Page 53 - F. Cell biology

Continuous exposure to 60 Hz uniform electromagnetic field promotes human
cell proliferation by increasing mitochondrial reactive oxygen species

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Donghwa Suh , Dae Yong Um , Sang Hyeon Im , Gwan Soo Park , Kiwon Song 1,*
BACKGROUND AIM
Electromagnetic waves are generated when an electric field and a magnetic field
A considerable amount of wire is distributed on the ground and
change with time, and can be transmitted without a medium substance. underground of the city to maintain modern civilization, and the majority of
Electromagnetic spectrum can be divided into ionizing radiation and non-ionizing
radiation whether carrying sufficient energy to ionize other molecules and atoms or them generate extremely low frequency electromagnetic fields (ELF-EMF).
Thus we are continuously exposed to ELF-EMF in daily life. However, the
not. One of the non-ionizing radiation ranges, radiofrequency electromagnetic
fields (RF-EMF), had classified as ‘possibly carcinogen to humans (Group B)’ in physiological effects of the ELF-EMF and their mechanisms are not clearly
documented. Previous studies showed controversial results depending on the
2011. WHO/International Agency for Research on Cancer (IARC) announced that frequency and conditions of ELF-EMF, and types of cells: cells can either
they can increase the risks of brain cancer. The extremely low-frequency proliferate or undergo apoptosis, DNA damage with an increase or decrease
electromagnetic fields (ELF-EMF), another non-ionizing radiation, also have been in the level of ROS. In this study, we aim to monitor the cellular effect of
suggested for physiological effects, but their generalized risks have not been
systemically studied. Here, we investigate the cellular effects of ELF-EMF and their strong EMFs, greater than 10 mT, on various human cells. Also, we
investigate the specific molecular mechanisms of ELF-EMF for cellular effects.
specific molecular mechanisms.
METHODS
We designed a closed-type device to generate uniform ELF-EMF. We focused the sole effect of ELF-EMF excluding thermal effects by installing the digitalized
thermometer. In this device, 6 dishes can be simultaneously exposed to ELF-EMF with an intensity of 10 to 16 mT. Cells were plated in 35 mm culture plates, and
exposed to a 60 Hz uniform ELF-EMF over 10mT after 18 h of incubation. We tested the cellular effect of these ELF-EMF on various human cells, including human
cervical carcinoma HeLa, liver cancer stem cells Huh7 and Hep3B, immortalized normal hepatic cell MIHA, and normal fibroblast IMR90. Both MTT assay and cell
counting system were conducted to monitor cell proliferation. To observed changes in protein expression following ELF-EMF treatment, we normalized band intensity
after western blot analysis. Flow cytometer analysis was performed for cell cycle analysis with propidium iodide (PI) staining, intracellular and mitochondrial ROS
levels were measured with H2-DCFDA and MitoSOX staining, respectively.
RESULTS

EMF strength (mT)
Cell type
10 14 16
HeLa 119.54±3.45* 138.60±3.03*** 142.28±12.78***
Huh7 119.12±1.90*** 127.29±4.43*** 128.45±2.82***
Hep3B 106.77±2.52*** 108.43±1.92*** 109.20±3.24**
Figure 2. Continuous exposure to a uniform ELF-
MIHA 119.56±2.52** 119.54±0.94** 116.97±5.55* EMF decreases the expression of the tumor
suppressor p16 in HeLa
IMR90 115.47±3.99*** 109.14±1.81** 102.42±2.11 ns

Table 1. A continuous exposure to 60 Hz ELF-EMF
promotes cell proliferation in various human cells
HeLa, Huh7, Hep3B, MIHA and IMR90 were continuously Figure 1. Cell proliferation by a continuous
exposed to 10, 14, 16 mT ELF-EMF for 72 h. exposure to 14 mT is reversible and
Values of *P<0.05, **P<0.01, ***p<0.001 were considered transient
statistically significant, and P>0.05 was considered After 6 h of ELF-EMF exposure, each cells
statistically not significant. were further incubated without exposure of
ELF-EMF for up to 72 h.
Figure 3. Continuous exposure to a uniform ELF-
EMFs increases phosphorylation of Erk1/2 in
Figure 4. Continuous exposure HeLa
to a uniform ELF-EMF does
not disturb cell cycle
HeLa was exposed to an ELF-
EMF at 14 mT for up to 72 h.
Cell cycle distributions of HeLa
exposed to the ELF-EMFs were
determined by flow cytometry
using PI staining.

CONCLUSION REFERENCES
• A continuous exposure to ELF-EMF accelerated the • Song K, Im SH, Yoon YJ, Kim HM, Lee HJ,
proliferation in HeLa, Huh7, Hep3B, MIHA, and IMR90 et al. (2018) PLOS ONE 13(7): e0199753. Figure 5. Continuous exposure to a uniform ELF-
cells. • Lekovic, M.H., Drekovic, N.E., Granica, N.D. EMF increases intracellular and mitochondrial
• The increased cell proliferation by ELF-EMF was et al. (2020) Environ Sci Pollut Res. ROS in HeLa
transient and reversible. https://doi.org/10.1007/s11356-020-10039-0 Contact information
• ELF-EMF decreased the expression of the tumor ACKNOWLEDGEMENTS
suppressor p16, and increased the expression of 1 Department of Biochemistry, College of Life Science
phosphorylated Erk1/2. and Biotechnology, Yonsei University, Seoul, 03722,
• ELF-EMF activated cell cycle, but did not lead to This work was supported by the ICT R&D South Korea
significant cell cycle perturbation. program of MSIT/IITP. [2019-0-00102, A 2 Department of Electrical Engineering, Pusan
• ELF-EMF triggered slight increase of intracellular and Study on Public Health and Safety in a National University, Pusan, 46241, South Korea
mitochondrial ROS levels, suggesting that ELF-EMF Complex EMF Environment]
may activate the electron transport system. althehdghk@yonsei.ac.kr & bc5012@yonsei.ac.kr 1,*
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