: María José
authors.initials: MJ
authors.lastname: Fábrega
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Institut de Biomedicina de la Universitat de Barcelona, Universitat de Barcelona Barcelona, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Aguilera
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Institut de Biomedicina de la Universitat de Barcelona, Universitat de Barcelona Barcelona, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Giménez
authors.affiliation: Department of Gastroenterology, Digestive System Research Unit, Institut de Recerca Vall d'Hebron, CIBER EHD, Instituto de Salud Carlos III, University Hospital Vall d'Hebron, Universitat Autònoma de Barcelona Barcelona, Spain.
authors.forename: Encarna
authors.initials: E
authors.lastname: Varela
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Institut de Biomedicina de la Universitat de Barcelona, Universitat de Barcelona Barcelona, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Alexandra Cañas
authors.affiliation: Department of Gastroenterology, Digestive System Research Unit, Institut de Recerca Vall d'Hebron, CIBER EHD, Instituto de Salud Carlos III, University Hospital Vall d'Hebron, Universitat Autònoma de Barcelona Barcelona, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Antolín
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Institut de Biomedicina de la Universitat de Barcelona, Universitat de Barcelona Barcelona, Spain.
authors.forename: Josefa
authors.initials: J
authors.lastname: Badía
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Institut de Biomedicina de la Universitat de Barcelona, Universitat de Barcelona Barcelona, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Baldomà
keywords: Caco-2/PBMC co-culture; Nissle 1917; gut microbes; intestinal mucosa; membrane vesicles; microbiota-host crosstalk; probiotics