Effects of extremely low frequency electromagnetic fields on membrane-associated enzymes

Interactions between electromagnetic radiation and biological systems

Even though the bioeffects of electromagnetic radiation (EMR) have been extensively investigated during the past several decades, our understandings of the bioeffects of EMR and the mechanisms of the interactions between the biological systems and the EMRs are still far from satisfactory. In this article, we introduce and summarize the consensus, controversy, limitations, and unsolved issues. The published works have investigated the EMR effects on different biological systems including humans, animals, cells, and biochemical reactions. Alternative methodologies also include dielectric spectroscopy, detection of bioelectromagnetic emissions, and theoretical predictions. In many studies, the thermal effects of the EMR are not properly controlled or considered. The frequency of the EMR investigated is limited to the commonly used bands, particularly the frequencies of the power line and the wireless communications; far fewer studies were performed for other EMR frequencies. In addition, the bioeffects of the complex EM environment were rarely discussed. In summary, our understanding of the bioeffects of the EMR is quite restrictive and further investigations are needed to answer the unsolved questions.

Static electromagnetic field and recombinant human fibroblasts encoding miR-451 and miR-16 increased cell trans-differentiation to CD71+ and CD235a+ erythroid like progenitor

Introduction

Ex vivo blood production is an urgent need of most countries, and creating production protocols can save the lives of many patients. Despite the recent advances in blood production in ex vivo conditions, its high-scale production is not yet possible, and requires further studies. Therefore, by transfecting fibroblast cells with miR-16, and miR-451 genes, as well as applying low frequency electromagnetic fields (ELF-EMF) treatment, we tried to increase the differentiation of these cells into CD71+ and CD235a+ erythroid like progenitors.

Methods

After preparation, and cultivation of human dermal transgenic fibroblast cells, they were transfected by Plenti3-hsa-miR451, Plenti3-hsa-miR16 and Plenti3-backbone inserted into E. coli Stbl4 genome. Then, transgenic fibroblast cells were treated with 10mT ELF-EMF every day for 20 minutes for 7 days. Using a flow cytometer, the expressions of CD71, and CD235a were studied in these cells, and the expressions of genes involved in hematopoiesis were studied using the RT-PCR technique.

Results

The results indicated an increase in the differentiation of fibroblast cells treated with 10mT ELF-EMF to erythroid like progenitors. Furthermore, the percentage of CD71+ and CD235a+ cells was the highest in irradiated cells encoding miR-16 and miR-451, which indicates their differentiation into erythroid like progenitors. Also, in the transgenic cells treated with ELF-EMF, an increase in the expressions of α-chain, β-chain, γ-chain and GATA1 genes was observed, which indicates the potential of these cells for hematopoiesis. However, there was no significant difference in the expression of CD34 and CD38 genes in these cell lines.

Conclusion

Both ELF-EMF and upregulations of miR-16 and miR-451 lead to improved differentiation of fibroblast cells into erythroid like progenitors.

Stopped Flow of Glycerol Induces the Enhancement of Adsorption and Aggregation of HRP on Mica

Glycerol is a usable component of heat-transfer fluids, and is thus suitable for the use in microchannel-based heat exchangers in biosensors and microelectronic devices. The flow of a fluid can lead to the generation of electromagnetic fields, which can affect enzymes. Herein, by means of atomic force microscopy (AFM) and spectrophotometry, a long-term effect of stopped flow of glycerol through a coiled heat exchanger on horseradish peroxidase (HRP) has been revealed. Samples of buffered HRP solution were incubated near either the inlet or the outlet sections of the heat exchanger after stopping the flow. It has been found that both the enzyme aggregation state and the number of mica-adsorbed HRP particles increase after such an incubation for 40 min. Moreover, the enzymatic activity of the enzyme incubated near the inlet section has been found to increase in comparison with that of the control sample, while the activity of the enzyme incubated near the outlet section remained unaffected. Our results can find application in the development of biosensors and bioreactors, in which flow-based heat exchangers are employed.

The Effect of a Rotating Cone on Horseradish Peroxidase Aggregation on Mica Revealed by Atomic Force Microscopy

Our study reported herein aims to determine whether an electromagnetic field, induced triboelectrically by a metallic cone, rotating at a frequency of 167 Hz, has an effect on the properties of the horseradish peroxidase (HRP) enzyme. Atomic force microscopy (AFM) was employed to detect even the most subtle effects on single enzyme molecules. In parallel, a macroscopic method (spectrophotometry) was used to reveal whether the enzymatic activity of HRP in solution was affected. An aqueous solution of the enzyme was incubated at a distance of 2 cm from the rotating cone. The experiments were performed at various incubation times. The control experiments were performed with a non-rotating cone. The incubation of the HRP solution was found to cause the disaggregation of the enzyme. At longer incubation times, this disaggregation was found to be accompanied by the formation of higher-order aggregates; however, no change in the HRP enzymatic activity was observed. The results of our experiments could be of interest in the development of enzyme-based biosensors with rotating elements such as stirrers. Additionally, the results obtained herein are important for the correct interpretation of data obtained with such biosensors.

Static and Electromagnetic Fields Differently Affect Proliferation and Cell Death Through Acid Enhancement of ROS Generation in Mesenchymal Stem Cells

Magnetic fields remotely influence cellular homeostasis as a physical agent through the changes in cell physicochemical reactions. Magnetic fields affect cell fate, which may provide an important and interesting challenge in stem cell behaviors. Here, we investigated the effects of the static magnetic field (SMF, 20 mT) and electromagnetic field (EMF, 20 mT-50 Hz) on reactive oxygen species (ROS) production and the acidic pH conditions as stimuli to change cell cycle progression and cell death in mesenchymal stem cells. Results show that SMF, EMF, and their simultaneous (SMF+EMF) administration increase ROS and expression of nuclear factor erythroid 2-related factor 2 (Nrf2), superoxide dismutase 2 (SOD2), and glutathione-S-transferase (GST) as an antioxidant defense system. Besides, intracellular pH (pHi) decreases in presence of either EMF or SMF+EMF, but not SMF. Decreased ROS content using ascorbic acid in these treatments leads to increased pH compared to the magnetic field treatments alone. Furthermore, each magnetic field has different effects on the cellular process of stem cells, including cell cycle, apoptosis and necrosis. Moreover, treatment by SMF enhances the cell viability after 24 h, while EMF or SMF+EMF decreases it. These observations indicate that fluctuations of ROS generation and acid enhancement during SMF and EMF treatments may reveal their beneficial and adverse effects on the molecular and cellular mechanisms involved in the growth, death, and differentiation of stem cells.

Do magnetic fields related to submarine power cables affect the functioning of a common bivalve?

The aim of the study was to determine the effect of static magnetic field (SMF) and electromagnetic field (EMF), of values usually recorded near submarine cables, on the bioenergetics, oxidative stress, and neurotoxicity in the cockle Cerastoderma glaucum. Bivalves maintained a positive energy balance, but the filtration rate and energy available for individual production were significantly lower in SMF-exposed animals compared to the control treatment. No changes in the respiration were noted but ammonia excretion rate was significantly lower after exposure to EMF. Changes in the activities of antioxidant enzymes and the lipid peroxidation were not observed however, exposure to both fields resulted in increased protein carbonylation. After exposure to EMF a significant inhibition of acetylcholinesterase activity was observed. As the present study for the first time revealed the oxidative damage and neurotoxicity in marine invertebrate after exposure to artificial magnetic fields, the need for further research is highlighted.

Biological effects of chronic exposure of Blaptica dubia (Blattodea: Blaberidae) nymphs to static and extremely low frequency magnetic fields

In this paper, we analyzed the effects of chronic exposure (5 months) to static magnetic field (110 mT; SMF) and extremely low frequency magnetic field (ELF MF; 10 mT, 50 Hz) on Blaptica dubia nymphs. We have examined acetylcholinesterase (AChE) activity and heat shock protein 70 (HSP70) level, two sensitive biomarkers of stress in terrestrial insects. Relative growth rate (RGR), as a life history trait, was estimated. AChE activity was determined spectrophotometrically and HSP70 levels were quantified using indirect non-competitive ELISA and Western blotting. Calculated RGR was significantly changed upon exposure to both types of ambiental MFs. The effects of chronic exposure of B. dubia nymphs to SMF and ELF MF (50 Hz) were observed as decreased activity of AChE. The increased level of HSP70 was present only after exposure to SMF. The strength of ELF MF was most likely below the energy level needed to induce the expression of this stress protein. Different patterns of the expression of two HSP70 isoforms, where isoform 2 was sensitive only to SMF, are most likely a possibly switch - off in the expression of constitutive and/or inducible HSP70 isoforms.

Effects of modulation on sodium and potassium channel currents by extremely low frequency electromagnetic fields stimulation on hippocampal CA1 pyramidal cells

To investigate the effects of extremely low-frequency electromagnetic fields (ELF-EMFs) stimulation on sodium channel currents (I_Na), transient outward potassium channel currents (I_A) and delayed rectifier potassium channel currents (I_K) on hippocampal CA1 pyramidal neurons of young Sprague-Dawley rats. CA1 pyramidal neurons of rat hippocampal slices were subjected to ELF-EMFs stimulation with different frequencies (15 and 50 Hz), intensities (0.5, 1 and 2 mT) and durations (10, 20 and 30 min). The I_Na, I_A and I_K of neurons were recorded by a whole-cell patch-clamp method. ELF-EMFs stimulation enhanced I_Na densities, and depressed I_A and I_K densities. In detail, I_Na was more sensitive to the variation of intensities and frequencies of ELF-EMFs, whereas I_A and I_K were mainly affected by the variation of the duration of ELF-EMFs. ELF-EMFs stimulation altered activation and deactivation properties of I_Na, I_A and I_K. ELF-EMFs stimulation plays a role as a regulator rather than an inducer for ion channels. It might change the transition probability of ion channel opening or closing, and might also change the structure and function of the ion channel which need to be proved by the further technical method.

Hematobiochemical and histopathological alterations of kidney and testis due to exposure of 4G cell phone radiation in mice

The radiofrequency electromagnetic radiation emitted by smart phones on biological systems has wide media coverage and public concern in recent years. The aim of this study was to explore the effects of fourth-generation cell phone radiation exposure on hematological (Total leukocyte count, Total erythrocyte count, and hemoglobin %), biochemical (Serum creatinine) parameters, and histopathological changes in the kidney and testis of Swiss albino mice. A total of 30 male Swiss albino mice weighing 45–65 g was randomly divided into three groups (n = 10). The first group A was the control group, the second group B, was exposed to 40 minutes of mobile phone radiation daily, the third group C was exposed to 60 minutes of radiation daily from two 2400 Megahertz fourth-generation connected mobile phones for 60 days, respectively. The electromagnetic radiation frequency radiometer measured the frequency of electromagnetic radiation emitted from cell phones. The specific absorption rate was calculated as 0.087 W/kg. The control group was kept under similar conditions, but the electromagnetic field was not given for the same period. All the mice were sacrificed at the end of the experiment. The blood samples were collected for hematobiochemical study, and then kidney and testis tissues were collected for histopathological study. Results of the study showed that the body weight and total erythrocyte count values were significantly (p < 0.05) decreased while total leukocyte count, hemoglobin %, and serum creatinine values were significantly (p < 0.05) increased in both the radiation exposure groups relative to the control group. Histopathological observation showed the kidney of 60 minutes exposed mice interstitial inflammation that causes marked mononuclear cellular infiltration compared to the 40 minutes and control mice. Compared to control mice, histopathological examinations of testicular tissue from the exposed mice, showed irregular in shapes and non-uniform sizes and fewer spermatogenic cells layer that leads to the larger lumen in the seminiferous tubules. It is concluded that fourth-generation cell phone radiation exposure may affect blood hemostasis and inflammation of mice's kidney and testis tissue. Based on these studies, it is important to increase public consciousness of potential adverse effects of mobile phone radiofrequency electromagnetic radiation exposure.

Skeptical approaches concerning the effect of exposure to electromagnetic fields on brain hormones and enzyme activities

This review discusses the effects of various frequencies of electromagnetic fields (EMF) on brain hormones and enzyme activity. In this context, the mechanism underlying the effects of EMF exposure on tissues generally and cellular pathway specifically has been discussed. The cell membrane plays important roles in mediating enzymatic activities as to response and reacts with extracellular environment. Alterations in the calcium signaling pathways in the cell membrane are activated in response to the effects of EMF exposure. Experimental and epidemiological studies have demonstrated that no changes occur in serum prolactin levels in humans following short-term exposure to 900 Mega Hertz (MHz) EMF emitted by mobile phones. The effects of EMF on melatonin and its metabolite, 6-sulfatoxymelatonin, in humans have also been investigated in the clinical studies to show a disturbance in metabolic activity of melatonin. In addition, although 900 MHz EMF effects on NF-κB inflammation, its effects on NF-κB are not clear. Abbreviations: ELF-EMF, extremely low frequency electromagnetic fields; EMF, electromagnetic fields; RF, Radiofrequency; ROS, reactive oxygen species; VGCCs, voltage-gated calcium channels; MAPK, mitogen-activated phosphokinase; NF-κB, nuclear factor kappa B; ERK-1/2, extracellular signal-regulated kinase; GSH-Px, glutathione peroxidase; JNK, Jun N-terminal kinases; SOD, superoxide dismutase; MnSOD, manganese-dependent superoxide dismutase; GLUT1, glucose transporter 1; GSSG-Rd, glutathione reductase MDA malondialdehyde; NO, nitric oxide; LH, luteinizing hormone; FSH, follicle-stimulating hormone.

Photobiomodulation by Infrared Diode Laser: Effects on Intracellular Calcium Concentration and Nitric Oxide Production of Paramecium

In Paramecium, cilia beating is correlated to intracellular calcium concentration ([Ca²⁺ ]i) and nitric oxide (NO) synthesis. Recent findings affirm that photobiomodulation (PBM) can transiently increase the [Ca²⁺ ]i in mammalian cells. In this study, we investigated the effect of both 808 and 980 nm diode laser irradiated with flat-top hand-piece on [Ca²⁺ ]i and NO production of Paramecium primaurelia, to provide basic information for the development of new therapeutic approaches. In the experiments, the laser power in CW varied (0.1; 0.5; 1; and 1.5 W) to generate the following respective fluences: 6.4; 32; 64; and 96 J cm^-2 . The 6.4 J cm^-2 did not induce PBM if irradiated by both 808 and 980 nm diode laser. Conversely, the 32 J cm^-2 fluence had no effect on Paramecium cells if irradiated by the 808 nm laser, while if irradiated by the 980 nm laser induced increment in swimming speed (suggesting an effect on the [Ca²⁺ ]i, NO production, similar to the 64 J cm^-2 with the 808 nm wavelength). The more evident discordance occurred with the 96 J cm^-2 fluence, which had the more efficient effect on PBM among the parameters if irradiated with the 808 nm laser and killed the Paramecium cells if irradiated by the 980 nm laser. Lastly, the 980 nm and 64 or 96 J cm^-2 were the only parameters to induce a release of stored calcium.

A Further Investigation of the Effects of Extremely Low Frequency Magnetic Fields on Alkaline Phosphatase and Acetylcholinesterase

Using a custom build spectrophotometer equipped with Helmholtz coils and designed to study the effects of magnetic fields on enzyme reactions in real-time we have investigated the influence of fields, from 100 μT to 10 mT and at a variety of field frequencies, on the membrane bound enzymes alkaline phosphatase and acetylcholinesterase. We have also employed other methods to apply a magnetic field, e.g. Biostim. In contrast to earlier reports we have been unable to detect any field effects on these enzymes under any field/frequency regime. We discuss possible reasons for the discrepancy between this and earlier work and note the particularly complex influence of small temperature changes that may confound analysis.

Activity and expression of acetylcholinesterase in PC12 cells exposed to intermittent 1.8 GHz 217-GSM mobile phone signal

PURPOSE

Due to its role in learning, memory and in many neurodegenerative diseases, acetylcholinesterase (AChE) represents an interesting endpoint to assess possible targets of exposure to radiofrequency electromagnetic fields (RF-EMF) generated by mobile phones. We investigated possible alterations of enzymatic activity, gene and protein expression of AChE in neuronal-like cells exposed to a 1.8 GHz Global System for Mobile Communication (GSM) modulated signal (217-GSM).

MATERIALS AND METHODS

Rat PC12 cells were exposed for 24 h to 1.8 GHz 217-GSM signal. Specific adsorption rate (SAR) was 2 W/kg. AChE enzyme activity was assessed spectrophotometrically by Ellman's method, mRNA expression level was evaluated by real time polymerase chain reaction, and protein expression was assessed by Western blotting.

RESULTS

AChE enzymatic activity increased of 1.4-fold in PC12 cells exposed to 217-GSM signal for 24 h, whilst AChE transcriptional or translational pathways were not affected.

CONCLUSION

Our results provide the first evidence of effects on AChE activity after in vitro exposure of mammalian cells to the RF-EMF generated by GSM mobile phones, at the SAR value 2 W/kg. The obtained evidence promotes further investigations on AChE as a possible target of RF-EMF and confirm the ability of 1.8 GHz 217-GSM signal to induce biological effects in different mammalian cells.

Melatonin protects rat cerebellar granule cells against electromagnetic field-induced increases in Na(+) currents through intracellular Ca(2+) release

Although melatonin (MT) has been reported to protect cells against oxidative damage induced by electromagnetic radiation, few reports have addressed whether there are other protective mechanisms. Here, we investigated the effects of MT on extremely low-frequency electromagnetic field (ELF-EMF)-induced Nav activity in rat cerebellar granule cells (GCs). Exposing cerebellar GCs to ELF-EMF for 60 min. significantly increased the Nav current (INa ) densities by 62.5%. MT (5 μM) inhibited the ELF-EMF-induced INa increase. This inhibitory effect of MT is mimicked by an MT2 receptor agonist and was eliminated by an MT2 receptor antagonist. The Nav channel steady-state activation curve was significantly shifted towards hyperpolarization by ELF-EMF stimulation but remained unchanged by MT in cerebellar GC that were either exposed or not exposed to ELF-EMF. ELF-EMF exposure significantly increased the intracellular levels of phosphorylated PKA in cerebellar GCs, and both MT and IIK-7 did not reduce the ELF-EMF-induced increase in phosphorylated PKA. The inhibitory effects of MT on ELF-EMF-induced Nav activity was greatly reduced by the calmodulin inhibitor KN93. Calcium imaging showed that MT did not increase the basal intracellular Ca(2+) level, but it significantly elevated the intracellular Ca(2+) level evoked by the high K(+) stimulation in cerebellar GC that were either exposed or not exposed to ELF-EMF. In the presence of ruthenium red, a ryanodine-sensitive receptor blocker, the MT-induced increase in intracellular calcium levels was reduced. Our data show for the first time that MT protects against neuronal INa that result from ELF-EMF exposure through Ca(2+) influx-induced Ca(2+) release.

The effects of different intensities, frequencies and exposure times of extremely low-frequency electromagnetic fields on the growth of Staphylococcus aureus and Escherichia coli O157:H7

The impact of different types of extremely low-frequency electromagnetic fields (ELF-EMF) on the growth of Staphylococcus aureus and Escherichia coli O157:H7 was investigated. The cultures of bacteria in broth media were exposed to sinusoidal homogenous ELF-EMF with 2 and 4 mT magnetic intensities. Each intensity for each bacteria was combined with three different frequencies (20, 40 and 50 Hz), and four different exposure times (1, 2, 4 and 6 h). A cell suspension of each experiment was diluted for the appropriate range and inoculated to Mueller-Hinton Agar (MHA) plates after exposure to ELF-EMF. The number of colony forming units (CFU) of both strains was obtained after incubation at 37 °C for 24 h. Data were statistically evaluated by one-way analysis of variance (ANOVA), statistical significance was described at p < 0.05 and data were compared with their non-exposed controls. Magnetic intensity, frequency and exposure time of ELF-EMFs changed the characteristic responses for both microorganisms. Samples exposed to ELF-EMF showed a statistically significant decrease compared to their controls in colony forming capability, especially at long exposure times. An exposure to 4 mT-20 Hz ELF-EMF of 6 h produced maximum inhibition of CFU compared to their controls for both microorganisms (95.2% for S. aureus and 85% for E. coli).

Does the magnetic field of a magnetic stirrer in an optical aggregometer affect concurrent platelet aggregation?

Platelets are subjected to extremely low frequency electromagnetic fields during standard aggregometry measurements owing to the use of a magnetic stir bar in the instrument. This study evaluates the effects of this magnetic field exposure on platelet aggregation by comparing the results obtained in a modified aggregometer. Blood samples from healthy volunteers were anticoagulated using citrate or heparin. Platelet-rich plasma (PRP) samples were prepared. A mechanical stirring device was attached to the aggregometer instead of the magnetic stir bar system. The PRP samples were stirred using a stirring rod tip that did not produce any magnetic fields in one channel of the aggregometer; in the other channel, a stirring rod carrying a small magnet at its tip was used. As a result, a magnetic field in the extremely low frequency range and in the amplitude range of 1.9-65 mT was applied to the platelets assigned to the channel where the magnetic stirring rod tip was used. Aggregation was induced using adenosine diphosphate (ADP), collagen, or epinephrine. The slopes, maximum aggregation values, and areas under the aggregation curves were compared between the magnetic and neutral stirring rod tip groups. For samples stirred with the magnetic stirring rod tip, a significant decrease was observed in 12 of the 14 parameters evaluated for aggregations induced with ADP or collagen compared to the neutral stirring rod tip, regardless of the method used for anticoagulation. This observation indicates that the magnetic stir bars used in standard aggregometry may significantly alter aggregation parameters and platelets may be possible targets of electromagnetic fields.

Exposure to extremely low-frequency electromagnetic fields modulates Na+ currents in rat cerebellar granule cells through increase of AA/PGE2 and EP receptor-mediated cAMP/PKA pathway

Although the modulation of Ca²⁺ channel activity by extremely low-frequency electromagnetic fields (ELF-EMF) has been studied previously, few reports have addressed the effects of such fields on the activity of voltage-activated Na⁺ channels (Na_v). Here, we investigated the effects of ELF-EMF on Na_v activity in rat cerebellar granule cells (GCs). Our results reveal that exposing cerebellar GCs to ELF-EMF for 10–60 min significantly increased Na_v currents (I_Na) by 30–125% in a time- and intensity-dependent manner. The Na_v channel steady-state activation curve, but not the steady-state inactivation curve, was significantly shifted (by 5.2 mV) towards hyperpolarization by ELF-EMF stimulation. This phenomenon is similar to the effect of intracellular application of arachidonic acid (AA) and prostaglandin E₂ (PGE₂) on I_Na in cerebellar GCs. Increases in intracellular AA, PGE₂ and phosphorylated PKA levels in cerebellar GCs were observed following ELF-EMF exposure. Western blottings indicated that the Na_V 1.2 protein on the cerebellar GCs membrane was increased, the total expression levels of Na_V 1.2 protein were not affected after exposure to ELF-EMF. Cyclooxygenase inhibitors and PGE₂ receptor (EP) antagonists were able to eliminate this ELF-EMF-induced increase in phosphorylated PKA and I_Na. In addition, ELF-EMF exposure significantly enhanced the activity of PLA₂ in cerebellar GCs but did not affect COX-1 or COX-2 activity. Together, these data demonstrate for the first time that neuronal I_Na is significantly increased by ELF-EMF exposure via a cPLA2 AA PGE₂ EP receptors PKA signaling pathway.

Investigation of the effects of 50 Hz magnetic fields on platelet aggregation using a modified aggregometer

PURPOSE

Electromagnetic fields have various effects on intracellular calcium levels, free oxygen radicals and various enzymes. The platelet activation pathway involves an increase in intracellular calcium levels and protein kinase C activation; and free oxygen radicals play a mediating role in this pathway. This study investigated whether 1 mT and 6 mT, 50 Hz magnetic fields had any effects on platelet aggregation.

MATERIALS AND METHODS

Blood from healthy volunteers was anticoagulated with either citrate or heparin. Each sample was divided in half and assigned to exposure and control groups. Platelet rich plasma samples in the exposure group were exposed to a 1 mT or a 6 mT, 50 Hz magnetic field for 1.5 or 1 h, respectively. The samples from both exposure and control groups were simultaneously evaluated using a modified optical aggregometer. Adenosine-diphosphate, collagen, and epinephrine were used as inducing agents. The slopes of the aggregation curve, the maximum values and the areas under the curves were recorded and compared.

RESULTS

A significant effect was observed only in the 1 mT-citrate group. It was found that magnetic field exposure significantly increased the maximum values and slopes of the collagen-induced aggregations.

CONCLUSIONS

It was found that magnetic field exposure has an activating effect on platelet aggregation.

Extremely low-frequency electromagnetic fields affect lipid-linked carbonic anhydrase

In the last years, the effect of extremely low-frequency electromagnetic fields (ELF-EMF) on the activity of different enzymes were investigated. Only the membrane-anchored enzymes did decrease their activity, up to 50%. In this work, the effect of ELF-EMF on bovine lung membrane carbonic anhydrase (CA) were studied. Carbonic anhydrases are a family of 14 zinc-containing isozymes catalyzing the reversible reaction: CO(2)+H(2)O = HCO(3)(- )+H(+). CA differ in catalytic activity and subcellular localization. CA IV, IX, XII, XIV, and XV are membrane bound. In particular, CA IV, which is expressed in the lung, is glycosyl phosphatidyl inositol-linked to the membrane, therefore it was a candidate to inhibition by ELF-EMF. Exposure to the membranes to a field of 75 Hz frequency and different amplitudes caused CA activity to a reproducible decrease in enzymatic activity by 17% with a threshold of about 0.74 mT. The decrease in enzymatic activity was independent of the time of permanence in the field and was completely reversible. When the source of enzyme was solubilized with Triton, the field lost its effect on CA enzymatic activity, suggesting a crucial role of the membrane, as well as of the particular linkage of the enzyme to it, in determining the conditions for CA inactivation. Results are discussed in terms of the possible physiologic effects of CA inhibition in target organs.

50 Hz extremely low frequency electromagnetic fields enhance protein carbonyl groups content in cancer cells: effects on proteasomal systems

Electromagnetic fields are an assessed cause of prolonging free radicals lifespan. This study was carried out to investigate the influence of extremely low frequency electromagnetic fields on protein oxidation and on the 20S proteasome functionality, the complex responsible for the degradation of oxidized proteins. Caco 2 cells were exposed, for 24-72 hours, to 1 mT, 50 Hz electromagnetic fields. The treatment induced a time-dependent increase both in cell growth and in protein oxidation, more evident in the presence of TPA, while no changes in cell viability were detected. Exposing the cells to 50 Hz electromagnetic fields caused a global activation of the 20S proteasome catalytic components, particularly evident at 72 hours exposure and in the presence of TPA. The finding that EGCG, a natural antioxidant compound, counteracted the field-related pro-oxidant effects demonstrates that the increased proteasome activity was due to an enhancement in intracellular free radicals.

First Cell Cycles of Sea Urchin Paracentrotus lividus Are Dramatically Impaired by Exposure to Extremely Low-Frequency Electromagnetic Field

Exposure of fertilized eggs of the sea urchin Paracentrotus lividus to an electromagnetic field of 75-Hz frequency and low amplitudes (from 0.75 to 2.20 mT of magnetic component) leads to a dramatic loss of synchronization of the first cell cycle, with formation of anomalous embryos linked to irregular separation of chromatids during the mitotic events. Because acetylcholinesterase (ACHE) is thought to regulate the embryonic first developmental events of the sea urchin, its enzymatic activity was assayed in embryo homogenates and decreased by 48% when the homogenates were exposed to the same pulsed field. This enzymatic inactivation had a threshold of about 0.75 +/- 0.01 mT. The same field threshold was found for the effect on the formation of anomalous embryos of P. lividus. Moreover, ACHE inhibitors seem to induce the same teratological effects as those caused by the field, while blockers of acetylcholine (ACh) receptors are able to antagonize those effects. We conclude that one of the main causes of these dramatic effects on the early development of the sea urchin by field exposure could be the accumulation of ACh due to ACHE inactivation. The crucial role of the membrane in determining the conditions for enzyme inactivation is discussed.