Medical/biological study (experimental study)

STAT3 signalling pathway is involved in the activation of microglia induced by 2.45 GHz electromagnetic fields med./bio.

By: Hao Y, Yang X, Chen C, Yuan-Wang, Wang X, Li M, Yu Z

Published in: Int J Radiat Biol 2010; 86 (1): 27-36

To study the activation of microglia and involvement of signal transducer and activator of transcription 3 (STAT3; mediates signal transduction from the extracellular environment to the nucleus) in microglia activation after 2.45 GHz electromagnetic fields exposure.

Microglia is considered as a specialised macrophages residing form in the central nervous system. In response to a variety of insults, microglia adopts an activated phenotype. Microglia activation plays a pivotal role in the initiation and progression of several neurodegenerative diseases.
Some cell samples were pretreated with the JAK inhibitor pyridone 6 (P6) to study whether P6 could affect the STAT3 activation (to further demonstrate JAK2-STAT3 signal transduction (JAK is a STAT3 activator and is able to phosphorylate STAT3)). Cells were investigated 1 h, 6 h, and 12 h after exposure.

Exposure	Parameters
Exposure 1: 2.45 GHz Modulation type: pulsed Exposure duration: continuous for 20 min	power: 90 mW average over time SAR: 6.2 W/kg spatial average (+/- 1.5 W/kg)

Exposure source	horn antenna anechoic chamber
Distance between exposed object and exposure source	90 cm
Sham exposure	A sham exposure was conducted.

Measurand	Value	Type	Method	Mass	Remarks
power	90 mW	average over time	-	-	-
SAR	6.2 W/kg	spatial average	calculated	-	+/- 1.5 W/kg

Exposed system:

Investigated system:

Time of investigation:

The data showed a significant increase of STAT3 DNA-binding ability after exposure. Consistent with this, the electromagnetic field exposure rapidly induced phosphorylation of STAT3 and activated JAK1 and JAK2. Additionally, electromagnetic field exposure increased transcription levels of the inflammation-associated genes (iNOS and TNF-alpha), which are reported to contain STAT-binding elements in their promoter region.
P6 reduced induction of iNOS and TNF-alpha, DNA binding activity, and activation of STAT3 in exposure-stimulated microglia cells. These findings indicate that the electromagnetic field exposure induces phosphorylation and activation of STAT3 through phosphorylation and activation of JAK.
The authors conclude that the data provide evidence that electromagnetic field exposure can initiate the activation of microglia cells and that STAT3 signal transduction is involved in electromagnetic field-induced microglial activation.

Study character:

Lu Y et al. (2014): Differential Pro-Inflammatory Responses of Astrocytes and Microglia Involve STAT3 Activation in Response to 1800 MHz Radiofrequency Fields
Karaca E et al. (2012): The genotoxic effect of radiofrequency waves on mouse brain
Finnie JW et al. (2010): Microglial activation as a measure of stress in mouse brains exposed acutely (60 minutes) and long-term (2 years) to mobile telephone radiofrequency fields
Yang X et al. (2010): The role of the JAK2-STAT3 pathway in pro-inflammatory responses of EMF-stimulated N9 microglial cells
Xiao-Feng P et al. (2005): The influence of electromagnetic field irradiated by high-voltage transmission lines on properties of cells
Mausset-Bonnefont AL et al. (2004): Acute exposure to GSM 900-MHz electromagnetic fields induces glial reactivity and biochemical modifications in the rat brain