The Effects Of 50Hz Magnetic Fields Exposure On DNA Damage In Different Cells From Reproductive System

With the development of electric power industrial and popularization of house hold applications, public concerns have been raised about the potential health effect of increasing environmental exposure to extremely low frequency magnetic fields (ELF-MF) from different sources, such as high-voltage transmission lines and home appliance. Some epidemiological studies have suggested that ELF-MF exposure is associated with increased risk of cancers, e.g., brain tumor, leukemia, of neurodegenerative diseases, such as Alzheimer’s disease and amyotrophic lateral sclerosis, and of infertility and adverse pregnancy outcomes, including abortion, low birth weight, and congenital malformations. On the other hand, some other epidemiological studies show no relationship between ELF-MF exposure and risk of human health hazards. Thus, it remains inconclusive on the health effects of ELF-MF exposure. Based on limited evidence that residential ELF-MF exposure was associated with increased risk of children leukemia, the International Agency for Research on Cancer (IARC) has classified ELF-MF as possible carcinogen to human (2B). However, the current available laboratory data did not clarify or support the carcinogenic and genotoxic effects of ELF-MF.To systematically investigate the biological effects of ELF-MF, our group has evaluated the genotoxic effects of ELF-MF exposure on DNA damage in different cells, including different representive cells from different systems/organs, different cell lines from same system/organ (e.g., nevous system, reproductive system) and aims to screen out the ELF-MF sensitive cells/cell lines as feasible cell model to explore the mechanisms of ELF-MF acting on organism. In this study, we have examined the genotoxic effects of ELF-MF on different cell lines from reproductive system, i.e., GC-1 spermatogonial cells (GC-1 spg) and GC-2 spermatocyte cells (GC-2 spd) from male reproductive system, and Chinese hamster ovary (CH0-K1) and dihydrofolate dehydrogenase deficient CHO cells (CHO/dhfr-) from female reproductive system. The cells were exposed to 50 Hz magnetic fields (MF) for 24 hours at 2.0 mT or 3.0 mT. After exposure, the cellular DNA damage and DNA fragmentation were evaluated by yH2AX foci formation assay and alkaline comet assay respectively. The cell viability, cell proliferation and cell cycle progression were examined by cell counting kit 8 (CCK-8) assay, cell counting with hemocytometry and flow cytometry analysis with with propidium iodide (PI) staining. In addition, we also investigated the effect of co-exposure to 50 MF and hydrogen peroxide (H2O2) on DNA damage in these cells.For the cells from male reproductive system, the results of yH2AX foci formation assay showed that the average number of yH2AX foci was not significantly different between the sham exposure group and 50 Hz MF exposure group at either 2.0 mT or 3.0 mT in both GC-1 spg and GC-2 spd cells. No significant change of DNA fragmentation was found in GC-1 spg and GC-2 spd cells after 2.0 mT or 3.0 mT of 50 Hz MF exposure as evaluated by alkaline comet assay. Exposure to 3.0 mT but not 2.0 mT of 50 Hz MF significantly enhanced cell viability of GC-1 spg cells, while no significant change of cell viability was found in GC-2 spd cells after the exposure. Exposure to 50 Hz MF at 2.0 mT or 3.0 mT did not influence cell proliferation and cell cycle progression in GC-1 spg and GC-2 spd cells as evaluated by cell counting with hemocytometry and flow cytometry with PI staining respectively. In addition, exposure to 2.0 mT of 50 Hz MF significantly influence the formation of yH2AX foci in GC-2 spd cells but not GC-1 spg cells induced by treatment with 10^M of H2O2, while the exposure did not significantly influence the DNA fragmentation in both GC-1 spg and GC-2 spd cells induced by 10 uM of H2O2.As to cells from female reproductive system, we found that 50 Hz MF expsoure at 2.0 mT or 3.0 mT did not significant affect the yH2AX foci formation in CHO-K1 and CHO/dhfr’cells. Exposure to 50 Hz MF at 2.0 mT but not 3.0 mT significantly decreased DNA fragmentation in CHO-K1 cells, while the exposure did not significantly change the DNA fragmentation in CHO/dhfr" cells. Neither 2.0 mT nor 3.0 mT of 50 Hz MF exposure significantly changed the cell viability in CHO-K1 cells, while 2.0 mT but not 3.0 mT of 50 Hz MF exposure significantly enhanced cell viability in CHO/dhfr" cells. Exposure to 50 Hz MF did not significantly change the cell proliferation in CHO-K1 cells, while 3.0 mT but not 2.0 mT of 50 Hz MF exposure significantly promoted cell proliferation in CHO/dhfr" cells. No significant change of cell cycle progression was found in CHO-K1 and CHO/dhfr" cells after exposure to 2.0 mT or 3.0 mT of 50 Hz MF. Exposure to 2.0 mT of 50 Hz MF did not significantly influence the formation of yH2AX focis in CHO-K1 and CHO/dhfr" cells induced by 50 uM of H2O2, while the exposure significantly alleviated the DNA fragmentation induced by H2O2 in CHO-K1 cells but not CHO/dhfr’cells.In conclusions, this study demonstrated that 50 Hz MF under current exposure conditions did not trigger the genotoxicity in GC-1 spg and GC-2 spd cells, while 50 Hz MF exposure significantly enhanced the cell viability in GC-1 spg cells and promoted the yH2AX foci formation induced by H2O2 in GC-2 spd cells. Exposure to 50 Hz MF significantly decreased the DNA fragmentaion and alleviated the DNA fragmentation induced by H2O2 in CHO-K1, while 50 Hz MF exposure slightly but significantly enhanced the cell viability and proliferation in CHO/dhfr- cells cells. Our data suggest that the cells derived from reproductive system differentially respond to 50 Hz MF exposure, and its underlying mechanisms and significance await further investigation.