Continuous exposure to 60 Hz extremely low frequency magnetic field at 10-14 mT promotes various human cell proliferation by activating extracellular-signal-regulated kinase

Abstract

We previously showed that 60 Hz extremely low-frequency magnetic fields (ELF-MF) at 6 mT promote various humancell proliferation. This study investigated the effects of 60 Hz ELF-MF at 10-16 mT on various mammalian cells, including human cervical carcinoma, rat neuroblastoma, liver cancer stem cells, immortalized normal hepatic cells, and normal fibroblasts. Using a revised ELF-MF-generating device that increases magnetic flux density stably without thermal effects, we exposed cells to 10 and 16 mT ELF-MF for 72 h. All cell types exhibited an approximately 20 % or greater increase in proliferation compared to the sham exposure group at 14 mT, with no further increase observed at 16 mT. In cells with activated proliferation at 14 mT, we observed activation of the MEK-ERK pathway and NF kappa B, but not Akt, and a slight increase in S phase population. Intracellular and mitochondrial ROS levels remained unchanged, and the proliferation-activating effects persisted when oxidative phosphorylation was interrupted. No changes in intracellular calcium levels were observed, and the proliferation-activating effects were maintained in the presence of a calcium chelator. These findings suggest that ROS and intracellular calcium do not mediate ELF-MF's proliferation-activating physiological effect. In conclusion, exposure to 60 Hz ELF-MF at 10-14 mT promotes cell proliferation by activating ERK1/2 without affecting intracellular ROS and calcium levels.