Pulsating Extremely Low-Frequency Electromagnetic Fields Influence Differentiation of Mouse Neural Stem Cells towards Astrocyte-like Phenotypes: In Vitro Pilot Study

Even though electromagnetic fields have been reported to assist endogenous neurogenesis, little is known about the exact mechanisms of their action. In this pilot study, we investigated the effects of pulsating extremely low-frequency electromagnetic fields on neural stem cell differentiation towards specific phenotypes, such as neurons and astrocytes. Neural stem cells isolated from the telencephalic wall of B6(Cg)-Tyrc-2J/J mouse embryos (E14.5) were randomly divided into three experimental groups and three controls. Electromagnetic field application setup included a solenoid placed within an incubator. Each of the experimental groups was exposed to 50Hz ELF-EMFs of varied strengths for 1 h. The expression of each marker (NES, GFAP, β-3 tubulin) was then assessed by immunocytochemistry. The application of high-strength ELF-EMF significantly increased and low-strength ELF-EMF decreased the expression of GFAP. A similar pattern was observed for β-3 tubulin, with high-strength ELF-EMFs significantly increasing the immunoreactivity of β-3 tubulin and medium- and low-strength ELF-EMFs decreasing it. Changes in NES expression were observed for medium-strength ELF-EMFs, with a demonstrated significant upregulation. This suggests that, even though ELF-EMFs appear to inhibit or promote the differentiation of neural stem cells into neurons or astrocytes, this effect highly depends on the strength and frequency of the fields as well as the duration of their application. While numerous studies have demonstrated the capacity of EMFs to guide the differentiation of NSCs into neuron-like cells or β-3 tubulin+ neurons, this is the first study to suggest that ELF-EMFs may also steer NSC differentiation towards astrocyte-like phenotypes.

Nasal mucociliary clearance after extremely low frequency by scintigraphic and histopathologic evaluation

OBJECTIVE

To investigate the effect of exposure to extremely low-frequency magnetic fields (ELF-MFs) on nasal mucociliary clearance (MCC) by rhinosintigrapic and histopathological evaluation.

MATERIALS AND METHODS

The rats were separated into three groups according to ELF-MFs intensity and control group. The exposure groups were standardized for the ELF-MFs of 1, 1.5, and 2 mT emitted by 3 Helmholtz coils for 4 h/day for 30 days. Rhinoscintigraphy was performed to measure nasal MCC. The nasal tissues were examined for edema, inflammation, hyperemia, necrosis, ciliary loss, goblet cell density, and fibroblast proliferation. The data were evaluated statistically (p < 0.05).

RESULTS

Nasal mucociliary clearance rates (NMCR) were calculated as 33.13 ± 5.91% in control, 27.78 ± 4.7% in 1 mT, 22.67 ± 5.43% in 1.5 mT, and 18.11 ± 6.33% in 2 mT. NMCR were decreased with increasing ELF-MFs, in 1.5 and 2 mT groups (p < 0.05) compared to control. Nasal mucociliary transport rate (NMTR) values were found to be 2.17 ± 0.33 mm/min in control, 1.82 ± 0.32 mm/min in 1 mT, 1.46 ± 0.34 mm/min in 1.5 mT and 1.24 ± 0.29 mm/min in 2 mT. NMTR was decreased in the groups exposed to 1.5 and 2 mT (p < 0.05) compared to control. The edema, hyperemia, inflammation, ciliary loss, and goblet cell density were statistically significant differences between control and groups exposed to 1.5 and 2 mT (p < 0.05).

CONCLUSION

Our rat model has shown nasal mucosa damage and decreased NMCR and NMTR by rhinoscintigraphy as ELF-MFs intensity increases. It may be detrimental to nasal mucosa mucociliary function depending on the ELF-MFs intensity.

LEVEL OF EVIDENCE

N/A Laryngoscope, 133:2081-2089, 2023.

Occupational exposure to metal-rich particulate matter modifies the expression of repair genes in foundry workers

Foundry workers are exposed to numerous occupational health hazards, which may result in increased risk of cancer, respiratory disease, and other diseases. Oxidative stress is known to be involved in the pathogenesis of such diseases. The present study aimed to investigate the association between multiple occupational exposures in foundry workers and expression of deoxyribonucleic acid (DNA) repair genes as a biomarker of oxidative DNA damage. The study sample comprised 17 foundry workers and 27 matched control subjects. Expression of 8-oxoguanine DNA glycosylase-1 (OGG1), inosine triphosphate pyrophosphate (ITPA), and MutT homolog 1 (MTH1) in peripheral blood was examined using the real-time polymerase chain reaction method. Air sampling to determine exposure to metal-rich particulate matter and measurement of extremely low-frequency electromagnetic fields (ELF-EMFs) were conducted according to the National Institute for Occupational Safety and Health standard methods. Personal air sampling revealed that occupational exposure to particulate matter exceeded the threshold limit values (TLVs) in 76% of the workstations, whereas ELF-EMF exposure appeared to be lower than the TLV. ITPA was significantly upregulated in foundry workers compared with control subjects, whereas no significant difference was observed for OGG1 and MTH1. Moreover, ITPA was strongly and positively correlated with the concentration of metal-rich particulate matter in foundry workers. No significant correlation was found between ELF-EMF exposure and expression of DNA repair genes. DNA repair gene expression may be a sensitive biomarker for occupational exposures, which suggests an involvement of oxidative stress in metal-induced toxicity. Further studies are needed to determine the role of DNA repair gene expression in response to occupational/environmental hazards.

Conformational changes of β-thalassemia major hemoglobin and oxidative status of plasma after in vitro exposure to extremely low-frequency electromagnetic fields: An artificial neural network analysis

Electromagnetic fields (EMF) can generate reactive oxygen species and induce oxidative modifications. We investigated the effects of extremely low-frequency electromagnetic fields (ELF-EMF) on oxidative status of plasma and erythrocytes in β-thalassemia major patients and design artificial neural networks (ANN) for evaluating the oxyHb concentration. Blood samples were obtained from age and sex-matched healthy donors (n = 12) and major β-thalassemia patients (n = 12) and subjected to 0.5 and 1 mT and 50 Hz of EMF. Plasma oxidative status was estimated after 1 and 2 h exposure to ELE-EMF. Structural changes of plasma proteins were investigated by Native PAGE and SDS-PAGE. Moreover; multilayer perceptron (MLP) method was applied for designing a feed forward ANN model to predict the impact of these oxidative and antioxidative parameters on oxyHb concentration. Two hour exposure to ELF-EMF induced significant oxidative changes on major β-thalassemia samplesElectrophoretic profiles showed two high molecular weight (HMW) protein aggregates in plasma samples from healthy donors and major β-thalassemia patients. According to our ANN design, the main predictors of oxyHb concentration were optical density of Hb at 542, 340, 569, 630, 577, and 420 nm and metHb and hemichrome (HC) concentration. Accuracy of the proposed ANN model was shown by predicted by observed chart (y = 1.3 + 0.96x, R² = 0.942), sum of squares errors (SSR), and relative errors (RE). Our results showed the detailed effects of ELF-EMF on Hb structure and oxidative balance of plasma in major β-thalassemia patients and significance of ANN analysis during normal and pathologic conditions.

The effect of electromagnetic fields on survival and proliferation rate of dental pulp stem cells

Aims: Extremely low-frequency electromagnetic fields (ELF-EMF) can affect biological systems and alter some cell functions like proliferation rate. Dental pulp tissue is known as a source of multipotent stromal stem cells (MSCs), which can be obtained by a less invasive and more available process compared to bone marrow-derived stem cells (BMSCs). This study aimed to consider the effect of ELF-EMF on proliferation rates of human dental pulp stem cells (hDPSCs).Material and methods: ELF-EMF was generated by a system including autotransformer, multi-meter, solenoid coils, teslameter and its probe. The effect of ELF-EMF with the intensity of 0.5 and 1 mT and 50 Hz on the proliferation rate of hDPSCs was assessed in 20 and 40 min per day for 7 days. MTT assay and DAPI test were used to determine the growth and proliferation of DPSCs.Results: Based on MTT, ELF-EMF has maximum effect with the intensity of 1 mT for 20 min/day on the proliferation of hDPSCs. The survival and proliferation rate in all exposure groups were significantly higher than the control group. Based on the data obtained from MTT and DAPI assay, the number of viable cells in the group exposed to 1 mT for 20 min/day was higher than other groups (p < .05).Conclusions: Regarding to the results of this study, 0.5 and 1 mT ELF-EMF can enhance survival and proliferation rates of hDPSCs.

A comprehensive overview on utilizing electromagnetic fields in bone regenerative medicine

Stem cells are one of the most important sources to develope  a new strategy for repairing bone lesions through tissue engineering. Osteogenic differentiation of stem cells can be affected by various factors such as biological, chemical, physiological, and physical ones. The application of ELF-EMFs has been the subject of many research in bone tissue engineering and evidence suggests that this exogenous physical stimulus can promote osteogenic differentiation in several types of  cells. The purpose of this paper is to review the current knowledge on the effects of EMFs on stem cells in bone tissue engineering studies. We recapitulated and analyzed 39 articles that were focused on the application of EMFs for bone tissue engineering purposes. We tabulated scattered information from these articles for easy use and tried to provide an overview of conducted research and identify the knowledge gaps in the field.

Extremely low-frequency electromagnetic field promotes astrocytic differentiation of human bone marrow mesenchymal stem cells by modulating SIRT1 expression

It has been shown that extremely low-frequency electromagnetic fields (ELFMF) affect regulation of cell fate and differentiation. Thus, the aim of this study was to investigate the role of ELFMFs in the enhancement of astrocytic differentiation. ELFMF exposure reduced the rate of proliferation and enhanced astrocytic differentiation. The ELFMF-treated cells showed increased levels of the astrocyte marker (GFAP), while those of the early neuronal marker (Nestin) and stemness marker (OCT3/4) were downregulated. The reactive oxygen species (ROS) level was observed to be significantly elevated after ELFMF exposure, which strengthens the modulatory role of SIRT1 and SIRT1 downstream molecules (TLE1, HES1, and MASH1) during astrocytic differentiation. After nicotinamide (5 mM) mediated inhibition of SIRT1, levels of TLE1, HES1, and MASH1 were examined; TLE1 was significantly upregulated and MASH1 was downregulated. These results suggest that ELFMFs induce astrocytic differentiation through activation of SIRT1 and SIRT1 downstream molecules.

Effect of extremely low-frequency electromagnetic fields on antioxidant activity in the human keratinocyte cell line NCTC 2544

Some epidemiological studies have suggested possible associations between exposure to extremely low-frequency electromagnetic fields (ELF-EMFs) and various diseases. Recently, ELF-EMF has been considered as a therapeutic agent. To support ELF-EMF use in regenerative medicine, in particular in the treatment of skin injuries, we investigated whether significant cell damage occurs after ELF-EMF exposure. Reactive oxygen species (ROS) production was evaluated in the human keratinocyte exposed for 1 H to 50 Hz ELF-EMF in a range of field strengths from 0.25 to 2 G. Significant ROS increases resulted at 0.5 and 1 G and under these flux densities ROS production, glutathione content, antioxidant defense activity, and lipid peroxidation markers were assessed for different lengths of time. Analyzed parameters of antioxidant defense and membrane integrity showed a different trend at two selected magnetic fluxes, with a greater sensitivity of the cells exposed to 0.5 G, especially after 1 H. All significant alterations observed in the first 4 H of exposure reverted to controls 24 H after suggesting that under these conditions, ELF-EMF induces a slight oxidative stress that does not overwhelm the metabolic capacity of the cells or have a cytotoxic effect.

Increased apoptosis and DNA double-strand breaks in the embryonic mouse brain in response to very low-dose X-rays but not 50 Hz magnetic fields

The use of X-rays for medical diagnosis is enhancing exposure to low radiation doses. Exposure to extremely low-frequency electromagnetic or magnetic fields is also increasing. Epidemiological studies show consistent associations of childhood leukaemia with exposure to magnetic fields but any causal relationship is unclear. A limitation in assessing the consequence of such exposure is the availability of sensitive assays. The embryonic neuronal stem and progenitor cell compartments are radiosensitive tissues. Using sensitive assays, we report a statistically significant increase in DNA double-strand break (DSB) formation and apoptosis in the embryonic neuronal stem cell compartment following in utero exposure to 10–200 mGy X-rays. Both endpoints show a linear response. We also show that DSB repair is delayed following exposure to doses below 50 mGy compared with 100 mGy. Thus, we demonstrate in vivo consequences of low-dose radiation. In contrast to these impacts, we did not observe any significant induction of DSBs or apoptosis following exposure to 50 Hz magnetic fields (100 or 300 µT). We conclude that any DSB induction by treatment with magnetic fields is lower than following exposure to 10 mGy X-rays. For comparison, certain procedures involving computed tomography scanning are equivalent to 1–5 mGy X-rays.

Effect of magnetic fields on cryptochrome-dependent responses in Arabidopsis thaliana

The scientific literature describing the effects of weak magnetic fields on living systems contains a plethora of contradictory reports, few successful independent replication studies and a dearth of plausible biophysical interaction mechanisms. Most such investigations have been unsystematic, devoid of testable theoretical predictions and, ultimately, unconvincing. A recent study, of magnetic responses in the model plant Arabidopsis thaliana, however, stands out; it has a clear hypothesis-that seedling growth is magnetically sensitive as a result of photoinduced radical-pair reactions in cryptochrome photoreceptors-tested by measuring several cryptochrome-dependent responses, all of which proved to be enhanced in a magnetic field of intensity 500 muT. The potential importance of this study in the debate on putative effects of extremely low-frequency electromagnetic fields on human health prompted us to subject it to the 'gold standard' of independent replication. With experimental conditions chosen to match those of the original study, we have measured hypocotyl lengths and anthocyanin accumulation for Arabidopsis seedlings grown in a 500 microT magnetic field, with simultaneous control experiments at 50 microT. Additionally, we have determined hypocotyl lengths of plants grown in 50 microT, 1 mT and approximately 100 mT magnetic fields (with zero-field controls), measured gene (CHS, HY5 and GST) expression levels, investigated blue-light intensity effects and explored the influence of sucrose in the growth medium. In no case were consistent, statistically significant magnetic field responses detected.

Design issues in small-area studies of environment and health

BACKGROUND

Small-area studies are part of the tradition of spatial epidemiology, which is concerned with the analysis of geographic patterns of disease with respect to environmental, demographic, socioeconomic, and other factors. We focus on etiologic research, where the aim is to make inferences about spatially varying environmental factors influencing the risk of disease.

METHODS AND RESULTS

We illustrate the approach through three exemplars: a) magnetic fields from overhead electric power lines and the occurrence of childhood leukemia, which illustrates the use of geographic information systems to focus on areas with high exposure prevalence; b) drinking-water disinfection by-products and reproductive outcomes, taking advantage of large between- to within-area variability in exposures from the water supply; and c) chronic exposure to air pollutants and cardiorespiratory health, where issues of socioeconomic confounding are particularly important.

DISCUSSION

The small-area epidemiologic approach assigns exposure estimates to individuals based on location of residence or other geographic variables such as workplace or school. In this way, large populations can be studied, increasing the ability to investigate rare exposures or rare diseases. The approach is most effective when there is well-defined exposure variation across geographic units, limited within-area variation, and good control for potential confounding across areas.

CONCLUSIONS

In conjunction with traditional individual-based approaches, small-area studies offer a valuable addition to the armamentarium of the environmental epidemiologist. Modeling of exposure patterns coupled with collection of individual-level data on subsamples of the population should lead to improved risk estimates (i.e., less potential for bias) and help strengthen etiologic inference.

Public health impact of extremely low-frequency electromagnetic fields

INTRODUCTION

The association between exposure to extremely low-frequency electric and magnetic fields (ELF) and childhood leukemia has led to the classification of magnetic fields by the International Agency for Research on Cancer as a "possible human carcinogen." This association is regarded as the critical effect in risk assessment. Creating effective policy in light of widespread exposure and the undisputed value of safe, reliable, and economic electricity to society is difficult and requires estimates of the potential public health impact and associated uncertainties.

OBJECTIVES

Although a causal relationship between magnetic fields and childhood leukemia has not been established, we present estimates of the possible pubic health impact using attributable fractions to provide a potentially useful input into policy analysis under different scenarios.

METHODS

Using ELF exposure distributions from various countries and dose-response functions from two pooled analyses, we calculate country-specific and worldwide estimates of attributable fractions (AFs) and attributable cases.

RESULTS

Even given a wide range of assumptions, we find that the AF remains < 10%, with point estimates ranging from < 1% to about 4%. For small countries with low exposure, the number of attributable cases is less than one extra case per year. Worldwide the range is from 100 to 2,400 cases possibly attributable to ELF exposure.

CONCLUSION

The fraction of childhood leukemia cases possibly attributable to ELF exposure across the globe appears to be small. There remain, however, a number of uncertainties in these AF estimates, particularly in the exposure distributions.

The Bernal Lecture 2004 Are low-frequency electromagnetic fields a health hazard?

Electric power is an essential commodity of the developed world, and is critical to the continuing progress of our technology-based society, as well as to the growth of less privileged societies. In contrast to its overwhelming benefits, there is a suspicion that the magnetic component of the electromagnetic fields (EMFs) associated with power distribution and electrical appliances has adverse health effects, especially a small increased incidence of childhood leukaemia. The possibility that environmental EMFs represent a health hazard has serious economic implications for government, the electricity industry and society, as well as raising several profound scientific challenges, including, in particular, biophysical mechanisms, experimental replication and scientific uncertainty. These challenges are explored in relation to the experiences of the EMF Biological Research Trust, a UK medical research charity which funds basic research on the biological effects of extremely low-frequency electromagnetic fields (ELF-EMFs). As judged from these experiences, at the present time there is no compelling experimental evidence that environmental ELF-EMFs induce biological responses.