Enteroaggregative Escherichia coli Disrupts Epithelial Cell Tight Junctions

Abstract

Enteroaggregative Escherichia coli (EAEC) is responsible for inflammatory diarrhea in diverse populations, but its mechanisms of pathogenesis have not been fully elucidated. We have used a previously characterized polarized intestinal T84 cell model to investigate the effects of infection with EAEC strain 042 on tight junction integrity. We find that infection with strain 042 induces a decrease in transepithelial electrical resistance (TER) compared to uninfected controls and to cells infected with commensal E. coli strain HS. When the infection was limited after 3 h by washing and application of gentamicin, we observed that the TER of EAEC-infected monolayers continued to decline, and they remained low even as long as 48 h after the infection. Cells infected with the afimbrial mutant strain 042aafA exhibited TER measurements similar to those seen in uninfected monolayers, implicating the aggregative adherence fimbriae II (AAF/II) as necessary for barrier dysfunction. Infection with wild-type strain 042 induced aberrant localization of the tight junction proteins claudin-1 and, to a lesser degree, occludin. EAEC-infected T84 cells exhibited irregular shapes, and some cells became elongated and/or enlarged; these effects were not observed after infection with commensal E. coli strain HS or 042aafA. The effects on tight junctions were also observed with AAF/I-producing strain JM221, and an afimbrial mutant was similarly deficient in inducing barrier dysfunction. Our results show that EAEC induces epithelial barrier dysfunction in vitro and implicates the AAF adhesins in this phenotype.

Arcobacter

“…Further work is required to better understand the relationship between these putative virulence markers and human clinical outcomes, though some tantalizing evidence suggests that Arcobacter has the potential to induce tight junction dysfunction (Bücker et al, 2009;Karadas et al, 2016), which may lead to diarrhea . This is similar to the effect observed with enteroaggregative E. coli (EAEC) infection (Strauman et al, 2010 (Wesley et al, 2000;van Driessche et al, 2005;Merga et al, 2011;Shah et al, 2013;Grove-White et al, 2014). Isolation rates vary between studies, but young cattle/calves were consistently shown to have higher Arcobacter carriage rates.…”

Escherichia coli Heat-Stable Toxin b Impairs Intestinal Epithelial Barrier Function by Altering Tight Junction Proteins

“…T84 human colon intestinal epithelial cells, used as a model to study the effects of enterotoxins on TJ proteins (24,25,26,27,28,29), were obtained from the American Type Culture Collection. Cells (passage 5 to 18) were maintained in equal volumes of Dulbecco's modified eagle medium (DMEM) and F-12 supplemented with 5% (vol/vol) fetal bovine serum (FBS) (Invitrogen, Canada).…”

“…STb24-31 was also tested at 4 nmol, and the effect on TJ proteins was similar to what is reported for 12 nmol (data not shown). The T84 cell line was used in our study because it was used for other E. coli enterotoxins (LT and STa) as well as V. cholerae and Yersinia enterocolitica enterotoxins although these act not in the colon but in the small intestine (24,25,26,27,28,29). This cell line exhibits tight junctions and desmosomes and maintains electrolyte vectorial transport; thus, T84 cells represent a reference for the work we had undertaken.…”

“…Binding of Zot and STb to their respective receptors involves this shared sequence, and for Zot toxin it has been shown to be involved in TJ disassembly. The aim of the present study was to examine the effects of STb on TJ structure and function in T84 intestinal epithelial cells, a cell line commonly used to study bacterial enterotoxin secretory processes (24,25,26,27,28,29).…”

Role for the Bacterial Signal Indole in Promoting Epithelial Cell Barrier Function

“…Similar mechanism of action of P. aeruginosa was reported in bronchial epithelial cells where reduction in TER and disruption of ZO-1 were observed during infection [34]. Strauman et al, [35] showed that enteroaggregative Data represent mean ± SD from three independent experiments. *, statistical significance, using Student's t test, at P < 0.05; **, significance at P < 0.005.…”