Release of ?-Amyloid from High-Density Platelets
The main component of Alzheimer's disease (AD) senile plaques in the brain is amyloid-? peptide (A?), a proteolytic fragment of the amyloid precursor protein (APP). Platelets contain both APP and A? and much evidence suggests that these cells may represent a useful tool to study both amyloidogenic and nonamyloidogenic pathways of APP processing. It has been demonstrated that platelets activated by physiological agonists, such as thrombin and collagen, specifically secrete A? ending at residue 40. To verify whether APP ?-processing could be observed also in an in vitro system of highly concentrated platelets, we measured the A? released in the incubation media of 5  109 platelets/mL by enzyme-linked immunosorbent assay (ELISA). The activation status of platelets was investigated by ultrastructural analysis. We found that A?40 levels were significantly higher in incubation media of 5  109/mL platelets in comparison with 108/mL platelets (normalized values), while A?42 levels were not affected by cell density. The ultrastructural analysis showed platelets at different phases of activatio
?-amyloid platelets alzheimer's disease platelet activation cell density