Authors

Franzellitti S, Valbonesi P, Ciancaglini N, Biondi C, Contin A, Bersani F, Fabbri E. Transient DNA damage induced by high frequency electromagnetic fields (GSM 1.8 GHz) in the human trophoblast HTR-8/SVneo cell line evaluated with the alkaline Comet assay. Mutat Res. Ahead of print. Oct 9, 2009.

Introduction
Although no convincing evidence exists that exposure to high frequency electromagnetic fields (HF-EMF) at non-thermal power densities can damage DNA molecule, some laboratory studies provide positive findings.

Objective
The aim of this study was to provide further insight into possible DNA alterations caused by high frequency electromagnetic fields through investigation on the human trophoblast-derived HTR-8/SVneo cell line under various exposure conditions. High responsiveness of these cells to external stimuli makes them a good model for studying possible effects of high frequency electromagnetic fields.

Methods
DNA integrity was evaluated by alkaline Comet assay after intermittent exposure (5 minutes field on, 10 minutes field off) to 1800 MHz continuous wave (CW) and two different GSM signals (GSM-217 Hz and GSM-talk) for 4, 16, and 24 hours at SAR of 2 W/kg. Tail DNA, tail length, and tail moment Comet assay parameters were evaluated. The ability of HTR-8/SVneo cells to repair potential DNA damage was evaluated 30 and 120 minutes after irradiation.  There were 3 control groups: sham-exposed cells, a negative control (incubator) and a positive control (exposure to H2O2 for detection of DNA damage levels).

Results
No significant differences in cell viability was observed between the negative control and the sham exposed cells (>98%), or between the sham-exposed cells and EMF-exposed cells immediately after the exposure, 30 or 120 minutes post-exposure.  Cell viability was 82% after a 30 minute treatment with H2O2 and did not change after 30 or 120 minute recovery. No differences in Comet assay parameters were observed between the negative control, sham-exposed cells and cells exposed to the un-modulated CW signal. For GSM-217Hz, a significant increase in the tail DNA was observed in cells exposed for 4, 16, and 24 hours; the tail length and tail moment were significantly elevated after exposure for 16 and 24 hours.  For GSM-talk, the tail DNA was significantly increased in cells exposed for 4, 16, and 24 hours; the tail length remained unchanged relative to sham-exposed and negative control at any time; the tail moment was increased only after exposure for 24 hours. Within 0.5-2 hours after the EMF exposure, the comet assay parameters of the exposed cells became similar to those of the sham-exposed cells.

Interpretation and conclusion
The data suggest that the amplitude-modulated GSM signals may affect the DNA integrity in HTR-8/SVneo cells. The fact that high frequency electromagnetic fields effects on DNA integrity were observed only after 16-24 hours of exposure may indicate that the effect of EMF on the DNA molecule is indirect.  The alterations induced by high frequency electromagnetic fields exposure were rapidly recovered.


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