Glutamate-mediated Excitotoxicity Research Articles

Genetic Variations of Ionotropic Glutamate Receptor Pathways on Interferon-α-induced Depression in Patients with Hepatitis C Viral Infection

ImportanceThe most supportive evidence of the inflammation theory of depression is that up to one-third of patients with Hepatitis C virus infection (HCV) develop clinical depressive episodes during interferon-α (IFN-α) therapy. As glutamate-mediated excitotoxicity has been found to be a consequence of excessive inflammation and a pathogenic mechanism of depression, it is plausible to investigate genes on ionotropic glutamate receptor pathways. ObjectiveTo identify the at-risk genetic variations on ionotropic glutamate receptor pathways for interferon-α-induced depression. MethodWe assessed 291 patients with chronic HCV undergoing IFN-α therapy and analyzed the single nucleotide polymorphisms (SNPs) in genes related to ionotropic glutamate receptors in this prospective case-control study. Patients who developed IFN-α-induced depression anytime during the treatment were defined as the case group, while those who did not were defined as the control group. Genomic DNA was extracted from peripheral blood and analyzed by Affymetrix TWB array. Allelic and haplotype association tests were conducted using χ2 tests to assess the difference in allele and haplotype frequencies between cases and controls. Additionally, we performed 5000 permutations to control gene-wide family-wise error rates and create empirical p-values. Stratified analyses were then done to control for confounders and adjust odds ratios for our significant SNPs. We also did an additional stratified analysis to re-assess genes with near-significant SNPs (empirical p-value=0.05-0.10), employing Bonferroni correction with the effective number of independent tests to control gene-wide family-wise error rates. ResultsThe minor and major allele frequencies of rs7542 (empirical p-value=0.0310) in MAPK3, rs3026685 (empirical p-value=0.0378) in PICK1, rs56005409 (empirical p-value=0.0332) in PRKCA, rs12914792 (empirical p-value=0.0096), rs17245773 (empirical p-value=0.0340) in RASGRF1, and rs78387863 (empirical p-value=0.0086), rs74365480 (empirical p-value=0.0200) in RASGRF2 were found significantly different between cases and controls. Haplotype association tests also revealed one significant haplotype in PRKCA (empirical p-value=0.0200) and one in RASGRF1 (empirical p-value=0.0048). Stratified analyses showed no signs of confounders for most of our significant SNPs, except for rs78387863 in RASGRF2. After a re-assessment of our near-significant genes by stratified analyses, two SNPs in GRIN2B turned significant. ConclusionsThis study provided supportive evidence of the involvement of the RAS/RAF/mitogen-activated protein kinase (MAPK) signaling pathway and glutamate ionotropic receptor AMPA type subunit 2(GluR2) transportation in the pathogenesis of IFN-α-induced depression.

In vivo neuroprotective effect of a self-assembled peptide hydrogel

Traumatic brain injury (TBI) is associated with poor intrinsic healing responses and long-term cognitive decline. A major pathological outcome of TBI is acute glutamate-mediated excitotoxicity (GME) experienced by neurons. Short peptides based on the neuroprotective extracellular glycoprotein ependymin have shown the ability to slow down the effect of GME — however, such short peptides tend to diffuse away from target sites after in vivo delivery. We have designed a self-assembling peptide containing an ependymin mimic that can form nanofibrous matrices. The peptide was evaluated in situ to assess neuroprotective utility after an acute fluid-percussion injury. This biomimetic matrix can conform to the intracranial damaged site after delivery, due its shear-responsive rheological properties. We demonstrated the potential efficacy of the peptide for supporting neuronal survival in vitro and in vivo. Our study demonstrates the potential of these implantable acellular hydrogels for managing the acute (up to 7 days) pathophysiological sequelae after traumatic brain injury. Further work is needed to evaluate less invasive administrative routes and long-term functional and behavioral improvements after injury.

Exciting Complexity: The Role of Motor Circuit Elements in ALS Pathophysiology.

Amyotrophic lateral sclerosis (ALS) is a fatal disease, characterized by the degeneration of both upper and lower motor neurons. Despite decades of research, we still to date lack a cure or disease modifying treatment, emphasizing the need for a much-improved insight into disease mechanisms and cell type vulnerability. Altered neuronal excitability is a common phenomenon reported in ALS patients, as well as in animal models of the disease, but the cellular and circuit processes involved, as well as the causal relevance of those observations to molecular alterations and final cell death, remain poorly understood. Here, we review evidence from clinical studies, cell type-specific electrophysiology, genetic manipulations and molecular characterizations in animal models and culture experiments, which argue for a causal involvement of complex alterations of structure, function and connectivity of different neuronal subtypes within the cortical and spinal cord motor circuitries. We also summarize the current knowledge regarding the detrimental role of astrocytes and reassess the frequently proposed hypothesis of glutamate-mediated excitotoxicity with respect to changes in neuronal excitability. Together, these findings suggest multifaceted cell type-, brain area- and disease stage- specific disturbances of the excitation/inhibition balance as a cardinal aspect of ALS pathophysiology.

Hippocampal Degeneration Involves Glutamate Excitoxicity During the Pathogenesis of Alzheimer's Disease

Impairment of dentate gyrus (DG) neurochemistry and neuronal morphology complicates hippocampal-related functions during Alzheimer’s disease (AD) pathogenesis. A reciprocal relationship between amyloid-β accumulation and N-methyl-D-aspartate (NMDA) enhanced activity has been shown, but the specific mechanism mediating neurodegeneration in DG following glutamatergic dysregulation in vivo is poorly understood. This study tested the hypotheses that glutamate-mediated excitotoxicity may directly impede neural processes modulating hippocampal-related behavior/function.

Positive allosteric activation of glial EAAT-2 transporter protein: A novel strategy for Alzheimer’s disease

Excitatory amino acid transporter-2 (EAAT-2) protein localized in the membrane of glial cells are responsible for the clearance of glutamate in synapse and it plays a key role among the five glutamate transporters (EAATs) in regulating synaptic transmission and preventing excitotoxicity in neurons. EAAT-2 dysfunction has been associated with the neuropathology of Alzheimer’s disease (AD). Impairment of EAAT-2 transporter function results excess accumulation of glutamate in synaptic cleft that acts on post-synaptic glutaminergic receptors excessively resulting in influx of Na+ and Ca2+ ions into the neurons. This triggers excitotoxicity in post-synaptic neurons by activating apoptotic or necrotic pathways causing neurodegeneration in AD. The compounds that increase the EAAT-2 activity may have therapeutic potential for neuroprotection in AD. The positive allosteric site activation of EAAT-2 represents a promising entry point for the identification of novel pharmacological compounds for the management of neurodegenerative conditions involving glutamate-mediated excitotoxicity. We hypothesize, therefore, that the positive allosteric activators may enhance glutamate clearance from the synaptic cleft by promoting orthosteric binding of glutamate ligand in EAAT-2 transporter protein and attenuate the excitotoxicity in neurons and prevent the disease progression of AD.

Chinese Herbal Medicine Interventions in Neurological Disorder Therapeutics by Regulating Glutamate Signaling.

Glutamate is the major excitatory neurotransmitter in the central nervous system, and its signaling is critical for excitatory synaptic transmission. The well-established glutamate system involves glutamate synthesis, presynaptic glutamate release, glutamate actions on the ionotropic glutamate receptors (NMDA, AMPA, and kainate receptors) and metabotropic glutamate receptors, and glutamate uptake by glutamate transporters. When the glutamate system becomes dysfunctional, it contributes to the pathogenesis of neurodegenerative and neuropsychiatric diseases such as Alzheimer's disease, Parkinson's disease, depression, epilepsy, and ischemic stroke. In this review, based on regulating glutamate signaling, we summarize the effects and underlying mechanisms of natural constituents from Chinese herbal medicines on neurological disorders. Natural constituents from Chinese herbal medicine can prevent the glutamate-mediated excitotoxicity via suppressing presynaptic glutamate release, decreasing ionotropic and metabotropic glutamate receptors expression in the excitatory synapse, and promoting astroglial glutamate transporter expression to increase glutamate clearance from the synaptic cleft. However, some natural constituents from Chinese herbal medicine have the ability to restore the collapse of excitatory synapses by promoting presynaptic glutamate release and increasing ionotropic and metabotropic glutamate receptors expression. These regulatory processes involve various signaling pathways, which lead to different mechanistic routes of protection against neurological disorders. Hence, our review addresses the underlying mechanisms of natural constituents from Chinese herbal medicines that regulate glutamate systems and serve as promising agents for the treatment of the above-mentioned neurological disorders.

Glutamatergic neurometabolites and cortical thickness in treatment-resistant schizophrenia: Implications for glutamate-mediated excitotoxicity

Treatment-resistant schizophrenia may be related to structural brain alterations. However, the mechanisms underlying these changes remain unclear. The present study had two main aims: (1) to explore differences in cortical thickness between patients with treatment-resistant schizophrenia non-responsive to clozapine (ultra-treatment-resistant schizophrenia, UTRS), patients with treatment-resistant schizophrenia responsive to clozapine (Cloz-Resp), patients responsive to first-line non-clozapine antipsychotics (FL-Resp), and healthy controls (HCs); and (2) to test our hypothesis of structural compromise as a manifestation of neurotoxic effects from elevated glutamate (Glu) (i.e. glutamate-mediated excitotoxicity) by examining the relationships between glutamatergic neurometabolite levels (Glu and glutamate + glutamine (Glx)) in the dorsal anterior cingulate cortex (dACC) and cortical thickness. T1-weighted images and 1H-MRS data were obtained from UTRS (n = 24), Cloz-Resp (n = 25), FL-Resp (n = 19), and HCs (n = 26). Vertex-wise analyses showed that patients with UTRS had widespread cortical thinning in the bilateral frontal, temporal, parietal, and occipital gyri compared to HCs and FL-Resp patients. In the patient group, negative associations were found between dACC Glx levels and cortical thickness in the right dorsolateral prefrontal cortex after correcting for multiple comparisons and controlling for age, sex, antipsychotic dose, and illness severity. In conclusion, glutamate-mediated excitotoxicity may be one of the mechanisms underlying structural compromise seen in treatment-resistant schizophrenia. Future studies should longitudinally examine the associations between glutamatergic neurometabolite levels and cortical thickness in the context of treatment and illness progression.

Less NMDA Receptor Binding in Dorsolateral Prefrontal Cortex and Anterior Cingulate Cortex Associated With Reported Early-Life Adversity but Not Suicide.

BackgroundGlutamate is an excitatory neurotransmitter binding to 3 classes of receptors, including the N-methyl, D-aspartate (NMDA) receptor. NMDA receptor binding is lower in major depression disorder and suicide. NMDA receptor blocking with ketamine can have antidepressant and anti-suicide effects. Early-life adversity (ELA) may cause glutamate-mediated excitotoxicity and is more common with major depression disorder and in suicide decedents. We sought to determine whether NMDA-receptor binding is altered with suicide and ELA.MethodsA total 52 postmortem cases were organized as 13 quadruplets of suicide and non-suicide decedents matched for age, sex, and postmortem interval, with or without reported ELA (≤16 years). Tissue blocks containing dorsal prefrontal (BA8), dorsolateral prefrontal (BA9), or anterior cingulate (BA24) cortex were collected at autopsy. Psychiatrically healthy controls and suicide decedents underwent psychological autopsy to determine psychiatric diagnoses and details of childhood adversity. NMDA receptor binding was determined by quantitative autoradiography of [3H]MK-801 binding (displaced by unlabeled MK-801) in 20-µm-thick sections.Results[3H]MK-801 binding was not associated with suicide in BA8, BA9, or BA24. However, [3H]MK-801 binding with ELA was less in BA8, BA9, and BA24 independent of suicide (P < .05). [3H]MK-801 binding was not associated with age or postmortem interval in any brain region or group.ConclusionsLess NMDA receptor binding with ELA is consistent with the hypothesis that stress can cause excitotoxicity via excessive glutamate, causing either NMDA receptor downregulation or less receptor binding due to neuron loss consequent to the excitotoxicity.

Transforming growth factor-β plasma levels and its role in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive muscle paralysis. Respiratory complications are the main cause of death in ALS. For this reason, initial respiratory status and its decline over disease progression are strong independent predictors of survival. Riluzole, a glutamatergic neurotransmission inhibitor, is the only drug that has shown to extend survival. Therefore, both novel molecular biomarkers and treatment strategies are needed. Transforming growth factor-β (TGF-β) family cytokines are important regulators of cell fate affecting both neurogenesis and neurodegeneration. Several studies demonstrate that TGF-β signalling protects neurons from glutamate-mediated excitotoxicity, a recognized mechanism underlying the pathogenesis of various neurodegenerative disorders such as ALS. Recent studies report dysregulations of the TGF-β system as a common feature of neurodegenerative disorders. The upregulation of this system has been linked with ALS progression. We have quantified TGF-β1, TGF-β2 and TGF-β3 serum levels in 23 ALS patients and 12 healthy controls, our preliminary results support the hypothesis that TGF-β3 levels can be a marker disease severity ALS. Further results are necessary to confirm this hypothesis.

Achyranthes bidentata polypeptides prevent apoptosis by inhibiting the glutamate current in cultured hippocampal neurons.

Glutamate-induced excitotoxicity plays a critical role in the neurological impairment caused by middle cerebral artery occlusion. Achyranthes bidentata polypeptides have been shown to protect against neurological functional damage caused by middle cerebral artery occlusion, but the underlying neuroprotective mechanisms and the relationship to glutamate-induced excitotoxicity remain unclear. Therefore, in the current study, we investigated the protective effects of Achyranthes bidentata polypeptides against glutamate-induced excitotoxicity in cultured hippocampal neurons. Hippocampal neurons were treated with Mg2+-free extracellular solution containing glutamate (300 µM) for 3 hours as a model of glutamate-mediated excitotoxicity (glutamate group). In the normal group, hippocampal neurons were incubated in Mg2+-free extracellular solution. In the Achyranthes bidentata polypeptide group, hippocampal neurons were incubated in Mg2+-free extracellular solution containing glutamate (300 µM) and Achyranthes bidentata polypeptide at different concentrations. At 24 hours after exposure to the agents, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and Hoechst 33258 staining were used to assess neuronal viability and nuclear morphology, respectively. Caspase-3 expression and activity were evaluated using western blot assay and colorimetric enzymatic assay, respectively. At various time points after glutamate treatment, reactive oxygen species in cells were detected by H2DCF-DA, and mitochondrial membrane potential was detected by rhodamine 123 staining. To examine the effect of Achyranthes bidentata polypeptides on glutamate receptors, electrophysiological recording was used to measure the glutamate-induced inward current in cultured hippocampal neurons. Achyranthes bidentata polypeptide decreased the percentage of apoptotic cells and reduced the changes in caspase-3 expression and activity induced by glutamate. In addition, Achyranthes bidentata polypeptide attenuated the amplitude of the glutamate-induced current. Furthermore, the glutamate-induced increase in intracellular reactive oxygen species and reduction in mitochondrial membrane potential were attenuated by Achyranthes bidentata polypeptide treatment. These findings collectively suggest that Achyranthes bidentata polypeptides exert a neuroprotective effect in cultured hippocampal neurons by suppressing the overactivation of glutamate receptors and inhibiting the caspase-3-dependent mitochondrial apoptotic pathway. All animal studies were approved by the Animal Care and Use Committee, Nantong University, China (approval No. 20120216-001) on February 16, 2012.

Transcriptional block of AMPK-induced autophagy promotes glutamate excitotoxicity in nutrient-deprived SH-SY5Y neuroblastoma cells.

We investigated the role of autophagy, a controlled lysosomal degradation of cellular macromolecules and organelles, in glutamate excitotoxicity during nutrient deprivation in vitro. The incubation in low-glucose serum/amino acid-free cell culture medium synergized with glutamate in increasing AMP/ATP ratio and causing excitotoxic necrosis in SH-SY5Y human neuroblastoma cells. Glutamate suppressed starvation-triggered autophagy, as confirmed by diminished intracellular acidification, lower LC3 punctuation and LC3-I conversion to autophagosome-associated LC3-II, reduced expression of proautophagic beclin-1 and ATG5, increase of the selective autophagic target NBR1, and decreased number of autophagic vesicles. Similar results were observed in PC12 rat pheochromocytoma cells. Both glutamate-mediated excitotoxicity and autophagy inhibition in starved SH-SY5Y cells were reverted by NMDA antagonist memantine and mimicked by NMDA agonists D-aspartate and ibotenate. Glutamate reduced starvation-triggered phosphorylation of the energy sensor AMP-activated protein kinase (AMPK) without affecting the activity of mammalian target of rapamycin complex 1, a major negative regulator of autophagy. This was associated with reduced mRNA levels of autophagy transcriptional activators (FOXO3, ATF4) and molecules involved in autophagy initiation (ULK1, ATG13, FIP200), autophagosome nucleation/elongation (ATG14, beclin-1, ATG5), and autophagic cargo delivery to autophagosomes (SQSTM1). Glutamate-mediated transcriptional repression of autophagy was alleviated by overexpression of constitutively active AMPK. Genetic or pharmacological AMPK activation by AMPK overexpression or metformin, as well as genetic or pharmacological autophagy induction by TFEB overexpression or lithium chloride, reduced the sensitivity of nutrient-deprived SH-SY5Y cells to glutamate excitotoxicity. These data indicate that transcriptional inhibition of AMPK-dependent cytoprotective autophagy is involved in glutamate-mediated excitotoxicity during nutrient deprivation in vitro.

Effect of ceftriaxone on paired-pulse response and long-term potentiation of hippocampal dentate gyrus neurons in rats with Alzheimer-like disease

AimsGlutamatergic dysfunction is posed as a main stage in neurodegenerative disorders such as Alzheimer's disease (AD). Glutamate-mediated excitotoxicity contributes to cognitive dysfunction and cell death in AD. Ceftriaxone (CFT), a well-known upregulator of GLT-1, selectively induces the expression of glutamate transporter-1 (GLT-1) in different brain regions and therefore can be posed as a potential candidate for elimination of glutamate-induced excitotoxicity which is an early prominent event in AD brains. This study was designed to investigate the electrophysiological and behavioral effects of the β-lactam antibiotic ceftriaxone in okadaic acid (OKA)-induced model of AD. Materials and methodsMale Wistar rats divided into four control, ceftriaxone (CFT), OKA, and OKA plus ceftriaxone (OKA + CFT) groups. OKA was injected intracerebroventricularly (i.c.v., 200 ng/5 μl) into lateral ventricles and after two weeks the evoked field potential recorded from hippocampal perforant path-DG synapses in order to evaluate the effect of ceftriaxone treatment (200 mg/kg/day, i.p.) on long-term potentiation (LTP) and paired-pulse responses. Key findingsResults of this study revealed that ceftriaxone treatment significantly ameliorates the OKA-induced attenuation of field excitatory post-synaptic potential (fEPSP) slope and population spike (PS) amplitude following high-frequency stimulation and paired-pulse paradigm indicating its beneficial effects on both short-term and long-term plasticity in these neurons. Ceftriaxone also has an improving effect on OKA-induced impairment in short- and long-term memories evaluated by alternation behavior and passive avoidance tasks in rats. SignificanceTherefore, this study suggests that GLT-1 might be a promising therapeutic target for treatment of neurodegenerative disorders such as AD in the future.

Site-specific phosphorylation of Fbxw7 by Cdk5/p25 and its resulting decreased stability are linked to glutamate-induced excitotoxicity

Cyclin-dependent kinase 5 (Cdk5) is a serine/threonine protein kinase that regulates brain development and neurodegeneration. Cdk5 is activated by p25 that is generated from calpain-dependent cleavage of p35. The generation of p25 is responsible for the aberrant hyper-activation of Cdk5, which causes neurodegeneration. Using in vitro assays, we discovered that F-box/WD repeat-containing protein 7 (Fbxw7) is a new substrate of Cdk5. Additionally, Cdk5-dependent phosphorylation of Fbxw7 was detected in the presence of p25, and two amino acid residues (S349 and S372) were determined to be major phosphorylation sites. This phosphorylation was eventually linked to decreased stability of Fbxw7. Using a culture model of cortical neurons challenged with glutamate, we confirmed that decreased stability of Fbxw7 was indeed Cdk5-dependent. Furthermore, diminished levels of Fbxw7 led to increased levels of transcription factor AP-1 (c-Jun), a known substrate of Fbxw7. Given that previous reports demonstrate that c-Jun plays a role in accelerating neuronal apoptosis in these pathological models, our data support the concepts of a molecular cascade in which Cdk5-mediated phosphorylation of Fbxw7 negatively regulates Fbxw7 expression, thereby contributing to neuronal cell death following glutamate-mediated excitotoxicity.

Novel Positive Allosteric Modulators of Glutamate Transport Have Neuroprotective Properties in an in Vitro Excitotoxic Model.

Dysfunction of excitatory amino acid transporters (EAATs) has been implicated in the pathogenesis of various neurological disorders, such as stroke, brain trauma, epilepsy, and several neurodegenerative disorders. EAAT2 is the main transporter subtype responsible for glutamate clearance in the brain, and plays a key role in regulating neurotransmission and preventing excitotoxicity. Therefore, compounds that increase the activity of EAAT2 have therapeutic potential for neuroprotection. In previous studies, we used virtual screening approaches to identify novel positive allosteric modulators (PAMs) of EAAT2. These compounds were shown to selectively increase the activity of EAAT2 and increase Vmax of transport, without changing substrate affinity. In this work, our major effort was to investigate whether increasing the activity of EAAT2 by allosteric modulation would translate to neuroprotection in in vitro primary culture models of excitotoxicity. To investigate potential neuroprotective effects of one EAAT2 PAM, GT949, we subjected cultures to acute and prolonged excitotoxic insults by exogenous application of glutamate, or oxidative stress by application of hydrogen peroxide. GT949 administration did not result in neuroprotection in the oxidative stress model, likely due to damage of the glutamate transporters. However, GT949 displayed neuroprotective properties after acute and prolonged glutamate-mediated excitotoxicity. We propose that this compound prevents excess glutamate signaling by increasing the rate of glutamate clearance by EAAT2, thereby preventing excitotoxic damage and cell death. This novel class of compounds is therefore an innovative approach for neuroprotection with potential for translation in in vivo animal models of excitotoxicity.

Mechanism of neuroprotective effect of mGluR4 agonists

Introduction: This review of literature is to demonstrate a role of group III metabotropic glutamate receptors in maintaining the level of extracellular glutamate in ischemic stroke and neurodegenerative diseases.&#x0D; Metabotropic glutamate receptors: mGluRs are classified into three groups. It is suggested that the activation of mGluR4 may have a neuroprotective effect.&#x0D; Role of excitotoxicity in the development and severity of various brain diseases: An increase in the concentrationьof intracellular Ca2+ is the result of excessive accumulation of glutamate in the extracellular space. And a death of nerve cells occurs after a sequence of biochemical reactions, which was called excitotoxicity. It is followed by an imbalance&#x0D; between glutamatergic excitation and GABA-ergic inhibition. As a result of untimely activation of the inhibitory mechanisms, the accumulation of extracellular glutamate, and consequently the death of neurons, continues, which leads to more severe manifestations of the cerebral ischemia.&#x0D; Role of modulation of mGluRs activity in neuroprotection: The literature describes a large number of studies proving that inhibition of hyperactive glutamatergic transmission has a neuroprotective effect. The most likely mechanisms&#x0D; of neuroprotection are inhibition of glutamate production in the substantia nigra, which in turn protects against glutamate-mediated excitotoxicity, and the reduction of the inflammatory effects.&#x0D; Anti-inflammatory effect of mGluR4 agonists in the mechanism of neuroprotective action: The astroglial component may contribute to the protective action of mGluR4 modulators, since astrocytes and microglia have mGluR4.&#x0D; Conclusion: mGluR4 agonists have the neuroprotective and anti-inflammatory effects.

Peripheral T cells from multiple sclerosis patients trigger synaptotoxic alterations in central neurons.

The crucial step in the pathogenic events that lead to the development and the progression of multiple sclerosis (MS) is the infiltration of autoreactive T cells in the brain. Data from experimental autoimmune encephalomyelitis (EAE) mice indicate that, together with microglia, T cells are responsible for the enhancement of the glutamatergic transmission in central neurons, contributing to glutamate-mediated excitotoxicity, a pathological hallmark of both EAE and MS brains. Here, we addressed the synaptic role of T cells taken from MS patients. A chimeric model of human T cells and murine brain slices was established to record, by Patch Clamp technique, the glutamatergic transmission in the presence of T cells isolated from the peripheral blood of healthy subjects (HS), active (a) and nonactive (na) relapsing remitting MS patients. Intracellular staining and flow cytometry were used to assess tumour necrosis factor (TNF) expression in T cells. Chimeric experiments indicated that, compared to HS and naMS, T cells from aMS induced an increase in glutamatergic kinetic properties of striatal neurons. Such alteration, reminiscent of the those induced by EAE T cells, was blocked by incubation of the slices with etanercept, a TNF receptor antagonist. Of note, T cells from aMS expressed more TNF than naMS patients and HS subjects. These data highlight the synaptotoxic potential retained by MS T cells, suggesting that during the inflammatory phase of the disease infiltrating T cells could influence the neuronal activity contributing to the TNF-mediated mechanisms of glutamate excitotoxicity in central neurons.

Continuous infusion of an agonist of the tumor necrosis factor receptor 2 in the spinal cord improves recovery after traumatic contusive injury.

SummaryAimThe activation of the TNFR2 receptor is beneficial in several pathologies of the central nervous system, and this study examines whether it can ameliorate the recovery process following spinal cord injury.MethodsEHD2‐sc‐mTNFR2, an agonist specific for TNFR2, was used to treat neurons exposed to high levels of glutamate in vitro. In vivo, it was infused directly to the spinal cord via osmotic pumps immediately after a contusion to the cord at the T9 level. Locomotion behavior was assessed for 6 weeks, and the tissue was analyzed (lesion size, RNA and protein expression, cell death) after injury. Somatosensory evoked potentials were also measured in response to hindlimb stimulation.ResultsThe activation of TNFR2 protected neurons from glutamate‐mediated excitotoxicity through the activation of phosphoinositide‐3 kinase gamma in vitro and improved the locomotion of animals following spinal cord injury. The extent of the injury was not affected by infusing EHD2‐sc‐mTNFR2, but higher levels of neurofilament H and 2′, 3′‐cyclic‐nucleotide 3′‐phosphodiesterase were observed 6 weeks after the injury. Finally, the activation of TNFR2 after injury increased the neural response recorded in the cortex following hindlimb stimulation.ConclusionThe activation of TNFR2 in the spinal cord following contusive injury leads to enhanced locomotion and better cortical responses to hindlimb stimulation.

Research advances in vagus nerve stimulation for traumatic brain injury

Patients with coma caused by traumatic brain injury (TBI) suffer from poor quality of life and many complications, which brings heavy burden to their families. The exploration of TBI treatment will help patients restore function, reduce disability rate and improve quality of life. At present, the clinical treatment of TBI mainly includes mild hypothermia treatment, hyperbaric oxygen treatment, awakening drugs and median nerve electrical stimulation, which have their own limitations. Currently, a number of studies have focused on the application of vagus nerve stimulation (VNS) in TBI. The possible mechanisms of VNS include anti-inflammatory effect, brain edema reduction and stabilization of intracranial pressure, promoting nerve function recovery, attenuation of blood-brain barrier breakdown, glutamate-mediated excitotoxicity, synaptic plasticity and recruitment of endogenous neural stem cells. VNS can be used as a new method of clinical treatment for patients with TBI, but it also carries risks of complication as an invasive electrical stimulation. The author summarizes the usage, possible mechanism and safety of VNS, so as to provide reference for further understanding the application of VNS in TBI treatment. Key words: Brain injuries; Vagus nerve; Electric stimulation therapy

Rethinking to riluzole mechanism of action: the molecular link among protein kinase CK1δ activity, TDP-43 phosphorylation, and amyotrophic lateral sclerosis pharmacological treatment.

Rethinking to riluzole mechanism of action: the molecular link among protein kinase CK1δ activity, TDP-43 phosphorylation, and amyotrophic lateral sclerosis pharmacological treatment.

Axonal degeneration induced by glutamate excitotoxicity is mediated by necroptosis.

Neuronal excitotoxicity induced by glutamate leads to cell death and functional impairment in a variety of central nervous system pathologies. Glutamate-mediated excitotoxicity triggers neuronal apoptosis in the cell soma as well as degeneration of axons and dendrites by a process associated with Ca2+ increase and mitochondrial dysfunction. Importantly, degeneration of axons initiated by diverse stimuli, including excitotoxicity, has been proposed as an important pathological event leading to functional impairment in neurodegenerative conditions. Here, we demonstrate that excitotoxicity-induced axonal degeneration proceeds by a mechanism dependent on the necroptotic kinases RIPK1 and RIPK3, and the necroptotic mediator MLKL. Inhibition of RIPK1, RIPK3 or MLKL prevents key steps in the axonal degeneration cascade, including mitochondrial depolarization, the opening of the permeability transition pore and Ca2+ dysregulation in the axon. Interestingly, the same excitotoxic stimuli lead to apoptosis in the cell soma, demonstrating the co-activation of two independent degenerative mechanisms in different compartments of the same cell. The identification of necroptosis as a key mechanism of axonal degeneration after excitotoxicity is an important initial step in the development of novel therapeutic strategies for nervous system disorders.