Magnetic field exposure enhances DNA repair through the induction of DnaK/J synthesis

The effect of 50 Hz magnetic fields on cellular sensitivity of mouse spermatogenic cell lines to hydrogen peroxide

With the widespread application of electromagnetic technology, electromagnetic fields (EMFs) emitted from various electric and electronic devices have significantly altered the electromagnetic environment. This has raised concerns about the potential health impacts of EMFs. Previous studies have indicated that EMFs may influence male infertility, with oxidative stress proposed as a key factor; however, the underlying mechanisms remain unclear. In this study, we aimed to determine whether EMFs enhance the impact of oxidative stress on male infertility. We investigated the effects of 50 Hz magnetic fields (MFs) on the sensitivity of mouse spermatogenic cell lines (GC-1 spg and GC-2 spd) to low-dose hydrogen peroxide (H2O2, 5 and 10 μM). Our findings revealed that pre-exposure to 2.0 mT 50 Hz MFs for 24 h increased the sensitivity of GC-2 spd cells to low-dose H2O2 in terms of γH2AX foci formation, a marker for DNA damage repair. However, no significant changes were observed in DNA fragmentation, cell viability, or cell cycle progression in either GC-1 spg or GC-2 spd cells. In conclusion, our results suggest that 50 Hz MFs do not significantly enhance the sensitivity of mouse spermatogenic cell lines to low-dose H2O2.

Role of HSP40 proteins in genome maintenance, insulin signaling and cancer therapy

The DnaJ heat shock protein family (HSP40) is the biggest chaperone family in mammalian cells, mainly functioning as cochaperone of HSP70 to maintain proteostasis and cellular homeostasis under both normal and stressful conditions. Although the functions of HSP70s have been extensively studied in diverse biological pathways and senesces including genome maintenance, HSP40s' biological functions at basal state or in response to exogenous insults remain largely under-investigated. Emerging evidence shows that HSP40 proteins participate in genome maintenance pathways and modulate cancer therapy efficacy. This review aims to summarize recent progresses regarding HSP40's functions in genome maintenance and cancer therapy, and provides hints for future studies in the field.

Cellular and molecular effects of non-ionizing electromagnetic fields

The way that living cells respond to non-ionizing electromagnetic fields (EMF), including static/extremely-low frequency and radiofrequency electromagnetic fields, fits the pattern of 'cellular stress response' - a mechanism manifest at the cellular level intended to preserve the entire organism. It is a set pattern of cellular and molecular responses to environmental stressors, such as heat, ionizing radiation, oxidation, etc. It is triggered by cellular macromolecular damage (in proteins, lipids, and DNA) with the goal of repairing and returning cell functions to homeostasis. The pattern is independent of the type of stressor encountered. It involves cell cycle arrest, induction of specific molecular mechanisms for repair, damage removal, cell proliferation, and cell death if damage is too great. This response could be triggered by EMF-induced alternation in oxidative processes in cells. The concept that biological response to EMF is a 'cellular stress response' explains many observed effects of EMF, such as nonlinear dose- and time-dependency, increased and decreased risks of cancer and neurodegenerative diseases, enhanced nerve regeneration, and bone healing. These responses could be either detrimental or beneficial to health, depending on the duration and intensity of the exposure, as well as specific aspects of the living organism being exposed. A corollary to electromagnetic hypersensitivity syndrome (EHS) could be an inappropriate response of the hippocampus/limbic system to EMF, involving glucocorticoids on the hypothalamic-pituitary-adrenal axis.

Static magnetic field reduces cisplatin resistance via increasing apoptosis pathways and genotoxicity in cancer cell lines

Cisplatin is a chemotherapy drug widely used in cancer treatment. Alongside its clinical benefits, however, it may inflict intolerable toxicity and other adverse effects on healthy tissues. Due to the limitation of administering a high dose of cisplatin as well as cancer drug resistance, it is necessary to utilize new methods optimizing treatment modalities through both higher therapeutic efficacy and reduced administered doses of radiation and drugs. In this study, sensitive (A2780) and resistant (A2780CP) ovarian carcinoma cells underwent treatment with cisplatin + static magnetic field (SMF). First, the levels of genotoxicity after treatment were evaluated by Comet assay. Then, cell cycle analysis and apoptosis assay were conducted by a flow cytometer. Lastly, the expression levels of genes involved in apoptosis and cellular drug uptake were investigated by PCR. After treating different groups of cells for 24, 48, and 96 h, the co-treatment of SMF and cisplatin as a combination managed to increase the amount of DNA damage in both sensitive and resistant cell lines. A considerable increase in mortality of cells was also observed mostly in the form of apoptosis, which was caused by inhibition of the cell cycle. The combination also increased the expression levels of apoptotic genes, namely P53 and P21; however, it did not have much effect on the expression levels of BCL2. Besides, the levels of CTR1 gene expression increased significantly in the groups receiving the aforementioned combination. Our study suggests that the combination of cisplatin + SMF might have clinical potential which needs further investigations through future studies.

A systematic review on cellular responses of Escherichia coli to nonthermal electromagnetic irradiation

Investigation of Escherichia coli under electromagnetic fields is of significance in human studies owing to its short doubling time and human-like DNA mechanisms. The present review aims to systematically evaluate the literature to conclude causality between 0 and 300 GHz electromagnetic fields and biological effects in E. coli. To that end, the OHAT methodology and risk of bias tool were employed. Exponentially growing cells exposed for over 30 min at temperatures up to3 7 ∘ C $3{7}^{\circ }\,{\rm{C}}$ with fluctuations below1 ∘ C ${1}^{\circ }\,{\rm{C}}$ were included from the Web-of-Knowledge, PubMed, or EMF-Portal databases. Out of 904 records identified, 25 articles satisfied the selection criteria, with four excluded during internal validation. These articles examined cell growth (11 studies), morphology (three studies), and gene regulation (11 studies). Most experiments (85%) in the included studies focused on the extremely low-frequency (ELF) range, with 60% specifically at 50 Hz. Changes in growth rate were observed in 74% of ELF experiments and 71% of radio frequency (RF) experiments. Additionally, 80% of ELF experiments showed morphology changes, while gene expression changes were seen in 33% (ELF) and 50% (RF) experiments. Due to the limited number of studies, especially in the intermediate frequency and RF ranges, establishing correlations between EMF exposure and biological effects on E. coli is not possible.

Effects of non-ionizing electromagnetic fields on flora and fauna, Part 2 impacts: how species interact with natural and man-made EMF

Ambient levels of nonionizing electromagnetic fields (EMF) have risen sharply in the last five decades to become a ubiquitous, continuous, biologically active environmental pollutant, even in rural and remote areas. Many species of flora and fauna, because of unique physiologies and habitats, are sensitive to exogenous EMF in ways that surpass human reactivity. This can lead to complex endogenous reactions that are highly variable, largely unseen, and a possible contributing factor in species extinctions, sometimes localized. Non-human magnetoreception mechanisms are explored. Numerous studies across all frequencies and taxa indicate that current low-level anthropogenic EMF can have myriad adverse and synergistic effects, including on orientation and migration, food finding, reproduction, mating, nest and den building, territorial maintenance and defense, and on vitality, longevity and survivorship itself. Effects have been observed in mammals such as bats, cervids, cetaceans, and pinnipeds among others, and on birds, insects, amphibians, reptiles, microbes and many species of flora. Cyto- and geno-toxic effects have long been observed in laboratory research on animal models that can be extrapolated to wildlife. Unusual multi-system mechanisms can come into play with non-human species - including in aquatic environments - that rely on the Earth's natural geomagnetic fields for critical life-sustaining information. Part 2 of this 3-part series includes four online supplement tables of effects seen in animals from both ELF and RFR at vanishingly low intensities. Taken as a whole, this indicates enough information to raise concerns about ambient exposures to nonionizing radiation at ecosystem levels. Wildlife loss is often unseen and undocumented until tipping points are reached. It is time to recognize ambient EMF as a novel form of pollution and develop rules at regulatory agencies that designate air as 'habitat' so EMF can be regulated like other pollutants. Long-term chronic low-level EMF exposure standards, which do not now exist, should be set accordingly for wildlife, and environmental laws should be strictly enforced - a subject explored in Part 3.

T-Cell Differentiation to T Helper 9 Phenotype is Elevated by Extremely Low-Frequency Electromagnetic Fields Via Induction of IL-2 Signaling

Owing to the development of information technology and the electronics industry, and the increase in the use of electronic products, an increasing number of people are exposed to electromagnetic fields (EMFs) in daily life. There has been concern about the effects of EMFs on the human body. Th9 cells, which are characterized by the generation of interleukin-(IL-9), are a recently defined subset of T helper (Th) cells. In this study, we investigated the effect of extremely low-frequency (60 Hz) EMFs, such as those generated by household power sources, at 0.8 mT intensity on CD4⁺ T cells. The exposure of CD4⁺ T cells to such EMFs under Th9-polarizing conditions increased IL-9 secretion and gene expression of transcription factors that are important for Th9 development. The expression of GATA3 increased in the early stage, and the phosphorylation of STAT5 and STAT6, which regulate the expression of GATA3, increased. In addition, EMFs increased the expression of IL-2 by the T cells. In conclusion, the differentiation of CD4⁺ T cells to the Th9 phenotype was increased by exposure to extremely low-frequency EMFs, and this appeared to be dependent on the IL-2 signaling pathway. Furthermore, co-cultures of EMF-exposed Th9 cells and mast cells showed an increased expression of mast cell proteases, FcεR1α, and mast cell-derived inflammatory cytokines compared with co-cultures of non-EMF-exposed Th9 cells and mast cells. Our results suggest that EMFs enhance the differentiation of CD4⁺ T cells to the Th9 phenotype, resulting in mast cell activation and inflammation. Bioelectromagnetics. 2019;40:588-601. © 2019 Bioelectromagnetics Society.

Effects of prolonged exposure to moderate static magnetic field and its synergistic effects with alkaline pH on Enterococcus faecalis

Static magnetic field (SMF) has been shown to biologically affect various microorganisms, but its effects on Enterococcus faecalis, which is associated with multiple dental infections, have not been reported yet. Besides, Enterococcus faecalis was found to be resistant to the alkaline environment provided by a major dental antimicrobial, calcium hydroxide. Therefore, the antibacterial activity of prolonged exposure to moderate SMF (170 mT) and its possible synergistic activity with alkaline pH (pH = 9) were evaluated in the study. The ability to form a biofilm under these conditions was examined by crystal violet assay. Real-time quantitative PCR was performed to evaluate the relative expression of stress (dnaK and groEL) and virulence (efaA, ace, gelE and fsrC) related genes. As the results indicated, cell proliferation was inhibited after 120 h of SMF exposure. What's more, the combined treatment of SMF and alkaline pH showed significantly improved antimicrobial action when compared to single SMF and alkaline pH treatment for more than 24 h and 72 h respectively. However, the ability to form a biofilm was also enhanced under SMF and alkaline pH treatments. SMF can induce stress response by up-regulating the expression of dnaK and elevate virulence gene expression (efaA and ace). These responses were more significant and more genes were up-regulated including groEL, gelE and fsrC when exposed to SMF and alkaline pH simultaneously. Hence, combination of SMF and alkaline pH could be a promising disinfection strategy in dental area and other areas associated with Enterococcus faecalis infections.

Unraveling the effects of static magnetic field stress on cytosolic proteins of Salmonella by using a proteomic approach

The present study investigated the adaptation of Salmonella enterica subsp. enterica serovar Hadar to static magnetic field (SMF) exposure (200 mT, 9 h). The proteomic analysis provides an overview of potentially important cytosolic proteins that Salmonella needs to regulate to survive and adapt to magnetic stress. Via 2-dimensional electrophoresis and liquid chromatography tandem mass spectrometry, we compared cytosolic proteomes before and after exposure to magnetic field. A total of 35 proteins displaying more than a 2-fold change were differentially expressed in exposed cells, among which 25 were upregulated and 10 were downregulated. These proteins can be classified mainly into 6 categories: (i) proteins involved in metabolic pathways of carbohydrates, (ii) chaperones and proteins produced in response to oxidative stress, (iii) proteins involved in energy homeostasis, (iv) elongation factors (EF-Tu and EF-Ts), (v) proteins involved in motility, and (vi) proteins involved in molecules transport. Many of the presented observations could be explained, while some represent still-unknown mechanisms. In addition, this study reveals 5 hypothetical proteins. It seems that the stress response to SMF (200 mT) is essentially set up to avoid oxidative damages, with the overexpression of proteins directly involved in oxidative stress response and metabolic switches to counteract oxidative stress. Interestingly, several proteins induced under SMF exposure are found to overlap with those induced by other stresses, such as heat shock and starvation.

Effects of rotating magnetic field exposure on the functional parameters of different species of bacteria

The aim of the present study was to determine the effect of the rotating magnetic field (RMF) on the growth, cell metabolic activity and biofilm formation by S. aureus, E. coli, A. baumannii, P. aeruginosa, S. marcescens, S. mutans, C. sakazakii, K. oxytoca and S. xylosus. Bacteria were exposed to the RMF (RMF magnetic induction B = 25-34 mT, RMF frequency f = 5-50 Hz, time of exposure t = 60 min, temperature of incubation 37 °C). The persistence of the effect of exposure (B = 34 mT, f = 50 Hz, t = 60 min) on bacteria after further incubation (t = 300 min) was also studied. The work showed that exposure to RMF stimulated the investigated parameters of S. aureus, E. coli, S. marcescens, S. mutans, C. sakazakii, K. oxytoca and S. xylosus, however inhibited cell metabolic activity and biofilm formation by A. baumannii and P. aeruginosa. The results obtained in this study proved, that the RMF, depending on its magnetic induction and frequency can modulate functional parameters of different species of bacteria.

Effect of time-varied magnetic field on inflammatory response in macrophage cell line RAW 264.7

The aim of this feasibility study was to determine the effectiveness of a commercially manufactured magnetic field (MF) device as an adjunct to pharmaceuticals during acute phase inflammatory response. The goal was to determine if inflammatory response interleukins IL-1, IL-6, IL-10, and tumor necrosis factor-alpha (TNF-α) would be affected by a 30 Hz time-varying magnetic field (MF). RAW 264.7 macrophage-like cells were induced with Gram-negative bacteria lipopolysaccharide (LPS) to initiate an acute inflammatory reaction. Following lipopolysaccharide (LPS) treatment, both inflamed and control cells were exposed to MF for 1 h. After MF exposure, cytokines of interest were measured and compared with controls. Outcomes revealed that LPS challenged cells continuously exposed to a 30 Hz time-varying magnetic field for 1 h demonstrated significant changes compared with controls. From cytokine test it was determined that MF exposure significantly decreased levels of IL-6 and IL-10 compared to unexposed counterparts. TNF-α production was significantly affected when MF was applied to cells only, but not to inflamed cells. Results suggest that the biological effect of 1 h exposure to a 30 Hz time-varied magnetic field may act to down regulate specific cytokines in an inflamed environment.

Effects of static magnetic fields on growth and membrane lipid composition of Salmonella typhimurium wild-type and dam mutant strains

This study was carried out to explore the adaptive mechanisms of S. typhimurium particularly, the implication of the Dam methyltransferase in the remodelling of membrane lipid composition to overcome magnetic field stress. With this aim, we focused our analyses on the increase in viable numbers and membrane lipid modifications of S. typhimurium wild-type and dam mutant cells exposed for 10h to static magnetic fields (SMF; 200 mT). For the wild-type strain, exposure to SMF induced a significant decrease (p<0.05) of CFU at 6h, followed by an increase between 8 and 10h. Growth of the dam mutant was significantly affected (p<0.05) after 6h and no recovery was observed until 10h, highlighting a different behavior of SMF stressed wild-type and dam mutant strains. SMF significantly affected the phospholipid proportions in the two strains. The most affected were those of the acidic phospholipids, cardiolipins (CL). In the dam strain the phospholipid response to SMF followed a globally similar trend as in the wild-type with however lower effects, leading mainly to an unusual accumulation of CL. This would in part explain the different behavior of the wild-type and the dam strain. Results showed a significant increase of membrane cyclic fatty acids Cyc17 and Cyc19 in the wild-type strain but only the Cyc17 in the dam strain and a meaningful increase of the total unsaturated fatty acids (UFAs) to total saturated fatty acids (SFAs) ratios of the exposed cells compared to controls from 3 to 9h (p<0.05) for both strains. The net increase of the total UFAs to total SFAs ratios seemed to result mainly from the increase of (C18:1) proportion (p<0.05) and to a lower extent from that of (C16:1) (p<0.05). These modifications of cyclic and unsaturated fatty acid proportions constitute an adaptive response to SMF stress in S. typhimurium wild-type and dam mutants to maintain an optimum level of membrane fluidity under SMF.

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.

Nm23-H1 protein binds to APE1 at AP sites and stimulates AP endonuclease activity following ionizing radiation of the human lung cancer A549 cells

Non-metastatic protein-23 homolog-1 (Nm23-H1) is a multifunctional protein with DNase and histidine protein kinase activities. Human apurinic endonuclease-1 (APE1) is the AP endonuclease DNA base excision repair (BER) enzyme involved in several important cellular functions. Since the relationship between Nm23-H1 and APE1 proteins is unclear, we evaluated their interaction at different time points after irradiating human lung cancer A549 cells with X-rays. We found that Nm23-H1 and APE1 overexpression was induced by irradiation in a dose- and time-dependent manner. Subcellular distribution pattern of both proteins was reversed after irradiation. After irradiation, APE1 that initially showed nuclear localization was gradually increased in the cytoplasm, whereas Nm23-H1 that mainly showed cytoplasmic localization was gradually increased in the nuclei of A549 cells. Nm23-H1 and APE1 interaction was demonstrated by His-pull-down and co-immunoprecipitation assays. The presence of Nm23-H1/APE1 complex in X-ray-irradiated A549 cells was also detected by DNA affinity precipitation analysis of a DNA fragment containing an AP site. Although the AP endonuclease activity of Nm23-H1 was too weak to be detected, the AP endonuclease activity of APE1 was increased with the enhanced Nm23-H1 expression. In conclusion, our data point to a mechanism by which Nm23-H1 protects cells against oxidative stress through the engagement of DNA BER enzyme APE1.

Adaptation of Salmonella enterica Hadar under static magnetic field: effects on outer membrane protein pattern

Background

Salmonella enterica serovar Hadar (S. Hadar) is a highly prevalent foodborne pathogen and therefore a major cause of human gastroenteritis worldwide. Outer membrane proteins whose production is often regulated by environmental conditions also play important roles in the adaptability of bacterial pathogens to various environments.

Results

The present study investigated the adaptation of S. Hadar under the effect of acute static magnetic field exposure (200 mT, 9 h) and the impact on the outer membrane protein pattern. Via two-dimensional electrophoresis (2-DE) and LC-MS/MS spectrometry, we compared the proteome of enriched-outer membrane fraction before and after exposure to a magnetic field. A total of 11 proteins, displaying more than a two-fold change, were differentially expressed in exposed cells, among which 7 were up-regulated and 4 down-regulated. These proteins were involved in the integrity of cell envelope (TolB, Pal), in the response to oxidative stress (OmpW, dihydrolipoamide dehydrogenase, UspF), in the oxidative stress status (bacterioferritin), in virulence (OmpX, Yfgl) or in motility (FlgE and UspF). Complementary experiments associated the down-regulation of FlgE and UspF with an alteration of swarming, a flagella-driven motility, under SMF. Furthermore, the antibiotic disc diffusion method confirmed a decrease of gentamicin susceptibility in exposed cells. This decrease could be partly associated with the up-regulation of TolC, outer membrane component of an efflux pump. OmpA, a multifunctional protein, was up-regulated.

Conclusions

SMF (200 mT) seems to maintain the cell envelope integrity and to submit the exposed cells to an oxidative stress. Some alterations suggest an increase of the ability of exposed cells to form biofilms.

Effect of extremely low frequency magnetic field exposure on DNA transposition in relation to frequency, wave shape and exposure time

PURPOSE

To examine the effect of extremely low frequency magnetic field (ELF-MF) exposure on transposon (Tn) mobility in relation to the exposure time, the frequency and the wave shape of the field applied.

MATERIALS AND METHODS

Two Escherichia coli model systems were used: (1) Cells unable to express β-galactosidase (LacZ(-)), containing a mini-transposon Tn10 element able to give ability to express β-galactosidase (LacZ(+)) upon its transposition; therefore in these cells transposition activity can be evaluated by analysing LacZ(+) clones; (2) cells carrying Fertility plasmid (F(+)), and a Tn5 element located on the chromosome; therefore in these cells transposition activity can be estimated by a bacterial conjugation assay. Cells were exposed to sinusoidal (SiMF) or pulsed-square wave (PMF) magnetic fields of various frequencies (20, 50, 75 Hz) and for different exposure times (15 and 90 min).

RESULTS

Both mini-Tn10 and Tn5 transposition decreased under SiMF and increased under PMF, as compared to sham exposure control. No significant difference was found between frequencies and between exposure times.

CONCLUSIONS

ELF-MF exposure affects transposition activity and the effects critically depend on the wave shape of the field, but not on the frequency and the exposure time, at least in the range observed.

Pre-exposure to 50 Hz magnetic fields modifies menadione-induced genotoxic effects in human SH-SY5Y neuroblastoma cells

BACKGROUND

Extremely low frequency (ELF) magnetic fields (MF) are generated by power lines and various electric appliances. They have been classified as possibly carcinogenic by the International Agency for Research on Cancer, but a mechanistic explanation for carcinogenic effects is lacking. A previous study in our laboratory showed that pre-exposure to ELF MF altered cancer-relevant cellular responses (cell cycle arrest, apoptosis) to menadione-induced DNA damage, but it did not include endpoints measuring actual genetic damage. In the present study, we examined whether pre-exposure to ELF MF affects chemically induced DNA damage level, DNA repair rate, or micronucleus frequency in human SH-SY5Y neuroblastoma cells.

METHODOLOGY/PRINCIPAL FINDINGS

Exposure to 50 Hz MF was conducted at 100 µT for 24 hours, followed by chemical exposure for 3 hours. The chemicals used for inducing DNA damage and subsequent micronucleus formation were menadione and methyl methanesulphonate (MMS). Pre-treatment with MF enhanced menadione-induced DNA damage, DNA repair rate, and micronucleus formation in human SH-SY5Y neuroblastoma cells. Although the results with MMS indicated similar effects, the differences were not statistically significant. No effects were observed after MF exposure alone.

CONCLUSIONS

The results confirm our previous findings showing that pre-exposure to MFs as low as 100 µT alters cellular responses to menadione, and show that increased genotoxicity results from such interaction. The present findings also indicate that complementary data at several chronological points may be critical for understanding the MF effects on DNA damage, repair, and post-repair integrity of the genome.

Static magnetic field exposure fails to affect the viability of different bacteria strains

The viability of the microbes Saccharomyces cerevisiae, Bacillus circulans, Escherichia coli, Micrococcus luteus, Pseudomonas fluorescens, Salmonella enteritidis, Serratia marcescens, and Staphylococcus aureus was tested under static magnetic field exposure up to 24 h in either a homogeneous (159.2 +/- 13.4 mT) or three types of inhomogeneous static magnetic fields: (i) peak-to-peak magnetic flux density 476.7 +/- 0.1 mT with a lateral magnetic flux density gradient of 47.7 T/m, (ii) 12.0 +/- 0.1 mT with 1.2 T/m, or (iii) 2.8 +/- 0.1 mT with 0.3 T/m. Even the longest period of exposure failed to produce any effect in the growth of bacteriae that could be correlated with static magnetic field exposure.

Correlations and co-localizations of Hsp70 with XPA, XPG in human bronchial epithelia cells exposed to benzo[a]pyrene

Benzo[a]pyrene (BaP) is a ubiquitously distributed environmental pollutant known to cause DNA damage, which may be repaired through nucleotide excision repair (NER). The significantly negative correlation between Hsp70 levels and the level of DNA damage in workers exposed to coke oven emission had been found. However, little is known about how Hsp70 modulate the DNA repair process. In a series of experiments using the human bronchial epithelia cells (16HBE) exposed to different concentrations of BaP for 24h, we measured expression of NER subunit xeroderma pigmentosum (XP) group A, C, F, G (XPA, XPC, XPF, XPG), excision repair cross-complementing 1 (ERCC1) and Hsp70, and analyzed their possible correlations. Co-localizations of Hsp70 with NER subunit were detected by confocal microscope. We found that in vitro exposure to BaP reduced cell viability in a dose-dependent manner ranging from 2 to 64 microM. Our results showed that levels of XPA, XPG and Hsp70 significantly increased at cells exposed to 1 or 2muM BaP. In addition, curve estimation showed there was a significant correlation between relative ratios of Hsp70 and XPA, XPG in cells exposed to different concentrations of BaP. Moreover, confocal microscopy demonstrated increased co-localization of Hsp70 with XPA, XPG in nuclei of cells exposed to BaP. These results suggested that Hsp70 might play a role in nucleotide excision repair. However, the mechanisms underlying this observation need further investigation.

Electromagnetic field therapy delays cellular senescence and death by enhancement of the heat shock response

Hormesis may result when mild repetitive stress increases cellular defense against diverse injuries. This process may also extend in vitro cellular proliferative life span as well as delay and reverse some of the age-dependent changes in both replicative and non-replicative cells. This study evaluated the potential hormetic effect of non-thermal repetitive electromagnetic field shock (REMFS) and its impact on cellular aging and mortality in primary human T lymphocytes and fibroblast cell lines. Unlike previous reports employing electromagnetic radiation, this study used a long wave length, low energy, and non-thermal REMFS (50MHz/0.5W) for various therapeutic regimens. The primary outcomes examined were age-dependent morphological changes in cells over time, cellular death prevention, and stimulation of the heat shock response. REMFS achieved several biological effects that modified the aging process. REMFS extended the total number of population doublings of mouse fibroblasts and contributed to youthful morphology of cells near their replicative lifespan. REMFS also enhanced cellular defenses of human T cells as reflected in lower cell mortality when compared to non-treated T cells. To determine the mechanism of REMFS-induced effects, analysis of the cellular heat shock response revealed Hsp90 release from the heat shock transcription factor (HSF1). Furthermore, REMFS increased HSF1 phosphorylation, enhanced HSF1-DNA binding, and improved Hsp70 expression relative to non-REMFS-treated cells. These results show that non-thermal REMFS activates an anti-aging hormetic effect as well as reduces cell mortality during lethal stress. Because the REMFS configuration employed in this study can potentially be applied to whole body therapy, prospects for translating these data into clinical interventions for Alzheimer's disease and other degenerative conditions with aging are discussed.

Magnetoreception in microorganisms and fungi

The ability to respond to magnetic fields is ubiquitous among the five kingdoms of organisms. Apart from the mechanisms that are at work in bacterial magnetotaxis, none of the innumerable magnetobiological effects are as yet completely understood in terms of their underlying physical principles. Physical theories on magnetoreception, which draw on classical electrodynamics as well as on quantum electrodynamics, have greatly advanced during the past twenty years, and provide a basis for biological experimentation. This review places major emphasis on theories, and magnetobiological effects that occur in response to weak and moderate magnetic fields, and that are not related to magnetotaxis and magnetosomes. While knowledge relating to bacterial magnetotaxis has advanced considerably during the past 27 years, the biology of other magnetic effects has remained largely on a phenomenological level, a fact that is partly due to a lack of model organisms and model responses; and in great part also to the circumstance that the biological community at large takes little notice of the field, and in particular of the available physical theories. We review the known magnetobiological effects for bacteria, protists and fungi, and try to show how the variegated empirical material could be approached in the framework of the available physical models.

Gut myoelectrical activity induces heat shock response in Escherichia coli and Caco-2 cells

The heat shock response is associated with the intracellular expression of a number of highly conserved heat shock proteins (Hsps). According to their molecular size, Hsps have been divided into several groups, which are strongly conserved and show high homology between the species, e.g., Hsp70, MW 70 kDa (Lindquist & Craig, 1998; Morimoto, 1998; Jolly & Morimoto, 2000; Zylicz et al. 2001). In all organisms the Hsp expression under stress conditions is regulated at transcriptional level, e.g., in humans by the heat shock transcription factor Hsf1 (Morimoto, 1998; Wu, 1995), while in Escherichia coli by replacement of the sigma factor sigma(70) in RNA polymerase by the sigma factor sigma(32) (Gross, 1987). The Hsps allow cell survival under stress conditions by renaturating of denaturated proteins, protecting of stress-labile proteins, preventing protein aggregation (chaperone functions), and by degradation of damaged proteins (protease activities) (Lindquist & Craig, 1988; Morimoto, 1998; Jolly & Morimoto, 2000). They have also many housekeeping functions under non-stressful conditions during the cell cycle, growth, development, and differentiation (Morimoto, 1998). Among a number of plausible inducing factors already studied, extremely low artificial electromagnetic fields have been shown to induce stress response in various cells, such as expression of sigma(32) mRNA (Cairo et al. 1998) and induction of DnaJ and DnaK proteins in Eschericha coli (Chow & Tung, 2000); expression of hsp-16 gene in Caenorhabditis elegans (Miyakawa et al., 2001); induction of heat shock transcription factor Hsf1 and Hsp70, Hsp90 and Hsp27 in human cells (Lin et al. 1997; Lin et al. 1998; Goodman & Blank, 1998; Pipkin et al. 1999). Nevertheless, the role of endogenous electromagnetic fields, i.e., generated by electrically active cells within a body remains controversial. Heat shock proteins (Hsps) protect cells against various environmental and endogenous stressors. Cytoprotection caused by Hsps involves tolerance induced by one agent against other, more severe agents. We have found that exposure of prokaryotic (Escherichia coli) and eukaryotic (Caco-2) cells to an electrical field (EF) connected with a myoelectrical migrating complex (MMC) generated by the small intestine smooth muscle induces the heat shock response. Using Western blot analysis, we have detected an elevated level of sigma factor 32 in E. coli cells exposed to MMC-related EF, and confocal microscopy indicated an increased level of the inducible form of Hsp70 protein in EF-stimulated Caco-2 cells. Additionally, we have found that this induced level of Hsp70 protected the Caco-2 cells against apoptosis caused by camptothecin. Our observations suggest that the myoelectrical activity of the gut may induce heat shock mechanisms in the cells of gut epithelium as well as in gastrointestinal micro-organisms.

Synthesis of DnaK and GroEL in Escherichia coli cells exposed to different magnetic field signals

The effects of extremely low frequency magnetic field (ELF-MF)(1 mT, 50 Hz) on the heat shock protein (HSP) synthesis in Escherichia coli were investigated. Two magnetic field signals were studied: sinusoidal (SMF) and pulsed square wave (PMF). It was found that bacteria exposed to SMF showed a significantly higher level of DnaK and GroEL proteins as compared to sham-exposed bacteria as revealed by Western blot, whereas a lower level was observed after PMF exposure. Similar results were obtained when bacterial cells were exposed to heat shock (HS) after ELF-MF exposure: again SMF and PMF resulted in an increase and in a reduction of HSP amount in comparison with sham control, respectively. In conclusion, the MF influences the synthesis of HSPs in E. coli in a way that critically depends on the signal characteristics.

The influence of extremely low frequency magnetic fields on cytoprotection and repair

Ischemia-reperfusion injuries, such as those suffered from various types of cardiovascular disease, are major causes of death and disability. For relatively short periods of ischemia, much of the damage is potentially reversible and in fact, does not occur until the influx of oxygen during the reperfusion stage. Because of this, there is a window of opportunity to protect the ischemic tissue. Here, we review several mechanisms of protection, such as heat shock proteins, opioids, collateral blood flow, and nitric oxide induction, and the evidence indicating that magnetic fields may be used as a means of providing protection via each of these mechanisms. While there are few studies demonstrating direct protection with magnetic field therapies, there are a number of published reports indicating that electromagnetic fields may be able to influence some of the biochemical systems with protective applications.

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.

Bioeffects of moderate-intensity static magnetic fields on cell cultures

The interaction of static magnetic fields (SMFs) with living organisms is a rapidly growing field of investigation. However, despite the increasing number of studies on the effects of the interaction of SMFs with living organisms, many gaps in our knowledge still remain. One reason why it is extremely important to deeply understand the true mode of action of MFs on living organisms, is the need to protect human health in consideration of the probable future introduction of new technologies such as magnetically levitated trains and the therapeutical use of MFs (e.g. magnetic resonance imaging, MRI, coupling of MF exposure with chemotherapy). The lack of knowledge of the morphological modifications brought about by exposure to moderate-intensity SMFs prompted us to investigate the bioeffects of 6mT SMFs on different cell types, by means of light and electron microscopy, confocal laser scanning microscopy and immuno- or cytochemistry. In the present article we report our own and other data from the literature on the morphological studies of the bioeffects of moderate-intensity SMFs. We focus on morphological modifications related to cell shape, cell surface, cytoskeleton, and plasma membrane expression of molecules and carbohydrate residues. The effects of exposure to moderate-intensity SMF for 24 or 48 h, on apoptosis, on apoptotic related gene products, on macrophagic differentiation and on phagocytosis of apoptotic cells in primary cell cultures (transformed or stabilized cell lines) will be also discussed. Moderate-intensity (6mT) SMFs induced modifications of cell shape, cell surface and cytoskeleton, progressively achieved during the entire period of exposure. In general, at the end of the exposure period, the cells had a less flat shape due to partial detachment from the culture dishes or a more round-elongated shape (in relation to adhesion growth or in suspension growth respectively) with many irregular lamellar microvilli, while the morphology of the organelles remained unmodified. In parallel with cell shape changes, the microfilaments and microtubules, as well as the quantity and distribution of surface ConA-FITC and Ricinus Comm.-FITC labelling sites, were modified in a time-dependent manner. Apoptosis was influenced in a cell type-dependent manner: for some cells spontaneous apoptosis decreased while, for others, it increased to about 20% after 24h of continuous exposure. The induction of apoptosis was likely due to the increment of [Ca(2+)]i during exposure. Cell proliferation was only slightly affected. Indeed, in addition to the cell type, the time of exposure was also an important factor in the intensity of the effects produced. Both apoptotic rate and cell and surface shape were influenced by exposure to SMFs when simultaneously administered with apoptogenic drugs. Apoptotic cells were cleared by an efficient and fast process of phagocytosis mediated by specific epitopes, externalized during the formation of the apoptotic cells, on the dead cells and by specific receptors on the phagocytes (both "professional" and "nonprofessional"). The recognition of apoptotic lymphocytes as well as of control cells exposed for at least 24h to 6mT SMF by liver sinusoidal cells was influenced by the cell surface modifications which both apoptotic or normal exposed cells underwent during the induction of apoptosis or SMF exposure. The degree of macrophagic differentiation of human pro-monocytic U937 cells induced by phorbol ester was decreased by exposure to 6mT SMFs, with a consequent fall in cell adhesion and increased polarization of pseudopodia and cytoplasmic protrusions. Differentiation alone, or in combination with exposure to SMFs, affects distribution and quantity of cell surface carbohydrate residues, surface expression of markers of macrophage differentiation, and phagocytic capability. The increasing amount of data reporting on the bioeffects of SMFs is leading researchers to an understanding of how important it is to fully understand the mode of action of MFs on living organisms. Indeed, even if the perturbations of biological systems by SMFs are sublethal at shorter times of exposure, these perturbations could, especially at longer times of exposure, evolve into a progressive accumulation of modifications, whose ultimate effects still need to be clarified.

Various effects on transposition activity and survival of Escherichia coli cells due to different ELF-MF signals

Previous assays with weak sinusoidal magnetic fields (SMF) have shown that bacteria that had been exposed to a 50 Hz magnetic field (0.1-1 mT) gave colonies with significantly lower transposition activity as compared to sham-exposed bacteria. These experiments have now been extended by using a pulsed-square wave magnetic field (PMF) and, unexpectedly, it was found that bacteria exposed to PMF showed a higher transposition activity compared to the controls. The increase of the transposition activity was positively correlated with the intensity of the magnetic fields (linear dose-effect relation). This phenomenon was not affected by any bacterial cell proliferation, since no significant difference was observed in number and size of PMF-exposed and sham-exposed colonies. In addition, the cell viability of E. coli was significantly higher than that of the controls when exposed to SMF, and lower than that of the controls when exposed to PMF. Under our experimental conditions it was shown that exposure to PMF stimulates the transposition activity and reduces cell viability of bacteria, whereas exposure to SMF reduces the transposition mobility and enhances cell viability. These results suggest that the biological effects of magnetic fields may critically depend on the physical characteristics of the magnetic signal, in particular the wave shape.

Effects of a static magnetic field on cell growth and gene expression in Escherichia coli

Escherichia coli cultures exposed to a 300mT static magnetic field (SMF) were studied in order to analyse possible induced changes in cellular growth and gene expression. Biomass was evaluated by visible-light spectrometry and gene expression analyses were carried out by use of RNA arbitrarily primed PCR. The bacterial strain XL-1Blue, cultivated in traditional and modified Luria-Bertani medium, was exposed to SMF generated by permanent neodymium magnetic disks. The results show alterations induced by SMF in terms of increased cell proliferation and changes in gene expression compared with control groups. Three cDNAs were found to be expressed only in the exposed cells, whereas one cDNA was more expressed in the controls. One clone, expressed only in the exposed cells, corresponds to a putative transposase. This is of particular interest in that it suggests that exposure to a magnetic field may stimulate transposition activity.

Pulsed electric field alters molecular chaperone expression and sensitizes Listeria monocytogenes to heat

Pulsed electric field (PEF)-resistant and PEF-sensitive Listeria monocytogenes strains were sublethally treated with electric pulses at 15 kV/cm for 29 micro s and held at 25 degrees C for 5 to 30 min prior to protein extraction. The levels of the molecular chaperones GroEL, GroES, and DnaJ were determined by immunoblotting. After 10 to 20 min after sublethal PEF treatment, a transient decrease in molecular chaperone expression was observed in the PEF-sensitive strain (Scott A). The levels of GroEL and DnaJ increased back to the basal expression level within 30 min. A substantial decrease in GroES expression persisted for at least 30 min after PEF treatment. Chaperone expression was suppressed after PEF treatment to a smaller extent in the PEF-resistant (OSY-8578) than in the PEF-sensitive strain, and no clear expression pattern was identified in OSY-8578. Inactivation of Scott A and OSY-8578 in phosphate buffer was compared when lethal PEF (27.5 kV/cm, 144 micro s) and heat (55 degrees C, 10 min) were applied in sequence. When PEF and heat treatments were applied separately, the populations of L. monocytogenes Scott A and OSY-8578 decreased 0.5 to 0.6 log CFU/ml. Cells treated first with PEF and incubated at 25 degrees C for 10 min showed substantial sensitivity to subsequent heat treatment; the decrease in counts for Scott A and OSY-8578 was 6.1 and 2.8 log CFU/ml, respectively. The sequence and time lapse between the two treatments were crucial for achieving high inactivation rates. It is concluded that PEF sensitized L. monocytogenes to heat and that maximum heat sensitization occurred when chaperone expression was at a minimum level.

Expression levels of heat shock protein 60 in human endothelial cells in vitro are unaffected by exposure to 50 Hz magnetic fields

Magnetic fields (MFs) from domestic power sources have been implicated as being a potential risk to human health. A number of epidemiological studies have found a significant link between exposure to MFs and increased rates of cancers. There have also been a number of in vivo and in vitro studies reporting effects of MFs in animal disease models and on the expression or activity of a range of proteins. In the past decade, our group proposed that atherosclerosis may have an autoimmune component, with heat shock protein 60 (Hsp60) expressed in endothelial cells as the dominant autoantigen. A number of stressors have been shown to induce the expression of Hsp60, including the classical risk factors for atherosclerosis. We were interested to see if the exposure of endothelial cells to an MF elicited increased expression of Hsp60, as has been reported previously for Hsp70. The present work describes the exposure of endothelial cells to domestic power supply (50 Hz) MFs at an intensity of 700 microT. The results from our system indicate that cultured endothelial cells exposed to a high intensity of MF either alone or in combination with classical heat stress show no effects on the expression of Hsp60 at either the messenger ribonucleic acid or the protein level. As such, there is no evidence that exposure to extremely low-frequency MF would be expected to increase the expression of Hsp60 and therefore the initiation or progression of atherosclerosis.

Microwave exposure induces Hsp70 and confers protection against hypoxia in chick embryos

To determine if microwave exposure could elicit a biological effect in the absence of thermal stress, studies were designed in which chick embryos were exposed to athermal microwave radiation (915 MHz) to look for induction of Hsp70, a protein produced during times of cellular stress that aids in the protection of cellular components. Levels of Hsp70 were found to increase within 2 h, with maximum expression ( approximately 30% higher than controls) typically occurring by 3 h from the start of exposure. Other embryos were exposed to microwave radiation prior to being subjected to hypoxic stress, and were found to have significantly higher survival (P < 0.05) following re-oxygenation than non-exposed controls. The results of these studies indicate that not only can athermal microwave exposures activate the stress protein response pathway; they can also enhance survivability following exposure to a subsequent, potentially lethal stress. From a public health standpoint, it is important that more studies be performed to determine if repeated exposures, a condition likely to be found in cell phone use, are still beneficial.

Decreased DNA repair rates and protection from heat induced apoptosis mediated by electromagnetic field exposure

In this study, we demonstrate that electromagnetic field (EMF) exposure results in protection from heat induced apoptosis in human cancer cell lines in a time dependent manner. Apoptosis protection was determined by growing HL-60, HL-60R, and Raji cell lines in a 0.15 mT 60 Hz sinusoidal EMF for time periods between 4 and 24 h. After induction of apoptosis, cells were analyzed by the neutral comet assay to determine the percentage of apoptotic cells. To discover the duration of this protection, cells were grown in the EMF for 24 h and then removed for 24 to 48 h before heat shock and neutral comet assays were performed. Our results demonstrate that EMF exposure offers significant protection from apoptosis (P<.0001 for HL-60 and HL-60R, P<.005 for Raji) after 12 h of exposure and that protection can last up to 48 h after removal from the EMF. In this study we further demonstrate the effect of the EMF on DNA repair rates. DNA repair data were gathered by exposing the same cell lines to the EMF for 24 h before damaging the exposed cells and non-exposed cells with H2O2. Cells were allowed to repair for time periods between 0 and 15 min before analysis using the alkaline comet assay. Results showed that EMF exposure significantly decreased DNA repair rates in HL-60 and HL-60R cell lines (P<.001 and P<.01 respectively), but not in the Raji cell line. Importantly, our apoptosis results show that a minimal time exposure to an EMF is needed before observed effects. This may explain previous studies showing no change in apoptosis susceptibility and repair rates when treatments and EMF exposure were administered concurrently. More research is necessary, however, before data from this in vitro study can be applied to in vivo systems.

Heat shock protein 70 binds to human apurinic/apyrimidinic endonuclease and stimulates endonuclease activity at abasic sites

The interaction of human heat shock protein 70 (HSP70) with human apurinic/apyrimidinic endonuclease (HAP1) was demonstrated by coimmunoprecipitation. A combination of HSP70 and HAP1 also caused a shift in the electrophoretic mobility of a DNA fragment containing an apurinic/apyrimidinic site. The functional consequence of the HSP70/HAP1 interaction was a 10-100-fold enhancement of endonuclease activity at abasic sites. The physical and functional interaction between HSP70 and HAP1 did not require the addition of ATP. The association of HSP70 and a key base excision repair enzyme suggests a role for heat shock proteins in promoting base excision repair. These findings provide a possible mechanism by which HSP70 protects cells against oxidative stress.

Magnetic field exposure induces DNA degradation

In our earlier experiments, we discovered that magnetic field exposure could bring both stabilizing and destabilizing effects to the DNA of Escherichia coli, depending on our parameters of assessment, and both of these effects were associated with the induced synthesis of the heat shock proteins Hsp70/Hsp40 (DnaK/DnaJ). These contradicting results prompted us to explore in this study the effect of magnetic field exposure on the DNA stability in vivo when the heat shock response of the cell was suppressed. By using plasmid pUC18 in E. coli as the indicator, we found that without the protection of the heat shock response, magnetic field exposure indeed induced DNA degradation and this deleterious effect could be diminished by the presence of an antioxidant, Trolox C. In our in vitro test, we also showed that the magnetic field could potentiate the activity of oxidant radicals.