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

No description available.

Introdução: Com o envelhecimento da população mundial projeta-se o crescimento das taxas de doenças potencialmente relacionadas à idade como as demências, especialmente a doença de Alzheimer (DA). Os sujeitos com Comprometimento Cognitivo Leve (CCL) são considerados uma população de risco para desenvolver demência, no entanto, as taxas de incidência de CCL e conversão para demência apresentam considerável variabilidade em parte atribuída a características da amostra e aos diferentes critérios utilizados. Objetivos: Determinar a incidência de demência e Comprometimento Cognitivo Leve em uma coorte de idosos saudáveis de base comunitária; determinar as variáveis demográficas, clínicas e sociais associadas ao desenvolvimento de prejuízo cognitivo, e avaliar o risco de progressão dos indivíduos com Comprometimento Cognitivo Leve para demência comparada com sujeitos cognitivamente normais. Métodos: Os dados foram derivados de uma coorte de idosos residentes na comunidade (N = 345), inicialmente saudáveis e independentes (Estudo PALA - Porto Alegre Longitudinal Aging - study). O seguimento inicial com duração máxima de oito anos teve o objetivo de avaliar a incidência de DA e CCL. Para avaliar a progressão de CCL para DA partimos de 10 anos de seguimento, incluindo os oito anos da primeira análise e consideramos um máximo de 70 meses (média de 45 meses) para avaliar a ocorrência dos novos desfechos. Os participantes que preencheram os critérios de inclusão do estudo e consentiram em participar foram avaliados com uma detalhada entrevista clínica composta de variáveis demográficas, clínicas e sociais. Os sintomas psiquiátricos foram avaliados pela escala SRQ - Self Report Questionnaire, escala MADRS - Montgomery-Asberg Depression Rating Scale e aplicados os critérios para depressão maior do Manual de Diagnóstico e Estatístico de Transtornos Mentais (4ª Edição; DSM-IV). O Mini Exame do Estado Mental (MEEM) e a Escala Clínica de Demência (CDR – Clinical Dementia Rating) foram aplicados para avaliação cognitiva. Adicionalmente a independência para as atividades da vida diária foram acessadas pela escala ADL - Activities of Daily Living. Para diagnóstico dos casos incidentes de doença de Alzheimer foi utilizado os critérios diagnósticos do DSM-IV e do NINCDS/ADRDA, associado à descrição dos critérios de Kawas para DA consistente. Para diagnóstico de Comprometimento Cognitivo Leve, o critério da Clínica Mayo foi aplicado para a primeira análise, e o critério para CCL do tipo Alzheimer (ou DA prodrômica) foi utilizado para a segunda análise tendo em vista a incorporação de dados disponíveis e a evolução dos critérios. As trajetórias possíveis do CCL foram classificadas em três categorias: conversão, estabilização e reconversão. Os sujeitos considerados para a primeira análise - casos incidentes de CCL e DA foram os participantes que apresentavam pelo menos uma visita de seguimento no período de oito anos a partir da linha de base (N = 245) e as análises estatísticas foram baseadas no diagnóstico estabelecido na última visita de seguimento. Para os falecidos durante o período, dados retrospectivos foram obtidos através de uma entrevista telefônica com um informante confiável. Os dados clínicos e demográficos de linha de base foram utilizados para cálculo dos fatores preditivos dos desfechos do estudo. Para a segunda análise – risco de conversão de CCL para DA – trajetórias do CCL, a amostra foi composta dos 21 indivíduos que desenvolveram CCL e 220 indivíduos cognitivamente normais (N = 241). Resultados: Os resultados da primeira análise mostraram taxa de incidência de CCL de 13,2 por 1.000 pessoas-ano e incidência de DA de 14,8 por 1.000 pessoas-ano. O desenvolvimento de prejuízo cognitivo foi associado com educação (razão de chance [RC] = 0,86) e o escore do MEEM de base (RC = 0,81). Os resultados da segunda análise mostraram que dos 21 sujeitos com CCL, 38% desenvolveram demência, 24% permaneceram estáveis e 38% melhoraram. A taxa de conversão anual para DA foi de 8,5%, CCL foi associado significativamente a maior risco de conversão para DA (HR = 49,83; p = 0,004), mesmo ajustado para idade, escolaridade, sexo e escore no MEEM. Conclusão: A incidência de DA nessa amostra foi maior do que a descrita em estudo prévio realizado no Brasil, mas está dentro da variabilidade observada internacionalmente. Escores mais baixos no Mini Exame do Estado Mental na linha de base, mesmo que dentro da normalidade, e níveis mais baixos de educação foram preditores da ocorrência de prejuízo cognitivo. Quanto à trajetória do CCL, independentemente da heterogeneidade observada, os participantes com CCL do tipo Alzheimer apresentaram risco significativamente maior de desenvolver demência na DA, demonstrando o impacto do uso destes critérios que enfatizam o comprometimento da memória episódica de longo prazo e buscam identificar sujeitos com maior probabilidade de ser portadores de patologia Alzheimer. / Background: The increase of the rates of age-related diseases as dementia, especially Alzheimer's disease (AD), is projected with the aging of the world population. Subjects with Mild Cognitive Impairment (MCI) are considered a population at risk for developing dementia. However, MCI incidence rates and rates of conversion to dementia have shown considerable variability that could be partially attributed to characteristics of the sample and to different criteria. Objective: To determine the incidence of dementia and mild cognitive impairment in a cohort of community-based healthy elderly individuals; to determine the demographic, clinical and social variables associated with the development of cognitive impairment; and to assess the risk of progression of individuals with mild cognitive impairment to dementia compared with cognitively normal subjects. Methods: Data were derived from a cohort of elderly community residents (N = 345), who were initially healthy and independent (PALA – Porto Alegre Longitudinal Aging – study). The follow-up of a maximum of eight years was used to evaluate the incidence of AD and MCI. To evaluate the progression of MCI to dementia due to AD we set off the 10-year follow-up, including the previous 8-year of the first analysis, and consider the maximum of 70 months (mean 45 months) for these new outcomes. Participants who met the inclusion criteria of the study and consented to participate were evaluated with a detailed clinical interview consisted of demographic, clinical and social variables. Psychiatric symptoms were assessed with the SRQ scale (Self Report Questionnaire), the MADRS (Montgomery-Asberg Depression Rating Scale), and the Diagnostic and Statistical Manual of Mental Disorders (4th edition, DSM-IV) criteria for Major Depression. Cognitive assessment was checked with the Mini Mental State Examination (MMSE) and the Clinical Dementia Rating Scale (CDR). Independence for the activities of daily living was assessed with the ADL scale (Activities of Daily Living). Incident cases of probable Alzheimer's disease were assigned through the DSM-IV and the NINCDS-ADRDA diagnostic criteria, with the additional designation from Kawas and colleagues of consistent AD. Detection of Mild Cognitive Impairment for the first analysis was carried out with the MCI Mayo Clinic criteria. The MCI of the Alzheimer type criteria (or Prodromal AD) were used for the second analysis, incorporating available data of the sample and the ongoing evolution of the criteria. The possible MCI trajectories were classified into three categories: conversion, stabilization, and reconversion. The subjects for the first analysis – MCI and AD incidence – were the participants who had at least one follow-up visit in the 8-year period from the baseline (N = 245), and the statistical analyzes were based on the diagnosis established in last follow-up interview. For the deceased during the period, retrospective data were obtained through a telephone interview with a knowledgeable collateral source focusing on dementia. The baseline clinical and demographic data were analyzed as predictors of the study outcomes. For the second analysis – risk of MCI progression to AD, and MCI trajectories – the sample was composed of 21 individuals who developed MCI and 220 cognitively normal subjects (N = 241). Results: The results of the first analysis showed the MCI incidence rate of 13.2 per 1,000 person-years and the AD incidence of 14.8 per 1,000 person-years. The development of cognitive impairment was associated with education (odds ratio [OR] = 0.86) and baseline MMSE scores (OR = 0.81). The results of second analysis showed that of the 21 MCI subjects, 38% developed dementia, 24% remained stable, and 38% improved. The annual AD conversion rate was 8.5%, and MCI was significantly associated with increased risk of progression to AD (HR = 49.83; p = 0.004), even adjusted for age, education, gender and MMSE scores. Conclusion: The AD incidence in this sample was higher than that described in a previous study carried out in Brazil, but was within the international estimates. Lower baseline scores on the Mini Mental State Examination, although within the normal range, and lower levels of education were predictors of cognitive impairment. Regardless the observed heterogeneity of the MCI trajectories, participants with MCI of the Alzheimer type showed significantly higher risk of developing dementia due to AD, demonstrating the impact of the emphasis on the episodic long-term memory impairment of the criteria, which finally searches to identify those individuals more likely to have Alzheimer's pathology.

A doença de Alzheimer (DA) é uma patologia neurodegenerativa progressiva e a forma de demência mais prevalente no mundo. As alterações fisiopatológicas da DA têm sido associadas a dois marcadores neuropatológicos clássicos: a deposição de placas de β- amilóide e a formação de emaranhados neurofibrilares da proteína tau hiperfosforilada. Porém, devido a complexidade da DA, outros mecanismos têm sido propostos como coadjuvantes no processo neurodegenerativo, entre eles eventos neuroinflamatórios, a quebra da homeostasia de sistemas de neurotransmissão e disfunção sináptica. Esta pletora de eventos patológicos parece preceder a fase de demência por um longo período onde a doença age de forma silenciosa, ou seja, onde não existem evidências sintomatológicas. Na presente tese, avançamos no entendimento de vias de sinalização associadas com a hipersforforilação da proteína tau envolvendo a disfunção da proteína fosfatase 2A e neurotoxicidade do sistema glutamatérgico. Além disso, avaliamos os radiofármacos de tomografia de emissão de pósitrons (PET) disponíveis para visualização in vivo e não invasiva da fisiopatologia da DA. Finalmente, avaliamos um novo biomarcador de PET, o [11C]ABP688, para visualizar flutuações no sistema glutamatérgico e avançamos no entendimento do impacto das células gliais no sinal do PET [18F]FDG, o radiofármaco mais utilizado na clínica atualmente para visualizar metabolismo de glicose cerebral. O [11C]ABP688 pode ser diretamente incluído em estudos clínicos e a reconceptualização do [18F]FDG proposta nesta tese pode alterar a maneira atual como vemos o metabolismo de glicose na DA e em outras doenças neurodegenerativas. Finalmente, nesta tese, avançamos em termos de mecanismos, e no contexto da busca por um diagnóstico precoce e acurado da DA. / Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most prevalent cause of dementia worldwide. The AD pathophysiological features have been associated to two main classic neuropathological markers: depositon of β-amyloid plaques and formation of neurofibrillary tangles of hyperphosphorylated tau. Due to AD complexity, however, additional mechanisms have been proposed as contributors to the neurodegenerative process, such as neuroinflammatory changes, altered neurotransmission, and synaptic dysfunction. These pathological events seem to precede the dementia phase by many years, resulting in a long silent period, i.e., a preclinical phase. In this thesis, we advanced in the understanding of signaling pathways associated with tau hyperphosphorylation, which includes dysfunction of protein phosphatase 2A (PP2A) and glutamatergic neurotoxicity. Furthermore, we underscored radiopharmaceuticals currently available for imaging AD pathophysiology in vivo and non-invasively with positron emission tomography (PET). Finally, we evaluated a new PET biomarker, [11C]ABP688, for visualizing glutamatergic fluctuations and advanced in the understating of how glial cells contribute to the [18F]FDG signal, the widely used radiopharmaceutical in clinical settings for visualizing cerebral glucose metabolism. Our findings have high translational value and direct impact in clinical settings, which can potentially alter the way we interpret glucose metabolism in AD and other neurodegenerative disorders. In summary, in this thesis, we have advanced in terms of molecular mechanisms, and in the use of PET biomarkers toward an early and accurate diagnosis of AD.

Introdução: Com o envelhecimento da população mundial projeta-se o crescimento das taxas de doenças potencialmente relacionadas à idade como as demências, especialmente a doença de Alzheimer (DA). Os sujeitos com Comprometimento Cognitivo Leve (CCL) são considerados uma população de risco para desenvolver demência, no entanto, as taxas de incidência de CCL e conversão para demência apresentam considerável variabilidade em parte atribuída a características da amostra e aos diferentes critérios utilizados. Objetivos: Determinar a incidência de demência e Comprometimento Cognitivo Leve em uma coorte de idosos saudáveis de base comunitária; determinar as variáveis demográficas, clínicas e sociais associadas ao desenvolvimento de prejuízo cognitivo, e avaliar o risco de progressão dos indivíduos com Comprometimento Cognitivo Leve para demência comparada com sujeitos cognitivamente normais. Métodos: Os dados foram derivados de uma coorte de idosos residentes na comunidade (N = 345), inicialmente saudáveis e independentes (Estudo PALA - Porto Alegre Longitudinal Aging - study). O seguimento inicial com duração máxima de oito anos teve o objetivo de avaliar a incidência de DA e CCL. Para avaliar a progressão de CCL para DA partimos de 10 anos de seguimento, incluindo os oito anos da primeira análise e consideramos um máximo de 70 meses (média de 45 meses) para avaliar a ocorrência dos novos desfechos. Os participantes que preencheram os critérios de inclusão do estudo e consentiram em participar foram avaliados com uma detalhada entrevista clínica composta de variáveis demográficas, clínicas e sociais. Os sintomas psiquiátricos foram avaliados pela escala SRQ - Self Report Questionnaire, escala MADRS - Montgomery-Asberg Depression Rating Scale e aplicados os critérios para depressão maior do Manual de Diagnóstico e Estatístico de Transtornos Mentais (4ª Edição; DSM-IV). O Mini Exame do Estado Mental (MEEM) e a Escala Clínica de Demência (CDR – Clinical Dementia Rating) foram aplicados para avaliação cognitiva. Adicionalmente a independência para as atividades da vida diária foram acessadas pela escala ADL - Activities of Daily Living. Para diagnóstico dos casos incidentes de doença de Alzheimer foi utilizado os critérios diagnósticos do DSM-IV e do NINCDS/ADRDA, associado à descrição dos critérios de Kawas para DA consistente. Para diagnóstico de Comprometimento Cognitivo Leve, o critério da Clínica Mayo foi aplicado para a primeira análise, e o critério para CCL do tipo Alzheimer (ou DA prodrômica) foi utilizado para a segunda análise tendo em vista a incorporação de dados disponíveis e a evolução dos critérios. As trajetórias possíveis do CCL foram classificadas em três categorias: conversão, estabilização e reconversão. Os sujeitos considerados para a primeira análise - casos incidentes de CCL e DA foram os participantes que apresentavam pelo menos uma visita de seguimento no período de oito anos a partir da linha de base (N = 245) e as análises estatísticas foram baseadas no diagnóstico estabelecido na última visita de seguimento. Para os falecidos durante o período, dados retrospectivos foram obtidos através de uma entrevista telefônica com um informante confiável. Os dados clínicos e demográficos de linha de base foram utilizados para cálculo dos fatores preditivos dos desfechos do estudo. Para a segunda análise – risco de conversão de CCL para DA – trajetórias do CCL, a amostra foi composta dos 21 indivíduos que desenvolveram CCL e 220 indivíduos cognitivamente normais (N = 241). Resultados: Os resultados da primeira análise mostraram taxa de incidência de CCL de 13,2 por 1.000 pessoas-ano e incidência de DA de 14,8 por 1.000 pessoas-ano. O desenvolvimento de prejuízo cognitivo foi associado com educação (razão de chance [RC] = 0,86) e o escore do MEEM de base (RC = 0,81). Os resultados da segunda análise mostraram que dos 21 sujeitos com CCL, 38% desenvolveram demência, 24% permaneceram estáveis e 38% melhoraram. A taxa de conversão anual para DA foi de 8,5%, CCL foi associado significativamente a maior risco de conversão para DA (HR = 49,83; p = 0,004), mesmo ajustado para idade, escolaridade, sexo e escore no MEEM. Conclusão: A incidência de DA nessa amostra foi maior do que a descrita em estudo prévio realizado no Brasil, mas está dentro da variabilidade observada internacionalmente. Escores mais baixos no Mini Exame do Estado Mental na linha de base, mesmo que dentro da normalidade, e níveis mais baixos de educação foram preditores da ocorrência de prejuízo cognitivo. Quanto à trajetória do CCL, independentemente da heterogeneidade observada, os participantes com CCL do tipo Alzheimer apresentaram risco significativamente maior de desenvolver demência na DA, demonstrando o impacto do uso destes critérios que enfatizam o comprometimento da memória episódica de longo prazo e buscam identificar sujeitos com maior probabilidade de ser portadores de patologia Alzheimer. / Background: The increase of the rates of age-related diseases as dementia, especially Alzheimer's disease (AD), is projected with the aging of the world population. Subjects with Mild Cognitive Impairment (MCI) are considered a population at risk for developing dementia. However, MCI incidence rates and rates of conversion to dementia have shown considerable variability that could be partially attributed to characteristics of the sample and to different criteria. Objective: To determine the incidence of dementia and mild cognitive impairment in a cohort of community-based healthy elderly individuals; to determine the demographic, clinical and social variables associated with the development of cognitive impairment; and to assess the risk of progression of individuals with mild cognitive impairment to dementia compared with cognitively normal subjects. Methods: Data were derived from a cohort of elderly community residents (N = 345), who were initially healthy and independent (PALA – Porto Alegre Longitudinal Aging – study). The follow-up of a maximum of eight years was used to evaluate the incidence of AD and MCI. To evaluate the progression of MCI to dementia due to AD we set off the 10-year follow-up, including the previous 8-year of the first analysis, and consider the maximum of 70 months (mean 45 months) for these new outcomes. Participants who met the inclusion criteria of the study and consented to participate were evaluated with a detailed clinical interview consisted of demographic, clinical and social variables. Psychiatric symptoms were assessed with the SRQ scale (Self Report Questionnaire), the MADRS (Montgomery-Asberg Depression Rating Scale), and the Diagnostic and Statistical Manual of Mental Disorders (4th edition, DSM-IV) criteria for Major Depression. Cognitive assessment was checked with the Mini Mental State Examination (MMSE) and the Clinical Dementia Rating Scale (CDR). Independence for the activities of daily living was assessed with the ADL scale (Activities of Daily Living). Incident cases of probable Alzheimer's disease were assigned through the DSM-IV and the NINCDS-ADRDA diagnostic criteria, with the additional designation from Kawas and colleagues of consistent AD. Detection of Mild Cognitive Impairment for the first analysis was carried out with the MCI Mayo Clinic criteria. The MCI of the Alzheimer type criteria (or Prodromal AD) were used for the second analysis, incorporating available data of the sample and the ongoing evolution of the criteria. The possible MCI trajectories were classified into three categories: conversion, stabilization, and reconversion. The subjects for the first analysis – MCI and AD incidence – were the participants who had at least one follow-up visit in the 8-year period from the baseline (N = 245), and the statistical analyzes were based on the diagnosis established in last follow-up interview. For the deceased during the period, retrospective data were obtained through a telephone interview with a knowledgeable collateral source focusing on dementia. The baseline clinical and demographic data were analyzed as predictors of the study outcomes. For the second analysis – risk of MCI progression to AD, and MCI trajectories – the sample was composed of 21 individuals who developed MCI and 220 cognitively normal subjects (N = 241). Results: The results of the first analysis showed the MCI incidence rate of 13.2 per 1,000 person-years and the AD incidence of 14.8 per 1,000 person-years. The development of cognitive impairment was associated with education (odds ratio [OR] = 0.86) and baseline MMSE scores (OR = 0.81). The results of second analysis showed that of the 21 MCI subjects, 38% developed dementia, 24% remained stable, and 38% improved. The annual AD conversion rate was 8.5%, and MCI was significantly associated with increased risk of progression to AD (HR = 49.83; p = 0.004), even adjusted for age, education, gender and MMSE scores. Conclusion: The AD incidence in this sample was higher than that described in a previous study carried out in Brazil, but was within the international estimates. Lower baseline scores on the Mini Mental State Examination, although within the normal range, and lower levels of education were predictors of cognitive impairment. Regardless the observed heterogeneity of the MCI trajectories, participants with MCI of the Alzheimer type showed significantly higher risk of developing dementia due to AD, demonstrating the impact of the emphasis on the episodic long-term memory impairment of the criteria, which finally searches to identify those individuals more likely to have Alzheimer's pathology.

A doença de Alzheimer (DA) é uma patologia neurodegenerativa progressiva e a forma de demência mais prevalente no mundo. As alterações fisiopatológicas da DA têm sido associadas a dois marcadores neuropatológicos clássicos: a deposição de placas de β- amilóide e a formação de emaranhados neurofibrilares da proteína tau hiperfosforilada. Porém, devido a complexidade da DA, outros mecanismos têm sido propostos como coadjuvantes no processo neurodegenerativo, entre eles eventos neuroinflamatórios, a quebra da homeostasia de sistemas de neurotransmissão e disfunção sináptica. Esta pletora de eventos patológicos parece preceder a fase de demência por um longo período onde a doença age de forma silenciosa, ou seja, onde não existem evidências sintomatológicas. Na presente tese, avançamos no entendimento de vias de sinalização associadas com a hipersforforilação da proteína tau envolvendo a disfunção da proteína fosfatase 2A e neurotoxicidade do sistema glutamatérgico. Além disso, avaliamos os radiofármacos de tomografia de emissão de pósitrons (PET) disponíveis para visualização in vivo e não invasiva da fisiopatologia da DA. Finalmente, avaliamos um novo biomarcador de PET, o [11C]ABP688, para visualizar flutuações no sistema glutamatérgico e avançamos no entendimento do impacto das células gliais no sinal do PET [18F]FDG, o radiofármaco mais utilizado na clínica atualmente para visualizar metabolismo de glicose cerebral. O [11C]ABP688 pode ser diretamente incluído em estudos clínicos e a reconceptualização do [18F]FDG proposta nesta tese pode alterar a maneira atual como vemos o metabolismo de glicose na DA e em outras doenças neurodegenerativas. Finalmente, nesta tese, avançamos em termos de mecanismos, e no contexto da busca por um diagnóstico precoce e acurado da DA. / Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most prevalent cause of dementia worldwide. The AD pathophysiological features have been associated to two main classic neuropathological markers: depositon of β-amyloid plaques and formation of neurofibrillary tangles of hyperphosphorylated tau. Due to AD complexity, however, additional mechanisms have been proposed as contributors to the neurodegenerative process, such as neuroinflammatory changes, altered neurotransmission, and synaptic dysfunction. These pathological events seem to precede the dementia phase by many years, resulting in a long silent period, i.e., a preclinical phase. In this thesis, we advanced in the understanding of signaling pathways associated with tau hyperphosphorylation, which includes dysfunction of protein phosphatase 2A (PP2A) and glutamatergic neurotoxicity. Furthermore, we underscored radiopharmaceuticals currently available for imaging AD pathophysiology in vivo and non-invasively with positron emission tomography (PET). Finally, we evaluated a new PET biomarker, [11C]ABP688, for visualizing glutamatergic fluctuations and advanced in the understating of how glial cells contribute to the [18F]FDG signal, the widely used radiopharmaceutical in clinical settings for visualizing cerebral glucose metabolism. Our findings have high translational value and direct impact in clinical settings, which can potentially alter the way we interpret glucose metabolism in AD and other neurodegenerative disorders. In summary, in this thesis, we have advanced in terms of molecular mechanisms, and in the use of PET biomarkers toward an early and accurate diagnosis of AD.

La maladie d’Alzheimer (MA) est une maladie neurodégénérative du système nerveux central qui se caractérise notamment par l’accumulation de peptide beta-amyloïde (Aβ) dans le tissus nerveux. Dans la première partie de cette thèse nous avons montré que l’interaction des oligomères Aβ1-42 de haut poids moléculaire avec la membrane plasmique des cellules PC12 différenciées ou des cellules nerveuses (neurones et astrocytes primaires) provoque des variations de la [Ca2+]i dépendant de l’activation des récepteurs NMDA. Dans la seconde partie nous avons montré qu’une pré-exposition des cellules PC12 et des cellules nerveuses à de faibles concentrations de peptide Aβ module l’interaction ultérieure des oligomères avec la membrane plasmique. Enfin dans le cadre d’une collaboration avec l’entreprise Innovative Health Diagnostics (IHD) nous avons participé à la caractérisation d’une sonde amyloïde fluorescente développée pour réaliser des tests de détection de la MA à partir d’échantillons sanguins. / Alzheimer’s disease (AD) is a neurodegenerative disease of the central nervous system which is characterized in particular by the accumulation of beta amyloïde peptide (Aβ) in nerve tissues. In the first part of this thesis we showed that the interaction of high molecular weight Aβ1-42 oligomers with the plasma membrane of differenciated PC12 or nerve cells (neurons and astrocytes) triggers variations of their depending on the activation of the NMDA receptors. In the second part we showed that a pre-exposure of PC12 and nerve cells with low concentrations Aβ1-42 of modulates the later interaction of oligomers with the plasma membrane. Finally in collaboration with the company Innovative Health Diagnostics (IHD) we participated in the characterization of a fluorescent amyloid probe developed to realize detection test of AD from blood samples.

Introdução: Com o envelhecimento da população mundial projeta-se o crescimento das taxas de doenças potencialmente relacionadas à idade como as demências, especialmente a doença de Alzheimer (DA). Os sujeitos com Comprometimento Cognitivo Leve (CCL) são considerados uma população de risco para desenvolver demência, no entanto, as taxas de incidência de CCL e conversão para demência apresentam considerável variabilidade em parte atribuída a características da amostra e aos diferentes critérios utilizados. Objetivos: Determinar a incidência de demência e Comprometimento Cognitivo Leve em uma coorte de idosos saudáveis de base comunitária; determinar as variáveis demográficas, clínicas e sociais associadas ao desenvolvimento de prejuízo cognitivo, e avaliar o risco de progressão dos indivíduos com Comprometimento Cognitivo Leve para demência comparada com sujeitos cognitivamente normais. Métodos: Os dados foram derivados de uma coorte de idosos residentes na comunidade (N = 345), inicialmente saudáveis e independentes (Estudo PALA - Porto Alegre Longitudinal Aging - study). O seguimento inicial com duração máxima de oito anos teve o objetivo de avaliar a incidência de DA e CCL. Para avaliar a progressão de CCL para DA partimos de 10 anos de seguimento, incluindo os oito anos da primeira análise e consideramos um máximo de 70 meses (média de 45 meses) para avaliar a ocorrência dos novos desfechos. Os participantes que preencheram os critérios de inclusão do estudo e consentiram em participar foram avaliados com uma detalhada entrevista clínica composta de variáveis demográficas, clínicas e sociais. Os sintomas psiquiátricos foram avaliados pela escala SRQ - Self Report Questionnaire, escala MADRS - Montgomery-Asberg Depression Rating Scale e aplicados os critérios para depressão maior do Manual de Diagnóstico e Estatístico de Transtornos Mentais (4ª Edição; DSM-IV). O Mini Exame do Estado Mental (MEEM) e a Escala Clínica de Demência (CDR – Clinical Dementia Rating) foram aplicados para avaliação cognitiva. Adicionalmente a independência para as atividades da vida diária foram acessadas pela escala ADL - Activities of Daily Living. Para diagnóstico dos casos incidentes de doença de Alzheimer foi utilizado os critérios diagnósticos do DSM-IV e do NINCDS/ADRDA, associado à descrição dos critérios de Kawas para DA consistente. Para diagnóstico de Comprometimento Cognitivo Leve, o critério da Clínica Mayo foi aplicado para a primeira análise, e o critério para CCL do tipo Alzheimer (ou DA prodrômica) foi utilizado para a segunda análise tendo em vista a incorporação de dados disponíveis e a evolução dos critérios. As trajetórias possíveis do CCL foram classificadas em três categorias: conversão, estabilização e reconversão. Os sujeitos considerados para a primeira análise - casos incidentes de CCL e DA foram os participantes que apresentavam pelo menos uma visita de seguimento no período de oito anos a partir da linha de base (N = 245) e as análises estatísticas foram baseadas no diagnóstico estabelecido na última visita de seguimento. Para os falecidos durante o período, dados retrospectivos foram obtidos através de uma entrevista telefônica com um informante confiável. Os dados clínicos e demográficos de linha de base foram utilizados para cálculo dos fatores preditivos dos desfechos do estudo. Para a segunda análise – risco de conversão de CCL para DA – trajetórias do CCL, a amostra foi composta dos 21 indivíduos que desenvolveram CCL e 220 indivíduos cognitivamente normais (N = 241). Resultados: Os resultados da primeira análise mostraram taxa de incidência de CCL de 13,2 por 1.000 pessoas-ano e incidência de DA de 14,8 por 1.000 pessoas-ano. O desenvolvimento de prejuízo cognitivo foi associado com educação (razão de chance [RC] = 0,86) e o escore do MEEM de base (RC = 0,81). Os resultados da segunda análise mostraram que dos 21 sujeitos com CCL, 38% desenvolveram demência, 24% permaneceram estáveis e 38% melhoraram. A taxa de conversão anual para DA foi de 8,5%, CCL foi associado significativamente a maior risco de conversão para DA (HR = 49,83; p = 0,004), mesmo ajustado para idade, escolaridade, sexo e escore no MEEM. Conclusão: A incidência de DA nessa amostra foi maior do que a descrita em estudo prévio realizado no Brasil, mas está dentro da variabilidade observada internacionalmente. Escores mais baixos no Mini Exame do Estado Mental na linha de base, mesmo que dentro da normalidade, e níveis mais baixos de educação foram preditores da ocorrência de prejuízo cognitivo. Quanto à trajetória do CCL, independentemente da heterogeneidade observada, os participantes com CCL do tipo Alzheimer apresentaram risco significativamente maior de desenvolver demência na DA, demonstrando o impacto do uso destes critérios que enfatizam o comprometimento da memória episódica de longo prazo e buscam identificar sujeitos com maior probabilidade de ser portadores de patologia Alzheimer. / Background: The increase of the rates of age-related diseases as dementia, especially Alzheimer's disease (AD), is projected with the aging of the world population. Subjects with Mild Cognitive Impairment (MCI) are considered a population at risk for developing dementia. However, MCI incidence rates and rates of conversion to dementia have shown considerable variability that could be partially attributed to characteristics of the sample and to different criteria. Objective: To determine the incidence of dementia and mild cognitive impairment in a cohort of community-based healthy elderly individuals; to determine the demographic, clinical and social variables associated with the development of cognitive impairment; and to assess the risk of progression of individuals with mild cognitive impairment to dementia compared with cognitively normal subjects. Methods: Data were derived from a cohort of elderly community residents (N = 345), who were initially healthy and independent (PALA – Porto Alegre Longitudinal Aging – study). The follow-up of a maximum of eight years was used to evaluate the incidence of AD and MCI. To evaluate the progression of MCI to dementia due to AD we set off the 10-year follow-up, including the previous 8-year of the first analysis, and consider the maximum of 70 months (mean 45 months) for these new outcomes. Participants who met the inclusion criteria of the study and consented to participate were evaluated with a detailed clinical interview consisted of demographic, clinical and social variables. Psychiatric symptoms were assessed with the SRQ scale (Self Report Questionnaire), the MADRS (Montgomery-Asberg Depression Rating Scale), and the Diagnostic and Statistical Manual of Mental Disorders (4th edition, DSM-IV) criteria for Major Depression. Cognitive assessment was checked with the Mini Mental State Examination (MMSE) and the Clinical Dementia Rating Scale (CDR). Independence for the activities of daily living was assessed with the ADL scale (Activities of Daily Living). Incident cases of probable Alzheimer's disease were assigned through the DSM-IV and the NINCDS-ADRDA diagnostic criteria, with the additional designation from Kawas and colleagues of consistent AD. Detection of Mild Cognitive Impairment for the first analysis was carried out with the MCI Mayo Clinic criteria. The MCI of the Alzheimer type criteria (or Prodromal AD) were used for the second analysis, incorporating available data of the sample and the ongoing evolution of the criteria. The possible MCI trajectories were classified into three categories: conversion, stabilization, and reconversion. The subjects for the first analysis – MCI and AD incidence – were the participants who had at least one follow-up visit in the 8-year period from the baseline (N = 245), and the statistical analyzes were based on the diagnosis established in last follow-up interview. For the deceased during the period, retrospective data were obtained through a telephone interview with a knowledgeable collateral source focusing on dementia. The baseline clinical and demographic data were analyzed as predictors of the study outcomes. For the second analysis – risk of MCI progression to AD, and MCI trajectories – the sample was composed of 21 individuals who developed MCI and 220 cognitively normal subjects (N = 241). Results: The results of the first analysis showed the MCI incidence rate of 13.2 per 1,000 person-years and the AD incidence of 14.8 per 1,000 person-years. The development of cognitive impairment was associated with education (odds ratio [OR] = 0.86) and baseline MMSE scores (OR = 0.81). The results of second analysis showed that of the 21 MCI subjects, 38% developed dementia, 24% remained stable, and 38% improved. The annual AD conversion rate was 8.5%, and MCI was significantly associated with increased risk of progression to AD (HR = 49.83; p = 0.004), even adjusted for age, education, gender and MMSE scores. Conclusion: The AD incidence in this sample was higher than that described in a previous study carried out in Brazil, but was within the international estimates. Lower baseline scores on the Mini Mental State Examination, although within the normal range, and lower levels of education were predictors of cognitive impairment. Regardless the observed heterogeneity of the MCI trajectories, participants with MCI of the Alzheimer type showed significantly higher risk of developing dementia due to AD, demonstrating the impact of the emphasis on the episodic long-term memory impairment of the criteria, which finally searches to identify those individuals more likely to have Alzheimer's pathology.

Cette thèse montre que le GHB et les neurostéroïdes protègent efficacement contre la mort neuronale induite par les facteurs étiologiques de la maladie d'Alzheimer, notamment la sur-expression de l'amyloid precursor protein et le stress oxydant. Nous avons identifié un effet additif du GHB et de l'alloprégnanolone qui pourrait résulter de la combinaison des stimulations partielles évoquées par ces molécules sur l'expression des protéines anti-apoptotiques. L'effet du GHB est bloqué par un inhibiteur de l'aromatase, suggérant que le GHB induirait la neuroprotection via la stimulation de la neurostéroïdogenèse. Pour étudier les effets du GHB et des neurostéroïdes sur l’activité des MMP-2 et MMP-9, qui dégradent les peptides amyloïdes, nous avons optimisé un test enzymatique basé sur l’expression de ces protéases dans la levure. Nos résultats préliminaires ne permettent pas encore de conclure mais leur amélioration et combinaison avec des données de RT-qPCR contribueront à déterminer l'action du GHB et des neurostéroïdes sur l'activité et/ou l'expression des MMP. Notre travail suggère que le GHB et les neurostéroïdes pourraient être associés pour élaborer des stratégies neuroprotectrices contre les pertes neuronales provoquées par la maladie d'Alzheimer. / This PhD work showed that GHB and neurosteroids efficiently protect against nerve cell death caused by Alzheimer's disease etiological factors including amyloid precursor protein overexpression and oxidative stress. Interestingly, we identified an additive action of GHB and allopregnanolone that may result from the combination of partial stimulations of anti-apoptotic protein expression induced by both compounds. GHB protective effect was blocked by aromatase inhibitor, suggesting that GHB may also induce neuroprotection via the activation of neurosteroidogenesis. Finally, we have used a yeast-based MMP activity assay to check whether GHB and neurosteroids regulate MMP-2 and MMP-9 activities which control Aβ peptide degradation. We cannot yet conclude from our preliminary results but their improvement and combination with RT-qPCR analyzes will help to determine the modulatory action of GHB and neurosteroids on MMP activity and/or expression. Together, our data suggest that GHB and neurosteroids may be used to develop combined neuroprotective strategies against neuronal loss in AD.

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.