The Investigation Of Urate’s Neuroprotection And Itsmechanism On6-OHDA-lesioned Rat Model Of Parkinson’s Disease

Part I Assessment the urate levels both in rats’ plasma and brain tissuesafter intraperitoneal (i.p.) injection of urateObjective: To observe temporal changes of plasma and striatal urate levels after urateinjection via intraperitoneal.Methods:70male SD rats were used and randomly divided into two treatment groups,and subject to injection for5and10consecutive days, respectively. Rats were injected (i.p.)with urate at doses of50，100，200，400mg/kg, or its vehicle twice daily. On the5th and10th day,1h after first injection, blood was sampled via caudal vein and then rats werekilled to harvest the brain tissues (striatum) to assess the urate levels.Results: It was found that at doses above200mg/kg, urate administration was able toenhance the urate levels both in plasma and striatum in a dose-dependent manner. On the5th and10th day after injection with urate at200mg/kg twice daily, the plasma urate levelincreased by52.9%(from130.1土0.46u mol/L to198.9±0.71u mol/L) and55%(from142.5±0.49u mol/L to220.8±0.58u mol/L), whereas the urate level in striatumincreased by32.3%(from6.8±0.17nmol/mg to9.0±0.18nmol/mg) and36.8%(from6.9±0.13nmol/mg to9.5±0.12nmol/mg)，respectively.Conclusion: Intraperitoneal injection of urate raises plasma and striatum urate levelsin rats. Part II The investigation of urate’s neuroprotection and itsmechanism on6-OHDA-lesioned rat model of Parkinson’s diseaseObjective: To explore the effects of urate on dopaminergic neurons in nigrostriatal pathway in the6-OHDA unilaterally lesioned rats and the underlying mechanisms.Methods:60rats in total were randomly divided into four groups (n=15for eachgroup):sham-operated group, urate treatment plus sham-operated group,6-OHDA-injectedgroup, and urate treatment plus6-OHDA-injected group. Rats were injected (i.p.) withurate or its vehicle twice daily for nve consecutive days before and after stereotaxicsurgery. On the5th day between the two injections, all rats received a unilateral stereotaxicinjection of6-OHDA or saline into the right striatum. Forepaw adjusting steps wasdhobserved at1st,2n，3rd,4th,5t week after unilateral lesion. Dopaminergic neuron andterminal degeneration were determined by immunostaining at5weeks after surgery. Thephosphorylation levels of Akt at Ser473and GSK3P at Ser9and Tyr216sites in thestriatum were examined by western blot analysis.Results: This regimen of urate was found to ameliorate the behavioral deficits,dopaminergic neuron loss as well as dopamine depletion in the nigrostriatal system.Moreover, the phosphorylation of both Akt and GSK3J3in the lesioned striata of6-OHDA-lesioned rats was dramatically reduced as compared to sham-operated rats. Thisreduction was attenuated in the parkinsonian rats receiving urate treatment.Conclusion: Urate was able to protect dopaminergic neurons in rat nigrostriatalpathway against the neurotoxicity of6-OHDA and showed that its beneficial effects maybe mediated by Akt/GSK3signaling pathway.