The Protective Effects Of Salidroside On Dopaminergic Neurons In MPTP-iduced Mouse Model Of Parkinson’s Disease

Objectives To observe the impacts of salidroside(Sal)on the expression of tyrosine hydroxylase(TH),NADPH oxidase,AngⅡ,AT1 in the substantia nigra of Parkinson’s disease(PD)model mice,and investigate the possible neuroprotective mechanism of Sal on dopaminergic(DA)neurons.Methods 123 male C57/BL mice were randomly divided into 3 groups,with 41 mice in each group.The control group: mice were intraperitoneally injected with normal saline for 7 days(once a day);The model group: mice were intraperitoneally injected with MPTP for 7 days(30mg/kg/d);The Sal group: mice were intraperitoneally administration of MPTP(30mg/kg/d)followed by intraperitoneal injection of Sal(50mg/kg/d)an hour later for 7 days.The behavioral changes of the mice in each group were observed,and their exercise capacity was measured via pole test.Immunohistochemistry methods were used to analyze the positive expression of TH and NOX2 in the SN,and western blotting methods were used to test the expression level of TH,AngⅡ,AT1 and NOX2 in the SN.Assay kit was used to test the levels of SOD,ROS and MDA.Results 1 Compared with the control group,mice in the model group showed PD-like typical symptoms,such as gait instability,erecting tail,static tremor,and slowness in autonomic activity.With the increasing times of drug administration,these symptoms were more obvious in the model group.The results of pole test showed that the score of the model group was significant lower than that ofthe control group(8.24±0.54 vs 3.73±0.51,P<0.01),indicating the prolonged crawling time and the decreased coordination ability of motion balance in the model group.The behavioral symptoms were alleviated in mice of the Sal group.The pole test results showed that the score in the Sal group were significantly increased than that of the model group(3.37±0.51 vs 5.96±1.07,P<0.01),indicating that the ability of movement balance and coordination of mice in the Sal group was improved by Sal treatment.2 Compared with mice in the control group,mice in the model group showed significant increase in the expression of NOX2(10.09±1.10 vs 60.01±7.45,P<0.01),and significant decrease in the expression of TH(120.73±15.04 vs 46.93±12.59,P < 0.01).The results of western blotting displayed the model group possessed a significant lower expression of TH(1.68±0.075 vs 0.55±0.118,P<0.01),and higher expressions of AngⅡ(0.60±0.051 vs 0.80±0.071,P<0.01),AT1(0.18±0.014 vs 0.36±0.015,P<0.01)and NOX2(0.41±0.03 vs 1.04±0.07,P<0.01)than the control group.The results of assay kit showed SOD of in SN was expressed at significantly lower level(123.15±13.33 vs 85.96±13.22,P<0.01)in model group than in the control group,but ROS(47.74±7.88 vs 102.88±11.22,P<0.01)and MDA(0.85±0.088 vs 1.30±0.081,P<0.01)was expressed at significantly higher level,which indicated administration of MPTP regulated the expression levels of AT1 receptor,NOX2,SOD,ROS and MDA,further caused oxidative stress damage to SN and finally led to DA neurons degeneration.3 The results of immunohistochemistry exhibited the Sal group possessed a significant higher expression of TH(46.93±12.59 vs 76.03±18.02,P<0.01),and a significant lower expression of NOX2(60.01±7.45 vs 35.05±5.49,P<0.01)than the model group.The results of western blotting indicated TH(0.55±0.118 vs 1.02±0.085,P<0.01)and AngⅡ(0.80±0.071 vs 1.08±0.128,P<0.01)of in SN was expressed at significantly higher level,and AT1 receptor(0.36±0.015 vs 0.26±0.028,P<0.01)and NOX2(1.04±0.07 vs 0.69±0.05,P<0.01)were expressed at significantly lower levels in the Sal group than in the model group.The results of assay kit displayed the level of SOD(85.96±13.22 vs 100.74±11.53,P<0.01)was significantly increased in the Sal group as compared to the model group,whereas the levels of ROS(102.88±11.22 vs 68.86±8.04,P<0.01)and MDA(1.30±0.081 vs 1.04±0.079,P<0.01)were significantly decreased,which indicated Sal treatment controlled the expression of AngⅡ-AT1 axis in RAS and generation of NOX2,ROS and MDA,further counteracted oxidative stress damage,and finally exerted the effects of protecting DA neurons.Conclusions Sal treatment can regulate the expresstion of AngⅡ-AT1 axis in brain RAS,affect the activity of NADPH oxidase,reduce the generation of ROS,and finally exert the neuroprotective effects on DA neurons.