Endoplasmic reticulum stress and apoptosis induced by manganese trigger alpha-synuclein accumulation

Abstract

Purpose: To explore whether alpha-synuclein aggregation is linked to endoplasmic reticulum (ER) stress and apoptosis induced by manganese (Mn) on CATH.a dopaminergic cell lines. Methods: Western blot analysis for the expression of 78 kDa glucose-regulated protein (GRP78), phosphorylated eukaryotic initiation factor 2 alpha (p-eIF-2 alpha), eIF2 alpha, inositol requiring enzyme 1(IRE-1 alpha), cleaved caspase-3, and C/EBP homologous protein (CHOP) was performed, including overexpression of recombinant adenovirus-mediated alpha-synuclein on CATH.a dopaminergic cell line. Results: It was observed that cell viability (p < 0.05) was significantly reduced by 250 mu M exposed for 3 h and 1,000 mu M of MnCl2 exposed for 24 h. The expression of p-elF-2 alpha, IRE-1 alpha, and GRP78 was especially induced by 1,000 mu M of MnCl2 exposed at 3, 6, and 12 h, respectively (p < 0.05). Twenty four-hour exposure of 250 uM of MnCl2 and the 3 h exposure of 1,000 uM of MnCl2 significantly induced CHOP, active caspase 3 and alpha-synuclein expression (p < 0.05). alpha-Synuclein combined with recombinant adenoviral transduction increased GRP78, IRE-1 alpha and eIF2a, CHOP and caspase 3 expression at longer times and at higher concentrations of manganese exposure on CATH.a dopaminergic cells. Conclusion: Based on these findings, Mn is a risk factor for diseases associated with alpha-synuclein accumulation. Furthermore, alpha-synuclein accumulation is associated with apoptosis via ER stress induced by Mn.