Ginsenosides Decrease β-Amyloid Production via Potentiating Capacitative Calcium Entry

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disorder characterized by extracellular amyloid plaques composed of amyloid beta-peptide (A beta). Studies have indicated that Ca2+ dysregulation is involved in AD pathology. It is reported that decreased capacitative Ca2+ entry (CCE), a refilling mechanism of intracellular Ca2+, resulting in increased A beta production. In contrast, constitutive activation of CCE could decrease A beta production. Panax ginseng Meyer is known to enhance memory and cognitive functions in healthy human subjects. We have previously reported that some ginsenosides decrease A beta levels in cultured primary neurons and AD mouse model brains. However, mechanisms involved in the A beta-lowering effect of ginsenosides remain unclear. In this study, we investigated the relationship between CCE and A beta production by examining the effects of various ginsenosides on CCE levels. A beta-lowering ginsenosides such as Rk1, Rg5, and Rg3 potentiated CCE. In contrast, ginsenosides without A beta-lowering effects (Re and Rb2) failed to potentiate CCE. The potentiating effect of ginsenosides on CCE was inhibited by the presence of 2-aminoethoxydiphenyl borate (2APB), an inhibitor of CCE. 2APB alone increased A beta 42 production. Furthermore, the presence of 2APB prevented the effects of ginsenosides on A beta 42 production. Our results indicate that ginsenosides decrease A beta production via potentiating CCE levels, confirming a close relationship between CCE levels and A beta production. Since CCE levels are closely related to A beta production, modulating CCE could be a novel target for AD therapeutics.