RESUMEN
Neurological damage caused by intoxication with Shiga toxin (Stx) from enterohemorrhagic Escherichia coli is the most unrepairable and untreatable outcome of Hemolytic Uremic Syndrome, and occurs in 30% of affected infants. In this work intracerebroventricular administration of Stx2 in rat brains significantly increased the expression of its receptor globotriaosylceramide (Gb(3)) in neuronal populations from striatum, hippocampus and cortex. Stx2 was immunodetected in neurons that expressed Gb(3) after intracerebroventricular administration of the toxin. Confocal immunofluorescence of microtubule-associated protein 2 showed aberrant dendrites in neurons expressing increased Gb(3). The pro-apoptotic Bax protein was concomitantly immunodetected in neurons and other cell populations from the same described areas including the hypothalamus. Confocal immunofluorescence showed that Gb(3) colocalized also with glial fibrillary acidic protein only in reactive astrocytic processes, and not in vehicle-treated normal ones. Rats showed weight variation and motor deficits as compared to controls. We thus suggest that Stx2 induces the expression of Gb(3) in neurons and triggers neuronal dysfunctions.
Asunto(s)
Encéfalo/efectos de los fármacos , Dendritas/efectos de los fármacos , Síndromes de Neurotoxicidad/microbiología , Toxina Shiga II/toxicidad , Trihexosilceramidas/agonistas , Animales , Apoptosis/efectos de los fármacos , Apoptosis/fisiología , Biomarcadores/metabolismo , Encéfalo/metabolismo , Encéfalo/patología , Chlorocebus aethiops , Dendritas/metabolismo , Dendritas/patología , Infecciones por Escherichia coli/complicaciones , Proteína Ácida Fibrilar de la Glía/metabolismo , Inmunohistoquímica , Inyecciones Intraventriculares , Masculino , Microscopía Confocal , Proteínas Asociadas a Microtúbulos/metabolismo , Degeneración Nerviosa/metabolismo , Degeneración Nerviosa/microbiología , Degeneración Nerviosa/patología , Síndromes de Neurotoxicidad/metabolismo , Síndromes de Neurotoxicidad/patología , Ratas , Ratas Sprague-Dawley , Trihexosilceramidas/metabolismo , Regulación hacia Arriba/efectos de los fármacos , Regulación hacia Arriba/fisiología , Células Vero , Proteína X Asociada a bcl-2/efectos de los fármacos , Proteína X Asociada a bcl-2/metabolismoRESUMEN
Shiga toxin (Stx) from enterohemorrhagic Escherichia coli (STEC) is the main cause of hemorrhagic colitis which may derive into Hemolytic Uremic Syndrome (HUS) and acute encephalopathy, one of the major risk factors for infant death caused by the toxin. We have previously demonstrated that intracerebroventricular administration of Stx2 causes neuronal death and glial cell damage in rat brains. In the present work, we observed that the intracerebroventricular administration of Stx2 increased the expression of glial fibrillary acidic protein (GFAP) leading to astrogliosis. Confocal microscopy showed reactive astrocytes in contact with Stx2-containing neurons. Immunocolocalization of increased GFAP and Stx2 in astrocytes was also observed. This insult in the brain was correlated with changes in the expression and activity of neuronal nitric oxide synthase (nNOS) by using the NADPH-diaphorase histochemical technique (NADPH-d HT). A significant decrease in NOS/NADPH-d-positive neurons and NOS/NADPH-d activity was observed in cerebral cortex and striatum, whereas an opposite effect was found in the hypothalamic paraventricular nucleus. We concluded that the i.c.v. administration of Stx2 promotes a typical pattern of brain injury showing reactive astrocytes and an alteration in the number and activity of nNOS/NADPH-d. According to the functional state of nNOS/NADPH-d and to brain cell morphology data, it could be inferred that the i.c.v. administration of Stx2 leads to either a neurodegenerative or a neuroprotective mechanism in the affected brain areas. The present animal model resembles the encephalopathy developed in Hemolytic Uremic Syndrome (HUS) patients by STEC intoxication.
Asunto(s)
Química Encefálica/efectos de los fármacos , Proteína Ácida Fibrilar de la Glía/biosíntesis , Óxido Nítrico Sintasa de Tipo I/biosíntesis , Toxina Shiga II/toxicidad , Animales , Apoptosis/efectos de los fármacos , Astrocitos/efectos de los fármacos , Astrocitos/metabolismo , Relación Dosis-Respuesta a Droga , Proteína Ácida Fibrilar de la Glía/genética , Inmunohistoquímica , Inyecciones Intraventriculares , Masculino , Microscopía Confocal , Microscopía Electrónica de Transmisión , NADPH Deshidrogenasa/metabolismo , Neostriado/fisiología , Óxido Nítrico Sintasa de Tipo I/genética , Células Piramidales/efectos de los fármacos , Células Piramidales/enzimología , Células Piramidales/metabolismo , Ratas , Ratas Sprague-Dawley , Toxina Shiga II/administración & dosificación , Toxina Shiga II/aislamiento & purificaciónRESUMEN
Shiga toxin (Stx) from enterohemorrhagic Escherichia coli (STEC) is the main cause of hemorrhagic colitis which may derive to hemolytic-uremic syndrome (HUS). HUS is characterized by acute renal failure, thrombocytopenia and microangiopathic hemolytic anemia. Mortality in the acute stage has been lower than 5% of total affected argentine children with endemic HUS. Common signs of severe CNS involvement leading to death included seizures, alteration of consciousness, hemiparesis, visual disturbances, and brainstem symptoms. The main purpose of the present work was to study the direct involvement of Stx2 in brain cells by intracerebroventricular (i.c.v.) administration of Stx2. Immunodetection of Stx2 was confirmed by immunoelectron cytochemistry in different subsets and compartments of affected caudate putamen cells of corpus striatum. Transmission electron microscopy (TEM) studies revealed apoptotic neurons, glial ultrastructural alterations and demyelinated fibers. The i.c.v. microinfusion was applied for the first time in rats to demonstrate the direct action of Stx2 in neurons and glial cells. The toxin may affect brain neuroglial cells without the involvement of proinflammatory or systemic neurotoxic elements.
Asunto(s)
Cuerpo Estriado/citología , Neuroglía/efectos de los fármacos , Neuroglía/ultraestructura , Neuronas/efectos de los fármacos , Neuronas/ultraestructura , Toxina Shiga II/administración & dosificación , Análisis de Varianza , Animales , Relación Dosis-Respuesta a Droga , Proteína Ácida Fibrilar de la Glía/metabolismo , Inyecciones Intraventriculares/métodos , Masculino , Microscopía Inmunoelectrónica/métodos , Neuronas/patología , Ratas , Ratas Sprague-Dawley , Toxina Shiga II/metabolismoRESUMEN
In the last years, infection associated with Shiga toxin-producing Escherichia coli (STEC) and subsequent Hemolitic-Uremic Syndrome (HUS) became relevant as a public health since it was considered as one of the most important emergent patogen present in the food contaminated by cattle feces. STEC infection may be asymptomatic or begins with a watery diarrhea that may or may not progress to bloody diarrhea (hemorrhagic colitis) and HUS. In Argentina, HUS is the most common pediatric cause of acute renal insufficiency and the second cause of chronic renal failure. Up to now, STEC infection lacks of known effective treatment strategies that diminish risk of progression to HUS. The mechanisms by which Shiga toxin (Stx) induce HUS may help to find strategies to prevent or ameliorate HUS. In this article, recent progress that has contributed to understanding the disease pathogenesis of STEC is reviewed. New strategies to prevent further uptake of Shiga from the gut, either during the diarrheal phase or once HUS has developed are discussed.
Asunto(s)
Infecciones por Escherichia coli/microbiología , Síndrome Hemolítico-Urémico/microbiología , Toxinas Shiga/metabolismo , Sistema Nervioso Central/metabolismo , Sistema Nervioso Central/microbiología , Escherichia coli/metabolismo , Escherichia coli/patogenicidad , Infecciones por Escherichia coli/metabolismo , Infecciones por Escherichia coli/fisiopatología , Vacunas contra Escherichia coli/administración & dosificación , Síndrome Hemolítico-Urémico/metabolismo , Síndrome Hemolítico-Urémico/fisiopatología , Humanos , Mucosa Intestinal/metabolismo , Intestinos/microbiología , Riñón/metabolismo , Riñón/microbiología , Toxinas Shiga/antagonistas & inhibidoresRESUMEN
In the last years, infection associated with Shiga toxin-producing Escherichia coli (STEC) and subsequent Hemolitic-Uremic Syndrome (HUS) became relevant as a public health since it was considered as one of the most important emergent patogen present in the food contaminated by cattle feces. STEC infection may be asymptomatic or begins with a watery diarrhea that may or may not progress to bloody diarrhea (hemorrhagic colitis) and HUS. In Argentina, HUS is the most common pediatric cause of acute renal insufficiency and the second cause of chronic renal failure. Up to now, STEC infection lacks of known effective treatment strategies that diminish risk of progression to HUS. The mechanisms by which Shiga toxin (Stx) induce HUS may help to find strategies to prevent or ameliorate HUS. In this article, recent progress that has contributed to understanding the disease pathogenesis of STEC is reviewed. New strategies to prevent further uptake of Shiga from the gut, either during the diarrheal phase or once HUS has developed are discussed.(AU)
Asunto(s)
Humanos , Infecciones por Escherichia coli/microbiología , Toxinas Shiga/metabolismo , Sistema Nervioso Central/metabolismo , Sistema Nervioso Central/microbiología , Vacunas contra Escherichia coli/administración & dosificación , Escherichia coli/metabolismo , Infecciones por Escherichia coli/metabolismo , Infecciones por Escherichia coli/fisiopatología , Intestinos/metabolismo , Intestinos/microbiología , Riñón/metabolismo , Riñón/microbiología , Toxinas Shiga/antagonistas & inhibidores , Escherichia coli/patogenicidadRESUMEN
In the last years, infection associated with Shiga toxin-producing Escherichia coli (STEC) and subsequent Hemolitic-Uremic Syndrome (HUS) became relevant as a public health since it was considered as one of the most important emergent patogen present in the food contaminated by cattle feces. STEC infection may be asymptomatic or begins with a watery diarrhea that may or may not progress to bloody diarrhea (hemorrhagic colitis) and HUS. In Argentina, HUS is the most common pediatric cause of acute renal insufficiency and the second cause of chronic renal failure. Up to now, STEC infection lacks of known effective treatment strategies that diminish risk of progression to HUS. The mechanisms by which Shiga toxin (Stx) induce HUS may help to find strategies to prevent or ameliorate HUS. In this article, recent progress that has contributed to understanding the disease pathogenesis of STEC is reviewed. New strategies to prevent further uptake of Shiga from the gut, either during the diarrheal phase or once HUS has developed are discussed.