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Medical/biological study (experimental study)

Differential Pro-Inflammatory Responses of Astrocytes and Microglia Involve STAT3 Activation in Response to 1800 MHz Radiofrequency Fields.

Published in: PLoS One 2014; 9 (9): e108318

Aim of study (acc. to author)

To investigate the radiofrequency field-induced proinflammatory responses of microglia and astrocytes and the involved molecular mechanisms.
Background/further details: STAT3 (signal transducer and activator of transcription 3) mediates signal transduction from the extracellular environment to the nucleus. To test the potential involvement of STAT3 in the response to radiofrequency fields, the STAT3 inhibitor "Stattic" was partially added to the culture medium 24 hours before the radiofrequency field exposure.
Positive controls were performed via treatment with lipopolysaccharides (1 µg/ml).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 1,800 MHz
Modulation type: pulsed
Exposure duration: intermittent for 1, 3, 6, 12, or 24 hours (5 min on and 10 min off)
Exposure 1
Main characteristics
Frequency 1,800 MHz
Type
Waveform
Exposure duration intermittent for 1, 3, 6, 12, or 24 hours (5 min on and 10 min off)
Modulation
Modulation type pulsed
Repetition frequency 217 Hz
Pulse type rectangular
Exposure setup
Exposure source
Chamber cells were cultured in 35 mm plastic Petri dishes
Setup system consisted of two resonating waveguides; in each waveguide chamber, a Petri dish holder for six dishes ensured that each dish was positioned accurately in the H-field maximum of the standing wave; two ventilation holes were located on the waveguide, a ventilator fan was fixed to one hole to cool the culture medium; waveguides were placed in an incubator to ensure constant environmental conditions (37 ± 0.2°C, 5% CO2, 95% air atmosphere)
Sham exposure A sham exposure was conducted.
Additional info temperature rise due to radiofrequency field was less than 0.05°C
Parameters
Measurand Value Type Method Mass Remarks
SAR 2 W/kg mean measured and calculated - -
Reference articles
Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated material:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

Radiofrequency exposure induced activation of both cell types: After 12 and 24 hours exposure, the protein expression of CD11b in microglia was significantly increased compared to the corresponding sham exposure. In astrocytes, the protein expression of glial fibrillary acidic protein was significantly increased after 24 hours exposure compared to the sham exposure as shown via immunohistochemistry and Western blot.
Microglia and astrocytes exposed to radiofrequency fields showed both proinflammatory responses compared to the sham exposure: However, the expression and release profiles of interleukin-1alpha, tumor necrosis factor-alpha, interleukin-6, prostaglandin E2, nitric oxide, inducible nitric oxide synthase, and cyclooxygenase-2 differed between the two cell types. The expression of STAT 3 was only activated in microglia. Hence, an addition of the STAT3 inhibitor "Stattic" attenuated the exposure induced effects in microglia but not in astrocytes.
The authors conclude that exposure to radiofrequency fields induces differential proinflammatory responses in microglia and astrocytes which could be mediated through different activation of STAT3 in each cell type.
Study character:

Study funded by

  • National Basic Research Program of China
  • National Natural Science Foundation (NSFC), China

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