Relevance of neutrophils in the murine model of haemolytic uraemic syndrome: mechanisms involved in Shiga toxin type 2-induced neutrophilia

Abstract

SummaryIt has been demonstrated that infections due to Shiga toxins (Stx) producing Escherichia coli are the main cause of the haemolytic uraemic syndrome (HUS). However, the contribution of the inflammatory response in the pathogenesis of the disease has also been well established. Neutrophils (PMN) represent a central component of inflammation during infections, and patients with high peripheral PMN counts at presentation have a poor prognosis. The mouse model of HUS, by intravenous injection of pure Stx type 2 (Stx2), reproduces human neutrophilia and allows the study of early events in the course of Stx2-induced pathophysiological mechanisms. The aim of this study was to address the contribution of PMN on Stx2 toxicity in a murine model of HUS, by evaluating the survival and renal damage in mice in which the granulocytic population was depleted. We found that the absence of PMN reduced Stx2-induced lethal effects and renal damage. We also investigated the mechanisms underlying Stx2-induced neutrophilia, studying the influence of Stx2 on myelopoyesis, on the emergence of cells from the bone marrow and on the in vivo migration into tissues. Stx2 administration led to an accelerated release of bone marrow cells, which egress at an earlier stage of maturation, together with an increase in the proliferation of myeloid progenitors. Moreover, Stx2-treated mice exhibited a lower migratory capacity to a local inflammatory site. In conclusion, PMN are essential in the pathogenesis of HUS and neutrophilia is not merely an epiphenomenon, but contributes to Stx2-damaging mechanism by potentiating Stx2 toxicity.

Pathogenesis of Renal Disease Due to Enterohemorrhagic Escherichia coli in Germ-Free Mice

“…A few studies showed that there were consistent vascular or glomerular lesions (12,16,48), and the descriptions of these lesions varied between studies, confirming our findings that glomerular disease is present but mild in EHEC-infected mice. Several studies that used an injection model, in which Stx or Stx in combination with lipopolysaccharide was injected parenterally into mice, described glomerular lesions (11,13,15,20,45), supporting our finding that virulent EHEC is capable of inducing glomerular disease in mice.…”

“…Donohue-Rolf et al (10) showed that isogenic Stx2-negative mutants failed to cause neurologic lesions or signs in gnotobiotic piglets, but renal lesions were not described. Finally, several studies have demonstrated the nephrotoxic effect of parenterally injected Stx1 or Stx2 (11,13,15,20,25,45,51), again providing indirect evidence that Stx is at least partially responsible for renal disease.…”

Comparative Analysis of the Abilities of Shiga Toxins 1 and 2 To Bind to and Influence Neutrophil Apoptosis

“…Neutrophils are activated during HUS (10), resulting in the release of factors capable of causing tissue damage. Furthermore, recent studies of a murine model of disease suggest that Stx2-induced lethality and renal damage are reduced in neutrophil-depleted mice (8). However, there have been conflicting reports regarding whether Stx directly promotes neutrophil activation or whether Stx indirectly promotes neutrophil activation by inducing an inflammatory response in other cells.…”

“…In addition, the neutrophils of HUS patients were shown to induce endothelial injury in vitro (10). Recent studies have shown that neutrophil depletion in mice results in a reduction in Stx2-induced lethality and renal damage (8).…”

Regulation of Innate Immune Response toCandida albicansInfections by αMβ2-Pra1p Interaction

“…Peripheral blood PMNs were isolated from pooled heparinized murine blood taken from tail veins of WT or ⌬␣ M mice, both males and females, by centrifugation through Ficoll-Hypaque, followed by 6% dextran sedimentation; the contaminating erythrocytes were removed by hypotonic lysis (102). The cells obtained by this technique were Ͼ90% PMNs (21,33,106). For each experiment, PMNs from five to seven mice were pooled.…”