Author(s):
Marjanović Čermak AM*, Ilić K, Pavičić I.
* Institute for Medical Research and Occupational Health, Ksaverska cesta 2, HR-10001 Zagreb.
Croatia
Published in:
Arh Hig Rada Toksikol 2020; 71 (3): 205-210
Published: 01.09.2020
on EMF:data since 11.11.2024
Further publications:
Keywords for this study:
Cell proliferation/growth
Medical/biological studies
Go to EMF:data assessment

Microtubular structure impairment after GSM-modulated RF radiation exposure.

Original Abstract

The objective of the study was to investigate whether low-level 915 MHz GSM-modulated radiofrequency (RF) radiation impairs microtubular structure and affects normal cell growth. V79 cells were exposed to a GSM-modulated field in a Gigahertz Transversal Electromagnetic Mode cell (GTEM cell) for 1, 2, and 3 h. Signal generator combined with power and chip modulator generated the electromagnetic field (EMF). The electric field strength was adjusted to 10, 20, and 30 V/m, and the average specific absorption rate (SAR) was calculated to be 0.23, 0.8, and 1.6 W/kg. The structure of microtubule proteins was assessed by indirect immunocytochemistry, and cell growth was determined based on cell counts taken every day over six post-exposure days. Three-hour radiation exposure significantly altered microtubule structure regardless of the electric field strength. Moreover, on the third post-exposure day, three-hour radiation significantly reduced cell growth, regardless of field strength. The same was observed with two-hour exposure at 20 and 30 V/m. In conclusion, 915 MHz GSM-modulated RF radiation affects microtubular proteins in a time-dependent manner, which, in turn, affects cell proliferation. Our future research will focus on microtubule structure throughout the cell cycle and RF radiation effects on mitotic spindle.

Keywords

915 MHz | cell growth | cytoskeleton | in vitro | mobile phone radiation

Exposure:

915 MHz
GSM
SAR = 0,23; 0,8; 1,6 W/kg

EMF:data assessment

Summary

Numerous biological effects claimed to be caused by radiofrequency (RF) radiation are of questionable significance for living organisms. However, RF radiation has been found to interact with various apoptosis pathways in living cells. A number of studies have also investigated its genotoxic and other effects on the cell cycle, enzyme activity, gene expression, DNA, oxidative stress and chromosomes. There must be a physical mechanism for RF energy to affect physiological functions or cause disease in humans or animals. This mechanism should explain how the forces exerted by electric and magnetic fields or charged particles alter molecules, chemical reactions, the cell membrane or biological structures. This mechanism could be linked to microtubule dynamics. It is known that the assembly and disassembly of microtubules occurs at specific times in the cell cycle and that the dynamic exchange of charged tubulin subunits influences the movement of cytoplasmic vesicles and organelles such as mitochondria or chromosomes during mitosis. The dynamic instability of microtubule arrangement controls many aspects of cell proliferation, so it stands to reason that microtubules might be suitable for studying bioelectromagnetic effects. The aim of the study was to investigate whether weak 915 MHz GSM-modulated RF radiation affects microtubule structure and influences normal cell growth.

Source: ElektrosmogReport - Issue 4/2024

Study design and methods

The Chinese hamster fibroblast cell line (V79) was used due to its known properties and frequent use in cytotoxic studies. V79 cells were exposed to a GSM-modulated field in a Gigahertz Transversal Electromagnetic Mode cell (GTEM cell, ETS-Lindgren) for 1, 2 and 3 hours.

An Anritsu 2721B signal generator combined with a Polaris RF 2722 power and signal modulator (RF Micro Devices) generated the electromagnetic field (EMF). The electric field strength was set to 10, 20 and 30 V/m (265 mW/m², 1.06 W/m², 2.39 W/m²), and the average specific absorption rate (SAR) was calculated to be 0.23, 0.8 and 1.6 W/kg.

Each exposure protocol was performed on three independent cell samples. In addition to the negative control, irradiated cells treated with colchicine were used as positive controls. Colchicine is an antimitotic agent that attaches to free tubulin subunits and suppresses the polymerization and destruction of microtubules. The temperature of the culture medium was measured continuously using a temperature sensor. The temperature did not rise during irradiation and was maintained at 36.3 °C, which corresponds to the physiological cell temperature. Microtubular proteins in irradiated cell samples as well as negative and positive control cell samples were determined by indirect immunocytochemical analysis. A complex of a primary IgG anti-β-tubulin antibody produced in the mouse to label microtubular proteins and a secondary antibody representing a conjugate of anti-mouse IgG and fluorescein isothiocyanate was used.

Microtubule damage was assessed by determining the structural differences in the irradiated cells. The changes identified as granular fluorescent clusters were compared with those observed in positive control cells. This granular structure indicates that the microtubule fibers are highly dispersed and therefore damaged. To measure the cell proliferation rate, cells from each group were seeded on 24-well plates and counted daily under a light microscope up to six days after exposure.

Results

Three hours of irradiation led to considerable damage to the microtubules (independent of the field strength, i.e. approximately the same effect at 10 V/m as at 30 V/m). With shorter irradiation, the microtubules developed normally and did not differ from the negative controls.

Three days after the three-hour exposure, the cell count was significantly lower than in the negative control (p < 0.05). A two-hour exposure to 20 and 30 V/m (corresponding to 0.8 and 1.6 W/kg SAR) also led to a significantly lower proliferation rate on day 3 after exposure. However, on day 4 after exposure, cell counts returned to normal in each exposed group.

Conclusions

The results show that 915 MHz radiation affects microtubular proteins of V79 cells in a time-dependent manner. This confirms the hypothesis that electromagnetic fields in the GSM frequency range could interfere with the mechanisms that drive the cytoskeletal network, since this process relies on the electrical charge of the tubulin subunits. Microtubules as part of the cytoskeleton fulfill the basic requirements for the onset of a so-called "Fröhlich resonance" (synchronized electromagnetic oscillations within a system). In a healthy cell, this endogenous electromagnetic field is perfectly balanced, but external electromagnetic fields might disturb it. The results of this study show that the effects of radiation on the microtubules do not depend significantly on the electric field strength and the corresponding SAR. Further studies are needed to better understand these processes. (AT)