aDepartment of Biochemistry and Molecular Biology, Georgetown University Medical Center, 3900 Reservoir Road, NW, Washington, DC 20057, USA
bInstitut Henri Beaufour-IPSEN, 24 rue Erlanger, Paris 75116, France
Abstract:
Ginkgo biloba extract (EGb 761) can improve cognitive function in patients with Alzheimer's disease, but the molecular mechanisms underlying this effect remain undefined. Because free cholesterol may be involved in the production of β-amyloid precursor protein and amyloid β-peptide, key events in the development of Alzheimer's disease, we examined EGb 761 in relation to cholesterol and amyloidogenesis. In aging rats, EGb 761 treatment lowered circulating free cholesterol and inhibited the production of brain β-amyloid precursor protein and amyloid β-peptide. Exposure of PC12 cells to EGb 761 decreased the processing of β-amyloid precursor protein and abolished cholesterol-induced overproduction of this protein. Exposure of human NT2 cells to EGb 761 decreased free cholesterol influx and increased free cholesterol efflux. Our findings indicate that free circulating and intracellular cholesterol levels affect the processing of β-amyloid precursor protein and amyloidogenesis. Our findings also provide the first demonstration that EGb 761 can influence these mechanisms.