Search Results (71)

The objective of this study was to investigate alterations in nutrient utilization, standardized ileal digestibility of amino acids (SIDAA), and intestinal health in response to heat stress (HS) in Pekin ducks. A total of 240 healthy 28-day-old male Pekin ducks were randomly allocated to three groups: a normal control (NC) group, an HS group, and a pair-fed (PF; provided an amount of feed equal to that consumed by the HS group to eliminate the effects of feed intake) group, each with eight replicate cages of ten birds. The results showed that HS significantly reduced the apparent utilization of dietary energy, ether extract, and crude protein compared to both the NC and PF groups (p < 0.05), but yielded comparable SIDAA to the PF group. The HS group exhibited reduced mRNA levels of EAAT3 and PepT1, along with elevated mRNA levels of CAT1, GLUT5, and FATP6 in the jejunum compared to the NC or PF groups, respectively (p < 0.05). Furthermore, HS resulted in a significant deterioration of jejunal morphology and goblet cell count compared to the NC and PF groups (p < 0.05). Serum fluorescein isothiocyanate-dextran levels were significantly higher in HS ducks than in NC ducks (p < 0.05), but did not differ from PF ducks. At order-level classification of ileal mucosal microbiota, HS markedly increased the relative abundance of Bacillales, Deferribacterales, and Actinomycetales versus NC (p < 0.05), while significantly decreasing Bifidobacteriales abundance relative to PF (p < 0.05). Collectively, HS induces a leaky gut and microbiota dysbiosis that compromises gut health, thereby reducing dietary nutrient utilization in Pekin ducks. The observed reduction in feed intake constitutes a primary driver of intestinal health deterioration in heat-stressed Pekin ducks. Full article

We have previously shown that the mitochondrial respiratory chain (RC) can switch between the following two states: (i) an “ATP-producing” state characterized by the low production of reactive oxygen species (ROS), the vigorous translocation of hydrogen ions (H⁺), and the storage of energy from the H⁺ gradient in the form of ATP, and (ii) an “ROS-producing” state, where the translocation of H⁺ is slow but the production of ROS is high. Here, we suggest that the RC transition from an ATP-producing to an ROS-producing state initiates a mitochondrial permeability transition (MPT) by generating a burst of ROS. Numerous MPT activators induce the transition of the RC to an ROS-producing state, and the ROS generated in this state activate the MPT. The MPT, in turn, induces changes in conditions that are necessary for the RC to return to an ATP-producing state, decreasing the ROS production rate and restoring the normal permeability of the inner membrane. In this way, the transient MPT prevents cell damage from oxidative stress that would occur if the RC remained in an ROS-producing state. It is shown that an overload of glutamate, which enters through excitatory amino acid transporters (EAATs), induces the RC to switch to an ROS-producing state. Subsequent MPT activation causes a transition back to an ATP-producing state. The model was used to predict the spatial–temporal dynamics of glutamate concentrations and H₂O₂ production rates in a three-dimensional digital phantom of nervous tissue. Full article

Lead (Pb) is a pervasive neurotoxicant with well-documented detrimental effects on the central nervous system, particularly in vulnerable populations such as children. Despite historical recognition of its toxicity, Pb exposure remains a significant public health concern due to its environmental persistence, historical industrial use, and ongoing applications in modern technologies. This review focuses on the mechanisms by which Pb disrupts glutamatergic signaling, a critical pathway for learning, memory, and synaptic plasticity. Pb’s interference with glutamate receptors (ionotropic NMDA and AMPA, as well as metabotropic receptors), transporters (EAATs, VGLUTs, and SNATs), and metabolic pathways (glutamate–glutamine cycle, TCA cycle, and glutathione synthesis) are detailed. By mimicking divalent cations like Ca²⁺ and Zn²⁺, Pb²⁺ disrupts calcium homeostasis, exacerbates excitotoxicity, and induces oxidative stress, ultimately impairing neuronal communication and synaptic function. These molecular disruptions manifest cognitive deficits, behavioral abnormalities, and increased susceptibility to neurodevelopmental and neurodegenerative disorders. Understanding Pb’s impact on glutamatergic neurotransmission offers critical insights into its neurotoxic profile and highlights the importance of addressing its effects on neural function. Full article

Background: Glutamate, a nutritionally non-essential amino acid, is a key intermediate in nitrogen metabolism. Despite more studies on its functional role in intestine health, it remains unknown how glutamate regulates nitrogen metabolism in animals fed a low-protein diet. Methods: Herein, we investigated the effects of glutamate supplementation on colonic amino acid transport, barrier protein expression, microbiota alterations, fecal nitrogen emissions, hepatic amino acid transport, and protein synthesis in weaned rats. Results: We found that protein restriction diminished the mucus thickness, reduced goblet cell numbers, and the expression of EAAT3, y⁺LAT2 in the colon. In contrast, glutamate supplementation reversed these effects, increasing the colon length and enhancing the expression of ZO-1, Occludin, and Claudin-1 in the colon. At the genus level, glutamate increased the abundance of Lactococcus and Clostridia_sensu_stricto_18. Additionally, glutamate supplementation resulted in an increased apparent nitrogen digestibility, reduced the ratio of fecal nitrogen to total nitrogen intake, and increased the ratio of fecal microbial nitrogen to total nitrogen intake. Protein restriction decreased the mRNA level of ATP1A1, EAAT3, SNAT9/2, and ASCT2, and the protein level of p-mTOR, mTOR, p-mTOR/mTOR, and p-p70S6K/p70S6K as well as p-4EBP1/4EBP1 in the liver. These effects were reversed by glutamate supplementation. Conclusions: In conclusion, glutamate supplementation upregulates amino acid transporters and barrier protein expression in the colon, modulates microbiota composition to reduce fecal nitrogen excretion, and enhances amino acid transport and protein synthesis in the liver by activating the mTOR/p70S6K/4EBP1 pathway, which influences nitrogen metabolism in weaned rats fed a low-protein diet. Full article

Background/Objectives: Late epilepsy occurring in the late stage after glioblastoma (GBM) resection is suggested to be caused by increased extracellular glutamate (Glu). To elucidate the mechanism underlying postoperative late epilepsy, the present study aimed to investigate the expressions and relations of molecules related to Glu metabolism in tumor tissues from GBM patients and cultured glioma stem-like cells (GSCs). Methods: Expressions of CD44, xCT and excitatory amino acid transporter (EAAT) 2 and extracellular Glu concentration in GBM patients with and without epilepsy were examined and their relationships were analyzed. For the study using GSCs, expressions and relationships of the same molecules were analyzed and the effects of CD44 knock-down on xCT, EAAT2, and Glu were investigated. In addition, the effects of hypoxia on the expressions of these molecules were investigated. Results: Tumor tissues highly expressed CD44 and xCT in the periphery of GBM with epilepsy, whereas no significant difference in EAAT2 expression was seen between groups with and without epilepsy. Extracellular Glu concentration was higher in patients with epilepsy than those without epilepsy. GSCs displayed reciprocal expressions of CD44 and xCT. Concentrations of extracellular Glu coincided with the degree of xCT expression, and CD44 knock-down elevated xCT expression and extracellular Glu concentrations. Hypoxia of 1% O₂ elevated expression of CD44, while 5% O₂ increased xCT and extracellular Glu concentration. Conclusions: Late epilepsy after GBM resection was related to extracellular Glu concentrations that were regulated by reciprocal expression of CD44 and xCT, which were stimulated by differential hypoxia for each molecule. Full article

Background/Objectives: Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition requiring personalised therapeutic approaches. This study evaluated the effectiveness of Equine-Assisted Activities and Therapies (EAATs) in 86 children with varying ASD severity levels (levels 1–3). Methods: Vineland Adaptive Behaviour Scales and the Parenting Stress Index were used. Between May 2022 and October 2023, participants completed 20 weekly sessions of 45 min each, tailored to their individual needs. Results: Children with level 3 ASD demonstrated greater challenges in communication (level 1: 67.1 ± 29.0 vs. level 3: 30.0 ± 12.6; p < 0.001), daily living skills (81.0 ± 26.8 vs. 42.6 ± 18.1; p < 0.001), and socialisation (72.2 ± 23.2 vs. 37.3 ± 14.2; p < 0.001). Parental distress was higher in cases of greater ASD severity. Nevertheless, significant improvements were observed across the entire cohort in daily living skills (58.3 ± 25.5 vs. 67.8 ± 29.0; p = 0.023), with particularly notable outcomes in children with level 1 ASD (65.7 ± 26.9 vs. 81.0 ± 26.8; p = 0.010). While increases in socialisation were noted among children with level 1 ASD, these were not statistically significant (p = 0.073). Conclusions: EAAT fosters improvements in daily living skills, particularly in children with level 1 ASD, and has a positive impact on socialisation. For children with more severe ASD, targeted interventions are required. Full article

Background: 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. Methodology: 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. Results: 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. Conclusions: 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. Full article

Glutamate transporters (GLTs) are integral to the glutamatergic system, modulating glutamate homeostasis to enhance resilience and resistance against environmental stress. There are six GLTs identified in the Pacific oyster (Crassostrea gigas), which were categorized into two subfamilies: excitatory amino acid transporters (CgEAATs) and vesicular glutamate transporters (CgVGLUTs). The CgEAATs harbor a GltP domain, while CgVGLUTs feature an MFS domain, both with conserved sequence and structural characteristics. The expression of CgGLTs is elevated during the planktonic larval stage compared to the fertilized egg stage and is constitutively expressed in various tissues of adult oysters, suggesting its critical role in both larval development and the physiological processes of adult oysters. Transcriptomic analysis revealed diverse expression patterns of GLTs in oyster gills after 7 days of high-temperature stress, with CgEAAT3 showing a significant upregulation. A KEGG pathway enrichment analysis identified glutathione metabolism and ferroptosis as prominently enriched pathways. At 48 h after high-temperature stress, the expression levels of Glutathione Peroxidase 4 (CgGPX4) and CgEAAT3, along with elevated Fe content in the gills, significantly increased. Moreover, the RNAi-mediated the inhibition of CgEAAT3 expression under high-temperature stress, resulting in a significant reduction in CgGPX4 expression and a further increase in Fe accumulation in oyster gills. These results indicate that CgEAAT3 contributes to the regulation of ferroptosis and redox homeostasis by modulating CgGPX4 expression. This study provides new insights into the adaptive mechanisms of bivalves to environmental stress. Full article

Obesity has been associated with a chronic increase in sympathetic nerve activity, which can lead to hypertension and other cardiovascular diseases. Preliminary studies from our lab found that oxidative stress and neuroinflammation in the brainstem contribute to sympathetic overactivity in high-fat-diet-induced obese mice. However, with glial cells emerging as significant contributors to various physiological processes, their role in causing these changes in obesity remains unknown. In this study, we wanted to determine the role of palmitic acid, a major form of saturated fatty acid in the high-fat diet, in regulating sympathetic outflow. Human brainstem astrocytes (HBAs) were used as a cell culture model since astrocytes are the most abundant glial cells and are more closely associated with the regulation of neurons and, hence, sympathetic nerve activity. In the current study, we hypothesized that palmitic acid-mediated oxidative stress induces senescence and downregulates glutamate reuptake transporters in HBAs. HBAs were treated with palmitic acid (25 μM for 24 h) in three separate experiments. After the treatment period, the cells were collected for gene expression and protein analysis. Our results showed that palmitic acid treatment led to a significant increase in the mRNA expression of oxidative stress markers (NQO1, SOD2, and CAT), cellular senescence markers (p21 and p53), SASP factors (TNFα, IL-6, MCP-1, and CXCL10), and a downregulation in the expression of glutamate reuptake transporters (EAAT1 and EAAT2) in the HBAs. Protein levels of Gamma H2AX, p16, and p21 were also significantly upregulated in the treatment group compared to the control. Our results showed that palmitic acid increased oxidative stress, DNA damage, cellular senescence, and SASP factors, and downregulated the expression of glutamate reuptake transporters in HBAs. These findings suggest the possibility of excitotoxicity in the neurons of the brainstem, sympathoexcitation, and increased risk for cardiovascular diseases in obesity. Full article

Background: Ceftriaxone upregulates GLT1 glutamate transporter in the brain and may have anti-CFC and anti-OCD effects. Methods: Twenty WZ-5HT rats were used to investigate the effects of ceftriaxone on obsessive–compulsive (OCD)-like behaviour in the marble-burying (MB) test, freezing behaviour in contextual fear conditioning (CFC) and expression of GLT1 protein in the hippocampus or amygdala using immunoblots. Fifteen DBA/2J mice were used in the MB test. We also compared diazepam with ceftriaxone in open-field, beam-walking, and wire-hanging tests on 47 DBA/2J mice. Ceftriaxone (200 mg/kg) and saline were applied intraperitoneally, once daily for 7 (rats) or 5 (mice) consecutive days. A single dose of diazepam (1.5–3.0 mg/kg) or saline was injected 30 min before the behavioural tests. Results: Ceftriaxone significantly diminished OCD-like behaviour (↓ number of marbles buried) and freezing behaviour in CFC context session (↑ latencies, ↓ total duration, ↓ duration over four 2 min periods of the session) but increased GLT1 protein expression in the amygdala and hippocampus of rats. Diazepam induced sedation, ataxia and myorelaxation in mice. Ceftriaxone did not have these side effects. Conclusions: The results of this study confirm the anti-CFC and anti-OCD effects of ceftriaxone, which did not produce the unwanted effects typical of diazepam. Full article

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. Full article

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. Full article

Reactive astrocytes are key players in HIV-associated neurocognitive disorders (HAND), and different types of reactive astrocytes play opposing roles in the neuropathologic progression of HAND. A recent study by our group found that gp120 mediates A1 astrocytes (neurotoxicity), which secrete proinflammatory factors and promote HAND disease progression. Here, by comparing the expression of A2 astrocyte (neuroprotective) markers in the brains of gp120 tgm mice and gp120⁺/α7nAChR^−/− mice, we found that inhibition of alpha 7 nicotinic acetylcholine receptor (α7nAChR) promotes A2 astrocyte generation. Notably, kynurenine acid (KYNA) is an antagonist of α7nAChR, and is able to promote the formation of A2 astrocytes, the secretion of neurotrophic factors, and the enhancement of glutamate uptake through blocking the activation of α7nAChR/NF-κB signaling. In addition, learning, memory and mood disorders were significantly improved in gp120 tgm mice by intraperitoneal injection of kynurenine (KYN) and probenecid (PROB). Meanwhile, the number of A2 astrocytes in the mouse brain was significantly increased and glutamate toxicity was reduced. Taken together, KYNA was able to promote A2 astrocyte production and neurotrophic factor secretion, reduce glutamate toxicity, and ameliorate gp120-induced neuropathological deficits. These findings contribute to our understanding of the role that reactive astrocytes play in the development of HAND pathology and provide new evidence for the treatment of HAND via the tryptophan pathway. Full article

In our recent report, we clarified the direct interaction between the excitatory amino acid transporter (EAAT) 1/2 and polyunsaturated fatty acids (PUFAs) by applying electrophysiological and molecular biological techniques to Xenopus oocytes. Xenopus oocytes have a long history of use in the scientific field, but they are still attractive experimental systems for neuropharmacological studies. We will therefore summarize the pharmacological significance, advantages (especially in the study of EAAT2), and experimental techniques that can be applied to Xenopus oocytes; our new findings concerning L-glutamate (L-Glu) transporters and PUFAs; and the significant outcomes of our data. The data obtained from electrophysiological and molecular biological studies of Xenopus oocytes have provided us with further important questions, such as whether or not some PUFAs can modulate EAATs as allosteric modulators and to what extent docosahexaenoic acid (DHA) affects neurotransmission and thereby affects brain functions. Xenopus oocytes have great advantages in the studies about the interactions between molecules and functional proteins, especially in the case when the expression levels of the proteins are small in cell culture systems without transfections. These are also proper to study the mechanisms underlying the interactions. Based on the data collected in Xenopus oocyte experiments, we can proceed to the next step, i.e., the physiological roles of the compounds and their significances. In the case of EAAT2, the effects on the neurotransmission should be examined by electrophysiological approach using acute brain slices. For new drug development, pharmacokinetics pharmacodynamics (PKPD) data and blood brain barrier (BBB) penetration data are also necessary. In order not to miss the promising candidate compounds at the primary stages of drug development, we should reconsider using Xenopus oocytes in the early phase of drug development. Full article

Glutamate excitotoxicity and oxidative stress represent two major pathological mechanisms implicated in retinal disorders. In Diabetic Retinopathy (DR), oxidative stress is correlated to NADPH oxidase (NOX), a major source of Reactive Oxygen Species (ROS), and glutamate metabolism impairments. This study investigated the role of NOX2 and the novel NOX2 inhibitor, GLX7013170, in two models of a) retinal AMPA excitotoxicity [AMPA+GLX7013170 (10⁻⁴ M, intravitreally)] and b) early-stage DR paradigm (ESDR), GLX7013170: 14-day therapeutic treatment (topically, 20 μL/eye, 10 mg/mL (300 × 10⁻⁴ M), once daily) post-streptozotocin (STZ)-induced DR. Immunohistochemical studies for neuronal markers, nitrotyrosine, micro/macroglia, and real-time PCR, Western blot, and glutamate colorimetric assays were conducted. Diabetes increased NOX2 expression in the retina. NOX2 inhibition limited the loss of NOS-positive amacrine cells and the overactivation of micro/macroglia in both models. In the diabetic retina, GLX7013170 had no effect on retinal ganglion cell axons, but reduced oxidative damage, increased Bcl-2, reduced glutamate levels, and partially restored excitatory amino acid transporter (EAAT1) expression. These results suggest that NOX2 in diabetes is part of the triad, oxidative stress, NOX, and glutamate excitotoxicity, key players in the induction of DR. GLX7013170 is efficacious as a neuroprotective/anti-inflammatory agent and a potential therapeutic in retinal diseases, including ESDR. Full article