Abstract
Gut microbiota dysbiosis toward adherent-invasive Escherichia coli (AIEC) plays an important role in Crohn’s disease (CD). The OmpR transcriptional regulator is required for the AIEC LF82 prototype strain to adhere and invade intestinal epithelial cells. In this study, we explored the role of OmpR in AIEC pathogenesis using a panel of eight Escherichia coli strains isolated from CD patients and identified as AIEC. The deletion of ompR together with the implementation of two cell-based assays revealed that the role of OmpR in adhesion in vitro was not conserved in AIEC clinical strains. Nevertheless, we showed that OmpR was required for robust gut colonization of transgenic mice expressing human CEACAM receptors, suggesting that OmpR is involved in alternative virulence mechanisms in AIEC strains. We found that deletion of ompR compromised the ability of AIEC strains to cope with the stress induced by bile salts, which may be key for AIEC pathogenesis. More specifically, we demonstrated that OmpR was involved in a tolerance mechanism toward sodium deoxycholate (DOC), one of bile salts main component. We showed that the misregulation of OmpF or the loss of outer membrane integrity are not the drivers of OmpR-mediated DOC tolerance, suggesting that OmpR regulates a specific mechanism enhancing AIEC survival in the presence of DOC. In conclusion, the newly discovered role of OmpR in AIEC bile tolerance suggests that OmpR inhibition would interfere with different aspects of AIEC virulence arsenal and could be an alternative strategy for CD-treatment.
Highlights
Crohn’s disease (CD) is a type of inflammatory bowel disease (IBD), which is a complex chronic disorder that primarily disturbs the digestive system (Crohn’s disease, 2020)
adherent-invasive Escherichia coli (AIEC) adhesion and invasion is mainly mediated by the type 1 pili and their adhesin FimH that bind to the glycoproteins, such as carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) that are enriched at the surface of ileal epithelial cells of CD patients (Boudeau et al, 2001; Barnich et al, 2007)
The results from a previous study showed that OmpR is involved in in vitro adhesion and invasion capacities of the LF82 AIEC reference strain, suggesting that OmpR may contribute to AIEC-mediated exacerbation of CD (Rolhion et al, 2007)
Summary
Crohn’s disease (CD) is a type of inflammatory bowel disease (IBD), which is a complex chronic disorder that primarily disturbs the digestive system (Crohn’s disease, 2020). AIEC adhesion and invasion is mainly mediated by the type 1 pili and their adhesin FimH that bind to the glycoproteins, such as carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) that are enriched at the surface of ileal epithelial cells of CD patients (Boudeau et al, 2001; Barnich et al, 2007). AIEC strains have been described as moderate to strong in vitro biofilm producers (Martinez-Medina et al, 2009). These attributes potentially contribute to AIEC mediated exacerbation of CD through their enrichment in ileal mucosa leading to chronic intestinal inflammation
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