Endogenous glucocorticoids modulate neutrophil function in a murine model of haemolytic uraemic syndrome

Abstract

SummaryHaemolytic uraemic syndrome (HUS) is caused by Shiga-toxin-producing Escherichia coli (STEC). Although, Shiga toxin type 2 (Stx2) is responsible for the renal pathogenesis observed in patients, the inflammatory response, including cytokines and polymorphonuclear neutrophils (PMN), plays a key role in the development of HUS. Previously, we demonstrated that Stx2 injection generates an anti-inflammatory reaction characterized by endogenous glucocorticoid (GC) secretion, which attenuates HUS severity in mice. Here, we analysed the effects of Stx2 on the pathogenic function of PMN and the potential role of endogenous GC to limit PMN activation during HUS development in a murine model. For this purpose we assessed the functional activity of isolated PMN after in vivo treatment with Stx2 alone or in simultaneous treatment with Ru486 (GC receptor antagonist). We found that Stx2 increased the generation of reactive oxygen intermediates (ROI) under phobol-myristate-acetate (PMA) stimulation and that the simultaneous treatment with Ru486 strengthened this effect. Conversely, both treatments significantly inhibited in vitro phagocytosis. Furthermore, Stx2 augmented in vitro PMN adhesion to fibrinogen (FGN) and bovine serum albumin (BSA) but not to collagen type I (CTI). Stx2 + + + + Ru486 caused enhanced adhesion to BSA and CTI compared to Stx2. Whereas Stx2 significantly increased migration towards N -formyl-methionyl-leucyl-phenylalanine (fMLP), Stx2 + + + + Ru486 treatment enhanced and accelerated this process. The percentage of apoptotic PMN from Stx2-treated mice was higher compared with controls, but equal to Stx2 + + + + Ru486 treated mice. We conclude that Stx2 activates PMN and that the absence of endogenous GC enhances this activation suggesting that endogenous GC can, at least partially, counteract PMN inflammatory functions.

Production of Nitric Oxide Is Lower in Shiga Toxin-Stimulated Neutrophils of Infants Compared to Those of Children or Adults

“…Though several studies have addressed neutrophil ROS production after stimulation by Stx (King et al 1999;Liu et al 2002;Fernandez et al 2005;Gomez et al 2005;Holle et al 2005), none has focused on cellular NO production under Stx stimulation. The pathophysiological role of NO has been extensively studied in hypotension associated with septic shock, i.e., excessive production of NO lowers the blood pressure (Fernandes and Assreuy 2008).…”

“…First, ROS were not measured under the experimental conditions. ROS production should be evaluated in combination with NO to verify the hypothesis, although numerous studies have already confirmed increased production of ROS in HUS (King et al 1999;Liu et al 2002;Gomez et al 2005;Holle et al 2005). Secondly, patients with HUS caused by Stx were not included.…”

“…It has been reported that reactive oxygen species (ROS) have an antibacterial action (Cohen 1994) and contribute to the development of HUS (King et al 1999;Liu et al 2002;Gomez et al 2005;Holle et al 2005). However, the role of nitric oxide (NO), another pivotal biological reactive species generated by vascular endothelial cells or white blood cells, has not been extensively studied.…”

The oxidative stress induced in vivo by Shiga toxin-2 contributes to the pathogenicity of haemolytic uraemic syndrome

“…Stx2 treatment. Stx2 alone or in combination with LPS has been used with mouse models able to reproduce the features of human HUS [17,24,25]. We decided to inject intravenously (i.v.)…”

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

“…Liu et al previously reported that Stx2 significantly inhibits the rate of neutrophil apoptosis (23,24). However, in vivo injection of Stx2 in mice was reported to increase the rate of neutrophil apoptosis after about 72 h (14), leading those authors to hypothesize that the enhancement occurred by an indirect mechanism rather than a direct effect of Stx2 on neutrophils. King et al previously reported that Stx1 exhibited no effect on neutrophil apoptosis (20).…”