Ginsenoside F1 Protects the Brain against Amyloid Beta-Induced Toxicity by Regulating IDE and NEP

Ginsenoside F1, the metabolite of Rg1, is one of the most important constituents of Panax ginseng. Although the effects of ginsenosides on amyloid beta (Aβ) aggregation in the brain are known, the role of ginsenoside F1 remains unclear. Here, we investigated the protective effect of ginsenoside F1 against Aβ aggregation in vivo and in vitro. Treatment with 2.5 μM ginsenoside F1 reduced Aβ-induced cytotoxicity by decreasing Aβ aggregation in mouse neuroblastoma neuro-2a (N2a) and human neuroblastoma SH-SY5Y neuronal cell lines. Western blotting, real-time PCR, and siRNA analysis revealed an increased level of insulin-degrading enzyme (IDE) and neprilysin (NEP). Furthermore, liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis confirmed that ginsenoside F1 could pass the blood-brain barrier within 2 h after administration. Immunostaining results indicate that ginsenoside F1 reduces Aβ plaques in the hippocampus of APPswe/PSEN1dE9 (APP/PS1) double-transgenic Alzheimer's disease (AD) mice. Consistently, increased levels of IDE and NEP protein and mRNA were observed after the 8-week administration of 10 mg/kg/d ginsenoside F1. These data indicate that ginsenoside F1 is a promising therapeutic candidate for AD.