Acute Neuroinflammation Promotes Cell Responses to 1800 MHz GSM Electromagnetic Fields in the Rat Cerebral Cortex.

The authors of this paper claim that the effects of microwaves on health and well-being are not clear. This study aimed to investigate specifically how the brain reacts to microwave exposure with regard to memory, blood-brain barrier, oxidative stress, survival of nerve cells and salutatory conduction. The researchers induced an inflammatory reaction in the nervous tissue of young rats (2 weeks old) and adult rats (2 months old) by injecting lipopolysaccharides (LPS, cell wall components of gram-negative bacteria). After injection, the question was studied as to whether a 2-hour microwave exposure of the head would have positive or negative effects on this inflammatory response. The focus of the investigation was on the cerebral cortex. Since the inflammation of nervous tissue is frequently associated with a change in the level of excitatory transmissions, AMPA receptors (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors) were studied, among others. These receptors are common cation channels for neurotransmitters in the nervous system.

Two main groups were investigated: young developing rats (14 days old) and adult male rats (2 months old). At first, the effect of LPS by itself on pro-inflammatory gene expression was analyzed in both groups (6 animals each per group). The LPS was injected into the abdomen of the study animals. Twenty-four hours after injection, the inflammation markers in the cortex were analyzed. The two main groups were then further divided into 6 subgroups with young animals (5–7 animals each) and 10 subgroups with adult animals (6 animals each). These groups were given a single exposure of 1800 MHz (2.9 W/kg) to the head or a combination of microwave exposure and LPS injection. In the groups with the combined treatment (microwave exposure + LPS injection), the microwave exposure occurred 24 hours after injection. Half of the groups were sham-exposed. The brains were removed either 24 or 72 hours after the microwave exposure. In the tissue of the cerebral cortex, the gene expression of different inflammation markers (TNF-α, IL-1ß, IL-6, CCL2, NOX2, NOS2) was determined and the morphology of microglia cells assessed.

In adult rats, a significant increase in the gene expression of inflammation markers was observed 24 hours after the LPS injection. The transcripts of NOX2 and IL-1ß, in particular, had increased 4-fold or 12-fold, respectively. The young rats had a similar response. The dministration of LPS, however, resulted in a decrease in NOS2 and IL-6 gene expression in young rats, while the TNF-α transcription level did not differ significantly from the controls. In adult rats, this was not observed.
In both young and adult rats, the described microwave exposure led to a downregulation of the LPS-induced IL-1ß expression. The NOX2 transcript was only significantly reduced by microwave exposure in young rats. These effects were only seen 24 hours after exposure, but not after 72 hours.
To investigate an association between neuroinflammation and changes in excitatory neurotransmission, the scientists analyzed changes in the expression and phosphorylation of AMPA receptors. The microwave exposure at 1800 MHz caused a decrease in phosphorylation at two residues on the subunit GluA1 AMPAR (serine 831 and 845). Seventy-two hours after the LPS injection, the microwave exposure-induced changes in gene expression and GluA1 phosphorylation were not seen anymore, and the changes were not seen at all in those animals who had not been pretreated with LPS.
 

The data show that a single short exposure of 1800 MHz GSM radiation at 2.9 W/kg to the head of rats is sufficient in temporarily changing pro-inflammatory gene expression and activating microglia cells, which results in changes to functional markers of excitatory neurotransmission. The data also show that inflamed cells in the cerebral cortex respond to microwave exposure and that their inflammatory response is reduced by microwave exposure. These responses do not occur when healthy brains are exposed to microwave radiation at 1800 MHz. The exposure levels resulting in 2.9 W/kg used here were above the currently permissible exposure limit for humans (2 W/kg). Further research is called for in this area to understand the possible advantageous or damaging effects of microwave exposure, depending on the neuropathological state of a given brain. (IW)