Glutamate Transporter Research Articles

Dexamethasone alleviates etomidate-induced myoclonus by reversing the inhibition of excitatory amino acid transporters.

Etomidate can induce myoclonus with an incidence of 50 ~ 85% during anesthesia induction. Dexamethasone, as a long-acting synthetic glucocorticoid, has neuroprotective effects. However, the effects of dexamethasone on the etomidate-induced myoclonus remain uncertain. Adult male Sprague-Dawley rats were randomly assigned to receive etomidate (1.5 mg/kg) plus dexamethasone (4 mg/kg) (etomidate plus dexamethasone group) or etomidate (1.5 mg/kg) plus the same volume of normal saline (NS) (etomidate plus NS group). The mean behavioral scores, local field potentials and muscular tension were recorded to explore the effects of dexamethasone on etomidate-induced myoclonus. Liquid chromatography coupled with tandem mass spectrometric system (LC-MS/MS), quantitative real-time polymerase chain reaction (qRT-PCR), and western blotting were applied to analyze the levels of glutamate and γ-aminobutyric acid (GABA), the mRNA and protein expression of excitatory amino acid transporters (EAATs), and plasma corticosterone levels at different time points after anesthesia. Compared with the etomidate plus NS treatment, the etomidate plus dexamethasone treatment significantly decreased the mean behavioral score at 1, 3, 4, and 5 min after administration; the peak power spectral density (PSD) (p = 0.0197) in the analysis of ripple waves; and the glutamate level (p = 0.0139) in the neocortex. However, compared with etomidate plus NS, etomidate plus dexamethasone increased the expression of the neocortical proteins of EAAT1 (p = 0.0207) and EAAT2 (p = 0.0022) and aggravated the inhibition of corticosterone at 4 h (p = 0.0019), 5 h (p = 0.0041), and 6 h (p = 0.0009) after administration. Dexamethasone can attenuate the myoclonus, inhibit the glutamate accumulation, and reverse the suppression of EAATs in the neocortex induced by etomidate following myoclonus, while conversely aggravating etomidate-induced adrenal suppression.

Effects of MC-100093 on Ethanol Drinking and the Expression of Astrocytic Glutamate Transporters in the Mesocorticolimbic Brain Regions of Male and Female Alcohol-Preferring Rats

Chronic ethanol consumption increased extracellular glutamate concentrations in several reward brain regions. Glutamate homeostasis is regulated in majority by astrocytic glutamate transporter 1 (GLT-1) as well as the interactive role of cystine/glutamate antiporter (xCT). In this study, we aimed to determine the attenuating effects of a novel beta-lactam MC-100093, lacking the antibacterial properties, on ethanol consumption and GLT-1 and xCT expression in the subregions of nucleus accumbens (NAc core and NAc shell) and medial prefrontal cortex (Infralimbic, mPFC-IL and Prelimbic, mPFC-PL) in male and female alcohol-preferring (P) rats. Female and male rats were exposed to free access to ethanol (15% v/v) and (30% v/v) and water for five weeks, and on Week 6, rats were administered 100 mg/kg (i.p) of MC-100093 or saline for five days. MC-100093 reduced ethanol consumption in both male and female P rats from Day 1–5. Additionally, MC-100093 upregulated GLT-1 and xCT expression in the mPFC and NAc subregions as compared to ethanol-saline groups in female and male rats. Chronic ethanol intake reduced GLT-1 and xCT expression in the IL and PL in female and male rats, except there was no reduction in GLT-1 expression in the mPFC-PL in female rats. Although, MC-100093 upregulated GLT-1 and xCT expression in the subregions of NAc, we did not observe any reduction in GLT-1 and xCT expression with chronic ethanol intake in female rats. These findings strongly suggest that MC-100093 treatment effectively reduced ethanol intake and upregulated GLT-1 and xCT expression in the mPFC and NAc subregions in male and female P rats.

Calycosin promotes axon growth by inhibiting PTPRS and alleviates spinal cord injury.

Our former studies have identified the alleviating effect of Calycosin (CA) on spinal cord injury (SCI). In this study, our purpose is to explore the influence of CA on SCI from the perspective of promoting axon growth. The SCI animal model was constructed by spinal cord compression, wherein rat primary cortex neuronal isolation was performed, and the axonal growth restriction cell model was established via chondroitin sulfate proteoglycan (CSPG) treatment. The expressions of axon regeneration markers were measured via immunofluorescent staining and western blot, and the direct target of CA was examined using silver staining. Finally, the expression of the protein tyrosine phosphatase receptor type S (PTPRS) was assessed using western blot. CA treatment increased neuronal process outgrowth and the expressions of axon regeneration markers, such as neurofilament H (NF-H), vesicular glutamate transporter 1 (vGlut1), and synaptophysin (Syn) in both SCI model rats and CSPG-treated primary cortical neurons, and PTPRS levels were elevated after SCI induction. In addition, PTPRS was the direct target of CA, and according to in vivo findings, exposure to CA reduced the PTPRS content. Furthermore, PTPRS overexpression inhibited CA's enhancement of axon regeneration marker content and neuronal axon lengths. CA improves SCI by increasing axon development through regulating PTPRS expression.

Exogenous leptin improves cerebral ischemia-reperfusion-induced glutamate excitotoxic injury in mice by up-regulating GLT-1 and GLAST expression in astrocytes

To investigate the protective effect of exogenous leptin against focal cerebral ischemia-reperfusion (I/R) injury in mice and explore the underlying mechanism. A total of 100 C57BL/6 mice were randomly divided into 5 groups, including a sham-operated group, cerebral I/R model group, and 3 leptin treatment groups with intraperitoneal injections of 0.5, 1.0 or 2.0 leptin immediately after occlusion of the internal carotid artery. At 24 h after reperfusion, neurological function scores of the mice were assessed, and TTC staining was used to determine the area of cerebral infarction. The pathological changes in the cortical brain tissue of the mice were observed using HE staining, and degenerative damage of the cortical neurons were assessed with Fluoro-Jade C staining. The expression of glial fibrillary acidic protein in cortical brain tissues was detected using immunohistochemistry and Western blotting. In another 45 C57BL/6 mice with sham operation, I/R modeling, or leptin (1 mg/kg) treatment, glutamic acid in the cortical brain tissue was detected using glutamate assay, and cortical glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) protein expressions were detected using immunohistochemistry. Compared with the I/R model mice, the leptin-treated mice had significantly lower neurological deficit scores, smaller cerebral infarct area, milder pathologies in the cortical brain tissue, and lessened cortical neuronal damage with normal morphology and less excessive proliferation of the astrocytes. Leptin treatment significantly up-regulated the expressions of GLT-1 and GLAST and lowered the content of glutamic acid in the brain tissue of the I/R mice. Exogenous leptin has obvious neuroprotective effect against cerebral I/R injury in mice, mediated probably by controlling excessive astrocyte proliferation and up-regulating cortical GLT-1 and GLAST expressions to reduce glutamate-mediated excitotoxic injury of the astrocytes.

Inhibition of CSPG-PTPσ Activates Autophagy Flux and Lysosome Fusion, Aids Axon and Synaptic Reorganization in Spinal Cord Injury.

Chondroitin sulfate proteoglycans (CSPGs) and proteoglycan receptor protein tyrosine phosphatase σ (PTPσ) play a critical role in the pathology of spinal cord injury (SCI). CSPGs can be induced by autophagy inhibition in astrocyte. However, CSPG's impact on autophagy and its role in SCI is still unknown. We investigate intracellular sigma peptide (ISP) targeting PTPσ, its effects on autophagy, and synaptic reorganization in SCI. We found that ISP increased the level of autophagosome marker LC3B-II/I and decreased autophagosome degradation marker p62 in SCI, suggesting activated autophagy flux. ISP restored autophagosome-lysosome fusion-related protein syntaxin 17 (STX17) and lysosome-associated membrane protein 2 (LAMP2), indicating activated autophagosome-lysosome fusion. ISP increased pre-synaptic marker synaptophysin (SYN) and postsynaptic density protein-95 (PSD-95) expression and improved excitatory synapse marker vesicular glutamate transporter 1 (VGLUT1) and SYN in SCI, suggesting improved synaptic reorganization. ISP promoted axon marker neurofilament and growth-related GAP-43 expression in SCI. ISP rescued a preserved number of motor neurons and improved neurobehavioral recovery after SCI. Our study extended the CSPG-PTPσ inhibition role in activating autophagy flux, axon and synaptic reorganization, and functional recovery in SCI.

Identification of Polymorphisms in EAAT1 Glutamate Transporter Gene SLC1A3 Associated with Reduced Migraine Risk.

Dysfunction in ion channels or processes involved in maintaining ionic homeostasis is thought to lower the threshold for cortical spreading depression (CSD), and plays a role in susceptibility to associated neurological disorders, including pathogenesis of a migraine. Rare pathogenic variants in specific ion channels have been implicated in monogenic migraine subtypes. In this study, we further examined the channelopathic nature of a migraine through the analysis of common genetic variants in three selected ion channel or transporter genes: SLC4A4, SLC1A3, and CHRNA4. Using the Agena MassARRAY platform, 28 single-nucleotide polymorphisms (SNPs) across the three candidate genes were genotyped in a case-control cohort comprised of 182 migraine cases and 179 matched controls. Initial results identified significant associations between migraine and rs3776578 (p = 0.04) and rs16903247 (p = 0.05) genotypes within the SLC1A3 gene, which encodes the EAAT1 glutamate transporter. These SNPs were subsequently genotyped in an independent cohort of 258 migraine cases and 290 controls using a high-resolution melt assay, and association testing supported the replication of initial findings-rs3776578 (p = 0.0041) and rs16903247 (p = 0.0127). The polymorphisms are in linkage disequilibrium and localise within a putative intronic enhancer region of SLC1A3. The minor alleles of both SNPs show a protective effect on migraine risk, which may be conferred via influencing the expression of SLC1A3.

Sodium Houttuyfonate Prevents Seizures and Neuronal Cell Loss by Maintaining Glutamatergic System Stability in Male Rats with Kainic Acid-Induced Seizures.

The present study evaluated the antiseizure and neuroprotective effects of sodium houttuyfonate (SH), a derivative of Houttuynia cordata Thunb. (H. cordata), in a kainic acid (KA)- induced seizure rat model and its underlying mechanism. Sprague Dawley rats were administered normal saline, SH (50 or 100 mg/kg), or carbamazepine (300 mg/kg) by oral gavage for seven consecutive days before the intraperitoneal administration of KA (15 mg/kg). SH showed antiseizure effects at a dose of 100 mg/kg; it prolonged seizure latency and decreased seizure scores. SH also significantly decreased neuronal loss in the hippocampi of KA-treated rats, which was associated with the prevention of glutamate level increase, the upregulation of glutamate reuptake-associated proteins (excitatory amino acid transporters 1-3), glutamate metabolism enzyme glutamine synthetase, the downregulation of the glutamate synthesis enzyme glutaminase, and significant alterations in the expression of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor) and NMDA (N-methyl-D-aspartic acid receptor) receptor subunits in the hippocampus. Furthermore, the effects of SH were similar to those of the antiseizure drug carbamazepine. Therefore, the results of the present study suggest that SH has antiseizure effects on KA-induced seizures, possibly through the prevention of glutamatergic alterations. Our findings suggest that SH is a potential alternative treatment that may prevent seizures by preserving the normal glutamatergic system.

Astrocytic PAR1 and mGluR2/3 control synaptic glutamate time course at hippocampal CA1 synapses.

Astrocytes play an essential role in regulating synaptic transmission. This study describes a novel form of modulation of excitatory synaptic transmission in the mouse hippocampus by astrocytic G-protein-coupled receptors (GPCRs). We have previously described astrocytic glutamate release via protease-activated receptor-1 (PAR1) activation, although the regulatory mechanisms for this are complex. Through electrophysiological analysis and modeling, we discovered that PAR1 activation consistently increases the concentration and duration of glutamate in the synaptic cleft. This effect was not due to changes in the presynaptic glutamate release or alteration in glutamate transporter expression. However, blocking group II metabotropic glutamate receptors (mGluR2/3) abolished PAR1-mediated regulation of synaptic glutamate concentration, suggesting a role for this GPCR in mediating the effects of PAR1 activation on glutamate release. Furthermore, activation of mGluR2/3 causes glutamate release through the TREK-1 channel in hippocampal astrocytes. These data show that astrocytic GPCRs engage in a novel regulatory mechanism to shape the time course of synaptically-released glutamate in excitatory synapses of the hippocampus.

Three-needle electroacupuncture ameliorates depressive-like behaviors in a mouse model of post-stroke depression by promoting excitatory synapse formation via the NGL-3/L1cam pathway

Three-needle electroacupuncture (TNEA) has shown promise as a non-pharmacological treatment for post-stroke depression (PSD). However, the underlying mechanisms of its therapeutic effects remain unclear. In this study, we investigated the potential molecular and synaptic mechanisms by which TNEA ameliorates depressive-like behaviors in a mouse model of PSD. Male C57BL/6 mice were subjected to middle cerebral artery occlusion (MCAO) to induce PSD and subsequently treated with TNEA for three weeks at specific acupoints (GV24 and bilateral GB13). Through a combination of behavioral tests, neuronal activation assessment, synaptic function examination, transcriptomic analysis, and various molecular techniques, we found that TNEA treatment significantly improved anxiety and depressive-like behaviors in PSD mice. These improvements were accompanied by enhanced neuronal activation in the medial prefrontal cortex (mPFC) and primary somatosensory cortex (PSC), as well as the promotion of excitatory synapse formation and transmission function in the mPFC. Transcriptomic analysis revealed that TNEA upregulated the expression of Netrin-G Ligand-3 (NGL-3), a postsynaptic cell adhesion molecule, in the mPFC. Further investigation showed that the extracellular domain of NGL-3 binds to the presynaptic protein L1cam, promoting the formation of Vesicular Glutamate Transporter 1 (vGluT1) puncta on neuronal dendrites. Notably, cortical neuron-specific knockout of NGL-3 abolished the antidepressant-like effects of TNEA in PSD mice, confirming the crucial role of the NGL-3/L1cam pathway in mediating the therapeutic effects of TNEA. These findings provide novel insights into the molecular and synaptic mechanisms underlying the therapeutic effects of acupuncture in the treatment of PSD and highlight the potential of targeting the NGL-3/L1cam pathway for the development of alternative interventions for PSD and other depressive disorders.

Regulatory drugs of glutamate transporter 1 (EAAT2/GLT-1) expression and activity: role in quenching oxidative damage

l-glutamate is one of the major neurotransmitters in the central nervous system, directly and indirectly involved in numerous brain functions. In several neurodegenerative diseases, it has been observed that an excess of extracellular glutamate overstimulates glutamate receptors, leading to exacerbated neuronal excitation in a process of excitotoxicity and oxidative damage that promotes neuronal death. A number of l-glutamate transporters have been identified in the membrane of neurons and astrocytes. They are responsible for the reuptake of glutamate released into the synaptic cleft after excitatory neurotransmission concomitantly regulating the extracellular concentration of glutamate, protecting neurons from its excitotoxic action. Among all of them, literature highlights glutamate transporter 1, known as excitatory amino acid transporter type 2 in humans and glutamate transporter type 1 in rodents, also known as solute carrier family 1 member 2. It is the predominant glutamate transporter in the brain and ensures the majority of l-glutamate reuptake. Decreased expression of this transporter along with increased levels of oxidative stress have been observed in several chronic and acute neurodegenerative disorders. For this reason, the use of drugs capable of both increasing the expression of glutamate transporter 1 and mitigating oxidative damage has been proposed as an effective therapeutic strategy for these pathologies. We present in this work an overview of the main drugs displaying such a double effect.

Dysregulated Transcript Expression but Not Function of the Glutamate Transporter EAAT2 in the Dorsolateral Prefrontal Cortex in Schizophrenia.

Schizophrenia (SCZ) is a serious mental illness with complex pathology, including abnormalities in the glutamate system. Glutamate is rapidly removed from the synapse by excitatory amino acid transporters (EAATs). Changes in the expression and localization of the primary glutamate transporter EAAT2 are found in the brain in central nervous system (CNS) disorders including SCZ. We hypothesize that neuronal expression and function of EAAT2 are increased in the frontal cortex in subjects diagnosed with SCZ. EAAT2 protein expression and glutamate transporter function were assayed in synaptosome preparations from the dorsolateral prefrontal cortex (DLPFC) of SCZ subjects and age- and sex-matched nonpsychiatrically ill controls. EAAT2 splice variant transcript expression was assayed in enriched populations of neurons and astrocytes from the DLPFC. Pathway analysis of publicly available transcriptomic datasets was carried out to identify biological changes associated with EAAT2 perturbation in different cell types. We found no significant changes in EAAT2 protein expression or glutamate uptake in the DLPFC in SCZ subjects compared with controls (n = 10/group). Transcript expression of EAAT2 and signaling molecules associated with EAAT2b trafficking (CaMKIIa and DLG1) were significantly altered in enriched populations of astrocytes and pyramidal neurons (P < .05) in SCZ (n = 16/group). These changes were not associated with antipsychotic medications. Pathway analysis also identified cell-type-specific enrichment of biological pathways associated with perturbation of astrocyte (immune pathways) and neuronal (metabolic pathways) EAAT2 expression. Overall, these data support the growing body of evidence for the role of dysregulation of the glutamate system in the pathophysiology of SCZ.

Early and selective localization of tau filaments to glutamatergic subcellular domains within the human anterodorsal thalamus

Widespread cortical accumulation of misfolded pathological tau proteins (ptau) in the form of paired helical filaments is a major hallmark of Alzheimer’s disease. Subcellular localization of ptau at various stages of disease progression is likely to be informative of the cellular mechanisms involving its spread. Here, we found that the density of ptau within several distinct rostral thalamic nuclei in post-mortem human tissue (n = 25 cases) increased with the disease stage, with the anterodorsal nucleus (ADn) consistently being the most affected. In the ADn, ptau-positive elements were present already in the pre-cortical (Braak 0) stage. Tau pathology preferentially affected the calretinin-expressing subpopulation of glutamatergic neurons in the ADn. At the subcellular level, we detected ptau immunoreactivity in ADn cell bodies, dendrites, and in a specialized type of presynaptic terminal that expresses vesicular glutamate transporter 2 (vGLUT2) and likely originates from the mammillary body. The ptau-containing terminals displayed signs of degeneration, including endosomal/lysosomal organelles. In contrast, corticothalamic axon terminals lacked ptau. The data demonstrate the involvement of a specific cell population in ADn at the onset of the disease. The presence of ptau in subcortical glutamatergic presynaptic terminals supports hypotheses about the transsynaptic spread of tau selectively affecting specialized axonal pathways.

The Role of Vesicular Glutamate Transporter Type 3 in Social Behavior, with a Focus on the Median Raphe Region.

Social behavior is important for our well-being, and its dysfunctions impact several pathological conditions. Although the involvement of glutamate is undeniable, the relevance of vesicular glutamate transporter type 3 (VGluT3), a specific vesicular transporter, in the control of social behavior is not sufficiently explored. Since midbrain median raphe region (MRR) is implicated in social behavior and the nucleus contains high amount of VGluT3+ neurons, we compared the behavior of male VGluT3 knock-out (KO) and VGluT3-Cre mice, the latter after chemogenetic MRR-VGluT3 manipulation. Appropriate control groups were included. Behavioral test battery was used for social behavior (sociability, social discrimination, social interaction, resident intruder test) and possible confounding factors (open field, elevated plus maze, Y-maze tests). Neuronal activation was studied by c-Fos immunohistochemistry. Human relevance was confirmed by VGluT3 gene expression in relevant human brainstem areas. VGluT3 KO mice exhibited increased anxiety, social interest, but also aggressive behavior in anxiogenic environment and impaired social memory. For KO animals, social interaction induced lower cell activation in the anterior cingulate, infralimbic cortex, and medial septum. In turn, excitation of MRR-VGluT3+ neurons was anxiolytic. Inhibition increased social interest 24 h later but decreased mobility and social behavior in aggressive context. Chemogenetic activation increased the number of c-Fos+ neurons only in the MRR. We confirmed the increased anxiety-like behavior and impaired memory of VGluT3 KO strain and revealed increased, but inadequate, social behavior. MRR-VGluT3 neurons regulated mobility and social and anxiety-like behavior in a context-dependent manner. The presence of VGluT3 mRNA on corresponding human brain areas suggests clinical relevance.

Ceftriaxone reverses diet-induced deficits in goal-directed control.

Obesity is associated with numerous health risks and ever-increasing rates are a significant global concern. However, despite weight loss attempts many people have difficulty maintaining weight loss. Previous studies in animals have shown that chronic access to an obesogenic diet can disrupt goal-directed behavior, impairing the ability of animals to flexibly adjust food-seeking behavior following changes in the value of earned outcomes. Changes in behavioral control have been linked to disruption of glutamate transmission in the dorsal medial striatum (DMS), a region critical for the acquisition and expression of goal-directed behavior. The goal of this study was to test whether ceftriaxone, a beta-lactam antibiotic shown elsewhere to upregulate the expression of the glutamate transporter GLT-1, would improve goal-directed control following long-term exposure to an obesogenic diet. Male and female rats were given access to either standard chow or chow plus sweetened condensed milk (SCM) for 6 weeks. Access to SCM was ended and rats received daily injections of either ceftriaxone or saline for 6 days. Rats were then trained to press a lever to earn a novel food reward and, finally, were assessed for sensitivity to outcome devaluation. Histological analyses examined changes to GLT-1 protein levels and morphological changes to astrocytes, within the DMS. We found that ceftriaxone robustly restored goal-directed behavior in animals following long-term exposure to SCM. While we did not observe changes in protein levels of GLT-1 in the DMS, we observed that SCM induced changes in the morphology of astrocytes in the DMS, and that ceftriaxone mitigated these changes. These results demonstrate that long-term access to a SCM diet impairs goal-directed behavior while also altering the morphology of astrocytes in the DMS. Furthermore, these results suggest that ceftriaxone administration can reverse the impairment of goal-directed behavior potentially through its actions on astrocytes in decision-making circuitry.

Aging disrupts the coordination between mRNA and protein expression in mouse and human midbrain.

Age-related dopamine (DA) neuron loss is a primary feature of Parkinson's disease. However, it remains unclear whether similar biological processes occur during healthy aging, albeit to a lesser degree. We therefore determined whether midbrain DA neurons degenerate during aging in mice and humans. In mice, we identified no changes in midbrain neuron numbers throughout aging. Despite this, we found age-related decreases in midbrain mRNA expression of tyrosine hydroxylase (Th), the rate limiting enzyme of DA synthesis. Among midbrain glutamatergic cells, we similarly identified age-related declines in vesicular glutamate transporter 2 (Vglut2) mRNA expression. In co-transmitting Th +/Vglut2 + neurons, Th and Vglut2 transcripts decreased with aging. Importantly, striatal Th and Vglut2 protein expression remained unchanged. In translating our findings to humans, we found no midbrain neurodegeneration during aging and identified age-related decreases in TH and VGLUT2 mRNA expression similar to mouse. Unlike mice, we discovered diminished density of striatal TH+ dopaminergic terminals in aged human subjects. However, TH and VGLUT2 protein expression were unchanged in the remaining striatal boutons. Finally, in contrast to Th and Vglut2 mRNA, expression of most ribosomal genes in Th + neurons was either maintained or even upregulated during aging. This suggests a homeostatic mechanism where age-related declines in transcriptional efficiency are overcome by ongoing ribosomal translation. Overall, we demonstrate species-conserved transcriptional effects of aging in midbrain dopaminergic and glutamatergic neurons that are not accompanied by marked cell death or lower striatal protein expression. This opens the door to novel therapeutic approaches to maintain neurotransmission and bolster neuronal resilience.

Oxytocin ameliorates cognitive impairments by attenuating excitation/inhibition imbalance of neurotransmitters acting on parvalbumin interneurons in a mouse model of sepsis-associated encephalopathy.

Inflammation plays a crucial role in the initiation and progression of sepsis, and it also induces alterations in brain neurotransmission, thereby contributing to the development of sepsis-associated encephalopathy (SAE). Parvalbumin (PV) interneurons are pivotal contributors to cognitive processes in various central dysfunctions including SAE. Oxytocin, known for its ability to augment the firing rate of gamma-aminobutyric acid (GABA)ergic interneurons and directly stimulate inhibitory interneurons to enhance the tonic inhibition of pyramidal neurons, has prompted an investigation into its potential effects on cognitive dysfunction in SAE. In the current study, we administered intranasal oxytocin to the SAE mice induced by lipopolysaccharide (LPS). Behavioral assessments, including open field, Y-maze, and fear conditioning, were used to evaluate cognitive performance. Golgi staining revealed hippocampal synaptic deterioration, local field potential recordings showed weakened gamma oscillations, and immunofluorescence analysis demonstrated decreased PV expression in the cornu ammonis 1 (CA1) region of the hippocampus following LPS treatment, which was alleviated by oxytocin. Furthermore, immunofluorescence staining of PV co-localization with vesicular glutamate transporter 1 or vesicular GABA transporter indicated a balanced excitation/inhibition effect of neurotransmitters on PV interneurons after oxytocin administration in the SAE mice, leading to improved cognitive function. In conclusion, cognitive function improved after oxytocin treatment. The number of PV neurons in the hippocampal CA1 region and the balance of excitatory/inhibitory synaptic transmission on PV interneurons, as well as changes in local field potential gamma oscillations in the hippocampal CA1 region, may represent its specific mechanisms.

GFAP as Astrocyte-Derived Extracellular Vesicle Cargo in Acute Ischemic Stroke Patients-A Pilot Study.

The utility of serum glial fibrillary acidic protein (GFAP) in acute ischemic stroke (AIS) has been extensively studied in recent years. Here, we aimed to assess its potential role as a cargo protein of extracellular vesicles (EVs) secreted by astrocytes (ADEVs) in response to brain ischemia. Plasma samples from eighteen AIS patients at 24 h (D1), 7 days (D7), and one month (M1) post-symptoms onset, and nine age, sex, and cardiovascular risk factor-matched healthy controls were obtained to isolate EVs using the Exoquick ULTRA EV kit. Subsets of presumed ADEVs were identified further by the expression of the glutamate aspartate transporter (GLAST) as a specific marker of astrocytes with the Basic Exo-Flow Capture kit. Western blotting has tested the presence of GFAP in ADEV cargo. Post-stroke ADEV GFAP levels were elevated at D1 and D7 but not M1 compared to controls (p = 0.007, p = 0.019, and p = 0.344, respectively). Significant differences were highlighted in ADEV GFAP content at the three time points studied (n = 12, p = 0.027) and between D1 and M1 (z = 2.65, p = 0.023). A positive correlation was observed between the modified Rankin Scale (mRS) at D7 and ADEV GFAP at D1 (r = 0.58, p = 0.010) and D7 (r = 0.57, p = 0.013), respectively. ADEV GFAP may dynamically reflect changes during the first month post-ischemia. Profiling ADEVs from peripheral blood could provide a new way to assess the central nervous system pathology.

Impaired synaptic plasticity and decreased glutamatergic neuron excitability induced by SIRT1/BDNF downregulation in the hippocampal CA1 region are involved in postoperative cognitive dysfunction

BackgroundPostoperative cognitive dysfunction (POCD) is a common complication after anesthesia/surgery, especially among elderly patients, and poses a significant threat to their postoperative quality of life and overall well-being. While it is widely accepted that elderly patients may experience POCD following anesthesia/surgery, the exact mechanism behind this phenomenon remains unclear. Several studies have indicated that the interaction between silent mating type information regulation 2 homologue 1 (SIRT1) and brain-derived neurotrophic factor (BDNF) is crucial in controlling cognitive function and is strongly linked to neurodegenerative disorders. Hence, this research aims to explore how SIRT1/BDNF impacts cognitive decline caused by anesthesia/surgery in aged mice.MethodsOpen field test (OFT) was used to determine whether anesthesia/surgery affected the motor ability of mice, while the postoperative cognitive function of 18 months old mice was evaluated with Novel object recognition test (NORT), Object location test (OLT) and Fear condition test (FC). The expressions of SIRT1 and other molecules were analyzed by western blot and immunofluorescence staining. The hippocampal synaptic plasticity was detected by Golgi staining and Long-term potentiation (LTP). The effects of SIRT1 and BDNF overexpression as well as chemogenetic activation of glutamatergic neurons in hippocampal CA1 region of 18 months old vesicular glutamate transporter 1 (VGLUT1) mice on POCD were further investigated.ResultsThe research results revealed that older mice exhibited cognitive impairment following intramedullary fixation of tibial fracture. Additionally, a notable decrease in the expression of SIRT1/BDNF and neuronal excitability in hippocampal CA1 glutamatergic neurons was observed. By increasing levels of SIRT1/BDNF or enhancing glutamatergic neuron excitability in the CA1 region, it was possible to effectively mitigate synaptic plasticity impairment and ameliorate postoperative cognitive dysfunction.ConclusionsThe decline in SIRT1/BDNF levels leading to changes in synaptic plasticity and neuronal excitability in older mice could be a significant factor contributing to cognitive impairment after anesthesia/surgery.Graphical

Astrocytic ALKBH5 in stress response contributes to depressive-like behaviors in mice

Epigenetic mechanisms bridge genetic and environmental factors that contribute to the pathogenesis of major depression disorder (MDD). However, the cellular specificity and sensitivity of environmental stress on brain epitranscriptomics and its impact on depression remain unclear. Here, we found that ALKBH5, an RNA demethylase of N6-methyladenosine (m6A), was increased in MDD patients’ blood and depression models. ALKBH5 in astrocytes was more sensitive to stress than that in neurons and endothelial cells. Selective deletion of ALKBH5 in astrocytes, but not in neurons and endothelial cells, produced antidepressant-like behaviors. Astrocytic ALKBH5 in the mPFC regulated depression-related behaviors bidirectionally. Meanwhile, ALKBH5 modulated glutamate transporter-1 (GLT-1) m6A modification and increased the expression of GLT-1 in astrocytes. ALKBH5 astrocyte-specific knockout preserved stress-induced disruption of glutamatergic synaptic transmission, neuronal atrophy and defective Ca2+ activity. Moreover, enhanced m6A modification with S-adenosylmethionine (SAMe) produced antidepressant-like effects. Our findings indicate that astrocytic epitranscriptomics contribute to depressive-like behaviors and that astrocytic ALKBH5 may be a therapeutic target for depression.

Revisiting Glutamate Excitotoxicity in Amyotrophic Lateral Sclerosis and Age-Related Neurodegeneration.

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disorder. While there are five FDA-approved drugs for treating this disease, each has only modest benefits. To design new and more effective therapies for ALS, particularly for sporadic ALS of unknown and diverse etiologies, we must identify key, convergent mechanisms of disease pathogenesis. This review focuses on the origin and effects of glutamate-mediated excitotoxicity in ALS (the cortical hyperexcitability hypothesis), in which increased glutamatergic signaling causes motor neurons to become hyperexcitable and eventually die. We characterize both primary and secondary contributions to excitotoxicity, referring to processes taking place at the synapse and within the cell, respectively. 'Primary pathways' include upregulation of calcium-permeable AMPA receptors, dysfunction of the EAAT2 astrocytic glutamate transporter, increased release of glutamate from the presynaptic terminal, and reduced inhibition by cortical interneurons-all of which have been observed in ALS patients and model systems. 'Secondary pathways' include changes to mitochondrial morphology and function, increased production of reactive oxygen species, and endoplasmic reticulum (ER) stress. By identifying key targets in the excitotoxicity cascade, we emphasize the importance of this pathway in the pathogenesis of ALS and suggest that intervening in this pathway could be effective for developing therapies for this disease.