Abstract

BackgroundEnterohemorrhagic Escherichia coli (EHEC) O157:H7, the causative agent of hemorrhagic colitis and the hemolytic uremic syndrome (HUS), produces long bundles of type IV pili (TFP) called hemorrhagic coli pili (HCP). HCP are capable of mediating several phenomena associated with pathogenicity: i) adherence to human and bovine epithelial cells; ii) invasion of epithelial cells; iii) hemagglutination of rabbit erythrocytes; iv) biofilm formation; v) twitching motility; and vi) specific binding to laminin and fibronectin. HCP are composed of a 19 kDa pilin subunit (HcpA) encoded by the hcpA chromosomal gene (called prepilin peptidase-dependent gene [ppdD] in E. coli K-12).Methodology/Principal FindingsIn this study we investigated the potential role of HCP of E. coli O157:H7 strain EDL933 in activating the release of pro- and anti-inflammatory cytokines from a variety of host epithelial cells. We found that purified HCP and a recombinant HcpA protein induced significant release of IL-8 and TNF-α, from cultured polarized intestinal cells (T84 and HT-29 cells) and non-intestinal HeLa cells. Levels of proinflammatory IL-8 and TNF-α, but not IL-2, IL6, or IL-10 cytokines, were increased in the presence of HCP and recombinant HcpA after 6 h of incubation with ≥50 ng/ml of protein, suggesting that stimulation of IL-8 and TNF-α are dose and time-dependent. In addition, we also demonstrated that flagella are potent inducers of cytokine production. Furthermore, MAPK activation kinetics studies showed that EHEC induces p38 phosphorylation under HCP-producing conditions, and ERK1/2 and JNK activation was detectable after 3 h of EHEC infection. HT-29 cells were stimulated with epidermal growth factor stimulation of HT-29 cells for 30 min leading to activation of three MAPKs.Conclusions/SignificanceThe HcpA pilin monomer of the HCP produced by EHEC O157:H7 is a potent inducer of IL-8 and TNF-α release, an event which could play a significant role in the pathogenesis of hemorrhagic colitis caused by this pathogen.

Highlights

  • Enterohemorrhagic Escherichia coli O157:H7 (EHEC) causes infection that range from asymptomatic or mild diarrhea to hemorrhagic colitis, in some cases causing Hemolytic Uremic Syndrome (HUS) that may lead to death [1,2,3]

  • In this study we investigated the role of Hemorrhagic Coli Pilus (HCP) produced by EHEC O157:H7 in the activation and release of several proinflammatory and antiinflammatory cytokines from human colonic epithelial cells (T84 and HT-29) and non-intestinal HeLa cells

  • The HCP of EHEC O157:H7 displays several biological functions associated with pathogenicity [24], not much is known regarding its immunobiological properties or the environmental and nutritional factors involved in the production of HCP

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Summary

Introduction

Enterohemorrhagic Escherichia coli O157:H7 (EHEC) causes infection that range from asymptomatic or mild diarrhea to hemorrhagic colitis, in some cases causing Hemolytic Uremic Syndrome (HUS) that may lead to death [1,2,3]. Previous studies have shown that some enteropathogens induce target epithelial cells to produce this cytokine causing only mild gastroenteritis [5,6]. Shigella infection triggers the production of IL-8 that can lead to epithelial cell destruction and histopathologic lesions of the colon [7]. Enterohemorrhagic Escherichia coli (EHEC) O157:H7, the causative agent of hemorrhagic colitis and the hemolytic uremic syndrome (HUS), produces long bundles of type IV pili (TFP) called hemorrhagic coli pili (HCP). HCP are composed of a 19 kDa pilin subunit (HcpA) encoded by the hcpA chromosomal gene (called prepilin peptidase-dependent gene [ppdD] in E. coli K-12)

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