RESUMEN
Shiga toxin 2 (Stx2) from enterohemorrhagic Escherichia coli (EHEC) produces hemorrhagic colitis, hemolytic uremic syndrome (HUS), and acute encephalopathy. The mortality rate in HUS increases significantly when the central nervous system (CNS) is involved. Besides, EHEC also releases lipopolysaccharide (LPS). Many reports have described cognitive dysfunctions in HUS patients, the hippocampus being one of the brain areas targeted by EHEC infection. In this context, a translational murine model of encephalopathy was employed to establish the deleterious effects of Stx2 and the contribution of LPS in the hippocampus. The purpose of this work is to elucidate the signaling pathways that may activate the inflammatory processes triggered by Stx2, which produces cognitive alterations at the level of the hippocampus. Results demonstrate that Stx2 produced depression-like behavior, pro-inflammatory cytokine release, and NF-kB activation independent of the ERK1/2 signaling pathway, while co-administration of Stx2 and LPS reduced memory index. On the other hand, LPS activated NF-kB dependent on ERK1/2 signaling pathway. Cotreatment of Stx2 with LPS aggravated the pathologic state, while dexamethasone treatment succeeded in preventing behavioral alterations. Our present work suggests that the use of drugs such as corticosteroids or NF-kB signaling inhibitors may serve as neuroprotectors from EHEC infection.
Asunto(s)
Encefalopatías , Disfunción Cognitiva , Escherichia coli Enterohemorrágica , Infecciones por Escherichia coli , Síndrome Hemolítico-Urémico , Ratones , Humanos , Animales , Toxina Shiga II/toxicidad , Lipopolisacáridos/farmacología , Sistema de Señalización de MAP Quinasas , FN-kappa B , Encéfalo/patología , Infecciones por Escherichia coli/complicaciones , Infecciones por Escherichia coli/tratamiento farmacológico , Infecciones por Escherichia coli/patología , Hipocampo/patología , CogniciónRESUMEN
Infections by Enterohemorrhagic Escherichia coli may cause in addition to hemolytic uremic syndrome neurological disorders which may lead to fatal outcomes in patients. The brain striatum is usually affected during this outcome. The aim of this study was to determine in this area the role of the microglia in pro-inflammatory events that may occur during Shiga toxin 2 intoxication and consequently to this, whether oligodendrocytes were being affected. In the present paper we demonstrated that anti-inflammatory treatments reduced deleterious effects in brain striatal cells exposed to Shiga toxin 2 and LPS. While dexamethasone treatment decreased microglial activation and recovered myelin integrity in the mice striatum, etanercept treatment decreased neuronal uptake of Stx2 in rat striatal neurons, improving the affected area from toxin-derived injury. In conclusion, microglial activation is related to pro-inflammatory events that may deteriorate the brain function during intoxication with Stx2 and LPS. Consequently, the role of anti-inflammatory agents in the treatment of EHEC-derived encephalopathy should be studied in clinical trials.
Asunto(s)
Antiinflamatorios/administración & dosificación , Encefalopatías/tratamiento farmacológico , Escherichia coli Enterohemorrágica/patogenicidad , Infecciones por Escherichia coli/tratamiento farmacológico , Microglía/efectos de los fármacos , Toxina Shiga II/toxicidad , Animales , Encefalopatías/microbiología , Dexametasona/administración & dosificación , Dexametasona/farmacología , Infecciones por Escherichia coli/microbiología , Etanercept/administración & dosificación , Etanercept/farmacología , Humanos , Lipopolisacáridos/toxicidad , Masculino , Ratones , Microglía/patología , Oligodendroglía/efectos de los fármacos , Oligodendroglía/patología , Ratas , Ratas Sprague-DawleyRESUMEN
Shiga toxin 2 (Stx2) from enterohemorrhagic Escherichia coli (EHEC) causes bloody diarrhea and Hemolytic Uremic Syndrome (HUS) that may derive to fatal neurological outcomes. Neurological abnormalities in the striatum are frequently observed in affected patients and in studies with animal models while motor disorders are usually associated with pyramidal and extra pyramidal systems. A translational murine model of encephalopathy was employed to demonstrate that systemic administration of a sublethal dose of Stx2 damaged the striatal microvasculature and astrocytes, increase the blood brain barrier permeability and caused neuronal degeneration. All these events were aggravated by lipopolysaccharide (LPS). The injury observed in the striatum coincided with locomotor behavioral alterations. The anti-inflammatory Dexamethasone resulted to prevent the observed neurologic and clinical signs, proving to be an effective drug. Therefore, the present work demonstrates that: (i) systemic sub-lethal Stx2 damages the striatal neurovascular unit as it succeeds to pass through the blood brain barrier. (ii) This damage is aggravated by the contribution of LPS which is also produced and secreted by EHEC, and (iii) the observed neurological alterations may be prevented by an anti-inflammatory treatment.
Asunto(s)
Antiinflamatorios/farmacología , Trastornos Cerebrovasculares/tratamiento farmacológico , Dexametasona/farmacología , Lipopolisacáridos/toxicidad , Trastornos del Movimiento/tratamiento farmacológico , Toxina Shiga II/toxicidad , Animales , Astrocitos/efectos de los fármacos , Astrocitos/inmunología , Astrocitos/patología , Barrera Hematoencefálica/efectos de los fármacos , Barrera Hematoencefálica/inmunología , Barrera Hematoencefálica/patología , Permeabilidad Capilar/efectos de los fármacos , Permeabilidad Capilar/fisiología , Trastornos Cerebrovasculares/etiología , Trastornos Cerebrovasculares/inmunología , Trastornos Cerebrovasculares/patología , Cuerpo Estriado/irrigación sanguínea , Cuerpo Estriado/efectos de los fármacos , Cuerpo Estriado/inmunología , Cuerpo Estriado/patología , Modelos Animales de Enfermedad , Escherichia coli , Femenino , Ratones , Microvasos/efectos de los fármacos , Microvasos/inmunología , Microvasos/patología , Actividad Motora/efectos de los fármacos , Actividad Motora/fisiología , Trastornos del Movimiento/etiología , Trastornos del Movimiento/inmunología , Trastornos del Movimiento/patología , Fármacos Neuroprotectores/farmacologíaRESUMEN
Shiga toxin producing Escherichia coli may damage the central nervous system before or concomitantly to manifested hemolytic-uremic syndrome symptoms. The cerebellum is frequently damaged during this syndrome, however, the deleterious effects of Shiga toxin 2 has never been integrally reported by ultrastructural, physiological and behavioral means. The aim of this study was to determine the cerebellar compromise after intravenous administration of a sub-lethal dose of Shiga toxin 2 by measuring the cerebellar blood-brain barrier permeability, behavioral task of cerebellar functionality (inclined plane test), and ultrastructural analysis (transmission electron microscope). Intravenous administration of vehicle (control group), sub-lethal dose of 0.5 and 1 ηg of Stx2 per mouse were tested for behavioral and ultrastructural studies. A set of three independent experiments were performed for each study (n = 6). Blood-brain barrier resulted damaged and consequently its permeability was significantly increased. Lower scores obtained in the inclined plane task denoted poor cerebellar functionality in comparison to their controls. The most significant lower score was obtained after 5 days of 1 ηg of toxin administration. Transmission electron microscope micrographs from the Stx2-treated groups showed neurons with a progressive neurodegenerative condition in a dose dependent manner. As sub-lethal intravenous Shiga toxin 2 altered the blood brain barrier permeability in the cerebellum the toxin penetrated the cerebellar parenchyma and produced cell damaged with significant functional implications in the test balance.
RESUMEN
Shiga toxin 2 (Stx2)-producing Escherichia coli (STEC) causes hemorrhagic colitis and hemolytic uremic syndrome (HUS) that can lead to fatal encephalopathies. Neurological abnormalities may occur before or after the onset of systemic pathological symptoms and motor disorders are frequently observed in affected patients and in studies with animal models. As Stx2 succeeds in crossing the blood-brain barrier (BBB) and invading the brain parenchyma, it is highly probable that the observed neurological alterations are based on the possibility that the toxin may trigger the impairment of the neurovascular unit and/or cell damage in the parenchyma. Also, lipopolysaccharide (LPS) produced and secreted by enterohemorrhagic Escherichia coli (EHEC) may aggravate the deleterious effects of Stx2 in the brain. Therefore, this study aimed to determine (i) whether Stx2 affects the neurovascular unit and parenchymal cells, (ii) whether the contribution of LPS aggravates these effects, and (iii) whether an inflammatory event underlies the pathophysiological mechanisms that lead to the observed injury. The administration of a sub-lethal dose of Stx2 was employed to study in detail the motor cortex obtained from a translational murine model of encephalopathy. In the present paper we report that Stx2 damaged microvasculature, caused astrocyte reaction and neuronal degeneration, and that this was aggravated by LPS. Dexamethasone, an anti-inflammatory, reversed the pathologic effects and proved to be an important drug in the treatment of acute encephalopathies.
Asunto(s)
Antiinflamatorios/farmacología , Dexametasona/farmacología , Lipopolisacáridos/toxicidad , Corteza Motora/irrigación sanguínea , Corteza Motora/efectos de los fármacos , Toxina Shiga II/toxicidad , Animales , Astrocitos/efectos de los fármacos , Astrocitos/patología , Modelos Animales de Enfermedad , Sinergismo Farmacológico , Femenino , Ratones , Microvasos/efectos de los fármacos , Corteza Motora/patología , Neuronas/efectos de los fármacos , Neuronas/patología , Síndromes de Neurotoxicidad/tratamiento farmacológico , Síndromes de Neurotoxicidad/etiología , Toxina Shiga II/aislamiento & purificación , Escherichia coli Shiga-Toxigénica/química , Organismos Libres de Patógenos EspecíficosRESUMEN
Infection by Shiga toxin-producing Escherichia coli causes hemorrhagic colitis, hemolytic uremic syndrome (HUS), acute renal failure, and also central nervous system complications in around 30% of the children affected. Besides, neurological deficits are one of the most unrepairable and untreatable outcomes of HUS. Study of the striatum is relevant because basal ganglia are one of the brain areas most commonly affected in patients that have suffered from HUS and since the deleterious effects of a sub-lethal dose of Shiga toxin have never been studied in the striatum, the purpose of this study was to attempt to simulate an infection by Shiga toxin-producing E. coli in a murine model. To this end, intravenous administration of a sub-lethal dose of Shiga toxin 2 (0.5 ηg per mouse) was used and the correlation between neurological manifestations and ultrastructural changes in striatal brain cells was studied in detail. Neurological manifestations included significant motor behavior abnormalities in spontaneous motor activity, gait, pelvic elevation and hind limb activity eight days after administration of the toxin. Transmission electron microscopy revealed that the toxin caused early perivascular edema two days after administration, as well as significant damage in astrocytes four days after administration and significant damage in neurons and oligodendrocytes eight days after administration. Interrupted synapses and mast cell extravasation were also found eight days after administration of the toxin. We thus conclude that the chronological order of events observed in the striatum could explain the neurological disorders found eight days after administration of the toxin.