Alzheimer’s disease is a progressive neurodegenerative disorder leading to dementia. Interestingly, AD is more prevalent in women than men, where two third of the diagnosed AD population is female. The underlying neuropathology is characterized by extracellular A𝛽 plaques and intracellular tau tangles leading to neuronal cell death. The hippocampus, the main site for learning and memory exhibits the most significant neuronal loss in AD. It is also one of the primary neurogenic niches in the adult brain. A decline of hippocampal neural stem cells is a common feature of AD indicating a defect in neurogenesis. To model AD neuropathology, a triple transgenic model of AD (3xTg) was used. We hypothesize that the defects associated with adult neurogenesis precede the onset of AD hallmarks. Our data showed that neurogenesis defects are present as early as post-natal day 5 of age in the 3xTg model of AD, well before the development of the neuropathology. The early defects were also observed in the TgCRND8 model of AD at 3 months of age. Moreover, no statistically significant difference was detected between male and female mice at 3 months and 9 months of age when investigating NSC populations. This could indicate that sex may not need to be taken in consideration in research design when investigating NSC decline in 3xTg mice. These findings are of clinical relevance, as they may identify early changes that may open opportunities for therapeutic interventions aiming at preventing or delaying neurodegeneration.

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There is an urgent need for the development of new therapeutic strategies for Alzheimer's disease (AD). The dual-specificity tyrosine phosphorylation-regulated kinase-1A (Dyrk1a) is a protein kinase that phosphorylates the amyloid precursor protein (APP) and tau and thus represents a link between two key proteins involved in AD pathogenesis. Furthermore, Dyrk1a is upregulated in postmortem human brains, and high levels of Dyrk1a are associated with mental retardation. Here, we sought to determine the effects of Dyrk1 inhibition on AD-like pathology developed by 3xTg-AD mice, a widely used animal model of AD. We dosed 10-month-old 3xTg-AD and nontransgenic (NonTg) mice with a Dyrk1 inhibitor (Dyrk1-inh) or vehicle for eight weeks. During the last three weeks of treatment, we tested the mice in a battery of behavioral tests. The brains were then analyzed for the pathological markers of AD. We found that chronic Dyrk1 inhibition reversed cognitive deficits in 3xTg-AD mice. These effects were associated with a reduction in amyloid-beta (Ab) and tau pathology. Mechanistically, Dyrk1 inhibition reduced APP and insoluble tau phosphorylation. The reduction in APP phosphorylation increased its turnover and decreased Ab levels. These results suggest that targeting Dyrk1 could represent a new viable therapeutic approach for AD.

Alzheimer's disease (AD), marked by a serious and progressive decline in cognitive abilities, is a severely debilitating disease that is becoming an increasing concern with our aging population. Defects in neurogenesis have been shown to exist in AD and aggravate the neuropathology and cognitive deficits associated with the disease. In this study, I aimed to characterize the cellular and molecular defects of neurogenesis in the triple transgenic mouse model of AD (3xTG). To do so, I first performed a detailed immunohistochemistry characterization using neurogenic markers that were quantified and analyzed in the hippocampus of control and 3xTG mice. This analysis not only revealed an overall decrease in the pool of neural stem and progenitor cells (NSPCs) in 3xTG brains, but also defects in proliferation, differentiation and a loss within the neuroblast, immature neuron and mature neuron populations. Subsequent immunohistochemistry analysis of two molecular targets, Hopx and LPAR1, involved in NSC maintenance and proliferation respectively, revealed their dysregulation in 3xTG brains, providing some indication of molecular defects underlying this loss. The neurosphere assay was next employed to assess cell-autonomous defects and fewer neurospheres were formed from cultured 3xTG NSPCs, suggesting a defect in NSPC pool expansion that is intrinsic to 3xTG NSPC function. Molecular characterization of these cultured NSPCs via qPCR revealed the upregulation of mitochondrial and fatty acid oxidation genes in 3xTG NSPCs, suggesting not only a dysregulation of metabolic functions, but also an acclimation to oxidative stress conditions. Interestingly, 3xTG NSPCs formed larger and more neurospheres when grown in galactose medium - which is used to simulate oxidative stress - relative to the control, confirming an adaptative response to oxidative stress conditions. Further characterization of these cellular defects and underlying molecular mechanisms can reveal novel therapeutic strategies for AD.

BACKGROUND: Alzheimer's disease (AD) is the most common aging-associated neurodegenerative dementia. Current epidemiological trends indicate that a rapidly aging population, in conjunction with the economic impact of AD and lack of disease-modifying agents for AD, make AD an enormous public health challenge. AD pathology has been well characterized: it consists of extracellular plaques composed of Aß protein and intraneuronal tangles of hyperphosphorylated tau protein. Genetic analyses of AD cases have identified causative mutations in the pathways of Aß protein production but these mutations are rare. Therefore environmental factors that modify AD risk are of increasing importance. One such environmental factor that has received attention recently is stress. Biomarkers of stress (i.e., plasma and urinary cortisol) are associated with increased AD risk and more precipitous AD decline. Animal models have also largely recapitulated these results: stress exacerbates the AD phenotype in several studies. One of the actions of stress hormones such as glucocorticoids, is to upregulate the activity of the 5-lipoxygenase protein (5LO). 5LO is widely expressed in the central nervous system and is responsible for producing leukotrienes from arachidonic acid. 5LO has been previously shown to positively modulate Aß production as well the phosphorylation of tau protein. Therefore, while stress is associated with increased AD vulnerability, stress hormones modulate the 5LO protein, and the 5LO protein has been shown to modulate AD pathology, but the importance of 5LO in the stress-mediated exacerbation of the AD phenotype has not yet been explored. HYPOTHESIS: The central hypothesis of this thesis is that 5LO plays a central role in the stress-mediated exacerbation of the AD phenotype. METHODS: We used the 3xTg animal system, an AD transgenic mouse model which expresses both plaques and tangles and crossed 3xTg animals with 5LO knockout mice to create 3xTg animals without 5LO (3xTg/5LO-/-). We challenged both 3xTg and 3xTg/5LO-/- animals with dexamethasone (7 d, 5mg/kg i.p.) and restraint/isolation stress (28 d, 60 min/d) in separate studies to interrogate how the stress-response to Aß, tau and fear-conditioned memory were altered by lack of 5LO in the AD context. RESULTS: In our study with dexamethasone, we found that no memory insults occurred in either 3xTg or 3xTg/5LO-/- animals as a result of a 7 d 5mg/kg dexamethasone i.p. injection challenge. We also found no elevation in brain levels of Aß after dexamethasone exposure, although 3xTg/5LO-/- animals had less Aß than 3xTg animals, a finding our group has previously published. However we found that 3xTg animals had greater phosphorylation of tau and generation of insoluble tau following dexamethasone treatment. This tau pathology was associated with elevation in GSK3ß activity. 3xTg/5LO-/- animals lacked any dexamethasone-associated advancement of tau pathology or elevation in GSK3ß activity. In our study with restraint/isolation stress, we found that 3xTg/5LO-/- animals were protected against fear-conditioned contextual and cued insult recall caused by stress found in 3xTg animals. No change in Aß was found as a function of either genotype or stress condition. As with our study with dexamethasone, we found that 3xTg animals had greater phosphorylation of tau and generation of insoluble tau following restraint/isolation stress. This tau pathology was associated with elevation in GSK3ß activity. 3xTg/5LO-/- animals lacked any restraint/isolation-associated tau pathology or GSK3ß activity. We additionally found that knockout of 5LO exerted a protective effect against restraint/isolation-mediated impairment in long-term potentiation. CONCLUSION: Our work reveals, for the first time, the importance of the 5LO protein in stress-mediated exacerbation of the AD phenotype. These data indicate that 5LO-targeted interventions could be of use in individuals vulnerable to this environmental risk factor, and more broadly, in a preventative strategy against AD. / Pharmacology

A Doença de Alzheimer é a causa mais freqüente de demência senil e os gastos com pacientes com demência já supera os de pacientes com câncer ou com doenças cardiovasculares. As lesões características dessa doença são as placas amilóides e os emaranhados neurofibrilares. A neuroinflamação também está presente na maioria dos pacientes com Alzheimer, e parece contribuir para o dano no tecido neuronal. Adicionalmente, estudos vêm demonstrando que pacientes com Alzheimer também apresentam alterações sistêmicas, e, dessas, a mais relatada é o estado pró-inflamatório em tecidos periféricos, permitindo que a Doença de Alzheimer seja estudada em um contexto neuroimunológico. Utilizando um modelo murino para a Doença de Alzheimer, o camundongo 3xTg-AD (que desenvolve ambas as patologias β-amilóide e tau), investigamos se aumento de mediadores inflamatórios também pode ser detectado nesse modelo, tanto no hipocampo (estrutura relevante para os sintomas da doença) como no sangue. Alterações cognitivas e comportamentais e a presença do precursor da proteína amilóide (APP) e/ ou peptídeo β-amilóide em estruturas cerebrais relevantes para a doença (córtex, hipocampo, subículo e amígdala) permitiram validar o camundongo 3xTg-AD como um modelo murino da Doença de Alzheimer. Análises da expressão de mediadores inflamatórios no hipocampo demonstraram que a presença de APP e/ ou peptídeo β-amilóide no cérebro não induz um estado pró-inflamatório no hipocampo ou no sangue, até os 12 meses de idade. Porém, a expressão de APP e/ ou peptídeo β-amilóide no cérebro parece induzir distúrbios sistêmicos, já que algumas alterações periféricas foram encontradas. Como a resposta ao LPS envolve tanto tecidos periféricos, como o Sistema Nervoso Central, avaliou-se os efeitos da administração periférica de LPS nesse camundongo, aos 12 meses de idade. A resposta inflamatória ao LPS diferiu entre camundongos Wild Type (grupo controle) e 3xTg-AD. No sangue, menor aumento de IL-6 e MCP-1 e maior aumento de IFN-γ foram encontrados nos camundongos 3xTg-AD. As conseqüências deste perfil de citocinas séricas no Sistema Nervoso Central foram distintas, dependendo da resposta avaliada: enquanto que a ativação do eixo HPA foi semelhante, a produção de citocinas inflamatórias no hipocampo foi atenuada. Portanto, no camundongo 3xTg-AD, a diferente resposta inflamatória ao LPS no sangue promoveu menor produção de mediadores inflamatórios no hipocampo. / Alzheimer\'s Disease is the most frequent cause of senil dementia and the costs with demented patients already exceeds that of patients with cancer or cardiovascular diseases. The characteristic lesions of this disease are amyloid plaques and neurofibrillary tangles. Neuroinflammation is also present in most of Alzheimer\'s patients, and seems to contribute to neuronal tissue damage. In addition, studies have demonstrated that patients with Alzheimer also display systemic alterations, and of those, the most reported is the pro-inflammatory state in peripheral tissues, allowing Alzheimer\'s Disease to be studied in a neuroimmunology context. Using a murine model of Alzheimer\'s Disease, the 3xTg-AD mice (which develops both amyloid-βand tau pathologies), we investigated whether enhancement of inflammatory mediators can also be detected in this model, in both hippocampus (a relevant structure for the symptoms of the disease) and in blood. Cognitive and behavioral alterations and the presence of amyloid precursor protein (APP) and/ or amyloid-β peptide in relevant brain structures for the disease (cortex, hippocampus, subiculum and amigdala) allowed the validation of 3xTg-AD mice as a murine model of Alzheimer\'s Disease. Analysis of inflammatory mediators expression in hippocampus demonstrated that the presence of APP and/ or amyloid-β peptide in the brain does not induce a pro-inflammatory state in hippocampus or in the blood, until 12 months of age. Nevertheless, APP and/or amyloid-β peptide expression in the brain seems to induce systemic disturbances, once peripheral alterations were detected. As LPS response includes both peripheral tissues and the Central Nervous System, we evaluated peripheral administration effects of LPS in these mice, at 12 months of age. The inflammatory response to LPS differed between Wild Type (control group) and 3xTg-AD. In the blood, smaller enhancement of IL-6 and MCP-1 and higher enhancement of IFN-γ were found in 3xTg-AD mice. The consequences of this serum cytokine profile on the Central Nervous System were distinct, depending on the response evaluated: while HPA axis activation was similar, production of inflammatory cytokines in hippocampus was attenuated. Therefore, in the 3xTg-AD mice, a different inflammatory response to LPS in blood promoted lesser inflammatory mediators production in hippocampus.

A Doença de Alzheimer é a causa mais freqüente de demência senil e os gastos com pacientes com demência já supera os de pacientes com câncer ou com doenças cardiovasculares. As lesões características dessa doença são as placas amilóides e os emaranhados neurofibrilares. A neuroinflamação também está presente na maioria dos pacientes com Alzheimer, e parece contribuir para o dano no tecido neuronal. Adicionalmente, estudos vêm demonstrando que pacientes com Alzheimer também apresentam alterações sistêmicas, e, dessas, a mais relatada é o estado pró-inflamatório em tecidos periféricos, permitindo que a Doença de Alzheimer seja estudada em um contexto neuroimunológico. Utilizando um modelo murino para a Doença de Alzheimer, o camundongo 3xTg-AD (que desenvolve ambas as patologias β-amilóide e tau), investigamos se aumento de mediadores inflamatórios também pode ser detectado nesse modelo, tanto no hipocampo (estrutura relevante para os sintomas da doença) como no sangue. Alterações cognitivas e comportamentais e a presença do precursor da proteína amilóide (APP) e/ ou peptídeo β-amilóide em estruturas cerebrais relevantes para a doença (córtex, hipocampo, subículo e amígdala) permitiram validar o camundongo 3xTg-AD como um modelo murino da Doença de Alzheimer. Análises da expressão de mediadores inflamatórios no hipocampo demonstraram que a presença de APP e/ ou peptídeo β-amilóide no cérebro não induz um estado pró-inflamatório no hipocampo ou no sangue, até os 12 meses de idade. Porém, a expressão de APP e/ ou peptídeo β-amilóide no cérebro parece induzir distúrbios sistêmicos, já que algumas alterações periféricas foram encontradas. Como a resposta ao LPS envolve tanto tecidos periféricos, como o Sistema Nervoso Central, avaliou-se os efeitos da administração periférica de LPS nesse camundongo, aos 12 meses de idade. A resposta inflamatória ao LPS diferiu entre camundongos Wild Type (grupo controle) e 3xTg-AD. No sangue, menor aumento de IL-6 e MCP-1 e maior aumento de IFN-γ foram encontrados nos camundongos 3xTg-AD. As conseqüências deste perfil de citocinas séricas no Sistema Nervoso Central foram distintas, dependendo da resposta avaliada: enquanto que a ativação do eixo HPA foi semelhante, a produção de citocinas inflamatórias no hipocampo foi atenuada. Portanto, no camundongo 3xTg-AD, a diferente resposta inflamatória ao LPS no sangue promoveu menor produção de mediadores inflamatórios no hipocampo. / Alzheimer\'s Disease is the most frequent cause of senil dementia and the costs with demented patients already exceeds that of patients with cancer or cardiovascular diseases. The characteristic lesions of this disease are amyloid plaques and neurofibrillary tangles. Neuroinflammation is also present in most of Alzheimer\'s patients, and seems to contribute to neuronal tissue damage. In addition, studies have demonstrated that patients with Alzheimer also display systemic alterations, and of those, the most reported is the pro-inflammatory state in peripheral tissues, allowing Alzheimer\'s Disease to be studied in a neuroimmunology context. Using a murine model of Alzheimer\'s Disease, the 3xTg-AD mice (which develops both amyloid-βand tau pathologies), we investigated whether enhancement of inflammatory mediators can also be detected in this model, in both hippocampus (a relevant structure for the symptoms of the disease) and in blood. Cognitive and behavioral alterations and the presence of amyloid precursor protein (APP) and/ or amyloid-β peptide in relevant brain structures for the disease (cortex, hippocampus, subiculum and amigdala) allowed the validation of 3xTg-AD mice as a murine model of Alzheimer\'s Disease. Analysis of inflammatory mediators expression in hippocampus demonstrated that the presence of APP and/ or amyloid-β peptide in the brain does not induce a pro-inflammatory state in hippocampus or in the blood, until 12 months of age. Nevertheless, APP and/or amyloid-β peptide expression in the brain seems to induce systemic disturbances, once peripheral alterations were detected. As LPS response includes both peripheral tissues and the Central Nervous System, we evaluated peripheral administration effects of LPS in these mice, at 12 months of age. The inflammatory response to LPS differed between Wild Type (control group) and 3xTg-AD. In the blood, smaller enhancement of IL-6 and MCP-1 and higher enhancement of IFN-γ were found in 3xTg-AD mice. The consequences of this serum cytokine profile on the Central Nervous System were distinct, depending on the response evaluated: while HPA axis activation was similar, production of inflammatory cytokines in hippocampus was attenuated. Therefore, in the 3xTg-AD mice, a different inflammatory response to LPS in blood promoted lesser inflammatory mediators production in hippocampus.

No description available.

No description available.

No description available.