NR2B Subunit Research Articles

Sinapinic acid as a potential therapeutic agent for epilepsy through targeting NMDA receptors and nitrite level

Epilepsy, a widespread neural ailment considered by prolonged neuronal depolarization and repetitive discharge, has been linked to extreme stimulus of N-methyl-D-aspartate receptors (NMDARs). Despite the availability of approved anti-seizure medications (ASMs) in many developed nations, approximately 30% of epilepsy patients continue to experience drug-resistant seizures. Thus, a growing interest in discovering natural compounds as potential sources for new medications is growing. Sinapinic acid, a natural derivative of cinnamic acid found in food sources, is known for its neuroprotective properties. This study investigated how sinapinic acid interacts with NMDA receptors and its potential role in providing anticonvulsant effects. Male mice were randomly allocated into nine groups: a control group receiving normal saline (1 ml/kg), groups treated with sinapinic acid at doses of 1, 3, and 10 mg/kg, a group treated with diazepam at 10 mg/kg, a group treated with an NMDA agonist at 75 mg/kg, a group treated with an NMDA antagonist at 0.5 mg/kg, a group receiving the ineffective dose of sinapinic acid (1 mg/kg) along with the NMDA antagonist, and a group receiving the effective dose of sinapinic acid (10 mg/kg) along with the NMDA agonist. Sinapinic acid and other treatments were administered intraperitoneally 30 min prior to inducing seizures with PTZ injection. Seizure onset time was recorded following PTZ injection. Blood and brain samples were collected after anesthesia to determine serum and brain nitrite levels. Real-time PCR assessed NMDAR gene expression in the prefrontal cortex (PFC). Data were analyzed using Prism software. The time seizures began was notably extended in groups treated with sinapinic acid at doses of 3 and 10 mg/kg compared to those treated with saline (P < 0.05). Additionally, in the receiving group of an ineffective dose of sinapinic acid alongside ketamine, the beginning of seizure time was significantly prolonged compared to the group that received the ineffective dose of sinapinic acid alone (P < 0.05). Serum and prefrontal cortex (PFC) nitrite levels were significantly lower in mice treated with sinapinic acid at doses of 1, 3, and 10 mg/kg compared to the saline-treated group (P < 0.05). The gene expression of the NMDAR NR2B subunit in the PFC was decreased in groups treated with sinapinic acid at 1 and 10 mg/kg compared to the saline-treated group. Furthermore, co-administration of sinapinic acid (10 mg/kg) with NMDA resulted in significantly lower NR2A gene expression than the group treated with 10 mg/kg of sinapinic acid alone. Conversely, co-administration of ketamine with sinapinic acid (1 mg/kg) significantly increased NR2B subunit gene expression compared to the group treated with sinapinic acid at 1 mg/kg alone. Sinapinic acid showed anticonvulsant effects through reduced serum and PFC nitrite and modulation of glutamatergic signaling.

Regulating the NMDA/NR2B signaling pathway mediates anticonvulsant, antineuroinflammation, and anti-oxidative stress effects of 1,3,benzothiazole derivative 1M in pentylenetetrazole-induced kindling in mice.

Periodic epileptic episodes are the hallmark of epilepsy, a prevalent neurological disorder. Research suggests a significant correlation between neuroinflammation and oxidative stress in a variety of neurological diseases, such as epilepsy. A substantial amount of evidence supports the role of N-methyl-D-aspartate receptors (NMDARs) in the progression of epilepsy. Although several lines of research have disclosed numerous biochemical effects of early seizures, its connection with disturbed NMDAR/NR2B subunit expression remains unclear. 2-Mercaptobenzothiazole (MBT) is a vital scaffold with several biological activities, and its various substitutes show promising anti-inflammatory potential. The current study aimed to investigate the newly synthesized 1,3-(benzothiazole-2-sulfanyl)-1-(morpholine-4-yl)ethan-1-one (1M), a substituted MBT, for its neuroprotective potential in a mice model of pentylenetetrazole-induced epilepsy (PTZ), by modulating NMDA/NR2B pathway. The compound was tested for docking and simulation analysis, demonstrating a solid and stable bond with the NR2B subunit of NMDA. To ascertain the effects of 1M, as well as to further illustrate its mechanism of neuroprotection via NMDA/NR2B in PTZ-induced kindling model, mice of either sex were given two doses of test compound, 1M (10mg/kg and 20mg/kg). The behavioral assessments were evaluated using open-field, Y-maze, and elevated-plus maze tests, which indicated improved behavioral alterations caused by PTZ after 1M treatment. The antioxidant profiling was done by estimating glutathione-S-transferase (GST), catalase (CAT), reduced glutathione (GSH), and LPO (lipid peroxidation) in hippocampal tissues, where the test compound 1M significantly restored the depleted antioxidants, showcasing its antioxidant potential. Moreover, the cellular morphological damages induced by PTZ were detected by H&E staining, which was rescued after 1M administration. Furthermore, the activation of the inflammatory pathway was confirmed by quantitative analysis of inflammatory mediators tumor necrotic factor (TNF-α), nuclear factor kappa B (NF-κB), and cylooxegenase2 (COX-2) by enzyme-linked immunosorbent assay (ELISA), where 1M administration significantly ameliorated their expression. Furthermore, to demonstrate the involvement of the NR2B pathway, NR2B-antagonist ifenprodil was employed, and results were further confirmed through RT-PCR analysis. Our results, when considered collectively, indicate that 1M may act by inhibiting the NR2B subunit of the NMDA receptor, subsequently mitigating downstream oxidative stress and inflammatory mediators through various pathways.

Chemical characterization, neuroprotective effect, and in-silico evaluation of the petroleum ether extract of three palm tree species against glutamate-induced excitotoxicity in rats

The burden of neurological disorders is growing substantially with limited therapeutic options, urging the consideration and assessment of alternative strategies. In this regard, we aimed to elucidate the phytochemical profile of the petroleum ether extract (PEE) of three palm tree species: Aiphanes eggersii Burret, Carpoxylon macrospermum H. Wendl. & Drude, and Jubaeopsis caffra Becc. (Family Arecaceae), and to evaluate their neuroprotective effect in monosodium glutamate (MSG)-induced excitotoxicity model for the first time. We identified a total of 48, 18, and 45 compounds in A. eggersii, C. macrospermum, and J. caffra, constituting 79.41 %, 60.45 %, and 76.35 % of the total detected compounds, respectively. A. eggersii extract was rich in the methyl esters of fatty acids (65.08 %) especially methyl dodecanoate (17.72 %). C. macrospermum was exclusively prolific by the triterpene 3β-methoxy-d:c-friedo-b’:a'-neogammacer-9(11)-ene (40.36 %), while J. caffra was noticeable by hydrocarbons (30.14 %) and lupeol derivatives (19.79 %). The biochemical and histopathological analysis showed that the tested extracts significantly reduced the oxidative stress, especially at the highest tested dose (1000 mg/kg). The extracts also reduced the activity of induced nitric oxide synthetase, Ca+2 level, and NR2B subunit expression and attenuated apoptosis and DNA damage. The docking results show that most active natural compounds bind to SOD-1 and NR2B-NMDARs, verifying the credibility of the biological findings. To sum up, the PEE of the three investigated palm tree species possessed a unique blend of lipophilic bioactive constituents that exert promising neuroprotective potential against MSG-induced excitoneurotoxicity. However, further preclinical investigation and pharmaceutical formulation are needed.

Contrasting Effects of an Atherogenic Diet and High-Protein/Unsaturated Fatty Acids Diet on the Accelerated Aging Mouse Model SAMP8 Phenotype.

Background/Objectives: Aging has been extensively studied, with a growing interest in memory impairment by a neurobiological approach. Mitochondrial dysfunction is a hallmark of aging, contributing to the aging phenotype; therefore, mitochondrial interventions seem fundamental. The diet is a physiological approximation for modifying mitochondria, which could impact the age-related phenotype. Methods: We studied two diets with low-carbohydrate and high-fat compositions, differing in the amount of protein and the fat type disposable-the atherogenic diet Cocoa (high protein/high saturated fat/high cholesterol) and the South Beach diet (very high-protein/high-unsaturated fat)-on oxidative stress, mitochondrial state, and hippocampus-dependent memory in 3-month-old Senescence-Accelerated Mouse Model (SAMP8) seed over 3 months to determine their pro- or anti-aging effects. Results: Despite its bad reputation, the Cocoa diet reduces the reactive oxygen species (ROS) content without impacting the energy state and hippocampus-dependent spatial acuity. In contrast to the beneficial impact proposed for the South Beach diet, it induced a pro-aging phenotype, increasing oxidative damage and the levels of NR2B subunit of the NMDA, impairing energy and spatial acuity. Surprisingly, despite the negative changes observed with both diets, this led to subtle memory impairment, suggesting the activation of compensatory mechanisms preventing more severe cognitive decline. Conclusions: Our results demonstrated that diets usually considered good could be detrimental to the onset of aging. Also, probably due to the brain plasticity of non-aged animals, they compensate for the damage, preventing a more aggravated phenotype. Nevertheless, these silent changes could predispose or increase the risk of suffering pathologies at advanced age.

Postnatal Neuronal Nogo-A Knockdown Decreased the Message of Glutamatergic Synaptic Proteins.

It is well known that oligodendrocyte-associated Nogo-A protein is an important regulator of axonal outgrowth and an important inhibitor of functional recovery and anatomical plasticity after central nervous system (CNS) injury. Abundant studies of oligodendrocyte-associated Nogo-A function in the uninjured rodent have suggested a role in neuronal development and synaptic function. On the other hand, the roles of neuron-associated (i.e., neuronal) Nogo-A have not been fully investigated. We have previously shown that neuronal Nogo-A influence dendritic spine density and morphology in pyramidal neurons of the intact neocortex. To further examine the role of neuronal Nogo-A in this synaptic population, we designed an RNAi directed against Nogo-A, delivered to the developing rat sensorimotor cortex using a neurotropic viral vector adeno-associated virus (AAV) 2/8. We examined the transduced neocortex for molecules important for synaptic plasticity, including N-Methyl-D-Aspartate (NMDA) receptor subunits GRIN2A; glutamate receptor subunit epsilon-1 (NR2A), and GRIN2B; glutamate receptor subunit epsilon-2 (NR2B), as well as postsynaptic density-95 (PSD-95). Furthermore, we also determined the density of excitatory synapses by examining the presynaptic protein vesicular glutamate transporter 1 (vGLut1) as a marker for potential excitatory synapses. Our results showed that neuronal Nogo-A knockdown in postnatal pyramidal neurons of the sensorimotor cortex led to a significant decrease in NMDA receptor subunits NR2A and NR2B messenger RNA when examined as adults. However, there was no difference in PSD-95 expression in comparison to controls. In addition, the decrease in the number of vGlut1(+) puncta on branches of apical dendrites of pyramidal neurons indicated the loss of synapses that have a strong influence on direct current entering the dendrite. Taken together, these results indicate that neuronal Nogo-A may regulate synaptic plasticity by modulating the components of excitatory synapses. This finding represents a novel role in excitatory synaptic formation for neuronal Nogo-A in developing neurons of the uninjured CNS.

Recombinant chitinase-3-like protein 1 alleviates learning and memory impairments via M2 microglia polarization in postoperative cognitive dysfunction mice.

Postoperative cognitive dysfunction is a severe complication of the central nervous system that occurs after anesthesia and surgery, and has received attention for its high incidence and effect on the quality of life of patients. To date, there are no viable treatment options for postoperative cognitive dysfunction. The identification of postoperative cognitive dysfunction hub genes could provide new research directions and therapeutic targets for future research. To identify the signaling mechanisms contributing to postoperative cognitive dysfunction, we first conducted Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses of the Gene Expression Omnibus GSE95426 dataset, which consists of mRNAs and long non-coding RNAs differentially expressed in mouse hippocampus 3 days after tibial fracture. The dataset was enriched in genes associated with the biological process "regulation of immune cells," of which Chill was identified as a hub gene. Therefore, we investigated the contribution of chitinase-3-like protein 1 protein expression changes to postoperative cognitive dysfunction in the mouse model of tibial fracture surgery. Mice were intraperitoneally injected with vehicle or recombinant chitinase-3-like protein 1 24 hours post-surgery, and the injection groups were compared with untreated control mice for learning and memory capacities using the Y-maze and fear conditioning tests. In addition, protein expression levels of proinflammatory factors (interleukin-1β and inducible nitric oxide synthase), M2-type macrophage markers (CD206 and arginase-1), and cognition-related proteins (brain-derived neurotropic factor and phosphorylated NMDA receptor subunit NR2B) were measured in hippocampus by western blotting. Treatment with recombinant chitinase-3-like protein 1 prevented surgery-induced cognitive impairment, downregulated interleukin-1β and nducible nitric oxide synthase expression, and upregulated CD206, arginase-1, pNR2B, and brain-derived neurotropic factor expression compared with vehicle treatment. Intraperitoneal administration of the specific ERK inhibitor PD98059 diminished the effects of recombinant chitinase-3-like protein 1. Collectively, our findings suggest that recombinant chitinase-3-like protein 1 ameliorates surgery-induced cognitive decline by attenuating neuroinflammation via M2 microglial polarization in the hippocampus. Therefore, recombinant chitinase-3-like protein 1 may have therapeutic potential for postoperative cognitive dysfunction.

Anxiolytic effects of Enterococcus faecalis 2001 on a mouse model of colitis

Ulcerative colitis (UC) is a refractory inflammatory bowel disease, which is known to cause psychiatric disorders such as anxiety and depression at a high rate in addition to peripheral inflammatory symptoms. However, the pathogenesis of these psychiatric disorders remains mostly unknown. While prior research revealed that the Enterococcus faecalis 2001 (EF-2001) suppressed UC-like symptoms and accompanying depressive-like behaviors, observed in a UC model using dextran sulfate sodium (DSS), whether it has an anxiolytic effect remains unclear. Therefore, we examined whether EF-2001 attenuates DSS-induced anxiety-like behaviors. Treatment with 2% DSS for seven days induced UC-like symptoms and anxiety-like behavior through the hole-board test, increased serum lipopolysaccharide (LPS) and corticosterone concentration, and p-glucocorticoid receptor (GR) in the prefrontal cortex (PFC), and decreased N-methyl-d-aspartate receptor subunit (NR) 2A and NR2B expression levels in the PFC. Interestingly, these changes were reversed by EF-2001 administration. Further, EF-2001 administration enhanced CAMKII/CREB/BDNF-Drebrin pathways in the PFC of DSS-treated mice, and labeling of p-GR, p-CAMKII, and p-CREB showed colocalization with neurons. EF-2001 attenuated anxiety-like behavior by reducing serum LPS and corticosterone levels linked to the improvement of UC symptoms and by facilitating the CAMKII/CREB/BDNF-Drebrin pathways in the PFC. Our findings suggest a close relationship between UC and anxiety.

NMDA receptor within nucleus accumbens shell regulates propofol self-administration through D1R/ERK/CREB signalling pathway.

Addictive properties of propofol have been demonstrated in both humans and animals. The nucleus accumbens (NAc) shell (NAsh) in the brain, along with the interactions between N-methyl-D-aspartate receptor (NMDAR) and the dopamine D1 receptor (D1R), as well as their downstream ERK/CREB signalling pathway in the NAc, are integral in regulating reward-seeking behaviour. Nevertheless, it remains unclear whether NMDARs and the NMDAR-D1R/ERK/CREB signalling pathway in the NAsh are involved in mediating propofol addiction. To investigate it, we conducted experiments with adult male Sprague-Dawley rats to establish a model of propofol self-administration behaviour. Subsequently, we microinjected D-AP5 (a competitive antagonist of NMDARs, 1.0-4.0μg/0.3μL/site) or vehicle into bilateral NAsh in rats that had previously self-administered propofol to examine the impact of NMDARs within the NAsh on propofol self-administration behaviour. Additionally, we examined the protein expressions of NR2A and NR2B subunits, and the D1R/ERK/CREB signalling pathways within the NAc. The results revealed that propofol administration behaviour was enhanced by D-AP5 pretreatment in NAsh, accompanied by elevated expressions of phosphorylation of NR2A (Tyr1246) and NR2B (Tyr1472) subunits. There were statistically significant increases in the expressions of D1Rs, as well as in the phosphorylated ERK1/2 (p-ERK1/2) and CREB (p-CREB). This evidence substantiates a pivotal role of NMDARs in the NAsh, with a particular emphasis on the NR2A and NR2B subunits, in mediating propofol self-administration behaviour. Furthermore, it suggests that this central reward processing mechanism may operate through the NMDAR-D1R/ERK/CREB signal transduction pathway.

Dual Role of NMDAR Containing NR2A and NR2B Subunits in Alzheimer's Disease.

Alzheimer's disease (AD) is the main cause of dementia worldwide. Given that learning and memory are impaired in this pathology, NMDA receptors (NMDARs) appear as key players in the onset and progression of the disease. NMDARs are glutamate receptors, mainly located at the post-synapse, which regulate voltage-dependent influx of calcium into the neurons. They are heterotetramers, and there are different subunits that can be part of the receptors, which are usually composed of two obligatory GluN1 subunits plus either two NR2A or two NR2B subunits. NR2A are mostly located at the synapse, and their activation is involved in the expression of pro-survival genes. Conversely, NR2B are mainly extrasynaptic, and their activation has been related to cell death and neurodegeneration. Thus, activation of NR2A and/or inactivation of NR2B-containing NMDARS has been proposed as a therapeutic strategy to treat AD. Here, we wanted to investigate the main differences between both subunits signalling in neuronal primary cultures of the cortex and hippocampus. It has been observed that Aβ induces a significant increase in calcium release and also in MAPK phosphorylation signalling in NR2B-containing NMDAR in cortical and hippocampal neurons. However, while NR2A-containing NMDAR decreases neuronal death and favours cell viability after Aβ treatment, NR2B-containing NMDAR shows higher levels of cytotoxicity and low levels of neuronal survival. Finally, it has been detected that NMDAR has no effect on pTau axonal transport. The present results demonstrate a different role between GluNA and GluNB subunits in neurodegenerative diseases such as Alzheimer's.

Computational Modeling of Extrasynaptic NMDA Receptors: Insights into Dendritic Signal Amplification Mechanisms.

Dendritic structures play a pivotal role in the computational processes occurring within neurons. Signal propagation along dendrites relies on both passive conduction and active processes related to voltage-dependent ion channels. Among these channels, extrasynaptic N-methyl-D-aspartate channels (exNMDA) emerge as a significant contributor. Prior studies have mainly concentrated on interactions between synapses and nearby exNMDA (100 nm-10 µm from synapse), activated by presynaptic membrane glutamate. This study concentrates on the correlation between synaptic inputs and distal exNMDA (>100 µm), organized in clusters that function as signal amplifiers. Employing a computational model of a dendrite, we elucidate the mechanism underlying signal amplification in exNMDA clusters. Our findings underscore the pivotal role of the optimal spatial positioning of the NMDA cluster in determining signal amplification efficiency. Additionally, we demonstrate that exNMDA subunits characterized by a large conduction decay constant. Specifically, NR2B subunits exhibit enhanced effectiveness in signal amplification compared to subunits with steeper conduction decay. This investigation extends our understanding of dendritic computational processes by emphasizing the significance of distant exNMDA clusters as potent signal amplifiers. The implications of our computational model shed light on the spatial considerations and subunit characteristics that govern the efficiency of signal amplification in dendritic structures, offering valuable insights for future studies in neurobiology and computational neuroscience.

Prenatal treatment with corticosterone via maternal injection induces learning and memory impairments via delaying postsynaptic development in hippocampal CA1 neurons of rats.

Previously, we reported that prenatal exposure to high corticosterone induced attention-deficit hyperactivity disorder (ADHD)-like behaviors with cognitive deficits after weaning. In the present study, cellular mechanisms underlying cortisol-induced cognitive dysfunction were investigated using rat pups (Corti.Pups) born from rat mothers that were repetitively injected with corticosterone during pregnancy. In results, Corti.Pups exhibited the failure of behavioral memory formation in the Morris water maze (MWM) test and the incomplete long-term potentiation (LTP) of hippocampal CA1 neurons. Additionally, glutamatergic excitatory postsynaptic currents (EPSCs) were remarkably suppressed in Corti.Pups compared to normal rat pups. Incomplete LTP and weaker EPSCs in Corti.Pups were attributed to the delayed postsynaptic development of CA1 neurons, showing a higher expression of NR2B subunits and lower expression of PSD-95 and BDNF. These results indicated that the prenatal treatment with corticosterone to elevate cortisol level might potently downregulate the BDNF-mediated signaling critical for the synaptic development of hippocampal CA1 neurons during brain development, and subsequently, induce learning and memory impairment. Our findings suggest a possibility that the prenatal dysregulation of cortisol triggers the epigenetic pathogenesis of neurodevelopmental psychiatric disorders, such as ADHD and autism.

Ciprofol alleviates remifentanil-induced hyperalgesia by regulating α2GABAARs, NR2B, and P-CaMKIIα levels in the spinal cord and hippocampus.

Several studies have shown that propofol administration during surgery effectively attenuates remifentanil-induced hyperalgesia (RIH). Ciprofol, a novel intravenous sedative agent analogous to propofol, has not yet been proven efficacious in alleviating RIH. The present study aimed to investigate the effect of ciprofol on RIH and the possible mechanisms involved. The RIH model was established by an infusion of remifentanil (1 μg·kg-1·min-1) 60min in rats with incisional pain. Ciprofol (0.1, 0.25, and 0.4 mg·kg-1·min-1) was simultaneously infused to evaluate its effect on RIH. The antinociception of ciprofol was verified by measured paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL). γ-aminobutyric acid type A receptor α2 subunit (α2GABAAR), N-methyl-d-aspartate receptor NR2B subunit (NR2B), calcium/calmodulin-dependent protein kinase II α (CaMKIIα), and phosphorylated CaMKIIα (P-CaMKIIα) in the spinal cord and hippocampus of rats were assessed by western blotting and immunohistochemistry. The results showed that ciprofol dose-dependently increased PWMT and PWTL values in RIH rats. Moreover, ciprofol upregulated α2GABAAR and downregulated NR2B and P-CaMKIIα in the rat spinal cord and hippocampus. Ciprofol alleviates RIH effectively, and the anti-hyperalgesic mechanisms may involve increasing α2GABAAR levels and decreasing NR2B and P-CaMKIIα levels in the spinal cord and hippocampus.

Repeated Morphine Exposure Alters Temporoamonic-CA1 Synaptic Plasticity in Male Rat Hippocampus

In this study, the electrophysiological and biochemical consequences of repeated exposure to morphine in male rats on glutamatergic synaptic transmission, synaptic plasticity, the expression of GABA receptors and glutamate receptors at the temporoammonic-CA1 synapse along the longitudinal axis of the hippocampus (dorsal, intermediate, ventral, DH, IH, VH, respectively) were investigated. Slice electrophysiological methods, qRT-PCR, and western blotting techniques were used to characterize synaptic plasticity properties. We showed that repeated morphine exposure (RME) reduced excitatory synaptic transmission and ability for long-term potentiation (LTP) in the VH as well as eliminated the dorsoventral difference in paired-pulse responses. A decreased expression of NR2B subunit in the VH and an increased expression GABAA receptor of α1 and α5 subunits in the DH were observed following RME. Furthermore, RME did not affect the expression of NR2A, AMPA receptor subunits, and γ2GABAA and GABAB receptors in either segment of the hippocampus. In sum, the impact of morphine may differ depending on the region of the hippocampus studied. A distinct change in the short- and long-term synaptic plasticity along the hippocampus long axis due to repeated morphine exposure, partially mediated by a change in the expression profile of glutamatergic receptor subunits. These findings can be useful in further understanding the cellular mechanism underlying deficits in information storage and, more generally, cognitive processes resulting from chronic opioid abuse.

NMDA Receptors Regulate Oxidative Damage in Keratinocytes during Complex Regional Pain Syndrome in HaCaT Cells and Male Rats.

Complex regional pain syndrome (CRPS), a type of primary chronic pain, occurs following trauma or systemic disease and typically affects the limbs. CRPS-induced pain responses result in vascular, cutaneous, and autonomic nerve alterations, seriously impacting the quality of life of affected individuals. We previously identified the involvement of keratinocyte N-methyl-d-asparagic acid (NMDA) receptor subunit 2 B (NR2B) in both peripheral and central sensitizations in CRPS, although the mechanisms whereby NR2B functions following activation remain unclear. Using an in vivo male rat model of chronic post-ischemia pain (CPIP) and an in vitro oxygen-glucose deprivation/reoxygenation (OGD/R) cell model, we discovered that oxidative injury occurs in rat keratinocytes and HaCaT cells, resulting in reduced cell viability, mitochondrial damage, oxidative damage of nucleotides, and increased apoptosis. In HaCaT cells, OGD/R induced increases in intracellular reactive oxygen species levels and disrupted the balance between oxidation and antioxidation by regulating a series of antioxidant genes. The activation of NMDA receptors via NMDA exacerbated these changes, whereas the inhibition of the NR2B subunit alleviated them. Co-administration of ifenprodil (an NR2B antagonist) and NMDA (an NMDA receptor agonist) during the reoxygenation stage did not result in any significant alterations. Furthermore, intraplantar injection of ifenprodil effectively reversed the altered gene expression that was observed in male CPIP rats, thereby revealing the potential mechanisms underlying the therapeutic effects of peripheral ifenprodil administration in CRPS. Collectively, our findings indicate that keratinocytes undergo oxidative injury in CRPS, with NMDA receptors playing regulatory roles.

Bilirubin impairs neuritogenesis and synaptogenesis in NSPCs by downregulating NMDAR-CREB-BDNF signaling.

Neonatal jaundice is one of the most common disorders in the first 2 wk after birth. Unconjugated bilirubin (UCB) is neurotoxic and can cause neurological dysfunction; however, the underlying mechanisms remain unclear. Neurogenesis, neuronal growth, and synaptogenesis are exuberant in the early postnatal stage. In this study, the impact of UCB on neuritogenesis and synaptogenesis in the early postnatal stage was evaluated both in vitro and in vivo. Primary culture neuronal stem and progenitor cells (NSPCs) were treated with UCB during differentiation, and then the neurite length and synapse puncta were measured. In the bilirubin encephalopathy (BE) animal model, DCX+-marked developing neurons were used to detect apical length and dendritic arborization. According to the data, UCB significantly reduced neurite length and synapse density, as well as decreased the apical dendrite length and dendritic arborization. Furthermore, the NMDAR subunit NR2B was downregulated in NSPCs, while pCREB expression in the hippocampus progressively decreased during disease progression in the BE model. Next, we tested the expression of NR2B, pCREB, mBDNF, and p-mTOR in NSPCs in vitro, and found that UCB treatment reduced the expression of these proteins. In summary, this suggests that UCB causes chronic neurological impairment and is related to the inhibition of NMDAR-CREB-BDNF signaling in NSPCs, which is associated with reduced neuritogenesis and synaptogenesis. This finding may inspire the development of novel pharmaceuticals and treatments.

Back Cover Image

ON THE BACK COVER: Schematic illustration that shows: In pathology, Tau (in green) targets the tyrosine kinase Fyn (yellow) to dendritic spines, where it phosphorylates subunit NR2b of the NMDA receptor (NMDAR, dark blue at the postsynaptic density), which leads to recruitment of PSD‐95 (light blue) and formation of NMDAR/PSD95 complexes. Aβ oligomers (orange, extracellular) induce excitotoxicity by signalling through NMDAR/PSD95 complexes.Credit: Alison Carlisle, Queensland Brain Institute, The University of Queensland.image

Protective effects of the salt-induced kinase inhibitor HG-9-91-01 on sepsis-associated cognitive dysfunction in mice and the underlying mechanisms.

Sepsis-associated cognitive dysfunction is a common complication in patients with sepsis and lack of effective treatment. Its pathological mechanisms remain unclear. Salt-induced kinase (SIK) is an important molecule in the regulation of metabolism, immunity, and inflammatory response. It is associated with the development of many neurological diseases. This study aims to investigate the expression of SIK in the hippocampus of septic mice, and to evaluate the role and mechanism of the SIK inhibitor HG-9-91-01 in sepsis-associated cognitive dysfunction. Firstly, C57BL/6 mice were randomly divided into a control group (Con group) and a sepsis model group [lipopolysaccharide (LPS) group]. The model group was injected intraperitoneally with LPS at a dose of 8 mg/kg and the Con group was injected with an equal volume of normal saline. Hippocampal tissues were harvested at 1, 3, and 6 days after injection and the expressions of SIK1, SIK2, and SIK3 were detected by real-time fluorescence quantitative PCR (qPCR) and Western blotting. Secondly, C57BL/6 mice were randomly divided into a Con group, a LPS group, and a SIK inhibitor group (HG group). The LPS and HG groups were injected with LPS to establish a sepsis model; in the HG group, HG-9-91-01 (10 mg/kg) was injected intraperitoneally at 3-6 days after LPS injection, and the LPS group was injected with the same volume of vehicle. Cognitive function was assessed at 7-11 days after LPS injection using the Morris water maze (MWM). Hippocampal tissues were harvested after the behavioral tests, and the mRNA levels of inflammatory factors and microglial markers were assessed by qPCR. The protein levels of inducible nitric oxide synthase (iNOS), CD68, ionized calcium binding adaptor molecule 1 (Iba-1), N-methyl-D-aspartate (NMDA) receptor (NR) subunit, cAMP response element-binding protein (CREB)-regulated transcription coactivator 1 (CRTC1), and insulin-like growth factor 1 (IGF-1) were detected by Western blotting. Immunohistochemistry (IHC) was used to detect the expression of Iba-1 positive cells in the CA1, CA3 and dentate gyrus (DG) of the hippocampus, followed by Sholl analysis. Compared with the Con group, the mRNA and protein levels of SIK1, SIK2, and SIK3 in the hippocampus were increased in the LPS group (all P<0.05). Compared with the Con group, mice in the LPS group had a significantly longer escape latency, a lower percentage of target quadrant dwell time and a reduced locomotor speed (all P<0.05); the HG group had a decreased escape latency and an increased percentage of time spent in the target quadrant in comparison with the LPS group (both P<0.05). The mRNA levels of inflammatory factors [tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6)], and the M1-type microglial markers iNOS and CD68 in the hippocampus of the LPS group were increased in comparison with the Con group, while the M2-type microglial markers CD206 and arginase-1 (Arg-1) were decreased. Compared with the LPS group, the mRNA levels of TNF-α, IL-1β, IL-6, and iNOS were downregulated, while the levels of CD206 and Arg-1 were upregulated in the HG group (all P<0.05). The protein levels of iNOS, CD68, and Iba-1 in the hippocampus of the LPS group were increased in comparison with the Con group, but they were downregulated in the HG group in comparison with the LPS group (all P<0.05). The number of Iba-1 positive cells in CA1, CA3, and DG of the hippocampus was increased in the LPS group in comparison with the Con group, but they were decreased in the HG group in comparison with the LPS group (all P<0.05). Sholl analysis showed that the number of intersections at all radii between 8-38 µm from the microglial soma was decreased in the LPS group in comparison with the Con group (all P<0.05). Compared with the LPS group, the number of intersections at all radii between 14-20 µm was significantly increased in the HG group (all P<0.05). The protein levels of NR subunit NR1, NR2A, NR2B, and IGF-1 were downregulated in the hippocampus of the LPS group in comparison with the Con group, while the expression of phosphorylated CRTC1 (p-CRTC1) was increased. Compared with the LPS group, the levels of NR1, NR2A, NR2B, and IGF-1 were upregulated, while p-CRTC1 was downregulated in the HG group (all P<0.05). SIK expression is upregulated in the hippocampus of septic mice. The SIK inhibitor HG-9-91-01 ameliorates sepsis-associated cognitive dysfunction in mice, and the mechanism may involve in the activation of the CRTC1/IGF-1 pathway, inhibition of neuroinflammation, and enhancement of synaptic plasticity.

Prolonged Zaleplon Treatment Increases the Expression of Proteins Involved in GABAergic and Glutamatergic Signaling in the Rat Hippocampus.

Zaleplon is a positive allosteric modulator of the γ-aminobutyric acid (GABA)A receptor approved for the short-term treatment of insomnia. Previous publications on zaleplon have not addressed the proteins involved in its mechanism of action but have mostly referred to behavioral or pharmacological studies. Since both GABAergic and glutamatergic signaling have been shown to regulate wakefulness and sleep, we examined the effects of prolonged zaleplon treatment (0.625 mg/kg for 5 days) on these systems in the hippocampus of male Wistar rats. Western blot and immunohistochemical analyses showed that the upregulated components of GABAergic signaling (glutamate decarboxylase, vesicular GABA transporter, GABA, and α1 subunit of the GABAA receptor) were accompanied by increased protein levels in the glutamatergic system (vesicular glutamate transporter 1 and NR1, NR2A, and NR2B subunits of N-methyl-d-aspartate receptor). Our results, showing that zaleplon enhances GABA neurotransmission in the hippocampus, were not surprising. However, we found that treatment also increased glutamatergic signaling. This could be the result of the downregulation of adenosine A1 receptors, important modulators of the glutamatergic system. Further studies are needed to investigate the effects of the zaleplon-induced increase in hippocampal glutamatergic neurotransmission and the possible involvement of the adenosine system in zaleplon's mechanism of action.

The extent of Lead‐induced Pathogenesis of Alzheimer’s disease, Synaptic Dysfunction and Cognitive Impairment in Rats

AbstractBackgroundThe hallmarks of Alzheimer’s disease (AD), like amyloid plaques and neurofibrillary tangles, are constituted of amyloid beta (Aβ) peptide and phosphorylated tau, respectively. Many studies reported the relationship between lead exposure and the progression of AD. However, the extent of lead‐induced pathogenesis and changes in proteins regulating synaptic plasticity in AD is lacking. The proposed study is designed to evaluate the pathogenesis of AD, synaptic dysfunction and cognitive impairment following lead exposure in rats.MethodThirty (30) Wistar rats (3 weeks old) will be obtained, acclimatized for one week, and randomly divided into five groups (n = 6). The rats will receive distilled deionized water containing 0% lead acetate [Pb2+] (ddH2O) or 0.5% [Pb2+] (ddH2O + 0.5% Pb2+) solution with a standard rat diet. Group I (baseline) will receive ddH2O for three (3) weeks. Group II (control) will receive ddH2O for nine (9) weeks. Groups III, IV, and V will receive (ddH2O + 0.5% Pb2+) solution for 3, 6, and 9 weeks respectively. Cognitive function will be conducted using 8‐ARWM as well as object recognition tests. The hippocampus will be extracted for immunohistochemical and biochemical studies. The levels of β‐secretase, Aβ42, tau protein (p‐tau), NMDAR subunit NR2B, postsynaptic density protein 95 (PSD‐95), Synaptophysin (SYP), and brain‐derived neurotrophic factor (BDNF) will be determined using Enzyme‐linked immunosorbent assay (ELISA) method. The expression levels of Aβ42, neurofibrillary tangle (NFT), NR2B, PSD‐95, and SYN will be determined using the immunohistochemical method. The expression of β‐secretase and BDNF will be determined using quantitative real‐time PCR.ResultLead could affect the levels of β‐secretase, Aβ42, p‐tau, NR2B, PSD‐95, SYP BDNF; the expression of Aβ42, NFT, NR2B, PSD‐95, SYN, and BDNF; and cognitive function.ConclusionThe results could reveal the extent to which lead‐induced pathogenesis, synaptic dysfunction and cognitive impairment in AD

Multivalent Tau/PSD-95 interactions arrest in vitro condensates and clusters mimicking the postsynaptic density

Alzheimer’s disease begins with mild memory loss and slowly destroys memory and thinking. Cognitive impairment in Alzheimer’s disease has been associated with the localization of the microtubule-associated protein Tau at the postsynapse. However, the correlation between Tau at the postsynapse and synaptic dysfunction remains unclear. Here, we show that Tau arrests liquid-like droplets formed by the four postsynaptic density proteins PSD-95, GKAP, Shank, Homer in solution, as well as NMDA (N-methyl-D-aspartate)-receptor-associated protein clusters on synthetic membranes. Tau-mediated condensate/cluster arrest critically depends on the binding of multiple interaction motifs of Tau to a canonical GMP-binding pocket in the guanylate kinase domain of PSD-95. We further reveal that competitive binding of a high-affinity phosphorylated peptide to PSD-95 rescues the diffusional dynamics of an NMDA truncated construct, which contains the last five amino acids of the NMDA receptor subunit NR2B fused to the C-terminus of the tetrameric GCN4 coiled-coil domain, in postsynaptic density-like condensates/clusters. Taken together, our findings propose a molecular mechanism where Tau modulates the dynamic properties of the postsynaptic density.