Activation of Signaling Cascades by Weak Extremely Low Frequency Electromagnetic Fields

Einat Kapri-Pardes, Tamar Hanoch, Galia Maik-Rachline, Manuel Murbach, Patricia L. Bounds, Niels Kuster, and Rony Seger Cellular Physiology and Biochemistry, Volume 43, pp. 1533–1546, online October 16, 2017, doi: 10.1159/000481977

Results from recent studies suggest that extremely low frequency magnetic fields (ELF-MF) interfere with intracellular signaling pathways related to proliferative control. The mitogen-activated protein kinases (MAPKs), central signaling components that regulate essentially all stimulated cellular processes, include the extracellular signal-regulated kinases 1/2 (ERK1/2) that are extremely sensitive to extracellular cues. Anti-phospho-ERK antibodies serve as a readout for ERK1/2 activation and are able to detect minute changes in ERK stimulation. The objective of this study was to explore whether activation of ERK1/2 and other signaling cascades can be used as a readout for responses of a variety of cell types, both transformed and non-transformed, to ELF-MF. We applied ELF-MF at various field strengths and time periods to eight different cell types with an exposure system housed in a tissue culture incubator and followed the phosphorylation of MAPKs and Akt by western blotting. We found that the phosphorylation of ERK1/2 is increased in response to ELF-MF. However, the phosphorylation of ERK1/2 is likely too low to induce ELF-MF-dependent proliferation or oncogenic transformation. The p38 MAPK was very slightly phosphorylated, but JNK or Akt were not. The effect on ERK1/2 was detected for exposures to ELF-MF strengths as low as 0.15 µT and was maximal at ∼10 µT. We also show that ERK1/2 phosphorylation is blocked by the flavoprotein inhibitor diphenyleneiodonium, indicating that the response to ELF-MF may be exerted via NADP oxidase similar to the phosphorylation of ERK1/2 in response to microwave radiation. Our results further indicate that cells are responsive to ELF-MF at field strengths much lower than previously suspected and that the effect may be mediated by NADP oxidase. However, the small increase in ERK1/2 phosphorylation is probably insufficient to affect proliferation and oncogenic transformation. Therefore, the results cannot be regarded as proof of the involvement of ELF-MF in cancer in general or childhood leukemia in particular.

The scientific and technical impact of the study can be summarized as:

• Phosphorylation of the ERK1/2A kinases can be used as a readout for exposure to ELF-MF in a variety of transformed and non-transformed cells.  
• COS7 and HeLa cell are responsive to ELF-MF at field strengths as low as as low as 0.15 µT, much lower than previously suspected.
• Phosphorylation occurs in all cells of the exposed cultures rather than in only subpopulations of cells, and the phosphorylated ERK1/2 is distributed mostly in the cytosol.
• The level of phosphorylation observed in response to exposure to ELF-MF at all strengths is too low to induce any physiological or pathological effects by themselves.

DOWNLOAD ARTICLE