Neuroprotective Effects And Mechanisms Of Polydatin In Parkinson’s Disease Rat Model

Parkinson disease（PD）is the second most common neurodegenerative disease,with a prevalence of 2-3%of the population over 65 years of age.The death and loss of dopaminergic neurons in the substantia nigra（SNpc）and the accumulation ofα-synuclein in dopaminergic neurons are the neuropathological hallmarks of PD.The underlying molecular pathogenesis involves multiple pathways and mechanisms:α-synuclein aggregation,mitochondrial dysfunction,oxidative stress,calcium homeostasis imbalance and so on.In recent years,studies have shown that neuroinflammation mediated by microglia play an important role in the pathogenesis of PD.Microglia have specific immune surveillance functions and mediate the innate immune response to invading pathogens by secreting a variety of active substances.These active substances include cytokines,chemokines,prostaglandins,reactive oxygen species and growth factors.Studies have confirmed that the existence of over-activated microglia in the SNpc of the brain in PD patients.Over-activated microglia can release pro-inflammatory mediators to trigger neuro-inflammatory response,which leads to dopaminergic neuronal cell degeneration and death.Therefore,inhibiting the excessive activation of microglia in the midbrain region is a potential strategy to prevent and treat PD.Polydatin（PLD）is a polyphenol compound extracted from the plant Polydatin,which has anti-inflammatory,anti-oxidant,anti-tumor and anti-bacterial pharmacological effects.Studies have reported that PLD can pass through the blood-brain barrier and ameliorate motor dysfunction in various PD animal models.But the underlying molecular mechanism is unclear.According to the role of neuroinflammation induced by activated microglia in PD and the anti-inflammatory activity of PLD,we speculate that PLD may play a neuroprotective effect in PD by inhibiting the neuroinflammatory response mediated by microglia.In order to verify this hypothesis,we first explored the role and mechanism of PLD in microglia-medicated inflammation,and then explored the role and mechanism of PLD in the neuroinflammation-mediated PD rat model.In the study of LPS-activated microglia cell line BV-2 cells and primary microglia,we found that PLD significantly inhibited the neuroinflammation induced by activated microglia and the expression of pro-inflammatory mediators.In the study of molecular mechanism,we found that PLD activated the Nrf2 signaling pathway and inhibits the NF-κB signaling pathway,and up-regulates the protein expression of p-AKT,p-GSK-3β^Ser9 and Nrf2 in microglia.After pretreating with MK2206（AKT inhibitor）,NP-12（GSK-3βinhibitor）and Brusatol（Nrf2 inhibitor）in BV-2 cells,we found that PLD inhibited the activation of NF-κB signaling pathway and the release of pro-inflammatory mediators in activated BV-2 cells by activating the AKT/GSK-3β-Nrf2signal axis.After pretreating with AKT si RNA,GSK-3βsi RNA and Nrf2 si RNA in primary microglia,we found that PLD inhibited activation of NF-κB signaling pathway and release of pro-inflammatory mediators via activating the AKT/GSK-3β-Nrf2 signal axis in primary microglia.Our results showed that PLD inhibited the neuroinflammation triggered by activated microglia.In order to further explore whether PLD could play neuroprotective effect in the neuroinflammation-mediated PD rat model,we used LPS of three-dimensional brain injection to make a neuroinflammation-mediated PD rat model to explore the effect and mechanism of PLD.The experimental results show that PLD improved the behavioral motor dysfunction of PD rats,inhibited the reduction of dopamine and its metabolites,protected dopaminergic neurons and inhibited the activation of microglia and microglia–indued neuroinflammation.In the mechanism study,we found that PLD inhibited the activation of the NF-κB signal pathway via activation of the AKT/GSK-3β-Nrf2 signal axis in the PD rat model.The above results indicated that PLD inhibited neuroinflammation induced by activated microglia via activating the AKT/GSK-3β-Nrf2/NF-κB signal axis in microglia.In the PD rat model,PLD improved motor dysfunction by activating the AKT/GSK-3β-Nrf2/NF-κB signal axis,and inhibited the reduction of dopamine and its metabolites and neuroinflammation,and protected dopaminergic neurons.