Synaptic Failure: Focus in an Integrative View of ALS

From early description by Charcot, the classification of the Amyotrophic Lateral Sclerosis (ALS) is evolving from a subtype of Motor Neuron (MN) Disease to be considered rather a multi-systemic, non-cell autonomous and complex neurodegenerative disease. In the last decade, the huge amount of knowledge acquired has shed new insights on the pathological mechanisms underlying ALS from different perspectives. However, a whole vision on the multiple dysfunctional pathways is needed with the inclusion of information often excluded in other published revisions. We propose an integrative view of ALS pathology, although centered on the synaptic failure as a converging and crucial player to the etiology of the disease. Homeostasis of input and output synaptic activity of MNs has been proved to be severely and early disrupted and to definitively contribute to microcircuitry alterations at the spinal cord. Several cells play roles in synaptic communication across the MNs network system such as interneurons, astrocytes, microglia, Schwann and skeletal muscle cells. Microglia are described as highly dynamic surveying cells of the nervous system but also as determinant contributors to the synaptic plasticity linked to neuronal activity. Several signaling axis such as TNFα/TNFR1 and CX3CR1/CX3CL1 that characterize MN-microglia cross talk contribute to synaptic scaling and maintenance, have been found altered in ALS. The presence of dystrophic and atypical microglia in late stages of ALS, with a decline in their dynamic motility and phagocytic ability, together with less synaptic and neuronal contacts disrupts the MN-microglia dialogue, decreases homeostatic regulation of neuronal activity, perturbs “on/off” signals and accelerates disease progression associated to impaired synaptic function and regeneration. Other hotspot in the ALS affected network system is the unstable neuromuscular junction (NMJ) leading to distal axonal degeneration. Reduced neuromuscular spontaneous synaptic activity in ALS mice models was also suggested to account for the selective vulnerability of MNs and decreased regenerative capability. Synaptic destabilization may as well derive from increased release of molecules by muscle cells (e.g. NogoA) and by terminal Schwann cells (e.g. semaphorin 3A) conceivably causing nerve terminal retraction and denervation, as well as inhibition of re-connection to muscle fibers. Indeed, we have overviewed the alterations on the metabolic pathways and self-regenerative capacity presented in skeletal muscle cells that contribute to muscle wasting in ALS. Finally, a detailed footpath of pathologic changes on MNs and associated dysfunctional and synaptic alterations is provided. The oriented motivation in future ALS studies as outlined in the present article will help in fruitful novel achievements on the mechanisms involved and in developing more target-driven therapies that will bring new hope in halting or delaying disease progression in ALS patients

Are circulating cytokines reliable biomarkers for amyotrophic lateral sclerosis?

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that has no effective treatment. The lack of any specific biomarker that can help in the diagnosis or prognosis of ALS has made the identification of biomarkers an urgent challenge. Multiple panels have shown alterations in levels of numerous cytokines in ALS, supporting the contribution of neuroinflammation to the progressive motor neuron loss. However, none of them is fully sensitive and specific enough to become a universal biomarker for ALS. This review gathers the numerous circulating cytokines that have been found dysregulated in both ALS animal models and patients. Particularly, it highlights the opposing results found in the literature to date, and points out another potential application of inflammatory cytokines as therapeutic targets

Inflammatory and non-inflammatory monocytes as novel prognostic biomarkers of survival in SOD1G93A mouse model of Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) has lately become a suitable scenario to study the interplay between the hematopoietic system and disease progression. Recent studies in C9orf72 null mice have demonstrated that C9orf72 is necessary for the normal function of myeloid cells. In this study, we aimed to analyze in depth the connection between the hematopoietic system and secondary lymphoid (spleen) and non-lymphoid (liver and skeletal muscle) organs and tissues along the disease progression in the transgenic SOD1G93A mice. Our findings suggested that the inflammatory response due to the neurodegeneration in this animal model affected all three organs and tissues, especially the liver and the skeletal muscle. However, the liver was able to compensate this inflammatory response by means of the action of non-inflammatory monocytes, while in the skeletal muscle inflammatory monocytes prompted a further inflammation process until the terminal state of the animals. Interestingly, in blood, a positive correlation was found between non-inflammatory monocytes and survival of the transgenic SOD1G93A mice, while the contrary (a negative correlation) was found in the case of inflammatory monocytes, supporting their potential role as biomarkers of disease progression and survival in this animal model. These findings could prompt future translational studies in ALS patients, promoting the identification of new reliable biomarkers of disease progression

Lack of synergistic effect of resveratrol and sigma-1 receptor agonist (PRE-084) in SOD1G?³A ALS mice: overlapping effects or limited therapeutic opportunity?

Background: amyotrophic lateral sclerosis (ALS) is an adult onset neurodegenerative disease characterized by the loss of motoneurons (MNs) in the spinal cord, brainstem and motor cortex, causing progressive paralysis and death. Nowadays, there is no effective therapy and most patients die 2-5 years after diagnosis. Sigma-1R is a transmembrane protein highly expressed in the CNS and specially enriched in MNs. Mutations on the Sigma-1R leading to frontotemporal lobar degeneration-ALS were recently described in human patients. We previously reported the therapeutic role of the selective sigma-1R agonist 2-(4-morpholi-nethyl)1-phenylcyclohexanecarboxylate (PRE-084) in SOD1G93A ALS mice, that promoted spinal MN preservation and extended animal survival by controlling NMDA receptor calcium influx. Resveratrol (RSV, trans-3,4',5-trihydroxystilbene) is a natural polyphenol with promising neuroprotective effects. We recently found that RSV administration to SOD1G93A mice preserves spinal MN function and increases mice survival. These beneficial effects were associated to activation of Sirtuin 1 (Sirt1) and AMP-activated protein kinase (AMPK) pathways, leading to the modulation of autophagy and an increase of mitochondrial biogenesis. The main goal of this work was to assess the effect of combined RSV and PRE-084 administration in SOD1G93A ALS mice.Methods: we determined the locomotor performance of the animals by rotarod test and evaluated spinal motoneuron function using electrophysiological tests.Results: RSV plus PRE-084 treatment from 8 weeks of age significantly improved locomotor performance and spinal MN function, accompanied by a significant reduction of MN degeneration and an extension of mice lifespan. In agreement with our previous findings, there was an induction of PKC-specific phosphorylation of the NMDA-NR1 subunit and an increased expression and activation of Sirt1 and AMPK in the ventral spinal cord of treated SOD1G93A animals.Conclusions: although combined PRE and RSV treatment significantly ameliorated SOD1G93A mice, it did not show a synergistic effect compared to RSV-only and PRE-084-only treated groups.<br/

Nuevas terapias en enfermedades neurodegenerativas de la motoneurona

La esclerosis lateral amiotrófica (ELA) es una enfermedad neurodegenerativa, en la que resultan afectadas tanto las motoneuronas superiores como las inferiores, acabando con la muerte del enfermo dentro de los 3-5 años después de la aparición de los primeros síntomas. Hasta el momento no existe ningún tratamiento curativo frente a ella. El 5-Fluorouracilo (5-FU), quimioterápico ampliamente utilizado en el tratamiento del cáncer, ha demostrado en estudios previos en el modelo murino de ELA SOD1G93A una mejora significativa de la supervivencia y los síntomas motores. El objetivo general del presente trabajo es mejorar la aplicación terapéutica del 5-FU para la Esclerosis Lateral Amiotrófica, investigando su mecanismo de acción e incrementando su eficacia en los modelos animales de SOD1G93A. Los resultados de los estudios realizados muestran que el 5-FU produce una depleción de las células de la serie blanca y disminuye el número de agregados de proteína SOD1 mal plegada. Además, se ha observado que una pauta de administración continuada del 5-FU no modifica la supervivencia ni los síntomas motores de los animales

Amyotrophic Lateral Sclerosis: A Focus on Disease Progression

Since amyotrophic lateral sclerosis (ALS) was discovered and described in 1869 as a neurodegenerative disease in which motor neuron death is induced, a wide range of biomarkers have been selected to identify therapeutic targets. ALS shares altered molecular pathways with other neurodegenerative diseases, such as Alzheimer’s, Huntington’s, and Parkinson’s diseases. However, the molecular targets that directly influence its aggressive nature remain unknown.What is the first link in the neurodegenerative chain of ALS that makes this disease so peculiar? In this review, we will discuss the progression of the disease from the viewpoint of the potential biomarkers described to date in human and animal model samples. Finally, we will consider potential therapeutic strategies for ALS treatment and future, innovative perspectives

Hemizygous Granzyme A Mice Expressing the hSOD1G93A Transgene Show Slightly Extended Lifespan

Granzyme A (gzmA), a serine protease involved in the modulation of the inflammatory immune response, is found at an elevated level in the serum from ALS patients. However, the influence of gzmA on the progression of ALS remains unclear. The aim of our work was to assess whether the absence of gzmA in an ALS murine model could help slow down the progression of the disease. Homozygous and hemizygous gzmA-deficient mice expressing the hSOD1G93A transgene were generated, and survival of these mice was monitored. Subsequently, gene and protein expression of inflammatory and oxidative stress markers was measured in the spinal cord and quadriceps of these mice. We observed the longest lifespan in gzmA+/− mice. GzmA gene and protein expression was downregulated in the spinal cord and serum from gmzA+/− mice, confirming that the increased survival of hemizygous mice is correlated with lower levels of gzmA. In addition, mRNA and protein levels of glutathione reductase (GSR), involved in oxidative stress, were found downregulated in the spinal cord and quadriceps of gmzA+/− mice, together with lower IL-1β and IL-6 mRNA levels in hemyzigous mice. In summary, our findings indicate for the first time that reduced levels, but not the absence, of gzmA could slightly ameliorate the disease progression in this animal model

Estudio de biomarcadores para diagnosticar y monitorizar la evolución de la sarcopenia

La sarcopenia es la pérdida gradual y generalizada de la masa y función de músculo esquelético con el envejecimiento. Es uno de los principales problemas de salud en personas mayores, dada su alta prevalencia y enormes implicaciones clínicas y socioeconómicas. El progresivo envejecimiento poblacional hace que la sarcopenia sea un problema de salud global cada vez mayor, más aún teniendo en cuenta su gran impacto económico en el consumo de atención médica debido a sus costes directos e indirectos.Actualmente se emplean técnicas como la Resonancia Magnética (RMN), la Tomografía Axial Computarizada (TAC), la Absorciometría Dual de Rayos X (DXA), el Análisis de Impedancia Bioeléctrica (BIA) y pruebas de función física, como la fuerza de agarre y la velocidad de la marcha para estimar la masa, fuerza y rendimiento muscular. Sin embargo, estas pruebas solo son operativos tras el inicio o la progresión de la enfermedad. Además, los aparatos necesarios y las personas formadas para usarlos suelen encontrarse en hospitales y grandes centros médicos, por lo que estos métodos no son prácticos para su uso en los centros de salud o residencias, donde se encuentran la mayoría de los pacientes sarcopénicos.Por ello, es necesario desarrollar nuevos métodos diagnósticos para la enfermedad que sean sensibles, específicos y de fácil realización y medición en centros de salud pequeños o residencias, que no necesiten personal ni infraestructuras muy especializadas y costosas. En este trabajo se exponen distintos biomarcadores moleculares que podrían conformar un panel múltiple y proporcionar un nuevo método diagnóstico para la identificación precoz de la sarcopenia en la práctica clínica habitual. Se espera que con este nuevo método diagnóstico, los profesionales tengan más posibilidades de prevenir, retrasar, tratar y, a veces, incluso revertir la sarcopenia a través de intervenciones tempranas y efectivas.<br /

Estudio comparativo de dos métodos de aislamiento de exosomas en plasma humano para la búsqueda de biomarcadores en sarcopenia

La sarcopenia, la pérdida gradual y generalizada de la masa y función muscular con el envejecimiento, es uno de los principales problemas de salud en personas mayores, dada su alta prevalencia y enormes implicaciones clínicas y socioeconómicas.El plasma sanguíneo es una fuente mínimamente invasiva para descubrir biomarcadores de proteínas para el diagnóstico, seguimiento y evaluación de respuestas terapéuticas en enfermedades. Centrar el análisis en los exosomas, un subtipo de vesículas extracelulares (VE) contenidas en el plasma, es una nueva posibilidad de diagnóstico, que permite el análisis de biomarcadores proteicos a pesar de la complejidad del plasma. Un tamaño y morfología similar dificultan la diferenciación entre los exosomas y el resto de subtipos de VE y proteínas plasmáticas. La búsqueda de un método adecuado que permita una buena separación de los subtipos de VE supone un importante paso para la utilización de los mismos como biomarcadores.El objetivo de este trabajo fue poner a punto un método de extracción de exosomas de plasma humano con la mayor pureza posible basado en la Cromatografía de Exclusión por Tamaño (SEC) para, en un futuro, estudiar su aplicación a la búsqueda de biomarcadores para la sarcopenia. Para ello, tras realizar dos métodos distintos, evaluamos las diferencias en la abundancia de proteínas y la contaminación de la muestra según la caracterización del proteoma por espectrometría de masas (MS) y su comparación con las bases de datos existentes.Los resultados muestran que la combinación de SEC con el uso de dos filtros podría mejorar significativamente la pureza y disminuir la contaminación en base al análisis del perfil proteómico de los exosomas derivados de plasma aislados por este método dada la disminución de contaminantes comunes, como las lipoproteínas y las cadenas de inmunoglobulinas.<br /