Activation Of Glutamate Receptors Research Articles

Endoplasmic Reticulum Calcium Signaling in Hippocampal Neurons

The endoplasmic reticulum (ER) is a key organelle in cellular homeostasis, regulating calcium levels and coordinating protein synthesis and folding. In neurons, the ER forms interconnected sheets and tubules that facilitate the propagation of calcium-based signals. Calcium plays a central role in the modulation and regulation of numerous functions in excitable cells. It is a versatile signaling molecule that influences neurotransmitter release, muscle contraction, gene expression, and cell survival. This review focuses on the intricate dynamics of calcium signaling in hippocampal neurons, with particular emphasis on the activation of voltage-gated and ionotropic glutamate receptors in the plasma membrane and ryanodine and inositol 1,4,5-trisphosphate receptors in the ER. These channels and receptors are involved in the generation and transmission of electrical signals and the modulation of calcium concentrations within the neuronal network. By analyzing calcium fluctuations in neurons and the associated calcium handling mechanisms at the ER, mitochondria, endo-lysosome and cytosol, we can gain a deeper understanding of the mechanistic pathways underlying neuronal interactions and information transfer.

Real-time Neurochemical Sensing of Hydrogen Peroxide Production in Brain Tissue using Advanced Nanostructured Au Microelectrodes Functionalized with Ruthenium Purple Film

Real-time monitoring of H2O2 is essential for understanding its role in neurological physio(path)ology. In this study, we developed an advanced electrochemical sensor utilizing nanostructured gold wire microelectrodes functionalized with a Ruthenium Purple (RP) film, a polynuclear transition metal hexacyanoferrate analog of the prototypical Prussian blue (PB). The RP film exhibits enhanced stability in neutral buffer solutions and reduced interference from biologically relevant cations such as Na+, Mg2+, and Ca2+. By integrating gold nanoparticles onto a nanoporous gold surface, we significantly increased the electroactive surface area of the microwire (ρ=26.1 ± 10.2). The electrodeposition of a thin RP film (4.23 ± 1.2 nm) resulted in a highly selective H2O2 sensor, operating at an optimal potential of -0.05 V vs. Ag/AgCl, with a linear detection range of 0.5-500 µM, sensitivity of 1.18 ± 0.37 µA µM-1 cm-2, and a low limit of detection (LOD) of 66.6 ± 34.9 nM. Adding a Nafion® layer enhanced the sensor's operational stability, maintaining optimal performance over three hours under physiological conditions of pH and ion concentration. We validated the sensor's capability to monitor transient changes in H2O2 concentration in brain tissue by assessing its response to exogenously applied H2O2. Furthermore, we demonstrated that glutamate receptor activation in hippocampal slices induces a rapid and transient increase in extracellular H2O2 levels, underscoring the sensor's potential for studying oxidative stress in neurobiological contexts.

New insight into the molecular etiopathogenesis of konzo: Cyanate could be a plausible neurotoxin contributing to konzo, contrary to thiocyanate

IntroductionChronic cassava-derived cyanide poisoning is associated with the appearance of konzo, a tropical spastic paraparesis due to selective upper motor neuron damage. Whether the disease is caused by a direct action of cyanide or its metabolites is still an open question. This preliminary study assessed the neurotoxic effects of thiocyanate (SCN) and cyanate (OCN), two cyanide metabolites hypothesized to be plausible toxic agents in konzo. MethodsCultured mouse neuroblastoma (Neuro-2A) and human neuroblastoma (SH-SY5Y) cell lines were incubated (24, 48, and 72hours) in sodium OCN or sodium SCN in a disease-relevant concentration range. Cell viability, caspase (3, 8, and 9) activities, and reactive oxygen species (ROS) generation were evaluated using appropriate assay kits. Additionally, electrophysiological responses induced by OCN and SCN in primary spinal cord neurons (from Sprague Dawley rats) were assessed by whole-cell patch-clamp techniques. ResultsBoth OCN and SCN were toxic in a dose-dependent way, even if SCN toxicity appeared at very high concentrations (30mM, corresponding to more than 100-fold higher than normal plasmatic levels), contrary to OCN (0.3-3mM). OCN was markedly more toxic in a poor culture medium (MEM; IC50 = 3.2mM) compared to a glucose- and amino acid-rich medium (DMEM; IC50=7.6mM). OCN treatment increased the ROS generation by 8.9 folds, as well as the Caspase-3, Caspase-8, and Caspase-9 activities by 3.2, 2.5, and 2.6 folds, respectively. Finally, OCN (and SCN to a lesser extent) induced depolarizing currents in primary spinal cord neurons, through an activation of ionotropic glutamate receptors. ConclusionOur results suggest OCN as the most plausible neurotoxic agent involved in konzo, while SCN toxicity could be questioned at such high concentrations. Also, they support apoptosis, oxidative stress, and excitotoxicity as probable mechanisms of OCN neurotoxicity.

Developmental Spike Timing-Dependent Long-Term Depression Requires Astrocyte d-Serine at L2/3-L2/3 Synapses of the Mouse Somatosensory Cortex.

Spike timing-dependent plasticity (STDP) is a learning rule important for synaptic refinement and for learning and memory during development. While different forms of presynaptic t-LTD have been deeply investigated, little is known about the mechanisms of somatosensory cortex postsynaptic t-LTD. In the present work, we investigated the requirements and mechanisms for induction of developmental spike timing-dependent long-term depression (t-LTD) at L2/3-L2/3 synapses in the juvenile mouse somatosensory cortex. We found that postnatal day (P) 13-21 mice of either sex show t-LTD at L2/3-L2/3 synapses induced by pairing single presynaptic activity with single postsynaptic action potentials at low stimulation frequency (0.2 Hz) that is expressed postsynaptically and requires the activation of ionotropic postsynaptic NMDA-type glutamate receptors containing GluN2B subunits. In addition, it requires postsynaptic Ca2+, Ca2+ release from internal stores, calcineurin, postsynaptic endocannabinoid synthesis, activation of CB1 receptors, and astrocytic signaling to release the gliotransmitter d-serine to activate postsynaptic NMDARs to induce t-LTD. These results show direct evidence of the mechanism involved in developmental postsynaptic t-LTD at L2/3-L2/3 synapses, revealing a central role of astrocytes and their release of d-serine in its induction.

Monosodium glutamate disrupts zebrafish sleep-like state likely through activation of peripheral nervous system glutamate receptors

Monosodium glutamate (MSG), a widely used flavor enhancer, has raised concerns about its effects on behavior and sleep. This study investigates how MSG influences zebrafish sleep-like state (SLS) and interacts with other substances affecting neurobehavioral responses. Adult zebrafish were exposed to MSG at concentrations of 50, 100, and 150 mg/L, and their swimming speeds and SLS durations were recorded over a 14-hour night period. The results indicated that higher MSG concentrations increased swimming speeds and decreased SLS duration, suggesting heightened excitability and reduced sleep recovery. The study further evaluated how MSG impacts anesthesia sensitivity induced by 2-phenoxyethanol (POE) compared to alcohol and nicotine. Zebrafish were pre-treated with 50 mg/L MSG, 0.5% alcohol, or 0.5 mg/L nicotine before being anesthetized with POE. Nicotine decreased anesthesia sensitivity in a concentration-dependent manner by enhancing neurotransmitter release. In contrast, MSG and alcohol had minimal effects on anesthesia. The limited impact of MSG on anesthesia sensitivity suggests that MSG primarily affects peripheral nervous system functions rather than central nervous system functions, likely due to its poor ability to cross the blood-brain barrier. Overall, the findings demonstrate that MSG disrupts zebrafish behavior through peripheral mechanisms, affecting both swimming activity and sleep patterns. Nicotine, on the other hand, influences behavior through central nervous system interactions. These results highlight the need for further research to better understand how dietary additives like MSG impact neurobehavioral functions in aquatic models, offering insights into their broader implications for sleep and behavior.

Possible roles of heteroreceptor complexes in excitotoxic processes

Excitotoxicity represents a neuropathological process, describing the toxic actions of excitatory neurotransmitters, where the excessive or prolonged activation of glutamate receptors triggers a cascade of events leading to neuronal injury or death. Under conditions of reduced energy availability and increased oxidative stress neurons become particularly vulnerable to excitotoxicity and a large body of available evidence indicates that excitotoxicity represents a central mechanism in the pathogenesis of acute and degenerative diseases of the central nervous system. Astrocytes represent key elements in the regulation of glutamate homeostasis by their opposing functions of glutamate uptake and release, and microglial cells play an important role in the response to damage. Depending on the phenotype they assume when activated, microglial cells can trigger immune defense or neuroprotective processes. To perform their functions both glial cell populations monitor the extracellular space through a panel of receptors. Furthermore, a variety of signaling pathways also contribute to the modulation of the glutamatergic transmission, acting on specific cell receptors expressed by neurons, astrocytes, and microglia. In the last decades, evidence has been provided that receptors of almost all families can establish structural receptor-receptor interactions, leading to the formation of heteroreceptor complexes at the cell membrane of neurons and glial cells. The cooperativity that emerges in the actions of ligands of the monomers forming these assemblies provides the cell decoding apparatus with flexible dynamics in terms of recognition and signal transduction and allows an integration of the incoming signals already at the membrane level. Available data on possible modulatory roles played by heteroreceptor complexes in excitotoxic processes will be here reviewed and discussed. From the pharmacological standpoint, these findings may offer possibilities to explore novel therapeutic strategies targeting receptor complexes to address disorders of the central nervous system associated with dysregulation of glutamatergic signaling.

Increased forebrain EAAT3 expression confers resilience to chronic stress.

Depression is a disabling and highly prevalent psychiatric illness. Multiple studies have linked glutamatergic dysfunction with the pathophysiology of depression, but the exact alterations in the glutamatergic system that contribute to depressive-like behaviors are not fully understood. Recent evidence suggests that a decreased level in neuronal glutamate transporter (EAAT3), known to control glutamate levels and limit the activation of glutamate receptors at synaptic sites, may contribute to the manifestation of a depressive phenotype. Here, we tested the possibility that increased EAAT3 expression at excitatory synapses could reduce the susceptibility of mice to develop depressive-like behaviors when challenged to a 5-week unpredictable chronic mild stress (UCMS) protocol. Mice overexpressing EAAT3 in the forebrain (EAAT3glo/CMKII) and control littermates (EAAT3glo) were assessed for depressive-like behaviors and long-term memory performance after being subjected to UCMS conditions. We found that, after UCMS, EAAT3glo/CMKII mice did not exhibit depressive-like behaviors or memory alterations observed in control mice. Moreover, we found that EAAT3glo/CMKII mice did not show alterations in phasic dopamine release in the nucleus accumbens neither in long-term synaptic plasticity in the CA1 region of the hippocampus after UCMS, as observed in control littermates. Altogether these results suggest that forebrain EAAT3 overexpression may be related to a resilient phenotype, both at behavioral and functional level, to the deleterious effect of chronic stress, highlighting the importance of neuronal EAAT3 in the pathophysiology of depressive-like behaviors.

Activation of nociception-sensitive ionotropic glutamate receptor-expressing rostroventrolateral medulla neurons by stimulation of cardiac afferents in rats.

Myocardial ischemia causes the release of bradykinin, which activates afferent nerve endings in the ventricular epicardium. This elicits a sympathetically mediated increase in arterial pressure and heart rate, referred to as the cardiogenic sympathetic afferent reflex. The rostroventrolateral medulla (RVLM) is a key sympathetic brain stem site for regulating cardiovascular activity. This study aimed to determine the importance of non-barosensitive nociception sympathetic activity and the role of glutamate receptor activation of RVLM neurons in the cardiogenic sympathetic afferent reflex. We tested the hypothesis that inhibition of barosensitive sympathetic activity attenuates but does not abolish the reflex response to cardiac visceral afferents. Renal sympathetic nerve activity (RSNA), arterial pressure, and heart rate responses to epicardial bradykinin application were recorded in anesthetized rats before and after bilateral RVLM microinjection of either GABAA agonist muscimol, ionotropic glutamate receptor antagonist kynurenic acid, N-methyl-d-aspartate (NMDA) receptor antagonist 2-amino-5- phosphonopentanoic acid (AP5), or non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Baroreceptor loading-induced inhibition of barosensitive activity attenuated the bradykinin-induced RSNA response (93 ± 14% increase) and tachycardia (18 ± 3 bpm). While RVLM muscimol microinjection abolished the RSNA response (1.6 ± 4.2% from baseline, 0.49 ± 0.38 μV*s), surprisingly, it did not abolish the tachycardia (27 ± 4 bpm). Kynurenic acid microinjection blocked the arterial pressure and RSNA responses, while AP5 or CNQX only attenuated the responses. These data suggest that nociception-sensitive sympathetic activity that does not appear to be barosensitive is also involved in the cardiogenic sympathetic afferent reflex. Importantly, while muscimol and kynurenic acid abolished the arterial pressure and RSNA response, neither affected the tachycardia, suggesting an alternate cardiac pathway independent of RVLM.

The mGluR5-mediated Arc activation protects against experimental traumatic brain injury in rats.

Traumatic brain injury (TBI) is a complex pathophysiological process, and increasing attention has been paid to the important role of post-synaptic density (PSD) proteins, such as glutamate receptors. Our previous study showed that a PSD protein Arc/Arg3.1 (Arc) regulates endoplasmic reticulum (ER) stress and neuronal necroptosis in traumatic injury invitro. In this study, we investigated the expression, regulation and biological function of Arc in both invivo and invitro experimental TBI models. Traumatic neuronal injury (TNI) induced a temporal upregulation of Arc in cortical neurons, while TBI resulted in sustained increase in Arc expression up to 24 h in rats. The increased expression of Arc was mediated by the activity of metabotropic glutamate receptor 5 (mGluR5), but not dependent on the intracellular calcium (Ca2+) release. By using inhibitors and antagonists, we found that TNI regulates Arc expression via Gq protein and protein turnover. In addition, overexpression of Arc protects against TBI-induced neuronal injury and motor dysfunction both invivo and invitro, whereas the long-term cognitive function was not altered. To determine the role of Arc in mGluR5-induced protection, lentivirus-mediated short hairpin RNA (shRNA) transfection was performed to knockdown Arc expression. The mGluR5 agonist (RS)-2-chloro-5-hydroxyphenylglycine (CHPG)-induced protection against TBI was partially prevented by Arc knockdown. Furthermore, the CHPG-induced attenuation of Ca2+ influx after TNI was dependent on Arc activation and followed regulation of AMPAR subunits. The results of Co-IP and Ca2+ imaging showed that the Arc-Homer1 interaction contributes to the CHPG-induced regulation of intracellular Ca2+ release. In summary, the present data indicate that the mGluR5-mediated Arc activation is a protective mechanism that attenuates neurotoxicity following TBI through the regulation of intracellular Ca2+ hemostasis. The AMPAR-associated Ca2+ influx and ER Ca2+ release induced by Homer1-IP3R pathway might be involved in this protection.

Pharmacological Potential of Bioactive Peptides for the Treatment of Diseases Associated with Alzheimer's and Brain Disorders.

Bioactive peptides are a promising class of therapeutics for the treatment of diseases associated with Alzheimer's and brain disorders. These peptides are derived from naturally occurring proteins and have been shown to possess a variety of beneficial properties. They may modulate neurotransmitter systems, reduce inflammation, and improve cognitive performance. In addition, bioactive peptides have the potential to target specific molecular pathways involved in the pathogenesis of Alzheimer's and brain disorders. For example, peptides have been shown to interact with amyloid-beta, a major component of amyloid plaques found in Alzheimer's disease, and have been shown to reduce its accumulation in the brain. Furthermore, peptides have been found to modulate the activity of glutamate receptors, which are important for memory and learning, as well as to inhibit the activity of enzymes involved in the formation of toxic amyloid-beta aggregates. Finally, bioactive peptides have the potential to reduce oxidative stress and inflammation, two major components of many neurological disorders. These peptides could be used alone or in combination with traditional pharmacological treatments to improve the management of diseases associated with Alzheimer's and brain disorders.

Structural basis of positive allosteric modulation of metabotropic glutamate receptor activation and internalization

The metabotropic glutamate receptors (mGluRs) are neuromodulatory family C G protein coupled receptors which assemble as dimers and allosterically couple extracellular ligand binding domains (LBDs) to transmembrane domains (TMDs) to drive intracellular signaling. Pharmacologically, mGluRs can be targeted at the LBDs by glutamate and synthetic orthosteric compounds or at the TMDs by allosteric modulators. Despite the potential of allosteric compounds as therapeutics, an understanding of the functional and structural basis of their effects is limited. Here we use multiple approaches to dissect the functional and structural effects of orthosteric versus allosteric ligands. We find, using electrophysiological and live cell imaging assays, that both agonists and positive allosteric modulators (PAMs) can drive activation and internalization of group II and III mGluRs. The effects of PAMs are pleiotropic, boosting the maximal response to orthosteric agonists and serving independently as internalization-biased agonists across mGluR subtypes. Motivated by this and intersubunit FRET analyses, we determine cryo-electron microscopy structures of mGluR3 in the presence of either an agonist or antagonist alone or in combination with a PAM. These structures reveal PAM-driven re-shaping of intra- and inter-subunit conformations and provide evidence for a rolling TMD dimer interface activation pathway that controls G protein and beta-arrestin coupling.

Molecular mechanism of ligand gating and opening of NMDA receptor.

Glutamate transmission and activation of ionotropic glutamate receptors are the fundamental means by which neurons control their excitability and neuroplasticity1. The N-methyl-D-aspartate receptor (NMDAR) is unique among all ligand-gated channels, requiring two ligands-glutamate and glycine-for activation. These receptors function as heterotetrameric ion channels, with the channel opening dependent on the simultaneous binding of glycine and glutamate to the extracellular ligand-binding domains (LBDs) of the GluN1 and GluN2 subunits, respectively2,3. The exact molecular mechanism for channel gating by the two ligands has been unclear, particularly without structures representing the open channel and apo states. Here we show that the channel gate opening requires tension in the linker connecting the LBD and transmembrane domain (TMD) and rotation of the extracellular domain relative to the TMD. Using electron cryomicroscopy, we captured the structure of theGluN1-GluN2B(GluN1-2B) NMDAR in its open state bound to a positive allosteric modulator. This process rotates and bends the pore-forming helices in GluN1 and GluN2B, altering the symmetry of the TMD channel from pseudofourfold to twofold. Structures of GluN1-2B NMDAR in apo and single-liganded states showed that binding of either glycine or glutamate alone leads to distinct GluN1-2B dimer arrangements but insufficient tension in the LBD-TMD linker for channel opening. This mechanistic framework identifies a key determinant for channel gating and a potential pharmacological strategy for modulating NMDAR activity.

Small Structural Differences in Proline-Rich Decapeptides Have Specific Effects on Oxidative Stress-Induced Neurotoxicity and L-Arginine Generation by Arginosuccinate Synthase.

The proline-rich decapeptide 10c (Bj-PRO-10c; ENWPHPQIPP) from the Bothrops jararaca snake modulates argininosuccinate synthetase (AsS) activity to stimulate L-arginine metabolite production and neuroprotection in the SH-SY5Y cell line. The relationships between structure, interactions with AsS, and neuroprotection are little known. We evaluated the neuroprotective effects of Bj-PRO-10c and three other PROs (Bn-PRO-10a, <ENWPRPKIPP; Bn-PRO-10a-MK, <ENWPRPKIPPMK; and, Bn-PRO-10c, <ENWPRPKVPP) identified from Bitis nasicornis snake venom, with a high degree of similarity to Bj-PRO-10c, on oxidative stress-induced toxicity in neuronal PC12 cells and L-arginine metabolite generation via AsS activity regulation. Cell integrity, metabolic activity, reactive oxygen species (ROS) production, and arginase activity were examined after 4 h of PRO pre-treatment and 20 h of H2O2-induced damage. Only Bn-PRO-10a-MK and Bn-PRO-10c restored cell integrity and arginase function under oxidative stress settings, but they did not reduce ROS or cell metabolism. The MK dipeptide in Bn-PRO-10a-MK and valine (V8) in Bn-PRO-10c are important to these effects when compared to Bn-PRO-10a. Bj-PRO-10c is not neuroprotective in PC12 cells, perhaps because of their limited NMDA-type glutamate receptor activity. The PROs interaction analysis on AsS activation can be rated as follows: Bj-PRO-10c > Bn-PRO-10c > Bn-PRO-10a-MK > Bn-PRO-10a. The structure of PROs and their correlations with enzyme activity revealed that histidine (H5) and glutamine (Q7) in Bj-PRO-10c potentiated their affinity for AsS. Our investigation provides the first insights into the structure and molecular interactions of PROs with AsS, which could possibly further their neuropharmacological applications.

Pre-clinical Evidence-based Neuroprotective Potential of Naringin against Alzheimer's Disease-like Pathology: A Comprehensive Review.

Neurodegenerative disorders (NDs) are a group of progressive, chronic, and disabling disorders that are highly prevalent and the incidence is on a constant rise globally. Alzheimer's disease (AD), one of the most common neurodegenerative disorders is hallmarked by cognitive impairment, amyloid-β (Aβ) deposition, hyperphosphorylation of tau protein, cholinergic dysfunction, mitochondrial toxicity, and neurodegeneration. Available therapeutic agents only provide symptomatic relief and their use are limited due to serious side effects. Recent research has recognized flavonoids as potential multi-target biomolecules that can reduce the pathogenesis of AD. Naringin, a natural citrus flavonoid has been traditionally used to treat various NDs including AD, and has gained special attention because exhibits a neuroprotective effect by affecting numerous signaling pathways with minimum adverse effects. Naringin reduces deposition of Aβ, hyperphosphorylation of tau protein, cholinergic dysfunction, oxidative stress burden, mitochondrial toxicity, the activity of glutamate receptors, and apoptosis of the neuronal cells. Additionally, it reduces the expression of phosphorylated-P38/P38 and the NF-κB signaling pathway, showing that a wide range of molecular targets is involved in naringin's neuroprotective action. The present study describes the possible pharmacological targets, signaling pathways, and molecular mechanisms of naringin involved in neuroprotection against AD-like pathology. Based on the above pre-clinical reports it can be concluded that naringin could be an alternative therapeutic agent for the management of AD-like manifestation. Thus, there is a strong recommendation to perform more preclinical and clinical studies to develop naringin as a novel molecule that could be a multi-target drug to counteract AD.

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.

Investigating the role of miR-26b-5p and PTGS2 in schizophrenia treatment using Wendan decoction: Network pharmacology and experimental validation

IntroductionThis study aimed to identify the target of action of Wendan decoction, a classical Chinese herbal formula used for the treatment of psychiatric disorders, specifically schizophrenia, using network pharmacology. MethodsTraditional Chinese Medicine (TCM) bioinformatics and network pharmacology were employed to predict the genes regulated by miR-26b-5p and identify the active ingredients and related targets of the Wendan decoction from public databases. Key components and targets were screened by constructing a "TCM-component-target" network, followed by pathway enrichment analysis of the related targets. The expression levels of miR-26b-5p and prostaglandin-endoperoxide synthase 2 (PTGS2) in the peripheral blood of patients with schizophrenia patients and healthy individuals were determined using RT-qPCR. Molecular docking was performed to explore the interaction between the active ingredients of the Wendan decoction and key differentially expressed molecules, investigating the role of miR-26b-5p in the treatment of schizophrenia with the Wendan decoction. ResultsA total of 135 active constituents were extracted from the Wendan decoction, and 144 molecules, including PTGS2 and other derivatives, were screened for drug-target and disease-target inter-mapping. Compared to peripheral blood samples from healthy controls and patients with depression, peripheral blood samples from patients with schizophrenia patients showed low miR-26b-5p expression and elevated PTGS2 expression, with no significant difference observed in the expression between healthy controls and patients with depression. Molecular docking revealed that several active compounds were found in five of the six constituents of the Wendan decoction bound with PTGS2. Pathway enrichment analysis suggested that the Wendan decoction may have a potential therapeutic role in treating schizophrenia by regulating the circadian rhythm, N-methyl-d-aspartate glutamate receptor activity, inflammatory mediator regulation of transient receptor potential channels, and other pathways implicated in schizophrenia. ConclusionWendan decoction may treat schizophrenia via the miR-26b-5p targeting factor PTGS2 and inflammation-related pathways. miR-26b-5p, combined with PTSG2, holds the potential as a differential diagnostic marker for schizophrenia.

Promiscuous involvement of metabotropic glutamate receptors in the storage of N-methyl-d-aspartate receptor-dependent short-term potentiation.

Short- and long-term forms of N-methyl-d-aspartate receptor (NMDAR)-dependent potentiation (most commonly termed short-term potentiation (STP) and long-term potentiation (LTP)) are co-induced in hippocampal slices by theta-burst stimulation, which mimics naturally occurring patterns of neuronal activity. While NMDAR-dependent LTP (NMDAR-LTP) is said to be the cellular correlate of long-term memory storage, NMDAR-dependent STP (NMDAR-STP) is thought to underlie the encoding of shorter-lasting memories. The mechanisms of NMDAR-LTP have been researched much more extensively than those of NMDAR-STP, which is characterized by its extreme stimulation dependence. Thus, in the absence of low-frequency test stimulation, which is used to test the magnitude of potentiation, NMDAR-STP does not decline until the stimulation is resumed. NMDAR-STP represents, therefore, an inverse variant of Hebbian synaptic plasticity, illustrating that inactive synapses can retain their strength unchanged until they become active again. The mechanisms, by which NMDAR-STP is stored in synapses without a decrement, are unknown and we report here that activation of metabotropic glutamate receptors may be critical in maintaining the potentiated state of synaptic transmission. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.

A multi-ancestry cerebral cortex transcriptome-wide association study identifies genes associated with smoking behaviors.

Transcriptome-wide association studies (TWAS) have provided valuable insight in identifying genes that may impact cigarette smoking. Most of previous studies, however, mainly focused on European ancestry. Limited TWAS studies have been conducted across multiple ancestries to explore genes that may impact smoking behaviors. In this study, we used cis-eQTL data of cerebral cortex from multiple ancestries in MetaBrain, including European, East Asian, and African samples, as reference panels to perform multi-ancestry TWAS analyses on ancestry-matched GWASs of four smoking behaviors including smoking initiation, smoking cessation, age of smoking initiation, and number of cigarettes per day in GWAS & Sequencing Consortium of Alcohol and Nicotine use (GSCAN). Multiple-ancestry fine-mapping approach was conducted to identify credible gene sets associated with these four traits. Enrichment and module network analyses were further performed to explore the potential roles of these identified gene sets. A total of 719 unique genes were identified to be associated with at least one of the four smoking traits across ancestries. Among those, 249 genes were further prioritized as putative causal genes in multiple ancestry-based fine-mapping approach. Several well-known smoking-related genes, including PSMA4, IREB2, and CHRNA3, showed high confidence across ancestries. Some novel genes, e.g., TSPAN3 and ANK2, were also identified in the credible sets. The enrichment analysis identified a series of critical pathways related to smoking such as synaptic transmission and glutamate receptor activity. Leveraging the power of the latest multi-ancestry GWAS and eQTL data sources, this study revealed hundreds of genes and relevant biological processes related to smoking behaviors. These findings provide new insights for future functional studies on smoking behaviors.

Rapid Antidepressant-Like Potential of Chaihu Shugan San Depends on Suppressing Glutamate Neurotransmission and Activating Synaptic Proteins in Hippocampus of Female Mice.

To explore the rapid antidepressant potential and the underlying mechanism of Chaihu Shugan San (CSS) in female mice. Liquid chromatography mass spectrometry (LC-MS)/MS was used to determine the content of main components in CSS to determine its stability. Female C57BL/6J mice were randomly divided into 4 groups, including control (saline), vehicle (saline), CSS (4 g/kg) and ketamine (30 mg/kg) groups. Mice were subjected to irregular stress stimulation for 4 weeks to establish the chronic mild stress (CMS) model, then received a single administration of drugs. Two hours later, the behavioral tests were performed, including open field test, tail suspension test (TST), forced swimming test (FST), novelty suppression feeding test (NSF), and sucrose preference test (SPT). Western blot analysis was used to detect the expression levels of N-methyl-D-aspartate receptor (NMDA) subtypes [N-methyl-D-aspartate receptor 1 (NR1), NR2A, NR2B], synaptic proteins [synapsin1 and post synaptic density protein 95 (PSD95)], and brain-derived neurotrophic factor (BDNF). Moreover, the rapid antidepressant effect of CSS was tested by pharmacological technologies and optogenetic interventions that activated glutamate receptors, NMDA. Compared with the vehicle group, a single administration of CSS (4 g/kg) reversed all behavioral defects in TST, FST, SPT and NSF caused by CMS (P<0.05 or P<0.01). CSS also significantly decreased the expressions of NMDA subtypes (NR1, NR2A, NR2B) at 2 h in hippocampus of mice (all P<0.01). In addition, similar to ketamine, CSS increased levels of synaptic proteins and BDNF (P<0.05 or P<0.01). Furthermore, the rapid antidepressant effects of CSS were blocked by transient activation of NMDA receptors in the hippocampus (all P<0.01). Rapid antidepressant effects of CSS by improving behavioral deficits in female CMS mice depended on rapid suppression of NMDA receptors and activation of synaptic proteins.

Control of astrocytic Ca2+ signaling by nitric oxide-dependent S-nitrosylation of Ca2+ homeostasis modulator 1 channels

BackgroundAstrocytes Ca2+ signaling play a central role in the modulation of neuronal function. Activation of metabotropic glutamate receptors (mGluR) by glutamate released during an increase in synaptic activity triggers coordinated Ca2+ signals in astrocytes. Importantly, astrocytes express the Ca2+-dependent nitric oxide (NO)-synthetizing enzymes eNOS and nNOS, which might contribute to the Ca2+ signals by triggering Ca2+ influx or ATP release through the activation of connexin 43 (Cx43) hemichannels, pannexin-1 (Panx-1) channels or Ca2+ homeostasis modulator 1 (CALHM1) channels. Hence, we aim to evaluate the participation of NO in the astrocytic Ca2+ signaling initiated by stimulation of mGluR in primary cultures of astrocytes from rat brain cortex.ResultsAstrocytes were stimulated with glutamate or t-ACPD and NO-dependent changes in [Ca2+]i and ATP release were evaluated. In addition, the activity of Cx43 hemichannels, Panx-1 channels and CALHM1 channels was also analyzed. The expression of Cx43, Panx-1 and CALHM1 in astrocytes was confirmed by immunofluorescence analysis and both glutamate and t-ACPD induced NO-mediated activation of CALHM1 channels via direct S-nitrosylation, which was further confirmed by assessing CALHM1-mediated current using the two-electrode voltage clamp technique in Xenopus oocytes. Pharmacological blockade or siRNA-mediated inhibition of CALHM1 expression revealed that the opening of these channels provides a pathway for ATP release and the subsequent purinergic receptor-dependent activation of Cx43 hemichannels and Panx-1 channels, which further contributes to the astrocytic Ca2+ signaling.ConclusionsOur findings demonstrate that activation of CALHM1 channels through NO-mediated S-nitrosylation in astrocytes in vitro is critical for the generation of glutamate-initiated astrocytic Ca2+ signaling.