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L'autofàgia és un mecanisme cel·lular endogen amb doble funció: pot intervenir en els processos de mort cel·lular i apoptosis però també actuar en la regeneració de la cèl·lula. Un equip de recerca conjunt de l'Institut de Neurociència de la UAB i de l'Hospital Clínic ha dut a terme un estudi sobre l'efecte de la inducció de l'autofàgia per manipulació genètica i farmacològica en la regeneració del nervi motor després de sofrir una lesió. Els resultats han permès descobrir una nova diana terapèutica en observar que es pot accelerar el procés regeneratiu de la cèl·lula, la qual cosa afavoreix la recuperació funcional. La autofagia es un mecanismo celular endógeno con doble función: puede intervenir en los procesos de muerte celular y apoptosis pero también actuar en la regeneración de la célula. Un equipo de investigación conjunto del Instituto de Neurociencias de la UAB y del Hospital Clínico ha llevado a cabo un estudio sobre el efecto de la inducción de la autofagia por manipulación genética y farmacológica en la regeneración del nervio motor tras sufrir una lesión. Los resultados han permitido descubrir una nueva diana terapéutica al observar que se puede acelerar el proceso regenerativo de la célula, lo que favorece la recuperación funcional.

Peripheral nerve injury (PNI) leads to the loss of motor, sensory, and autonomic functions, and often triggers neuropathic pain. During the last years, many efforts have focused on finding new therapies to increase axonal regeneration or to alleviate painful conditions. Still only a few of them have targeted both phenomena. Incipient or aberrant sensory axon regeneration is related to abnormal unpleasant sensations, such as hyperalgesia or allodynia. We recently have discovered NeuroHeal, a combination of two repurposed drugs, Acamprosate and Ribavirin. NeuroHeal is a neuroprotective agent that also enhances motor axon regeneration after PNI. In this work, we investigated its effect on sensory fiber regeneration and PNI-induced painful sensations in a rat model of spare nerve injury and nerve crush. The follow up of the animals showed that NeuroHeal treatment reduced the signs of neuropathic pain in both models. Besides, the treatment favored sensory axon regeneration, as observed in dorsal root ganglion explants. Mechanistically, the effects observed in vivo may improve the resolution of cell-protective autophagy. Additionally, NeuroHeal treatment modulated the P2X4-BDNF-KCC2 axis, which is an essential driver of neuropathic pain. These data open a new therapeutic avenue based on autophagic modulation to foster endogenous regenerative mechanisms and reduce the appearance of neuropathic pain in PNI.

Ajuts: This work was supported by grants from Fundació LaMarató-TV3 (110430/31/32) and TERCEL and CIBERNED funds from the Fondo de Investigación Sanitaria of Spain, by FEDER (COMPETE Programme) and Portugal National funds (FCT -Fundação para a Ciência e a Tecnologia --project PTDC/SAU-FAR/118787/2010 to DB and PEst-OE/SAU/UI4013/2011-14 to iMed.ULisboa). ARV is recipient of a Post-Doctoral fellowship (FCT -SFRH/BPD/76590/2011). Authors declare no conflict of interest. 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 TNF α /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.

Les malalties neurodegeneratives es desenvolupen gràcies a diferents mecanismes moleculars, que produeixen agregació de proteïnes mal plegades en diverses àrees cerebrals. D'una banda, l'α-sinucleïna es troba als cossos de Lewy presents a la malaltia de Parkinson i a les demències amb cossos de Lewy (DCL: DCL de tipus pur, DCLp; DCL de tipus comuna, DCLc) i a les inclusions citoplasmàtiques glials, que són la característica neuropatològica de l'atròfia multisistèmica (AMS). D'altra banda, les plaques senils formades principalment per β-amiloide i cabdells neurofibril·lars amb tau hiperfosforilada són la peculiaritat principal de la malaltia d'Alzheimer (MA). A més, la MA es caracteritza per un dèficit colinèrgic, el qual és encara més acusat a les DCL. En el present treball s'ha estudiat la genètica de la butirilcolinesterasa (BChE), un enzim de tipus glicoproteic que intervé en el metabolisme de l'acetilcolina, sobre les sinucleïnopaties en comparació amb la MA com a control de neurodegeneració, així com mostres control. L'estudi es va iniciar analitzant la freqüència de la variant K (A1699G, A539T) de BChE que està descrit com un possible factor de risc a patir la MA a les mostres post mortem (25 MA, 12 DCLp, 24 DCLc, 5 MP, 6 AMS i 25 controls). Es va observar una marcada acumulació de l'al·lel K de BChE en totes les demències en comparació amb els controls. A continuació es va caracteritzar el promotor de BChE mitjançant seqüenciació i s'hi van trobar quatre polimorfismes no descrits. Aquests es van genotipar a totes les mostres post mortem i els resultats van ser analitzats conjuntament per identificar possibles combinacions genotípiques específiques formades pels polimorfismes del promotor i la variant K de BChE. El resultat més rellevant va ser la detecció d'una combinació genotípica, AAAGCC8+K+, específica per al 17% de les mostres amb DCL. L'aplicació del genotipat de BChE com a eina per al diagnòstic diferencial augmentaria l'especificitat diagnòstica de les DCL, que tot i que l'any 2005 es van establir nous criteris per al seu diagnòstic clínic, es diagnostiquen erròniament entre el 40 i el 80 % dels casos. Per corroborar les dades obtingudes a partir de mostres post mortem, es va fer un estudi a partir de mostres de sang de 230 pacients amb MA, 21 amb AMS, 23 amb MP i 160 controls. Per completar l'anàlisi de BChE, es va analitzar l'expressió relativa de les quatre variants de splicing a nivell d'mRNA al còrtex frontal, còrtex temporal, nucli caudat i cerebel utilitzant PCR a temps real. El resultat va ser l'obtenció de patrons d'expressió determinats per a cada malaltia estudiada. Finalment, per immunohistoquímica es va concloure que BChE no es troba en els cossos de Lewy, ja que no colocalitza amb α-sinucleïna. Encara que per a la MA s'han descrit diferents marcadors genètics, fins al moment no se'n coneix cap per a les DCL. Mentre que els patrons d'expressió de mRNA característics de cada patologia trobats poden ajudar a elucidar els possibles mecanismes moleculars involucrats en el desenvolupament de les DCL, la determinació de les combinacions genotípiques específiques podran ajudar en el seu diagnòstic diferencial., Neurodegenerative diseases develop through different molecular mechanisms that produce aggregation of unfolded proteins in different brain areas. On one hand, α-synuclein is present in Lewy bodies that can be found in Parkinson's disease and in dementia with Lewy bodies (DLB: pure DLB, pDLB; common DLB, cDLB) and in glial cytoplasmic inclusions (GCI) that are the pathological hallmark of multiple system atrophy (MSA). On the other hand, senile plaques composed primarily of β-amyloid and neurofibrillary tangles with hyperphosphorilated tau are the main characteristic of Alzheimer's disease (AD). In addition, AD is characterized by a cholinergic deficit, which is even more pronounced in DLB. In this thesis we have studied Butyrylcholinesterase (BChE), a glycoproteic enzyme that mediates acetylcholine metabolism, in synucleinopathies compared with AD, as a control of neurodegeneration, as well as, with control samples.The study began by analysing the frequency of BChE K-variant (A1699G, A539T), that is described as a possible risk factor to suffer AD, in post mortem samples (25 AD, 12 pDLB , 24 cDLB, 5 PD, 6 MSA and 25 controls). There was a marked accumulation of BChE K allele in all dementias compared with controls.Then BChE promoter was characterized and four new polymorphisms were found. These were genotyped in all post mortem samples, results were analyzed together to identify specific genotypic combinations formed by polymorphisms of the promoter and BChE K-variant. The most relevant result was the detection of a genotypic combination, AAAGCC8+K+, specific for 17% of DLB samples. The application of BChE genotyping as a tool for differential diagnosis would increase the diagnostic specificity of DLB, that although in 2005 new criteria for its clinical diagnosis were established, between 40-80% cases are misdiagnosed. To corroborate the data obtained from post mortem samples, a study from blood samples of 230 AD patients, 21 with MSA, 23 with PD and 160 controls was done.To complete the analysis of BChE, we examined the relative expression of four splice variants in frontal cortex, temporal cortex, caudate nucleus and cerebellum using real time PCR. Specific expression patterns for each disease studied were obtained. Finally, immunohistochemistry concluded that BChE is not found in Lewy bodies, as it does not colocalize with α-synuclein.Although several AD genetic markers have been described, until this moment none is known for DLB. While the mRNA expression patterns characteristic of the disease may help to elucidate the possible molecular mechanisms involved in the development of DLB, the determination of the specific genotypic combination can help in their differential diagnosis.

En la presente tesis doctoral se ha establecido y caracterizado un modelo in vitro de lesión excitotóxica por glutamato basado en cultivos organotípicos de médula espinal de rata postnatal de 7-8 días. La optimización del medio de cultivo sin suero permite mantener los explantes más de 15 días in vitro con unas características en cuanto a la citoarquitectura y al número de motoneuronas similares a las obtenidas con medio con suero. Sobre los explantes se han establecido dos modelos de lesión; una mecánica y otra excitotóxica. Para establecer la lesión excitotóxica se han utilizado diferentes concentraciones de glutamato que provocan una respuesta dependiente de dosis. Esta respuesta se ha evaluado cuantificando la cantidad de homodímero-1 de etidio, un marcador fluorescente que es captado por las células dañadas, mediante el análisis de imágenes y cuantificando el número de motoneuronas supervivientes. Asimismo, se ha caracterizado que esta lesión está mediada principalmente por el receptor de glutamato NMDA. Las motoneuronas en desarrollo postnatal sufren un cambio en las subunidades NR2A y NR3B el cual se mimetiza en los explantes organotípicos en nuestras condiciones de cultivo. Una vez estandarizado el modelo de lesión excitotóxica se ha utilizado para evaluar el efecto neuroprotector de diversos fármacos como son la eritropoyetina, el riluzol, el rolipram, el valproato, la región c terminal de la toxina tetánica y la metilprednisolona (ver Trabajo I). Este modelo ha sido de utilidad asimismo para analizar los mecanismos moleculares de algunos de estos fármacos como el FK506 y el ligando PRE084 del receptor sigma 1. El análisis ha permitido establecer que el FK506 preserva el parénquima tisular frente a la lesión, efecto que es favorecido por la modulación de los niveles de la chaperona Hsp70 que el FK506 produce sobre la microglia (ver Trabajo II). Por último, se ha podido observar que el PRE084 ejerce un efecto neuroprotector e inductor de la elongación neurítica en las motoneuronas del explante, y que dichos efectos son mediados por la PKC aunque no por la activación de CREB (ver Trabajo III)., We have established and characterized an in vitro model of excitotoxic injury by glutamate based on organotypic cultures of spinal cord from postnatal rats of 7-8 days. The optimized culture medium without serum allows the culture of the explants over 15 days in vitro. The cultures maintain a cytoarchitecture and a motoneuron number similar to those observed with the serum-containing medium. On the explants we have established a mechanical injury model and an excytotoxic model. On the excytotoxic injury we have used different glutamate concentrations with a doses-dependent response that was evaluated by the image analysis of the EthD (Ethidium homodimer-1) uptake, and the quantification of the number of surviving motoneurons. We observed that this lesion is mainly mediated by the NMDA receptor. The spinal cord explants underwent a NR2A and NR3B subunit change similar to that observed on the rat postnatal development. The established in vitro injury model of excitotoxic lesion has been used to assess the neuroprotector effect of different drugs like erithropoyetin, riluzole, rolipram, valproate, the tetanus toxin c-terminus, and methilprednisolone (see section I). This model has been useful to analyze the molecular mechanisms of FK506 and the ligand of the sigma receptor 1, PRE084. We observed that FK506 protects the tissular parenchyma against the glutamate excitotoxic injury thanks to the modulation of Hsp70 levels induced by FK506 on the microglia (see section II). We observed that PRE084 has a neuroprotector effect and that it is an inductor of the neurite elongation on the explant motoneurons. The aforementioned effects are mediated by the PKC, although not by the activation of CREB (see section III).