The MT1G Gene in LUHMES Neurons Is a Sensitive Biomarker of Neurotoxicity
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ORIGINAL ARTICLE
The MT1G Gene in LUHMES Neurons Is a Sensitive Biomarker of Neurotoxicity Zhi-Bin Tong 1 & John Braisted 1 & Pei-Hsuan Chu 1 & David Gerhold 1 Received: 30 April 2020 / Revised: 19 July 2020 / Accepted: 10 August 2020 # This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2020
Abstract Identification of toxicants that underlie neurological diseases is a neglected area awaiting a valid strategy to identify such toxicants. We sought biomarkers that respond to known neurotoxicants in LUHMES immortalized neurons and evaluated these biomarkers for use in screening libraries of environmental toxicants. LUHMES immortalized human dopaminergic neurons were surveyed by RNA sequencing following challenge with parkinsonian toxicants rotenone, 6-hydroxydopamine, MPP+, and ziram (zinc dimethyldithiocarbamate; Zn2+DDC2), as well as additional toxicants paraquat, MS275, and methylmercury. The metallothionein gene MT1G was the most dynamic gene expression response to all seven toxicants. Multiple toxicants also increased transcripts for SLC30A1 and SLC30A2 zinc secretion transporters, the SLC7A11 xCT cystine/glutamate antiporter important for glutathione synthesis, DNA damage inducible transcript 3 (DDIT3), and secreted growth factors FIBIN and CXCL12, whereas several toxicants decreased expression of the apelin growth factor (APLN). These biomarker genes revealed stress responses to many toxicants at sub-cytotoxic concentrations. Since several of these biomarker genes and prior neurological disease studies implicated disruption of metal distribution, we tested metal chelator thiram (dimethyldithiocarbamate, DDC), ziram, and several other metals and metal chelates for cytotoxicity and induction of MT1G expression. Metals and chelators that caused dynamic increases in MT1G expression also caused cytotoxicity, except Ni2+DDC2 induced MT1G at 5 μM, but lacked cytotoxicity up to 100 μM. These results bolster prior work suggesting that neurons are characteristically sensitive to depletion of glutathione or to disruption of cellular metal distribution and provide biomarkers to search for such neurotoxicants in chemical libraries. Keywords Dopaminergic neurons . LUHMES . Metallothionein . MT1G . Metal metabolism . Chelator
Introduction Neurodegenerative diseases are characterized by the death of mature neurons. Although Alzheimer’s disease (AD) is primarily a genetic disease, other neurodegenerative diseases appear to have a large environmental component such as Parkinson’s disease (PD), amyotrophic lateral sclerosis, and frontotemporal dementia (Tanner et al. 2014). Research on AD and PD has focused on preventing accumulation of Aβ Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12640-020-00272-3) contains supplementary material, which is available to authorized users. * David Gerhold [email protected] 1
Division of Preclinical Innovation, National Center for Advancing Translational Sciences (NCATS), Na
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