Pro-Coagulant Endothelial Dysfunction Results from EHEC Shiga Toxins and Host Damage-Associated Molecular Patterns

Hemolytic uremic syndrome (HUS) remains a major cause of acute kidney failure in children with no known prior health issues. While the role of Shiga toxins in causing coagulopathy is well established, the contribution of host-derived inflammatory signals remains unclear. Prior research has shown that Shiga toxins damage endothelial cells, but the extent to which this damage leads to the release of inflammatory molecules is not fully understood. No prior work has resolved how Shiga toxins might interact with host-derived signals to worsen disease. This gap motivated an investigation into whether these signals could amplify endothelial dysfunction. The uncertainty around the role of damage-associated molecular patterns (DAMPs) in HUS pathogenesis remains a key unresolved issue. Understanding the interplay between bacterial toxins and host injury signals could clarify disease mechanisms. The lack of clarity about how DAMPs influence coagulation in HUS is a significant research gap. This paper aims to address this uncertainty by exploring the combined effects of Shiga toxins and DAMPs on endothelial function.

This study aimed to determine whether Shiga toxins from enterohemorrhagic Escherichia coli (EHEC) and host-derived damage-associated molecular patterns (DAMPs) contribute to endothelial dysfunction in HUS. The researchers focused on how these factors affect anti-coagulant and barrier functions of endothelial cells. They sought to identify whether DAMPs could worsen the pro-thrombotic effects of Shiga toxins. The specific problem addressed is the unclear mechanism by which HUS leads to kidney injury and coagulopathy. The motivation stems from the need to understand how both bacterial toxins and host signals contribute to disease severity. The study also aimed to assess whether DAMPs are produced in response to Shiga toxin exposure. The researchers wanted to determine if DAMPs could act synergistically with toxins to increase endothelial damage. This work could help clarify the role of host-derived signals in HUS progression.

The researchers used in vitro models of human aortic and renal glomerular endothelial cells to study the effects of Shiga toxins and DAMPs. They exposed cells to Stx1, Stx2, and DAMPs such as histones and HMGB1. They measured changes in anti-coagulant and barrier functions using molecular assays. The study also assessed protein C pathway molecules and PAR1 expression levels. In mice, they administered lethal doses of Stx2 and monitored plasma levels of HMGB1 and histones. Mice were also colonized with Stx2-expressing Citrobacter rodentium to model infection. They used anti-histone antibodies to test whether DAMP levels could be reduced. The study combined cell culture experiments with in vivo mouse models to examine endothelial dysfunction.

Exposure to Shiga toxins and DAMPs significantly reduced anti-coagulant protein C pathway molecules on endothelial cells. The study found increased expression of pro-thrombotic PAR1 in response to toxin and DAMP exposure. Protein C activation was reduced by 15-27% in treated cells. Histones nearly eliminated the protective effect of activated protein C against thrombin-induced permeability. In mice, Stx2 challenge increased plasma HMGB1 by 321% and extracellular histones by 158%. Mice colonized with Stx2-expressing bacteria showed elevated HMGB1 and histones. Anti-histone antibodies lowered DAMP levels but did not improve survival or kidney function. These findings suggest that Shiga toxins may trigger DAMP release, which in turn worsens endothelial injury.

The authors suggest that Shiga toxins may trigger the release of DAMPs, which in turn contribute to endothelial injury and a pro-thrombotic environment. They propose that DAMPs could act synergistically with toxins to worsen HUS pathology. The data indicate that histones and HMGB1 are elevated in response to Shiga toxin exposure. The findings suggest that DAMPs may amplify endothelial dysfunction beyond the effects of toxins alone. The researchers note that reducing DAMP levels with anti-histone antibodies did not improve survival or kidney function. This suggests that DAMP inhibition alone may not be sufficient to halt disease progression. The authors conclude that both Shiga toxins and DAMPs may play a role in HUS pathogenesis. These findings may help guide future studies on the interplay between bacterial toxins and host-derived signals.