development of Alzheimer's disease pathology.

Brain A? is elevated in people with sporadic Alzheimer's disease. A? is the main constituent of brain parenchymal and vascular amyloid; it contributes to cerebrovascular lesions and is neurotoxic. It is unresolved how A? accumulates in the central nervous system and subsequently initiates the disease of cells. Significant efforts have been focused on the mechanisms responsible for A? production, including the proteolytic enzymes gamma- and ?-secretases