Neuroprotective Effects Of Geniposide On MPTP Induced Parkinson’s Disease In C57BL/6 Mice

Objective:Parkinson’s disease(PD)is a neurodegenerative movement disease usually affecting large numbers of people in middle to old age.The pathological characteristics of PD is related to the degeneration of the number of dopaminergic neurons in the substantia nigra and depletion of striatal dopamine.The etiology and pathogenesis of PD are still not clear.Many studies have shown that it is related to oxidative stress and cell apoptosis. Diabetes is a close connection with PD. It is known that the Diabetes people are more likely to suffer PD. So It is possible to treat PD utilizing GLP-1 receptor agonist which is used extensively in treating for diabetes.Geniposide is the main component of the Gardenia fruit and is also an agonist of GLP-1 receptor which has been proved as an effective drug for diabetic. At the same time, many studies suggest that Geniposide posses powerful neurotrophic and neuroprotective activity.Therefore, we make a hypothesis that Geniposide can protect dopaminergic neurons in substantia nigra from the Parkinson s disease in mice and we have taken some Methods to test it.To investigate the neuroprotective effects of Geniposide against MPTP induced dopaminergic(DA) toxicity and the relative mechanism.Methods:1.PD mice model were induced with MPTP.56 C57BL/6 mice were randomly divided into four treatments: the control group were injected with 0.2ml saline for each day; MPTP group were treated by MPTP with a dose of 30mg/kg; Geniposide group were treated with100mg/kg Geniposide; the treatment group(MPTP+Geniposide), Geniposide were injected in a dose of 100mg/kg after MPTP treatment. All the treatment would be received for 8consecutive days at 8:00-9:00 in the morning.Behavior effects of Geniposide were tested by Rotarod and Swimming trails.2.The number of TH positive neurons was quantified by tyrosine hydroxylase(TH)immunohistochemical analysis.3.The number of apoptosis neurons were quantified by TUNEL stain technology.4.The expression of Bcl-2、Bax、Pro-caspase3 and Cleaved-caspase3 in substantia nigra of the Parkinson s disease model mouse were detected by Western blot.Results:1.MPTP group mice manifested the abnormal behavior of Vertical tail, rigidity, tremor and bradykinesia5-10 min after MPTP injection. This phenomenon could last for 30-60 min. Rotarod and Swimming trails showed that the dropping latency and swimming score of MPTP group were significantly lower than control(P<0.01).Compared with MPTP group, Geniposide could statistically improve the behavior deficit, the dropping latency and swimming score of the treatment group were increased(P<0.01).2.Compared with the control group, MPTP decreased the number of TH-positive neurons in SNpc area(P<0.001).the number of TH-positive neurons in treatment group were significantly higher than MPTP group(P<0.001).3.For group of MPTP, the number of apoptotic neurons in SNpc area were significantly higher than the group of control(P<0.001). Compared with MPTP group,Geniposide could decrease the number of apoptotic neurons(P<0.001).4.Compared with control group, MPTP could decrease the expression of Bcl-2 and pro-caspase-3 protein(P<0.01), the expression of Bax and Cleaved-caspase3 protein were increased(P<0.01).All the effects of above were reversed by treatment with geniposide.Conclusion:1.Geniposide could significantly improve the behavior impairment and reverse the decrease of the number of TH positive neurons in midbrain nigra induced by MPTP.therefore,it suggested the neuroprotective effects of geniposide against MPTP-induced neurotoxicity.2.Geniposide could prevent the apoptosis of neurons in midbrain nigra compactai from MPTP in mice.3.Geniposide would perform an anti-apoptptic effects by which regulate with the expression of apoptosis related biomarker including Bcl-2 、 Bax 、 Pro-caspase3 、Cleaved-caspase3.