Cerebrospinal Fluid Glutamate Research Articles

Effects of swimming exercise on neuropathic pain in a rat model: role of glutamate

ABSTRACT Objective The pain-reducing effects of the exercise were exerted through different mechanisms. Knowing more clear mechanisms helps to find more approach that is therapeutic. The objective of the present study is the evaluation of cerebrospinal fluid (CSF) glutamate level alteration in neuropathic pain rats and whether physical activity could modulate it. Methods In the present study 104 male Wistar rats weighing 180–220 g were randomly divided into 4 groups (Sham, Sham + Exe, Neuropathy, and Neuropathy + Exe) which in turn each group subdivided into 4 groups according to time points for behavioral testing and CSF sampling (Baseline, 2 weeks, 3 weeks, and 4 weeks). To induction of neuropathy (by chronic constriction injury,), after anesthetizing with a mixture of ketamine (80 mg/kg) and xylazine (10 mg/kg), the animal’s right sciatic nerve was exposed and was ligated using four movable catgut chromic suture 4/0. The exercise protocol included 25 min of daily swimming, 5 days a week for 4 weeks. Thermal hyperalgesia and mechanical tactile threshold were detected using the plantar test and Von Frey filaments, respectively. CSF glutamate level was determined using high-performance liquid chromatography. Results Findings indicated that mechanical and thermal thresholds significantly (p < 0.01, p < 0.05 respectively) decreased in the neuropathy group against that in sham groups. On the other hand, exercise significantly increased mechanical tactile threshold (p < 0.0012) and thermal threshold (p < 0.05) compared to the neuropathy group. Moreover, CSF glutamate level prominently (p < 0.01) was increased in the neuropathy group compared to the sham group, and swimming exercise significantly (p < 0.001) reduced it. In conclusion The present findings provide new evidence showing that medium-intensity swimming exercise attenuates pain-like behaviors in neuropathic pain animals, which is possibly due to decreasing CSF glutamate level and its neurotransmission.

Telmisartan Is a Promising Agent for Managing Neuropathic Pain and Delaying Opioid Analgesic Tolerance in Rats.

Despite the large arsenal of analgesic medications, neuropathic pain (NP) management is not solved yet. Angiotensin II receptor type 1 (AT1) has been identified as a potential target in NP therapy. Here, we investigate the antiallodynic effect of AT1 blockers telmisartan and losartan, and particularly their combination with morphine on rat mononeuropathic pain following acute or chronic oral administration. The impact of telmisartan on morphine analgesic tolerance was also assessed using the rat tail-flick assay. Morphine potency and efficacy in spinal cord samples of treated neuropathic animals were assessed by [35S]GTPγS-binding assay. Finally, the glutamate content of the cerebrospinal fluid (CSF) was measured by capillary electrophoresis. Oral telmisartan or losartan in higher doses showed an acute antiallodynic effect. In the chronic treatment study, the combination of subanalgesic doses of telmisartan and morphine ameliorated allodynia and resulted in a leftward shift in the dose-response curve of morphine in the [35S]GTPγS binding assay and increased CSF glutamate content. Telmisartan delayed morphine analgesic-tolerance development. Our study has identified a promising combination therapy composed of telmisartan and morphine for NP and opioid tolerance. Since telmisartan is an inhibitor of AT1 and activator of PPAR-γ, future studies are needed to analyze the effect of each component.

Substantially elevated serum glutamate and CSF GOT-1 levels associated with cerebral ischemia and poor neurological outcomes in subarachnoid hemorrhage patients

Brain injury and cerebral vasospasm during the 14 days after the subarachnoid hemorrhage (SAH) are considered the leading causes of poor outcomes. The primary injury induces a cascade of events, including increased intracranial pressure, cerebral vasospasm and ischemia, glutamate excitotoxicity, and neuronal cell death. The objective of this study was to monitor the time course of glutamate, and associated enzymes, such as glutamate–oxaloacetate transaminase (GOT1), glutamate-pyruvate transaminase (GPT) in cerebrospinal fluid (CSF) and serum, shortly after SAH, and to assess their prognostic value. A total of 74 participants participated in this study: 45 participants with SAH and 29 controls. Serum and CSF were sampled up to 14 days after SAH. SAH participants' clinical and neurological status were assessed at hospitalization, at discharge from the hospital, and 3 months after SAH. Furthermore, a logistic regression analysis was carried out to evaluate the ability of GOT1 and glutamate levels to predict neurological outcomes. Our results demonstrated consistently elevated serum and CSF glutamate levels after SAH. Furthermore, serum glutamate level was significantly higher in patients with cerebral ischemia and poor neurological outcome. CSF GOT1 was significantly higher in patients with uncontrolled intracranial hypertension and cerebral ischemia post-SAH, and independently predicted poor neurological outcomes.

Hyponatremia in elderly patients with fractures around the hip; role of glutamate (CSF glutamate study)

Background &amp; objective: Hyponatremia is the most common electrolyte disorder and is a predictor of osteoporosis, inflammation and cognitive dysfunction leading to falls in the elderly patients. We compared glutamate levels in normonatremic elderly patients with those with hyponatremia, admitted with osteoarthritis, to find correlation between the cognitive status with cerebrospinal fluid (CSF) glutamate as a biomarker for hyponatremia.&#x0D; Methodology: In an observational prospective study; 70 patients, more than 70 y of age, admitted to trauma unit of Assiut University Hospital with fractures around the hip, were investigated for the frequency of on-admission hyponatremia. The CSF glutamate level was determined using radio-immune assay. We compared glutamate level in 18 hyponatremic patients with 10 normonatremic elderly patients admitted with osteoarthritis for elective joint replacement (control group) to find correlation between the cognitive status assessed by Modified Mini-Mental State (3MS) examination and CSF glutamate as a biomarker for hyponatremia.&#x0D; Results: Hyponatremia is highly prevalent in elderly with fractures around the hip; we recorded it in 41.4% of the study sample. Most patients were females (62.86%). CSF glutamate was significantly increased in hyponatremic patients than the controls (P &lt; 0.001).&#x0D; Conclusion: Prevalence of hyponatremia is high in old aged patients probably due to due to prevalent hot weather in the south of Egypt. CSF glutamate level can be a marker for mild cognitive impairment caused by hyponatremia.&#x0D; Abbreviations: 3MS: Modified Mini-Mental State examination; CSF: cerebrospinal fluid; RPM: revolutions per minute; ELISA: enzyme-linked immunosorbent assay; SD: standard deviation&#x0D; Key words: Geriatric anesthesia; Chronic Disease; Cognition Disorders / blood; Cognition Disorders / etiology; Glutamic Acid / metabolism; Hyponatremia / blood; Hyponatremia / complications; Hyponatremia / psychology; Inappropriate ADH Syndrome / complications; 3MS&#x0D; Citation: Kotb HI, Hassan A, Sayed AA, Seddik MI, Maghraby HH, Kamel EZ. Hyponatremia in elderly patients with fractures around the hip; role of glutamate (CSF glutamate study). Anaesth. pain intensive care 2022;26(3):332-337&#x0D; DOI: 10.35975/apic.v26i3.1900&#x0D; Received: November 28, 2020; Reviewed: December 25, 2020; Accepted: April 25, 2022

Elevation of brain gamma‐aminobutyric acid levels is associated with vigabatrin‐associated brain abnormalities on magnetic resonance imaging

ObjectiveVigabatrin (VGB) is an effective antiseizure medication for West syndrome. It works by irreversibly inhibiting gamma-aminobutyric acid (GABA) transaminase and increasing central GABA levels. Vigabatrin-associated brain abnormalities on magnetic resonance imaging (VABAM) are an adverse effect of VGB that has only been reported in children, but the pathophysiology of this effect is unknown. In this study, we evaluated the relationship of VGB and brain GABA levels as well as the association between VABAM and GABA. MethodsFor the 15 consecutive pediatric patients treated with VGB, free GABA, glutamine, and glutamate in cerebrospinal fluid (CSF) and plasma, GABA to creatine and phosphocreatine (Cr) peak ratio (GABA/Cr), glutamine (Gln)/Cr, and glutamate (Glu)/Cr as quantified by proton MR spectroscopy (1H-MRS) were retrospectively examined. GABA/Cr was compared with in-house normal pediatric controls. Differences in the levels of each metabolite in VABAM and non-VABAM cases were also examined. ResultsThirteen of the included subjects underwent magnetic resonance imaging (MRI) and 1H-MRS, and two of them presented VABAM; both cases were very-low-birth-weight preterm infants with post-hemorrhagic hydrocephalus. CSF levels of free GABA were significantly higher in VABAM (5.26 ± 1.95 μmol/L) than in non-VABAM (0.59 ± 0.63 μmol/L) cases (P = 0.03). The GABA/Cr was significantly higher in patients with VGB (0.34 ± 0.16) than in pediatric controls (0.20 ± 0.05) (P = 0.02). The GABA/Cr tended to be higher in VABAM (0.48 ± 0.10) than in non-VABAM cases (0.31 ± 0.15) (P = 0.31). SignificanceElevated brain GABA levels were observed in VABAM patients, suggesting its involvement in the pathogenesis of this condition. In particular, a marked increase in CSF-free GABA was characteristic. Although the elevation of the GABA/Cr is mild, it may be useful for early identification of patients with risk of VABAM.

Assessing the effect of modified Mediterranean‐ketogenic diet on mild cognitive impairment patients through plasma neuron‐derived exosomes

AbstractBackgroundRecently, we compared the effect of a high‐fat and low‐carb Modified Mediterranean‐Ketogenic Diet (MMKD) and a low‐fat American Heart Association Diet (AHAD) on 11 cognitively normal (CN) and 9 with mild cognitive impairment (MCI) older adults as a suggestive preventative intervention for Alzheimer’s disease (AD). We reported the promising effect of the MMKD on MCI patients as it was well‐tolerated and associated with increased cerebrospinal fluid (CSF) Aβ1‐42, decreased tau, and increased cerebral perfusion. Here, we characterized the plasma neuron‐derived exosomes (NDE) to further understand the molecular mechanisms underlying the efficacy of the MMKD against MCI.MethodThe completed study consisted of a randomized crossover design in which participants (both CN and MCI) consumed either the MMKD or the control AHAD for six weeks. Total exosomes (TE) were isolated from plasma by precipitation method, and NDE were enriched using Biotin‐tagged CD171 antibody attached with streptavidin‐magnetic beads. The purity, concentration, and size of TE and NDE were assessed by flow cytometry, nanoparticle tracking, immunogold‐labeling, electron microscopy, and exosome antibody array. NDE was characterized for several AD and neurodegeneration‐related biomarkers, advanced glycation endproducts (AGEs), glutamate, glutamate receptors, and β‐hydroxybutyrate (BHB) by ELISA and colorimetric assays. NDE effect on NF‐kB activity in human monocytes was studied as a molecular surrogate for inflammation.ResultWe confirmed the size, shape, and purity of both TE and NDE by multiple methods. Importantly, the MMKD treatment strongly reduced the level of Aβ1‐42 (by 50%, p=0.001), p(181)Tau (by 17%), and neurofilament L (by 55%, p=0.03) in the MCI group, but not with AHAD. MMKD reduced the AGEs in both CN and MCI groups and strongly increased the glutamate level in NDEs from the MCI group (6 fold, p&lt;0.001) but did not affect glutamate in CSF. The MMKD also modulated the expression of various glutamate receptors (GRIN1, GRIA1, GRIN2A, and GRIN2b). Interestingly, we detected BHB in NDEs, though no significant change was observed. MMKD inhibited the NF‐κB activity in monocytes suggesting a strong anti‐inflammatory effect.ConclusionNDE offers a promising peripheral measure to assess the efficacy and molecular mechanism of MMKD action against MCI.

Behavioral aspects and neurobiological properties underlying medical cannabis treatment in Shank3 mouse model of autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disease with a wide spectrum of manifestation. The core symptoms of ASD are persistent deficits in social communication, and restricted and repetitive patterns of behavior, interests, or activities. These are often accompanied by intellectual disabilities. At present, there is no designated effective treatment for the core symptoms and co-morbidities of ASD. Recently, interest is rising in medical cannabis as a treatment for ASD, with promising clinical data. However, there is a notable absence of basic pre-clinical research in this field. In this study, we investigate the behavioral and biochemical effects of long-term oral treatment with CBD-enriched medical cannabis oil in a human mutation-based Shank3 mouse model of ASD. Our findings show that this treatment alleviates anxiety and decreases repetitive grooming behavior by over 70% in treated mutant mice compared to non-treated mutant mice. Furthermore, we were able to uncover the involvement of CB1 receptor (CB1R) signaling in the Avidekel oil mechanism, alongside a mitigation of cerebrospinal fluid (CSF) glutamate concentrations. Subsequently, RNA sequencing (RNA seq) of cerebellar brain samples revealed changes in mRNA expression of several neurotransmission-related genes post-treatment. Finally, our results question the relevancy of CBD enrichment of medical cannabis for treating the core symptoms of ASD, and emphasize the importance of the THC component for alleviating deficits in repetitive and social behaviors in ASD.

Ifenprodil Improves Long-Term Neurologic Deficits Through Antagonizing Glutamate-Induced Excitotoxicity After Experimental Subarachnoid Hemorrhage.

Excessive glutamate leading to excitotoxicity worsens brain damage after SAH and contributes to long-term neurological deficits. The drug ifenprodil is a non-competitive antagonist of GluN1-GluN2B N-methyl-d-aspartate (NMDA) receptor, which mediates excitotoxic damage in vitro and in vivo. Here, we show that cerebrospinal fluid (CSF) glutamate level within 48h was significantly elevated in aSAH patients who later developed poor outcome. In rat SAH model, ifenprodil can improve long-term sensorimotor and spatial learning deficits. Ifenprodil attenuates experimental SAH-induced neuronal death of basal cortex and hippocampal CA1 area, cellular and mitochondrial Ca2+ overload of basal cortex, blood-brain barrier (BBB) damage, and cerebral edema of early brain injury. Using in vitro models, ifenprodil declines the high-concentration glutamate-mediated intracellular Ca2+ increase and cell apoptosis in primary cortical neurons, reduces the high-concentration glutamate-elevated endothelial permeability in human brain microvascular endothelial cell (HBMEC). Altogether, our results suggest ifenprodil improves long-term neurologic deficits through antagonizing glutamate-induced excitotoxicity.

Exercise modifies glutamate and other metabolic biomarkers in cerebrospinal fluid from Gulf War Illness and Myalgic encephalomyelitis / Chronic Fatigue Syndrome

Myalgic encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS) and Gulf War Illness (GWI) share many symptoms of fatigue, pain, and cognitive dysfunction that are not relieved by rest. Patterns of serum metabolites in ME/CFS and GWI are different from control groups and suggest potential dysfunction of energy and lipid metabolism. The metabolomics of cerebrospinal fluid was contrasted between ME/CFS, GWI and sedentary controls in 2 sets of subjects who had lumbar punctures after either (a) rest or (b) submaximal exercise stress tests. Postexercise GWI and control subjects were subdivided according to acquired transient postexertional postural tachycardia. Banked cerebrospinal fluid specimens were assayed using Biocrates AbsoluteIDQ® p180 kits for quantitative targeted metabolomics studies of amino acids, amines, acylcarnitines, sphingolipids, lysophospholipids, alkyl and ether phosphocholines. Glutamate was significantly higher in the subgroup of postexercise GWI subjects who did not develop postural tachycardia after exercise compared to nonexercise and other postexercise groups. The only difference between nonexercise groups was higher lysoPC a C28:0 in GWI than ME/CFS suggesting this biochemical or phospholipase activities may have potential as a biomarker to distinguish between the 2 diseases. Exercise effects were suggested by elevation of short chain acylcarnitine C5-OH (C3-DC-M) in postexercise controls compared to nonexercise ME/CFS. Limitations include small subgroup sample sizes and absence of postexercise ME/CFS specimens. Mechanisms of glutamate neuroexcitotoxicity may contribute to neuropathology and "neuroinflammation" in the GWI subset who did not develop postural tachycardia after exercise. Dysfunctional lipid metabolism may distinguish the predominantly female ME/CFS group from predominantly male GWI subjects.

Severe systemic inflammation promotes persistent brain metabolic abnormalities

AbstractBackgroundSevere systemic inflammation can spread to the central nervous system, promoting neuronal dysfunction. Individuals who survive to a severe inflammatory episode, have greater chances to develop cognitive impairment. In this context, brain inflammatory changes have been considered a risk factor for Alzheimer’s disease (AD). We previously demonstrated, a significant [18F]FDG hypometabolism 24 h after the induction of severe systemic inflammation by cecal ligation and perforation (CLP), a sepsis model. However, whether severe systemic inflammation causes long‐term effects on brain energy metabolism remains unclear. Here, we aim at Investigating persistent consequences of a severe systemic inflammatory episode on brain energy metabolism. We hypothesized that brain energetic metabolism does not completely recover from a systemic inflammatory episode, which could be a trigger for neurodegeneration.MethodWistar rats (90 days old) were submitted to CLP and, examined in vivo via Micro‐PET [18F]FDG imaging 30 days later. Albumin and cellularity in the cerebrospinal fluid (CSF) were assessed by HPLC and flow cytometry, respectively, as an index of blood brain barrier (BBB) integrity. HPLC was also used for evaluating glutamate levels in CSF and glutamate uptake was evaluated in hippocampal and cortical slices using a radioactive assay.ResultWe found a persistent brain [18F]FDG hypometabolism in the CLP group. A 4‐fold increase in albumin levels was observed, along with a prominent increase in cellularity in the CSF of CLP animals. Additionally, decreased glutamate uptake in cortex (32%) and hippocampus (16%) along with increased levels of glutamate in CSF was found in the CLP group (Figure 1).ConclusionThese results that an episode of severe systemic inflammatory causes persistent brain metabolic disturbances and BBB damage. It is very likely that the long period of BBB disruption, allowing for communication between peripheral mediators/cells and the brain, compromises brain energy metabolism. Together, these findings suggest a link between peripheral inflammation and neurodegeneration.

Cerebrospinal fluid glutamate changes in functional movement disorders

The aim of this study was to assess cerebrospinal fluid (CSF) concentrations of specific amino acids using a high-performance liquid chromatography system in a sample of patients with functional movement disorders (FMDs) and in a sample of controls. CSF levels of glutamate were significantly lower in patients with FMD than in controls. This finding argues in favor of glutamatergic dysfunction in the pathophysiology of FMD.

Early High Cerebrospinal Fluid Glutamate: A Potential Predictor for Delayed Cerebral Ischemia after Aneurysmal Subarachnoid Hemorrhage.

Delayed cerebral ischemia (DCI) is an important complication after aneurysmal subarachnoid hemorrhage (aSAH). Early identification of cerebrospinal fluid (CSF) markers is helpful for warning of impending DCI. This study assessed whether early high CSF glutamate levels can be observed in aSAH patients who later developed DCI. In this prospective clinical study, patients with normal pressure hydrocephalus or aSAH were enrolled. We found that the early CSF levels of glutamate were significantly elevated in aSAH patients compared to patients with normal pressure hydrocephalus. There was a significant difference in early CSF levels of glutamate between aSAH patients without DCI and with DCI. The early CSF levels of glutamate are significantly related to the Hunt and Hess grade, the World Federation of Neurological Surgeons (WFNS) grade, and the modified Fisher score on admission and occurrence of DCI in aSAH patients. Preliminary evidence of this study suggests that early high CSF glutamate levels are correlated with DCI in aSAH patients.

Application of the UV–vis spectrophotometry method for the determination of glutamate in the cerebrospinal fluid of rats

In experimental nociception models, there is an increase in the glutamate cerebrospinal fluid (CSF) and a decrease in its levels in analgesic treatments. For the determination of glutamate in CSF, an analytical UV spectrophotometric method was developed and validated. The measurements on the UV–vis spectrophotometer were performed after the derivatization reaction of the neurotransmitter, when reading in the ultraviolet (UV) region, at the maximum absorption wavelength of 265 nm. The technique presented excellent linearity, as well as good intraday and interday precision, with coefficients of variation less than 15 %, and a correlation coefficient close to 1.0 (lower dispersion of the experimental set points and lower uncertainty of the estimated regression coefficients). The analytical conditions that were established by the ultraviolet spectrophotometric method demonstrated selectivity, linearity, precision, specificity, robustness, and accuracy. This is suitable for the quantitative determination of glutamate in the CSF. The technique developed by UV–vis spectrophotometry for glutamate dosing was fast, efficient, easy to perform, and more economically accessible when compared to current standard techniques. When comparing the data obtained in this study with the results of the official methodology, in which HPLC and spectrofluorimetry were used, it was observed that the closest values of glutamate release occurred between the spectrofluorimeter and the UV–vis spectrophotometer. The UV–vis spectrophotometry method for the determination of CSF glutamate has been shown to be accurate, reproducible, and satisfactory, making it an extremely advantageous and a viable alternative for the determination of amino acid glutamate.

Protective effects and mechanisms of Xingnaojing Injection on early global brain ischemic-induced deep coma in rats

To study the protective effect of Xingnaojing Injection on early global brain ischemia-induced deep coma in rats. Methods: The deep coma model was induced by global brain ischemia by using four-vessel occlusion method in male SD rats. According to the body weight, the rats were randomly divided into 8 groups: a model control group, three different dose of Xingnaojing Injection (1.8, 3.6 and 5.4 mL.kg-1) groups, a Xingnaojing Injection (3.6 mL.kg-1) plus PI3K inhibitor group, a naloxone injection (0.04 mL.kg-1) group and a naloxone injection (0.04 mL.kg-1) plus Xingnaojing Injection (3.6 mL.kg-1) group (n=8 per group). In addition, eight animals served as the sham group were performed same operation with the model group excepting no blockage of the blood vessels. After the operation, three different doses of Xingnaojing Injection and/or naloxone injection were given intravenously once a day for three days. Ten μL PI3K inhibitor (LY294002, 10 mmol/L) was injected via anterior cerebral ventricle at once after global brain ischemia. The awakening time after the first drug treatment, the grasping power and the autonomous activity within 10 min after the last drug treatment were recorded. The levels of both dopamine (DA) and glutamate (Glu) in cerebrospinal fluid were detected by ELISA. The pathological changes were observed in brain tissue slices with HE staining and the protein levels of Akt/p-Akt and cAMP-response element binding protein (CREB)/p-CREB in hippocampus were detected by Western blotting. Results: Comparing with the model group, single administration of Xingnaojing Injection could significantly shorten the waking time (P<0.05) and continuous administration of Xingnaojing Injection for 3 d could increase grasping power, distance, frequency and duration of autonomous activities (P<0.05 or P<0.01) in the deep coma rat. Also, Xingnaojing Injection could inhibit these increases in neurotransmitters DA and Glu contents (P<0.05 or P<0.01), and improve pathological changes of hippocampal tissue. Xingnaojing Injection significantly induced protein phosphorylation of both Akt and CREB (P<0.05 or P<0.01); this effect was inhibited by PI3K inhibitor (P<0.05 or P<0.01). Moreover, the protective effects of naloxone on awakening time, grasping power, the autonomous activity and hippocampus damage in global brain ischemia-induced deep coma could be enhanced by joint use of Xingnaojing Injection (P<0.05 or P<0.01). Conclusion: Xingnaojing Injection could significantly improve deep coma induced by global brain ischemia in rat, which is related to inducing PI3K/Akt-dependent protein phosphorylation of CREB, and reducing hippocampal damage. The protective effect of Xingnaojing Injection is synergistically enhanced by naloxone.

Selective mGluR1 Negative Allosteric Modulator Reduces Blood-Brain Barrier Permeability and Cerebral Edema After Experimental Subarachnoid Hemorrhage.

The blood-brain barrier (BBB) disruption leads to the vasogenic brain edema and contributes to the early brain injury (EBI) after subarachnoid hemorrhage (SAH). However, the mechanisms underlying the BBB damage following SAH are poorly understood. Here we reported that the neurotransmitter glutamate of cerebrospinal fluid (CSF) was dramatically increased in SAH patients with symptoms of cerebral edema. Using the rat SAH model, we found that SAH caused the increase of CSF glutamate level and BBB permeability in EBI, intracerebroventricular injection of exogenous glutamate deteriorated BBB damage and cerebral edema, while intraperitoneally injection of metabotropic glutamate receptor 1(mGluR1) negative allosteric modulator JNJ16259685 significantly attenuated SAH-induced BBB damage and cerebral edema. In an in vitro BBB model, we showed that glutamate increased monolayer permeability of human brain microvascular endothelial cells (HBMEC), whereas JNJ16259685 preserved glutamate-damaged BBB integrity in HBMEC. Mechanically, glutamate downregulated the level and phosphorylation of vasodilator-stimulated phosphoprotein (VASP), decreased the tight junction protein occludin, and increased AQP4 expression at 72h after SAH. However, JNJ16259685 significantly increased VASP, p-VASP, and occludin, and reduced AQP level at 72h after SAH. Altogether, our results suggest an important role of glutamate in disruption of BBB function and inhibition of mGluR1 with JNJ16259685 reduced BBB damage and cerebral edema after SAH.

Mass spectrometry‐based method for quantification of nimodipine and glutamate in cerebrospinal fluid. Pilot study with patients after aneurysmal subarachnoid haemorrhage

Delayed cerebral ischaemia is an important cause of morbidity and mortality after aneurysmal subarachnoid haemorrhage (aSAH). Nimodipine is the only drug approved by the FDA for improving outcome after aSAH. Clinically, however, there are no specific values of this drug in cerebrospinal fluid (CSF) during aSAH treatment that could be associated to outcome improvement. Furthermore, the neurotransmitter glutamate acts as a secondary marker for brain injury. The aim was to establish a method to measure nimodipine and glutamate concentrations simultaneously in CSF of patients after aSAH. From June 2017 to June 2018, we prospectively collected clinical data of patients with aSAH admitted to our neurointensive care unit. All included patients received nimodipine orally (60mg every 4hours). Patients, who developed clinical vasospasm during their in-hospital stay, underwent intra-arterial application of nimodipine (IAN), followed by angiographic control. A method using high-performance liquid chromatography coupled with mass spectrometric analysis (LC-MS/MS) was established for quantification of both analytes in CSF. In 15 (60%) of 25 patients, nimodipine and glutamate concentrations were measured. After IAN for treatment of vasospasms, CSF nimodipine concentrations were slightly higher than in patients who received nimodipine only orally (0.60±0.27ng/mL vs 0.48±0.18ng/mL). Patients developing vasospasm exhibited higher glutamate concentrations than patients without vasospasm (188.84ng/mL vs136.07ng/mL). The developed method allowed the simultaneous quantification of nimodipine and glutamate in CSF. Furthermore, we demonstrated that IAN resulted in higher concentrations in CSF, when compared to oral application only.

Glutamine Antagonist JHU083 Normalizes Aberrant Glutamate Production and Cognitive Deficits in the EcoHIV Murine Model of HIV-Associated Neurocognitive Disorders.

HIV-associated neurocognitive disorders (HAND) have been linked to dysregulation of glutamate metabolism in the central nervous system (CNS) culminating in elevated extracellular glutamate and disrupted glutamatergic neurotransmission. Increased glutamate synthesis via upregulation of glutaminase (GLS) activity in brain immune cells has been identified as one potential source of excess glutamate in HAND. However, direct evidence for this hypothesis in an animal model is lacking, and the viability of GLS as a drug target has not been explored. In this brief report, we demonstrate that GLS inhibition with the glutamine analogue 6-diazo-5-oxo-L-norleucine (DON) can reverse cognitive impairment in the EcoHIV-infected mouse model of HAND. However, due to peripheral toxicity DON is not amenable to clinical use in a chronic disease such as HAND. We thus tested JHU083, a novel, brain penetrant DON prodrug predicted to exhibit improved tolerability. Systemic administration of JHU083 reversed cognitive impairment in EcoHIV-infected mice similarly to DON, and simultaneously normalized EcoHIV-induced increases in cerebrospinal fluid (CSF) glutamate and GLS activity in microglia-enriched brain CD11b + cells without observed toxicity. These studies support the mechanistic involvement of elevated microglial GLS activity in HAND pathogenesis, and identify JHU083 as a potential treatment option. Graphical Abstract Please provide Graphical Abstract caption.Glutamine Antagonist JHU083 Normalizes Aberrant Glutamate Production and Cognitive Deficits in the EcoHIV Murine Model of HIV-Associated Neurocognitive Disorders .

Effects of L-theanine on Anxiety-like Behavior, Cerebrospinal Fluid Amino Acid Profile, and Hippocampal Activity in Wistar Kyoto Rats (P14-022-19)

ObjectivesL-theanine (N-ethyl-L-glutamine), an amino acid is well known as a relaxing agent. In the present study, we examined the effects of repeated L-theanine administration on behavior, hippocampal activity in Wistar Kyoto (WKY) rats, levels of amino acids in the cerebrospinal fluid (CSF), and studied an animal model of anxiety and depressive disorders. MethodsBehavioral tests were performed after 7–10 days of L-theanine (0.4 mg kg−1 day−1) or saline administration, followed by CSF sampling for high-performance liquid chromatography (HPLC) analysis. An independent set of animals was subjected to [18F] fluorodeoxyglucose positron emission tomography (PET) scanning after an identical dose of L-theanine or saline administration for 7 days. ResultsIn an elevated plus maze test, the time spent in open arms was significantly longer in the L-theanine group compared to saline group (P = 0.035). Also, significantly lower CSF glutamate (P = 0.039) and higher methionine (P = 0.024) concentrations were observed in the L-theanine group. Further, a significant increase in the standard uptake value ratio was observed in the hippocampus/cerebellum of the L-theanine group (P < 0.001). ConclusionsThese results suggest that L-theanine enhances hippocampal activity and exerts anxiolytic effects, which may be mediated by changes in glutamate and methionine levels in the brain. However, further study is required to effectively elucidate the mechanisms underlying the effects of L-theanine. Funding SourcesThis research study was funded by an unrestricted research grant provided by Taiyo Life Insurance, Himawari Foundation, Tokyo, Japan.

Anesthetic effects of isoflurane and propofol on cerebrospinal fluid biochemical markers in healthy dogs.

The study of brain energy metabolism (BEM) markers in the cerebrospinal fluid (CSF) is a potential diagnostic and prognostic tool for many central nervous system (CNS) diseases. To date, in veterinary medicine, few studies are reporting physiologic ranges for some BEM markers. Recently, the influence of anesthetic drugs on BEM markers has been described in mice; subsequently, the study of CSF-BEM markers has gained increasing attention. The effects of anesthetic agents on BEM are poorly understood in dogs. The aim of this study was to evaluate the influence of propofol, isoflurane, and the duration of anesthesia on CSF-BEM markers in dogs. Nine dogs were anesthetized at two different periods, one month apart. In the first period, the dogs were intravenously anesthetized with propofol (PRO-group), and in the second period, the dogs received inhalant anesthesia with isoflurane (ISO-group). In both cases, CSF and blood were collected 15minutes (T0) and 3hours after induction (T3) and analyzed for lactate, pyruvate, glucose, creatine kinase, glutamate, and electrolyte concentrations. CSF lactate (CSF-L) showed variation depending on the anesthetic agent and time, being significantly lower after 3hours of anesthesia in the PRO-group and showing a trend to increase over time in the ISO-group. No changes were detected over time or between groups in CSF glutamate, glucose, or electrolytes. The results of this study support that the anesthetic drug choice and length of the general anesthesia should be considered when CSF-L analyses are interpreted in dogs.

Memantine mediates astrocytic activity in response to excitotoxicity induced by PP2A inhibition

Reduced activity of protein phosphatase 2 A (PP2A) is a common feature in Alzheimer’s disease (AD) and non-AD tauopathies. The administration of okadaic acid (OKA), a potent PP2A and PP1 inhibitor, is a common research tool for inducing AD-like alterations such as tau hyperphosphorylation and cognitive decline. Recently, we showed that OKA increases cerebrospinal fluid (CSF) glutamate levels, which was strongly correlated with cognitive decline. Also, we demonstrated that memantine (MN), a glutamatergic NMDAR channel blocker, was capable of preventing the increase in CSF glutamate levels and cognitive decline. Here, we aimed to analyze whether the protective effects of MN involve intrinsic astrocytic properties, particularly related to glutamate uptake and astrocytic reactivity – indexed by the expression of S100B and glial fibrillary acidic protein (GFAP). Rats received intraperitoneal injections of MN or saline over 3 consecutive days before receiving intrahippocampal infusion of OKA or saline. Afterward, they were submitted to behavioral tasks and then, euthanatized for neurochemical analysis. Here, we showed that the neuroprotective effects of MN in response to OKA neurotoxicity involve astrocytic activation. MN decreased glutamate uptake in the hippocampus and increased the release of S100B protein in the CSF in response to OKA neurotoxicity, which indicates a possible neurons-astrocyte coupling protective mechanism. These findings shed light on astrocytes as potential targets for treating neurological disorders associated with decreased PP2A activity.