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Membranes biomimétiques pour la caractérisation de nouveaux agents thérapeutiques : application à la maladie d'Alzheimer

Abstract : The study of molecular interactions at the level of biological membranes is a key issue for the screening and the development of new drugs. Alzheimer's disease (AD) is the most common form of senile dementia in the world and is the leading socio-economic problem in health care. The appearance and progression of this neurodegenerative disease are associated with the aggregation of the amyloid-β peptide (Aβ). A therapeutic strategy against AD consists in the development of molecules able to interfere with specific steps of Aβ aggregation. To identify such compounds, experimental methods are required to monitor and characterize the Aβ peptide during its fibrillation process. These methods must be simple enough to remain compatible with drug discovery. In this PhD project, we have proposed to combine experimental methods to allow a multiparametric characterization of potential Aβ1-42 fibrillation modulators, by integrating liposomes of defined composition as biomimetic neuronal membranes. It is indeed established that neuronal lipids are an important factor in the formation of amyloid fibers and their toxicity. The liposomes were formulated by the lipid film rehydration method, and their physicochemical properties characterized by NMR, DLS, ζ potential. The experimental determination of the compounds partition coefficient could be carried out by spectrophotometry, including in an original way, by fluorescence, these liposomes, in miniaturized tests. Kinetic studies of Aβ1-42 peptide aggregation were performed in the presence of liposomes.The ThT fluorescence was monitored to follow the Aβ peptide fibrillation pathway, used in its wild form or with an oligomeric mutant, oG37C. A fluorophore leakage analysis from liposomes, supported by DLS measurements, was performed to evaluate the impact of peptide/membranes interactions to predict any destabilization effects. The toxic fibers formed by Aβ being mainly organized in β-sheets, the data were correlated with the analysis of the peptide secondary structure by ATR-FTIR spectroscopy. After the implementation of this approach on different model molecules and a hit of potential interest in the AD treatment, all of this work has resulted in a multiparametric test allowing the molecules/Aβ/membranes interactome characterization and the discrimination of Aβ1-42 peptide aggregation modulators. This approach may be advantageously transposed to other amyloid diseases.
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Willy Smeralda. Membranes biomimétiques pour la caractérisation de nouveaux agents thérapeutiques : application à la maladie d'Alzheimer. Médecine humaine et pathologie. Normandie Université, 2019. Français. ⟨NNT : 2019NORMC419⟩. ⟨tel-02870883⟩

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