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.
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.
Exposure duration: 15 min, 2 h, 12 h, or 24 h
|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.|
|magnetic flux density||200 µT||-||measured||-||-|
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.