Thiamine deficiency results in downregulation of the GLAST glutamate transporter in cultured astrocytes

Stem Cell Therapy and Thiamine Deficiency-Induced Brain Damage

Wernicke's encephalopathy (WE) is a major central nervous system disorder resulting from thiamine deficiency (TD) in which a number of brain regions can develop serious damage including the thalamus and inferior colliculus. Despite decades of research into the pathophysiology of TD and potential therapeutic interventions, little progress has been made regarding effective treatment following the development of brain lesions and its associated cognitive issues. Recent developments in our understanding of stem cells suggest they are capable of repairing damage and improving function in different maladys. This article puts forward the case for the potential use of stem cell treatment as a therapeutic strategy in WE by first examining the effects of TD on brain functional integrity and its consequences. The second half of the paper will address the future benefits of treating TD with these cells by focusing on their nature and their potential to effectively treat neurodegenerative diseases that share some overlapping pathophysiological features with TD. At the same time, some of the obstacles these cells will have to overcome in order to become a viable therapeutic strategy for treating this potentially life-threatening illness in humans will be highlighted.

Traditional uses, chemical compounds, pharmacological activities and clinical studies on the traditional Chinese prescription Yi-Gan San

ETHNOPHARMACOLOGICAL RELEVANCE

A widely used traditional prescription, Yi-Gan San (YGS) is a remedy for neurodegenerative disorders. The formulation consists of seven Chinese medicinal materials in specific proportions, namely Uncariae Ramulus cum Uncis (Uncaria rhynchophylla (Miq.) Miq. ex Havil.), Bupleuri Radix (Bupleurum chinense DC.), Angelicae Sinensis Radix (Angelica sinensis (Oliv.) Diels), Chuanxiong Rhizoma (Ligusticum wallichii Franch.), Poria (Poria cocos (Schw.) Wolf), Atractylodis Macrocephalae Rhizoma (Atractylodes macrocephala Koidz.) and Glycyrrhizae Radix et Rhizoma (Glycyrrhiza uralensis Fisch.). Using YGS has been shown to alleviate various behavioural and psychological symptoms of dementia (BPSD).

AIM OF THIS REVIEW

The goal of this review is to give up-to-date information about the traditional uses, chemistry, pharmacology and clinical efficacy of YGS based on the scientific literature and to learn the current focus and provide references in the next step.

MATERIALS AND METHODS

The database search room was accessed using the search terms "Yi-Gan San" and "Yokukansan" to obtain results from resources such as Web of Science, PubMed, Google Scholar and Sci Finder Scholar. We not only consulted the literature of fellow authors for this review but also explored classical medical books.

RESULTS

YGS has been used to cure neurosis, sleeplessness, night weeping and restlessness in infants. Its chemical components primarily consist of triterpenes, flavonoids, phenolics, lactones, alkaloids and other types of compounds. These active ingredients displayed diverse pharmacological activities to ameliorate BPSD by regulating serotonergic, glutamatergic, cholinergic, dopaminergic, adrenergic, and GABAergic neurotransmission. In addition, YGS showed neuroprotective, antistress, and anti-inflammatory effects. The majority of cases of neurodegenerative disorders are treated with YGS, including Alzheimer's disease and dementia with Lewy bodies.

CONCLUSIONS

Based on previous studies, YGS has been used as a traditional prescription in East Asia, such as Japan, Korea and China, and it has diverse chemical compounds and multiple pharmacological activities. Nevertheless, few experimental studies have focused on chemical and quantitative YGS studies, suggesting that further comprehensive research on its chemicals and quality assessments is critical for future evaluations of drug efficacy.

Thiamine insufficiency induces Hypoxia Inducible Factor-1α as an upstream mediator for neurotoxicity and AD-like pathology

Insufficiencies of the micronutrient thiamine (Vitamin B1) have been associated with inducing Alzheimer's disease (AD)-like neuropathology. The hypometabolic state associated with chronic thiamine insufficiency (TI) has been demonstrated to be a contributor towards the development of amyloid plaque deposition and neurotoxicity. However, the molecular mechanism underlying TI induced AD pathology is still unresolved. Previously, we have established that TI stabilizes the metabolic stress transcriptional factor, Hypoxia Inducible Factor-1α (HIF1α). Utilizing neuronal hippocampal cells (HT22), TI-induced HIF1α activation triggered the amyloidogenic cascade through transcriptional expression and increased activity of β-secretase (BACE1). Knockdown and pharmacological inhibition of HIF1α during TI significantly reduced BACE1 and C-terminal Fragment of 99 amino acids (C99) formation. TI also increased the expression of the HIF1α regulated pro-apoptotic protein, BCL2/adenovirus E1B 19 kDa protein-interacting protein (BNIP3). Correspondingly, cell toxicity during TI conditions was significantly reduced with HIF1α and BNIP3 knockdown. The role of BNIP3 in TI-mediated toxicity was further highlighted by localization of dimeric BNIP3 into the mitochondria and nuclear accumulation of Endonuclease G. Subsequently, TI decreased mitochondrial membrane potential and enhanced chromatin fragmentation. However, cell toxicity via the HIF1α/BNIP3 cascade required TI induced oxidative stress. HIF1α, BACE1 and BNIP3 expression was induced in 3xTg-AD mice after TI and administration with the HIF1α inhibitor YC1 significantly attenuated HIF1α and target genes levels in vivo. Overall, these findings demonstrate a critical stress response during TI involving the induction of HIF1α transcriptional activity that directly promotes neurotoxicity and AD-like pathology.

Analgesic Effect of Combined Therapy with the Japanese Herbal Medicine "Yokukansan" and Electroacupuncture in Rats with Acute Inflammatory Pain

Background: Japanese herbal medicine, called Kampo medicine, and acupuncture are mainly used in Japanese traditional medicine. In this experiment, the analgesic effect of Yokukansan (YKS) alone and a combination of YKS and electroacupuncture (EA) on inflammatory pain induced by formalin injection were examined. Methods: Animals were divided into four groups: a control group, formalin injection group (formalin), YKS-treated formalin group (YKS), and YKS- and EA-treated formalin group (YKS + EA). The duration of pain-related behaviors and extracellular signal-regulated protein kinase (ERK) activation in the spinal cord after formalin injection in the right hind paw were determined. Results: The duration of pain-related behaviors was dramatically prolonged in the late phase (10–60 min) in the formalin group. The YKS treatment tended to reduce (p = 0.08), whereas YKS + EA significantly suppressed the pain-related behaviors (p < 0.01). Immunohistochemical and Western blot analyses revealed that the number of phosphorylated ERK1/2 (pERK1/2)-positive cells and the pERK expression level, which were increased by formalin injection, were significantly inhibited by YKS (p < 0.05) and YKS + EA (p < 0.01). Conclusions: The YKS + EA combination therapy elicited an analgesic effect on formalin-induced acute inflammatory pain.

Endocrine cross-talk between the gut microbiome and glial cells in development and disease

Glial cells make up the major cellular component of the nervous system. Glial development is usually investigated through perturbations of host genetics, although non-host-derived signalling molecules can also regulate glial cells. Indeed, gut microbiome colonisation and the presence of microbiome-derived factors in the blood coincide with glial cell development. Emerging data suggest that the gut microbiome can regulate gliogenesis, myelination and glial epigenetics. Neurodegenerative diseases are characterised by changes in the gut microbiome and glial dysfunction. This perspective discusses the ways in which microbiome-derived molecules can engage in cross-talk with glial cells during development and in dysfunctional glial diseases.

Wernicke's encephalopathy - from basic science to clinical practice. Part 1: Understanding the role of thiamine

Wernicke's encephalopathy (WE) is an acute neuropsychiatric state. Untreated, WE can lead to coma or death, or progress to Korsakoff syndrome (KS) - a dementia characterized by irreversible loss of anterograde memory. Thiamine (vitamin B1) deficiency lies at the heart of this condition. Yet, our understanding of thiamine regarding prophylaxis and treatment of WE remains limited. This may contribute to the current undertreatment of WE in clinical practice. The overall aim of this review is to identify the best strategies for prophylaxis and treatment of WE in regard to (a) dose of thiamine, (b) mode of administration, (c) timing of switch from one mode of administration to another, (d) duration of administration, and (e) use of magnesium along thiamine as an essential cofactor. Evidence from randomized controlled trials and other intervention studies is virtually absent. Therefore, we have to resort to basic science for proof of principle instead. Here, we present the first part of our clinical review, in which we explore the physiology of thiamine and the pathophysiology of thiamine deficiency. We first explore both of these in their historical context. We then review the pharmacodynamics and pharmacokinetics of thiamine, exploring the roles of the six currently known thiamine compounds, their transporters, and target enzymes. We also explore the significance of magnesium as a cofactor in thiamine-facilitated enzymatic reactions and thiamine transport. In the second (forthcoming) part of this review, we will use the findings of the current review to make evidence-based inferences about strategies for prophylaxis and treatment of WE.

Don't seek, don't find: The diagnostic challenge of Wernicke's encephalopathy

Wernicke’s encephalopathy is caused by thiamine deficiency and has a range of presenting features, including gait disturbance, altered cognitive state, nystagmus and other eye movement disorders. In the past, Wernicke’s encephalopathy was described almost exclusively in the alcohol-dependent population. However, in current times, Wernicke’s encephalopathy is also well recognized in many other patient groups, including patients following bariatric surgery, gastrointestinal surgery, cancer and pancreatitis. Early recognition of Wernicke’s encephalopathy is vital, as prompt treatment can restore cognitive or ocular function and can prevent permanent disability. Unfortunately, Wernicke’s encephalopathy is often undiagnosed – presumably because it is relatively uncommon and has a variable clinical presentation. Clinical biochemists have a unique role in advising clinicians about potential nutritional or metabolic causes of unexplained neurological symptoms and to prompt consideration of thiamine deficiency as a potential cause in high-risk patient groups. The aim of this review is to summarize the clinical features, diagnosis and treatment of Wernicke’s encephalopathy and to highlight some non-traditional causes, such as after bariatric surgery.

Aggravated effects of coexisting marginal thiamine deficits and zinc excess on SN56 neuronal cells

Objectives: Zinc excitotoxicity and thiamine pyrophosphate deficiency (TD) are known pathogenic signals contributing to mechanism of different encephalopathies through inhibition of enzymes responsible for energy metabolism such as pyruvate dehydrogenase, aconitase or ketoglutarate dehydrogenase. The aim of this work was to investigate whether subclinical Zn excess and TD, frequent in aging brain, may combine yielding overt neuronal impairment.Results: Clonal SN56 cholinergic neuronal cells of septal origin were used as the model of brain cholinergic neurons, which are particularly susceptible to neurodegeneration in the course of Alzheimer's disease, hypoxia and other dementia-linked brain pathologies. Neither subtoxic concentration of Zn (0.10 mM) nor mild 20-25% TD deficits alone caused significant negative changes in cultured cholinergic neurons viability and their acetyl-CoA/acetylcholine metabolism. However, cells with mild TD accumulated Zn in excess, which impaired their energy metabolism causing a loss of neurons viability and their function as neurotransmitters. These negative effects of Zn were aggravated by amprolium which is an inhibitor of thiamine intracellular transport.Conclusion: Our data indicate that TD may amplify otherwise non-harmful border-line Zn excitotoxic signals yielding progress of neurodegeneration.

Comparison of the Effects of Yokukansan and Yokukansankachimpihange on Glutamate Uptake by Cultured Astrocytes and Glutamate-Induced Excitotoxicity in Cultured PC12 Cells

The traditional Japanese Kampo medicine yokukansan (YKS) is effective for behavioral and psychological symptoms of dementia (BPSD) in patients with Alzheimer's disease. As the pharmacological mechanisms, YKS is known to protect astrocytes from thiamine-deficiency (TD)-induced decreased glutamate (Glu) uptake and neuron model cells (PC 12 cells) from Glu-induced death. Yokukansankachimpihange (YKSCH) is an alternative formula to YKS, in which Citrus unshiu peel and Pinellia tuber are added to the YKS components, and is sometimes used to treat BPSD, but its pharmacological properties remain unknown. This study aims to investigate the cellular pharmacological effects of YKS and YKSCH on glutamatergic pathways, compare their efficacy, and determine the differences and similarities in the activities between these formulations. First, we examined the effects of YKS and YKSCH on Glu uptake by cultured astrocytes under TD conditions. We observed significant ameliorative effects of YKS and YKSCH on the TD-induced decrease in Glu uptake, with a 50% effective dose of 8.9 ± 1.8 μg/mL and 45.3 ± 9.2 μg/mL, respectively. Second, using cultured PC12 cells as a model for neurons, we examined the effects of YKS and YKSCH on Glu-induced cell death. We observed that YKS and YKSCH had significant inhibitory effects on Glu-induced cell death, with a 30% effective dose of 51.4 ± 20.8 μg/mL and 49.2 ± 11.0 μg/mL, respectively. Thus, while YKSCH was less effective than YKS in ameliorating the TD-induced decrease in Glu uptake by astrocytes, the two drugs showed similar inhibitory effects on Glu-induced PC12 cell death. These findings are important for understanding the differences and similarities in pharmacological actions between these drugs.

Biotin-Thiamine Responsive Encephalopathy: Report of an Egyptian Family with a Novel SLC19A3 Mutation and Review of the Literature

Biotin-thiamine responsive basal ganglia disease (BTRBGD) is an autosomal recessive neurometabolic disorder with poor genotype-phenotype correlation, caused by mutations in the SLC19A3 gene on chromosome 2q36.6. The disease is characterized by three stages: stage 1 is a sub-acute encephalopathy often triggered by febrile illness; stage 2 is an acute encephalopathy with seizures, loss of motor function, developmental regression, dystonia, external ophthalmoplegia, dysphagia, and dysarthria; stage 3 is represented by chronic or slowly progressive encephalopathy. Clinical and biochemical findings, as well as the magnetic resonance imaging (MRI) pattern, resemble those of Leigh's syndrome, so that BTRBGD can be misdiagnosed as a mitochondrial encephalopathy.Here we report the clinical and radiological phenotypes of two siblings diagnosed with BTRBGD in which a novel SLC19A3 mutation (NM_025243.3: c.548C > T; p.Ala183Val) was found by whole exome sequencing (WES) of the family members.

Stabilization of the hypoxia-inducible transcription Factor-1 alpha (HIF-1α) in thiamine deficiency is mediated by pyruvate accumulation

Vitamin B1, or thiamine is a critical enzyme cofactor required for metabolic function and energy production. Thiamine deficiency (TD) is common in various diseases, and results in severe neurological complications due to diminished mitochondrial function, oxidative stress, excitotoxicity and inflammation. These pathological sequelae result in apoptotic cell death in both neurons and astrocytes in distinct regions, in particular the thalamus and mammillary bodies. Comparable histological injuries in patients with hypoxia/ischemia (H/I) have also been described, suggesting a congruency between the cellular responses to these stresses. Analogous to H/I, TD stabilizes and activates Hypoxia Inducible Factor-1α (HIF-1α) even without changes in physiological oxygen levels. However, the mechanism of HIF-1α stabilization in TD is currently unknown. Using a pyruvate assay, we have demonstrated that TD induces pyruvate accumulation in mouse primary astrocytes which correlates to an increase in HIF-1α expression. Additionally, we utilized an enzymatic assay for pyruvate dehydrogenase to demonstrate a reduction in catalytic activity during TD due to lack of available thiamine pyrophosphate cofactor, resulting in the observed pyruvate accumulation. Finally, a pyruvate kinase inhibitor which limited pyruvate accumulation was utilized to demonstrate the role of pyruvate accumulation in HIF-1α stabilization during TD. These results reveal that stabilization of HIF-1α protein in TD centralizes on pyruvate accumulation in mouse primary astrocytes due to metabolic disruption of PDH.

Thiamine deficiency activates hypoxia inducible factor-1α to facilitate pro-apoptotic responses in mouse primary astrocytes

Thiamine is an essential enzyme cofactor required for proper metabolic function and maintenance of metabolism and energy production in the brain. In developed countries, thiamine deficiency (TD) is most often manifested following chronic alcohol consumption leading to impaired mitochondrial function, oxidative stress, inflammation and excitotoxicity. These biochemical lesions result in apoptotic cell death in both neurons and astrocytes. Comparable histological injuries in patients with hypoxia/ischemia and TD have been described in the thalamus and mammillary bodies, suggesting a congruency between the cellular responses to these stresses. Consistent with hypoxia/ischemia, TD stabilizes and activates Hypoxia Inducible Factor-1α (HIF-1α) under physiological oxygen levels. However, the role of TD-induced HIF-1α in neurological injury is currently unknown. Using Western blot analysis and RT-PCR, we have demonstrated that TD induces HIF-1α expression and activity in primary mouse astrocytes. We observed a time-dependent increase in mRNA and protein expression of the pro-apoptotic and pro-inflammatory HIF-1α target genes MCP1, BNIP3, Nix and Noxa during TD. We also observed apoptotic cell death in TD as demonstrated by PI/Annexin V staining, TUNEL assay, and Cell Death ELISA. Pharmacological inhibition of HIF-1α activity using YC1 and thiamine repletion both reduced expression of pro-apoptotic HIF-1α target genes and apoptotic cell death in TD. These results demonstrate that induction of HIF-1α mediated transcriptional up-regulation of pro-apoptotic/inflammatory signaling contributes to astrocyte cell death during thiamine deficiency.

Cellular Pharmacological Effects of the Traditional Japanese Kampo Medicine Yokukansan on Brain Cells

Yokukansan (YKS) is a traditional Japanese Kampo medicine currently used for the treatment of the behavioral psychological symptoms associated with dementia (BPSD), which is frequently problematic in neurodegenerative disorders such as Alzheimer’s disease. Regarding the pharmacological mechanisms underlying its efficacy, we recently reviewed the multiple effects of YKS on the neurotransmitter systems (e.g., glutamatergic, serotonergic, dopaminergic, cholinergic, GABAergic, and adrenergic neurotransmission) in various brain regions that are related to the psychological, emotional, cognitive, or memory functions. These multiple effects are thought to be caused by multiple components included in YKS. In addition, YKS exhibits various effects on brain cells (i.e., neurons, glial cells including astrocytes, oligodendrocytes, and microglial cells, and endothelial cells). In this review, we summarize recent evidence demonstrating the cellular pharmacological effects of YKS on these brain cells, and discuss the current understanding of its efficacy and mechanism. In particular, YKS maintains the neuronal survival and function by multiple beneficial effects, including anti-apoptosis, anti-oxidation, anti-endoplasmic reticulum stress, and neurogenesis. YKS also acts on glial cells by: facilitating the transport of glutamate into astrocytes; promoting the proliferation and differentiation of oligodendrocytes; and enhancing the anti-inflammatory properties of microglial cells. These glial effects are thought to support neuronal functioning within the brain. Various ingredients involved in these effects have been identified, some of which can pass through the artificial blood–brain barrier without disrupting the endothelial tight junctions. This multitude of interactive effects displayed by YKS on neuronal and glial cells is suggested to be involved in the multitude of neuropsychopharmacological actions of YKS, which are related to the improvement of BPSD.

Treatment of rats with the JAK-2 inhibitor fedratinib does not lead to experimental Wernicke's encephalopathy

Recent clinical trials suggest that patients with myelofibrosis can develop Wernicke's encephalopathy (WE) when treated with fedratinib, a specific Janus kinase-2 (JAK-2) inhibitor. To investigate this issue, we have examined (1) if fedratinib can produce or alter the course of this disorder, (2) its effects on thiamine-dependent enzyme activity and thiamine status, and (3) its influence on the uptake of thiamine. Animals administered fedratinib for 28days at a comparable dose used to treat human cases of myelofibrosis showed no evidence of clinical signs of thiamine deficiency (TD). Rats treated with a combination of fedratinib and TD exhibited no neurological differences in their progress to the symptomatic stage when compared to thiamine-deficient animals only. Treatment with the JAK-2 inhibitor did not compromise erythrocyte transketolase activity, and thiamine status was not affected in a major way unlike animals with TD. In addition, treatment of cultured astrocytes with fedratinib did not diminish the uptake of thiamine into these cells. Our findings suggest that treatment with fedratinib does not lead to or alter the progress of TD, and do not support the notion that administration of this JAK-2 inhibitor directly results in the development of WE due to inhibition of thiamine transport. Known adverse effects of fedratinib involving compromised gastrointestinal function may be an important indirect contributing factor to previously reported cases of WE in patients with myelofibrosis.

Neuropharmacological efficacy of the traditional Japanese Kampo medicine yokukansan and its active ingredients

Dementia is a progressive neurodegenerative disorder with cognitive dysfunction, and is often complicated by behavioral and psychological symptoms of dementia (BPSD) including excitement, aggression, and hallucinations. Typical and atypical antipsychotics are used for the treatment of BPSD, but induce adverse events. The traditional Japanese Kampo medicine yokukansan (YKS), which had been originated from the traditional Chinese medicine Yi-Gan-San, has been reported to improve BPSD without severe adverse effects. In the preclinical basic studies, there are over 70 research articles indicating the neuropharmacological efficacies of YKS. In this review, we first describe the neuropharmacological actions of YKS and its bioactive ingredients. Multiple potential actions for YKS were identified, which include effects on serotonergic, glutamatergic, cholinergic, dopaminergic, adrenergic, and GABAergic neurotransmissions as well as neuroprotection, anti-stress effect, promotion of neuroplasticity, and anti-inflammatory effect. Geissoschizine methyl ether (GM) in Uncaria hook and 18β-glycyrrhetinic acid (GA) in Glycyrrhiza were responsible for several pharmacological actions of YKS. Subsequently, we describe the pharmacokinetics of GM and GA in rats. These ingredients were absorbed into the blood, crossed the blood-brain barrier, and reached the brain, in rats orally administered YKS. Moreover, autoradiography showed that [(3)H]GM predominantly distributed in the frontal cortex and [(3)H]GA in the hippocampus. Thus, YKS is a versatile herbal remedy with a variety of neuropharmacological effects, and may operate as a multicomponent drug including various active ingredients.

Role of astrocytes in thiamine deficiency

Thiamine deficiency (TD) is the underlying cause of Wernicke's encephalopathy (WE), an acute neurological disorder characterized by structural damage to key periventricular structures in the brain. Increasing evidence suggests these focal histological lesions may be representative of a gliopathy in which astrocyte-related changes are a major feature of the disorder. These changes include a loss of the glutamate transporters GLT-1 and GLAST concomitant with elevated interstitial glutamate levels, lowered brain pH associated with increased lactate production, decreased levels of GFAP, reduction in the levels of glutamine synthetase, swelling, alterations in levels of aquaporin-4, and disruption of the blood-brain barrier. This review focusses on how these manifestations contribute to the pathophysiology of TD and possibly WE.

Thiamine deficiency: an update of pathophysiologic mechanisms and future therapeutic considerations

Thiamine is an essential vitamin that is necessary to maintain the functional integrity of cells in the brain. Its deficiency is the underlying cause of Wernicke's encephalopathy (WE), a disorder primarily associated with, but not limited to, chronic alcoholism. Thiamine deficiency leads to the development of impaired energy metabolism due to mitochondrial dysfunction in focal regions of the brain resulting in cerebral vulnerability. The consequences of this include oxidative stress, excitotoxicity, inflammatory responses, decreased neurogenesis, blood-brain barrier disruption, lactic acidosis and a reduction in astrocyte functional integrity involving a loss of glutamate transporters and other astrocyte-specific proteins which together contribute in a major way to the resulting neurodegeneration. Exactly how these factors acting in concert lead to the demise of neurons is unclear. In this review we reassess their relative importance in the light of more recent findings and discuss therapeutic possibilities that may provide hope for the future for individuals with WE.

Thiamine deficiency results in release of soluble factors that disrupt mitochondrial membrane potential and downregulate the glutamate transporter splice-variant GLT-1b in cultured astrocytes

Loss of astrocytic glutamate transporters is a major feature of both thiamine deficiency (TD) and Wernicke's encephalopathy. However, the underlying basis of this process is not well understood. In the present study we have investigated the possibility of release of astrocytic soluble factors that might be involved in the regulation of the glutamate transporter GLT-1b in these cells. Treatment of naïve astrocytes with conditioned media from astrocytes exposed to TD conditions resulted in a progressive decrease in glutamate uptake over 24 h. Immunoblotting and flow cytometry measurements indicated this was accompanied by a 20-40% loss of GLT-1b. Astrocytes exposed to either TD or TD conditioned media showed increased disruption of mitochondrial membrane potential compared to control cells, and treatment of astrocytes with TD resulted in an increase in the pro-inflammatory cytokine TNF-α and elevated levels of phospho-IκB fragment, indicative of increased activation of NF-κB. Inhibition of TNF-α activity with the use of a neutralizing antibody blocked the increased NF-κB activation, while inhibition of NF-κB ameliorated the decrease in GLT-1b and reversed the decrease in glutamate uptake occurring with TD treatment. Together, these findings indicate that astrocytes exposed to TD conditions show responses suggesting that soluble factors released by these cells under conditions of TD play a regulatory role in terms of glutamate transport function and mitochondrial integrity.

Pyrithiamine-induced thiamine deficiency alters proliferation and neurogenesis in both neurogenic and vulnerable areas of the rat brain

Thiamine deficiency (TD) leads to Wernicke's encephalopathy (WE), in which focal histological lesions occur in periventricular areas of the brain. Recently, impaired neurogenesis has been reported in the hippocampus during the dietary form of TD, and in pyrithiamine-induced TD (PTD), a well-characterized model of WE. To further characterize the consequences of PTD on neural stem/progenitor cell (NSPC) activity, we have examined the effect of this treatment in the rat on both the subventricular zone (SVZ) of the rostral lateral ventricle and subgranular layer (SGL) of the hippocampus, and in the thalamus and inferior colliculus, two vulnerable brain regions in this disorder. In both the SVZ and SGL, PTD led to a decrease in the numbers of bromodeoxyuridine-stained cells, indicating that proliferation of NSPCs destined for neurogenesis in these areas was reduced. Doublecortin (DCX) immunostaining in the SGL was decreased, indicating a reduction in neuroblast formation, consistent with impaired NSPC activity. DCX labeling was not apparent in focal areas of vulnerability. In the thalamus, proliferation of cells was absent while in the inferior colliculus, numerous actively dividing cells were apparent, indicative of a differential response between these two brain regions. Exposure of cultured neurospheres to PTD resulted in decreased proliferation of NSPCs, consistent with our in vivo findings. Together, these results indicate that PTD considerably affects cell proliferation and neurogenesis activity in both neurogenic areas and parts of the brain known to display structural and functional vulnerability, confirming and extending recent findings on the effects of TD on neurogenesis. Future use of NSPCs in vitro may allow a closer and more detailed examination of the mechanism(s) underlying inhibition of these cells during TD.

Experimentally-induced Wernicke's encephalopathy modifies crucial rat brain parameters: the importance of Na+, K+ -ATPase and a potentially neuroprotective role for antioxidant supplementation

Wernicke's encephalopathy (WE) is a serious neuropsychiatric syndrome caused by chronic alcoholism and thiamine (T) deficiency. Our aim was to shed more light on the pathophysiology of WE, by introducing a modified in vivo experimental model of WE and by focusing on changes provoked in the total antioxidant status (TAS) and three crucial brain enzyme activities in adult rats. Rats were placed on ethanol (EtOH) consumption (20 % v/v) for a total of 5 weeks. By the end of the third week, rats were fed a T-deficient diet (TDD) and were treated with pyrithiamine (PT; 0.25 mg/kg) for the remaining 2 weeks. Following the induction of WE symptomatology, rats were treated with three consecutive (every 8 h) injections of saline or T (100 mg/kg) and were sacrificed. Brain homogenates were generated and used for spectrophotometrical evaluation of TAS and enzymatic activities. Additionally, in vitro experiments were conducted on brain homogenates or pure enzymes incubated with T or neuromodulatory antioxidants. Pre-exposure to EtOH provided a successful protocol modification that did not affect the expected time of WE symptomatology onset. Administration of T ameliorated this symptomatology. WE provoked oxidative stress that was partially limited by T administration, while T itself also caused oxidative stress to a smaller extent. Brain acetylcholinesterase (AChE) was found inhibited by WE and was further inhibited by T administration. In vitro experiments demonstrated a potential neuroprotective role for L-carnitine (Carn). Brain sodium-potassium adenosine triphosphatase (Na(+),K(+)-ATPase) activity was found increased in WE and was reduced to control levels by in vivo T administration; this increase was also evident in groups exposed to PT or to TDD, but not to EtOH. In vitro experiments demonstrated a potential neuroprotective role for this Na(+),K(+)-ATPase stimulation through T or L-cysteine (Cys) administration. Brain magnesium adenosine triphosphatase (Mg(2+)-ATPase) activity was found decreased by prolonged exposure to EtOH, but was not affected by the experimental induction of WE. Our data suggest that T administration inhibits AChE, which is also found inhibited in WE. Moreover, increased brain Na(+),K(+)-ATPase activity could be a marker of T deficiency in WE, while combined T and antioxidant co-supplementation of Cys and/or Carn could be neuroprotective in terms of restoring the examined crucial brain enzyme activities to control levels.

The impact of oxidative stress in thiamine deficiency: a multifactorial targeting issue

Thiamine (vitamin B1) deficiency, the underlying cause of Wernicke-Korsakoff syndrome, is associated with the development of focal neuronal loss in vulnerable areas of the brain. Although the actual mechanism(s) that lead to the selective histological lesions characteristic of this disorder remain unresolved, oxidative stress has been shown to play a major role in its pathophysiology. In this review, the multifactorial influence of oxidative stress on a variety of processes known to take part in the development of structural lesions in TD including excitotoxicity, neuroinflammation, blood-brain barrier integrity, mitochondrial integrity, apoptosis, nucleic acid function, and neural stem cells will be discussed, and therapeutic strategies undertaken for treating neurodegeneration examined which may have an impact on the future treatment of this important vitamin deficiency.

Role of thiamine in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia in elderly individuals and is associated with progressive neurodegeneration of the human neocortex. Thiamine levels and the activity of thiamine-dependent enzymes are reduced in the brains and peripheral tissues of patients with AD. Genetic studies have provided the opportunity to determine what proteins link thiamine to AD pathology (ie, transketolase, apolipoprotein E, α-1-antitrypsin, pyruvate dehydrogenase complex, p53, glycogen synthetase kinase-3β, c-Fos gene, the Sp1 promoter gene, and the poly(ADP-ribosyl) polymerase-1 gene). We reviewed the association between histopathogenesis and neurotransmitters to understand the relationship between thiamine and AD pathology. Oral thiamine trials have been shown to improve the cognitive function of patients with AD; however, absorption of thiamine is poor in elderly individuals. In the early stage of thiamine-deficient encephalopathy (Wernicke's encephalopathy), however, parental thiamine has been used successfully. Therefore, further studies are needed to determine the benefits of using parental thiamine as a treatment for AD.

Acetyl-CoA metabolism in amprolium-evoked thiamine pyrophosphate deficits in cholinergic SN56 neuroblastoma cells

Inhibition of pyruvate (PDHC) and ketoglutarate (KDHC) dehydrogenase complexes induced by thiamine pyrophosphate deficits is known cause of disturbances of cholinergic transmission in the brain, yielding clinical symptoms of cognitive, vegetative and motor deficits. However, particular alterations in distribution of key acetylcholine precursor, acetyl-CoA, in the cholinergic neuron compartment of thiamine pyrophosphate-deficient brain remain unknown. Therefore, the aim of our work was to find out how amprolium-induced thiamine pyrophosphate deficits (TD) affect distribution of acetyl-CoA in the compartment of pure cholinergic neuroblastoma SN56 cells originating from murine septum. Amprolium caused similar concentration-dependent decreases in thiamine pyrophosphate levels in nondifferentiated (NC) and differentiated (DC) cells cultured in low thiamine medium. In such conditions DC displayed significantly greater loss of viability than the NC ones, despite of lesser suppressions of PDHC activities and tetrazolium salt reduction rates in the former. On the other hand, intramitochondrial acetyl-CoA levels in DC were 73% lower than in NC, which explains their greater susceptibility to TD. Choline acetyltransferase activity and acetylcholine content in DC were two times higher than in NC. TD caused 50% decrease of cytoplasmic acetyl-CoA levels that correlated with losses of acetylcholine pool in DC but not in NC. These data indicate that particular sensitivity of DC to TD may result from relative shortage of acetyl-CoA due to its higher utilization in acetylcholine synthesis.

Identification of complexin II in astrocytes: a possible regulator of glutamate release in these cells

Complexins are a family of SNARE complex-binding proteins which regulate neurotransmitter release by playing a crucial role in triggering fast exocytosis at the synapse. Current evidence indicates astrocytes can release glutamate via a vesicular mechanism similar to that at nerve terminals and thereby modulate synaptic activity. In addition, components of the biochemical machinery associated with synaptic release have been identified in these cells. However, whether complexins are also present in astrocytes and may therefore participate in the vesicular release of glutamate is a key issue that is yet to be determined. In the present study we therefore examined if astrocytes express complexin I (Cpx I) and/or complexin II (Cpx II). Our results indicate these cells contain Cpx II but not Cpx I in primary culture. In addition, serum deprivation for 24 h led to a 2.6-fold increase in Cpx II, suggesting this protein is responsive to insults. These findings point to Cpx II being a likely key modulator of synaptic activity at the level of these glial cells. Given the considered involvement of complexins in neurologic and psychiatric illness, astrocytic Cpx II represents a potentially important therapeutic target for the future treatment of such maladies.

ErbB receptor signaling in astrocytes: a mediator of neuron-glia communication in the mature central nervous system

Astrocytes are now recognized as active players in the developing and mature central nervous system. Each astrocyte contacts vascular structures and thousands of synapses within discrete territories. These cells receive a myriad of inputs and generate appropriate responses to regulate the function of brain microdomains. Emerging evidence has implicated receptors of the ErbB tyrosine kinase family in the integration and processing of neuronal inputs by astrocytes: ErbB receptors can be activated by a wide range of neuronal stimuli; they control critical steps of glutamate-glutamine metabolism; and they regulate the biosynthesis and release of various glial-derived neurotrophic factors, gliomediators and gliotransmitters. These key properties of astrocytic ErbB signaling in neuron-glia interactions have significance for the physiology of the mature central nervous system, as exemplified by the central control of reproduction within the hypothalamus, and are also likely to contribute to pathological situations, since both dysregulation of ErbB signaling and glial dysfunction occur in many neurological disorders.

The effects of alcoholism on the human basolateral amygdala

Alcohol affects gene expression in several brain regions. The amygdala is a key structure in the brain's emotional system and in recent years the crucial importance of the amygdala in drug-seeking and relapse has been increasingly recognized. In this study gene expression screening was used to identify genes involved in alcoholism in the human basolateral amygdala of male patients. The results show that alcoholism affects a broad range of genes and many systems including genes involved in synaptic transmission, neurotransmitter transport, structural plasticity, metabolism, energy production, transcription and RNA processing and the circadian cycle. In particular, genes involved in the glutamate system were affected in the alcoholic patients. In the amygdala the glutamate system is involved in the acquisition, consolidation, expression and extinction of associative learning, which is a vital part of addiction, and in alcohol abusers it is associated with withdrawal anxiety and neurodegeneration. Downregulation of the excitatory amino acid transporters GLAST, GLT-1 and the AMPA glutamate receptor 2 (GluR2) revealed by the microarray were confirmed by Western blots. The decreased expression of GLAST, GLT-1 and GluR2 in the alcoholic patients may increase glutamate tone and activity in the basolateral amygdala and this may contribute to neurodegeneration as well as the expression of associative memories and anxiety which underlie continued drug-seeking and chronic relapse.

Neurologic presentations of nutritional deficiencies

Optimal functioning of the central and peripheral nervous system is dependent on a constant supply of appropriate nutrients. The first section of this review discusses neurologic manifestations related to deficiency of key nutrients such as vitamin B(12), folate, copper, vitamin E, thiamine, and others. The second section addresses neurologic complications related to bariatric surgery. The third sections includes neurologic presentations caused by nutrient deficiencies in the setting of alcoholism. The concluding section addresses neurologic deficiency diseases that have a geographic predilection.

Loss of astrocytic glutamate transporters in Wernicke encephalopathy

Wernicke encephalopathy (WE), a neurological disorder caused by thiamine deficiency (TD), is characterized by structural damage in brain regions that include the thalamus and cerebral cortex. The basis for these lesions is unclear, but may involve a disturbance of glutamatergic neurotransmission. We have therefore investigated levels of the astrocytic glutamate transporters EAAT1 and EAAT2 in order to evaluate their role in the pathophysiology of this disorder. Histological assessment of the frontal cortex revealed a significant loss of neurons in neuropathologically confirmed cases of WE compared with age-matched controls, concomitant with decreases in alpha-internexin and synaptophysin protein content of 67 and 52% by immunoblotting. EAAT2 levels were diminished by 71% in WE, with levels of EAAT1 also reduced by 62%. Loss of both transporter sites was confirmed by immunohistochemical methods. Development of TD in rats caused a profound loss of EAAT1 and EAAT2 in the thalamus accompanied by decreases in other astrocyte-specific proteins. Treatment of TD rats with N-acetylcysteine prevented the downregulation of EAAT2 in the medial thalamus, and ameliorated the loss of several other astrocyte proteins, concomitant with increased neuronal survival. Our results suggest that (1) loss of EAAT1 and EAAT2 glutamate transporters is associated with structural damage to the frontal cortex in patients with WE, (2) oxidative stress plays an important role in this process, and (3) TD has a profound effect on the functional integrity of astrocytes. Based on these findings, we recommend that early treatment using a combination of thiamine AND antioxidant approaches should be an important consideration in cases of WE.

Glycyrrhizin and its metabolite 18 beta-glycyrrhetinic acid in glycyrrhiza, a constituent herb of yokukansan, ameliorate thiamine deficiency-induced dysfunction of glutamate transport in cultured rat cortical astrocytes

Effects of yokukansan, a traditional Japanese medicine, on thiamine deficiency (TD)-induced decrease of glutamate uptake were examined in cultured rat cortical astrocytes. Yokukansan (100-500 microg/ml) ameliorated the TD-induced decrease in glutamate uptake by astrocytes, implying that yokukansan may contain active herbs and compounds possessing this effect. Among the seven constituent herbs of yokukansan, significant effects were found for glycyrrhiza. Furthermore, glycyrrhizin and its metabolite 18 beta-glycyrrhetinic acid (10(-7)-10(-4)M), among the eight components of glycyrrhiza, ameliorated the TD-induced decrease of glutamate uptake in astrocytes in a concentration-dependent manner. These substances inhibited protein kinase C (PKC) activity under the in vitro conditions. These lines of evidence suggest that glycyrrhizin, a main component of glycyrrhiza, and its metabolite 18 beta-glycyrrhetinic acid are likely responsible for amelioration of dysfunction of glutamate transport in astrocytes. The inhibition of the PKC activity might be related to the pharmacological efficacy of these substances.

Astrocytes are a major target in thiamine deficiency and Wernicke's encephalopathy

Thiamine deficiency (TD) is the underlying cause, and an established model, of Wernicke's encephalopathy (WE). Although the neurologic dysfunction and brain damage that results from TD has been well-described, the precise mechanisms that lead to the selective histological lesions characteristic of this disorder remain a mystery. Over the course of many years, various processes have been proposed that could lead to focal neuronal cell death in this disorder. But despite a concerted effort to relate these processes to a clear sequelae of events culminating in development of the focal neuropathology, little success has resulted. In recent years, however, a role for astrocytes in the pathophysiology of TD has been emerging. Here, alterations in glutamate uptake, and levels of the astrocytic glutamate transporters EAAT1 and EAAT2 in TD and WE, are discussed in terms of an excitotoxic event, along with the GABA transporter subtype GAT-3, and changes in other astrocytic proteins including GFAP and glutamine synthetase. Lactic acidosis, changes in the water channel protein AQP-4 and brain edema are also a focus of attention in relation to astrocyte dysfunction, while involvement of oxidative stress and inflammatory processes, along with white matter injury in terms of excitotoxicity are other key issues considered. In summary, a new appraisal of the extent of involvement of astrocytes in TD and WE is presented, with the evidence suggesting these cells represent a major target for damage during the disease process.

Neuroprotective effects of yokukansan, a traditional Japanese medicine, on glutamate-mediated excitotoxicity in cultured cells

To clarify the mechanism of yokukansan (TJ-54), a traditional Japanese medicine, against glutamate-mediated excitotoxicity, the effects of TJ-54 on glutamate uptake function were first examined using cultured rat cortical astrocytes. Under thiamine-deficient conditions, the uptake of glutamate into astrocytes, and the levels of proteins and mRNA expressions of glutamate aspartate transporter of astrocytes significantly decreased. These decreases were ameliorated in a dose-dependent manner by treatment with TJ-54 (100-700 microg/ml). The improvement of glutamate uptake with TJ-54 was completely blocked by the glutamate transporter inhibitor DL-threo-beta-hydroxyaspartic acid. Effects of TJ-54 on glutamate-induced neuronal death were next examined by using cultured PC12 cells as a model for neurons. Addition of 17.5 mM glutamate to the culture medium induced an approximately 50% cell death, as evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. TJ-54 (1-1000 microg/ml) inhibited the cell death in a dose-dependent manner. Furthermore, competitive binding assays to glutamate receptors showed that TJ-54 bound potently to N-methyl-D-aspartate receptors, in particular, to its glutamate and glycine recognition sites. These results suggest that TJ-54 may exert a neuroprotective effect against glutamate-induced excitotoxicity not only by amelioration of dysfunction of astrocytes but also by direct protection of neuronal cells.

Wernicke's encephalopathy: new clinical settings and recent advances in diagnosis and management

Wernicke's encephalopathy is an acute neuropsychiatric syndrome resulting from thiamine deficiency, which is associated with significant morbidity and mortality. According to autopsy-based studies, the disorder is still greatly underdiagnosed in both adults and children. In this review, we provide an update on the factors and clinical settings that predispose to Wernicke's encephalopathy, and discuss the most recent insights into epidemiology, pathophysiology, genetics, diagnosis, and treatment. To facilitate the diagnosis, we classify the common and rare symptoms at presentation and the late-stage symptoms. We emphasise the optimum dose of parenteral thiamine required for prophylaxis and treatment of Wernicke's encephalopathy and prevention of Korsakoff's syndrome associated with alcohol misuse. A systematic approach helps to ensure that patients receive a prompt diagnosis and adequate treatment.

Acute thiamine deficiency in diabetic ketoacidosis: Diagnosis and management

OBJECTIVE

Persistent encephalopathy in a patient with diabetic ketoacidosis is often feared as a sign of cerebral edema. Although thiamine deficiency is a rare diagnosis in children, marginal nutritional status and osmotic diuresis may be risk factors. The objective was to describe a heretofore unreported cause of encephalopathy in a child with diabetic ketoacidosis and review the mechanisms and pathophysiology of thiamine deficiency in this clinical scenario.

DESIGN

Case report and review of the literature.

SETTING

Pediatric intensive care unit of a tertiary care pediatric hospital.

PATIENT

A 13-yr-old girl.

INTERVENTIONS

Treatment of dehydration and hyperglycemia, osmotherapy, and intravenous thiamine administration.

MEASUREMENTS AND MAIN RESULTS

The patient presented with new-onset diabetes mellitus, severe diabetic ketoacidosis, and significant encephalopathy. Despite biochemical improvement with treatment of dehydration and hyperglycemia, her encephalopathy persisted. Computed tomography did not show cerebral edema and she showed no response to osmotherapy. Quantitative and functional assays revealed severe thiamine deficiency. The patient showed an immediate and dramatic response to intravenous thiamine administration.

CONCLUSIONS

The clinical improvement as well as lab investigations suggests that thiamine deficiency was the cause of this child's encephalopathy. Because potential mechanisms exist for thiamine deficiency in diabetes mellitus and institution of insulin and glucose therapy may stress thiamine body stores, thiamine deficiency should be considered in children with diabetic ketoacidosis whose encephalopathy does not improve with improvement of biochemical status.

Gene expression changes in thalamus and inferior colliculus associated with inflammation, cellular stress, metabolism and structural damage in thiamine deficiency

Identification of gene expression changes that promote focal neuronal death and neurological dysfunction can further our understanding of the pathophysiology of these disease states and could lead to new pharmacological and molecular therapies. Impairment of oxidative metabolism is a pathogenetic mechanism underlying neuronal death in many chronic neurodegenerative diseases as well as in Wernicke's encephalopathy (WE), a disorder induced by thiamine deficiency (TD). To identify functional pathways that lead to neuronal damage in this disorder, we have examined gene expression changes in the vulnerable thalamus and inferior colliculus of TD rats using Affymetrix Rat Genome GeneChip analysis in combination with gene ontology and functional categorization assessment utilizing the NetAffx GO Mining Tool. Of the 15 927 transcripts analysed, 125 in thalamus and 141 in inferior colliculus were more abundantly expressed in TD rats compared with control animals. In both regions, the major functional categories of transcripts that were increased in abundance after TD were those associated with inflammation (approximately 33%), stress (approximately 20%), cell death and repair ( approximately 26%), and metabolic perturbation (approximately 19%), together constituting approximately 98% of all transcripts up-regulated. These changes occurred against a background of neuronal cell loss and reactive astro- and microgliosis in both structures. Our results indicate that (i) TD produces changes in gene expression that are consistent with the observed dysfunction and pathology, and (ii) similar alterations in expression occur in thalamus and inferior colliculus, brain regions previously considered to differ in pathology. These findings provide important new insight into processes responsible for lesion development in TD, and possibly WE.

Enhancement of glutamate uptake mediates the neuroprotection exerted by activating group II or III metabotropic glutamate receptors on astrocytes

We investigated whether the activation of astroglial group II and III metabotropic glutamate receptors (mGluRs) could exert neuroprotective effects and whether the neuroprotection was related to glutamate uptake. Our results showed that the activation of astroglial group II or III mGluRs exerted neuroprotection against 1-methyl-4-phenylpyridinium (MPP+) astroglial conditioned medium-induced neurotoxicity in midbrain neuron cultures. Furthermore, MPP+ decreased glutamate uptake of primary astrocytes and C6 glioma cells, which was recovered by activating group II or III mGluRs. Specific group II or III mGluRs antagonists completely abolished the neuroprotective effects and the enhancement of glutamate uptake of their respective agonists. Our results showed that the primary cultured rat astrocytes and C6 glioma cells expressed receptor proteins for group II mGluR2/3, group III mGluR4, mGluR6 and mGluR7. C6 glioma cells expressed mRNA for group II mGluR3, group III mGluR4, mGluR6, mGluR7 and mGluR8. In conclusion, we confirmed that the activation of astroglial mGluRs exerted neuroprotection, and demonstrated that the mechanism underlying this protective role was at least partially related to the enhancement of glutamate uptake.

Primary cultures of rat astrocytes respond to thiamine deficiency-induced swelling by downregulating aquaporin-4 levels

Imaging studies indicate that cerebral edema is an important consequence of Wernicke's encephalopathy (WE), a disorder caused by thiamine deficiency (TD). We have investigated this problem using a recently developed in vitro astrocyte model of TD. Measurement of cell volume using the 3-O-methylglucose uptake method revealed a dose-dependent swelling of astrocytes during exposure to TD conditions. Time course studies indicated a progressive volume increase up to a maximum of 93% above controls after 4 days of treatment. This swelling then partially resolved, and remained stable for up to 10 days following commencement of TD treatment. Measurement of aquaporin-4 (AQP-4) levels showed a 44% loss after 10 days and a temporal profile consistent with an important role for this water channel protein in astrocyte cell volume changes during TD. Our findings of astrocyte swelling in TD are consistent with previous reports of focal brain edema in cases of WE, and indicate that AQP-4 may be an important target for ameliorating some of the clinical problems associated with this disorder.

Glutamate transporters: animal models to neurologic disease

Glutamate is the primary excitatory amino acid neurotransmitter in the central nervous system and its activity is carefully modulated in the synaptic cleft by glutamate transporters. A number of glutamate transporters have been identified in the central nervous system and each has a unique physiologic property and distribution. Glutamate transporter dysfunction may either be an initiating event or part of a cascade leading to cellular dysfunction and ultimately cell death. Animal models of glutamate transporter dysfunction have revealed a significant role for these proteins in pathologic conditions such as neurodegenerative diseases, epilepsy, stroke, and central nervous system tumors. Recent work has focused on glutamate transporter biology in human diseases with an emphasis on how manipulation of these transporter proteins may lead to therapeutic interventions in neurologic disease.

Early loss of the glutamate transporter splice-variant GLT-1v in rat cerebral cortex following lateral fluid-percussion injury

Glutamate transporter proteins are essential for the control of interstitial glutamate levels, with an impairment of their function or levels being a major potential contributor to excitotoxicity. We have investigated the effects of lateral fluid percussion on the levels of the glutamate transporter proteins GLT-1alpha, its splice variant GLT-1v, GLAST, and EAAC1 in the rat in order to evaluate their pathogenetic role in this model of traumatic brain injury (TBI). Immunoblot analysis revealed neuronal loss in the cerebral cortex was accompanied by a 54% decrease in GLT-1v 6 h following the insult which progressed to an 83% loss of the transporter after 24 h. No changes in GLT-1alpha, GLAST, or EAAC1 were observed in this brain region at either time point. GLT-1v content was also decreased by 55% and 68% in the hippocampus and thalamus, respectively, at 6 h post-injury, but recovered fully after 24 h in both brain regions. In contrast, levels of GLT-1alpha were increased in the hippocampus at 6 h and 24 h post-TBI. These alterations in transporter protein content were also confirmed using immunohistochemical methods. Our results show for the first time a pattern of early, dynamic changes in the levels of GLT-1 transporter splice variants in different brain regions in this trauma model. In addition, correlation of GLT-1v levels with both neuronal cell loss and alpha-internexin content in the injured cortex suggests that loss of this novel glutamate transporter may be a key factor in determining cerebral vulnerability following this type of brain injury.