Abstract
The gut barrier plays an important role in human health. When barrier function is impaired, altered permeability and barrier dysfunction can occur, leading to inflammatory bowel diseases, irritable bowel syndrome or obesity. Several bacteria, including pathogens and commensals, have been found to directly or indirectly modulate intestinal barrier function. The use of probiotic strains could be an important landmark in the management of gut dysfunction with a clear impact on the general population. Previously, we found that Lactobacillus rhamnosus CNCM I-3690 can protect intestinal barrier functions in mice inflammation model. Here, we investigated its mechanism of action. Our results show that CNCM I-3690 can (i) physically maintain modulated goblet cells and the mucus layer and (ii) counteract changes in local and systemic lymphocytes. Furthermore, mice colonic transcriptome analysis revealed that CNCM I-3690 enhances the expression of genes related to healthy gut permeability: motility and absorption, cell proliferation; and protective functions by inhibiting endogenous proteases. Finally, SpaFED pili are clearly important effectors since an L. rhamnosus ΔspaF mutant failed to provide the same benefits as the wild type strain. Taken together, our data suggest that CNCM I-3690 restores impaired intestinal barrier functions via anti-inflammatory and cytoprotective responses.
Highlights
The genus Lactobacillus is a phylogenetically diverse group of Gram-positive bacteria
We determined which of 63 adhesin proteins found in lactobacilli were present in L. rhamnosus CNCM I-3690 (Fig. 1)
The spaFED operon has been observed in all L. rhamnosus strains analyzed, including CNCM I-3690
Summary
The genus Lactobacillus is a phylogenetically diverse group of Gram-positive bacteria. The intestinal barrier separates the self from the non-self and serves as the first line of defence against external threats such as toxins and pathogens It presents a functional unit of a physical barrier consisting of a mucus layer and a monolayer of epithelial cells and of a mucosal lymphoid system that together efficiently discriminate between pathogenic and commensal microorganisms[16]. We reported that L. rhamnosus CNCM I-3690 counteracts the increased intestinal permeability induced by mild inflammation as efficiently as the commensal Faecalibacterium prausnitzii A2-16522. This strain protects against oxidative stress in Caenorhabditis elegans[23]. We aimed to decipher the mechanisms underlying L. rhamnosus CNCM I-3690’s effects on gut barrier and identify the bacterial effectors involved
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