Study type: Medical/biological study (experimental study)

Effects of the exposure to intermittent 1.8 GHz radio frequency electromagnetic fields on HSP70 expression and MAPK signaling pathways in PC12 cells. med./bio.

Published in: Int J Radiat Biol 2014; 90 (5): 382-391

Aim of study (acc. to author)

To investigate the stress responses mediated by Hsp70 and mitogen-activated protein kinases rat PC12 cells exposed to a 1.8 GHz-electromagnetic field.

Background/further details

In a previous study (Franzellitti et al., 2008 ), the authors reported the effects on the gene expression of Hsp70 in human trophoblast cells. In the present work, the same experimental conditions were applied but PC12 cells were used.
Cell cultures were subjected to one of the following conditions: 1.) sham exposure, 2.) exposure to a continuous wave, 3.) exposure to a GSM-217 Hz signal (simulates mobile phone speaking mode) and 4.) exposure to a GSM-217 Hz and GSM-DTX signal (simulates a typical mobile phone conversation with speaking and hearing). Cell cultures were exposed for 4, 16 or 24 hours. For every condition and time period, 6 experiments with 6 petri dishes were performed, respectively. Positive controls were performed (heat shock for Hsp70 gene expression, treatment with H2O2 for phosphorylation of mitogen-activated protein kinases).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 1,800 MHz
Modulation type: CW
Exposure duration: intermittent, 5 min on/10 min off, for 4, 16, and 24 h
  • SAR: 2 W/kg average over time (± 0.4 W/kg)
Exposure 2: 1,800 MHz
Modulation type: pulsed
Exposure duration: intermittent, 5 min on/10 min off, for 4, 16, and 24 h
  • SAR: 2 W/kg average over time (± 0.4 W/kg)
Exposure 3: 1,800 MHz
Modulation type: pulsed
Exposure duration: intermittent, 5 min on/10 min off, for 4, 16, and 24 h
  • SAR: 2 W/kg average over time (± 0.4 W/kg)

Exposure 1

Main characteristics
Frequency 1,800 MHz
Type
Exposure duration intermittent, 5 min on/10 min off, for 4, 16, and 24 h
Additional info continuous wave
Modulation
Modulation type CW
Exposure setup
Exposure source
Chamber The exposure system was developed and built following the specifications in [Schonborn et al., 2000]. Two 128.5 x 65 x 424 mm³ brass single-mode waveguide resonators equipped with ventilators and air temperature probes were placed inside one of the two incubators.
Setup Six 35-mm Petri dishes per resonator, each containing 3 ml of medium, were arranged in two stacks using a plastic holder and were placed in the H-field maximum of the standing wave (E-polarization).
Sham exposure A sham exposure was conducted.
Additional info Within each experiment, six dishes each were RF and sham exposed. Signal characteristics and the exposure/sham condition were assigned to the two waveguides by a computer-controlled signal unit ensuring blinded conditions.
Parameters
Measurand Value Type Method Mass Remarks
SAR 2 W/kg average over time measured and calculated - ± 0.4 W/kg

Exposure 2

Main characteristics
Frequency 1,800 MHz
Type
Waveform
Exposure duration intermittent, 5 min on/10 min off, for 4, 16, and 24 h
Additional info GSM-217 Hz signal
Modulation
Modulation type pulsed
Duty cycle 12.5 %
Repetition frequency 217 Hz
Pulse type rectangular
Additional info

GSM-217 Hz signal (speaking only) with every 26th frame being idle, adding an 8 Hz modulation component [Pedersen, 1997]

Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 2 W/kg average over time measured and calculated - ± 0.4 W/kg

Exposure 3

Main characteristics
Frequency 1,800 MHz
Type
Exposure duration intermittent, 5 min on/10 min off, for 4, 16, and 24 h
Additional info GSM-DTX signal + GSM-217 Hz signal
Modulation
Modulation type pulsed
Duty cycle 12.5 %
Repetition frequency 217 Hz
Pulse type rectangular
Additional info

GSM-Talk signal (33% speaking and 67% hearing) with temporal changes between GSM-217 Hz and GSM-DTX (transmission reduced to 12 active frames per 104 frames) resulting in 2, 8, and 217 Hz modulation components

Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 2 W/kg average over time measured and calculated - ± 0.4 W/kg

Reference articles

  • Valbonesi P et al. (2008): Evaluation of HSP70 expression and DNA damage in cells of a human trophoblast cell line exposed to 1.8 GHz amplitude-modulated radiofrequency fields.
  • Schuderer J et al. (2004): High Peak SAR Exposure Unit With Tight Exposure and Environmental Control for In Vitro Experiments at 1800 MHz
  • Kuster N et al. (2000): Recommended minimal requirements and development guidelines for exposure setups of bio-experiments addressing the health risk concern of wireless communications.
  • Pedersen GF (1997): Amplitude modulated RF fields stemming from a GSM/DCS-1800 phone.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

After 16 or 24 hours of exposure to the GSM-217 Hz signal (group 3), the gene expression of Hsp70 was significantly increased compared to the sham exposed cell cultures, while no significant effect was observed in the other exposure groups. Additionally, no differences between the groups were observed regarding protein expression levels and cell viability.
The authors conclude that the observed increase in the Hsp70 gene expression in PC12 cells confirmed the results of the previous study with trophoblasts.

Study character:

Study funded by

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