Abstract
Extremely low-frequency electromagnetic fields (ELF-EMFs) can affect male reproductive function, but the underlying mechanism of this effect remains unknown. miRNA-mediated regulation has been implicated as an important epigenetic mechanism for regulatory pathways. Herein, we profiled miRNA expression in response to ELF-EMFs in vitro. Mouse spermatocyte-derived GC–2 cells were intermittently exposed to a 50 Hz ELF-EMF for 72 h (5 min on/10 min off) at magnetic field intensities of 1 mT, 2 mT and 3 mT. Cell viability was assessed using the CCK–8 assay. Apoptosis and the cell cycle were analyzed with flow cytometry. miRNA expression was profiled using Affymetrix Mouse Genechip miRNA 3.0 arrays. Our data showed that the growth, apoptosis or cell cycle arrest of GC–2 cells exposed to the 50 Hz ELF-EMF did not significantly change. However, we identified a total of 55 miRNAs whose expression significantly changed compared with the sham group, including 19 differentially expressed miRNAs (7 miRNAs were upregulated, and 12 were downregulated) in the 1 mT exposure group and 36 (9 miRNAs were upregulated, and 27 were downregulated) in the 3 mT exposure group. The changes in the expression of 15 selected miRNAs measured by real-time PCR were consistent with the microarray results. A network analysis was used to predict core miRNAs and target genes, including miR-30e-5p, miR-210-5p, miR-196b-5p, miR-504-3p, miR-669c-5p and miR-455-3p. We found that these miRNAs were differentially expressed in response to different magnetic field intensities of ELF-EMFs. GO term and KEGG pathway annotation based on the miRNA expression profiling results showed that miRNAs may regulate circadian rhythms, cytokine-cytokine receptor interactions and the p53 signaling pathway. These results suggested that miRNAs could serve as potential biomarkers, and the miRNA-mediated regulation of signaling pathways might play significant roles in the biological effects of ELF-EMFs.
Highlights
Humans are surrounded by power supply lines as well as many household and commercial devices, and exposure to extremely low-frequency electromagnetic fields (ELF-EMFs) is increasing
The cell viability was detected with the CCK–8 kit following 50 Hz ELF-EMF exposure at different magnetic intensities for 72 h to explore the effects of the ELF-EMF on the growth of GC–2 cells
We found that 50 Hz ELF-EMF did not induce apoptosis in GC–2 cells compared with the sham group (Fig 2A and 2B)
Summary
Humans are surrounded by power supply lines as well as many household and commercial devices, and exposure to extremely low-frequency electromagnetic fields (ELF-EMFs) is increasing. Prenatal exposure to ELF-EMFs did not increase miscarriages or induce gross external, skeletal or visceral malformations when fields up to 20 mT were tested [8]. Because of such contradictory results, the potential hazards of ELF-EMFs exposure remain unclear, and convincing evidence is lacking. MicroRNAs, a group of endogenous small non-coding RNAs (19~25 nucleotides), are expressed in almost all biota, including animals, viruses and plants [9, 10] Their primary biological function is the regulation of gene expression at the post-transcriptional level, mainly via binding to the 3’-untranslated region of target genes [11, 12]. Considering the biological role of miRNAs, we investigated the expression of miRNAs in the mouse spermatocyte-derived GC–2 cell line and examined whether some miRNAs could act as biomarkers of exposure to ELF-EMFs
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