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

An in silico analysis of neuromodulation for pain relief: Determining the role of classical electrodynamics

There has been ongoing debate about the efficacy and mechanism of action of neuromodulation devices in pain relief applications. It has recently been suggested that both issues may be resolved if electromagnetic theory is incorporated into the understanding and application of this technology, and we therefore undertook an in silico analysis to further explore this idea. We created a CAD replication of a standard neuromodulation electrode array with a generic linear 3/6 mm 8-contact lead, developed a parameterized algorithmic model for the pulse delivered by the device and assigned material properties to biologic media to accurately reflect their electromagnetic properties. We then created a physical simulation of the device's output both in air and in the biophysical environment. The simulations confirmed the presence of an electromagnetic field (EM field). Variations in programming of the device affected the strength of the EM field by orders of magnitude. The biologic media all absorbed the EM field, an effect which was particularly pronounced in cerebrospinal fluid and muscle. We discuss the implications of all these findings in relation to the literature. We suggest that knowledge of electromagnetic theory and its application within the biophysical space is required for the optimal use of neuromodulation devices in pain relief applications.

Efficient generation of brain organoids using magnetized gold nanoparticles

Brain organoids, which are three-dimensional cell culture models, have the ability to mimic certain structural and functional aspects of the human brain. However, creating these organoids can be a complicated and difficult process due to various technological hurdles. This study presents a method for effectively generating cerebral organoids from human induced pluripotent stem cells (hiPSCs) using electromagnetic gold nanoparticles (AuNPs). By exposing mature cerebral organoids to magnetized AuNPs, we were able to cultivate them in less than 3 weeks. The initial differentiation and neural induction of the neurosphere occurred within the first week, followed by maturation, including regional patterning and the formation of complex networks, during the subsequent 2 weeks under the influence of magnetized AuNPs. Furthermore, we observed a significant enhancement in neurogenic maturation in the brain organoids, as evidenced by increased histone acetylation in the presence of electromagnetic AuNPs. Consequently, electromagnetic AuNPs offer a promising in vitro system for efficiently generating more advanced human brain organoids that closely resemble the complexity of the human brain.

Electromagnetic fields regulate calcium-mediated cell fate of stem cells: osteogenesis, chondrogenesis and apoptosis

Electromagnetic fields (EMF) are increasing in popularity as a safe and non-invasive therapy. On the one hand, it is widely acknowledged that EMF can regulate the proliferation and differentiation of stem cells, promoting the undifferentiated cells capable of osteogenesis, angiogenesis, and chondroblast differentiation to achieve bone repair purpose. On the other hand, EMF can inhibit tumor stem cells proliferation and promote apoptosis to suppress tumor growth. As an essential second messenger, intracellular calcium plays a role in regulating cell cycle, such as proliferation, differentiation and apoptosis. There is increasing evidence that the modulation of intracellular calcium ion by EMF leads to differential outcomes in different stem cells. This review summarizes the regulation of channels, transporters, and ion pumps by EMF-induced calcium oscillations. It furtherly discusses the role of molecules and pathways activated by EMF-dependent calcium oscillations in promoting bone and cartilage repair and inhibiting tumor stem cells growth.

50 Hz Magnetic Field Exposure Inhibited Spontaneous Movement of Zebrafish Larvae through ROS-Mediated syn2a Expression

Extremely low frequency electromagnetic field (ELF-EMF) exists widely in public and occupational environments. However, its potential adverse effects and the underlying mechanism on nervous system, especially behavior are still poorly understood. In this study, zebrafish embryos (including a transfected synapsin IIa (syn2a) overexpression plasmid) at 3 h post-fertilization (hpf) were exposed to a 50-Hz magnetic field (MF) with a series of intensities (100, 200, 400 and 800 μT, respectively) for 1 h or 24 h every day for 5 days. Results showed that, although MF exposure did not affect the basic development parameters including hatching rate, mortality and malformation rate, yet MF at 200 μT could significantly induce spontaneous movement (SM) hypoactivity in zebrafish larvae. Histological examination presented morphological abnormalities of the brain such as condensed cell nucleus and cytoplasm, increased intercellular space. Moreover, exposure to MF at 200 μT inhibited syn2a transcription and expression, and increased reactive oxygen species (ROS) level as well. Overexpression of syn2a could effectively rescue MF-induced SM hypoactivity in zebrafish. Pretreatment with N-acetyl-L-cysteine (NAC) could not only recover syn2a protein expression which was weakened by MF exposure, but also abolish MF-induced SM hypoactivity. However, syn2a overexpression did not affect MF-increased ROS. Taken together, the findings suggested that exposure to a 50-Hz MF inhibited spontaneous movement of zebrafish larvae via ROS-mediated syn2a expression in a nonlinear manner.

The effect of magnetic fields on tumor occurrence and progression: Recent advances

Malignancies are the leading human health threat worldwide. Despite rapidly developing treatments, poor prognosis and outcome are still common. Magnetic fields have shown good anti-tumoral effects both in vitro and in vivo, and represent a potential non-invasive treatment; however, the specific underlying molecular mechanisms remain unclear. We here review recent studies on magnetic fields and their effect on tumors at three different levels: organismal, cellular, and molecular. At the organismal level, magnetic fields suppress tumor angiogenesis, microcirculation, and enhance the immune response. At the cellular level, magnetic fields affect tumor cell growth and biological functions by affecting cell morphology, cell membrane structure, cell cycle, and mitochondrial function. At the molecular level, magnetic fields suppress tumors by interfering with DNA synthesis, reactive oxygen species level, second messenger molecule delivery, and orientation of epidermal growth factor receptors. At present, scientific experimental evidence is still lacking; therefore, systematic studies on the biological mechanisms involved are urgently needed for the future application of magnetic fields to tumor treatment.

Thapsigargin blocks electromagnetic field-elicited intracellular Ca2+ increase in HEK 293 cells

Biological effects of electromagnetic fields (EMFs) have previously been identified for cellular proliferation and changes in expression and conduction of diverse types of ion channels. The major effect elicited by EMFs seems to be directed toward Ca²⁺ homeostasis. This is particularly remarkable since Ca²⁺ acts as a central modulator in various signaling pathways, including, but not limited to, cell differentiation and survival. Despite this, the mechanisms underlying this modulation have yet to be unraveled. Here, we assessed the effect of EMFs on intracellular [Ca²⁺], by exposing HEK 293 cells to both radio‐frequency electromagnetic fields (RF‐EMFs) and static magnetic fields (SMFs). We detected a constant and significant increase in [Ca²⁺] subsequent to exposure to both types of fields. Strikingly, the increase was nulled by administration of 10 μM Thapsigargin, a blocker of sarco/endoplasmic reticulum Ca²⁺‐ATPases (SERCAs), indicating the involvement of the endoplasmic reticulum (ER) in EMF‐related modulation of Ca²⁺ homeostasis.

Neurogenesis as a Tool for Spinal Cord Injury

Spinal cord injury is a devastating medical condition with no effective treatment. One approach to SCI treatment may be provided by stem cells (SCs). Studies have mainly focused on the transplantation of exogenous SCs, but the induction of endogenous SCs has also been considered as an alternative. While the differentiation potential of neural stem cells in the brain neurogenic regions has been known for decades, there are ongoing debates regarding the multipotent differentiation potential of the ependymal cells of the central canal in the spinal cord (SCECs). Following spinal cord insult, SCECs start to proliferate and differentiate mostly into astrocytes and partly into oligodendrocytes, but not into neurons. However, there are several approaches concerning how to increase neurogenesis in the injured spinal cord, which are discussed in this review. The potential treatment approaches include drug administration, the reduction of neuroinflammation, neuromodulation with physical factors and in vivo reprogramming.

Cellular stress response to extremely low-frequency electromagnetic fields (ELF-EMF): An explanation for controversial effects of ELF-EMF on apoptosis

Impaired apoptosis is one of the hallmarks of cancer, and almost all of the non‐surgical approaches of eradicating tumour cells somehow promote induction of apoptosis. Indeed, numerous studies have stated that non‐ionizing non‐thermal extremely low‐frequency magnetic fields (ELF‐MF) can modulate the induction of apoptosis in exposed cells; however, much controversy exists in observations. When cells are exposed to ELF‐EMF alone, very low or no statistically significant changes in apoptosis are observed. Contrarily, exposure to ELF‐EMF in the presence of a co‐stressor, including a chemotherapeutic agent or ionizing radiation, can either potentiate or inhibit apoptotic effects of the co‐stressor. In our idea, the main point neglected in interpreting these discrepancies is “the cellular stress responses” of cells following ELF‐EMF exposure and its interplay with apoptosis. The main purpose of the current review was to outline the triangle of ELF‐EMF, the cellular stress response of cells and apoptosis and to interpret and unify discrepancies in results based on it. Therefore, initially, we will describe studies performed on identifying the effect of ELF‐EMF on induction/inhibition of apoptosis and enumerate proposed pathways through which ELF‐EMF exposure may affect apoptosis; then, we will explain cellular stress response and cues for its induction in response to ELF‐EMF exposure; and finally, we will explain why such controversies have been observed by different investigators.

Pulsed electromagnetic field (PEMF) as an adjunct therapy for pain management in interstitial cystitis/bladder pain syndrome

INTRODUCTION AND HYPOTHESIS

Patients with interstitial cystitis/bladder pain syndrome (IC/BPS) often experience chronic pelvic and even systemic pain that can be difficult to clinically manage. Pulsed electromagnetic field (PEMF) therapy, a non-invasive strategy that has shown significant efficacy for pain reduction in other chronic pain conditions, may provide benefit for pain management in patients with IC/BPS.

METHODS

PEMF delivery to patients occurs via a bio-electromagnetic-energy device which consists of a flexible mat (180 × 50 cm) that the patient lies on for systemic, full-body delivery and/or a flexible pad (50 × 15 cm) for targeted delivery to a specific body region (e.g., pelvic area). The duration of individual sessions, number of sessions per day, total number of sessions, and follow-up observation period vary between previously published studies. Positive outcomes are typically reported as a significant reduction in visual analog scale (VAS) pain score and functional improvement assessed using validated questionnaires specific to the condition under study.

RESULTS AND CONCLUSIONS

The use of PEMF has been evaluated as a therapeutic strategy for pain management in several clinical scenarios. Randomized, double-blinded, placebo-controlled trials have reported positive efficacy and safety profiles when PEMF was used to treat non-specific low back pain, patellofemoral pain syndrome, chronic post-operative pain, osteoarthritis-related pain, rheumatoid arthritis-related pain, and fibromyalgia-related pain. Based on these positive outcomes in a variety of pain conditions, clinical trials to evaluate whether PEMF can provide a safe, non-invasive therapeutic approach to improve symptoms of chronic pain and fatigue in patients with IC/BPS are warranted.

Effects of electromagnetic fields on neuronal ion channels: a systematic review

Many aspects of chemistry and biology are mediated by electromagnetic field (EMF) interactions. The central nervous system (CNS) is particularly sensitive to EMF stimuli. Studies have explored the direct effect of different EMFs on the electrical properties of neurons in the last two decades, particularly focusing on the role of voltage-gated ion channels (VGCs). This work aims to systematically review published evidence in the last two decades detailing the effects of EMFs on neuronal ion channels as per the PRISM guidelines. Following a predetermined exclusion and inclusion criteria, 22 papers were included after searches on three online databases. Changes in calcium homeostasis, attributable to the voltage-gated calcium channels, were found to be the most commonly reported result of EMF exposure. EMF effects on the neuronal landscape appear to be diverse and greatly dependent on parameters, such as the field's frequency, exposure time, and intrinsic properties of the irradiated tissue, such as the expression of VGCs. Here, we systematically clarify how neuronal ion channels are particularly affected and differentially modulated by EMFs at multiple levels, such as gating dynamics, ion conductance, concentration in the membrane, and gene and protein expression. Ion channels represent a major transducer for EMF-related effects on the CNS.

Brain-to-brain communication: the possible role of brain electromagnetic fields (As a Potential Hypothesis)

Up now, the communication between brains of different humans or animals has been confirmed and confined by the sensory medium and motor facilities of body. Recently, direct brain-to-brain communication (DBBC) outside the conventional five senses has been verified between animals and humans. Nevertheless, no empirical studies or serious discussion have been performed to elucidate the mechanism behind this process. The validation of DBBC has been documented via recording similar pattern of action potentials occurring in the brain cortex of two animals. With regard to action potentials in brain neurons, the magnetic field resulting from the action potentials created in neurons is one of the tools where the brain of one animal can affect the brain of another. It has been shown that different animals, even humans, have the power to understand the magnetic field. Cryptochrome, which exists in the retina and in different regions of the brain, has been confirmed to be able to perceive magnetic fields and convert magnetic fields to action potentials. Recently, iron particles (Fe₃O₄) believed to be functioning as magnets have been found in various parts of the brain, and are postulated as magnetic field receptors. Newly developed supersensitive magnetic sensors made of iron magnets that can sense the brain's magnetic field have suggested the idea that these Fe₃O₄ particles or magnets may be capable of perceiving the brain's extremely weak magnetic field. The present study suggests that it is possible the extremely week magnetic field in one animal's brain to transmit vital and accurate information to another animal's brain.

Multimodal treatment for spinal cord injury: a sword of neuroregeneration upon neuromodulation

Spinal cord injury is linked to the interruption of neural pathways, which results in irreversible neural dysfunction. Neural repair and neuroregeneration are critical goals and issues for rehabilitation in spinal cord injury, which require neural stem cell repair and multimodal neuromodulation techniques involving personalized rehabilitation strategies. Besides the involvement of endogenous stem cells in neurogenesis and neural repair, exogenous neural stem cell transplantation is an emerging effective method for repairing and replacing damaged tissues in central nervous system diseases. However, to ensure that endogenous or exogenous neural stem cells truly participate in neural repair following spinal cord injury, appropriate interventional measures (e.g., neuromodulation) should be adopted. Neuromodulation techniques, such as noninvasive magnetic stimulation and electrical stimulation, have been safely applied in many neuropsychiatric diseases. There is increasing evidence to suggest that neuromagnetic/electrical modulation promotes neuroregeneration and neural repair by affecting signaling in the nervous system; namely, by exciting, inhibiting, or regulating neuronal and neural network activities to improve motor function and motor learning following spinal cord injury. Several studies have indicated that fine motor skill rehabilitation training makes use of residual nerve fibers for collateral growth, encourages the formation of new synaptic connections to promote neural plasticity, and improves motor function recovery in patients with spinal cord injury. With the development of biomaterial technology and biomechanical engineering, several emerging treatments have been developed, such as robots, brain-computer interfaces, and nanomaterials. These treatments have the potential to help millions of patients suffering from motor dysfunction caused by spinal cord injury. However, large-scale clinical trials need to be conducted to validate their efficacy. This review evaluated the efficacy of neural stem cells and magnetic or electrical stimulation combined with rehabilitation training and intelligent therapies for spinal cord injury according to existing evidence, to build up a multimodal treatment strategy of spinal cord injury to enhance nerve repair and regeneration.

The impact of chronic exposure to a magnetic field on energy metabolism and locomotion of Blaptica dubia

Purpose: This study deals with a comparative analysis of the effects of chronic exposure to a static magnetic field (SMF) and an extremely low frequency magnetic field (ELF MF) in Blaptica dubia nymphs. The outcome of such treatment on insect and fat body mass, glycogen and total lipid content in the fat body and locomotion, as an energy demanding process, were examined.Materials and methods: One-month-old nymphs of B. dubia were exposed to an SMF (110 mT) or ELF MF (50 Hz, 10 mT) for 5 months. Their locomotion was monitored in the 'open-field' test for 10 min and expressed as travel distance, time in movement and average speed while in motion. After that, fat body mass and content of its main components (glycogen and total lipids) were determined. Nymph body mass was also estimated after 1 and 5 months of MF treatment.Results: Chronic exposure to the SMF and ELF MF decreased nymph body mass and glycogen content in the fat body but increased all examined parameters of locomotion. In addition, chronic SMF treatment elevated total lipid content in the fat body, while chronic ELF MF treatment reduced fat body mass and total lipid content.Conclusions: These findings indicate that B. dubia nymphs are sensitive to the applied MFs and possess different strategies for fuel usage in response to the SMF and ELF MF in order to satisfy increased energy demands and to overcome stressful conditions.

Targeting Mesenchymal Stromal Cells/Pericytes (MSCs) With Pulsed Electromagnetic Field (PEMF) Has the Potential to Treat Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of synovium (synovitis), with inflammatory/immune cells and resident fibroblast-like synoviocytes (FLS) acting as major players in the pathogenesis of this disease. The resulting inflammatory response poses considerable risks as loss of bone and cartilage progresses, destroying the joint surface, causing joint damage, joint failure, articular dysfunction, and pre-mature death if left untreated. At the cellular level, early changes in RA synovium include inflammatory cell infiltration, synovial hyperplasia, and stimulation of angiogenesis to the site of injury. Different angiogenic factors promote this disease, making the role of anti-angiogenic therapy a focus of RA treatment. To control angiogenesis, mesenchymal stromal cells/pericytes (MSCs) in synovial tissue play a vital role in tissue repair. While recent evidence reports that MSCs found in joint tissues can differentiate to repair damaged tissue, this repair function can be repressed by the inflammatory milieu. Extremely-low frequency pulsed electromagnetic field (PEMF), a biophysical form of stimulation, has an anti-inflammatory effect by causing differentiation of MSCs. PEMF has also been reported to increase the functional activity of MSCs to improve differentiation to chondrocytes and osteocytes. Moreover, PEMF has been demonstrated to accelerate cell differentiation, increase deposition of collagen, and potentially return vascular dysfunction back to homeostasis. The aim of this report is to review the effects of PEMF on MSC modulation of cytokines, growth factors, and angiogenesis, and describe its effect on MSC regeneration of synovial tissue to further understand its potential role in the treatment of RA.

Celecoxib Ameliorates Seizure Susceptibility in Autosomal Dominant Lateral Temporal Epilepsy

Autosomal dominant lateral temporal epilepsy (ADLTE) is an inherited syndrome caused by mutations in the leucine-rich glioma inactivated 1 (LGI1) gene. It is known that glutamatergic transmission is altered in LGI1 mutant mice, and seizures can be reduced by restoring LGI1 function. Yet, the mechanism underlying ADLTE is unclear. Here, we propose that seizures in male LGI1-/- mice are due to nonsynaptic epileptiform activity in cortical neurons. We examined the intrinsic excitability of pyramidal neurons in the temporal cortex of male LGI1-/- mice and found that the voltage-gated K+ channel Kv1.2 was significantly downregulated. We also found that cytosolic phospholipase A2 (cPLA2)-cyclooxygenase 2 (Cox2) signaling was enhanced in LGI1-/- mice. Interestingly, Cox2 inhibition effectively restored the dysregulated Kv1.2 and reduced the intrinsic excitability of pyramidal neurons. Moreover, in vivo injection of celecoxib, an FDA-approved nonsteroidal anti-inflammatory drug, rescued the defective Kv1.2 (an ∼1.9-fold increase), thereby alleviating the seizure susceptibility and extending the life of LGI1-/- mice by 5 d. In summary, we conclude that LGI1 deficiency dysregulates cPLA2-Cox2 signaling to cause hyperexcitability of cortical pyramidal neurons, and celecoxib is a potential agent to manage human ADLTE.SIGNIFICANCE STATEMENT Haploinsufficiency of the leucine-rich glioma inactivated 1 (LGI1) gene is the major pathogenic basis for ADLTE, an inherited syndrome with no cure to date. Existing studies suggest that altered glutamatergic transmission in the hippocampus causes this disease, but the data are paradoxical. We demonstrate that the loss of LGI1 decreases Kv1.2 expression, enhances intrinsic excitability, and thereby causes epilepsy. Interestingly, for the first time, we show that an FDA-approved drug, celecoxib, rescues the Kv1.2 defect and alleviates seizure susceptibility in LGI1-/- mice, as well as improving their survival. Thus, we suggest that celecoxib is a promising drug for the treatment of ADLTE patients.

RKIP-Mediated NF-κB Signaling is involved in ELF-MF-mediated improvement in AD rat

In a previous study, we reported the positive effects of extremely low frequency electromagnetic field (ELF-MF) exposure on Alzheimer's disease (AD) rats; however, the underlying mechanism remains unclear. In addition, we found that Raf-1 kinase inhibitor protein (RKIP) was downregulated by microwave exposure in the rat hippocampus. Our hypothesis was that RKIP-mediated NF-κB pathway signaling is involved in the effect of ELF-MF on the AD rat. In this study, D-galactose intraperitoneal (50 mg/kg/d for 42 d) and Aβ_25-35 hippocampal (5 μL/unilateral, bilateral, single-dose) injection were implemented to establish an AD rat model. Animals were exposed to 50 Hz and 400 µT ELF-MF for 60 continuous days. The spatial memory ability of the rat was then tested using the Morris water maze. Protein expression and interaction were detected by western blotting and co-immunoprecipitation for RKIP-mediated NF-κB pathway factors. The results showed that ELF-MF exposure partially improved the cognitive disorder, upregulated the levels of RKIP, TAK1, and the RKIP/TAK1 interaction, but downregulated p-IKK levels in AD rats. These results indicated that RKIP-mediated NF-κB pathway signaling plays an important role in the ELF-MF exposure-mediated improvements in the AD rat. Our study suggested that ELF-MF exposure might have a potential therapeutic value for AD. Further in depth studies are required in the future.

Acute exposure to high-induction electromagnetic field affects activity of model peripheral sensory neurons

Exposure to repetitive low‐frequency electromagnetic field (LF‐EMF) shows promise as a non‐invasive approach to treat various sensory and neurological disorders. Despite considerable progress in the development of modern stimulation devices, there is a limited understanding of the mechanisms underlying their biological effects and potential targets at the cellular level. A significant impact of electromagnetic field on voltage‐gated calcium channels and downstream signalling pathways has been convincingly demonstrated in many distinct cell types. However, evidence for clear effects on primary sensory neurons that particularly may be responsible for the analgesic actions of LF‐EMF is still lacking. Here, we used F11 cells derived from dorsal root ganglia neurons as an in vitro model of peripheral sensory neurons and three different protocols of high‐induction magnetic stimulation to determine the effects on chemical responsiveness and spontaneous activity. We show that short‐term (<180 sec.) exposure of F11 cells to LF‐EMF reduces calcium transients in response to bradykinin, a potent pain‐producing inflammatory agent formed at sites of injury. Moreover, we characterize an immediate and reversible potentiating effect of LF‐EMF on neuronal spontaneous activity. Our results provide new evidence that electromagnetic field may directly modulate the activity of sensory neurons and highlight the potential of sensory neuron‐derived cell line as a tool for studying the underlying mechanisms at the cellular and molecular level.

Protective effects of melatonin and omega-3 on the hippocampus and the cerebellum of adult Wistar albino rats exposed to electromagnetic fields

The purpose of the study was to investigate the effects of pulsed digital electromagnetic radiation emitted by mobile phones on the central nervous system of the adult Wistar albino rats. The study evaluated structural and functional impacts of four treatment arms: electromagnetic field (EMF) exposed; EMF exposed + melatonin treated group (EMF + Mel); EMF exposed + omega-3 (ω3) treated group (EMF + ω3); and control group (Cont). The 12-weeks-old rats were exposed to 900 MHz EMF for 60 min/day (4:00–5:00 p.m.) for 15 days. Stereological, biochemical and electrophysiological techniques were applied to evaluate protective effects of Mel and ω3. Significant cell loss in the CA1 and CA2 regions of hippocampus were observed in the EMF compared to other groups (p < 0.01). In the CA3 region of the EMF + ω3, a significant cell increase was found compared to other groups (p < 0.01). Granular cell loss was observed in the dentate gyrus of the EMF compared to the Cont (p < 0.01). EMF + ω3 has more granular cells in the cerebellum than the Cont, EMF + Mel (p < 0.01). Significant Purkinje cell loss was found in the cerebellum of EMF group compared to the other (p < 0.01). EMF + Mel and EMF + ω3 showed the same protection compared to the Cont (p > 0.05). The passive avoidance test showed that entrance latency into the dark compartment was significantly shorter in the EMF (p < 0.05). Additionally, EMF had a higher serum enzyme activity than the other groups (p < 0.01). In conclusion, our analyses confirm that EMF may lead to cellular damage in the hippocampus and the cerebellum, and that Mel and ω3 may have neuroprotective effects.

Extremely low-frequency electromagnetic fields enhance the proliferation and differentiation of neural progenitor cells cultured from ischemic brains

In the mammalian brain, neurogenesis persists throughout the embryonic period and adulthood in the subventricular zone of the lateral ventricle and the granular zone (dentate gyrus) of the hippocampus. Newborn neural progenitor cells (NPCs) in the two regions play a critical role in structural and functional plasticity and neural regeneration after brain injury. Previous studies have reported that extremely low-frequency electromagnetic fields (ELF-EMF) could promote osteogenesis, angiogenesis, and cardiac stem cells' differentiation, which indicates that ELF-EMF might be an effective tool for regenerative therapy. The present studies were carried out to examine the effects of ELF-EMF on hippocampal NPCs cultured from embryonic and adult ischemic brains. We found that exposure to ELF-EMF (50 Hz, 0.4 mT) significantly enhanced the proliferation capability both in embryonic NPCs and in ischemic NPCs. Neuronal differentiation was also enhanced after 7 days of cumulative ELF-EMF exposure, whereas glial differentiation was not influenced markedly. The expression of phosphorylated Akt increased during the proliferation process when ischemic NPCs were exposed to ELF-EMF. However, blockage of the Akt pathway abolished the ELF-EMF-induced proliferation of ischemic NPCs. These data show that ELF-EMF promotes neurogenesis of ischemic NPCs and suggest that this effect may occur through the Akt pathway.Video abstract, Supplemental Digital Content 1, http://links.lww.com/WNR/A347.

Extremely Low Frequency Electromagnetic Fields Facilitate Vesicle Endocytosis by Increasing Presynaptic Calcium Channel Expression at a Central Synapse

Accumulating evidence suggests significant biological effects caused by extremely low frequency electromagnetic fields (ELF-EMF). Although exo-endocytosis plays crucial physical and biological roles in neuronal communication, studies on how ELF-EMF regulates this process are scarce. By directly measuring calcium currents and membrane capacitance at a large mammalian central nervous synapse, the calyx of Held, we report for the first time that ELF-EMF critically affects synaptic transmission and plasticity. Exposure to ELF-EMF for 8 to 10 days dramatically increases the calcium influx upon stimulation and facilitates all forms of vesicle endocytosis, including slow and rapid endocytosis, endocytosis overshoot and bulk endocytosis, but does not affect the RRP size and exocytosis. Exposure to ELF-EMF also potentiates PTP, a form of short-term plasticity, increasing its peak amplitude without impacting its time course. We further investigated the underlying mechanisms and found that calcium channel expression, including the P/Q, N, and R subtypes, at the presynaptic nerve terminal was enhanced, accounting for the increased calcium influx upon stimulation. Thus, we conclude that exposure to ELF-EMF facilitates vesicle endocytosis and synaptic plasticity in a calcium-dependent manner by increasing calcium channel expression at the nerve terminal.

cAMP/PKA Pathways and S56 Phosphorylation Are Involved in AA/PGE2-Induced Increases in rNaV1.4 Current

Arachidonic acid (AA) and its metabolites are important second messengers for ion channel modulation. The effects of extracellular application of AA and its non-metabolized analogue on muscle rNa_V1.4 Na⁺ current has been studied, but little is known about the effects of intracellular application of AA on this channel isoform. Here, we report that intracellular application of AA significantly augmented the rNa_V1.4 current peak without modulating the steady-state activation and inactivation properties of the rNa_V1.4 channel. These results differed from the effects of extracellular application of AA on rNa_V1.4 current. The effects of intracellular AA were mimicked by prostaglandin E₂ but not eicosatetraynoic acid (ETYA), the non-metabolized analogue of AA, and were eliminated by treatment with cyclooxygenase inhibitors, flufenamic acid, or indomethacin. AA/PGE₂-induced activation of rNa_V1.4 channels was mimicked by a cAMP analogue (db-cAMP) and eliminated by a PKA inhibitor, PKAi. Furthermore, inhibition of EP2 and EP4 (PGE₂ receptors) with AH6809 and AH23848 reduced the intracellular AA/PGE₂-induced increase of rNa_V1.4 current. Two mutated channels, rNa_V1.4S56A and rNa_V1.4T21A, were designed to investigate the role of predicted phosphorylation sites in the AA/PGE₂–mediated regulation of rNa_V1.4 currents. In rNa_V1.4S56A, the effects of intracellular db-cAMP, AA, and PGE₂ were significantly reduced. The results of the present study suggest that intracellular AA augments rNa_V1.4 current by PGE₂/EP receptor-mediated activation of the cAMP/PKA pathway, and that the S56 residue on the channel protein is important for this process.

Exposure to 50 Hz magnetic field modulates GABAA currents in cerebellar granule neurons through an EP receptor-mediated PKC pathway

Previous work from both our lab and others have indicated that exposure to 50 Hz magnetic fields (ELF-MF) was able to modify ion channel functions. However, very few studies have investigated the effects of MF on γ-aminobutyric acid (GABA) type A receptors (GABA(A) Rs) channel functioning, which are fundamental to overall neuronal excitability. Here, our major goal is to reveal the potential effects of ELF-MF on GABA(A) Rs activity in rat cerebellar granule neurons (CGNs). Our results indicated that exposing CGNs to 1 mT ELF-MF for 60 min. significantly increased GABA(A) R currents without modifying sensitivity to GABA. However, activation of PKA by db-cAMP failed to do so, but led to a slight decrease instead. On the other hand, PKC activation or inhibition by PMA or Bis and Docosahexaenoic acid (DHA) mimicked or eliminated the field-induced-increase of GABA(A) R currents. Western blot analysis indicated that the intracellular levels of phosphorylated PKC (pPKC) were significantly elevated after 60 min. of ELF-MF exposure, which was subsequently blocked by application of DHA or EP1 receptor-specific (prostaglandin E receptor 1) antagonist (SC19220), but not by EP2-EP4 receptor-specific antagonists. SC19220 also significantly inhibited the ELF-MF-induced elevation on GABA(A) R currents. Together, these data obviously demonstrated for the first time that neuronal GABA(A) currents are significantly increased by ELF-MF exposure, and also suggest that these effects are mediated via an EP1 receptor-mediated PKC pathway. Future work will focus on a more comprehensive analysis of the physiological and/or pathological consequences of these effects.

Exposure to 50 Hz electromagnetic field changes the efficiency of the scorpion alpha toxin

BACKGROUND

Extremely low-frequency (50 Hz) electromagnetic field (ELF-EMF) is produced by electric power transmission lines and electronic devices of everyday use. Some phenomena are proposed as "first effects" of ELF-EMF: the discrete changes in the membrane potential and the increase of the calcium channel activity as well as the intracellular concentration of Ca(2+). Interaction of the scorpion alpha toxin with the sodium channel depends on the orientation of the charges and may be perturbed by changes in the membrane polarization. The toxin induces overexcitability in the nervous system and an increase in the neurotransmitters released with different consequences, mainly the paralysis of muscles. We assumed that the exposure to ELF-EMF 0.7 mT will change the effects of the insect selective scorpion alpha toxin (recombinant LqhαIT from Leiurus quinquestriatus hebraeus) at the level of the cercal nerve function, the synaptic transmission and on the level of entire insect organism. Taking into account the compensatory mechanisms in organisms, we tested in addition ten times higher ELF-EMF on whole insects.

METHODS

Experiments were performed in vivo on cockroaches (Periplaneta americana) and in vitro - on isolated cockroach abdominal nerve cord with cerci. In biotests, the effects of LqhαIT (10(-8) M) were estimated on the basis of the insect ability to turn back from dorsal to ventral side. Three groups were compared: the control one and the two exposed to ELF-EMF - 0.7 and 7 mT. Bioelectrical activity of the cercal nerve and of the connective nerve that leaves the terminal abdominal ganglion was recorded using extracellular electrodes. LqhαIT (5 × 10(-8) M) induced modifications of neuronal activity that were observed in the control cockroach preparations and in the ones exposed to ELF-EMF (0.7 mT). The exposure to ELF-EMF was carried out using coils with a size appropriate to the examined objects.

RESULTS

The exposure to ELF-EMF (0.7 mT) modified the effects of LqhαIT (5 × 10(-8) M) on activity of the cercal nerve and of the connective nerve. We observed a decrease of the toxin effect on the cercal nerve activity, but the toxic effect of LqhαIT on the connective nerve was increased. Biotests showed that toxicity of LqhαIT (10(-8) M) on cockroaches was reduced by the exposure to ELF-EMF (0.7 and 7 mT).

CONCLUSIONS

The exposure to 50 Hz ELF-EMF modified the mode of action of the anti-insect scorpion alpha toxin LqhαIT at cellular level of the cockroach nervous system and in biotests. Toxin appeared as a usefull tool in distinguishing between the primary and the secondary effects of ELF-EMF.

Improvement of spatial memory disorder and hippocampal damage by exposure to electromagnetic fields in an Alzheimer's disease rat model

Although some epidemiological investigations showed a potential association between long-term exposure of extremely low frequency electromagnetic fields (ELF-EMF) and Alzheimer’s disease (AD), no reasonable mechanism can explain this association, and the related animal experiments are rare. In this study, ELF-EMF exposure (50Hz 400µT 60d) combined with D-galactose intraperitoneal (50mg/kg, q.d., 42d) and Aβ_25–35 hippocampal (5μl/unilateral, bilateral, single-dose) injection was implemented to establish a complex rat model. Then the effects of ELF-EMF exposure on AD development was studied by using the Morris water maze, pathological analysis, and comparative proteomics. The results showed that ELF-EMF exposure delayed the weight gain of rats, and partially improved cognitive and clinicopathologic symptoms of AD rats. The differential proteomic analysis results suggest that synaptic transmission, oxidative stress, protein degradation, energy metabolism, Tau aggregation, and inflammation involved in the effects mentioned above. Therefore, our findings indicate that certain conditions of ELF-EMF exposure could delay the development of AD in rats.

Early exposure to intermediate-frequency magnetic fields alters brain biomarkers without histopathological changes in adult mice

Recently we have reported that intermediate-frequency magnetic field (IF-MF) exposure transiently altered the mRNA expression levels of memory function-related genes in the hippocampi of adult male mice. However, the effects of IF-MF exposure during brain development on neurological biomarkers have not yet been clarified. In the present study, we investigated the effect of IF-MF exposure during development on neurological and immunological markers in the mouse hippocampus in 3- and 7-week-old male mice. Pregnant C57BL/6J mice were exposed to IF-MF (21 kHz, 3.8 mT) for one hour per day from organogenesis period day 7 to 17. At adolescence, some IF-MF-exposed mice were further divided into exposure, recovery, and sham-exposure groups. The adolescent-exposure groups were exposed again to IF-MF from postnatal day 27 to 48. The expression of mRNA in the hippocampi was examined using a real-time RT-PCR method, and microglia activation was examined by immunohistochemical analysis. The expression levels of NR1 and NR2B as well as transcription factors (CaMKIV, CREB1), inflammatory mediators (COX2, IL-1 β,TNF-α), and the oxidative stress marker heme-oxygenase (HO)-1 were significantly increased in the IF-MF-exposed mice, compared with the control group, in the 7-week-old mice, but not in the 3-week-old mice. Microglia activation was not different between the control and other groups. This study provides the first evidence that early exposure to IF-MF reversibly affects the NMDA receptor, its related signaling pathways, and inflammatory mediators in the hippocampus of young adult mice; these changes are transient and recover after termination of exposure without histopathological changes.

Effect of pulsed electromagnetic field treatment on programmed resolution of inflammation pathway markers in human cells in culture

Inflammation is a complex process involving distinct but overlapping biochemical and molecular events that are highly regulated. Pulsed electromagnetic field (PEMF) therapy is increasingly used to treat pain and edema associated with inflammation following surgery involving soft tissue. However, the molecular and cellular effects of PEMF therapy on pathways involved in the resolution of inflammation are poorly understood. Using cell culture lines relevant to trauma-induced inflammation of the skin (human dermal fibroblasts, human epidermal keratinocytes, and human mononuclear cells), we investigated the effect of PEMF on gene expression involved in the acute and resolution phases of inflammation. We found that PEMF treatment was followed by changes in the relative amount of messenger (m)RNAs encoding enzymes involved in heme catabolism and removal of reactive oxygen species, including an increase in heme oxygenase 1 and superoxide dismutase 3 mRNAs, in all cell types examined 2 hours after PEMF treatment. A relative increase in mRNAs encoding enzymes involved in lipid mediator biosynthesis was also observed, including an increase in arachidonate 12- and 15-lipoxygenase mRNAs in dermal fibroblasts and epidermal keratinocytes, respectively. The relative amount of both of these lipoxygenase mRNAs was elevated in mononuclear cells following PEMF treatment relative to nontreated cells. PEMF treatment was also followed by changes in the mRNA levels of several cytokines. A decrease in the relative amount of interleukin 1 beta mRNA was observed in mononuclear cells, similar to that previously reported for epidermal keratinocytes and dermal fibroblasts. Based on our results, we propose a model in which PEMF therapy may promote chronic inflammation resolution by mediating gene expression changes important for inhibiting and resolving inflammation.

Analysis of the effect of locally applied inhomogeneous static magnetic field-exposure on mouse ear edema--a double blind study

The effect static magnetic field (SMF)-exposure may exert on edema development has been investigated. A 6 h long whole-body (WBSMF) or local (LSMF), continuous, inhomogeneous SMF-exposure was applied on anesthetized mice in an in vivo model of mustard oil (MO)-induced ear edema. LSMF was applied below the treated ear, below the lumbar spine, or below the mandible. Ear thickness (v) was checked 8 times during the exposure period (at 0, 0.25, 1, 2, 3, 4, 5, and 6 h). The effect size of the applied treatment (η) on ear thickness was calculated by the formula η = 100% × (1–v_j/v_i), where group i is the control group and j is the treated group. Results showed that MO treatment in itself induced a significant ear edema with an effect of 9% (p<0.001). WBSMF or LSMF on the spine in combination with MO treatment increased ear thickness even further resulting in an effect of η>11% in both cases compared to SMF-exposure alone (p<0.001). In these cases SMF-exposure alone without MO treatment reduced ear thickness significantly (p<0.05), but within estimated experimental error. In cases of LSMF-exposure on the head, a significant SMF-exposure induced ear thickness reduction was found (η = 5%, p<0.05). LSMF-exposure on the spine affected ear thickness with and without MO treatment almost identically, which provides evidence that the place of local SMF action may be in the lower spinal region.

Exposure to 900 MHz electromagnetic fields activates the mkp-1/ERK pathway and causes blood-brain barrier damage and cognitive impairment in rats

With the rapid increase in the number of mobile phone users, the potential adverse effects of the electromagnetic field radiation emitted by a mobile phone has become a serious concern. This study demonstrated, for the first time, the blood-brain barrier and cognitive changes in rats exposed to 900 MHz electromagnetic field (EMF) and aims to elucidate the potential molecular pathway underlying these changes. A total of 108 male Sprague-Dawley rats were exposed to a 900 MHz, 1 mW/cm(2) EMF or sham (unexposed) for 14 or 28 days (3h per day). The specific energy absorption rate (SAR) varied between 0.016 (whole body) and 2 W/kg (locally in the head). In addition, the Morris water maze test was used to examine spatial memory performance determination. Morphological changes were investigated by examining ultrastructural changes in the hippocampus and cortex, and the Evans Blue assay was used to assess blood brain barrier (BBB) damage. Immunostaining was performed to identify heme oxygenase-1 (HO-1)-positive neurons and albumin extravasation detection. Western blot was used to determine HO-1 expression, phosphorylated ERK expression and the upstream mediator, mkp-1 expression. We found that the frequency of crossing platforms and the percentage of time spent in the target quadrant were lower in rats exposed to EMF for 28 days than in rats exposed to EMF for 14 days and unexposed rats. Moreover, 28 days of EMF exposure induced cellular edema and neuronal cell organelle degeneration in the rat. In addition, damaged BBB permeability, which resulted in albumin and HO-1 extravasation were observed in the hippocampus and cortex. Thus, for the first time, we found that EMF exposure for 28 days induced the expression of mkp-1, resulting in ERK dephosphorylation. Taken together, these results demonstrated that exposure to 900 MHz EMF radiation for 28 days can significantly impair spatial memory and damage BBB permeability in rat by activating the mkp-1/ERK pathway.

Exposure to extremely low frequency electromagnetic fields alters the calcium dynamics of cultured entorhinal cortex neurons

Previous studies have revealed that extremely low frequency electromagnetic field (ELF-EMF) exposure affects neuronal dendritic spine density and NMDAR and AMPAR subunit expressions in the entorhinal cortex (EC). Although calcium signaling has a critical role in control of EC neuronal functions, however, it is still unclear whether the ELF-EMF exposure affects the EC neuronal calcium homeostasis. In the present study, using whole-cell recording and calcium imaging, we record the whole-cell inward currents that contain the voltage-gated calcium currents and show that ELF-EMF (50Hz, 1mT or 3mT, lasting 24h) exposure does not influence these currents. Next, we specifically isolate the high-voltage activated (HVA) and low-voltage activated (LVA) calcium channels-induced currents. Similarly, the activation and inactivation characteristics of these membrane calcium channels are also not influenced by ELF-EMF. Importantly, ELF-EMF exposure reduces the maximum amplitude of the high-K(+)-evoked calcium elevation in EC neurons, which is abolished by thapsigargin, a Ca(2+) ATPase inhibitor, to empty the intracellular calcium stores of EC neurons. Together, these findings indicate that ELF-EMF exposure specifically influences the intracellular calcium dynamics of cultural EC neurons via a calcium channel-independent mechanism.

Using medaka embryos as a model system to study biological effects of the electromagnetic fields on development and behavior

The electromagnetic fields (EMFs) of anthropogenic origin are ubiquitous in our environments. The health hazard of extremely low frequency and radiofrequency EMFs has been investigated for decades, but evidence remains inconclusive, and animal studies are urgently needed to resolve the controversies regarding developmental toxicity of EMFs. Furthermore, as undersea cables and technological devices are increasingly used, the lack of information regarding the health risk of EMFs to aquatic organisms needs to be addressed. Medaka embryos (Oryzias latipes) have been a useful tool to study developmental toxicity in vivo due to their optical transparency. Here we explored the feasibility of using medaka embryos as a model system to study biological effects of EMFs on development. We also used a white preference test to investigate behavioral consequences of the EMF developmental toxicity. Newly fertilized embryos were randomly assigned to four groups that were exposed to an EMF with 3.2kHz at the intensity of 0.12, 15, 25, or 60µT. The group exposed to the background 0.12µT served as the control. The embryos were exposed continually until hatch. They were observed daily, and the images were recorded for analysis of several developmental endpoints. Four days after hatching, the hatchlings were tested with the white preference test for their anxiety-like behavior. The results showed that embryos exposed to all three levels of the EMF developed significantly faster. The endpoints affected included the number of somites, eye width and length, eye pigmentation density, midbrain width, head growth, and the day to hatch. In addition, the group exposed to the EMF at 60µT exhibited significantly higher levels of anxiety-like behavior than the other groups did. In conclusion, the EMF tested in this study accelerated embryonic development and heightened anxiety-like behavior. Our results also demonstrate that the medaka embryo is a sensitive and cost-efficient in vivo model system to study developmental toxicity of EMFs.

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.