Discovery And Pharmacology Mechanism Investigation Of Drug Lead Compounds Agianst Alzheimer’s Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, which is characterized by cognitive impairment and memory dysfunction. High-risk population of AD is the aged especially the one aged65and over. In the next few years, the incidence of AD is expected to rise with the growing aging population and causes increasingly heavy burden to the families and society. The most common causative factors of this disease are suggested to be the intracellular neurofibrillary tangles composed of a hyperphosphorylated form of the microtubule-associated protein tau and extracellular neuritic plaques aggregated by β-amyloid (Aβ) peptides (Aβ40and Aβ42). Currently, no efficient compounds have been found to halt or slow down the progression of AD, while the clinical treatments offer only temporary relief.The membrane-spanning-amyloid precursor protein (APP) is sequentially cleaved into Aβ by beta-site APP-cleaving enzyme1(β-secretase, BACE1) and y-secretase. BACE1initiatively cleaves APP at the N-terminus yielding the soluble APPβ (sAPPβ) and the C-terminal membrane-bound stub of99amino acids (C99). C99is further cleaved by y-secretase to generate Aβ (Aβ40and Aβ42) and amyloid intracellular domain (AICD). Since BACE1is a rate-limiting enzyme for Aβ production, BACE1is considered as a therapeutic target for AD. Here we discovered a novel BACE1inhibitor L655,240(1-[(4-Chlorophenyl)methyl]-5-fluoro-a,a,3-trimethyl-lH-indole-2-propanoic acid) which inhibited the recombinant human BACE1activity by an IC50value of4.47+1.37μmol/L, and the surface plasmon resonance (SPR) technology based assay determined the binding affinity of L655,240to BACE1with KD of17.9±0.72μmol/L. Moreover, this compound efficiently reduced Aβ40, Aβ42and sAPPβ productions in HEK293-APPswe cells through inhibiting BACE1activity without affecting APP or BACE1expression. It was no influence on a-secratase or y-secretase activities. Our findings have provided a small molecular L655,240that can effectively decrease Ap production, thus highlighting its potential in the anti-AD drug lead compound discovery.In addition, we screened our in-house library and found a compound ACT, which could reduce Aβ content in HEK293-APPswe cells. To further investigate the related mechanism of its effect on Aβ reduction, we firstly evaluate its effect on BACE1and found that ACT could potently decrease the protein levels of BACE1in cells, which might contribute to the Aβ reduction. Besides the effect of ACT on BACE1, we also found that it could phosphorylate Raptor (Regulatory-associated protein of TOR) and inhibit mTOR (Mammalian target of rapamycin) pathway by activating AMPK (AMP-activated protein kinase) or inhibiting Akt (Protein Kinase B) and subsequently induce Ulkl dephosphorylation to activate autophagy which have indivisible relationship with Aβclearence in cells. Therefore, our findings have provided a lead compound ACT that could potently inhibit Aβ content in cells via BACE1inhibition and autophagy induction. Our work also suggests that target autophagy may be a potential anti-Aβ therapeutic strategy for AD.