Effect of Acetylcholinesterase inhibitors on amyloid precursor protein metabolism in platelets

Alzheimer\'s disease (AD) is a neurodegenerative disease and the major cause of dementia in the elderly. The main mechanisms in AD are: extracellular aggregates of beta amyloid peptide (Abeta) and neurofibrillary tangles formation (NFT). Amyloid Precursor Protein (APP) is cleaved by the secretases alfa (ADAM10), beta (BACE1) and ? (Presenilin 1 [PSEN1]). Platelets containing 95% of the circulating APP and possess all the machinery necessary to study peripherically APP and its secretases. The search for biomarkers in AD aims to identify, in life, the pathogenic process indicators in body fluids and/or brain image methods. The aim of this study was to investigate proteins involved in APP metabolism in platelets of AD patients, and the potential modification of these pathways by treatment with Donepezil hydrochloride. Therefore, 23 patients with mild to moderate AD evaluated before and after 6 months treatment and 38 healthy elderly subjects (controls) were analyzed. Outcome variables were: (1) ADAM10, BACE1 and PSEN1 expression; (2) APP secreted metabolites expression (110 and 130kDa), allowing the APP ratio (rAPP) estimate; (3) APP-secretase ADAM10 and BACE1 enzymatic activity. Western blotting and fluorimetric methods were used. We found in AD patients pre-treatment, a decrease of rAPP compared to controls; however, we did not identify differences of this parameter after six months of treatment. The ADAM10 levels were lower in AD patients at baseline when compared to controls, however no differences were observed after treatment. Treatment was associated with a reduction of BACE1 expression in AD patients, although we have not found differences between patients and controls at baseline. PSEN1 expression was lower in pre-treatment AD patients compared to controls. No differences were observed after treatment. Concerning to BACE1 and ADAM10 enzymatic activity, we did not observe differences in pre and post-treatment. Our findings strengthen the use of platelets as a biological matrix for the APP metabolism as well as the modifying effects on AD pathogenicity of antidementia drugs (AU)