RESUMEN
Mechanisms underlying motor neuron degeneration in amyotrophic lateral sclerosis (ALS) are yet unclear. Specific deletion of the ER-component membralin in astrocytes manifested postnatal motor defects and lethality in mice, causing the accumulation of extracellular glutamate through reducing the glutamate transporter EAAT2. Restoring EAAT2 levels in membralin KO astrocytes limited astrocyte-dependent excitotoxicity in motor neurons. Transcriptomic profiles from mouse astrocytic membralin KO motor cortex indicated significant perturbation in KEGG pathway components related to ALS, including downregulation of Eaat2 and upregulation of Tnfrsf1a. Changes in gene expression with membralin deletion also overlapped with mouse ALS models and reactive astrocytes. Our results shown that activation of TNF receptor (TNFR1)-NFκB pathway known to suppress Eaat2 transcription was upregulated with membralin deletion. Further, reduced membralin and EAAT2 levels correlated with disease progression in spinal cord from SOD1-mutant mouse models, and reductions in membralin/EAAT2 were observed in human ALS spinal cord. Importantly, overexpression of membralin in SOD1G93A astrocytes decreased TNFR1 levels and increased EAAT2 expression, and improved motor neuron survival. Importantly, upregulation of membralin in SOD1G93A mice significantly prolonged mouse survival. Together, our study provided a mechanism for ALS pathogenesis where membralin limited glutamatergic neurotoxicity, suggesting that modulating membralin had potentials in ALS therapy.
Asunto(s)
Esclerosis Amiotrófica Lateral/metabolismo , Astrocitos/metabolismo , Ácido Glutámico/metabolismo , Corteza Motora/metabolismo , Proteínas del Tejido Nervioso/deficiencia , Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/patología , Animales , Astrocitos/patología , Regulación hacia Abajo , Transportador 2 de Aminoácidos Excitadores/biosíntesis , Transportador 2 de Aminoácidos Excitadores/genética , Ácido Glutámico/genética , Humanos , Ratones , Ratones Noqueados , Corteza Motora/patología , Proteínas del Tejido Nervioso/metabolismo , Receptores Tipo I de Factores de Necrosis Tumoral/biosíntesis , Receptores Tipo I de Factores de Necrosis Tumoral/genética , Superóxido Dismutasa/biosíntesis , Superóxido Dismutasa/genética , Transcripción Genética , Regulación hacia ArribaRESUMEN
Injection of large doses of ammonia (1.2 g/kg, i.p.) was used to induce acute toxicity in mice which was characterized by hyperresponsivenes, taquipnea, clonic and tonic seizures and dealth. Pretreatment with 20,40, or 80 mg/kg i.p. of ketamine increased 30 to 55 per cent survival rate. This pretreatment significantly retarded the beginning of the first tonic convulsió attenuating its intensity and delayed the time of the animal death; but did not alter onset of the first clonic seizures. These experiments may be an evidence that support the hypothesis that seizures due to hyperammonemia involve activation of excitatory amino acid receptors