Injured neurons can initiate their own
neurotoxin-induced repair mechanisms by expressing protective genes and activating specific intracellular signal transduction pathways. Although
glial cell-derived neurotrophic factor (
GDNF) plays a key role in the repair of dopaminergic (DA) neurons, whether there is high expression of
GDNF in DA neurons at an early stage of injury has not yet been reported. In this study,
neurotoxin-induced
GDNF overexpression was detected for the first time in MES23.5 DA immortalized
neuroblastoma (MES23.5 DA) cells soon after
6-hydroxydopamine (6-OHDA) treatment. We also observed that the phosphorylation of Akt1, a member of the
protein kinase B family, was increased. Further studies showed that activated Akt1 increased the phosphorylation of the
protein phosphatase Eya1, which is a member of the eyes absent (Eya) family of transcriptional cofactors. Then, activated Eya1 decreased the phosphorylation of the sine oculis-related homeobox 2 (Six2)
transcription factor. In addition,
chromatin immunoprecipitation coupled with quantitative polymerase chain reaction (ChIP-qPCR) revealed that Six2 promoted
GDNF transcription in MES23.5 DA cells by directly binding to the
GDNF promoter. Finally, we showed that inhibiting
neurotoxin-induced
GDNF overexpression increased MES23.5 DA cell death, while promoting
GDNF expression via Six2 overexpression decreased DA neuronal death. These results suggest that MES23.5 DA cells with early 6-OHDA-induced injury can promote the overexpression of
GDNF by activating the Akt1/Eya1/Six2 signaling pathway, and this overexpression of
GDNF has protective effects on injured MES23.5 DA cells. Hence, this study highlights a new target for drug development for the treatment of
Parkinson's disease.