Abstract
Manganese (Mn)-induced neurotoxicity resembles Parkinson's disease (PD), but the mechanisms underpinning its effects remain unknown. Mn dysregulates astrocytic glutamate transporters, GLT-1 and GLAST, and dopaminergic function, including tyrosine hydroxylase (TH). Our previous in vitro studies have shown that Mn repressed GLAST and GLT-1 via activation of transcription factor Yin Yang 1 (YY1). Here, we investigated if in vivo astrocytic YY1 deletion mitigates Mn-induced dopaminergic neurotoxicity, attenuating Mn-induced reduction in GLAST/GLT-1 expression in murine substantia nigra (SN). AAV5-GFAP-Cre-GFP particles were infused into the SN of 8-week-old YY1 flox/flox mice to generate a region-specific astrocytic YY1 conditional knockout (cKO) mouse model. 3 weeks after adeno-associated viral (AAV) infusion, mice were exposed to 330 μg of Mn (MnCl2 30 mg/kg, intranasal instillation, daily) for 3 weeks. After Mn exposure, motor functions were determined in open-field and rotarod tests, followed by Western blotting, quantitative PCR, and immunohistochemistry to assess YY1, TH, GLAST, and GLT-1 levels. Infusion of AAV5-GFAP-Cre-GFP vectors into the SN resulted in region-specific astrocytic YY1 deletion and attenuation of Mn-induced impairment of motor functions, reduction of TH-expressing cells in SN, and TH mRNA/protein levels in midbrain/striatum. Astrocytic YY1 deletion also attenuated the Mn-induced decrease in GLAST/GLT-1 mRNA/protein levels in midbrain. Moreover, YY1 deletion abrogated its interaction with histone deacetylases in astrocytes. These results indicate that astrocytic YY1 plays a critical role in Mn-induced neurotoxicity in vivo, at least in part, by reducing astrocytic GLAST/GLT-1. Thus, YY1 might be a potential target for treatment of Mn toxicity and other neurological disorders associated with dysregulation of GLAST/GLT-1.
Highlights
Manganese (Mn) is an essential trace element that is naturally found in the environment and is a necessary cofactor for several enzymes that support metabolism, development, and neuronal function [1]
After mice were randomly grouped, AAV5GFAP-Cre-GFP vectors to express Cre recombinase or AAV5GFAP-GFP vectors were infused into both sides of the substantia nigra (SN) region of the mouse brain (Fig. 1A). This control vector was used to eliminate potential effects of the associated viral (AAV) vector injection itself [54]. Because this Yin Yang 1 (YY1) loxP mouse model has an insertion of loxP-flanked sequences on exon 1 of YY1 [55], AAV5-glial fibrillary acidic protein (GFAP)-Cre vectors will delete exon 1 of the YY1 gene in the Cre recombinase (Cre)-expressing astrocytes, resulting in astrocyte-specific YY1 deletion (Fig. 1B)
The results showed that Mn significantly decreased mRNA and protein levels of glutamate aspartate transporter 1 (GLAST) and glutamate transporter 1 (GLT-1) in the SN/midbrain of mice treated with the control AAV5-GFAP-GFP vectors (Fig. 8, A–D)
Summary
Manganese (Mn) is an essential trace element that is naturally found in the environment and is a necessary cofactor for several enzymes that support metabolism, development, and neuronal function [1]. The results showed that elevated Mn levels in the brain significantly decreased levels of Fe, Mn-induced increase in YY1 expression and its interaction with HDACs were attenuated by astrocytic YY1 deletion in the SN region Astrocytic YY1 deletion by Cre in the SN region of YY1-loxP mice decreased YY1 mRNA and protein levels in the midbrain (Fig. 5, B and C).
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