title: The Effects of Shiga Toxin 1, 2 and Their Subunits on Cytokine and Chemokine Expression by Human Macrophage-Like THP-1 Cells.
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.
authors.affiliation: Department of Microbiology, Immunology, and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 1N4, Canada. jrbrande@ucalgary.ca.
authors.forename: Jeremy R
authors.initials: JR
authors.lastname: Brandelli
authors.affiliation: Department of Microbiology, Immunology, and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 1N4, Canada. tpgriene@ucalgary.ca.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Griener
authors.affiliation: Department of Microbiology, Immunology, and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 1N4, Canada. aglaing@ucalgary.ca.
authors.forename: Austin
authors.initials: A
authors.lastname: Laing
authors.affiliation: Department of Microbiology, Immunology, and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 1N4, Canada. gmulvey@ucalgary.ca.
authors.forename: George
authors.initials: G
authors.lastname: Mulvey
authors.affiliation: Department of Microbiology, Immunology, and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 1N4, Canada. glen.armstrong@ucalgary.ca.
authors.forename: Glen D
authors.initials: GD
authors.lastname: Armstrong
mesh_terms: D018929:Cell Culture Techniques; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D018925:Chemokines / Q000096:biosynthesis / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis* / Q000276:immunology; D006801:Humans; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology; D022621:Shiga Toxin / Q000633:toxicity*; D022622:Shiga Toxin 1 / Q000633:toxicity*; D022641:Shiga Toxin 2 / Q000633:toxicity*
chemical_list: D018925:Chemokines; D016207:Cytokines; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2; C493898:Shiga toxin subunit A; C450841:shiga toxin 2 B subunit; D022621:Shiga Toxin
keywords: HUS; STEC; Shiga toxin; Stx; Stx subunits; THP-1; cytokine