Medical/biological study (experimental study)

Enhanced cytotoxic and genotoxic effects of gadolinium following ELF-EMF irradiation in human lymphocytes med./bio.

By: Cho S, Lee Y, Lee S, Choi YJ, Chung HW

Published in: Drug Chem Toxicol 2014; 37 (4): 440-447

Aim of study (acc. to author)

To investigate the effects of extremely low frequency electromagnetic fields (ELF-EMF) on the toxicity of gadolinium in human lymphocytes.

Background/further details

The chemical element gadolinium with the atomic number 64 is used as a contrast agent in magnetic resonance imaging. Gadolinium is known to be toxic. However, the combined effects of gadolinium and extremely low frequency magnetic fields, as patients are exposed to during magnetic resonance imaging, have not been investigated by now.
Human lymphocytes were treated with different concentrations of gadolinium (0 mM (control group), 0.2 mM, 0.4 mM, 0.8 mM, 1.2 mM) while exposed to a 60 Hz magnetic field or sham exposed.

Endpoint

genotoxicity/mutation: DNA damage
cell viability/cell division/proliferation: apoptosis; cell viability

Exposure

Exposure	Parameters
Exposure 1: 60 Hz Exposure duration: continuous for up to 72 hours	magnetic flux density: 0.8 mT

Exposure 1

Main characteristics

Frequency	60 Hz
Type	magnetic field
Exposure duration	continuous for up to 72 hours

Exposure setup

Exposure source	solenoid
Setup	two identical, electrically coupled solenoid coils (length 0.30 m, diameter 0.15 m) were wound with 350 turns/m of number-16 bifilar magnet wire on a cylindrical acrylic support; uniformity of the magnetic field in the active exposure volume was ± 2.5%; no significant temperature variations were observed during sham exposure and magnetic field exposure (37 ± 0.5°C)
Sham exposure	A sham exposure was conducted.
Additional info	sham exposed cultures were tested before the experiments with the same exposure system but with the power supply switched off

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	0.8 mT	-	measured	-	-

Reference articles

Walleczek J et al. (1999): Increase in radiation-induced HPRT gene mutation frequency after nonthermal exposure to nonionizing 60 Hz electromagnetic fields

Exposed system:

intact cell/cell culture
human lymphocytes

Methods Endpoint/measurement parameters/methodology

genotoxicity/mutation: DNA strand breaks after 12 h of exposure (comet assay); micronucleus formation after 72 h of exposure (cytokinesis block micronucleus assay, Giemsa stain, light microscopy)
cell viability/cell division/proliferation: apoptosis after 24 h of exposure (staining with propidium iodide, flow cytometry); cell viability after 0 h, 24 h, and 48 h of exposure (trypan blue exclusion assay)
intracellular level of reactive oxygen species after 30 min of exposure in the presence or absence of the free radical scavenger N-acetylcysteine (reaction with dichlorofluorescein, flow cytometry)

Investigated system:

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

Time of investigation:

before exposure
during exposure
after exposure

Main outcome of study (acc. to author)

Lymphocytes which were treated with gadolinium showed a time-dependent and concentration-dependent significant decrease in cell viability in comparison to the control group. A combined treatment of gadolinium (0.4 mM, 0.8 mM, or 1.2 mM) and 60 Hz magnetic field resulted in a further significant decrease compared to gadolinium treatment alone. The apoptosis rate and the micronucleus formation were significantly increased in cells treated with 1.2 mM gadolinium and a 60 Hz magnetic field compared to the control group and compared to gadolinium alone. The number of DNA strand breaks was significantly increased in gadolinium treated cells (0.2 mM, 0.4 mM, or 0.8 mM) compared to the control. Furthermore, exposure to the 60 Hz magnetic field alone led to a significant increase in the number of strand breaks compared to the control. A combined treatment of gadolinium and exposure to the 60 Hz magnetic field led to a further significant increase in the number of strand breaks compared to gadolinium treatment alone.
In gadolinium treated cells (0.2 mM, 0.4 mM, or 0.8 mM), the level of reactive oxygen species was significantly increased in a concentration-dependent manner compared to the control. A combined treatment with 0.8 mM gadolinium and a 60 Hz magnetic field resulted in higher levels of reactive oxygen species in comparison to gadolinium treatment alone. An addition of N-acetylcysteine prevented this increase.
The data suggest that gadolinium induces DNA damage and apoptotic cell death in human lymphocytes and that these effects could be enhanced by extremely low frequency magnetic fields.

Study character:

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

Study funded by

National Research Foundation (NRF) of Korea

Sarimov R et al. (2011): Fifty hertz magnetic fields individually affect chromatin conformation in human lymphocytes: Dependence on amplitude, temperature, and initial chromatin state
Wahab MA et al. (2007): Elevated sister chromatid exchange frequencies in dividing human peripheral blood lymphocytes exposed to 50 Hz magnetic fields
Hone P et al. (2006): Chromatid damage in human lymphocytes is not affected by 50 Hz electromagnetic fields
Zmyslony M et al. (2004): The effect of weak 50 Hz magnetic fields on the number of free oxygen radicals in rat lymphocytes in vitro
Capri M et al. (2004): 50 Hz sinusoidal magnetic fields do not affect human lymphocyte activation and proliferation in vitro
Zeni O et al. (2001): Combined exposure to extremely low frequency (ELF) magnetic fields and chemical mutagens: Lack of genotoxic effects in human lymphocytes
Maes A et al. (2000): Cytogenetic effects of 50 Hz magnetic fields of different magnetic flux densities
Yamazaki E et al. (1993): Effect of Gd-DTPA and/or magnetic field and radiofrequency exposure on sister chromatid exchange in human peripheral lymphocytes