A consensus panel review of central nervous system effects of the exposure to low-intensity extremely low-frequency magnetic fields

The Effect of Extremely Low-Frequency Magnetic Field on Stroke Patients: A Systematic Review

BACKGROUND

The aim of this study was to review the current state of scientific evidence on the effect of extremely low-frequency magnetic fields stimulation (ELF-MFs) on stroke patients.

METHODS

A systematic review of PubMed, ScienceDirect, PeDro and Embase databases was conducted. Only articles published in English, involving adult participants and focusing on individuals who had experienced a stroke, specifically examining the impact of ELF-MFs on post-stroke patients and had well-defined criteria for inclusion and exclusion of participants, were included. The methodological quality of the included studies was assessed using the Quality Assessment Tool for Quantitative Studies (QATQS).

RESULTS

A total of 71 studies were identified through database and reference lists' search, from which 9 were included in the final synthesis. All included studies showed a beneficial effect of ELF-MFs on stroke patients, however seven of the included studies were carried by the same research group. Improvements were observed in domains such as oxidative stress, inflammation, ischemic lesion size, functional status, depressive symptoms and cognitive abilities.

CONCLUSIONS

The available literature suggests a beneficial effect of ELF-MFs on post-stroke patients; however, the current data are too limited to broadly recommend the use of this method. Further research with improved methodological quality is necessary.

Continuous high-frequency repetitive transcranial magnetic stimulation at extremely low intensity affects exploratory behavior and spatial cognition in mice

High-frequency repetitive transcranial magnetic stimulation (HF-rTMS) has been shown to be effective for cognitive intervention. However, whether HF-rTMS with extremely low intensity could influence cognitive functions is still under investigation. The present study systematically investigated the effects of continuous 40 Hz and 10 Hz rTMS on cognition in young adult mice at extremely low intensity (10 mT and 1 mT) for 11 days (30 min/day). Cognitive functions were assessed using diverse behavioral tasks, including the open field, Y-maze, and Barnes maze paradigms. We found that 40 Hz rTMS significantly impaired exploratory behavior and spatial memory in both 10 mT and 1 mT conditions. In addition, 40 Hz rTMS induced remarkably different effects on exploratory behavior between 10 mT and 1mT, compared to 10 Hz stimulation. Our results indicate that extremely low intensity rTMS can significantly alter cognitive performance depending on intensity and frequency, shedding light on the understanding of the mechanism of rTMS effects.

Magnetic Stimulation as a Therapeutic Approach for Brain Modulation and Repair: Underlying Molecular and Cellular Mechanisms

Neurological and psychiatric diseases generally have no cure, so innovative non-pharmacological treatments, including non-invasive brain stimulation, are interesting therapeutic tools as they aim to trigger intrinsic neural repair mechanisms. A common brain stimulation technique involves the application of pulsed magnetic fields to affected brain regions. However, investigations of magnetic brain stimulation are complicated by the use of many different stimulation parameters. Magnetic brain stimulation is usually divided into two poorly connected approaches: (1) clinically used high-intensity stimulation (0.5-2 Tesla, T) and (2) experimental or epidemiologically studied low-intensity stimulation (μT-mT). Human tests of both approaches are reported to have beneficial outcomes, but the underlying biology is unclear, and thus optimal stimulation parameters remain ill defined. Here, we aim to bring together what is known about the biology of magnetic brain stimulation from human, animal, and in vitro studies. We identify the common effects of different stimulation protocols; show how different types of pulsed magnetic fields interact with nervous tissue; and describe cellular mechanisms underlying their effects-from intracellular signalling cascades, through synaptic plasticity and the modulation of network activity, to long-term structural changes in neural circuits. Recent advances in magneto-biology show clear mechanisms that may explain low-intensity stimulation effects in the brain. With its large breadth of stimulation parameters, not available to high-intensity stimulation, low-intensity focal magnetic stimulation becomes a potentially powerful treatment tool for human application.

Targeting Adenosine Signalling in Knee Chondropathy: The Combined Action of Polydeoxyribonucleotide and Pulsed Electromagnetic Fields: A Current Concept Review

Chondropathy of the knee is one of the most frequent degenerative cartilage pathologies with advancing age. Scientific research has, in recent years, advanced new therapies that target adenosine A2 receptors, which play a significant role in human health against many disease states by activating different protective effects against cell sufferance and damage. Among these, it has been observed that intra-articular injections of polydeoxyribonucleotides (PDRN) and Pulsed Electromagnetic Fields (PEMF) can stimulate the adenosine signal, with significant regenerative and healing effects. This review aims to depict the role and therapeutic modulation of A2A receptors in knee chondropathy. Sixty articles aimed at providing data for our study were included in this review. The present paper highlights how intra-articular injections of PDRN create beneficial effects by reducing pain and improving functional clinical scores, thanks to their anti-inflammatory action and the important healing and regenerating power of the stimulation of cell growth, production of collagen, and the extracellular matrix. PEMF therapy is a valid option in the conservative treatment of different articular pathologies, including early OA, patellofemoral pain syndrome, spontaneous osteonecrosis of the knee (SONK), and in athletes. PEMF could also be used as a supporting therapy after an arthroscopic knee procedure total knee arthroplasty to reduce the post-operative inflammatory state. The proposal of new therapeutic approaches capable of targeting the adenosine signal, such as the intra-articular injection of PDRN and the use of PEMF, has shown excellent beneficial results compared to conventional treatments. These are presented as an extra weapon in the fight against knee chondropathy.

Cognitive improvement via a modulated rhythmic pulsed magnetic field in D-galactose-induced accelerated aging mice

Rhythmic physical stimulations have emerged as effective noninvasive intervention strategies in the treatment of pathological cognitive deficits. Transcranial magnetic stimulation (TMS) can regulate neural firing and improve the learning and memory abilities of rodents or patients with cognitive deterioration. However, the effects of elaborate magnetic stimulation with low intensity during aging or other neurological disordering processes on cognitive decline remain unclear. In this study, we developed an elaborate modulated pulsed magnetic field (PMF) stimulation with a complex pattern in the theta repeated frequency and gamma carrier frequency and then determined the effects of this rhythmic PMF on the cognitive function of accelerated aging mice established by chronic subcutaneous injection of D-galactose (D-gal). The results of the Morris water maze (MWM) test showed that mice treated with modulated PMF displayed shorter swimming distance and latency time in the spatial exploration acquisition trial and exhibited a significant preference in the target presumptive platform area in the probe trial, all of which indicated the enhancement in spatial learning and memory abilities upon PMF stimulation of the accelerated aging mice. The novel object recognition (NOR) test results showed a similar tendency as the MWM results although without statistical significance. Further determination of histological structures demonstrated that the cognitive function-related hippocampal CA3 neurons degenerated upon D-gal injection, which could also be partially rescued by PMF application. In comparison with the high-intensity TMS approach, low-intensity magnetic stimulation could be much safer and allow deeper penetration without adverse effects such as seizure. In summary, modulated PMF, even with low intensity, could effectively improve rodent cognitive functions impaired by D-gal-induced accelerated aging, which might provide a new safe therapeutic strategy for cognitive deficits as well as other neurological disorders.

A Review of Aspects of Synaptic Plasticity in Hippocampus via mT Extremely Low-Frequency Magnetic Fields

The subthreshold magnetic modulation technique stimulates cells with mT extremely low-frequency magnetic fields (ELF-MFs), which are insufficient to induce neuronal action potentials. Although they cannot directly induce resting neurons to discharge, mT magnetic stimulation can regulate the excitability of the nervous system, which regulates learning and memory by some unknown mechanisms. Herein, we describe the regulation of mT ELF-MFs with different parameters on synaptic plasticity in hippocampal neurons. Additionally, we summarize the latest research on the possible mechanism of the effect of ELF-MFs on synaptic plasticity. Some studies have shown that ELF-MFs are able to inhibit long-term potentiation (LTP) by increasing concentration of intracellular Ca²⁺ concentration ([Ca²⁺ ]_i ), as well as concentration of reactive oxygen species. The research in this paper has significance for the comprehensive understanding of relevant neurological mechanisms of learning and memory by mT ELF-MFs stimulation. However, more high-quality research is necessary to determine the regulatory mechanism of mT ELF-MFs on synaptic plasticity in order to optimize this technique as a treatment for neurological diseases. © 2023 Bioelectromagnetics Society.

Frequency-tuned electromagnetic field therapy improves post-stroke motor function: A pilot randomized controlled trial

BACKGROUND AND PURPOSE

Impaired upper extremity (UE) motor function is a common disability after ischemic stroke. Exposure to extremely low frequency and low intensity electromagnetic fields (ELF-EMF) in a frequency-specific manner (Electromagnetic Network Targeting Field therapy; ENTF therapy) is a non-invasive method available to a wide range of patients that may enhance neuroplasticity, potentially facilitating motor recovery. This study seeks to quantify the benefit of the ENTF therapy on UE motor function in a subacute ischemic stroke population.

METHODS

In a randomized, sham-controlled, double-blind trial, ischemic stroke patients in the subacute phase with moderately to severely impaired UE function were randomly allocated to active or sham treatment with a novel, non-invasive, brain computer interface-based, extremely low frequency and low intensity ENTF therapy (1-100 Hz, < 1 G). Participants received 40 min of active ENTF or sham treatment 5 days/week for 8 weeks; ~three out of the five treatments were accompanied by 10 min of concurrent physical/occupational therapy. Primary efficacy outcome was improvement on the Fugl-Meyer Assessment - Upper Extremity (FMA-UE) from baseline to end of treatment (8 weeks).

RESULTS

In the per protocol set (13 ENTF and 8 sham participants), mean age was 54.7 years (±15.0), 19% were female, baseline FMA-UE score was 23.7 (±11.0), and median time from stroke onset to first stimulation was 11 days (interquartile range (IQR) 8-15). Greater improvement on the FMA-UE from baseline to week 4 was seen with ENTF compared to sham stimulation, 23.2 ± 14.1 vs. 9.6 ± 9.0, p = 0.007; baseline to week 8 improvement was 31.5 ± 10.7 vs. 23.1 ± 14.1. Similar favorable effects at week 8 were observed for other UE and global disability assessments, including the Action Research Arm Test (Pinch, 13.4 ± 5.6 vs. 5.3 ± 6.5, p = 0.008), Box and Blocks Test (affected hand, 22.5 ± 12.4 vs. 8.5 ± 8.6, p < 0.0001), and modified Rankin Scale (-2.5 ± 0.7 vs. -1.3 ± 0.7, p = 0.0005). No treatment-related adverse events were reported.

CONCLUSIONS

ENTF stimulation in subacute ischemic stroke patients was associated with improved UE motor function and reduced overall disability, and results support its safe use in the indicated population. These results should be confirmed in larger multicenter studies.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT04039178, identifier: NCT04039178.

In vivo low-intensity magnetic pulses durably alter neocortical neuron excitability and spontaneous activity

KEY POINTS

Repetitive transcranial magnetic stimulation (rTMS) is a promising technique to alleviate neurological and psychiatric disorders caused by alterations in cortical activity. Our knowledge of the cellular mechanisms underlying rTMS-based therapies remains limited. We combined in vivo focal application of low-intensity rTMS (LI-rTMS) to the rat somatosensory cortex with intracellular recordings of subjacent pyramidal neurons to characterize the effects of weak magnetic fields at single cell level. Ten minutes of LI-rTMS delivered at 10 Hz reliably evoked action potentials in cortical neurons during the stimulation period, and induced durable attenuation of their intrinsic excitability, synaptic activity, and spontaneous firing. These results help us better understand the mechanisms of weak magnetic stimulation and should allow optimizing the effectiveness of stimulation protocols for clinical use.

ABSTRACT

Magnetic brain stimulation is a promising treatment for neurological and psychiatric disorders. However, a better understanding of its effects at the individual neuron level is essential to improve its clinical application. We combined focal low-intensity repetitive transcranial magnetic stimulation (LI-rTMS) to the rat somatosensory cortex with intracellular recordings of subjacent pyramidal neurons in vivo. Continuous 10 Hz LI-rTMS reliably evoked firing at ∼4-5 Hz during the stimulation period and induced durable attenuation of synaptic activity and spontaneous firing in cortical neurons, through membrane hyperpolarization and a reduced intrinsic excitability. However, inducing firing in individual neurons by repeated intracellular current injection did not reproduce LI-rTMS effects on neuronal properties. These data provide novel understanding of mechanisms underlying magnetic brain stimulation showing that, in addition to inducing biochemical plasticity, even weak magnetic fields can activate neurons and enduringly modulate their excitability. Abstract figure legend We examined by means of in vivo intracellular recordings in the rodent the effects of low-intensity (10 mT) repetitive transcranial magnetic stimulation (LI-rTMS) on the functional properties of primary somatosensory cortex pyramidal neurons. After a baseline period, during which cortical spontaneous activity and excitability were measured (Pre), LI-rTMS was applied at 10 Hz for 10 minutes. Despite their low intensity, magnetic pulses reliably evoked action potentials in cortical neurons. Ten minutes of LI-rTMS induced a progressive and long-lasting hyperpolarization of the neuronal membrane and a marked decrease in cell firing rate (Post). This was associated with an altered intrinsic neuronal excitability, characterized by reduced membrane input resistance and increased minimal current required to induce neuronal firing. A portion of this figure was created with biorender.com. This article is protected by copyright. All rights reserved.

Low-Frequency Magnetic Field Exposure System for Cells Electromagnetic Biocompatibility Studies

The advancement in science and technology has resulted in the invention and widespread usage of many electrical devices in the daily lives of humans. The exponential use of modern electronic facilities has increased electromagnetic field exposure in the current population. Therefore, the presented article deals with designing, constructing, and testing a new applicator system developed for cells electromagnetic biocompatibility studies. The applicator system is intended for studying the non-thermal impacts of low-frequency magnetic field on cell cultures growth. Main attention is focused on increasing the capacity of the applicator and effectivity of the experiments. The key idea is to reach high level of the magnetic field homogeneity in an area of interest and the temperature stability during the biocompatibility studies. The applicator system is designed based on numerical simulations and its construction, measurements, and properties evaluation are also reported for proving the applicator’s functionality. The new applicator allows performing five parallel experiments at the same time under the same conditions. The simulation together with the experimental results confirm that the magnetic field homogeneity reaches 99% in the area of interest and the maximum temperature instability is lower than 2% during the experiments. The effectiveness of new applicator is tested and proved during preliminary experiments with Saccharomyces Cerevisiae cells. The observed effects of MF exposure represent maximal stimulation of 74% and maximal inhibition of 49%. The reason why MF with the same parameters induces inhibition in one sample and stimulation in the other will be the subject of further research.

Technological Improvement Rates and Evolution of Energy-Based Therapeutics

This paper examines the field of energy-based medical therapies based on the analysis of patents. We define the field as the use of external stimuli to achieve biomedical modifications to treat disease and to increase health. Based upon distinct sets of patents, the field is subdivided into sub-domains for each energy category used to achieve the stimulation: electrical, magnetic, microwave, ultrasound, and optical. Previously developed techniques are used to retrieve the relevant patents for each of the stimulation modes and to determine main paths along the trajectory followed by each sub-domain. The patent sets are analyzed to determine key assignees, number of patents, and dates of emergence of the sub-domains. The sub-domains are found to be largely independent as to patent assignees. Electrical and magnetic stimulation patents emerged earliest in the 1970s and microwave most recently around 1990. The annual rate of improvement of all sub-domains (12-85%) is found to be significantly higher than one we find for an aggregate pharmaceutical domain (5%). Overall, the results suggest an increasingly important role for energy-based therapies in the future of medicine.

New tools for shaping plasticity to enhance recovery after stroke

Stroke is the second most common cause of death worldwide and its prevalence is projected to increase in the coming years in parallel with the increase of life expectancy. Despite the great improvements in the management of the acute phase of stroke, some residual disability persists in most patients thus requiring rehabilitation. One third of patients do not reach the maximal recovery potential and different approaches have been explored with the aim to boost up recovery. In this regard, noninvasive brain stimulation techniques have been widely used to induce neuroplasticity phenomena. Different protocols of repetitive transcranial magnetic stimulation (rTMS) and transcranial electrical stimulation (tES) can induce short- and long-term changes of synaptic excitability and are promising tools for enhancing recovery in stroke patients. New options for neuromodulation are currently under investigation. They include: vagal nerve stimulation (VNS) that can be delivered invasively, with implanted stimulators and noninvasively with transcutaneous VNS (tVNS); and extremely low-frequency (1-300Hz) magnetic fields. This chapter will provide an overview on the new techniques that are used for neuroprotection and for enhancing recovery after stroke.

Biological effects of ultrashort electric pulses in a neuroblastoma cell line: the energy density role

BACKGROUND

Despite the numerous literature results about biological effects of electromagnetic field (EMF) exposure, the interaction mechanisms of these fields with organisms are still a matter of debate. Extremely low frequency (ELF) MFs can modulate redox homeostasis and we showed that 24 h exposure to 50 Hz-1 mT has a pro-oxidant effect and effects on the epigenome of SH-SY5Y cells, decreasing miR-34b/c expression through the hypermethylation of their promoter.

METHODS

Here, we investigated the role of the electromagnetic deposited energy density (ED) during exposures lasting 24 h to 1 mT amplitude MFs at a frequency of 50 Hz in inducing the above mentioned effects. To this end, we delivered ultrashort electric pulses, in the range of microsecond and nanosecond duration, with the same ED of the previously performed magnetic exposure to SH-SY5Y cells. Furthermore, we explored the effect of higher deposited energy densities. Analysis of i) gene and microRNA expression, ii) cell morphology, iii) reactive oxygen species (ROS) generation, and iv) apoptosis were carried out.

RESULTS

We observed significant changes in egr-1 and c-fos expression at very low deposited ED levels, but no change of the ROS production, miR-34b/c expression, nor the appearance of indicators of apoptosis. We thus sought investigating changes in egr-1 and c-fos expression caused by ultrashort electric pulses at increasing deposited ED levels. The pulses with the higher deposited ED caused cell electroporation and even other morphological changes such as cell fusion. The changes in egr-1 and c-fos expression were more intense, but, again, no change of the ROS production, miR-34b/c expression, nor apoptosis induction was observed.

CONCLUSIONS

These results, showing that extremely low levels of electric stimulation (never investigated until now) can cause transcriptional changes, also reveal the safety of the electroporating pulses used in biomedical applications and open up the possibility to further therapeutic applications of this technology.

Low-field thoracic magnetic stimulation increases peripheral oxygen saturation levels in coronavirus disease (COVID-19) patients: A single-blind, sham-controlled, crossover study

ABSTRACT

Severe acute respiratory syndrome coronavirus-2 may cause low oxygen saturation (SpO2) and respiratory failure in patients with coronavirus disease (COVID-19). Hence, increased SpO2 levels in COVID-19 patients could be crucial for their quality of life and recovery. This study aimed to demonstrate that a 30-minute single session of dorsal low-field thoracic magnetic stimulation (LF-ThMS) can be employed to increase SpO2 levels in COVID-19 patients significantly. Furthermore, we hypothesized that the variables associated with LF-ThMS, such as frequency, magnetic flux density, and temperature in the dorsal thorax, might be correlated to SpO2 levels in these patients.Here we employed an LF-ThMS device to noninvasively deliver a pulsed magnetic field from 100 to 118 Hz and 10.5 to 13.1 milliTesla (i.e., 105 to 131 Gauss) to the dorsal thorax. These values are within the intensity range of several pulsed electromagnetic field devices employed in physical therapy worldwide. We designed a single-blind, sham-controlled, crossover study on 5 COVID-19 patients who underwent 2 sessions of the study (real and sham LF-ThMS) and 12 patients who underwent only the real LF-ThMS.We found a statistically significant positive correlation between magnetic flux density, frequency, or temperature, associated with the real LF-ThMS and SpO2 levels in all COVID-19 patients. However, the 5 patients in the sham-controlled study did not exhibit a significant change in their SpO2 levels during sham stimulation. The employed frequencies and magnetic flux densities were safe for the patients. We did not observe adverse events after the LF-ThMS intervention.This study is a proof-of-concept that a single session of LF-ThMS applied for 30 minutes to the dorsal thorax of 17 COVID-19 patients significantly increased their SpO2 levels. However, future research will be needed to understand the physiological mechanisms behind this finding.The study was registered at ClinicalTrials.gov (Identifier: NCT04895267, registered on May 20, 2021) retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT04895267.

Use of Fast Gamma Magnetic Stimulation Over the Left Prefrontal Dorsolateral Cortex for the Treatment of MCI and Mild Alzheimer's Disease: A Double-Blind, Randomized, Sham-Controlled, Pilot Study

Background: Alzheimer's disease (AD) animal models have shown a reduced gamma power in several brain areas, and induction of these oscillations by non-invasive methods has been shown to modify several pathogenic mechanisms of AD. In humans, the application of low-intensity magnetic fields has shown to be able to produce neural entrainment at the magnetic pulse frequency, making it useful to induce gamma frequencies. Objective: The aim of this study was to assess if the application of fast gamma magnetic stimulation (FGMS) over the left prefrontal dorsolateral cortex would be a safe and well-tolerated intervention that could potentially improve cognitive scores in subjects with mild cognitive impairment and mild AD. Methods: In these randomized, double-blind, sham-controlled study, participants were assigned to either receive daily sessions two times a day of active or sham FGMS for 6 months. Afterward, measurements of adverse effects, cognition, functionality, and depression were taken. Results: Thirty-four patients, 17 in each group, were analyzed for the primary outcome. FGMS was adequately tolerated by most of the subjects. Only four patients from the active FGMS group (23.52%) and one patient from the sham FGMS group (5.88%) presented any kind of adverse effects, showing no significant difference between groups. Nevertheless, FGMS did not significantly change cognitive, functionality, or depressive evaluations. Conclusion: FGMS over the left prefrontal dorsolateral cortex applied twice a day for 6 months resulted to be a viable intervention that can be applied safely directly from home without supervision of a healthcare provider. However, no statistically significant changes in cognitive, functionality, or depression scores compared to sham stimulation were observed. Clinical Trial Registration:www.ClinicalTrials.gov, Identifier: NCT03983655, URL: https://clinicaltrials.gov/ct2/show/NCT03983655.

Epigenetic dysregulation in various types of cells exposed to extremely low-frequency magnetic fields

Epigenetic mechanisms regulate gene expression, without changing the DNA sequence, and establish cell-type-specific temporal and spatial expression patterns. Alterations of epigenetic marks have been observed in several pathological conditions, including cancer and neurological disorders. Emerging evidence indicates that a variety of environmental factors may cause epigenetic alterations and eventually influence disease risks. Humans are increasingly exposed to extremely low-frequency magnetic fields (ELF-MFs), which in 2002 were classified as possible carcinogens by the International Agency for Research on Cancer. This review summarizes the current knowledge of the link between the exposure to ELF-MFs and epigenetic alterations in various cell types. In spite of the limited number of publications, available evidence indicates that ELF-MF exposure can be associated with epigenetic changes, including DNA methylation, modifications of histones and microRNA expression. Further research is needed to investigate the molecular mechanisms underlying the observed phenomena.

High-Frequency and Low-Intensity Patterned Transcranial Magnetic Stimulation over Left Dorsolateral Prefrontal Cortex as Treatment for Major Depressive Disorder: A Report of 3 Cases

Current transcranial magnetic stimulation devices apply intense (near 1 tesla) repetitive magnetic pulses over a specific area of the skull at relatively lower frequencies (1-50 Hz). Nevertheless, different studies have shown that very small magnetic fields, at higher frequencies (50-1000 Hz.), produce therapeutic effects in major depressive disorder. We report the application of high-frequency and low-intensity patterned magnetic pulses over the left prefrontal dorsolateral cortex in three subjects diagnosed with clinical major depressive disorder. All three patients showed sharp changes in their self-reports as well as in the standardized clinical assessment. Hypothesized mechanisms of action of this new variant of magnetic stimulation are discussed.

Progress in the Knowledge, Application and Influence of Extremely Low Frequency Signals

This paper describes the characteristics of contributions made by researchers worldwide in the field of ELF (extremely low frequency) waves from 1957 to 2019. The data were collected through the Scopus database and processed with analytical and bibliometric techniques. The selection of the keywords is an essential step, because ELF has a very different meaning in some areas of medicine, where it is associated with a gene. A total of 12,436 documents were worked on in 12 thematic communities according to their collaborative relationships between authors and documents. Studies included authors publishing in the different thematic areas and the country where the USA stands first with more researchers in this theme than China and Japan. Documents were analyzed from the temporal perspective, their overall contribution, means of publication, and the language of the publication. Research requires extra effort and multidisciplinary collaboration to improve the knowledge, the application, and influence of these fields.

Patient Semi-specific Computational Modeling of Electromagnetic Stimulation Applied to Neuroprotective Treatments in Acute Ischemic Stroke

Neuroprotective effects of pulsed electromagnetic fields (PEMFs) have been demonstrated both in vivo and in vitro. Moreover, preliminary clinical studies have been conducted and suggested PEMFs as a possible alternative therapy to treat acute ischemic stroke. In this work, we show that it's possible to build-up a patient semi-specific head model, where the 3D reconstruction of the ischemic lesion of the patient under treatment is inserted in the head of the human body model "Duke" (v.1.0, Zurich MedTech AG). The semi-specific model will be used in the randomized, placebo-controlled, double-blind study currently ongoing. Three patients were modelled and simulated, and results showed that each ischemic lesion experiences a magnetic flux density field comparable to the one for which biological effects have been attested. Such a kind of dosimetric analysis reveals a reliable tool to assess the correlation between levels of exposure and the beneficial effect. Thus, once the on-going double blind study is complete it will prove if PEMFs treatment triggers a clinical effect, and we will then be able to characterize a dose-response curve with the methodology arranged in this study.

Extremely Low Frequency Magnetic Fields Do Not Affect LTP-Like Plasticity in Healthy Humans

Introduction

Several studies explored the biological effects of extremely low-frequency magnetic fields (ELF-MFs) in vitro, reporting the induction of functional changes in neuronal activity. In particular, ELF-MFs can influence synaptic plasticity both in vitro and in animal models but some studies reported an increase in long-term potentiation (LTP) whereas others suggested its reduction. However, no specific study has investigated such effect on humans.

Aims

To evaluate whether ELF-MFs affect the propensity of the human cortex to undergo LTP-like plasticity.

Methods

We designed a randomized, single-blind, sham-controlled, cross-over study on 10 healthy subjects. Cortical plasticity was induced by intermittent theta burst stimulation (iTBS) before and after 45-min ELF-MFs (75 Hz; 1.8 mT) or sham exposure and was estimated by measuring the changes of motor evoked potentials (MEP) amplitude before and after each iTBS.

Results

No adverse events were reported. No significant effects of ELF-MFs on cortical plasticity were found.

Conclusion

Whole-brain exposure to ELF-MFs (75 Hz; 1.8 mT) is safe and does not seem to significantly affect LTP-like plasticity in human motor cortex.

Neural circuit repair by low-intensity magnetic stimulation requires cellular magnetoreceptors and specific stimulation patterns

Although electromagnetic brain stimulation is a promising treatment in neurology and psychiatry, clinical outcomes are variable, and underlying mechanisms are ill-defined, which impedes the development of new effective stimulation protocols. Here, we show, in vivo and ex vivo, that repetitive transcranial magnetic stimulation at low-intensity (LI-rTMS) induces axon outgrowth and synaptogenesis to repair a neural circuit. This repair depends on stimulation pattern, with complex biomimetic patterns being particularly effective, and the presence of cryptochrome, a putative magnetoreceptor. Only repair-promoting LI-rTMS patterns up-regulated genes involved in neuronal repair; almost 40% of were cryptochrome targets. Our data open a new framework to understand the mechanisms underlying structural neuroplasticity induced by electromagnetic stimulation. Rather than neuronal activation by induced electric currents, we propose that weak magnetic fields act through cryptochrome to activate cellular signaling cascades. This information opens new routes to optimize electromagnetic stimulation and develop effective treatments for different neurological diseases.

Pulsed electromagnetic field and relief of hypoxia-induced neuronal cell death: The signaling pathway

Low-energy low-frequency pulsed electromagnetic fields (PEMFs) exert several protective effects, such as the regulation of kinases, transcription factors as well as cell viability in both central and peripheral biological systems. However, it is not clear on which bases they affect neuroprotection and the mechanism responsible is yet unknown. In this study, we have characterized in nerve growth factor-differentiated pheochromocytoma PC12 cells injured with hypoxia: (i) the effects of PEMF exposure on cell vitality; (ii) the protective pathways activated by PEMFs to relief neuronal cell death, including adenylyl cyclase, phospholipase C, protein kinase C epsilon and delta, p38, ERK1/2, JNK1/2 mitogen-activated protein kinases, Akt and caspase-3; (iii) the regulation by PEMFs of prosurvival heat-shock proteins of 70 (HSP70), cAMP response element-binding protein (CREB), brain-derived neurotrophic factor (BDNF), and Bcl-2 family proteins. The results obtained in this study show a protective effect of PEMFs that are able to reduce neuronal cell death induced by hypoxia by modulating p38, HSP70, CREB, BDNF, and Bcl-2 family proteins. Specifically, we found a rapid activation (30 min) of p38 kinase cascade, which in turns enrolles HSP70 survival chaperone molecule, resulting in a significant CREB phosphorylation increase (24 hr). In this cascade, later (48 hr), BDNF and the antiapoptotic pathway regulated by the Bcl-2 family of proteins are recruited by PEMFs to enhance neuronal survival. This study paves the way to elucidate the mechanisms triggered by PEMFs to act as a new neuroprotective approach to treat cerebral ischemia by reducing neuronal cell death.

Changes in pyramidal and granular neuron numbers in the rat hippocampus 7 days after exposure to a continuous 900-MHz electromagnetic field during early and mid-adolescence

The aim of this study was to investigate qualitative and quantitative changes in pyramidal and granule neurons in the male rat hippocampus after exposure to a continuous 900-megahertz (MHz) electromagnetic field (EMF) for 25 days during early and mid-adolescence. Three-week-old (21 day) healthy Sprague Dawley male rats were divided equally into control (CON), pseudo-exposed (PEX) and EMF groups. EMF rats were exposed to a 900-MHz EMF in an EMF-application cage, while the PEX rats were placed in the same cage without being exposed to EMF. No procedure was performed in CON. EMF was applied for 1 h/day, every day for 25 days. Following the 900-MHz EMF and pseudo-exposed applications, behavioral tests were performed for seven days. Then, all animals were euthanized and their brains were removed. Following histological tissue procedures, sections were taken from tissues and stained with toluidine blue. The optical fractionation technique was performed to estimate the pyramidal neuron numbers in the CA1, CA2-3 and hilus regions of the hippocampus and granule neuron numbers in the dentate gyrus region. Our findings indicated that the number of pyramidal and granule neurons in the hippocampus of the EMF group was statistically higher than PEX. Furthermore, the histopathological results showed that the cytoplasm of pyramidal (in the hilus, CA1, CA2 and CA3 region) and granular (in the dentate gyrus region) cells at the hippocampus were disrupted, as evident by intensive staining around cytoplasm and some artifacts were detected in the EMF group. In addition, statistical comparisons of the mean body weights and brain weights of the study groups revealed no significant differences. There was no statistically significant difference between the PEX and EMF groups in terms of temperature (p > 0.05) or humidity (p > 0.05) in the cages. In conclusion, higher numbers of both pyramidal and granule neurons were found in the male rat hippocampus after continuous 900-MHz EMF treatment.

Low frequency pulsed electromagnetic field promotes differentiation of oligodendrocyte precursor cells through upregulation of miR-219-5p in vitro

AIM

Spinal cord injury (SCI) is a common demyelinating disorder of the central nervous system. The differentiation of oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes (OLs), which induce myelination, plays a critical role in the functional recovery following SCI. In this study, the effect of low frequency pulsed electromagnetic field (PEMF) on the differentiation of OPCs and the potential underlying mechanisms were investigated.

MAIN METHODS

OPCs were randomly divided into the PEMF and non-PEMF (NPEMF) groups. Immunofluorescence and western blot assays were performed to assess the expression levels of OLs stage-specific markers after 3, 7, 14, and 21 days of PEMF or NPEMF exposure. qRT-PCR was used to further assess the expression levels of miR-219-5p, miR-338, miR-138, and miR-9, which are associated with OPCs differentiation, and the expression levels of genes associated with miR-219-5p. Finally, following PEMF or NPEMF exposure, qRT-PCR and western blot assays were performed to explore the relationship between miR-219-5p and Lingo1 and between miR-219-5p and PEMF in promoting OPCs differentiation.

KEY FINDINGS

PEMF promoted the differentiation of OPCs. PEMF upregulated the expression level of miR-219-5p and downregulated the expression level of Lingo1 during the differentiation of OPCs. Under PEMF exposure, miR-219-5p targeted Lingo1 and reversed the inhibitory effect of miR-219-5p inhibitor on OPCs differentiation. In addition, PEMF synergized with miR-219-5p to promote OPCs differentiation.

SIGNIFICANCE

Our results, for the first time, indicated that PEMF promoted OPCs differentiation by regulating miR-219-5p activity in vitro.

The effect of 8 weeks of treatment with transcranial pulsed electromagnetic fields on hand tremor and inter-hand coherence in persons with Parkinson's disease

Background

Parkinson’s disease (PD) tremor comprises asymmetric rest and postural tremor with unilateral onset. Tremor intensity can be amplified by stress and reduced by attention, and the medical treatment is complex. Mirror movements and unintentional synchronization of bimanual movements, possibly caused by insufficient inhibition of inter-hemispheric crosstalk, have been reported in PD, indicating a lag of lateralization.

Potential neuroprotective effects of pulsed electromagnetic fields (PEMF) have been reported in-vitro and in rodents, as have influences of PEMF on human tremor.

The aim was to investigate the effect of 8 weeks daily transcranial PEMF treatment (T-PEMF) of persons with PD on rest and postural hand tremor characteristics and on inter-hand coherence.

Methods

Hand accelerations of 50 PD participants with uni- or bilateral tremor participating in a clinical trial were analysed. A rest and postural tremor task performed during serial subtraction was assessed before and after 8 weeks of T-PEMF (30 min/day, 50 Hz, ±50 V, 3 ms squared pulses) or placebo treatment (sham stimulation 30 min/day). Forty matched healthy persons (no treatment) were included as reference. Intensity and inter-hand coherence related measures were extracted.

Results

The T-PEMF treatment decreased the inter-hand coherence in the PD group with unilateral postural tremor. The PD group with unilateral postural tremor was less clinically affected by the disease than the PD group with bilateral postural tremor. However, no differences between T-PEMF and placebo treatment on either intensity related or coherence related measures were found when all persons with PD were included in the analyses. The peak power decreased and the tremor intensity tended to decrease in both treatment groups.

Conclusions

Eight weeks of T-PEMF treatment decreased inter-hand coherence in the PD group with unilateral postural tremor, while no effects of T-PEMF treatment were found for the entire PD group. The unilateral postural tremor group was less clinically affected than the bilateral postural tremor group, suggesting that early treatment initiation may be beneficial. In theory, a reduced inter-hand coherence could result from a neuronal treatment response increasing inter-hemispheric inhibition. However, this requires further studies to determine. Studies of even longer treatment periods would be of interest.

Trial registration

ClinicalTrials.gov, NCT02125032. Registered 29 April 2014, https://clinicaltrials.gov/ct2/show/NCT02125032?term=NCT02125032&rank=1

Electronic supplementary material

The online version of this article (10.1186/s12984-019-0491-2) contains supplementary material, which is available to authorized users.

Effect of transcranial pulsed electromagnetic fields (T-PEMF) on functional rate of force development and movement speed in persons with Parkinson's disease: A randomized clinical trial

Background

Parkinson’s disease is caused by dopaminergic neurodegeneration resulting in motor impairments as slow movement speed and impaired balance and coordination. Pulsed electromagnetic fields are suggested to have neuroprotective effects, and could alleviate symptoms.

Objective

To study 1) effects of 8-week daily transcranial pulsed electromagnetic field treatment on functional rate of force development and movement speed during two motor tasks with different levels of complexity, 2) if treatment effects depend on motor performance at baseline.

Methods

Ninety-seven persons with Parkinson’s disease were randomized to active transcranial pulsed electromagnetic field (squared bipolar 3 ms pulses, 50 Hz) or placebo treatment with homebased treatment 30 min/day for 8 weeks. Functional rate of force development and completion time of a sit-to-stand and a dynamic postural balance task were assessed pre and post intervention. Participants were sub-grouped in high- and low-performers according to their baseline motor performance level. Repeated measure ANOVAs were used.

Results

Active treatment tended to improve rate of force development during chair rise more than placebo (P = 0.064). High-performers receiving active treatment improved rate of force development during chair rise more than high-performers receiving placebo treatment (P = 0.049, active/placebo: 11.9±1.1 to 12.5±1.9 BW/s ≈ 5% / 12.4±1.3 to 12.2±1.3 BW/s, no change). No other between-treatment-group or between-treatment-subgroup differences were found. Data on rate of force development of the dynamic balance task and completion times of both motor tasks improved but did not allow for between-treatment differentiation.

Conclusion

Treatment with transcranial pulsed electromagnetic fields was superior to placebo regarding functional rate of force development during chair rise among high-performers. Active treatment tended to increase functional rate of force development while placebo did not. Our results suggest that mildly affected persons with Parkinson’s disease have a larger potential for neural rehabilitation than more severely affected persons and indicate that early treatment initiation may be beneficial.

Duration-dependent effect of exposure to static electric field on learning and memory ability in mice

With the rapid development of ultra-high-voltage direct-current (UHVDC) transmission, the strength of environmental static electric field (SEF) around UHVDC transmission lines increased substantially, which has aroused widely public attention on the potential health effects of SEF. In this study, the effect of SEF exposure on learning and memory ability was investigated. Institute of Cancer Research mice were exposed to 56.3 kV/m SEF for a short term (7 days) or long term (49 days). Behaviors in the Morris water maze (MWM) test, hippocampal neurotransmitter contents, and oxidative stress indicators were examined. Results showed that short-term SEF exposure significantly prolonged escape latency and decreased the number of platform-site crossovers, as well as decreased the time spent in the target quadrant in the MWM test. Meanwhile, serotonin level and the ratio of glutamate level to γ-aminobutyric acid level changed significantly. Besides, malondialdehyde content and glutathione peroxidase activity increased significantly, while superoxide dismutase activity decreased significantly. After long-term SEF exposure, all indices above showed no significant differences between the SEF and sham exposure groups. These data indicated that short-term exposure to 56.3 kV/m SEF could cause abnormal neurotransmitter levels and oxidative stress in the hippocampus, which led to the decline in learning and memory ability. Under the condition of long-term exposure, the SEF-induced disturbances in neurotransmitter contents and redox balance were offset by the compensatory responses of mice, and thus, the learning and memory ability returned to normal level. The temporary and reversible decline in learning and memory ability was only a common biological effect of SEF rather than a health hazard.

Role of BDNF Signaling in Memory Enhancement Induced by Transcranial Direct Current Stimulation

In the recent years numerous studies have provided encouraging results supporting the use of transcranial direct current stimulation (tDCS) as non-invasive brain stimulation technique to improve motor and cognitive functions in patients suffering from neurological and neuropsychiatric disorders as well as in healthy subjects. Among the multiple effects elicited by tDCS on cognitive functions, experimental evidence and clinical findings have highlighted the beneficial impact on long-term memory. Memory deficits occur during physiological aging as well as in neurological and neurodegenerative disorders, including Alzheimer’s disease (AD). In this scenario, non-invasive techniques for memory enhancement, such as tDCS, are receiving increasing attention. The knowledge of molecular mechanisms subtending tDCS effects is of pivotal importance for a more rationale use of this technique in clinical settings. Although we are still far from having a clear picture, recent literature on human and animal studies has pointed to the involvement of synaptic plasticity mechanisms in mediating tDCS effects on long-term memory. Here we review these studies focusing on the neurotrophin “brain-derived neurotrophic factor” (BDNF) as critical tDCS effector.

Reactive oxygen species mediates 50-Hz magnetic field-induced EGF receptor clustering via acid sphingomyelinase activation

PURPOSE

Exposure to extremely low frequency electromagnetic fields (ELF-EMFs) could elicit biological effects including carcinogenesis. However, the detailed mechanisms by which these ELF-EMFs interact with biological system are currently unclear. Previously, we found that a 50-Hz magnetic field (MF) exposure could induce epidermal growth factor receptor (EGFR) clustering and phosphorylation on cell membranes. In the present experiment, the possible roles of reactive oxygen species (ROS) in MF-induced EGFR clustering were investigated.

MATERIALS AND METHODS

Human amnion epithelial (FL) cells were exposed to a 50-Hz MF with or without N-acetyl-l-cysteine (NAC) or pyrrolidine dithiocarbamate (PDTC). EGFR clustering on cellular membrane surface was analyzed using confocal microscopy after indirect immunofluorescence staining. The intracellular ROS level and acid sphingomyelinase (ASMase) activity were detected using an ROS assay kit and an Amplex^® Red Sphingomyelinase Assay Kit, respectively.

RESULTS

Results showed that exposure of FL cells to a 50-Hz MF at 0.4 mT for 15 min significantly enhanced the ROS level, induced EGFR clustering and increased ASMase activity. However, pretreatment with NAC or PDTC, the scavenger of ROS, not only counteracted the effects of a 50-Hz MF on ROS level and AMS activity, but also inhibited the EGFR clustering induced by MF exposure.

CONCLUSIONS

The present and previous data suggest that ROS mediates the MF-induced EGFR clustering via ASMase activation.

Repetitive low intensity magnetic field stimulation in a neuronal cell line: a metabolomics study

Low intensity repetitive magnetic stimulation of neural tissue modulates neuronal excitability and has promising therapeutic potential in the treatment of neurological disorders. However, the underpinning cellular and biochemical mechanisms remain poorly understood. This study investigates the behavioural effects of low intensity repetitive magnetic stimulation (LI-rMS) at a cellular and biochemical level. We delivered LI-rMS (10 mT) at 1 Hz and 10 Hz to B50 rat neuroblastoma cells in vitro for 10 minutes and measured levels of selected metabolites immediately after stimulation. LI-rMS at both frequencies depleted selected tricarboxylic acid (TCA) cycle metabolites without affecting the main energy supplies. Furthermore, LI-rMS effects were frequency-specific with 1 Hz stimulation having stronger effects than 10 Hz. The observed depletion of metabolites suggested that higher spontaneous activity may have led to an increase in GABA release. Although the absence of organised neural circuits and other cellular contributors (e.g., excitatory neurons and glia) in the B50 cell line limits the degree to which our results can be extrapolated to the human brain, the changes we describe provide novel insights into how LI-rMS modulates neural tissue.

Effects of short and long term electromagnetic fields exposure on the human hippocampus

The increasing use of mobile phones may have a number of physiological and psychological effects on human health. Many animal and human studies have reported various effects on the central nervous system and cognitive performance from of exposure to electromagnetic fields (EMF) emitted by mobile phones. The aim of the present study was to evaluate the effects of mobile phones on the morphology of the human brain and on cognitive performance using stereological and spectroscopic methods and neurocognitive tests. Sixty healthy female medical school students aged 18-25 years were divided into a low exposure group (30 subjects, <30 min daily use by the head) and high exposure group (30 subjects, >90 min daily use by the head). Magnetic resonance images (MRI) of the brain analysed on OsiriX 3.2.1 workstation. Neuropsychological tests were performed for each subject. In addition, three dominant specific metabolites were analysed, choline at 3.21 ppm, creatine at 3.04 ppm and N-acetyl aspartate at 2.02 ppm. Analysis of the spectroscopic results revealed no significant difference in specific metabolites between the groups (p > 0.05). There was also no significant difference in terms of hippocampal volume between the groups (p > 0.05). In contrast, the results of the stroop and digit span (backward) neurocognitive tests of high exposure group for evaluating attention were significantly poorer from low exposure group (p < 0.05). Based on these results, we conclude that a lack of attention and concentration may occur in subjects who talk on mobile phones for longer times, compared to those who use phones relatively less.

An open-label, one-arm, dose-escalation study to evaluate safety and tolerability of extremely low frequency magnetic fields in acute ischemic stroke

Extremely low frequency magnetic fields (ELF-MF) could be an alternative neuroprotective approach for ischemic stroke because preclinical studies have demonstrated their effects on the mechanisms underlying ischemic damage. The purpose of this open-label, one arm, dose-escalation, exploratory study is to evaluate the safety and tolerability of ELF-MF in patients with acute ischemic stroke. Within 48 hours from the stroke onset, patients started ELF-MF treatment, daily for 5 consecutive days. Clinical follow-up lasted 12 months. Brain MRI was performed before and 1 month after the treatment. The distribution of ELF-MF in the ischemic lesion was estimated by dosimetry. Six patients were stimulated, three for 45 min/day and three for 120 min/day. None of them reported adverse events. Clinical conditions improved in all the patients. Lesion size was reduced in one patient stimulated for 45 minutes and in all the patients stimulated for 120 minutes. Magnetic field intensity within the ischemic lesion was above 1 mT, the minimum value able to trigger a biological effect in preclinical studies. Our pilot study demonstrates that ELF-MF are safe and tolerable in acute stroke patients. A prospective, randomized, placebo-controlled, double-blind study will clarify whether ELF-MFs could represent a potential therapeutic approach.

Benign Effect of Extremely Low-Frequency Electromagnetic Field on Brain Plasticity Assessed by Nitric Oxide Metabolism during Poststroke Rehabilitation

Nitric oxide (NO) is one of the most important signal molecules, involved in both physiological and pathological processes. As a neurotransmitter in the central nervous system, NO regulates cerebral blood flow, neurogenesis, and synaptic plasticity. The aim of our study was to investigate the effect of the extremely low-frequency electromagnetic field (ELF-EMF) on generation and metabolism of NO, as a neurotransmitter, in the rehabilitation of poststroke patients. Forty-eight patients were divided into two groups: ELF-EMF and non-ELF-EMF. Both groups underwent the same 4-week rehabilitation program. Additionally, the ELF-EMF group was exposed to an extremely low-frequency electromagnetic field of 40 Hz, 7 mT, for 15 min/day. Levels of 3-nitrotyrosine, nitrate/nitrite, and TNFα in plasma samples were measured, and NOS2 expression was determined in whole blood samples. Functional status was evaluated before and after a series of treatments, using the Activity Daily Living, Geriatric Depression Scale, and Mini-Mental State Examination. We observed that application of ELF-EMF significantly increased 3-nitrotyrosine and nitrate/nitrite levels, while expression of NOS2 was insignificantly decreased in both groups. The results also show that ELF-EMF treatments improved functional and mental status. We conclude that ELF-EMF therapy is capable of promoting recovery in poststroke patients.

The effects of 50 Hz magnetic field exposure on DNA damage and cellular functions in various neurogenic cells

Epidemiological studies have indicated a possible association between extremely low-frequency magnetic field (ELF-MF) exposure and the risk of nervous system diseases. However, laboratory studies have not provided consistent results for clarifying this association, despite many years of studies. In this study, we have systematically investigated the effects of 50 Hz MF exposure on DNA damage and cellular functions in both neurogenic tumor cell lines (U251, A172, SH-SY5Y) and primary cultured neurogenic cells from rats (astrocytes, microglia, cortical neurons). The results showed that exposure to a 50 Hz MF at 2.0 mT for up to 24 h did not influence γH2AX foci formation (an early marker of DNA double-strand breaks) in any of six different neurogenic cells. Exposure to a 50 Hz MF did not affect cell cycle progression, cell proliferation or cell viability in neurogenic tumor U251, A172 or SH-SY5Y cells. Furthermore, the MF exposure for 24 h did not significantly affect the secretion of cytokines (TNF-α, IL-6 or IL-1β) in astrocytes or microglia, or the phagocytic activity of microglia. In addition, MF exposure for 1 h per day did not significantly influence expression levels of microtubule-associated protein tau, microtubule-associated protein 2, postsynaptic density 95 or gephyrin in cortical neurons, indicating an absence of effects of MF exposure on the development of cortical neurons. In conclusion, our data suggest that exposure to a 50 Hz MF at 2.0 mT did not elicit DNA damage effects or abnormal cellular functions in the neurogenic cells studied.

Oscillatory Activities in Neurological Disorders of Elderly: Biomarkers to Target for Neuromodulation

Non-invasive brain stimulation (NIBS) has been under investigation as adjunct treatment of various neurological disorders with variable success. One challenge is the limited knowledge on what would be effective neuronal targets for an intervention, combined with limited knowledge on the neuronal mechanisms of NIBS. Motivated on the one hand by recent evidence that oscillatory activities in neural systems play a role in orchestrating brain functions and dysfunctions, in particular those of neurological disorders specific of elderly patients, and on the other hand that NIBS techniques may be used to interact with these brain oscillations in a controlled way, we here explore the potential of modulating brain oscillations as an effective strategy for clinical NIBS interventions. We first review the evidence for abnormal oscillatory profiles to be associated with a range of neurological disorders of elderly (e.g., Parkinson's disease (PD), Alzheimer's disease (AD), stroke, epilepsy), and for these signals of abnormal network activity to normalize with treatment, and/or to be predictive of disease progression or recovery. We then ask the question to what extent existing NIBS protocols have been tailored to interact with these oscillations and possibly associated dysfunctions. Our review shows that, despite evidence for both reliable neurophysiological markers of specific oscillatory dis-functionalities in neurological disorders and NIBS protocols potentially able to interact with them, there are few applications of NIBS aiming to explore clinical outcomes of this interaction. Our review article aims to point out oscillatory markers of neurological, which are also suitable targets for modification by NIBS, in order to facilitate in future studies the matching of technical application to clinical targets.

Adenosine Receptors as a Biological Pathway for the Anti-Inflammatory and Beneficial Effects of Low Frequency Low Energy Pulsed Electromagnetic Fields

Several studies explored the biological effects of low frequency low energy pulsed electromagnetic fields (PEMFs) on human body reporting different functional changes. Much research activity has focused on the mechanisms of interaction between PEMFs and membrane receptors such as the involvement of adenosine receptors (ARs). In particular, PEMF exposure mediates a significant upregulation of A_2A and A₃ARs expressed in various cells or tissues involving a reduction in most of the proinflammatory cytokines. Of particular interest is the observation that PEMFs, acting as modulators of adenosine, are able to increase the functionality of the endogenous agonist. By reviewing the scientific literature on joint cells, a double role for PEMFs could be hypothesized in vitro by stimulating cell proliferation, colonization of the scaffold, and production of tissue matrix. Another effect could be obtained in vivo after surgical implantation of the construct by favoring the anabolic activities of the implanted cells and surrounding tissues and protecting the construct from the catabolic effects of the inflammatory status. Moreover, a protective involvement of PEMFs on hypoxia damage in neuron-like cells and an anti-inflammatory effect in microglial cells have suggested the hypothesis of a positive impact of this noninvasive biophysical stimulus.

In vitro Magnetic Stimulation: A Simple Stimulation Device to Deliver Defined Low Intensity Electromagnetic Fields

Non-invasive brain stimulation (NIBS) by electromagnetic fields appears to benefit human neurological and psychiatric conditions, although the optimal stimulation parameters and underlying mechanisms remain unclear. Although, in vitro studies have begun to elucidate cellular mechanisms, stimulation is delivered by a range of coils (from commercially available human stimulation coils to laboratory-built circuits) so that the electromagnetic fields induced within the tissue to produce the reported effects are ill-defined. Here, we develop a simple in vitro stimulation device with plug-and-play features that allow delivery of a range of stimulation parameters. We chose to test low intensity repetitive magnetic stimulation (LI-rMS) delivered at three frequencies to hindbrain explant cultures containing the olivocerebellar pathway. We used computational modeling to define the parameters of a stimulation circuit and coil that deliver a unidirectional homogeneous magnetic field of known intensity and direction, and therefore a predictable electric field, to the target. We built the coil to be compatible with culture requirements: stimulation within an incubator; a flat surface allowing consistent position and magnetic field direction; location outside the culture plate to maintain sterility and no heating or vibration. Measurements at the explant confirmed the induced magnetic field was homogenous and matched the simulation results. To validate our system we investigated biological effects following LI-rMS at 1 Hz, 10 Hz and biomimetic high frequency, which we have previously shown induces neural circuit reorganization. We found that gene expression was modified by LI-rMS in a frequency-related manner. Four hours after a single 10-min stimulation session, the number of c-fos positive cells increased, indicating that our stimulation activated the tissue. Also, after 14 days of LI-rMS, the expression of genes normally present in the tissue was differentially modified according to the stimulation delivered. Thus we describe a simple magnetic stimulation device that delivers defined stimulation parameters to different neural systems in vitro. Such devices are essential to further understanding of the fundamental effects of magnetic stimulation on biological tissue and optimize therapeutic application of human NIBS.

Pulsed Electromagnetic Field Exposure Reduces Hypoxia and Inflammation Damage in Neuron-Like and Microglial Cells

In the present study, the effect of low-frequency, low-energy pulsed electromagnetic fields (PEMFs) has been investigated by using different cell lines derived from neuron-like cells and microglial cells. In particular, the primary aim was to evaluate the effect of PEMF exposure in inflammation- and hypoxia-induced injury in two different neuronal cell models, the human neuroblastoma-derived SH-SY5Y cells and rat pheochromocytoma PC12 cells and in N9 microglial cells. In neuron-like cells, live/dead and apoptosis assays were performed in hypoxia conditions from 2 to 48 h. Interestingly, PEMF exposure counteracted hypoxia damage significantly reducing cell death and apoptosis. In the same cell lines, PEMFs inhibited the activation of the hypoxia-inducible factor 1α (HIF-1α), the master transcriptional regulator of cellular response to hypoxia. The effect of PEMF exposure on reactive oxygen species (ROS) production in both neuron-like and microglial cells was investigated considering their key role in ischemic injury. PEMFs significantly decreased hypoxia-induced ROS generation in PC12, SH-SY5Y, and N9 cells after 24 or 48 h of incubation. Moreover, PEMFs were able to reduce some of the most well-known pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, and IL-8 release in N9 microglial cells stimulated with different concentrations of LPS for 24 or 48 h of incubation time. These results show a protective effect of PEMFs on hypoxia damage in neuron-like cells and an anti-inflammatory effect in microglial cells suggesting that PEMFs could represent a potential therapeutic approach in cerebral ischemic conditions. J. Cell. Physiol. 232: 1200-1208, 2017. © 2016 Wiley Periodicals, Inc.

Low-intensity repetitive magnetic stimulation lowers action potential threshold and increases spike firing in layer 5 pyramidal neurons in vitro

Repetitive transcranial magnetic stimulation (rTMS) has become a popular method of modulating neural plasticity in humans. Clinically, rTMS is delivered at high intensities to modulate neuronal excitability. While the high-intensity magnetic field can be targeted to stimulate specific cortical regions, areas adjacent to the targeted area receive stimulation at a lower intensity and may contribute to the overall plasticity induced by rTMS. We have previously shown that low-intensity rTMS induces molecular and structural plasticity in vivo, but the effects on membrane properties and neural excitability have not been investigated. Here we investigated the acute effect of low-intensity repetitive magnetic stimulation (LI-rMS) on neuronal excitability and potential changes on the passive and active electrophysiological properties of layer 5 pyramidal neurons in vitro. Whole-cell current clamp recordings were made at baseline prior to subthreshold LI-rMS (600 pulses of iTBS, n=9 cells from 7 animals) or sham (n=10 cells from 9 animals), immediately after stimulation, as well as 10 and 20min post-stimulation. Our results show that LI-rMS does not alter passive membrane properties (resting membrane potential and input resistance) but hyperpolarises action potential threshold and increases evoked spike-firing frequency. Increases in spike firing frequency were present throughout the 20min post-stimulation whereas action potential (AP) threshold hyperpolarization was present immediately after stimulation and at 20min post-stimulation. These results provide evidence that LI-rMS alters neuronal excitability of excitatory neurons. We suggest that regions outside the targeted region of high-intensity rTMS are susceptible to neuromodulation and may contribute to rTMS-induced plasticity.

Elimination of the geomagnetic field stimulates the proliferation of mouse neural progenitor and stem cells

Living organisms are exposed to the geomagnetic field (GMF) throughout their lifespan. Elimination of the GMF, resulting in a hypogeomagnetic field (HMF), leads to central nervous system dysfunction and abnormal development in animals. However, the cellular mechanisms underlying these effects have not been identified so far. Here, we show that exposure to an HMF (<200 nT), produced by a magnetic field shielding chamber, promotes the proliferation of neural progenitor/stem cells (NPCs/NSCs) from C57BL/6 mice. Following seven-day HMF-exposure, the primary neurospheres (NSs) were significantly larger in size, and twice more NPCs/NSCs were harvested from neonatal NSs, when compared to the GMF controls. The self-renewal capacity and multipotency of the NSs were maintained, as HMF-exposed NSs were positive for NSC markers (Nestin and Sox2), and could differentiate into neurons and astrocyte/glial cells and be passaged continuously. In addition, adult mice exposed to the HMF for one month were observed to have a greater number of proliferative cells in the subventricular zone. These findings indicate that continuous HMF-exposure increases the proliferation of NPCs/NSCs, in vitro and in vivo. HMF-disturbed NPCs/NSCs production probably affects brain development and function, which provides a novel clue for elucidating the cellular mechanisms of the bio-HMF response.

Influences of Electromagnetic Energy on Bio-Energy Transport through Protein Molecules in Living Systems and Its Experimental Evidence

The influences of electromagnetic fields (EMFs) on bio-energy transport and its mechanism of changes are investigated through analytic and numerical simulation and experimentation. Bio-energy transport along protein molecules is performed by soliton movement caused by the dipole-dipole electric interactions between neighboring amino acid residues. As such, EMFs can affect the structure of protein molecules and change the properties of the bio-energy transported in living systems. This mechanism of biological effect from EMFs involves the amino acid residues in protein molecules. To study and reveal this mechanism, we simulated numerically the features of the movement of solitons along protein molecules with both a single chain and with three channels by using the Runge-Kutta method and Pang's soliton model under the action of EMFs with the strengths of 25,500, 51,000, 76,500, and 102,000 V/m in the single-chain protein, as well as 17,000, 25,500, and 34,000 V/m in the three-chain protein, respectively. Results indicate that electric fields (EFs) depress the binding energy of the soliton, decrease its amplitude, and change its wave form. Also, the soliton disperses at 102,000 V/m in a single-chain protein and at 25,500 and 34,000 V/m in three-chain proteins. These findings signify that the influence of EMFs on the bio-energy transport cannot be neglected; however, these variations depend on both the strength and the direction of the EF in the EMF. This direction influences the biological effects of EMF, which decrease with increases in the angle between the direction of the EF and that of the dipole moment of amino acid residues; however, randomness at the macroscopic level remains. Lastly, we experimentally confirm the existence of a soliton and the validity of our conclusion by using the infrared spectra of absorption of the collagens, which is activated by another type of EF. Thus, we can affirm that both the described mechanism and the corresponding theory are correct and that EMFs or EFs can influence the features of energy transport in living systems and thus have certain biological effects.

Time resolved dosimetry of human brain exposed to low frequency pulsed magnetic fields

An accurate dosimetry is a key issue to understanding brain stimulation and related interaction mechanisms with neuronal tissues at the basis of the increasing amount of literature revealing the effects on human brain induced by low-level, low frequency pulsed magnetic fields (PMFs). Most literature on brain dosimetry estimates the maximum E field value reached inside the tissue without considering its time pattern or tissue dispersivity. Nevertheless a time-resolved dosimetry, accounting for dispersive tissues behavior, becomes necessary considering that the threshold for an effect onset may vary depending on the pulse waveform and that tissues may filter the applied stimulatory fields altering the predicted stimulatory waveform's size and shape. In this paper a time-resolved dosimetry has been applied on a realistic brain model exposed to the signal presented in Capone et al (2009 J. Neural Transm. 116 257-65), accounting for the broadband dispersivity of brain tissues up to several kHz, to accurately reconstruct electric field and current density waveforms inside different brain tissues. The results obtained by exposing the Duke's brain model to this PMF signal show that the E peak in the brain is considerably underestimated if a simple monochromatic dosimetry is carried out at the pulse repetition frequency of 75 Hz.

The effects of magnetic fields exposure on relative permittivity of saline solutions measured by a high resolution SPR system

A measurement system for the relative permittivity of a physiological solution under 50 Hz magnetic fields (MF) is presented. It is based on a phase-sensitive surface plasmon resonance (SPR) system. Relative permittivity was analyzed for different solute concentrations of sodium chloride under various MF exposure parameters. We found that MF exposure at 0.2-4.0 mT step-wise decreased significantly the SPR phase signal of a 0.9% sodium chloride solution while 0.1 mT of MF exposure did not. The decreases in the SPR phase signal depended on the duration of MF exposure, and the signal reached a plateau after 15 min of exposure. Interestingly, the decreased SPR phase signal showed a gradual increase and approached the background level when the exposure was drawn off. In addition, we found that the response of the sodium chloride solution to MF also depended on its concentration. In brief, the relative permittivity of sodium chloride in solutions appears to be practically affected by 50 Hz MF exposure. Our data indicates that the relative permittivity of the saline solution influenced by MF exposure should be considered when investigating the biological effects of MF exposure on organisms in experimental study.

Exposure to an Extremely-Low-Frequency Magnetic Field Stimulates Adrenal Steroidogenesis via Inhibition of Phosphodiesterase Activity in a Mouse Adrenal Cell Line

Extremely low-frequency magnetic fields (ELF-MFs) are generated by power lines and household electrical devices. In the last several decades, some evidence has shown an association between ELF-MF exposure and depression and/or anxiety in epidemiological and animal studies. The mechanism underlying ELF-MF-induced depression is considered to involve adrenal steroidogenesis, which is triggered by ELF-MF exposure. However, how ELF-MFs stimulate adrenal steroidogenesis is controversial. In the current study, we investigated the effect of ELF-MF exposure on the mouse adrenal cortex-derived Y-1 cell line and the human adrenal cortex-derived H295R cell line to clarify whether the ELF-MF stimulates adrenal steroidogenesis directly. ELF-MF exposure was found to significantly stimulate adrenal steroidogenesis (p < 0.01–0.05) and the expression of adrenal steroid synthetic enzymes (p < 0.05) in Y-1 cells, but the effect was weak in H295R cells. Y-1 cells exposed to an ELF-MF showed significant decreases in phosphodiesterase activity (p < 0.05) and intracellular Ca²⁺ concentration (p < 0.01) and significant increases in intracellular cyclic adenosine monophosphate (cAMP) concentration (p < 0.001–0.05) and cAMP response element-binding protein phosphorylation (p < 0.05). The increase in cAMP was not inhibited by treatment with NF449, an inhibitor of the Gs alpha subunit of G protein. Our results suggest that ELF-MF exposure stimulates adrenal steroidogenesis via an increase in intracellular cAMP caused by the inhibition of phosphodiesterase activity in Y-1 cells. The same mechanism may trigger the increase in adrenal steroid secretion in mice observed in our previous study.

Effects of exposure to gradient magnetic fields emitted by nuclear magnetic resonance devices on clonogenic potential and proliferation of human hematopoietic stem cells

This study investigates effects of gradient magnetic fields (GMFs) emitted by magnetic resonance imaging (MRI) devices on hematopoietic stem cells. Field measurements were performed to assess exposure to GMFs of staff working at 1.5 T and 3 T MRI units. Then an exposure system reproducing measured signals was realized to expose in vitro CD34+ cells to GMFs (1.5 T-protocol and 3 T-protocol). CD34+ cells were obtained by Fluorescence Activated Cell Sorting from six blood donors and three MRI-exposed workers. Blood donor CD34+ cells were exposed in vitro for 72 h to 1.5 T or 3 T-protocol and to sham procedure. Cells were then cultured and evaluated in colony forming unit (CFU)-assay up to 4 weeks after exposure. Results showed that in vitro GMF exposure did not affect cell proliferation but instead induced expansion of erythroid and monocytes progenitors soon after exposure and for the subsequent 3 weeks. No decrease of other clonogenic cell output (i.e., CFU-granulocyte/erythroid/macrophage/megakaryocyte and CFU-granulocyte/macrophage) was noticed, nor exposed CD34+ cells underwent the premature exhaustion of their clonogenic potential compared to sham-exposed controls. On the other hand, pilot experiments showed that CD34+ cells exposed in vivo to GMFs (i.e., samples from MRI workers) behaved in culture similarly to sham-exposed CD34+ cells, suggesting that other cells and/or microenvironment factors might prevent GMF effects on hematopoietic stem cells in vivo. Accordingly, GMFs did not affect the clonogenic potential of umbilical cord blood CD34+ cells exposed in vitro together with the whole mononuclear cell fraction.

Extremely Low Frequency Magnetic Field (ELF-MF) Exposure Sensitizes SH-SY5Y Cells to the Pro-Parkinson's Disease Toxin MPP(.)

Parkinson's disease (PD) is a neurodegenerative disorder characterized by dopaminergic neuron loss, with an etiopathogenesis involving both genetic and environmental factors. The occupational/residential exposure to the electromagnetic fields has been recently associated with an increased risk of neurodegenerative diseases; it has been thus proposed that the extremely low frequency magnetic field (ELF-MF) may contribute to neurodegenerative etiopathogenesis, as its interaction with biological systems directly impairs redox homeostasis in specific areas of the brain. The molecular mechanisms elicited by ELF-MF, and their potential involvement in PD onset, still remain unclear. To this end, we set up a generator of ELF-MF able to stably and homogeneously reproduce environmental prolonged exposure to ELF-MF (50 Hz, 1 mT). Results obtained indicate that ELF-MF exposure alters cell response of SH-SY5Y cells to MPP(+). We demonstrate that ELF-MF does not affect per se survival, shape, and morphology of both proliferating and differentiated SH-SY5Y cells but significantly impairs redox homeostasis and thiol content, triggering an increase in protein carbonylation. As a result, toxicity of MPP(+), even at low doses, is highly enhanced in ELF-MF-exposed cells due to a significant increase in ROS levels, potentiation of oxidative damage, and induction of a caspase-dependent apoptosis. Pre-incubation with the thiol antioxidants N-acetyl-L-cysteine and GSH ethyl-ester significantly reduces the extent of oxidative damage and protects cells from death induced by the combined treatment ELF-MF/MPP(+). Taken overall, our results demonstrate the redox-based molecular interaction between ELF-MF and PD neurotoxins in vitro, and open a new scenario for defining the synergy of environmental factors in PD onset.