Study type: Medical/biological study (experimental study)

The duration of exposure to 50 Hz magnetic fields: Influence on circadian genes and DNA damage responses in murine hematopoietic FDC-P1 cells. med./bio.

Published in: Mutation Research - Fundamental and Molecular Mechanism of Mutagenesis 2021; 823: 111756 [in press]

Aim of study (acc. to author)

The aim of the study was to investigate the effects of 50 Hz extremely low frequency magnetic fields on gene expression related to the circadian rhythm or DNA damage signaling and whether the magnetic fields modify DNA repair rate after bleomycin treatment.

Background/further details

The circadian rhythm plays a vital role in regulating major cellular activities and anomalies in these activities are associated with cancer development and progression.
To assess DNA damage signaling and DNA repair rate, the cells were treated with bleomycin (20 μg/ml) for 1 h and then either investigated immediately or 1 or 2 h later.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: 15 min, 2 h, 12 h, or 24 h

Exposure 1

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration 15 min, 2 h, 12 h, or 24 h
Exposure setup
Exposure source
Chamber magnetic field exposure and sham exposure were done in two identical temperature-controlled and atmosphere-regulated cell culture incubators (37°C, 5% CO2); the incubators housed two identical coil systems that produced a horizontal magnetic field; the 24-well plates were positioned in the center of the coil system to guarantee either a uniform magnetic flux density or identical sham exposure conditions; heterogeneity of the field in the area that contained the plates during exposures was < 2 %; the exposure system also had a computerized blinding system
Setup each coil system was made of a cuboid graphite rack (36 cm height × 36 cm width × 26 cm depth); each rack contained three coils, 13 cm apart from each other. The outermost coils had twelve turns of copper wire (1.5 mm diameter) each, while the coil in the middle had five turns
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 200 µT - measured - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

Circadian rhythm-related genes were upregulated after 12 h of magnetic field exposure and downregulated after 24 h of magnetic field exposure, but none of the affected genes were core genes controlling the circadian rhythm suggesting that cellular responses to magnetic fields do not originate from the circadian rhythm itself. In addition, the DNA repair rate for bleomycin-induced DNA damage was only decreased after magnetic field exposure for 24 h.
In conclusion, the findings suggest that the effects of magnetic fields are exposure duration-dependent; they were observed predominantly after long exposures.

Study character:

Study funded by

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