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Extremely low-frequency electromagnetic fields cause G1 phase arrest through the activation of the ATM-Chk2-p21 pathway.

Huang CY, Chang CW, Chen CR, Chuang CY, Chiang CS, Shu WY, Fan TC, Hsu IC - PLoS ONE (2014)

Bottom Line: The ELF-EMF could cause G1 arrest and decrease colony formation.In addition, the p21 protein, a regulator of cell cycle progression at G1 and G2/M, exhibited a higher level of expression in exposed HaCaT cells compared with the expression of sham-exposed cells.These findings indicate that ELF-EMFs activate the ATM-Chk2-p21 pathway in HaCaT cells, resulting in cell cycle arrest at the G1 phase.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan.

ABSTRACT
In daily life, humans are exposed to the extremely low-frequency electromagnetic fields (ELF-EMFs) generated by electric appliances, and public concern is increasing regarding the biological effects of such exposure. Numerous studies have yielded inconsistent results regarding the biological effects of ELF-EMF exposure. Here we show that ELF-EMFs activate the ATM-Chk2-p21 pathway in HaCaT cells, inhibiting cell proliferation. To present well-founded results, we comprehensively evaluated the biological effects of ELF-EMFs at the transcriptional, protein, and cellular levels. Human HaCaT cells from an immortalized epidermal keratinocyte cell line were exposed to a 1.5 mT, 60 Hz ELF-EMF for 144 h. The ELF-EMF could cause G1 arrest and decrease colony formation. Protein expression experiments revealed that ELF-EMFs induced the activation of the ATM/Chk2 signaling cascades. In addition, the p21 protein, a regulator of cell cycle progression at G1 and G2/M, exhibited a higher level of expression in exposed HaCaT cells compared with the expression of sham-exposed cells. The ELF-EMF-induced G1 arrest was diminished when the CHK2 gene expression (which encodes checkpoint kinase 2; Chk2) was suppressed by specific small interfering RNA (siRNA). These findings indicate that ELF-EMFs activate the ATM-Chk2-p21 pathway in HaCaT cells, resulting in cell cycle arrest at the G1 phase. Based on the precise control of the ELF-EMF exposure and rigorous sham-exposure experiments, all transcriptional, protein, and cellular level experiments consistently supported the conclusion. This is the first study to confirm that a specific pathway is triggered by ELF-EMF exposure.

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ELF-EMF inhibited cell growth and decreased cell colony formation.(A) Growth curves of HaCaT cells for the sham (•) and exposed (▪) groups. The HaCaT cells were seeded and incubated for 12 h prior to ELF-EMF exposure. The results were presented as the mean ± SD fold change in the cell count relative to the initial cell count of three independent experiments. (B) Colony formation assay. In the upper panel, the bars show the colony formation of the sham and exposed cells for 144 h of ELF-EMF exposure. The results are presented as the mean ± SD of three independent experiments. In the lower panel, they were representative for sham (left) and exposed (right). The Student’s t-test was used to analyze the differences between the sham and exposure groups. *P<0.05.
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pone-0104732-g001: ELF-EMF inhibited cell growth and decreased cell colony formation.(A) Growth curves of HaCaT cells for the sham (•) and exposed (▪) groups. The HaCaT cells were seeded and incubated for 12 h prior to ELF-EMF exposure. The results were presented as the mean ± SD fold change in the cell count relative to the initial cell count of three independent experiments. (B) Colony formation assay. In the upper panel, the bars show the colony formation of the sham and exposed cells for 144 h of ELF-EMF exposure. The results are presented as the mean ± SD of three independent experiments. In the lower panel, they were representative for sham (left) and exposed (right). The Student’s t-test was used to analyze the differences between the sham and exposure groups. *P<0.05.

Mentions: In our original cell growth study, no significant differences were observed between the sham and exposed groups after up to 96 h of ELF-EMF exposure. Inspired by the gene expression results of cell cycle-related SGs, we extended the exposure time to 144 h to further investigate the effects of ELF-EMFs on the growth of HaCaT cells. As shown in Figure 1A, sham-exposed cells grew exponentially at all the time points whereas the growth rate of the exposed cells significantly decreased (68.43%±8.46% of sham-exposed cells) at the 144-h time point. The data suggested that exposure to ELF-EMFs for 144 h inhibited HaCaT cell growth.


Extremely low-frequency electromagnetic fields cause G1 phase arrest through the activation of the ATM-Chk2-p21 pathway.

Huang CY, Chang CW, Chen CR, Chuang CY, Chiang CS, Shu WY, Fan TC, Hsu IC - PLoS ONE (2014)

ELF-EMF inhibited cell growth and decreased cell colony formation.(A) Growth curves of HaCaT cells for the sham (•) and exposed (▪) groups. The HaCaT cells were seeded and incubated for 12 h prior to ELF-EMF exposure. The results were presented as the mean ± SD fold change in the cell count relative to the initial cell count of three independent experiments. (B) Colony formation assay. In the upper panel, the bars show the colony formation of the sham and exposed cells for 144 h of ELF-EMF exposure. The results are presented as the mean ± SD of three independent experiments. In the lower panel, they were representative for sham (left) and exposed (right). The Student’s t-test was used to analyze the differences between the sham and exposure groups. *P<0.05.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128733&req=5

pone-0104732-g001: ELF-EMF inhibited cell growth and decreased cell colony formation.(A) Growth curves of HaCaT cells for the sham (•) and exposed (▪) groups. The HaCaT cells were seeded and incubated for 12 h prior to ELF-EMF exposure. The results were presented as the mean ± SD fold change in the cell count relative to the initial cell count of three independent experiments. (B) Colony formation assay. In the upper panel, the bars show the colony formation of the sham and exposed cells for 144 h of ELF-EMF exposure. The results are presented as the mean ± SD of three independent experiments. In the lower panel, they were representative for sham (left) and exposed (right). The Student’s t-test was used to analyze the differences between the sham and exposure groups. *P<0.05.
Mentions: In our original cell growth study, no significant differences were observed between the sham and exposed groups after up to 96 h of ELF-EMF exposure. Inspired by the gene expression results of cell cycle-related SGs, we extended the exposure time to 144 h to further investigate the effects of ELF-EMFs on the growth of HaCaT cells. As shown in Figure 1A, sham-exposed cells grew exponentially at all the time points whereas the growth rate of the exposed cells significantly decreased (68.43%±8.46% of sham-exposed cells) at the 144-h time point. The data suggested that exposure to ELF-EMFs for 144 h inhibited HaCaT cell growth.

Bottom Line: The ELF-EMF could cause G1 arrest and decrease colony formation.In addition, the p21 protein, a regulator of cell cycle progression at G1 and G2/M, exhibited a higher level of expression in exposed HaCaT cells compared with the expression of sham-exposed cells.These findings indicate that ELF-EMFs activate the ATM-Chk2-p21 pathway in HaCaT cells, resulting in cell cycle arrest at the G1 phase.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan.

ABSTRACT
In daily life, humans are exposed to the extremely low-frequency electromagnetic fields (ELF-EMFs) generated by electric appliances, and public concern is increasing regarding the biological effects of such exposure. Numerous studies have yielded inconsistent results regarding the biological effects of ELF-EMF exposure. Here we show that ELF-EMFs activate the ATM-Chk2-p21 pathway in HaCaT cells, inhibiting cell proliferation. To present well-founded results, we comprehensively evaluated the biological effects of ELF-EMFs at the transcriptional, protein, and cellular levels. Human HaCaT cells from an immortalized epidermal keratinocyte cell line were exposed to a 1.5 mT, 60 Hz ELF-EMF for 144 h. The ELF-EMF could cause G1 arrest and decrease colony formation. Protein expression experiments revealed that ELF-EMFs induced the activation of the ATM/Chk2 signaling cascades. In addition, the p21 protein, a regulator of cell cycle progression at G1 and G2/M, exhibited a higher level of expression in exposed HaCaT cells compared with the expression of sham-exposed cells. The ELF-EMF-induced G1 arrest was diminished when the CHK2 gene expression (which encodes checkpoint kinase 2; Chk2) was suppressed by specific small interfering RNA (siRNA). These findings indicate that ELF-EMFs activate the ATM-Chk2-p21 pathway in HaCaT cells, resulting in cell cycle arrest at the G1 phase. Based on the precise control of the ELF-EMF exposure and rigorous sham-exposure experiments, all transcriptional, protein, and cellular level experiments consistently supported the conclusion. This is the first study to confirm that a specific pathway is triggered by ELF-EMF exposure.

Show MeSH
Related in: MedlinePlus