Magnetic stimulation modulates structural synaptic plasticity and regulates BDNF–TrkB signal pathway in cultured hippocampal neurons

Double-target magnetic stimulation attenuates oligodendrocyte apoptosis and oxidative stress impairment after spinal cord injury via GAP43

BACKGROUND CONTEXT

Spinal cord injury (SCI) causes neural circuit interruption and permanent functional damage. Magnetic stimulation in humans with SCI aims to engage residual neural networks to improve neurological functional, but the detailed mechanism remains unknown.

PURPOSE

This study evaluates functional recovery and neural circuitry improvements in rodent with double-target (brain and spinal cord) magnetic stimulation (DTMS) treatment and explores the effect of DTMS on the modulation of glial cells in vivo and in vitro.

STUDY DESIGN

In vivo animal study.

METHODS

SCI model rats at T10 level were induced via a weight-drop method and underwent long-time DTMS treatment. A series of behavioral assessments and tissue staining were used to evaluate neurological function and neural circuitry improvements. More importantly, single-cell RNA sequencing was conducted to identify the most significant glial cells after DTMS treatment. Furthermore, transmission electron microscopy, western blotting, immunofluorescence staining, TUNEL staining, Annexin V-FITC apoptosis kit and Lipid ROS kit were used to explore the mechanism underlying the observed changes. Study funding sources: National Natural Science Foundation of China (Grant number: U22A20297; Dollar amount: 62500); Key Research and Development Program of Guangzhou (Grant number: 202206060003; Dollar amount: 63750). There are no conflicts of interest or disclosures to report.

RESULTS

DTMS promoted the improvements of motor and sensory neural circuitry by modulating remyelination and neuronal survival, while silencing growth-associated protein 43 (GAP43) in oligodendrocytes suppressed these effects of DTMS in vivo. Mechanically, GAP43 played a crucial part to promote the branching and mature of oligodendrocytes and axonal regeneration via anti-apoptotic and antioxidative stress effects. Furthermore, oligodendrocytes subjected to magnetic stimulation exerted neuroprotective effects on neurons by secreting exosomes containing GAP43.

CONCLUSIONS

Our study revealed the neuroprotection of DTMS on SCI. The GAP43 in oligodendrocytes were associated with this relationship between magnetic stimulation and myelin and neuronal regeneration after SCI.

CLINICAL SIGNIFICANCE

The current study demonstrated the beneficial effects of DTMS on SCI based on functional, electrophysiological, cellular and histological evidence. According to these findings, we expect DTMS to make a positive and significant difference for SCI therapeutic screening.

Repetitive transcranial magnetic stimulation in Alzheimer's disease: effects on neural and synaptic rehabilitation

Alzheimer's disease is a neurodegenerative disease resulting from deficits in synaptic transmission and homeostasis. The Alzheimer's disease brain tends to be hyperexcitable and hypersynchronized, thereby causing neurodegeneration and ultimately disrupting the operational abilities in daily life, leaving patients incapacitated. Repetitive transcranial magnetic stimulation is a cost-effective, neuro-modulatory technique used for multiple neurological conditions. Over the past two decades, it has been widely used to predict cognitive decline; identify pathophysiological markers; promote neuroplasticity; and assess brain excitability, plasticity, and connectivity. It has also been applied to patients with dementia, because it can yield facilitatory effects on cognition and promote brain recovery after a neurological insult. However, its therapeutic effectiveness at the molecular and synaptic levels has not been elucidated because of a limited number of studies. This study aimed to characterize the neurobiological changes following repetitive transcranial magnetic stimulation treatment, evaluate its effects on synaptic plasticity, and identify the associated mechanisms. This review essentially focuses on changes in the pathology, amyloidogenesis, and clearance pathways, given that amyloid deposition is a major hypothesis in the pathogenesis of Alzheimer's disease. Apoptotic mechanisms associated with repetitive transcranial magnetic stimulation procedures and different pathways mediating gene transcription, which are closely related to the neural regeneration process, are also highlighted. Finally, we discuss the outcomes of animal studies in which neuroplasticity is modulated and assessed at the structural and functional levels by using repetitive transcranial magnetic stimulation, with the aim to highlight future directions for better clinical translations.

Harnessing Brain Plasticity: The Therapeutic Power of Repetitive Transcranial Magnetic Stimulation (rTMS) and Theta Burst Stimulation (TBS) in Neurotransmitter Modulation, Receptor Dynamics, and Neuroimaging for Neurological Innovations

Transcranial magnetic stimulation (TMS) methods have become exciting techniques for altering brain activity and improving synaptic plasticity, earning recognition as valuable non-medicine treatments for a wide range of neurological disorders. Among these methods, repetitive TMS (rTMS) and theta-burst stimulation (TBS) show significant promise in improving outcomes for adults with complex neurological and neurodegenerative conditions, such as Alzheimer's disease, stroke, Parkinson's disease, etc. However, optimizing their effects remains a challenge due to variability in how patients respond and a limited understanding of how these techniques interact with crucial neurotransmitter systems. This narrative review explores the mechanisms of rTMS and TBS, which enhance neuroplasticity and functional improvement. We specifically focus on their effects on GABAergic and glutamatergic pathways and how they interact with key receptors like N-Methyl-D-Aspartate (NMDA) and AMPA receptors, which play essential roles in processes like long-term potentiation (LTP) and long-term depression (LTD). Additionally, we investigate how rTMS and TBS impact neuroplasticity and functional connectivity, particularly concerning brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase receptor type B (TrkB). Here, we highlight the significant potential of this research to expand our understanding of neuroplasticity and better treatment outcomes for patients. Through clarifying the neurobiology mechanisms behind rTMS and TBS with neuroimaging findings, we aim to develop more effective, personalized treatment plans that effectively address the challenges posed by neurological disorders and ultimately enhance the quality of neurorehabilitation services and provide future directions for patients' care.

Cellular signaling pathways in the nervous system activated by various mechanical and electromagnetic stimuli

Mechanical stimuli, such as stretch, shear stress, or compression, activate a range of biomolecular responses through cellular mechanotransduction. In the nervous system, studies on mechanical stress have highlighted key pathophysiological mechanisms underlying traumatic injury and neurodegenerative diseases. However, the biomolecular pathways triggered by mechanical stimuli in the nervous system has not been fully explored, especially compared to other body systems. This gap in knowledge may be due to the wide variety of methods and definitions used in research. Additionally, as mechanical stimulation techniques such as ultrasound and electromagnetic stimulation are increasingly utilized in psychological and neurorehabilitation treatments, it is vital to understand the underlying biological mechanisms in order to develop accurate pathophysiological models and enhance therapeutic interventions. This review aims to summarize the cellular signaling pathways activated by various mechanical and electromagnetic stimuli with a particular focus on the mammalian nervous system. Furthermore, we briefly discuss potential cellular mechanosensors involved in these processes.

How conductivity boundaries influence the electric field induced by transcranial magnetic stimulation in in vitro experiments

BACKGROUND

Although transcranial magnetic stimulation (TMS) has become a valuable method for non-invasive brain stimulation, the cellular basis of TMS activation of neurons is still not fully understood. In vitro preparations have been used to understand the biophysical mechanisms of TMS, but in many cases these studies have encountered substantial difficulties in activating neurons.

OBJECTIVE/HYPOTHESIS

The hypothesis of this work is that conductivity boundaries can have large effects on the electric field in commonly used in vitro preparations. Our goal was to analyze the resulting difficulties in in vitro TMS using a simulation study, using a charge-based boundary element model.

METHODS

We decomposed the total electric field into the sum of the primary electric field, which only depends on coil geometry and current, and the secondary electric field arising from conductivity boundaries, which strongly depends on tissue and chamber geometry. We investigated the effect of the conductivity boundaries on the electric field strength for a variety of in vitro experimental settings to determine the sources of difficulty.

RESULTS

We showed that conductivity boundaries can have large effects on the electric field in in vitro preparations. Depending on the geometry of the air-saline and the saline-tissue interfaces, the secondary electric field can significantly enhance, or attenuate the primary electric field, resulting in a much stronger or weaker total electric field inside the tissue; we showed this using a realistic preparation. Submerged chambers are generally much more efficient than interface chambers since the secondary field due to the thin film of saline covering the tissue in the interface chamber opposes the primary field and significantly reduces the total field in the tissue placed in the interface chamber. The relative dimensions of the chamber and the TMS coil critically determine the total field; the popular setup with a large coil and a small chamber is particularly sub-optimal because the secondary field due to the air-chamber boundary opposes the primary field, thereby attenuating the total field. The form factor (length vs width) of the tissue in the direction of the induced field can be important since a relatively narrow tissue enhances the total field at the saline-tissue boundary.

CONCLUSIONS

Overall, we found that the total electric field in the tissue is higher in submerged chambers, higher if the chamber size is larger than the coil and if the shorter tissue dimension is in the direction of the electric field. Decomposing the total field into the primary and secondary fields is useful for designing in vitro experiments and interpreting the results.

High-frequency rTMS alleviates cognitive impairment and regulates synaptic plasticity in the hippocampus of rats with cerebral ischemia

Poststroke cognitive impairment (PSCI) is a common complication of stroke, but effective treatments are currently lacking. Repetitive transcranial magnetic stimulation (rTMS) is gradually being applied to treat PSCI, but there is limited evidence of its efficacy. To determine rTMS effects on PSCI, we constructed a transient middle cerebral artery occlusion (tMCAO) rat model. Rats were then grouped by random digital table method: the sham group (n = 10), tMCAO group (n = 10) and rTMS group (n = 10). The shuttle box and Morris water maze (MWM) tests were conducted to detect the cognitive functions of the rats. In addition, synaptic density and synaptic ultrastructural parameters, including the active zone length, synaptic cleft width, and postsynaptic density (PSD) thickness, were quantified and analyzed using an electron microscope. What's more, synaptic associated proteins, including PSD95, SYN, and BDNF were detected by western blot. According to the shuttle box and MWM tests, rTMS improved tMCAO rats' cognitive functions, including spatial learning and memory and decision-making abilities. Electron microscopy revealed that rTMS significantly increased the synaptic density, synaptic active zone length and PSD thickness and decreased the synaptic cleft width. The western blot results showed that the expression of PSD95, SYN, and BDNF was markedly increased after rTMS stimulation. Based on these results, we propose that 20 Hz rTMS can significantly alleviate cognitive impairment after stroke. The underlying mechanism might be modulating the synaptic plasticity and up-regulating the expression PSD95, SYN, and BDNF in the hippocampus.

Repetitive transcranial magnetic stimulation ameliorates cognitive deficits in mice with radiation-induced brain injury by attenuating microglial pyroptosis and promoting neurogenesis via BDNF pathway

BACKGROUND

Radiation-induced brain injury (RIBI) is a common and severe complication during radiotherapy for head and neck tumor. Repetitive transcranial magnetic stimulation (rTMS) is a novel and non-invasive method of brain stimulation, which has been applied in various neurological diseases. rTMS has been proved to be effective for treatment of RIBI, while its mechanisms have not been well understood.

METHODS

RIBI mouse model was established by cranial irradiation, K252a was daily injected intraperitoneally to block BDNF pathway. Immunofluorescence staining, immunohistochemistry and western blotting were performed to examine the microglial pyroptosis and hippocampal neurogenesis. Behavioral tests were used to assess the cognitive function and emotionality of mice. Golgi staining was applied to observe the structure of dendritic spine in hippocampus.

RESULTS

rTMS significantly promoted hippocampal neurogenesis and mitigated neuroinflammation, with ameliorating pyroptosis in microglia, as well as downregulation of the protein expression level of NLRP3 inflammasome and key pyroptosis factor Gasdermin D (GSDMD). BDNF signaling pathway might be involved in it. After blocking BDNF pathway by K252a, a specific BDNF pathway inhibitor, the neuroprotective effect of rTMS was markedly reversed. Evaluated by behavioral tests, the cognitive dysfunction and anxiety-like behavior were found aggravated with the comparison of mice in rTMS intervention group. Moreover, the level of hippocampal neurogenesis was found to be attenuated, the pyroptosis of microglia as well as the levels of GSDMD, NLRP3 inflammasome and IL-1β were upregulated.

CONCLUSION

Our study indicated that rTMS notably ameliorated RIBI-induced cognitive disorders, by mitigating pyroptosis in microglia and promoting hippocampal neurogenesis via mediating BDNF pathway.

Efficacy of repetitive transcranial magnetic stimulation with different application parameters for post-stroke cognitive impairment: a systematic review

Background

Cognitive impairment is a prevalent consequence of stroke, seriously affecting recovery and quality of life while imposing substantial burdens on both patients' families and society. Repetitive transcranial magnetic stimulation (rTMS) has emerged as an effective intervention for post-stroke cognitive impairment (PSCI). However, the a lack of standardized and explicit guidelines regarding rTMS application parameters. Therefore, this study systematically evaluated the efficacy of various parameters of rTMS in treating PSCI and explored its potential mechanism.

Methods

We conducted a comprehensive search across seven scientific databases, namely China National Knowledge Infrastructure (CNKI), Wanfang Data Knowledge Service Platform (Wanfang), China Science and Technology Journal Database (VIP), Web of Science, PubMed, Embase, and Cochrane Library, to identify randomized controlled trials (RCTs) investigating the efficacy of rTMS for PSCI. The search encompassed the period from database creation until July 28, 2023. To evaluate the risk of bias in included studies, we employed the Cochrane recommended risk of bias assessment tool. Furthermore, we extracted relevant clinical application parameters associated with rTMS and performed comparative analyses to assess their therapeutic effects under different parameter settings.

Results

The present study included 45 RCTs involving a total of 3,066 patients with PSCI. Both high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) and low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) demonstrated safety and efficacy, yet failed to exhibit significant differentiation in terms of cognitive improvement. Furthermore, intermittent theta burst stimulation (iTBS), although yielding positive results, did not surpass traditional rTMS in effectiveness. Combining HF-rTMS with LF-rTMS resulted in superior efficacy compared to single rTMS intervention. Moreover, the combination of rTMS with other cognitive therapies exhibited potential for enhanced benefits among patients.

Conclusion

rTMS can effectively and safely enhance cognitive function, improve quality of life, and enhance activities of daily living in patients with PSCI. Furthermore, the combination of rTMS with other conventional rehabilitation methods can yield additional positive effects. However, due to insufficient evidence, an optimal parameter protocol for rTMS can not be currently recommended. Future research should prioritize orthogonal experimental design methods that incorporate multiple parameters and levels to determine the optimal parameter protocol for rTMS in PSCI.

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.

Annexin A6 mitigates neurological deficit in ischemia/reperfusion injury by promoting synaptic plasticity

AIMS

Alleviating neurological dysfunction caused by acute ischemic stroke (AIS) remains intractable. Given Annexin A6 (ANXA6)'s potential in promoting axon branching and repairing cell membranes, the study aimed to explore ANXA6's potential in alleviating AIS-induced neurological dysfunction.

METHODS

A mouse middle cerebral artery occlusion model was established. Brain and plasma ANXA6 levels were detected at different timepoints post ischemia/reperfusion (I/R). We overexpressed and down-regulated brain ANXA6 and evaluated infarction volume, neurological function, and synaptic plasticity-related proteins post I/R. Plasma ANXA6 levels were measured in patients with AIS and healthy controls, investigating ANXA6 expression's clinical significance.

RESULTS

Brain ANXA6 levels initially decreased, gradually returning to normal post I/R; plasma ANXA6 levels showed an opposite trend. ANXA6 overexpression significantly decreased the modified neurological severity score (p = 0.0109) 1 day post I/R and the infarction area at 1 day (p = 0.0008) and 7 day (p = 0.0013) post I/R, and vice versa. ANXA6 positively influenced synaptic plasticity, upregulating synaptophysin (p = 0.006), myelin basic protein (p = 0.010), neuroligin (p = 0.078), and tropomyosin-related kinase B (p = 0.150). Plasma ANXA6 levels were higher in patients with AIS (1.969 [1.228-3.086]) compared to healthy controls (1.249 [0.757-2.226]) (p < 0.001), that served as an independent risk factor for poor AIS outcomes (2.120 [1.563-3.023], p < 0.001).

CONCLUSIONS

This study is the first to suggest that ANXA6 enhances synaptic plasticity and protects against transient cerebral ischemia.

rTMS reduces spatial learning and memory deficits induced by sleep deprivation possibly via suppressing the expression of kynurenine 3-monooxygenase in rats

INTRODUCTION

Impairment of learning and memory caused by sleep deprivation is a common symptom that significantly affects quality of life. Repetitive transcranial magnetic stimulation (rTMS) is a promising approach to exert a positive effect on cognitive impairment. However, there is less known about the mechanism of rTMS for learning and memory induced by chronic REM sleep deprivation (CRSD). This study was to detect the effects of rTMS on spatial learning and memory deficits by CRSD and explore possible mechanism.

METHODS

Sixty male Sprague-Dawley rats were randomly divided into four groups: wide platform (Control), sleep deprivation (SD), sleep deprivation + rTMS (TMS), and sleep deprivation + sham rTMS (Sham-TMS). Morris water maze (MWM) and open field test (OFT) assessed spatial learning and memory and anxiety of rats with pre/post-intervention. Golgi staining and transmission electron microscope (TEM) were used to observe structural variations of synapses in the hippocampus. The alteration in gene expression of different groups was analyzed by RNA-sequencing (RNA-Seq), and the key gene was screened and identified by quantitative polymerase chain reaction (qPCR) and subsequently verified with western blotting and immunofluorescence.

RESULTS

The behavioral test showed spatial learning and memory decreased and anxiety increased in the SD group compared to the Control and TMS groups. Moreover, rTMS improved spine density, ultrastructural damage, and quantities of synapses. In accordance with RNA-Seq, 56 differentially expressed genes (DEGs) were identified by comparing alternations in four groups and concentrated on kynurenine 3-monooxygenase (KMO). The expression of KMO increased significantly in rats of the SD group compared to the Control and TMS groups identified by qPCR, western blotting, and immunofluorescence.

CONCLUSION

1 Hz rTMS alleviated spatial learning and memory deficits induced by CRSD probably via down-regulating the expression of KMO and improving the structure and quantity of synapses in the hippocampus of rats.

Repetitive Transcranial Magnetic Stimulation (rTMS) in Major Depression

Major depressive disorder (MDD) is a psychiatric disorder with several effective therapeutic approaches, being antidepressants and psychotherapies the first-line treatments. Nonetheless, due to side effects, limited efficacy, and contraindications for these treatments, alternative treatment options are required. Neurostimulation is a non-pharmacological and non-psychotherapeutic approach that has been under study for diverse neuropsychiatric conditions in the form of electrical or magnetic stimulation of the brain. Repetitive transcranial magnetic stimulation (rTMS) is a neurostimulation method designed to generate magnetic fields and deliver magnetic pulses to stimulate the brain cortex. The magnetic pulses produce electrical currents in the brain which are not intense enough to provoke seizures, differentiating this method from other forms of neurostimulation that produce seizures. Although the exact rTMS mechanisms of action are not completely understood, rTMS seems to cause its beneficial effects through changes in neuroplasticity. Devices and protocols for rTMS are still evolving, becoming more efficient over time. There are still some challenges to be addressed, including further refinement of parameters (coil/device type, location, intensity, frequency, number of sessions, and duration of treatment); treatment cost and burden for patients; and treatment resistance. However, the efficacy, tolerability, and safety of some rTMS protocols have been demonstrated in different double-blind sham-controlled randomized controlled trials and meta-analyses for treatment-resistant depression.

Alternating current stimulation promotes neurite outgrowth and plasticity in neurons through activation of the PI3K/AKT signaling pathway

As a commonly used physical intervention, electrical stimulation (ES) has been demonstrated to be effective in the treatment of central nervous system disorders. Currently, researchers are studying the effects of electrical stimulation on individual neurons and neural networks, which are dependent on factors such as stimulation intensity, duration, location, and neuronal properties. However, the exact mechanism of action of electrical stimulation remains unclear. In some cases, repeated or prolonged electrical stimulation can lead to changes in the morphology or function of the neuron. In this study, immunofluorescence staining and Sholl analysis are used to assess changes in the neurite number and axon length to determine the optimal pattern and stimulation parameters of ES for neurons. Neuronal death and plasticity are detected by TUNEL staining and microelectrode array assays, respectively. mRNA sequencing and bioinformatics analysis are applied to predict the key targets of the action of ES on neurons, and the identified targets are validated by western blot analysis and qRT-PCR. The effects of alternating current stimulation (ACS) on neurons are more significant than those of direct current stimulation (DCS), and the optimal parameters are 3 μA and 20 min. ACS stimulation significantly increases the number of neurites, the length of axons and the spontaneous electrical activity of neurons, significantly elevates the expression of growth-associated protein-43 (GAP-43) without significant changes in the expression of neurotrophic factors. Furthermore, application of PI3K/AKT-specific inhibitors significantly abolishes the beneficial effects of ACS on neurons, confirming that the PI3K/AKT pathway is an important potential signaling pathway in the action of ACS.

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.

Repetitive Transcranial Magnetic Stimulation Reduces Depressive-like Behaviors, Modifies Dendritic Plasticity, and Generates Global Epigenetic Changes in the Frontal Cortex and Hippocampus in a Rodent Model of Chronic Stress

Depression is the most common affective disorder worldwide, accounting for 4.4% of the global population, a figure that could increase in the coming decades. In depression, there exists a reduction in the availability of dendritic spines in the frontal cortex (FC) and hippocampus (Hp). In addition, histone modification and DNA methylation are also dysregulated epigenetic mechanisms in depression. Repetitive transcranial magnetic stimulation (rTMS) is a technique that is used to treat depression. However, the epigenetic mechanisms of its therapeutic effect are still not known. Therefore, in this study, we evaluated the antidepressant effect of 5 Hz rTMS and examined its effect on dendritic remodeling, immunoreactivity of synapse proteins, histone modification, and DNA methylation in the FC and Hp in a model of chronic mild stress. Our data indicated that stress generated depressive-like behaviors and that rTMS reverses this effect, romotes the formation of dendritic spines, and favors the presynaptic connection in the FC and DG (dentate gyrus), in addition to increasing histone H3 trimethylation and DNA methylation. These results suggest that the antidepressant effect of rTMS is associated with dendritic remodeling, which is probably regulated by epigenetic mechanisms. These data are a first approximation of the impact of rTMS at the epigenetic level in the context of depression. Therefore, it is necessary to analyze in future studies as to which genes are regulated by these mechanisms, and how they are associated with the neuroplastic modifications promoted by rTMS.

Bioactive superparamagnetic iron oxide-gold nanoparticles regulated by a dynamic magnetic field induce neuronal Ca2+ influx and differentiation

Treating neurodegenerative diseases, e.g., Alzheimer's Disease, remains a significant challenge due to the limited neuroregeneration rate in the brain. The objective of this study is to evaluate the hypothesis that external magnetic field (MF) stimulation of nerve growth factor functionalized superparamagnetic iron oxide-gold (NGF-SPIO-Au) nanoparticles (NPs) can induce Ca²⁺ influx, membrane depolarization, and enhance neuron differentiation with dynamic MF (DMF) outperforming static MF (SMF) regulation. We showed the that total intracellular Ca²⁺ influx of PC-12 cells was improved by 300% and 535% by the stimulation of DMF (1 Hz, 0.5 T, 30min) with NGF-SPIO-Au NPs compared to DMF alone and SMF with NGF-SPIO-Au NPs, respectively, which was attributed to successive membrane depolarization. Cellular uptake performed with the application of sodium azide proved that DMF enhanced cellular uptake of NGF-SPIO-Au NPs via endocytosis. In addition, DMF upregulated both the neural differentiation marker (β3-tubulin) and the cell adhesive molecule (integrin-β1) with the existence of NGF-SPIO-Au NPs, while SMF did not show these effects. The results imply that noninvasive DMF-stimulated NPs can regulate intracellular Ca²⁺ influx and enhance neuron differentiation and neuroregeneration rate.

Activation of MAP2K signaling by genetic engineering or HF-rTMS promotes corticospinal axon sprouting and functional regeneration

Facilitating axon regeneration in the injured central nervous system remains a challenging task. RAF-MAP2K signaling plays a key role in axon elongation during nervous system development. Here, we show that conditional expression of a constitutively kinase-activated BRAF in mature corticospinal neurons elicited the expression of a set of transcription factors previously implicated in the regeneration of zebrafish retinal ganglion cell axons and promoted regeneration and sprouting of corticospinal tract (CST) axons after spinal cord injury in mice. Newly sprouting axon collaterals formed synaptic connections with spinal interneurons, resulting in improved recovery of motor function. Noninvasive suprathreshold high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) activated the BRAF canonical downstream effectors MAP2K1/2 and modulated the expression of a set of regeneration-related transcription factors in a pattern consistent with that induced by BRAF activation. HF-rTMS enabled CST axon regeneration and sprouting, which was abolished in MAP2K1/2 conditional null mice. These data collectively demonstrate a central role of MAP2K signaling in augmenting the growth capacity of mature corticospinal neurons and suggest that HF-rTMS might have potential for treating spinal cord injury by modulating MAP2K signaling.

Intermittent theta burst transcranial magnetic stimulation induces hippocampal mossy fibre plasticity in male but not female mice

Transcranial magnetic stimulation (TMS) induces electric fields that depolarise or hyperpolarise neurons. Intermittent theta burst stimulation (iTBS), a patterned form of TMS that is delivered at the theta frequency (~5 Hz), induces neuroplasticity in the hippocampus, a brain region that is implicated in memory and learning. One form of plasticity that is unique to the hippocampus is adult neurogenesis; however, little is known about whether TMS or iTBS in particular affects newborn neurons. Here, we therefore applied repeated sessions of iTBS to male and female mice and measured the extent of adult neurogenesis and the morphological features of immature neurons. We found that repeated sessions of iTBS did not significantly increase the amount of neurogenesis or affect the gross dendritic morphology of new neurons, and there were no sex differences in neurogenesis rates or aspects of afferent morphology. In contrast, efferent properties of newborn neurons varied as a function of sex and stimulation. Chronic iTBS increased the size of mossy fibre terminals, which synapse onto Cornu Ammonis 3 (CA3) pyramidal neurons, but only in males. iTBS also increased the number of terminal-associated filopodia, putative synapses onto inhibitory interneurons but only in male mice. This efferent plasticity could result from a general trophic effect, or it could reflect accelerated maturation of immature neurons. Given the important role of mossy fibre synapses in hippocampal learning, our results identify a neurobiological effect of iTBS that might be associated with sex-specific changes in cognition.

VX-765 Alleviates β-Amyloid Deposition and Secondary Degeneration in the Ipsilateral Hippocampus and Ameliorates Cognitive Decline after Focal Cortical Infarction in Rats

Focal cortical infarction leads to secondary degeneration of the ipsilateral hippocampus, which is associated with poststroke cognitive impairment. VX-765 is a potent small-molecule caspase-1 inhibitor that protects against central nervous system diseases. The present study aimed to determine the protective effects of VX-765 on β-amyloid (Aβ) deposition and secondary degeneration in the hippocampus as well as cognitive decline after cortical infarction. Sprague-Dawley rats were used to establish a distal middle cerebral artery occlusion (dMCAO) model and randomly divided into the vehicle and VX-765 groups. Rats in the vehicle and VX-765 groups, respectively, were subcutaneously injected with VX-765 (50 mg/kg/d) and an isopycnic vehicle once a day for 28 days, starting 1 h after dMCAO. At the end of this 28-day period, cognitive impairment was evaluated with the Morris water maze, and secondary hippocampal damage was evaluated with Nissl staining and immunostaining methods. Neuronal damage and pyroptosis were detected by TUNEL and immunoblotting. The results revealed that VX-765 treatment ameliorated poststroke cognitive dysfunction after ischemia. VX-765 reduced Aβ deposition, neuronal loss, and glial activation compared with the vehicle control. In addition, VX-765 treatment increased BDNF levels and normalized synaptophysin protein levels in the hippocampus after cortical infarction. Notably, VX-765 treatment significantly reduced the expression of the pyroptosis-related molecules caspase-1, NLRP3, apoptosis-associated speck-like protein (ASC), gasdermin D, IL-1β, and IL-18. Additionally, VX-765 significantly decreased the numbers of TUNEL-positive cells and the levels of Bax and cleaved caspase-3 (cC3) and enhanced the levels of Bcl-2 and Bcl-xl after ischemia. Inflammatory pathways, such as the NF-κB and mitogen-activated protein kinase (MAPK) pathways, were inhibited by VX-765 treatment after ischemia. These findings revealed that VX-765 reduced Aβ deposition, pyroptosis, and apoptosis in the ipsilateral hippocampus, which may be associated with reduced secondary degeneration and cognitive decline following focal cortical infarction.

Effectiveness and safety of repetitive transcranial magnetic stimulation on memory disorder in stroke: A protocol for systematic review and meta-analysis

BACKGROUND

Approximately 23% to 55% of patients have memory impairments with a greatly negative effect on daily life 3 months after stroke. Repetitive transcranial magnetic stimulation (rTMS) has been widely used in the rehabilitation of stroke as it is safe, painless, and noninvasive. Moreover, few studies have investigated the effect of rTMS on poststroke memory disorder (PSMD). However, the efficacy of rTMS is not consistent and the optional stimulation frequency is unclear. Therefore, this protocol aims to evaluate the clinical effect and safety of rTMS on PSMD by analyzing results from randomized controlled trials.

METHODS

Search strategies will be performed on seven databases: PubMed, EMBASE, CENTRAL, Chinese Biomedical Literature Database (CBM), Chinese National Knowledge Infrastructure (CNKI), Wan Fang, and Technology Periodical Database (VIP). Only randomized controlled trials registered before August 2021 will be included. Additionally, the language will be limited to English or Chinese. For the outcome, we will focus on the Rivermead Behavioral Memory Test. Additionally, the Montreal Cognitive Assessment, Mini-mental State Examination, Modified Barthel Index, and advent events will be included. Two authors will independently select the study, extract data, and assess quality. Moreover, disagreements will be resolved by the third author. STATA 14 and Review Manager 5.4 will be used to perform the analysis. We will evaluate bias risk in accordance with the Cochrane Handbook for Systematic Reviews of Interventions. To assess the quality of evidence, the Grading of Recommendations Assessment, Development, and Evaluation method will be employed.

RESULTS

This study will provide a comprehensive analysis of the current evidence on rTMS for PSMD.

CONCLUSION

A reliable conclusion regarding whether rTMS is an effective and safe intervention for patients with PSMD and the effect of stimulation frequency and sham stimulation will be provided. This study will provide new insights for TMS in treating PSMD, and offer appropriate treatmentoptions to patients and clinicians.

PROSPERO REGISTRATION NUMBER

CRD42021282439.

Physical Stimulation Combined with Biomaterials Promotes Peripheral Nerve Injury Repair

Peripheral nerve injury (PNI) is a clinical problem with high morbidity that can cause severe damage. Surgical suturing or implants are usually required due to the slow speed and numerous factors affecting repair after PNI. An autologous nerve graft is the gold standard for PNI repair among implants. However, there is a potential problem of the functional loss of the donor site. Therefore, tissue-engineered nerve biomaterials are often used to bridge the gap between nerve defects, but the therapeutic effect is insufficient. In order to enhance the repair effect of nerve biomaterials for PNI, researchers are seeking to combine various stimulation elements, such as the addition of biological factors such as nerve growth factors or physical factors such as internal microstructural modifications of catheters and their combined application with physical stimulation therapy. Physical stimulation therapy is safer, is more convenient, and has more practical features than other additive factors. Its feasibility and convenience, when combined with nerve biomaterials, provide broader application prospects for PNI repair, and has therefore become a research hot spot. This paper will review the combined application of physical stimulation and biomaterials in PNI repair in recent years to provide new therapeutic ideas for the future use of physical stimulation in PNI repair.

Selective activation of ABCA1/ApoA1 signaling in the V1 by magnetoelectric stimulation ameliorates depression via regulation of synaptic plasticity

Emerging evidence suggests that dysfunction of the visual cortex may be involved in major depressive disorder (MDD). However, the underlying mechanisms remain unclear. We previously established that combined magnetic stimulation system treatment (c-MSST) resulted in an antidepressant effect in mice. In the present study, we found that V1-targeted c-MSST induced significant antidepressant effects in chronic unpredictable mild stress (CUMS)- and lipopolysaccharide (LPS)-treated mice. Proteomic screening investigation and repeatable validation revealed that expression of the V1 neuronal ATP-binding cassette transporter A1 (ABCA1) and apolipoprotein A-1 (ApoA1) was downregulated in CUMS mice, an effect that was normalized by c-MSST. Neuron-specific knockdown of ABCA1 in V1 blocked c-MSST’s antidepressant effects. Mechanistically, CUMS reduced dendritic spine density and long-term plasticity in V1, and these deficits were reversed by c-MSST. V1-targeted c-MSST was found to induce rapid antidepressant effects that are mediated by alterations in synaptic plasticity via the ABCA1/ApoA1 signaling pathway in V1.

•

c-MSST targeting the primary visual cortex induced antidepressant effects

•

ABCA1/ApoA1 signaling contributed to c-MSST-mediated antidepressant actions

•

Magnetic stimulation of primary visual cortex enhanced synaptic plasticity

•

Circulating levels of ApoA1 were lower in patients with depression

The Preventive and Therapeutic Effect of Repetitive Transcranial Magnetic Stimulation on Radiation-Induced Brain Injury in Mice

PURPOSE

To clarify the preventive and therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) on brain injury induced by X-ray cranial irradiation, preliminarily identify the mechanism and provide a novel clinical approach for the prevention and treatment of radiation-induced brain injury (RBI).

MATERIALS AND METHODS

Male C57BL/6 mice were randomly divided into the sham group, large fractionated dose (5 Gy ×4 d) group, large fractionated dose + rTMS (5 Gy ×4 d + rTMS) group, conventional fractionated dose (2 Gy ×10 d) group and conventional fractionated dose + rTMS (2 Gy ×10 d + rTMS) group. After cranial irradiation and rTMS, behavioral experiments, morphological staining and molecular biology experiments were performed. We further determined the mechanism of rTMS on the prevention and treatment of RBI, including changes in hippocampal neuronal apoptosis, neural stem cell (NSC) proliferation and differentiation, and neuronal synaptic plasticity.

RESULTS

rTMS alleviated the negative effects of cranial radiation on the general health of mice and promoted their recovery. rTMS ameliorated the impairment of spatial learning and memory induced by cranial radiation, and this beneficial effect was more robust in the conventional fractionated dose group than the large fractionated dose group. Moreover, rTMS alleviated the alterations in hippocampal structure and neuronal death and had preventive and therapeutic effects against RBI. In addition, rTMS reduced hippocampal cell apoptosis, promoted NSC proliferation and differentiation in the hippocampus after cranial irradiation, and enhanced neuronal synaptic plasticity in the hippocampus. Subsequent studies showed that rTMS upregulated the expression of learning- and memory-related proteins.

CONCLUSION

rTMS could alleviate learning and memory impairment caused by RBI, and the preventive and therapeutic effects of rTMS were better for the conventional fraction radiation paradigms.

Magnetic Fields and Magnetically Stimulated Gold-Coated Superparamagnetic Iron Oxide Nanoparticles Differentially Modulate L-Type Voltage-Gated Calcium Channel Activity in Midbrain Neurons

Nanoparticles (NPs) generate localized magnetic forces during magnetic stimulation, which can, in turn, modulate neuronal excitability and regulate downstream signaling in neurons. In agreement with this idea, under static magnetic field stimulation (SMS), gold-coated superparamagnetic iron oxide (Au-SPIO) core-shell nanoparticles (NPs) can promote and guide the direction of neurite outgrowth. Inspired by these promising results, this study investigates how SMS on Au-SPIO (SMS-Au-SPIO) affects the physiology of midbrain neurons. Transmission electron microscopy (TEM) images showed quasispherical shapes and a diameter of 20 ± 4 nm of Au-SPIO NPs synthesized by forming an Au layer on SPIO using a hydroxylamine hydrochloride-assisted seed growth method. We found that SMS enhanced intracellular uptake of Au-SPIO and that SMS-Au-SPIO resulted in a delayed blockade of an L-type voltage-gated Ca2+ channel (VGCC) in midbrain neurons. Specifically, the frequency of spontaneous L-type VGCC-induced Ca2+ fluxes was significantly reduced in midbrain neurons exposed to either SMS or Au-SPIO or SMS-Au-SPIO. A power spectrum density analysis of Ca2+ fluxes showed that SMS decreased Ca2+ fluxes amplitudes (<0.1 Hz) before and after L-type VGCC blockade. By contrast, SMS-Au-SPIO decreased Ca2+ flux amplitudes only after L-type VGCC blockade, suggesting a modulation of L-type VGCC by SMS-Au-SPIO. Finally, while SMS alone induced apoptosis of dopaminergic (DA) neurons, SMS-Au-SPIO did not. Thus, SMS and SMS-Au-SPIO differentially modulate L-type VGCC-mediated Ca2+ fluxes, and downstream apoptotic signaling in midbrain neurons, implying the possible application of SMS-Au-SPIO as a drug delivery strategy to treat Parkinson's disease.

Comparisons of Neurotrophic Effects of Mesenchymal Stem Cells Derived from Different Tissues on Chronic Spinal Cord Injury Rats

Cell-based therapies with mesenchymal stem cells (MSCs) are considered as promising strategies for spinal cord injury (SCI). MSCs have unique characteristics due to differences in the derived tissues. However, relatively few studies have focused on differences in the therapeutic effects of MSCs derived from different tissues. In this study, the therapeutic effects of adipose tissue-derived MSCs, bone marrow-derived MSCs, and cranial bone-derived MSCs (cMSCs) on chronic SCI model rats were compared. MSCs were established from the collected adipose tissue, bone marrow, and cranial bone. Neurotrophic factor expression of each MSC type was analyzed by real-time PCR. SCI rats were established using the weight-drop method and transplanted intravenously with MSCs at 4 weeks after SCI. Hindlimb motor function was evaluated from before injury to 4 weeks after transplantation. Endogenous neurotrophic factor and neural repair factor expression in spinal cord (SC) tissue were examined by real-time PCR and western blot analyses. Although there were no differences in the expression levels of cell surface markers and multipotency, expression of Bdnf, Ngf, and Sort1 (Nt-3) was relatively higher in cMSCs. Transplantation of cMSCs improved motor function of chronic SCI model rats. Although there was no difference in the degree of engraftment of transplanted cells in the injured SC tissue, transplantation of cMSCs enhanced Bdnf, TrkB, and Gap-43 messenger RNA expression and synaptophysin protein expression in injured SC tissue. As compared with MSCs derived other tissues, cMSCs highly express many neurotrophic factors, which improved motor function in chronic SCI model rats by promoting endogenous neurotrophic and neural plasticity factors. These results demonstrate the efficacy of cMSCs in cell-based therapy for chronic SCI.

Association between Blood Pressure, Blood Pressure Variability, and Post-Stroke Cognitive Impairment

After stroke, dynamic changes take place from necrotic-apoptotic continuum, inflammatory response to poststroke neurogenesis, and remodeling of the network. These changes and baseline brain pathology such as small vessel disease (SVD) and amyloid burden may be associated with the occurrence of early or late poststroke cognitive impairment (PSCI) or dementia (PSD), which affect not only stroke victims but also their families and even society. We reviewed the current concepts and understanding of the pathophysiology for PSCI/PSD and identified useful tools for the diagnosis and the prediction of PSCI in serological, CSF, and image characteristics. Then, we untangled their relationships with blood pressure (BP) and blood pressure variability (BPV), important but often overlooked risk factors for PSCI/PSD. Finally, we provided evidence for the modifying effects of BP and BPV on PSCI as well as pharmacological and non-pharmacological interventions and life style modification for PSCI/PSD prevention and treatment.

The protective function of taurine on pesticide-induced permanent neurodevelopmental toxicity in juvenile rats

Numerous studies have confirmed that prenatal or early postnatal exposure to pesticides can lead to functional deficits in the developing brain. This study aimed to investigate whether combined exposure to paraquat (PQ) and maneb (MB) during puberty could cause permanent toxic effects in the neural system of rats. In addition, the neuroprotective function of taurine (T) and its possible mechanism were investigated. Rats were administered PQ + MB intragastrically for 12 continuous weeks, while taurine dissolved in water was fed to the rats for 24 continuous weeks. In the behavioral tests, the rats' trajectories became complex, and the reaction latencies and mistake frequencies increased. Significant changes were found in the hippocampal neurons of the PQ + MB groups but not in the taurine treatment groups. PQ + MB stimulated cAMP to reduce the production of protein kinase A (PKA) and inhibited the activation of other elements, such as brain-derived neurotrophic factor (BDNF), cAMP response element binding protein (CREB), phospho-CREB (p-CREB), immediate-early genes (IEGs)Arc, and c-Fos. Importantly, taurine regulated the level of cAMP and the expression of the abovementioned proteins. Together, our findings implied that adolescent exposure to PQ + MB may impact the behavior and cognitive function of rats via the cAMP-PKA-CREB signaling pathway, while taurine may in turn exert neuroprotection by diminishing these impacts.

The mTOR/NF-κB Pathway Mediates Neuroinflammation and Synaptic Plasticity in Diabetic Encephalopathy

Diabetic encephalopathy, a severe complication of diabetes mellitus, is characterized by neuroinflammation and aberrant synaptogenesis in the hippocampus leading to cognitive decline. Mammalian target of rapamycin (mTOR) is associated with cognition impairment. Nuclear factor-κB (NF-κB) is a transcription factor of proinflammatory cytokines. Although mTOR has been ever implicated in processes occurring in neuroinflammation, the role of this enzyme on NF-κB signaling pathway remains unclear in diabetic encephalopathy. In the present study, we investigated whether mTOR regulates the NF-κB signaling pathway to modulate inflammatory cytokines and synaptic plasticity in hippocampal neurons. In vitro model was constructed in mouse HT-22 hippocampal neuronal cells exposed to high glucose. With the inhibition of mTOR or NF-κB by either chemical inhibitor or short-hairpin RNA (shRNA)-expressing lentivirus-vector, we examined the effects of mTOR/NF-κB signaling on proinflammatory cytokines and synaptic proteins. The diabetic mouse model induced by a high-fat diet combined with streptozotocin injection was administrated with rapamycin (mTOR inhibitor) and PDTC (NF-κB inhibitor), respectively. High glucose significantly increased mTOR phosphorylation in HT-22 cells. While inhibiting mTOR by rapamycin or shmTOR significantly suppressed high glucose-induced activation of NF-κB and its regulators IKKβ and IκBα, suggesting mTOR is the upstream regulator of NF-κB. Furthermore, inhibiting NF-κB by PDTC and shNF-κB decreased proinflammatory cytokines expression (IL-6, IL-1β, and TNF-α) and increased brain-derived neurotrophic factor (BDNF) and synaptic proteins (synaptophysin and PSD-95) in HT-22 cells under high glucose conditions. Besides, the mTOR and NF-κB inhibitors improved cognitive decline in diabetic mice. The inhibition of mTOR and NF-κB suppressed mTOR/NF-κB signaling pathway, increased synaptic proteins, and improved ultrastructural synaptic plasticity in the hippocampus of diabetic mice. Activating mTOR/NF-κB signaling pathway regulates the pathogenesis of diabetic encephalopathy, such as neuroinflammation, synaptic proteins loss, and synaptic ultrastructure impairment. The findings provide the implication that mTOR/NF-κB is potential new drug targets to treat diabetic encephalopathy.

Transcranial Magnetic Stimulation in Psychiatry: Is There a Need for Electric Field Standardization?

Single-pulse and repetitive transcranial magnetic stimulation (rTMS) are used in clinical practice for diagnostic and therapeutic purposes. However, rTMS-based therapies that lead to a significant and sustained reduction in neuropsychiatric symptoms remain scarce. While it is generally accepted that the stimulation frequency plays a crucial role in producing the therapeutic effects of rTMS, less attention has been dedicated to determining the role of the electric field strength. Conventional threshold-based intensity selection approaches, such as the resting motor threshold, produce variable stimulation intensities and electric fields across participants and cortical regions. Insufficient standardization of electric field strength may contribute to the variability of rTMS effects and thus therapeutic success. Computational approaches that can prospectively optimize the electric field and standardize it across patients and cortical targets may overcome some of these limitations. Here, we discuss these approaches and propose that electric field standardization will be instrumental for translational science frameworks (e.g., multiscale modeling and basic science approaches) aimed at deciphering the subcellular, cellular, and network mechanisms of rTMS. Advances in understanding these mechanisms will be important for optimizing rTMS-based therapies in psychiatry.

Astrocytes contribute to the neuronal recovery promoted by high-frequency repetitive magnetic stimulation in in vitro models of ischemia

After decades of effort, there are no effective clinical treatments to induce the recovery of ischemia-injured tissues, and among the several strategies that have been explored, repetitive transcranial magnetic stimulation has proven to be one of the most promising, with beneficial effects in limb motor function, aphasia, hemispatial neglect, or dysphagia. Despite the clinical evidences, little is known about the mechanisms underlying those effects. The present study aimed to explore the cellular and molecular effects of high-frequency repetitive magnetic stimulation (HF-rMS) on an in vitro model of ischemia. Using primary cortical cultures exposed to oxygen and glucose deprivation followed by reperfusion, we observed that HF-rMS treatment prevents the ischemia-induced neuronal death by 21.2%, and the neurite degeneration triggered by ischemia. Our results also demonstrate that with this treatment there is an increase of 89.2% on the number cells expressing ERK1/2, of 20.1% on the number of cells expressing c-Fos, and a synaptogenic effect, through an increase of 62.9% in the number of synaptic puncta as well as of 49.4% in their intensity. Interestingly, our results indicate that astrocytes are crucial to the beneficial effects triggered by HF-rMS after ischemia, thus suggesting a direct effect of HF-rMS on these cells. The modulation of astrocytes with this non-invasive brain stimulation technique is a promising approach to promote the recovery of ischemia-induced injured tissues; however, it is essential to understand how these effects can be modulated in order to optimize the protocols and enhance the beneficial outcomes.

Interleukin 10 Restores Lipopolysaccharide-Induced Alterations in Synaptic Plasticity Probed by Repetitive Magnetic Stimulation

Systemic inflammation is associated with alterations in complex brain functions such as learning and memory. However, diagnostic approaches to functionally assess and quantify inflammation-associated alterations in synaptic plasticity are not well-established. In previous work, we demonstrated that bacterial lipopolysaccharide (LPS)-induced systemic inflammation alters the ability of hippocampal neurons to express synaptic plasticity, i.e., the long-term potentiation (LTP) of excitatory neurotransmission. Here, we tested whether synaptic plasticity induced by repetitive magnetic stimulation (rMS), a non-invasive brain stimulation technique used in clinical practice, is affected by LPS-induced inflammation. Specifically, we explored brain tissue cultures to learn more about the direct effects of LPS on neural tissue, and we tested for the plasticity-restoring effects of the anti-inflammatory cytokine interleukin 10 (IL10). As shown previously, 10 Hz repetitive magnetic stimulation (rMS) of organotypic entorhino-hippocampal tissue cultures induced a robust increase in excitatory neurotransmission onto CA1 pyramidal neurons. Furthermore, LPS-treated tissue cultures did not express rMS-induced synaptic plasticity. Live-cell microscopy in tissue cultures prepared from a novel transgenic reporter mouse line [C57BL/6-Tg(TNFa-eGFP)] confirms that ex vivo LPS administration triggers microglial tumor necrosis factor alpha (TNFα) expression, which is ameliorated in the presence of IL10. Consistent with this observation, IL10 hampers the LPS-induced increase in TNFα, IL6, IL1β, and IFNγ and restores the ability of neurons to express rMS-induced synaptic plasticity in the presence of LPS. These findings establish organotypic tissue cultures as a suitable model for studying inflammation-induced alterations in synaptic plasticity, thus providing a biological basis for the diagnostic use of transcranial magnetic stimulation in the context of brain inflammation.

Transcranial Magnetic Stimulation-Induced Plasticity Mechanisms: TMS-Related Gene Expression and Morphology Changes in a Human Neuron-Like Cell Model

Transcranial Magnetic Stimulation (TMS) is a form of non-invasive brain stimulation, used to alter cortical excitability both in research and clinical applications. The intermittent and continuous Theta Burst Stimulation (iTBS and cTBS) protocols have been shown to induce opposite after-effects on human cortex excitability. Animal studies have implicated synaptic plasticity mechanisms long-term potentiation (LTP, for iTBS) and depression (LTD, for cTBS). However, the neural basis of TMS effects has not yet been studied in human neuronal cells, in particular at the level of gene expression and synaptogenesis. To investigate responses to TBS in living human neurons, we differentiated human SH-SY5Y cells toward a mature neural phenotype, and stimulated them with iTBS, cTBS, or sham (placebo) TBS. Changes in (a) mRNA expression of a set of target genes (previously associated with synaptic plasticity), and (b) morphological parameters of neurite outgrowth following TBS were quantified. We found no general effects of stimulation condition or time on gene expression, though we did observe a significantly enhanced expression of plasticity genes NTRK2 and MAPK9 24 h after iTBS as compared to sham TBS. This specific effect provides unique support for the widely assumed plasticity mechanisms underlying iTBS effects on human cortex excitability. In addition to this protocol-specific increase in plasticity gene expression 24 h after iTBS stimulation, we establish the feasibility of stimulating living human neuron with TBS, and the importance of moving to more complex human in vitro models to understand the underlying plasticity mechanisms of TBS stimulation.

Enhancement of Neural Stem Cell Proliferation in Rats with Spinal Cord Injury by a Combination of Repetitive Transcranial Magnetic Stimulation (rTMS) and Human Umbilical Cord Blood Mesenchymal Stem Cells (hUCB-MSCs)

BACKGROUND This study was designed to explore the combined effects of repetitive transcranial magnetic stimulation (rTMS) and human umbilical cord blood mesenchymal stem cells (hUCB-MSCs) transplantation on neural stem cell proliferation in rats with spinal cord injury (SCI). MATERIAL AND METHODS SCI was induced in 90 rats by laminectomy at T10. Fifteen rats each were treated with 0.5 Hz rTMS or 10 Hz rTMS or underwent hUCB-MSC transplantation; 15 each were treated with 0.5 Hz rTMS+hUCB-MSCs or 10 Hz rTMS+hUCB-MSCs; and 15 were untreated (control group). The Basso, Beattie, and Bresnahan (BBB) scores and motor evoked potentials (MEPs) were measured, and all rats underwent biotin dextran-amine (BDA) tracing of the corticospinal tract (CST). The levels of expression of neural stem cell proliferation related proteins, including BrdU, nestin, Tuj1, Ng2+ and GFAP, were measured, and the levels of bFGF and EGF determined by Western blotting. RESULTS BBB scores and MEPs were increased after rTMS and hUCB-MSC transplantation, while histologically determined SCI-induced neuron apoptosis was attenuated. The numbers of BDA-positive fibers and Brdu-, nestin- and Tuj1-positive cells were markedly increased and the numbers of Ng2+- and GFAP-positive cells were markedly decreased following treatment with rTMS alone or rTMS plus hUCB-MSC transplantation. The levels of expression of bFGF and EGF were significantly upregulated following rTMS treatment and hUCB-MSC transplantation. Higher performance was observed after combined treatment with rTMS and hUCB-MSC transplantation than after either alone. CONCLUSIONS The combination of rTMS treatment and hUCB-MSC transplantation could attenuate SCI-induced neural stem cell apoptosis and motor dysfunction in rats.

Regulation of gene expression after combined scalp acupuncture and transcranial magnetic stimulation in middle cerebral artery occlusion mice

BACKGROUND

The effect of combined repetitive transcranial magnetic stimulation (rTMS) and scalp acupuncture stimulation (SAS) on middle cerebral artery occlusion (MCAO) mice has not yet been reported. The regulation of gene expression after combined stimulation remains unclear.

OBJECTIVE

To analyze gene expression patterns through ribonucleic acid (RNA) sequencing.

METHODS

Thirty-six 8-weeks-old C57BL/6J male mice weighing 50-60 grams were used for this experiment. The MCAO was induced with 60-min occlusion and subsequent reperfusion of the middle cerebral artery. Experimental mice were randomly assigned to four groups, with nine mice in each group, as follows: control group (no treatment), SAS group (10 minutes SAS), rTMS group (1 Hz rTMS), and combined group (1 Hz rTMS and SAS). Stimulation was performed from the 3rd day to the 7th day after the induction of MCAO. All mice were sacrificed, and brain tissues were taken from the motor area of the MCAO lesion. We analyzed their gene expression profiles using RNA sequencing technology.

RESULTS

After stimulation, the grip strength increased in the SAS and rTMS group compared to the control and combined group. The nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) was the key up-regulated protein in the SAS group while src homologus and collagene gene (SHC) and p90 ribosomal protein S6 kinases (p90RSK) were key up-regulated proteins in the rTMS group. However, the C-terminal src kinase-homologous kinase (CHK) was down-regulated whereas p90RSK was up-regulated in the combined group based on the RNA sequencing analysis.

CONCLUSIONS

Each stimulation method showed different patterns with neurotrophin signaling pathway including NFκB, SHC, p90RSK, and CHK. These can be used in further mechanistic studies about gene expression related to neurorecovery.

Repetitive Transcranial Magnetic Stimulation Elicits Antidepressant- and Anxiolytic-like Effect via Nuclear Factor-E2-related Factor 2-mediated Anti-inflammation Mechanism in Rats

Repetitive transcranial magnetic stimulation (rTMS) treatment is widely accepted as an evidence-based treatment option for depression and anxiety. However, the underlying mechanism of this treatment maneuver has not been clearly understood. The chronic unpredictable mild stress (CUMS) procedure was used to establish depression and anxiety-like behavior in rats. The rTMS was performed with a commercially available stimulator for seven consecutive days, and then depression and anxiety-like behaviors were subsequently measured. The expression of nuclear factor-E2-related factor 2 (Nrf2) was measured by western-blot, and the level of tumor necrosis factor-α (TNF-α), inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), and interleukin-6 (IL-6) was measured with Enzyme-linked immunesorbent assay (ELISA) analyzing kits. Furthermore, a small interfering RNA was employed to knockdown Nrf2, after which the neurobehavioral assessment, Nrf2 nuclear expression, and the amount of inflammation factors were evaluated. Application of rTMS exhibited a significant antidepressant and anxiolytic-like effect, which was associated with the increased Nrf2 nuclear translocation and reduced level of TNF-α, iNOS, IL-1β, and IL-6 in the hippocampus. Following Nrf2 silencing, the antidepressant and anxiolytic-like effect produced by rTMS was abolished. Moreover, the elevated Nrf2 nuclear translocation, and the reduced production of TNF-α, iNOS, IL-1β, and IL-6 in hippocampus mediated by rTMS, were reversed by Nrf2 knockdown. Together, these results reveal that the Nrf2-induced anti-inflammation effect is crucial in regulating antidepressant-related behaviors produced by rTMS.

The effect of magnetic stimulation on differentiation of human induced pluripotent stem cells into neuron

The effect of stem cell transplantation in the treatment of neural lesions is so far not satisfactory. Magnetic stimulation is a feasible exogenous interference to improve transplantation outcome. However, the effect of magnetic stimulation on the differentiation of induced pluripotent stem cells (iPSCs) into neuron has not been studied. In this experiment, an in vitro neuron differentiation system from human iPSCs were established and confirmed. Three magnetic stimuli (high frequency [HF], low frequency [LF], intermittent theta-burst stimulation [iTBS]) were applied twice a day during the differentiation process. Immunofluorescence and quantitative polymerase chain reaction (Q-PCR) were performed to analyze the effect of magnetic stimulation. Neural stem cells were obtained on day 12, manifested as floating neurospheres expressing neural precursor markers. All groups can differentiate into neurons while glial cell markers were not detected. Both Immunofluorescence and PCR results showed LF and iTBS increased the transcription and expression of neuronal nuclei (NeuN). HF significantly increased vesicular glutamate transporters2 transcription while iTBS promoted transcription of both synaptophysin and postsynaptic density protein 95. These results indicate that LF and iTBS can promote the generation of mature neurons from human iPSCs; HF may promote differentiate into glutamatergic neurons while iTBS may promote synapse formation during the differentiation.

Combined effect of repetitive transcranial magnetic stimulation and physical exercise on cortical plasticity

Physical exercise can minimize dysfunction and optimize functional motor recovery after stroke by modulating cortical plasticity. However, the limitation of physical exercise is that large amounts of time and effort are necessary to significantly improve motor function, and even then, substantial exercise may not be sufficient to normalize the observed improvements. Thus, interventions that could be used to strengthen physical exercise-induced neuroplasticity may be valuable in treating hemiplegia after stroke. Repetitive transcranial magnetic stimulation seems to be a viable strategy for enhancing such plasticity. As a non-invasive cortical stimulation technique, repetitive transcranial magnetic stimulation is able to induce long-term plastic changes in the motor system. Recently, repetitive transcranial magnetic stimulation was found to optimize the plastic changes caused by motor training, thereby enhancing the long-term effects of physical exercise in stroke patients. Therefore, it is believed that the combination of repetitive transcranial magnetic stimulation and physical exercise may represent a superior method for restoring motor function after stroke.

rTMS Ameliorates Prenatal Stress-Induced Cognitive Deficits in Male-Offspring Rats Associated With BDNF/TrkB Signaling Pathway

BACKGROUND

Growing evidences suggest that brain-derived neurotrophic factor/tropomyosin receptor kinase B (BDNF/TrkB) plays a key role in the regulation of hippocampal synaptic plasticity in a prenatal stress (PNS) rat model. Repetitive transcranial magnetic stimulation (rTMS) is currently being acknowledged to affect attention and memory in both preclinical and clinical studies, although the mechanism is still unclear.

OBJECTIVE

The current study aimed to explore whether a whole brain rTMS (5 Hz, 14 days) could ameliorate cognitive dysfunction-induced PNS in male offspring, and examine if the positive effect of rTMS was associated with the BDNF/TrkB signaling in the hippocampus.

METHODS

The rats were randomly divided into 5 groups: CON, PNS, PNS + rTMS, PNS + rTMS + DMSO (dimethyl sulfoxide), and PNS + rTMS + K252a. Spatial cognition was evaluated by using Morris water maze test. Following behavioral assessment, both paired-pulse facilitation and long-term potentiation were recorded from Schaffer collaterals to CA1 region in the hippocampus. Synaptic, apoptotic, and BDNF/TrkB signaling proteins were measured by Western blot.

RESULTS

PNS-exposed offspring exhibited cognitive deficits, long-term potentiation inhibition in the hippocampus, the decrease of synaptic and BDNF/TrkB signaling proteins expression, apoptosis, and reduced number of cells in the CA1 region. Five-hertz rTMS significantly alleviated the PNS-induced abnormalities. However, the effect of rTMS was antagonized by intracerebroventricular infusion of K252a (a TrkB inhibitor).

CONCLUSIONS

The findings suggest that 5-Hz rTMS significantly improves the impairment of spatial cognition and hippocampal synaptic plasticity, which is possibly associated with the activation of BDNF/TrkB signaling.

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.

High Frequency Repetitive Transcranial Magnetic Stimulation Alleviates Cognitive Impairment and Modulates Hippocampal Synaptic Structural Plasticity in Aged Mice

Normal aging is accompanied by hippocampus-dependent cognitive impairment, which is a risk factor of Alzheimer’s disease. This study aims to investigate the effect of high frequency-repetitive transcranial magnetic stimulation (HF-rTMS) on hippocampus-dependent learning and memory in aged mice and explore its underlying mechanisms. Forty-five male Kunming mice (15 months old) were randomly divided into three groups: aged sham, 5 Hz rTMS, and 25 Hz rTMS. Two sessions of 5 Hz or 25 Hz rTMS comprising 1,000 pulses in 10 trains were delivered once a day for 14 consecutive days. The aged sham group was treated by the reverse side of the coil. In the adult sham group, 15 male Kunming mice (3 months old) were treated the same way as the aged sham group. A Morris water maze (MWM) was conducted following the stimulation, and synaptic ultrastructure was observed through a transmission electron microscope. HF-rTMS improved spatial learning and memory impairment in the aged mice, and 5 Hz was more significant than 25 Hz. Synaptic plasticity-associated gene profiles were modified by HF-rTMS, especially neurotrophin signaling pathways and cyclic adenosine monophosphate response element binding protein (CREB) cofactors. Compared to the aged sham group, synaptic plasticity-associated proteins, i.e., synaptophysin (SYN) and postsynaptic density (PSD)-95 were increased; brain-derived neurotrophic factor (BDNF) and phosphorylated CREB (pCREB) significantly increased after the 5 Hz HF-rTMS treatment. Collectively, our results suggest that HF-rTMS ameliorated cognitive deficits in naturally aged mice. The 5 Hz rTMS treatment significantly enhanced synaptic structural plasticity and activated the BDNF/CREB pathway in the hippocampus.

HMG-CoA Reductase Inhibitors Attenuate Neuronal Damage by Suppressing Oxygen Glucose Deprivation-Induced Activated Microglial Cells

Ischemic stroke is usually followed by inflammatory responses mediated by microglia. However, the effect of statins on directly preventing posthypoxia microglia inflammatory factors to prevent injury to surrounding healthy neurons is unclear. Atorvastatin and rosuvastatin, which have different physical properties regarding their lipid and water solubility, are the most common HMG-CoA reductase inhibitors (statins) and might directly block posthypoxia microglia inflammatory factors to prevent injury to surrounding neurons. Neuronal damage and microglial activation of the peri-infarct areas were investigated by Western blotting and immunofluorescence after 24 hours in a middle cerebral artery occlusion (MCAO) rat model. The decrease in neurons was in accordance with the increase in microglia, which could be reversed by both atorvastatin and rosuvastatin. The effects of statins on blocking secretions from posthypoxia microglia and reducing the secondary damage to surrounding normal neurons were studied in a coculture system in vitro. BV2 microglia were cultured under oxygen glucose deprivation (OGD) for 3 hours and then cocultured following reperfusion for 24 hours in the upper wells of transwell plates with primary neurons being cultured in the bottom wells. Inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and cyclooxygenase-2 (COX2), which are activated by the nuclear factor-kappa B (NF-κB) signaling pathway in OGD-induced BV2 microglia, promoted decreased release of the anti-inflammatory cytokine IL-10 and apoptosis of neurons in the coculture systems according to ELISA and Western blotting. However, pretreatment with atorvastatin or rosuvastatin significantly reduced neuronal death, synaptic injury, and amyloid-beta (Aβ) accumulation, which might lead to increased low-density lipoprotein receptors (LDLRs) in BV2 microglia. We concluded that the proinflammatory mediators released from postischemia damage could cause damage to surrounding normal neurons, while HMG-CoA reductase inhibitors prevented neuronal apoptosis and synaptic injury by inactivating microglia through blocking the NF-κB signaling pathway.

Memory Integration as a Challenge to the Consolidation/Reconsolidation Hypothesis: Similarities, Differences and Perspectives

We recently proposed that retrograde amnesia does not result from a disruption of the consolidation/reconsolidation processes but rather to the integration of the internal state induced by the amnesic treatment within the initial memory. Accordingly, the performance disruption induced by an amnesic agent does not result from a disruption of the memory fixation process, but from a difference in the internal state present during the learning phase (or reactivation) and at the later retention test: a case of state-dependency. In the present article, we will review similarities and differences these two competing views may have on memory processing. We will also consider the consequences the integration concept may have on the way memory is built, maintained and retrieved, as well as future research perspectives that such a new view may generate.

Effects of repetitive magnetic stimulation on the growth of primarily cultured hippocampus neurons in vitro and their expression of iron-containing enzymes

Background: The mechanism of action of repetitive transcranial magnetic stimulation (rTMS) involves the generation of neuronal and action potentials utilizing induced currents in time-varying magnetic fields. However, the long-lasting and effective biological impact of magnetic stimulation does not appear to be completely explained by the transient magnetic field pulses. In this context, we hypothesized magnetic stimulation may affect the expression of iron-containing enzymes in neurons, mediating the long-lasting biological effects associated with this stimulus. Methods: Primarily cultured hippocampus neurons from SD rats were used as the cell model in this study. These were randomly divided into control, sham, and magnetic stimulation groups to probe into the effect of the magnetic field directly. The latter group received 40%, 60%, and 100% maximal stimulator output Tesla (1.68, 2.52, and 4.2 T) with low-frequency rTMS (1 Hz). The expression of iron-containing enzymes (catalase and aconitase) and non-ferrous enzymes (protein kinase A) was measured with Western blotting and ELISA. Results: The survival rates of neurons in the 40%T and 60%T groups were significantly increased in comparison to the controls (P<0.05), while those in the 100%T group showed cell damage, with slightly disturbed neurite connections and decreased survival rate. Furthermore, catalase and aconitase expression was higher in all of the stimulated groups in comparison to controls (P<0.05). On the other hand, the expression of the iron-containing enzymes decreased in the 100%T group in comparison with the 40%T and 60%T groups (P<0.05). Meanwhile, the expression of protein kinase A was not significantly increased in the groups which underwent magnetic stimulation. Conclusion: rTMS may increase the expression of ferrous enzymes but does not have a strong effect on non-ferrous enzymes. Excessive intensity of magnetic stimulation may reduce neuronal survival rate and affect the expression of iron-containing enzymes. The mechanism underlying the lasting effect of rTMS may be related to the increase of ferriferous expression induced by magnetic stimulation, with a clear correlation with stimulation intensity.

Repetitive transcranial magnetic stimulation promotes functional recovery and differentiation of human neural stem cells in rats after ischemic stroke

Stem cells hold great promise as a regenerative therapy for ischemic stroke by improving functional outcomes in animal models. However, there are some limitations regarding the cell transplantation, including low rate of survival and differentiation. Repetitive transcranial magnetic stimulation (rTMS) has been widely used in clinical trials as post-stroke rehabilitation in ischemic stroke and has shown to alleviate functional deficits following stroke. The present study was designed to evaluate the therapeutic effects and mechanisms of combined human neural stem cells (hNSCs) with rTMS in a middle cerebral artery occlusion (MCAO) rat model. The results showed that human embryonic stem cells (hESCs) were successfully differentiated into forebrain hNSCs for transplantation and hNSCs transplantation combined with rTMS could accelerate the functional recovery after ischemic stroke in rats. Furthermore, this combination not only significantly enhanced neurogenesis and the protein levels of brain-derived neurotrophic factor (BDNF), but also rTMS promoted the neural differentiation of hNSCs. Our findings are presented for the first time to evaluate therapeutic benefits of combined hNSCs and rTMS for functional recovery after ischemic stroke, and indicated that the combination of hNSCs with rTMS might be a potential novel therapeutic target for the treatment of stroke.

Repetitive Transcranial Magnetic Stimulation (rTMS) Modulates Hippocampal Structural Synaptic Plasticity in Rats

Repetitive transcranial magnetic stimulation (rTMS) was shown to have therapeutic potential for some neurological and psychiatric disorders. Previous studies reported that low-frequency rTMS (</=1 Hz) affected synaptic plasticity in rats, however, there were few investigations to examine the possible effects of rTMS on structural synaptic plasticity changes in rats, which included the effects on synaptic morphology in the hippocampus, synaptic protein markers and Ca(2+)/calmodulin-dependent protein II (CaMKII). Sprague-Dawley rats were subject to 500 pulses of 0.5 Hz rTMS for 15 days, or sham stimulation. After last stimulation, transmission electron microscope (TEM) and real-time PCR were used to determine the effects of rTMS on synaptic plasticity. Results showed that rTMS could cause the change of structural synaptic plasticity, increase the expression of synaptic protein markers: synaptophysin (SYN) and increase the expression of CaMKII, relative to normal rats. suggesting a modulatory effect of chronic rTMS on synaptic plasticity that may be attributed to the increased expression of CaMKII in rats.

Planar coil-based contact-mode magnetic stimulation: synaptic responses in hippocampal slices and thermal considerations

Implantable magnetic stimulation is an emerging type of neuromodulation using coils that are small enough to be implanted in the brain. A major advantage of this method is that stimulation performance could be sustained even though the coil is encapsulated by gliosis due to foreign body reactions. Magnetic fields can induce indirect electric fields and currents in neurons. Compared to transcranial magnetic stimulation, the coil size used in implantable magnetic stimulation can be greatly reduced. However, the size reduction is accompanied by an increase in coil resistance. Hence, the coil could potentially damage neurons from the excess heat generated. Therefore, it is necessary to study the stimulation performance and possible thermal damage by implantable magnetic stimulation. Here, we devised contact-mode magnetic stimulation (CMS), wherein magnetic stimulation was applied to hippocampal slices through a customized planar-type coil underneath the slice in the contact mode. With acute hippocampal slices, we investigated the synaptic responses to examine the field excitatory postsynaptic responses of CMS and the temperature rise during CMS. A long-lasting synaptic depression was exhibited in the CA1 stratum radiatum after CMS, while the temperature remained in a safe range so as not to seriously affect the neural responses.

Repetitive transcranial magnetic stimulation inhibits Sirt1/MAO-A signaling in the prefrontal cortex in a rat model of depression and cortex-derived astrocytes

Repetitive transcranial magnetic stimulation (rTMS) is a useful monotherapy for depression or adjunctive therapy for resistant depression. However, the anti-depressive effects of different parameters and the underlying mechanisms remain unclear. Here, we aimed to assess the effect of rTMS with different parameters (1/5/10 Hz, 0.84/1.26 T) on the depressive-like behaviors, 5-hydroxytryptamine (5-HT), 5-HIAA (5-hydroxyindoleacetic acid) and DA and NE levels, and monoamine oxidase A (MAO-A) activity in chronic unpredictable stress-treated rats, along with the expression of sirtuin 1 (Sirt1) and MAO-A in the prefrontal cortex (PFC) and cortex-derived astrocytes from new-born rats. Moreover, the depressive-like behaviors were monitored following the transcranial injection of the Sirt1 inhibitor EX527 (1 mM) daily for 1 week. We found that rTMS treatment (5/10 Hz, 0.84/1.26 T) ameliorated depressive-like behaviors, increased 5-HT, DA and NE levels, decreased the 5-HIAA level and Sirt1 and MAO-A expression, and reduced MAO-A activity in the PFC. The depressive-like behaviors were also ameliorated after the transcranial injection of EX527. Importantly, rTMS (5/10 Hz, 0.84/1.26 T) inhibited Sirt1 and MAO-A expressions in astrocytes and Sirt1 knockdown with short hairpin RNA decreased MAO-A expression in astrocytes. These results suggest that the inhibition of Sirt1/MAO-A expression in astrocytes in the PFC may contribute to the different anti-depressive effects of rTMS with different parameters, and may also provide a novel insight into the mechanisms underlying major depressive disorder.

The Differential Effects of Repetitive Magnetic Stimulation in an In Vitro Neuronal Model of Ischemia/Reperfusion Injury

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive therapy that has been implicated in treatment of serious neurological disorders. However, the neurobiological mechanisms underlying the effects of rTMS remain unclear. Therefore, this study examined the differential effects of repetitive magnetic stimulation (rMS) in an in vitro neuronal model of ischemia/reperfusion (I/R) injury, depending on low and high frequency. Neuro-2a cells were differentiated with retinoic acid and established for in vitro neuronal model of I/R injury under a subsequent 3 h of oxygen and glucose deprivation/reoxygenation (OGD/R) condition. After the I/R injury, the differentiated neuronal cells were stimulated with rMS on day 1 and randomly divided into three groups: OGD/R+sham, OGD/R+low-frequency, and OGD/R+high-frequency groups. High-frequency rMS increases cell proliferation through activation of extracellular signal-regulated kinases and AKT-signaling pathway and inhibits apoptosis in OGD/R-injured cells. Furthermore, high-frequency rMS increases Ca²⁺–calmodulin-dependent protein kinase II (CaMKII)-cAMP-response element binding protein (CREB) signaling pathway, further leading to alternation of brain-derived neurotrophic factor expression and synaptic plasticity in OGD/R injured cells. These results verified the neurobiological mechanisms of frequency-dependent rMS in I/R injury-treated neuronal cells. These mechanisms will help develop more powerful and credible rTMS stimulation treatment protocols.