Medical/biological study (experimental study)

Weak power frequency magnetic fields induce microtubule cytoskeleton reorganization depending on the epidermal growth factor receptor and the calcium related signaling med./bio.

By: Wu X, Du J, Song W, Cao M, Chen S, Xia R

Published in: PLoS One 2018; 13 (10): e0205569

Aim of study (acc. to author)

The effects of exposure of two different cell lines to a 50 Hz magnetic field on the microtubule-cytoskeleton and the involvements of EGFR and calcium signal pathways should be investigated.

Background/further details

In a previous study (Wu et al. 2014), the authors found that exposure to a 50 Hz magnetic field affected cell migration and the actin-cytoskeleton. If and how microtubules as another major component of the cytoskeleton are affected as well, should be investigated in this study.
Human amniotic epithelium cells (FL) and rat pheochromocytoma cells (PC12) were divided into the following groups: 1) MF: exposure to the magnetic field, 2) sham exposure, 3) EGF: EGF treatment (and sham exposure), 4) EGF + MF, 5) PD: treatment with EGFR tyrosine kinase (TK) inhibitor PD153035 (PD) (used to investigate involvement of EGFR signal pathway) (and sham exposure), 6) PD + MF, 7) PD + EGF. 8) NIF: treatment with L-type calcium channel inhibitor nifedipine (NIF) (used to investigate involvement of calcium signal pathway) (and sham exposure), 9) PD + NIF, 10) PD + NIF + MF, 11) PD + NIF + EGF.

Endpoint

cell function: effects on microtubule cytoskeleton and associated signal pathways

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: 30 minutes	magnetic flux density: 0.4 mT

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Exposure duration	30 minutes

Exposure setup

Exposure source	not specified exposure system is described in detail in reference article
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	0.4 mT	-	-	-	-

Reference articles

Wu X et al. (2014): Weak Power Frequency Magnetic Field Acting Similarly to EGF Stimulation, Induces Acute Activations of the EGFR Sensitive Actin Cytoskeleton Motility in Human Amniotic Cells

Exposed system:

intact cell/cell culture
human amniotic epithelium cells (FL), rat pheochromocytoma cells (PC12)

Methods Endpoint/measurement parameters/methodology

cell function: EGFR clustering in cells (Fluorescence Resonance Energy Transfer (FRET), fluorescence spectrometry); cytosolic calcium concentration (flow cytometry); amount of microtubules, EGFR, L-type voltage-dependent calcium channel subunits CaV1.2, calcium and focal adhesion in cells (confocal laser scanning microscopy)
cell viability/cell division/proliferation: differentiation of PC12 cells (microscopy)
molecular biosynthesis: content of EGFR, L-type voltage-dependent calcium channel subunit CaV1.2 as well as signal proteins vinculin, tau, protein kinase C, MARCKS, calmodulin and calmodulin-dependent protein kinase II (CAMK II) and respective phosphorylated variants (Western Blot)

Investigated system:

intact cell/cell culture
isolated bio./chem. substance
cell lysate

Time of investigation:

after exposure

Main outcome of study (acc. to author)

The amount of microtubules was significantly reduced and focal adhesion was significantly increased in both cell lines in group 1 (magnetic field exposure) and group 3 (EGF treatment) compared to the sham exposure group (group 2). Clustering of the EGFR could be detected in both groups 1 and 3. These effects were strongly depending on the calcium signal pathway through the L-type calcium channel and elevation of the intracellular calcium level. The magnetic field-induced reorganization of the cytoskeleton network was mediated via phosphorylation of the signaling proteins in the EGFR and calcium signal pathways, including the important microtubule protein tau.
The authors conclude that exposure of cells to a 50 Hz magnetic field activates the microtubule-cytoskeleton in a way similar to EGF through a mechanism related to both EGFR and calcium signaling pathways.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

East China Normal University, Shanghai, China
National Natural Science Foundation (NSFC), China

Gholami D et al. (2019): Comparison of polymerization and structural behavior of microtubules in rat brain and sperm affected by the extremely low-frequency electromagnetic field
Zhang Y et al. (2018): Extremely low frequency electromagnetic fields promote mesenchymal stem cell migration by increasing intracellular Ca2+ and activating the FAK/Rho GTPases signaling pathways in vitro
Feng B et al. (2016): NADPH oxidase-produced superoxide mediated a 50-Hz magnetic field-induced epidermal growth factor receptor clustering
Wu X et al. (2014): Weak Power Frequency Magnetic Field Acting Similarly to EGF Stimulation, Induces Acute Activations of the EGFR Sensitive Actin Cytoskeleton Motility in Human Amniotic Cells
Iorio R et al. (2013): ELF-MF transiently increases skeletal myoblast migration: possible role of calpain system
Ke XQ et al. (2008): 50-Hz magnetic field induces EGF-receptor clustering and activates RAS
Jia C et al. (2007): EGF receptor clustering is induced by a 0.4 mT power frequency magnetic field and blocked by the EGF receptor tyrosine kinase inhibitor PD153035
Kroupova J et al. (2007): Low-frequency magnetic field effect on cytoskeleton and chromatin
Chu KP et al. (2007): [Effect of 50 Hz power frequency magnetic field on microfilament cytoskeleton assembly of human amnion FL cells]
Sul AR et al. (2006): Effects of sinusoidal electromagnetic field on structure and function of different kinds of cell lines
Bodega G et al. (2005): Acute and chronic effects of exposure to a 1-mT magnetic field on the cytoskeleton, stress proteins, and proliferation of astroglial cells in culture
Spadinger I et al. (1995): 3T3 cell motility and morphology before, during, and after exposure to extremely-low-frequency magnetic fields
Lindstrom E et al. (1993): Intracellular calcium oscillations induced in a T-cell line by a weak 50 Hz magnetic field
Walleczek J et al. (1992): Pulsed magnetic field effects on calcium signaling in lymphocytes: dependence on cell status and field intensity
Walleczek J et al. (1990): Nonthermal 60 Hz sinusoidal magnetic-field exposure enhances 45Ca2+ uptake in rat thymocytes: dependence on mitogen activation