Medical/biological study (experimental study)

Fifty-hertz magnetic fields induce free radical formation in mouse bone marrow-derived promonocytes and macrophages med./bio.

By: Rollwitz J, Lupke M, Simko M

Published in: Biochimica et Biophysica Acta - General Subjects 2004; 1674 (3): 231-238

Aim of study (acc. to author)

To study the effects of 50 Hz magnetic field on free radical production in mouse bone marrow-derived macrophages and monocytes.

Background/further details

LPS (lipopolysaccharides; to study the influence of the magnetic field on differentiated macrophages and their nitric oxide production; LPS activates the nitric oxide synthase) and TPA (tetradecanoylphorbol acetate; TPA is known to induce a direct activation of NADPH-oxidase) were used as positive controls.
Enzymes such as NAD(P)H-oxidases mediate the main production of free radicals (ROS) in macrophages. The authors assume that the activation of NADH-oxidase plays a major role in phagocytic cells and is responsible for the magnetic field-induced free radical production. To study this, the specific NADPH-oxidase inhibitor DPI (diphenyleneiodonium chloride) was used, which does not affect NADH-oxidase activity. It makes it possible to distinguish between the two pathways (NADH-oxidase/NADPH-oxidase).

Endpoint

molecular biosynthesis: production of free radicals

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: experiment 1: 45 min; experiment 2: 45 min up to 24 h	magnetic flux density: 1 mT unspecified

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Exposure duration	experiment 1: 45 min; experiment 2: 45 min up to 24 h

Exposure setup

Exposure source	Helmholtz coils
Chamber	Incubator containg 5% CO2 and maintained at 37°C
Setup	Cultue plates were placed in the center of the coils, which were located in the middle of the incubator
Sham exposure	A sham exposure was conducted.

Parameters

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

Exposed system:

intact cell/cell culture

Methods Endpoint/measurement parameters/methodology

molecular biosynthesis: production of free radicals (reactive oxygen species/ROS (flow cytometry); superoxide anion radical generation (nitro blue tetrazolium test); nitrogen generation (NO₂^-)

Investigated system:

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

Time of investigation:

after exposure

Main outcome of study (acc. to author)

The results show a significant increase of free radical production after exposure to 50 Hz electromagnetic fields to promonocytes and macrophages, indicating the cell-activating capacity of extremely low frequency magnetic fields.
After exposure mainly superoxide anion radicals were produced, both in macrophages and also in their precursor cells (monocytes). Magnetic field-induced free radical production was not inhibited by DPI, whereas TPA-induced free radical production was diminished by about 70%. Since DPI lacks an inhibitory effect in magnetic field-exposed cells, the authors suggest that 50 Hz magnetic field stimulates the NADH-oxidase pathway to produce superoxide anion radicals, but not the NADPH pathway. Magnetic field-exposed cells show no detectable production of NO₂^-.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Bundesministerium für Bildung und Forschung (BMBF; Federal Ministry for Education and Research), Germany
VERUM Foundation (Stiftung für Verhalten und Umwelt), Germany

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