Direct modulation of microglial function by electrical field

Vibrotactile stimulation at 40 Hz inhibits Aβ-induced changes in SH-SY5Y, BV2 cells, and pericytes

Alzheimer's disease (AD) poses a major societal challenge, yet no definitive cure exists. Noninvasive brain stimulation methods, such as transcranial magnetic stimulation and transcranial direct current stimulation, have shown promise in alleviating cognitive symptoms associated with neurodegenerative disorders. This study investigated the effects of 40 Hz vibrotactile stimulation on AD-related cellular responses using SH-SY5Y neuroblastoma cells, primary human brain pericytes, and BV2 microglia. SH-SY5Y cells and brain pericytes treated with oligomeric beta-amyloid (Aβ) underwent 40 Hz vibrational stimulation for varying durations. Cell viability was determined via the CCK-8 assay, while intracellular calcium levels in pericytes were assessed. Protein expression was measured using western blotting, and gene expression was quantified via a real-time quantitative polymerase chain reaction. Detailed vibrational parameters were employed to ensure precise stimulation. Notably, 40 Hz vibrotactile stimulation improved cell viability in Aβ-exposed SH-SY5Y cells, reduced intracellular calcium ion (Ca2+) levels in Aβ-treated pericytes, activated autophagy, and mitigated tau hyperphosphorylation in SH-SY5Y cells. Additionally, it exhibited anti-neuroinflammatory properties in BV2 microglia. These findings highlight the potential of 40 Hz vibrotactile stimulation as a therapeutic strategy for AD.

Optimal transcorneal electrical stimulation parameters for preserving photoreceptors in a mouse model of retinitis pigmentosa

JOURNAL/nrgr/04.03/01300535-202419110-00034/figure1/v/2024-03-08T184507Z/r/image-tiff Retinitis pigmentosa is a hereditary retinal disease that affects rod and cone photoreceptors, leading to progressive photoreceptor loss. Previous research supports the beneficial effect of electrical stimulation on photoreceptor survival. This study aims to identify the most effective electrical stimulation parameters and functional advantages of transcorneal electrical stimulation (tcES) in mice affected by inherited retinal degeneration. Additionally, the study seeked to analyze the electric field that reaches the retina in both eyes in mice and post-mortem humans. In this study, we recorded waveforms and voltages directed to the retina during transcorneal electrical stimulation in C57BL/6J mice using an intraocular needle probe with rectangular, sine, and ramp waveforms. To investigate the functional effects of electrical stimulation on photoreceptors, we used human retinal explant cultures and rhodopsin knockout (Rho-/-) mice, demonstrating progressive photoreceptor degeneration with age. Human retinal explants isolated from the donors' eyes were then subjected to electrical stimulation and cultured for 48 hours to simulate the neurodegenerative environment in vitro. Photoreceptor density was evaluated by rhodopsin immunolabeling. In vivo Rho-/- mice were subjected to two 5-day series of daily transcorneal electrical stimulation using rectangular and ramp waveforms. Retinal function and visual perception of mice were evaluated by electroretinography and optomotor response (OMR), respectively. Immunolabeling was used to assess the morphological and biochemical changes of the photoreceptor and bipolar cells in mouse retinas. Oscilloscope recordings indicated effective delivery of rectangular, sine, and ramp waveforms to the retina by transcorneal electrical stimulation, of which the ramp waveform required the lowest voltage. Evaluation of the total conductive resistance of the post-mortem human compared to the mouse eyes indicated higher cornea-to-retina resistance in human eyes. The temperature recordings during and after electrical stimulation indicated no significant temperature change in vivo and only a subtle temperature increase in vitro (~0.5-1.5°C). Electrical stimulation increased photoreceptor survival in human retinal explant cultures, particularly at the ramp waveform. Transcorneal electrical stimulation (rectangular + ramp) waveforms significantly improved the survival and function of S and M-cones and enhanced visual acuity based on the optomotor response results. Histology and immunolabeling demonstrated increased photoreceptor survival, improved outer nuclear layer thickness, and increased bipolar cell sprouting in Rho-/- mice. These results indicate that transcorneal electrical stimulation effectively delivers the electrical field to the retina, improves photoreceptor survival in both human and mouse retinas, and increases visual function in Rho-/- mice. Combined rectangular and ramp waveform stimulation can promote photoreceptor survival in a minimally invasive fashion.

Preservation of vision by transpalpebral electrical stimulation in mice with inherited retinal degeneration

Introduction

The potential neuroprotective and regenerative properties of electrical stimulation (ES) were studied in rhodopsin knockout mice (Rho -/- ), a murine model of inherited retinal degeneration. The study focused on assessing the impact of varying ES frequencies on visual functions and photoreceptor cell survival in Rho -/- mice.

Methods

To elucidate the impact of electrical stimulation on cone survival, Rho -/- mice received either sham or transpalpebral ES using biphasic ramp or rectangular waveforms at 100 µA amplitude, starting at six weeks of age. The treatment duration spanned from one to three weeks. The optimal treatment frequency of ES sessions was determined by applying ES every one, two, or three days in three separate groups of Rho -/- mice. The sham group received daily treatments without the application of ES.

Results

Our study revealed significant improvement of visual function in Rho -/- mice following daily or every-other-day noninvasive transpalpebral ES, as evidenced by electroretinogram and optomotor response-based visual behavior assays. Concurrently, assessment of outer nuclear thickness and immunohistochemistry for the cone photoreceptor cell marker PNA demonstrated pronounced increases in the survival of rods and cones and improvement in the morphology of the inner and outer segments.

Discussion

This study underscores the protective effect of non-invasive ES in rhodopsin knockout-induced retinal degenerative disorders, providing a foundation for developing targeted therapeutic interventions for retinitis pigmentosa.

High-Frequency Spinal Stimulation Suppresses Microglial Kaiso-P2X7 Receptor Axis-Induced Inflammation to Alleviate Neuropathic Pain in Rats

OBJECTIVE

Neuropathic pain poses a persistent challenge in clinical management. Neuromodulation has emerged as a last-resort therapy. Conventional spinal cord stimulation (Con SCS) often causes abnormal sensations and provides short analgesia, whereas high-frequency spinal cord stimulation (HF SCS) is a newer therapy that effectively alleviates pain without paresthesia. However, the modes of action of 10kHz HF SCS (HF10 SCS) in pain relief remain unclear. To bridge this knowledge gap, we employed preclinical models that mimic certain features of clinical SCS to explore the underlying mechanisms of HF10 SCS. Addressing these issues would provide the scientific basis for improving and evaluating the effectiveness, reliability, and practicality of different frequency SCS in clinical settings.

METHODS

We established a preclinical SCS model to examine its effects in a neuropathic pain rat model. We conducted bulk and single-cell RNA sequencing in the spinal dorsal horn (SDH) to examine cellular and molecular changes under different treatments. We employed genetic manipulations through intrathecal injection of a lentiviral system to explore the SCS-mediated signaling axis in pain. Various behavioral tests were performed to evaluate pain conditions under different treatments.

RESULTS

We found that HF10 SCS significantly reduces immune responses in the SDH by inactivating the Kaiso-P2X7R pathological axis in microglia, promoting long-lasting pain relief. Targeting Kaiso-P2X7R in microglia dramatically improved efficacy of Con SCS treatment, leading to reduced neuroinflammation and long-lasting pain relief.

INTERPRETATION

HF10 SCS could improve the immunopathologic state in the SDH, extending its benefits beyond symptom relief. Targeting the Kaiso-P2X7R axis may enhance Con SCS therapy and offer a new strategy for pain management. ANN NEUROL 2024;95:966-983.

In vitro biocompatibility evaluation of functional electrically stimulating microelectrodes on primary glia

Neural interfacing devices interact with the central nervous system to alleviate functional deficits arising from disease or injury. This often entails the use of invasive microelectrode implants that elicit inflammatory responses from glial cells and leads to loss of device function. Previous work focused on improving implant biocompatibility by modifying electrode composition; here, we investigated the direct effects of electrical stimulation on glial cells at the electrode interface. A high-throughput in vitro system that assesses primary glial cell response to biphasic stimulation waveforms at 0 mA, 0.15 mA, and 1.5 mA was developed and optimized. Primary mixed glial cell cultures were generated from heterozygous CX3CR-1+/EGFP mice, electrically stimulated for 4 h/day over 3 days using 75 μm platinum-iridium microelectrodes, and biomarker immunofluorescence was measured. Electrodes were then imaged on a scanning electron microscope to assess sustained electrode damage. Fluorescence and electron microscopy analyses suggest varying degrees of localized responses for each biomarker assayed (Hoescht, EGFP, GFAP, and IL-1β), a result that expands on comparable in vivo models. This system allows for the comparison of a breadth of electrical stimulation parameters, and opens another avenue through which neural interfacing device developers can improve biocompatibility and longevity of electrodes in tissue.

Neuroinflammation in the Evolution of Motor Function in Stroke and Trauma Patients: Treatment and Potential Biomarkers

Neuroinflammation has a significant impact on different pathologies, such as stroke or spinal cord injury, intervening in their pathophysiology: expansion, progression, and resolution. Neuroinflammation involves oxidative stress, damage, and cell death, playing an important role in neuroplasticity and motor dysfunction by affecting the neuronal connection responsible for motor control. The diagnosis of this pathology is performed using neuroimaging techniques and molecular diagnostics based on identifying and measuring signaling molecules or specific markers. In parallel, new therapeutic targets are being investigated via the use of bionanomaterials and electrostimulation to modulate the neuroinflammatory response. These novel diagnostic and therapeutic strategies have the potential to facilitate the development of anticipatory patterns and deliver the most beneficial treatment to improve patients' quality of life and directly impact their motor skills. However, important challenges remain to be solved. Hence, the goal of this study was to review the implication of neuroinflammation in the evolution of motor function in stroke and trauma patients, with a particular focus on novel methods and potential biomarkers to aid clinicians in diagnosis, treatment, and therapy. A specific analysis of the strengths, weaknesses, threats, and opportunities was conducted, highlighting the key challenges to be faced in the coming years.

Electrical stimulation alters DNA methylation and promotes neurite outgrowth

Electrical stimulation (ES) influences neural regeneration and functionality. We here investigate whether ES regulates DNA demethylation, a critical epigenetic event known to influence nerve regeneration. Retinal ganglion cells (RGCs) have long served as a standard model for central nervous system neurons, whose growth and disease development are reportedly affected by DNA methylation. The current study focuses on the ability of ES to rescue RGCs and preserve vision by modulating DNA demethylation. To evaluate DNA demethylation pattern during development, RGCs from mice at different stages of development, were analyzed using qPCR for ten-eleven translocation (TETs) and immunostained for 5 hydroxymethylcytosine (5hmc) and 5 methylcytosine (5mc). To understand the effect of ES on neurite outgrowth and DNA demethylation, cells were subjected to ES at 75 µAmp biphasic ramp for 20 min and cultured for 5 days. ES increased TETs mediated neurite outgrowth, DNA demethylation, TET1 and growth associated protein 43 levels significantly. Immunostaining of PC12 cells following ES for histone 3 lysine 9 trimethylation showed cells attained an antiheterochromatin configuration. Cultured mouse and human retinal explants stained with β-III tubulin exhibited increased neurite growth following ES. Finally, mice subjected to optic nerve crush injury followed by ES exhibited improved RGCs function and phenotype as validated using electroretinogram and immunohistochemistry. Our results point to a possible therapeutic regulation of DNA demethylation by ES in neurons.

Immunological perturbations, psychiatric disorders and associated therapeutics: a new era for psychiatry?

The three main theories explaining major mental illness, namely mood disorders, psychoses and dementias, have been partially discredited. Alongside this, there are emerging links between perturbations of the immune system and the onset and phenotypic features of these disorders. This article outlines the alternative pathophysiology and suggests potential treatments which could improve disease burden and avoid the need for psychotropic medication, with their associated side effects and relapse following withdrawal.

Neuronal activity and NIBS in developmental myelination and remyelination - current state of knowledge

Oligodendrocytes are responsible for myelinating central nervous system (CNS) axons. and rapid electrical transmission through saltatory conduction of action potentials. Myelination and myelin repair rely partially on oligodendrogenesis, which comprises. oligodendrocyte precursor cell (OPC) migration, maturation, and differentiation into. oligodendrocytes (OL). In multiple sclerosis (MS), demyelination occurs due to an. inflammatory cascade with auto-reactive T-cells. When oligodendrogenesis fails, remyelination becomes aberrant and conduction impairments are no longer restored. Although current disease modifying therapies have achieved results in modulating the. faulty immune response, disease progression continues because of chronic. inflammation, neurodegeneration, and failure of remyelination. Therapies have been. tried to promote remyelination. Modulation of neuronal activity seems to be a very. promising strategy in preclinical studies. Additionally, studies in people with MS. (pwMS) have shown symptom improvement following non-invasive brain stimulation. (NIBS) techniques. The aforementioned mechanisms are yet unknown and probably. involve both the activation of neurons and glial cells. Noting neuronal activity. contributes to myelin plasticity and that NIBS modulates neuronal activity; we argue. that NIBS is a promising research horizon for demyelinating diseases. We review the. hypothesized pathways through which NIBS may affect both neuronal activity in the. CNS and how the resulting activity can affect oligodendrogenesis and myelination.

Transcorneal but not transpalpebral electrical stimulation disrupts mucin homeostasis of the ocular surface

PURPOSE

Transcorneal electrical stimulation (TcES) is increasingly applied as a therapy for preserving and improving vision in retinal neurodegenerative and ischemic disorders. However, a common complaint about TcES is its induction of eye pain and dryness in the clinic, while the mechanisms remain unknown.

METHOD

TcES or transpalpebral ES (TpES) was conducted in C57BL6j mice for 14 days. The contralateral eyes were used as non-stimulated controls. Levels of intracellular [Ca2+] ([Ca2+]i) were assessed by Fura-2AM. The conductance resistances of the eye under various ES conditions were measured in vivo by an oscilloscope.

RESULTS

Although TcES did not affect tear production, it significantly induced damage to the ocular surface, as revealed by corneal fluorescein staining that was accompanied by significantly decreased mucin (MUC) 4 expression compared to the control. Similar effects of ES were detected in cultured primary corneal epithelium cells, showing decreased MUC4 and ZO-1 levels after the ES in vitro. In addition, TcES decreased secretion of MUC5AC from the conjunctiva in vivo, which was also corroborated in goblet cell cultures, where ES significantly attenuated carbachol-induced [Ca2+]i increase. In contrast to TcES, transpalpebral ES (TpES) did not induce corneal fluorescein staining while significantly increasing tear production. Importantly, the conductive resistance from orbital skin to the TpES was significantly smaller than that from the cornea to the retina in TcES.

CONCLUSION

TcES, but not TpES, induces corneal epithelial damage in mice by disrupting mucin homeostasis. TpES thus may represent a safer and more effective ES approach for treating retinal neurodegeneration clinically.