Therapeutic Strategies to Protect the Central Nervous System against Shiga Toxin from Enterohemorrhagic Escherichia coli

Autonomic activity and cardiovascular system risk assessment in pediatric patients with hemolytic uremic syndrome

In pediatric patients with hemolytic uremic syndrome (HUS), cardiac involvement and autonomic nervous system function can be evaluated by a non-invasive method called heart rate variability (HRV). This study aims to evaluate heart rate variability and electrocardiography findings in patients with HUS by comparing a healthy group. Patients who are diagnosed with HUS at a university hospital from December 2020 to June 2022 are screened by electrocardiography (ECG), echocardiography, and 24-h Holter ECG. A healthy control group, compatible in age and gender with the patient group, was selected from healthy subjects. HRV parameters, laboratory values, and ECG findings were analyzed and compared with the healthy group and each other. There were 25 patients with HUS and 51 participants in the healthy control group. Statistically significant differences were found in some HRV parameters: standard deviation of normal to normal intervals, the mean of the 5-min RR interval standard deviations, the standard deviation of 5-min RR interval means, the triangular interpolation of normal to normal interval, and very-low-frequency power. HUS patients had impaired and declined HRV values compared to the healthy group. There was a significant decrease in the PR distance, while a significant increase in the corrected QT and QT dispersion values was detected in the electrocardiographic findings of the patient group. HRV values impaired as renal failure parameters increased.  Conclusion: Patients with HUS may have autonomic nervous system dysfunction. HRV measurement is a non-invasive method that can evaluate this. It can be thought that there may be an increased risk of cardiovascular events and arrhythmias in some patients with HUS. ECG should be also considered to detect arrhythmia. What is Known: • Hemolytic uremic syndrome (HUS) primarily effects the hematologic parameters and kidney. • Secondary cardiomyopathy with hypertension and renal failure could be observed in these patients. • Rhythm problems are not expected primarily in these patients. • There is very limited data in evaluating autonomic function and arrhythmia risk for these patients. What is New: • Patients with HUS may have autonomic nervous system dysfunction. • HRV measurement is a non-invasive method that can evaluate this. • Cardiovascular events and arrhythmias due to the deterioration of the balance between the sympathetic and parasympathetic systems could manifest in patients with HUS. • An ECG and screening patients for cardiac events, and monitoring them closely should be considered.

Nasal immunization with H7 flagellin protects mice against hemolytic uremic syndrome secondary to Escherichia coli O157:H7 gastrointestinal infection

Introduction

Shiga-toxin (Stx) producing Escherichia coli (STEC) O157:H7 is the most frequent serotype associated with hemolytic uremic syndrome (HUS) after gastrointestinal infections. Protection against HUS secondary to STEC infections has been experimentally assayed through the generation of different vaccine formulations. With focus on patients, the strategies have been mainly oriented to inhibit production of Stx or its neutralization. However, few approaches have been intended to block gastrointestinal phase of this disease, which is considered the first step in the pathogenic cascade of HUS. The aim of this work was to assay H7 flagellin as a mucosal vaccine candidate to prevent the systemic complications secondary to E. coli O157:H7 infections.

Materials and methods

The cellular and humoral immune response after H7 nasal immunization in mice were studied by the analysis of systemic and intestinal specific antibody production, as well as cytokine production and lymphocyte proliferation against H7 flagellin ex vivo.

Results

Immunized mice developed a strong and specific anti-H7 IgG and IgA response, at systemic and mucosal level, as well as a cellular Th1/Th2/Th17 response. H7 induced activation of bone marrow derived dendritic cells in vitro and a significant delayed-type hypersensitivity (DTH) response in immunized mice. Most relevant, immunized mice were completely protected against the challenge with an E. coli O157:H7 virulent strain in vivo, and surviving mice presented high titres of anti-H7 and Stx antibodies.

Discussion

These results suggest that immunization avoids HUS outcome and allows to elicit a specific immune response against other virulence factors.

Cytokines expression from altered motor thalamus and behavior deficits following sublethal administration of Shiga toxin 2a involve the induction of the globotriaosylceramide receptor

Encephalopathy associated with hemolytic uremic syndrome is produced by enterohemorrhagic E. coli (EHEC) infection, which releases the virulence factors Shiga toxin (Stx) and lipopolysaccharide (LPS). Neurological compromise is a poor prognosis and mortality factor of the disease, and the thalamus is one of the brain areas most frequently affected. We have previously demonstrated the effectiveness of anti-inflammatory drugs to ameliorate the deleterious effects of these toxins. However, the thalamic production of cytokines involved in pro-inflammatory processes has not yet been acknowledged. The aim of this work attempts to determine whether systemic sublethal Stx2a or co-administration of Stx2a with LPS are able to rise a proinflammatory profile accompanying alterations of the neurovascular unit in anterior and lateral ventral nuclei of the thalamus (VA-VL) and motor behavior in mice. After 4 days of treatment, Stx2a affected the lectin-bound microvasculature distribution while increasing the expression of GFAP in reactive astrocytes and producing aberrant NeuN distribution in degenerative neurons. In addition, increased swimming latency was observed in a motor behavioral test. All these alterations were heightened when Stx2a was co-administered with LPS. The expression of pro-inflammatory cytokines TNFα, INF-γ and IL-2 was detected in VA-VL. All these effects were concomitant with increased expression of the Stx receptor globotriaosylceramide (Gb3), which hints at receptor involvement in the neuroinflammatory process as a key finding of this study. In conclusion, Stx2a to Gb3 may be determinant in triggering a neuroinflammatory event, which may resemble clinical outcomes and should thus be considered in the development of preventive strategies.

Protective mechanisms harnessing against injurious heme and preventing kidney damage in STEC-HUS: toward new therapies?

Hemolytic uremic syndrome can be initiated by Escherichia coli infections (Shiga-toxin-producing enterohemorrhagic Escherichia coli hemolytic uremic syndrome). When hemoglobin and heme released from ruptured erythrocytes interact with the kidney cells, this can result in platelet activation, vascular inflammation and occlusion, and kidney injury. Pirschel et al. now report that in the absence of protective mechanisms against free hemoglobin and heme, heme-induced kidney injury can be exacerbated. Therapeutic strategies should therefore also target heme-mediated deleterious effects in (severely ill) patients with Shiga-toxin-producing enterohemorrhagic Escherichia coli hemolytic uremic syndrome.

Role of Globotriaosylceramide in Physiology and Pathology

At first glance, the biological function of globoside (Gb) clusters appears to be that of glycosphingolipid (GSL) receptors for bacterial toxins that mediate host-pathogen interaction. Indeed, certain bacterial toxin families have been evolutionarily arranged so that they can enter eukaryotic cells through GSL receptors. A closer look reveals this molecular arrangement allocated on a variety of eukaryotic cell membranes, with its role revolving around physiological regulation and pathological processes. What makes Gb such a ubiquitous functional arrangement? Perhaps its peculiarity is underpinned by the molecular structure itself, the nature of Gb-bound ligands, or the intracellular trafficking unleashed by those ligands. Moreover, Gb biological conspicuousness may not lie on intrinsic properties or on its enzymatic synthesis/degradation pathways. The present review traverses these biological aspects, focusing mainly on globotriaosylceramide (Gb3), a GSL molecule present in cell membranes of distinct cell types, and proposes a wrap-up discussion with a phylogenetic view and the physiological and pathological functional alternatives.

Extracellular Vesicles and Renal Endothelial Cells: A Fatal Attraction in Hemolytic Uremic Syndrome

This review focuses on typical hemolytic uremic syndrome (HUS), a life-threatening sequela of human infections caused, particularly in children, by Shiga toxin-producing Escherichia coli strains. Thrombotic microangiopathy of the brain and the kidney is the end point of toxin action, resulting in the hallmarks of HUS (ie, thrombocytopenia, anemia, and acute renal failure). A growing body of evidence points to the role of extracellular vesicles released in the blood of patients by toxin-challenged circulating cells (monocytes, neutrophils, and erythrocytes) and platelets, as a key factor in the pathogenesis of HUS. This review provides i) an updated description of the pathogenesis of Shiga toxin-producing E. coli infections; ii) an analysis of blood cell-derived extracellular vesicles, and of their parent cells, as triggering factors in HUS; and iii) a model explaining why Shiga toxin-containing vesicles dock preferentially to the endothelia of target organs.