Genotoxic effects of strong static magnetic fields in DNA-repair defective mutants of Drosophila melanogaster

Cellular and Molecular Effects of Magnetic Fields

Recently, magnetic fields (MFs) have received major attention due to their potential therapeutic applications and biological effects. This review provides a comprehensive analysis of the cellular and molecular impacts of MFs, with a focus on both in vitro and in vivo studies. We investigate the mechanisms by which MFs influence cell behavior, including modifications in gene expression, protein synthesis, and cellular signaling pathways. The interaction of MFs with cellular components such as ion channels, membranes, and the cytoskeleton is analyzed, along with their effects on cellular processes like proliferation, differentiation, and apoptosis. Molecular insights are offered into how MFs modulate oxidative stress and inflammatory responses, which are pivotal in various pathological conditions. Furthermore, we explore the therapeutic potential of MFs in regenerative medicine, cancer treatment, and neurodegenerative diseases. By synthesizing current findings, this article aims to elucidate the complex bioeffects of MFs, thereby facilitating their optimized application in medical and biotechnological fields.

Effects of Magnetic Field Applied Just Before, During or Immediately after Carbon-Ion Beam Irradiation on its Biological Effectiveness

Previously reported studies have revealed that the application of a magnetic field longitudinal to a carbon-ion beam enhances its biological effectiveness. Here we investigated how timing of the magnetic field application with respect to beam irradiation influenced this effect. Human cancer cells were exposed to carbon-ion beams with linear energy transfer (LET) of 12 and 50 keV/µm. The longitudinal magnetic field of 0.3 T was applied to the cells just before, during or immediately after the beam irradiation. The effects of the timing on the biological effectiveness were evaluated by cell survival. The biological effectiveness increased only if the magnetic field was applied during beam irradiation for both LETs.

Biological responses of human solid tumor cells to X-ray irradiation within a 1.5-Tesla magnetic field generated by a magnetic resonance imaging-linear accelerator

Devices that combine magnetic resonance imaging with linear accelerators (MRL) represent a novel tool for MR-guided radiotherapy. However, whether magnetic fields (MFs) generated by these devices affect the radiosensitivity of tumors is unknown. We investigated the influence of a 1.5-T MF on cell viability and radioresponse of human solid tumors. Human head/neck cancer and lung cancer cells were exposed to single or fractionated 6-MV X-ray radiation; effects of the MF on cell viability were determined by cell plating efficiency and on radioresponsiveness by clonogenic cell survival. Doses needed to reduce the fraction of surviving cells to 37% of the initial value (D0s) were calculated for multiple exposures to MF and radiation. Results were analyzed using Student's t-tests. Cell viability was no different after single or multiple exposures to MRL than after exposure to a conventional linear accelerator (Linac, without MR-generated MF) in 12 of 15 experiments (all P > 0.05). Single or multiple exposures to MF had no influence on cell radioresponse (all P > 0.05). Cells treated up to four times with an MRL or a Linac further showed no changes in D0s with MF versus without MF (all P > 0.05). In conclusion, MF within the MRL does not seem to affect in vitro tumor radioresponsiveness as compared with a conventional Linac. Bioelectromagnetics. 37:471-480, 2016. © 2016 Wiley Periodicals, Inc.

Effects of 36.6 GHz and static magnetic field on degree of endoreduplication in Drosophila melanogaster polytene chromosomes

Purpose To study the effect of microwave (MW) irradiation and consistent action of microwaves and static magnetic field (MF) on the giant chromosomes endoreduplication in Drosophila melanogaster Meig. Materials and methods Experiments were carried out on inbred wild type Canton-S strain. Exposure to microwaves (frequency - 36.64 GHz, power density - 1 W/m(2), exposure time - 30 sec) and static magnetic field (intensity - 25 mT, exposure time - 5 min) applied at the egg stage after a 2-h oviposition. Giant chromosomes were investigated in squashed preparations of the salivary glands stained by acetoorcein by the cytomorphometric method. Preparations were obtained from Drosophila larvae at the 0 h prepupae stage. Results Exposure to microwaves increased the degree of polyteny in chromosomes (DPC) by 7.5%, and the statistical power of the impact was: h(2) = 35.3%. A similar effect occurred after the sequential action of microwaves and static magnetic field: The polyteny level of chromosomes increased by 7.4%, statistical power was: h(2) = 30.6%. Conclusions Exposure to microwaves on the stage of embryogenesis has a stimulating effect on endoreduplication in Drosophila development. The effect of microwaves was not modified by the action of the static magnetic field.

Estimation of changes in fitness components and antioxidant defense of Drosophila subobscura (Insecta, Diptera) after exposure to 2.4 T strong static magnetic field

As an ecological factor, a magnetic field can affect insects causing a wide range of responses. The main purpose of this study was to analyze the fitness components (postembryonic development and viability of individuals) and the antioxidant defense (superoxide dismutase, catalase, and total glutathione) in laboratory strains of Drosophila subobscura, originating from oak and beech forests after exposure to the strong static magnet (2.4 T, VINCY Cyclotron magnet). The first instar larvae were placed near the north pole (N group) or the south pole (S group) of the magnet for 2 h. Oak and beech populations of D. subobscura had longer development time and lower viability in N and S groups compared to controls. These differences were significant only in S group of oak population and in N group of beech population. Total glutathione content was significantly decreased in both exposed groups of oak population, while catalase activity was significantly increased in both exposed groups of beech population. Being significantly decreased in both exposed groups of oak population and significantly increased in S group of beech population in comparison to controls, superoxide dismutase activity was observed in different values. According to the results, it can be stated that applied static magnetic field could be considered a potential stressor influencing the fitness components and antioxidant defense in Drosophila flies.

The influence of electromagnetic pollution on living organisms: historical trends and forecasting changes

Current technologies have become a source of omnipresent electromagnetic pollution from generated electromagnetic fields and resulting electromagnetic radiation. In many cases this pollution is much stronger than any natural sources of electromagnetic fields or radiation. The harm caused by this pollution is still open to question since there is no clear and definitive evidence of its negative influence on humans. This is despite the fact that extremely low frequency electromagnetic fields were classified as potentially carcinogenic. For these reasons, in recent decades a significant growth can be observed in scientific research in order to understand the influence of electromagnetic radiation on living organisms. However, for this type of research the appropriate selection of relevant model organisms is of great importance. It should be noted here that the great majority of scientific research papers published in this field concerned various tests performed on mammals, practically neglecting lower organisms. In that context the objective of this paper is to systematise our knowledge in this area, in which the influence of electromagnetic radiation on lower organisms was investigated, including bacteria, E. coli and B. subtilis, nematode, Caenorhabditis elegans, land snail, Helix pomatia, common fruit fly, Drosophila melanogaster, and clawed frog, Xenopus laevis.

Bio-effects of near-zero magnetic fields on the growth, development and reproduction of small brown planthopper, Laodelphax striatellus and brown planthopper, Nilaparvata lugens

Magnetic fields markedly affect the growth and development of many species of organisms potentially due to cryptochrome and endogenous presence of magnetic materials. Sensitivity to magnetic fields can also be involved in geomagnetic orientation by some long-distance migratory insects. In this study, near-zero magnetic fields (NZMF) in relation to normal geomagnetic fields (GMF) were setup using the Hypomagnetic Field Space System (HMFs) to investigate the effects of magnetic fields on the growth, development and reproduction of two species of migratory planthopper, the small brown planthopper (abbr. SBPH), Laodelphax striatellus, and the brown planthopper (abbr. BPH), Nilaparvata lugens. Exposure of both L. striatellus and N. lugens to NZMF delayed egg and nymphal developmental durations and decreased adult weight and female fecundity. The 1st-5th instars of SBPH and BPH showed different responses to NZMF. The 4th instar was significantly affected by NZMF, especially for BPH males, in which NZMF exposure reduced the difference in development duration between females and males. Compared with GMF, the vitellogenin transcript levels of newly molted female adults and the number of eggs per female were significantly reduced in both planthopper species, indicating a negative effect on fertility under NZMF. Our findings provided experimental evidence that NZMF negatively affected the growth and development of SBPH and BPH, with particularly strong effects on reproduction.

Effect of static magnetic field on the induction of micronuclei by some mutagens

OBJECTIVES

It is important to assess the risk of static magnetic fields (SMFs) on human health, because epidemiological studies have indicated that SMFs play a role in the development of diseases such as leukemia and brain tumor. In our environment, we have numerous chances to be exposed to not only SMFs but also many chemicals containing mutagens. The aim of this study is to investigate the effect of SMFs on the induction of micronuclei induced by some mutagens.

METHODS

BALB/c mice were exposed to 4.7 tesla (T) SMF for 24 hr immediately after the injection of carboquone (alkylating agent), colcemid (spindle poison), mitomycin C (cross-linking agent), vincristine (spindle poison), sodium fluoride (a byproduct of aluminum plants under strong SMF) or 1-ethyl-1-nitrosourea (brain tumor-, gliomas- and thymic lymphoma-inducing chemical).

RESULTS

The frequency of micronuclei induced by six mutagens increased after co-exposure to SMF.

CONCLUSIONS

An additive/synergistic effect of SMF and chemicals was observed from the results of increased frequency of micronuclei induced by mutagens in mouse bone marrow erythrocytes.

Effects of homogeneous and inhomogeneous static magnetic fields combined with gamma radiation on DNA and DNA repair

The aim of this study was to reveal whether static magnetic fields (SMFs) influence the repair of radiation-damaged DNA on leukocytes or has any effect on DNA. After 4 Gy of (60)Co-gamma irradiation, some of the samples were exposed to inhomogeneous SMFs with a lateral magnetic flux density gradient of 47.7, 1.2, or 0.3 T/m by 10 mm lateral periodicity, while other samples were exposed to homogeneous SMF of 159.2 +/- 13.4 mT magnetic flux density for a time period of 0.5 min, 1, 2, 4, 6, 18, 20, or 24 h. Another set of samples was exposed to the aforementioned SMFs before gamma irradiation. The following three groups were examined: (i) exposed to SMF only, (ii) exposed to SMF following irradiation by (60)Co-gamma, and (iii) exposed to SMF before (60)Co-gamma irradiation. The analysis of the DNA damage was made by single-cell gel electrophoresis technique (comet assay). Statistically significant differences were found at 1 h (iSMF), 4 h (hSMF), and 18 h (hSMF) if samples were exposed to only SMF, compared to control. When the SMF exposure followed the (60)Co-gamma irradiation, statistically significant differences were found at 1 h (iSMF) and 4 h (hSMF). If exposure to SMF preceded (60)Co-gamma irradiation, no statistically significant difference was found compared to 4 Gy gamma-irradiated group.

Cellular ATP content was decreased by a homogeneous 8.5 T static magnetic field exposure: role of reactive oxygen species

The literature on the impact of strong static magnetic fields (SMF) on human health is vast and contradictory. The present study focused on the cellular effects of strong homogeneous SMF in human-hamster hybrid (A(L) ) cells, mitochondria-deficient (ρ(0) A(L) ) cells, and double-strand break (DSB) repair-deficient (XRS-5) cells. Adenosine triphosphate (ATP) content was significantly decreased in A(L) cells exposed to 8.5 Tesla (T) but not 1 or 4 T SMF for either 3 or 5 h. In addition, ATP content significantly decreased in the two deficient cell lines exposed to 8.5 T SMF for 3 h. With further incubation of 12 or 24 h without SMF exposure, ATP content could retrieve to the control level in the A(L) cells but not ρ(0) A(L) and XRS-5 cells. Under a fluorescence reader, the levels of reactive oxygen species (ROS) in the three cell lines were significantly increased by exposure to 8.5 T SMF for 3 h. Concurrent treatment with ROS inhibitor, DMSO, dramatically suppressed the ATP content in exposed A(L) cells. However, the CD59 mutation frequency and the cell cycle distribution were not significantly affected by exposure to 8.5 T SMF for 3 h. Our results indicated that the cellular ATP content was reduced by 8.5 T SMF for 3 h exposure, which was partially mediated by mitochondria and the DNA DSB repair process. Moreover, ROS were involved in the process of the cellular perturbations from the SMF.

Influence of a static magnetic field (250 mT) on the antioxidant response and DNA integrity in THP1 cells

The aim of this study was to investigate the effect of static magnetic field (SMF) exposure in antioxidant enzyme activity, the labile zinc fraction and DNA damage in THP1 cells (monocyte line). Cell culture flasks were exposed to SMF (250 mT) during 1 h (group 1), 2 h (group 2) and 3 h (group 3). Our results showed that cell viability was slightly lower in SMF-exposed groups compared to a sham exposed group. However, SMF exposure failed to alter malondialdehyde (MDA) concentration (+6%, p>0.05) and glutathione peroxidase (GPx) (-5%, p>0.05), catalase (CAT) (-6%, p>0.05) and superoxide dismutase (SOD) activities (+38%, p>0.05) in group 3 compared to the sham exposed group. DNA analysis by single cell gel electrophoresis (comet assay) revealed that SMF exposure did not exert any DNA damage in groups 1 and 2. However, it induced a low level of DNA single strand breaks in cells of group 3. To further explore the oxidative DNA damage, cellular DNA for group 3 was isolated, hydrolyzed and analysed by HPLC-EC. The level of 8-oxodGuo in this group remained unchanged compared to the sham exposed group (+6.5%, p>0.05). Cells stained with zinc-specific fluorescent probes zinpyr-1 showed a decrease of labile zinc fraction in all groups exposed to SMF. Our data showed that SMF exposure (250 mT, during 3 h) did not cause oxidative stress and DNA damage in THP1 cells. However, SMF could alter the intracellular labile zinc fraction.