Parkinsonian Toxicant Mechanisms Reveal Pathways and Biomarkers

Identification: Gerhold, David


Parkinsonian Toxicant Mechanisms Reveal Pathways and Biomarkers
David Gerhold, Zhi-Bin Tong, John Braisted, Pei-Hsuan Chu and Anton Simeonov
NIH-NCATS, Rockville MD, 20850
We propose a strategy for identifying chemicals that selectively kill dopaminergic neurons, in a search for those that cause Parkinson's disease (PD). We first compared 3 human neuronal cell models: SH-SY5Y, neural stem cells, and LUHMES immortalized dopaminergic neurons. These comparisons showed that LUHMES neurons were most sensitive to 16 of 32 putative neurotoxicants, and expressed low levels of anti-apoptotic genes BCL2 and BIRC5/Survivin.(1) We also used matrix chemical screening to identify chemical interactions to gain insights into what makes dopa-neurons sensitive to Parkinsonian toxicants.(2)  These interactions indicated that all 3 neuronal cell models were sensitized to 1-methyl-4-phenylpyridinium (MPP+) by increased mitochondrial beta-oxidation activity, and to 6-hydroxydopamine (6HD) by inhibition of glutathione synthesis; both hallmarks of oxidative stress.  These three models were also protected from 6HD by Fe2+ chelators. (2)
Focusing on LUHMES cells we studied mechanisms among chemicals known to cause Parkinsonism i.e. MPP+ and 6HD, or to increase risk for PD i.e. paraquat, rotenone, and ziram. This study identified commonalities in gene expression responses among these five toxicants using RNAseq, including CNN2, FIBIN, ELFN2, PDK4, CMKLR1, SLC30A2, and several metallothionein genes. These responses may serve as biomarkers to identify mechanistically similar toxicants. For one biomarker gene that responded dynamically to all 5 toxicants, a promoter-reporter gene construct is being engineered in LUHMES cells using the CRISPR technique. This engineered cell line will enable us to screen large chemical libraries using NCATS' quantitative high-throughput screening format in order to identify and characterize neurotoxic compounds relevant to pathomechanisms of Parkinson's disease.
  1. Tong ZB, et al. Characterization of three human cell line models for high-throughput neuronal cytotoxicity screening. J Appl Toxicol. 2017 Feb;37(2):167-180.
  2. Tong Z-B, et al. The Toxmatrix: Chemo-genomic profiling identifies interactions that reveal mechanisms of toxicity. Chem Res Toxicol. 2017 Dec 4. doi: 10.1021/acs.chemrestox.7b00290



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