Calcium Permeable-AMPA Receptors and Excitotoxicity in Neurological Disorders

Targeting harmful effects of non-excitatory amino acids as an alternative therapeutic strategy to reduce ischemic damage

The involvement of the excitatory amino acids glutamate and aspartate in cerebral ischemia and excitotoxicity is well-documented. Nevertheless, the role of non-excitatory amino acids in brain damage following a stroke or brain trauma remains largely understudied. The release of amino acids by necrotic cells in the ischemic core may contribute to the expansion of the penumbra. Our findings indicated that the reversible loss of field excitatory postsynaptic potentials caused by transient hypoxia became irreversible when exposed to a mixture of just four non-excitatory amino acids (L-alanine, glycine, L-glutamine, and L-serine) at their plasma concentrations. These amino acids induce swelling in the somas of neurons and astrocytes during hypoxia, along with permanent dendritic damage mediated by N-methyl-D-aspartate receptors. Blocking N-methyl-D-aspartate receptors prevented neuronal damage in the presence of these amino acids during hypoxia. It is likely that astroglial swelling caused by the accumulation of these amino acids via the alanine-serine-cysteine transporter 2 exchanger and system N transporters activates volume-regulated anion channels, leading to the release of excitotoxins and subsequent neuronal damage through N-methyl-D-aspartate receptor activation. Thus, previously unrecognized mechanisms involving non-excitatory amino acids may contribute to the progression and expansion of brain injury in neurological emergencies such as stroke and traumatic brain injury. Understanding these pathways could highlight new therapeutic targets to mitigate brain injury.

Structural and material basis of neuron-glioma interactions

The intricate interplay between neurons and gliomas has emerged as an important area of investigation in glioma biology. Accumulating evidence underscores that structural and material alterations constitute the fundamental basis of neuron‒glioma interactions and their pathological consequences. This review comprehensively examines the mechanisms underlying these interactions, with a particular emphasis on specialized structures that facilitate neuron‒glioma communication, including synapses, cell surface ion channels, and tumor microtubules (TMs). In addition to classical neurotransmitters, we highlight the exchange of cytokines, proteins, and extracellular vesicles (EVs) between these cell types. By synthesizing current research findings, this review establishes a conceptual framework for developing innovative therapeutic strategies targeting neuron‒glioma interfaces, offering new perspectives for glioma treatment approaches.

ADAR2-mediated Q/R editing of GluA2 in homeostatic synaptic plasticity

Homeostatic synaptic plasticity is a negative feedback mechanism through which neurons modify their synaptic strength to counteract chronic increases or decreases in activity. In response to activity deprivation, synaptic strength is enhanced by increasing the number of AMPA receptors (AMPARs), particularly Ca2+-permeable AMPARs, at the synapse. Here, we found that this increase in Ca2+-permeable AMPARs during homeostatic upscaling was mediated by decreased posttranscriptional editing of GRIA2 mRNA encoding the AMPAR subunit GluA2. In cultured neurons, activity deprivation resulted in increases in the amount of unedited GluA2, such that its ion channel pore contains a glutamine (Q) codon instead of arginine (R), and in the number of Ca2+-permeable AMPARs at the synapse. These effects were mediated by a splicing factor-dependent decrease in ADAR2 abundance and activity in the nucleus. Overexpression of ADAR2 or CRISPR-Cas13-directed editing of GluA2 transcripts blocked homeostatic upscaling in activity-deprived primary neurons. In mice, dark rearing resulted in decreased Q-to-R editing of GluA2-encoding transcripts in the primary visual cortex (V1), and viral overexpression of ADAR2 in the V1 blocked the induction of homeostatic synaptic plasticity. The findings indicate that activity-dependent regulation of GluA2 editing contributes to homeostatic synaptic plasticity.

Dysfunction of cholinergic neuron in nucleus ambiguous aggravates sepsis-induced lung injury via a GluA1-dependment mechanism

Clinical and neuropathological observations suggest that patients with sepsis may have brainstem autonomic dysfunction. However, the influence of peripheral inflammation on vagal preganglionic neurons is poorly understood. Our hypothesis is that sepsis-induced central vagus dysfunction affects the cholinergic anti-inflammatory pathway and consequently contributes to respiratory failure. Here, we identified neuron apoptosis in the nucleus ambiguus (NA) after sepsis; NA is not only a component of the efferent arm of the inflammatory reflex but also plays an important role in respiratory regulation. Conditional ablation of cholinergic neurons in the NA leads to a decrease in vagus nerve firing, significant impairment of respiratory function, and inflammatory changes in lung tissues. The accumulation of glutamate and increased expression of Ca2+-permeable (CP)-AMPA receptors (AMPARs) mediated the excitotoxicity of NA neurons. Microinjection of IEM1460 (a selective blocker of GluA2- lacking AMPARs) partly rescued vagus firing and respiratory function in mice with sepsis. We showed that peripheral sepsis caused brainstem inflammation and impaired the cholinergic anti-inflammatory pathway after infection. We conclude that central efferent vagus dysfunction may impact vital organ systems in sepsis.

Exploring the role of AMPA receptor auxiliary proteins in synaptic functions and diseases

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) ionotropic glutamate receptors (AMPARs) mediate rapid excitatory synaptic transmission in the mammalian brain, primarily driven by the neurotransmitter glutamate. The modulation of AMPAR activity, particularly calcium-permeable AMPARs (CP-AMPARs), is crucially influenced by various auxiliary subunits. These subunits are integral membrane proteins that bind to the receptor's core and modify its functional properties, including ion channel kinetics and receptor trafficking. This review comprehensively catalogs all known AMPAR auxiliary proteins, providing vital insights into the biochemical mechanisms governing synaptic modulation and the specific impact of CP-AMPARs compared to their calcium-impermeable AMPA receptor (CI-AMPARs). Understanding the complex interplay between AMPARs and their auxiliary subunits in different brain regions is essential for elucidating their roles in cognitive functions such as learning and memory. Importantly, alterations in these auxiliary proteins' expression, function or interactions have been implicated in various neurological disorders. Aberrant signaling through CP-AMPARs, in particular, is associated with severe synaptic dysfunctions across neurodevelopmental, neurodegenerative and psychiatric conditions. Targeting the distinct properties of AMPAR-auxiliary subunit complexes, especially those involving CP-AMPARs, could disclose new therapeutic strategies, potentially allowing for more precise interventions in treating complex neuronal disorders.

Inhibiting SNX14 Alleviates Epileptic Seizures by Regulating GluA2 Degradation via the Lysosomal Pathway

Epilepsy is a common chronic neurological condition, and temporal lobe epilepsy (TLE) is the most common form of refractory epilepsy. However, the underlying causes of TLE remain unclear. Our initial findings revealed that the expression of sorting nexin 14 (SNX14), which is a member of the sorting nexin protein family, was significantly upregulated in brain tissues from both patients with TLE and mouse models of TLE. Moreover, modulation of SNX14 expression in the hippocampus of mice demonstrated that SNX14 downregulation significantly decreased the susceptibility to and severity of seizures, whereas SNX14 overexpression exerted the opposite effects. Mechanistically, we revealed that GluA2, which is a subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor, was a downstream target of SNX14. Further studies indicated that SNX14 modulated GluA2 protein levels by regulating GluA2 degradation via the lysosomal pathway, which in turn influenced glutamatergic synaptic transmission. In conclusion, our findings suggest that the SNX14-GluA2 pathway could be a promising target for the development of novel treatments for epilepsy.

Cannabinoids as Multitarget Drugs for the Treatment of Autoimmunity in Glaucoma

Diseases of multifactorial origin like neurodegenerative and autoimmune diseases require a multitargeted approach. The discovery of the role of autoimmunity in glaucoma and retinal ganglionic cell (RGC) death has led to a paradigm shift in our understanding of the etiopathology of glaucoma. Glaucoma can cause irreversible vision loss that affects up to an estimated 3% of the population over 40 years of age. The current pharmacotherapy primarily aims to manage only intraocular pressure (IOP), a modifiable risk factor in the glaucomatous neurodegeneration of RGCs. However, neurodegeneration continues to happen in normotensive patients (where the IOP is below a reference value), and the silent nature of the disease can cause significant visual impairment and take a massive toll on the healthcare system. Cannabinoids, although known to reduce IOP since the 1970s, have received renewed interest due to their neuroprotective, anti-inflammatory, and immunosuppressive effects on autoimmunity. Additionally, the role of the gut-retina axis and abnormal Wnt signaling in glaucoma makes cannabinoids even more relevant because of their action on multiple targets, all converging in the pathogenesis of glaucomatous neurodegeneration. Cannabinoids also cause epigenetic changes in immune cells associated with autoimmunity. In this Review, we are proposing the use of cannabinoids as a multitargeted approach for treating autoimmunity associated with glaucomatous neurodegeneration, especially for the silent nature of glaucomatous neurodegeneration in normotensive patients.

Ykt6 SNARE protein drives GluA1 insertion at synaptic spines during LTP

Long-Term Potentiation (LTP), a crucial form of synaptic plasticity essential for memory and learning, depends on protein synthesis and the upregulation of GluA1 at postsynaptic terminals. While extensive research has focused on the role of endosomal trafficking in GluA1 regulation, the contribution of endoplasmic reticulum (ER) trafficking pathways remains largely unexplored. A key opportunity to investigate this emerged from Ykt6, an evolutionarily conserved SNARE protein and a master regulator of vesicular fusion along ER-trafficking pathways. Here, we demonstrate that Ykt6 is highly expressed in the mammalian hippocampus, where it localizes to synaptic spines and regulates GluA1 surface expression in an LTP-dependent manner. Furthermore, we found that Ykt6 modulates synaptic vesicle pool dynamics as well as the amplitude and frequency of miniature excitatory postsynaptic currents. Ykt6 loss of function has been linked to α-synuclein pathology, a hallmark of Lewy Body Dementias (LBDs), where α-synuclein misfolding in the hippocampus disrupts LTP. Taken together, our findings establish Ykt6 as a critical SNARE protein in hippocampal function during LTP, with significant implications for neurodegenerative disorders such as LBDs.

Predictors of delayed encephalopathy after acute carbon monoxide poisoning: a literature review

Delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) is one of the severe complications that can occur after acute carbon monoxide poisoning (ACOP). The pathogenesis of DEACMP is complex, featuring a delitescence onset and poor prognosis. As a result, many scholars are concentrating on identifying predictors of DEACMP and evaluating their effects, including clinical characteristics, laboratory indicators, neuroelectrophysiology, imaging examination, and genetic susceptibility. However, current identified predictors lack consensus and their clinical application is limited. Therefore, we need to explore new predictors. Exosomes, the smallest extracellular vesicles (EVs) with nano-size, participate in both the physiological and pathological processes of the brain, and the changes in their content can provide valuable information for clinical diagnosis and evaluation of neurodegenerative diseases, suggesting that they may serve as a potential biomarker. However, the practicability of exosomes as biomarkers of DEACMP remains unclear. In the present review, we first introduced the pathogenesis of DEACMP and the currently identified predictors. Then, we also discussed the possibility of exosomes as the biomarkers of DEACMP, aiming to stimulate more attention and discussion on this topic, thereby providing meaningful insights for future research.

Regulating AMPA Receptors with Isoxazole-4-Carboxamide Derivatives: An Electrophysiological Study

Isoxazole carboxamide derivatives are intriguing modulators of ionotropic glutamate receptors; more specifically, their prospective analgesic activities based on non-opioid pathways have sparked widespread research. α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, especially Ca2+-permeable subtypes that are highly expressed in the spinal dorsal horn, play a critical role in nociceptive transmission and inflammatory pain. Herein, the neuromodulatory effects of these derivatives on AMPA receptor activity have been studied, focusing on their potential as modulators of AMPA receptors, a target implicated in pain and neurological disorders. The whole-cell patch clamp technique for electrophysiological recordings was used to investigate the effect of twelve isoxazole-4-carboxamide derivatives (CIC-1-12) on AMPA receptors' whole-cell currents and kinetics, including deactivation and desensitization. The isoxazole-4-carboxamide derivatives tested as inhibitors of AMPA receptor activity were very potent, with an 8-fold inhibition by CIC-1 and a 7.8-fold reduction by CIC-2. Additionally, these compounds profoundly altered the biophysical gating properties of both homomeric and heteromeric receptor subunits. These findings emphasize the therapeutic promise of isoxazole-4-carboxamide derivatives due to their potential as AMPA receptor modulators. Their ability to affect receptor activity and gating properties makes them promising candidates for future treatments for controlling pain.

Emerging Ferroptosis Involvement in Amyotrophic Lateral Sclerosis Pathogenesis: Neuroprotective Activity of Polyphenols

Neurodegenerative diseases are a group of diseases that share common features, such as the generation of misfolded protein deposits and increased oxidative stress. Among them, amyotrophic lateral sclerosis (ALS), whose pathogenesis is still not entirely clear, is a complex neurodegenerative disease linked both to gene mutations affecting different proteins, such as superoxide dismutase 1, Tar DNA binding protein 43, Chromosome 9 open frame 72, and Fused in Sarcoma, and to altered iron homeostasis, mitochondrial dysfunction, oxidative stress, and impaired glutamate metabolism. The purpose of this review is to highlight the molecular targets common to ALS and ferroptosis. Indeed, many pathways implicated in the disease are hallmarks of ferroptosis, a recently discovered type of iron-dependent programmed cell death characterized by increased reactive oxygen species (ROS) and lipid peroxidation. Iron accumulation results in mitochondrial dysfunction and increased levels of ROS, lipid peroxidation, and ferroptosis triggers; in addition, the inhibition of the Xc- system results in reduced cystine levels and glutamate accumulation, leading to excitotoxicity and the inhibition of GPx4 synthesis. These results highlight the potential involvement of ferroptosis in ALS, providing new molecular and biochemical targets that could be exploited in the treatment of the disease using polyphenols.

Effects of Electroacupuncture on Syt3 and GluA2 in Rats With Limb Spasms After Intracerebral Hemorrhage

BACKGROUND

Clinical studies have confirmed that electroacupuncture (EA) has the potential to improve spasticity after intracerebral hemorrhage (ICH), yet its precise mechanism remains unclear. Synaptotagmin-3 (SYT-3), by mediating the internalization of the glutamate AMPA receptor GLUA2, may be related to EA's mechanism. This study aims to explore the mechanism by which EA improves limb spasticity after ICH, providing scientific evidence for its clinical application.

METHODS

ICH models were established using stereotaxic injection of autologous tail blood into the right striatum. SD rats were randomly divided into Sham, ICH, ICH + SCRAMBLE, EA, and ICH + TAT-GLUA2-3Y groups. Rats in the EA group received 30 min of EA treatment daily after ICH. Muscle tone, neurological deficits, and motor function were assessed. After 3 and 7 days of intervention, the motor cortex was dissected for Western blot analysis of SYT-3, GLUA2, and P-GLUA2-Ser880 expression. Immunoprecipitation was used to detect the interaction between SYT-3 and GLUA2. Nissl staining and NeuN staining were employed to evaluate brain damage. Fluorescence double-labeling technique was used to observe the expression of SYT-3 and GLUA2 in the cell membrane and cytoplasm. Transmission electron microscopy was utilized to examine the microstructure of neurons and synapses.

RESULTS

Compared to the ICH group, rats in the EA group showed reduced muscle tone in the left limbs and significant improvement in neurological deficits and motor function. In the ICH + TAT-GLUA2-3Y group, the binding of SYT-3 and GLUA2 was inhibited, spastic symptoms were alleviated, and membrane expression of GLUA2 increased. In the EA group, SYT-3 levels were significantly reduced, GLUA2 expression increased in the membrane and cytoplasm, and P-GLUA2-Ser880 expression decreased. Rats in the EA group showed increased neuron numbers, normal mitochondrial morphology, and improved synaptic structure in Nissl staining, immunofluorescence, and transmission electron microscopy.

CONCLUSION

EA effectively improves limb spasticity following ICH by inhibiting the SYT-3/GLUA2 pathway.

TRP Channels in Excitotoxicity

Glutamate excitotoxicity is a central mechanism contributing to cellular dysfunction and death in various neurological disorders and diseases, such as stroke, traumatic brain injury, epilepsy, schizophrenia, addiction, mood disorders, Huntington's disease, Alzheimer's disease, Parkinson's disease, multiple sclerosis, pathologic pain, and even normal aging-related changes. This detrimental effect emerges from glutamate binding to glutamate receptors, including α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors, N-methyl-d-aspartate receptors, kainate receptors, and GluD receptors. Thus, excitotoxicity could be prevented by targeting glutamate receptors and their downstream signaling pathways. However, almost all the glutamate receptor antagonists failed to attenuate excitotoxicity in human patients, mainly due to the limited understanding of the underlying mechanisms regulating excitotoxicity. Transient receptor potential (TRP) channels serve as ancient cellular sensors capable of detecting and responding to both external and internal stimuli. The study of human TRP channels has flourished in recent decades since the initial discovery of mammalian TRP in 1995. These channels have been found to play pivotal roles in numerous pathologic conditions, including excitotoxicity. In this review, our focus centers on exploring the intricate interactions between TRP channels and glutamate receptors in excitotoxicity.

AMPA Receptors in Synaptic Plasticity, Memory Function, and Brain Diseases

Tetrameric AMPA-type ionotropic glutamate receptors are primary transducers of fast excitatory synaptic transmission in the central nervous system, and their properties and abundance at the synaptic surface are crucial determinants of synaptic efficacy in neuronal communication across the brain. The induction of long-term potentiation (LTP) leads to the insertion of GluA1-containing AMPA receptors at the synaptic surface, whereas during long-term depression (LTD), these receptors are internalized into the cytoplasm of the spine. Disruptions in the trafficking of AMPA receptors to and from the synaptic surface attenuate both forms of synaptic plasticity. Homeostatic scaling up and scaling down, which are additional types of plasticity similar to LTP and LTD, are also regulated by the insertion and removal of GluA1-containing AMPA receptors from the synaptic surface. The trafficking of AMPA receptors is an intricate process assisted by various proteins. Furthermore, AMPA receptors are critical for the formation and consolidation of various types of memory, and alterations in their function are intimately associated with cognitive dysfunction in aging and several neurological and psychiatric diseases. In this review, we will provide an overview of the current understanding of how AMPA receptors regulate various forms of synaptic plasticity, their contribution to memory functions, and their role in aging and brain diseases.

DNA damage and its links to neuronal aging and degeneration

DNA damage is a major risk factor for the decline of neuronal functions with age and in neurodegenerative diseases. While how DNA damage causes neurodegeneration is still being investigated, innovations over the past decade have provided significant insights into this issue. Breakthroughs in next-generation sequencing methods have begun to reveal the characteristics of neuronal DNA damage hotspots and the causes of DNA damage. Chromosome conformation capture-based approaches have shown that, while DNA damage and the ensuing cellular response alter chromatin topology, chromatin organization at damage sites also affects DNA repair outcomes in neurons. Additionally, neuronal activity results in the formation of programmed DNA breaks, which could burden DNA repair mechanisms and promote neuronal dysfunction. Finally, emerging evidence implicates DNA damage-induced inflammation as an important contributor to the age-related decline in neuronal functions. Together, these discoveries have ushered in a new understanding of the significance of genome maintenance for neuronal function.

Role of α-amino-3‑hydroxy-5-methyl-4-isoxazolepropionic acid receptors and the antagonist perampanel in geriatric epilepsy and status epilepticus

The α-amino-3‑hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) is an ionotropic glutamate receptor recognized for its active involvement in epilepsy. Through AMPAR functional alterations, multiple factors contribute to the increased susceptibility to seizures in the geriatric population. These factors include changes in the hippocampus, neuroinflammation, ischemic insults, amyloid deposition, previous seizures, alterations in the microenvironment, and neurovascular unit dysfunction. Perampanel, a noncompetitive AMPAR antagonist, has been approved for the treatment of focal and generalized epilepsy. However, a complete understanding of AMPAR's role in epileptogenesis and the pharmacotherapy of perampanel in the geriatric population remains elusive. To address this gap, we conducted a comprehensive literature review, screening 1557 articles and ultimately selecting 94 relevant ones. We provided insights into AMPAR functionality changes and perampanel's role in treating geriatric epilepsy. Various clinical trials and retrospective studies have demonstrated that the safety and efficacy of perampanel in the older population are comparable to those in the younger population, with overall good tolerability. It is also effective for treating focal and generalized onset seizures and possibly for managing status epilepticus. In conclusion, the existing body of evidence supports the safety and efficacy of perampanel in the geriatric population, indicating its potential as a valuable therapeutic option for focal and generalized epilepsy. Additional research is warranted to deepen our understanding of AMPAR's involvement in epileptogenesis and to refine the pharmacotherapeutic nuances in this specific demographic.

Low-dose diazepam improves cognitive function in APP/PS1 mouse models: Involvement of AMPA receptors

Previous studies have indicated a close association between cognitive impairment in patients with neurodegenerative diseases, such as Alzheimer's disease (AD), and synaptic damage. Diazepam (DZP), a benzodiazepine class drug, is used to control symptoms such as seizures, anxiety, and sleep disorders. These symptoms can potentially manifest throughout the entire course of AD. Therefore, DZP may be utilized in the treatment of AD to manage these symptoms. However, the specific role and mechanisms of DZP in AD remain unclear. In this study, we discovered that long-term administration of a low dose of DZP (0.5  mg/kg) improved cognitive function and protected neurons from damage in APP/PS1 mice. Mechanistic investigations revealed that DZP exerted its neuroprotective effects and reduced Aβ deposition by modulating GluA1 (glutamate AMPA receptor subunit) to influence synaptic function. In conclusion, these findings highlight the potential benefits of DZP as a novel therapeutic approach, suggesting that long-term use of low-dose DZP in early-stage AD patients may be advantageous in slowing disease progression.

Calcium Ions in the Physiology and Pathology of the Central Nervous System

Calcium ions play a key role in the physiological processes of the central nervous system. The intracellular calcium signal, in nerve cells, is part of the neurotransmission mechanism. They are responsible for stabilizing membrane potential and controlling the excitability of neurons. Calcium ions are a universal second messenger that participates in depolarizing signal transduction and contributes to synaptic activity. These ions take an active part in the mechanisms related to memory and learning. As a result of depolarization of the plasma membrane or stimulation of receptors, there is an extracellular influx of calcium ions into the cytosol or mobilization of these cations inside the cell, which increases the concentration of these ions in neurons. The influx of calcium ions into neurons occurs via plasma membrane receptors and voltage-dependent ion channels. Calcium channels play a key role in the functioning of the nervous system, regulating, among others, neuronal depolarization and neurotransmitter release. Channelopathies are groups of diseases resulting from mutations in genes encoding ion channel subunits, observed including the pathophysiology of neurological diseases such as migraine. A disturbed ability of neurons to maintain an appropriate level of calcium ions is also observed in such neurodegenerative processes as Alzheimer's disease, Parkinson's disease, Huntington's disease, and epilepsy. This review focuses on the involvement of calcium ions in physiological and pathological processes of the central nervous system. We also consider the use of calcium ions as a target for pharmacotherapy in the future.

Steroidogenic pathway in girls diagnosed with autism spectrum disorders

The diagnostic prevalence of autism spectrum disorders (ASD) shows boys to be more affected than girls. Due to this reason, there is a lack of research including and observing ASD girls. Present study was aimed to detect hormones of steroidogenesis pathway in prepubertal girls (n = 16) diagnosed with ASD and sex and age matched neurotypical controls (CTRL, n = 16). Collected plasma served for detection of conjugated and unconjugated steroids using gas chromatography tandem-mass spectrometry. We observed higher levels of steroids modulating ionotropic receptors, especially, GABAergic steroids and pregnenolone sulfate in ASD group. Concentration of many steroids throughout the pathway tend to be higher in ASD girls compared to CTRL. Pregnenolone and its isomers together with polar progestins and androstanes, i.e. sulfated steroids, were found to be higher in ASD group in comparison with CTRL group. Based on steroid product to precursor ratios, ASD group showed higher levels of sulfated/conjugated steroids suggesting higher sulfotransferase or lower steroid sulfatase activity and we also obtained data indicating lower activity of steroid 11β-hydroxylase compared to CTRL group despite higher corticosterone level observed in ASD. These findings need to be generalized in future studies to examine both genders and other age groups.

3,4,5-trimethoxycinnamic acid methyl ester isolated from Polygala tenuifolia enhances hippocampal LTP through PKA and calcium-permeable AMPA receptor

Alzheimer's disease (AD) is a degenerative brain disorder characterized by progressive cognitive decline and neuronal death due to extracellular deposition of amyloid β (Aβ) and intracellular deposition of tau proteins. Recently approved antibody drugs targeting Aβ have been shown to slow the progression of the disease, but they have minimal effects on cognitive improvement. Therefore, there is a need to develop drugs with cognitive-enhancing effects that can be used in conjunction with these antibody treatments. In this study, we investigated whether Polygala tenuifolia (PT), traditionally known for its cognitive-enhancing effects, can improve synaptic plasticity and identified its active components and mechanisms. PT demonstrated a dose-dependent effect in enhancing long-term potentiation (LTP), and among its components, 3,4,5-trimethoxycinnamic acid methyl ester (TMCA) showed a similar LTP-enhancing effect. TMCA increased the phosphorylation of the GluA1 subunit of the α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors and increased the amount of GluA1 on the synapse without affecting the amount of GluA2. Additionally, the increase in GluA1 induced by TMCA was inhibited by a PKA inhibitor. Consistent with these results, the enhancement of LTP by TMCA was inhibited by a GluA1 antagonist and a PKA inhibitor. In silico molecular docking experiments confirmed that TMCA binds to PKA. Finally, we confirmed the LTP-enhancing effect of TMCA in hippocampal slices from 5XFAD mice. These results suggest that PT and its active component, TMCA, can interact with PKA to enhance LTP, indicating the potential for improving cognitive function in AD patients.

Vascular Cognitive Impairment-The Molecular Basis and Potential Influence of the Gut Microbiota on the Pathological Process

Cognitive impairment is a major healthcare challenge worldwide, with vascular cognitive impairment (VCI) being its second leading cause after Alzheimer's disease. VCI is a heterogeneous group of cognitive disorders resulting from various vascular pathologies. Therefore, it is particularly difficult to determine its underlying cause and exact molecular basis. Nevertheless, the current understanding of the pathophysiological processes underlying VCI has changed and evolved in the last decades. The aim of this narrative review is to summarize the current state of knowledge on VCI pathogenesis and to analyze the potential role of the gut microbiota in this process, considering the most recent scientific reports and in accordance with the current understanding of these processes. Chronic cerebral hypoperfusion, which results in impaired blood supply, i.e., oxygen and nutrient deficiency, is the main underlying mechanism of VCI. Furthermore, chronic cerebral hypoperfusion triggers a cascade of molecular changes, starting with an energy imbalance, leading to glutamate excitotoxicity, acidotoxicity, and oxidative stress. Also, all of the above provoke the activation of microglia and the release of pro-inflammatory cytokines that recruit systemic immune cells and lead to their infiltration into the central nervous system, resulting in neuroinflammation. Blood-brain barrier dysfunction may occur at various stages of chronic cerebral hypoperfusion, ultimately increasing its permeability and allowing potentially toxic substances to enter the brain parenchyma. Gut microbiota and their metabolites, which have been identified in numerous inflammatory conditions, may also influence the pathophysiological processes of VCI.

Unveiling the role of astrogliosis in Alzheimer's disease Pathology: Insights into mechanisms and therapeutic approaches

Alzheimer's disease (AD) is one of the most debilitating age-related disorders that affect people globally. It impacts social and cognitive behavior of the individual and is characterized by phosphorylated tau and Aβ accumulation. Astrocytesmaintain a quiescent, anti-inflammatory state on anatomical level, expressing few cytokines and exhibit phagocytic activity to remove misfolded proteins. But in AD, in response to specific stimuli, astrocytes overstimulate their phagocytic character with overexpressing cytokine gene modules. Upon interaction with generated Aβ and neurofibrillary tangle, astrocytes that are continuously activated release a large number of inflammatory cytokines. This cytokine storm leads to neuroinflammation which is also one of the recognizable features of AD. Astrogliosis eventually promotes cholinergic dysfunction, calcium imbalance, oxidative stress and excitotoxicity. Furthermore, C5aR1, Lcn2/, BDNF/TrkB and PPARα/TFEB signaling dysregulation has a major impact on the disease progression. This review clarifies numerous ways that lead to astrogliosis, which is stimulated by a variety of processes that exacerbate AD pathology and make it a suitable target for AD treatment. Drugs under clinical and preclinical investigations that target several pathways managing astrogliosis and are efficacious in ameliorating the pathology of the disease are also included in this study. D-ALA2GIP, TRAM-34, Genistein, L-serine, MW150 and XPro1595 are examples of few drugs targeting astrogliosis. Therefore, this study may aid in the development of a potent therapeutic agent for ameliorating astrogliosis mediated AD progression.

Pervasive expostulation of p53 gene promoting the precipitation of neurogenic convulsions: A journey in therapeutic advancements

Epilepsy, a neurological disorder characterized by prolonged and excessive seizures, has been linked to elevated levels of the tumor suppressor gene p53, which contributes to neuronal dysfunction. This review explores the molecular mechanisms of p53 in epilepsy and discusses potential future therapeutic strategies. Research indicates that changes in p53 expression during neuronal apoptosis, neuroinflammation, and oxidative stress play a significant role in the pathogenesis of epilepsy. Elevated p53 disrupts glutamatergic neurotransmission and hyperactivates NMDA and AMPA receptors, leading to increased neuronal calcium influx, mitochondrial oxidative stress, and activation of apoptotic pathways mediated neuronal dysfunction, exacerbating epileptogenesis. The involvement of p53 in epilepsy suggests that targeting this protein could be beneficial in mitigating neuronal damage and preventing seizure recurrence. Pharmacological agents like pifithrin-α have shown promise in reducing p53-mediated apoptosis and seizure severity. Gene therapy approaches, such as viral vector-mediated delivery of wild-type p53 or RNA interference targeting mutant p53, have also been effective in restoring normal p53 function and reducing seizure susceptibility. Despite these advances, the heterogeneous nature of epilepsy and potential long-term side effects of p53 modulation present challenges. Future research should focus on elucidating the precise molecular mechanisms of p53 and developing personalized therapeutic strategies. Modulating p53 activity holds promise for reducing seizure susceptibility and improving the quality of life for individuals with epilepsy. The current review provides the understanding the intricate role of p53 in neuroinflammatory pathways, including JAK-STAT, JNK, NF-κB, Sonic Hedgehog, and Wnt, is crucial for developing targeted therapies.

The interplay between epitranscriptomic RNA modifications and neurodegenerative disorders: Mechanistic insights and potential therapeutic strategies

Neurodegenerative disorders encompass a group of age-related conditions characterized by the gradual decline in both the structure and functionality of the central nervous system (CNS). RNA modifications, arising from the epitranscriptome or RNA-modifying protein mutations, have recently been observed to contribute significantly to neurodegenerative disorders. Specific modifications like N6-methyladenine (m6A), N1-methyladenine (m1A), 5-methylcytosine (m5C), pseudouridine and adenosine-to-inosine (A-to-I) play key roles, with their regulators serving as crucial therapeutic targets. These epitranscriptomic changes intricately control gene expression, influencing cellular functions and contributing to disease pathology. Dysregulation of RNA metabolism, affecting mRNA processing and noncoding RNA biogenesis, is a central factor in these diseases. This review underscores the complex relationship between RNA modifications and neurodegenerative disorders, emphasizing the influence of RNA modification and the epitranscriptome, exploring the function of RNA modification enzymes in neurodegenerative processes, investigating the functional consequences of RNA modifications within neurodegenerative pathways, and evaluating the potential therapeutic advancements derived from assessing the epitranscriptome.

n-Butylidenephthalide recovered calcium homeostasis to ameliorate neurodegeneration of motor neurons derived from amyotrophic lateral sclerosis iPSCs

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease that causes muscle atrophy and primarily targets motor neurons (MNs). Approximately 20% of familial ALS cases are caused by gain-of-function mutations in superoxide dismutase 1 (SOD1), leading to MN degeneration and ion channel dysfunction. Previous studies have shown that n-Butylidenephthalide (BP) delays disease progression and prolongs survival in animal models of ALS. However, no studies have been conducted on models from human sources. Herein, we examined the protective efficacy of BP on MNs derived from induced pluripotent stem cells (iPSCs) of an ALS patient harboring the SOD1G85R mutation as well as on those derived from genetically corrected iPSCs (SOD1G85G). Our results demonstrated that the motor neurons differentiated from iPSC with SOD1G85R mutation exhibited characteristics of neuron degeneration (as indicated by the reduction of neurofilament expression) and ion channel dysfunction (in response to potassium chloride (KCl) and L-glutamate stimulation), in contrast to those derived from the gene corrected iPSC (SOD1G85G). Meanwhile, BP treatment effectively restored calcium ion channel function by reducing the expression of glutamate receptors including glutamate ionotropic receptor AMPA type subunit 3 (GluR3) and glutamate ionotropic receptor NMDA type subunit 1 (NMDAR1). Additionally, BP treatment activated autophagic pathway to attenuate neuron degeneration. Overall, this study supports the therapeutic effects of BP on ALS patient-derived neuron cells, and suggests that BP may be a promising candidate for future drug development.

Alterations in GABAA receptor-mediated inhibition triggered by status epilepticus and their role in epileptogenesis and increased anxiety

The triggers of status epilepticus (SE) in non-epileptic patients can vary widely, from idiopathic causes to exposure to chemoconvulsants. Regardless of its etiology, prolonged SE can cause significant brain damage, commonly resulting in the development of epilepsy, which is often accompanied by increased anxiety. GABAA receptor (GABAAR)-mediated inhibition has a central role among the mechanisms underlying brain damage and the ensuing epilepsy and anxiety. During SE, calcium influx primarily via ionotropic glutamate receptors activates signaling cascades which trigger a rapid internalization of synaptic GABAARs; this weakens inhibition, exacerbating seizures and excitotoxicity. GABAergic interneurons are more susceptible to excitotoxic death than principal neurons. During the latent period of epileptogenesis, the aberrant reorganization in synaptic interactions that follow interneuronal loss in injured brain regions, leads to the formation of hyperexcitable, seizurogenic neuronal circuits, along with disturbances in brain oscillatory rhythms. Reduction in the spontaneous, rhythmic "bursts" of IPSCs in basolateral amygdala neurons is likely to play a central role in anxiogenesis. Protecting interneurons during SE is key to preventing both epilepsy and anxiety. Antiglutamatergic treatments, including antagonism of calcium-permeable AMPA receptors, can be expected to control seizures and reduce excitotoxicity not only by directly suppressing hyperexcitation, but also by counteracting the internalization of synaptic GABAARs. Benzodiazepines, as delayed treatment of SE, have low efficacy due to the reduction and dispersion of their targets (the synaptic GABAARs), but also because themselves contribute to further reduction of available GABAARs at the synapse; furthermore, benzodiazepines may be completely ineffective in the immature brain.

Toxin-derived peptides: An unconventional approach to alleviating cerebral stroke burden and neurobehavioral impairments

Cerebral stroke is a pressing global health concern, ranking as the second leading cause of mortality and resulting in persistent neurobehavioral impairments. Cerebral strokes, triggered by various embolic events, initiate complex signaling pathways involving neuroexcitotoxicity, ionic imbalances, inflammation, oxidative stress, acidosis, and mitochondrial dysfunction, leading to programmed cell death. Currently, the FDA has approved tissue plasminogen activator as a relatively benign intervention for cerebral stroke, leaving a significant treatment gap. However, a promising avenue has emerged from Earth's toxic creatures. Animal venoms harbor bioactive molecules, particularly neuropeptides, with potential in innovative healthcare applications. These venomous components, affecting ion channels, receptors, and transporters, encompass neurochemicals, amino acids, and peptides, making them prime candidates for treating cerebral ischemia and neurological disorders. This review explores the composition, applications, and significance of toxin-derived peptides as viable therapeutic agents. It also investigates diverse toxins from select venomous creatures, with the primary objective of shedding light on current stroke treatments and paving the way for pioneering therapeutic strategies capable of addressing neurobehavioral deficits.

Improving Outcomes After Post-Cardiac Arrest Brain Injury: A Scientific Statement From the International Liaison Committee on Resuscitation

This scientific statement presents a conceptual framework for the pathophysiology of post-cardiac arrest brain injury, explores reasons for previous failure to translate preclinical data to clinical practice, and outlines potential paths forward. Post-cardiac arrest brain injury is characterized by 4 distinct but overlapping phases: ischemic depolarization, reperfusion repolarization, dysregulation, and recovery and repair. Previous research has been challenging because of the limitations of laboratory models; heterogeneity in the patient populations enrolled; overoptimistic estimation of treatment effects leading to suboptimal sample sizes; timing and route of intervention delivery; limited or absent evidence that the intervention has engaged the mechanistic target; and heterogeneity in postresuscitation care, prognostication, and withdrawal of life-sustaining treatments. Future trials must tailor their interventions to the subset of patients most likely to benefit and deliver this intervention at the appropriate time, through the appropriate route, and at the appropriate dose. The complexity of post-cardiac arrest brain injury suggests that monotherapies are unlikely to be as successful as multimodal neuroprotective therapies. Biomarkers should be developed to identify patients with the targeted mechanism of injury, to quantify its severity, and to measure the response to therapy. Studies need to be adequately powered to detect effect sizes that are realistic and meaningful to patients, their families, and clinicians. Study designs should be optimized to accelerate the evaluation of the most promising interventions. Multidisciplinary and international collaboration will be essential to realize the goal of developing effective therapies for post-cardiac arrest brain injury.

Current potential pathogenic mechanisms of copper-zinc superoxide dismutase 1 (SOD1) in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a rare neurodegenerative disease which damages upper and lower motor neurons (UMN and LMN) innervating the muscles of the trunk, extremities, head, neck and face in cerebrum, brain stem and spinal cord, which results in the progressive weakness, atrophy and fasciculation of muscle innervated by the related UMN and LMN, accompanying with the pathological signs leaded by the cortical spinal lateral tract lesion. The pathogenesis about ALS is not fully understood, and no specific drugs are available to cure and prevent the progression of this disease at present. In this review, we reviewed the structure and associated functions of copper-zinc superoxide dismutase 1 (SOD1), discuss why SOD1 is crucial to the pathogenesis of ALS, and outline the pathogenic mechanisms of SOD1 in ALS that have been identified at recent years, including glutamate-related excitotoxicity, mitochondrial dysfunction, endoplasmic reticulum stress, oxidative stress, axonal transport disruption, prion-like propagation, and the non-cytologic toxicity of glial cells. This review will help us to deeply understand the current progression in this field of SOD1 pathogenic mechanisms in ALS.

Dopamine D2 Receptor Activation Blocks GluA2/ROS Positive Feedback Loop to Alienate Chronic-Migraine-Associated Pain Sensitization

Chronic migraine is a disabling disorder without effective therapeutic medicine. AMPA receptors have been proven to be essential to pathological pain and headaches, but the related regulatory mechanisms in chronic migraine have not yet been explored. In this study, we found that the level of surface GluA2 was reduced in chronic migraine rats. Tat-GluR23Y (a GluA2 endocytosis inhibitor) reduced calcium inward flow and weakened synaptic structures, thus alleviating migraine-like pain sensitization. In addition, the inhibition of GluA2 endocytosis reduced the calcium influx and alleviated mitochondrial calcium overload and ROS generation in primary neurons. Furthermore, our results showed that ROS can induce allodynia and GluA2 endocytosis in rats, thus promoting migraine-like pain sensitization. In our previous study, the dopamine D2 receptor was identified as a potential target in the treatment of chronic migraine, and here we found that dopamine D2 receptor activation suppressed chronic-migraine-related pain sensitization through blocking the GluA2/ROS positive feedback loop in vivo and in vitro. Additionally, ligustrazine, a core component of ligusticum chuanxiong, was shown to target the dopamine D2 receptor, thereby alleviating ROS production and abnormal nociception in CM rats. This study provides valuable insight into the treatment of chronic migraine.

CD3ζ-Mediated Signaling Protects Retinal Ganglion Cells in Glutamate Excitotoxicity of the Retina

Excessive levels of glutamate activity could potentially damage and kill neurons. Glutamate excitotoxicity is thought to play a critical role in many CNS and retinal diseases. Accordingly, glutamate excitotoxicity has been used as a model to study neuronal diseases. Immune proteins, such as major histocompatibility complex (MHC) class I molecules and their receptors, play important roles in many neuronal diseases, while T-cell receptors (TCR) are the primary receptors of MHCI. We previously showed that a critical component of TCR, CD3ζ, is expressed by mouse retinal ganglion cells (RGCs). The mutation of CD3ζ or MHCI molecules compromises the development of RGC structure and function. In this study, we investigated whether CD3ζ-mediated molecular signaling regulates RGC death in glutamate excitotoxicity. We show that mutation of CD3ζ significantly increased RGC survival in NMDA-induced excitotoxicity. In addition, we found that several downstream molecules of TCR, including Src (proto-oncogene tyrosine-protein kinase) family kinases (SFKs) and spleen tyrosine kinase (Syk), are expressed by RGCs. Selective inhibition of an SFK member, Hck, or Syk members, Syk or Zap70, significantly increased RGC survival in NMDA-induced excitotoxicity. These results provide direct evidence to reveal the underlying molecular mechanisms that control RGC death under disease conditions.

Evaluating the Neuroprotective Potential of Novel Benzodioxole Derivatives in Parkinson's Disease via AMPA Receptor Modulation

Parkinson's disease (PD) is a significant health issue because it gradually damages the nervous system. α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors play a significant role in the development of PD. The current investigation employed hybrid benzodioxole-propanamide (BDZ-P) compounds to get information on AMPA receptors, analyze their biochemical and biophysical properties, and assess their neuroprotective effects. Examining the biophysical characteristics of all the subunits of the AMPA receptor offers insights into the impact of BDZ-P on the desensitization and deactivation rate. It demonstrates a partial improvement in the locomotor capacities in a mouse model of Parkinson's disease. In addition, the in vivo experiment assessed the locomotor activity by utilizing the open-field test. Our findings demonstrated that BDZ-P7 stands out with its remarkable potency, inhibiting the GluA2 subunit nearly 8-fold with an IC50 of 3.03 μM, GluA1/2 by 7.5-fold with an IC50 of 3.14 μM, GluA2/3 by nearly 7-fold with an IC50 of 3.19 μM, and GluA1 by 6.5-fold with an IC50 of 3.2 μM, significantly impacting the desensitization and deactivation rate of the AMPA receptor. BDZ-P7 showed an in vivo impact of partially reinstating locomotor abilities in a mouse model of PD. The results above suggest that the BDZ-P7 compounds show great promise as top contenders for the development of novel neuroprotective therapies.

An innate immune response to adeno-associated virus genomes decreases cortical dendritic complexity and disrupts synaptic transmission

Recombinant adeno-associated viruses (AAVs) allow rapid and efficient gene delivery to the nervous system, are widely used in neuroscience research, and are the basis of FDA-approved neuron-targeting gene therapies. Here we find that an innate immune response to the AAV genome reduces dendritic length and complexity and disrupts synaptic transmission in mouse somatosensory cortex. Dendritic loss is apparent 3 weeks after injection of experimentally relevant viral titers, is not restricted to a particular capsid serotype, transgene, promoter, or production facility, and cannot be explained by responses to surgery or transgene expression. AAV-associated dendritic loss is accompanied by a decrease in the frequency and amplitude of miniature excitatory postsynaptic currents and an increase in the proportion of GluA2-lacking, calcium-permeable AMPA receptors. The AAV genome is rich in unmethylated CpG DNA, which is recognized by the innate immunoreceptor Toll-like receptor 9 (TLR9), and acutely blocking TLR9 preserves dendritic complexity and AMPA receptor subunit composition in AAV-injected mice. These results reveal unexpected impacts of an immune response to the AAV genome on neuronal structure and function and identify approaches to improve the safety and efficacy of AAV-mediated gene delivery in the nervous system.

Familial Alzheimer's Disease Neurons Bearing Mutations in PSEN1 Display Increased Calcium Responses to AMPA as an Early Calcium Dysregulation Phenotype

Familial Alzheimer's disease (FAD) can be caused by mutations in PSEN1 that encode presenilin-1, a component of the gamma-secretase complex that cleaves amyloid precursor protein. Alterations in calcium (Ca2+) homeostasis and glutamate signaling are implicated in the pathogenesis of FAD; however, it has been difficult to assess in humans whether or not these phenotypes are the result of amyloid or tau pathology. This study aimed to assess the early calcium and glutamate phenotypes of FAD by measuring the Ca2+ response of induced pluripotent stem cell (iPSC)-derived neurons bearing PSEN1 mutations to glutamate and the ionotropic glutamate receptor agonists NMDA, AMPA, and kainate compared to isogenic control and healthy lines. The data show that in early neurons, even in the absence of amyloid and tau phenotypes, FAD neurons exhibit increased Ca2+ responses to glutamate and AMPA, but not NMDA or kainate. Together, this suggests that PSEN1 mutations alter Ca2+ and glutamate signaling as an early phenotype of FAD.

Hspb1 and Lgals3 in spinal neurons are closely associated with autophagy following excitotoxicity based on machine learning algorithms

Excitotoxicity represents the primary cause of neuronal death following spinal cord injury (SCI). While autophagy plays a critical and intricate role in SCI, the specific mechanism underlying the relationship between excitotoxicity and autophagy in SCI has been largely overlooked. In this study, we isolated primary spinal cord neurons from neonatal rats and induced excitotoxic neuronal injury by high concentrations of glutamic acid, mimicking an excitotoxic injury model. Subsequently, we performed transcriptome sequencing. Leveraging machine learning algorithms, including weighted correlation network analysis (WGCNA), random forest analysis (RF), and least absolute shrinkage and selection operator analysis (LASSO), we conducted a comprehensive investigation into key genes associated with spinal cord neuron injury. We also utilized protein-protein interaction network (PPI) analysis to identify pivotal proteins regulating key gene expression and analyzed key genes from public datasets (GSE2599, GSE20907, GSE45006, and GSE174549). Our findings revealed that six genes-Anxa2, S100a10, Ccng1, Timp1, Hspb1, and Lgals3-were significantly upregulated not only in vitro in neurons subjected to excitotoxic injury but also in rats with subacute SCI. Furthermore, Hspb1 and Lgals3 were closely linked to neuronal autophagy induced by excitotoxicity. Our findings contribute to a better understanding of excitotoxicity and autophagy, offering potential targets and a theoretical foundation for SCI diagnosis and treatment.

Neuronal Circuit Dysfunction in Amyotrophic Lateral Sclerosis

The primary neural circuit affected in Amyotrophic Lateral Sclerosis (ALS) patients is the corticospinal motor circuit, originating in upper motor neurons (UMNs) in the cerebral motor cortex which descend to synapse with the lower motor neurons (LMNs) in the spinal cord to ultimately innervate the skeletal muscle. Perturbation of these neural circuits and consequent loss of both UMNs and LMNs, leading to muscle wastage and impaired movement, is the key pathophysiology observed. Despite decades of research, we are still lacking in ALS disease-modifying treatments. In this review, we document the current research from patient studies, rodent models, and human stem cell models in understanding the mechanisms of corticomotor circuit dysfunction and its implication in ALS. We summarize the current knowledge about cortical UMN dysfunction and degeneration, altered excitability in LMNs, neuromuscular junction degeneration, and the non-cell autonomous role of glial cells in motor circuit dysfunction in relation to ALS. We further highlight the advances in human stem cell technology to model the complex neural circuitry and how these can aid in future studies to better understand the mechanisms of neural circuit dysfunction underpinning ALS.

Pathological mechanisms of amyotrophic lateral Sclerosis

Amyotrophic lateral sclerosis refers to a neurodegenerative disease involving the motor system, the cause of which remains unexplained despite several years of research. Thus, the journey to understanding or treating amyotrophic lateral sclerosis is still a long one. According to current research, amyotrophic lateral sclerosis is likely not due to a single factor but rather to a combination of mechanisms mediated by complex interactions between molecular and genetic pathways. The progression of the disease involves multiple cellular processes and the interaction between different complex mechanisms makes it difficult to identify the causative factors of amyotrophic lateral sclerosis. Here, we review the most common amyotrophic lateral sclerosis-associated pathogenic genes and the pathways involved in amyotrophic lateral sclerosis, as well as summarize currently proposed potential mechanisms responsible for amyotrophic lateral sclerosis disease and their evidence for involvement in amyotrophic lateral sclerosis. In addition, we discuss current emerging strategies for the treatment of amyotrophic lateral sclerosis. Studying the emergence of these new therapies may help to further our understanding of the pathogenic mechanisms of the disease.

Anti-Apoptotic Effects of AMPA Receptor Antagonist Perampanel in Early Brain Injury After Subarachnoid Hemorrhage in Mice

This study was aimed to investigate if acute neuronal apoptosis is induced by activation of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionate) receptors (AMPARs) and inhibited by a clinically available selective AMPAR antagonist and antiepileptic drug perampanel (PER) in subarachnoid hemorrhage (SAH), and if the mechanisms include upregulation of an inflammation-related matricellular protein periostin. Sham-operated and endovascular perforation SAH mice randomly received an administration of 3 mg/kg PER or the vehicle intraperitoneally. Post-SAH neurological impairments and increased caspase-dependent neuronal apoptosis were associated with activation of AMPAR subunits GluA1 and GluA2, and upregulation of periostin and proinflammatory cytokines interleukins-1β and -6, all of which were suppressed by PER. PER also inhibited post-SAH convulsion-unrelated increases in the total spectral power on video electroencephalogram (EEG) monitoring. Intracerebroventricularly injected recombinant periostin blocked PER's anti-apoptotic effects on neurons. An intracerebroventricular injection of a selective agonist for GluA1 and GluA2 aggravated neurological impairment, neuronal apoptosis as well as periostin upregulation, but did not increase the EEG total spectral power after SAH. A higher dosage (10 mg/kg) of PER had even more anti-apoptotic effects compared with 3 mg/kg PER. Thus, this study first showed that AMPAR activation causes post-SAH neuronal apoptosis at least partly via periostin upregulation. A clinically available AMPAR antagonist PER appears to be neuroprotective against post-SAH early brain injury through the anti-inflammatory and anti-apoptotic effects, independent of the antiepileptic action, and deserves further study.

GABAergic and glutamatergic inputs to the medulla oblongata and locus coeruleus noradrenergic pathways are critical for seizures and postictal antinociception neuromodulation

We investigated the participation of the nucleus of the tractus solitarius (NTS) in tonic‒clonic seizures and postictal antinociception control mediated by NMDA receptors, the role of NTS GABAergic interneurons and noradrenergic pathways from the locus coeruleus (LC) in these phenomena. The NTS-lateral nucleus reticularis paragigantocellularis (lPGi)-LC pathway was studied by evaluating neural tract tracer deposits in the lPGi. NMDA and GABAergic receptors agonists and antagonists were microinjected into the NTS, followed by pharmacologically induced seizures. The effects of LC neurotoxic lesions caused by DSP-4, followed by NTS-NMDA receptor activation, on both tonic‒clonic seizures and postictal antinociception were also investigated. The NTS is connected to lPGi neurons that send outputs to the LC. Glutamatergic vesicles were found on dendrites and perikarya of GABAergic interneurons in the NTS. Both tonic‒clonic seizures and postictal antinociception are partially dependent on glutamatergic-mediated neurotransmission in the NTS of seizing rats in addition to the integrity of the noradrenergic system since NMDA receptor blockade in the NTS and intrathecal administration of DSP-4 decrease the postictal antinociception. The GABAA receptor activation in the NTS decreases both seizure severity and postictal antinociception. These findings suggest that glutamatergic inputs to NTS-GABAergic interneurons, in addition to ascending and descending noradrenergic pathways from the LC, are critical for the control of both seizures and postictal antinociception.

Upregulation of Spinal MDGA1 in Rats After Nerve Injury Alters Interactions Between Neuroligin-2 and Postsynaptic Scaffolding Proteins and Increases GluR1 Subunit Surface Delivery in the Spinal Cord Dorsal Horn

Previous studies suggested that postsynaptic neuroligin-2 may shift from inhibitory toward excitatory function under pathological pain conditions. We hypothesize that nerve injury may increase the expression of spinal MAM-domain GPI-anchored molecule 1 (MDGA1), which can bind to neuroligin-2 and thereby, alter its interactions with postsynaptic scaffolding proteins and increase spinal excitatory synaptic transmission, leading to neuropathic pain. Western blot, immunofluorescence staining, and co-immunoprecipitation studies were conducted to examine the critical role of MDGA1 in the lumbar spinal cord dorsal horn in rats after spinal nerve ligation (SNL). Small interfering ribonucleic acids (siRNAs) targeting MDGA1 were used to examine the functional roles of MDGA1 in neuropathic pain. Protein levels of MDGA1 in the ipsilateral dorsal horn were significantly upregulated at day 7 post-SNL, as compared to that in naïve or sham rats. The increased levels of GluR1 in the synaptosomal membrane fraction of the ipsilateral dorsal horn tissues at day 7 post-SNL was normalized to near sham level by pretreatment with intrathecal MDGA1 siRNA2308, but not scrambled siRNA or vehicle. Notably, knocking down MDGA1 with siRNAs reduced the mechanical and thermal pain hypersensitivities, and inhibited the increased excitatory synaptic interaction between neuroligin-2 with PSD-95, and prevented the decreased inhibitory postsynaptic interactions between neuroligin-2 and Gephyrin. Our findings suggest that SNL upregulated MDGA1 expression in the dorsal horn, which contributes to the pain hypersensitivity through increasing the net excitatory interaction mediated by neuroligin-2 and surface delivery of GluR1 subunit in dorsal horn neurons.

[Tacrolimus Induces Pain by Upregulating the Synaptic Expression of AMPA Receptors in the Spinal Cord Dorsal Horn]

Objective

To investigate the effects of long-term administration of tacrolimus (also known as FK506) on the pain-related behaviors in mice and to study the underlying mechanism of pain induced by FK506 via measuring the effect of FK506 on the synaptic expression and phosphorylation of alpha-amino-3-hyroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor in the spinal cord dorsal horn of mice.

Methods

1) A total of 24 mice were evenly and randomly assigned to two groups, a FK506 group and a Saline group. The FK506 group was given daily intraperitoneal injection of FK506 and the Saline group received normal saline. Both groups received injection once a day for 7 days in a row. Some of the mice ( n=6 in each group) were monitored for the changes in the paw withdrawal threshold (PWT), the paw withdrawal latency (PWL), and the spontaneous pain behaviors to establish the pain model. The other mice ( n=6 in each group) of each group underwent isolation of the dorsal horn when obvious pain symptoms were induced on day 7 of injection. Then, immunoblotting was performed to determine the synaptic expression and phosphorylation levels of GluA1 and GluA2 subunits of AMPA receptors. 2) The mice were randomly divided into two groups, FK506+calcineurin (CaN) group and FK506+Saline group ( n=6 in each group). After the pain model was constructed, the mice were given intrathecal injection of recombinant CaN (also know as 33 U) or normal saline. Then, 60 minutes later, the PWT and the PWL of the mice were measured to investigate the role of CaN in FK506-induced pain. 3) Another18 mice were selected. The mice were randomly and evenly assigned to three groups, a control group (receiving intraperitoneal injection of normal saline followed by intrathecal injection of normal saline), FK506+Saline group (receiving intraperitoneal injection of FK506 followed by intrathecal injection of normal saline) and FK506+CaN group (receiving intraperitoneal injection of FK506 followed by intrathecal injection of CaN). Then, 60 minutes later, the spinal cords were isolated and subjected to immunoblotting assay to determine the role of CaN in FK506-induced AMPA receptor modification.

Results

1) After 7 consecutive days of intraperitoneal injection of FK506, the PWT and PWL of mice dropped significantly, reaching on day 7 as low as 22.3%±0.05% and 66.6%±0.05% of the control group, respectively ( P<0.01). The FK506-treated mice displayed evident spontaneous pain behavior, presenting significantly increased licking activities ( P<0.01). These results indicated that FK506-induced pain model was successfully established. Immunoblotting assay showed that the total expressions of GluA1 and GluA2 subunits in the spinal dorsal horn of the FK506 group remained unchanged in comparison with those of the Saline group. However, FK506 specifically induced an increase in the synaptic expression of GluA1. In addition, the phosphorylation levels of GluA1 at Ser845 and Ser831 in FK506-treated mice were significantly increased in comparison with those of the control group ( P<0.05). 2) Compared with those of the mice in the FK506+Saline group, the PWT and the PWL of mice in the FK506+CaN group were significantly increased ( P<0.05). 3) Compared with those of the FK506+Saline group, the synaptic expression of GluA1 were decreased in FK506+CaN group ( P<0.01) and the phosphorylation levels of GluA1 at Ser845 and Ser831 were significantly downregulated ( P<0.001).

Conclusion

The hyper-expression and hyperphosphorylation of GluA1 subunit in the spinal cord dorsal horn resulting from CaN inhibition contributes to the FK506-induced pain syndrome. FK506 induces the synaptic hyper-expression and hyperphosphorylation of GluA1 in the dorsal horn of the spinal cord through CaN inhibition, thereby inducing pain.

Reversible synaptic adaptations in a subpopulation of murine hippocampal neurons following early-life seizures

Early-life seizures (ELSs) can cause permanent cognitive deficits and network hyperexcitability, but it is unclear whether ELSs induce persistent changes in specific neuronal populations and whether these changes can be targeted to mitigate network dysfunction. We used the targeted recombination of activated populations (TRAP) approach to genetically label neurons activated by kainate-induced ELSs in immature mice. The ELS-TRAPed neurons were mainly found in hippocampal CA1, remained uniquely susceptible to reactivation by later-life seizures, and displayed sustained enhancement in α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated (AMPAR-mediated) excitatory synaptic transmission and inward rectification. ELS-TRAPed neurons, but not non-TRAPed surrounding neurons, exhibited enduring decreases in Gria2 mRNA, responsible for encoding the GluA2 subunit of the AMPARs. This was paralleled by decreased synaptic GluA2 protein expression and heightened phosphorylated GluA2 at Ser880 in dendrites, indicative of GluA2 internalization. Consistent with increased GluA2-lacking AMPARs, ELS-TRAPed neurons showed premature silent synapse depletion, impaired long-term potentiation, and impaired long-term depression. In vivo postseizure treatment with IEM-1460, an inhibitor of GluA2-lacking AMPARs, markedly mitigated ELS-induced changes in TRAPed neurons. These findings show that enduring modifications of AMPARs occur in a subpopulation of ELS-activated neurons, contributing to synaptic dysplasticity and network hyperexcitability, but are reversible with early IEM-1460 intervention.

Astrocyte Regulation of Neuronal Function and Survival in Stroke Pathophysiology

The interactions between astrocytes and neurons in the context of stroke play crucial roles in the disease's progression and eventual outcomes. After a stroke, astrocytes undergo significant changes in their morphology, molecular profile, and function, together termed reactive astrogliosis. Many of these changes modulate how astrocytes relate to neurons, inducing mechanisms both beneficial and detrimental to stroke recovery. For example, excessive glutamate release and astrocytic malfunction contribute to excitotoxicity in stroke, eventually causing neuronal death. Astrocytes also provide essential metabolic support and neurotrophic signals to neurons after stroke, ensuring homeostatic stability and promoting neuronal survival. Furthermore, several astrocyte-secreted molecules regulate synaptic plasticity in response to stroke, allowing for the rewiring of neural circuits to compensate for damaged areas. In this chapter, we highlight the current understanding of the interactions between astrocytes and neurons in response to stroke, explaining the varied mechanisms contributing to injury progression and the potential implications for future therapeutic interventions.

Hydrogel and Nanomedicine-Based Multimodal Therapeutic Strategies for Spinal Cord Injury

Spinal cord injury (SCI) is a severe neurodegenerative disease caused by mechanical and biological factors, manifesting as a loss of motor and sensory functions. Inhibition of injury expansion and even reversal of injury in the acute damage stage of SCI are important strategies for treating this disease. Hydrogels and nanoparticle (NP)-based drugs are the most effective, widely studied, and clinically valuable therapeutic strategies in the field of repair and regeneration. Hydrogels are 3D flow structures that fill the pathological gaps in SCI and provide a microenvironment similar to that of the spinal cord extracellular matrix for nerve cell regeneration. NP-based drugs can easily penetrate the blood-spinal cord barrier, target SCI lesions, and are noninvasive. Hydrogels and NPs as drug carriers can be loaded with various drugs and biological therapeutic factors for slow release in SCI lesions. They help drugs function more efficiently by exerting anti-inflammatory, antioxidant, and nerve regeneration effects to promote the recovery of neurological function. In this review, the use of hydrogels and NPs as drug carriers and the role of both in the repair of SCI are discussed to provide a multimodal strategic reference for nerve repair and regeneration after SCI.

Kynurenine attenuates mitochondrial depolarization and neuronal cell death induced by rotenone exposure independently of AhR-mediated parkin induction in SH-SY5Y differentiated cells

Rotenone is a pesticide commonly used in agriculture that is associated with the risk of developing Parkinson's disease (PD) by inducing mitochondrial damage. As a protective cell response to different challenges, they activate mitophagy, which involves parkin activity. Parkin is an E3 ubiquitin ligase necessary in the initial steps of mitophagy, and its overexpression protects against parkinsonian effects in different models. Recent studies have reported that the aryl hydrocarbon receptor (AHR), a ligand-dependent transcription factor, induces parkin expression. Kynurenine, an endogenous AHR ligand, promotes neuroprotection in chronic neurodegenerative disorders, such as PD, although its neuroprotective mechanism needs to be fully understood. Therefore, we evaluated whether the overexpression of parkin by AHR activation with kynurenine promotes autophagy and reduces the neurotoxicity induced by rotenone in SH-SY5Y cells differentiated to dopaminergic neurons. SH-SY5Y neurons were treated with rotenone or pretreated with kynurenine or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and parkin levels, apoptosis, mitochondrial potential membrane, and autophagy were determined. The results showed that kynurenine and TCDD treatments induced parkin expression in an AHR-dependent manner. Kynurenine pretreatment inhibited rotenone-induced neuronal apoptosis in 17%, and the loss of mitochondrial membrane potential in 30% when compare to rotenone alone, together with a decrease in autophagy. By contrast, although TCDD treatment increased parkin levels, non-neuroprotective effects were observed. The kynurenine protective activity was AHR independent, suggesting that parkin induction might not be related to this effect. On the other hand, kynurenine treatment inhibited alpha amine-3-hydroxy-5-methyl-4-isoxazol propionic acid and N-methyl-D-aspartate receptors, which are well-known excitotoxicity mediators activated by rotenone exposure.

Hemokinin-1 induces transcriptomic alterations in pain-related signaling processes in rat primary sensory neurons independent of NK1 tachykinin receptor activation

The tachykinin hemokinin-1 (HK-1) is involved in immunological processes, inflammation, and pain. Although the neurokinin 1 receptor (NK1R) is described as its main target, several effects are mediated by currently unidentified receptor(s). The role of HK-1 in pain is controversial, depending on the involvement of peripheral and central sensitization mechanisms in different models. We earlier showed the ability of HK-1 to activate the trigeminovascular system, but the mechanisms need to be clarified. Therefore, in this study, we investigated HK-1-induced transcriptomic alterations in cultured rat trigeminal ganglion (TRG) primary sensory neurons. HK-1 was applied for 6 or 24 h in 1 μM causing calcium-influx in these neurons, 500 nM not inducing calcium-entry was used for comparison. Next-generation sequencing was performed on the isolated RNA, and transcriptomic changes were analyzed to identify differentially expressed (DE) genes. Functional analysis was performed for gene annotation using the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Reactome databases. NK1R and Neurokinin receptor 2 (NK2R) were not detected. Neurokinin receptor 3 (NK3R) was around the detection limit, which suggests the involvement of other NKR isoforms or other receptors in HK-1-induced sensory neuronal activation. We found protease-activated receptor 1 (PAR1) and epidermal growth factor receptor (EGFR) as DE genes in calcium signaling. The transmembrane protein anthrax toxin receptor 2 (ANTXR2), a potential novel pain-related target, was upregulated. Acid-sensing ion channel 1; 3 (Asic1,3), N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptors decreased, myelin production and maintenance related genes (Mbp, Pmp2, Myef2, Mpz) and GNDF changed by HK-1 treatment. Our data showed time and dose-dependent effects of HK-1 in TRG cell culture. Result showed calcium signaling as altered event, however, we did not detect any of NK receptors. Presumably, the activation of TRG neurons is independent of NK receptors. ANTXR2 is a potential new target, PAR-1 has also important role in pain, however their connection to HK-1 is unknown. These findings might highlight new targets or key mediators to solve how HK-1 acts on TRG.

Parkinson's disease, epilepsy, and amyotrophic lateral sclerosis-emerging role of AMPA and kainate subtypes of ionotropic glutamate receptors

Ionotropic glutamate receptors (iGluRs) mediate the majority of excitatory neurotransmission and are implicated in various neurological disorders. In this review, we discuss the role of the two fastest iGluRs subtypes, namely, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptors, in the pathogenesis and treatment of Parkinson's disease, epilepsy, and amyotrophic lateral sclerosis. Although both AMPA and kainate receptors represent promising therapeutic targets for the treatment of these diseases, many of their antagonists show adverse side effects. Further studies of factors affecting the selective subunit expression and trafficking of AMPA and kainate receptors, and a reasonable approach to their regulation by the recently identified novel compounds remain promising directions for pharmacological research.