Abstract
More than ever before, people around the world are frequently exposed to different sections of the electromagnetic spectrum, mainly emitted from wireless modern communication technologies. Especially, the level of knowledge on non-thermal biological EMF effects remains controversial. New technologies allow for a more detailed detection of non-coding RNAs which affect the post-transcriptional control. Such method shall be applied in this work to investigate the response of human blood cells to electromagnetic irradiation. In this ex vivo in vitro study, we exposed peripheral blood cells from 5 male donors to a continuous wave of 900 MHz EMF for 0, 30, 60 and 90 min. Significant micro RNA (miRNA) expression changes (p ≤ 0.05) above or below the SHAM exposed samples were evaluated using a quantitative real time PCR platform for simultaneous detection of 667 miRNAs called low density array. Only significant miRNA expression changes which were detectable in at least 60% of the samples per exposure group were analyzed. The results were compared with data from room temperature + 2 °C (RT + 2 °C) samples (here referred to as hyperthermia) to exclude miRNA expression altered by hyperthermia. The validation study by using the same donors and study design was performed after an interval of 2 years. When analyzing a total of 667 miRNAs during the screening study, 2 promising candidate miRNAs were identified, which were down regulated almost twice and showed a complete separation from the unexposed control group (miR-194 at 30 min and miR-939 at 60 min). The p-values even survived the Bonferroni correction for multiple comparisons (p = 0.0007 and p = 0.004, respectively). None of these miRNAs were expressed at a second time point after EMF exposure. Following an alternative analysis approach, we examined for miRNAs revealing an expected significant association of differential miRNA expression with the dose-time EMF exposure product, separately for each donor. Donors 2 and 3 revealed 11 and 10 miRNA species being significantly associated with EMF exposure which differed significantly from the other donors showing a minor number of differentially expressed miRNAs and could identify donors 2 and 3 as particularly EMF-responsive. The measurements were repeated after 2 years. The number of expressed/non-expressed miRNAs was almost similar (97.4%), but neither the number nor the previously differentially expressed miRNAs could be reproduced. Our data neither support evidence of early changes at miRNA expression level in human whole blood cells after 900 MHz EMF exposure nor the identification of EMF-responsive individuals.
Highlights
The targeted utilization of radiofrequency electromagnetic fields (EMF) is the basis for all wireless communication technologies and cannot be substituted within an era of steady information and data exchange
In a previous publication on changes at the transcriptional level searching for protein coding messenger ribonucleic acids and using the same biosamples we already reported about the normal values of differential blood cell counts observed in all donors[13]
Based on our current assessment this is the first study that examines the athermal influence of 900 MHz EMF on micro RNA (miRNA) expressions in human peripheral blood cells
Summary
The targeted utilization of radiofrequency electromagnetic fields (EMF) is the basis for all wireless communication technologies and cannot be substituted within an era of steady information and data exchange. Protein coding genes will be activated by increasing the gene copy number and corresponding proteins will be synthesized leading to certain biological responses such as cell cycle control, apoptosis or DNA repair These protein coding genes are controlled by so called micro ribonucleic acids (miRNAs). MiRNA contribution is common in various cellular stress responses such as regulation of coding genes with involvement, inter alia, in apoptosis, cell cycle and DNA repair[2]. Other authors proved that miRNAs act as crucial elements in posttranscriptional control of erythroid c ells[9,10,11] These and many other studies highlight the pivotal role of miRNAs and raised questions regarding an involvement in an EMF specific response in order to stabilize cellular homeostasis
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