The effects of extremely low frequency magnetic fields on mutation induction in mice

Genetic effects of non-ionizing electromagnetic fields

This is a review of the research on the genetic effects of non-ionizing electromagnetic field (EMF), mainly on radiofrequency radiation (RFR) and static and extremely low frequency EMF (ELF-EMF). The majority of the studies are on genotoxicity (e.g., DNA damage, chromatin conformation changes, etc.) and gene expression. Genetic effects of EMF depend on various factors, including field parameters and characteristics (frequency, intensity, wave-shape), cell type, and exposure duration. The types of gene expression affected (e.g., genes involved in cell cycle arrest, apoptosis and stress responses, heat-shock proteins) are consistent with the findings that EMF causes genetic damages. Many studies reported effects in cells and animals after exposure to EMF at intensities similar to those in the public and occupational environments. The mechanisms by which effects are induced by EMF are basically unknown. Involvement of free radicals is a likely possibility. EMF also interacts synergistically with different entities on genetic functions. Interactions, particularly with chemotherapeutic compounds, raise the possibility of using EMF as an adjuvant for cancer treatment to increase the efficacy and decrease side effects of traditional chemotherapeutic drugs. Other data, such as adaptive effects and mitotic spindle aberrations after EMF exposure, further support the notion that EMF causes genetic effects in living organisms.

Cell physiological responses of RAW264 macrophage cells to a 50-Hz magnetic field

PURPOSE

We previously showed that a 0.5-mT, 50-Hz sinusoidal magnetic field (LFMF) enhanced DNA single-strand breaks (SSB) and necrosis in RAW264 macrophages that had been stimulated by bacterial endotoxin (lipopolysaccharide; LPS). LPS enhances production of nitric oxide (NO) and superoxide anion (O₂ ^-) that react with each other to generate peroxynitrite (ONOO^-). ONOO^- causes DNA strand breaks. Hence, we anticipated that 0.5-mT, 50-Hz sinusoidal magnetic field increased production of NO, thereby increasing intracellular ONOO^- concentration and promoted DNA strand breaks. However, the NO production was not increased. In this study, we examined if the exposure of the cell to 0.5-mT, 50-Hz magnetic field for 24 h (1) promotes O₂ ^- production, (2) elevated the degree of apoptosis, because apoptosis is an upstream event of necrosis, (3) lowers mitochondrial membrane potential (ΔΦ_m), because it would also promote necrosis.

MATERIALS AND METHODS

O₂ ^-, was measured with nitroblue tetrazolium and water-soluble tetrazolium salt. Necrosis and apoptosis were quantified with propidium iodide and fluorescence labelling of caspases, respectively. The ΔΦ_m was measured with a fluorescent probe (JC-1) that reflects ΔΦ_m. Results and conclusions: In the LPS-stimulated macrophage, the LFMF did not promote O₂ ^- production. Thus, the LFMF-promoted DNA strand breaks did not result from the increase in the O₂ ^- production. The LFMF did not promote apoptosis, whereas it tended to increase the degree of necrosis, as we showed previously. The ΔΦ_m slightly declined in the LFMF-exposed cell without statistical significance.

Effect of 50-Hz Magnetic Fields on Serum IL-1β and IL-23 and Expression of BLIMP-1, XBP-1, and IRF-4

Investigations demonstrated that magnetic fields (MFs) change cytokine production and expression of some immune system genes. This alteration can affect the immune system function and may lead to some diseases. Therefore, this study investigated two important inflammatory cytokines, i.e., IL-1β and IL-23 at two phases of pre- and post-immunization of the immune system. In addition, the expressions of three important genes in the humoral immunity, i.e., B lymphocyte-induced maturation protein-1 (BLIMP-1), X-box-binding protein-1 (XBP-1), and interferon regulatory factor-4 (IRF-4) were evaluated at post-immunization phase. Eighty adult male rats were divided into four experimental groups and a control. The experimental groups were exposed to 50 -Hz MFs with magnetic flux densities of 1, 100, 500, and 2000 μT, 2 h/day for 2 months. The animals were injected by human serum albumin (100 μg/rat) on days 31, 44, and 58 of exposure. The cytokine levels in serum were measured with enzyme-linked immunosorbent assay (ELISA), and the expression of genes was evaluated with reverse transcription quantitative polymerase chain reaction (RT-qPCR). Serum IL-1β was decreased at pre-immunization phase after exposure to 1 and 100 μT of 50-Hz MFs. In contrast, serum IL-23 was increased at post-immunization phase in 100 μT group. No change was observed in serum IL-1β and IL-23 in each group at pre-immunization phase compared with post-immunization. Furthermore, exposure to 100 μT downregulated expression of BLIMP-1, XBP-1, and IRF-4. In conclusion, exposure to 50-Hz MFs may decrease inflammation at short time and increase it at longer time exposures. In addition, 50-Hz MF exposure may decrease the humoral immune responses. It seems that 50-Hz MFs cause more alteration in immune system function at lower densities (100 μT).

Mutation Induction in Humans and Mice: Where Are We Now?

The analysis of mutation induction in human families exposed to mutagens provides the only source of reliable estimates of factors contributing to the genetic risk of human exposure to mutagens. In this paper, I briefly summarize the results of recent studies on the pattern of mutation induction in the human and mouse germline. The results of recent studies on the genome-wide effects of exposure to mutagens on mutation induction in the mammalian germline are presented and discussed. Lastly, this review also addresses the issue of transgenerational effects of parental exposure to mutagens on mutation rates in their non-exposed offspring, which are known as transgenerational instability. The possible contribution of transgenerational instability to the genetic risk of human exposure to mutagens is discussed.

Potential therapeutic mechanism of extremely low-frequency high-voltage electric fields in cells

The aim of this survey was to provide background theory based on previous research to elucidate the potential pathway by which medical devices using extremely low-frequency high-voltage electric fields (ELF-HVEF) exert therapeutic effects on the human body, and to increase understanding of the AC high-voltage electrotherapeutic apparatus for consumers and suppliers of the relevant devices. Our review revealed that an ELF field as weak as 1-10 μ V/m can induce diverse alterations of membrane proteins such as transporters and channel proteins, including changes in Ca + + binding to a specific site of the cell surface, changes in ion (e.g., Ca + + ) influx or efflux, and alterations in the ligand-receptor interaction. These alterations then induce cytoplasmic responses within cells (Ca + + , cAMP, kinases, etc.) that can have impacts on cell growth, differentiation, and other functional properties by promoting the synthesis of macromolecules. Moreover, increased cytoplasmic Ca + + involves calmodulin-dependent signaling and consequent Ca + + /calmodulin-dependent stimulation of nitric oxide synthesis. This event in turn induces the nitric oxide-cGMP-protein kinase G pathway, which may be an essential factor in the observed physiological and therapeutic responses.