• experimental
  
• epidemiological
  

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Medical/biological Study (experimental study)

DNA fragmentation in human fibroblasts under extremely low frequency electromagnetic field exposure. med./biol.

PubMed Entry

Journal web site

Aim of study (according to author)
The aim of the study was to replicate previous studies by Ivancsits et al. (Ivancsits et al. 2002, Ivancsits et al. 2003), implicating an increase of DNA strand breaks in primary human fibroblasts intermittently exposed to 50 Hz extremely low frequency electromagnetic fields (ELF-EMF). The aim of the present work was to test the reproducibility of these observations and to explore the origin and nature of the ELF-EMF induced DNA effects (identical experimental conditions and procedures were applied).
Background/further details:
Hydrogen peroxide treatment was used to study oxidative stress induced DNA damage.

Endpoint

• genotoxicity/mutation: DNA damage, DNA strand breaks

Exposure
General category: low frequency field, 50/60 Hz (AC), power transmission line

Field characteristics	Parameters
field 1: 50 Hz exposure duration: 5 min on - 10 min off - for 15 hr	magnetic flux density: 1 mT electric field strength: 33.2 mV/m max value (induced field at the edge of a 10 cm petri dish) electric field strength: 0 mV/m (in the center of the petri dish)
field 2: 50 Hz exposure duration: continuous for 15 hr	magnetic flux density: 1 mT electric field strength: 33.2 mV/m max value (induced field at the edge of a 10 cm petri dish) electric field strength: 0 mV/m (in the center of the petri dish)

Exposed system:
intact cell/cell culture (in vitro)
HeLa cell line (human adenocarcinoma cell line), MRC-5 (human primary fetal lung fibroblasts), and human primary fibroblasts

Methods
Endpoint/Measurement parameters/Methodology

• genotoxicity/mutation: DNA damage, DNA strand breaks (alkaline Comet assay and Fpg (formamidopyrimidine-DNA-glycosylase)-modified Comet assay (to measure oxidative stress-induced DNA damage)
• molecular biosynthesis: DNA synthesis (bromodeoxyuridine incorporation; flow cytometry)
• cell viability/cell division/proliferation: cell cycle analysis (propidium iodide stain; flow cytometry); apoptosis (Annexin V-FITC or propidium iodide staining; flow cytometry)

Main outcome of study (according to author)
The data confirmed that intermittent (but not continuous) exposure of human primary fibroblasts to a 50 Hz electromagnetic field (at a magnetic flux density of 1 mT) induces a slight but significant increase of DNA fragmentation in the Comet assay. The authors provide first evidence for this to be caused by the magnetic field rather than the electric field (for this purpose cells of the central and peripheral areas of the Petri dishes were compared). Moreover, the authors showed that electromagnetic field-induced responses in the Comet assay were dependent on cell proliferation, suggesting that processes of DNA replication rather than the DNA itself may be affected. Consistently, the effects in the Comet assay correlated with a reduction of actively replicating cells and a concomitant increase of apoptotic cells in exposed cell cultures, whereas a combined Fpg-Comet assay failed to produce evidence for a notable contribution of oxidative DNA base damage.
Hence, ELF-EMF induced effects in the Comet assay are reproducible under specific conditions and can be explained by minor disturbances in S phase processes and occasional triggering of apoptosis rather than by the generation of DNA damage. Finally, this S phase dependency may explain issues of reproducibility of the ELF-EMF induced Comet assay effects (the fraction of S phase cells in a population is determined by the culture conditions and the cell lines used, and these parameters may vary between laboratories).

(Study character: medical/biological study, experimental study, replication/reproduction study, blind study)

Study funded by

• Swiss National Science Foundation (SNF)
• Forschungsstiftung Mobilkommunikation (FSM; Research Foundation on Mobile Communication; at the Swiss Federal Institute of Technology Zurich (ETH)), Switzerland
• Nationales Forschungsprogramm NFP 57 (National Research Programme NRP 57), Switzerland

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