Methylmercury can induce Parkinson’s-like neurotoxicity similar to 1-methyl-4- phenylpyridinium: A genomic and proteomic analysis on MN9D dopaminergic neuron cells

Abstract

Exposure to environmental chemicals has been implicated as a possible risk factor for the development of neurodegenerative diseases. Our previous study showed that methylmercury (MeHg) exposure can disrupt synthesis, uptake and metabolism of dopamine similar to 1-methyl-4- phenylpyridinium (MPP+). The objective of this study was to investigate the effects of MeHg exposure on gene and protein profiles in a dopaminergic MN9D cell line. MN9D cells were treated with MeHg (1-5 μM) and MPP+ (10-40 μM) for 48 hr. Real-time PCR Parkinson’s disease (PD) arrays and highperformance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/ MS) were performed for the analysis. PD PCR array results showed that 19% genes were significantly changed in the 2.5 μM MeHg treated cells, and 39% genes were changed in the 5 μM MeHg treated cells. In comparison, MPP+ treatment (40 μM) resulted in significant changes in 25% genes. A total of 15 common genes were altered by both MeHg and MPP+, and dopaminergic signaling transduction was the most affected pathway. Proteomic analysis identified a total of 2496 proteins, of which 188, 233 and 395 proteins were differentially changed by 1 μM and 2.5 μM MeHg, and MPP+ respectively. A total of 61 common proteins were changed by both MeHg and MPP+ treatment. The changed proteins were mainly involved in energetic generation-related metabolism pathway (propanoate metabolism, pyruvate metabolism and fatty acid metabolism), oxidative phosphorylation, proteasome, PD and other neurodegenerative disorders. A total of 7 genes/proteins including Ube2l3 (Ubiquitin-conjugating enzyme E2 L3) and Th (Tyrosine 3-monooxygenase) were changed in both genomic and proteomic analysis. These results suggest that MeHg and MPP+ share many similar signaling pathways leading to the pathogenesis of PD and other neurodegenerative diseases.