Medical/biological study (experimental study)

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

By: Martinez MA, Ubeda A, Cid MA, Trillo MA

Published in: Cell Physiol Biochem 2012; 29 (5-6): 675-686

Aim of study (acc. to author)

To study whether a 50 Hz magnetic field can induce cell proliferation in the human neuroblastoma cell line NB69, and whether the signaling pathway MAPK-ERK1/2 is involved in that proliferative response.

Background/further details

The possible involvement of the transcription factor CREB in the proliferative response to the magnetic field was also investigated.

Endpoint

Exposure

- 50 Hz
- 50/60 Hz
- magnetic field
- low frequency

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: continuous or intermittent (5 min on/10 min off or 3 h on/3 h off) for up to 63 h	magnetic flux density: 100 µT

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	sinusoidal
Polarization	linear
Exposure duration	continuous or intermittent (5 min on/10 min off or 3 h on/3 h off) for up to 63 h
Additional info	field perpendicular to the cell's growth surface

Exposure setup

Exposure source	Helmholtz coils
Setup	two pairs of Helmholtz coils set in two magnetically shielded conetic alloy chambers which were placed inside two identical CO₂ incubators; cells in Petri dishes placed in the center of the coil system; only one set of coils was energized (samples in the unenergized set were considered as sham-exposed controls)
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	100 µT	-	-	-	-

Additional parameter details

field variation in the center of the coil system: ± 0.1 µT background AC field inside the shielded chambers: 0.04 µT ± 0.03 µT background DC field inside the shielded chambers: 0.05 µT ± 0.04 µT

Reference articles

Trillo MA et al. (2012): Influence of a 50 Hz magnetic field and of all-transretinol on the proliferation of human cancer cell lines.
Focke F et al. (2010): DNA fragmentation in human fibroblasts under extremely low frequency electromagnetic field exposure.
Ivancsits S et al. (2002): Induction of DNA strand breaks by intermittent exposure to extremely-low-frequency electromagnetic fields in human diploid fibroblasts.

Exposed system:

intact cell/cell culture
NB69 cells (human neuroblastoma cells)

Methods Endpoint/measurement parameters/methodology

cell viability/cell division/proliferation: cell number and cell viability (Trypan blue exclusion assay); cell proliferation (BrdU incorporation; fluorescence microscopy)
ERK1/2 and CREB activation (percentage of phospho-ERK1/2 and phospho-CREB positive cells; immunocytochemistry) and protein expression (Western blot) after short-term exposure (15-120 min) and at 30 min during two "on" intervals and one "off" interval (3 h/3 h exposure)

Investigated system:

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

Time of investigation:

during exposure
after exposure

Main outcome of study (acc. to author)

The continuous exposure did not induce significant changes in cell proliferation. In contrast, both intermittent exposure to the 50 Hz magnetic field significantly stimulated cell proliferation in NB69 cells. The magnetic field exposure induced repeated transient activation of the MAPK- ERK1/2 signaling pathway, occurring early after the onset of each of the exposure cycles of the intermittent exposure (peak during "on"-interval).
When a specific inhibitor (PD98059) of the MAPK-ERK1/2 pathway was added to the culture medium, the early activation of ERK1/2 and the proliferative response observed subsequently, were blocked. From this, the authors conclude that activation of ERK1/2 is involved in the molecular mechanisms through which the 50 Hz magnetic field induces a proliferative response in NB69 cells. Additionally, the data showed that the magnetic field exposure also activated CREB, a downstream target of the MAPK- ERK1/2 pathway. However, such activation was independent of ERK1/2, suggesting that other pathways could be involved in the cellular and molecular response to the magnetic field.
These findings provide a further insight into the mechanisms through which weak, 50 Hz magnetic field could influence cancer-related processes in human cells.

Study character:

medical/biological study
experimental study
full/main study
blind study

Study funded by

European Union (EU)/European Commission
Quality of Life and Management of Living Resources program of European Union
Ministerio de Defensa de Espana (Ministry of Defence, Spain)
European Defence Agency (EDA)

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