Inhibition of B16F10 Cancer Cell Growth by Exposure to the Square Wave with 7.83+/-0.3Hz Involves L- and T-Type Calcium Channels

Extremely low-frequency electromagnetic field (ELF-EMF) exposure influences many biological systems; these effects are mainly related to the intensity, duration, frequency, and pattern of the ELF-EMF. In this study, exposure to square wave with 7.83±0.3 Hz (sweep step 0.1 Hz) was shown to inhibit the growth of B16F10 melanoma tumor cells. In addition, the distribution of the magnetic field was calculated by Biot-Savart Law and plotted using MATLAB. In vitro studies demonstrated a decrease in B16F10 cell proliferation and an increase of Ca2+ influx after 48 h of exposure to the square wave. Ca2+ influx was also partially blocked by inhibition of voltage-gated L- and T-type Ca2+ channels. The data confirmed that the specific time-varying ELF-EMF had an anti-proliferation effect on B16F10 cells and that the inhibition is related to Ca2+ and voltage-gated L- and T-type Ca2+ channels.

Evaluation of the neuroprotective effects of electromagnetic fields and coenzyme Q10 on hippocampal injury in mouse

Electromagnetic fields (EMFs) are reported to interfere with chemical reactions involving free radical production. Coenzyme Q10 (CoQ10) is a strong antioxidant with some neuroprotective activities. The purpose of this study was to examine and compare the neuroprotective effects of EMF and CoQ10 in a mouse model of hippocampal injury. Hippocampal injury was induced in mature female mice (25-30 g), using an intraperitoneal injection of trimethyltin hydroxide (TMT; 2.5 mg/kg). The experimental groups were exposed to EMF at a frequency of 50 Hz and intensity of 5.9 mT for 7 hr daily over 1 week or treated with CoQ10 (10 mg/kg) for 2 weeks following TMT injection. A Morris water maze apparatus was used to assess learning and spatial memory. Nissl staining and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) tests were also performed for the histopathological analysis of the hippocampus. Antiapoptotic genes were studied, using the Western blot technique. The water maze test showed memory improvement following treatment with CoQ10 and coadministration of CoQ10 + EMF. The Nissl staining and TUNEL tests indicated a decline in necrotic and apoptotic cell count following treatment with CoQ10 and coadministration of CoQ10 + EMF. The Western blot study indicated the upregulation of antiapoptotic genes in treatment with CoQ10, as well as coadministration. Also, treatment with EMF had no significant effects on reducing damage induced by TMT in the hippocampus. According to the results, EMF had no significant neuroprotective effects in comparison with CoQ10 on hippocampal injury in mice. Nevertheless, coadministration of EMF and CoQ10 could improve the neuroprotective effects of CoQ10.

Effects of extremely low-frequency electromagnetic fields on B16F10 cancer cells

This paper presents a method to inhibit B16F10 cancer cells using extremely low-frequency electromagnetic fields (ELF-EMFs) and to evaluate cell viability using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. The study examined the effect of a natural EMF resonance frequency (7.83 Hz) and a power line frequency (60 Hz) on B16F10 cancer cells for 24 and 48 h. The B16F10 cancer cells were also exposed to sweep frequencies in several sweep intervals to quantitatively analyze the viability of cancer cells. The results yielded a 17% inhibition rate under 7.83 Hz compared with that of the control group. Moreover, sweep frequencies in narrow intervals (7.83 ± 0.1 Hz for the step 0.05 Hz) caused an inhibition rate of 26.4%, and inhibitory effects decreased as frequency sweep intervals increased. These results indicate that a Schumann resonance frequency of 7.83 Hz can inhibit the growth of cancer cells and that using a specific frequency type can lead to more effective growth inhibition.

In Vivo Cytotoxicity Induced by 60 Hz Electromagnetic Fields under a High-Voltage Substation Environment

Living beings permanently receive electromagnetic radiation, particularly from extremely low-frequency electromagnetic fields (ELF-EMFs), which may cause adverse health effects. In this work, we studied the in vivo cytotoxic effects of exposing BALB/c mice to 60 Hz and 8.8 µT EMFs during 72 h and 240 h in a switchyard area, using animals exposed to 60 Hz and 2.0 mT EMFs or treated with 5 mg/kg mitomycin C (MMC) as positive controls. Micronucleus (MN) frequency and male germ cell analyses were used as cytological endpoints. ELF-EMF exposure was observed to significantly (p < 0.05) increase MN frequency at all conditions tested, with the 2 mT/72 h treatment causing the highest response, as compared with untreated control. In addition, increased sperm counts were observed after switchyard area ELF-EMF exposure, as compared with untreated control. In contrast, low sperm counts were obtained for 72 h/2.0 mT-exposed animals and for MMC-treated mice (p < 0.05), without altering male germ cell morphological characteristics.

Electromagnetized gold nanoparticles mediate direct lineage reprogramming into induced dopamine neurons in vivo for Parkinson's disease therapy

Electromagnetic fields (EMF) are physical energy fields generated by electrically charged objects, and specific ranges of EMF can influence numerous biological processes, which include the control of cell fate and plasticity. In this study, we show that electromagnetized gold nanoparticles (AuNPs) in the presence of specific EMF conditions facilitate an efficient direct lineage reprogramming to induced dopamine neurons in vitro and in vivo. Remarkably, electromagnetic stimulation leads to a specific activation of the histone acetyltransferase Brd2, which results in histone H3K27 acetylation and a robust activation of neuron-specific genes. In vivo dopaminergic neuron reprogramming by EMF stimulation of AuNPs efficiently and non-invasively alleviated symptoms in mouse Parkinson's disease models. This study provides a proof of principle for EMF-based in vivo lineage conversion as a potentially viable and safe therapeutic strategy for the treatment of neurodegenerative disorders.

Influence of Cardiac MR Imaging on DNA Double-Strand Breaks in Human Blood Lymphocytes

PURPOSE

To evaluate the ability of magnetic resonance (MR) imaging to induce deoxyribonucleic acid (DNA) damage in patients who underwent cardiac MR imaging in daily routine by using γ-H2AX immunofluorescence microscopy.

MATERIALS AND METHODS

This study complies with the Declaration of Helsinki and was performed according to local ethics committee approval. Informed patient consent was obtained. Blood samples from 45 patients (13 women, 32 men; mean age, 50.3 years [age range, 20-89 years]) were obtained before and after contrast agent-enhanced cardiac MR imaging. MR imaging-induced double-strand breaks (DSBs) were quantified in isolated blood lymphocytes by using immunofluorescence microscopy after staining the phosphorylated histone variant γ-H2AX. Twenty-nine patients were examined with a myocarditis protocol (group A), 10 patients with a stress-testing protocol (group B), and six patients with flow measurements and angiography (group C). Paired t test was performed to compare excess foci before and after MR imaging.

RESULTS

The mean baseline DSB level before MR imaging and 5 minutes after MR imaging was, respectively, 0.116 DSB per cell ± 0.019 (standard deviation) and 0.117 DSB per cell ± 0.019 (P = .71). There was also no significant difference in DSBs in these subgroups (group A: DSB per cell before and after MR imaging, respectively, 0.114 and 0.114, P = .91; group B: DSB per cell before and after MR imaging, respectively, 0.123 and 0.124, P = .78; group C: DSB per cell before and after MR imaging, respectively, 0.114 and 0.115, P = .36).

CONCLUSION

By using γ-H2AX immunofluorescence microscopy, no DNA DSBs were detected after cardiac MR imaging.

Circadian gene expression and extremely low-frequency magnetic fields: an in vitro study

It is well known that circadian clocks are mainly regulated by light targeting signaling pathways in the hypothalamic suprachiasmatic nucleus. However, an entrainment mediated by non-photic sensory stimuli was also suggested for peripheral clocks. Exposure to extremely low frequency (ELF) electromagnetic fields might affect circadian rhythmicity. The goal of this research was to investigate effects of ELF magnetic fields (ELF-MF) on circadian clock genes in a human fibroblast cell line. We found that an ELF-MF (0.1 mT, 50 Hz) exposure was capable of entraining expression of clock genes BMAL1, PER2, PER3, CRY1, and CRY2. Moreover, ELF-MF treatment induced an alteration in circadian clock gene expression previously entrained by serum shock stimulation. These results support the hypothesis that ELF-MF may be able to drive circadian physiologic processes by modulating peripheral clock gene expression.

Effects of long-term 50Hz power-line frequency electromagnetic field on cell behavior in Balb/c 3T3 cells

Power-line frequency electromagnetic field (PF-EMF) was reported as a human carcinogen by some epidemiological research, but the conclusion is lack of robust experiment evidence. To identify the effects of long-term PF-EMF exposure on cell behavior, Balb/c 3T3 cells in exponential growth phase were exposed or sham-exposed to 50 Hertz (Hz) PF-EMF at 2.3 mT for 2 hours (h) one day, 5 days every week. After 11 weeks exposure, cells were collected instantly. Cell morphology was observed under invert microscope and Giemsa staining, cell viability was detected by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, cell cycle and apoptosis was examined by flow cytometry, the protein level of Proliferating Cell Nuclear Antigen (PCNA) and CyclinD1 was detected by western blot, cell transformation was examined by soft agar clone assay and plate clone forming test, and cell migration ability was observed by scratch adhesion test. It was found that after PF-EMF exposure, cell morphology, apoptosis, cell migration ability and cell transformation didn't change. However, compared with sham group, cell viability obviously decreased and cell cycle distribution also changed after 11 weeks PF-EMF exposure. Meanwhile, the protein level of PCNA and CyclinD1 significantly decreased after PF-EMF exposure. These data suggested that although long-term 50Hz PF-EMF exposure under this experimental condition had no effects on apoptosis, cell migration ability and cell transformation, it could affect cell proliferation and cell cycle by down-regulation the expression of PCNA and CyclinD1 protein.

Power frequency magnetic fields induced reactive oxygen species-related autophagy in mouse embryonic fibroblasts

Power frequency magnetic fields (PFMF) have been reported to affect several cellular functions, such as cell proliferation and apoptosis. In this study, we investigated the effects of PFMF on mouse embryonic fibroblasts (MEF) autophagy. After cells were exposed to 50 Hz PFMF at 2 mT for 0.5 h, 2 h, 6 h, 12 h, and 24 h, we observed a significant increase in autophagic markers at 6 h, including (i) higher microtubule-associated protein 1 light chain 3-II (LC3-II), (ii) the increased formation of GFP-LC3 puncta, and (iii) increased numbers of autophagic vacuoles under transmission electron microscope. Moreover, we provide convincing evidence using chloroquine (CQ) that the increase of autophagic markers was the result of enhanced autophagic flux and not the suppression of lysosomal function. In a search for molecular mechanisms underlying PFMF-mediated autophagy, we observe that the autophagic process involved reactive oxygen species (ROS) and was independent of the mammalian target of rapamycin (mTOR) signaling pathway.

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.

Gene expression and reproductive abilities of male Drosophila melanogaster subjected to ELF-EMF exposure

Extremely low frequency electromagnetic field (ELF-EMF) exposure is attracting increased attention as a possible disease-inducing factor. The in vivo effects of short-term and long-term ELF-EMF exposure on male Drosophila melanogaster were studied using transcriptomic analysis for preliminary screening and QRT-PCR for further verification. Transcriptomic analysis indicated that 439 genes were up-regulated and 874 genes were down-regulated following short-term exposures and that 514 genes were up-regulated and 1206 genes were down-regulated following long-term exposures (expression >2- or <0.5-fold, respectively). In addition, there are 238 up-regulated genes and 598 down-regulated genes in the intersection of short-term and long-term exposure (expression >2- or <0.5-fold). The DEGs (differentially expressed genes) in D. melanogaster following short-term exposures were involved in metabolic processes, cytoskeletal organization, mitotic spindle organization, cell death, protein modification and proteolysis. Long-term exposure let to changes in expression of genes involved in metabolic processes, response to stress, mitotic spindle organization, aging, cell death and cellular respiration. In the intersection of short-term and long-term exposure, a series of DEGs were related to apoptosis, aging, immunological stress and reproduction. To check the ELF-EMF effects on reproduction, some experiments on male reproduction ability were performed. Their results indicated that short-term ELF-EMF exposure may decrease the reproductive ability of males, but long-term exposures had no effect on reproductive ability. Down-regulation of ark gene in the exposed males suggests that the decrease in reproductive capacity may be induced by the effects of ELF-EMF exposure on spermatogenesis through the caspase pathway. QRT-PCR analysis confirmed that jra, ark and decay genes were down regulated in males exposed for 1 Generation (1G) and 72 h, which suggests that apoptosis may be inhibited in vivo. ELF-EMF exposure may have accelerated cell senescence, as suggested by the down-regulation of both cat and jra genes and the up-regulation of hsp22 gene. Up-regulation of totA and hsp22 genes during exposure suggests that exposed flies might induce an in vivo immune response to counter the adverse effects encountered during ELF-EMF exposure. Down-regulation of cat genes suggests that the partial oxidative protection system might be restrained, especially during short-term exposures. This study demonstrates the bioeffects of ELF-EMF exposure and provides evidence for understanding the in vivo mechanisms of ELF-EMF exposure on male D. melanogaster.

Can safe and long-term exposure to extremely low frequency (50 Hz) magnetic fields affect apoptosis, reproduction, and oxidative stress?

PURPOSE

To determine whether 50 Hz extremely low frequency-magnetic fields (ELF-MF) affects apoptotic processes, oxidative damage, and reproductive characteristics such as sperm count and morphology in rat testes.

MATERIALS AND METHODS

Thirty male Sprague-Dawley rats were used in the present study, which were divided into three groups (sham group, n = 10, and two experimental groups, n = 10 for each group). Rats in the experimental group were exposed to 100 and 500 μT ELF-MF (2 h/day, 7 days/week, for 10 months) corresponding to exposure levels that are considered safe for humans. The same experimental procedures were applied to the sham group, but the ELF generator was turned off. Tissues from the testes were immunohistochemically stained for active (cleaved) caspase-3 in order to measure the apoptotic index by a semi-quantitative scoring system. The levels of catalase (CAT), malondialdehyde (MDA), myeloperoxidase (MPO), total antioxidative capacity (TAC), total oxidant status (TOS), and oxidative stress index (OSI) were also measured. Additionally, epididymal sperm count and sperm morphology was evaluated.

RESULTS

There were no significant differences in the reproductive and oxidative stress parameters between the sham group and the exposed groups (p > 0.05). While no difference was observed between the final apoptosis score of the sham and the 100 μT ELF-MF group (p > 0.05), the final apoptosis score was higher in the 500 μT ELF-MF exposure group than in the sham group (p < 0.05).

CONCLUSION

Long-term exposure to 100 μT and 500 μT ELF-MF did not affect oxidative or antioxidative processes, lipid peroxidation, or reproductive components such as sperm count and morphology in testes tissue of rats. However, long-term exposure to 500 μT ELF-MF did affect active-caspase-3 activity, which is a well-known apoptotic indicator.

Retinoic acid inhibits the cytoproliferative response to weak 50‑Hz magnetic fields in neuroblastoma cells

We previously reported that intermittent exposure to a 50‑Hz magnetic field (MF) at 100 µT stimulates cell proliferation in the human neuroblastoma cell line NB69. The present study aimed to investigate whether the magnetic field-induced growth promotion also occurs at a lower magnetic flux density of 10 µT. To this purpose, NB69 cells were subjected for 42 h to intermittent exposure, 3 h on/3 h off, to a 50‑Hz MF at a 10 or 100 µT magnetic flux density. The field exposure took place either in the presence or in the absence of the antiproliferative agent retinoic acid. At the end of the treatment and/or incubation period, the cell growth was estimated by hemocytometric counting and spectrophotometric analysis of total protein and DNA contents. Potential changes in DNA synthesis were also assessed through proliferating cell nuclear antigen (PCNA) immunolabeling. The results confirmed previously reported data that a 42-h exposure to a 50‑Hz sine wave MF at 100 µT promotes cell growth in the NB69 cell line, and showed that 10 µT induces a similar proliferative response. This effect, which was significantly associated and linearly correlated with PCNA expression, was abolished by the presence of retinoic acid in the culture medium.

Short-term exposure to 50 Hz ELF-EMF alters the cisplatin-induced oxidative response in AT478 murine squamous cell carcinoma cells

The aim of this study was to assess the influence of cisplatin and an extremely low frequency electromagnetic field (ELF-EMF) on antioxidant enzyme activity and the lipid peroxidation ratio, as well as the level of DNA damage and reactive oxygen species (ROS) production in AT478 carcinoma cells. Cells were cultured for 24 and 72 h in culture medium with cisplatin. Additionally, the cells were irradiated with 50 Hz/1 mT ELF-EMF for 16 min using a solenoid as a source of the ELF-EMF. The amount of ROS, superoxide dismutase (SOD) isoenzyme activity, glutathione peroxidase (GSH-Px) activity, DNA damage, and malondialdehyde (MDA) levels were assessed. Cells that were exposed to cisplatin exhibited a significant increase in ROS and antioxidant enzyme activity. The addition of ELF-EMF exposure to cisplatin treatment resulted in decreased ROS levels and antioxidant enzyme activity. A significant reduction in MDA concentrations was observed in all of the study groups, with the greatest decrease associated with treatment by both cisplatin and ELF-EMF. Cisplatin induced the most severe DNA damage; however, when cells were also irradiated with ELF-EMF, less DNA damage occurred. Exposure to ELF-EMF alone resulted in an increase in DNA damage compared to control cells. ELF-EMF lessened the effects of oxidative stress and DNA damage that were induced by cisplatin; however, ELF-EMF alone was a mild oxidative stressor and DNA damage inducer. We speculate that ELF-EMF exerts differential effects depending on the exogenous conditions. This information may be of value for appraising the pathophysiologic consequences of exposure to ELF-EMF.

Magnetic nanoparticles sensitize MCF-7 breast cancer cells to doxorubicin-induced apoptosis

Background

Resistance of breast cancer cells to the available chemotherapeutics is a major obstacle to successful treatment. Recent studies have shown that magnetic nanoparticles might have significant application in different medical fields including cancer treatment. The goal of this study is to verify the ability of magnetic nanoparticles to sensitize cancer cells to the clinically available chemotherapy.

Methods

The role of iron oxide nanoparticles, static magnetic field, or a combination in the enhancement of the apoptotic potential of doxorubicin against the resistant breast cancer cells, MCF-7 was evaluated using the MTT assay and the propidium iodide method.

Results

In the present study, results revealed that pre-incubation of MCF-7 cells with iron oxide nanoparticles before the addition of doxorubicin did not enhance doxorubicin-induced growth inhibition. Pre-incubation of MCF-7 cells with iron oxide nanoparticles followed by a static magnetic field exposure significantly (P < 0.05) increased doxorubicin-induced cytotoxicity. Sensitization with pre-exposure to the magnetic field was dose-dependent where the highest cytotoxicity was seen at 1 tesla. Further experiments revealed that the anti-proliferative effect of this treatment procedure is due to induction of apoptotic cell death.

Conclusions

These results might point to the importance of combining magnetic nanoparticles with a static magnetic field in treatment of doxorubicin-refractory breast cancer cells.

Effects on micronuclei formation of 60-Hz electromagnetic field exposure with ionizing radiation, hydrogen peroxide, or c-Myc overexpression

PURPOSE

Epidemiological studies have demonstrated a possible correlation between exposure to extremely low-frequency magnetic fields (ELF-MF) and cancer. However, this correlation has yet to be definitively confirmed by epidemiological studies. The principal objective of this study was to assess the effects of 60 Hz magnetic fields in a normal cell line system, and particularly in combination with various external factors, via micronucleus (MN) assays.

MATERIALS AND METHODS

Mouse embryonic fibroblast NIH3T3 cells and human lung fibroblast WI-38 cells were exposed for 4 h to a 60 Hz, 1 mT uniform magnetic field with or without ionizing radiation (IR, 2 Gy), H(2)O(2) (100 μM) and cellular myelocytomatosis oncogene (c-Myc) activation.

RESULTS

The results obtained showed no significant differences between the cells exposed to ELF-MF alone and the unexposed cells. Moreover, no synergistic effects were observed when ELF-MF was combined with IR, H(2)O(2), and c-Myc activation.

CONCLUSIONS

Our results demonstrate that ELF-MF did not enhance MN frequency by IR, H(2)O(2) and c-Myc activation.

Can cytogenetics explain the possible association between exposure to extreme low-frequency magnetic fields and Alzheimer's disease?

Recently, a number of epidemiological studies have suggested that occupational as well as residential exposure to extreme low-frequency electromagnetic fields (ELF-EMFs) may be a risk factor for Alzheimer's disease. This is not proven yet and there are no known biological mechanisms to explain this alleged association. Alzheimer's disease is characterized by a number of events that have, at least partially, a genetic origin. In particular, trisomy of chromosomes 17 and 21 seems to be involved. Overall ELF-EMFs have not been identified as genotoxic agents, but there are some papers in the scientific literature that indicate that they may enhance the effects of agents that are known to induce mutations or tumors. There are also some indications that ELF-EMFs may induce aneuploïdy. This opens some perspectives for investigating the alleged association between ELF-EMFs and Alzheimer's. This paper reviews the possibility of a cytogenetic association between the electromagnetic fields and Alzheimer's disease.

Toxicity and SOS response to ELF magnetic field and nalidixic acid in E. coli cells

Extremely low frequency (ELF) magnetic fields have previously been shown to affect conformation of chromatin and cell proliferation. Possible genotoxic and carcinogenic effects of ELF have also been discussed and tested. In this study, we analyzed the effect of ELF on chromatin conformation in E. coli GE499 cells by the anomalous viscosity time dependence (AVTD) technique. Possible genotoxic ELF effects at the specific combination of static and ELF magnetic fields, that has been proven to have effects on chromatin conformation, were investigated by clonogenic assay, cell growth kinetics, and analysis of SOS-response using inducible recA-lacZ fusion and the β-galactosidase assay. Genotoxic agent nalidixic acid (NAL) was used as positive control and in combination with ELF. Nalidixic acid at 3-30μg/ml decreased the AVTD peaks and induced cytotoxic effect. In contrast to NAL, ELF increased AVTD, stimulated cell growth, and increased cloning efficiency. These effects depended on frequency within the frequency range of 7-11Hz. While NAL induced SOS response, ELF exposure did not induce the recA-lacZ fusion. Exposure to ELF did not modify the genotoxic effects of NAL either. All together, the data show that ELF, under specific conditions of exposure, acted as nontoxic but cell growth stimulating agent.

Toxicity and SOS-response to ELF magnetic fields and nalidixic acid in E. coli cells

Extremely low-frequency magnetic fields (ELF-MF) have previously been shown to affect conformation of chromatin and cell proliferation. Possible genotoxic and carcinogenic effects of ELF-MF have also been discussed and tested. In this study, we analysed the effect of ELF-MF on chromatin conformation in E. coli GE499 cells by the anomalous viscosity time-dependence (AVTD) technique. Possible genotoxic effects of the specific combination of static and ELF-MF, which has been proven to affect chromatin conformation, were investigated by a clonogenic assay, by assessing cell-growth kinetics, and by analysis of the SOS-response by means of inducible recA-lacZ fusion-gene products and the β-galactosidase assay. The genotoxic agent nalidixic acid (NAL) was used as a positive control and in combination with ELF-MF. Nalidixic acid at 3-30μg/ml decreased the AVTD peaks and induced a cytotoxic effect. In contrast to NAL, ELF-MF fields increased AVTD, stimulated cell growth, and increased cloning efficiency. These effects depended on the frequency within the range of 7-11Hz. While NAL induced an SOS-response, exposure to ELF-MF did not induce the recA-lacZ fusion-gene product. Exposure to ELF-MF did not modify the genotoxic effects of NAL either. All together, the data show that ELF-MF, under specific conditions of exposure, acted as a non-toxic but cell-growth stimulating agent.

50 Hz extremely low frequency electromagnetic fields enhance protein carbonyl groups content in cancer cells: effects on proteasomal systems

Electromagnetic fields are an assessed cause of prolonging free radicals lifespan. This study was carried out to investigate the influence of extremely low frequency electromagnetic fields on protein oxidation and on the 20S proteasome functionality, the complex responsible for the degradation of oxidized proteins. Caco 2 cells were exposed, for 24-72 hours, to 1 mT, 50 Hz electromagnetic fields. The treatment induced a time-dependent increase both in cell growth and in protein oxidation, more evident in the presence of TPA, while no changes in cell viability were detected. Exposing the cells to 50 Hz electromagnetic fields caused a global activation of the 20S proteasome catalytic components, particularly evident at 72 hours exposure and in the presence of TPA. The finding that EGCG, a natural antioxidant compound, counteracted the field-related pro-oxidant effects demonstrates that the increased proteasome activity was due to an enhancement in intracellular free radicals.

Extremely low frequency magnetic fields and the promotion of H2O2‐induced cell death in HL‐60 cells

PURPOSE

To test whether exposure to an extremely low frequency magnetic field (60 Hz, 5 mT) affects hydrogen peroxide (H2O2)-induced cell death in human leukaemia HL-60 cells.

MATERIALS AND METHODS

Cells were treated with H2O2 with or without exposure to an extremely low frequency magnetic fields. Viable cells, apoptotic and necrotic cells were determined by annexin V flow cytometry assay. The levels of apoptosis-related proteins (caspase-3, caspase-7, Bcl-2 and Bax) and poly(ADP-ribose) polymerase were detected using Western blotting.

RESULTS

Simultaneous treatment with exposure to the magnetic field and H2O2 (85 or 100 microM) for 24 h increased the number of apoptotic and necrotic cells significantly, and significantly decreased the number of viable cells compared with cells treated with H2O2 alone. The protein levels of Bax and Bcl-2 showed no differences between H2O2-treated cells and those treated with both H2O2 and an extremely low frequency magnetic field. Exposure to the magnetic field also had no effect on H2O2-induced caspase-3 activation. However, the protein levels of active caspase-7 in cells simultaneously exposed to an extremely low frequency magnetic field and H2O2 for 2 and 8 h was higher than that of H2O2 treatment alone. In addition, simultaneous exposure to an extremely low frequency magnetic field and H2O2 caused poly(ADP-ribose) polymerase cleavage and induced early inactivation at 2 h, while H2O2 treatment alone did not produce this effect until 4 h.

CONCLUSIONS

The data suggest that although the magnetic field itself cannot induce apoptosis and necrosis, it exerts a promoting effect on H2O2-induced cell death, and it demonstrates that caspase-7 as well as poly(ADP-ribose) polymerase might be involved in this process.

Enhancement of the cell-killing effect of ultraviolet-C radiation by short-term exposure to a pulsed magnetic field

PURPOSE

To investigate whether low frequency pulsed magnetic field (PMF) exposures produce alterations in the cell killing induced by ultraviolet C (UVC) radiation.

MATERIALS AND METHODS

MCF-7 breast cancer cells of exponentially growing cultures were exposed to PMF (25 Hz, 0.75 mT) and UVC (from 6.6 J/m2 to 59.4 J/m2) in two different protocols: (a) cells were exposed to PMF for 30 min and then exposed to UVC at different doses; (b) cells were exposed to PMF for 30 min. After 15 min of the PMF exposure they were exposed simultaneously to PMF+different doses of UVC. After an additional time of 72 h of incubation, viability was measured by the neutral red stain cytotoxicity test.

RESULTS

Both exposure protocols produced a significant decrease in the post UVC survival at 13.2 J/m2 and 19.8 J/m2, as compared to controls. The simultaneous exposition of PMF and UVC produced an additional increment in cell killing at 26.4 J/m2, being the greater effects obtained for this second exposure protocol.

CONCLUSIONS

Results of the present study show that PMF in combination with UVC have the ability to augment the cell killing effects of UVC radiation. In addition, the effects appear to be greater when PMF and UVC are applied at the same time.

Detection of DNA double-strand breaks using gammaH2AX after MRI exposure at 3 Tesla: an in vitro study

PURPOSE

To evaluate the effects of the static magnetic field and typical imaging sequences of a high-field magnetic resonance scanner (3 Tesla) on the induction of double-strand breaks (DSBs) in two different human cell lines.

MATERIALS AND METHODS

Human promyelocytic leukemia cells (HL-60) and human acute myeloid leukemia cells (KG-1a) were exposed to the static magnetic field alone and to turbo spin-echo (TSE) and gradient-echo (GE) sequences. Flow cytometry was used to quantify gammaH2AX (serine 139 phosphorylated form of histone H2AX) expression of antibody-stained cells as a marker for deoxyribonucleic acid (DNA) DSBs one hour and 24 hours after magnetic field exposure. X-ray-treated cells were used as positive control.

RESULTS

Neither exposure to the static magnetic field alone nor to the applied imaging sequences showed significant differences in gammaH2AX expression between exposed and sham-exposed cells. X-ray-treated cells as positive control showed a significant increase in gammaH2AX expression.

CONCLUSION

The static magnetic field alone and MRI sequences at 3 Tesla have no effect on the induction of DSBs in HL-60 and KG-1a cells.

Cytogenetic effects of extremely low frequency magnetic field on Wistar rat bone marrow

In this study, the genotoxic and cytotoxic potential of extremely low frequency magnetic fields (ELF-MF) was investigated in Wistar rat tibial bone marrow cells, using the chromosomal aberration (CA) and micronucleus (MN) test systems. In addition to these test systems, we also investigated the mitotic index (MI), and the ratio of polychromatic erythrocytes (PCEs) to normochromatic erythrocytes (NCEs). Wistar rats were exposed to acute (1 day for 4h) and long-term (4h/day for 45 days) to a horizontal 50Hz, 1mT uniform magnetic field generated by a Helmholtz coil system. Mitomycin C (MMC, 2mg/kg BW) was used as positive control. Results obtained by chromosome analysis do not show any statistically significant differences between the negative control and both acute and long-term ELF-MF exposed samples. When comparing the group mean CA of long-term exposure with the negative control and acute exposure, the group mean of the long-term exposed group was higher, but this was not statistically significant. However, the mean micronucleus frequency of the longer-term exposed group was considerably higher than the negative control and acutely exposed groups. This difference was statistically significant (p<0.01). The results of the MI in bone marrow showed that the averages of both A-MF and L-MF groups significantly decreased when compared to those in the negative control (p<0.001 and p<0.01, respectively). No significant differences were found between the group mean MI of A-MF exposure with L-MF. We found that the average of PCEs/NCEs ratios of A-MF exposed group was significantly lower than the negative control and L-MF exposed groups (p<0.001 and p<0.01, respectively). In addition, the group mean of the PCEs/NCEs ratios of L-MF was significantly lower than negative control (p<0.01). We also found that the MMC treated group showed higher the number of CA and the frequency of MN formation when compared to those in all other each groups (p-values of all each groups <0.01) and also MMC treated group showed lower MI and the PCEs/NCEs ratios when compared to those in all other each groups (p-values of all groups <0.01). These observations indicate the in vivo suspectibility of mammals to the genotoxicity potential of ELF-MF.

In vitro evaluation of magnetic resonance imaging at 3.0 tesla on clonogenic ability, proliferation, and cell cycle in human embryonic lung fibroblasts

OBJECTIVES

We investigated the influence of magnetic resonance (MR) at 3.0 T on clonogenic ability, proliferation, and cell cycle in an embryonic human cell line.

MATERIALS AND METHODS

Cells (human lung fibroblasts Hel 299) were exposed to the static magnetic field (3.0 T) of a magnetic resonance imager (MRI) and to a turbo spin echo sequence at 3.0 T within clinical limitations (specific absorption rate 0.92 W/kg). A special MR-compatible incubation system was used. A control group (sham-exposed) and a MRI group (exposed) were set up. We investigated 3 biologic endpoints: colony forming, cell cycle, and proliferation ability. The exposure time was 2 hours in each experiment.

RESULTS

In the statistical analysis, none of these tests showed relevant differences between the exposed and sham-exposed group.

CONCLUSIONS

No influences of the static field alone as well as a turbo spin echo sequence at 3.0 T on clonogenic ability, proliferation, or cell cycle in eugenic human lung fibroblasts were found.

Induced mitogenic activity in AML-12 mouse hepatocytes exposed to low-dose ultra-wideband electromagnetic radiation

Ultra–wideband (UWB) technology has increased with the use of various civilian and military applications. In the present study, we hypothesized that low-dose UWB electromagnetic radiation (UWBR) could elicit a mitogenic effect in AML-12 mouse hepatocytes, in vitro. To test this hypothesis, we exposed AML-12 mouse hepatocytes, to UWBR in a specially constructed gigahertz transverse electromagnetic mode (GTEM) cell. Cells were exposed to UWBR for 2 h at a temperature of 23°C, a pulse width of 10 ns, a repetition rate of 1 kHz, and field strength of 5–20 kV/m. UWB pulses were triggered by an external pulse generator for UWBR exposure but were not triggered for the sham exposure. We performed an MTT Assay to assess cell viability for UWBR-treated and sham-exposed hepatocytes. Data from viability studies indicated a time-related increase in hepatocytes at time intervals from 8–24 h post exposure. UWBR exerted a statistically significant (p < 0.05) dose-dependent response in cell viability in both serum-treated and serum free medium (SFM) -treated hepatocytes. Western blot analysis of hepatocyte lysates demonstrated that cyclin A protein was induced in hepatocytes, suggesting that increased MTT activity after UWBR exposure was due to cell proliferation. This study indicates that UWBR has a mitogenic effect on AML-12 mouse hepatocytes and implicates a possible role for UWBR in hepatocarcinoma.

Effects on apoptosis and reactive oxygen species formation by Jurkat cells exposed to 50 Hz electromagnetic fields

The effect of exposure to 50 Hz electromagnetic field on a human T-leukaemia cell line (Jurkat) was investigated by evaluating the reactive oxygen species (ROS) production and apoptosis, both spontaneous and induced by a specific anti Fas/CD95 monoclonal antibody (anti-Fas). Our results suggest that 1 h intermittent (5 min field on/10 min field off) exposure does not affect ROS formation, while a slight but statistically significant decrease of both spontaneous and anti-Fas-induced apoptosis was observed.

Alteration in cellular functions in mouse macrophages after exposure to 50 Hz magnetic fields

The aim of the present study is to investigate whether extremely low frequency electromagnetic fields (ELF-EMF) affect certain cellular functions and immunologic parameters of mouse macrophages. In this study, the influence of 50 Hz magnetic fields (MF) at 1.0 mT was investigated on the phagocytic activity and on the interleukin-1beta (IL-1beta) production in differentiated macrophages. MF-exposure led to an increased phagocytic activity after 45 min, shown as a 1.6-fold increased uptake of latex beads in MF-exposed cells compared to controls. We also demonstrate an increased IL-1beta release in macrophages after 24 h exposure (1.0 mT MF). Time-dependent IL-1beta formation was significantly increased already after 4 h and reached a maximum of 12.3-fold increase after 24 h compared to controls. Another aspect of this study was to examine the genotoxic capacity of 1.0 mT MF by analyzing the micronucleus (MN) formation in long-term (12, 24, and 48 h) exposed macrophages. Our data show no significant differences in MN formation or irregular mitotic activities in exposed cells. Furthermore, the effects of different flux densities (ranging from 0.05 up to 1.0 mT for 45 min) of 50 Hz MF was tested on free radical formation as an endpoint of cell activation in mouse macrophage precursor cells. All tested flux densities significantly stimulated the formation of free radicals. Here, we demonstrate the capacity of ELF-EMF to stimulate physiological cell functions in mouse macrophages shown by the significantly elevated phagocytic activity, free radical release, and IL-1beta production suggesting the cell activation capacity of ELF-EMF in the absence of any genotoxic effects.

Pulsed electromagnetic fields accelerate apoptotic rate in osteoclasts

Selective control of cell function by applying specifically configured, low-energy, time-varying electromagnetic fields (EMF) has added a new, exciting dimension to biology and medicine. However, the mechanism involved is less clear. In our study, we investigated the effect of pulsed electromagnetic fields (PEMF) on induction of osteoclasts apoptosis. A statistically significant increase of apoptotic rate in osteoclasts (48 hr after isolation) was found when exposed to 7.5 Hz PEMF with induced electric fields intensity of 3.0 muv/cm for 8 (105%, p < 0.001) and 16 hr (30%, p < 0.05). However, exposure of osteoclasts to PEMF for only 1 hr showed no statistically significant differences. These findings suggest that PEMF have the ability to speed up apoptosis of osteoclasts derived from primary osteoblasts and bone marrow cells cocultures. This in vitro study, therefore, could be considered as groundwork for in vivo PEMF applications on some osteoclasts-associated bone diseases such as osteoporosis.

Genotoxic effects of extremely low frequency (ELF) magnetic fields (MF) evaluated by the Tradescantia-micronucleus assay

Extremely low frequency (ELF) electric fields (EF) and magnetic fields (MF) are generated during the production, transmission, and use of electrical energy. Although epidemiology studies suggest that there is a cancer risk associated with exposure to ELF-MF, short-term genotoxicity assays with bacteria and mammalian cells have produced inconsistent results. In the present study, we investigated the possible genotoxicity of ELF-MF by using the Tradescantia-micronucleus (Trad-MN) assay, a sensitive, reproducible, well-standardized assay for genotoxicity testing. A 50 Hz ELF-MF was generated by a laboratory exposure system consisting of a pair of parallel coils in a Helmholtz configuration. Exposure of Tradescantia (clone # 4430) inflorescences to the ELF-MF, at a flux density (B) corresponding to 1 mT, for 1, 6, and 24 h resulted in a time-dependent increase in MN frequency. The results indicate that a 50 Hz MF of 1 mT field strength is genotoxic in the Trad-MN bioassay and suggest that this assay may be suitable as a biomonitor for detecting the genotoxicity of ELF-MF in the field.

Controversial cytogenetic observations in mammalian somatic cells exposed to extremely low frequency electromagnetic radiation: a review and future research recommendations

During the years 1990-2003, a large number of investigations were conducted using animals, cultured rodent and human cells as well as freshly collected human blood lymphocytes to determine the genotoxic potential of exposure to nonionizing radiation emitted from extremely low frequency electromagnetic fields (EMF). Among the 63 peer reviewed scientific reports, the conclusions from 29 studies (46%) did not indicate increased damage to the genetic material, as assessed from DNA strand breaks, incidence of chromosomal aberrations (CA), micronuclei (MN), and sister chromatid exchanges (SCE), in EMF exposed cells as compared with sham exposed and/or unexposed cells, while those from 14 investigations (22%) have suggested an increase in such damage in EMF exposed cells. The observations from 20 other studies (32%) were inconclusive. This study reviews the investigations published in peer reviewed scientific journals during 1990-2003 and attempts to identify probable reason(s) for the conflicting results. Recommendations are made for future research to address some of the controversial observations.

Chromosomal damage in human diploid fibroblasts by intermittent exposure to extremely low-frequency electromagnetic fields

Environmental exposure to extremely low-frequency electromagnetic fields (ELF-EMFs) has been implicated in the development of cancer in humans. An important basis for assessing a potential cancer risk due to ELF-EMF exposure is knowledge of biological effects on human cells at the chromosomal level. Therefore, we investigated in the present study the effect of intermittent ELF electromagnetic fields (50 Hz, sinusoidal, 5'field-on/10'field-off, 2-24 h, 1 mT) on the induction of micronuclei (MN) and chromosomal aberrations in cultured human fibroblasts. ELF-EMF radiation resulted in a time-dependent increase of micronuclei, which became significant after 10 h of intermittent exposure at a flux density of 1 mT. After approximately 15 h a constant level of micronuclei of about three times the basal level was reached. In addition, chromosomal aberrations were increased up to 10-fold above basal levels. Our data strongly indicate a clastogenic potential of intermittent low-frequency electromagnetic fields, which may lead to considerable chromosomal damage in dividing cells.

Effects of co-exposure to extremely low frequency (ELF) magnetic fields and benzene or benzene metabolites determined in vitro by the alkaline comet assay

In the present study, we investigated in vitro the possible genotoxic and/or co-genotoxic activity of 50 Hz (power frequency) magnetic fields (MF) by using the alkaline single-cell microgel-electrophoresis (comet) assay. Sets of experiments were performed to evaluate the possible interaction between 50 Hz MF and the known leukemogen benzene. Three benzene hydroxylated metabolites were also evaluated: 1,2-benzenediol (1,2-BD, catechol), 1,4-benzenediol (1,4-BD, hydroquinone), and 1,2,4-benzenetriol (1,2,4-BT). MF (1 mT) were generated by a system consisting of a pair of parallel coils in a Helmholtz configuration. To evaluate the genotoxic potential of 50 Hz MF, Jurkat cell cultures were exposed to 1 mT MF or sham-exposed for 1h. To evaluate the co-genotoxic activity of MF, the xenobiotics (benzene, catechol, hydroquinone, and 1,2,4-benzenetriol) were added to Jurkat cells subcultures at the beginning of the exposure time. In cell cultures co-exposed to 1 mT (50 Hz) MF, benzene and catechol did not show any genotoxic activity. However, co-exposure of cell cultures to 1 mT MF and hydroquinone led to the appearance of a clear genotoxic effect. Moreover, co-exposure of cell cultures to 1 mT MF and 1,2,4-benzenetriol led to a marked increase in the genotoxicity of the ultimate metabolite of benzene. The possibility that 50 Hz (power frequency) MF might interfere with the genotoxic activity of xenobiotics has important implications, since human populations are likely to be exposed to a variety of genotoxic agents concomitantly with exposure to this type of physical agent.

50-Hz extremely low frequency electromagnetic fields enhance cell proliferation and DNA damage: possible involvement of a redox mechanism

HL-60 leukemia cells, Rat-1 fibroblasts and WI-38 diploid fibroblasts were exposed for 24-72 h to 0.5-1.0-mT 50-Hz extremely low frequency electromagnetic field (ELF-EMF). This treatment induced a dose-dependent increase in the proliferation rate of all cell types, namely about 30% increase of cell proliferation after 72-h exposure to 1.0 mT. This was accompanied by increased percentage of cells in the S-phase after 12- and 48-h exposure. The ability of ELF-EMF to induce DNA damage was also investigated by measuring DNA strand breaks. A dose-dependent increase in DNA damage was observed in all cell lines, with two peaks occurring at 24 and 72 h. A similar pattern of DNA damage was observed by measuring formation of 8-OHdG adducts. The effects of ELF-EMF on cell proliferation and DNA damage were prevented by pretreatment of cells with an antioxidant like alpha-tocopherol, suggesting that redox reactions were involved. Accordingly, Rat-1 fibroblasts that had been exposed to ELF-EMF for 3 or 24 h exhibited a significant increase in dichlorofluorescein-detectable reactive oxygen species, which was blunted by alpha-tocopherol pretreatment. Cells exposed to ELF-EMF and examined as early as 6 h after treatment initiation also exhibited modifications of NF kappa B-related proteins (p65-p50 and I kappa B alpha), which were suggestive of increased formation of p65-p50 or p65-p65 active forms, a process usually attributed to redox reactions. These results suggest that ELF-EMF influence proliferation and DNA damage in both normal and tumor cells through the action of free radical species. This information may be of value for appraising the pathophysiologic consequences of an exposure to ELF-EMF.

Exposure to ELF magnetic field tuned to Zn inhibits growth of cancer cells

The effects of ELF alternating magnetic fields tuned to Zn(2+) on the growth of cancer cells with different status of p53 were investigated using a cell proliferation assay. Human cancer cells HeLa (cervix cancer, p53(+/+)), Saos-2 and Saos-2-His-273 (osteosarcoma, p53(-/-) and p53 His-273 mutant, respectively), H1299tTA and H1299tTA-His175 (lung carcinoma, p53(-/-) and p53 His-175 mutant), and normal human fibroblasts VH-10 (p53(+/+)) were used. Exposure parameters were calculated for the first harmonic of Zn(2+) based either on the magnetic parametric resonance (MPR) model of Lednev or the ion parametric resonance (IPR) model of Blanchard and Blackman. ELF exposure was for 72 and 96 h. The vertical alternating field was 20 Hz at amplitudes of either 38.7 or 77.4 microT (peaks, IPR or MPR, respectively). The vertical static magnetic field was 43 microT, and the horizontal static magnetic field was zeroed. Treatments of cells with PRIMA-1 and gamma-rays were used as positive controls. Growth inhibition was observed in cells after exposure to ELF at 38.7 microT. Inhibition of HeLa, VH-10, and Saos-2-His-273 cells was statistically significant, P=0.0003, 0.02, and 0.006, respectively. No consistent ELF effects following exposure 77.4 microT were seen. PRIMA-1 inhibited the growth of all cell lines with the strongest effect in mutant p53-carrying cell line H1299tTA-His175. The effects of gamma-rays were relatively weak, suggesting that the cell proliferation assay under conditions employed in this study is not very sensitive to apoptosis. In conclusion, ELF under conditions of exposure tuned to Zn(2+) according to the IPR model inhibited the growth of cancer and normal cells. No clear relationship of the observed growth inhibition to p53 status was found. Further experiments, using complementary techniques, are required to test whether p53 reactivation by ELF is feasible.

915 MHz microwaves and 50 Hz magnetic field affect chromatin conformation and 53BP1 foci in human lymphocytes from hypersensitive and healthy persons

We used exposure to microwaves from a global system for mobile communication (GSM) mobile phone (915 MHz, specific absorption rate (SAR) 37 mW/kg) and power frequency magnetic field (50 Hz, 15 muT peak value) to investigate the response of lymphocytes from healthy subjects and from persons reporting hypersensitivity to electromagnetic field (EMF). The hypersensitive and healthy donors were matched by gender and age and the data were analyzed blind to treatment condition. The changes in chromatin conformation were measured with the method of anomalous viscosity time dependencies (AVTD). 53BP1 protein, which has been shown to colocalize in foci with DNA double strand breaks (DSBs), was analyzed by immunostaining in situ. Exposure at room temperature to either 915 MHz or 50 Hz resulted in significant condensation of chromatin, shown as AVTD changes, which was similar to the effect of heat shock at 41 degrees C. No significant differences in responses between normal and hypersensitive subjects were detected. Neither 915 MHz nor 50 Hz exposure induced 53BP1 foci. On the contrary, a distinct decrease in background level of 53BP1 signaling was observed upon these exposures as well as after heat shock treatments. This decrease correlated with the AVTD data and may indicate decrease in accessibility of 53BP1 to antibodies because of stress-induced chromatin condensation. Apoptosis was determined by morphological changes and by apoptotic fragmentation of DNA as analyzed by pulsed-field gel electrophoresis (PFGE). No apoptosis was induced by exposure to 50 Hz and 915 MHz microwaves. In conclusion, 50 Hz magnetic field and 915 MHz microwaves under specified conditions of exposure induced comparable responses in lymphocytes from healthy and hypersensitive donors that were similar but not identical to stress response induced by heat shock.

Extremely low frequency electromagnetic fields as effectors of cellular responses in vitro: Possible immune cell activation

There is presently an intense discussion if electromagnetic field (EMF) exposure has consequences for human health. This include exposure to structures and appliances that emit in the extremely low frequency (ELF) range of the electromagnetic spectrum, as well as emission coming from communication devices using the radiofrequency part of the spectrum. Biological effects of such exposures have been noted frequently, although the implication for specific health effects is not that clear. The basic interaction mechanism(s) between such fields and living matter is unknown. Numerous hypotheses have been suggested, although none is convincingly supported by experimental data. Various cellular components, processes, and systems can be affected by EMF exposure. Since it is unlikely that EMF can induce DNA damage directly, most studies have examined EMF effects on the cell membrane level, general and specific gene expression, and signal transduction pathways. In addition, a large number of studies have been performed regarding cell proliferation, cell cycle regulation, cell differentiation, metabolism, and various physiological characteristics of cells. Although 50/60 Hz EMF do not directly lead to genotoxic effects, it is possible that certain cellular processes altered by exposure to EMF indirectly affect the structure of DNA causing strand breaks and other chromosomal aberrations. The aim of this article is to present a hypothesis of a possible initial cellular event affected by exposure to ELF EMF, an event which is compatible with the multitude of effects observed after exposure. Based on an extensive literature review, we suggest that ELF EMF exposure is able to perform such activation by means of increasing levels of free radicals. Such a general activation is compatible with the diverse nature of observed effects. Free radicals are intermediates in natural processes like mitochondrial metabolism and are also a key feature of phagocytosis. Free radical release is inducible by ionizing radiation or phorbol ester treatment, both leading to genomic instability. EMF might be a stimulus to induce an "activated state" of the cell such as phagocytosis, which then enhances the release of free radicals, in turn leading to genotoxic events. We envisage that EMF exposure can cause both acute and chronic effects that are mediated by increased free radical levels: (1) Direct activation of, for example macrophages (or other cells) by short-term exposure to EMF leads to phagocytosis (or other cell specific responses) and consequently, free radical production. This pathway may be utilized to positively influence certain aspects of the immune response, and could be useful for specific therapeutic applications. (2) EMF-induced macrophage (cell) activation includes direct stimulation of free radical production. (3) An increase in the lifetime of free radicals by EMF leads to persistently elevated free radical concentrations. In general, reactions in which radicals are involved become more frequent, increasing the possibility of DNA damage. (4) Long-term EMF exposure leads to a chronically increased level of free radicals, subsequently causing an inhibition of the effects of the pineal gland hormone melatonin. Taken together, these EMF induced reactions could lead to a higher incidence of DNA damage and therefore, to an increased risk of tumour development. While the effects on melatonin and the extension of the lifetime of radicals can explain the link between EMF exposure and the incidence of for example leukaemia, the two additional mechanisms described here specifically for mouse macrophages, can explain the possible correlation between immune cell system stimulation and EMF exposure.

Differences in lethality between cancer cells and human lymphocytes caused by LF-electromagnetic fields

The lethal response of cultured cancer cells lines K-562, U-937, DG-75, and HL-60 were measured directly after a 4 h exposure to a pulsating electromagnetic field (PEMF, sinusoidal wave form, 35 mT peak, 50 Hz) [Traitcheva et al. (2003): Bioelectromagnetics 24:148-158] and 24 h later, to determine the post-exposure effect. The results were found to depend on the medium, pH value, conductivity, and temperature. From these experiments, suitable conditions were chosen to compare the vitality between K-562 cells and normal human lymphocytes after PEMF treatment and photodynamic action. Both agents enhance necrosis synergistically for diseased as well as for healthy cells, but the lymphocytes are more resistant. The efficacy of PEMF on the destruction of cancer cells is further increased by heating (hyperthermia) of the suspension up to 44 degrees C or by lowering the pH-value (hyperacidity) to pH 6.4. Similar apoptosis and necrosis can be obtained using moderate magnetic fields (B < or = 15 mT 50/60 Hz), but this requires longer treatment of at least over a week. PEMF application combined with anticancer drugs and photodynamic therapy will be very effective.

Non-thermal effects of power-line magnetic fields (50Hz) on gene expression levels of pluripotent embryonic stem cells—the role of tumour suppressor p53

The diffusion of extremely low-frequency (50 Hz) electromagnetic fields (ELF-EMF) in the human environment raises the question of the induction of biological effects of EMF on mammalian cells. We used the model of mouse pluripotent embryonic stem (ES) cells, which have the capacity to develop in vitro into cells of all lineages, to analyse non-thermal effects of ELF-EMF. Wild type (wt) and p53-deficient ES cells were exposed under controlled conditions to ELF-EMF signals simulating power-line (50 Hz) magnetic field (PL-MF) exposure. Different flux densities of 0.1 mT, 1.0 mT or 2.3 mT and intermittency schemes with various ON/OFF cycles were applied for 6 h or 48 h during the first stages of cell differentiation. Transcript levels of regulatory genes, such as egr-1, p21, c-jun, c-myc, hsp70 and bcl-2, were analysed by semi-quantitative RT-PCR immediately after exposure or after a recovery time of 18 h. Intermittent PL-MF exposure to 5 min ON/30 min OFF cycles at a flux density of 2.3 mT for 6 h resulted in a significant up-regulation of c-jun, p21 and egr-1 mRNA levels in p53-deficient, but not in wild-type cells. No significant effects were observed in both cell systems by PL-MF at lower flux densities, longer exposure time or after 18 h recovery time. Our data indicate that 5 min ON/30 min OFF intermittent PL-MF exposure is capable of evoking non-thermal responses in ES cells, dependent on the cellular p53 function. The nature of the biological responses triggered by PL-MF is discussed.

Evaluation of genotoxic effect of low level 50 Hz magnetic fields on human blood cells using different cytogenetic assays

The question whether extremely low frequency magnetic fields (ELFMFs) may contribute to mutagenesis or carcinogenesis is of current interest. In order to evaluate the possible genotoxic effects of ELFMFs, human blood cells from four donors were exposed in vitro for 48 h to 50 Hz, 1 mT uniform magnetic field generated by a Helmholtz coil system. Comet assay (SCGE), sister chromatid exchanges (SCE), chromosome aberrations (CAs), and micronucleus (MN) test were used to assess the DNA damage. ELF pretreated cells were also irradiated with 1 Gy of X-ray to investigate the possible combined effect of ELFMFs and ionizing radiation. Furthermore, nuclear division index (NDI) and proliferation index (PRI) were evaluated. Results do not evidence any DNA damage induced by ELFMF exposure or any effect on cell proliferation. Data obtained from the combined exposure to ELFMFs and ionizing radiation do not suggest any synergistic or antagonistic effect.