Author(s):
Kim JH*, Seok JY, Kim YH, Kim HJ, Lee JK, Kim HR.
* Department of Pharmacology, College of Medicine, Dankook University, Cheonan 31116.
South Korea
Published in:
Int J Mol Sci 2024; 25 (16): 8589
Published: 06.08.2024
on EMF:data since 11.11.2024
Further publications: Studie gefördert durch:

Basic Science Research Program through the National
Research Foundation (NRF) of Korea (grant number NRF-2022R1A2C1012144 to J.H.K.).

Keywords for this study:
Memory, learning, behavior
Medical/biological studies
Go to EMF:data assessment

Exposure to Radiofrequency Induces Synaptic Dysfunction in Cortical Neurons Causing Learning and Memory Alteration in Early Postnatal Mice.

Original Abstract

The widespread use of wireless communication devices has necessitated unavoidable exposure to radiofrequency electromagnetic fields (RF-EMF). In particular, increasing RF-EMF exposure among children is primarily driven by mobile phone use. Therefore, this study investigated the effects of 1850 MHz RF-EMF exposure at a specific absorption rate of 4.0 W/kg on cortical neurons in mice at postnatal day 28. The results indicated a significant reduction in the number of mushroom-shaped dendritic spines in the prefrontal cortex after daily exposure for 4 weeks. Additionally, prolonged RF-EMF exposure over 9 days led to a gradual decrease in postsynaptic density 95 puncta and inhibited neurite outgrowth in developing cortical neurons. Moreover, the expression levels of genes associated with synapse formation, such as synaptic cell adhesion molecules and cyclin-dependent kinase 5, were reduced in the cerebral cortexes of RF-EMF-exposed mice. Behavioral assessments using the Morris water maze revealed altered spatial learning and memory after the 4-week exposure period. These findings underscore the potential of RF-EMF exposure during childhood to disrupt synaptic function in the cerebral cortex, thereby affecting the developmental stages of the nervous system and potentially influencing later cognitive function.

Keywords

radiofrequency electromagnetic fields | cerebral cortex | synapse | cell adhesion molecules | cyclin-dependent kinase 5 | spatial learning and memory

Exposure:

1850 MHz

EMF:data assessment

Summary

As mobile phone use is typically associated with close head proximity, potential effects of mobile phone exposure on the central nervous system (CNS) are of particular concern. Despite scientific controversy, there is accumulating evidence that mobile phone radiation may have harmful effects, such as impairment of intracellular calcium homeostasis, neuronal damage and disruption of neurotransmitters in the CNS. Previous studies have demonstrated that the specific absorption rate (SAR) of five-year-old children is twice that of 20-year-old adults. Therefore, effects of mobile phone emission may be more severe in children, since their CNS is still developing. Of particular relevance is the cerebral cortex, which is involved in various crucial functions, including sensory perception, motor control, higher cognitive processes and complex behaviors. Dysfunction of the cerebral cortex is associated with neurodegenerative diseases such as Alzheimer’s disease and, in cases of impaired development in children, with attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD).

This study investigates the influence of mobile phone irradiation on the synaptic development of cortical neurons in mice. The focus was on altered expression of key genes and proteins involved in synapse formation, including neurexin, neuroligin, and cyclin-dependent kinase 5 (CDK5). Behavioral changes in the mice were also studied.

Source: ElektrosmogReport - Issue 4/2024

Study design and methods

The authors exposed newborn mice to radiofrequency radiation for four weeks, starting on the first day after birth. For the first three weeks, this exposure was conducted in the presence of the mother. The young mice were exposed to continuous 1850 MHz waves without frequency modulation for 5 hours per day. The SAR value was 4 W/kg. This is the maximum allowed exposure level for normal mobile phone users in several countries, based on recommendations from organizations such as CENELEC, ICNIRP, and IEEE. (However, 4 W/kg applies to the extremities, while the maximum values for the head and torso are 1.6 and 2.0 W/kg, respectively. Editor’s note.) The researchers used electron microscopy to study neuronal development and synapse formation, focusing on dendritic spines. In vitro analyses of cultured primary neurons included the expression of PSD95, a key regulator of synaptic plasticity, and neurite outgrowth. The expression of key components of synapse formation (genes: nlgn2, nlgn3, nrxn1a; proteins: CDK5) was subsequently evaluated. Finally, potential behavioral changes as a consequence of radiofrequency exposure were assessed using the Morris water maze test.

Results

The authors observed a statistically significant reduction in dendritic spines in the cortical neurons of the exposed mice, particularly mushroom-shaped spines, which are known for their strong synaptic signal transmission. Both dendrite formation (PSD95) as well as neurite length and branching were significantly reduced in cultured cortical neurons. These findings suggest that mobile phone irradiation impairs synaptic structure, density, and neurite outgrowth. The expression of synaptic cell adhesion proteins (nlgn2, nlgn3, nrxn1α), which are crucial for maintaining synapses and neuronal connections, was significantly decreased at the mRNA level in the prefrontal cortex of the exposed mice. Additionally, the protein expression of CDK5, which plays a vital role in various neuronal development processes, including synapse growth and maturation, spine formation, and synaptic plasticity, was significantly reduced. Behavioral tests supported the molecular findings. A significant impairment in spatial learning and memory was observed in the young exposed mice.

Conclusions

Overall, the results of the present publication suggest that under the selected exposure conditions (continuous 1850 MHz field, 4 W/kg SAR, 5 hours/day, 4 weeks), mobile phone radiation impairs synapse formation and function, reducing the levels of essential synaptic molecules. This ultimately leads to diminished cognitive capacity in newborn mice. Dysregulation of synaptic adhesion molecules is associated with various cognitive diseases, including autism spectrum disorders, schizophrenia, and intellectual disabilities. CDK5 is associated with learning and memory processes. For example, CDK5 deficient mice have significant impairments in spatial learning. The findings highlight the harmful potential of mobile phone radiation during development, particularly regarding neurodevelopmental disorders such as autism spectrum disorder. (RH)