Salidroside Protection Against Oxidative Stress Injury Through the Wnt/β-Catenin Signaling Pathway in Rats with Parkinson’s Disease

BACKGROUND/AIMS: Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease, and recent studies suggested that oxidative stress (OS) contributes to the cascade that leads to dopamine cell degeneration in PD. In this study, we hypothesized that salidroside (SDS) offers protection against OS injury in 6-hydroxydopamine (6-OHDA) unilaterally lesioned rats as well as the underlying mechanism. METHODS: SDS and LiCl (activators of the Wnt/β-catenin signaling pathway) administration alone and in combination with 6-OHDA injection in rats was performed 3 days before modeling for 17 consecutive days to verify the regulatory mechanism by which SDS affects the Wnt/β-catenin signaling pathway as well as to evaluate the protective effect of SDS on PD in relation to OS in vivo. In addition, pheochromocytoma 12 (PC12) cells were incubated with 10 µmol/L SDS or LiCl alone or with both in combination for 1 h followed by a 24-h incubation with 100 µmol/L 6-OHDA to obtain in vitro data. RESULTS: In vivo the administration of LiCl was found to ameliorate behavioral deficits and dopaminergic neuron loss; increase superoxide dismutase (SOA) activity, glutathione peroxidase (GSH-Px) levels, and glycogen synthase kinase 3β phosphorylation (GSK-3β-Ser9); reduce malondialdehyde (MDA) accumulation in the striatum and the GSK-3β mRNA level; as well as elevate β-catenin and cyclinD1 mRNA and protein levels in 6-OHDA-injected rats. This SDS treatment regimen was found to strengthen the beneficial effect of LiCl on 6-OHDA-injected rats. In vitro LiCl treatment decreased the toxicity of 6-OHDA on PC12 cells and prevented apoptosis. Additionally, LiCl treatment increased SOA activity, GSH-Px levels, and GSK-3β-Ser9 phosphorylation; decreased MDA accumulation in the striatum and GSK-3β mRNA levels; as well as increased β-catenin and cyclinD1 mRNA and protein levels in 6-OHDA-treated PC12 cells. Additionally, SDS treatment increased the protective effect of LiCl on 6-OHDA-treated PC12 cells. CONCLUSION: Evidence from experimental models suggested that SDS may confer neuroprotection against the neurotoxicity of 6-OHDA in response to OS injury and showed that these beneficial effects may be related to regulation of the Wnt/β-catenin signaling pathway. Therefore, SDS might be a potential therapeutic agent for treating PD.