Medical/biological study (experimental study)

miRNA expression profile is altered differentially in the rat brain compared to blood after experimental exposure to 50 Hz and 1 mT electromagnetic field med./bio.

By: Erdal ME, Yilmaz SG, Gürgül S, Uzun C, Derici D, Erdal N

Published in: Prog Biophys Mol Biol 2018; 132: 35-42

To examine whether long-term exposure of rats to a 50 Hz magnetic field has an influence on the expression level of miRNAs in blood and brain tissue.

MicroRNAs (miRNA) are small, non-coding RNA molecules, which play a critical role in gene regulation. In this study, miRNAs related to brain and human diseases were analyzed.
Eight groups of rats were examined (n=8, respectively): 1) adult (10 weeks old) sham exposed female, 2) young (3 weeks old) sham exposed female, 3) adult sham exposed male, 4) young sham exposed male, 5) adult magnetic field exposed female, 6) young magnetic field exposed female, 7) adult magnetic field exposed male and 8) young magnetic field exposed male.

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: 4 hours/day on 60 consecutive days	magnetic flux density: 1 mT (± 0.02 mT)

Frequency	50 Hz
Type	magnetic field
Waveform	sinusoidal
Exposure duration	4 hours/day on 60 consecutive days

Exposure source	Helmholtz coils
Chamber	respectively 4 rats in a polycarbonate cage (26 x 17 x 13 cm³)
Setup	Helmholtz coil apparatus was placed in a Faraday cage (70 x 65 x 65 cm³) to shield against electric fields components, electrical noise, and vibrations; diameter of coils was 42.75 cm and a gap of 21.375 cm; coils were made of electrically and thermally insulated copper wire (2.2 mm) and constisted of 160 turns; temperature was 22-24°C with no significant difference between experiments
Sham exposure	A sham exposure was conducted.
Additional info	geomagnetic field of 50 µT

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	-	measured	-	± 0.02 mT

Gurgul S et al. (2008): Deterioration of bone quality by long-term magnetic field with extremely low frequency in rats

Exposed system:

molecular biosynthesis: microRNA expression-rates in the brain and blood (quantitative RT-PCR of microRNAs rno-miR-26b-5p, rno-miR-9-5p, rno-miR-29a-3p, rno-miR-106b-5p, rno-miR-107 and rno-miR-125a-3p)

Investigated system:

Time of investigation:

In young exposed females (group 6), adult exposed males (group 7), and young exposed males (group 8), significant differences (down-regulation and up-regulation) in the expression of diverse miRNAs were found when compared to the corresponding sham exposure groups (groups 2, 3, 4).
The authors conclude that 50 Hz magnetic fields could influence the miRNA expression in the brain and blood of rats and that these altered expression levels differ depending on age and are differently down-regulated or up-regulated in blood and brain.

Study character:

Consales C et al. (2018): Fifty-Hertz Magnetic Field Affects the Epigenetic Modulation of the miR-34b/c in Neuronal Cells
Li H et al. (2018): Exosomal small RNA sequencing uncovers the microRNA dose markers for power frequency electromagnetic field exposure
Cuccurazzu B et al. (2010): Exposure to extremely low-frequency (50 Hz) electromagnetic fields enhances adult hippocampal neurogenesis in C57BL/6 mice
Falone S et al. (2008): Chronic exposure to 50Hz magnetic fields causes a significant weakening of antioxidant defence systems in aged rat brain