Using model organism Saccharomyces cerevisiae to evaluate the effects of ELF-MF and RF-EMF exposure on global gene expression

The use of the electromagnetic field in microbial process bioengineering

An electromagnetic field (EMF) has been shown to have various stimulatory or inhibitory effects on microorganisms. Over the years, growing interest in this topic led to numerous discoveries suggesting the potential applicability of EMF in biotechnological processes. Among these observations are stimulative effects of this physical influence resulting in intensified biomass production, modification of metabolic activity, or pigments secretion. In this review, we present the current state of the art and underline the main findings of the application of EMF in bioprocessing and their practical meaning in process engineering using examples selected from studies on bacteria, archaea, microscopic fungi and yeasts, viruses, and microalgae. All biological data are presented concerning the classification of EMF. Furthermore, we aimed to highlight missing parts of contemporary knowledge and indicate weak spots in the approaches found in the literature.

Electromagnetic Fields Change the Expression of Suppressor of Cytokine Signaling 3 (SOCS3) and Cathepsin L2 (CTSL2) Genes in Adenocarcinoma Gastric (AGS) Cell Line

Background: Gastric cancer is one of the most prevalent and deadliest cancers in the world. Environmental factors including chemicals, sunlight, and electromagnetic fields can induce changes in gene expression. Though the resizing mechanism of its effect has not been fully recognized, free radicals are seen as the possible mechanism involved. Although low-frequency electromagnetic fields are not considered a carcinogenic factor, some studies have shown disruption in deoxyribonucleic acid (DNA) and gene expression in different cell categories. Objectives: This study was intendant to examine the effects of low-frequency electromagnetic flux densities of 0.2 and 2 mT on the expression of cathepsin L2 (CTSL2) and suppressor of cytokine signaling 3 (SOCS3) genes in adenocarcinoma gastric (AGS) cell lines. Methods: The AGS cell line was cultured in Hamas12 and was exposed to electromagnetic fields continuously and discontinuously for 18 hours. Moreover, Cell viability was assessed by the MTT (3-(4, 5-Dimethylthiazol-2-yl)) assay. The change in the expression of genes was measured by real-time polymerase chain reaction (PCR). Results: Low-frequency electromagnetic fields increased gene expression compared to the control group. The changes in the expression are directly associated with the electromagnetic field strength. Expression levels of CTSL2 were increased under the exposure of electromagnetic fields and this increase was significant when discontinuous exposure was applied (33.26 ± 7.4 fold change for 0.2mT and 64.4 ± 7.7 for 2mT, p- value

Biological autoluminescence as a noninvasive monitoring tool for chemical and physical modulation of oxidation in yeast cell culture

Normal or excessive oxidative metabolism in organisms is essential in physiological and pathophysiological processes, respectively. Therefore, monitoring of biological oxidative processes induced by the chemical or physical stimuli is nowadays of extreme importance due to the environment overloaded with various physicochemical factors. Current techniques typically require the addition of chemical labels or light illumination, which perturb the samples to be analyzed. Moreover, the current techniques are very demanding in terms of sample preparation and equipment. To alleviate these limitations, we propose a label-free monitoring tool of oxidation based on biological autoluminescence (BAL). We demonstrate this tool on Saccharomyces cerevisiae cell culture. We showed that BAL can be used to monitor chemical perturbation of yeast due to Fenton reagents initiated oxidation-the BAL intensity changes with hydrogen peroxide concentration in a dose-dependent manner. Furthermore, we also showed that BAL reflects the effects of low-frequency magnetic field on the yeast cell culture, where we observed a disturbance of the BAL kinetics in the exposed vs. control case. Our results contribute to the development of novel techniques for label-free, real-time, noninvasive monitoring of oxidative processes and approaches for their modulation.

Radio frequency-induced superoxide accumulation affected the growth and viability of Saccharomyces cerevisiae

With the development of the electric technologies, the biological effects of electromagnetic fields (EMF) were widely studied. However, the results remain controversial and the biophysical mechanisms are still unknown. To our knowledge, little studies pay attention to the radio frequency (RF) of 2.6-5 MHz. In the present study, we investigated the effect of these radio frequencies on the growth and cell viability of Saccharomyces cerevisiae at very low power density below 0.1 mT. The result appeared to be time-dependent. The growth of the yeast cells was obviously affected by the RF-EMF with a 43.5% increase when exposed for 30 h, and the growth-promoting effect decreased along with the radiation time and eventually turned to an inhibiting effect retarding growth by 20.7% at 89 h. The cell viability was improved to 70.1% at 8 h and reduced by 33.5% at 28 h. The superoxide accumulated in exposed cells as radiation time increased which may lead to the inhibition of viability and growth of the cells. However, the efficient frequency, power density, and exposure dosage await further investigation. Nevertheless, the wave band studied in this research is effective to produce biological effect, and therefore, it may provide an optional new radio frequency which is valuable for the development and utilization in therapy technique and medical use.

Electromagnetic Fields, Genomic Instability and Cancer: A Systems Biological View

This review discusses the use of systems biology in understanding the biological effects of electromagnetic fields, with particular focus on induction of genomic instability and cancer. We introduce basic concepts of the dynamical systems theory such as the state space and attractors and the use of these concepts in understanding the behavior of complex biological systems. We then discuss genomic instability in the framework of the dynamical systems theory, and describe the hypothesis that environmentally induced genomic instability corresponds to abnormal attractor states; large enough environmental perturbations can force the biological system to leave normal evolutionarily optimized attractors (corresponding to normal cell phenotypes) and migrate to less stable variant attractors. We discuss experimental approaches that can be coupled with theoretical systems biology such as testable predictions, derived from the theory and experimental methods, that can be used for measuring the state of the complex biological system. We also review potentially informative studies and make recommendations for further studies.

50-Hz magnetic field impairs the expression of iron-related genes in the in vitro SOD1G93A model of amyotrophic lateral sclerosis

PURPOSE

We characterized the response to the extremely low frequency magnetic field (ELF-MF) in an in vitro model of familial Amyotrophic Lateral Sclerosis (fALS), carrying two mutant variants of the superoxide dismutase 1 (SOD1) gene.

MATERIALS AND METHODS

SH-SY5Y human neuroblastoma cells, stably over-expressing the wild type, the G93A or the H46R mutant SOD1 cDNA, were exposed to either the ELF-MF (50 Hz, 1 mT) or the sham control field, up to 72 h. Analysis of (i) viability, proliferation and apoptosis, (ii) reactive oxygen species generation, and (iii) assessment of the iron metabolism, were carried out in all clones in response to the MF exposure.

RESULTS

We report that 50-Hz MF exposure induces: (i) no change in proliferation and viability; (ii) no modulation of the intracellular superoxide and H₂O₂ levels; (iii) a significant deregulation in the expression of iron-related genes IRP1, MFRN1 and TfR1, this evidence being exclusive for the SOD1^G93A clone and associated with a slight (p = .0512) difference in the total iron content.

CONCLUSIONS

50-Hz MF affects iron homeostasis in the in vitro SOD1^G93A ALS model.

Ataxia telangiectasia mutated deficiency does not result in genetic susceptibility to 50 Hz magnetic fields exposure in mouse embryonic fibroblasts

Extremely low frequency magnetic field (ELF-MF) has been classified as a possible carcinogen to humans by the International Agency for Research on Cancer [2002]. However, debate on the genotoxic effects of ELF-MF has continued due to lack of sufficient experimental evidence. Ataxia telangiectasia mutated (ATM) plays a central role in DNA damage repair; its deficiency can result in cellular sensitivity to DNA-damaging agents. To evaluate the genotoxicity of ELF-MF, we investigated the effects of 50 Hz MF on DNA damage in ATM-proficient (Atm^+/+ ) mouse embryonic fibroblasts (MEFs) and ATM-deficient (Atm^-/- ) MEFs, a radiosensitive cell line. Results showed no significant difference in average number of γH2AX foci per cell (9.37 ± 0.44 vs. 9.08 ± 0.28, P = 0.58) or percentage of γH2AX foci positive cells (49.22 ± 1.86% vs. 49.74 ± 1.44%, P = 0.83) between sham and exposure groups when Atm^+/+ MEFs were exposed to 50 Hz MF at 2.0 mT for 15 min. Extending exposure duration to 1 or 24 h did not significantly change γH2AX foci formation in Atm^+/+ MEFs. Similarly, the exposure did not significantly affect γH2AX foci formation in Atm^-/- MEFs. Furthermore, 50 Hz MF exposure also did not significantly influence DNA fragmentation, cell viability, or cell cycle progression in either cell types. In conclusion, exposure to 50 Hz MF did not induce significant DNA damage in either Atm^+/+ or Atm^-/- MEFs under the reported experimental conditions. Bioelectromagnetics. 39:476-484, 2018. © 2018 Wiley Periodicals, Inc.

Semi-quantitative proteomics of mammalian cells upon short-term exposure to non-ionizing electromagnetic fields

The potential effects of non-ionizing electromagnetic fields (EMFs), such as those emitted by power-lines (in extremely low frequency range), mobile cellular systems and wireless networking devices (in radio frequency range) on human health have been intensively researched and debated. However, how exposure to these EMFs may lead to biological changes underlying possible health effects is still unclear. To reveal EMF-induced molecular changes, unbiased experiments (without a priori focusing on specific biological processes) with sensitive readouts are required. We present the first proteome-wide semi-quantitative mass spectrometry analysis of human fibroblasts, osteosarcomas and mouse embryonic stem cells exposed to three types of non-ionizing EMFs (ELF 50 Hz, UMTS 2.1 GHz and WiFi 5.8 GHz). We performed controlled in vitro EMF exposures of metabolically labeled mammalian cells followed by reliable statistical analyses of differential protein- and pathway-level regulations using an array of established bioinformatics methods. Our results indicate that less than 1% of the quantitated human or mouse proteome responds to the EMFs by small changes in protein abundance. Further network-based analysis of the differentially regulated proteins did not detect significantly perturbed cellular processes or pathways in human and mouse cells in response to ELF, UMTS or WiFi exposure. In conclusion, our extensive bioinformatics analyses of semi-quantitative mass spectrometry data do not support the notion that the short-time exposures to non-ionizing EMFs have a consistent biologically significant bearing on mammalian cells in culture.

Exposure of ELF-EMF and RF-EMF Increase the Rate of Glucose Transport and TCA Cycle in Budding Yeast

In this study, we investigated the transcriptional response to 50 Hz extremely low frequency electromagnetic field (ELF-EMF) and 2.0 GHz radio frequency electromagnetic field (RF-EMF) exposure by Illumina sequencing technology using budding yeast as the model organism. The transcription levels of 28 genes were upregulated and those of four genes were downregulated under ELF-EMF exposure, while the transcription levels of 29 genes were upregulated and those of 24 genes were downregulated under RF-EMF exposure. After validation by reverse transcription quantitative polymerase chain reaction (RT-qPCR), a concordant direction of change both in differential gene expression (DGE) and RT-qPCR was demonstrated for nine genes under ELF-EMF exposure and for 10 genes under RF-EMF exposure. The RT-qPCR results revealed that ELF-EMF and RF-EMF exposure can upregulate the expression of genes involved in glucose transportation and the tricarboxylic acid (TCA) cycle, but not the glycolysis pathway. Energy metabolism is closely related with the cell response to environmental stress including EMF exposure. Our findings may throw light on the mechanism underlying the biological effects of EMF.

Extremely low-frequency electromagnetic fields cause G1 phase arrest through the activation of the ATM-Chk2-p21 pathway

In daily life, humans are exposed to the extremely low-frequency electromagnetic fields (ELF-EMFs) generated by electric appliances, and public concern is increasing regarding the biological effects of such exposure. Numerous studies have yielded inconsistent results regarding the biological effects of ELF-EMF exposure. Here we show that ELF-EMFs activate the ATM-Chk2-p21 pathway in HaCaT cells, inhibiting cell proliferation. To present well-founded results, we comprehensively evaluated the biological effects of ELF-EMFs at the transcriptional, protein, and cellular levels. Human HaCaT cells from an immortalized epidermal keratinocyte cell line were exposed to a 1.5 mT, 60 Hz ELF-EMF for 144 h. The ELF-EMF could cause G1 arrest and decrease colony formation. Protein expression experiments revealed that ELF-EMFs induced the activation of the ATM/Chk2 signaling cascades. In addition, the p21 protein, a regulator of cell cycle progression at G1 and G2/M, exhibited a higher level of expression in exposed HaCaT cells compared with the expression of sham-exposed cells. The ELF-EMF-induced G1 arrest was diminished when the CHK2 gene expression (which encodes checkpoint kinase 2; Chk2) was suppressed by specific small interfering RNA (siRNA). These findings indicate that ELF-EMFs activate the ATM-Chk2-p21 pathway in HaCaT cells, resulting in cell cycle arrest at the G1 phase. Based on the precise control of the ELF-EMF exposure and rigorous sham-exposure experiments, all transcriptional, protein, and cellular level experiments consistently supported the conclusion. This is the first study to confirm that a specific pathway is triggered by ELF-EMF exposure.

Modulation effect of low-frequency electric and magnetic fields on CO2 production and rates of acetate and pyruvate formation in Saccharomyces cerevisiae cell culture

We studied action of one-dimensional, two-dimensional and three-dimensional low-frequency oscillating electric and magnetic fields on sugar metabolism in Saccharomyces cerevisiae cell culture. S. cerevisiae cells were grown on a minimal medium containing glucose (10%) as a carbon source and salts (0.3-0.5%) that supplied nitrogen, phosphorus and trace metals. We found that appropriate three-dimensional field patterns can either accelerate or inhibit sugar metabolism in yeast cells, as compared to control experiments. We also studied aerobic sugar metabolism, with similar results. Sugar metabolism was monitored by formation of pyruvate, acetate and CO2. We found that for the P1 parameter set the cell metabolism accelerates as evaluated by all of the monitored chemical products, and the cell density growth rate also accelerates, with opposite effects observed for the P2 parameter set. These parameter sets are introduced using D, ω, φ, B, ω', and φ' - vectors defining amplitudes, frequencies and phases of periodic electric and magnetic fields, respectively. Thus, the P1 parameter set: D = (2.6, 3.1, 2.2) V/cm; ω = (0.8, 1.6, 0.2) kHz; φ = (1.31, 0.9, 1.0) rad; B = (3.1, 7.2, 7.2) × 10(-4) T; ω' = (2.1, 1.3, 3.1) kHz; φ' = (0.4, 2.1, 2.8) rad; and the P2 parameter set: D = (4.3, 1.6, 3.8) V/cm; ω = (3.3, 1.8, 2.8) kHz; φ = (0.86, 1.1, 0.4) rad; B = (5.4, 1.3, 1.3) × 10(-4) T; ω' = (1.3, 1.7, 0.9) kHz; φ' = (2.6, 1.7, 1.7) rad. The effects obtained for the less complex field combinations that used one-dimensional or two-dimensional configurations, or omitted either the electric or the magnetic contribution, were significantly weaker than those obtained for the complete P1 and P2 parameter sets.

A review of the ecological effects of radiofrequency electromagnetic fields (RF-EMF)

OBJECTIVE

This article presents a systematic review of published scientific studies on the potential ecological effects of radiofrequency electromagnetic fields (RF-EMF) in the range of 10 MHz to 3.6 GHz (from amplitude modulation, AM, to lower band microwave, MW, EMF).

METHODS

Publications in English were searched in ISI Web of Knowledge and Scholar Google with no restriction on publication date. Five species groups were identified: birds, insects, other vertebrates, other organisms, and plants. Not only clear ecological articles, such as field studies, were taken into consideration, but also biological articles on laboratory studies investigating the effects of RF-EMF with biological endpoints such as fertility, reproduction, behaviour and development, which have a clear ecological significance, were also included.

RESULTS

Information was collected from 113 studies from original peer-reviewed publications or from relevant existing reviews. A limited amount of ecological field studies was identified. The majority of the studies were conducted in a laboratory setting on birds (embryos or eggs), small rodents and plants. In 65% of the studies, ecological effects of RF-EMF (50% of the animal studies and about 75% of the plant studies) were found both at high as well as at low dosages. No clear dose-effect relationship could be discerned. Studies finding an effect applied higher durations of exposure and focused more on the GSM frequency ranges.

CONCLUSIONS

In about two third of the reviewed studies ecological effects of RF-EMF was reported at high as well as at low dosages. The very low dosages are compatible with real field situations, and could be found under environmental conditions. However, a lack of standardisation and a limited number of observations limit the possibility of generalising results from an organism to an ecosystem level. We propose in future studies to conduct more repetitions of observations and explicitly use the available standards for reporting RF-EMF relevant physical parameters in both laboratory and field studies.