An Incoherent Magnetic Field Inhibited EGF Receptor Clustering and Phosphorylation Induced by a 50-Hz Magnetic Field in Cultured FL Cells

Abstract

Previously, we found that exposure to a 50-Hz magnetic field (MF) at 0.4 mT could induce epidermal growth factor (EGF) receptor clustering in Chinese hamster lung (CHL) fibroblast cells and superposition of an incoherent MF with the same intensity could inhibit the effect. In the present experiment, we investigated the effects of 50-Hz MF exposure at different intensities on EGF receptor clustering and phosphorylation in human amniotic cells (FL), and explored the interaction effect of an incoherent MF. Clustering and phosphorylation of EGF receptors on cellular membrane surface were analyzed using immunofluorescence assessed by confocal microscopy and western blot technology, respectively. EGF treatment served as a positive control. The results showed that, compared with sham exposure, exposure to a 50-Hz MF at 0.1, 0.2 or 0.4 mT for 15 min could significantly induce EGF receptor clustering and enhance phosphorylation on tyrosine-1173 residue in FL cells, whereas exposure to a 0.05 mT field for 15 min did not caused a significant effect. Exposure to an incoherent MF (frequency range between 30 to 90 Hz) at 0.2 mT for the same time neither induced EGF receptor clustering nor enhanced phosphorylation of EGF receptor in FL cells. When superposed, the incoherent MF at 0.2 mT completely inhibited EGF receptor clustering and phosphorylation induced by a 50-Hz MF at 0.1 and 0.2 mT. However, the incoherent MF could not completely eliminate the effects induced by a 0.4 mT 50-Hz MF. Based on the results of this experiment, we conclude that membrane receptors could be one of the main targets where extremely-low frequency (ELF) MF interacts with cells, and the intensity threshold, in the case of EGF receptors, is between 0.05 and 0.1 mT. An incoherent MF could completely inhibit the effects induced by an ELF-MF of equal or lower intensity.

Superimposition of an Incoherent Magnetic Field Eliminated the Inhibition of Hormone Secretion Induced by a 50-Hz Magnetic Field in Human Villous Trophoblasts <i>in vitro</i>

“…When the incoherent MF was superimposed, the inhibitory effects on hormone secretion induced by the 50-Hz MF were eliminated. Our previous studies also found that superposition of an incoherent MF with the same intensity could inhibit 50-Hz MF-induced gap junction intercellular communication suppression [38], EGF receptor clustering and phosphorylation [18], and Ras protein activation [39]. The present result further confirmed the hypothesis with a different cell model and biological endpoint.…”

“…The same MF exposure system used in our previous experiments [18] was used in this experiment. It consists of three groups of square copper coils (36×36 cm 2 ) placed inside an incubator (Model 3164, Forma, Marietta, GA, USA).…”

The Proliferative Response of NB69 Human Neuroblastoma Cells to a 50 Hz Magnetic Field is mediated by ERK1/2 Signaling

“…There, signal transduction pathways would be triggered through a complex program of transcriptional events involving activation of transcription factors. On the basis of these premises, the epidermal growth factor receptor (EGFR) has been proposed as one potential target of 50 Hz MF [42][43][44]. Also, activation of transcription factors associated to ERK activation has been described in human leukaemia cells HL-60, in human breast cancer cells MCF-7, and in rat fibroblast 3Y1, exposed to a 60 Hz, 100 µT MF [31].…”

Moderate and strong static magnetic fields directly affect EGFR kinase domain orientation to inhibit cancer cell proliferation

“…SMFs have been shown to inhibit cancer cell proliferation in multiple studies, but the mechanism was unclear [1–7]. Cancer cells often proliferate in response to signaling from Receptor Tyrosine Kinases (RTKs), and the effect of magnetic fields on EGFR phosphorylation was the subject of several studies [8–10]. A 0.4 mT 50 Hz and a 2 μT 1.8GHz pulsed magnetic fields (electromagnetic waves frequency) both increased EGFR phosphorylation, which were reversed by incoherent (“noise”) magnetic fields of the same intensities [9, 10].…”