Glutamine Synthetase Levels Research Articles

Targeting glutamine synthetase with AS1411-modified exosome-liposome hybrid nanoparticles for inhibition of choroidal neovascularization.

Choroidal neovascularization (CNV) is a leading cause of visual impairment in wet age-related macular degeneration (wAMD). Recent investigations have validated the potential of reducing glutamine synthetase (GS) to inhibit neovascularization formation, offering prospects for treating various neovascularization-related diseases. In this study, we devised a CRISPR/Cas9 delivery system employing the nucleic acid aptamer AS1411 as a targeting moiety and exosome-liposome hybrid nanoparticles as carriers (CAELN). Exploiting the binding affinity between AS1411 and nucleolin on endothelial cell surfaces, the delivery system was engineered to specifically target the glutamine synthetase gene (GLUL), thereby attenuating GS levels and continuously suppressing CNV. CAELN exhibited spherical and uniform dispersion. In vitro cellular investigations demonstrated gene editing efficiencies of CAELN ranging from 42.05 to 55.02% and its capacity to inhibit neovascularization in HUVEC cells. Moreover, in vivo pharmacodynamic studies conducted in CNV rabbits revealed efficacy of CAELN in restoring the thickness of intra- and extranuclear tissues. The findings suggest that GS is a novel target for the inhibition of pathological CNV, while the development of AS1411-modified exosome-liposome hybrid nanoparticles represents a novel delivery method for the treatment of neovascular-related diseases.

Salidroside ameliorates cerebral ischemic injury and regulates the glutamate metabolism pathway in astrocytes

Background and AimSalidroside (SA) is the main active component of Rhodiola rosea L., with potential in treating cardiovascular and cerebrovascular diseases and cerebral ischemia. However, its efficacy and mechanism in cerebral ischemia remain unclear, particularly regarding its effect on glutamate (Glu) metabolism. In this paper, we aimed to investigate the efficacy of SA in treating cerebral ischemia and its pharmacological mechanism.Experimental procedureWe studied the effects of SA on SD rats with cerebral ischemia, evaluating neurobehavior, cerebral water content, infarct size, and brain microstructure. We also assessed its impact on glial fibrillary acidic protein (GFAP), glutamine synthetase (GS), and glutamate transporter 1 (GLT-1) proteins using immunohistochemistry and Western blot. Additionally, we used SVGp12 cells to simulate cerebral ischemia and measured Glu levels and used Western blot to observe the level of GS and GLT-1.ResultsSA improved neural function, reduced infarct size, and regulated GSH and Glu levels in rats. In cell experiments, SA increased cell viability and decreased Glu concentration after ischemia induction. It also regulated the expression of GFAP, GS, and GLT-1.ConclusionSA alleviates cerebral ischemia-induced injury by acting on astrocytes, possibly through regulating the glutamate metabolic pathway.

Evaluating the Effects of Ketamine on Serum Glutamate Dehydrogenase, Glutamine Synthetase and Asparagine Synthetase Levels in Patients with Major Depressive Disorder Before and After Ketamine Treatment

Introduction: It has been revealed that major depressive disorder (MDD)is a common and debilitating psychiatric disorder. Dysfunctional enzymes involved in neurotransmission glutamate dehydrogenase (GDH), Glutamine synthetase (GS) and Asparagine synthetase (ASNS) may underlie the pathophysiology of MDD. The present project aimed to explore the effects of Ketamine on GDH, GS and ASNS in MDD patients. This study provides evidence of interactions between ketamine and GDH, ASNS and GS levels in patients with MDD. Materials and Methods: Patients with MDD are referred to the psychiatric ward of Shaheed Yahyanejad Hospital for regular follow-up. Patients diagnosed with MDD were based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), structured clinical interviews, as well as the severity of depression based on clinical criteria determined by a specialist physician. Serum samples from MDD patients before and after ketamine administration were taken to examine the changes in GDH, ASNS and GS levels. In this project, 29 patients with MDD therapy were evaluated with ketamine (0.75 mg/kg). Results: Our study showed that after administrating ketamine, the level of ASNS and Glutamate dehydrogenase GDH in patients with MDD was reduced compared to pre-treatment. However, the level of GS was increased compared to before treatment. The results show that ketamine occurs at the metabolism level in MDD patients. Also, our results demonstrated that GDH, ASNS, and GS levels can be measured to evaluate the effect of Ketamine on MDD patients. Conclusions: Patient success has improved depression after two months of administrating ketamine. Marginally, more than 80% of patients diagnosed with MDD treated with ketamine showed complete remission. Current results may be helpful in understanding the mechanisms responsible for ketamine’s clinical efficacy.

AQP4- and Kir4.1-Mediated Müller Cell Oedema Is Involved in Retinal Injury Induced By Hypobaric Hypoxia.

Hypobaric hypoxia is the main cause of high-altitude retinopathy (HAR). Retinal oedema is the key pathological change in HAR. However, its pathological mechanism is not clear. In this study, a 5000-m hypobaric hypoxic environment was simulated. Haematoxylin and eosin (H&E) staining and electrophysiological (ERG) detection were used to observe the morphological and functional changes in the retina of mice under hypobaric hypoxia for 2-72h. Toluidine blue staining and transmission electron microscopy were used to observe the morphology of Müller cells in the hypobaric hypoxia groups. The functional changes and oedema mechanism of Müller cells were detected by immunofluorescence and western blotting. The expression levels of glutamine synthetase (GS), glial fibrillary acidic protein (GFAP), aquaporin 4 (AQP4), and inwardly rectifying potassium channel subtype 4.1 (Kir4.1) in Müller cells were quantitatively analysed. This study revealed that retinal oedema gradually increased with prolonged exposure to a 5000-m hypobaric hypoxic environment. In addition, the ERG showed that the time delay and amplitude of the a-wave and b-wave decreased. The expression of GS decreased, and the expression of GFAP increased in Müller cells after exposure to hypobaric hypoxia for 4h. At the same time, retinal AQP4 expression increased, and Kir4.1 expression decreased. The oedema and functional changes in Müller cells are consistent with the time point of retinal oedema. In conclusion, Müller cell oedema is involved in retinal oedema induced by hypobaric hypoxia. An increase in AQP4 and a decrease in Kir4.1 are the main causes of Müller cell oedema caused by hypobaric hypoxia.

Pentylenetetrazole-Induced Seizures in Wistar Male Albino Rats with Reference to Glutamate Metabolism.

Epilepsy is a common and heterogenous neurological disorder characterized by recurrent spontaneous seizures. Animal models like rats play a crucial role in finding of mechanism of epilepsy in different brain regions. i.e., cerebral cortex, cerebellum, hippocampus, and pons medulla. Glutamate is an important excitatory neurotransmitter in the central nervous system and also glutamate plays a vital role in neuronal development and memory. The process of neuronal death evolved by glutamate receptor activation, has been hypothesized in both acute and chronic degenerative disorders including epilepsy. Considering the multifactorial neurochemical and neurophysiological malfunctions consequent to epileptic seizures, a few antiepileptic drugs are designed, to mitigate the debilitating aspects of epilepsy. Rat model, pentylenetetrazole (PTZ), an anticonvulsant drug, was selected for the present study. Induction of epilepsy/convulsions was induced by an intraperitoneal injection of PTZ (60 mg/kg body weight) in saline. Biochemical assays performed through spectrophotometer. Glutamine and Glutamine synthetase levels were decreased in the epileptic rats brain regions i.e., hippocampus, cerebellum, cerebral cortex, and pons medulla; glutamate dehydrogenase and glutaminase levels were increased in all the regions of epilepsy induced rats. Highest values are recorded in hippocampus when compared to other brain regions. PTZ suppresses the function of Glutamine and Glutamine synthetase activities in selected brain regions of rat and enhances the activities of the glutaminase and glutamate dehydrogenase when compared to control rats.

Clustered de novo start-loss variants in GLUL result in a developmental and epileptic encephalopathy via stabilization of glutamine synthetase

Glutamine synthetase (GS), encoded by GLUL, catalyzes the conversion of glutamate to glutamine. GS is pivotal for the generation of the neurotransmitters glutamate and gamma-aminobutyric acid and is the primary mechanism of ammonia detoxification in the brain. GS levels are regulated post-translationally by an N-terminal degron that enables the ubiquitin-mediated degradation of GS in a glutamine-induced manner. GS deficiency in humans is known to lead to neurological defects and death in infancy, yet how dysregulation of the degron-mediated control of GS levels might affect neurodevelopment is unknown. We ascertained nine individuals with severe developmental delay, seizures, and white matter abnormalities but normal plasma and cerebrospinal fluid biochemistry with de novo variants in GLUL. Seven out of nine were start-loss variants and two out of nine disrupted 5' UTR splicing resulting in splice exclusion of the initiation codon. Using transfection-based expression systems and mass spectrometry, these variants were shown to lead to translation initiation of GS from methionine 18, downstream of the N-terminal degron motif, resulting in a protein that is stable and enzymatically competent but insensitive to negative feedback by glutamine. Analysis of human single-cell transcriptomes demonstrated that GLUL is widely expressed in neuro- and glial-progenitor cells and mature astrocytes but not in post-mitotic neurons. One individual with a start-loss GLUL variant demonstrated periventricular nodular heterotopia, a neuronal migration disorder, yet overexpression of stabilized GS in mice using in utero electroporation demonstrated no migratory deficits. These findings underline the importance of tight regulation of glutamine metabolism during neurodevelopment in humans.

Effect of MTA3 Inhibition of Glutamine Synthetase-Mediated Glutaminolysis on Radiosensitivity of Patients with Esophageal Cancer

Metastasis-associated protein 3 (MTA3) can serve as a tumor suppressor in many cancer types. However, the role of MTA3 in radiosensitivity of patients with esophageal squamous cell cancer (ESCC) remains unclear. We thus investigated the function of MTA3 in radiosensitivity for ESCC, one of the most common digestive cancers. The colony formation assay and nude mice xenograft tumor assay were performed to investigate the effect of MTA3 on radiosensitivity in ESCC. Glutamine consumption assay kit and glutamate production assay kit were used to assess the glutaminolysis. Glutaminase (GLS) Activity Assay Kit and Glutamine Synthetase (GS) Activity Assay Kit were used to analyze the activity of specific metabolic enzymes dominate glutaminolysis. The regulatory mechanism of glutaminolysis by MTA3 was confirmed using Chromatin immunoprecipitation assay and Gaussia luciferase assay. The expression levels of MTA3 and GS in ESCC primary tissues were evaluated using immunohistochemistry. Survival curves were plotted with the Kaplan-Meier method and compared by log-rank test. The colony formation assay showed that MTA3 depletion and overexpression caused significantly higher and lower clonogenic survival after different doses of irradiation (IR), respectively. When these cells were subcutaneously injected into nude mice, the tumors derived from the cells with MTA3 overexpression and MTA3 knockdown were significantly smaller and bigger after IR, respectively. These findings suggest that MTA3 can enhance radiosensitivity in vitro and in vivo. Meanwhile, overexpressed and knockdown MTA3 can repress and expedite glutamine consumption and glutamate production uniformly, respectively. To determine how MTA3 acts on glutaminolysis, the activity of two specific metabolic enzymes dominate this metabolism, GS and GLS, were evaluated. It found that overexpressed and knockdown MTA3 can restrain and enhance the activity of GS, respectively, but have less effect on GLS. Moreover, the decreased radiosensitivity mediated by MTA3 knockdown is significantly increased when treated with GS inhibitor, suggesting that GS plays a crucial role in MTA3-mediated radiosensitivity enhancement. Mechanistically, Chromatin immunoprecipitation assay and Gaussia luciferase assay showed that MTA3 was recruited to the promoter of GS and suppressed GS transcription. However, knockdown of GATA3 abolished MTA3's repressive effect on GS and inhibited the MTA3's occupation on the promoter region of GS. These results collectively demonstrated that, in ESCC cells, MTA3 is recruited by GATA3 to inhibit GS expression, then ultimately represses glutaminolysis and enhances radiosensitivity. Finally, we showed that the ESCC patients in the MTA3low/GShigh group is significantly associated with shorter overall survival. MTA3 is capable of enhancing radiosensitivity through downregulating GS and MTA3low/GShigh might be a potential prognostic factor for ESCC patients.

Effects of local nitrogen supply and nitrogen fertilizer variety coupling on rice nitrogen transport and soil nitrogen balance in paddy fields

IntroductionThis study aimed to provide the theoretical basis for formulating scientific and reasonable on-farm nitrogen (N) management measures and efficient strategic fertilization to understand the effects of localized N supply (LNS) and N fertilizer variety coupling on N transport and soil N balance in rice fields.MethodsA 2-year field experiment (2020 and 2021) was conducted in Jingzhou, Hubei Province, which included the following six treatments: no N application (CK), farmers' fertilizer practice (FFP), and four LNS treatments, including two N application methods including mechanical side-deep fertilization (M) and root-zone fertilization (R), two N fertilizer types with urea (U), and controlled-release urea (CRU).ResultsCompared with FFP, LNS increased the N apparent translocation level from stems, sheathes, and leaves (TNT) and N uptake by 10.70–50.59% and 11.28–29.71%, respectively. In LNS, the levels of nitrite reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT) under R increased by 13.81, 9.56, and 15.59%, respectively, compared with those under M, resulting in a significant increase in TNT by 8.58% and N uptake by 1.87%. Regarding the N fertilizer type, CRU significantly increased chlorophyll content by 7.27%, superoxide dismutase (SOD) and catalase (CAT) by 14.78 and 29.95% (p < 0.05), and NR, GS, and GOGAT by 44.41, 16.12, and 28.41% (p < 0.05), respectively, compared with that in U, which contributed to N absorption and transport. Moreover, CRUR significantly decreased N apparent loss by 50.04% compared with CRUM (p < 0.05).DiscussionConsidering the risk of soil N leaching and environmental protection, R should be selected as the recommended fertilization method. The combination of CRU and R is the most effective fertilization approach.

Dietary kelp meal (Thallus laminariae) improves the immunity of hybrid snakeheads under ammonia stress

This study determined the effect of dietary kelp meal (KM) on metabolism of the hybrid snakeheads (Channa maculatus ♀ × Channa argus ♂), and the spatiotemporal changes in their resistance to ammonia stress, including survival rate, histopathology, biochemical parameters, and the expression of immune-related genes. The experimental diets contained: 0% KM, 5% KM, 10% KM, 15% KM, 15% KM + 5% binder. After eight weeks of feeding, six fish per diet were sampled for metabolic studies, and the remaining fish were placed under ammonia stress at two concentrations (1200 mg/L and 120 mg/L) for 48 h. Our results showed that replacing flour with kelp meal to the diet could alter the activities of some metabolic enzymes and reduced the lethality of hybrid snakeheads under high ammonia exposure. Histopathological results revealed a variety of pathological features in the liver after exposure to ammonia nitrogen. The levels of glutamate dehydrogenase (GDH), glutamine synthetase (GS), superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) showed the trend of first increasing and then decreasing with the decrease of the flour concentration in the diet under high concentration of ammonia stress. Besides, kidneys receive more severe oxidative damage than the liver. Similar results were found in the mRNA abundance of immune-related genes, and the kidney were mostly significantly down-regulated, but feeding moderate amounts of kelp meal can alleviate this damage. The transcriptome analysis showed that kelp meal can affect antigen processing and presentation process by the MHCⅠ signaling pathway mechanism, and thus regulate the immune response of hybrid snakeheads. Our study suggests that adding kelp meal in the diets could improve the ability of hybrid snakeheads to resist ammonia stress and the optimal replacement group is 10% KM group.

Multiple oxidative post-translational modifications of human glutamine synthetase mediate peroxynitrite-dependent enzyme inactivation and aggregation

Glutamine synthetase (GS), which catalyzes the ATP-dependent synthesis of L-glutamine from L-glutamate and ammonia, is a ubiquitous and conserved enzyme that plays a pivotal role in nitrogen metabolism across all life domains. In vertebrates, GS is highly expressed in astrocytes, where its activity sustains the glutamate-glutamine cycle at glutamatergic synapses and is thus essential for maintaining brain homeostasis. In fact, decreased GS levels or activity have been associated with neurodegenerative diseases, with these alterations attributed to oxidative post-translational modifications of the protein, in particular tyrosine nitration. In this study, we expressed and purified human GS (HsGS) and performed an in-depth analysis of its oxidative inactivation by peroxynitrite (ONOO-) invitro. We found that ONOO- exposure led to a dose-dependent loss of HsGS activity, the oxidation of cysteine, methionine, and tyrosine residues and also the nitration of tryptophan and tyrosine residues. Peptide mapping by LC-MS/MS through combined H216O/H218O trypsin digestion identified up to 10 tyrosine nitration sites and five types of dityrosine cross-links; these modifications were further scrutinized by structural analysis. Tyrosine residues 171, 185, 269, 283, and 336 were the main nitration targets; however, tyrosine-to-phenylalanine HsGS mutants revealed that their sole nitration was not responsible for enzyme inactivation. In addition, we observed that ONOO- induced HsGS aggregation and activity loss. Thiol oxidation was a key modification to elicit aggregation, as it was also induced by hydrogen peroxide treatment. Taken together, our results indicate that multiple oxidative events at various sites are responsible for the inactivation and aggregation of human GS.

Glycine-Induced Phosphorylation Plays a Pivotal Role in Energy Metabolism in Roots and Amino Acid Metabolism in Leaves of Tea Plant.

Phosphorylation is the most extensive post-translational modification of proteins and thus regulates plant growth. However, the regulatory mechanism of phosphorylation modification on the growth of tea plants caused by organic nitrogen is still unclear. In order to explore the phosphorylation modification mechanism of tea plants in response to organic nitrogen, we used glycine as the only nitrogen source and determined and analyzed the phosphorylated proteins in tea plants by phosphoproteomic analysis. The results showed that the phosphorylation modification induced by glycine-supply played important roles in the regulation of energy metabolism in tea roots and amino acid metabolism in tea leaves. In roots, glycine-supply induced dephosphorylation of proteins, such as fructose-bisphosphate aldolase cytoplasmic isozyme, glyceraldehyde-3-phosphate dehydrogenase, and phosphoenolpyruvate carboxylase, resulted in increased intensity of glycolysis and decreased intensity of tricarboxylic acid cycle. In leaves, the glycine-supply changed the phosphorylation levels of glycine dehydrogenase, aminomethyltransferase, glutamine synthetase, and ferredoxin-dependent glutamate synthase, which accelerated the decomposition of glycine and enhanced the ability of ammonia assimilation. In addition, glycine-supply could improve the tea quality by increasing the intensity of amino acids, such as theanine and alanine. This research clarified the important regulatory mechanism of amino acid nitrogen on tea plant growth and development through protein phosphorylation.

Age-Associated Upregulation of Glutamate Transporters and Glutamine Synthetase in Senescent Astrocytes In Vitro and in the Mouse and Human Hippocampus.

Aging is marked by complex and progressive physiological changes, including in the glutamatergic system, that lead to a decline of brain function. Increased content of senescent cells in the brain, such as glial cells, has been reported to impact cognition both in animal models and human tissue during normal aging and in the context of neurodegenerative disease. Changes in the glutamatergic synaptic activity rely on the glutamate-glutamine cycle, in which astrocytes handle glutamate taken up from synapses and provide glutamine for neurons, thus maintaining excitatory neurotransmission. However, the mechanisms of glutamate homeostasis in brain aging are still poorly understood. Herein, we showed that mouse senescent astrocytes in vitro undergo upregulation of GLT-1, GLAST, and glutamine synthetase (GS), along with the increased enzymatic activity of GS and [3H]-D-aspartate uptake. Furthermore, we observed higher levels of GS and increased [3H]-D-aspartate uptake in the hippocampus of aged mice, although the activity of GS was similar between young and old mice. Analysis of a previously available RNAseq dataset of mice at different ages revealed upregulation of GLAST and GS mRNA levels in hippocampal astrocytes during aging. Corroborating these rodent data, we showed an increased number of GS + cells, and GS and GLT-1 levels/intensity in the hippocampus of elderly humans. Our data suggest that aged astrocytes undergo molecular and functional changes that control glutamate-glutamine homeostasis upon brain aging.

Pancreatic stellate cells exploit Wnt/β-catenin/TCF7-mediated glutamine metabolism to promote pancreatic cancer cells growth

Pancreatic stellate cells (PSCs) are crucial for metabolism and disease progression in pancreatic ductal adenocarcinoma (PDAC). However, detailed mechanisms of PSCs in glutamine (Gln) metabolism and tumor-stromal metabolic interactions have not been well clarified. Here we showed that tumor tissues displayed Gln deficiency in orthotopic PDAC models. Single-cell RNA sequencing analysis revealed metabolic heterogeneity in PDAC, with significantly higher expression of Gln catabolism pathway in stromal cells. Significantly higher glutamine synthetase (GS) protein expression was further validated in human tissues and cells. Elevated GS levels in tumor and stroma were independently prognostic of poorer prognosis in PDAC patients. Gln secreted by PSCs increased basal oxygen consumption rate in PCCs. Depletion of GS in PSCs significantly decreased PCCs proliferation in vitro and in vivo. Mechanistically, activation of Wnt signaling induced directly binding of β-catenin/TCF7 complex to GS promoter region and upregulated GS expression. Rescue experiments testified that GS overexpression recovered β-catenin knockdown-mediated function on Gln synthesis and tumor-promoting ability of PSCs. Overall, these findings identify the Wnt/β-catenin/TCF7/GS-mediated growth-promoting effect of PSCs and provide new insights into stromal Gln metabolism, which may offer novel therapeutic strategies for PDAC.

Arundic acid (ONO-2506) downregulates neuroinflammation and astrocyte dysfunction after status epilepticus in young rats induced by Li-pilocarpine

Astrocytes, the most abundant glial cells, have several metabolic functions, including ionic, neurotransmitter and energetic homeostasis for neuronal activity. Reactive astrocytes and their dysfunction have been associated with several brain disorders, including the epileptogenic process. Glial Fibrillary Acidic Protein (GFAP) and S100 calcium-binding protein B (S100B) are astrocyte biomarkers associated with brain injury. We hypothesize that arundic acid (ONO-2506), which is known as an inhibitor of S100B synthesis and secretion, protects the hippocampal tissue from neuroinflammation and astrocyte dysfunction after status epileptics (SE) induction by Li-pilocarpine in young rats. Herein, we investigated the effects of arundic acid treatment, at time points of 6 or 24 h after the induction of SE by Li-pilocarpine, in young rats. In SE animals, arundic acid was able to prevent the damage induced by Li-pilocarpine in the hippocampus, decreasing neuroinflammatory signaling (reducing IL-1β, COX2, TLR4 and RAGE contents), astrogliosis (decreasing GFAP and S100B) and astrocytic dysfunction (recovering levels of GSH, glutamine synthetase and connexin-43). Furthermore, arundic acid improved glucose metabolism and reduced the glutamate excitotoxicity found in epilepsy. Our data reinforce the role of astrocytes in epileptogenesis development and the neuroprotective role of arundic acid, which modulates astrocyte function and neuroinflammation in SE animals.

Unbiased analysis of the dorsal root ganglion after peripheral nerve injury: no neuronal loss, no gliosis, but satellite glial cell plasticity.

Pain syndromes are often accompanied by complex molecular and cellular changes in dorsal root ganglia (DRG). However, the evaluation of cellular plasticity in the DRG is often performed by heuristic manual analysis of a small number of representative microscopy image fields. In this study, we introduce a deep learning-based strategy for objective and unbiased analysis of neurons and satellite glial cells (SGCs) in the DRG. To validate the approach experimentally, we examined serial sections of the rat DRG after spared nerve injury (SNI) or sham surgery. Sections were stained for neurofilament, glial fibrillary acidic protein (GFAP), and glutamine synthetase (GS) and imaged using high-resolution large-field (tile) microscopy. After training of deep learning models on consensus information of different experts, thousands of image features in DRG sections were analyzed. We used known (GFAP upregulation), controversial (neuronal loss), and novel (SGC phenotype switch) changes to evaluate the method. In our data, the number of DRG neurons was similar 14 d after SNI vs sham. In GFAP-positive subareas, the percentage of neurons in proximity to GFAP-positive cells increased after SNI. In contrast, GS-positive signals, and the percentage of neurons in proximity to GS-positive SGCs decreased after SNI. Changes in GS and GFAP levels could be linked to specific DRG neuron subgroups of different size. Hence, we could not detect gliosis but plasticity changes in the SGC marker expression. Our objective analysis of DRG tissue after peripheral nerve injury shows cellular plasticity responses of SGCs in the whole DRG but neither injury-induced neuronal death nor gliosis.

The glutamate/GABA system in the retina of male rats: effects of aging, neurodegeneration, and supplementation with melatonin and antioxidant SkQ1.

Glutamate and -aminobutyric acid (GABA) are the most abundant amino acids in the retina. An imbalance of the glutamate/GABA system is involved in the pathogenesis of various neurodegenerative disorders. Here we for the first time analyzed alterations of expression of glutamate- and GABA-synthesizing enzymes, transporters, and relevant receptors in the retina with age in Wistar rats and in senescence-accelerated OXYS rats who develop AMD-like retinopathy. We noted consistent age-dependent expression changes of GABAergic-system proteins (GAD67, GABA-T, and GAT1) in OXYS and Wistar rats: upregulation by age 3months and downregulation at age 18months. At a late stage of AMD-like retinopathy in OXYS rats (18months), there was significant upregulation of glutaminase and downregulation of glutamine synthetase, possibly indicating an increasing level of glutamate in the retina. AMD-like-retinopathy development in the OXYS strain was accompanied by underexpression of glutamate transporter GLAST. Prolonged supplementation with both melatonin and SkQ1 (separately) suppressed the progression of the AMD-like pathology in OXYS rats without affecting the glutamate/GABA system but worsened the condition of the Wistar rat's retina during normal aging. We observed decreasing protein levels of glutamine synthetase, GLAST, and GABAAR1 and an increasing level of glutaminase in Wistar rats. In summary, both melatonin and mitochondrial antioxidant SkQ1 had different effect on the retinal glutamate / GABA in healthy Wistar and senescence-accelerated OXYS rats.

The role of glutamine synthetase expression and cystine/glutamate transporter (SLC7A11, xCT) in epilepsy pathogenesis of patients with supratentorial brain gliomas

Background. Epileptic seizures represent one of the leading clinical manifestations of glial brain tumors that develop on average in 51% of cases. In gliomas, epileptogenesis is quite complex and multifactorial. Objective: to study a role of the expressed glutamine synthetase enzyme, as well as cystine/glutamate transporter (xCT system, SLC7A11) in the pathogenesis of epilepsy developing in patients with cerebral gliomas. Material and methods. The study included 32 patients with supratentorial gliomas. The average age of the disease onset (diagnosis) was 50.69±18.01 years. All patients underwent inpatient examination and treatment at the Neurosurgery and Nervous Diseases Clinics of Kirov Military Medical Academy from 2018 to 2020. In all cases, a biopsy of tumor tissue was collected. Histological and immunohistochemical studies were performed (expression of glutamine synthetase and cystine/ glutamate transporter (SLC7A11, xCT)). Results. Significant (ANOVA p=0.027, Mann–Whitney U-test p=0.033) differences in the expression of cystine/glutamate transporter (xCT system, SLC7A11) were revealed, by showing the following median values (lower quartile; upper quartile): 50% (45; 75) in the group of patients with seizures, 40% (40; 50) in the seizure-free group. The expression level of glutamine synthetase did not significantly differ in the groups with and without seizures. Conclusion. The data obtained confirmed that one of the pathogenetic mechanisms for epilepsy development in patients with gliomas was related to highly expressed cystine/glutamate transporter (xCT system, SLC7A11) and, as a consequence, an increase in the extracellular glutamate level.

On-Demand Generation of Peroxynitrite from an Integrated Two-Dimensional System for Enhanced Tumor Therapy.

Nanosystem-mediated tumor radiosensitization strategy combining the features of X-ray with infinite penetration depth and high atomic number elements shows considerable application potential in clinical cancer therapy. However, it is difficult to achieve satisfactory anticancer efficacy using clinical radiotherapy for the majority of solid tumors due to the restrictions brought about by the tumor hypoxia, insufficient DNA damage, and rapid DNA repair during and after treatment. Inspired by the complementary advantages of nitric oxide (NO) and X-ray-induced photodynamic therapy, we herein report a two-dimensional nanoplatform by the integration of the NO donor-modified LiYF4:Ce scintillator and graphitic carbon nitride nanosheets for on-demand generation of highly cytotoxic peroxynitrite (ONOO-). By simply adjusting the Ce3+ doping content, the obtained nanoscintillator can realize high radioluminescence, activating photosensitive materials to simultaneously generate NO and superoxide radical for the formation of ONOO- in the tumor. Obtained ONOO- effectively amplifies therapeutic efficacy of radiotherapy by directly inducing mitochondrial and DNA damage, overcoming hypoxia-associated radiation resistance. The level of glutamine synthetase (GS) is downregulated by ONOO-, and the inhibition of GS delays DNA damage repair, further enhancing radiosensitivity. This work establishes a combinatorial strategy of ONOO- to overcome the major limitations of radiotherapy and provides insightful guidance to clinical radiotherapy.

Therapeutic efficacy of atezolizumab plus bevacizumab for hepatocellular carcinoma with WNT/β-catenin signal activation.

Atezolizumab plus bevacizumab therapy has high response rates in patients with advanced hepatocellular carcinoma (HCC). It has been reported that HCC with immune exclusion associated with the signal activation of WNT/β-catenin is resistant to immune checkpoint inhibitors; however, to the best of our knowledge, the effectiveness of atezolizumab plus bevacizumab for HCC with WNT/β-catenin signal activation has not been reported. The present study aimed to analyze the efficacy of atezolizumab plus bevacizumab for HCC with WNT/β-catenin signal activation. A total of 24 patients who underwent liver tumor biopsy for HCC were classified into WNT/β-catenin signal activation and inactivation groups according to the expression levels of β-catenin and glutamine synthetase, which are indicative of WNT/β-catenin signal activation. The differences in the clinical responses to treatment between the groups were analyzed. A total of 15 patients had HCC with WNT/β-catenin signal activation, whereas 9 patients had HCC with WNT/β-catenin signal inactivation. There were no significant differences between both groups regarding objective responses (P=0.519) and disease control (P=0.586). In the WNT/β-catenin signal activation group, the median progression-free survival rate was 6.9 months compared with 6.2 months in the WNT/β-catenin signal inactivation group (P=0.674). Although a small number of patients was included in the present study, the present findings suggested that the efficacy of atezolizumab plus bevacizumab might be unaffected by WNT/β-catenin signal activation.

Immunohistochemical study of the brain glutamine synthetase expression in the rat septic model

Severe sepsis is accompanied by multiple organ dysfunction where acute liver failure (ALF) plays one of the most critical roles. The principal sign of acute hepatic encephalopathy accompanying ALF is ammonia induced edema of astrocytes. In case of ALF in sepsis, one can suppose increase in systemic and brain ammonia. Astroglia are target cells for ammonia metabolism as they are principal source of glutamine-synthetase (GS). Previous studies have reported that ALF stimulates increase in astroglial GS which correlates with deterioration of the animal state. The aim of the study was to determine the level of glutamine synthetase expression in different brain regions of rats in the conditions of experimental sepsis. Materials and methods. The study was conducted in Wistar rats: 5 sham-operated (control) animals and 20 rats with cecum ligation and puncture (CLP) septic model. Immunohistochemical study of GS expression was performed in the cortex, white matter, hippocampus, thalamus, caudate nucleus/putamen in the period of 20–48 h after CLP. Results. Starting at 12th h after CLP, operated animals displayed progressive impairment finished by profound lethargy and respiratory failure. Between 20–38 h, 9 animals expressed final mentioned symptoms and were euthanized (CLP-B, non-survived), 11 rats displayed less expressed suffering up to 48 h (CLP-A, survived). At 23 h in CLP-B and 48 h in CLP-A rats, liver tissue displayed morphological signs of the focal irreversible damage which was aggravated with time after CLP which could be observed dynamically in non-survived group. Both CLP-A and CLP-B rats showed gradual elevation of GS in all studied brain regions. From 24 to 38 h after CLP, non-survived animals showed significant region-specific dynamic increase in GS expression: in the cortex – by 69.35 %, hippocampus – by 53.6 %, thalamus – by 50.0 %; with the most substantive elevation in the cortex – 1.69-fold increase compared to control. Conclusions. In CLP model, 24 h after operation there is significant dynamic increase in GS level in the cortical, hippocampal and thalamic regions of the rat brain with the most prominent in the cortex. Heterogeneous increase in GS indicates regions more or less vulnerable for incoming systemic agents as well as region-specific reactiveness of the brain tissue, including local astroglia, to these factors in septic conditions. Morphological signs of sepsis-associated liver damage preceding significant increase in the brain GS by 1 h, might suppose addition of the liver failure to the course of sepsis which is accompanied by increased level of hepatogenic toxins (presumably including ammonia) in the blood and in the brain parenchyma by 23 h after CLP. The latter might propose an active implication of hepatogenic detrimental agents in sepsis pathophysiology and involvement of reactively increased brain GS levels in the complex mechanisms of sepsis-associated encephalopathy.