By 2040, the World Health Organization expects neurodegenerative diseases, such as Alzheimer’s disease, amyotrophic lateral sclerosis (ALS), and Parkinson’s disease, to surpass cancer as the second most common cause of death worldwide. Currently, only treatments for symptoms of these diseases are available. Thus, research is critical to alleviate this public health burden by elucidating the pathogenic processes and developing novel therapies. While exact mechanisms by which these heterogeneous neuropathological conditions become manifest in patients remain unclear, growing evidence suggests that oxidative stress (OS) makes a significant contribution to neuronal dysfunction and apoptosis in all major neurodegenerative diseases. Recently, the gene oxidation resistance 1 (Oxr1) has emerged as a critical regulator of neuronal survival in response to OS. Oxr1 is expressed throughout the central nervous system, and its highly conserved TLDc domain protects neurons from oxidative damage through an unknown mechanism. This thesis aimed to define mechanisms by which Oxr1 confers neuronal sensitivity to OS, and to determine its role in neurodegenerative diseases. I found that Oxr1 mediates cytoplasmic localization of ALS-associated proteins Fused in Sarcoma (FUS) and transactive response DNA binding protein 43 kDa (TDP-43) through a TLDc domain- and arginine methylation-dependent pathway. Next, I investigated in vivo neuroprotective functions of Oxr1, and demonstrated that neuronal Oxr1 over-expression extends survival and ameliorates behavioural dysfunction and pathology of an ALS mouse model. In particular, neuronal Oxr1 over-expression strikingly delays neuroinflammation during ALS pathogenesis. Finally, I characterised a mouse model that specifically deletes Oxr1 from motor neurons. While loss of Oxr1 in ChAT-positive motor neurons does not cause overt neurodegeneration in the spinal cord, constitutive loss of Oxr1 leads to neuroinflammation in the cerebellum and spinal cord. Taken together, these studies illuminate functions of Oxr1 in the complex antioxidant defence network and present implications for future therapeutic strategies.

Les Granule de Stress (GS) sont des inclusions cytoplasmiques contenant des protéines et des ARNm qui s’assemblent en réponse à l’exposition à un stress. Leur formation fait partie intégrante de la réponse cellulaire au stress et est considérée comme une étape déterminante pour la résistance au stress et la survie cellulaire. Actuellement, les GS sont reliés à divers pathologies allant des infections virales aux maladies neurovégétatives. L’une d’entre elle, la Sclérose Latérale Amyotrophique (SLA) est particulièrement agressive, caractérisée par une perte des neurones moteurs aboutissant à la paralysie et à la mort du patient en cinq ans en moyenne. Les mécanismes de déclenchement de la pathologie restent encore à déterminer. TDP-43 (TAR DNA binding protein 43) et FUS (Fused in liposarcoma) sont deux protéines reliées à la pathologie qui présentent des similarités de structure et de fonction, suggérant un mécanisme commun de toxicité. TDP-43 et FUS sont toutes les deux recrutées au niveau des GS en condition de stress. Nous avons démontré pour la première fois que la fonction des GS est de protéger les ARNm de la dégradation induite par l’exposition au stress. Cette fonction n’était que suspectée jusqu’alors. De plus nous avons mis en évidence que G3BP1 (Ras GTPase-activating protein-binding protein 1) est l’effectrice de cette fonction via son implication dans la dynamique de formation des GS. TDP-43 étant un régulateur de G3BP1, nous prouvons ainsi que la perte de fonction de TDP-43/G3BP1 aboutit à un défaut de réponse au stress aboutissant à une vulnérabilisation cellulaire. Le mécanisme de toxicité emprunter par FUS diffère de celui de TDP-43 et ne semble pas passer par une perte de fonction dans le cadre de la réponse au stress. / Stress Granule (SGs) are cytoplasmic inclusions sequestering proteins and mRNAs following a stress exposure. Their assembly is part of the cell stress response and is considered an important step for stress resistance and cell survival. SG are currently linked to different pathogenesis from viral infection to neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS).ALS is an aggressive disease, characterized by neuronal death leading to paralysis and death within five years. Pathogenesis mechanisms are still not fully understood. TDP-43 (TAR DNA binding protein 43) and FUS (Fused in liposarcoma) are two proteins linked to the disease that share many structural features and functions suggesting a common toxicity mechanism. TDP-43 and FUS are both recruited to SGs in stress conditions. We demonstrate for the first time that SGs function to protect mRNA from degradation induced after stress exposure, a function that was only suspected until now. We also prove that G3BP1 (Ras GTPase-activating protein-binding protein 1) is the effector of this function via it’s implication in the dynamics of SG formation. As TDP-43 is a regulator of G3BP1, we prove that loss of TDP-43/G3BP1 function leads to a stress response defect yielding increased cellular vulnerability. Furthermore, we have discovered that the mechanism of toxicity for FUS is different from TDP-43, and does not implicate a loss of function mechanism during the cell stress response.

Cerca de 20 % dos casos familiares de esclerose lateral amiotrófica (ELAf) são causados por mutações na enzima Cu,Zn-superóxido dismutase (SOD1). Inicialmente se supôs que as enzimas mutantes teriam a atividade SOD comprometida, entretanto isto não foi comprovado. Atualmente, considera-se que as enzimas mutantes adquiram propriedades tóxicas. Quais seriam estas propriedades e como levariam à degeneração do neurônio motor são questões ainda não respondidas. Neste trabalho, comparamos neuroblastomas humanos transfectados com SOD1 G93A associada à ELAf (SH-SY5YG93A), e SOD1 selvagem (SH-SY5YWT) com células parentais (SH-SY5Y) em relação ao crescimento, viabilidade, produção basal de oxidantes, atividades SOD e peroxidásica e modificações estruturais da SOD. As células transfectadas apresentaram aumento na taxa de crescimento e na produção basal de oxidantes. As células SH-SY5YWT e SH-SY5YG93A mantiveram a expressão de SOD1 e atividade consistente com o aumento esperado de duas vezes, em estágios iniciais de cultura. A atividade peroxidásica do homogenato da célula SH-SY5YG93A foi maior. Após quatro semanas, a linhagem SH-SY5YG93A manteve a expressão de SOD1, mas as atividades dismutásica e peroxidásica diminuíram. A expressão de SOD1 aumentou a proporção de formas alteradas de SOD1, como enzima reduzida, multímeros formados por ponte dissulfeto e formas insolúveis em detergente, particularmente na linhagem SH-SY5YG93A. Entre estas formas insolúveis, identificamos um dímero covalente de SOD. Estas formas alteradas provavelmente são responsáveis pela ativação do proteassomo e estresse do retículo endoplasmático, verificados nas células transfectadas. Concluindo, a superexpressão da SOD1 foi suficiente para elevar as formas imaturas e oligomerizadas de SOD1 e a oxidação basal, e a mutação G93A ressaltou estes processos. / Some familial ALS (fALS) are caused by mutations in the Cu,Zn-superoxide dismutase enzyme (SOD1). It was thought that the mutated enzymes would have impaired SOD activity, but this has not been corroborated so far. Presently, it is more accepted that the mutated enzymes acquire a new toxic function. What this new toxic function is and how it relates to the degeneration of motor neurons remains debatable. Here, we compared human neuroblastoma cells transfected with fALS mutant G93A (SH-SY5YG93A) or wild-type SOD1 (SH-SY5YWT) with parent cells (SH-SY5Y) in regard to growth, viability, basal oxidant production, SOD and peroxidase activities, and SOD forms. Transfected cells presented increased growth rate and basal oxidant production. SH-SY5YWT and SH-SY5YG93A cells in early culture stage showed SOD expression and activity consistent with the expected two-fold increase; SH-SY5YWT homogenates showed increased peroxidase activity. After four weeks, SH-SY5YG93A maintained SOD1 expression levels but peroxidase and dismutase activities were lower. SOD1 expression increased the levels of altered SOD1 forms such as the reduced enzyme, disulfide multimers and detergent-insoluble forms, particularly in SH-SY5YG93A cells. Among the insoluble forms a covalent SOD dimer was identified. These altered SOD forms are probably responsible for proteasome activation and endoplasmatic reticulum stress response verified in transfected cells. In conclusion, SOD1 over-expression was sufficient to increase intracellular immature and oligomerized SOD1 forms and basal oxidation and the G93A mutation enhanced these processes.

A Esclerose Lateral Amiotrófica (ELA) é a doença neurodegenerativa do neurônio motor que acomete indivíduos adultos e promove a perda progressiva das funções motoras. A evolução é rápida (2 a 5 anos) e culmina na morte por complicações e falência dos músculos respiratórios. Descrições recentes sugerem a contribuição de tipos celulares não neuronais, particularmente o astrócito e a microglia, para a morte do neurônio motor. O camundongo transgênico SOD1G93A, que carrega a SOD1 humana mutada, foi utilizado neste trabalho. Estudos comportamentais apontaram alterações motoras importantes no animal transgênico a partir de 90 dias de vida e permitiram selecionar, então, as idades pré-sintomáticas de 40 dias e 80 dias para os estudos moleculares. A análise da expressão gênica nos animais transgênicos e selvagens destas duas idades foi realizada por microarray utilizando-se a plataforma que contém o genoma completo do camundongo e detectou 492 e 1105 transcritos diferencialmente expressos nos animais de 40 e 80 dias, respectivamente. Estes resultados foram validados por PCR quantitativa (qPCR). As análises bioinformáticas dos resultados identificaram 17 e 11 vias moleculares super-representadas nas idades de 40 dias e 80 dias, respectivamente. Destas, as vias endocitose, sinapse glutamatérgica, proteólise mediada por ubiquitina, via de sinalização de quimiocina, fosforilação oxidativa, processamento e apresentação de antígeno e junção oclusiva foram comuns a ambas as idades. Ainda, as vias sinapse glutamatérgica e fagossomo foram sugeridas como potencialmente mais importantes em animais transgênicos de 40 dias e 80 dias, respectivamente. Transcritos específicos foram analisados em amostras enriquecidas de células (astrócito, microglia e neurônio motor) microdissecadas a laser do corno anterior da medula espinal dos animais. Os transcritos Cxcr4, Slc1a2 e Ube2i foram avaliados por qPCR nas amostras enriquecidas de astrócitos dos animais de 40 dias, enquanto que Cxcr4 e Slc17a6 foram avaliados nas amostras de neurônios motores dos animais desta idade. Cxcr4 apresentou expressão diminuída nos astrócitos transgênicos e aumentada nos neurônios destes animais. Slc1a2, Ube2i e Slc17a6 estavam aumentados nos tipos celulares estudados nos animais transgênicos. Tap2 e Tuba1a foram avaliados nas amostras enriquecidas de microglias dos animais de 80 dias e mostraram-se aumentados nas amostras dos transgênicos. Finalmente, Akt1 apresentou expressão diminuída nos neurônios motores microdissecados dos animais transgênicos em comparação aos selvagens. Os resultados sugerem que alterações na sinalização glutamatérgica podem exercer papel essencial em fases pré-sintomáticas mais precoces da doença (40 dias), enquanto que em fases pré-clínicas mais próximas ao aparecimento dos sintomas (80 dias), as respostas mais importantes parecem estar relacionadas à neuroimmunomodulação. Dessa forma, este trabalho aponta para novas perspectivas para o estudo da ELA / Amyotrophic Lateral Sclerosis (ALS) is an adult onset motor neuron neurodegenerative disease that leads to the progressive loss of muscular functions. It is a fast progression disorder (2 to 5 years) culminating in death by respiratory failure. Recent findings suggest that non neuronal cell types, especially astrocytes and microglia, might contribute to the neuronal death. The transgenic mouse SOD1G93A, carring human mutant SOD1, was used in this study. Behavioral studies pointed to the onset of the clinical symptoms occurring at 90 days in the animal model, thus, allowing the selection of the pre-symptomatic ages of 40 and 80 days to the molecular studies. Gene expression analysis of transgenic mice and their non-transgenic littermates at those ages was performed by using a microarray platform containing the whole mouse genome and has detected 492 and 1105 differentially expressed genes at 40 days and 80 days old mice, respectively. These results were validated by quantitative PCR (qPCR). Bioinformatic analysis of the results identified 17 and 11 over-represented molecular pathways at 40 days and 80 days, respectively. Of these, endocytosis, glutamatergic synapse, ubiquitin-mediated proteolysis, chemokine signaling pathway, oxidative phosphorylation, antigen processing and presentation and also tight junction were common to both ages. Furthermore, glutamatergic synapse and fagosome were suggested as potentially more important at 40 and 80 days, respectively. Specific transcripts were analyzed on enriched samples of cells (astrocytes, microglia and motor neuron) obtained by laser microdissection from the ventral horn of mouse spinal cord. The transcripts Cxcr4, Slc1a2 and Ube2i were evaluated by qPCR in enriched samples of astrocytes of the 40 days old mice, and Cxcr4 and Slc17a6 were analyzed in motor neuron samples at this age. Cxcr4 has been found decreased in astrocytes from transgenic mice and increased in the motor neurons of these animals. Slc1a2, Ube2i and Slc17a6 have increased in the cell type in which they were evaluated in the transgenic mice. Tap2 and Tuba1a were evaluated at microglia enriched samples of 80 days old mice and were found to be increased. Finally, Akt1 has decreased in enriched samples of motor neurons from 80 days old mice. The results suggest that glutamatergic signaling might play essential role in early stages of the disease (40 days), while in phases closer to the appearance of the symptoms (80 days), the neuroimmunomodulation takes place. Thus, this study points to new perspectives for ALS study

Doenças do neurônio motor (DNM) representam um grupo de doenças que cursam com fraqueza muscular progressiva e inexorável, e o manejo clínico é baseado no controle dos sintomas. Estes doentes sofrem de acometimentos motores e não motores intensos e de evolução progressiva. Entretanto, além dos sintomas motores, de humor e de déficits cognitivos, uma caracterização mais profunda de sintomas não- motores nesses doentes raramente foi relatada. Este estudo transversal objetivou descrever os sintomas não motores na DMN e seu impacto na qualidade de vida e no estado funcional, com foco na dor e alterações sensoriais. Oitenta doentes (31 mulheres, 55,7 ± 12,9 anos) com DNM foram submetidos a exame clínico extenso, avaliação de dor (questionário de dor McGill, Inventário breve de dor, questionário douleur neuropathique-4), avaliação psicofísica [teste quantitativo da sensibilidade (TQS) e modulação condicionada da dor (MCD)], avaliações de humor e catastrofismo, e foram comparados com controles saudáveis (CS) pareados por sexo e idade. Dor crônica (presente a maior parte dos dias por mais de três meses) foi presente em 46% dos doentes (escala numérica da dor = 5,18 ± 2,0). A dor de origem musculo- esquelética ocorreu em 40,5% e foi localizada principalmente na região da cabeça/pescoço (51%) e da região lombar (35%). A dor neuropática não presente nesta amostra. Comparado aos CS, os doentes com DNM apresentaram menor limiar de detecção de frio (p < 0,002) e valores de MCD significativamente menores (4,9 ± 0,2% vs. 22,1 ± 0,2%, p = 0,012). Os resultados do TQS/MCD não diferiram entre os doentes com DNM com e sem dor. A intensidade da dor foi correlacionada estatisticamente com ansiedade, depressão e catastrofismo, e os escores de espasticidade foram correlacionados inversamente com a MCD (rho = -0,30, p = 0,026). A dor é um sintoma frequentemente relatado por doentes com DNM. Alterações somatossensoriais e de MCD existem em DNM e podem estar relacionadas com a natureza neurodegenerativa da doença. Estudos adicionais devem investigar formas de melhor quantificar estas alterações e explorar estratégias de tratamento mais apropriadas para o seu controle / Motor neuron disorders (MNDs) represent a group of diseases that curse with inexorable muscle weakness and medical management is based on symptom control. These patients suffer from intense motor and non-motor progressive symptoms. However, apart from motor symptoms, mood and cognitive impairments, deeper characterization of non-motor symptoms in these patients have been rarely reported. This cross-sectional study aimed to describe non-motor symptoms in MND and their impact on quality of life and functional status, with a focus on clinical pain and sensory changes. Eighty patients (31 females, 55.7±12.9 years old) with MND underwent a extensive clinical examination, pain (McGill pain questionnaire, brief pain inventory, douleur neuropathique-4), psychophysics [quantitative sensory testing (QST) and conditioned pain modulation (CPM)], mood and catastrophizing assessments, and were compared to sex- and age-matched healthy controls (HC). Chronic pain (present on most days for more than three months) was present in 46% of patients (numerical visual scale=5.18±2.0). Pain of musculoskeletal origin occurred in 40.5% and was mainly located in the head/neck (51%) and lower back (35%). Neuropathic pain was not present in this sample. Compared to HC, MND patients had a lower cold detection threshold (p < 0.002), and significantly lower CPM scores (4.9±0.2% vs. 22.1±0.2%, p=0.012). QST/CPM results did not differ between MND patients with and without pain. Pain intensity was statistically correlated with anxiety, depression, and catastrophism, and spasticity scores were inversely correlated with CPM (rho=-0.30, p=0.026). Pain is frequently reported by patients with MNDs. Somatosensory and CPM changes exist in MNDs and may be related to the neurodegenerative nature of the disease. Further studies should investigate ways to better quantify these changes and explore the treatment strategies most appropriated for their control

No description available.

Doenças do neurônio motor (DNM) representam um grupo de doenças que cursam com fraqueza muscular progressiva e inexorável, e o manejo clínico é baseado no controle dos sintomas. Estes doentes sofrem de acometimentos motores e não motores intensos e de evolução progressiva. Entretanto, além dos sintomas motores, de humor e de déficits cognitivos, uma caracterização mais profunda de sintomas não- motores nesses doentes raramente foi relatada. Este estudo transversal objetivou descrever os sintomas não motores na DMN e seu impacto na qualidade de vida e no estado funcional, com foco na dor e alterações sensoriais. Oitenta doentes (31 mulheres, 55,7 ± 12,9 anos) com DNM foram submetidos a exame clínico extenso, avaliação de dor (questionário de dor McGill, Inventário breve de dor, questionário douleur neuropathique-4), avaliação psicofísica [teste quantitativo da sensibilidade (TQS) e modulação condicionada da dor (MCD)], avaliações de humor e catastrofismo, e foram comparados com controles saudáveis (CS) pareados por sexo e idade. Dor crônica (presente a maior parte dos dias por mais de três meses) foi presente em 46% dos doentes (escala numérica da dor = 5,18 ± 2,0). A dor de origem musculo- esquelética ocorreu em 40,5% e foi localizada principalmente na região da cabeça/pescoço (51%) e da região lombar (35%). A dor neuropática não presente nesta amostra. Comparado aos CS, os doentes com DNM apresentaram menor limiar de detecção de frio (p < 0,002) e valores de MCD significativamente menores (4,9 ± 0,2% vs. 22,1 ± 0,2%, p = 0,012). Os resultados do TQS/MCD não diferiram entre os doentes com DNM com e sem dor. A intensidade da dor foi correlacionada estatisticamente com ansiedade, depressão e catastrofismo, e os escores de espasticidade foram correlacionados inversamente com a MCD (rho = -0,30, p = 0,026). A dor é um sintoma frequentemente relatado por doentes com DNM. Alterações somatossensoriais e de MCD existem em DNM e podem estar relacionadas com a natureza neurodegenerativa da doença. Estudos adicionais devem investigar formas de melhor quantificar estas alterações e explorar estratégias de tratamento mais apropriadas para o seu controle / Motor neuron disorders (MNDs) represent a group of diseases that curse with inexorable muscle weakness and medical management is based on symptom control. These patients suffer from intense motor and non-motor progressive symptoms. However, apart from motor symptoms, mood and cognitive impairments, deeper characterization of non-motor symptoms in these patients have been rarely reported. This cross-sectional study aimed to describe non-motor symptoms in MND and their impact on quality of life and functional status, with a focus on clinical pain and sensory changes. Eighty patients (31 females, 55.7±12.9 years old) with MND underwent a extensive clinical examination, pain (McGill pain questionnaire, brief pain inventory, douleur neuropathique-4), psychophysics [quantitative sensory testing (QST) and conditioned pain modulation (CPM)], mood and catastrophizing assessments, and were compared to sex- and age-matched healthy controls (HC). Chronic pain (present on most days for more than three months) was present in 46% of patients (numerical visual scale=5.18±2.0). Pain of musculoskeletal origin occurred in 40.5% and was mainly located in the head/neck (51%) and lower back (35%). Neuropathic pain was not present in this sample. Compared to HC, MND patients had a lower cold detection threshold (p < 0.002), and significantly lower CPM scores (4.9±0.2% vs. 22.1±0.2%, p=0.012). QST/CPM results did not differ between MND patients with and without pain. Pain intensity was statistically correlated with anxiety, depression, and catastrophism, and spasticity scores were inversely correlated with CPM (rho=-0.30, p=0.026). Pain is frequently reported by patients with MNDs. Somatosensory and CPM changes exist in MNDs and may be related to the neurodegenerative nature of the disease. Further studies should investigate ways to better quantify these changes and explore the treatment strategies most appropriated for their control

A esclerose lateral amiotrófica (ELA) é uma doença neurodegenerativa que afeta os neurônios motores levando a atrofia muscular e morte por insuficiência respiratória. Esta patologia se manifesta de forma esporádica ou familiar, que são indistinguíveis clinicamente. Mutações na enzima antioxidante superóxido dismutase 1 (hSod1) respondem por aproximadamente 20% dos casos familiares de ELA. Além disso, o caráter autossômico dominante destas mutações revela que a hSod1 adquire propriedades tóxicas aos neurônios motores. Atualmente, duas hipóteses não mutuamente excludentes existem para explicar o caráter tóxico das mutantes da hSod1 relacionadas à ELA. A primeira refere-se à produção de oxidantes pela atividade peroxidásica exacerbada das mutantes contribuindo para o estresse oxidativo observado em ELA. A segunda refere-se à agregação de proteínas como ocorre em outras doenças neurodegenerativas. Digno de nota, o radical carbonato produzido na atividade peroxidásica da hSod1 causa a formação de um dímero covalente da proteína análogo a uma espécie de hSod1 frequentemente detectada em modelos experimentais e pacientes da doença e associada à propriedade tóxica das mutantes. Desta forma, o presente trabalho buscou esclarecer o mecanismo de produção do radical carbonato pela hSod1, bem como caracterizar o dímero covalente da proteína para posterior estudo de sua formação em um modelo de ELA em ratos que superexpressam a mutante G93A da hSod1. Os estudos cinéticos da variação do pH sobre os efeitos de bicarbonato/CO2, nitrito e formato na atividade peroxidásica da hSod1, medidos pelo consumo de peróxido de hidrogênio e produção de radical, permitiram excluir o mecanismo de Fenton para explicar o ciclo peroxidativo da enzima em tampão bicarbonato em favor de outros intermediários reativos. Já, os experimentos de 13C RMN, modelagem molecular e cinética de fluxo interrompido com mistura assimétrica demonstraram que o ânion peroxomonocarbonato constitui o precursor do radical carbonato produzido pela hSod1. A caracterização do dímero covalente da hSod1 por proteólise com tripsina seguida de análise por HPLC/UV-vis e HPLC/ESI-MS identificou um peptídeo característico do dímero covalente da hSod1. A digestão enzimática em H2 18O demonstrou de forma inequívoca a natureza dímerica deste peptídeo pela marcação da extremidade C-terminal. Ainda, o sequenciamento do peptídeo dimérico por MS/MS revelou a estrutura primária ESNGPVKVW(ESNGPVKVWGSIK)GSIK, na qual as cadeias polipeptídicas estão ligadas através de um aduto de ditriptofano composto por resíduos Trp32 da proteína. Por fim, este peptídeo dimérico pode ser empregado como marcador bioquímico específico para o estudo do dímero covalente da hSod1 in vivo. A análise do extrato de proteínas das medulas dos ratos modelo de ELA identificou quinze candidatos a dímero covalente da hSod1 por Western-blot, sendo que dois deles foram excluídos por espectrometria de massa, pois tiveram o resíduo Trp32 identificado. O peptídeo ESNGPVKVW(ESNGPVKVWGSIK)GSIK não foi observado, porém as treze espécies restantes permanecem candidatas e deverão ser reexaminadas em trabalhos que darão sequência a esta tese de doutorado. Em suma, o peroxomonocarbonato constitui o intermediário na produção do radical carbonato pela hSod1 e o peptídeo ESNGPVKVW(ESNGPVKVWGSIK)GSIK uma ferramenta importante no estudo da agregação covalente da hSod1 em ELA. / Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of motors neurons that causes muscle atrophy, weakness, and death by respiratory failure. This pathology occurs in both sporadic and familiar forms that are clinically indistinguishable. Mutations in the antioxidant enzyme superoxide dismutase 1 (hSod1) respond to about 20% of the familiar cases of ALS. Besides, the autosomal dominant nature of these hSod1-associated ALS suggests that the mutants gain toxic properties to motor neurons. Currently, two hypotheses exist to explain the toxicity of hSod1 mutants but they do not exclude each other. The first one is related to the production of oxidants by the increased peroxidase activity of the ALS-linked mutants that could contribute to the oxidative stress reported in ALS. The second refers to protein aggregation as proposed in other neurodegenerative diseases. Noteworthy, the carbonate radical produced during hSod1 peroxidase activity leads to the formation of a covalent dimer of the protein similar to a hSod1 species often detected in experimental models and patients of the disease and implicated in the toxic properties of hSod1 mutants. Thus, the present work aimed to determine the mechanism of carbonate radical production by hSod1 and to characterize the covalent dimer of the protein in vitro followed by the study of covalent aggregates of hSod1 in a rat model of ALS that overexpresses the G93A mutant of the protein. The kinetic studies of the effect of bicarbonate/CO2, nitrite and formate in the peroxidase activity of hSod1 at various pH, measured by hydrogen peroxide consumption and radical production, permitted to exclude the Fenton mechanism to explain the enzyme peroxidative cycle in bicarbonate buffer in favor of other reactive intermediates. Furthermore, 13C NMR, molecular docking and stopped-flow experiments with asymmetric mixing demonstrated that the anion peroxomonocarbonate is the precursor of the carbonate radical produced by hSod1. The characterization of hSod1 covalent dimer by proteolysis with trypsin followed by HPLC/UV-vis and HPLC/ESI-MS analysis identified a peptide characteristic of the covalent dimer of the protein. The enzymatic digestion in H2 18 O irrefutably demonstrated the dimeric nature of this peptide because of the C-terminal labeling with oxygen-18 isotopes. In addition, sequencing of the dimeric peptide by MS/MS determined the primary structure ESNGPVKVW(ESNGPVKVWGSIK)GSIK, in which the polipeptide chains are crosslinked through a ditryptophan adduct formed by a covalent bond between the Trp32 residues of each subunit. So, this dimeric peptide can be employed as a biochemical marker for studying the hSod1 covalent dimer in vivo. The analysis of protein extracts from the spinal cord of the rat model of ALS by Western-blot identified fifteen candidates to hSod1 covalent dimer, but two of them were excluded by mass spectrometry analysis that identified unmodified Trp32 residues. Moreover, neither the dimeric peptide nor the Trp32 residue were observed in the remaining species. Therefore, these thirteen candidates must be reexamined in subsequent studies. In conclusion, the anion peroxomonocarbonate is the key intermediate in the production of the carbonate radical by hSod1 and the dimeric peptide constitutes a specific tool to study hSod1 covalent aggregation in ALS

No description available.

<p>Amyotrophic lateral sclerosis is a fatal, progressive neurodegenerative disease with unknown ethiology. The aim of this study was to increase understanding of the pathophysiological mechanisms of dying motor neurons and wasting muscle tissue in this particular disorder.</p><p>Quantitative receptor autoradiographic methodology was applied on cervical spinal cord sections from patients with ALS to evaluate the specific binding of the acetylcholine transporter ³H-vesamicol in motor neurons. Despite a significant reduction of the number of ventral motor neurons in ALS, the ³H-vesamicol binding was not reduced in ALS compared to control cases, which suggests an increased metabolic activity in remaining motor neurons.</p><p>Motor neurons dying in ALS might go through apoptosis (programmed cell death), so immunohistochemical and TUNEL techniques were applied on thoracic spinal cord from ALS patients to evaluate the possibility of an apoptotic process. The increased Bax expression indicates an apoptotic process and further, motor neurons were TUNEL-positive, indicating DNA degradation caused by programmed cell death.</p><p>Muscle biopsies were obtained from ALS patients, and mRNA levels for the neurotrophic factors GDNF and BDNF were measured and compared to control subjects. GDNF levels were increased in muscle tissue in ALS whereas BDNF levels were unaltered.</p><p>Levels of GDNF and BDNF were also measured in cerebrospinal fluid from ALS patients and controls using ELISA methodology. Levels of BDNF were unaltered in ALS cornpared to controls. GDNF however was not detectable in controls whereas 12 out of 15 ALS patients had measurab1e levels of GDNW. A marked upregulation of endogenous GDNF and GDNF mRNA in ALS CSF and muscle respectively is of special interest in relation to clinical trials where GDNF is administered to this group of patients.</p>