NR1 Subunit Research Articles

Anti-NMDA-Receptor Encephalitis: Case Report and Literature Review of a Frequently Misdiagnosed Condition

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is a potentially fatal autoimmune syndrome in which IgG antibodies target the NR1 subunit of the NMDA receptor resulting in profound dysregulation and neurotransmission.

The dose-dependent effect of 1.5-GHz microwave exposure on spatial memory and the NMDAR pathway in Wistar rats

A certain power of microwave radiation could cause changes in the nervous, cardiovascular, and other systems of the body, and the brain was a sensitive target organ of microwave radiation injury. Studies have shown that microwaves can impair cognitive functions in humans and animals, such as learning and memory, attention, and orientation. The dose-dependent effect of microwave radiation is still unclear. Our study aimed to investigate the effects of 1.5-GHz microwaves with different average power densities on locative learning and memory abilities, hippocampal structure, and related N-methyl D-aspartate receptor (NMDAR) signalling pathway proteins in rats. A total number of 140 male Wistar rats were randomly divided into four groups: S group (sham exposure), L5 group (1.5-GHz microwaves with average power density = 5 mW/cm2), L30 group (1.5-GHz microwaves with average power density = 30 mW/cm2), and L50 group (1.5-GHz microwaves with average power density = 50 mW/cm2). Changes in spatial learning and memory, EEG activity, hippocampal structure, and NMDAR signalling pathway molecules were detected from 6 h to 28 d after microwave exposure. After exposure to 1.5-GHz microwaves, rats in the L30 and L50 groups showed impaired spatial memory, inhibited EEG activity, pyknosis and hyperchromatism of neuron nucleus, and changes in NMDAR subunits and downstream signalling molecules. In conclusion, 1.5-GHz microwaves with an average power density of 5, 30, and 50 mW/cm2 could induce spatial memory dysfunction, hippocampal structure changes, and changes in protein levels in rats, and there was a defined dose-dependent effect.

Acute intrahippocampal administration of melanin-concentrating hormone impairs memory consolidation and decreases the expression of MCHR-1 and TrkB receptors

Interest in the role of melanin-concentrating hormone (MCH) in memory processes has increased in recent years, with some studies reporting memory-enhancing effects, while others report deleterious effects. Due to these discrepancies, this study seeks to provide new evidence about the role of MCH in memory consolidation and its relation with BDNF/TrkB system. To this end, in the first experiment, increased doses of MCH were acutely administered in both hippocampi to groups of male rats (25, 50, 200, and 500 ng). Microinjections were carried out immediately after finishing the sample trial of two hippocampal-dependent behavioral tasks: the Novel Object Recognition Test (NORT) and the modified Elevated Plus Maze (mEPM) test. Results indicated that a dose of 200 ng of MCH or higher impaired memory consolidation in both tasks. A second experiment was performed in which a dose of 200 ng of MCH was administered alone or co-administered with the MCHR-1 antagonist ATC-0175 at the end of the sample trial in the NORT. Results showed that MCH impaired memory consolidation, while the co-administration with ATC-0175 reverted this detrimental effect. Moreover, MCH induced a significant decrease in hippocampal MCHR-1 and TrkB expression with no modification in the expression of BDNF and NMDA receptor subunits NR1, NR2A, and NR2B. These results suggest that MCH in vivo elicits pro-amnesic effects in the rat hippocampus by decreasing the availability of its receptor and TrkB receptors, thus linking both endogenous systems to memory processes.

GluN2D expression is regulated by restraint stress and supports active stress coping bouts

Stress coping strategies represent critical responses to environmental challenges, and active coping has been linked to stress resilience in humans. Understanding the neuroadaptations that support these strategies may provide insights into adaptive and maladaptive stress responses. NMDA receptors (NMDARs) play key roles in neuroadaptation, and NMDARs have been specifically implicated in stress responsiveness. Constitutive knockout mice have been used to implicate the GluN2D NMDAR subunit in regulation of stress-sensitive and affective behavior, but the brain regions in which GluN2D expression changes drive these effects remain unknown. Here we report that following an acute restraint stressor, GluN2D subunit expression is specifically decreased in the bed nucleus of the stria terminalis (BNST), a key region involved in stress processing, in male but not female mice, with no differences found in the thalamus or ventral hippocampus in either sex. Rodents engage in active struggling events during restraint stress that may represent active coping strategies to stress. Thus, we assessed active coping bouts during acute and chronic restraint stress sessions in GluN2D knockout mice. During the first restraint session, GluN2D knockout mice exhibited a pronounced decrease in struggling bouts during restraint stress relative to wild-type littermates, consistent with a role of GluN2D in active coping responses to stress. Repeated, daily restraint sessions revealed a sex-specific role of GluN2D expression on certain aspects of active coping behaviors, with male GluN2D KO mice exhibiting a decrease in total coping bouts measured across five sessions. However, BNST-specific knockdown of GluN2D in male mice did not alter active coping bouts, suggesting either a multi-synaptic role of GluN2D and/or a developmental role of GluN2D in this behavior. Altogether, these data are consistent with a growing literature suggesting that exploration of GluN2D control of stress circuit actions may lead to a novel therapeutic target to consider for stress-related mood disorders.

Endogenous d-serine exists in the mammalian brain independent of synthesis by serine racemase

Activation of N-methyl-d-aspartate receptors (NMDARs) requires binding of a co-agonist in addition to l-glutamate. d-serine binds to the co-agonist site on GluN1 subunits of NMDARs and modulates glutamatergic neurotransmission. While loss of GluN1 subunits in mice results in neonatal death due to respiratory failure, animals that lack a d-serine synthetic enzyme, serine racemase (SR), show grossly normal growth. However, SR-independent origins of d-serine in the brain remain unclarified. In the present study, we investigated the origin of brain d-serine in mice. Loss of SR significantly reduced d-serine in the cerebral cortex, but a portion of d-serine remained in both neonates and adults. Although d-serine was also produced by intestinal bacteria, germ-free experiments did not influence d-serine levels in the cerebral cortex. In addition, treatment of SR-knockout mice with antibiotics showed a significant reduction of intestinal d-serine, but no reduction in the brain. On the other hand, restriction of dietary intake reduced systemic circulation of d-serine and resulted in a slight decrease of d-serine in the cerebral cortex, but did not account for brain d-serine found in the SR-knockout mice. Therefore, our findings show that endogenous d-serine of non-SR origin exists in the brain. Such previously unrecognized, SR-independent, endogenous d-serine may contribute baseline activity of NMDARs, especially in developing brain, which has minimal SR expression.

Inhibition of GluN2B pathway is involved in the neuroprotective effect of silibinin on streptozotocin-induced Alzheimer's disease models

BackgroundOver-activation of N-methyl-D-aspartate receptors (NMDARs) is involved in sporadic Alzheimer's disease. Silibinin, a natural flavonoid gained from the seeds of Silybum marianum, exerts neuroprotective effects on sporadic AD models, but its impacts on NMDARs remain unknown. PurposeTo study silibinin's regulatory effects on NMDARs pathway in sporadic AD models. MethodsMTT assay, western blotting, confocal microscopy, flow cytometry, RT-PCR, and siRNA transfection etc. were used for cellular and molecular studies. The direct interactions between silibinin and NMDAR subunits were evaluated by computational molecular docking, drug affinity responsive target stability (DARTS) assay and cellular thermal shift assay (CETSA). Y maze test, novel objects recognition test and Morris water maze test were conducted to examine the learning and memory ability of rats. ResultsAn in vitro AD model was established by treating HT22 murine hippocampal neurons with streptozotocin (STZ), as evidenced by the amyloid β (Aβ) deposition and hyperphosphorylation of tau proteins. Silibinin shows protection of neurons against STZ-induced cell damage. It is noteworthy that STZ-induced cellular calcium influx is inhibited by silibinin-treatment, indicating the possible modulation of calcium channels. Studies on NMDARs, the most widely distributed calcium channel, by using molecular docking, DARTS and CESTA, reveal that the GluN2B subunit, but not GluN2A, is the potential target of silibinin. Further studies using the pharmacological agonist (NMDA) and the GluN2B-specific inhibitor (Ifenprodil) or siRNA, indicate that the protection by silibinin treatment from STZ-induced cytotoxicity is medicated through interference with GluN2B-containing NMDARs, followed by the upregulation of CaMKIIα/ BDNF/ TrkB signaling pathway and improved levels of synaptic proteins (SYP and PSD-95). The results in vivo using rats intracerebroventricularly injected with STZ (ICV-STZ), a well-established sporadic AD model, confirm that silibinin improves learning and memory ability in association with modulation of the GluN2B/CaMKIIα/ BDNF/TrkB signaling pathway. ConclusionInhibiting over-activation of GluN2B-containing NMDARs is involved in the neuroprotective effect of silibinin on STZ-induced sporadic AD models.

Active Immunization Against NMDA NR1 Subunit as a Model of Autoimmune Encephalitis

Objective To identify and develop the optimal active immunization induction method for NMDAR encephalitis in rodents. Background Encephalitis is a devastating neurologic disorder with high morbidity and mortality. Many cases are autoimmune. N-Methyl-D-aspartic acid receptor (NMDAR) encephalitis (NMDARE), characterized by antibodies against the NMDAR in the blood and spinal fluid of patients, is the most common form of autoimmune encephalitis (AE). A translational rodent model of NMDARE would allow for in-depth studies into AE pathophysiology, leading to advances in the diagnosis and treatment of this debilitating neuropsychiatric disorder. Design/Methods 7-week-old female C57BL/6J mice were injected subcutaneously with an emulsion of complete Freund's adjuvant, attenuated Mycobacterium tuberculosis (TB), and a 30 amino acid peptide flanking the NMDAR NR1 subunit N368/G369 residue targeted by antibodies in NMDARE patients. Three different induction methods were tested by varying the amount and injection method of pertussis toxin, subcutaneous injection sites, reimmunization, and amounts of TB. Mice were bled biweekly and sacrificed at 2, 4, 6, 8, and 14 weeks. Serum and CSF NMDAR antibody titer; mouse behavior; hippocampal NMDAR protein and cluster density; and brain immune cell entry and cytokine content were examined. Results Immunized mice had serum and CSF NMDAR antibodies. Mice exhibited behavioral changes, altered hippocampal NMDAR protein, brain immune cell entry, and elevated cytokines in their brains. Titers were higher and changes were sustained in reimmunized mice. Conclusions Active immunization against the portion of the NMDAR targeted in patients with NMDARE resulted in robust production of NMDAR antibodies in the blood and spinal fluid, changes in hippocampal NMDAR protein, elevations in brain immune cells and cytokines, and behavioral changes in mice. Reimmunization was needed to sustain the responses. Active immunization therefore holds potential as a translational model of NMDARE, allowing for the creation of a novel generation of diagnostics and therapeutics.

False Positive Cerebrospinal Fluid NMDA Receptor Antibodies: A Single Center Case Series

Objective To report the presence of CSF NMDA receptor antibodies in four patients without NMDA receptor encephalitis encountered at a single tertiary care center. Background The diagnosis and confirmation of anti-NMDA encephalitis relies heavily on detection of IgG antibodies to the NR1 subunit of the NMDA receptor in cerebrospinal fluid. While this is generally considered a highly specific test for anti-NMDA encephalitis, there have been rare reports of false positive testing. Design/Methods A retrospective chart review of medical records for patients with positive CSF NMDA receptor antibody testing at University of Texas Southwestern Medical Center between 2011 to 2021 was performed. Results 40 patients were identified who had positive CSF NMDA receptor antibodies. Of these 40 patients, 4 (10%) were concluded to have false positive results. The false positive results consisted of 1 patient with refractory status epilepticus from suspected synthetic cannabinoid use, 1 patient with an anaplastic astrocytoma, 1 patient with fungal meningitis from Candida dubliniensis, and 1 patient with bifrontal cerebritis of suspected infectious etiology. Of the 4 patients with false positive antibody testing, 3 were immediately recognized as likely false positives while 1 patient was misdiagnosed and treated for an autoimmune encephalitis prior to a final diagnosis with tissue biopsy. Conclusions Although uncommon, false positive CSF NMDA receptor antibodies pose significant diagnostic and therapeutic challenges for clinicians. In our case series, false positive tests occurred in patients with apparent central nervous system disorders, including seizure, infection, and neoplasm. While antibody testing is an essential tool for the diagnosis of NMDA receptor encephalitis, caution should be exercised in interpreting positive results when the clinical and paraclinical data are not consistent with the well characterized phenotype of NMDA receptor encephalitis.

Targeting mGlu1 Receptors in the Treatment of Motor and Cognitive Dysfunctions in Mice Modeling Type 1 Spinocerebellar Ataxia

Type 1 spinocerebellar ataxia (SCA1) is a progressive neurodegenerative disorder with no effective treatment to date. Using mice modeling SCA1, it has been demonstrated that a drug that amplifies mGlu1 receptor activation (mGlu1 receptor PAM, Ro0711401) improves motor coordination without the development of tolerance when cerebellar dysfunction manifests (i.e., in 30-week-old heterozygous ataxin-1 [154Q/2Q] transgenic mice). SCA1 is also associated with cognitive dysfunction, which may precede cerebellar motor signs. Here, we report that otherwise healthy, 8-week-old SCA1 mice showed a defect in spatial learning and memory associated with reduced protein levels of mGlu1α receptors, the GluN2B subunit of NMDA receptors, and cannabinoid CB1 receptors in the hippocampus. Systemic treatment with Ro0711401 (10 mg/kg, s.c.) partially corrected the learning deficit in the Morris water maze and restored memory retention in the SCA1 mice model. This treatment also enhanced hippocampal levels of the endocannabinoid, anandamide, without changing the levels of 2-arachidonylglycerol. These findings suggest that mGlu1 receptor PAMs may be beneficial in the treatment of motor and nonmotor signs associated with SCA1 and encourage further studies in animal models of SCA1 and other types of SCAs.

Transgenerational transmission of aspartame-induced anxiety and changes in glutamate-GABA signaling and gene expression in the amygdala

We report the effects of aspartame on anxiety-like behavior, neurotransmitter signaling and gene expression in the amygdala, a brain region associated with the regulation of anxiety and fear responses. C57BL/6 mice consumed drinking water containing 0.015% or 0.03% aspartame, a dose equivalent of 8 to 15% of the FDA recommended maximum human daily intake, or plain drinking water. Robust anxiety-like behavior (evaluated using open field test and elevated zero maze) was observed in male and female mice consuming the aspartame-containing water. Diazepam, an allosteric modulator of the GABA-A receptor, alleviated the anxiety-like behavior. RNA sequencing of the amygdala followed by KEGG biological pathway analysis of differentially expressed genes showed glutamatergic and GABAergic synapse pathways as significantly enriched. Quantitative PCR showed upregulation of mRNA for the glutamate NMDA receptor subunit 2D (Grin2d) and metabotropic receptor 4 (Grm4) and downregulation of the GABA-A receptor associated protein (Gabarap) mRNA. Thus, taken together, our diazepam and gene expression data show that aspartame consumption shifted the excitation-inhibition equilibrium in the amygdala toward excitation. Even more strikingly, the anxiety-like behavior, its response to diazepam, and changes in amygdala gene expression were transmitted to male and female offspring in two generations descending from the aspartame-exposed males. Extrapolation of the findings to humans suggests that aspartame consumption at doses below the FDA recommended maximum daily intake may produce neurobehavioral changes in aspartame-consuming individuals and their descendants. Thus, human population at risk of aspartame's potential mental health effects may be larger than current expectations, which only include aspartame-consuming individuals.

Deficiency of NMDA receptor subunit GluN3A as a pathogenic factor for endogenous amyloid deposition and sporadic Alzheimer’s disease

AbstractBackgroundAlzheimer’s disease (AD) is a neurodegenerative disease, evolving amyloidosis and tau protein hyperphosphorylation, synapse dysfunction, neuron degeneration and cognitive deficits. Investigations based on the Aβ/tau hypothesis have been performed in transgenic animal models expression familial/mutated AD genes. However, treatments based on this hypothesis have not provided effective clinical therapies. Hyperactivity of the glutamatergic NMDA receptor (NMDAR) is a common pathophysiology of AD and has been viewed as a consequence of Aβ pathology. Among NMDAR subunits, GluN3A is a unique inhibitory subunit that suppresses NMDA currents and Ca2+ influx. Recent evidence from rodent and human studies shows that GluN3A is widely expressed and plays important functional roles in neonatal and adult brains. Ca2+ overload is a trigger of excitotoxicity, while GluN3A plays a regulatory role of Ca2+ homeostasis. The role of GluN3A regulation in AD is unknown.MethodGluN3A knockout mice, gene modifications, immunohistochemistry, Western blotting, MEA recordings, Ca2+ imaging, pathological examinations, functional and behavioral tests.ResultChronic neuronal hyperactivity and Ca2+ dysregulation caused by GluN3A deficiency lead to slowly advanced “neurodegenerative excitotoxicity”, dementia and AD pathology in an age‐dependent manner. Ca2+ imaging and MultiElectrode Array recordings in GluN3A KO brain slices revealed moderate but sustained elevation of cytosolic Ca2+ levels, neuronal hyperactivity, and impaired synaptic plasticity compared to age matched controls. Aging GluN3A KO mice showed increased Ca2+‐dependent signals, chronic inflammation, neuronal loss and disease symptoms including early onset of olfactory dysfunction followed by cognitive deficits. β‐Amyloid deposition and tau protein hyperphosphorylation were identified as a late pathology in the cortex and hippocampus. Expression of GluN3A in the GluN3A KO brain prevented AD progression. Early treatment at the pre‐clinical stage using the NMDAR antagonist memantine prevented symptoms in GluN3A KO mice. Western blot analysis of AD patient’s brains showed lower levels of GluN3A in the cortex compared to normal aging subjects.ConclusionOur results identified a novel amyloid‐independent mechanism that the deficiency of GluN3A alone causes a slight lifelong Ca2+ dyshomeostasis, leading to AD pathophysiology and amyloid pathology. The long‐term GluN3A modulation of NMDARs signifies new therapeutic targets and possible preventive interventions for a sporadic type of AD.

Post synaptic density 95 (PSD95)–Actin interaction: A critical regulator of synaptic strength and plasticity in Alzheimer’s disease pathology

AbstractBackgroundPSD95 serves as a scaffolding protein to several neurotransmitter receptors, signal transduction components, and adhesion molecules at the synapse. It is a potential regulator of synaptic strength and plasticity by regulating glutamatergic receptor trafficking, which is impaired in AD. PSD95 interacts directly with NMDA receptors while the interactions with AMPA receptors are through an auxiliary subunit TARPs. Actin cytoskeleton is highly enriched at the synapse. However, the interaction of PSD‐95 – actin and its consequences in synaptic transmission is not understood. Therefore, we investigated the critical role of PSD‐95 association at the synapse with actin and its impact on AMPA and NMDA receptors using AD mice.MethodsSynaptosomes were isolated from adolescent and middle aged wildtype and APP/PS1 mice. Immunoprecipitation was performed using the synaptosomes and F‐actin fractions with anti‐PSD95 antibody followed immunoblotting against glutamatergic receptor subunit antibodies and actin antibody. Statistical comparisons between two groups were performed with the two‐tailed unpaired Mann–Whitney U test.ResultsPSD95 association with actin is detected in synaptosomes isolated from adolescent and middle aged WT and APP/PS1 mouse brain cortex. We found that PSD95‐actin association is significantly decreased in middle aged APP/PS1 mice compared with WT while it remains unaffected in the F‐actin fraction of synaptosomes in APP/PS1 mice. Then, we examined the levels of AMPA and NMDA receptor subunits in APP/PS1 mice. GluA1 and GluA2 subunits of AMPAR are significantly decreased in middle aged but not in adolescent APP/PS1 mice in comparison to age matched WT mice. Protein levels of GluN1 and GluN2B subunits are significantly decreased in both adolescent and middle aged APP/PS1 mice, while GluN2A levels are reduced only in adolescent mice. We detected that PSD95 is physically associated with both AMPAR and NMDAR subunits and this association with GluA1 subunit is affected only in middle aged APP/PS1 mice. Interestingly, interaction of NMDAR subunits (GluN1 and GluN2B) with PSD‐95 is greatly enhanced at adolescent APP/PS1 mice even though these subunit protein levels are significantly diminished.ConclusionOur findings indicate that perturbation of PSD95‐actin association and glutamatergic receptors in AD leads to synaptic dysfunction. It may have critical implications in defective glutamatergic neurotransmission.

High Morphine Use Disorder Susceptibility Is Predicted by Impaired Learning Ability in Mice.

An obvious reason for substance uses disorders (SUDs) is drug craving and seeking behavior induced by conditioned context, which is an abnormal solid context memory. The relationship between susceptibility to SUD and learning ability remains unclear in humans and animal models. In this study, we found that susceptibility to morphine use disorder (MUD) was negatively correlated with learning ability in conditioned place preference (CPP) in C57 mice. By using behavioral tests, we identified the FVB mouse as learning impaired. In addition, we discovered that learning-relevant proteins, such as the glutamate receptor subunits GluA1, NR1, and NR2A, were decreased in FVB mice. Finally, we assessed the context learning ability of FVB mice using the CPP test and priming. We found that FVB mice had lower learning performance with respect to normal memory but higher performance of morphine-reinstatement memory. Compared to C57 mice, FVB mice are highly sensitive to MUDs. Our results suggest that SUD susceptibility is predicted by impaired learning ability in mice; therefore, learning ability can play a simple and practical role in identifying high-risk SUD groups.

MiR-146a and miR-200b alter cognition by targeting NMDA receptor subunits.

MicroRNAs fine-tune gene regulation and can be targeted for therapeutic purposes. We investigated the physiological roles of miR-146a and miR-200b that are differentially expressed in neurological disorders such as Alzheimer's disease and schizophrenia, particularly in learning and memory mechanisms. Using bioinformatics tools and luciferase assay, we show interaction of these miRNAs with transcripts of N-methyl-D-aspartate receptor (NMDAR) subunits Grin2A and Grin2B. Overexpression of these miRNAs in primary hippocampal neurons caused downregulation of GluN2B and GluN2A proteins. Stereotactic injections of these miRNAs into rat hippocampus caused cognitive deficits in multiple behavioral tests with decreased protein levels of GluN1, GluN2A, GluN2B, AMPAR subunit GluR1, and Neuregulin 1. In pharmacologically treated rat models [MK-801 treated and methylazoxymethanol acetate (MAM) treated], we found upregulated levels of these miRNAs, implying their involvement in downregulating NMDAR subunits in these models. These results suggest the importance of miR-146a-5p and miR-200b-3p in hippocampus-dependent learning and memory.

NMDA receptor hypofunction underlies deficits in parvalbumin interneurons and social behavior in neuroligin 3 R451C knockin mice.

Neuroligins (NLs), a family of postsynaptic cell-adhesion molecules, have been associated with autism spectrum disorder. We have reported that dysfunction of the medial prefrontal cortex (mPFC) leads to social deficits in an NL3 R451C knockin (KI) mouse model of autism. However, the underlying molecular mechanism remains unclear. Here, we find that N-methyl-D-aspartate receptor (NMDAR) function and parvalbumin-positive (PV+) interneuron number and expression are reduced in the mPFC of the KI mice. Selective knockdown of NMDAR subunit GluN1 in the mPFC PV+ interneuron decreases its intrinsic excitability. Restoring NMDAR function by its partial agonist D-cycloserine rescues the PV+ interneuron dysfunction and social deficits in the KI mice. Interestingly, early D-cycloserine administration at adolescence prevents adult KI mice from social deficits. Together, our results suggest that NMDAR hypofunction and the resultant PV+ interneuron dysfunction in the mPFC may constitute a central node in the pathogenesis of social deficits in the KI mice.

THE GLUTAMATERGIC SYSTEM IN ALZHEIMER’S DISEASE: A SYSTEMATIC REVIEW WITH META‐ANALYSIS

AbstractBackgroundGlutamate is the most important excitatory neurotransmitter in the human brain, and the regulation of its homeostasis is of utmost importance for brain proper functioning. At the synapse level, glutamate binds to ionotropic (NMDAR, AMPAR and KAR) and metabotropic receptors (8 isoforms, mGluR1 to mGluR8). Also located at the glutamatergic synapse are the vesicular transporters (vGLUT), a synaptic marker, and glutamate transporters (GLT1), which are responsible for glutamate re‐uptake. Increases in the glutamate concentration in the synaptic cleft leads to a phenomenon called excitotoxicity, which causes progressive neuronal death. Nonetheless, glutamate excitotoxicity has been described as a common feature in neurodegenerative disorders, including Alzheimer’s Disease (AD). Multiple studies reported alterations in the glutamatergic system in the AD brain. Thus, considering the large number of publications, we sought to perform a systematic review with meta‐analysis to assess whether the glutamatergic system is consistently altered in AD patients.MethodPubMed and Web of Science databases were searched for articles that evaluated glutamatergic system components in AD. Pooled effect sizes were determined with standardized mean differences using the Hedge G method with random effects.ResultThe search initially retrieved 6000 articles. Following exclusion criteria, 59 articles were included in this study. We found that regions typically affected with AD pathology presented reduced NMDAR subunit NR1 (p = 0.017, z = 2.38, i2 = 71.3%) (Figure 1), NR2A (p = 0.001, z = 3.38, i2 = 0%) (Figure 2), NR2B (p < 0.0001, z = 3.86, i2 = 0%) (Figure 3), AMPAR subunits GluA2/3 (p = 0.018, z = 2.36, i2 = 84.5%) (Figure 4). Conversely, we did not observe significant differences in the level of GLT1, vGLUT1, vGLUT2, AMPAR subunit GluA1 and mGluRs in postmortem brain tissue. Further analyses are in process to assess other glutamatergic components, as well sensitivity analysis considering risk of bias for each study.ConclusionIn conclusion, the early results of this meta‐analysis suggest that changes in the glutamatergic system in AD are not generalized, but specifically related to ionotropic receptors.

Epigenetic histone acetylation modulating prenatal Poly I:C induced neuroinflammation in the prefrontal cortex of rats: a study in a maternal immune activation model.

Introduction: Neuroinflammation in the central nervous system, particularly the prefrontal cortex (PFC), plays a role in the pathogenesis of schizophrenia, which has been found to be associated with maternal immune activation (MIA). Recent evidence suggests that epigenetic regulation involves in the MIA-induced neurodevelopmental disturbance. However, it is not well-understood how epigenetic modulation is involved in the neuroinflammation and pathogenesis of schizophrenia. Methods: This study explored the modulation of histone acetylation in both neuroinflammation and neurotransmission using an MIA rat model induced by prenatal polyriboinosinic-polyribocytidylic acid (Poly I:C) exposure, specifically examining those genes that were previously observed to be impacted by the exposure, including a subunit of nuclear factor kappa-B (Rela), Nod-Like-Receptor family Pyrin domain containing 3 (Nlrp3), NMDA receptor subunit 2A (Grin2a), 5-HT2A (Htr2a), and GABAA subunit β3 (Gabrb3). Results: Our results revealed global changes of histone acetylation on H3 (H3ace) and H4 (H4ace) in the PFC of offspring rats with prenatal Poly I:C exposure. In addition, it revealed enhancement of both H3ace and H4ace binding on the promoter region of Rela, as well as positive correlations between Rela and genes encoding histone acetyltransferases (HATs) including CREB-binding protein (CBP) and E1A-associated protein p300 (EP300). Although there was no change in H3ace or H4ace enrichment on the promoter region of Nlrp3, a significant enhancement of histone deacetylase 6 (HDAC6) binding on the promoter region of Nlrp3 and a positive correlation between Nlrp3 and Hdac6 were also observed. However, prenatal Poly I:C treatment did not lead to any specific changes of H3ace and H4ace on the promoter region of the target genes encoding neurotransmitter receptors in this study. Discussion: These findings demonstrated that epigenetic modulation contributes to NF-κB/NLRP3 mediated neuroinflammation induced by prenatal Poly I:C exposure via enhancement of histone acetylation of H3ace and H4ace on Rela and HDAC6-mediated NLRP3 transcriptional activation. This may further lead to deficits in neurotransmissions and schizophrenia-like behaviors observed in offspring.

Sex-specific effects of different types of prenatal stress on foetal testosterone levels and NMDA expression in mice

Prenatal stress is a critical life event often resulting in mental illnesses in the offspring. The critical developmental processes, which might trigger a cascade of molecular events resulting in mental disorders in adulthood, are still to be elucidated. Here we proposed that sex hormones, particularly testosterone, might determine the “developmental programming” of long-term consequences of prenatal stress in foetuses of both sexes. We observed that severe prenatal stress in the model of repeated corticosterone injections enhanced brain levels of corticosterone and testosterone in male foetuses. The expression of GluN1 and GluN2A, but not GluN2B NMDA receptor subunits were significantly reduced in the brain of stressed male foetuses. However, female foetuses were protected against stress effects on the brain corticosterone and testosterone levels. More moderate types of stress, such as repeated restraint stress and chronic unpredictable stress, did not induce an increase in brain corticosterone in dams and testosterone concentrations in foetuses of both sexes. Moreover, chronic unpredictable stress reduced brain testosterone concentration in male foetuses. Altogether, changes in brain testosterone level might be one of the crucial mechanisms determining the development of long-term consequences of severe prenatal stress in male, but not in female foetuses. Targeting this mechanism might allow to develop principally new prediction and therapeutic approaches for prenatal stress-associated psychiatric disorders.

Discovery of (R)-2-amino-3-triazolpropanoic acid derivatives as NMDA receptor glycine site agonists with GluN2 subunit-specific activity.

N-Methyl-d-aspartate (NMDA) receptors play critical roles in central nervous system function and are involved in variety of brain disorders. We previously developed a series of (R)-3-(5-furanyl)carboxamido-2-aminopropanoic acid glycine site agonists with pronounced variation in activity among NMDA receptor GluN1/2A-D subtypes. Here, a series of (R)-2-amino-3-triazolpropanoic acid analogues with a novel chemical scaffold is designed and their pharmacological properties are evaluated at NMDA receptor subtypes. We found that the triazole can function as a bioisostere for amide to produce glycine site agonists with variation in activity among NMDA receptor subtypes. Compounds 13g and 13i are full and partial agonists, respectively, at GluN1/2C and GluN1/2D with 3- to 7-fold preference in agonist potency for GluN1/2C-D over GluN1/2A-B subtypes. The agonist binding mode of these triazole analogues and the mechanisms by which the triazole ring can serve as a bioisostere for amide were further explored using molecular dynamics simulations. Thus, the novel (R)-2-amino-3-triazolpropanoic acid derivatives reveal insights to agonist binding at the GluN1 subunit of NMDA receptors and provide new opportunities for the design of glycine site agonists.

Glutamate from nerve cells promotes perineural invasion in pancreatic cancer by regulating tumor glycolysis through HK2 mRNA-m6A modification

BackgroundPerineural invasion (PNI) has a high incidence and poor prognosis in pancreatic ductal adenocarcinoma (PDAC). Our study aimed to identify the underlying molecular mechanism of PNI and propose effective intervention strategies. MethodsTo observe PNI in vitro and in vivo, a Matrigel/ dorsal root ganglia (DRG) model and a murine sciatic nerve invasion model were respectively used. Magnetic resonance (MR) imaging and positron emission tomography/computed tomography (PET-CT) imaging were also used to evaluate tumor growth. Publicly available datasets and PDAC tissues were used to verify how the nerve cells regulate PDAC cells' PNI. ResultsOur results showed that glutamate from nerve cells could cause calcium influx in PDAC cells via the N-methyl-d-aspartate receptor (NMDAR), subsequently activating the downstream Ca2+ dependent protein kinase CaMKII/ERK-MAPK pathway and promoting the mRNA transcription of gene METTL3. Next, METTL3 upregulates the expression of hexokinase 2 (HK2) through N6-methyladenosine (m6A) modification in mRNA, enhances the PDAC cells' glycolysis, and promotes PNI. Furthermore, the IONPs-PEG-scFvCD44v6-scAbNMDAR2B nanoparticles dual targeting CD44 variant isoform 6 (CD44v6) and t NMDAR subunit 2B (NMDAR2B) on PDAC cells were synthesized and verified showing a satisfactory blocking effect on PNI. ConclusionsHere, we firstly provided evidence that glutamate from the nerve cells could upregulate the expression of HK2 through mRNA m6A modification via NMDAR2B and downstream Ca2+ dependent CaMKII/ERK-MAPK pathway, enhance the glycolysis in PDAC cells, and ultimately promote PNI. In addition, the dual targeting nanoparticles we synthesized were verified to block PNI effectively in PDAC.