Secretion of Alpha-Hemolysin by Escherichia coli Disrupts Tight Junctions in Ulcerative Colitis Patients

Abstract

Objectives:The potential of Escherichia coli (E. coli) isolated from inflammatory bowel disease (IBD) patients to damage the integrity of the intestinal epithelium was investigated.Methods:E. coli strains isolated from patients with ulcerative colitis (UC) and healthy controls were tested for virulence capacity by molecular techniques and cytotoxic assays and transepithelial electric resistance (TER). E. coli isolate p19A was selected, and deletion mutants were created for alpha-hemolysin (α-hemolysin) (hly) clusters and cytotoxic necrotizing factor type 1 (cnf1). Probiotic E. coli Nissle and pathogenic E. coli LF82 were used as controls.Results:E. coli strains from patients with active UC completely disrupted epithelial cell tight junctions shortly after inoculation. These strains belong to phylogenetic group B2 and are all α-hemolysin positive. In contrast, probiotic E. coli Nissle, pathogenic E. coli LF82, four E. coli from patients with inactive UC and three E. coli strains from healthy controls did not disrupt tight junctions. E. coli p19A WT as well as cnf1, and single loci of hly mutants from cluster I and II were all able to damage Caco-2 (Heterogeneous human epithelial colorectal adenocarcinoma) cell tight junctions. However, this phenotype was lost in a mutant with knockout (Δ) of both hly loci (P<0.001).Conclusions:UC-associated E. coli producing α-hemolysin can cause rapid loss of tight junction integrity in differentiated Caco-2 cell monolayers. This effect was abolished in a mutant unable to express α-hemolysin. These results suggest that high Hly expression may be a mechanism by which specific strains of E. coli pathobionts can contribute to epithelial barrier dysfunction and pathophysiology of disease in IBD.

Escherichia coli Pathobionts Associated with Inflammatory Bowel Disease

“…The potential causal role of IBD-associated E. coli in the pathophysiology of IBD has been linked to the ability to adhere to and invade epithelial cells and multiply within macrophages, such as that seen with the prototypical AIEC strain, LF82. Our studies have shown that UC-associated E. coli (p19A) from the B2 phylogenetic group (ExPEC), harboring two alpha-hemolysin genes, induces cell death in dendritic cells, stimulates the release of the cytokines TNF-␣, IL-6, and IL-23 (99), and causes rapid loss of the TJ integrity in differentiated Caco2-cell monolayers (38). The difference between p19A and strain LF82 is that LF82 does not disturb the epithelial TJ, obviously indicating that these two IBD-associated strains, both from the B2 phylogenetic group, differ in their pathogenic mechanisms.…”

“…(34), Listeria monocytogenes (35), Aeromonas hydrophila (36), Proteus spp. (37), E. coli (38,39), and some viruses (40) have all been linked to IBD and are suspected to play a causal role in disease relapses. On looking at these possible IBD pathogenesis links, it is currently unresolved whether the major part is played by specific microorganisms or by the reduced diversity of the microbiota as such.…”

“…A previous study showed that UCA patients colonized with B2 E. coli display increased burdens of inflammation as measured by the colitis activity index (CAI) and fecal calprotectin levels (98). Mirsepasi-Lauridsen et al (38) showed that UC-associated E. coli p19A, an ExPEC strain harboring alpha-hemolysin, dissolved the TJ protein occludin in cell lines and disrupted the TJ in Caco-2 cells in vitro, followed by increasing barrier permeability (38). Additionally, the UC-associated E. coli strain p19A induces cell death in dendritic cells and stimulates the release of the cytokines TNF-␣, IL-6, and IL-23 (99).…”

The Host Microbiome Regulates and Maintains Human Health: A Primer and Perspective for Non-Microbiologists

“…Ulcerative colitis (UC) is thought to be caused by some strains of E. coli (340). In cell culture models it has been showed that UC-associated E. coli producing α-hemolysin can cause rapid loss of TJ integrity (341). The human intestinal epithelium is formed by a single layer of epithelial cells that separates the intestinal lumen from the underlying lamina propria and the space between these cells is sealed by TJ, which regulate the permeability of the intestinal barrier (342).…”

VSL#3 probiotic differently influences IEC‐6 intestinal epithelial cell status and function

“…Indeed, for example, progression and flares of Inflammatory Bowel Diseases (IBD) may result also from the presence of microbes and microbe‐derived substances in the gut, even after the inciting agents responsible for the initiation of inflammation are controlled (Li et al, ; Wu & Shen, ). Recently, it has been reported that the secretion of alpha‐hemolysin by Escherichia coli disrupts tight junctions in ulcerative colitis patients (Mirsepasi‐Lauridsen et al, ). Meta‐analysis of broad spectrum antibiotic therapy in patients with IBD suggested a short treatment with antibiotics active against hemolysin‐producing E. coli to induce remission in active disease.…”