Alzheimer's disease (AD) is developing into the single greatest healthcare challenge in the coming decades. The development of early and effective treatments that can prevent the pathological damage responsible for AD-related dementia is of utmost priority for healthcare authorities. The role of the APOE-ε4 genotype, which has been shown to increase an individual's risk of developing AD, is of central interest to this goal. Understanding the mechanism by which possession of this gene modulates brain function, leading to a predisposition towards AD is an active area of research. Functional connectivity (FC) is an excellent candidate for linking APOE-related differences in brain function to sites of AD pathology. Magnetoencephalography (MEG) is a neuroimaging tool that can provide a unique insight into the electrophysiology underpinning resting-state networks (RSNs) - whose dysfunction is postulated to lead to a predisposition to AD. This thesis presents a range of methods for measuring functional connectivity in MEG data. We first develop a set of novel adaptations for preprocessing MEG data and performing source reconstruction using a beamformer (chapter 3). We then develop a range of analyses for measuring FC through correlations in the slow envelope oscillations of band-limited source-space MEG data (chapter 4). We investigate the optimum time scales for detecting FC. We then develop methods for extracting single networks (using seed-based correlation) and multiple networks (using ICA). We proceed to develop a group-statistical framework for detecting spatial differences in RSNs and present a preliminary finding for APOE-genotype-dependent differences in RSNs (chapter 5). We also develop a statistical framework for quantifying task-locked temporal differences in functional networks during task-positive experiments (chapter 6). Finally, we demonstrate a data-driven parcellation and network analysis pipeline that includes a novel correction for signal leakage between parcels. We use this framework to show evidence of stationary cross-frequency FC (chapter 7).

Alzheimer's disease is the most common form (~60-80%) of dementia, currently affecting approximately half a million people in the UK and ~30 million people worldwide. The autosomal dominant form of AD represents a small proportion (~1-2%) of AD cases and is genetically well characterised. The vast majority of AD cases that show symptoms later in life (>65 years of age) are genetically complex. This type of AD, also known as late onset Alzheimer's disease (LOAD) disease, is still highly heritable with an estimated heritability of up to 76% (Gatz et al., 2006). Unfortunately, there is no cure for this devastating disease. Investigating genetic factors influencing the risk of LOAD is imperative for development of effective therapeutic treatments and more accurate diagnosis. A cross-platform comparison of four Genome-wide association studies (GWAS) was performed in an effort to identify novel genetic associations with LOAD (Chapter 3). A TRIM15 SNP rs929156 demonstrated significant evidence of association with LOAD with a p-value approaching genome-wide significance (p = 8.77 x 10-8) and an odds ratio that showed consistent effect on risk (OR = 1.1, p = 0.03). Within this chapter, a bio-informatic program to automate the process of GWAS meta-analysis taking into account linkage disequilibrium (LD) is also presented. Subsequently two fragments of the TRIM15 gene (including both 5’ and 3’ end flanking regions) were sequenced using the ABI SOLiDTM next generation sequencing technology. This was a pilot study using a DNA pooling strategy to determine whether this region harbours multiple rare variants which are associated with the disease (Chapter 4). Lastly, a candidate gene study combined with whole genome analysis was performed in an effort to search for genetic variants influencing human ageing using LOAD GWAS data (Chapter 5).

The aim of the research presented in this thesis was to improve the characterisation of the changes in brain structure and function that occur at different stages of Alzheimer’s disease (AD) progression, from pre-symptomatic AD, to mild cognitive impairment (MCI), to clinically evident dementia, using magnetic resonance imaging (MRI) techniques. Baseline structural MRI data from a cohort of healthy older adults who were followed prospectively for ten years, during which time some developed MCI and some AD, were analysed. It was found that structural MRI could detect volume loss in medial-temporal lobes up to 7-10 years before clinical symptoms of AD appear. In addition, volumetric variability of medial-temporal regions detected by structural MRI across cognitively healthy older adults correlated with their performance on a task of visuospatial associative memory, and functional activation of the same regions occurred during successful performance of the same task on functional MRI (fMRI). Three groups of participants - cognitively healthy controls, people with MCI, and patients with probable AD - were then recruited and underwent a multimodal MRI protocol, which included functional sequences acquired at rest and during the execution of two different cognitive tasks (visuospatial associative memory and self-appraisal). Cross-sectional comparisons showed: (i) that successful visuospatial associative memory performance was associated with increased functional activity (measured with task fMRI) in lateral prefrontal regions in AD patients relative to controls and (ii) that increased functional activity overlapped with frontal brain networks showing increased functional connectivity (measured with resting fMRI) in the same AD patients. Further, by demonstrating group- and condition-specific decreased frontal activity in AD patients relative to controls during a self-appraisal fMRI task, it was shown the specific utility of fMRI to unravel cognitive mechanisms underlying specific neuropsychological symptoms such as unawareness of cognitive impairment (anosognosia) in MCI and AD. In conclusion, structural MRI can detect morphological changes in the preclinical stage of AD, possibly earlier than previously described, and these reliably match cognitive functioning in older adults. In the MCI and AD stages, once symptoms of cognitive impairment are clinically evident and measurable, task-related and resting functional MRI can inform on residual brain function detectable over and above the known changes in brain morphology and cognitive performance that have already occurred at these stages, emerging as a sensitive marker of residual ability that could potentially be used to measure the effect of new treatments.

Alzheimer’s disease (AD) is a neurodegenerative disorder, characterised by severe memory loss and the accumulation of amyloid-beta (Aβ) and tau pathology within neocortex and medial temporal lobe (MTL) structures. Episodic memory impairment is a defining feature of early AD. The hippocampal formation (HF), a major network involved in both memory formation and retrieval is one of the first areas affected by AD pathology. However, the aetiology of AD is unknown; specifically how Aβ and tau pathologies cause memory impairment and how the physiological function of HF is affected. In this thesis, the 3xTgAD mouse was used as a high fidelity model of human AD pathological progression to study the function of HF during early (intracellular Aβ) and more progressive (extracellular plaque and hyperphosphorylated tau pathology) AD stages, referred to as ‘young’ and ‘old’ respectively. Specifically we: i) applied the hippocampal-dependent What-Where-Which (WWWhich) task to study the onset and progression of episodic-like memory decline (previously uncharacterised in the 3xTgAD mouse); ii) examined allocentric spatial memory in radial arm water maze (RAWM) and spontaneous alternation (SA) behaviour in T-Maze to discern whether cognitive differences exist between spontaneous and negatively reinforced tasks (the latter could be influenced by an exaggerated stress response); and iii) performed electrophysiological recordings in vivo from the HF of urethane-anaesthetised 3xTgAD and control mice to study basic synaptic connectivity, short-term synaptic plasticity and neuronal reverberation across the CA1-DG axis using a multi-site electrode. Our results showed an early and specific deficit for WWWhich episodic-like memory in the 3xTgAD model, with a decline in performance witnessed in mice as young as 3 months. In contrast, 3xTgAD component memory comprising single or dual associations of ‘What’, ‘Where’, ‘Which’ and ‘When’ remained intact suggesting the episodic impairment was due to dysfunction during the association of three component information streams within hippocampus (Chapters 3 and 4). 3xTgAD mice were equally impaired for allocentric spatial memory in RAWM and in their SA behaviour, suggesting no inherent advantage of examining cognition in paradigms which elicit behavioural distress (Chapter 5). We witnessed the development of subtle synaptic abnormalities in young 3xTgAD mice in the form of enhanced short-term paired pulse facilitation in CA1 and DG, however, a paucity of response facilitation in CA1 in response to train stimulation. In contrast, we saw intact basic synaptic function (fibre integrity and synaptic connectivity) in 3xTgAD mice of both young and old ages, suggesting gross hippocampal circuitry remained in place (Chapter 6). Finally, we saw an effect of normal ageing on cognition in the WWWhich and spatial tasks (Chapters 4 and 5), and a decline in neuronal reverberation with age in control and 3xTgAD mice. Dysfunction in these two parameters (behavioural and electrophysiological) coincided with the onset of intracellular Aβ accumulation within HF in 3xTgAD mice. This suggests a role of intracellular Aβ in impairing the physiological function of HF in AD which translates as cognitive decline in hippocampal-dependent forms of memory. Episodic memory was found to be especially sensitive to AD-related pathology and impairment, thus the WWWhich task may be applied to faithfully study the onset of cognitive decline in other AD mouse models. Further examination of the relative contribution of Aβ to hippocampal dysfunction in the 3xTgAD model is required.

Le Plan Alzheimer 2008-2012 a mis en lumière les représentations négatives de la maladie d’Alzheimer et leurs conséquences sur la mise en place de l’alliance thérapeutique. Les travaux récents montrent également l’impact de ces représentations chez des personnes exprimant une plainte mnésique subjective ou présentant des troubles cognitifs légers sans démence. L’objectif de ce projet était de mettre au point un questionnaire évaluant les perceptions des troubles mnésiques et d’analyser ces perceptions dans une population en cours de démarche diagnostique. Nous avons recruté des patients seuls ainsi que des dyades de patients et d’aidants. Nous cherchions à étudier l’influence des perceptions des troubles mnésiques sur l’humeur, les stratégies de coping et la qualité de vie. Les résultats mettent en lumière les facteurs d’entrée dans une démarche de soins ainsi que l’influence significative des perceptions des troubles mnésiques du patient sur ses stratégies de coping et sa qualité de vie. Nous avons également étudié l’influence des perceptions des troubles mnésiques dans une approche dyadique (patient et aidant). Ces analyses dyadiques montrent l’influence des perceptions du patient sur l’humeur et les stratégies de coping de l’aidant et l’influence des perceptions de l’aidant sur la qualité de vie psychique du patient. Ce travail de recherche souligne l’importance de mener des études longitudinales sur l’évolution des perceptions des troubles mnésiques avant et après l’annonce diagnostique afin de proposer des pistes de prise en charge adaptée aux patients et aux aidants. / The 2008-2012 Alzheimer French National Plan has highlighted the negative representations of Alzheimer's disease and their consequences on therapeutic alliance. Recent works also shows the impact of these representations in people with subjective memory complaint or with mild cognitive impairment.This research aims to develop a questionnaire evaluating the perceptions of memory disorders and to analyze these perceptions in a population engaged in a diagnosis process. We recruited a group of patients and a group of patient/caregiver dyads.We investigated the influence of subjective perceptions on mood, coping strategies and quality of life. Participants had to express a memory complaint and to start a diagnosis process at the Memory Center of Nancy. The results highlight the factors to beginning a diagnosis process and the significant influence of perceptions of memory disorders on coping strategies and quality of life. Actual level of cognitive disorders do not seem to be related to perceptions of memory disorders. We also studied the influence of perceptions of memory disorders in a dyadic approach (patient and caregiver). These dyadic analyzes show the influence of patient's perceptions on caregiver's mood and coping strategies and the influence of caregiver's perceptions on patient's quality of life. This research emphasizes the importance of conducting longitudinal studies on the evolution of perceptions of memory disorders before and after the diagnosis, in order to propose psychosocial interventions adapted to patients and caregivers

Η νόσος Αλτσχάιμερ καταλαμβάνει την πρωτοκαθεδρία στις μη αναστρέψιμες άνοιες με τους επιδημιολογικούς της δείκτες να αυξάνονται όσο μεγαλώνει το προσδόκιμο ζωής του ανθρώπου. Η χρήση φαρμάκων, με αρχική στόχευση άλλη πάθηση, στη νόσο Αλτσχάιμερ αποκαλείται φαρμακευτικός επαναπροσδιορισμός και προσφέρει σαφή πλεονεκτήματα στην ασφάλεια, την ταχύτητα και το κόστος ανάπτυξης μίας εν δυνάμει θεραπείας, ιδιαίτερα όταν η μέχρι σήμερα αντιμετώπιση της πάθησης περιορίζεται στην καθυστέρηση εξέλιξης της βλάβης και τις δευτερογενείς εκδηλώσεις. Στην παρούσα εργασία, εκμεταλλευτήκαμε εργαλεία φαρμακευτικής επαναστόχευσης που βασίζονται στις γονιδιακές υπογραφές πέντε μελετών μικροσυστοιχιών της νόσου Αλτσχάιμερ. Καίριο στάδιο στη συγκρότηση γονιδιακών υπογραφών είναι ο προσδιορισμός της διαφορικής έκφρασης των γονιδίων. Εφαρμόζοντας τρεις διαφορετικές τεχνικές (Limma, ChDir, mAP-KL) για το σκοπό αυτό και τοποθετώντας τα αποτέλεσματα σε τέσσερα ξεχωριστά εργαλεία φαρμακευτικής επαναστόχευσης (cMap, SPIEDw, sscMap, LINCS-L1000), αναδείξαμε φάρμακα που συστηματικά αντιστρατεύονται τη νόσο. Η περαιτέρω ανάλυση σε επίπεδο χημικής δομής, λειτουργικών μονοπατιών και δικτυακής θεώρησης προσδιόρισε το μηχανισμό δράσης των φαρμάκων και πρότεινε νέα βιοδραστικά μόρια ως δυνατικές θεραπευτικές επιλογές. / Alzheimer’s disease dominates dementias of irreversible cause with alarming epidemiologic characteristics due to rise of human life expectancy. The use of initially otherwise purposed drugs in Alzheimer is described as drug repositioning and offers clear advantages in terms of safety, speed and cost issues in the development of a potential therapy, particularly when current treatments are limitited to symptoms’ delay and secondary comorbidities. In this study, we exploited drug repurposing tools based on gene signatures from five microarray experiments of Alzheimer’s disease. A fundamental step in constructing gene signatures is to define differential gene expression. For this purpose, we used three different methods (Limma, ChDir, mAP-KL) which we analyzed with four distinct drug repurposing tools (cMap, SPIEDw, sscMap, LINCS-L1000) and found drugs that systematically reverse the disease signature. Further processing of the results with regard to chemical structure, pathway and network analysis revealed the mode of the drugs’ actions and highlighted them as potential therapeutic choices for Alzheimer’s disease.

L’originalité de cette recherche est de s’intéresser aux caractéristiques de l’environnement physique et à leur impact sur les capacités de navigation et de mémoire spatiale. Ce domaine jusqu’alors peu investigué, représente pourtant un enjeu sociétal pour l’autonomie et le bien-être de la personne. Des difficultés de navigation ont notamment été décrites dans le vieillissement normal et la maladie d’Alzheimer (MA) dès le stade débutant. Or, l’environnement physique peut soutenir les capacités/compétences spatiales des individus, ou au contraire les perturber. L’objectif de cette recherche est d’évaluer l’effet structurant des éléments d’un environnement réel riche en repères, le jardin thérapeutique « art, mémoire et vie » du CHRU de Nancy, sur l’apprentissage d’un trajet et l’acquisition des connaissances spatiales, chez une population de sujets atteints de MA. En effet l'organisation spatiale de ce jardin a été conçue pour contribuer entre autres, à atténuer les difficultés de ces personnes en termes de cognition spatiale.L’ensemble des éléments du jardin a été répertorié et intégré dans une classification inspirée des travaux de Lynch (1960) et Zeisel et Tyson (1999). Trente sujets à un stade léger à modéré de la MA et 30 sujets âgés sains appariés ont réalisé le protocole suivant : (1) un apprentissage de trajet (aller et retour), durant lequel leur description verbale du parcours était enregistrée ; (2) une série de tâches évaluant l’acquisition des connaissances spatiales ; (3) des tests cognitifs standards. Le discours a été retranscrit verbatim et soumis à une analyse de contenu. Les résultats montrent une capacité d’apprentissage de trajet résiduelle significative chez les sujets du groupe MA, tant à l’aller qu’au retour. La répétition du trajet et la richesse de l’environnement en termes de repère semblent avoir contribué à ce résultat. Les performances aux tâches expérimentales ont été croisées avec l’analyse du discours et avec les tests cognitifs standards. Les résultats mettent en évidence un rôle prépondérant de certaines caractéristiques des éléments de l’environnement, telles que la saillance et l’affordance, sur les performances d’apprentissage de trajet et de mémoire spatiale et ceci de manière encore plus marquée chez les sujets du groupe MA. L’effet structurant des éléments de l’environnement est discuté d'une part chez les sujets âgés sains au regard des processus cognitifs impliqués dans la navigation et l’acquisition des connaissances spatiales et d'autre part des processus préservés et dysfonctionnels au cours de la MA / The originality of this research is to focus on the characteristics of the physical environment and their impact on navigation and spatial memory capabilities. This field, until then little investigated, represents a societal stake for the autonomy and the well-being of the person. In particular, navigation difficulties have been described in normal aging and Alzheimer's disease (AD) in the early stage. However, the physical environment can support individuals' spatial abilities/skills, or, on the contrary, disrupt them.The aim of the present study is to assess the structuring effect of the elements of a real environment rich in landmarks, the “art, memory and life” healing garden of the CHRU of Nancy, on route learning, and on the acquisition of the spatial knowledge, in a population of subjects with AD. Indeed, the spatial organization of this garden has been designed to contribute, among other things, to alleviate the difficulties of these people in terms of spatial cognition.All the elements of the garden have been listed and integrated into a classification inspired by the works of Lynch (1960) and Zeisel and Tyson (1999). Thirty subjects with mild to moderate AD and 30 matched healthy subjects underwent the following protocol: (1) route learning (forward and return trips), during which the verbal description of the route was recorded; (2) a series of tasks assessing the acquisition of spatial knowledge of the garden as well as (3) standard cognitive tests. The speech was transcribed verbatim and subjected to a content analysis.The results show a significant residual route learning ability in the MA group, both on the forward and return trips. The repetition of the route and the richness of the environmental landmarks seem to have contributed to this result. Experimental task performances were cross-checked with discourse analysis and standard cognitive tests. The results highlight a preponderant role of certain characteristics of environmental elements, such as saliency and affordance, on the learning performances of route and spatial memory, and this even more markedly in the subjects of the MA group.The structuring effect of the elements of the environment is discussed on the one hand in healthy older subjects with regard to cognitive processes involved in the navigation and acquisition of spatial knowledge and on the other hand preserved and dysfunctional processes in the course of Alzheimer’s disease

La maladie d’Alzheimer (MA) se caractérise par une perte mnésique progressive et au plan neuropathologique par le dépôt extracellulaire de plaques amyloïdes, résultant de l’agrégation de peptides amyloïdes (Aβ), et par l’apparition d’une dégénérescence neurofibrillaire (DNF) constituée d’agrégats intraneuronaux de protéines Tau hyper et anormalement phosphorylées. L’évolution des déficits cognitifs des patients est particulièrement corrélée à la progression spatio-temporelle de la DNF. A l’heure actuelle, il n’existe aucun traitement curatif de la maladie. Le cholestérol joue un rôle central dans la physiopathologie de la MA. En particulier, l’allèle ε4 du gène de l’apolipoprotéine E, transporteur cérébral essentiel du cholestérol, est le principal facteur de risque génétique des formes sporadiques de la MA. De nombreuses études in vitro montrent qu’une surcharge en cholestérol induit la production d’Aβ pathogènes et qu’inversement, une déplétion en cholestérol entraîne une diminution de la voie amyloïde. Le cholestérol ne peut pas passer librement la barrière hémato-encéphalique (BHE). Le cholestérol cérébral est exclusivement synthétisé in situ. Le cholestérol cérébral en excès doit être exporté dans la circulation sanguine pour être métabolisé. Pour franchir la BHE, sa conversion en 24(S)-hydroxycholestérol est nécessaire, étape contrôlée par la cholestérol 24-hydroxylase (CYP46A1). Deux précédents travaux de thèse effectués dans le laboratoire ont permis de mettre en évidence des connexions étroites entre le métabolisme du cholestérol et la MA in vivo. La surexpression intracérébrale de CYP46A1 dans un modèle murin amyloïde à l’aide d’un vecteur viral adéno-associé (AAV) a conduit à la diminution de la production d’Aβ, des plaques amyloïdes et à l’amélioration des performances mnésiques des animaux. A l’inverse, l’inhibition de l’expression de CYP46A1 dans l’hippocampe de souris sauvages induit la production d’Aβ, la phosphorylation de Tau et des défauts mnésiques chez la souris. L’objectif de mon travail de doctorat a été de déterminer s’il existait un lien direct entre CYP46A1 et la pathologie Tau et si la modulation du métabolisme du cholestérol pourrait avoir un effet bénéfique sur la pathologie Tau associée à la MA. Pour répondre à ces questions, le modèle murin THY-Tau22, qui développe une pathologie Tau de type Alzheimer, a été utilisé. Cette pathologie, essentiellement hippocampique, est évolutive et associée à des déficits mnésiques. Dans l’hippocampe des souris THY-Tau22, le cholestérol libre total n’est pas modifié, alors que l’expression protéique de CYP46A1 est diminuée, et en conséquence le contenu en 24(S)-hydroxycholestérol. L’expression protéique de CYP46A1 dans l’hippocampe est également réduite dans un autre modèle murin de pathologie Tau, le modèle THY-Tau30. Ainsi, la pathologie Tau semble être à l’origine de la diminution de l’expression protéique de CYP46A1. Afin de déterminer si la surexpression de CYP46A1 chez la souris THY-Tau22 pouvait améliorer son phénotype biochimique, neuropathologique et clinique, un vecteur AAV codant pour CYP46A1 a été injecté dans l’hippocampe de souris THY-Tau22 âgées de trois mois et demi. Deux mois et demi après injection, la surexpression de CYP46A1 chez les souris THY-Tau22 induit une restauration de la concentration hippocampique en 24(S)-hydroxycholestérol et une augmentation de l’expression des gènes impliqués dans la synthèse du cholestérol, et plus particulièrement dans la voie du mévalonate. Deux mois et demi et cinq mois et demi post-injection, la surexpression de CYP46A1 entraîne une restauration complète des performances mnésiques des animaux qui s’accompagne d’un rétablissement de la dépression à long terme, de la longueur des dendrites secondaires, de la densité synaptique et de l’expression des gènes d’activité précoce dans l’hippocampe. (...) / Alzheimer’s disease (AD) is characterized by a progressive memory loss and neuropathologically by senile plaques and neurofibrillary tangles (NFTs). Senile plaques are constituted of extracellular amyloid peptide (Aβ) deposits while NFTs result from the accumulation and the aggregation of intracellular hyperphosphorylated Tau proteins. Spatiotemporal progression of NFTs particularly correlates with cognitive impairments. To date, there is no curative treatment for this disease. Cholesterol plays a central role in AD physiopathology. Indeed, the ε4 allele of the apolipoprotein E, the brain’s principal cholesterol-carrier protein, is the main genetic risk factor for sporadic forms of AD. Numerous in vitro studies have shown that cholesterol overload induces production of pathogenic Aβ and conversely, cholesterol depletion causes a reduction of the amyloidogenic pathway. In adult, brain cholesterol is exclusively synthesized in situ. Brain cholesterol is not able to freely cross the blood brain barrier and its major exportable form is 24(S)-hydroxycholesterol generated by the cholesterol 24-hydroxylase (CYP46A1). Two previous thesis works in this laboratory highlighted narrow connections between cholesterol metabolism and AD in vivo. The intracerebral overexpression of CYP46A1 mediated by an adeno-associated viral (AAV) vector, in a murine amyloid model, led to the decrease of Aβ production, senile plaques and improvement of memory abilities. At the opposite, hippocampal CYP46A1 inhibition in wild-type (WT) mice induced Aβ production, Tau phosphorylation and memory impairments. The aim of this thesis work was to determine whether there was a direct link between CYP46A1 and Tau pathology and whether cholesterol metabolism modulation could have a beneficial effect on AD-like Tau pathology. In order to answer these questions, the THY-Tau22 mouse model, that develops AD-like Tau pathology, was used. In this model, the pathology mainly occurs in the hippocampus, it is progressive, and associated with memory deficits. In THY-Tau22 mice, total free cholesterol in the hippocampus was unchanged, whereas both CYP46A1 protein expression and 24(S)-hydroxycholesterol content were decreased. Furthermore, we also demonstrated that CYP46A1 protein expression was reduced in another murine model of Tau pathology, the THY-Tau30 model. Therefore, it may suggest that Tau pathology can be responsible for CYP46A1 decrease. We next determined whether CYP46A1 overexpression in the THY-Tau22 mouse could improve its biochemical, clinical and neuropathologic phenotype. For this purpose, an AAV vector encoding CYP46A1 was injected in the hippocampus of 3.5-month-old WT and THY-Tau22 mice. Two and a half months after injection, hippocampal CYP46A1 overexpression in THY-Tau22 mice induced restoration of hippocampal 24(S)-hydroxycholesterol content and increased expression of genes involved in cholesterol synthesis, more particularly in the mevalonate pathway. Two and a half and five and a half months post-injection, CYP46A1 overexpression resulted in a complete restoration of memory abilities and was accompanied by restoration of long-term depression, length of secondary dendrites, synaptic density and expression of immediate-early genes in hippocampus. Despite this, abnormal Tau hyperphosphorylation and gliosis, that characterizes this model, remained unchanged after CYP46A1 overexpression. Altogether, these results suggest a direct connection between Tau pathology and CYP46A1 in vivo. In other words, Tau pathology could lead to memory deficits via CYP46A1 decrease. These data, together with the fact that CYP46A1 overexpression can modulate the amyloid pathology in mice, suggest that CYP46A1 may be a relevant therapeutic target for AD.

Les transporteurs vésiculaires du glutamate (VGLUTs) sont impliqués dans la recapture du glutamate du cytosol vers les vésicules présynaptiques. Depuis leurs caractérisations récentes en 2000, leurs implications dans plusieurs maladies neurodégénératives ont été démontrées. Ils jouent ainsi un rôle primordial dans la transmission nerveuse glutamatergique. Deux colorants naturels, le Rose Bengale et le Bleu Trypan, restent les meilleurs inhibiteurs connus à ce jour, avec respectivement des CI50 de 25 et 50 nM. Dans un premier temps, nous avons conçu et optimisé une série d’analogues basée sur le synthon Rose Bengale (inhibiteur non-compétitif). Ce travail a notamment permis de mettre en évidence l’effet des formes tautomères (quinone et lactone) sur l’inhibition des VGLUTs. Ainsi la forme quinonique, présente à pH physiologique, a été confirmée comme étant la seule capable de bloquer la recapture du glutamate. Dans un second temps, nous nous sommes intéressés à la famille du Bleu Trypan (inhibiteur compétitif) et nous avons déterminé la structure minimale active avec l’objectif de rendre ces molécules plus « drug-like ». En effet, l’intérêt de ce projet est de développer de petites structures aisément radiomarquables pour une utilisation dans un contexte physio-pathologique. / Vesicular glutamate transporters (VGLUTs) are involved in the recapture and storage of glutamate from cytol to secretory synaptic vesicules. Since their recent characterization in 2000, their implication in several neurodegenerative disorders have been demonstrated. They play a crucial role in glutamatergic neurotransmission. Natural dyes, such as Rose Bengal and Tryptan Blue are the best known inhibitors with IC50 values of 25 and 50 nM, respectively. Firstly, we designed and optimized a series of analogues based on the synthon Rose Bengal (non-competitive inhibitor). This work has especially enabled to highlight the effect of tautomeric forms (quinone and lactone) on the inhibition of VGLUTs. Thus, the quinone form, present at physiological pH, was confirmed as the only able to block the reuptake of glutamate. Secondly, we have been interested in the family of Trypan Blue (competitive inhibitor) and we determined the minimal active structure in order to render these molecules more "drug-like". Indeed, the interest of this project is to develop small structures easily radiomarquable to use in a physiopathological context.

Aucun traitement de la maladie d’Alzheimer (MA) n’existe, justifiant le développement de stratégies thérapeutiques. La toxicité des oligomères solubles du peptide amyloïde β (Aβ) est centrale dans les pertes synaptiques et cellulaires précoces dans la maladie. Dans le cadre de cette hypothèse, nous proposons qu’empêcher ces effets puisse prévenir le déclin cognitif dans la MA. Les facteurs neurotrophiques sont de bons candidats pour prévenir la mort cellulaire mais nécessitent une application ciblée et continue. Nous avons utilisé la technologie d’encapsulation cellulaire pour produire des bioréacteurs implantables contenant des cellules C2C12 sécrétant le facteur neurotrophique ciliaire (CNTF). Notre objectif était d’établir la preuve du concept que la production à long terme de CNTF in situ dans le cerveau puisse prévenir les déficits cognitifs liés à l’Aβ.Nos études prouvent que le CNTF produit par les bioréacteurs prévient la cytotoxicité et l’apoptose induites par le peptide Aβ in vitro. La neuroprotection dépend de l’activation de la PI3-Kinase et du facteur STAT3. In vivo, l’implantation des bioréacteurs dans le cerveau prévient les troubles cognitifs induits par l’injection icv d’Aβ ou retarde leur apparition chez la souris Tg2576. Dans nos deux modèles précliniques de la MA, la protection comportementale est associée au maintien des protéines synaptiques dans l’hippocampe. Aussi, la production in situ de CNTF est une approche thérapeutique préventive efficace contre la toxicité et les déficits cognitifs liés à l’Aβ. Ces résultats suggèrent également que l’implantation de cellules encapsulées est un bon procédé pour délivrer des molécules thérapeutiques au cerveau / No cure against Alzheimer’s Disease (AD) exists yet, justifying the development of therapeutic strategies. Toxicity of soluble amyloid β peptide is a key-player in early synaptic and cellular loss in AD. According to this hypothesis, we propose that preventing Aβ peptide effects could prevent cogninitive decline in AD. Neurotrophic factors are good candidates to prevent cell death but require a targeted and continuous delivery. We used the cell encapsulation technology to produce graftable bioreactors that contain C2C12 cells secreting the Ciliary Neurotrophic factor (CNTF). Our goal was to realize the proof-of-concept that CNTF long term in situ delivery could prevent Aβ-induced cognitive decline.Our studies prove that bioreactor-produced CNTF prevents Aβ-induced cytotoxicity and apoptosis in vitro. Neuroprotection relies on PI3K and STAT3 activation. In vivo, bioreactor implantation in brain prevents cognitive impairment induced by Aβ icv injection or delays their appearance in Tg2576 mice. In both of our preclinical model of AD, behavioral protection was associated with synapse maintenance in hippocampus.Therefore, in situ long term CNTF delivery is an efficient preventive therapeutic strategy against toxicity and Aβ-linked cognitive disturbances. These results also suggest that encapsulated cells graft is a good way to deliver therapeutic molecules to the brain