Myricetin Attenuated MPP~+-induced Cytotoxicity By Anti-oxidation And Inhibition Of MKK4 And JNK Activation In MES23.5 Cells

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by selectively loss of dopaminergic neurons in the substantia nigra (SN), giving rise to dopamine (DA) depletion in the striatum. Although the precise pathogenic mechanism leading to neurodegeneration in PD is not known, a number of factors have been implicated in the pathogenesis of DA neuron loss. The generation of reactive oxygen species (ROS), mitochondrial dysfunction, excitotoxicity and inflammation are all considered important mediators of neuronal death in PD. It is more likely that multiple factors converge to give rise to PD than any single reason.The approaches to prevent dopamine neuron degeneration reflect the current notion on the pathogenesis of PD. Drugs directed against a single target will be ineffective and a single drug with multiple pharmacological properties maybe more suitable, in which flavonoids are considered to be the most promising candidate because of their well-reported biological properties. Myricetin is one of such flavonoids. It has many biological functions, including anti-oxidation, anti-apoptosis, free radical scavenging and anti-inflammation. Recently, several studies demonstrated the neuroprotective effects of myricetin. However, the underlying mechanisms of myricetin-mediated neuroprotection are uncertain.The aim of present study is to further explore the neuroprotective effects of myricetin on dopaminergic neurons against PD, as well as the underlying mechanisms. We conduct our experiment in vitro in MPP+-treated MES 23.5 cells, use MTT assay, Hochest staining, flow cytometry assay, Western blotting and RT-PCR methods to elucidate possible neuroprotective mechanisms of myricetin. The results were as follows:1.200μmol/L MPP+ treatment resulted in a significant decrease of cell viability (P<0.01).10-8,10-9 mol/L myricetin treatment for 24 h could attenuate these effects (P<0.05).2.200μmol/L MPP+ treatment resulted in nuclear morphological changes such as chromatin condensation and fragmentation in the MES 23.5 cells (P<0.001).10-9 mol/L myricetin treatment for 24 h could attenuate MPP+-induced chromatin condensation and fragmentation (P<0.05).3.200μmol/L MPP+treatment resulted in a reduction of the mitochondrial transmembrane potential (ΔΦm) (P<0.05). This effect was inhibited by 10-9 mol/L myricetin treatment for 24 h (P<0.05).4.200μmol/L MPP+treatment increased the production of ROS in the MES 23.5 cells (P<0.01), while 10-9 mol/L myricetin treatment for 24 h could inhibit this action (P<0.05).5.200μmol/L MPP+ treatment resulted in an increase in the activated Caspase-3 (P<0.01).10-9 mol/L myricetin treatment for 24 h could attenuate these effects (P<0.05).6.200μmol/L MPP+ treatment resulted in a significant decrease of Bcl-2 mRNA level and increase of Bax mRNA level (P<0.05), and thus decreased the Bcl-2/Bax ratio. These effects were partly restored by 10-9 mol/L myricetin treatment for 24 h (P<0.05).7.200μmol/L MPP+ treatment increased the expressions of phosphorylated MKK4 and JNK protein (P<0.01).10-9 mol/L myricetin treatment for 24 h could inhibit the effects (P<0.05).The above results suggest that myricetin protect the MPP+-treated MES23.5 cells by anti-oxidation and inhibition of MKK4 and JNK activation. The present study provides experimental evidence to explore the possible use of myricetin and may provide a alternate therapeutic strategy for the treatment of PD.