As epilepsias acometem entre 1-2% da população mundial. De um modo geral, de todas as epilepsias quase um terço deste total de pacientes apresenta a síndrome epiléptica conhecida como Epilepsia de Lobo Temporal (ELT), a qual se instala geralmente após um insulto inicial ou em decorrência de outras patologias como, por exemplo, trauma ou tumor, e parece ser decorrente de anormalidades intrínsecas do lobo temporal tais como, amígdala, hipocampo e córtex piriforme. Depois de um período de latência variado, promove o surgimento de crises convulsivas. Dentre os pacientes que apresentam ELT, cerca de 20 a 30% deles apresentam resistência ao tratamento farmacológico. Para melhor estudar os processos plásticos envolvidos no processo de epileptogênese ocorridos após a instalação do insulto inicial que levam ao aparecimento de crises recorrentes espontâneas, ratos Wistar foram eletricamente estimulados na amígdala para indução de Status Epilepticus (SE). Foram feitas histoquímicas e immunohistoquímica para marcar neurônios ativados (c-Fos+), novos neurônios (Doublecortin DCX+) e em degeneração (FluoroJade C - FJC+) após as crises. Após a indução do SE observamos que quanto mais graves as crises, maior o número de áreas ativadas (c-Fos+) e maior número de neurônios em degeneração (FJC+). Além disso, não houve associação direta entre as áreas cerebrais ativadas e grau de neurodegeneração, nem associação entre gravidade do SE e intensidade de neurogênese (DCX). A segunda fase deste projeto, executada na University of Cincinnati, refere-se ao estudo do impacto do SE, induzido por pilocarpina (PILO) sistêmica, sobre a neurogênese hipocampal. Utilizando a injeção de BrdU, para marcar o dia do nascimento de novos neurônios granulares, em camundongos Thy1-GFP foram submetidos ao SE por PILO. Foram analisadas a plasticidade dendrítica de neurônios granulares em fase de maturação (imaturas, 1 semana) e maduras (8 semanas). As células imaturas sofreram drásticas modificações na sua morfologia e na densidade dendrítica. Por outro lado, as células maturas não sofreram alterações morfológicas na árvore dendrítica, mas apresentaram uma intensa redução na densidade dos espinhos dendríticos, mostrando assim que as células imaturas estão mais suceptíveis ao impacto das crises epilépticas. / The epilepsies affect between 1-2% of the world. In general, all epilepsies almost a third of total patients had an epilepsy syndrome known as temporal lobe epilepsy (TLE), which usually settles after the initial insult or due to other pathologies such as, for example, trauma or tumor, and seems to be due to intrinsic abnormalities such as temporal lobe, amygdala, hippocampus and piriform cortex. After latency period varied, promotes the emergence of seizures. Among the patients with TLE, about 20 to 30% of them are resistant to pharmacological treatment. To better study the processes involved in plastic epileptogenesis occurred after the installation of the initial insult leading to the appearance of spontaneous recurrent seizures, rats were electrically stimulated in the amygdala to induce status epilepticus (SE). Histochemical and immunohistochemistry were done to mark neurons activated (c-Fos +), newborn neurons (Doublecortin - DCX+) and degenerating (FluoroJade C - FJC+) after the crisis. After SE induction observed that the more serious crises, the greater the number of activated areas (c-Fos+) and greater number of degenerating neurons (FJC+). In addition, there was no direct association between the brain areas activated and the degree of neurodegeneration, or association between the severity and intensity of the SE of neurogenesis (DCX+). The second phase of this project, performed at the University of Cincinnati, refers to study the impact of SE induced by pilocarpine (Pilo) system on hippocampal neurogenesis. Using the injection of BrdU, to label the daybirth of new granule neurons in Thy1-GFP mice subjected to SE. We analyzed the dendritic plasticity of granule neurons undergoing maturation (immature, 1 week) and mature (8 weeks). The immature cells have undergone drastic changes in their dendritic morphology and density. On the other hand, the mature cells did not undergo morphological changes in dendritic tree but showed a marked decrease in the density of dendritic spines, thus showing that immature cells are more susceptible to the impact of epileptic seizures.

Pas de résumé en français / Pas de résumé en anglais

Chronic neurodegenerative diseases, such as Alzheimer’s disease, prion diseases and many others are unified by the aberrant folding of a host encoded protein to a disease-associated isoform and the predictable cell-to-cell spread of disease-associated misfolded proteins via a putative prion-like mechanism. Prion diseases, for example, are associated with the aberrant folding of host encoded prion protein (PrPC) to a disease-associated isoform, which acts as a seed for the further conversion of PrPC to misfolded protein species. The role of misfolded prion protein in neurodegeneration remains unclear. Accumulation and spread of misfolded prion protein is typically slow and progressive, correlating with neurodegeneration. A number of studies show that mice are susceptible to prion disease with characteristic hallmarks of prion pathology but in the presence of little detectable misfolded prion protein (e.g. the GSS/101LL model). In this thesis I test the hypothesis that detectable species of misfolded prion protein correlate with neurodegeneration and spreads in a predictable, progressive fashion from one anatomically distinct brain region to the next. Using the GSS/101LL model, misfolded prion protein was detected as mostly PK-sensitive isoforms (PrPsen). The progression and pathological presentation is comparable to other prion diseases with larger quantities of PK resistant prion isoforms. A highly sensitive in vitro assay system (the QuIC assay) was subsequently used to establish the extent that misfolded protein was present within the brain. Amyloidogenic prion seeds were found to be widespread throughout the brain from an early stage and spread rapidly throughout the brain. Absence of neurodegeneration in certain brain regions is not due to differing quantities of prion seeds between regions or time exposed to prion seeds, as unaffected regions are exposed to comparative quantities of prion seeds for the same time-period as regions of the brain which eventually succumb to neurodegeneration. These results indicate a clear dissociation between prion seeds and neurotoxicity. They highlight the need to understand regional host responses to prion seeds that may evoke neurodegeneration in some but resilience in others. To test this, transcriptomic analysis was carried out on brain samples from regions undergoing neurodegeneration and unaffected regions. A gene profile signature of hybrid pro-and anti-inflammatory response was observed in regions undergoing neurodegeneration. However, large cohorts of genes were down-regulated across all regions tested, including pro-inflammatory genes and a large proportion of genes involved within transcriptional and translational regulation and function. These results highlight the possible molecular pathways in response to the presence of misfolded protein. In summary, misfolded prion protein accumulates rapidly across the CNS but only specific brain regions undergo neurodegeneration. In the presence of the misfolded protein, the host elicits a robust molecular response. The additional activation of glial cells within regions undergoing neurodegeneration highlights their importance in disease. It is therefore proposed that misfolded prion protein, alone, is not sufficient to trigger neurodegeneration. This gives rise to a “multi-hit” hypothesis whereby two or more factors, for example the accumulation of misfolded protein and glial cell response, are required to trigger neurodegeneration.

The primary tauopathies are a group of neurodegenerative diseases affecting movement and cognition. In this thesis I study Progressive Supranuclear Palsy (PSP) and the Corticobasal Syndrome (CBS), two parkinsonian disorders associated with accumulation of hyperphos- phorylated and abnormally folded tau protein. I contrast these two disorders with Parkinson’s disease (PD), which is associated with the accumulation of alpha-synuclein but has a genetic association with the MAPT gene encoding tau. Understanding the tauopathies to develop effective treatments will require a better grasp of the relationships between clinical syndromes and cognitive measures and how the anatomical and neurochemical networks that underlie clinical features might be altered by disease. I investigate simple clinical biomarkers, showing that a two-minute test of verbal fluency is a potential diagnostic biomarker to distinguish between PD and PSP and that the ACE-R and its subscores could play a role in monitoring cognition over time in PD, PSP and CBS. I assess the implementation of network analysis in Functional Mag- netic Resonance Imaging (fMRI) data, introduce Maybrain software for graphical network analysis and visualisation. I go on to show an overlap between graph theory network measures and I identify three main factors underlying graph network measures of: efficiency and distance, hub characteristics, network community measures. I apply these measures in PD, PSP and the CBS. All three diseases caused a loss of functional connectivity in com- parison to the control group that was concentrated in more highly connected brain regions and in longer distance connections. In ad- dition, widely localised cognitive function of verbal fluency co-varied with the connection strength in highly connected regions across PD, PSP and CBS. To take this further, I investigated specific functional covariance networks. All three disease groups showed reduced connectivity between the basal ganglia network and other networks, and between the anterior salience network and other networks. Localised areas of increased co- variance suggest a breakdown of network boundaries which correlated with motor severity in PSP and CBS, and duration of disease in CBS. I explore the link between gene expression of the tau gene MAPT and its effects on functional connectivity showing that the expression of MAPT correlated with connection strength in highly connected hub regions that were more susceptible to a loss of connection strength in PD and PSP. I conclude by discussing how tau protein aggregates and soluble tau oligomers may explain the changes in functional brain networks. The primary tauopathies are a group of neurodegenerative diseases affecting movement and cognition. In this thesis I study Progressive Supranuclear Palsy (PSP) and the Corticobasal Syndrome (CBS), two parkinsonian disorders associated with accumulation of hyperphos- phorylated and abnormally folded tau protein. I contrast these two disorders with Parkinson’s disease (PD), which is associated with the accumulation of alpha-synuclein but has a genetic association with the MAPT gene encoding tau. Understanding the tauopathies to develop effective treatments will require a better grasp of the relationships between clinical syndromes and cognitive measures and how the anatomical and neurochemical networks that underlie clinical features might be altered by disease. I investigate simple clinical biomarkers, showing that a two-minute test of verbal fluency is a potential diagnostic biomarker to distinguish between PD and PSP and that the ACE-R and its subscores could play a role in monitoring cognition over time in PD, PSP and CBS. I assess the implementation of network analysis in Functional Mag- netic Resonance Imaging (fMRI) data, introduce Maybrain software for graphical network analysis and visualisation. I go on to show an overlap between graph theory network measures and I identify three main factors underlying graph network measures of: efficiency and distance, hub characteristics, network community measures. I apply these measures in PD, PSP and the CBS. All three diseases caused a loss of functional connectivity in com- parison to the control group that was concentrated in more highly connected brain regions and in longer distance connections. In ad- dition, widely localised cognitive function of verbal fluency co-varied with the connection strength in highly connected regions across PD, PSP and CBS. To take this further, I investigated specific functional covariance networks. All three disease groups showed reduced connectivity between the basal ganglia network and other networks, and between the anterior salience network and other networks. Localised areas of increased co- variance suggest a breakdown of network boundaries which correlated with motor severity in PSP and CBS, and duration of disease in CBS. I explore the link between gene expression of the tau gene MAPT and its effects on functional connectivity showing that the expression of MAPT correlated with connection strength in highly connected hub regions that were more susceptible to a loss of connection strength in PD and PSP. I conclude by discussing how tau protein aggregates and soluble tau oligomers may explain the changes in functional brain networks.

Parkinson's disease (PD) is the most common neurodegenerative motor disorder, whose clinical features are rest tremor, bradykinesia, muscular rigidity and postural instability. Although most reported cases are sporadic, a handful of familial cases and their causative genes have been identified. Loss-of-function mutations in DJ-1, one of these genes, are responsible for 1% of familial PD cases. Our laboratory has previously reported that DJ-1- lacking neurons are sensitive to oxidative stress, induced by hydrogen peroxide or the neurotoxin MPTP. To investigate the possible mechanisms through which DJ-1 protects against oxidative stress, we performed a proteomic screen and identified Von Hippel Lindau (VHL) and Paraoxonase2 (PON2) as potential DJ-1 interacting partners. VHL is an E3 ubiquitin ligase which, in normal conditions, poly-ubiquitinates HIF-1 , a subunit of a master hypoxic/oxidative stress transcription factor, whose function is protective in oxidative and hypoxic stresses. In the present study, we provided further evidence of interaction of DJ-1 with VHL. We also demonstrated that HIF-1 protein level, as an indicator of VHL activity, is lower in cells lacking DJ-1, suggesting the inhibitory role of DJ-1 on VHL. Our in vitro studies also showed that DJ-1 inhibits ubiquitin ligase activity of VHL on HIF-1 by reducing the VHL-HIF-1 interaction. Importantly, accumulation of HIF-1 protects embryonic cortical neurons against MPP+ induced neuronal death. Finally, we confirmed the impairment of HIF-1 response to oxidative stress in human lymphoblastoids of DJ-1-linked PD cases. In the second part of this study, we demonstrated the interaction of DJ-1 and PON2. Interestingly, PON2 lactonase activity is reduced in DJ-1 deficient cells which could be rescued by re-introduction of DJ-1, suggesting a modulating role of DJ-1 on PON2 activity. In addition, PON2 deficiency, like DJ-1 deficiency, hypersensitizes neurons to MPP+, which could be rescued by over-expression of PON2 in both cases. Taken together, our data provide evidence that DJ-1 exerts its protective role by inhibiting VHL activity, enhancing HIF-1 stability, and increasing PON2 pro-survival function in PD models.

Au cours du processus neurodégénératif lié à la Sclérose Latérale Amyotrophique (SLA), les motoneurones innervant les muscles des membres sont très atteints tandis que ceux innervant les muscles axiaux sont relativement préservés. Les motoneurones diffèrent aussi dans leur réponse à plusieurs facteurs neurotrophiques (NTF). Je me suis intéressée aux mécanismes moléculaires déterminant la morphologie distincte et les réponses aux NTF de sous-populations de motoneurones pertinentes dans la SLA. J'ai démontré que les sous-populations de motoneurones murins innervant les muscles axiaux (MN-MMC) ou les muscles des membres (MN-LMC) ont de fortes différences morphologiques. Ces différences sont dues à une régulation différentielle de gènes codant pour la Péripherine et la Diacylglycérol kinase beta (DGK-β) qui sont régulés par les facteurs de transcription LIM-HD FoxP1/HB9. J'ai montré que les MN-LMC et les MN-MMC répondaient distinctement à trois facteurs neurotrophiques: le HGF (Hepatocyte Growth Factor), l'Artémine et le CNTF (Ciliary Neurotrophic Factor). J'ai étudié les motoneurones lombaires dans deux situations pathologiques: 1) les altérations de l'appareil de Golgi et du trafic axonal suite à la perte de TBCE (Tubulin Binding Cofactor E), 2) l'effet de l'augmentation de KCC2 à la membrane plasmique des motoneurones sur la transmission synaptique inhibitrice après lésion.Enfin, j'ai développé une nouvelle méthode de purification de motoneurones dérivés d'iPS (induced Pluripotent Stem Cell) humains en utilisant un vecteur rapporteur lentiviral Hb9::GFP et un anticorps dirigé contre le récepteur de faible affinité des neurotrophines, p75. / Muscles are highly vulnerable whereas motor neurons innervating axial muscles are relatively resistant. Motor neurons also seem to differ in their response to several neurotrophic factors (NTF). I investigated the molecular mechanisms determining the distinct morphology and the differential NTF response of ALS-relevant motor neuron subsets. First, I demonstrated that mouse lumbar motor neurons innervating either axial muscles (MMC-MN) or hindlimb muscles (LMC-MN) display remarkable morphological differences. These differences involve a differential regulation of genes coding for Peripherin and Diacylglycerol kinase-b (DGK-β) which are regulated by the transcription factors FoxP1/HB9. Second, I showed that LMC-MN and MMC-MN respond differentially to the three neurotrophic factors HGF (Hepatocyte Growth Factor), Artemin and CNTF (Ciliary NeuroTrophic Factor). Their differential survival is explained by the corresponding receptor gene expression in specific pools of MMC-MN and LMC-MN. Third, I studied lumbar motor neurons in two pathological conditions: 1) alteration of Golgi apparatus and axonal trafficking induced by loss of TBCE (Tubulin Binding Cofactor E) 2) the effect of KCC2 increase at motor neuron plasma membrane on inhibitory synaptic transmission after trauma.Finally, I developed a new FACS-based method for isolating human iPS (induced Pluripotent Stem Cell)-derived motor neurons with both an HB9::GFP reporter lentivirus and an antibody directed against the low-affinity neurotrophin receptor p75.

No description available.

>Magister Scientiae - MSc / Alzheimer’s Disease (AD) is a neurodegenerative disease which results from the irreversible loss of neurons in the brain. The disease is characterized by progressive cognitive impairment with recurrent short-term memory loss. AD is the leading cause of dementia and 4th leading cause of death in the elderly. Success in the treatment of AD has been limited, with drugs only treating it at a symptomatic level due to its pathology being complex and poorly understood. However, it is known that the cholinesterase and MAO-B enzymes play an important role in the disease through their association with production of amyloid plaques and oxidative stress respectively, two mechanisms associated with cell death and the symptoms seen in AD.

Magister Pharmaceuticae - MPharm / Neurodegenerative diseases (ND) are chronic and progressive in nature, and characterized by the gradual loss of neurons in various regions of the central nervous system (CNS). ND include Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS) and cerebral ischemia/reperfusion (CIR). They have various progressive neurodegenerative pathologies that can result in several severe functional impairments for patients, and ultimately lead to serious health-related issues. According to more recent data, AD accounts for the most common cause of dementia and is believed to contribute to approximately 60–70% of cases. AD is thus seen as the most common form of dementia.

Alzheimer's disease (AD) is the most prevalent form of age-associated dementia. Cholesterol dysregulation is linked with AD onset. Besides age, the most important risk factor associated with AD is the inheritance of the epsilon-4 allele of apolipoprotein E, a cholesterol transporter. In addition, while hypercholesterolemia has been shown to be an independent risk factor for AD, the nature of the cholesterol-AD link is still not clear. This gap in our understanding is partly due to a lack of knowledge about cholesterol metabolism in the central nervous system (CNS). The low-density lipoprotein receptor (LDLR) is the main receptor of apoE and a central regulator of serum cholesterol levels. Therefore, we sought to characterize the potential participation of LDLR in AD pathogenesis and/or progression. Previous reports with similar aims came to contradictory conclusions. Such studies assessed potential changes in AD in the absence of LDLR by utilizing the LDLR-/- mouse model and crossing it to AD mouse models. Initially we evaluated LDLR-/- mice as a suitable model to study AD. We found that LDLR-/- mice overexpressed a functional splice-variant of LDLR, LDLRDelta4. Moreover, its protein localized in similar regions as the LDLR did in control mice. Finally, we determined that LDLRDelta4 bound apoE, which underscores the impact of the isoform's function in the CNS. We then focused on characterizing changes to LDLR in AD models. We found that APP overexpression in cells increased LDLR mRNA and protein. APP overexpression and Abeta treatment shifted LDLR localization. An AD mouse model showed increased LDLR in hippocampus. Conversely, LDLR levels were decreased in APP-/- mice. Finally, we found that microtubules were affected in cells overexpressing APP. In conclusion, the data presented argue for the importance of LDLR-mediated regulation of cholesterol during AD progression. Also, LDLR may participate in the initial pathogenic insults leading to amyloid deposition, which make it a potential therapeutic target to treat AD. Finally, we propose that APP/Abeta overexpression disrupts microtubule formation; this alteration affects protein trafficking. One of the proteins affected is LDLR, the repercussions of which may ultimately result in cholesterol dysregulation.