Ginsenoside Rk1 prevents 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's disease via activating silence information regulator 3-mediated Nrf2/HO-1 signaling pathway.

Objectives: Ginsenoside Rk1, a novel ginsenoside isolated from red ginseng, has anti-inflammatory and anti-tumor activities. This study was designed to elucidate the role of RK1 in an in vitro 1-methyl-4-phenylpyridinium (MPP⁺) cell model and an in vivo 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) of Parkinson's disease (PD).Methods: The grasping test, pole-climbing test, and rotarod test were performed to measure the effects of RK1 on MPTP-induced motor disorders. The expression of tyrosine hydroxylase (TH) and IBA-1 were evaluated by western blotting. CCK-8 and flow cytometry  assays were utilized to assess cell viability and apoptosis. Reactive oxygen species (ROS), Lactate dehydrogenase (LDH), and superoxide dismutase (SOD) were detected to analyze the effects of RK1 on oxidative stress. The levels of inflammatory cytokines were evaluated by enzyme-linked immunosorbent assay (ELISA).Results: The results showed that RK1 allayed motor deficit elicited by MPTP in a mouse model. RK1 administration augmented tyrosine hydroxylase (TH) expression in the brain striatum and substantia nigra (SN) of MPTP-treated mice. Moreover, RK1 pretreatment promoted viability and suppressed apoptosis in MPP⁺-induced PC-12 cells. Further, RK1 also attenuated MPP⁺-stimulated oxidative stress and inflammatory response in PC-12 cells. Besides, RK1 augmented the level of SIRT3, and SIRT3 deletion counteracted RK1-induced repression on MPP⁺-elicited apoptosis, oxidative stress, and inflammatory response in PC-12 cells via modulating the Nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1)  pathway.Conclusions: RK1 might exert neuroprotective effects against MPP⁺/MPTP-induced neurotoxicity via activating SIRT3-mediated Nrf2/HO-1 signaling. RK1 might be a promising candidate against PD.