Host Inflammatory Response Inhibits Escherichia coli O157:H7 Adhesion to Gut Epithelium through Augmentation of Mucin Expression

Abstract

c Escherichia coli O157:H7, a major Shiga toxin-producing pathogen, has a low infectious dose and causes serious illness in humans. The gastrointestinal tract of cattle is the primary reservoir of E. coli O157:H7, and thus, it is critical to eliminate or reduce E. coli O157:H7 gut colonization. Given that E. coli O157:H7 produces effectors that attenuate inflammatory signaling, we hypothesized that the host inflammatory response acts to perturb E. coli O157:H7 intestinal colonization. Tumor necrosis factor alpha (TNF-␣) treatment of HT-29 cells resulted in increased expression of inflammatory cytokine interleukin 1␤ (IL-1␤), IL-8, and TNF-␣ genes and increased IL-8 protein and resulted in decreased adhesion of E. coli O157:H7. Similarly, E. coli O157:H7 adhesion to cattle colonic explants was reduced by TNF-␣ treatment. Irrespective of the presence of E. coli O157:H7, TNF-␣ enhanced activation of p65, the key mediator of NF-B inflammatory signaling, whereas E. coli O157:H7 infection suppressed this pathway by inhibiting p65 activation in HT-29 cells. To further explore the mechanisms linking the inflammatory response to attenuated E. coli O157:H7 adhesion, mucin 2 (MUC2) expression was analyzed, considering that the intestinal mucus layer is the first defense against enteric pathogens and MUC2 is the major secretory mucin in the intestine. MUC2 expression in HT-29 cells was increased by TNF-␣ treatment and by E. coli O157:H7 infection. However, reducing mucin expression by blocking mitogen-activated protein kinase (MAPK) extracellular signal-regulated protein kinases 1/2 (ERK1/2) and/or phosphatidylinositol 3-kinase (PI3K)/Akt signaling increased E. coli O157:H7 adherence to HT-29 cells. These data suggest that the inflammatory cytokine response acts to protect host epithelial cells against E. coli O157:H7 colonization, at least in part, by promoting mucin production.

The StcE metalloprotease of enterohaemorrhagicEscherichia colireduces the inner mucus layer and promotes adherence to human colonic epitheliumex vivo

“…In our studies, no changes in MUC2 and MUC5AC gene expression were detected in EHEC‐infected LS174T cells. This is in contrast to previous studies demonstrating increased MUC2 gene expression in HT‐29 cells infected with EHEC (Xue et al, ). This discrepancy is likely related to the difference in cell line models, and as HT‐29 cells do not express MUC2 glycoproteins (Huet et al, ; Walsham et al, ), the relevance of this finding remains questionable.…”

Strain-Dependent Cellular Immune Responses in Cattle following Escherichia coli O157:H7 Colonization

“…In addition, the lack of induction of TNF-␣ in the challenge groups would also indicate that this cytokine is not an important component of the bovine response to colonization at the terminal rectum. This is significant, because TNF-␣ is upregulated during C. rodentium colonization in mice (77), while pretreatment of bovine colonic explants with TNF-␣ has been shown to upregulate mucin secretion and reduce EHEC O157:H7 colonization (78). The observation that TNF-␣ is not induced at the terminal rectum would imply that this pathway is not active in vivo and is likely to contribute to the difference between the pathogenicity of C. rodentium in mice, which results in weight loss, moderate mortality, and colonic hyperplasia (79,80), and that of EHEC O157:H7 in cattle, where the infection is asymptomatic and demonstrates only a mild neutrophilic infiltrate, suggesting that while immunogenic, colonization is not a major inflammatory event (42).…”

Dandelion extract suppresses reactive oxidative species and inflammasome in intestinal epithelial cells

“…Immunoblotting analysis was conducted according to procedures previously described (Fan et al, 2010;Xue et al, 2014). Briefly, 1 Â 10 6 HT-29 cells were seeded in 12-well plates.…”