Medical/biological study (experimental study)

Apoptosis is Induced by Radiofrequency Fields through the Caspase-Independent Mitochondrial Pathway in Cortical Neurons. med./bio.

By: Joubert V, Bourthoumieu S, Leveque P, Yardin C

Published in: Radiat Res 2008; 169 (1): 38-45

Aim of study (acc. to author)

To study whether continuous wave radiofrequency fields induce neuron apoptosis in vitro (in rat neuronal primary cultures).

Background/further details

During exposure a temperature increase of 2°C was measured in the medium; control experiments with neurons exposed to 39°C were then performed. Staurosporine was used as positive control.
The pathways leading to apoptosis may be dependent on or independent of caspases and in the caspase-independent apoptosis pathway, DNA fragmentation and chromatin condensation are triggered by the apoptosis-inducing factor.

Endpoint

cell viability/cell division/proliferation: apoptosis

Exposure

- RF field

Exposure	Parameters
Exposure 1: 900 MHz Modulation type: CW Exposure duration: continuous for 24 h	SAR: 2 W/kg

Exposure 1

Main characteristics

Frequency	900 MHz
Type	electromagnetic field
Exposure duration	continuous for 24 h

Modulation

Modulation type	CW

Exposure setup

Exposure source	wire-patch cell (WPC) [see reference articles]
Chamber	Cells plated in 35-mm Petri dishes in 2 ml of medium were placed inside an incubator at 37°C with 95% air and 5% CO₂ for at least 2 h before exposure.
Sham exposure	A sham exposure was conducted.
Additional info	In each experiment, dishes from the same cell culture were simultaneously RF or sham exposed in the same incubator or subjected to 37°C (control) or 39°C (heat control) in additional incubators.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
SAR	2 W/kg	-	calculated	-	-

Measurement and calculation details

Dosimetric assessments were performed on eight Petri dishes within the WPC. Theoretical calculations of the SAR distribution, using the FDTD method, and temperature simulations were validated experimentally using local electric field and temperature probes. During exposure, an optical fibre temperature probe was placed in the center of the medium in the dish.

Reference articles

Joubert V et al. (2007): No apoptosis is induced in rat cortical neurons exposed to GSM phone fields.
Joubert V et al. (2006): Microwave exposure of neuronal cells in vitro: Study of apoptosis.
Laval L et al. (2000): A new in vitro exposure device for the mobile frequency of 900 MHz.

Exposed system:

intact cell/cell culture

Methods Endpoint/measurement parameters/methodology

cell function: caspase 3 activity
cell viability/cell division/proliferation: apoptosis (condensation of nuclei (DAPI staining; epifluorescence microscopy); fragmentation of DNA (TUNEL assay; flow cytometry)); apoptosis-inducing factor labeling (epifluorescence microscopy)

Investigated system:

intact cell/cell culture
cell supernatant

Time of investigation:

after exposure

Main outcome of study (acc. to author)

A statistically significant difference (increase) in the apoptosis rate was found in the radiofrequency exposed neurons compared to the sham exposed, 37°C and 39°C exposed neurons either immediately or 24 h after exposure.
No increase in the caspase 3 enzyme activity was found, whereas the percentage of AIF-positive nuclei in irradiated neurons was increased by three- to sevenfold compared to other conditions.
The data show that exposure of primary rat neurons to continuous wave radiofrequency fields may induce a caspase-independent pathway to apoptosis that involves apoptosis-inducing factor.

Study character:

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

Study funded by

Conseil Régional du Limousin, France
University of Limoges, France

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