Manganese-Induced Neurotoxicity and Alterations in Gene Expression in Human Neuroblastoma SH-SY5Y Cells

Abstract

Manganese (Mn) is an essential trace element required for many physiological functions including proper biochemical and cellular functioning of the central nervous system (CNS). However, exposure to excess level of Mn through occupational settings or from environmental sources has been associated with neurotoxicity. The cellular and molecular mechanism of Mn-induced neurotoxicity remains unclear. In the current study, we investigated the effects of 30-day exposure to a sub-lethal concentration of Mn (100 μM) in human neuroblastoma cells (SH-SY5Y) using transcriptomic approach. Microarray analysis revealed differential expression of 1057 transcripts in Mn-exposed SH-SY5Y cells as compared to control cells. Gene functional annotation cluster analysis exhibited that the differentially expressed genes were associated with several biological pathways. Specifically, genes involved in neuronal pathways including neuron differentiation and development, regulation of neurogenesis, synaptic transmission, and neuronal cell death (apoptosis) were found to be significantly altered. KEGG pathway analysis showed upregulation of p53 signaling pathways and neuroactive ligand-receptor interaction pathways, and downregulation of neurotrophin signaling pathway. On the basis of the gene expression profile, possible molecular mechanisms underlying Mn-induced neuronal toxicity were predicted.

Early postnatal manganese exposure causes arousal dysregulation and lasting hypofunctioning of the prefrontal cortex catecholaminergic systems

“…Alternatively, or in addition, these lasting protein level changes may be mediated via epigenetic mechanisms, given that expression of several of them (e.g., TH, D2, DAT, and NET) are in part epigenetically regulated via DNA methylation (Archer, Berman, & Blum, ; Day et al, ; Groleau et al, ; Hillemacher et al, ) . This latter suggestion is supported by several studies in human neuroblastoma SH‐SY5Y cells showing that Mn exposure led to hypermethylated TH promoter and down‐regulated TH gene transcription (Gandhi, Sivanesan, & Kannan, ; Tarale et al, ). Recent evidence has also shown that TH expression can be mediated in part by the activity of c‐RET kinase, and that human neuroblastoma cells exposed to 30 µM Mn experienced a c‐RET mediated reduction in TH (Kumasaka et al, ).…”

Transcriptome Analysis Reveals Distinct Responses to Physiologic versus Toxic Manganese Exposure in Human Neuroblastoma Cells

“…Previously microarray analysis of human SH-SY5Y cells in response to 100 μM Mn for 30 days demonstrated upregulation of apoptotic pathways which was interpreted to be a causative mechanism for Mn-dependent chronic neuronal toxicity (Gandhi et al, 2018). Although information on the intracellular Mn concentration was not available (Gandhi et al, 2018), the Mn treatment probably resulted in higher accumulation than the 5-h treatment with 100 μM Mn that we used. Because we performed measurements before cell death was observed, the transcriptomic responses do not reflect immediate cell death.…”

Mechanism of Manganese Dysregulation of Dopamine Neuronal Activity

“…1). Lower concentrations of 10 and 30 mM are within the normal range of intracellular manganese (Bowman and Aschner, 2014), whereas 100 mM falls within the pathologic range (Gandhi et al, 2018). Acute exposure to manganese increased the spontaneous firing frequency and suppressed the amplitude of APs (red arrows) in a concentration-dependent manner.…”