Translocation of Shiga toxin across polarized intestinal cells in tissue culture

Abstract

Escherichia coli strains producing Shiga toxins (Stx) 1 and 2 colonize the lower gastrointestinal tract in humans and are associated with gastrointestinal and systemic diseases. Stx are detectable in the feces of infected patients, and it is likely that toxin passes from the intestinal tract lumen to underlying tissues. The objective of this study was to develop an in vitro model to study the passage of Stx across intact, polarized cell monolayers. Translocation of biologically active Stx was examined in four cell lines grown on polycarbonate filters. Stx1 translocated across intestinal cell monolayers (CaCo2A and T84 cells) in an energy-requiring and saturable manner, while the monolayers maintained a high level of electrical resistance. Stx1 had no effect on electrical resistance or inulin movement across these cell lines for at least 24 h. Induction of specific Stx receptors with sodium butyrate reduced the proportion of toxin translocated across CaCo2A monolayers but had no major effect on the movement of horseradish peroxidase or [ 3 H]inulin. We have shown that biologically active Stx1 is capable of moving across intact polarized intestinal epithelial cells without apparent cellular disruption, probably via a transcellular pathway. The data also suggest that the presence of Stx receptors on the apical surface of intestinal epithelial cells may offer some protection against the absorption of luminal Stx1.

Interaction of Shiga toxin from Escherichia coli with human intestinal epithelial cell lines and explants: Stx2 induces epithelial damage in organ culture

“…Interestingly, uptake of Stx1 was faster by T84 than by Caco‐2 cells. This is in agreement with previous studies showing that Gb3 expression has an inhibiting effect on Stx1 translocation across polarized epithelial monolayers (Acheson et al ., 1996). These findings might suggest the existence of different receptors for Stx transport across intestinal cells and for induction of cell death on target cells.…”

Verotoxin 1 binding to intestinal crypt epithelial cells results in localization to lysosomes and abrogation of toxicity

“…In humans, transcytosis of VT thus triggers cytotoxicity and inflammation, both of which are important in precipitating disease. Increasing levels of Gb3 on intestinal epithelial cells leads to diminished trans-cellular movement of VT (Acheson et al, 1996). We therefore propose that expression of Gb3 by crypt epithelial cells of the small and large intestine in cattle occludes translocation of VT which, combined with the receptor isoform(s) and organization on these cells, leads to an absence of local or systemic cytotoxicity or inflammation in the bovine host.…”

Virulence factors of Escherichia coli O157 and other Shiga toxin-producing E. coli

“…Damage to the intestinal epithelium by Shiga toxin, or other in£ammatory mediators, may aid translocation of the toxin to the bloodstream (Paton and Paton 1998b); gaps between cells may be a further pathway. However, Acheson et al (1996) have demonstrated that toxin can move through intact epithelial cells and this may be an additional transport mechanism allowing toxin to reach extraintestinal sites. Although both Stx1 and 2 are thought to cause direct damage to human glomerular cells, there is increasing evidence that cytokines such as interleukins and tumour necrosis factor in association with bacterial LPS may be involved in the process.…”