Shiga toxin 1 induces on lipopolysaccharide-treated astrocytes the release of tumor necrosis factor-alpha that alter brain-like endothelium integrity

Cognitive functioning of adolescents using Methamphetamine: The impact of inflammatory and oxidative processes

BACKGROUND

Methamphetamine is a substance that causes neurotoxicity and its use is increasing in recent years. Literature highlights cognitive impairment resulting from Methamphetamine use. The aim of the present study is to evaluate the relationship between cognitive impairment and inflammatory processes in adolescents with Methamphetamine use disorder.

METHODS

The study included 69 adolescents aged 15-19 years, comprising 37 participants with Methamphetamine Use Disorder and 32 healthy controls. Central Nervous System Vital Signs was used to detect cognitive impairment. Childhood Trauma Questionnaire-33 and The Children's Depression Inventory scales were used. In addition, venous blood was collected from the volunteers. Biochemical parameters (IL-1beta, IL-6, TNF-a, BDNF, FAM19A5, TAS, TOS) were analyzed.

RESULTS

Our study showed that (I) IL-6 and TNF-a levels of Methamphetamine users were lower than the healthy group; (II) BDNF levels of Methamphetamine users were higher than the healthy group; (III) mean Neurocognitive Index in cognitive tests of Methamphetamine using adolescents was negatively correlated with duration of Methamphetamine use and BDNF levels.

CONCLUSIONS

Our study suggests that Methamphetamine use may have a negative effect on cognitive functions.

Sodium dichloroacetate improves migration ability by suppressing LPS-induced inflammation in HTR-8/SVneo cells via the TLR4/NF-κB pathway

Objectives

Inadequate cytotrophoblast migration and invasion are speculated to result in preeclampsia, which is a pro-inflammatory condition. Sodium dichloroacetate (DCA) exerts anti-inflammatory actions. Thus,we sought to investigate the effect of DCA on the migration function of the lipopolysaccharide (LPS)-stimulated human-trophoblast-derived cell line (HTR-8/SVneo).

Materials and Methods

HTR-8/SVneo cells were treated with LPS to suppress cell migration. Cell migration was examined by both scratch wound healing assay and transwell migration assay. Western blotting was used to analyze the expression levels of toll-like receptor-4 (TLR4), nuclear factor-κB (NF-κB), TNF-α, IL-1β, and IL-6 in the cells.

Results

DCA reversed LPS-induced inhibition of migration in HTR-8/SVneo cells. Furthermore, DCA significantly suppressed LPS-induced activation of TLR4, phosphorylation of NF-κB (p65), translocation of p65 into the nucleus, and the production of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6). Treatment with inhibitors of TLR4 signal transduction (CLI095 or MD2-TLR-4-IN-1) reduced LPS-induced overexpression of pro-inflammatory cytokines, and a synergistic effect was found between TLR4 inhibitors and DCA in HTR-8/SVneo cells.

Conclusion

DCA improved trophoblast cell migration function by suppressing LPS-induced inflammation, at least in part, via the TLR4/NF-κB signaling pathway. This result indicates that DCA might be a potential therapeutic candidate for human pregnancy-related complications associated with trophoblast disorder.

Adenylate cyclase toxin of Bordetella parapertussis disrupts the epithelial barrier granting the bacterial access to the intracellular space of epithelial cells

B. parapertussis is one of the etiological agents of whooping cough. Once inhaled, the bacteria bind to the respiratory epithelium and start the infection. Little is known about this first step of host colonization and the role of the human airway epithelial barrier on B. parapertussis infection. We here investigated the outcome of the interaction of B. parapertussis with a polarized monolayer of respiratory epithelial cells. Our results show that B. parapertussis preferentially attaches to the intercellular boundaries, and causes the disruption of the tight junction integrity through the action of adenylate cyclase toxin (CyaA). We further found evidence indicating that this disruption enables the bacterial access to components of the basolateral membrane of epithelial cells to which B. parapertussis efficiently attaches and gains access to the intracellular location, where it can survive and eventually spread back into the extracellular environment. Altogether, these results suggest that the adenylate cyclase toxin enables B. parapertussis to overcome the epithelial barrier and eventually establish a niche of persistence within the respiratory epithelial cells.

Neonatal Meningitis-Causing Escherichia coli Induces Microglia Activation which Acts as a Double-Edged Sword in Bacterial Meningitis

Bacterial meningitis is a devastating disease occurring worldwide, with up to half of survivors left with permanent neurological sequelae. Neonatal meningitis-causing Escherichia coli (NMEC) is the most common Gram-negative bacillary organism that causes meningitis, particularly during the neonatal period. Here, RNA-seq transcriptional profiles of microglia in response to NMEC infection show that microglia are activated to produce inflammatory factors. In addition, we found that the secretion of inflammatory factors is a double-edged sword that promotes polymorphonuclear neutrophil (PMN) recruitment to the brain to clear the pathogens but, at the same time, induces neuronal damage, which may be related to the neurological sequelae. New neuroprotective therapeutic strategies must be developed for the treatment of acute bacterial meningitis. We found that transforming growth factor-β (TGF-β) may be a strong candidate in the treatment of acute bacterial meningitis, as it shows a therapeutic effect on bacterial-meningitis-induced brain damage. Prevention of disease and early initiation of the appropriate treatment in patients with suspected or proven bacterial meningitis are the key factors in reducing morbidity and mortality. Novel antibiotic and adjuvant treatment strategies must be developed, and the main goal for new therapies will be dampening the inflammatory response. Based on this view, our findings may help develop novel strategies for bacterial meningitis treatment.

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.

Neutrophil Extracellular Traps Induced by Shiga Toxin and Lipopolysaccharide-Treated Platelets Exacerbate Endothelial Cell Damage

Hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in the pediatric population. The etiology of HUS is linked to Gram-negative, Shiga toxin (Stx)-producing enterohemorrhagic bacterial infections. While the effect of Stx is focused on endothelial damage of renal glomerulus, cytokines induced by Stx or bacterial lipopolysaccharide (LPS) and polymorphonuclear cells (PMNs) are involved in the development of the disease. PMN release neutrophil extracellular traps (NETs) to eliminate pathogens, although NETs favor platelets (Plts) adhesion/thrombus formation and can cause tissue damage within blood vessels. Since thrombus formation and occlusion of vessels are characteristic of HUS, PMN–Plts interaction in the context of Stx may promote netosis and contribute to the endothelial damage observed in HUS. The aim of this study was to determine the relevance of netosis induced by Stx in the context of LPS-sensitized Plts on endothelial damage. We observed that Stx2 induced a marked enhancement of netosis promoted by Plts after LPS stimulation. Several factors seemed to promote this phenomenon. Stx2 itself increased the expression of its receptor on Plts, increasing toxin binding. Stx2 also increased LPS binding to Plts. Moreover, Stx2 amplified LPS induced P-selectin expression on Plts and mixed PMN–Plts aggregates formation, which led to activation of PMN enhancing dramatically NETs formation. Finally, experiments revealed that endothelial cell damage mediated by PMN in the context of Plts treated with LPS and Stx2 was decreased when NETs were disrupted or when mixed aggregate formation was impeded using an anti-P-selectin antibody. Using a murine model of HUS, systemic endothelial damage/dysfunction was decreased when NETs were disrupted, or when Plts were depleted, indicating that the promotion of netosis by Plts in the context of LPS and Stx2 plays a fundamental role in endothelial toxicity. These results provide insights for the first time into the pivotal role of Plts as enhancers of endothelial damage through NETs promotion in the context of Stx and LPS. Consequently, therapies designed to reduce either the formation of PMN–Plts aggregates or NETs formation could lessen the consequences of endothelial damage in HUS.

Microglia at the Crossroads of Pathogen-Induced Neuroinflammation

Microglia are the resident tissue macrophages of the central nervous system (CNS). Recent findings point out that in the steady state the major role of microglia, is to instruct and regulate the correct function of the neuronal networks and different components of the neurovascular unit in the adult CNS, while providing immune surveillance. Paradoxically, during CNS infection immune activation of microglia generates an inflammatory milieu that contributes to the clearance of the pathogen but can, in the process, harm nearby cells of CNS. Most of the knowledge about the harmful effects of activated microglia on CNS has arisen from studies on neurodegenerative diseases. In this review we will focus on the beneficial role and detrimental functions of microglial cells on the neighboring cells of the CNS upon infection.

Brucella abortus-Stimulated Platelets Activate Brain Microvascular Endothelial Cells Increasing Cell Transmigration through the Erk1/2 Pathway

Central nervous system invasion by bacteria of the genus Brucella results in an inflammatory disorder called neurobrucellosis. A common feature associated with this pathology is blood-brain barrier (BBB) activation. However, the underlying mechanisms involved with such BBB activation remain unknown. The aim of this work was to investigate the role of Brucella abortus-stimulated platelets on human brain microvascular endothelial cell (HBMEC) activation. Platelets enhanced HBMEC activation in response to B. abortus infection. Furthermore, supernatants from B. abortus-stimulated platelets also activated brain endothelial cells, inducing increased secretion of IL-6, IL-8, CCL-2 as well as ICAM-1 and CD40 upregulation on HBMEC compared with supernatants from unstimulated platelets. Outer membrane protein 19, a B. abortus lipoprotein, recapitulated B. abortus-mediated activation of HBMECs by platelets. In addition, supernatants from B. abortus-activated platelets promoted transendothelial migration of neutrophils and monocytes. Finally, using a pharmacological inhibitor, we demonstrated that the Erk1/2 pathway is involved in the endothelial activation induced by B. abortus-stimulated platelets and also in transendothelial migration of neutrophils. These results describe a mechanism whereby B. abortus-stimulated platelets induce endothelial cell activation, promoting neutrophils and monocytes to traverse the BBB probably contributing to the inflammatory pathology of neurobrucellosis.

Rescue from Stx2-Producing E. coli-Associated Encephalopathy by Intravenous Injection of Muse Cells in NOD-SCID Mice

Shiga toxin-producing Escherichia coli (STEC) causes hemorrhagic colitis, hemolytic uremic syndrome, and acute encephalopathies that may lead to sudden death or severe neurologic sequelae. Current treatments, including immunoglobulin G (IgG) immunoadsorption, plasma exchange, steroid pulse therapy, and the monoclonal antibody eculizumab, have limited effects against the severe neurologic sequelae. Multilineage-differentiating stress-enduring (Muse) cells are endogenous reparative non-tumorigenic stem cells that naturally reside in the body and are currently under clinical trials for regenerative medicine. When administered intravenously, Musecells accumulate to the damaged tissue, where they exert anti-inflammatory, anti-apoptotic, anti-fibrotic, and immunomodulatory effects, and replace damaged cells by differentiating into tissue-constituent cells. Here, severely immunocompromised non-obese diabetic/severe combined immunodeficiency (NOD-SCID) mice orally inoculated with 9 × 109 colony-forming units of STEC O111 and treated 48 h later with intravenous injection of 5 × 104 Muse cells exhibited 100% survival and no severe after-effects of infection. Suppression of granulocyte-colony-stimulating factor (G-CSF) by RNAi abolished the beneficial effects of Muse cells, leading to a 40% death and significant body weight loss, suggesting the involvement of G-CSF in the beneficial effects of Muse cells in STEC-infected mice. Thus, intravenous administration of Muse cells could be a candidate therapeutic approach for preventing fatal encephalopathy after STEC infection.

Prokaryotic RNA activates endothelial cells promoting neutrophil transmigration

Endothelial cell (EC)-neutrophil (PMN) interactions are crucial in the resolution of bacterial infections. Prokaryotic RNA (pRNA) has been reported as a pathogen-associated molecular pattern that is released from bacteria upon death and is able to activate PMN. In this work, we studied the effects of pRNA on EC and investigated whether these effects could modulate EC-PMN interaction. For this purpose, we purified total pRNA from Escherichia coli and used it as a stimulus for Human Umbilical Vein Endothelial Cells (HUVEC). We found that the incubation of pRNA with HUVEC caused the increase of surface intercellular adhesion molecule 1 (ICAM-1 or CD54) expression on HUVEC, and the secretion of IL-8 and von Willebrand factor, characteristics consistent with HUVEC activation, without causing toxic effects. Moreover, pRNA-treated HUVEC also induced PMN adhesion and the conditioned medium obtained from treated-HUVEC was chemotactic for PMN and caused their activation, as determined by CD11b upregulation. As reported previously, the degradation products of pRNA induced similar biological effects. The treatment of HUVEC with endocytosis inhibitors revealed that the entry of pRNA partially relied on a clathrin-dependent mechanism, whereas the effects of degradation products could not be inhibited by any of the inhibitors tested. Using a transwell system, we found that pRNA or degraded pRNA were also able to stimulate HUVEC when recognized from the basolateral side. Our results indicate that pRNA activates EC, resulting in the modulation of EC-PMN interaction by inducing PMN chemotaxis, adhesion and activation. In the context of infection, pRNA sensed by EC and PMN could favor bacterial clearance.

Roles of Shiga Toxins in Immunopathology

Shigella species and Shiga toxin-producing Escherichia coli (STEC) are agents of bloody diarrhea that may progress to potentially lethal complications such as diarrhea-associated hemolytic uremic syndrome (D+HUS) and neurological disorders. The bacteria share the ability to produce virulence factors called Shiga toxins (Stxs). Research over the past two decades has identified Stxs as multifunctional toxins capable of inducing cell stress responses in addition to their canonical ribotoxic function inhibiting protein synthesis. Notably, Stxs are not only potent inducers of cell death, but also activate innate immune responses that may lead to inflammation, and these effects may increase the severity of organ injury in patients infected with Stx-producing bacteria. In the intestines, kidneys, and central nervous system, excessive or uncontrolled host innate and cellular immune responses triggered by Stxs may result in sensitization of cells to toxin mediated damage, leading to immunopathology and increased morbidity and mortality in animal models (including primates) and human patients. Here, we review studies describing Stx-induced innate immune responses that may be associated with tissue damage, inflammation, and complement activation. We speculate on how these processes may contribute to immunopathological responses to the toxins.

Postdiarrheal hemolytic and uremic syndrome with severe multiorgan involvement and associated early risk factors

AIM

Identifying early clinical and biological factors associated with severe forms of postdiarrheal hemolytic uremic syndrome (D+HUS) that may help practitioners determine appropriate treatment.

METHODS

This retrospective study was conducted in 49 children with D+HUS between 2001 and 2011. Severe forms were defined as occurrence of one of the following conditions: death, major neurological involvement, cardiovascular involvement, and/or the presence of sequelae (neurological, cardiovascular, pancreatic, or renal).

RESULTS

During the acute phase, 35 children exhibited at least one type of extrarenal involvement including 13 severe forms with a median delayed occurrence after admission of 4.5 days (range: 1-8) for comatose children and 5 days (range: 2-6) for cardiovascular involvement; 32 children required dialysis and three died. In multivariate analysis, (i) major neurological involvement (n=13), (ii) dialysis (n=32), and (iii) sequelae (n=12) were associated with (i) fever during the prodromal phase requiring dialysis at admission, (ii) C-reactive protein level (CRP) >22mg/L at admission, and (iii) major neurological involvement and a white blood cell count (WBC)>20×10³/mm³ during the acute stage, respectively.

CONCLUSIONS

D+HUS is a multiorgan disease with a delayed occurrence of life-threatening extrarenal organ involvement. Severe forms appear to be associated with early biological and clinical inflammatory parameters.

Shiga Toxins Induce Apoptosis and ER Stress in Human Retinal Pigment Epithelial Cells

Shiga toxins (Stxs) produced by Shiga toxin-producing bacteria Shigella dysenteriae serotype 1 and select serotypes of Escherichia coli are the most potent known virulence factors in the pathogenesis of hemorrhagic colitis progressing to potentially fatal systemic complications such as acute renal failure, blindness and neurological abnormalities. Although numerous studies have defined apoptotic responses to Shiga toxin type 1 (Stx1) or Shiga toxin type 2 (Stx2) in a variety of cell types, the potential significance of Stx-induced apoptosis of photoreceptor and pigmented cells of the eye following intoxication is unknown. We explored the use of immortalized human retinal pigment epithelial (RPE) cells as an in vitro model of Stx-induced retinal damage. To the best of our knowledge, this study is the first report that intoxication of RPE cells with Stxs activates both apoptotic cell death signaling and the endoplasmic reticulum (ER) stress response. Using live-cell imaging analysis, fluorescently labeled Stx1 or Stx2 were internalized and routed to the RPE cell endoplasmic reticulum. RPE cells were significantly sensitive to wild type Stxs by 72 h, while the cells survived challenge with enzymatically deficient mutant toxins (Stx1A⁻ or Stx2A⁻). Upon exposure to purified Stxs, RPE cells showed activation of a caspase-dependent apoptotic program involving a reduction of mitochondrial transmembrane potential (Δψ_m), increased activation of ER stress sensors IRE1, PERK and ATF6, and overexpression CHOP and DR5. Finally, we demonstrated that treatment of RPE cells with Stxs resulted in the activation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38MAPK), suggesting that the ribotoxic stress response may be triggered. Collectively, these data support the involvement of Stx-induced apoptosis in ocular complications of intoxication. The evaluation of apoptotic responses to Stxs by cells isolated from multiple organs may reveal unique functional patterns of the cytotoxic actions of these toxins in the systemic complications that follow ingestion of toxin-producing bacteria.

Angiotensin-(1-7) protects from brain damage induced by shiga toxin 2-producing enterohemorrhagic Escherichia coli

Shiga toxin 2 (Stx2)-producing enterohemorrhagic induced brain damage. Since a cerebroprotective action was reported for angiotensin (Ang)-(1-7), our aim was to investigate whether Ang-(1-7) protects from brain damage induced by Stx2-producing enterohemorrhagic Escherichia coli The anterior hypothalamic area of adult male Wistar rats was injected with saline solution or Stx2 or Stx2 plus Ang-(1-7) or Stx2 plus Ang-(1-7) plus A779. Rats received a single injection of Stx2 at the beginning of the experiment, and Ang-(1-7), A779, or saline was administered daily in a single injection for 8 days. Cellular ultrastructural changes were analyzed by transmission electron microscopy. Stx2 induced neurodegeneration, axonal demyelination, alterations in synapse, and oligodendrocyte and astrocyte damage, accompanied by edema. Ang-(1-7) prevented neuronal damage triggered by the toxin in 55.6 ± 9.5% of the neurons and the Stx2-induced synapse dysfunction was reversed. In addition, Ang-(1-7) blocked Stx2-induced demyelination in 92 ± 4% of the axons. Oligodendrocyte damage caused by Stx2 was prevented by Ang-(1-7) but astrocytes were only partially protected by the peptide (38 ± 5% of astrocytes were preserved). Ang-(1-7) treatment resulted in 50% reduction in the number of activated microglial cells induced by Stx2, suggesting an anti-inflammatory action. All these beneficial effects elicited by Ang-(1-7) were blocked by the Mas receptor antagonist and thus it was concluded that Ang-(1-7) protects mainly neurons and oligodendrocytes, and partially astrocytes, in the central nervous system through Mas receptor stimulation.

Tumor necrosis factor-α modifies the effects of Shiga toxin on glial cells

Shiga toxin (STX) is one of the main factors inducing hemorrhagic colitis and hemolytic-uremic syndrome (HUS) in infections with STX-producing Escherichia coli (STEC). Approximately 62% of patients with HUS showed symptoms of encephalopathy in the 2011 Japanese outbreak of STEC infections. At that time, we reported elevated serum concentrations of tumor necrosis factor (TNF)-α in patients with acute encephalopathy during the HUS phase. In the current study, we investigated whether TNF-α augments the effects of STX in glial cell lines and primary glial cells. We found that TNF-α alone or STX in combination with TNF-α activates nuclear factor-κB (NF-κB) signaling and inhibits growth of glial cells. The magnitude of the NF-κB activation and the inhibition of cell growth by the STX and TNF-α combination was greater than that obtained with TNF-α alone or STX alone. Thus, this in vitro study reveals the role of TNF-α in glial cells during STEC infections.

Shiga Toxins as Multi-Functional Proteins: Induction of Host Cellular Stress Responses, Role in Pathogenesis and Therapeutic Applications

Shiga toxins (Stxs) produced by Shiga toxin-producing bacteria Shigella dysenteriae serotype 1 and select serotypes of Escherichia coli are primary virulence factors in the pathogenesis of hemorrhagic colitis progressing to potentially fatal systemic complications, such as hemolytic uremic syndrome and central nervous system abnormalities. Current therapeutic options to treat patients infected with toxin-producing bacteria are limited. The structures of Stxs, toxin-receptor binding, intracellular transport and the mode of action of the toxins have been well defined. However, in the last decade, numerous studies have demonstrated that in addition to being potent protein synthesis inhibitors, Stxs are also multifunctional proteins capable of activating multiple cell stress signaling pathways, which may result in apoptosis, autophagy or activation of the innate immune response. Here, we briefly present the current understanding of Stx-activated signaling pathways and provide a concise review of therapeutic applications to target tumors by engineering the toxins.

Glial Cell-Elicited Activation of Brain Microvasculature in Response to Brucella abortus Infection Requires ASC Inflammasome-Dependent IL-1β Production

Blood-brain barrier activation and/or dysfunction are a common feature of human neurobrucellosis, but the underlying pathogenic mechanisms are largely unknown. In this article, we describe an immune mechanism for inflammatory activation of human brain microvascular endothelial cells (HBMEC) in response to infection with Brucella abortus Infection of HBMEC with B. abortus induced the secretion of IL-6, IL-8, and MCP-1, and the upregulation of CD54 (ICAM-1), consistent with a state of activation. Culture supernatants (CS) from glial cells (astrocytes and microglia) infected with B. abortus also induced activation of HBMEC, but to a greater extent. Although B. abortus-infected glial cells secreted IL-1β and TNF-α, activation of HBMEC was dependent on IL-1β because CS from B. abortus-infected astrocytes and microglia deficient in caspase-1 and apoptosis-associated speck-like protein containing a CARD failed to induce HBMEC activation. Consistently, treatment of CS with neutralizing anti-IL-1β inhibited HBMEC activation. Both absent in melanoma 2 and Nod-like receptor containing a pyrin domain 3 are partially required for caspase-1 activation and IL-1β secretion, suggesting that multiple apoptosis-associated speck-like protein containing CARD-dependent inflammasomes contribute to IL-1β-induced activation of the brain microvasculature. Inflammasome-mediated IL-1β secretion in glial cells depends on TLR2 and MyD88 adapter-like/TIRAP. Finally, neutrophil and monocyte migration across HBMEC monolayers was increased by CS from Brucella-infected glial cells in an IL-1β-dependent fashion, and the infiltration of neutrophils into the brain parenchyma upon intracranial injection of B. abortus was diminished in the absence of Nod-like receptor containing a pyrin domain 3 and absent in melanoma 2. Our results indicate that innate immunity of the CNS set in motion by B. abortus contributes to the activation of the blood-brain barrier in neurobrucellosis and IL-1β mediates this phenomenon.

Enterohemorrhagic Escherichia coli Pathogenesis and the Host Response

Enterohemorrhagic Escherichia coli (EHEC) is a highly pathogenic bacterial strain capable of causing watery or bloody diarrhea, the latter termed hemorrhagic colitis, and hemolytic-uremic syndrome (HUS). HUS is defined as the simultaneous development of non-immune hemolytic anemia, thrombocytopenia, and acute renal failure. The mechanism by which EHEC bacteria colonize and cause severe colitis, followed by renal failure with activated blood cells, as well as neurological symptoms, involves the interaction of bacterial virulence factors and specific pathogen-associated molecular patterns with host cells as well as the host response. The innate immune host response comprises the release of antimicrobial peptides as well as cytokines and chemokines in addition to activation and/or injury to leukocytes, platelets, and erythrocytes and activation of the complement system. Some of the bacterial interactions with the host may be protective in nature, but, when excessive, contribute to extensive tissue injury, inflammation, and thrombosis, effects that may worsen the clinical outcome of EHEC infection. This article describes aspects of the host response occurring during EHEC infection and their effects on specific organs.

Increased levels of tumour necrosis factor alpha (TNFα) but not transforming growth factor-beta 1 (TGFβ1) are associated with the severity of congenital hydrocephalus in the hyh mouse

AIMS

Here, we tested the hypothesis that glial responses via the production of cytokines such as transforming growth factor-beta 1 (TGFβ1) and tumour necrosis factor alpha (TNFα), which play important roles in neurodegenerative diseases, are correlated with the severity of congenital hydrocephalus in the hyh mouse model. We also searched for evidence of this association in human cases of primary hydrocephalus.

METHODS

Hyh mice, which exhibit either severe or compensated long-lasting forms of hydrocephalus, were examined and compared with wild-type mice. TGFβ1, TNFα and TNFαR1 mRNA levels were quantified using real-time PCR. TNFα and TNFαR1 were immunolocalized in the brain tissues of hyh mice and four hydrocephalic human foetuses relative to astroglial and microglial reactions.

RESULTS

The TGFβ1 mRNA levels were not significantly different between hyh mice exhibiting severe or compensated hydrocephalus and normal mice. In contrast, severely hydrocephalic mice exhibited four- and two-fold increases in the mean levels of TNFα and TNFαR1, respectively, compared with normal mice. In the hyh mouse, TNFα and TNFαR1 immunoreactivity was preferentially detected in astrocytes that form a particular periventricular reaction characteristic of hydrocephalus. However, these proteins were rarely detected in microglia, which did not appear to be activated. TNFα immunoreactivity was also detected in the glial reaction in the small group of human foetuses exhibiting hydrocephalus that were examined.

CONCLUSIONS

In the hyh mouse model of congenital hydrocephalus, TNFα and TNFαR1 appear to be associated with the severity of the disease, probably mediating the astrocyte reaction, neurodegenerative processes and ischaemia.

The TNF-α/NF-κB signaling pathway has a key role in methamphetamine-induced blood-brain barrier dysfunction

Methamphetamine (METH) is a psychostimulant that causes neurologic and psychiatric abnormalities. Recent studies have suggested that its neurotoxicity may also result from its ability to compromise the blood-brain barrier (BBB). Herein, we show that METH rapidly increased the vesicular transport across endothelial cells (ECs), followed by an increase of paracellular transport. Moreover, METH triggered the release of tumor necrosis factor-alpha (TNF-α), and the blockade of this cytokine or the inhibition of nuclear factor-kappa B (NF-κB) pathway prevented endothelial dysfunction. Since astrocytes have a crucial role in modulating BBB function, we further showed that conditioned medium obtained from astrocytes previously exposed to METH had a negative impact on barrier properties also via TNF-α/NF-κB pathway. Animal studies corroborated the in vitro results. Overall, we show that METH directly interferes with EC properties or indirectly via astrocytes through the release of TNF-α and subsequent activation of NF-κB pathway culminating in barrier dysfunction.

Pathogens penetrating the central nervous system: infection pathways and the cellular and molecular mechanisms of invasion

The brain is well protected against microbial invasion by cellular barriers, such as the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). In addition, cells within the central nervous system (CNS) are capable of producing an immune response against invading pathogens. Nonetheless, a range of pathogenic microbes make their way to the CNS, and the resulting infections can cause significant morbidity and mortality. Bacteria, amoebae, fungi, and viruses are capable of CNS invasion, with the latter using axonal transport as a common route of infection. In this review, we compare the mechanisms by which bacterial pathogens reach the CNS and infect the brain. In particular, we focus on recent data regarding mechanisms of bacterial translocation from the nasal mucosa to the brain, which represents a little explored pathway of bacterial invasion but has been proposed as being particularly important in explaining how infection with Burkholderia pseudomallei can result in melioidosis encephalomyelitis.

Inflammation biomarkers and delirium in critically ill patients

Introduction

Delirium is a common occurrence in critically ill patients and is associated with an increase in morbidity and mortality. Septic patients with delirium may differ from a general critically ill population. The aim of this investigation was to study the relationship between systemic inflammation and the development of delirium in septic and non-septic critically ill patients.

Methods

We performed a prospective cohort study in a 20-bed mixed intensive care unit (ICU) including 78 (delirium = 31; non-delirium = 47) consecutive patients admitted for more than 24 hours. At enrollment, patients were allocated to septic or non-septic groups according to internationally agreed criteria. Delirium was diagnosed using the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) during the first 72 hours of ICU admission. Blood samples were collected within 12 hours of enrollment for determination of tumor necrosis factor (TNF)-α, soluble TNF Receptor (STNFR)-1 and -2, interleukin (IL)-1β, IL-6, IL-10 and adiponectin.

Results

Out of all analyzed biomarkers, only STNFR1 (P = 0.003), STNFR2 (P = 0.005), adiponectin (P = 0.005) and IL-1β (P < 0.001) levels were higher in delirium patients. Adjusting for sepsis and sedation, these biomarkers were also independently associated with delirium occurrence. However, none of them were significant influenced by sepsis.

Conclusions

STNFR1, STNFR2, adiponectin and IL-1β were associated with delirium. Sepsis did not modify the relationship between the biomarkers and delirium occurrence.

Promoter sequence of Shiga toxin 2 (Stx2) is recognized in vivo, leading to production of biologically active Stx2

Shiga toxins (Stx) are the main agent responsible for the development of hemolytic-uremic syndrome (HUS), the most severe and life-threatening systemic complication of infection with enterohemorrhagic Escherichia coli (EHEC) strains. We previously described Stx2 expression by eukaryotic cells after they were transfected in vitro with the stx₂ gene cloned into a prokaryotic plasmid (pStx2). The aim of this study was to evaluate whether mammalian cells were also able to express Stx2 in vivo after pStx2 injection. Mice were inoculated by hydrodynamics-based transfection (HBT) with pStx2. We studied the survival, percentage of polymorphonuclear leukocytes in plasma, plasma urea levels, and histology of the kidneys and the brains of mice. Mice displayed a lethal dose-related response to pStx2. Stx2 mRNA was recovered from the liver, and Stx2 cytotoxic activity was observed in plasma of mice injected with pStx2. Stx2 was detected by immunofluorescence in the brains of mice inoculated with pStx2, and markers of central nervous system (CNS) damage were observed, including increased expression of glial fibrillary acidic protein (GFAP) and fragmentation of NeuN in neurons. Moreover, anti-Stx2B-immunized mice were protected against pStx2 inoculation. Our results show that Stx2 is expressed in vivo from the wild stx₂ gene, reproducing pathogenic damage induced by purified Stx2 or secondary to EHEC infection.

Enterohemorrhagic Shiga toxin (Stx)-producing Escherichia coli (EHEC) infections are a serious public health problem, and Stx is the main pathogenic agent associated with typical hemolytic-uremic syndrome (HUS). In contrast to the detailed information describing the molecular basis for EHEC adherence to epithelial cells, very little is known about how Stx is released from bacteria in the gut, reaching its target tissues, mainly the kidney and central nervous system (CNS). In order to develop an efficient treatment for EHEC infections, it is necessary to understand the mechanisms involved in Stx expression. In this regard, the present study demonstrates that mammals can synthesize biologically active Stx using the natural promoter associated with the Stx-converting bacteriophage genome. These results could impact the comprehension of EHEC HUS, since local eukaryotic cells transduced and/or infected by bacteriophage encoding Stx2 could be an alternative source of Stx production.

Investigation of encephalopathy caused by Shiga toxin 2c-producing Escherichia coli infection in mice

A large outbreak of Shiga toxin (Stx)-producing enteroaggregative Escherichia coli (EAEC) O104:H4 occurred in northern Germany. From this outbreak, at least 900 patients developed hemolytic uremic syndrome (HUS), resulting in more than 50 deaths. Thirty percent of the HUS patients showed encephalopathy. We previously established a mouse model with encephalopathy associated with blood brain barrier (BBB) damage after oral infection with the Shiga toxin (Stx) 2c-producing Escherichia coli O157: H- strain E32511 (E32511). In this model, we detected high expression of the Stx receptor synthase enzyme, glycosphingolipid globotriaosylceramide (Gb3) synthase, in endothelial cells (ECs) and neurons in the reticular formation of the medulla oblongata by in situ hybridization. Caspase-3 was activated in neurons in the reticular formation of the medulla oblongata and the anterior horn of the spinal cord. Astrocytes (ASTs) were activated in the medulla oblongata and spinal cord, and a decrease in aquaporin 4 around the ECs suggested that BBB integrity was compromised directly by Stx2c or through the activation of ASTs. We also report the effectiveness of azithromycin (AZM) in our model. Moreover, AZM strongly inhibited the release of Stx2c from E32511 in vitro.

Shiga toxins and the pathophysiology of hemolytic uremic syndrome in humans and animals

Food-borne diseases are estimated at 76 million illnesses and 5000 deaths every year in the United States with the greatest burden on young children, the elderly and immunocompromised populations. The impact of efficient food distribution systems and a truly global food supply ensures that outbreaks, previously sporadic and contained locally, are far more widespread and emerging pathogens have far more frequent infection opportunities. Enterohemorrhagic E. coli is an emerging food- and water-borne pathogen family whose Shiga-like toxins induce painful hemorrhagic colitis with potentially lethal complications of hemolytic uremic syndrome (HUS). The clinical manifestations of Shiga toxin-induced HUS overlap with other related syndromes yet molecular mechanisms differ considerably. As discussed herein, understanding these differences and the novel properties of the toxins is imperative for clinical management decisions, design of appropriate animal models, and choices of adjunctive therapeutics. The emergence of new strains with rapidly aggressive virulence makes clinical and research initiatives in this field a high public health priority.