The Inhibition Of The Canonical Wnt Signaling Pathway In Parkinson’s Disease Models Induced By MPTP~*

Part I The establishment of Parkinson’s disease in mouse model induced by MPTPObjective:MPTP is a kind of neurotoxin which would cause neurodegeneration,and it is widely used to establish animal models of Parkinson’s disease.The purpose of this experiment was to investigate the behavior changes and dopaminergic neuron injury in mouse model of Parkinson’s disease induced by MPTP.Methods:The C57/BL6mice received intraperitoneal injection of MPTP(30mg/kg) once a day for5days to establish PD models. There were also LiCl+MPTP group and control group. Mice in LiCl+MPTP group were pretreated with LiCl(1mEq/kg, i.p., twice a day) for7days before MPTP treatment. Mice in control group received saline. Pole test was used to evaluate the motor changes in mice of different groups at1day before MPTP treatment, the5days during MPTP treatment, the following7days,the14th and21th day. The dopaminergic neuron injury was evaluated by TH immunohistochemistry.Results:Compared with the mice in control group, the mice treated with MPTP showed markedly hypoactive behavior. The pole test displayed that after treated with MPTP, the time of mice climing down the pole was significantly delayed. LiCl pretreatment could significantly improve the behavioral ability. TH immunohistochemistry showed that the number of TH-positive neurons was decreased in MPTP-treated mice compared to normal mice in control group while it was increased in LiCl preteated mice. Conclusions:Compared with the mice in control group, MPTP-treated mice show typical symptoms of PD with the number of TH-positive neurons significantly decreases. These all indicate that the mouse model of PD is successfully established. Part II Roles of the canonical Wnt signaling pathway in mouse model of Parkinson’s disease induced by MPTPObjective:Canonical Wnt signaling pathway plays an important role in modulating cell differentiation and proliferation states. The inhibition of the canonical Wnt signaling pathway in brain may cause neurondegeneration. The purpose of this study was to investigate the role of the canonical Wnt signaling pathway in mouse model of Parkinson’s disease induced by MPTP.Methods:①The C57/BL6mice received an intraperitoneal injection of MPTP (30mg/kg) once a day for5days to establish PD models. Mice in control group were treated with saline. After the last MPTP injection,mice were sacrificed at6hour,1,2,4,7,14and21days.Western blot was performed to analyze the expression of p-Ser9-GSK-3β, GSK-3β and β-catenin in the ventral midbrain, striatum and cortex of mice at different time points.②The C57/BL6mice received an intraperitoneal injection of MPTP (30mg/kg) once a day for5days to establish PD models. There were also LiCl+MPTP group and control group. Mice in LiCl+MPTP group were pretreated with LiCl(1mEq/kg, i.p., twice a day) for7days before MPTP treatment. Mice in control group were treated with saline. Western blot was also applied to analyze the expression of p-Ser9-GSK-3β, GSK-3β and β-catenin in the ventral midbrain of mice at different time points.Results:The inhibition of the canonical Wnt signaling pathway was detected in the ventral midbrain of PD mice induced by MPTP, including the decrease of p-Ser9-GSK-3β and β-catenin, which were both decreased by day0to7. After day7, the level of p-Ser9-GSK-3β and β-catenin showed a little reversion. Meanwhile, the canonical Wnt signaling pathway was not changed significantly in the striatum and cortex. LiCl pretreatment could reverse the reduction of p-Ser9-GSK-3β and β-catenin from day0to21after MPTP injection.Conclusions:The data suggestes that the inhibition of the canonical Wnt signaling pathway is detected in the ventral midbrain of PD mice induced by MPTP. PartⅢ Roles of Dickkopf-1in mouse model of Parkinson’s disease induced by MPTPObjective:To investigate the role of the canonical Wnt signaling pathway inhibitor Dickkopf-1(DKK1) in mouse model of Parkinson’s disease induced by MPTP.Methods:The C57/BL6mice received an intraperitoneal injection of MPTP(30mg/kg) once a day for5days to establish PD models. There were also LiCl+MPTP group and control group. Mice in LiCl+MPTP group were pretreated with LiCl(1mEq/kg, i.p., twice a day) for7days before MPTP treatment. Mice in control group were treated with saline. Mice were sacrificed respectively at6hour,1,2,4,7,14and21days after the last MPTP injection. Western blot was performed to analyze the expression of DKK1in the ventral midbrain of PD mice at different time points. Double-label immunofluorescence assays were adopted using tissue section prepared from ventral midbrain to show the co-expression of DKK1and TH.Results:Compared with the control group, the level of DKK1was significantly increased in mice treated with MPTP and reached the peak by day7. Pretreated with LiCl could significantly inhibit the expression of DKK1induced by MPTP. Double-label immunofluorescence assays showed that at7d after intraperitoneal injection with MPTP, DKK1was observed and expressed intensively in the substantia nigra of mice while the number of TH-positive neurons was noticeably decreased. LiCl pretreatment could improve the number of TH-positive neurons and also inhibit the expression of DKK1.Conclusions:The results suggest that DKK1is induced to express in MPTP-lesioned PD mice and it may contribute to the degeneration of dopaminergic neurons in the substantia nigra of PD mice via inhibition of the canonical Wnt signaling pathway.