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Alcoholism (Alcohol dependence) is considered a serial health problem because of tendency for consumption more alcohol, control losing and the physical dependence development. This cycle in most often featured by periods of craving, abstinence, and relapse. The cholinergic, adrenergic, dopaminergic, glutamatergic, GABAergic, serotonergic, peptidergic, and different neurotransmitter systems in the brain are affected by alcohol consumption. The development of alcohol dependence is attributed to neuro-adaptations within the extended amygdala and mesocorticolimbic systems. Principally, the glutamatergic neurotransmission variations that resulted by alcohol consumption, lead to researches recommended in a focus on normalization of glutamatergic neurotransmission and glutamatergic receptors as a targeting therapy. Glutamatergic receptors are classified to ionotropic glutamate receptors (AMPA, Kainate, and NMDA) and metabotropic receptors. Sodium dependent excitatory amino acid transporters (EAATs) and vesicular glutamate transporters (VGLUTs). Additionally, cysteine-glutamate antiporter which regulates cysteine -glutamate exchange at the synapse. At least 90% of extracellular glutamate displace particularly by GLT1. Ceftriaxone, GPI-1046 and MS-153, upregulate expression of glutamate transporter 1 (GLT1) in mesocorticolimbic brain region. [ABSTRACT FROM AUTHOR]

Voltage-gated potassium (Kv) channels open in response to changes in membrane potential to permit passage of K+ ions across the cell membrane, down their electrochemical gradient. Sodium-coupled solute transporters utilize the downhill sodium gradient to co-transport solutes, ranging from ions to sugars to neurotransmitters, into the cell. A variety of recent studies have uncovered cooperation between these two structurally and functionally unrelated classes of protein, revealing previously unnoticed functional crosstalk and in many cases physical interaction to form channel-transporter (chansporter) complexes. Adding to this field, Bartolomé-Martín and colleagues now report that the heteromeric KCNQ2/KCNQ3 (Kv7.2/7.3) potassium channel - the primary molecular correlate of the neuronal M-current - can physically interact with two sodium-coupled neurotransmitter transporters expressed in the brain, DAT and GLT1 (dopamine and glutamate transporters, respectively). The authors provide evidence that the interactions may enhance transporter activity while dampening the depolarizing effects of sodium influx. Cumulative evidence discussed here suggests that chansporter complexes represent a widespread form of cellular signaling hub, in the CNS and other tissues. This article is part of the issue entitled Special Issue on Neurotransmitter Transporters.

Voltage-gated potassium (Kv) channels open in response to changes in membrane potential to permit passage of K+ ions across the cell membrane, down their electrochemical gradient. Sodium-coupled solute transporters utilize the downhill sodium gradient to co-transport solutes, ranging from ions to sugars to neurotransmitters, into the cell. A variety of recent studies have uncovered cooperation between these two structurally and functionally unrelated classes of protein, revealing previously unnoticed functional crosstalk and in many cases physical interaction to form channel-transporter (chansporter) complexes. Adding to this field, Bartolomé-Martín and colleagues now report that the heteromeric KCNQ2/KCNQ3 (Kv7.2/7.3) potassium channel - the primary molecular correlate of the neuronal M-current - can physically interact with two sodium-coupled neurotransmitter transporters expressed in the brain, DAT and GLT1 (dopamine and glutamate transporters, respectively). The authors provide evidence that the interactions may enhance transporter activity while dampening the depolarizing effects of sodium influx. Cumulative evidence discussed here suggests that chansporter complexes represent a widespread form of cellular signaling hub, in the CNS and other tissues. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.

• Aging increases morphological complexity of astrocytes in SNpc, but not in SNpr. • In SNpc structural remodelling is not accompanied by changes in GFAP expression. • Aging reduces GLT1 gene expression only in SNpc, not in SNpr. • Age-dependent alterations in astroglial functions may occur in SNpc. Currently, little is known about the impact of aging on astrocytes in substantia nigra pars compacta (SNpc), where dopaminergic neurons degenerate both in physiological aging and in Parkinson's disease, an age-related neurodegenerative disorder. We performed a morphometric analysis of GFAP+ astrocytes in SNpc and, for comparison, in the pars reticulata (SNpr) of young (4–6 months), middle-aged (14–17 months) and old (20–24 months) C57BL/6J male mice. We demonstrated an age-dependent increase of structural complexity only in astrocytes localized in SNpc, and not in SNpr. Astrocytic structural remodelling was not accompanied by changes in GFAP expression, while GFAP increased in SNpr of old compared to young mice. In parallel, transcript levels of selected astrocyte-enriched genes were evaluated. With aging, decreased GLT1 expression occurred only in SNpc, while xCT transcript increased both in SNpc and SNpr, suggesting a potential loss of homeostatic control of extracellular glutamate only in the subregion where age-dependent neurodegeneration occurs. Altogether, our results support an heterogenous morphological and biomolecular response to aging of GFAP+ astrocytes in SNpc and SNpr. [ABSTRACT FROM AUTHOR]

Metabolism is a fundamental characteristic of life. In 2010, we discovered that the metabolic enzyme CTP synthase (CTPS) can assemble a snake like structure inside cells, which we call the cytoophidium. Including CTPS, an increasing number of metabolic enzymes have been found to form cytoophidia in cells. However, the distribution and relationship among cytoophidia formed by different metabolic enzymes remain elusive. Here we investigate five metabolic enzymes that can form cytoophidia, namely Asn1, Bna5, CTPS (i.e. Ura7), Glt1, and Prs5 in Saccharomyces cerevisiae. We find that multiple cytoophidia can be assembled into cytoophidium complexes by docking one after another. Glt1 cytoophidia tend to assemble in non-quiescent cells, while CTPS cytoophidia are more abundant in quiescent cells and form complexes with Prs5 and Asn1 cytoophidia. Blocking CTPS cytoophidium assembly can lead to a non-quiescent phenotype and increase the assembly of Glt1 cytoophidia, Bna5 cytoophidia, and a cytoophidium complex of them. Blocking CTPS cytoophidium assembly also inhibits the NAD biosynthesis pathway, which includes Bna5 and Sir2. Consistent with this result, the non-quiescent phenotype caused by blocking CTPS cytoophidium assembly can be rescued by blocking Glt1 cytoophidium assembly, supplementing nicotinic acid, or overexpressing Sir2. Our results indicate that the assembly of cytoophidium complexes with different compositions resonates with distinct cell fates., Competing Interests: Declarations. Ethics approval: Not applicable. Consent to participate: Not applicable. Consent to publish: Not applicable. Competing interests: The authors have no relevant financial or non-financial interests to disclose., (© 2025. The Author(s).)

Astrocytes are abundant within mature neural circuits and are involved in brain disorders. Here, we summarize our current understanding of astrocytes and Huntington's disease (HD), with a focus on correlative and causative dysfunctions of ion homeostasis, calcium signaling, and neurotransmitter clearance, as well as on the use of transplanted astrocytes to produce therapeutic benefit in mouse models of HD. Overall, the data suggest that astrocyte dysfunction is an important contributor to the onset and progression of some HD symptoms in mice. Additional exploration of astrocytes in HD mouse models and humans is needed and may provide new therapeutic opportunities to explore in conjunction with neuronal rescue and repair strategies.

Attention-deficit/hyperactivity disorder (ADHD) is a common neuropsychiatric disorder in children. Although animal models and human brain imaging studies indicate a significant role for glutamatergic dysfunction in ADHD, there is no direct evidence that glutamatergic dysfunction is sufficient to induce ADHD-like symptoms. The glial glutamate transporter GLT1 plays a critical role in glutamatergic neurotransmission. We report here the generation of mice expressing only 20% of normal levels of the GLT1. Unlike conventional GLT1 knockout mice, these mice survive to adulthood and exhibit ADHD-like phenotypes, including hyperactivity, impulsivity and impaired memory. These findings indicate that glutamatergic dysfunction due to GLT1 deficiency, a mechanism distinct from the dopaminergic deficit hypothesis of ADHD, underlies ADHD-like symptoms. • We generate mice expressing 20% of normal levels of the glutamate transporter GLT1. • Unlike GLT1 knockout mice, two thirds of GLT1 hypomorph mice survived to adulthood. • GLT1 hypomorph mice show attention-deficit/hyperactivity disorder-like phenotypes. • GLT1 hypomorph mice serve as a new model to study glutamatergic dysfunction in ADHD. [ABSTRACT FROM AUTHOR]

Diabetic neuropathy is one of the most common complications of diabetes mellitus. Excess glutamate release and oxidative stress are hypothesized to be involved in the pathophysiology of diabetes-induced neuropathy. This study was designed to investigate the effect of clavulanic acid (CLAV), a competitive beta-lactamase inhibitor, on the streptozocin (STZ)-induced neuropathic pain and possible mechanisms in the spinal cord of rats. Male Wistar rats were divided into naive group; control group which got a single dose of STZ (50 mg/kg, i.p.), as a model of diabetic neuropathic pain; prophylactic groups: animals received CLAV (10, 20 and 40 mg/kg, i.p.) 1 week after STZ for 10 days; and therapeutic group: animals received 20 mg/kg CLAV, 21 days after STZ for 10 days. Study of pain behaviors was started on days 0, 7, 14, 21, 28, 35 and 42 after STZ. The expression of the glutamate transport 1 (GLT1), genes of oxidative stress including inducible nitric oxide synthase (iNOS), proinflammatory cytokine, tumor necrosis factor alpha (TNF-α), as well as genes involved in the apoptosis including bcl2, bcl2-associated x (bax) were measured in the spinal cord tissue by Real Time PCR, on day 42. On day 21 post injection of STZ, diabetic animals showed significant mechanical allodynia, cold allodynia and thermal hyperalgesia. CLAV in all doses of 10, 20 and 40 mg/kg reduced symptoms of allodynia and hyperalgesia, in both prophylactic and therapeutic regimens. While iNOS, TNF-α, bax/bcl2 were found significantly overexpressed in spinal cord of diabetic animals, their expression in animals received CLAV had been reduced. In contrast, GLT1 that had decreased in the spinal cord of diabetic animals, significantly increased in those received CLAV. CLAV was found a promising candidate for reliving neuropathic pain in diabetes mellitus. Such beneficial effect of CLAV could be, in part, attributed to the increased expression of GLT 1, inhibition of nitrosative stress, anti-inflammation, and inhibition of some apoptotic mediators followed by administration into diabetic animals. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS), also known as a major type of motor neuron disease, is a disease characterized by the degeneration of both upper and lower motor neurons. Astragaloside IV (AST) is one of the most effective compounds isolated from Astragalus membranaceus. Echinacoside (ECH) is also an active constituent in Cistanche tubulosa. These two herbs had been used in treating disease described like ALS in ancient China under the guidance of traditional Chinese medicine theory and now they are still being used extensively for ALS in current Chinese medicine practice, but whether AST or ECH has effect on ALS disease condition is still unclear. Survivals of primary cultured neuron and astrocyte were determined by the MTS assay. Proteins including GLT1 and GFAP, from SOD1 G93A Tg (transgenic) astrocyte lysate were determined by Western blot. Synaptic markers, PSD95 and VGLUT1, were stained by immunofluorescence and observed by a confocal microscope. Proper dilution of AST and ECH was confirmed to be not harmful to both astrocytes and neurons. AST and ECH enhanced neuronal synaptic markers density or intensity/area in different aspects. Both AST and ECH could significantly rescue SOD1 astrocyte conditional medium–treated neuronal survival and synapse loss. Ten micromolars ECH could significantly rescue the suppressed GLT1 level expressed by SOD1 Tg astrocyte. This present research proved that AST and ECH could benefit neuronal properties and rescue certain dysfunction, such as GLT1 low expression, loss of neuron-supporting function, of astrocytes under SOD1 condition. [ABSTRACT FROM AUTHOR]

Locus coeruleus (LC) is considered to be the main source of norepinephrine in the central nervous system (CNS) and plays important role in relieving pain in the body. Changes in the activity of synaptic excitatory amino acid transporters (EAATs) would be an applicable way to regulate synaptic transmission in the LC. In the present study, we examined the role of astrocytic glutamate transporter−1 (GLT1) in the firing activity of LC neurons and the sensation of pain in rats. Male Wistar rats were divided into three control (CNT), ceftriaxone (CFT) and dihydrokainic acid (DHK) groups. Animals were given intraperitoneal injections for nine consecutive days after which the electrophysiological and behavioral experiments were performed to determine the single-unit activity of LC neurons and pain sensation. Results of this study revealed that CFT as a well−known up−regulator of GLT1 expression decreases the latency of pain sensation in rats but inhibition of GLT1 activity by DHK showed no significant effects. Furthermore, the results obtained by single-unit recording from LC showed a significant decrease in evoked response in CFT group compared to the CNT group. Therefore, this study suggests that GLT1 might be considered as a potential therapeutic target for pain modulation in the future. [ABSTRACT FROM AUTHOR]

Brain function is compromised in myotonic dystrophy type 1 (DM1), but the underlying mechanisms are not fully understood. To gain insight into the cellular and molecular pathways primarily affected, we studied a mouse model of DM1 and brains of adult patients. We found pronounced RNA toxicity in the Bergmann glia of the cerebellum, in association with abnormal Purkinje cell firing and fine motor incoordination in DM1 mice. A global proteomics approach revealed downregulation of the GLT1 glutamate transporter in DM1 mice and human patients, which we found to be the result of MBNL1 inactivation. GLT1 downregulation in DM1 astrocytes increases glutamate neurotoxicity and is detrimental to neurons. Finally, we demonstrated that the upregulation of GLT1 corrected Purkinje cell firing and motor incoordination in DM1 mice. Our findings show that glial defects are critical in DM1 brain pathophysiology and open promising therapeutic perspectives through the modulation of glutamate levels.

Alteration of glutamatergic synaptic plasticity in the Nucleus Accumbens (NAc) has been implicated in cocaine-seeking behaviors. Astroglial mechanisms for maintaining extracellular glutamate homeostasis through cysteine/glutamate exchanger (xCT) and glutamate transporter GLT1 are dysregulated following cocaine exposure and contribute to altered glutamatergic synaptic plasticity. However, how these astroglial proteins become dysregulated in cocaine addiction remains unknown. We recently showed that neuron to astroglial exosome signaling is essential to maintain GLT1 protein expression by transferring neuronal miR-124-3p into astrocytes to suppress GLT1-inhibiting microRNAs (miRs) in astrocytes. In the current study, by selectively labeling neuronal exosomes using CD63-GFPf/+ exosome reporter mice, we examined how the self-administration and extinction stages of the mouse cocaine self-administration model alter neuronal exosome signaling to astrocytes and microglia in the NAc. We found that cocaine (but not food) self-administration strongly reduces the internalization of neuronal exosomes, particularly in astrocytes in the NAc (but not in motor cortex), which can be effectively reversed by extinction training. In parallel, cocaine self-administration alone specifically and differentially affects activation of glial cells by decreasing GFAP expression in astrocytes but increasing Iba1 expression in microglia. However, extinction training fully reverses the increased Iba1 expression in microglia but only partially reverses the reduction of GFAP in astrocytes. Taken together, our study reveals altered in vivo dynamics of NAc neuronal exosomes in the cocaine addiction model, providing new insights about how altered neuron to glial exosome signaling may contribute to astroglial dysfunction in cocaine addiction.

Alteration of glutamatergic synaptic plasticity in the Nucleus Accumbens (NAc) has been implicated in cocaine-seeking behaviors. Astroglial mechanisms for maintaining extracellular glutamate homeostasis through cysteine/glutamate exchanger (xCT) and glutamate transporter GLT1 are dysregulated following cocaine exposure and contribute to altered glutamatergic synaptic plasticity. However, how these astroglial proteins become dysregulated in cocaine addiction remains unknown. We recently showed that neuron to astroglial exosome signaling is essential to maintain GLT1 protein expression by transferring neuronal miR-124-3p into astrocytes to suppress GLT1-inhibiting microRNAs (miRs) in astrocytes. In the current study, by selectively labeling neuronal exosomes using CD63-GFPf/+ exosome reporter mice, we examined how the self-administration and extinction stages of the mouse cocaine self-administration model alter neuronal exosome signaling to astrocytes and microglia in the NAc. We found that cocaine (but not food) self-administration strongly reduces the internalization of neuronal exosomes, particularly in astrocytes in the NAc (but not in motor cortex), which can be effectively reversed by extinction training. In parallel, cocaine self-administration alone specifically and differentially affects activation of glial cells by decreasing GFAP expression in astrocytes but increasing Iba1 expression in microglia. However, extinction training fully reverses the increased Iba1 expression in microglia but only partially reverses the reduction of GFAP in astrocytes. Taken together, our study reveals altered in vivo dynamics of NAc neuronal exosomes in the cocaine addiction model, providing new insights about how altered neuron to glial exosome signaling may contribute to astroglial dysfunction in cocaine addiction. [ABSTRACT FROM AUTHOR]

Objective To investigate the effect of histone deacetylase HDAC2 on the regulation of glutamate transporters in subarachnoid hemorrhage(SAH) mice, and the potential protective effect of selective HDAC2i on the cognitive impairment post-SAH. MethodsThe SAH mouse model was established by internal carotid artery puncture. Western Blot and immunofluorescence staining were used to detect the expression of HDAC subtypes and GLT1 in the hippocampal area of SAH mice, as well as their co-localization in astrocytes. Morris water maze(MWM) and open field test(OPT) were performed to examine the improvement of learning memory and depression in mice after intraperitoneally injection of a specific HDAC2i for 10 days after SAH. ResultsCompared with Sham group, GLT1 in astrocytes in hippocampus was decreased following SAH(P＜0.05-0.01), and HDAC subtypes were increased, with the most significant change in HDAC2(P＜0.05-0.01). Selective HDAC2 inhibitor treatment significantly reduced the escape latency in the training test(P＜0.05) and increased the traveling time in the target quadrant(P＜0.05) in MWM, and increased the traveling distance(P＜0.05) and time(P＜0.05) in the central area in OPT of SAH mice. Meanwhile, the effect of HDAC2i in improving behavioral deficits in SAH mice can be blocked by GLT1 antagonist. ConclusionHDAC2 may participate in the regulation of animal cognitive impairment after SAH by mediating the expression of GLT1 in astrocytes. Specific HDAC2i may exert the therapeutic effect of improving animal cognitive impairment after SAH. [ABSTRACT FROM AUTHOR]

Alcohol Use Disorder (AUD) is a highly prevalent medical condition characterized by impaired control over alcohol consumption, despite negative consequences on the individual's daily life and health. There is increasing evidence suggesting that chronic alcohol intake, like other addictive drugs, induces neuroinflammation and oxidative stress, disrupting glutamate homeostasis in the main brain areas related to drug addiction. This review explores the potential application of mesenchymal stem cells (MSCs)-based therapy for the treatment of AUD. MSCs secrete a broad array of anti-inflammatory and antioxidant molecules, thus, the administration of MSCs, or their secretome, could reduce neuroinflammation and oxidative stress in the brain. These effects correlate with an increase in the expression of the main glutamate transporter, GLT1, which, through the normalization of the extracellular glutamate levels, could mediate the inhibitory effect of MSCs' secretome on chronic alcohol consumption, thus highlighting GLT1 as a central target to reduce chronic alcohol consumption., (Copyright © 2024. Published by Elsevier Inc.)

Amyotrophic lateral sclerosis (ALS) is characterized by relatively rapid degeneration of both upper and lower motor neurons, with death normally occurring 2–5 years following diagnosis primarily due to respiratory paralysis resulting from phrenic motor neuron (PhMN) loss and consequent diaphragm denervation. In ALS, cellular abnormalities are not limited to MNs. For example, decreased levels and aberrant functioning of the major central nervous system (CNS) glutamate transporter, GLT1, occur in spinal cord and motor cortex astrocytes of both humans with ALS and in SOD1G93A rodents, a widely studied ALS animal model. This results in dysregulation of extracellular glutamate homeostasis and consequent glutamate excitotoxicity, a primary mechanism responsible for MN loss in ALS animal models and in the human disease. Given these observations of GLT1 dysfunction in areas of MN loss, as well as the importance of testing therapeutic strategies for preserving PhMNs in ALS, we evaluated intraspinal delivery of an adeno-associated virus type 8 (AAV8)–Gfa2 vector to the cervical spinal cord ventral horn of SOD1G93A ALS mice for focally restoring intraspinal GLT1 expression. AAV8 was specifically injected into the ventral horn bilaterally throughout the cervical enlargement at 110 days of age, a clinically-relevant time point coinciding with phenotypic/symptomatic disease onset. Intraspinal delivery of AAV8–Gfa2–GLT1 resulted in robust transduction primarily of GFAP+ astrocytes that persisted until disease endstage, as well as a 2–3-fold increase in total intraspinal GLT1 protein expression in the ventral horn. Despite this robust level of astrocyte transduction and GLT1 elevation, GLT1 overexpression did not protect PhMNs, preserve histological PhMN innervation of the diaphragm NMJ, or prevent decline in diaphragmatic respiratory function as assessed by phrenic nerve–diaphragm compound muscle action potential (CMAP) recordings compared to control AAV8–Gfa2–eGFP injected mice. In addition, AAV–Gfa2–GLT1 did not delay forelimb disease onset, extend disease duration (i.e. time from either forelimb or hindlimb disease onsets to endstage) or prolong overall animal survival. These findings suggest that focal restoration of GLT1 expression in astrocytes of the cervical spinal cord using AAV delivery is not an effective therapy for ALS.

Abstract Glutamate transporter GLT1 mediates glutamate uptake, and maintains glutamate homeostasis in the synaptic cleft. Previous studies suggest that blockade of glutamate uptake affects synaptic transmission and plasticity. However, the effect of GLT1 blockade on learning and memory still receives little attention. In the present study, we examined the effect of unilateral intracerebroventricular injection of dihydrokainic acid (DHK), a GLT-1 inhibitor, on novel object recognition (NOR) memory performance. The NOR task involved three sessions including habituation, sampling and test. In experiment 1, DHK injection 0.5 h pre-sampling impaired short-term NOR memory performance. In experiment 2, DHK injection 0.5 h pre-sampling impaired long-term NOR memory acquisition. In experiment 3, DHK injection immediately but not 6 h post-sampling impaired long-term NOR memory consolidation. In experiment 4, DHK injection 0.5 h pre-test impaired long-term NOR memory retrieval. Furthermore, DHK-induced memory performance impairment was not due to its effects on nonspecific responses such as locomotor activity and exploratory behavior. The current findings further extend previous studies on the effects of disruption of glutamate homeostasis on learning and memory. Highlights • DHK 0.5 h pre-sampling impairs short-term NOR memory performance. • DHK injection 0.5 h pre-sampling impairs long-term NOR memory acquisition. • DHK injection immediately but not 6 h post-sampling impairs long-term NOR memory consolidation. • DHK injection 0.5 h pre-test impairs long-term NOR memory retrieval. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) is a chronic neurodegenerative disorder characterized by the selective loss of motor neurons. The precise mechanisms that cause the selective death of motor neurons remain unclear, but a growing body of evidence suggests that glutamate-mediated excitotoxicity has been considered to play an important role in the mechanisms of motor neuron degeneration in ALS. Reductions in glutamate transporter GLT1 have been reported in animal models of ALS and the motor cortex and spinal cord of ALS patients. However, it remains unknown whether the reduction in GLT1 has a primary role in the induction of motor neuron degeneration in ALS. Here, we generated conditional knockout mice that lacked GLT1 specifically in the spinal cord by crossing floxed-GLT1 mice and Hoxb8-Cre mice. Hoxb8-Cre/GLT1 flox/flox mice showed motor deficits and motor neuron loss. Thus, loss of the glial glutamate transporter GLT1 is sufficient to cause motor neuron death in mice. [ABSTRACT FROM AUTHOR]

Summary Brain function is compromised in myotonic dystrophy type 1 (DM1), but the underlying mechanisms are not fully understood. To gain insight into the cellular and molecular pathways primarily affected, we studied a mouse model of DM1 and brains of adult patients. We found pronounced RNA toxicity in the Bergmann glia of the cerebellum, in association with abnormal Purkinje cell firing and fine motor incoordination in DM1 mice. A global proteomics approach revealed downregulation of the GLT1 glutamate transporter in DM1 mice and human patients, which we found to be the result of MBNL1 inactivation. GLT1 downregulation in DM1 astrocytes increases glutamate neurotoxicity and is detrimental to neurons. Finally, we demonstrated that the upregulation of GLT1 corrected Purkinje cell firing and motor incoordination in DM1 mice. Our findings show that glial defects are critical in DM1 brain pathophysiology and open promising therapeutic perspectives through the modulation of glutamate levels. [ABSTRACT FROM AUTHOR]

Abnormal buildup of the microtubule associated protein tau is a major pathological hallmark of Alzheimer’s disease (AD) and various tauopathies. The mechanisms by which pathological tau accumulates and spreads throughout the brain remain largely unknown. Previously, we demonstrated that a restoration of the major astrocytic glutamate transporter, GLT1, ameliorated a buildup of tau pathology and rescued cognition in a mouse model of AD. We hypothesized that aberrant extracellular glutamate and abnormal neuronal excitatory activities promoted tau pathology. In the present study, we investigated genetic interactions between tau and the GLT1 homolog dEaat1 in Drosophila melanogaster . Neuronal-specific overexpression of human wildtype tau markedly shortened lifespan and impaired motor behavior. RNAi depletion of dEaat1 in astrocytes worsened these phenotypes, whereas overexpression of dEaat1 improved them. However, the synaptic neuropil appeared unaffected, and we failed to detect any major neuronal loss with tau overexpression in combination with dEaat1 depletion. To mimic glutamate-induced aberrant excitatory input in neurons, repeated depolarization of neurons via transgenic TrpA1 was applied to the adult Drosophila optic nerves, and we examined the change of tau deposits. Repeated depolarization significantly increased the accumulation of tau in these neurons. We propose that increased neuronal excitatory activity exacerbates tau-mediated neuronal toxicity and behavioral deficits. [ABSTRACT FROM AUTHOR]

To understand why livers from aged donors are successfully used for transplants, we looked for markers of liver aging in 71 biopsies from donors aged 12-92 years before transplants and in 11 biopsies after transplants with high donor-recipient age-mismatch. We also assessed liver function in 36 age-mismatched recipients. The major findings were the following: (i) miR-31-5p, miR-141-3p, and miR-200c-3p increased with age, as assessed by micro RNAs (miRs) and mRNA transcript profiling in 12 biopsies and results were validated by RT- qPCR in a total of 58 biopsies; (ii) telomere length measured by qPCR in 45 samples showed a significant age-dependent shortage; (iii) a bioinformatic approach combining transcriptome and miRs data identified putative miRs targets, the most informative being GLT1, a glutamate transporter expressed in hepatocytes. GLT1 was demonstrated by luciferase assay to be a target of miR-31-5p and miR-200c-3p, and both its mRNA ( RT- qPCR) and protein (immunohistochemistry) significantly decreased with age in liver biopsies and in hepatic centrilobular zone, respectively; (iv) miR-31-5p, miR-141-3p and miR-200c-3p expression was significantly affected by recipient age (older environment) as assessed in eleven cases of donor-recipient extreme age-mismatch; (v) the analysis of recipients plasma by N-glycans profiling, capable of assessing liver functions and biological age, showed that liver function recovered after transplants, independently of age-mismatch, and recipients apparently 'rejuvenated' according to their glycomic age. In conclusion, we identified new markers of aging in human liver, their relevance in donor-recipient age-mismatches in transplantation, and offered positive evidence for the use of organs from old donors. [ABSTRACT FROM AUTHOR]

Several β-lactam derivatives upregulate astrocytic glutamate transporter type 1expression and are known to improve measures in models of mood and alcohol use disorders (AUD) through normalizing glutamatergic states. However, long-term, and high doses of β-lactams may cause adverse side effects for treating mood disorders and AUD. Studies suggest that MC-100093, a novel β-lactam lacking antimicrobial activity, rescues GLT1 expression. Thus, we sought to investigate whether MC-100093 improves affective behaviors and reduces voluntary ethanol drinking. We intraperitoneally administered MC-100093 (50 mg/kg) or vehicle once per day to C57BL/6J male and female mice (8–10 weeks old) over 6 days. We employed the open field test and the elevated plus maze to examine the effect of MC-100093 on anxiety-like behaviors. We assayed MC-100093's effects on depressive-like behaviors using the tail suspension and forced swim tests. Next, utilizing a separate cohort of male and female C57BL6 mice, we assessed the effects MC100093 treatment on voluntary ethanol drinking utilizing the 2-bottle choice continuous access drinking paradigm. After screening and selecting high-drinking mice, we systematically administered MC-100093 (50 mg/kg) or vehicle to the high-drinking mice over 6 days. Overall, we found that MC-100093 treatment resulted in sex-specific pharmacological effects with female mice displaying reduced innate depressive-like behaviors during the tail suspension and force swim testing juxtaposed with male treated mice who displayed no changes in tail suspension and a paradoxical increased depressive-like behavior during the forced swim testing. Additionally, we found that MC100093 treatment reduced female preference for 10% EtOH during the 2-bottle choice continuous access drinking with no effects of MC100093 treatment detected in male mice. Overall, this data suggests sex-specific regulation of innate depressive-like behavior and voluntary EtOH drinking by MC100093 treatment. Western blot analysis of the medial prefrontal cortex and hippocampus revealed no changes in male or female GLT1 protein abundance relative to GAPDH. [Display omitted] • MC-100093 exerts antidepressant-like effects in female mice only. • Sex-specific antidepressant-like effect was not dependent on enhanced GLT1 expression. • MC-100093 (50 mg/kg, 6 days, i.p.) decreases ethanol preference and increases water intake in female mice only. [ABSTRACT FROM AUTHOR]

Alcoholism is a serious public health concern that is characterized by the development of tolerance to alcohol’s effects, increased consumption, loss of control over drinking and the development of physical dependence. This cycle is often times punctuated by periods of abstinence, craving and relapse. The development of tolerance and the expression of withdrawal effects, which manifest as dependence, have been to a great extent attributed to neuroadaptations within the mesocorticolimbic and extended amygdala systems. Alcohol affects various neurotransmitter systems in the brain including the adrenergic, cholinergic, dopaminergic, GABAergic, glutamatergic, peptidergic and serotonergic systems. Due to the myriad of neurotransmitter and neuromodulator systems affected by alcohol, the efficacies of current pharmacotherapies targeting alcohol dependence are limited. Importantly, research findings of changes in glutamatergic neurotransmission induced by alcohol self- or experimenter-administration have resulted in a focus on therapies targeting glutamatergic receptors and normalization of glutamatergic neurotransmission. Glutamatergic receptors implicated in the effects of ethanol include the ionotropic glutamate receptors (AMPA, Kainate, and NMDA) and some metabotropic glutamate receptors. Regarding glutamatergic homeostasis, ceftriaxone, MS-153 and GPI-1046, which upregulate glutamate transporter 1 (GLT1) expression in mesocorticolimbic brain regions, reduce alcohol intake in genetic animal models of alcoholism. Given the hyperglutamatergic/hyperexcitable state of the central nervous system induced by chronic alcohol abuse and withdrawal, the evidence thus far indicates that a restoration of glutamatergic concentrations and activity within the mesocorticolimbic system and extended amygdala as well as multiple memory systems holds great promise for the treatment of alcohol dependence.

Huntington's disease (HD) affects both neurons and astrocytes. To target the latter and to ensure brain-wide transgene expression, adeno-associated viral (AAV) vectors can be administered intravenously, as AAV vectors cross the blood-brain barrier (BBB) and enable preferential transduction of astrocytes due to their close association with blood vessels. However, there is a possibility that the subclass of GFAP-expressing astrocytes performs a distinct role in HD and reacts differently to therapeutic measures than the rest of the astrocytes. The gfaABC1D promoter allows specific targeting of the GFAP-expressing astrocytes (~ 25% of S100β-expressing astrocytes). We have examined the expression of three different transgenes (GCaMP6f, Kir4.1 and GLT1) and tested the effects of the AAV serotypes 9 and rh8. The AAV vectors were injected into the tail vein of 1-year-old homozygous Z -Q175-KI HD mice and their wild-type (WT) littermates. At this age, HD mice exhibit motor symptoms, including pronounced hypokinesia and circling behaviour. The expression times ranged from 3 to 6 weeks. The target cell population was defined as the cells expressing S100β in addition to GFAP. Viewfields in the dorsal striatum and the overlaying cortex were evaluated and the transduction rate was defined as the percentage of target cells that expressed the reporter transgene (enhanced green fluorescent protein, EGFP, or Tomato). In all cases, the transduction rate was higher in the cortex than in the striatum. AAV9 was more efficient than AAVrh8. One of the injected constructs (AAV9-gfaABC1D-GLT1-Tomato) was tested for the first time. GLT1, the principal astrocytic glutamate transporter, is deficient in HD and therefore considered as a potential target for gene therapy. At a dose of 1.86 × 10 11 vector genome (vg) per animal, the fraction of GLT1-Tomato + cells in the striatum and the cortex amounted to 30% and 49%, respectively. In individual Tomato + HD astrocytes, treatment with the GLT1 vector increased the level of GLT1 immunofluorescence by 21% compared to the HD control. The described approach offers new and interesting opportunities to examine the pathophysiological consequences of brain-wide transgene expression in a specific astrocyte subpopulation. [ABSTRACT FROM AUTHOR]

Astrocytes regulate extracellular glutamate and water homeostasis through the astrocyte-specific membrane proteins glutamate transporter-1 (GLT1) and aquaporin-4 (AQP4), respectively. The role of astrocytes and the regulation of GLT1 and AQP4 in epilepsy are not fully understood. In this study, we investigated the expression of GLT1 and AQP4 in the intrahippocampal kainic acid (IHKA) model of temporal lobe epilepsy (TLE). We used real-time polymerase chain reaction (RT-PCR), Western blot, and immunohistochemical analysis at 1, 4, 7, and 30 days after kainic acid-induced status epilepticus (SE) to determine hippocampal glial fibrillary acidic protein (GFAP, a marker for reactive astrocytes), GLT1, and AQP4 expression changes during the development of epilepsy (epileptogenesis). Following IHKA, all mice had SE and progressive increases in GFAP immunoreactivity and GFAP protein expression out to 30 days post-SE. A significant initial increase in dorsal hippocampal GLT1 immunoreactivity and protein levels were observed 1 day post SE and followed by a marked downregulation at 4 and 7 days post SE with a return to near control levels by 30 days post SE. AQP4 dorsal hippocampal protein expression was significantly downregulated at 1 day post SE and was followed by a gradual return to baseline levels with a significant increase in ipsilateral protein levels by 30 days post SE. Transient increases in GFAP and AQP4 mRNA were also observed. Our findings suggest that specific molecular changes in astrocyte glutamate transporters and water channels occur during epileptogenesis in this model, and suggest the novel therapeutic strategy of restoring glutamate and water homeostasis. [ABSTRACT FROM AUTHOR]

Excessive accumulation of extracellular glutamate results in neuronal death. Termination of synaptic glutamate transmission and the prevention of excitotoxicity depend on rapid removal of glutamate by high affinity Na+-dependent transporters. The astroglial transporter GLT1 is the predominant subtype, responsible for the bulk of extracellular clearance and for limiting excitotoxicity. This protein is crucial in the prevention of chronic glutamate neurotoxicity, and is markedly decreased in amyotrophic lateral sclerosis (ALS). Recent studies have shown that GLT1 expression can be induced in vitro and in vivo by various factors, but little is known about the signaling pathways mediating its regulation. The FK506-binding protein (FKBP) immunophilins are ubiquitous cytosolic proteins, concentrated in neural tissue (neuroimmunophilins). GPI-1046 is a synthetic, nonimmunosuppressive derivative of FK506 shown to exert neuroprotective and neuroregenerative actions in several systems. In the present study, we demonstrated that GPI-1046 induces selective expression of GLT1 in vitro and in vivo, associated with a marked increase in DHK-sensitive Na+-dependent glutamate transport. Furthermore, treatment with GPI-1046 was shown to protect motor neurons in an in vitro model of chronic excitotoxicity, and to prolong the survival of transgenic ALS mice. These studies suggest that neuroimmunophilins can regulate GLT1 and that their ligands could serve as therapies for neurodegenerative disorders.

We have recently shown that upregulation of glutamate transporter 1 (GLT1) in the brain is associated in part with reduction in ethanol intake in alcohol-preferring (P) male rats. In this study, we investigated the effects of a synthetic compound, (R)-(−)-5-methyl-1-nicotinoyl-2-pyrazoline (MS-153), known to activate GLT1 on ethanol consumption as well as GLT1 expression and certain signaling pathways in P rats. P rats were given 24-hour concurrent access to 15% and 30% ethanol, water and food for five weeks. On week 6, P rats received MS-153 at a dose of 50 mg/kg (i.p.) or a vehicle (i.p.) for five consecutive days. We also tested the effect of MS-153 on daily sucrose (10%) intake. Our studies revealed a significant decrease in ethanol intake at the dose of 50 mg/kg MS-153 from Day 1 through Day 14. In addition, MS-153 at dose of 50 mg/kg did not induce any significant effect on sucrose intake. Importantly, we found that MS-153 upregulated the GLT1 level in the nucleus accumbens (NAc) but not in the prefrontal cortex (PFC). In accordance, we found upregulation of nuclear NFkB-65 level in NAc in MS-153-treated group, however, IkB was downregulated in MS-153-treated group in NAc. We did not find any changes in NFkB-65 and IkB levels in PFC. Interestingly, we revealed that p-Akt was downregulated in ethanol vehicle treated groups in the NAc; this downregulation was reversed by MS-153 treatment. We did not observe any significant differences in glutamate aspartate transporter (GLAST) expression among all groups. These findings reveal MS-153 as a GLT1 modulator that may have potential as a therapeutic drug for the treatment of alcohol dependence.

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common child psychiatric disorders. While it is typically treated with medications that target dopamine and norepinephrine transmission, there is increasing evidence that other neurotransmitter systems, such as glutamate and GABA, may be involved. The aetiology of ADHD is unknown; however, there is evidence that early life stress may contribute to the development of the disorder. In the present study we used proteomic analysis (iTRAQ) followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot analysis to investigate hippocampal protein profiles of three rat strains: an animal model of ADHD, spontaneously hypertensive rats (SHR), their control Wistar-Kyoto rats (WKY), and Sprague-Dawley rats (SD). We additionally investigated how these protein profiles are affected by maternal separation, a model of early life stress. Our findings show that solute carrier family 12 member 5 (KCC2) is increased in SHR hippocampus. The glutamate transporter GLT1 splice variant, GLT1b, was increased (proteomic analysis) while total GLT1 (comprised mostly of GLT1a splice variant) was reduced (Western blot analysis) in SHR hippocampus, compared to WKY and SD - a pattern that is consistent with elevated extracellular glutamate levels. Maternal separation increased total GLT1 in hippocampi of SHR, WKY, and SD, and reduced GLT1b in SHR hippocampus. Together these findings provide evidence for disturbed glutamatergic and GABAergic transmission in SHR hippocampus, maternal separation effects on glutamate uptake in hippocampi of all three strains, as well a unique effect of maternal separation on GLT1b levels in SHR hippocampus. These data suggest significant involvement of glutamatergic and GABAergic transmission in the neuropathophysiology of ADHD, and implicates changes in glutamatergic transmission as a result of early life stress. [ABSTRACT FROM AUTHOR]

Rationale: Several studies have demonstrated a correlation between extracellular glutamate concentration in the mesolimbic reward pathway and alcohol craving. Extracellular glutamate concentration is regulated by several glutamate transporters. Glial glutamate transporter 1 (GLT1) is one of them that regulates the majority of extracellular glutamate concentration. In addition, cystine/glutamate antiporter (xCT) is another transporter that regulates extracellular glutamate. Objectives: We focus in this study to determine the effects of ceftriaxone, β-lactam antibiotic, on glial proteins such as GLT1 isoforms, xCT, glutamate aspartate transporter (GLAST), and several associated signaling pathways as well as ethanol intake in P rats. Additionally, to examine the onset of signaling pathways associated with GLT1 upregulation following ceftriaxone treatment, we tested 2- versus 5-day daily dosing of ceftriaxone. Results: Ceftriaxone treatment (100 mg/kg), 2 and 5 days, resulted in about five fold reduction in ethanol intake by P rats. The reduction in ethanol intake was associated with significantly enhanced expression of GLT1, GLT1a, GLT1b, and xCT in the nucleus accumbens (NAc) and prefrontal cortex (PFC) of 5-day ceftriaxone-treated P rats. Two-day-treated P rats showed marked changes in expression of these glutamate transporters in the PFC but not in the NAc. Importantly, ceftriaxone-treated P rats (2 and 5 days) demonstrated enhanced phosphorylation of Akt and nuclear translocation of nuclear factor kappaB (NFκB) in the NAc and PFC compared to control animals. Conclusions: These findings demonstrate that ceftriaxone treatment induced upregulation of GLT1, GLT1 isoforms, and xCT in association with activation of the Akt-NFκB signaling pathway. [ABSTRACT FROM AUTHOR]

The study was undertaken to investigate whether sulbactam protects cerebral neurons against ischemia and whether the protection is mediated by regulating the expression and uptake activity of glial glutamate transporter-1 (GLT1) in a rat global brain ischemia model. The CA1 hippocampus was selected as the observing target. Real time quantitative PCR, Western blot and immunohistochemistry assays were used to detect GLT1 expression. Neuropathological evaluation was performed after thionin staining to determine the extent of the delayed neuronal death (DND) of pyramidal neurons. It was found that cerebral ischemia for 8 min induced obvious DND of pyramidal neurons and GLT1 downregulation. Sulbactam pretreatment significantly upregulated GLT1 expression in sham rats and prevented or reversed the GLT1 downregulation normally induced in the ischemic rat brain. Meanwhile, sulbactam pretreatment effectively prevented the DND of pyramidal neurons normally induced by brain ischemia in a dose-dependent manner. Sulbactam posttreatment also protected pyramidal neurons against DND induced by brain ischemia although the magnitude of the protective effect was weaker than that in sulbactam pretreatment. Furthermore, either antisense knockdown of GLT1 expression or inhibition of the GLT1 uptake activity with dihydrokainate, a selective inhibitor of GLT1, significantly blocked the neuronal protective effect of sulbactam. These findings indicate that sulbactam has a neuronal protective effect though upregulating GLT1. [ABSTRACT FROM AUTHOR]

The glutamate transporter GLT-1 (also called EAAT2 in humans) plays a critical role in regulating extracellular glutamate levels in the central nervous system (CNS). In Alzheimer's disease (AD), EAAT2 loss is associated with neuropathology and cognitive impairment. In keeping with this, we have reported that partial GLT-1 loss (GLT-1+/-) causes early-occurring cognitive deficits in mice harboring familial AD AβPPswe/PS1ΔE9 mutations. GLT-1 plays important roles in several molecular pathways that regulate brain metabolism, including Akt and insulin signaling in astrocytes. Significantly, AD pathogenesis also involves chronic Akt activation and reduced insulin signaling in the CNS. In this report we tested the hypothesis that GLT-1 heterozygosity (which reduces GLT-1 to levels that are comparable to losses in AD patients) in AβPPswe/PS1ΔE9 mice would induce sustained activation of Akt and disturb components of the CNS insulin signaling cascade. We found that partial GLT-1 loss chronically increased Akt activation (reflected by increased phosphorylation at serine 473), impaired insulin signaling (reflected by decreased IRβ phosphorylation of tyrosines 1150/1151 and increased IRS-1 phosphorylation at serines 632/635 - denoted as 636/639 in humans), and reduced insulin degrading enzyme (IDE) activity in brains of mice expressing familial AβPPswe/PS1ΔE9 AD mutations. GLT-1 loss also caused an apparent compensatory increase in IDE activity in the liver, an organ that has been shown to regulate peripheral amyloid-β levels and expresses GLT-1. Taken together, these findings demonstrate that partial GLT-1 loss can cause insulin/Akt signaling abnormalities that are in keeping with those observed in AD. [ABSTRACT FROM AUTHOR]

Alcoholism is a serious public health concern that is characterized by the development of tolerance to alcohol's effects, increased consumption, loss of control over drinking and the development of physical dependence. This cycle is often times punctuated by periods of abstinence, craving and relapse. The development of tolerance and the expression of withdrawal effects, which manifest as dependence, have been to a great extent attributed to neuroadaptations within the mesocorticolimbic and extended amygdala systems. Alcohol affects various neurotransmitter systems in the brain including the adrenergic, cholinergic, dopaminergic, GABAergic, glutamatergic, peptidergic, and serotonergic systems. Due to the myriad of neurotransmitter and neuromodulator systems affected by alcohol, the efficacies of current pharmacotherapies targeting alcohol dependence are limited. Importantly, research findings of changes in glutamatergic neurotransmission induced by alcohol self- or experimenter-administration have resulted in a focus on therapies targeting glutamatergic receptors and normalization of glutamatergic neurotransmission. Glutamatergic receptors implicated in the effects of ethanol include the ionotropic glutamate receptors (AMPA, Kainate, and NMDA) and some metabotropic glutamate receptors. Regarding glutamatergic homeostasis, ceftriaxone, MS-153, and GPI-1046, which upregulate glutamate transporter 1 (GLT1) expression in mesocorticolimbic brain regions, reduce alcohol intake in genetic animal models of alcoholism. Given the hyperglutamatergic/hyperexcitable state of the central nervous system induced by chronic alcohol abuse and withdrawal, the evidence thus far indicates that a restoration of glutamatergic concentrations and activity within the mesocorticolimbic system and extended amygdala as well as multiple memory systems holds great promise for the treatment of alcohol dependence. [ABSTRACT FROM AUTHOR]

Inorganic arsenic (iAs) is an important natural pollutant. Millions of individuals worldwide drink water with high levels of iAs. Chronic exposure to iAs has been associated with lower IQ and learning disabilities as well as memory impairment. iAs is methylated in tissues such as the brain generating mono and dimethylated species. iAs methylation requires cellular glutathione (GSH), which is the main antioxidant in the central nervous system (CNS). In humans, As species cross the placenta and are found in cord blood. A CD1 mouse model was used to investigate effects of gestational iAs exposure which can lead to oxidative damage, disrupted cysteine/glutamate transport and its putative impact in learning and memory. On postnatal days (PNDs) 1, 15 and 90, the expression of membrane transporters related to GSH synthesis and glutamate transport and toxicity, such as xCT, EAAC1, GLAST and GLT1, as well as LAT1, were analyzed. Also, the expression of the glutamate receptor N-methyl-D-aspartate (NMDAR) subunits NR2A and B as well as the presence of As species in cortex and hippocampus were investigated. On PND 90, an object location task was performed to associate exposure with memory impairment. Gestational exposure to iAs affected the expression of cysteine/glutamate transporters in cortex and hippocampus and induced a negative modulation of NMDAR NR2B subunit in the hippocampus. Behavioral tasks showed significant spatial memory impairment in males while the effect was marginal in females. [ABSTRACT FROM AUTHOR]

To maintain reliable signal transmission across a synapse, free synaptic neurotransmitters must be removed from the cleft in a timely manner. In the first visual synapse, this critical task is mainly undertaken by glutamate transporters (EAATs). Here we study the differential roles of the EAAT1, EAAT2 and EAAT5 subtypes in glutamate (GLU) uptake at the photoreceptor-to-depolarizing bipolar cell synapse in intact dark-adapted retina. Various doses of EAAT blockers and/or GLU were injected into the eye before the electroretinogram (ERG) was measured. Their effectiveness and potency in inhibiting the ERG b-wave were studied to determine their relative contributions to the GLU clearing activity at the synapse. The results showed that EAAT1 and EAAT2 plays different roles. Selectively blocking glial EAAT1 alone using UCPH101 inhibited the b-wave 2–24 h following injection, suggesting a dominating role of EAAT1 in the overall GLU clearing capacity in the synaptic cleft. Selectively blocking EAAT2 on photoreceptor terminals had no significant effect on the b-wave, but increased the potency of exogenous GLU in inhibiting the b-wave. These suggest that EAAT2 play a secondary yet significant role in the GLU reuptake activity at the rod and the cone output synapses. Additionally, we have verified our electrophysiological findings with double-label immunohistochemistry, and extend the literature on the spatial distribution of EAAT2 splice variants in the mouse retina. [ABSTRACT FROM AUTHOR]

Neuropathic pain is a form of pathological nociception that occurs in a significant portion of traumatic spinal cord injury (SCI) patients, resulting in debilitating and often long-term physical and psychological burdens. While many peripheral and central mechanisms have been implicated in neuropathic pain, central sensitization of dorsal horn spinothalamic tract (STT) neurons is a major underlying substrate. Furthermore, dysregulation of extracellular glutamate homeostasis and chronic astrocyte activation play important underlying roles in persistent hyperexcitability of these superficial dorsal horn neurons. To date, central sensitization and astrocyte changes have not been characterized in cervical SCI-induced neuropathic pain models, despite the fact that a major portion of SCI patients suffer contusion trauma to cervical spinal cord. In this study, we have characterized 2 rat models of unilateral cervical contusion SCI that behaviorally result in chronic persistence of thermal hyperalgesia in the ipsilateral forepaw. In addition, we find that STT neurons are chronically activated in both models when compared to laminectomy-only uninjured rats. Finally, persistent astrocyte activation and significantly reduced expression of the major CNS glutamate transporter, GLT1, in superficial dorsal horn astrocytes are associated with both excitability changes in STT neurons and the neuropathic pain behavioral phenotype. In conclusion, we have characterized clinically-relevant rodent models of cervical contusion-induced neuropathic pain that result in chronic activation of both STT neurons and astrocytes, as well as compromise in astrocyte glutamate transporter expression. These models can be used as important tools to further study mechanisms underlying neuropathic pain post-SCI and to test potential therapeutic interventions. [ABSTRACT FROM AUTHOR]

Alterations in glutamatergic neurotransmission have been suggested to affect many aspects of neuroplasticity associated with alcohol/drug addiction. We have previously shown that ceftriaxone, a β-lactam antibiotic known to upregulate glutamate transporter 1 (GLT1), reduced ethanol intake after 5 weeks of free choice ethanol drinking paradigm in male alcohol-preferring (P) rats. Evidence suggests that differential effects involving alterations of glutamatergic neurotransmission occur after long-term ethanol consumption. In this study, we tested whether the efficacy of administration of ceftriaxone persists after 14 weeks of free access to 15 and 30 % ethanol in male P rats. After 14 weeks of ethanol consumption, male P rats were administered ceftriaxone (100 mg/kg, intraperitoneal (i.p.)) or saline vehicle for 5 days. We found that ceftriaxone treatment resulted in a significant reduction in ethanol intake starting from day 2 (48 h after the first i.p. injections of ceftriaxone) through day 14, 10 days after final injection. Western blot analysis of brain samples from animals euthanized 24 h after treatment with the last dose of ceftriaxone revealed a significant upregulation of cystine/glutamate exchanger (xCT) and GLT1 levels in prefrontal cortex, nucleus accumbens, and amygdala as compared to saline vehicle-treated group. These findings demonstrated the effectiveness of ceftriaxone in attenuating ethanol intake in a chronic consumption paradigm. These might be due in part through the upregulation of both xCT and GLT1 levels in brain reward regions. Thus, the drug has a potential therapeutic action for the treatment of alcohol dependence. [ABSTRACT FROM AUTHOR]

Studies in our laboratory have been investigating the potential therapeutic role of glutamate transporter 1 (GLT1; its human homolog is excitatory amino acid transporter 2, EAAT2) on alcohol intake with a genetically selected high alcohol-consuming rat line, the alcoholpreferring (P) rat. Our central hypothesis is that glutamatergic transmission in central reward brain regions modulates alcohol intake, and perturbations of this system result in alcohol abuse/dependence. GLT1, a sodium-dependent transport protein, is responsible for the removal of the majority of extracellular glutamate at the synaptic cleft. Thus, upregulation or activation of GLT1 should attenuate alcohol intake and lead to the treatment of alcohol dependence. [ABSTRACT FROM AUTHOR]

Studies have demonstrated that deletion of equilibrative nucleoside transporter 1 (ENT1) is associated with reduced glutamate transporter 1 (GLT1) level, and consequently increased ethanol intake. In this study, we measured changes in GLT1 and ENT1 levels in prefrontal cortex (PFC), and nucleus accumbens (NAc) core and shell associated with alcohol drinking in alcohol-preferring (P) rats. We examined, then, whether ceftriaxone (CEF) would affect both GLT1 and ENT1 levels in these brain regions. P rats were given 24-h concurrent access to 15 and 30 % ethanol, water, and food for 5 weeks. On Week 6, P rats received 100 mg/kg CEF (i.p.) or a saline vehicle for five consecutive days. Ethanol intake was measured daily for 8 days starting on the first day of injections. We found a significant reduction in daily ethanol intake in CEF-treated group, starting on Day 2 of injections. Western blot for GLT1 and binding assay for ENT1 revealed downregulation of GLT1 level, whereas ENT1 levels were increased in the NAc core and NAc shell, respectively, but not in the PFC in saline vehicle group. Importantly, CEF treatment reversed these effects in both NAc core and shell. These findings provide evidence for potential regulatory effects of CEF on both GLT1 and ENT1 expression in reducing ethanol intake. [ABSTRACT FROM AUTHOR]

We have investigated whether simultaneous modification of cofactor metabolism and glycerol in a strain of Saccharomyces cerevisiae can eliminate glycerol synthesis during ethanol production. Two strains, S812 ( gpd1Δ gpd2Δ PGK1p- GLT1) and LE17 ( gpd1Δ gpd2Δ PGK1p- GLT1 PGKp- STL1) were generated that showed a 8 and 8.2 % increase in the ethanol yield, respectively, compared to the wild type KAM-2 strain. The ethanol titer was improved from 90.4 g/l for KAM-2 to 97.6 g/l for S812 and 97.8 g/l for LE17, respectively. These results provide a new insight into rationalization of metabolic engineering strategies for improvement of ethanol yield through elimination of glycerol production. [ABSTRACT FROM AUTHOR]

Recent studies have implicated potentially significant roles for astrocytes in the pathogenesis of neurodevelopmental disorders. Astrocytes undergo a dramatic maturation process following early differentiation from which typical morphology and important functions are acquired. Despite significant progress in understanding their early differentiation, very little is known about how astrocytes become functionally mature. In addition, whether functional maturation of astrocytes is disrupted in neurodevelopmental disorders and the consequences of this disruption remains essentially unknown. In this review, we discuss our perspectives about how astrocyte developmental maturation is regulated, and how disruption of the astrocyte functional maturation process, especially alterations in their ability to regulate glutamate homeostasis, may alter synaptic physiology and contribute to the pathogenesis of neurodevelopmental disorders [ABSTRACT FROM AUTHOR]

Purpose: Ceftriaxone, a β-lactam antibiotic, can selectively enhance the expression of glutamate transporter 1 (GLT1), the most abundant astrocytic glutamate transporter expressed in the cortex. It has been found to have neuroprotective effects when administered prior to brain ischemic damage or during the acute phase post-stroke, but its effects in chronic period have not been examined. Methods: We examined the effects of ceftriaxone on the acquisition of motor skill and the functional outcome after focal ischemic cortical lesions. In adult male rats, ceftriaxone (200 mg/kg) or vehicle was intraperitoneally injected daily for 5 days, a treatment regime previously established to upregulate GLT-1. This preceded 28 days of skilled reach training in intact animals or began 3 days following lesions, followed by 5 weeks of rehabilitative reach training. Results: In intact rats, ceftriaxone did not affect skill learning rate or final performance. Following ischemic lesions, though there was no significant difference in lesion sizes between groups, ceftriaxone exacerbated initial deficits in reaching performance. Conclusion: These findings of detrimental effects on motor functional outcome suggest that ceftriaxone may be more useful for neuroprotection during the acute phase of ischemia than for functional recovery in the post-acute period after ischemic damage. [ABSTRACT FROM AUTHOR]