Increased iPLA2 activity and levels of phosphorylated GSK3B in platelets are associated with donepezil treatment in Alzheimer's disease patients.

Abstract

Reduced phospholipase A2 (PLA2) activity and increased phosphorylation of glycogen synthase kinase 3B (GSK3B) participate in the production of beta-amyloid plaques and of neurofibrillary tangles, which are two neuropathological hallmarks of Alzheimer's disease (AD). Experimental evidences suggest a neuroprotective effect of the cholinesterase inhibitor donepezil in the treatment the disease. The aims of the present study were to evaluate in AD patients the effects of treatment with donepezil on PLA2 activity and GSK3B level. Thirty patients with AD were treated during 6 months with 10 mg daily of donepezil. Radio-enzymatic assays were used to measure PLA2 activity and Elisa assays for GSK3B level, both in platelets. Before treatment and after 3 and 6 months on donepezil, AD patients underwent a cognitive assessment and platelet samples were collected. Values were compared to a healthy control group of 42 sex- and age-matched elderly individuals. Before treatment, iPLA2 activity was lower in patients with AD as compared to controls (p < 0.001). At baseline, no differences were found in GSK3B level between both groups. After 3 and 6 months of treatment, we found a significant increase in iPLA2 activity (p = 0.015 and p < 0.001, respectively). iPLA2 increment was related to the cognitive improvement during treatment (p = 0.037). After 6 months, we found an increase in phosphorylated GSK3B (p = 0.02). The present findings suggest two possible mechanisms by which donepezil delays the progression of AD. The increment of iPLA2 activity may reduce the production of beta-amyloid plaques, whereas the phosphorylation of GSK3B inactivates the enzyme, reducing thus the phosphorylation of tau protein.