Study type: Medical/biological study (experimental study)

Exposure to 900 MHz electromagnetic fields activates the mkp-1/ERK pathway and causes blood-brain barrier damage and cognitive impairment in rats. med./bio.

Published in: Brain Res 2015; 1601: 92-101

Aim of study (acc. to author)

The effects of exposure of rats to a 900 MHz electromagnetic field on the spatial memory, neuronal and blood brain barrier damage and the potential underlying mechanisms of action should be investigated.

Background/further details

108 rats were divided into 3 groups (n=36 each): 1) sham exposure, 2) exposure to the magnetic field for 14 days and 3) 28 days. In each group, 3 rats were used for electron microscopy, 6 were used for immunohistochemistry, 12 for the evans blue assay, 6 for Western blot and 9 for the Morris water maze.
Heme oxygenase-1 (HO-1) is a marker for oxidative stress. MAPK phosphatase-1 (mkp-1) regulates the activity and expression of ERK 1 and 2. The authors hypothesized that the mkp-1/ERK pathway is potentially involved in the regulation of HO-1, the damaging of the blood brain barrier and resulting cognitive impairments.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 900 MHz
Exposure duration: continuous for 3 h/day for 14 days
Exposure 2: 900 MHz
Exposure duration: continuous for 3 h/day for 28 days

Exposure 1

Main characteristics
Frequency 900 MHz
Type
Exposure duration continuous for 3 h/day for 14 days
Exposure setup
Exposure source
  • monopole
Distance between exposed object and exposure source 1 m
Setup four rats were exposed simultaneously in an immobilization apparatus with their heads towards the antenna at a distance of at least 1 m; the propagation direction of the signal was in the direction of the long-axis of the rats; the position of the rats during exposure on each day was altered
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power 2 W peak value - - output power
power density 1 mW/cm² - measured - near the head
SAR 0.016 W/g - measured and calculated whole body determined in phantom
SAR 2 W/g - measured and calculated partial body in the head, determined in phantom

Exposure 2

Main characteristics
Frequency 900 MHz
Type
Exposure duration continuous for 3 h/day for 28 days
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
power 2 W peak value - - output power
power density 1 mW/cm² - measured - near the head
SAR 0.016 W/g - measured and calculated whole body determined in phantom
SAR 2 W/g - measured and calculated partial body in the head, determined in phantom

Reference articles

  • Hao D et al. (2013): Effects of long-term electromagnetic field exposure on spatial learning and memory in rats.
  • Tu WZ et al. (2012): Analgesic effect of electroacupuncture on chronic neuropathic pain mediated by P2X3 receptors in rat dorsal root ganglion neurons.
  • Odaci E et al. (2008): Effects of prenatal exposure to a 900 MHz electromagnetic field on the dentate gyrus of rats: a stereological and histopathological study.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

The spatial memory was significantly impaired after 28 days of exposure (group 3) compared to the 14-day exposure group (group 2) and sham exposure.
The neuronal ultrastructure was changed in groups 2 and 3 compared to sham exposure with edema between neurons and blood vessels. Group 3 showed additional swollen or missing organelles and cytoplasmic vacuolization in neurons.
The level of HO-1 was significantly higher in both exposure groups compared to the sham exposure and in group 3 compared to group 2.
In immunohistochemical analysis, a significant higher level of albumin was found in group 3 in the hippocampus and cortex compared to group 2 and sham exposure, but albumin could also be detected in neurons of group 2. Additionally, a significant higher amount of evans blue could be detected in groups 2 and 3 compared to sham exposure. The mkp-1 expression was significantly up-regulated and ERK phosphorylation significantly reduced in group 3 compared to the sham exposure.
The authors conclude, that exposure of rats to a 900 MHz electromagnetic field could impair the spatial memory and damage the blood brain barrier and that the mkp-1/ERK signaling pathway may be involved in this process.

Study character:

Study funded by

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