The secreted glycoprotein Dickkopf-1 (Dkk1), an antagonist of the Wnt/β-catenin pathway, has been implicated in many neurodegenerative diseases. However, it is unknown whether Dkk1 is involved in the pathogenesis of Parkinson's disease (PD). In this study, we discovered that Dkk1 was induced in MPP(+)-treated PC12 cells and the increase of Dkk1 preceded PC12 cell loss. RhDkk1 aggravated the neurotoxicity of MPP(+) in PC12 cells. Furthermore, the level of Dkk1 was correlated with the number of apoptotic PC12 cells. The apoptosis could be decreased by Dkk1-siRNA in MPP(+)-induced PC12 cells and Dkk1-siRNA regulated the expression of β-catenin and p-Ser9-GSK-3β in MPP(+)-induced PC12 cells. LiCl (an inhibitor of GSK-3β) also rescued the loss of PC12 cell viability and the apoptosis induced by MPP(+). These data suggest that the induction of Dkk1 contributes to the MPP(+)-induced neurotoxicity in PC12 cells via inhibition of the canonical Wnt pathway and Dkk1 antagonists which could rescue the Wnt pathway might be neuroprotective in PD.
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