ABSTRACT
The activation of N-methyl-d-aspartate receptor (NMDAR) is triggered by the closure of bilobed (D1 and D2) clamshell-like clefts upon binding glycine (Gly) and glutamate. There is evidence that cholinergic compounds modulate NMDAR-mediated currents via direct receptor-ligand interactions; however, molecular bases are unknown. Here, we first propose a mechanistic structure-based explanation for the observed ACh-induced submaximal potentiation of NMDA-elicited currents in striatal neurons by predicting competitive inhibition with Gly. Then, the model was validated, in principle, by confirming that the coapplication of Gly and ACh significantly reduces these neuronal currents. Finally, we delineate the interplay of ACh with the NMDAR by a combination of computational strategies. Crystallographic ACh-bound complexes were studied, revealing a similar ACh binding environment on the GluN1 subunit of the NMDAR. We illustrate how ACh can occupy X-ray monomeric open, dimeric "semiopen" cleft conformations obtained by molecular dynamics and a full-active cryo-EM NMDAR structure, explaining the suboptimal NMDAR electrophysiological activity under the "Venus Flytrap model". At an evolutionary biology level, the binding mode of ACh coincides with that of the homologous ornithine-bound periplasmic LAO binding protein complex. Our computed results indicate an analogous mechanism of action, inasmuch as ACh may stabilize the GluN1 subunit "semiclosed" conformations by inducing direct and indirect D1-to-D2 interdomain bonds. Additionally, an alternative binding site was detected, shared by the known NMDAR allosteric modulators. Experimental and computed results strongly suggest that ACh acts as a Gly-competitive, submaximal potentiating agent of the NMDAR, possibly constituting a novel chemotype for multitarget-directed drug development, e.g., to treat Alzheimer's, and it may lead to a new understanding of glutamatergic neurotransmission.
Subject(s)
Acetylcholine , Receptors, N-Methyl-D-Aspartate , Glycine/pharmacology , N-Methylaspartate , NeuronsABSTRACT
RESUMO Objetivos: Pouco se sabe sobre a atuação dos esteroides androgênicos anabolizantes (EAA) no cérebro humano e, por isso, resolvemos estudar a perda neuronal causada pelo uso e abuso de EAA em camundongos. Métodos: Utilizamos 60 camundongos da linhagem Swiss, sendo 30 machos e 30 fêmeas, divididos em três grupos: 20 animais foram tratados com Deposteron® (cipionato de testosterona); outros 20 animais foram tratados com Winstrol Depot® (stanozolol); os últimos 20 animais foram tratados com solução salina. Todos foram submetidos à natação por 15 minutos. Finalizado o tratamento, os animais foram sacrificados pelo método de inalação de Halotano. Os encéfalos foram retirados e armazenados em solução de formaldeído a 4% por 24 horas. De cada encéfalo foram retiradas amostras homotípicas da região média do cérebro em cortes frontais para que pudéssemos avaliar as áreas estabelecidas para este estudo. Resultados: As análises da estimativa dos perfis celulares mostraram que houve uma diminuição do número de perfis no núcleo pálido dos animais machos tratados com Winstrol Depot®. Conclusão: Esses resultados nos permitem inferir que o uso inadequado e sem orientação médica de EAA pode levar a degenerações celulares.
ABSTRACT Objectives: Little is known about the action of anabolic-androgenic steroids (AAS) on the human brain and, therefore, we decided to study the neuronal loss caused by use and abuse of AAS in mice. Methods: We used 60 Swiss mice, 30 males and 30 females, divided into three groups: 20 animals treated with Deposteron® (testosterone cypionate); another 20 animals were treated with Winstrol Depot® (stanozolol); the last 20 animals were treated with saline solution. All the animals were submitted to swimming for 15 minutes. After the treatment, the animals were euthanized by halothane inhalation (Halotano) method. The brains were removed and stored in 4% formal-dehyde solution for 24 hours. From each brain, homotypic samples were taken from the middle region of the brain in frontal cuts so that we could evaluate the areas established for this study. Results: Analyzes of the estimated cell profiles showed that there was a decrease in the number of profiles in the pallidal nucleus of the male animals treated with Winstrol Depot®. Conclusion: These results allow us to infer that inadequate and non-medical use of AAS can lead to cellular degeneration.
RESUMEN Objetivos: Poco se sabe acerca del efecto de la acción de los esteroides anabólicos androgénicos (EAA) en el cerebro humano y, por este motivo, decidimos estudiar la pérdida neuronal causada por el uso y abuso de EAA en ratones. Métodos: Utilizamos 60 ratones de linaje Swiss, siendo 30 machos y 30 hembras, divididos en tres grupos: 20 animales fueron tratados con Deposteron® (cipionato de testosterona); otros 20 animales fueron tratados con Winstrol Depot® (stanozolol); los últimos 20 animales fueron tratados con solución salina. Todos fueron sometidos a natación durante 15 minutos. Terminado el tratamiento, los animales fue-ron sacrificados por el método de inhalación de Halotano. Los cerebros fueron retirados y almacenados en solución de formaldehído al 4% durante 24 horas. De cada cerebro fueron retiradas muestras homotípicas de la región media del cerebro en cortes frontales, así que pudimos evaluar las áreas establecidas para este estudio. Resultados: El análisis de la estimación de los perfiles celulares mostró que hubo una disminución en el número de perfiles en el globo pálido de los animales machos tratados con Winstrol Depot®. Conclusión: Estos resultados permiten inferir que el uso inadecuado y sin orientación médica de EAA puede conducir a la degeneración celular.
ABSTRACT
Oxidative stress (OS) has been implicated in the etiology of certain neurodegenerative disorders. Some of these disorders have been associated with unbalanced levels of essential fatty acids (EFA). The response of certain brain regions to OS, however, is not uniform and a selective vulnerability or resilience can occur. In our previous study on rat brains, we observed that a two-generation EFA dietary restriction reduced the number and size of dopaminergic neurons in the substantia nigra (SN) rostro-dorso-medial. To understand whether OS contributes to this effect, we assessed the status of lipid peroxidation (LP) and anti-oxidant markers in both SN and corpus striatum (CS) of rats submitted to this dietary treatment for one (F1) or two (F2) generations. Wistar rats were raised from conception on control or experimental diets containing adequate or reduced levels of linoleic and α-linolenic fatty acids, respectively. LP was measured using the thiobarbituric acid reaction method (TBARS) and the total superoxide dismutase (t-SOD) and catalase (CAT) enzymatic activities were assessed. The experimental diet significantly reduced the docosahexaenoic acid (DHA) levels of SN phospholipids in the F1 (~28%) and F2 (~50%) groups. In F1 adult animals of the experimental group there was no LP in both SN and CS. Consistently, there was a significant increase in the t-SOD activity (p < 0.01) in both regions. In EF2 young animals, degeneration in dopaminergic and non-dopaminergic neurons and a significant increase in LP (p < 0.01) and decrease in the CAT activity (p < 0.001) were detected in the SN, while no inter-group difference was found for these parameters in the CS. Conversely, a significant increase in t-SOD activity (p < 0.05) was detected in the CS of the experimental group compared to the control. The results show that unbalanced EFA dietary levels reduce the redox balance in the SN and reveal mechanisms of resilience in the CS under this stressful condition.
ABSTRACT
La aciduria glutárica tipo I se produce por deficiencia de la enzima glutaril-CoA deshidrogenasa involucrada en el catabolismo de la L-lisina, L-hidroxilisina y L-triptófano lo que ocasiona acumulación de los ácidos glutárico y 3 hidroxiglutárico responsables del compromiso neurológico severo característico de esta enfermedad. La sospecha y diagnóstico de las enfermedades metabólicas constituyen un reto para el personal de salud dada su baja incidencia. En el caso de la aciduria glutárica tipo I se trata de una enfermedad para la cual se poseen los recursos técnicos para el diagnóstico y tratamiento nutricional, su instauración previa a la aparición de encefalopatía aguda, que ocasionan daños irreversibles en el sistema nervioso central, mejora el pronóstico y disminuye el grado de discapacidad. En esta publicación se reportan 5 casos con diagnóstico clínico y bioquímico de aciduria glutárica tipo I que ilustran el espectro clínico y el proceso diagnóstico y de tratamiento en el medio colombiano. Los pacientes se encuentran en seguimiento por los servicios de Neuropediatría.
Glutaric aciduria type i is a disorder resulting trom the deficiency ot the glutaryl-CoA dehydrogenase, enzyme involved in the catabolism ot L-lysine, L-hydroxy-lysine y L-tryptophan causing the accumulation ot its derivatives glutaric acid and 3-hydroxy-glutaric acid which are responsible tor the severe neurological involvement observed in this disease. The diagnosis ot metabolic disorders represents a challenge tor health-care services given its low incidence. Glutaric aciduria type I is a disease tor which there are available technical resources tor diagnosis as well as the nutritional therapy that when set prior to acute encephalopathy, who results in irreversible damage ot central nervous system, can improve the prognosis and decrease the disability ot patients. This publication report 5 cases with clinical and biochemical diagnosis ot glutaric aciduria type i that show the clinical spectrum the diagnostic and treatment approach ot this pathology in Colombia. All the patients are being followed by neuropediatrics services.