The Ability of New Non-Competitive Glutamate Receptor Blockers to Weaken Motor Disorders in Animals

The ability of mono- and dicationic phenylcyclohexyl derivatives, which are non-competitive glutamate antagonists, to prevent convulsions induced in mice by intragastric NMDA or kainate, to weaken catalepsy induced in rats by haloperidol, and to exert their own influences of movement activity and behavior in animals was studied. The actions of study compounds were compared with those of the known NMDA antagonists memantine and dizocilpine. NMDA-induced convulsions were effectively prevented by both mono- and dications, while only dications were effective against kainate convulsions. Anticataleptic activity was significantly more marked in monocations, which lacked the ability to block non-NMDA receptors. Side effects on motor coordination were less marked with study compounds than with dizocilpine. Thus, the effects of phenylcyclohexyl derivatives in in vivo experimental models correlate with their anti-NMDA and anti-AMPA activity. They can be regarded as potential agents for treating parkinsonism and other motor disorders.     

Glutamatergic neurotransmission in the nucleus tractus solitarii: Structural and functional characteristics

Glutamate is the main excitatory transmitter in the central nervous system. As such, it plays a major role in transmitting and processing visceral sensory information within the nucleus tractus solitarii (NTS). Here, we review current knowledge on NTS glutamatergic transmission. We describe the main organizational features of NTS glutamatergic synapses as determined by work performed during the last decade using antibodies against glutamate receptors and transporters proteins. In light of these recent neuronatomical findings, we discuss some functional properties of developing and adult NTS glutamatergic synapses.     

Autoantibodies to Glutamate Receptors and Products of Nitric Oxide Metabolism in Serum in Children in the Acute Phase of Craniocerebral Trauma

Levels of serum autoantibodies (aAb) to glutamate receptors and products of nitric oxide (NO) metabolism, i.e., nitrates and nitrites, were assayed in children with recent craniocerebral trauma (CCT) of different levels of severity. All the children showed increases in serum aAb to both AMPA and NMDA receptor subtypes from day 1 to day 10 after trauma. The highest levels of serum aAb were to the NMDA subtype of glutamate receptor, which was characteristic of children with mild CCT (MCCT), with Glasgow Coma Scale (GCS) scores of 14–15 points. Levels of aAb to NMDA (NR2A) receptors in children with severe CCT (SCCT, GCS < 9 points) were lower than in children with MCCT, the lowest levels being seen in the group of children with lethal CCT (SCCT-2). Serum concentrations of NO metabolites increased by large factors in the group of children with SCCT, indicating marked brain hypoxia. Translated from Zhurnal Nevrologii i Psikhiatrii imeni S. S. Korsakova, Vol. 108, No. 3, pp. 67–72, March, 2008.     

Comparison of the Anticonvulsive Activities of Organic Mono- and Dications with Their Abilities to Inhibit NMDA and AMPA Glutamate Receptors

The abilities of mono- and dicationic adamantane and phenylcyclohexyl derivatives to (a) block open NMDA and AMPA glutamate receptors in isolated rat brain neurons and (b) prevent convulsions induced in mice by intraventricular NMDA or kainate were studied. Monocations inhibited NMDA receptors in vitro and produced corresponding protection against NMDA-induced convulsions in vivo, but lacked the ability to block AMPA receptors or prevent kainate-induced convulsions. Dications (IEM-1754 and IEM-1925), which inhibited both NMDA and AMPA receptors, were highly effective at protecting against kainate convulsions and were more effective than the corresponding monocations in preventing NMDA convulsions. The origin of convulsions induced by NMDA appears to be based on a component mediated by activation of AMPA receptors. The anticonvulsive activity of IEM-1754 and IEM-1925 were comparable with those of the known NMDA receptor blockers memantine and MK-801. This was combined with an almost complete absence of the side effects characteristic of memantine and MK-801. The complete correspondence between the in vitro data and in vivo results seen with some of the study compounds is evidently associated with their pharmacokinetic properties.     

Proteinase-Activated Type 1 Receptors are Involved in the Mechanism of Protection of Rat Hippocampal Neurons from Glutamate Toxicity

Survival of cultured rat hippocampal neurons was estimated 4, 24, and 48 h after 15-min exposure to the toxic effect of glutamate under conditions of pre- or coincubation with 10 nM thrombin. Thrombin inhibited glutamate-induced apoptosis in neurons 24 and 48 h after treatment, but had no effect on necrosis. Selective peptide agonist of proteinase-activated type 1 receptors simulated, but receptor antagonist suppressed the neuroprotective effect of thrombin. Our results suggest that peptide antagonist of type 1 receptors play a role in the mechanisms of neuronal protection from glutamate toxicity. __________ Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 140, No. 9, pp. 265–268, September, 2005     

Role of glutamate transporters in corticostriatal synaptic transmission

High-affinity glutamate transporters (GTs) play a major role in controlling the extracellular level of this excitatory neurotransmitter in the CNS. Here we have characterized, by means of in vitro patch-clamp recordings from medium spiny neurons (MSNs), the role of GTs in regulating corticostriatal glutamatergic synaptic transmission in the adult rat. Charge transfer and decay-time, but not amplitude, of excitatory postsynaptic currents (EPSCs) were enhanced by dl-threo-β-benzyloxyaspartate (TBOA), a broad inhibitor of GTs. Moreover, TBOA also potentiated currents induced by high-frequency stimulation (HFS) protocols. Interestingly, the effect of TBOA on EPSCs was lost when MSNs were clamped at +40 mV, a condition in which neuronal GTs, that are voltage-dependent, are blocked. However, in this condition TBOA was still able to enhance HFS-induced currents, suggesting that glial GT's role is to regulate synaptic transmission when glutamate release is massive. These data suggest that neuronal GTs, rather than glial, shape EPSCs' kinetics and modulate glutamate transmission at corticostriatal synapse. Moreover, the control of glutamate concentration in the synaptic cleft by GTs may play a role in a number of degenerative disorders characterized by the hyperactivity of corticostriatal pathway, as well as in synaptic plasticity.     

Minocycline prevents impaired glial glutamate uptake in the spinal sensory synapses of neuropathic rats

Activation of glutamate receptors and glial cells in the spinal dorsal horn are two fundamental processes involved in the pathogenesis of various pain conditions, including neuropathic pain induced by injury to the peripheral or central nervous systems. Numerous studies have demonstrated that minocycline treatment attenuates allodynic and hyperalgesic behaviors induced by tissue inflammation or nerve injury. However, the synaptic mechanisms by which minocycline prevents hyperalgesia are not fully understood. We recently reported that deficient glutamate uptake by glial glutamate transporters (GTs) is key for the enhanced activation of N-methyl-d-aspartate (NMDA) receptors in the spinal sensory synapses of rats receiving partial sciatic nerve ligation (pSNL). In this study, we investigated how minocycline affects activation of NMDA receptors in the spinal sensory synapses in rats with pSNL by whole cell recordings of NMDA currents in spinal laminea I and II neurons from spinal slices. The effects of minocycline treatments on the dorsal horn expression of glial GTs and astrocyte marker glial fibrillary acidic protein (GFAP) were analyzed by immunohistochemistry. We demonstrated that normalized activation of NMDA receptors in synapses activated by both weak and strong peripheral input in the spinal dorsal horn is temporally associated with attenuated mechanical allodynia in rats with pSNL receiving intraperitoneal injection of minocycline. Minocycline ameliorated both the downregulation of glial GT expression and the activation of astrocytes induced by pSNL in the spinal dorsal horn. We further revealed that preventing deficient glial glutamate uptake at the synapse is crucial for preserving the normalized activation of NMDA receptors in the spinal sensory synapses in pSNL rats treated with minocycline. Our studies suggest that glial GTs may be a potential target for the development of analgesics.     

Glutamate transporter blockade affects Ca(2+) responses in astrocytes

Brief pretreatment of astrocytes in culture with glutamate (500 microM for 20 min), was earlier shown to significantly enhance the Ca(2+) responses to a depolarizing pulse. It is known that malfunction of glutamate transporters increases extracellular glutamate concentration. We hypothesized that pretreatment of astrocytes with glutamate in conditions where the glutamate transporter activity is blocked should cause further elevation of the Ca(2+) responses to a depolarizing pulse. To test the hypothesis we pretreated astrocytes in culture (primary rat astrocyte cultures) with glutamate (500 microM) and glutamate transport inhibitor, threo-beta-hydroxy-aspartate (200 microM, TBHA) or glutamate (500 microM) in Na(+) free extracellular solution for 20 min. The Ca(2+) responses were elicited by depolarization of the astrocyte to evoke voltage-gated Ca(2+) currents. Paradoxical attenuation of the Ca(2+) transients was observed when the glutamate pretreatment was done in conditions that blocked glutamate transport, accompanied by faster rise and decay times. When the experiments were done on astrocyte pairs that were pretreated with glutamate and TBHA, we observed attenuated Ca(2+) responses in the adjoining cell when compared with the depolarized cell. The results were contrary to our earlier observation of heightened responses in the adjoining cell of the astrocyte pair, in cells pretreated with glutamate alone. The attenuated Ca(2+) responses in astrocytes would imply decrease in the vesicular release of glutamate and ATP. Extracellular glutamate concentration dependent regulation of the Ca(2+) signaling mechanism thus seems to operate in astrocytes, which may be important in regulating the neurotoxic accumulation of glutamate in the extracellular space and the synapse.     

Involvement of group I metabotropic glutamate receptors and glutamate transporters in the slow excitatory synaptic transmission in the spinal cord dorsal horn

Our experiments demonstrate a novel role for group I metabotropic glutamate receptor (mGluR) subtypes 1 and 5 in generating a long-lasting synaptic excitation in the substantia gelatinosa (SG) and deep dorsal horn (DH) neurons of the rat spinal cord. In the present study we have investigated a slow excitatory postsynaptic current (EPSC), elicited by a brief high intensity (at Adelta/C fiber strength) and high frequency (20 or 100 Hz) stimulation of primary afferent fibers (PAFs) using whole-cell patch-clamp recordings from neurons located in the DH (laminae II-V) in spinal cord slices of young rats and wild-type and gene-targeted mice lacking mGluR1 subtype. The results shown here suggest that the activation of both mGluR1 and mGluR5 along with NK1 receptors, may be involved in the generation of the slow EPSC in the spinal cord DH. Inhibition of glial and neuronal glutamate transporters by dl-threo-beta-benzyloxyaspartate (TBOA) enhanced the group I mGluR-dependent slow EPSC about eightfold. Therefore, we conclude, that glutamate transporters strongly influence the group I mGluR activation by PAFs possibly at sensory synapses in the DH. Overall these data indicate that stimulus trains can generate a sustained and widespread glutamate signal that can further elicit prolonged EPSCs predominantly mediated by the group I mGluRs. These slow excitatory synaptic currents may have important functional implications for DH cell firing and synaptic plasticity of sensory transmission, including nociception.     

Vesicular Glutamate Transporter Immunoreactivity in the Periodontal Ligament of the Rat Incisor

The distribution of three vesicular glutamate transporter (VGluT) isoforms, VGluT1, VGluT2, and VGluT3, were investigated in the trigeminal ganglion of the periodontal ligament in the rat incisor—a receptive field of trigeminal ganglion neurons. In the trigeminal ganglion, mRNAs for all VGluT isoforms were detected and proteins were observed in the cytoplasm of trigeminal ganglion cells. VGluT1 immunoreactions were localized within the cytoplasm for all sizes of trigeminal neurons, although predominately in medium–large trigeminal neurons. Double‐labeling showed that most VGluT1 contained both VGluT2 and VGluT3. In the periodontal ligament of the incisor, the Ruffini endings, principal periodontal mechanoreceptors, displayed VGluT1 and VGluT2 immunoreactivities. However, lacked immunoreactions for VGluT3. At the electron microscopic level, VGluT1 immunoreactions were localized around the vesicle membranes at the axon terminal of Ruffini endings. The present results indicate that VGluT is expressed in the sensory nerve endings where apparent synapses are not present. Thus, glutamate in the sensory nerve endings is thought to be used in metabotropic functions. This is because glutamate is a general metabolic substrate, and/or acts as a neurotransmitter as proposed in muscle spindles. Anat Rec, 2012. © 2011 Wiley Periodicals, Inc.     

Glutamate Receptors GluR1 and GluR4 in the Hamster Superior Colliculus: Distribution and Co-localization with Calcium-Binding Proteins and GABA

We investigated the distributions of AMPA glutamate receptor subtypes GluR1 and GluR4 in the hamster superior colliculus (SC) with antibody immunocytochemistry and the effect of enucleation on these distributions. We compared these labelings to those of GluR2/3 in our previous report (Park et al., 2004, Neurosci Res., 49:139–155) and calcium-binding proteins calbindin D28K, calretinin, parvalbumin, and GABA. Anti-GluR1-immunoreactive (IR) cells were scattered throughout the SC. By contrast, anti-GluR4-IR cells formed distinct clusters within the lower lateral stratum griseum intermediale (SGI) and lateral stratum album intermediale (SAI). The GluR1- and GluR4-IR neurons varied in size and morphology. The average diameter of the GluR1-IR cells was 13.00 µm, while the GluR4-IR cells was 20.00 µm. The large majority of IR neurons were round or oval cells, but they also included stellate, vertical fusiform and horizontal cells. Monocular enucleation appeared to have no effect on the GluR1 and GluR4 immunoreactivity. Some GluR1-IR cells expressed calbindin D28K (9.50%), calretinin (6.59%), parvalbumin (2.53%), and GABA (20.54%). By contrast, no GluR4-IR cells expressed calcium-binding proteins or GABA. Although the function of the AMPA receptor subunits in SC is not yet clear, the distinct segregation of the GluR subunits, its differential colocalization with calcium-binding proteins and GABA, and differential responses to enucleation suggest the functional diversity of the receptor subunits in visuo-motor integration in the SC.     

Dysregulation of glutamine/glutamate metabolism in COVID-19 patients: A metabolism study in African population and mini meta-analysis

Coronavirus disease 2019 (COVID-19) remains a serious global threat. The metabolic analysis had been successfully applied in the efforts to uncover the pathological mechanisms and biomarkers of disease severity. Here we performed a quasi-targeted metabolomic analysis on 56 COVID-19 patients from Sierra Leone in western Africa, revealing the metabolomic profiles and the association with disease severity, which was confirmed by the targeted metabolomic analysis of 19 pairs of COVID-19 patients. A meta-analysis was performed on published metabolic data of COVID-19 to verify our findings. Of the 596 identified metabolites, 58 showed significant differences between severe and nonsevere groups. The pathway enrichment of these differential metabolites revealed glutamine and glutamate metabolism as the most significant metabolic pathway (Impact = 0.5; −log10P = 1.959). Further targeted metabolic analysis revealed six metabolites with significant intergroup differences, with glutamine/glutamate ratio significantly associated with severe disease, negatively correlated with 10 clinical parameters and positively correlated with SPO₂ (r_s= 0.442, p = 0.005). Mini meta-analysis indicated elevated glutamate was related to increased risk of COVID-19 infection (pooled odd ratio [OR] = 2.02; 95% confidence interval [CI]: 1.17–3.50) and severe COVID-19 (pooled OR = 2.28; 95% CI: 1.14–4.56). In contrast, elevated glutamine related to decreased risk of infection and severe COVID-19, the pooled OR were 0.30 (95% CI: 0.20–0.44), and 0.44 (95% CI: 0.19–0.98), respectively. Glutamine and glutamate metabolism are associated with COVID-19 severity in multiple populations, which might confer potential therapeutic target of COVID-19, especially for severe patients.     

CREPT基因在肿瘤中的研究进展

肿瘤的发生发展是多基因、多步骤、多通路作用的结果,目前的研究只能解决肿瘤防治过程中的小部分问题,仍有大片未知领域需要研究者去探索。CREPT基因作为全新的原癌基因出现,其作用集中在RNA转录、DNA复制与损伤修复及蛋白翻译等方面,在肿瘤的发生发展及转移侵袭中存在重要作用。本文将就CREPT的结构、作用机制及CREPT与肿瘤3方面进行综述。     

Pain in blood cancers

Patients with blood-related cancers (BRC) suffer from a substantial symptom burden, including several pain syndromes sustained by different causes and pathogenetic mechanisms. So, with regard to pain, a multifaceted clinical scenario may be observed in this setting. Indeed, pain may be correlated to disease itself, to disease-associated complications, to iatrogenic causes or may be due to unrelated clinical conditions. A close diagnostic procedure for the assessment of the underlying causes of the pain and of its pathogenetic mechanisms may direct the treatment approach which should be based on a multidisciplinary management and requires the integration of etiology-targeted interventions and painkilling drugs. The World Health Organization's three-step analgesic ladder for cancer pain relief can provide adequate pain control using oral drugs in most patients with BRC on pain, although more complex interventions may be necessary for many difficult-to-treat pain syndromes which are not infrequently encountered in this setting.     

Comparative Study of Action Mechanisms of Dimebon and Memantine on AMPA- and NMDA-Subtypes Glutamate Receptors in Rat Cerebral Neurons

Dimebon in low concentrations potentiated activity of AMPA-receptors in rat cerebellar Purkinje neurons, while memantine produced only an insignificant potentiation in a small group of these cells. In cortical neurons of rat brain memantine efficiently blocked NMDA-induced currents in dimebon-insensitive neurons. By contrast, its effect was far weaker in neurons, where the blocking action of dimebon on NMDA-receptors was most pronounced. It was hypothesized that the differences in the effects of memantine and dimebon are determined by their interaction with different sites of NMDA-receptors.     

Immune landscape of viral cancers: Insights from single-cell sequencing

Viral infections trigger a wide range of immune responses thought to drive tumorigenesis and malignant progression. Dissecting virus-induced changes in the tumor immune microenvironment (TIME) is therefore crucial to identify key leukocyte populations that may represent novel targets for cancer therapy. Single-cell sequencing approaches have now been widely applied to the analysis of various tumors, thus enabling multiomics characterization of the highly heterogeneous TIME that bulk-sequencing cannot fully elucidate. In this review, we summarized key recent findings from sequencing studies of the immune infiltrate and antitumor response in virus-associated cancers at single cell resolution. Additionally, we also reviewed recent developments in immunotherapy for virus-associated cancers. We anticipate that the strategic use of single-cell sequencing will advance our understanding of the TIME of viral cancers, leading to the development of more potent novel treatments.     

谷氨酸钠对新生豚鼠耳蜗螺旋神经节的毒性损伤

探讨谷氨酸钠不同给药时程及不同存活时程对新生豚鼠耳蜗螺旋神经节细胞及听力损伤的程度。谷氨酸钠按 2g kg腹腔注射给予 ,每天一次。G2 1 0组 :连续用药 2 1d ;G7 14组 :连续用药 7d ,停药后饲养 14d ;G7 35组 :用药 7d ,后饲养 35d。随后检测其听力水平以及螺旋神经节细胞的形态变化。结果表明各组听阈均有升高 ,伴有神经节细胞的部分消失 ,G2 1 0组听阈为 :6 5 3± 2 1 5dB ,神经节细胞密度为 :1985 3± 10 2 1 7 mm2 ;G7 14组 :听阈 6 3 8±19 2dB ,细胞密度 314 5 4± 12 2 5 3 mm2 ;G7 35组 :听阈 5 4 6± 14 3dB ,细胞密度 2 990 4± 10 2 2 1 mm2 。提示谷氨酸钠对新生豚鼠螺旋神经节细胞毒性损伤程度与用药时程有关 ;受损细胞大部死亡 ,部分细胞随再存活时间逐渐自我修复 ;听力恢复与停药后存活时间及节细胞状态关联     

Comparison of Changes in Glutamate Levels in the Nucleus Accumbens of the Rat Brain during Food Consumption in Conditions of Blockade of Dopamine D1 and D2 Receptors

The effects of blockade of D₁ and D₂ dopamine receptors in the nucleus accumbens on changes in glutamate levels in the intercellular space of this structure during food consumption were studied in Sprague–Dawley rats by intracerebral microdialysis combined with HPLC. These experiments showed that food consumption was accompanied by decreases in glutamate levels in the intercellular spaces of the nucleus accumbens. Blockade of D₁ dopamine receptors with SCH-23390 (0.01 mM) produced no changes in the dynamics of glutamate release during food consumption. Food consumption in conditions of blockade of D₂ dopamine receptors with raclopride (0.01 mM) induced increases in glutamate levels. These data suggest that glutamate levels during food consumption are controlled by the dopaminergic system of the nucleus accumbens, mediated by D₂ but not D₁ dopamine receptors.