Lipopolysaccharide Renders Transgenic Mice Expressing Human Serum Amyloid P Component Sensitive to Shiga Toxin 2

Abstract

Transgenic C57BL/6 mice expressing human serum amyloid P component (HuSAP) are resistant to Shiga toxin 2 (Stx2) at dosages that are lethal in HuSAP-negative wild-type mice. However, it is well established that Stx2 initiates extra-intestinal complications such as the haemolytic-uremic syndrome despite the presence of HuSAP in human sera. We now demonstrate that co-administering purified Escherichia coli O55 lipopolysaccharide (LPS), at a dosage of 300 ng/g body weight, to HuSAP-transgenic mice increases their susceptibility to the lethal effects of Stx2. The enhanced susceptibility to Stx2 correlated with an increased expression of genes encoding the pro-inflammatory cytokine TNFα and chemokines of the CXC and CC families in the kidneys of LPS-treated mice, 48 hours after the Stx2/LPS challenge. Co-administering the glucocorticoid dexamethasone, but not the LPS neutralizing cationic peptide LL-37, protected LPS-sensitized HuSAP-transgenic mice from lethal doses of Stx2. Dexamethasone protection was specifically associated with decreased expression of the same inflammatory mediators (CXC and CC-type chemokines and TNFα) linked to enhanced susceptibility caused by LPS. The studies reveal further details about the complex cascade of host-related events that are initiated by Stx2 as well as establish a new animal model system in which to investigate strategies for diminishing serious Stx2-mediated complications in humans infected with enterohemorrhagic E. coli strains.

The Crystal Structure of Shiga Toxin Type 2 with Bound Disaccharide Guides the Design of a Heterobifunctional Toxin Inhibitor

“…8). In this modified model, transgenic (HuSAP-tg) mice are pre-exposed to LPS to induce a sub-acute state of inflammation that ablates the confounding effects of HuSAP on toxicity of Stx2a (45). HuSAP-tg mice (C57BL/6-Tg(APSC)1Imeg) treated intraperitoneally with a lethal dose of Stx2a (225 pg/g mouse) combined with E. coli O55 LPS (300 ng/g mouse) were immediately given increasing intravenously concentrations of PolyBAIT-P k ( Fig.…”

“…HuSAP binds to and neutralizes Stx2a in the absence of glycan ligands, and based on the observation that HuSAP transgenic mice were completely resistant to Stx2a, this interaction was initially considered to be of potential therapeutic value in preventing Stx2a-initiated HUS in E. coli O157:H7-infected patients (44). However, it was subsequently revealed that there was no correlation between the circulating concentration of HuSAP and the risk for developing HUS in humans (45).…”

Genomic Instability in Liver Cells Caused by an LPS-Induced Bystander-Like Effect

“…CYP7A1 is involved in drug metabolism and synthesis of bile acid and steroids from cholesterol within liver tissue. Conversion of cholesterol into bile acid is controlled by this protein and is the main process of removing cholesterol from the body [43]. Removal of cholesterol from the body is important to the overall homeostatic state of organism.…”

Polymer antidotes for toxin sequestration

“…HuSAP producing transgenic mice were also found to be resistant to Stx2 [52]. However, introduction of lipopolysaccharide renders transgenic mice expressing HuSAP sensitive to Stx2 [53]. Bundle et al have since shown that HuSAP transgenic mice pre-exposed to LPS and challenged with a lethal amount of Stx2 (225 pg/g body weight) were moderately protected (~60%) by PolyBait (100 μg/g body weight) [54].…”