Wnt1 Promotes EAAT2 Expression and Mediates the Protective Effects of Astrocytes on Dopaminergic Cells in Parkinson's Disease.

Lei Wei,Zhengqi Lu,Jing Zou,Li Ding,Zhenze Lu,Haotian Wu,Haiyan Li,Chuan Chen,Yongqiang Dai,Pingyi Xu,Mingshu Mo

doi:10.1155/2019/1247276

Abstract

Background Wnt/β-catenin signaling has been reported to exert cytoprotective effects in a cellular model of Parkinson's disease (PD). Glutamate excitotoxicity has been suggested to contribute to the pathogenesis of PD, and excitatory amino acid transporters (EAATs) play a predominant role in clearing excessive glutamate. EAAT2 is mainly expressed in astrocytes, which are an important source of Wnt signaling in the brain. Methods Wnt1-overexpressing U251 astrocytes were indirectly cocultured with dopaminergic SH-SY5Y cells treated with 6-hydroxydopamine (6-OHDA). Cell toxicity was determined by cell viability and flow cytometric detection. Glutamate level in the culture medium was determined by enzyme-linked immunosorbent assay (ELISA). Western blot analysis was used to detect the expression of Wnt1, β-catenin, and EAAT2. Immunofluorescence was used to display the expression and translocation of NF-κB p65. Results 6-OHDA treatment significantly decreased cell viability in both U251 cells and SH-SY5Y cells, inhibited the expression of Wnt1, β-catenin, and EAAT2 in U251 cells, and increased the glutamate level in the culture medium. Coculture with Wnt1-overexpressing U251 cells attenuated 6-OHDA-induced apoptosis in SH-SY5Y cells. Overexpression of Wnt1 decreased the glutamate level in the culture media, upregulated β-catenin, EAAT2, and NF-κB levels, and promoted the translocation of NF-κB from the cytoplasm to the nucleus in U251 cells. Conclusion Wnt1 promoted EAAT2 expression and mediated the cytoprotective effects of astrocytes on dopaminergic cells. NF-κB might be involved in the regulation of EAAT2 by Wnt1.

Highlights

Parkinson’s disease (PD), characterized by the loss of dopaminergic neurons in the substantia nigra (SN), is the second most common neurodegenerative disease after Alzheimer’s disease in elderly people
Our present study demonstrated that Wnt1 levels in U251 cells were decreased after 6-OHDA treatment and that coculture with Wnt1-overexpressing U251 astrocytes attenuated the toxic effect of 6-OHDA on dopaminergic SH-SY5Y cells
Coculture with Wnt1-overexpressing U251 astrocytes could decrease the glutamate level in the culture medium

Summary

Introduction

Parkinson’s disease (PD), characterized by the loss of dopaminergic neurons in the substantia nigra (SN), is the second most common neurodegenerative disease after Alzheimer’s disease in elderly people. A wide range of studies have suggested that glutamate excitotoxicity contributes to the pathogenesis of PD and that excitatory amino acid transporters (EAATs) play a predominant role in clearing the excessive glutamate in the synaptic cleft [5]. Wnt1-overexpressing U251 astrocytes were indirectly cocultured with dopaminergic SH-SY5Y cells treated with 6-hydroxydopamine (6-OHDA). 6-OHDA treatment significantly decreased cell viability in both U251 cells and SH-SY5Y cells, inhibited the expression of Wnt, β-catenin, and EAAT2 in U251 cells, and increased the glutamate level in the culture medium. Overexpression of Wnt decreased the glutamate level in the culture media, upregulated β-catenin, EAAT2, and NF-κB levels, and promoted the translocation of NF-κB from the cytoplasm to the nucleus in U251 cells. Wnt promoted EAAT2 expression and mediated the cytoprotective effects of astrocytes on dopaminergic cells. NF-κB might be involved in the regulation of EAAT2 by Wnt

Methods

Results

Conclusion