Synthesis And Evaluation Of Covalent Inhibitor For Aβ Induced-neurotoxicity In Alzheimer’s Disease

Alzheimer’s disease (AD) is one of the most prevalent dementia. The patients ofAD will lose their cognitive competence, spatial ability, locomotivity, and eventuallythey will die due to AD. It has been widely accepted that increased level of amyloid β(Aβ) and its aggregates play key roles in Alzheimer’s disease. Aβ can aggregate intofibril with β-sheet structure, which can induce toxicity of nerve cells. In this thesis, inorder to inhibit the formation of this toxic Aβ aggregates, a series of covalent peptideinhibitors were designed and synthesized. To the best of our knowledge, covalentstrategy used in inhibitor design has not been widely applied intoneurodegenerative diseases, nor even been reported in the research ofAlzheimer’s disease. With this covalent strategy for designing molecules, I hope thisresearch will be benefit for drug research and detective regeant development ofAlzheimer’s disease in the future.First, several covalent inhibitors for β-sheet fibrillization of Aβ weredesigned and synthesized, which contains two sectioins: one forrecognition and the other one for covalent reaction. Because of high specificityfor some peptide-interactions, I selected peptides as recognition parts ininhibitors to bind the core region of Aβ aggregation, Aβ16-20. On the otherhand, isothiocyanate group was used to covalently react with amino group oflysine and generate thiourea bond in the mimic environment of physiology.Therefore, with different recoginition parts, six covalently reactive groupmodifed peptides were synthesized and purified. After several preliminaryexperiments, it made sure that these synthesized peptides can covalently reactwith Aβ. Among these modified peptides, P9-NCS was found to have verystrong ability of inhibiting β-sheet structure formation of Aβ.Further experiments were developed for studying the covalent reactionposition of Aβ and the character of Aβ aggregation with P9-NCS. The resultsshowed that P9-NCS can specifically covalent react with the ε-amino group oflysine16in Aβ peptide and form thiourea bond. In this process, the recognitionpart of P9-NCS can specifically interact with the region of Aβ16-20, which can help isothiocyanate group react with lysine16. Thus this process can strengthenthe interaction between Aβ and its inhibitors. Otherwise, P9-NCS can preventAβ aggregation with β-sheet structure but promote amorphous aggregatesformtaion. P9-NCS can inhibit the Aβ induced neurocytoxicity as well. Butsynthesized peptides without the covalently reactive group have no such effects.Based on high specificity and stable peptide interaction, I hope this kind ofcovalent group modified peptides could be widely studied and applied in thetreatment and detection of Alzheimer’s disease in the future.