Escherichia coli isolates from inflammatory bowel diseases patients survive in macrophages and activate NLRP3 inflammasome

Abstract

Crohn’s disease (CD) is a multifactorial pathology associated with the presence of adherent-invasive Escherichia coli (AIEC) and NLRP3 polymorphic variants. The presence of intracellular E. coli in other intestinal pathologies (OIP) and the role of NLRP3-inflammasome in the immune response activated by these bacteria have not been investigated. In this study, we sought to characterize intracellular strains isolated from patients with CD, ulcerative colitis (UC) and OIP, and analyze NLRP3-inflammasome role in the immune response and bactericidal activity induced in macrophages exposed to invasive bacteria. For this, intracellular E. coli isolation from ileal biopsies, using gentamicin-protection assay, revealed a prevalence and CFU/biopsy of E. coli higher in biopsies from CD, UC and OIP patients than in controls. To characterization of bacterial isolates, pulsed-field gel electrophoresis (PFGE) patterns, virulence genes, serogroup and phylogenetic group were analyzed. We found out that bacteria isolated from a given patient were closely related and shared virulence factors; however, strains from different patients were genetically heterogeneous. AIEC characteristics in isolated strains, such as invasive and replicative properties, were assessed in epithelial cells and macrophages, respectively. Some strains from CD and UC demonstrated AIEC properties, but not strains from OIP. Furthermore, the role of NLRP3 in pro-inflammatory cytokines production and bacterial elimination was determined in macrophages. E. coli strains induced IL-1β through NLRP3-dependent mechanism; however, their elimination by macrophages was independent of NLRP3. Invasiveness of intracellular E. coli strains into the intestinal mucosa and IL-1β production may contribute to CD and UC pathogenesis.

The IbeA Invasin of Adherent-Invasive Escherichia coli Mediates Interaction with Intestinal Epithelia and Macrophages

“…Our results further support the idea that AIEC might have more than one mechanism to interact with M cells and access the underlying macrophages present in the lymphoid tissue. The survival within murine macrophages by AIEC isolates has been well described (3), where the survival at 24 h postinfection can range from 32 to 100% of bacteria phagocytosed in the case of the Crohn's disease-associated strains (4,51). In our study, the survival of NRG857c in human macrophages at 24 h postinfection was 32.42%, which is consistent with what has been reported for other AIEC strains.…”

Alteration of the fecal microbiota and serum metabolite profiles in dogs with idiopathic inflammatory bowel disease

“…The qPCR results suggested that this increase was due to E. coli, and this group is of particular interest, as previous studies have reported an increased virulent potential of E. coli, such as adhesive capacity, invasive capacity, toxin production, and inflammatory cytokine stimulation, in human patients with IBD. 29,30 Adherent and invasive E. coli strains have been reported specifically in Boxer dogs with granulomatous colitis. 31 Whether the virulent potential of E. coli plays a similar role in other forms of canine inflammatory bowel disease remains to be determined.…”

Adherent-invasive Escherichia coli in inflammatory bowel disease

“…AIEC survival and replication in macrophages is promoted by the stress protein HtrA,67 the thiol-disulfide oxidoreductase DsbA,68 the RNA-binding protein Hfq69 and the FAD-dependent oxydoreductase IbeA70 that play a role in surviving reactive oxygen species (ROS) (table 1). In response to AIEC infection, tumour necrosis factor α (TNF-α)35 71 72 and other proinflammatory cytokines73 are released, further enhancing dysbiosis and proliferation of AIEC without inducing host cell death. AIEC are able to exploit host mechanisms of apoptosis by increasing S-nitrosylation and proteasomal degradation of caspase-3 in infected macrophages,74favouring their own intracellular replication through modulation of the ubiquitin proteasome system in infected-IEC,75 76 and through the release of exosomes from infected cells 77.…”