NMDAR2B Research Articles

GluR2 can Drive Neuroinflammation and Cognitive Impairments Following Peripherally Repeated Lipopolysaccharide Exposures.

Neuroinflammation is being increasingly recognized as a vital factor in the development of various neurological and neuropsychiatric diseases. Lipopolysaccharides (LPS), an outer membrane component of gram-negative bacteria, can trigger innate immune responses, resulting in neuroinflammation and subsequent cognitive deficits. The expression of glutamate receptors (GluRs) on glial cells can induce glial activation. Therefore, we hypothesized that repeated LPS exposure can increase GluR levels, promoting microglial activation and ultimately affecting synaptic plasticity and cognitive function. In this study, C57/BL6 mice were repeatedly exposed to LPS to construct a neuroinflammation animal model. The levels of GluRs, inflammatory cytokines, ionized calcium-binding adaptor molecule 1, postsynaptic density protein 95, synaptophysin 38, NMDA receptor 2A, and NMDA receptor 2B (GluN2B) were measured in the hippocampi. Furthermore, dendritic spine density in the CA1 hippocampal region was determined. Repeated LPS exposure induced cognitive impairments and microglial activation and increased GluR1 and GluR2 levels. This was accompanied by a significant decrease in GluN2B expression and dendritic spine density in the hippocampi. However, CFM-2, an α-amino-3- hydroxy-5-methyl-4-isoxazolepropionate receptor antagonist, reversed these anomalies. Furthermore, minocycline, a microglial inhibitor, reversed these anomalies and downregulated GluR2 but not GluR1 expression. In summary, we demonstrated that GluR2 plays an essential role in microglia-induced neuroinflammation, resulting in synaptic plasticity and cognitive impairment induced by repeated exposure to LPS.

Novel mechanisms of Anshen Dingzhi prescription against PTSD: Inhibiting DCC to modulate synaptic function and inflammatory responses

Ethnopharmacological relevanceAnshen Dingzhi prescription (ADP), documented in “Yi Xue Xin Wu”, is a famous prescription for treating panic-related mental disorders such as post-traumatic stress disorder (PTSD). However, the underlying mechanism remains unclear. Aim of the studyThis study aimed to investigate the mechanisms by which ADP intervened in PTSD-like behaviors. MethodsA mouse model of single prolonged stress (SPS) was established to evaluate the ameliorative effects and mechanisms of ADP on PTSD. Behavioral tests were used to assess PTSD-like behaviors in mice; transmission electron microscopy was used to observe changes in the ultrastructure of hippocampal synapses, and western blot, immunofluorescence, and ELISA were used to detect the expression of hippocampal deleted in colorectal cancer (DCC) and downstream Ras-related C3 botulinum toxin substrate 1 (Rac1) - P21-activated kinase 1 (PAK1) signal, as well as levels of synaptic proteins and inflammatory factors. Molecular docking technology simulated the binding of potential brain-penetrating components of ADP to DCC. ResultsSPS induced PTSD-like behaviors in mice and increased expression of hippocampal netrin-1 (NT-1) and DCC on the 14th day post-modeling, with concurrent elevation in serum NT-1 levels. Simultaneously, SPS also decreased p-Rac1 level and increased p-PAK1 level, the down-stream molecules of DCC. Lentiviral overexpression of DCC induced or exacerbated PTSD-like behaviors in control and SPS mice, respectively, whereas neutralization antibody against NT-1 reduced DCC activation and ameliorated PTSD-like behaviors in SPS mice. Interestingly, downstream Rac1-PAK1 signal was altered according to DCC expression. Moreover, DCC overexpression down-regulated N-methyl-d-aspartate (NMDA) receptor 2A (GluN2A) and postsynaptic density 95 (PSD95), up-regulated NMDA receptor 2B (GluN2B) and increased neuroinflammatory responses. Administration of ADP (36.8 mg/kg) improved PTSD-like behaviors in the SPS mice, suppressed hippocampal DCC, and downstream Rac1-PAK1 signal, upregulated GluN2A and PSD95, downregulated GluN2B, and reduced levels of inflammatory factors NOD-like receptor protein 3 (NLRP3), nuclear factor kappa-B (NF-κB) and interleukin-6 (IL-6). Importantly, DCC overexpression could also reduce the ameliorative effect of ADP on PTSD. Additionally, DCC demonstrated a favorable molecular docking pattern with the potential brain-penetrating components of ADP, further suggesting DCC as a potential target of ADP. ConclusionOur data indicate that DCC is a key target for the regulation of synaptic function and inflammatory response in the onset of PTSD, and ADP likely reduces DCC to prevent PTSD via modulating downstream Rac1-PAK1 pathway. This study provides a novel mechanism for the onset of PTSD and warrants the clinical application of ADP.

Effects of β-asarone on spatial learning and memory impairment by exhaustive exercise-induced fatigue: Role of NR-CaMKII-ERK/CREB signal in hippocampus of rats

ObjectiveIt is to investigate the effects of β-asarone on learning and memory, hippocampal morphology, synaptophysin (SYP) and postsynaptic density 95(PSD95) protein expression, N-methyl-D-aspartic acid receptor 2B (NR2B)- Ca2+/calmodulin (CaM)-dependent protein kinase II (CaMKII) - Extracellular signal-regulated kinase (ERK) / Cyclic-AMP response element binding protein (CREB) signal in hippocampus of rats with exhaustive exercise-induced fatigue. MethodsFifty Sprague-Dawley male rats were randomly divided into five groups: normal group, exercise group, exercise and β-asarone (2.5, 10, 40 mg/kg)–treated groups. The learning and memory in rats were tested by Morris water maze experiment. We measured the hippocampal morphology by Nissl staining. The levels of SYP, PSD95, NR2B, CaMKII, ERK1/2, CREB, p-NR2B, p-CaMKII, p-ERK1/2 and p-CREB expression were measured by western blot analysis. ResultsThe results demonstrated that β-asarone (10, 40 mg/kg) treatment significantly decreased the latency to find the platform, increased the time spent in the target quadrant and the number of crossing the platform of rats with exhaustive exercise-induced fatigue. β-asarone (10, 40 mg/kg) treatment increased the cell density in the hippocampus CA1 region, significantly up-regulated NR2B-CaMKII-ERK/CREB signal and improved the protein expression levels of SYP and PSD95 in hippocampus of rats with exhaustive exercise-induced fatigue. ConclusionsIt suggests that β-asarone could improve learning and memory of rats with exhaustive exercise-induced fatigue. The mechanism might be related to β-asarone protecting the morphology of hippocampus, increasing the protein expression levels of SYP and PSD95 and up-regulating NR2B-CaMKII-ERK/CREB signal in hippocampus of rats with exhaustive exercise-induced fatigue.

Kilohertz high-frequency electrical stimulation ameliorate hyperalgesia by modulating transient receptor potential vanilloid-1 and N-methyl-D-aspartate receptor-2B signaling pathways in chronic constriction injury of sciatic nerve mice.

The number of patients with neuropathic pain is increasing in recent years, but drug treatments for neuropathic pain have a low success rate and often come with significant side effects. Consequently, the development of innovative therapeutic strategies has become an urgent necessity. Kilohertz High Frequency Electrical Stimulation (KHES) offers pain relief without inducing paresthesia. However, the specific therapeutic effects of KHES on neuropathic pain and its underlying mechanisms remain ambiguous, warranting further investigation. In our previous study, we utilized the Gene Expression Omnibus (GEO) database to identify datasets related to neuropathic pain mice. The majority of the identified pathways were found to be associated with inflammatory responses. From these pathways, we selected the transient receptor potential vanilloid-1 (TRPV1) and N-methyl-D-aspartate receptor-2B (NMDAR2B) pathway for further exploration. Mice were randomly divided into four groups: a Sham group, a Sham/KHES group, a chronic constriction injury of the sciatic nerve (CCI) group, and a CCI/KHES stimulation group. KHES administered 30 min every day for 1week. We evaluated the paw withdrawal threshold (PWT) and thermal withdrawal latency (TWL). The expression of TRPV1 and NMDAR2B in the spinal cord were analyzed using quantitative reverse-transcriptase polymerase chain reaction, Western blot, and immunofluorescence assay. KHES significantly alleviated the mechanical and thermal allodynia in neuropathic pain mice. KHES effectively suppressed the expression of TRPV1 and NMDAR2B, consequently inhibiting the activation of glial fibrillary acidic protein (GFAP) and ionized calcium binding adapter molecule 1 (IBA1) in the spinal cord. The administration of the TRPV1 pathway activator partially reversed the antinociceptive effects of KHES, while the TRPV1 pathway inhibitor achieved analgesic effects similar to KHES. KHES inhibited the activation of spinal dorsal horn glial cells, especially astrocytes and microglia, by inhibiting the activation of the TRPV1/NMDAR2B signaling pathway, ultimately alleviating neuropathic pain.

Emerging trends in antipsychotic and antidepressant drug development: Targeting nonmonoamine receptors and innovative mechanisms.

The domain of psychiatric drug development is currently witnessing a notable transformation, with a paramount emphasis on targeting nonmonoamine receptors and exploring inventive mechanisms of action. This paper presents an overview of the ongoing advancements in antipsychotic and antidepressant drug development. Historically, antipsychotics predominantly targeted dopamine receptors, but there is now an escalating interest in drugs that act on alternative receptors, exemplified by the TAAR1 receptor. One noteworthy candidate is Ulotaront (SEP-363856), an agent acting as a TAAR1 agonist with 5-HT1A agonist activity, demonstrating promising outcomes in the treatment of schizophrenia, devoid of extrapyramidal symptoms or metabolic side-effects. Similarly, MIN-101 (Roluperidone) and KarXT are currently in development, with its focus on addressing the symptoms in schizophrenia. In the domain of antidepressants, novel therapeutic approaches have surfaced, such as Auvelity, a Food and Drug Administration (FDA)-approved NMDA receptor antagonist synergistically combined with Bupropion to enhance its effects. Another notable candidate is Zuranolone, operating as a GABA A receptor-positive allosteric modulator, showcasing efficacy in treating major depressive disorder (MDD) and postpartum depression. Additionally, TAK-653 (NBI-1065845) and MJI821 (Onfasprodil) have emerged as potential antidepressants targeting AMPA receptors and NMDA receptor 2B (NR2B) negative allosteric modulation, respectively. This paper underscores the transformative potential of these novel drug candidates in psychiatric treatment and their ability to address cases that were previously treatment-resistant. By focusing on nonmonoamine receptors and introducing innovative mechanisms, these drugs offer a promising prospect of improved outcomes for individuals suffering from schizophrenia and MDD. Thus, sustained attention and dedication to the development of such drugs are essential to augmenting the therapeutic options available for psychiatric patients.

Upregulation of Calhm2 in the anterior cingulate cortex contributes to the maintenance of bilateral mechanical allodynia and comorbid anxiety symptoms in inflammatory pain conditions

Peripheral inflammation-induced chronic pain tends to evoke concomitant anxiety disorders. It's common knowledge that the anterior cingulate cortex (ACC) plays a vital role in maintaining pain modulation and negative emotions. However, the potential mechanisms of chronic inflammation pain and pain-related anxiety remain elusive. Here, it was reported that injecting complete Freund’s adjuvant (CFA) unilaterally resulted in bilateral mechanical allodynia and anxiety-like symptoms in mice via behavioral tests. In addition, CFA induced the bilateral upregulation and activation of calcium homeostasis modulator 2 (Calhm2) in ACC pyramidal neurons by quantitative analysis and double immunofluorescence staining. The knockdown of Calhm2 in the bilateral ACC by a lentiviral vector harboring ribonucleic acid (RNA) interference sequence reversed CFA-induced pain behaviors and neuronal sensitization. Furthermore, the modulating of ACC pyramidal neuronal activities via a designer receptor exclusively activated by designer drugs (DREADD)-hM4D(Gi) greatly changed Calhm2 expression, mechanical paw withdrawal thresholds (PWTs) and comorbid anxiety symptoms. Moreover, it was found that Calhm2 regulates inflammation pain promoting the upregulation of N-methyl-D-aspartic acid (NMDA) receptor 2B (NR2B) subunits. Calhm2 knockdown in ACC exhibited a significant decrease in NR2B expression. These results demonstrated that Calhm2 in ACC pyramidal neurons modulates chronic inflammation pain and pain-related anxiety symptoms, which provides a novel underlying mechanism for the development of inflammation pain.

Prenatal THC exposure induces long-term, sex-dependent cognitive dysfunction associated with lipidomic and neuronal pathology in the prefrontal cortex-hippocampal network.

With increasing maternal cannabis use, there is a need to investigate the lasting impact of prenatal exposure to Δ9-tetrahydrocannabinol (THC), the main psychotropic compound in cannabis, on cognitive/memory function. The endocannabinoid system (ECS), which relies on polyunsaturated fatty acids (PUFAs) to function, plays a crucial role in regulating prefrontal cortical (PFC) and hippocampal network-dependent behaviors essential for cognition and memory. Using a rodent model of prenatal cannabis exposure (PCE), we report that male and female offspring display long-term deficits in various cognitive domains. However, these phenotypes were associated with highly divergent, sex-dependent mechanisms. Electrophysiological recordings revealed hyperactive PFC pyramidal neuron activity in both males and females, but hypoactivity in the ventral hippocampus (vHIPP) in males, and hyperactivity in females. Further, cortical oscillatory activity states of theta, alpha, delta, beta, and gamma bandwidths were strongly sex divergent. Moreover, protein expression analyses at postnatal day (PD)21 and PD120 revealed primarily PD120 disturbances in dopamine D1R/D2 receptors, NMDA receptor 2B, synaptophysin, gephyrin, GAD67, and PPARα selectively in the PFC and vHIPP, in both regions in males, but only the vHIPP in females. Lastly, using matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS), we identified region-, age-, and sex-specific deficiencies in specific neural PUFAs, namely docosahexaenoic acid (DHA) and arachidonic acid (ARA), and related metabolites, in the PFC and hippocampus (ventral/dorsal subiculum, and CA1 regions). This study highlights several novel, long-term and sex-specific consequences of PCE on PFC-hippocampal circuit dysfunction and the potential role of specific PUFA signaling abnormalities underlying these pathological outcomes.

Neuroprotection of Kaji-Ichigoside F1 via the BDNF/Akt/mTOR Signaling Pathways against NMDA-Induced Neurotoxicity.

Kaji-ichigoside F1 (KF1), a natural oleanane-type triterpenoid saponin, is the main active constituent from Rosa roxburghii. In the southwest regions of China, particularly in Guizhou Province, this plant was used as a Miao ethnic medicine to prevent and treat dyspepsia, dysentery, hypoimmunity, and neurasthenia. In the present study, the neuroprotective effect of KF1 was evaluated against N-methyl-D-aspartate (NMDA)-induced neurotoxicity in vivo and in vitro. An NMDA-induced PC12 cell neurotoxicity assay showed that KF1 effectively improved cellular viability, inhibited the release of lactate dehydrogenase (LDH), and reduced cell apoptosis. Furthermore, KF1-treated NMDA-induced excitotoxicity mice displayed a remarkable capacity for improving spatial learning memory in the Y-maze and Morris water maze tests. In addition, KF1 increased the levels of the neurotransmitters 5-hydroxytryptamine, dopamine, and monoamine oxidase and reduced the calcium ion concentration in the hippocampus of mice. Hematoxylin and eosin and Nissl staining indicated that KF1 effectively reduced the impairment of neurons. Furthermore, Western blot assays showed that KF1 decreased NMDAR1 expression. In contrast, the NMDAR2B (NR2B), glutamate receptor (AMPA), TrkB, protein kinase B (AKT), mammalian target of rapamycin (mTOR), PSD95, and synapsin 1 were upregulated in NMDA-induced PC12 cells and an animal model. These results suggest that KF1 has a remarkable protective effect against NMDA-induced neurotoxicity, which is directly related to the regulation of the NMDA receptor and the activation of the α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR) and BDNF/AKT/mTOR signaling pathways.

Muscarinic and NMDA Receptors in the Substantia Nigra Play a Role in Reward-Related Learning.

Reward-related learning, where animals form associations between rewards and stimuli (i.e., conditioned stimuli [CS]) that predict or accompany those rewards, is an essential adaptive function for survival. In this study, we investigated the mechanisms underlying the acquisition and performance of conditioned approach learning with a focus on the role of muscarinic acetylcholine (mACh) and NMDA glutamate receptors in the substantia nigra (SN), a brain region implicated in reward and motor processes. Using RNAscope in situ hybridization assays, we found that dopamine neurons of the SN express muscarinic (mACh5), NMDA2a, NMDA2b, and NMDA2d receptor mRNA but not mACh4. NMDA, but not mACh5, receptor mRNA was also found on SN GABA neurons. In a conditioned approach paradigm, rats were exposed to 3 or 7 conditioning sessions during which light/tone (CS) presentations were paired with delivery of food pellets, followed by a test session with CS-only presentations. Intra-SN microinjections of scopolamine (a mACh receptor antagonist) or AP-5 (a NMDA receptor antagonist) were made either prior to each conditioning session (to test their effects on acquisition) or prior to the CS-only test (to test their effects on expression of the learned response). Scopolamine and AP-5 produced dose-dependent significant reductions in the acquisition, but not performance, of conditioned approach. These results suggest that SN mACh and NMDA receptors are key players in the acquisition, but not the expression, of reward-related learning. Importantly, these findings redefine the role of the SN, which has traditionally been known for its involvement in motor processes, and suggest that the SN possesses attributes consistent with a function as a hub of integration of primary reward and CS signals.

Alcohol Exposure Induces Depressive and Anxiety-like Behaviors via Activating Ferroptosis in Mice.

Alcohol use disorder (AUD) is a global public health problem and is frequently comorbid with mental disorders, including anxiety and depression. Ferroptosis is an iron-dependent cell death, which is involved in the pathological process of various diseases such as neurodegenerative diseases, but the role of ferroptosis in the mediation of AUD and its induced mental disorders is unclear. In this study, we aimed to investigate whether ferroptosis was involved in alcohol-induced depressive and anxiety-like behaviors in mice. Following an 8-week period of intermittent alcohol exposure, the alcohol group showed noticeable depressive and anxiety-like behaviors. In addition, nissl staining revealed that alcohol exposure induced neuron damage in the hippocampus (Hip) and prefrontal cortex (PFC) of mice. The levels of synapse-related proteins were significantly reduced in the alcohol group. Iron staining demonstrated that alcohol increased the number of iron-positive staining cells. The protein expression of the transferrin receptor (TFRC) was increased, and the expression of glutathione peroxidase 4 (GPX4) was decreased, respectively, in the alcohol group. Furthermore, the ferroptosis inhibitor ferrostatin-1 significantly prevented alcohol-induced neuron damage and enhanced the expression of N-methyl-d-aspartic acid (NMDA) receptor 2B (NR2B), α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor 1 (GluA1) and GPX4 in vitro. These results indicated that alcohol exposure could induce depressive and anxiety-like behaviors, and that this effect may occur via activating ferroptosis.

Small extracellular vesicles in plasma reveal molecular effects of modified Mediterranean-ketogenic diet in participants with mild cognitive impairment.

Extracellular vesicles have emerged as a less-invasive nano-tool for discovering biomarkers of Alzheimer's disease and related dementia. Here, we analysed different neuron-enriched extracellular vesicles from plasma to predict response and molecular mechanisms of ketogenic diet's efficacy in mild cognitive impairment participants. The study was a randomized crossover design in which cognitively normal and mild cognitive impairment participants consumed a modified Mediterranean-ketogenic diet or American Heart Association diet for 6 weeks, followed by other diet after washout. L1 cell adhesion molecule, synaptophysin and neural cell adhesion molecule surface markers were used to enrich for neuron-secreted small extracellular vesicles (sEVL1CAM, sEVSYP and sEVNCAM). For the first time, we have presented multiple evidences, including immunogold labelling/transmission electron microscopy, clusters of differentiation 63-ELISA-based assay, confocal microscopy fluorescent images and flow cytometry data confirming the presence of L1 cell adhesion molecule on the surface of sEVL1CAM, validating purity and relative abundance of sEVL1CAM in the plasma. Cargo analysis of sEVL1CAM showed that modified Mediterranean-ketogenic diet intervention reduces amyloid beta 1-42 (50.3%, P = 0.011), p181-tau (34.9%, P = 0.033) and neurofilament light (54.2%, P = 0.020) in mild cognitive impairment participants. Moreover, sEVL1CAMshowed better sensitivity compared with CSF in analysing increased glutamate (6-folds, P < 0.0001) from mild cognitive impairment participants following modified Mediterranean-ketogenic diet intervention. sEVL1CAM characterization also suggested that modified Mediterranean-ketogenic diet differentially targets the expression of various glutamate receptors-glutamate receptor ionotropic NMDA1, glutamate receptor ionotropic NMDA2A, glutamate receptor ionotropic NMDA2B and glutamate receptor ionotropic AMPA type subunit 1. Importantly, these sEVL1CAM measures strongly correlated with corresponding clinical CSF biomarkers (neurogranin, amyloid beta 1-42, neurofilament light and tau). Furthermore, sEVL1CAM were loaded with less advanced glycation endproducts and exhibited anti-inflammatory activity following modified Mediterranean-ketogenic diet intervention. Most importantly, the expression of monocarboxylate transporter 2 on the surface of sEVL1CAM predicted the amyloid beta 1-42 response to modified Mediterranean-ketogenic diet intervention (area under the curve = 0.87, P = 0.0044) and offered a novel screening tool to identify participants responsive to this dietary intervention. Finally, sEVL1CAM, sEVSYP and sEVNCAM showed significantly high concordance in analysing amyloid beta 1-42 (Pearson correlation coefficient ≥ 0.63, P < 0.01) and neurofilament light (Pearson correlation coefficient ≥ 0.49, P < 0.05). Together, small extracellular vesicles in plasma offers promise in assessing the efficacy of dietary/therapeutic intervention against mild cognitive impairment/Alzheimer's disease.

Ibuprofen treatment ameliorates memory deficits in rats with collagen-induced arthritis by normalizing aberrant MAPK/NF-κB and glutamatergic pathways

Many studies have indicated that the risk of cognitive impairment is higher in patients with rheumatoid arthritis (RA). Additionally, patients with RA may have a lower incidence of cognitive impairment with long-term use of ibuprofen. This study was aimed at investigating the impacts of RA on memory function and the mechanisms that ibuprofen may exhibit to improve memory function in rats with collagen-induced arthritis (CIA). Ibuprofen (30 mg/kg) was given twice daily to CIA rats for two weeks starting from Day 18 following the first immunization. Memory function was measured by the Morris water maze (MWM) test and long-term potentiation (LTP). The proinflammatory cytokine levels and downstream signaling pathways, including mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB), were examined. Furthermore, the glutamatergic system, including glutamate transporters/receptors and brain extracellular levels of glutamate, was investigated. The results showed that the impaired learning memory in CIA rats, examined by the MWM test and LTP, can be ameliorated by ibuprofen treatment. Along with the improvement in memory deficits, ibuprofen attenuated both neuroinflammation and the associated elevated levels of phosphorylated p38, JNK, and p65 in the hippocampus of CIA rats. In addition, the decreased excitatory amino acid transporter 2 level, the increased extracellular glutamate, and the upregulated hippocampal NMDA receptor 2B of CIA rats were all normalized by ibuprofen treatment. These findings suggest that the effect of ibuprofen on the memory improvement in CIA rats is associated with the normalization of the activated MAPK and NF-κB pathways and the aberrant glutamatergic system.

Stimulation of Neurite Outgrowth in Cerebrocortical Neurons by Sodium Channel Activator Brevetoxin-2 Requires Both N-Methyl-D-aspartate Receptor 2B (GluN2B) and p21 Protein (Cdc42/Rac)-Activated Kinase 1 (PAK1).

N-methyl-D-aspartate (NMDA) receptors play a critical role in activity-dependent dendritic arborization, spinogenesis, and synapse formation by stimulating calcium-dependent signaling pathways. Previously, we have shown that brevetoxin 2 (PbTx-2), a voltage-gated sodium channel (VGSC) activator, produces a concentration-dependent increase in intracellular sodium [Na+]I and increases NMDA receptor (NMDAR) open probabilities and NMDA-induced calcium (Ca2+) influxes. The objective of this study is to elucidate the downstream signaling mechanisms by which the sodium channel activator PbTx-2 influences neuronal morphology in murine cerebrocortical neurons. PbTx-2 and NMDA triggered distinct Ca2+-influx pathways, both of which involved the NMDA receptor 2B (GluN2B). PbTx-2-induced neurite outgrowth in day in vitro 1 (DIV-1) neurons required the small Rho GTPase Rac1 and was inhibited by both a PAK1 inhibitor and a PAK1 siRNA. PbTx-2 exposure increased the phosphorylation of PAK1 at Thr-212. At DIV-5, PbTx-2 induced increases in dendritic protrusion density, p-cofilin levels, and F-actin throughout the dendritic arbor and soma. Moreover, PbTx-2 increased miniature excitatory post-synaptic currents (mEPSCs). These data suggest that the stimulation of neurite outgrowth, spinogenesis, and synapse formation produced by PbTx-2 are mediated by GluN2B and PAK1 signaling.

Differential roles of NMDAR subunits 2A and 2B in mediating peripheral and central sensitization contributing to orofacial neuropathic pain

The spinal N-methyl-d-aspartate receptor (NMDAR), particularly their subtypes NR2A and NR2B, plays pivotal roles in neuropathic and inflammatory pain. However, the roles of NR2A and NR2B in orofacial pain and the exact molecular and cellular mechanisms mediating nervous system sensitization are still poorly understood. Here, we exhaustively assessed the regulatory effect of NMDAR in mediating peripheral and central sensitization in orofacial neuropathic pain. Von-Frey filament tests showed that the inferior alveolar nerve transection (IANX) induced ectopic allodynia behavior in the whisker pad of mice. Interestingly, mechanical allodynia was reversed in mice lacking NR2A and NR2B. IANX also promoted the production of peripheral sensitization-related molecules, such as interleukin (IL)-1β, tumor necrosis factor (TNF)-α, brain-derived neurotrophic factor (BDNF), and chemokine upregulation (CC motif) ligand 2 (CCL2), and decreased the inward potassium channel (Kir) 4.1 on glial cells in the trigeminal ganglion, but NR2A conditional knockout (CKO) mice prevented these alterations. In contrast, NR2B CKO only blocked the changes of Kir4.1, IL-1β, and TNF-α and further promoted the production of CCL2. Central sensitization-related c-fos, glial fibrillary acidic protein (GFAP), and ionized calcium-binding adaptor molecule 1 (Iba-1) were promoted and Kir4.1 was reduced in the spinal trigeminal caudate nucleus by IANX. Differential actions of NR2A and NR2B in mediating central sensitization were also observed. Silencing of NR2B was effective in reducing c-fos, GFAP, and Iba-1 but did not affect Kir4.1. In contrast, NR2A CKO only altered Iba-1 and Kir4.1 and further increased c-fos and GFAP. Gain-of-function and loss-of-function approaches provided insight into the differential roles of NR2A and NR2B in mediating peripheral and central nociceptive sensitization induced by IANX, which may be a fundamental basis for advancing knowledge of the neural mechanisms’ reaction to nerve injury.

Chronic oral d-galactose intake provokes age-related changes in the rat prefrontal cortex

D-galactose (d-gal) is broadly used in animal aging studies as its chronic administration mimics learning and memory impairments related to aging in humans. However, within the few studies that utilize chronic oral d-gal intake, none of them is focused on alteration in synaptic structure and function. We examined the effects of 6-weeks oral d-gal intake (200 mg/kg and 500 mg/kg, dissolved in tap water) on age-related changes, with emphasis on the prefrontal cortex (PFC) and hippocampus (HIP) of adult male Wistar rats. Memory assessment was followed by histological examination of the PFC and HIP (Nissl staining and Iba-1 immunostaining), while in crude synaptosomal fractions the state of oxidative stress and the expression of proteins involved in glutamatergic signaling was determined. Although applied dosages compromised memory, alterations such as impaired sensory-motor function and aberrant morphology were not detected. In the PFC, analysis of microglia revealed reduction of branching pattern following d-gal intake, in parallel with increased oxidative damage of proteins, lipids and disturbed pro-oxidant antioxidant balance. These changes in the PFC were further accompanied with decreased levels of vesicular glutamate transporter 1, syntaxin-1 and NMDA receptor 2B subunit in both treated groups. Simultaneously, the increased hippocampal oxidative damage of lipids was detected. Results indicate successful provocation of age-related changes following oral d-gal intake, and suggest greater sensitivity of the PFC to d-gal treatment than HIP.

Casein kinase 2 attenuates brain injury induced by intracerebral hemorrhage via regulation of NR2B phosphorylation.

ObjectiveIntracerebral hemorrhage (ICH) is a common cerebrovascular disease with high incidence, disability, and mortality. Casein kinase 2 (CK2) is a serine/threonine kinase with hundreds of identified substrates and plays an important role in many diseases. This study aimed to explore whether CK2 plays protective roles in ICH-induced neuronal apoptosis, inflammation, and oxidative stress through regulation NR2B phosphorylation.MethodsCK2 expression level of brain tissues taken from ICH patients was determined by immunoblotting. Neurons from embryonic rat and astrocytes from newborn rats were cultured and treated by Hemoglobin chloride (Hemin). The proliferation of astrocytes, the apoptosis and oxidative stress of neurons and the inflammatory factors of astrocytes were detected. CK2 expression was determined in ICH model rats. The effects of CK2 overexpression plasmid (pc-CK2) on neurobehavioral defects and brain water content in ICH rats were observed.ResultsCK2 expression in ICH patients was down-regulated. Overexpression of CK2 promoted the astrocyte proliferation, inhibited neuronal apoptosis, and reduced astrocyte-mediated inflammation. N-methyl-D-aspartate receptor 2B (NR2B) reversed the effects of pc-CK2 on neurons and astrocytes. CK2 phosphorylated NR2B at the S1480 site, down-regulated the expression of NR2B and interfered with the interaction between NR2B and postsynaptic density protein 95 (PSD95). In vivo experiments showed that the expression of CK2 decreased and the expression of NR2B increased in ICH rats. Furthermore, pc-CK2 attenuated neurobehavioral defects, brain water content and neuronal damage in ICH rats.ConclusionCK2 phosphorylated NR2B, down-regulated the expression of NR2B, interfered with the interaction between NR2B and PSD95, alleviated inflammatory reactions, inhibited neuronal apoptosis and oxidative stress after ICH. CK2 and NR2B may be new potential therapeutic targets for the treatment of ICH. However, the limitation of this study is that we only investigated the regulation of NR2B by CK2.

Reactive Oxygen Species Contributes to Type 2 Diabetic Neuropathic Pain via the Thioredoxin-Interacting Protein-NOD-Like Receptor Protein 3- N -Methyl-D-Aspartic Acid Receptor 2B Pathway.

BACKGROUND:The number of patients with diabetic neuropathic pain (DNP) continues to increase, but available treatments are limited. This study aimed to examine the influence of reactive oxygen species (ROS)-thioredoxin-interacting protein (TXNIP)-NOD–like receptor protein 3 (NLRP3)-N-methyl-D-aspartic acid receptor 2B (NR2B) pathway on type 2 DNP.METHODS:Male Sprague-Dawley rats were fed with a high-fat and high-sugar diet for 8 weeks. Then, rats were intraperitoneally injected with streptozotocin (STZ, 35 mg/kg) to induce type 2 diabetes mellitus in rats. Diabetic rats with <85% of their basic levels in mechanical withdrawal threshold and thermal withdrawal latency were classified as DNP rats on day 14 after STZ injection. DNP rats were treated with ROS scavenger N-tert-Butyl-α-phenylnitrone (PBN, 100 mg·kg–1·d–1) or TXNIP small interfering ribonucleic acid (10 μg/d) once daily for 14 days. The level of ROS, protein levels of NLRP3, TXNIP, cysteinyl aspartate-specific proteinase-1 (caspase-1), interleukin-1β (IL-1β), NR2B phosphorylation at Tyr1472 (p-NR2B), total NR2B (t-NR2B), and distribution of NLRP3 in the spinal cord were examined. In vitro experiments, BV2 cells and PC12 cells were individually cultured and cocultured in a high-glucose environment (35 mmol/L D-glucose). The level of ROS and protein levels of NLRP3, TXNIP, caspase-1, and IL-1β in BV2 cells, and p-NR2B, t-NR2B in PC12 cells were detected. The level of ROS was detected by the flow cytometry approach. The protein levels were detected by the Western blot technique. The location of NLRP3 was observed by immunofluorescent staining. The interaction between TXNIP and NLRP3 was detected by coimmunoprecipitation assay.RESULTS:The level of spinal ROS increased in DNP rats. The mechanical allodynia and thermal hyperalgesia of DNP rats were alleviated after systemic administration of PBN. This administration decreased protein levels of NLRP3, TXNIP, caspase-1, IL-1β, and p-NR2B and the coupling of TXNIP to NLRP3 in spinal cords of DNP rats. Furthermore, knockdown of spinal TXNIP alleviated nociceptive hypersensitivity and decreased protein levels of NLRP3, TXNIP, caspase-1, IL-1β, and p-NR2B in DNP rats. The level of ROS and protein levels of NLRP3, TXNIP, caspase-1, IL-1β, the coupling of TXNIP to NLRP3, and the IL-1β secretion increased in BV2 cells, and the protein expression of p-NR2B increased in cocultured PC12 cells in a high-glucose environment. All of these in vitro effects were significantly blocked after treatment of PBN.CONCLUSIONS:Our findings suggest that spinal ROS can contribute to type 2 DNP through TXNIP-NLRP3-NR2B pathway.

Complement Receptor 3 Pathway and NMDA Receptor 2B Subunit Involve Neuropathic Pain Associated with Spinal Cord Injury

BackgroundNeuropathic pain (NP) after spinal cord injury (SCI-evoked NP) is clinically challenging; the underlying mechanisms are not fully understood, leading to a lack of promising treatment options. NP occurs in only a subset of patients with SCI. The injured spinal cord exhibits a series of histopathological changes, and the complement system has been shown to play an important role in these processes. In addition, NMDA receptor subunit 2B (NR2B) is involved in the development and maintenance of NP. This preliminary study was performed to investigate the correlations of the complement receptor 3/complement component 3 (CR3/C3) pathway and NR2B with SCI-evoked NP.MethodsA trauma-induced SCI animal model was established and SCI-evoked NP was evaluated by behavioural analysis. Transcriptome analysis was performed to identify genes in the CR3/C3 pathway related to synaptic modification, while the expression and distribution of NR2B in the injured spinal cord, and the relation to NP, were examined by immunohistochemical analysis.ResultsNine of seventeen SCI rats (52.9%) developed NP. C3 mRNA expression was significantly decreased in SCI-evoked NP rats and significantly increased in the non-NP SCI rats. C1q mRNA and CR3 mRNA expression were significantly increased in all SCI rats, but higher levels of expression were observed in the non-NP SCI rats. NR2B mRNA expression was significantly increased in the SCI-evoked NP rats and significantly decreased in the non-NP SCI rats. In addition, significantly elevated expression of NR2B-positive cells was seen in lamina II of the superficial dorsal horn in SCI-evoked NP rats in comparison with non-NP SCI rats.ConclusionNP occurred in only a subset of SCI rats, and the CR3/C3 pathway and NR2B were involved in SCI-evoked NP. Further studies are required to determine the mechanisms underlying the SCI-evoked NP associated with the CR3/C3 pathway and NR2B.

Gao-Zi-Yao improves learning and memory function in old spontaneous hypertensive rats

AimsGao-Zi-Yao has long been a unique way for treating various diseases. The present study is to explore the effect of Gao-Zi-Yao on learning and memory function in old spontaneous hypertensive rats (SHR) and its possible mechanism.MethodMale old SHR were received different doses of Gao-Zi-Yao for 4 weeks. Systolic blood pressure (SBP) and heart rate were monitored. Serum levels of nitric oxide (NO), interleukin (IL)-1β, IL-2, and tumor necrotic factor (TNF)-α were measured. Morris water maze was performed to test the learning and memory function of the rats. Number of neurons in hippocampus was counted by Nissl staining. Western blot was applied to detect the expressions of learning and memory function related proteins, N-methyl-d-aspartate receptor 2B (NMDAR 2B), glutamate receptor 1 (GluR1), phosphorylated-calmodulin-dependent protein kinase II (p-CaMK II), and phosphorylated-cAMP responsive element-binding protein (p-CREB) in rat hippocampus.ResultsData showed that Gao-Zi-Yao reduced SBP in old SHR, elevated NO level, and suppressed levels of IL-1β, IL-2, TNF-α. The results of Morris water maze experiment showed that Gao-Zi-Yao dose-dependently improved learning and memory function. Number of neurons in the hippocampal dentate gyrus (DG) region of the old SHR was increased by Gao-Zi-Yao treatment. In addition, Gao-Zi-Yao elevated the protein expressions of NMDAR 2B, GluR1, p-CaMK II, and p-CREB in hippocampus.ConclusionGao-Zi-Yao decreases SBP and improves the learning and memory function of the old SHR by regulation of oxidative stress, inflammatory factors and neuron number in hippocampal DG area and the expression of learning and memory function related proteins.

Botulinum toxin type a combined with transcranial direct current stimulation reverses the chronic pain induced by osteoarthritis in rats

Osteoarthritis (OA) is the most common cause to lead to chronic pain. Sensitization of pain pathways including central sensitization and peripheral sensitization has been regarded as a major cause of OA pain refractory to treatment. Addressing peripheral sensitization or central sensitization alone may not adequately treat OA pain. In our previous studies, botulinum toxin type A (BoNT/A) has been shown to reduce peripheral sensitization for analgesic effects. In addition, transcranial direct current stimulation (tDCS) has also been suggested to reduce central sensitization for analgesia. The present study was designed to investigate whether BoNT/A in combination with tDCS has better analgesic effects than isolated treatment to alleviate OA-induced chronic pain in rats. The Von Frey and hot plate tests were applied to assess the pain-related behaviors at different time points. The expression level of N-methyl-D-aspartate receptor-2B (NMDAR2B) was evaluated in midbrain periaqueductal gray (PAG) by Western blot the Immunohistochemistry staining after different treatments. The results showed that the combined treatment of BoNT/A and tDCS better improved the pain-related behaviors and significantly increased the expression level of NMDAR2B protein in PAG than each isolated treatment. These results suggested that the combined treatments for relief of chronic pain were more obvious than each isolated treatment. The combination of BoNT/A and tDCS may relieve pain by increasing N-methyl-D-aspartate (NMDA) receptors in the PAG, and then the descending inhibitory systems were activated to modulate peripheral and central sensitization.