No description available.

A feature of prion disease and other protein misfolding neurodegenerative disease is the formation of amyloid plaques. Amyloid is commonly found in the brain of individuals who have died from prion disease and Alzheimer’s disease. The formation and purpose of amyloid in such diseases is poorly understood and it is not currently known whether the material is neurotoxic, neuroprotective or an artefact. Several methods are used to investigate the formation of amyloid both in vitro and in vivo. A cell free protein conversion assay has been optimised to gain insight into the protein misfolding pathway and prion infection has been introduced to a newly characterised whole brain organotypic slice culture model. Fibrillar, but not oligomeric, recombinant PrP species induce a seeding effect on amyloid formation in the protein conversion assay. Brain homogenate containing amyloid from a β-amyloid aggregation mouse model is demonstrated to have a similar effect to recombinant fibril seeds with a PrP substrate indicating a cross-seeding effect. A whole brain organotypic slice culture (BOSC) model has been developed and slices maintained in culture for up to 8 months. During this time slices remain viable with low levels of stress and thin down from 400μm to 30-50μm with morphological consequences. A prominent glial scar forms on the surface of the slice as a result of astrocyte activation and proliferation. The neuronal population decreases while the microglia have a consistent presence throughout time in culture. Replication of misfolded prion protein has been successfully demonstrated within whole BOSC following prion infection after 2 months in culture. The BOSC model represents an accessible short term in vitro model of the brain which can offer insights into protein misfolding in a complex multicellular context. Amyloid formation has been investigated in vivo using a β-amyloid misfolding mouse model following seeding with a range of recombinant protein and brain homogenate seeds. No seeding effect was observed in animals which had received intracerebral inoculations compared to control animals within the time frame of the experiment. A lack of overall amyloid within all animals at the final time point investigated suggests later time points are required for observation of seeding. The functional role of amyloid in protein misfolding neurodegenerative diseases remains unclear. From the cell free protein conversion assay oligomers do not form on the direct pathway towards amyloid in prion misfolding. BOSC provide an accessible and useful short term in vitro model which retains multiple characteristics of the brain. BOSC support replication of misfolded protein and amyloid formation therefore this model can now be utilised to investigate plaque growth and the effect of amyloid formation on surrounding cells. Results from these assays provide important information to guide future in vivo studies and aid the search for therapeutic intervention in these devastating diseases.

Alzheimer's disease (AD) is characterized by anterograde amnesia followed by a progressive decline in cognitive function. Post mortem examination of forebrain tissue from sufferers reveals the presence of extracellular amyloid-beta plaques, intracellular neurofibrillary tangles, activation of glial cells and massive neuron loss. Transgenic mice expressing mutated forms of the amyloid precursor protein (APP) and presenilin-1 (PS1) genes develop neuritic amyloid plaques, glial cell activation and memory deficits, without the formation of intracellular tangles and neurodegeneration. The mechanisms by which these transgenic mice develop mnemonic deficiencies are unclear. Gene expression of aged memory-deficient APP+PS1 mice compared with non-transgenic littermates measured by microarray and subsequent quantitative real-time PCR (qRT-PCR) analysis revealed 6 inducible immediated-early genes (IEGs) and 5 other more stably expressed plasticity-related genes (PRGs) that were significantly down-regulated in amyloid-containing hippocampus, but not down-regulated in amyloid-free cerebellum. Other genes linked to memory remained stably expressed in both regions. Analysis of forebrain AD tissue revealed that all genes measured were down-regulated presumably due to neurodegeneration, while the amyloid-free region maintained stable expression. IEG expression in APP+PS1 mice was sensitive to lower levels of amyloid. However, only in the presence of a substantially larger amyloid burden, when memory deficits reliably persist, were both PRGs and IEGs down-regulated. Importantly, we found that IEG expression was decreased in APP+PS1 mice following exposure to a novel environment, indicating that the induction of these IEGs was impaired, rather than the basal expression of resting mice. Na+/K+ ATPase, an enzyme critical for the maintenance of membrane potential, was identified as a down-regulated PRG. We found that activity of this enzyme was both impaired in the hippocampi of APP+PS1 mice and specifically inhibited by high concentrations of amyloid-beta. Na+/K+ ATPase immunostaining revealed decreased protein in the area surrounding the amyloid plaque, where dystrophic neurites were visible, indicating amyloid may disrupt ionic gradients resulting in neuritic dystrophia. These findings suggest that amyloid accumulation may result in the impairment of IEG induction and disruption of the Na+/K+ ATPase, possibly eliciting the memory loss developed in APP+PS1 mice.

The misfolding and aggregation of the beta cell hormone islet amyloid polypeptide (IAPP) into amyloid fibrils is the main pathological finding in islets of Langerhans in type 2 diabetes. Pathological assemblies of IAPP are cytotoxic and believed to contribute to the loss of insulin-producing beta cells. Changes in the microenvironment that could trigger the aggregation of IAPP are largely unknown. So is the possibility that islet amyloid can spread within or between tissues. The present thesis have explored the roles of glycosaminoglycan heparan sulfate (HS) and the novel anti-amyloid chaperone Bri2 BRICHOS domain in the assembly of IAPP amyloid and cytotoxic IAPP aggregates. Furthermore, cross-seeding as a molecular interaction between the observed connection of type 2 diabetes and Alzheimer disease has been examined. The N-terminal region of IAPP was required for binding to HS structures and induction of binding promoted amyloid formation. Interference in the HS-IAPP interaction by heparanase degradation of HS or by introducing short, soluble HS-structure fragments reduced amyloid deposition in cultured islets. Cytotoxicity induced by extracellular, aggregating IAPP was mediated via interactions with cell-surface HS. This suggests that HS plays an important role in islet amyloid deposition and associated toxicity. BRICHOS domain containing protein Bri2 was highly expressed in human beta cells and colocalized with IAPP intracellularly and in islet amyloid deposits. The BRICHOS domain effectively attenuated both IAPP amyloid formation and IAPP-induced cytotoxicity. These results propose Bri2 BRICHOS as a novel chaperone preventing IAPP aggregation in beta cells. The intravenous injection of IAPP, proIAPP or amyloid-β (Aβ) fibrils enhanced islet amyloidosis in transgenic human IAPP mice, demonstrating that both homologous- and heterologous seeding of islet amyloid can occur in vivo. IAPP colocalized with Aβ in brain amyloid from AD patients, and AD patients diagnosed with T2D displayed increased proportions of neuritic plaques, the more pathogenic plaque subtype. In conclusion, both IAPP amyloid formation and the cytotoxic effects of IAPP is dependent on interactions with HS whereas interactions with Bri2 BRICHOS is protective. Cross-seeding between Aβ and IAPP can occur in vivo and the two peptides colocalize in brain amyloid in AD patients.

Les biomarqueurs de la maladie d’Alzheimer (MA) permettraient d’identifier les processus pathologiques de la maladie plusieurs années avant l’apparition des premiers signes cliniques. Ainsi, la tomographie par émission de positons (TEP) reposant sur les radio-traceurs liant les plaques amyloïdes, a ouvert de nouvelles perspectives en matière d’identification précoce de la maladie, in vivo, très en amont des premiers symptômes. Cependant, l’utilisation de ces biomarqueurs est restée limitée à de faibles effectifs de sujets, rarement suivis au-delà de quelques mois et le coût important de ces outils nous autorise à étudier leurs performances au regard des batteries de tests cognitifs et fonctionnels dont nous disposons. L’objectif général de ce travail était d’évaluer l’intérêt de l’utilisation du TEP scanner amyloïde au sein d’une population parfaitement phénotypée de sujets âgés présentant une plainte mnésique associée ou non à des signes cliniques objectifs. Notre population d’étude était constituée de 271 participants de l’essai MAPT âgés de 70 ans et plus, sans troubles cognitifs majeurs, ayant réalisé un TEP scanner amyloïde. Dans un premier travail, nous avons comparé les caractéristiques socio-démographiques et cliniques des sujets selon la présence ou non de plaques amyloïdes et d’une atteinte de la mémoire épisodique. Dans un second travail, nous avons analysé l’association transversale entre la charge amyloïde cérébrale et les performances pour les activités instrumentales de la vie quotidienne (IADL). Enfin, dans un troisième travail, nous avons comparé l’évolution des performances pour les IADL au cours des trois années de suivi en fonction de la charge amyloïde cérébrale.Les sujets avec une charge amyloïde positive au TEP présentaient de moins bonnes performances pour les IADL que ceux ayant un scanner négatif, en dépit d’un fonctionnement cognitif comparable. La présence de plaques amyloïdes cérébrales était associée à une évolution défavorable des performances pour les IADL, malgré la prise en compte de l’âge, du groupe d’intervention dans l’essai MAPT et du génotype ApoE. Notre travail montre que la présence de plaques amyloïdes cérébrales chez des sujets ayant une plainte mnésique est systématiquement associée à une moindre capacité à réaliser les activités complexes du quotidien malgré l’absence de troubles cognitifs avérés. Néanmoins, l’absence de traitement curatif de la MA et l’incertitude quant à l’évolution à long terme des sujets asymptomatiques présentant une anomalie isolée d’un biomarqueur motivent la réalisation d’autres études longitudinales, ciblées sur les sujets les plus âgés. / The biomarkers of Alzheimer’s disease (AD) have enabled the identification of its pathological features, many years before the onset of clinical symptoms. Positon Emission Tomography (PET) using radiotracers binding the amyloid plaques has, indeed, paved the way for new perspectives. However, these biomarkers have only been studies in small populations so far, with limited follow-up. Moreover, their high costs allow us to question their performances in view of their relationship to physical and cognitive assessment instruments. The main goal of our work was to assess the interest of amyloid PET in a well-phenotyped population of elderly subjects reporting memory complaints, associated with objective cognitive impairment or not. Our studied population comprised 271 participants from the MAPT trial aged 70 and over, without major cognitive impairment, who performed amyloid PET examination. The first analysis studied the socio-demographical and clinical characteristics of individuals depending on the presence of brain amyloid deposition or episodic memory impairment. A second study examined the cross-sectional association between brain amyloid load and Instrumental Activities of Daily Living (IADL) performance. The last analysis focused of the longitudinal change in IADL abilities between amyloid positive and amyloid negative participants over the 3-year follow-up.Amyloid positive subjects showed poorer abilities in IADL compared to their amyloid negative counterparts, despite similar cognitive performance. Brain amyloid load also impacted the daily functioning of individuals over time, taking in consideration confounding factors such as age, randomization group and ApoE genotyping. These findings confirmed the relationship of brain amyloid deposition to subtle changes in IADL abilities, even in the absence of cognitive impairment. Yet, the absence of disease modifying agents as well as uncertainties regarding the long-term evolution of asymptomatic individuals showing a positive biomarker are still to be determined. Further longitudinal studies including older old participants are warranted to address these concerns.

<div><b>Rationale:</b> Focal cortical dysplasia (FCD) is a neurodevelopmental disorder that is associated with abnormal cortical development and is one of the most common drug-resistant epilepsies. The mechanistic target of rapamycin (mTOR) pathway is a highly complex pathway </div><div>associated with cell proliferation, synaptic plasticity, neuroinflammation, and cortical development. Hyperactivation of this pathway has also been implicated in hyperexcitability, seizures, and accumulation of beta-amyloid (Aβ) plaques and neurofibrillary tangles (NFT) through hyperphosphorylation of tau. Interestingly, Aβ and hyperphosphorylated tau have been reported in both rodent models and human patients of temporal lobe epilepsy (TLE) and FCD however, the mechanisms through which this occurs are still yet to be defined. Therefore, to identify the possible link between Aβ and tau pathology in FCD, we determined the spatial distribution and protein levels of Aβ and phosphorylated tau (p-tau) along with mTOR signaling </div><div>molecules. We hypothesized that there would be presence of Aβ and tau pathology as well as an increase in Aβ and p-tau protein levels that would be correlated with hyperactivation of the mTOR and GSK3 signaling pathways in tissue biopsies from human FCD patients compared to brain tissues from non-epileptic (NE) individuals.</div><div><br></div><div><b>Methods:</b> Cortical brain samples surgically resected from patients with FCD were used and compared to NE samples surgically resected from glioblastoma patients with no history of seizures or epilepsy. Immunostaining was used to determine the distribution of phosphorylation of S6 (p-S6), a marker for mTOR activation, and NeuN, a marker for neurons, along with Aβ and p-tau. Additionally, western blotting (WB) was used to determine the levels of mTOR signaling through p-S6 and GSK3 (p-GSK) along with Aβ and p-tau.</div><div><br></div><div><b>Results:</b> We found cortical dyslamination, mTOR activation, p-tau, and Aβ accumulation in cortices of patients with FCD with drug-resistant epilepsy. However, we did not find a </div><div>significant difference in the protein levels of p-S6 (p = 0.422), p-GSK3 (p = 0.947), p-tau (p = 0.649), and Aβ (p = 0.852) in cortical tissue homogenates derived from FCD patients when compared to those of NE samples. Additionally, we did not find sex differences in the protein </div><div>levels of p-S6 (p = 0.401), p-GSK3 (p = 0.331), p-tau (p = 0.935), and Aβ (p = 0.526). There was no significant correlation between age and p-S6 (p = 0.920), age and p-GSK3 (p = 0.089), age and p-tau (p = 0.956), and age and Aβ (p = 0.889). Moreover, there was no significant correlation between mTOR activation (p-S6), Aβ (p = 0.586) and p-tau (p = 0.059) nor GSK3 activation (p-GSK3), Aβ (p = 0.326), and p-tau (p = 0.715). Lastly, there was no significant correlation within the mTOR and GSK3 pathway activation within the same patients (p = 0.602).</div><div><br></div><div><b>Conclusion:</b> These data suggest that mTOR hyperactivation occurs alongside the presence of Aβ and tau pathology. However, several unknown factors such as medical and medication history may be altering the expression or suppression of these proteins. Additionally, there may be alternative pathways that crosstalk with mTOR signaling therefore influencing Aβ and tau pathology in FCD patients with drug-resistant epilepsy. Further investigation will need to be conducted to understand the detailed mechanisms through which Aβ and tau pathology occur in </div><div>FCD.</div>

Intra- und extrazelluläre ß-Amyloid-Ablagerungen (Abeta) sind ein neuropathologisches Hauptmerkmal der Alzheimerschen Demenz (AD). Aktuelle Studien belegen, dass nicht Abeta-Plaques, sondern Abeta-Oligomere die Schädigung von Synapsen und Nervenzellen verursachen und dass ihre Konzentration gut mit der Schwere der kognitiven Dysfunktion korreliert. Allerdings sind Abeta-Peptide eine heterogene Gruppe schwer wasserlöslicher Peptide mit zahlreichen C- und N-terminalen Modifikationen. Dabei hängt die Tendenz von Abeta-Peptiden Oligomeren zu bilden, ihre proteolytische Resistenz und ihr neurotoxisches Potential maßgeblich von ihrer N-terminalen Struktur ab. Abeta-Peptide, die N-terminal einen Pyroglutamyl-Laktamring (pE-Abeta) aufweisen, machen einen Hauptbestandteil der Abeta-Last in den frühen Stadien der AD aus. Diese modifizierten Abeta-Peptide aggregieren schneller als unmodifiziertes Abeta, sind gegen Proteolyse geschützt und wirken als Aggregationskeim für andere Abeta-Spezies. Das Enzym Glutaminylzyklase (QC) katalysiert die n-terminale pE-Modifikation von Abeta in vitro und in vivo und wird in Neuronenpopulationen gefunden, für die ein starker Verlust von Synapsen und Neuronen im Zusammenhang mit der AD beschrieben wurde. Diese Arbeit stellt die schichtspezifische Verteilung von QC im temporalen Kortex und der hippocampalen Formation von Alzheimerpatienten und Kontrollen vergleichend dar und zeigt einen direkten Zusammenhang zwischen der Überexpression von QC und der Vulnerabilität betreffender Neuronenpopulationen auf. Darüber hinaus bestätigen die vorgestellten Ergebnisse die These, wonach QC und pE-Abeta das Potential haben, nach axonalem Transport eine Kaskade in efferenten Hirnregionen zu initiieren, an deren Ende der Verlust von Nervenzellen steht. Diese Erkenntnisse unterstützen das Interesse an QC als Gegenstand zukünftiger Grundlagenforschung und Wirkstoffentwicklungen für die Therapie der AD.:1. Einleitung 1 1.1. Fallbeispiel 1 1.2. Epidemiologie der Alzheimerschen Erkrankung 1-2 1.3. Derzeitige Pharmakotherapie 2 1.4. Neuropathologie der Alzheimerschen Demenz 3 1.5. Amyloidprozessierung 3-5 1.6. Das Enzym Glutaminylzyklase 7-8 1.7. Fragestellung 8-9 2. Material und Methoden 10 2.1. Humanes Hirngewebe von Alzheimer- und Kontrollfällen 10-11 2.2. Anfertigung von Gefrierschnitten 11 2.3. Kresylviolett-Färbung nach Nissl 12 2.4. Immunhistochemie 12-16 2.5. Vergleich von vier Anti-QC-Antikörpern 17-18 2.6. Zählmethodik 19-22 2.7. Verwendete Hard- und Software 20 3. Ergebnisse 23 3.1. Neuronendichten der untersuchten Hirnregionen in 23-24 Alzheimer- und Kontrollgehirnen 3.2. QC-Immunreaktivitat in Alzheimer- und Kontrollgehirnen 25 3.2.1. QC-Immunreaktivität im temporalen Kortex 25-26 3.2.2. QC-Immunreaktivität im entorhinalen Kortex 27-28 3.2.3. QC-Immunreaktivität im Subikulum und Ammonshorn 29-31 3.3. Stärke der QC-Immunreaktivität in Alzheimer- und Kontrollgehirnen 32 3.3.1. Stärke der QC-Immunreaktivität im temporalen Kortex 32-33 3.3.2. Stärke der QC-Immunreaktivität im entorhinalen Kortex 34-35 3.4. Schichtspezifische Verteilung der QC-Immunreaktivität im temporalen und entorhinalen Kortex in Alzheimer- und Kontrollgehirnen 36-38 3.5. QC-Immunreaktivität der Ammonshornregionen CA1 – CA4 39-40 4. Diskussion 41 4.1. Abeta-Spezies und QC in der AD 41-42 4.2. QC im temporalen Kortex 42-44 4.3. QC im entorhinalen Kortex 44-47 4.4. QC im Hippocampus 47-49 4.5. Regionale, schichtspezifische und neuronale Verteilung von QC 49-51 4.6. Ausblick 51-53 5. Zusammenfassung (Deutsch und Englisch) 54-55 6. Literaturverzeichnis 56-65 7. Anhang 66 7.1. Färbeprotokoll für Immunhistochemie 66 7.2. Erklärung über die eigenständige Abfassung der Arbeit 67 7.3. Lebenslauf 68 7.4. Danksagung 69 / Intra- and extracellular s-amyloid (Abeta) deposits are a major neuropathological hallmark of Alzheimer\''s disease (AD). Recent studies demonstrate that Abeta oligomers rather than Abeta plaques cause severe damage of synapses and nerve cells and in addition the concentration of Abeta oligomers correlates well with the severity of cognitive dysfunction. However, Abeta peptides are a heterogeneous group of poorly water-soluble peptides with various C- and N-terminal modifications. Biophysical properties of these peptides such as their propensity to form oligomers, their proteolytic resistance and their neurotoxic potential particularly depends on their N-terminal structure. Abeta-peptides that contain a pyroglutamyl-a-lactam ring at their N-Terminus (pE-Abeta) constitute a major component of the Abeta load in the early stages of AD. These modified Abeta-peptides aggregate faster than unmodified Abeta, are protected against proteolysis and act as aggregation seed for other Abeta-species. The enzyme glutaminyl cyclase (QC)catalyzes the cyclization of Abeta to pE-Abeta in vitro and in vivo and is found in neuronal populations for which a strong loss of synapses and neurons in the context of AD is described. This thesis presents the layer-specific distribution of QC in the temporal cortex and the hippocampal formation of Alzheimer\''s patients and controls, showing a direct correlation between the overexpression of QC and the vulnerability of respective neuronal populations. Moreover, the presented results confirm the hypothesis that QC and pE-Abeta have the potential to initiate a cascade leading to the loss of nerve cells due to axonal transport and release in efferent brain regions. These findings support the interest in QC as a subject of fundamental research and future drug developments for the treatment of AD.:1. Einleitung 1 1.1. Fallbeispiel 1 1.2. Epidemiologie der Alzheimerschen Erkrankung 1-2 1.3. Derzeitige Pharmakotherapie 2 1.4. Neuropathologie der Alzheimerschen Demenz 3 1.5. Amyloidprozessierung 3-5 1.6. Das Enzym Glutaminylzyklase 7-8 1.7. Fragestellung 8-9 2. Material und Methoden 10 2.1. Humanes Hirngewebe von Alzheimer- und Kontrollfällen 10-11 2.2. Anfertigung von Gefrierschnitten 11 2.3. Kresylviolett-Färbung nach Nissl 12 2.4. Immunhistochemie 12-16 2.5. Vergleich von vier Anti-QC-Antikörpern 17-18 2.6. Zählmethodik 19-22 2.7. Verwendete Hard- und Software 20 3. Ergebnisse 23 3.1. Neuronendichten der untersuchten Hirnregionen in 23-24 Alzheimer- und Kontrollgehirnen 3.2. QC-Immunreaktivitat in Alzheimer- und Kontrollgehirnen 25 3.2.1. QC-Immunreaktivität im temporalen Kortex 25-26 3.2.2. QC-Immunreaktivität im entorhinalen Kortex 27-28 3.2.3. QC-Immunreaktivität im Subikulum und Ammonshorn 29-31 3.3. Stärke der QC-Immunreaktivität in Alzheimer- und Kontrollgehirnen 32 3.3.1. Stärke der QC-Immunreaktivität im temporalen Kortex 32-33 3.3.2. Stärke der QC-Immunreaktivität im entorhinalen Kortex 34-35 3.4. Schichtspezifische Verteilung der QC-Immunreaktivität im temporalen und entorhinalen Kortex in Alzheimer- und Kontrollgehirnen 36-38 3.5. QC-Immunreaktivität der Ammonshornregionen CA1 – CA4 39-40 4. Diskussion 41 4.1. Abeta-Spezies und QC in der AD 41-42 4.2. QC im temporalen Kortex 42-44 4.3. QC im entorhinalen Kortex 44-47 4.4. QC im Hippocampus 47-49 4.5. Regionale, schichtspezifische und neuronale Verteilung von QC 49-51 4.6. Ausblick 51-53 5. Zusammenfassung (Deutsch und Englisch) 54-55 6. Literaturverzeichnis 56-65 7. Anhang 66 7.1. Färbeprotokoll für Immunhistochemie 66 7.2. Erklärung über die eigenständige Abfassung der Arbeit 67 7.3. Lebenslauf 68 7.4. Danksagung 69

Aujourd’hui, malgré la description des mécanismes à l’origine du développement de la dépression et de la MA, aucun traitement curatif n’existe pour ces pathologies suggérant l’implication d’un autre phénomène. L’un des processus retrouvé communément dans ces pathologies est la neuroinflammation. Or pour le moment, les essais cliniques entrepris dans la MA afin de réduire la neuroinflammation n’ont pas permis d’aboutir à une amélioration significative des symptômes. L’une des raisons de cet échec serait une mauvaise fenêtre thérapeutique qui aurait pour conséquence d’exacerber les effets délétères de la neuroinflammation. Ceci met en lumière la méconnaissance de la cinétique de la neuroinflammation dans la MA. Ainsi notre travail de thèse avait pour but, d’une part, d’étudier l’impact d’anti-inflammatoires comparativement à celui d’antidépresseur dans la dépression chez la souris, et d’autre part, d’étudier l’impact de l’utilisation d’antidépresseur et d’anti-inflammatoires dans un modèle murin de MA. / Today, despite the description of the mechanisms underlying the development of depression and AD (Alzheimer’s disease), no cure exists for these diseases suggesting the involvement of another phenomenon. One of the processes commonly found in these pathologies is neuroinflammation. However, clinical trials undertaken in the AD to reduce neuroinflammation have not led to a significant improvement of symptoms. One reason for this failure could be a bad therapeutic window which would result in the increase of deleterious effects of neuroinflammation. This highlights the lack of understanding of the kinetics of neuroinflammation in AD.

Le vieillissement des populations est corrélé à l’augmentation des pathologies neurodégénératives liées à l’âge, plus particulièrement la maladie d’Alzheimer. La recherche de marqueurs précoces de la maladie ainsi que l’élaboration de nouvelles stratégies thérapeutiques constituent un enjeu de taille. Parmi les mécanismes moléculaires de la formation des plaques amyloïdes actuellement explorés, les formes oligomériques tronquées de peptide amyloïde (Aß), notamment le peptide Aß3(?pE)??42? retrouvé à des stades précoces de la maladie, joueraient un rôle déterminant. Ces travaux de thèse ont permis de montrer, dans un premier temps, que l’injection intracérébrale de ce peptide chez la souris entraîne des altérations de la mémoire de travail et des capacités d’apprentissage, associées à une accumulation d’espèces réactives dérivées de l’oxygène dans des régions cérébrales spécifiques (hippocampe et bulbes olfactifs) de ces animaux. Des essais menés in vitro sur des cultures primaires de neurones de souris montrent leur implication dans les voies apoptotiques impliquant l’activation des caspases et la cascade métabolique de l’acide arachidonique. La seconde étape de ces travaux a constitué en l’étude des effets protecteurs d’un peptide antiapoptotique d’origine endogène, l’humanine (HN) et son variant S14G (HNG). In vitro, un effet protecteur de ces peptides a été mesuré après traitement de neurones en culture par le peptide A[bêta]3?(pE)42.??? Les résultats les plus marquants résident dans les observations faites in vivo : en effet, ces peptides inhibent l’effet délétère de l’injection intracérébroventriculaire du peptide Aß3?(pE??)42?? en restaurant les performances mnésiques des animaux dans les tests comportementaux. A la lumière de ces résultats, les peptides HN pourraient constituer de nouveaux outils thérapeutiques dans le traitement ou la prévention des dommages cellulaires précoces liés à la présence des oligomères solubles du peptide Aß / Aging of population is correlated to the increase of neurodegenerative disease, more particularly Alzheimer disease. Defining early diagnostic markers and new therapeutic strategies are highly relevant. Among the molecular pathways which are currently developed, N-terminal-truncated forms of amyloid-ß (Aß) peptide have been recently suggested to play a pivotal role in the disease. Among them, Aß3(?pE)42 ?peptide is the dominant Aß species in amyloid plaques. We first investigated the effects of soluble oligomeric Aß3(pE) 42 after intracerebroventricular injection on mice learning capacities and the molecular mechanisms of in vitro neurotoxicity. Mice injected with soluble Aß3(pE) 42 displayed impaired spatial working memory and delayed memory acquisition. These cognitive alterations were associated with free radical overproduction in hippocampus and olfactory bulbs. In vitro, Aß3(pE) 42 oligomers induced a redox-sensitive neuronal apoptosis involving caspase activation and an arachidonic acid-dependent pathway. The second goal of this work was to investigate the protective effects of the apoptosis rescue endogenous peptide humanin (HN) and its S14G mutant (HNG). In vitro, we measured their inhibitory effect on neuronal death and apoptotic events resulting from soluble Ab oligomer treatment. What’s of particular interest is the in vivo restoration of soluble Aß3(pE) 42 oligomer-induced mnesic impairment. Thus, HN peptides might serve as new drug candidates for treatment or prevention of early cellular damages linked to soluble A[bêta] oligomers

Alzheimers sjukdom är en smygande neurodegenerativ demenssjukdom som främst drabbar äldre och som karakteriseras av uppkomsten av amyloidplack och neurofibriller i hjärnan. De vanligaste symptomen är demens, kognitiva problem, inbillningar och aggressivitet. Alzheimer förekommer i två olika former, presenil och senil alzheimer. Den fullständiga mekanismen bakom alzheimer är ännu okänd men två proteiner, beta-amyloid och tau, anses ligga bakom orsaken till alzheimer. Ett tredje inblandat protein som man funnit via genetisk analys är apolipoprotein E. Idag är alzheimer ett växande problem, detta i takt med att världens befolkning blir allt äldre. En problematik finns idag då den symptomatiska behandling som finns mot alzheimer anses vara otillräcklig, ett botemedel eftersträvas därför. Immunterapi är ett botemedel som man i framtiden hoppas kunna erbjuda, detta i form av ett aktivt eller passivt vaccin verksamt mot beta-amyloid. Forskning för att finna ett sådant pågår därför just nu. AN-1792 (aktivt vaccin), CAD106 (aktivt vaccin), Bapineuzumab (passivt vaccin) och Solanezumab (passivt vaccin) är fyra vaccin som har tagits fram och testats på människor. I de vaccinstudier som gjorts har motgångar stötts på men även framgångar gjorts. AN-1792 är det vaccin som visat sig vara effektivast men med svåra biverkningar medan CAD106 är det vaccin som visat sig vara mindre effektivt men säkrast. Bapineuzumab och Solanezumab visade sig däremot båda två vara overksamma. Då flera av de vaccin som framställts har varit verksamma mot amyloidplack anser forskare att ett framtida vaccin mot alzheimer är möjligt att framställa. / Alzheimer’s disease is an insidious neurodegenerative dementia disease that primarily affects elderly and is characterized by the formation of amyloid plaques and neurofibrillary tangles in the brain. The most common symptoms are dementia, cognitive problems, delusions, and aggressiveness. Alzheimer’s occurs in two forms, presenile and senile Alzheimer’s disease. The complete mechanism behind Alzheimer’s is still unknown but two proteins, beta-amyloid and tau, are considered to be behind the cause of Alzheimer’s. A third protein involved that was found through genetic analysis is apolipoprotein E. Today, Alzheimer’s is a growing problem as the world’s population is getting older. A complex of problems exists as the symptomatic treatment available against Alzheimer’s is considered to be insufficient; a cure is therefore aimed at. Immunotherapy is a cure that hopes can be offered, this in the form of an active or a passive vaccine effective against beta-amyloid. Research to find such a vaccine is therefore under progress right now. AN-1792 (active vaccine), CAD106 (active vaccine), Bapineuzumab (passive vaccine), and Solanezumab (passive vaccine) are four vaccines that have been developed and tested on humans. In the vaccine studies that have been done setbacks have been encountered but also successes have been made. AN-1792 is the vaccine proved to be effective but with severe side effects while CAD106 is the vaccine proved to be less effective but safer. Both Bapineuzumab and Solanezumab showed to be ineffective. Since several of the produced vaccines have been active against amyloid plaques scientists believes that a future vaccine against Alzheimer’s disease is possible to make.