The Effects of Shiga Toxin 1, 2 and Their Subunits on Cytokine and Chemokine Expression by Human Macrophage-Like THP-1 Cells.

Jeremy Brandelli,George Mulvey,Austin Laing,Thomas Griener,Glen Armstrong

doi:10.3390/toxins7104054

Jeremy Brandelli, George Mulvey + Show 3 more

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https://doi.org/10.3390/toxins7104054

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Journal: Toxins	Publication Date: Oct 9, 2015
Citations: 37	License type: CC BY 4.0

Affiliation: University of Calgary

Abstract

Infection by Shiga toxin (Stx)-producing enterohemorrhagic Escherichia coli (EHEC) results in severe diarrhea, hemorrhagic colitis, and, occasionally, hemolytic-uremic syndrome (HUS). HUS is associated with an increase in pro-inflammatory cytokines and chemokines, many of which are produced by macrophages in the kidneys, indicating that localized host innate immunity likely plays a role in renal pathogenesis. EHEC serotypes may express one or two classes of serologically defined but structurally and functionally-related Shiga toxins called Stx1 and Stx2. Of these, Stx2 appears to be linked to higher rates of HUS than Stx1. To investigate a possible reason for this, we exposed human macrophage-like THP-1 cells to Stx1 or Stx2 and then used the Luminex multiplex system to assess cytokine/chemokine concentrations in culture supernatant solutions. This analysis revealed that, relative to Stx1, Stx2 significantly caused increased expression of GRO, G-CSF, IL-1β, IL-8 and TNFα in macrophage-like THP-1 cells. This was determined to not be due to a difference in cytotoxicity since both Stx1 and Stx2 displayed similar cytotoxic activities on macrophage-like THP-1 cells. These observations indicate that, in vitro, Stx2 can provoke a greater pro-inflammatory response than Stx1 in macrophages and provides a possible partial explanation for higher rates of HUS in patients infected with EHEC strains expressing Stx2. To begin to determine a mechanism for Shiga toxin-mediated cytokine production, we exposed macrophage-like THP-1 cells to Stx1 or Stx2 A and B subunits. Luminex analysis of cytokines in cell culture supernatant solutions demonstrated that neither subunit alone induced a cytokine response in THP-1 cells.

Highlights

Enterohemorrhagic Escherichia coli (EHEC) infection can result in severe diarrhea, hemorrhagic colitis, hemolytic-uremic syndrome (HUS) or damage to the central nervous system [1]
Shiga toxin 2 (Stx2) treatment resulted in altered levels that were significantly different from untreated cells
In six independent experiments, each performed in duplicate, Stx2 consistently altered concentrations of 14 out of the 40 cytokines/chemokines assessed (Table 1) in macrophage-like THP-1 cells

Summary

Introduction

Enterohemorrhagic Escherichia coli (EHEC) infection can result in severe diarrhea, hemorrhagic colitis, hemolytic-uremic syndrome (HUS) or damage to the central nervous system [1]. Depending on patient age and strain-related features, HUS can occur in 10% to 20% of those afflicted with EHEC-mediated hemorrhagic colitis, with children and the elderly being the more likely victims [3]. HUS is characterized by thrombocytopenia, hemolytic anemia and acute renal failure. When it occurs, HUS is believed to be initiated by Shiga toxin (Stx)-associated damage to glomerular endothelial cells which subsequently initiates an escalating cascade of localized inflammatory events that eventually lead to the clinical signs. Shiga toxins are bacterial exotoxins produced by Shigella dysenteriae serotype 1 and some EHEC strains. Two functionally related, yet serologically distinct Shiga toxins, Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2), exist [4] with Stx being more closely associated with higher rates of HUS than Stx1 [5]

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