Chronic exposure to 50Hz magnetic fields causes a significant weakening of antioxidant defence systems in aged rat brain

Several studies suggest that extremely low-frequency magnetic fields (ELF-MFs) may enhance the free radical endogenous production. It is also well known that one of the unavoidable consequences of ageing is an overall oxidative stress-based decline in several physiological functions and in the general resistance to stressors. On the basis of these assumptions, the aim of this study was to establish whether the ageing process can increase susceptibility towards widely present ELF-MF-mediated pro-oxidative challenges. To this end, female Sprague-Dawley rats were continuously exposed to a sinusoidal 50Hz, 0.1mT magnetic field for 10 days. Treatment-induced changes in the major antioxidant protection systems and in the neurotrophic support were investigated, as a function of the age of the subjects. All analyses were performed in brain cortices, due to the high susceptibility of neuronal cells to oxidative injury. Our results indicated that ELF-MF exposure significantly affects anti-oxidative capability, both in young and aged animals, although in opposite ways. Indeed, exposed young individuals enhanced their neurotrophic signalling and anti-oxidative enzymatic defence against a possible ELF-MF-mediated increase in oxygen radical species. In contrast, aged subjects were not capable of increasing their defences in response to ELF-MF treatment but, on the contrary, they underwent a significant decrease in the major antioxidant enzymatic activities. In conclusion, our data seem to suggest that the exposure to ELF-MFs may act as a risk factor for the occurrence of oxidative stress-based nervous system pathologies associated with ageing.     

Extremely low-frequency electromagnetic fields do not affect DNA damage and gene expression profiles of yeast and human lymphocytes

We studied the effects of extremely low-frequency (50 Hz) electromagnetic fields (EMFs) on peripheral human blood lymphocytes and DBY747 Saccharomyces cerevisiae. Graded exposure to 50 Hz magnetic flux density was obtained with a Helmholtz coil system set at 1, 10 or 100 microT for 18 h. The effects of EMFs on DNA damage were studied with the single-cell gel electrophoresis assay (comet assay) in lymphocytes. Gene expression profiles of EMF-exposed human and yeast cells were evaluated with DNA microarrays containing 13,971 and 6,212 oligonucleotides, respectively. After exposure to the EMF, we did not observe an increase in the amount of strand breaks or oxidated DNA bases relative to controls or a variation in gene expression profiles. The results suggest that extremely low-frequency EMFs do not induce DNA damage or affect gene expression in these two different eukaryotic cell systems.     

Neuronal Cellular Responses to Extremely Low Frequency Electromagnetic Field Exposure: Implications Regarding Oxidative Stress and Neurodegeneration

Neurodegenerative diseases comprise both hereditary and sporadic conditions characterized by an identifying progressive nervous system dysfunction and distinctive neuopathophysiology. The majority are of non-familial etiology and hence environmental factors and lifestyle play key roles in their pathogenesis. The extensive use of and ever increasing worldwide demand for electricity has stimulated societal and scientific interest on the environmental exposure to low frequency electromagnetic fields (EMFs) on human health. Epidemiological studies suggest a positive association between 50/60-Hz power transmission fields and leukemia or lymphoma development. Consequent to the association between EMFs and induction of oxidative stress, concerns relating to development of neurodegenerative diseases, such as Alzheimer disease (AD), have been voiced as the brain consumes the greatest fraction of oxygen and is particularly vulnerable to oxidative stress. Exposure to extremely low frequency (ELF)-EMFs are reported to alter animal behavior and modulate biological variables, including gene expression, regulation of cell survival, promotion of cellular differentiation, and changes in cerebral blood flow in aged AD transgenic mice. Alterations in inflammatory responses have also been reported, but how these actions impact human health remains unknown. We hence evaluated the effects of an electromagnetic wave (magnetic field intensity 1mT; frequency, 50-Hz) on a well-characterized immortalized neuronal cell model, human SH-SY5Y cells. ELF-EMF exposure elevated the expession of NOS and O₂ ⁻, which were countered by compensatory changes in antioxidant catylase (CAT) activity and enzymatic kinetic parameters related to CYP-450 and CAT activity. Actions of ELF-EMFs on cytokine gene expression were additionally evaluated and found rapidly modified. Confronted with co-exposure to H₂O₂-induced oxidative stress, ELF-EMF proved not as well counteracted and resulted in a decline in CAT activity and a rise in O₂ ⁻ levels. Together these studies support the further evaluation of ELF-EMF exposure in cellular and in vivo preclinical models to define mechanisms potentially impacted in humans.     

Proteomic response of Schizosaccharomyces pombe to static and oscillating extremely low-frequency electromagnetic fields

There is considerable public concern regarding the health effects of exposure to low-frequency electromagnetic fields. In addition, the association between exposure and disease incidence or the possible biological effects of exposure are unclear. Using 2D-DIGE and MS in a blind study, we have investigated the effects of static and oscillating extremely low-frequency electromagnetic fields (ELF EMFs) on the proteomes of wild type Schizosaccharomyces pombe and a Sty1p deletion mutant which displays increased sensitivity to a variety of cellular stresses. Whilst this study identifies a number of protein isoforms that display significant differential expression across experimental conditions, there was no correlation between their patterns of expression and the ELF EMF exposure regimen. We conclude that there are no significant effects of either static or oscillating EMF on the yeast proteome at the sensitivity afforded by 2D-DIGE. We hypothesise that the proteins identified must be sensitive to subtle changes in culture and/or handling conditions, and that the identification of these proteins in other proteomic studies should be treated with some caution when the results of such studies are interpreted in a biological context.     

Corilagin prevents tert-butyl hydroperoxide-induced oxidative stress injury in cultured N9 murine microglia cells

Oxidative stress plays an important role in neurodegenerative diseases. Reactive oxygen species (ROS)-mediated stress in microglia in vivo could result in cellular injuries and preferentially induces neuronal injury. Corilagin, a novel member of the phenolic tannin family, has been shown to possess antioxidant properties. In this study, we investigated the effects of corilagin on tert-butyl hydroperoxide (TBHP)-induced injury in cultured N9 murine microglial cells and the underlying mechanisms by a methyltetrazolium assay and oxidative damage assay. We found that exposure of N9 cells to TBHP induced cytotoxicity as demonstrated by cell shrinkage, loss of cell viability, increased lactate dehydrogenase (LDH) leakage, and increased intracellular levels of ROS. By contrast, TBHP reduced both superoxide dismutase activity and total cell anti-oxidation capacity, but glutathione was not reduced. Moreover, TBHP treatment was associated with the loss of mitochondrial membrane potential, and it induced cell apoptosis through the mitochondrial-mediated pathway involving the down-regulation of Bcl-2 expression and up-regulation of the Bax/Bcl-2 ratio. Interestingly, pre-treatment with corilagin reversed these reactions. These data collectively indicated that corilagin could attenuate TBHP-induced oxidative stress injury in microglial cells, and its protective effects may be ascribed to its antioxidant and antiapoptotic properties. Our findings suggest that corilagin should be a potential candidate for the treatment of oxidative stress-induced neurodegenerative diseases.     

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.     

Exposure to power frequency magnetic fields suppresses X-ray-induced apoptosis transiently in Ku80-deficient xrs5 cells

In an attempt to determine whether exposure to extremely low frequency (ELF) electromagnetic fields can affect cells, Ku80-deficient cells (xrs5) and Ku80-proficient cells (CHO-K1) were exposed to ELF electromagnetic fields. Cell survival, and the levels of the apoptosis-related genes p21, p53, phospho-p53 (Ser(15)), caspase-3 and the anti-apoptosis gene bcl-2 were determined in xrs5 and CHO-K1 cells following exposure to ELF electromagnetic fields and X-rays. It was found that exposure of xrs5 and CHO-K1 cells to 60 Hz ELF electromagnetic fields had no effect on cell survival, cell cycle distribution and protein expression. Exposure of xrs5 cells to 60 Hz ELF electromagnetic fields for 5 h after irradiation significantly inhibited G(1) cell cycle arrest induced by X-rays (1 Gy) and resulted in elevated bcl-2 expression. A significant decrease in the induction of p53, phospho-p53, caspase-3 and p21 proteins was observed in xrs5 cells when irradiation by X-rays (8 Gy) was followed by exposure to 5 mT ELF magnetic fields. Exposure of xrs5 cells to the ELF electromagnetic fields for 10 h following irradiation significantly decreased X-ray-induced apoptosis from about 1.7% to 0.7%. However, this effect was not found in CHO-K1 cells within 24 h of irradiation by X-rays alone and by X-rays combined with ELF electromagnetic fields. Exposure of xrs5 cells to 60 Hz ELF electromagnetic fields following irradiation can affect cell cycle distribution and transiently suppress apoptosis by decreasing the levels of caspase-3, p21, p53 and phospho-p53 and by increasing bcl-2 expression.     

Calcium ion cyclotron resonance (ICR) transfers information to living systems: effects on human epithelial cell differentiation

The specific aim of the present work concerns the effectiveness of low-frequency electromagnetic fields treatment to modify biochemical properties of human keratinocytes (HaCaT). Cells exposed to a 7 Hz electromagnetic field, tuned to calcium ion cyclotron resonance (ICR), showed modifications in the cytoskeleton. These modifications were related to different actin distributions as revealed by phalloidin fluorescence analysis. Indirect immunofluorescence with fluorescent antibodies against involucrin and beta catenin, both differentiation and adhesion markers, revealed an increase in involucrin and beta-catenin expression, indicating that exposure to electromagnetic field carries keratinocytes to an upper differentiation level. This study confirms our previous observation and supports the hypothesis that a 7 Hz calcium ICR electromagnetic field may modify cell biochemistry and interfere in the differentiation and cellular adhesion of normal keratinocytes, suggesting the possibility to use ICR electromagnetic therapy for the treatment of undifferentiated diseases.     

Extremely Low-Frequency Electromagnetic Fields Promote In Vitro Neuronal Differentiation and Neurite Outgrowth of Embryonic Neural Stem Cells via Up-Regulating TRPC1

Exposure to extremely low-frequency electromagnetic fields (ELF-EMFs) can enhance hippocampal neurogenesis in adult mice. However, little is focused on the effects of ELF-EMFs on embryonic neurogenesis. Here, we studied the potential effects of ELF-EMFs on embryonic neural stem cells (eNSCs). We exposed eNSCs to ELF-EMF (50 Hz, 1 mT) for 1, 2, and 3 days with 4 hours per day. We found that eNSC proliferation and maintenance were significantly enhanced after ELF-EMF exposure in proliferation medium. ELF-EMF exposure increased the ratio of differentiated neurons and promoted the neurite outgrowth of eNSC-derived neurons without influencing astrocyes differentiation and the cell apoptosis. In addition, the expression of the proneural genes, NeuroD and Ngn1, which are crucial for neuronal differentiation and neurite outgrowth, was increased after ELF-EMF exposure. Moreover, the expression of transient receptor potential canonical 1 (TRPC1) was significantly up-regulated accompanied by increased the peak amplitude of intracellular calcium level induced by ELF-EMF. Furthermore, silencing TRPC1 expression eliminated the up-regulation of the proneural genes and the promotion of neuronal differentiation and neurite outgrowth induced by ELF-EMF. These results suggest that ELF-EMF exposure promotes the neuronal differentiation and neurite outgrowth of eNSCs via up-regulation the expression of TRPC1 and proneural genes (NeuroD and Ngn1). These findings also provide new insights in understanding the effects of ELF-EMF exposure on embryonic brain development.     

Oxidative Stress and Apoptosis in Relation to Exposure to Magnetic Field

We investigated the effect of extremely low-frequency electromagnetic field (ELF-EMF) with pulse trains exposure on lipid peroxidation, and, hence, oxidative stress in the rat liver tissue. The parameters that we measured were the levels of plasma alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase as well as plasma albumin, bilirubin, and total protein levels in 30 adult male Wistar rats exposed to ELF. We also determined the percentage of apoptotic and necrotic cells of the kidney extracts from the animals by flow cytometry method. Apoptotic cell death was further characterized by monitoring DNA degradation using gel electrophoresis. The results showed an increase in the levels of oxidative stress indicators, and the flow cytometric data suggested a possible relationship between the exposure to magnetic field and the cell death. We showed significantly lower necrotic cell percentages in experimental animals compared to either unexposed or sham control groups. However, DNA ladder analyses did not differentiate between the groups. Our results were discussed in relation to the response of biological systems to EMF.     

GSM base station electromagnetic radiation and oxidative stress in rats

The ever increasing use of cellular phones and the increasing number of associated base stations are becoming a widespread source of nonionizing electromagnetic radiation. Some biological effects are likely to occur even at low-level EM fields. In this study, a gigahertz transverse electromagnetic (GTEM) cell was used as an exposure environment for plane wave conditions of far-field free space EM field propagation at the GSM base transceiver station (BTS) frequency of 945 MHz, and effects on oxidative stress in rats were investigated. When EM fields at a power density of 3.67 W/m2 (specific absorption rate = 11.3 mW/kg), which is well below current exposure limits, were applied, MDA (malondialdehyde) level was found to increase and GSH (reduced glutathione) concentration was found to decrease significantly (p < 0.0001). Additionally, there was a less significant (p = 0.0190) increase in SOD (superoxide dismutase) activity under EM exposure.     

Oxidative stress impairs glutamate uptake in fibroblasts from patients with Alzheimer's disease

Oxidative stress has been demonstrated in Alzheimer's disease (AD) brain and may affect glutamate transport (GT), thereby leading to excitotoxic neuronal death. Since oxidative stress markers have been shown also in peripheral tissues, we investigated possible GT alterations in fibroblast cultures obtained from 18 patients with AD and 15 control patients and analyzed the effects of the lipoperoxidation product 4-hydroxynonenal (4-HNE) and antioxidants. Basal GT was decreased by 60% in fibroblasts from patients with AD versus control patients. Exposure to HNE did not affect GT in control patients, but it reduced GT by 50% in patients with AD, without any concomitant change in cell viability; conversely, HNE exposure induced a larger increase in ROS intracellular levels in AD than in control fibroblasts. Glutathione and N-acetylcysteine completely blocked 4-HNE effects and also increased basal uptake in AD cells. Moreover, inhibition of glutathione synthesis in control fibroblasts by pretreatment with buthionine sulfoximine resulted in GT reduction (40%) and an increase in ROS levels after exposure to 4-HNE. Nevertheless, since there are no differences between GSH basal level in controls and patients with AD, the alteration of other antioxidant systems cannot be excluded. Our study supports the hypothesis of a systemic impairment of GT in AD, possibly linked to oxidative stress and to reduced antioxidant defenses, which may be partially reversed by antioxidant treatment. Therefore, we suggest fibroblast cultures as a tool for exploring pathogenetic mechanisms and possible therapeutic strategies in patients with AD.     

Inhibition of gap junction intercellular communication by extremely low-frequency electromagnetic fields in osteoblast-like models is dependent on cell differentiation.

Electromagnetic fields have been used to augment the healing of fractures because of its ability to increase new bone formation. The mechanism of how electromagnetic fields can promote new bone formation is unknown, although the interaction of electromagnetic fields with components of the plasma membrane of cells has been hypothesized to occur in bone cells. Gap junctions occur among bone forming cells, the osteoblasts, and have been hypothesized to play a role in new bone formation. Thus it was investigated whether extremely low-frequency (ELF) magnetic fields alter gap junction intercellular communication in the pre-osteoblastic model, MC3T3-E1, and the well-differentiated osteoblastic model, ROS 17/2.8. ELF magnetic field exposure systems were designed to be used for an inverted microscope stage and for a tissue culture incubator. Using these systems, it was found that magnetic fields over a frequency range from 30 to 120 Hz and field intensities up to 12.5 G dose dependently decreased gap junction intercellular communication in MC3T3-E1 cells during their proliferative phase of development. The total amount of connexin 43 protein and the distribution of connexin 43 gap junction protein between cytoplasmic and plasma membrane pools were unaltered by treatment with ELF magnetic fields. Cytosolic calcium ([Ca(2+)](i)) which can inhibit gap junction communication, was not altered by magnetic field exposure. Identical exposure conditions did not affect gap junction communication in the ROS 17/2.8 cell line and when MC3T3-E1 cells were more differentiated. Thus ELF magnetic fields may affect only less differentiated or pre-osteoblasts and not fully differentiated osteoblasts. Consequently, electromagnetic fields may aid in the repair of bone by effects exerted only on osteoprogenitor or pre-osteoblasts.     

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

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

1950 MHz射频电磁场对SRA01/04细胞周期和凋亡的影响

目的：研究显示射频电磁场与白内障的发生关系密切,为了评价晶状体上皮细胞在射频电磁场诱导的白内障发生中的作 用,本实验探讨了1950 MHz射频电磁场暴露对人眼晶状体上皮细胞株（SRA01/04）细胞周期与凋亡的影响。方法：将处于对数生 长期的SRA01/04 细胞暴露或假暴露于频率为1950 MHz,比吸收率（SAR）为2.79 W/kg 的射频电磁场中,每天暴露1 h,每周暴露 5 天,连续暴露4 周。暴露结束后立即收集细胞,显微镜下观察细胞形态变化,噻唑蓝（MTT）法检测细胞存活力,流式细胞仪 （FCM）检测细胞周期与凋亡。结果：与假辐照组相比,暴露组细胞形态未见明显变化;细胞存活力、细胞周期分布及细胞凋亡率亦 无显著改变（P>0.05）。结论：1950 MHz射频电磁场暴露4 周对SRA01/04 细胞的形态、活力、周期以及凋亡均无明显影响,提示在 本实验条件下1950 MHz 射频电磁场不会诱发白内障的发生。     

1950MHz射频电磁场对SRA01／04细胞周期和凋亡的影响

目的：研究显示射频电磁场与白内障的发生关系密切,为了评价晶状体上皮细胞在射频电磁场诱导的白内障发生中的作用,本实验探讨了1950MHz射频电磁场暴露对人眼晶状体上皮细胞株（SRA01／04）细胞周期与凋亡的影响。方法：将处于对数生长期的SRA01／04细胞暴露或假暴露于频率为1950MHz,比吸收率（SAR）为2．79W／kg的射频电磁场中,每天暴露1h,每周暴露5天,连续暴露4周。暴露结束后立即收集细胞,显微镜下观察细胞形态变化,噻唑蓝（MTT）法检测细胞存活力,流式细胞仪（FCM）检测细胞周期与凋亡。结果：与假辐照组相比,暴露组细胞形态未见明显变化;细胞存活力、细胞周期分布及细胞凋亡率亦无显著改变（P〉0．05）。结论：1950MHz射频电磁场暴露4周对SRA01／04细胞的形态、活力、周期以及凋亡均无明显影响,提示在本实验条件下1950MHz射频电磁场不会诱发白内障的发生。     

耐辐射奇球菌铁结合蛋白DRA0258的抗氧化功能

【目的】通过对极端环境耐受的耐辐射奇球菌Deinococcus radiodurans R1全基因组进行序列比对分析,获得具有铁储备蛋白Ferritin类似功能基序的未知功能蛋白DRA0258,采用分子生物学技术对该蛋白的功能和性质进行了验证和分析。【方法】首先对DRA0258进行克隆表达和纯化,并经络合物显色法测定蛋白上铁结合含量;通过三段连接敲除法构建dra0258突变株,检测突变株在双氧水协迫下的生存率、总抗氧化活性及过氧化氢酶活性;利用实时定量PCR检测突变株内抗氧化酶类及铁转运相关性调控蛋白的基因转录水平。【结果】经体内外蛋白铁含量检测证实DRA0258具有一定的铁结合能力;双氧水生存率实验表明dra0258的缺失导致细胞的抗氧化能力显著下降;过氧化氢酶活性、总抗氧化活性检测及抗氧化酶类的基因转录水平检测证实dra0258基因的缺失导致细胞内一些抗氧化基因转录水平下调,细胞的抗氧化应激系统受到损伤,并影响了一些铁调控网络蛋白的基因转录水平。【结论】本研究证实DRA0258是一种铁结合蛋白,该编码基因的缺失影响胞内铁转运系统并使细胞抗氧化能力下调。     

Effect of 2400 MHz mobile phone radiation exposure on the behavior and hippocampus morphology in Swiss mouse model

Electromagnetic field exposure to the nervous system can cause neurological changes. The effects of extremely low-frequency electromagnetic fields, such as second-generation and third-generation radiation, have been studied in most studies. The current study aimed to explore fourth-generation cellular phone radiation on hippocampal morphology and behavior in mice. Swiss albino male mice (n = 30) were randomly categorized into 3 groups; control, 40 min, and 60 min exposure to 2400 MHz radiofrequency electromagnetic radiation (RF-EMR) daily for 60 days. The control mice were housed in the same environments but were not exposed to anything. Anxiety-like behaviors were tested using the elevated plus-maze. For histological and stereological examination, the brain was dissected from the cranial cavity. On Cresyl violet stained brain slices, the number of pyramidal neurons in the cornu ammonis of the hippocampus were counted. In exposed mice compared to control mice, a significant increase in anxiety-like behavior has been observed. Histological observations have shown many black and dark blue cytoplasmic cells with shrunken morphology degenerative alterations in the neuronal hippocampus in the radiation exposed mice. In the RF-EMR mouse hippocampus, stereological analyses revealed a significant decrease in pyramidal and granule neurons compared to controls. Our findings suggest that 2400-MHz RF-EMR cell phone radiation affects the structural integrity of the hippocampus, which would lead to behavioral changes such as anxiety. However, it alerts us to the possible long-term detrimental effects of exposure to RF-EMR.