Deletion of RE1‐silencing transcription factor in striatal astrocytes exacerbates manganese‐induced neurotoxicity in mice

Abstract

Chronic manganese (Mn) overexposure causes a neurological disorder, referred to as manganism, exhibiting symptoms similar to parkinsonism. Dysfunction of the repressor element‐1 silencing transcription factor (REST) is associated with various neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, and Mn‐induced neurotoxicity, but its cellular and molecular mechanisms have yet to be fully characterized. Although neuronal REST is known to be neuroprotective, the role of astrocytic REST in neuroprotection remains to be established. We investigated if astrocytic REST in the striatal region of the mouse brain where Mn preferentially accumulates plays a role in Mn‐induced neurotoxicity. Striatal astrocytic REST was deleted by infusion of adeno‐associated viral vectors containing sequences of the glial fibrillary acidic protein promoter‐driven Cre recombinase into the striatum of RESTflox/flox mice for 3 weeks, followed by Mn exposure (30 mg/kg, daily, intranasally) for another 3 weeks. Striatal astrocytic REST deletion exacerbated Mn‐induced impairment of locomotor activity and cognitive function with further decrease in Mn‐reduced protein levels of tyrosine hydroxylase and glutamate transporter 1 (GLT‐1) in the striatum. Astrocytic REST deletion also exacerbated the Mn‐induced proinflammatory mediator COX‐2, as well as cytokines such as TNF‐α, IL‐1β, and IL‐6, in the striatum. Mn‐induced detrimental astrocytic products such as proinflammatory cytokines on neuronal toxicity were attenuated by astrocytic REST overexpression, but exacerbated by REST inhibition in an in vitro model using primary human astrocytes and Lund human mesencephalic (LUHMES) neuronal culture. These findings indicate that astrocytic REST plays a critical role against Mn‐induced neurotoxicity by modulating astrocytic proinflammatory factors and GLT‐1.

Neuron‐restrictive silencer factor/repressor element 1‐silencing transcription factor (NRSF/REST) controls spatial K+ buffering in primary cortical astrocytes

“…While Rest deletion did not affect astrocyte development or morphology, it induced a dramatic reduction of the mRNA and protein levels of GLT‐1, but not of GLAST. The diminished expression of GLT‐1 mRNA and protein that we found in our model is in full agreement with a recent report showing a positive transcriptional effect of Rest on the GLT‐1 gene through binding the two RE‐1 sites present in the GLT‐1 promoter (Pajarillo et al, 2021, 2022). Indeed, although the main action of Rest is to repress a variety of target genes, the occupancy of promoter RE‐1 sites can occasionally induce transcriptional activation (Bersten et al, 2014; Kallunki et al, 1998; Perera et al, 2015).…”

Mechanisms of manganese-induced neurotoxicity and the pursuit of neurotherapeutic strategies

“…Accordingly, REST was dysregulated in neurodegenerative diseases such as AD and PD ( Lu et al, 2014 ; Pajarillo et al, 2020a ). REST is expressed in various neural cell types, such as neurons, astrocytes, and microglia, implicating its diverse roles via different neural cells in the brain ( Pajarillo et al, 2021 ; Pajarillo et al, 2022a ). Mn decreased REST expression in dopaminergic neurons and astrocytes ( Pajarillo et al, 2021 ; Pajarillo et al, 2020a ), suggesting that impairing REST signals in neural cells might be involved in Mn toxicity mechanisms.…”

“…Moreover, Mn decreased REST expression in astrocytes, while overexpression of astrocytic REST exerted protection against Mn-induced neuronal cell toxicity by regulating inflammatory cytokines and glutamate transporter GLT-1/EAAT2 in astrocytes ( Pajarillo et al, 2021 ). Mn also reduced REST with a concomitant decrease in GLT-1 in the mouse striatum ( Pajarillo et al, 2022a ). REST has been shown to upregulate EAAT2 at the transcriptional levels by its binding to the RE1 sites of the EAAT2 promoter in astrocytes ( Pajarillo et al, 2021 ).…”

“…Conversely, downregulation of REST further decreased Mn-reduced EAAT2 in astrocytes and excitotoxic damage to dopaminergic neuronal cells in astrocyte-neuron co-culture ( Pajarillo et al, 2021 ). Deletion of astrocytic REST in the mouse striatum exacerbated Mn-reduced TH protein levels and behavioral deficits ( Pajarillo et al, 2022a ). REST’s protective mechanisms against Mn-induced neurotoxicity were also associated with repressing inflammatory cytokines ( McGann et al, 2021 ), at least in part, by its direct binding to their promoters and regulating gene expression ( McGann et al, 2021 ; Pajarillo et al, 2022a ).…”

“…Identifying the molecular targets, such as transcription factors (TFs) and intracellular proteins involved in Mn-induced neurotoxicity, could be critical for developing therapeutic strategies against Mn’s neurotoxicity. Several TFs have been found as potential molecular targets of Mn’s toxicity, namely RE1-silencing transcription factor (REST; neuron-restrictive silencer factor, NRSF) ( Pajarillo et al, 2020a ; Pajarillo et al, 2022a ), Yin Yang 1 (YY1) ( Karki et al, 2014a ; Karki et al, 2015a ), transcription factor EB (TFEB) ( Zhang et al, 2020 ) and nuclear factor erythroid 2-related factor 2 (Nrf2) ( Ijomone et al, 2022 ). Some intracellular proteins, particularly related to PD, were also dysregulated by Mn’s insults.…”