Protective Effect And Mechanism Of Silibinin On Mice With Parkinson’s Disease

Parkinson’s disease(PD)is a common neurodegenerative disease.In addition to the symptoms of motor dysfunction,there are also non-motor symptoms,including cognitive dysfunction,depression and anxiety,which seriously affect the life quality of PD patients.It is of great significance to explore and develop neuroprotective drugs with multiple therapeutic effects and multiple targets.Therefore,this study investigated the ameliorating effect of silibinin in motor symptoms,and non-motor symptoms including cognitive dysfunction,depression and anxiety,in PD model mice.This study provides a theoretical basis of the pharmacological study of silibinin in Parkinson’s disease.In this study,PD animal models were established by intraperitoneal injection of MPTP.Different doses of silibinin(70,140 and 280 mg/kg),the dopamine-like drug levodopa(130 mg/kg),another PD drugs menantine(3 mg/kg),imipramine(3 mg/kg)or control solvent were given by gavage.The effects of silibinin on motor dysfunction,cognitive dysfunction,depression and anxiety in PD model mice were examined by rod rotation test,pole climbing test,Morris water maze,Y maze,forced swimming test and elevated plus maze.Morphological changes of corresponding brain regions in mice were observed by Nissl staining and hematoxylin-eosin(HE)staining.The levels of tyrosine hydroxylase(TH),α-syn and mitophagy-related proteins were detected by immunohistochemical methods.The levels of neurotransmitters dopamine(DA),noradrenaline(NA)and 5-hydroxytryptophan(5-HT)were determined by ELISA.The levels of inflammation and mitochondrial function-related proteins were measured by Western-blot.In our study,the rotarod test,pole test and hang test results showed that silibinin improved the motor symptoms of PD model mice.Nissl staining and TH immunohistochemical results showed that silibinin protected dopaminergic nerves in the substantia nigra.Results from western blot and flow cytometry,glutathione peroxidase(GSH-PX)and malondialdehyde(MDA)kits and immunohistochemical staining showed that silibinin alleviated mitochondrial damage by reducing oxidative stress,inflammation and α-syn toxicity in PD mice.Then silibinin removed the damaged mitochondria by promoting mitophagy,thus protecting dopaminergic nerve and alleviating PD mouse motor dysfunction.We found that in terms of non-motor symptoms of PD,the results of water maze test,new object recognition test and Y maze test showed that silibinin improved cognitive dysfunction in PD model mice.Other assays showed that MPTP injection damaged hippocampal neurons by inducing α-syn toxicity,increasing oxidative stress,and disrupting mitochondrial homeostasis.Silibinin alleviated the apoptosis of hippocampal neurons and improved cognitive function by improving mitochondrial dynamics and reducing oxidative stress in PD mice,and had neuroprotective effects on the hippocampus of PD mice with cognitive dysfunction.In addition,open field test,elevated plus maze,tail suspension and forced swimming tests showed that silibinin relieved the symptoms of depression and anxiety in PD model mice.Other results showed that silibinin protected hippocampal neurons by reducing neuroinflammation and downregulating the STING-IRF3-IFN-β pathway,thereby alleviating the depressive and anxious-like behavior induced by MPTP in PD model mice.This study showed that silibinin improved motor symptoms,and non-motor symptoms including cognitive dysfunction,depression and anxiety,in PD model mice.It was found that silibinin improved the brain function by inhibiting the inflammation level and oxidative stress in the corresponding brain regions,promoting mitophagy,restoring mitochondrial dynamics and modulating the STING signaling pathway.This study laid a pharmacological foundation for the development of silibinin as an new anti-PD drug,and provides a strong theoretical basis for the development of drugs targeting oxidative stress-inflammation-mitophagy-mitochondrial kinetics-STING signaling pathway.