Effects Of Panax Notoginseng Saponins On Oxidative Stress And Mitochondrial Autophagy In The Treatment Of AD

Objective: The purpose of this study is to investigate the changes of oxidative stress-related autophagy signaling pathways in the brains of Alzheimer’s disease model mice and to explore the mechanism of the regulation of oxidative stress-mitochondrial autophagy in the AD model mice.Methods: SAMP8 mice were randomly divided into model group,PNS high dose group(200mg/kg),PNS middle dose group(100mg/kg)PNS low dose group(50mg/kg),Huperzine A(0.3mg/ Kg),non-aged SAMR1 mice served as normal controls.After successive 8 weeks of treatment,Morris water maze was used to test mouse learning and memorizing ability.Besides,the total brain superoxide dismutase(T-SOD),glutathione peroxidase(GSH-PX),glutathione(GSH),and malondialdehyde(MDA),and 8-Hydroxydeoxyguanosine(8-OHd G)Content were also tested;Transmission electron microscopy was used to observe autophagosomes in the mouse brain;real-time fluorescence quantitative PCR was used to detect the gene expression of mouse Lc3-I,p62,Pink1,Parkin,Ndp52,Optn,App and β-actin m RNAs,and Western blot was used to detect LC3,PINK1,Parkin,NDP52,OPTN,β-actin protein expression levels in the brains of mice.Results: In the water maze test,the learning and memorizing ability of mice in the medium and low dose groups of total saponins of Panax notoginseng was significantly improved.Further observations of the antioxidant enzyme system found in animal brain tissue,the activity of GSH-PX in the cerebellum of of mice in the PNS middle and low dose groups was significantly increased(P<0.01),compared with the normal group;The contents of GSH in mice of all groups were significantly increased(P<0.01);The activity of SOD in the PNS middle dose group was significantly increased(P<0.05).At the same time,The activity of MDA in mice in each group decreased significantly(P<0.05 or P<0.01).In addition,compared with the model group,in the detection of 8-ohdg in PNS medium and low-dose group,the content of it decreased significantly(P<0.05 or P<0.01).The ultrastructure of neurons in normal control mice was normal.SAMP8 mice suffered severe structural damage from neuron to the mitochondria and dispersed endoplasmic reticulum and lysosomal bodies;the ultrastructure of neurons in mice treated with Panax notoginseng saponins tended to be normal,and Panax notoginseng total saponins Autophagosomes appeared in the low dose group.The expression of LC3 protein in brain tissue of the medium and low dose groups of total saponins of Panax notoginseng increased significantly(P<0.05).RT-qPCR result showed that: The expression of Pink1 m RNA in the brain of mice with moderate dose of PNS increased significantly(P<0.05);The expression levels of Parkin m RNA(P<0.05),Optn m RNA(P<0.05),and Ndp52 m RNA(P<0.05)in the brain tissue of the middle dose group and low dose group were significantly higher than those in the model group.Western blot result showed that: Compared with the model group,The expression level of Parkin protein(P<0.05)and OPTN protein(P<0.05)increased significantly in the medium-dose group of total saponins of Panax notoginseng.In addition,The expression level of NDP52 protein in brain tissues of each group increased significantly(P<0.01).Conclusion: 100 mg/kg or 50 mg/kg of the total saponins improved the learning and memorizing ability of dementia model mice,reduced DNA damage in brain of SAMP8 mice,enhanced the function of antioxidant enzyme system,and reduced the oxidative stress damage of nerve cells.PNS can regulate the mitochondrial autophagic homeostasis of neurons,and produce the therapeutic effect of AD by controling the downstream pathway of PINK1 of mitochondrial autophagy,especially of mitochondrial autophagy with Parkin protein.