Excitotoxicity Research Articles

Hydrocortisone and vitamin B12 protect SHSY-5Y cells against glutamate excitotoxicity by altering VIP and GAL levels

Background: Prolonged elevation of extracellular glutamate levels triggers intracellular events, increases glutamate excitotoxicity, and activates apoptotic pathways, causing Alzheimer's disease (AD). The literature has reported that vitamin B12 exhibits anti-inflammatory and anti-apoptotic activities in various diseases. Hydrocortisone (HC) therapy also substantially inhibits microglia and astrocyte hyperactivation, minimizing pro-inflammatory cytokines and reducing neuroinflammation. That is why our study aimed to evaluate the therapeutic effects of HC and B12 combination on oxidative stress and VIP and GAL levels in an in vitro Alzheimer's model. Method: To create the Alzheimer's model, the neuroblastoma cell line (SH-SY5Y) was cultured. Then, all cells except the control group were treated with different doses of HC and B12 combination for 24 hours by applying Glutamate (10-5 mM) to create excitotoxicity. The results were evaluated using MTT and ELISA tests. Results: When the results were examined, it was determined that exceptionally high-dose combination groups showed protective activity against glutamate excitotoxicity. HC+B12 25 µg/ml groups observed the most statistically significant results. According to our results, oxidative stress decreased in the HC+B12 25 µg/ml group, and cell viability increased. Significant changes were also observed in Vasoactive Peptide (VIP) and Galanin (GAL) levels in correlation with other analyses obtained. Conclusion: This study is the first to report the potential of vitamin B12 combined with hydrocortisone to prevent oxidative stress and glutamate excitotoxicity in primary neurons. It provides a basis for further investigating its clinical application in neurodegenerative diseases.

EAAT2 Activation Regulates Glutamate Excitotoxicity and Reduces Impulsivity in a Rodent Model of Parkinson's Disease.

Parkinson's disease (PD) is a systemic disease characterized by motor and nonmotor impairments. Loss of dopaminergic neurons in the substantia nigra pars compacta region in PD disrupts dopamine-glutamate homeostasis in the corticostriatal circuit, contributing to cognitive impairment. In addition, excitatory amino acid transporter-2 (EAAT2), localized predominantly to astrocytes and responsible for > 80% of synaptic glutamate clearance, is downregulated in PD, causing glutamate spillover and excitotoxicity. This altered dopamine-glutamate homeostasis and excitotoxicity may affect reward-mediated decision-making behaviors and promote impulsive behaviors in PD. In this study, we hypothesized that GTS467, a small-molecule activator of EAAT2, could effectively reduce excitotoxicity and treat cognitive impairment without promoting impulsive behavior in PD. Rats that were unilaterally lesioned with the 6-OHDA toxin to produce Parkinsonian symptoms were referred to as lesioned rats. Lesioned rats were trained to meet baseline criteria in a 5-choice serial reaction time task, and the chronic effects of GTS467 were assessed after 3weeks of treatment. The results showed that chronic treatment with GTS467 significantly improved correct responses and reduced premature impulsive responses and omissions compared with saline treatment. This improvement in performance correlated with a reduction in glutamate levels, an increase in EAAT2 expression, and normalization of NMDA receptor subunit expression and signaling. Furthermore, transcriptomic studies on the prefrontal cortex tissue have shown the differential expression of genes involved in neuroprotection, neuroinflammation, learning, and memory. These results validate the role of glutamate excitotoxicity in promoting impulsive behaviors and suggest that GTS467 can be developed as a therapeutic agent to reduce cognitive impairment and impulsive behaviors in PD.

Effect of calcium ions on the aggregation of highly phosphorylated tau

Tau is typically an axonal protein, but in neurons of brains affected by Alzheimer's disease (AD), aggregation of hyperphosphorylated tau in the somatodendritic compartment causes neuronal death. We have previously demonstrated that tau mRNA is transported within dendrites and undergoes immediate translation and hyperphosphorylation of AD epitopes in response to NMDA receptor stimulation. Although this explains the emergence of hyperphosphorylated tau in dendrites, the relationship between tau hyperphosphorylation and aggregation is not well understood. In this study, we found that recombinant highly phosphorylated tau purified from NG108-15 rodent neuroblastoma/glioma cells transfected with both tau and GSK3β expression vectors bound calcium ions and formed sarkosyl-insoluble aggregates. In addition, thioflavin T analysis revealed that this highly phosphorylated tau tended to aggregate on its own, further facilitated by calcium ions. When NG108-15 cells expressing the highly phosphorylated tau were treated with calcium ionophore, sarkosyl-insoluble tau was generated. Interestingly, these cells exhibited resistance to both calcium ionophore-induced cytotoxicity and glutamate-induced excitotoxicity. We further found that sarkosyl-insoluble phosphorylated tau was increased in cultured hippocampal neurons due to glutamate-induced hyperactivity. Our data suggest that hyperphosphorylated tau synthesized in response to NMDA receptor stimulation contributes to regulation of neuronal activity by binding calcium ions, but that this calcium binding may cause tau to adopt an aggregated form.

Upregulated excitatory amino acid transporter 1 (EAAT1) expression in the human medial temporal lobe in Alzheimer's disease.

Alzheimer's disease (AD) is a growing health problem worldwide, particularly in the developed world due to an ageing population. Glutamate excitotoxicity plays a major role in the pathophysiology of AD, and glutamate re-uptake is controlled by excitatory amino acid transporters (EAATs). The EAAT2 isoform is the predominant transporter involved in glutamate reuptake, therefore EAAT1 has not been the focus of AD research. We investigated the layer-specific expression of EAAT1 in human medial temporal lobe regions such as the hippocampus, subiculum, entorhinal cortex and superior temporal gyrus, using fluorescent immunohistochemistry and laser scanning confocal microscopy in human post-mortem tissue. We observed low EAAT1 immunoreactivity in control cases, but upregulated labeling in AD across several brain regions of the medial temporal lobe. Significantly higher integrated density in AD cases was observed in the str. oriens and str. radiatum of the CA2 region, the str. pyramidale of CA3, and the str. moleculare and str. granulosum of the DG. Labeling of EAAT1 appeared astrocytic in nature, showing close association with astrocytic processes in AD cases. We also report that a higher EAAT1 density was positively correlated with the age of AD cases, but this relationship was not observed in control cases. Overall, our results indicate an upregulation of EAAT1 across several hippocampal subregions and layers in AD cases, indicating a potential physiological role for this transporter that needs further investigation.

Sinapic acid alleviates glutamate-induced excitotoxicity by inhibiting neuroinflammation and endoplasmic reticulum stress pathway in C6 glioma cells

Sinapic acid (SA) is a polyphenol compound derived from hydroxycinnamic acid found in various foods such as cereals and vegetables and has antioxidant, anti-inflammatory and neuroprotective properties. However, its effects on glutamate-induced excitotoxicity, which is important in neurodegenerative diseases, have not been fully elucidated. This study aimed to investigate the effect of SA on glutamate excitotoxicity and the possible role of proinflammatory cytokines and the endoplasmic reticulum (ER) stress pathway. In the study, C6 rat glioma cell line was used and the cells were divided into 4 groups: control, glutamate, SA and glutamate+SA. Cells were treated with 10 mM glutamate for 24 h to induce excitotoxicity. Additionally, SA was applied to cells at concentrations of 12.5 to 100 μM to examine its effects on glutamate excitotoxicity. XTT test was used for cell viability, and apoptotic cells were determined by immunofluorescence and flow cytometry methods. Proinflammatory cytokines (tumor necrosis factor-alpha, TNF-α and interleukin-beta, IL-1β), ER stress markers (glucose regulatory protein 78, GRP78; C/EBP homologous protein, CHOP and activating transcription factor-4, ATF-4) and caspase-3 was used to measure ELISA method. Findings indicated that SA (50 μM) significantly increased cell viability against glutamate-induced excitotoxicity (p < 0.05). Also, SA caused a significant decrease in TNF-α, IL-1β, GRP78, CHOP, ATF-4 and caspase-3 levels in glutamate-treated cells (p < 0.05). Flow cytometry and immunofluorescence staining results showed that SA reduced apoptosis in C6 glioma cells. In conclusion, our findings suggested that SA attenuated glutamate-induced excitotoxicity by preventing apoptosis through reducing proinflammatory cytokines and ER stress protein levels.

The Effect of glna Loss on the Physiological and Pathological Phenotype of Parkinson's Disease C. elegans.

Parkinson's disease (PD) is a common neurodegenerative disease. Glutamate(Glu) excitotoxicity is one of the main pathogenesis of PD. Glutaminase (Gls) is an enzyme primarily responsible for catalyzing the hydrolysis and deamidation of glutamine (Gln) to produce Glu and ammonia. Inhibiting the function of Gls may have a beneficial effect on the treatment of PD by reducing the production of Glu. The homologous gene of Gls in C. elegans is glna. To explore the effects of glna loss on physiological and pathological phenotype of PD C. elegans, and to provide new ideas and references for the research and treatment of PD. We used PD C. elegans UA44 and QIN27 to detect development and lifespan, behavior, degeneration of dopaminergic neurons, lipid levels, ROS levels, expression levels of common amino acids. Glna loss had no significant impact on the development and lifespan of PD C. elegans. Glna loss saved part of the decline of motor function, including the head thrash frequency and the body bend frequency, and the difference was significant. There was a trend of improvement in some motor behaviors, such as the ethanol avoidance experiment, while no improvement was observed in other experiments. Glna loss slowed down the degeneration of dopaminergic neurons. Glna loss increased the lipid levels and ROS levels in C. elegans. Glna loss decreased Glu content and increased Gln content in C. elegans. The effect of glna loss on PD C. elegans may be the result of multiple factors, such as the tissue types of α-syn expression in C. elegans, the PD C. elegans model used, the adverse effects of glna loss on other systems, and the changes in ROS levels in C. elegans. The specific mechanisms causing these phenomena are still unclear and need to be further explored. Glna loss has a certain protective effect on dopaminergic neurons in PD C. elegans, while the improvement effect on movement and behavior is limited.

Assessment of the neurotoxicity of monosodium glutamate on neural stem cells and hippocampal neurogenesis in a rodent model

Monosodium glutamate (MSG) is a widely used flavor enhancer in processed foods and valued for its ability to enhance the savory taste known as umami. MSG is classified as non-toxic and recognized as a safe food additive with no specific usage restrictions in many countries. However, neurotoxic studies on MSG have primarily focused on neurons, and the effects of MSG on neural stem cells (NSCs) have not been reported. This study aimed to evaluate the neurotoxic effect of MSG on NSCs and hippocampal neurogenesis in a rodent model. In vitro studies showed that MSG induces cytotoxicity in primary neuron cultures but has no toxic effect on NSCs. Furthermore, in vivo studies on 4-week-old male C57BL/6 mice orally administered MSG and sodium chloride (NaCl) for two weeks revealed that neither MSG nor NaCl induced changes in the expressions of neuronal markers or glutamate receptors in the hippocampus. In addition, no differences in NSC proliferation or survival were detected, and MSG did not adversely affect the neuronal differentiation of NSCs. Moreover, neurobehavioral tests showed that MSG treatment did not impair spatial learning and memory. These findings provide a first assessment of the neurotoxic effects of MSG on NSCs and hippocampal neurogenesis.

IL-1β promotes glutamate excitotoxicity: indications for the link between inflammatory and synaptic vesicle cycle in Ménière's disease.

Ménière's disease (MD) is a complex inner ear disorder characterized by a range of symptoms, with its pathogenesis linked to immune-related mechanisms. Our previous research demonstrated that IL-1β maturation and release can trigger cell pyroptosis, exacerbating the severity of the endolymphatic hydrops in a mouse model; however, the specific mechanism through which IL-1β influences MD symptoms remains unclear. This study conducted on patients with MD examined changes in protein signatures in the vestibular end organs (VO) and endolymphatic sac (ES) using mass spectrometry. Gene ontology and protein pathway analyses showed that differentially expressed proteins in the ES are closely related to adhesion, whereas those in the VO are related to synapse processes. Additionally, the study found elevated expression of Glutaminase (GLS) in the VO of MD patients compared to controls. Further investigations revealed that IL-1β increased glutamate levels by upregulating GLS expression in HEI-OC1 cells. Treatment with a GLS inhibitor or an IL-1β receptor antagonist alleviated auditory-vestibular dysfunction and reduced glutamate levels in mice with endolymphatic hydrops. These findings collectively suggest that imbalanced neurotransmitter release and immune responses contribute to the pathology of MD, potentially explaining the hearing loss and vertigo associated with the disease and offering new avenues for therapeutic interventions.

Effects of quercetin-immobilized albumin cerium oxide nanoparticles on glutamate toxicity: in vitro study.

One aspect of glutamate (Glut) toxicity may be the opening of the blood-brain barrier to albumin (Al), which in itself can cause nerve cell death. Quercetin (Q) is a polyphenolic substance and has a neuroprotective effect. Cerium oxide nanoparticles (Ce2O3NPs) are highly interested in biological applications due to their antioxidant properties. The current study aimed to investigate the impact of Q-immobilized Al+Ce2O3NPs in Glut-induced neurotoxicity, mainly focusing on cell viability and neurobiochemical changes. Hydrothermal synthesis and characterization of Q-immobilized Al+Ce2O3NPs were performed. After preparing the primary neuron culture, it was exposed to Glut to induce neurotoxicity. Then, various doses of Ce2O3NP, Al+Ce2O3NP, and Q+Al+Ce2O3NPs (1, 5, 10, and 25 µg/ml) were applied to the wells and incubated for 24 h. Then, cell viability was determined by MTT analysis. Additionally, oxidative stress parameters were measured. When the obtained data were examined, it was shown that cell viability decreased with Glut concentration but significantly increased with Q+Al+Ce2O3NPs treatment. When oxidative stress markers were considered, Glut treatment increased LDH, AChE, and TOS levels, while TAC and GSH levels decreased. However, the trend changed after Q+Al+Ce2O3NPs treatment, suggesting that damaged neurons were protected against oxidative stress. The results of this study indicate that Q+Al+Ce2O3NP can ameliorate Glut-induced neurotoxicity, especially when used at a dose of 25 µg/ml.

Enhancement of Glutamate Uptake as Novel Antiseizure Approach: Preclinical Proof of Concept.

Excitotoxicity is a common hallmark of epilepsy and other neurological diseases associated with elevated extracellular glutamate levels. Thus, here, we studied the protective effects of (R)-AS-1, a positive allosteric modulator (PAM) of glutamate uptake in epilepsy models. (R)-AS-1 was evaluated in a range of acute and chronic seizure models, while its adverse effect profile was assessed in a panel of standard tests in rodents. The effect of (R)-AS-1 on glutamate uptake was assessed in COS-7 cells expressing the transporter. WAY 213613, a selective competitive EAAT2 inhibitor, was used to probe the reversal of the enhanced glutamate uptake in the same transporter expression system. Confocal microscopy and Western blotting analyses were used to study a potential influence of (R)-AS-1 on GLT-1 expression in mice. (R)-AS-1 showed robust protection in a panel of animal models of seizures and epilepsy, including the maximal electroshock- and 6 Hz-induced seizures, corneal kindling, mesial temporal lobe epilepsy, lamotrigine-resistant amygdala kindling, as well as seizures induced by pilocarpine or Theiler's murine encephalomyelitis virus. Importantly, (R)-AS-1 displayed a favorable adverse effect profile in the rotarod, the minimal motor impairment, and the Irwin tests. (R)-AS-1 enhanced glutamate uptake in vitro and this effect was abolished by WAY 213613, while no influence on GLT-1 expression in vivo was observed after repeated treatment. Collectively, our results show that (R)-AS-1 has favorable tolerability and provides robust preclinical efficacy against seizures. Thus, allosteric enhancement of EAAT2 function could offer a novel therapeutic strategy for treatment of epilepsy and potentially other neurological disorders associated with glutamate excitotoxicity. ANN NEUROL 2024.

Decreased Expression of the EAAT5 Glutamate Transporter at Photoreceptor Synapses in Early, Pre-Clinical Experimental Autoimmune Encephalomyelitis, a Mouse Model of Multiple Sclerosis.

Multiple sclerosis is a frequent neuroinflammatory and neurodegenerative disease of the central nervous system that includes alterations in the white and gray matter of the brain. The visual system is frequently affected in multiple sclerosis. Glutamate excitotoxicity might play a role in disease pathogenesis. In the present study, we analyzed with qualitative and quantitative immunofluorescence microscopy and Western blot analyses whether alterations in the EAAT5 (SLC1A7) glutamate transporter could be involved in the previously observed alterations in structure and function of glutamatergic photoreceptor ribbon synapses in the EAE mouse model of MS. EAAT5 is a presynaptic glutamate transporter located near the presynaptic release sites. We found that EAAT5 was strongly reduced at the photoreceptor synapses of EAE retinas in comparison to the photoreceptor synapses of the respective control retinas as early as day 9 post-immunization. The Western blot analyses demonstrated a decreased EAAT5 expression in EAE retinas. Our data illustrate early alterations of the EAAT5 glutamate transporter in the early pre-clinical phase of EAE/MS and suggest an involvement of EAAT5 in the previously observed early synaptic changes at photoreceptor synapses. The precise mechanisms need to be elucidated by future investigations.

Restoring and sustaining human postmortem retinal light responses with scalable methods for testing degenerative disease therapies.

Neuro- and retinal degenerative diseases rob millions of aging individuals of their independence. Researching these diseases in human tissue has been hindered by the immediate loss of electric activity in neurons after the circulation ceases. Recent studies indicate that limited neuronal activity can be revived postmortem, even in the retina. We capitalized on this discovery by successfully restoring and maintaining in vivo -like light responses in eyes recovered up to four hours and stored for up to 48 hours postmortem. This breakthrough significantly increases the availability of functionally viable human retinas for research. Our AI-based postmortem retinal imaging platform identifies retinal structures and allows us to compare light responses in the healthy central and peripheral retina with ex vivo electroretinography. We use this platform to measure the dark adaptation of human macular cones from controls and donors with age-related macular degeneration for the first time in the absence of the retinal pigment epithelium. We developed increased throughput technology and a model to simulate disease-associated acute ischemia-reperfusion. In this model, we demonstrate the protective or toxic effects of several drugs targeting oxidative stress or glutamate excitotoxicity.

Regulatory roles of histamine receptor in astrocytic glutamate clearance under conditions of increased glucose variability

In diabetic patients, repeated episodes of hypoglycemia can increase glucose variability (GV), which may lead to glutamate neurotoxicity in the brain and consequently affect cognitive functions. Astrocytes play a crucial role in regulating the balance of glutamate within the brain, and their function is influenced by the histamine receptor (HR) signaling pathway. However, the specific role of this mechanism under conditions of high GV is not yet clear. The results showed that increased GV resulted in decreased expression of HRs in mice hippocampus and astrocytes cultured in vitro. Additionally, a decrease in the expression of proteins related to glutamate metabolic clearance was observed, accompanied by a reduction in glutamate reuptake capacity. Notably, the intervention with histidine/histamine was able to reverse the above changes. Further mechanistic studies showed that inhibition of HRs that increased GV led to significant disturbances in astrocytic mitochondrial function. These abnormalities encompassed increased fragmentation morphology and the accumulation of reactive oxygen species, accompanied by decreased mitochondrial respiratory capacity and dysregulation of dynamics. Distinct HR subtypes exhibited variations in the modulation of mitochondrial function, with H3R demonstrating the most pronounced impact. The overexpression of H3R could enhance glutamate metabolic by reversing disturbances in mitochondrial dynamics. Therefore, this study suggests that H3R is able to maintain glutamate metabolic clearance capacity and exert neuroprotective effects in astrocytes that increased GV by regulating mitochondrial dynamic balance. This provides an important basis for potential therapeutic targets for diabetes-related cognitive dysfunction.

Ethyl Acetate Fraction of Chestnut Honey Attenuates Scopolamine-Induced Cognitive Impairment in Mice and Glutamate-Induced Neurotoxicity in HT22 Cells.

Chestnut honey has various benefits, such as antioxidative, anti-inflammatory, immunomodulatory, antibacterial, and antiviral effects. However, the effects of chestnut honey or the ethyl acetate fraction of chestnut honey (EACH) on neurodegenerative diseases and their related cognitive impairment and neurotoxicity have not yet been established. Therefore, in this study, we investigated the mitigating effect of the EACH on scopolamine (SCO)-injected cognitive decline in mice and glutamate-exposed neurotoxicity in HT22 cells. EACH administration significantly reversed SCO-induced cognitive decline in mice, as demonstrated through the Morris water maze and passive avoidance tests. The EACH treatment showed a significant alleviation effect by recovering more than 80% of the cell viability decrease induced by glutamate exposure in the HT22 neuronal cell model. Furthermore, the EACH significantly reduced reactive oxygen species accumulation, lactate dehydrogenase release, mitochondrial depolarization, and neuronal apoptosis. The EACH regulated the level of apoptosis-related proteins, induced the nuclear translocation of nuclear factor-E2-related factor 2 (Nrf-2) and the expression of related antioxidant proteins, and induced the phosphorylation of tropomyosin-related kinase receptor B (TrkB)/cAMP-calcium response element-binding protein (CREB) and the expression of brain-derived neurotrophic factor. These data indicate that the EACH can prevent neurons from oxidative damage and improve cognitive dysfunction by activating Nrf-2 and TrkB/CREB signaling pathways. Therefore, the EACH demonstrates potential therapeutic value in mitigating oxidative stress-induced neurotoxicity, cognitive decline, and related neurodegenerative diseases.

CB1 Receptor Activation Provides Neuroprotection in an Animal Model of Glutamate-Induced Excitotoxicity Through a Reduction of NOX-2 Activity and Oxidative Stress.

Excitotoxicity is a process in which NADPH oxidase-2 (NOX-2) plays a pivotal role in the generation of reactive oxygen species (ROS). Oxidative stress influences the expression of Aquaporin 4 (AQP4), a water channel implicated in blood-brain barrier (BBB) permeability and edema formation. The endocannabinoid system is widely distributed in the brain, particularly through the cannabinoid receptor type 1 (CB1) and type 2 (CB2), which have been shown to have a neuroprotective function in brain injury. Given the significant involvement of NOX-2 in ROS production during excitotoxicity, our research aims to assess the participation of NOX-2 in the neuroprotective effect of the cannabinoid receptor agonist WIN55,212-2 against glutamate-induced excitotoxicity damage in the striatum using invivo model. Wild-type mice (C57BL/6) and NOX-2 KO (gp91Cybbtm1Din/J) were stereotactically injected in the striatum with monosodium glutamate or vehicle. Subsequently, a group of mice was administered an intraperitoneal dose of WIN55,212-2, AM251, or AM251/WIN55,212-2 following the intracerebral injection. Motor activity was assessed, and the lesion was examined through histological sections stained with cresyl violet. Additionally, brain water content and Evans blue assay were conducted. The activity of NOX was quantified, and the protein expression of CB1, gp91phox, AQP4, Iba-1, TNF-α, and NF-κB was analyzed using Western blot. Furthermore, ROS formation was measured through the DHE assay. The activation of the endocannabinoid receptors demonstrated a neuroprotective response during excitotoxicity, meditated by NOX-2. The reduction in ROS production led to a decrease in neuroinflammation, and AQP4 expression, resulting in reduced edema formation, and BBB permeability. During excitotoxic damage, WIN55,212-2 inhibits NOX-2-induced ROS production, reducing brain injury.

The bile acid chenodeoxycholic acid associates with reduced stroke in humans and mice

Bile acids (BAs) are liver-derived signaling molecules that can be found in the brain, but their role there remains largely unknown. We found increased brain chenodeoxycholic acid (CDCA) in mice with absent 12α-hydroxylase (Cyp8b1), a BA synthesis enzyme. In these Cyp8b1-/-, and in wild-type mice administered CDCA, stroke infarct area was reduced. Elevated glutamate-induced excitotoxicity mediated by aberrant N-methyl-D-aspartate receptor (NMDAR) over-activation contributes to neuronal death in ischemic stroke. We found reduced glutamate-induced excitotoxicity in neurons from Cyp8b1-/- and CDCA-treated wild-type mice. CDCA decreased NMDAR-mediated excitatory post-synaptic currents by reducing over-activation of NMDAR subunit GluN2B in wild-type brains. Synaptic NMDAR activity was also decreased in Cyp8b1-/- brains. Expression and synaptic distribution of GluN2B were unaltered in Cyp8b1-/- mice, suggesting CDCA may directly antagonize GluN2B-containing NMDARs. Supporting our findings, in a case-control cohort of acute ischemic stroke patients, we found lower circulatory CDCA. Together, our data suggest that CDCA, acting in the liver-brain axis, decreases GluN2B-containing NMDAR over-activation, contributing to neuroprotection in stroke.

The Role of Neuropeptide Y in the Pathogenesis of Alzheimer's Disease: Diagnostic Significance and Neuroprotective Functions.

Background. Alzheimer's disease (AD) is one of the most common neurodegenerative diseases. It has been suggested that the factors that cause pathologic changes and lead to the development of AD may also include changes in certain neuropeptides. The implication of the neuropeptide (NPY) in the pathogenesis of AD and its potential therapeutic role is possible due to the following properties: involvement in adult neurogenesis, regulatory effects on the immune system, the inhibition of potential-dependent Ca2+ channels, and the reduction in glutamate excitotoxicity. The aim of our review was to summarize recent data on the role of NPY in AD development and to explore its potential as a biomarker and a possible therapeutic target. Materials and methods. We performed a systematic review of studies, for which we search using the keywords "Alzheimer's disease and neuropeptide Y", "Alzheimer's disease and NPY", "AD and NPY", "Neuropeptide Y and Neurodegenerative disease". Nineteen articles were included in the review. Results. The NPY levels in cerebrospinal fluid and plasma have been found to be reduced or unchanged in AD patients; however, these findings need to be confirmed in more recent studies. Data obtained in transgenic animal models support the role of NPY in AD pathogenesis. The neuroprotective effects of NPY have been demonstrated in vitro and in vivo in AD models. Conclusion. The findings may open new possibilities for using NPY as a diagnostic marker to detect AD at earlier stages of the disease or as a potential therapeutic target due to its neuroprotective properties.

Icariin is a potential neurodegenerative candidate against ammonia–glutamate excitotoxicity–oxidative stress pathway

BackgroundHepatic encephalopathy (HE) is a pathological state characterized by the abrupt or chronic failure of the liver. This study intends to conduct a comparative analysis of potential benefits of icariin (ICA), a primary component of flavonoids found in the Chinese medicinal plant Epimedium, with silymarin (SLY) as a hepatic and brain support agent in a model of HE rats, focusing on assessment of the behavioral and biochemical effects. Thioacetamide (TAA) was given intraperitoneally to rats at a dosage of 200 mg/kg on three separate days to induce HE. Oral gavage of silymarin or ICA (100 mg/kg) was given daily for 14 days following HE induction. All rats underwent behavioral assessments (open field and Y maze). Estimates were made for hepatic functions and brain cortex oxidative stress indicators as well as cytochrome c and caspase-3.ResultsThe findings demonstrated that the administration of ICA to rodents with HE induced by TAA led to a recovery of hepatic enzymes activities and behavioral adjustments as shown by an improvement in locomotor and memory functions. Furthermore, Icariin demonstrated a reduction in cortex biochemical indicators through the amelioration of hyperammonemia and enhancement of antioxidant status. This was achieved by reducing malondialdehyde, calcium, nitric oxide contents and downregulating lactate dehydrogenase activities. In addition, ICA maintains alteration of glutamate and glutamine contents.ConclusionICA suggested to possess the capacity to serve as a beneficial hepatotherapeutic and neurotherapeutic adjunct in brain disorders associated with hyperammonemia–glutamate-mediated excitotoxicity.

Mechanism of Gastrodin against neurotoxicity based on network pharmacology, molecular docking and experimental verification

BackgroundDisorders of glutamate metabolism and excessive release participat in multiple neuronal pathologies including ischemic stroke (IS), Alzheimer's disease (AD), or Parkinson's disease (PD). Recently, herbal medicines have been widely used and have shown satisfactory results in the treatment of neurological disorders. Gastrodin is a traditional Chinese medicine (TCM) used for the treatment of nerve injuries, spinal cord injuries, and some central nervous system diseases as well. This research examines the neuroprotective effects of Gastrodin against glutamate-induced neurotoxicity in neuronal cells. MethodsThe HERB database was used to explore the active ingredients and target genes of Gastrodia Elata. The STRING database and Cytoscape software were used to screen and construct the Protein-Protein Interaction (PPI). Furthermore, we used molecular docking to predict the potential targets of Gastrodin. The effects of Gastrodin were revealed by western blot, calcium imaging, membrane clamp, CCK8 and flow cytometry. Neuronal oxidative stress and damage were assessed by measuring malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity. Neuronal morphology was examined using Golgi-Cox staining. Finally, animal behavior was examined using novel object recognition and fear conditioning tests. ResultsWe have obtained 22 components such as TM10, TM17, TM25 (Gastrodin), and 281 targets such as AKT, EGFR, and CDK1 through network pharmacology. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed these genes were significantly enriched in protein phosphorylation, protein serine/threonine/tyrosine kinase activity, apoptosis and HIF-1 signaling pathways, etc. A higher affinity between Gastrodin and AKT was revealed by PPI analysis and molecular docking. Further, Gastrodin significantly inhibited Ca2+ influxes and excitatory synaptic transmission in cortical neurons. In addition, Gastrodin effectively alleviated neuron apoptosis, oxidative stress and damage. ConclusionGastrodin has neuroprotective effects against glutamate-induced neurotoxicity.

Neuroprotection by 4R-cembranoid against Gulf War Illness-related Chemicals is mediated by ERK, PI3K, and CaMKII pathways

Gulf War Illness (GWI) has been consistently linked to exposure to pyridostigmine (PB), N,N-Diethyl-meta-toluamide (DEET), permethrin (PER), and traces of sarin. In this study, diisopropylfluorophosphate (DFP, sarin surrogate) and the GWI-related chemicals were found to reduce the number of functionally active neurons in rat hippocampal slices. These findings confirm a link between GWI neurotoxicants and N-Methyl-D-Aspartate (NMDA)-mediated excitotoxicity, which was successfully reversed by Edelfosine (a phospholipase Cβ (PLCβ3) inhibitor) and Flupirtine (a Kv7 channel agonist).To test whether 4R-cembranoid (4R), a nicotinic α7 acetylcholinesterase receptor (α7AChR) modulator known for its neuroprotective properties, can restore hippocampal neurons from glutamate-induced neurotoxicity, we exposed rat hippocampal slices with DFP for 10 min followed by 60 min treatment with 4R. We investigated the 4R mechanisms of neuroprotection after preincubation with LY294002, PD98059, and KN-62. The inhibition of the phosphatidylinositol 3-kinase (PI3K), mitogen-activated protein kinase (MEK1/2), and calcium/calmodulin-dependent protein kinase (CaMKII) abrogated the protective effect of 4R against DFP-induced neurotoxicity. In separate experiments, after incubation with DFP, followed by 4R for 1 h, cellular extracts were prepared for Western blotting of phospho-Akt, phospho-GSK3β, phosphorylated extracellular signal-regulated kinase (ERK)1/2, CaMKII and cAMP response element-binding protein (CREB). Our results show that DFP induces neuronal dysfunction by dephosphorylation, while 4R restores the phosphorylation of Akt, GSK3, ERK1/2, CREB, and CaMKII. Moreover, our proteomics analysis supported the notion that 4R activates additional signaling pathways related to enhancing neuronal signaling, synaptic plasticity, and apoptotic inhibition to promote cell survival against DFP, offering biomarkers for developing treatment against GWI.