α-synuclein is a small presynaptic protein whose misfolding and aggregation are considered drivers of the neurological disorders Parkinson’s disease, multiple system atrophy, dementia with Lewy bodies and related synucleopathies. α-synuclein exists in a dynamic state that changes from an α-helical conformation when bound to liposomes to natively unfolded in solution, the majority being in the latter state. The disease process by which native healthy α-synuclein undergoes a change in conformation to form β-sheet oligomers and fibrils is still unresolved. The fibrillation process has been widely studied by several different techniques and the structure of the fibrils has been determined by NMR, scanning transmission electron microscopy and X-ray diffraction. The early stages of aggregation into β-sheet rich oligomers, despite having been widely studied, has proven difficult to follow due to the heterogeneity of the species formed and the unpredictability of the process. The goal of the work reported here was to design and develop a novel, reproducible and quantitative assay to study the early stages of α-synuclein aggregation and to establish a platform for discovery of novel compounds that inhibit this process. These compounds could then be taken as a starting point for the development of new drugs for the treatment of synucleopathies. The assay developed herein has been designed, established and demonstrated to be suitable for the screening of α-synuclein aggregation inhibitors. The assay quantitatively measures aggregation using α- synuclein site-specifically labelled with green and red fluorescent dyes. Proteins labelled with the green dye are bound to microbeads. α-synuclein labelled with the red dye aggregates on the bead-linked green α-synuclein. The first part of the thesis describes the development of the tools required for the assay. α-synuclein single cysteine mutants were produced to introduce a specific attachment point to the protein. Single isomer carboxytetramethylrhodamine was synthesised in large scale for the label. Two different trifunctional tags that allow both the fluorescent labelling of the protein and the addition of a group for bead attachment in a single step were synthesised. Optimisation of the attachment of the functionalised proteins to beads of differing materials was accomplished enabling further development of the bead-based aggregation assay. With all tools established, the second part of the work comprised the development of the bead-based α-synuclein aggregation assay. Solid supports made of two different materials, TentaGel and Agarose, with two different types of bead surface attachment chemistry for α-synuclein were investigated, Ni-NTA on bead with His6-tag on the target or dibenzylcyclooctyne on bead and azide conjugation for the target. Only the combination of Ni-NTA agarose beads linking to His6-tag functionalised α-synuclein was found to be suitable for quantitative measurement of the aggregation process. Using 20 % EtOH, α-synuclein on-bead aggregation was reproducible within a 5 h time-frame with a linear dependence of aggregation rate as function of protein concentration on-bead. The third part of the thesis describes the research into novel starting points for the discovery of inhibitors of α-synuclein aggregation. In the peptides field, the most active peptides in the literature were selected and synthesised for study under the same conditions to find the most active ones. The most active peptide could be modified with non-natural amino acids to increase affinity and stability. While peptides and peptidomimetics would be applied in mechanistic studies, small molecular inhibitors of aggregation might represent lead compounds. One known inhibitor of α-synuclein aggregation was selected, NPT200-5, and an on-bead synthesis was developed so a diversity library could be generated around its four different building blocks. Finally the peptides, the NPT200-5 amide derivative and some known small molecule inhibitors of α-synuclein aggregation, such as curcumin, baicalein and EGCG amongst others, were screened on the bead-based α-synuclein aggregation assay. Strong inhibitory effects of curcumin and baicalein demonstrated the efficacy of the newly developed assay. In summary, the tools for the development of a novel micro-bead-based α-synuclein aggregation assay have been successfully produced. A novel bead-based α-synuclein early stage aggregation assay has been developed and optimised. Validation of this new technique was achieved with known small molecules inhibitors of α-synuclein aggregation.

Atualmente se tem bem estabelecido o tratamento para Doença de Parkinson, dentre eles o DBS (Deep Brain Stimulation). Embora haja controvérsias, muitos estudos têm demonstrado os efeitos adversos do DBS sobre a cognição, humor e comportamento. Assim, este estudo buscou investigar a associação entre os prejuízos cognitivos no pós-operatório e a volumetria cerebral em pacientes parkinsonianos submetidos a DBS, verificando se a correlação entre ambos pode ser considerada fator de risco para os prejuízos encontrados no pós-operatório. Fizeram parte da população estudada 25 indivíduos, 80% do sexo masculino, que foram submetidos ao procedimento cirúrgico de estimulação cerebral profunda (DBS) no Hospital de Clínicas de Porto Alegre (HCPA), em Porto Alegre entre 2012 e 2015. Estes sujeitos foram submetidos a uma bateria de testes cognitivos, bem como a testes clínicos e a ressonância magnética computadorizada nos períodos pré e pós-operatório em 6 meses. Os dados foram analisados através de estatísticas descritivas, coeficiente de correlação de Pearson e Teste t. Os resultados serão considerados significativos a um nível de significância máximo de 5% (p≤ 0,05) e o software estatístico utilizado para a análise será o SPSS versão 20.0. Quanto aos aspectos cognitivos avaliados, somente a fluência verbal fonêmica mostrou redução significativa entre os períodos pré e pós-operatório (p=0,003). A transfixação dos ventrículos foi associada à perda na fluência verbal semântica (p=0,009) e na memória (p=0,016) no pós-operatório. A presença de lesão na substância branca foi associada ao maior prejuízo na função executiva (p=0,017), fluência verbal semântica (p=0,039) e memória (p=0,050). Conclusão: Os prejuízos na fluência verbal semântica e memória no pós-operatório foram associados à presença de lesão na substância branca e a transfixação dos ventrículos pelo cabo com 6 eletrodos. A perda na função executiva foi associada a presença de lesão na substância branca. Os danos na fluência verbal fonêmica no pós-operatório, embora difiram estatisticamente, não foram associados a quaisquer achados da RM. / Currently, the treatment for Parkinson's Disease has been well established, among them DBS (Deep Brain Stimulation). Although controversial, many studies have demonstrated the adverse effects of DBS on cognition, mood, and behavior. Thus, this study sought to investigate the association between cognitive impairment in the postoperative period and cerebral volume in patients with Parkinson's disease who underwent DBS, and whether the correlation between the two can be considered as a risk factor for the possible postoperative losses. Twenty-five subjects, 80% male, who underwent deep brain stimulation (DBS) at the Hospital de Clínicas in Porto Alegre, Porto Alegre, between 2012 and 2015, were submitted to a cognitive battery, as well as clinical trials and computerized magnetic resonance imaging in the preoperative and postoperative periods at 6 months. Data were analyzed through descriptive statistics, Pearson's correlation coefficient and t-test. The results will be considered significant at a maximum significance level of 5% (p≤0.05) and the statistical software used for analysis will be SPSS version 20.0. Concerning the cognitive aspects evaluated, only phonemic verbal fluency showed a significant reduction between the pre and postoperative periods (p = 0.003). The transfixation of the ventricles was associated with loss of semantic verbal fluency (p = 0.009) and memory (p = 0.016) in the postoperative period. The presence of lesion in the white matter was associated with greater impairment in executive function (p = 0.017), semantic verbal fluency (p = 0.039) and memory (p = 0.050). Conclusion: The losses in the semantic verbal fluency and memory in the postoperative period were associated with the presence of white matter lesion and the transfixation of the ventricles by the cable with electrodes. The loss of executive function was associated with the presence of injury in the white matter. Damage to phonemic verbal fluency in 8 the postoperative period, although statistically different, was not associated with any MRI findings.

Atualmente se tem bem estabelecido o tratamento para Doença de Parkinson, dentre eles o DBS (Deep Brain Stimulation). Embora haja controvérsias, muitos estudos têm demonstrado os efeitos adversos do DBS sobre a cognição, humor e comportamento. Assim, este estudo buscou investigar a associação entre os prejuízos cognitivos no pós-operatório e a volumetria cerebral em pacientes parkinsonianos submetidos a DBS, verificando se a correlação entre ambos pode ser considerada fator de risco para os prejuízos encontrados no pós-operatório. Fizeram parte da população estudada 25 indivíduos, 80% do sexo masculino, que foram submetidos ao procedimento cirúrgico de estimulação cerebral profunda (DBS) no Hospital de Clínicas de Porto Alegre (HCPA), em Porto Alegre entre 2012 e 2015. Estes sujeitos foram submetidos a uma bateria de testes cognitivos, bem como a testes clínicos e a ressonância magnética computadorizada nos períodos pré e pós-operatório em 6 meses. Os dados foram analisados através de estatísticas descritivas, coeficiente de correlação de Pearson e Teste t. Os resultados serão considerados significativos a um nível de significância máximo de 5% (p≤ 0,05) e o software estatístico utilizado para a análise será o SPSS versão 20.0. Quanto aos aspectos cognitivos avaliados, somente a fluência verbal fonêmica mostrou redução significativa entre os períodos pré e pós-operatório (p=0,003). A transfixação dos ventrículos foi associada à perda na fluência verbal semântica (p=0,009) e na memória (p=0,016) no pós-operatório. A presença de lesão na substância branca foi associada ao maior prejuízo na função executiva (p=0,017), fluência verbal semântica (p=0,039) e memória (p=0,050). Conclusão: Os prejuízos na fluência verbal semântica e memória no pós-operatório foram associados à presença de lesão na substância branca e a transfixação dos ventrículos pelo cabo com 6 eletrodos. A perda na função executiva foi associada a presença de lesão na substância branca. Os danos na fluência verbal fonêmica no pós-operatório, embora difiram estatisticamente, não foram associados a quaisquer achados da RM. / Currently, the treatment for Parkinson's Disease has been well established, among them DBS (Deep Brain Stimulation). Although controversial, many studies have demonstrated the adverse effects of DBS on cognition, mood, and behavior. Thus, this study sought to investigate the association between cognitive impairment in the postoperative period and cerebral volume in patients with Parkinson's disease who underwent DBS, and whether the correlation between the two can be considered as a risk factor for the possible postoperative losses. Twenty-five subjects, 80% male, who underwent deep brain stimulation (DBS) at the Hospital de Clínicas in Porto Alegre, Porto Alegre, between 2012 and 2015, were submitted to a cognitive battery, as well as clinical trials and computerized magnetic resonance imaging in the preoperative and postoperative periods at 6 months. Data were analyzed through descriptive statistics, Pearson's correlation coefficient and t-test. The results will be considered significant at a maximum significance level of 5% (p≤0.05) and the statistical software used for analysis will be SPSS version 20.0. Concerning the cognitive aspects evaluated, only phonemic verbal fluency showed a significant reduction between the pre and postoperative periods (p = 0.003). The transfixation of the ventricles was associated with loss of semantic verbal fluency (p = 0.009) and memory (p = 0.016) in the postoperative period. The presence of lesion in the white matter was associated with greater impairment in executive function (p = 0.017), semantic verbal fluency (p = 0.039) and memory (p = 0.050). Conclusion: The losses in the semantic verbal fluency and memory in the postoperative period were associated with the presence of white matter lesion and the transfixation of the ventricles by the cable with electrodes. The loss of executive function was associated with the presence of injury in the white matter. Damage to phonemic verbal fluency in 8 the postoperative period, although statistically different, was not associated with any MRI findings.

Dans la maladie de Parkinson, un déficit d'activité électrique serait impliqué dans le processus de dégénérescence des neurones dopaminergiques (DA) de la substance noire. Or des structures non-DA, en particulier les neurones cholinergiques du noyau pédonculopontin (PPN) et orexinergiques de l'hypothalamus, sont affectés dans la pathologie. Ces neurones étant la source d'une innervation excitatrice pour les neurones DA, un déficit de ces inputs chez les patients pourrait jouer un rôle clé dans la progression de la perte DA. Le premier but de ce projet était d'évaluer l'impact d'une lésion des neurones cholinergiques du PPN sur la survie des neurones DA nigraux de rats et de macaques sains et parkinsoniens. Nous avons montré que 1) une déafférentation cholinergique induit une atrophie neuronale voire une dégénérescence DA, 2) une lésion DA induit une perte de neurones cholinergiques du PPN, et 3) combiner une lésion cholinergique du PPN à une lésion DA induit une exacerbation des pertes neuronales dans les deux systèmes. Enfin, le taux de dégénérescence DA est corrélé à l'intensité de la perte des neurones cholinergiques. Nos résultats confirment que le PPN joue un rôle clé dans la physiopathologie de la maladie de Parkinson et démontrent la forte interrelation existant entre ces deux systèmes. Concernant le système orexinergique, nous montrons que les fibres sont en position de moduler l'activité des neurones DA, mais qu'une lésion sélective du système DA chez le macaque n'est pas suffisante pour induire la mort des neurones à orexine. Ces résultats suggèrent que l'atteinte du système orexinergique chez des patients parkinsoniens pourrait résulter de lésions non-DA. / In Parkinson’s disease, there is evidence that dopaminergic (DA) neurons of the substantia nigra degenerate when they become electrically less active. Many non-DA structures including cholinergic neurons of the pedunculopontine nucleus (PPN) and orexinergic neurons of the hypothalamus, are also degenerating. Since these non-DA neurons are sources of excitatory inputs to the nigral DA neurons, their lesion in parkinsonian patients might play a key role in the progression of DA neuronal death. The first goal of this study was to evaluate the effect of a cholinergic PPN lesion on the survival of nigral DA neurons in healthy and parkinsonian rats and macaques. We found that 1) a PPN cholinergic lesion induced neuronal atrophy and death; 2) a DA lesion alone resulted in a loss of PPN cholinergic neurons; and 3) adding a PPN cholinergic lesion to a DA lesion in rats when the process of DA degeneration was in progress exacerbated neuronal losses in both systems. Last, the rate of DA degeneration was highly correlated to the level of cholinergic loss. Our results highlight the key role of the PPN in the physiopathology of Parkinson’s disease and clearly demonstrate strong reciprocal interactions with nigral DA neurons. The second aim of our study was to focus on the hypothalamic orexinergic system using a morphological approach in macaques. We show that orexinergic fibers are in position to modulate DA neurons activity. However, a relatively selective DA lesion in macaques was not sufficient to induce death of the orexinergic neurons. These data suggest that the loss of orexinergic neurons observed in parkinsonian patients likely results from non-DA lesions.

La maladie de Parkinson (MP) est caractérisée par une perte progressive des terminaisons présynaptiques dopaminergiques et reste actuellement incurable. Néanmoins, dans les études épidémiologiques, il a été montré que l’utilisation des statines, médicaments hypocholestérolémiants, diminue le risque de développer une MP. Les statines sont également capables d'inhiber les effets neurodégénératifs dans les modèles précliniques in-vitro et in-vivo de la MP. Cependant, les mécanismes moléculaires à l’origine de ces effets neuroprotecteurs ne sont pas encore complétement élucidés. Ainsi, nous avons étudié les effets potentiels des statines sur l'expression des marqueurs synaptiques et sur le transport de la dopamine. Dans nos études, les statines induisent la croissance des neurites dans les cellules dopaminergiques et déclenchent une augmentation de l’expression des protéines synaptiques dopaminergiques telles que le transporteur vésiculaire des monoamines (VMAT2) et le transporteur de la dopamine. Les statines induisent une diminution de la recapture de la dopamine cellulaire et des changements d’affinités aux niveaux des sites de liaison des inhibiteurs sélectifs du VMAT2. L’activation du facteur de transcription nucléaire protéine-1 se liant à l'élément de régulation des stérols (SREBP-1), cholestérol-dépendent, serait l’élément inducteur de la surexpression des marqueurs dopaminergiques présynaptiques induite par les statines. En outre, ces résultats soutiennent un potentiel thérapeutique neuroprotecteur et/ou neurorestaurateur des statines précédemment proposées dans la MP et permettent de mettre en évidence de nouvelles cibles thérapeutiques comme le facteur SREBP. / Parkinson disease (PD) is characterized by a progressive loss of dopaminergic presynaptic terminals and remains incurable. However in epidemiological studies, it has been shown that the use of statins, which are hypocholesterolemic drugs, diminishes the risk to develop a PD. Statins are able to inhibit the neurodegenerative effects in in-vitro and in-vivo models of PD. However, the molecular mechanisms driving neuroprotective effects are not yet fully understood. Consequently, we investigated the potential effects of statins on the synaptic expression and dopamine transport function in the dopaminergic system. In our studies, statins enhance the neurite outgrowth in the dopaminergic cells and trigger an increase in the expression levels of presynaptic dopaminergic proteins such as vesicular monoamine transporter 2 (VMAT2) and dopamine transporter. Statins induce a reduction of dopamine cellular uptake and modulate the binding-affinity of the specific inhibitors for VMAT2. The activation of the nuclear transcriptional factor sterol regulatory element-binding protein 1 (SREBP-1), cholesterol-dependent, could be the key element of the overexpression of dopaminergic presynaptic markers induced by the statins. Furthermore, these findings highlight the therapeutic neuroprotective and/or neurorestorative potentials of statins previously proposed in PD and allow to bring out new potential therapeutic targets such as SREBP factor.

La maladie de Parkinson est l’une des plus répandue dans le monde. Des analyses post mortem ont mis en évidences des inclusions dans les cerveaux des patients, composées d’α-synucléine. Plusieurs études ont visé à identifier des composés capables d’inhiber l’agrégation de cette protéine, étant donné que cette agrégation est liée à sa toxicité. Néanmoins, de nombreux composés restent encore à être identifiés afin de mettre en évidence des structures moléculaires actives partagées qui pourrait mener à la synthèse d’un principe actif. Les stilbènes sont des composés phénoliques démontrant régulièrement des activités biologiques intéressantes pour la santé. Dans cette étude, nous étudions le comportement anti-agrégatif des stilbènes monomériques (resvératrol, picéatannol) et oligomèriques (ampélopsine, viniférine, et isohopeaphénol). Les résultats présentés mettent en évidence la capacité des stilbènes à inhiber l’agrégation de l’α-synucléine et fournissent des éléments pour comprendre ce mécanisme. / Parkinson’s disease is one of the most spread neurodegenerative diseases in the world. Post mortem analyses have put in evidence small inclusion bodies in patient’s brain, composed of α-synuclein fibrils. Several studies attempted then to identify compounds that could inhibit α-synuclein aggregation, as its aggregation is linked to its toxicity. Still, numerous active compounds need to be identified in order to put on relief shared active structures that could lead to a potent drug design. Stilbenes are phenolic compounds that often display interesting health-related biological activities. In this study, the anti-aggregative behavior of stilbenes monomers (resveratrol, piceatannol) and oligomers such as ampelopsin and isohopeaphenol was assessed. The results put on evidence stilbene propensity to inhibit α-synuclein aggregation and provide an insight into their inhibition mechanisms.

Dans de nombreuses maladies neurodégénératives dont la Maladie de Parkinson, mais également dans le processus de vieillissement normal, il a été observé une accumulation excessive des niveaux de fer associée à une production accrue d‘espèces réactives de l’oxygène (ROS).Il est bien connu que le fer (i) participe à la réaction de Fenton pour produire le ROS le plus toxique, le radical hydroxyle, (ii) accélère l’auto-oxidation de la dopamine, augmentant le stress oxydant et (iii) augmente la peroxydation lipidique qui va déclencher l'agrégation des protéines, dont l’α-synucléine, une caractéristique de la maladie de Parkinson. Tous ces phénomènes rendent les neurones dopaminergiques très sensible au stress oxydant.Récemment, une nouvelle forme de mort cellulaire a été découverte sur des cellules cancéreuses. Cette mort cellulaire est appelée « ferroptose » car elle dépend essentiellement du fer intracellulaire. De plus, elle est liée à une très grande augmentation du stress lipidique.Le principal objectif de ce travail de thèse a donc porté sur la possible implication de la ferroptose dans la mort des cellules dopaminergiques.Dans un premier temps, nous avons montré que la lignée de neurones dopaminergiques (LUHMES) est un modèle particulièrement adapté à l’étude de mort cellulaire induite par le fer comparativement à d’autres modèles plus classique.La seconde partie du travail a donc été consacrée à l'étude de l’implication de la ferroptose dans les neurones dopaminergiques. D’abord par une approche cellulaire avec les cellules LUHMES, nous avons pu observer (i) que l’inducteur spécifique de cette mort, l’érastine, est très efficace pour induire la mort des cellules dopaminergiques, (ii) que l'inhibition de la ferroptose protégeait de la mort induite par des agents oxydants classiquement utilisés dans les études sur la maladie de Parkinson comme le MPP+ et (iii) que la PKC joue un rôle majeur dans la mort par ferroptose. Tous ces résultats ont ensuite été confirmés dans un modèle de culture organotypique, à l’interface entre la culture cellulaire et le modèle animal.Enfin, nous avons montré que l’utilisation des inhibiteurs de la ferroptose ainsi que celui de la PKC, confère une protection des neurones dopaminergiques dans un modèle de souris MPTP, modèle d’étude de la maladie de Parkinson.En conclusion ce travail de thèse montre pour la première fois l'implication de la ferroptose dans une maladie neurodégénérative comme la maladie de Parkinson et suggèrent que le développement d'inhibiteurs spécifiques de cette mort cellulaire pourrait être des futures cibles thérapeutiques possibles. / In many neurodegenerative diseases including Parkinson's disease, as well as in the regular aging process, an excessive accumulation of iron levels associated with increased production of oxygen species (ROS) have been observed.It is well known that iron (i) participates in the Fenton reaction to produce the most toxic ROS, the hydroxyl radical, (ii) accelerates auto-oxidation of dopamine, increasing the oxidative stress and (iii) increases lipid peroxidation that will trigger the aggregation of proteins, including α-synuclein, a hallmark of Parkinson's disease. All theses factors make dopamine neurons very sensitive to oxidative stress.Recently, a new form of cell death was found on cancer cells. This cell death is called ferroptosis because it essentially depends on the intracellular iron. In addition, it is linked to a very large increase in lipid stress.The main objective of this work has focused on the possible involvement of ferroptosis in the death of dopamine cells.First, we showed that the line of dopaminergic neurons (LUHMES) is a model particularly suited to the study of cell death induced by iron compared to other more conventional models.The second part of the work has been devoted to the study of the involvement of ferroptose in dopaminergic neurons. First by a cellular approach with LUHMES cells, we observed that (i) the specific inducer of this death, erastin, is very effective to induce the death of dopaminergic cells, (ii) inhibition of ferroptosis protected from death induced by oxidizing agents conventionally used in studies of Parkinson's disease like MPP+ and (iii) that PKC plays a major role in death by ferroptosis. These results were then confirmed in an organotypic culture model, at the interface between cell culture and animal models.Finally, we have shown that the use of ferroptosis inhibitors and PKC inhibitor, provides protection of dopaminergic neurons in MPTP mice model, animal model for studying of Parkinson's disease.In conclusion this study demonstrates for the first time the involvement of ferroptosis in a neurodegenerative disease such as Parkinson's disease and suggest that the development of specific inhibitors of this cell death could be possible future therapeutic targets.

Ces dernières années de nombreux marqueurs de l’atteinte nigrostriatale ont été élaborés et testés dans la maladie de Parkinson (MP). Ces marqueurs peuvent détecter et quantifier la neurodégénérescence dans la substance noire (SN) des patients ainsi que dans les formes précoces prémotrices de la maladie. Leur performance diagnostique reste mal connue de même que l’atteinte extra-nigrale.Dans ce travail nous avons étudié l’atteinte de la SN dans les formes précliniques et prémotrices de la MP. La charge en fer était augmentée chez des porteurs des mutations symptomatiques mais également chez des porteurs sains. De plus, nous avons observé une atteinte pré-motrice de la SN chez des sujets touchés par les troubles des comportements en sommeil paradoxal (TCSP) qui n’ont pas encore développé un syndrome parkinsonien. Chez ces sujets, l’atteinte de la SN a été le mieux mise en évidence par l’imagerie sensible à la neuromélanine et le tenseur de diffusion avec la fraction d’anisotropie, suggérant un intérêt dans la caractérisation prodromale de la MP. Ces mêmes marqueurs présentaient également la meilleure performance diagnostique dans la MP. Finalement, nous avons trouvé des anomalies bulbaires en tenseur de diffusion dans la MP, qui étaient corrélées aux symptômes dysautonomiques cardiaques et respiratoires, suggérant l’intérêt de ce marqueur pour étude de l’atteinte bulbaire. Ceci ouvre une possibilité d’étude bulbaire chez des sujets présymptomatiques car une atteinte bulbaire devrait apparaître avant les symptômes moteurs selon le modèle de Braak. Ces marqueurs sont peut-être la première étape vers un diagnostic présymptomatique de la MP dans la pratique clinique. / In recent years numerous biomarkers of nigro-striatal damage were proposed in Parkinson's disease (PD). These markers are able to detect and quantify neurodegenative changes in the substantia nigra (SN) of patients with PD as well as in subjects with premotor conditions. Their diagnostic performances to detect PD as well as the extent of extranigral pathology remain incompletely understood.In this work we observed the damage of the substantia nigra in preclinical and premotor forms of PD. Iron load was increased in both symptomatic and asymptomatic mutations carriers, suggesting the interest of the biomarker in PD related genetic mutations. In addition, we found a pre-clinical impairment of the SN in subjects affected by idiopathic sleep in REM behavioral disorders (iRBD) who have not yet converted to Parkinsonism. In these subjects, the SN damage was best demonstrated by neuromelanin-sensitive imaging and diffusion tensor imaging (DTI) with fractional anisotropy measure, suggesting an interest of these measures in the prodromal characterization of PD. These same markers had the best performance for PD diagnosis.Finally, we found medulla oblongata damage patients with PD using DTI. This damage was correlated with cardiac and respiratory autonomic symptoms, suggesting the importance of this biomarker in medulla oblongata damage exploration. It also opens a possibility of medulla oblongata study in presymptomatic subjects as medulla oblongata damage should appear before motor symptoms based on the Braak model.These biomarkers may be the first step towards a presymptomatic diagnosis of PD in clinical practice.

La maladie de Parkinson (MP) appartient à la famille des a-synucléinopathies. Ces pathologies ont en commun d'être liées à l'a-synucléine (a-syn), protéine neuronale dont les rôles précis sont encore mal définis. Dans un contexte où des pesticides, comme le paraquat, ont été liés épidémiologiquement au déclenchement précoce de la MP chez des agriculteurs, certaines substances sont devenues des substances de référence dans les études portant sur les synucléinopathies. Le paraquat induit une pathologie parkinsonienne comprenant des agrégations de l'a-syn ou des pertes spécifiques de neurones dopaminergiques. Dans nos études nous avons premièrement mis en place un modèle d'exposition par voie orale au paraquat en utilisant l'administration. Par la suite nous avons étudié les effets de cette administration orale au paraquat sur le système nerveux entérique présent dans l'intestin de souris C57Bl/6 et transgénique TgM83. Cette lignée transgénique possède la particularité de développer spontanément une synucléinopathie, simultanément dans l'intestin et le cerveau, présentant des dépôts d'a-syn phosphorylée. L'ingestion du paraquat induit une accélération de l'apparition de la synucléinopathie entérique. Dans une seconde étude biochimique, nous montrons que l'exposition orale au paraquat induit une augmentation globale des niveaux d'a-syn totale dans le système nerveux central et entérique des souris.Nous montrons ici les effets délétères de l'exposition orale au paraquat sur l'intestin en lien avec l'a-syn, par l'accélération d'une synucléinopathie mais aussi par l'induction d'une réponse générale, cérébrale et entérique, traduite par une hausse des niveaux d'a-syn / Parkinson's disease (PD) belongs to the a-synucleinopathies family. These pathologies have in common that they are linked to a-synuclein (a-syn), a neuronal protein whose precise roles are poorly defined. Some pesticides, such as paraquat, have been epidemiologically linked to the early onset of PD in farmers; some substances have become essential in the studies of synucleinopathies. Paraquat induces parkinsonian pathologies including a-syn aggregations or specific dopaminergic neurons loss. In our studies, we first set up a model of oral exposure to paraquat by drinking water. Subsequently, we studied the effects of this oral administration to paraquat on the enteric nervous system of the intestine of C57Bl/6 and TgM83 transgenic mice. This transgenic line has the peculiarity of simultaneously and spontaneously developing a synucleinopathy in the intestine and in the brain, displaying deposits of phosphorylated a-syn. The oral ingestion of paraquat induces acceleration in the appearance of enteric synucleinopathy. In a second biochemical study, we show that oral exposure to paraquat induces an overall increase in total a-syn levels in the central and enteric nervous systems of mice.Our results show the deleterious effects of paraquat oral administration on the intestine in relation to a-syn, by the acceleration of synucleinopathy but also by the induction of a widespread cerebral and enteric response, shown by an increase in cellular levels of a-syn

Doyenne de la thérapeutique antiparkinsonienne, puissant outil pharmacologique au profil singulier, l’apomorphine est aujourd’hui indiquée comme thérapeutique de deuxième intention, au stade où les fluctuations liées au traitement oral handicapent le quotidien des patients. Si ses effets sur la triade parkinsonienne et les fluctuations motrices sont connus et objectivés depuis le milieu du XXème siècle, son spectre d’action sur les troubles non moteurs a, quant à lui, été encore peu exploré. Ce travail de thèse avait deux objectifs : (1) établir un état de l’art quant aux connaissances actuelles sur l’apomorphine et (2) étudier les effets d’un traitement par pompe à apomorphine sur la symptomatologie non motrice parkinsonienne, en particulier aux plans cognitifs et émotionnels, sur une période de six mois. Pour ce faire, deux études ont été menées. La première, intitulée APO-TEP, s’intéressait à l’évolution de l’état cognitif et de la qualité de vie de patients présentant la maladie à un stade avancé, mais ne pouvant bénéficier de la chirurgie de stimulation cérébrale profonde du noyau subthalamique. Une exploration du métabolisme cérébral était associée à l’évaluation clinique. Ce travail a permis de mettre en évidence une amélioration significative des fonctions motrices, cognitivo-psychiatriques (fonctions exécutives et apathie) et de la qualité de vie après six mois de traitement. Des modifications d’activité cérébrale dans les réseaux fonctionnels cognitifs, moteurs et limbiques ont par ailleurs été observées, soutenant l’idée d’un substratum anatomo-fonctionnel diffus. La seconde étude, intitulée APO-EMO, évalue les effets du traitement par pompe à apomorphine sur la sphère émotionnelle, souvent altérée dans la maladie de Parkinson. Cette dernière étude est toujours en cours ; les résultats préliminaires ne mettent pour l’heure pas en évidence d’effets sur la perception individuelle des émotions (intelligence émotionnelle et expressivité). Les analyses visant à explorer les effets du traitement sur le mimétisme facial et la reconnaissance des expressions faciales émotionnelles seront menées dans un second temps. L’ensemble de ces résultats expérimentaux est discuté à la lumière des données de la littérature et plusieurs perspectives cliniques et de recherche sont développées. De nouveaux travaux, visant à mieux comprendre les réseaux neuronaux et les voies neurochimiques activées par l’apomorphine en perfusion continue, sont à mener. Longtemps cantonnée au rang de curiosité pharmacologique, l’apomorphine semble enfin trouver sa place dans l’arsenal thérapeutique. / Apomorphine is a peculiar drug, currently used as a second-line therapy in Parkinson’s disease (PD). If its motor efficacy has been amply established, questions remain about its effect on non motor symptoms, a common burden in PD. This thesis address these questions by (1) reviewing the state of the art of the current knowledge about apomorphine (history, pharmacology and current interest in neurological disorders) and (2) exploring the effect of continuous subcutaneous apomorphine infusion (CSAI) on cognitive and emotional symptoms in PD, while studying brain metabolism. Two studies were conducted: APO-TEP and APO-EMO. Well-tolerated, CSAI appears to be an interesting option in advanced PD. Changes in brain metabolism (motor, cognitive and limbic networks) were observed at 6 months and correlated to clinical improvement (executive functions, apathy and motricity) in patients with advanced PD and contra-indications for subthalamic nucleus deep brain stimulation. Preliminary results of the ongoing APO-EMO study suggest that CSAI does not seem to improve emotional self-perception in patients; however we will further explore its effect on facial mimicry and facial emotion recognition. If further research is still needed, apomorphine seems to be destined to become a key feature of future therapeutic strategies, in PD (nonmotor symptoms, advanced PD, withdrawal of oral medications) but also in other dopaminergic disorders, and rightly so.