50‐Hz MF does not affect global DNA methylation of SH‐SY5Y cells treated with the neurotoxin MPP⁺

Abstract

Exposure to extremely low frequency magnetic fields (ELF-MFs) has been associated with an increased risk of neurodegenerative disorders. The underlying mechanisms, however, are still debated. Since epigenetics play a key role in the neurodegenerative process, we investigated whether exposure to ELF-MF (50 Hz, 1 mT) might affect global DNA methylation of SH-SY5Y dopaminergic-like neuroblastoma cells. We assessed the percentage of 5-methylcytosine (5-mC) of three repetitive interspersed sequences (ALU, LINE-1, and SATa), through pyrosequencing analysis. We demonstrated that ELF exposure (up to 72 h) does not induce any change in the methylation pattern of ALU, LINE-1, or SATa in both proliferating and differentiated SH-SY5Y cells. Furthermore, when administered in combination with 1-methyl-4-phenylpyridinium (MPP þ ), a neurotoxin mimicking the Parkinson's Disease (PD) phenotype, ELF-MF exposure does not trigger any modulation in the percentage of 5-mC of the repetitive elements. Our findings demonstrate that exposure to 50-Hz MF does not affect global DNA methylation in proliferating and dopaminergic differentiated SH-SY5Y cells, either under basal culture conditions or under neurotoxic stress. Bioelectromagnetics. 40:33-41, 2019.

Epigenetic dysregulation in various types of cells exposed to extremely low-frequency magnetic fields

“…Four studies are reported below, whose research question was to explore if ELF-MF exposure could cause epigenetic alterations inducing effects on brain cells. To this aim, epigenetic marks in ELF-MF-exposed cells were analysed in vitro (Leone et al 2014 ; Consales et al 2018 ; Benassi et al 2019 ) or in vivo (Erdal et al 2018 ).…”

Exposure of the SH-SY5Y Human Neuroblastoma Cells to 50-Hz Magnetic Field: Comparison Between Two-Dimensional (2D) and Three-Dimensional (3D) In Vitro Cultures

“…Twenty-four hours after plating, proliferating SH-SY5Y cells underwent a continuous (72 h) exposure to either sham or ELF-MF, as previously detailed by our group [30][31][32][33][34]. For dopaminergic (DA) differentiation experiments, cells were treated with 10 μM retinoic acid (RA, 3 days), followed by 50 nM phorbol 12-myristate 13-acetate (PMA, for further 3 days) in reduced serum condition (5%) [44,45].…”

“…Angiogenetic Biomarkers in Proliferating SH-SY5Y Cells Grown in Both 2D and 3D Cultures We next exposed proliferating SH-SY5Y cells (grown in both 2D and 3D culture conditions) to 50-Hz MF (1 mT) for 72 h (continuous exposure), according to conditions previously characterized by our group [30][31][32][33][34].…”

“…All the in vitro findings addressing the issue of neuronal and neuroblastoma response to ELF-MF-including those from our group [30][31][32][33][34]-have been carried out in conventional 2D cultures. Therefore, the possibility to develop an in vitro study in a 3D matrix is challenging, to put the bases for further investigations in a model system that might be as close as possible to the in vivo condition.…”

“…We thus aimed at characterizing the effect triggered by the exposure to ELF-MF (50 Hz, 1 mT) in the SH-SY5Y human neuroblastoma cells grown (under both proliferative and differentiating conditions) [35,36] in a commercial, polystyrenebased 3D scaffold (Alvetex ® ) [12,17,37,38], compared to the conventional 2D monolayer culture. By applying the exposure conditions previously optimized and characterized by our group [30][31][32][33][34], we focused on different biological endpoints, ranging from the proliferation and differentiation pathways to the microRNA (miR)-related epigenetic changes; we also verified some key redox homeostasis modulators, as ELF-MF exposure has been extensively documented to exert pro-oxidant properties in various in vitro and in vivo models, including neuronal cells where the exposure to ELF-MF stimulates ROS generation and impairs the antioxidant defense [31][32][33][34][39][40][41][42].…”