Numerous experimental studies have shown that radiofrequency (RF) fields can induce various biological responses, including apoptosis, autophagy, DNA damage, inflammatory responses, oxidative stress, and altered gene expression. In the context of apoptosis, RF has been shown to specifically affect apoptotic markers, including pro-apoptotic proteins such as BAX and CASP, and anti-apoptotic markers such as BCL-2. While epidemiological studies suggest an increased risk of cancer, experimental research on the effects and mechanisms of RF fields remains controversial and limited. This underscores the urgent need for new, comprehensive experiments. The present study aims to investigate the effects of 2100 MHz RF exposure on cell viability, apoptosis, and gene expression in the human glioblastoma cell line U118-MG in vitro. The U118-MG cell line was chosen because it is derived from human glial cell cancer and epidemiological studies suggest an increased risk of glioma associated with mobile phone use.
The U118-MG cell line was exposed to 2100 MHz RF at 60 V/m, resulting in an average SAR (Specific Absorption Rate) of 1.12 ± 0.18 W/kg per 1 g. Cells were exposed for 1 h, 24 h, or 48 h, with sham-exposed cells used as controls. The SAR level used is consistent with current safety guidelines and is below recommended limits. Real-time temperature monitoring was performed to confirm no temperature variations. The exposure system was shielded from external electromagnetic fields. Exposure conditions and dosimetry were carefully characterized to ensure consistent and controlled exposure conditions in a stable and reproducible environment. Biologically, the study examined cell viability, cell apoptosis by Annexin-V flow cytometry, gene expression of apoptosis markers (CASP3, CASP8, CASP9, BCL-2, and BAX) by quantitative PCR, and expression of transcription factors (CYCD1, C-MYC, and c-FOS) associated with cell division and apoptosis by quantitative PCR.
Data showed that cell viability remained unchanged compared to sham-exposed controls after 1 hour and 24 hours of exposure. However, a statistically significant decrease in cell viability was observed after 48 hours of exposure. This trend was consistent with the proportion of apoptotic cells. No changes were observed after 1 hour and 24 hours, but after 48 hours, the rate of apoptotic cells was significantly increased compared to sham-exposed controls. The relative gene expression of CASP3, CASP8, and CASP9 was significantly increased after 24 hours and 48 hours of exposure, whereas the BAX/BCL-2 ratio showed a statistically significant increase only after 48 hours of exposure. In contrast, the relative gene expression of the transcription factors was increased only after 1 hour of exposure and showed no significant changes after 24 or 48 hours.
The data presented are consistent. Exposure to 2100 MHz RF at intensities below the recommended limits results in decreased cell viability and increased apoptosis after 48 hours. The BAX/BCL-2 mRNA ratio – considered a "cell death switch" and a critical regulator of cellular apoptosis – showed a 4.5-fold increase compared to sham-exposed controls. The authors hypothesize that during shorter exposure durations, cells activate stress response pathways (increased CASP3, CASP8, CASP9), but these changes in gene expression do not immediately lead to apoptosis. However, prolonged exposure exhausts the cell's ability to cope with RF-induced stress, resulting in significant apoptotic changes. The authors speculate that this may be related to exceeding the doubling time of U118-MG cells. The transient increase in transcription factor expression suggests a temporary RF effect on the cells, which warrants further investigation as it may provide insight into the cells' compensatory mechanisms. (RH)
"After 48 hours, there was a significant increase in the rate of apoptotic cells."