Ginsenoside Rg1 improves autophagy dysfunction to ameliorate Alzheimer's disease via targeting FGR proto-oncogene

Alzheimer's disease (AD) is a neurodegeneration driven by beta-amyloid (Aβ) deposits in the brain involving autophagy dysfunction. Ginsenoside Rg1, a pharmacologically active compound found in ginseng, has possible therapeutic effects for AD. This study discovered that FGR proto-oncogene (FGR) was a therapeutic target of Rg1 in AD and it was possibly involved in autophagy. C57BL/6 J mice were injected with 5 microL (1 microg/mL) Aβ_1-42 in the right lateral ventricle to establish an AD model. AD mouse hippocampus had high FGR expression. Intragastrically administered Rg1 (40 mg/kg) decreased FGR protein levels in AD mice's hippocampus and improved memory function in AD mice. Both sides of the mice hippocampal fissure were administered with 2 microL lentiviral particles (1 × 10⁷ TU) containing FGR overexpression plasmids. FGR overexpression rendered Rg1 ineffectual in restoring memory function and reducing hippocampal neuron damage. We injected 2 microL lentiviral particles (1 × 10⁷ TU) containing short hairpin RNA plasmids targeting FGR to the mice hippocampal fissures. FGR knockdown improved spatial memory function of AD mice, reduced hippocampal neuron apoptosis, and prevented Aβ accumulation. HT22 cells were transfected with small interfering RNA targeting FGR. FGR knockdown increased the viability of Aβ_1-42 treated HT22 cells. BACE1 and LC3II/I protein levels were decreased and p62 and SIRT1 were increased in AD mice and cells with FGR knockdown. LC3 was down-regulated after inhibiting FGR expression in Aβ_1-42 treated hippocampal neurons. In conclusion, Rg1 exerts anti-AD functions by targeting FGR and downregulating its expression.