N-methyl-D-aspartate receptors and thymoquinone induce apoptosis and alteration in mitochondria in colorectal cancer cells.

Colon cancer is on the rise in both men and women. In addition to traditional treatment methods, herbal treatments from complementary and alternative medicine are actively followed. Naturally derived from plants, thymoquinone (TQ) has drawn a lot of attention in the field of cancer treatment. MK-801, an N-methyl-D-aspartate agonist, is used to improve memory and plasticity, but it has also lately been explored as a potential cancer treatment. This study aimed to determine the roles of N-Methyl-D-Aspartate agonists and Thymoquinone on mitochondria and apoptosis. HT-29 cells were treated with different TQ and MK-801 concentrations. We analyzed cell viability, apoptosis, and alteration of mitochondria. Cell viability significantly decreased depending on doses of TQ and MK-801. Apoptosis and mitochondrial dysfunctions induced by low and high doses of TQ and MK-801. Our study emphasizes the need for further safety evaluation of MK-801 due to the potential toxicity risk of TQ and MK-801. Optimal and toxic doses of TQ and MK-801 were determined for the treatment of colon cancer. It should be considered as a possibility that colon cancer can be treated with TQ and MK-801.

Natural product Kaji-ichigoside F1 exhibits rapid antidepression via activating the AMPA-BDNF-mTOR pathway and inhibiting the NMDAR-CaMKIIα pathway.

BACKGROUND: Depression is a common and recurrent neuropsychiatric disorder. Recent studies have shown that the N-methyl-d-aspartate (NMDA) receptor (NMDAR) is involved in the pathophysiology of depression. Previous studies have found that Kaji-ichigoside F1 (KF1) has a protective effect against NMDA-induced neurotoxicity. However, the antidepressant mechanism of KF1 has not been confirmed yet. PURPOSE: In the present study, we aimed to evaluate the rapid antidepressant activity of KF1 and explore the underlying mechanism. STUDY DESIGN: First, we explored the effect of KF1 on NMDA-induced hippocampal neurons and the underlying mechanism. Second, depression was induced in C57BL/6 mice via chronic unpredictable mild stress (CUMS), and the immediate and persistent depression-like behavior was evaluated using the forced swimming test (FST) after a single administration of KF1. Third, the contributions of NMDA signaling to the antidepressant effect of KF1 were investigated using pharmacological interventions. Fourth, CUMS mice were treated with KF1 for 21 days, and then their depression-like behaviors and the underlying mechanism were further explored. METHODS: The FST was used to evaluate immediate and persistent depression-like behavior after a single administration of KF1 with or without NMDA pretreatment. The effect of KF1 on depressive-like behavior was investigated in CUMS mice by treating them with KF1 once daily for 21 days through the sucrose preference test, FST, open field test, and tail suspension test. Then, the effects of KF1 on the morphology and molecular and functional phenotypes of primary neuronal cells and hippocampus of mice were investigated by hematoxylin-eosin staining, Nissl staining, propidium iodide staining, TUNEL staining, Ca2+ imaging, JC-1 staining, ELISA, immunofluorescence analysis, RT-PCR, and Western blot. RESULTS: KF1 could effectively improve cellular viability, reduce apoptosis, inhibit the release of LDH and Ca2+, and increase the mitochondrial membrane potential and the number of dendritic spines numbers in hippocampal neurons. Moreover, behavioral tests showed that KF1 exerted acute and sustained antidepressant-like effects by reducing Glu-levels and ameliorating neuronal damage in the hippocampus. Additionally, in vivo and in vitro experiments revealed that PSD95, Syn1, α-amino-3­hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and brain-derived neurotrophic factor (BDNF) were upregulated at the protein level, and BDNF and AMPA were upregulated at the mRNA level. NR1 and NR2A showed the opposite trend. CONCLUSION: These results confirm that KF1 exerts rapid antidepressant effects mainly by activating the AMPA-BDNF-mTOR pathway and inhibiting the NMDAR-CaMKIIα pathway. This study serves as a new reference for discovering rapid antidepressants.

Design, Synthesis, and Biological Evaluation of Pierardine Derivatives as Novel Brain-Penetrant and In Vivo Potent NMDAR-GluN2B Antagonists for Ischemic Stroke Treatment.

A series of structurally novel GluN2B NMDAR antagonists were designed, synthesized, and biologically evaluated as anti-stroke therapeutics by optimizing the chemical structure of Pierardine, the active ingredient of traditional Chinese medicine Dendrobium aphyllum (Roxb.) C. E. Fischer identified via in silico screening. The systematic structure-activity relationship study led to the discovery of 58 with promising NMDAR-GluN2B binding affinity and antagonistic activity. Of the two enantiomers, S-58 exhibited significant inhibition (IC50 = 74.01 ± 12.03 nM) against a GluN1/GluN2B receptor-mediated current in a patch clamp assay. In addition, it displayed favorable specificity over other subtypes and off-target receptors. In vivo, S-58 exerted therapeutic efficacy comparable to that of the approved GluN2B NMDAR antagonist ifenprodil and excellent safety profiles. In addition to the attractive in vitro and in vivo potency, S-58 exhibited excellent brain exposure. In light of these merits, S-58 has been advanced to further preclinical investigation as a potential anti-stroke candidate.

Chronic Intermittent Hypobaric Hypoxia Reduces Hypothalamic N-Methyl-d-Aspartate Receptor Activity and Sympathetic Outflow in Spontaneously Hypertensive Rats.

Guo, Xinqi, Hongyu Ma, Ziye Cui, Qiyue Zhao, Ying Zhang, Lu Jia, Liping Zhang, Hui Guo, Xiangjian Zhang, Yi Zhang, Yue Guan, and Huijie Ma. Chronic intermittent hypobaric hypoxia reduces hypothalamic N-Methyl-d-Aspartate Receptor activity and sympathetic outflow in spontaneously hypertensive rats. High Alt Med Biol. 25:77-88, 2024. Objective: This study aims to determine the role of hypothalamic renin-angiotensin system (RAS) in the antihypertensive effect of chronic intermittent hypobaric hypoxia (CIHH). Methods: Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs) received 35 days of hypobaric hypoxia simulating an altitude of 4,000 m, 5 h/day. The levels of RAS, blood pressure, and N-methyl-d-aspartate receptor (NMDAR) activities of hypothalamic paraventricular nucleus (PVN) presympathetic neurons from each group of rats were determined. Results: The systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure (MAP) of SHRs significantly decreased from the third week of CIHH treatment. This blood pressure reduction effect could be maintained for at least 2 weeks after stopping the CIHH treatment. CIHH treatment also attenuated the decrease in MAP and renal sympathetic nerve activity induced by hexamethonium administration in SHRs, but not in WKY rats. Furthermore, CIHH reversed the increase in serum angiotensin (Ang)II concentration and the expression of PVN angiotensin-converting enzyme (ACE) and AngII type 1 (AT1) receptors, as well as the decrease in serum Ang1-7 concentration and the expression of PVN ACE2 and Mas receptors in SHRs. In addition, the administration of CIHH resulted in a reduction in the frequency of miniature excitatory postsynaptic currents and amplitude of NMDAR current in PVN presympathetic neurons of SHRs, which means that CIHH decreased the pre- and postsynaptic NMDAR activity of PVN presympathetic neurons in SHRs. However, pretreatment with A779 (a Mas receptor blocker) or AngII abrogated the above effects. Meanwhile, Ang1-7 pretreatment mimicked the CIHH effect on pre- and postsynaptic NMDAR activity of presympathetic neurons in SHRs. Conclusions: Our data indicate that CIHH reduces pre- and postsynaptic NMDAR activity of PVN presympathetic neurons, sympathetic outflow, and blood pressure by decreasing the activity of the ACE/AngII/AT1 axis and increasing the activity of ACE2/Ang1-7/Mas axis in the hypothalamus in hypertension.

Tonic NMDAR Currents of NR2A-Containing NMDARs Represent Altered Ambient Glutamate Concentration in the Supraoptic Nucleus.

NMDA receptors (NMDARs) modulate glutamatergic excitatory tone in the brain via two complementary modalities: a phasic excitatory postsynaptic current and a tonic extrasynaptic modality. Here, we demonstrated that the tonic NMDAR-current (I NMDA) mediated by NR2A-containing NMDARs is an efficient biosensor detecting the altered ambient glutamate level in the supraoptic nucleus (SON). I NMDA of magnocellular neurosecretory cells (MNCs) measured by nonselective NMDARs antagonist, AP5, at holding potential (V holding) -70 mV in low concentration of ECF Mg2+ ([Mg2+]o) was transiently but significantly increased 1-week post induction of a DOCA salt hypertensive model rat which was compatible with that induced by a NR2A-selective antagonist, PEAQX (I PEAQX) in both DOCA-H2O and DOCA-salt groups. In agreement, NR2B antagonist, ifenprodil, or NR2C/D antagonist, PPDA, did not affect the holding current (I holding) at V holding -70 mV. Increased ambient glutamate by exogenous glutamate (10 mM) or excitatory amino acid transporters (EAATs) antagonist (TBOA, 50 mM) abolished the I PEAQX difference between two groups, suggesting that attenuated EAATs activity increased ambient glutamate concentration, leading to the larger I PEAQX in DOCA-salt rats. In contrast, only ifenprodil but not PEAQX and PPDA uncovered I NMDA at V holding +40 mV under 1.2 mM [Mg2+]o condition. I ifenprodil was not different in DOCA-H2O and DOCA-salt groups. Finally, NR2A, NR2B, and NR2D protein expression were not different in the SON of the two groups. Taken together, NR2A-containing NMDARs efficiently detected the increased ambient glutamate concentration in the SON of DOCA-salt hypertensive rats due to attenuated EAATs activity.

Multi-faceted Anti-obesity Effects of N-Methyl-D-Aspartate (NMDA) Receptor Modulators: Central-Peripheral Crosstalk.

Hypothalamus is central to food intake and satiety. Recent data unveiled the expression of N-methyl-D-aspartate receptors (NMDAR) on hypothalamic neurons and their interaction with GABAA and serotoninergic neuronal circuits. However, the precise mechanisms governing energy homeostasis remain elusive. Notably, in females, the consumption of progesterone-containing preparations, such as hormonal replacement therapy and birth control pills, has been associated with hyperphagia and obesity-effects mediated through the hypothalamus. To elucidate this phenomenon, we employed the progesterone-induced obesity model in female Swiss albino mice. Four NMDAR modulators were selected viz. dextromethorphan (Dxt), minocycline, d-aspartate, and cycloserine. Obesity was induced in female mice by progesterone administration for 4 weeks. Mice were allocated into 7 groups, group-1 as vehicle control (arachis oil), group-2 (progesterone + arachis oil), and group-3 as positive-control (progesterone + sibutramine); other groups were treated with test drugs + progesterone. Various parameters were recorded like food intake, thermogenesis, serum lipids, insulin, AST and ALT levels, organ-to-body weight ratio, total body fat, adiposity index, brain serotonin levels, histology of liver, kidney, and sizing of fat cells. Dxt-treated group has shown a significant downturn in body weight (p < 0.05) by a decline in food intake (p < 0.01), organ-to-liver ratio (p < 0.001), adiposity index (p < 0.01), and a rise in body temperature and brain serotonin level (p < 0.001). Dxt demonstrated anti-obesity effects by multiple mechanisms including interaction with hypothalamic GABAA channels and anti-inflammatory and free radical scavenging effects, improving the brain serotonin levels, and increasing insulin release from the pancreatic ß-cells.

The role of glutamate NMDA receptors of the mediodorsal thalamus in scopolamine-induced amnesia in rats.

The current study was designed to examine the role of glutamate NMDA receptors of the mediodorsal thalamus (MD) in scopolamine-induced memory impairment. Adult male rats were bilaterally cannulated into the MD. According to the results, intraperitoneal (i.p.) administration of scopolamine (1.5 mg/kg) immediately after the training phase (post-training) impaired memory consolidation. Bilateral microinjection of the glutamate NMDA receptors agonist, N-Methyl-D-aspartic acid (NMDA; 0.05 µg/rat), into the MD significantly improved scopolamine-induced memory consolidation impairment. Co-administration of D-AP5, a glutamate NMDA receptor antagonist (0.001-0.005 µg/rat, intra-MD) potentiated the response of an ineffective dose of scopolamine (0.5 mg/kg, i.p.) to impair memory consolidation, mimicking the response of a higher dose of scopolamine. Noteworthy, post-training intra-MD microinjections of the same doses of NMDA or D-AP5 alone had no effect on memory consolidation. Moreover, the blockade of the glutamate NMDA receptors by 0.003 ng/rat of D-AP5 prevented the improving effect of NMDA on scopolamine-induced amnesia. Thus, it can be concluded that the MD glutamatergic system may be involved in scopolamine-induced memory impairment via the NMDA receptor signaling pathway.

Role of NMDA Receptor in High-Pressure Neurological Syndrome and Hyperbaric Oxygen Toxicity.

Professional divers exposed to pressures greater than 11 ATA (1.1 MPa) may suffer from high-pressure neurological syndrome (HPNS). Divers who use closed-circuit breathing apparatus and patients and medical attendants undergoing hyperbaric oxygen therapy (HBOT) face the risk of CNS hyperbaric oxygen toxicity (HBOTx) at oxygen pressure above 2 ATA (0.2 MPa). Both syndromes are characterized by reversible CNS hyperexcitability, accompanied by cognitive and motor deficits, and N-methyl-D-aspartate receptor (NMDAR) plays a crucial role in provoking them. Various NMDAR subtypes respond differently under hyperbaric conditions. The augmented currents observed only in NMDAR containing GluN2A subunit increase glutamatergic synaptic activity and cause dendritic hyperexcitability and abnormal neuronal activity. Removal of the resting Zn2+ voltage-independent inhibition exerted by GluN2A present in the NMDAR is the major candidate for the mechanism underlying the increase in receptor conductance. Therefore, this process should be the main target for future research aiming at developing neuroprotection against HPNS and HBOTx.

Amorphous selenium inhibits oxidative stress injury of neurons in vascular dementia rats by activating NMDAR pathway.

Vascular dementia (VD) is one of the most common causes of dementia, taking account for about 20% of all cases. Although studies have found that selenium supplementation can improve the cognitive ability of Alzheimer's patients, there is currently no research on the cognitive impairment caused by VD. This study aimed to investigate the role and mechanism of Amorphous selenium nanodots (A SeNDs) in the prevention of VD. The bilateral common carotid artery occlusion (BCCAO) method was used to establish a VD model. The neuroprotective effect of A SeNDs was evaluated by Morris water maze, Transcranial Doppler TCD, hematoxylin-eosin (HE) staining, Neuron-specific nuclear protein (Neu N) staining and Golgi staining. Detect the expression levels of oxidative stress and Calcium-calmodulin dependent protein kinase II (CaMK II), N-methyl-D-aspartate receptor subunit NR2A, and postsynaptic dense protein 95 (PSD95). Finally, measure the concentration of calcium ions in neuronal cells. The results showed that A SeNDs could significantly improve the learning and memory ability of VD rats, restore the posterior arterial blood flow of the brain, improve the neuronal morphology and dendritic remodeling of pyramidal cells in hippocampal CA1 area, reduce the level of oxidative stress in VD rats, increase the expression of NR2A, PSD95, CaMK II proteins and reduce intracellular calcium ion concentration, but the addition of selective NR2A antagonist NVP-AAMO77 eliminated these benefits. It suggests that A SeNDs may improve cognitive dysfunction in vascular dementia rats by regulating the NMDAR pathway.

Saffron carotenoids reversed the UCMS-induced depression and anxiety in rats: Behavioral and biochemical parameters, and hippocampal BDNF/ERK/CREB and NR2B signaling markers.

BACKGROUND: Depression is a debilitating condition that affects the mind and the individual's body. The improving effects of saffron on depression and anxiety have long been discussed, with limited information about the molecular mechanism of action. HYPOTHESIS/PURPOSE: Investigating the effect of saffron carotenoids, Crocin and Crocetin, on depression and anxiety in rats by emphasizing some signaling pathways involved. STUDY DESIGN: Depression and anxiety were induced in rats via unpredictable chronic mild stress (UCMS). Then different rat groups were treated with Crocin, Crocetin, Fluoxetine, and vehicle. Behavioral tests were done before and after treatment. METHODS: The serum Serotonin and Corticosterone and the expression of some hippocampal signaling proteins were studied. Furthermore, bioinformatics tools were used to predict the interactions of Crocin/ Crocetin with the Serotonin transporter and NMDA receptor subunit NR2B. Then, the patch-clamp was used to study the interaction of Crocetin with the NMDA receptor. RESULTS: Various behavioral tests confirmed the induction of depression and the improvement of depression by these natural carotenoids. In addition, Crocin/ Crocetin significantly increased the decreased serum Serotonin and reduced the increased serum Corticosterone in the depressed groups. They also increased or caused a trend of increase in the CREB, ERK, BAD, BDNF, p11, and 5-HT1B expression in the hippocampus of the depressed groups. In addition, there were an increase or a trend in p-CREB/CREB, p-ERK1/2 /ERK1/2, and p-BAD/BAD ratios in the Crocin/ Crocetin treated depressed groups. However, the NR2B and FOXO3a expression showed a trend of decrease in depressed groups after treatment. The bioinformatics data indicated that Crocin/ Crocetin could bind to the Serotonin transporter (SLC6A4) and NR2B subunit of the NMDA receptor. Both carotenoids bind to the same site as Fluoxetine in the SLC6A4. However, they bound to different sites on the NR2B. So, Crocetin binds to NR2B at the same site as Ifenprodil. But Crocin bound to another site. The whole cell patch-clamp recording on the normal rat hippocampus revealed a significant decrease in the NMDA peak amplitude after Crocetin treatment, indicating its inhibitory effect on this receptor. CONCLUSION: The antidepressant activities of Crocin/ Crocetin are possibly due to their effects on Serotonin and Corticosterone serum concentrations, NR2B expression, and the downstream signaling pathways. Furthermore, these natural carotenoids, like Fluoxetine, induced an increasing tendency in p11 and 5HT1B in depressed rats.

Chinese Tuina remodels the synaptic structure in neuropathic pain rats by downregulating the expression of N-methyl D-aspartate receptor subtype 2B and postsynaptic density protein-95 in the spinal cord dorsal horn.

OBJECTIVE: To investigate whether the Chinese massage system, Tuina, exerts analgesic effects in a rat model of chronic constriction injury (CCI) by remodeling the synaptic structure in the spinal cord dorsal horn (SCDH). METHODS: Sixty-nine male Sprague-Dawley rats were randomly and evenly divided into the normal group, sham group, CCI group, CCI + Tuina group, CCI + MK-801 [an -methyl D-aspartate receptor subtype 2B (NR2B) antagonist] group, and CCI + MK-801 + Tuina group. The neuropathic pain model was established using CCI with right sciatic nerve ligation. Tuina was administered 4 d after CCI surgery, using pressing manipulation for 10 min, once daily. Motor function was observed with the inclined plate test, and pain behaviors were observed by the Von Frey test and acetone spray test. At 19 d after surgery, the L3-L5 spinal cord segments were removed. Glutamate, interleukin 1ß (IL-1ß), and tumor necrosis factor-α (TNF-α) levels were detected by enzyme-linked immunosorbent assay. The protein expression levels of NR2B and postsynaptic density protein-95 (PSD-95) were detected by Western blot, and the synaptic structure was observed by transmission electron microscopy (TEM). RESULTS: CCI reduced motor function and caused mechanical and cold allodynia in rats, increased glutamate concentration and TNF-α and IL-1ß levels, and increased expression of synapse-related proteins NR2B and PSD-95 in the SCDH. TEM revealed that the synaptic structure of SCDH neurons was altered. Most of these disease-induced changes were reversed by Tuina and intrathecal injection of MK-801 ( < 0.05 or < 0.01). For the majority of experiments, no significant differences were found between the CCI + MK-801 and CCI + MK-801 + Tuina groups. CONCLUSIONS: Chinese Tuina can alleviate pain by remodeling the synaptic structure, and NR2B and PSD-95 receptors in the SCDH may be among its targets.

Symbiotic Supplementation (E. faecium and Agave Inulin) Improves Spatial Memory and Increases Plasticity in the Hippocampus of Obese Rats: A Proof-of-Concept Study.

Obesity has been linked to cognitive impairment through systemic low-grade inflammation. High fat and sugar diets (HFSDs) also induce systemic inflammation, either by induced Toll-like receptor 4 response, or by causing dysbiosis. This study aimed to evaluate the effect of symbiotics supplementation on spatial and working memory, butyrate concentration, neurogenesis, and electrophysiological recovery of HFSD-fed rats. In a first experiment, Sprague-Dawley male rats were given HFSD for 10 weeks, after which they were randomized into 2 groups (n = 10 per group): water (control), or Enterococcus faecium + inulin (symbiotic) administration, for 5 weeks. In the fifth week, spatial and working memory was analyzed through the Morris Water Maze (MWM) and Eight-Arm Radial Maze (RAM) tests, respectively, with 1 week apart between tests. At the end of the study, butyrate levels from feces and neurogenesis at hippocampus were determined. In a second experiment with similar characteristics, the hippocampus was extracted to perform electrophysiological studies. Symbiotic-supplemented rats showed a significantly better memory, butyrate concentrations, and neurogenesis. This group also presented an increased firing frequency in hippocampal neurons [and a larger N-methyl-d-aspartate (NMDA)/α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) current ratio] suggesting an increase in NMDA receptors, which in turn is associated with an enhancement in long-term potentiation and synaptic plasticity. Therefore, our results suggest that symbiotics could restore obesity-related memory impairment and promote synaptic plasticity.

GluN2D subunit-containing NMDA receptors regulate reticular thalamic neuron function and seizure susceptibility.

Thalamic regulation of cortical function is important for several behavioral aspects including attention and sensorimotor control. This region has also been studied for its involvement in seizure activity. Among the NMDA receptor subunits GluN2C and GluN2D are particularly enriched in several thalamic nuclei including nucleus reticularis of the thalamus (nRT). We have previously found that GluN2C deletion does not have a strong influence on the basal excitability and burst firing characteristics of reticular thalamus neurons. Here we find that GluN2D ablation leads to reduced depolarization-induced spike frequency and reduced hyperpolarization-induced rebound burst firing in nRT neurons. Furthermore, reduced inhibitory neurotransmission was observed in the ventrobasal thalamus (VB). A model with preferential downregulation of GluN2D from parvalbumin (PV)-positive neurons was generated. Conditional deletion of GluN2D from PV neurons led to a decrease in excitability and burst firing. In addition, reduced excitability and burst firing was observed in the VB neurons together with reduced inhibitory neurotransmission. Finally, young mice with GluN2D downregulation in PV neurons showed significant resistance to pentylenetetrazol-induced seizure and differences in sensitivity to isoflurane anesthesia but were normal in other behaviors. Conditional deletion of GluN2D from PV neurons also affected expression of other GluN2 subunits and GABA receptor in the nRT. Together, these results identify a unique role of GluN2D-containing receptors in the regulation of thalamic circuitry and seizure susceptibility which is relevant to mutations in GRIN2D gene found to be associated with pediatric epilepsy.

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

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

Anti-depressant-like effect of fermented Gastrodia elata Bl. by regulating monoamine levels and BDNF/NMDAR pathways in mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Gastrodia elata Blume (GE) is a Chinese medicinal herb commonly used to treat central nervous system-related diseases, including headaches, dizziness, epilepsy, numbness of the limbs and depression. AIM OF THE STUDY: Microbial-based fermentation has been successfully used to increase the extract efficiency of medicinal herbs in recent years. However, no study has hitherto explored the anti-depressant-like effect of GE processed by microorganisms. Herein, this subject aimed to clarify the anti-depressant-like effect of fermented Gastrodia elata Bl. (FGE) and its active chemical constituents. MATERIALS AND METHODS: The chronic unpredictable mild stress (CUMS) model, a well-established animal model of depression, was induced in Kunming (KM) mice. The mice were administrated with FGE for 3 weeks. The sucrose preference test (SPT), open field test (OFT) and tail suspension test (TST) were conducted. Moreover, the levels of serotonin (5-HT) and dopamine (DA) in brain tissue homogenates, the concentration of Ca2+ and the activity of MAO in serum, H&E and Nissl staining in the hippocampus, and the hippocampus protein expressions of BDNF, NMDAR1, NMDAR2A and NMDAR2B relevant to depression were detected. Furthermore, chemical constituents of FGE were further isolated, and the protective activity of the obtained compounds against NMDA-induced PC-12 cell damage was assessed. RESULTS: FGE could alleviate the depression state in CUMS-induced mice and reduce apoptosis of neuronal cells in the hippocampus. Furthermore, FGE could improve the contents of 5-HT, DA and decrease the concentration of Ca2+ and MAO activity in brain tissue and serum compared with the control group. It could reverse the decreased expression of BDNF, NMDAR2A and NMDAR2B and increase NMDAR1 protein expression. Investigation of the active constituents from FGE yielded two new compounds, (4-(((4-ethoxybenzyl) oxy)methyl)-phenol 1 and 3-((4-hydroxy benzyl)oxy)propane-1,2-diol) 2, with twelve known compounds (3-14). The compounds (3-((4-hydroxybenzyl)oxy)propane-1,2-diol 2, 4, 4'-dihydroxyd iphenyl methane 3, and bungein A 4) protected against NMDA-induced PC-12 cells damage. CONCLUSION: This study demonstrated that FGE could improve the depressive behavior of CUMS-induced mice and exert a protective effect on nerve cells in the brain. Importantly, compounds 2-4 are the active components of FGE. Overall, the above findings suggest that FGE has huge prospects for application in treating depression-related diseases.

Recovery from the damage of cranial radiation modulated by memantine, an NMDA receptor antagonist, combined with hyperbaric oxygen therapy.

BACKGROUND: Radiotherapy is an important treatment option for central nervous system malignancies. However, cranial radiation induces hippocampal dysfunction and white matter injury; this leads to cognitive dysfunction, and results in a reduced quality of life in patients. Excitatory glutamate signaling through N-methyl-d-aspartate receptors (NMDARs) plays a central role both in hippocampal neurogenesis and in the myelination of oligodendrocytes in the cerebrum. METHODS: We provide a method for quantifying neurogenesis in human subjects in live brain during cancer therapy. Neuroimaging using originally created behavioral tasks was employed to examine human hippocampal memory pathway in patients with brain disorders. RESULTS: Treatment with memantine, a non-competitive NMDAR antagonist, reversed impairment in hippocampal pattern separation networks as detected by functional magnetic resonance imaging. Hyperbaric preconditioning of the patients just before radiotherapy with memantine mostly reversed white matter injury as detected by whole brain analysis with Tract-Based Spatial Statics. Neuromodulation combined with the administration of hyperbaric oxygen therapy and memantine during radiotherapy facilitated the restoration of hippocampal function and white matter integrity, and improved higher cognitive function in patients receiving cranial radiation. CONCLUSIONS: The method described herein, for diagnosis of hippocampal dysfunction, and therapeutic intervention can be utilized to restore some of the cognitive decline experienced by patients who have received cranial radiation. The underlying mechanism of restoration is the production of new neurons, which enhances functionality in pattern separation networks in the hippocampi, resulting in an increase in cognitive score, and restoration of microstructural integrity of white matter tracts revealed by Tract-Based Spatial Statics Analysis.

Spinal cord astrocyte P2X7Rs mediate the inhibitory effect of electroacupuncture on visceral hypersensitivity of rat with irritable bowel syndrome.

This study explored the role of P2X7 receptors in spinal cord astrocytes in the electroacupuncture-induced inhibition of visceral hypersensitivity (VH) in rats with irritable bowel syndrome (IBS). Visceral hypersensitivity of IBS was intracolonically induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS). Visceromotor responses to colorectal distension (CRD-20,40,60,80 mmHg) and abdominal withdrawal reflex scoring (AWRs) were recorded after electroacupuncture at bilateral Zusanli (ST36) and Sanyinjiao (SP6) acupoints to evaluate the analgesic effect of electroacupuncture on visceral pain in rats with IBS. Fluorocitric acid (FCA), an astrocyte activity inhibitor, was injected intrathecally before electroacupuncture intervention and AWRs were recorded. Western blot and real-time qPCR were used to detect the expression of NMDA and P2X7 receptor to observe the regulation effect of electroacupuncture on NMDA receptor in the spinal cord of rats with visceral hypersensitivity. Intrathecal injection of P2X7 agonist or antagonist was administered before electroacupuncture treatment. To observe the effect of P2X7 receptor in spinal astrocytes on the inhibition of visceral hyperalgesia by electroacupuncture, the changes of AWR score, NMDA receptor in the spinal cord, and GFAP expression in astrocytes were detected. Inflammation of the colon had basically subsided at day 21 post-TNBS; persistent visceral hypersensitivity could be suppressed by electroacupuncture. This analgesic effect could be inhibited by FCA. The analgesic effect, downregulation of NMDA receptor NR1 subunit, and P2X7 protein of electroacupuncture were all reversed by FCA. P2X7 receptor antagonist A740003 can cooperate with EA to carry out analgesic effect in rats with visceral pain and downregulate the expression of NR1, NR2B, and GFAP in spinal dorsal horn. However, the P2X7 receptor agonist BzATP could partially reverse the analgesic effect of EA, inhibiting the downregulatory effect of EA on the expression of NR1, NR2B, and GFAP. These results indicate that EA may downregulate the expression of the NMDA receptor by inhibiting the P2X7 receptor in the spinal cord, thereby inhibiting spinal cord sensitization in IBS rats with visceral pain, in which astrocytes are an important medium.

Mechanisms Involved in the Neurotoxicity and Abuse Liability of Nitrous Oxide: A Narrative Review.

The recreational use of nitrous oxide (N2O) has increased over the years. At the same time, more N2O intoxications are presented to hospitals. The incidental use of N2O is relatively harmless, but heavy, frequent and chronic use comes with considerable health risks. Most importantly, N2O can inactivate the co-factor cobalamin, which, in turn, leads to paresthesia's, partial paralysis and generalized demyelinating polyneuropathy. In some patients, these disorders are irreversible. Several metabolic cascades have been identified by which N2O can cause harmful effects. Because these effects mostly occur after prolonged use, it raises the question of whether N2O has addictive properties, explaining its prolonged and frequent use at high dose. Several lines of evidence for N2O's dependence liability can be found in the literature, but the underlying mechanism of action remains controversial. N2O interacts with the opioid system, but N2O also acts as an N-methyl-D-aspartate (NMDA) receptor antagonist, by which it can cause dopamine disinhibition. In this narrative review, we provide a detailed description of animal and human evidence for N2O-induced abuse/dependence and for N2O-induced neurotoxicity.

ß-Elemene Improves Morphine Tolerance in Bone Cancer Pain via N-Methyl-D-Aspartate Receptor 2B Subunit-Mediated µ-Opioid Receptor.

Background: Improving morphine tolerance (MT) is an urgent problem in the clinical treatment of bone cancer pain. Considering that ß-Elemene is widely used in the treatment of cancer pain, we explored the effects and mechanism of ß-Elemene in preventing MT of bone cancer pain. Method: Bone cancer pain and chronic MT rat model was established by injecting MADB106 cells and morphine (10 mg/kg). SH-SY5Y cells were treated with morphine (10 µg/mL) for 48 h to establish a cell model. The mechanical withdrawal threshold and thermal withdrawal latency of rats were detected by mechanical allodynia and thermal hyperalgesia tests, respectively. The protein expressions of µ-opioid receptor (MOPR), cyclic adenosine monophosphate (cAMP), N-methyl-D-aspartate receptor subunit 2B (NR2B), phosphorylated-calmodulin-dependent protein kinase II (p-CaMKII), and CaMKII were detected by western blot. The viability of SH-SY5Y cells was determined by the cell counting kit-8 assay. cAMP content in SH-SY5Y cells was measured by a LANCE cAMP kit. Result: Animal experiments showed that MT strengthened over time, while increased ß-Elemene dosage alleviated MT. The viability of SH-SY5Y cells was down-regulated by high-dose ß-Elemene. In the rat and cell models, long-term morphine treatment decreased the expression of MOPR and increased the cAMP and NR2B expressions and p-CaMKII/CaMKII, while ß-Elemene and siNR2B counteracted the effects of morphine treatment. In addition, siNR2B reversed the effects of ß-Elemene on related protein expressions and cAMP content in the cell model. Conclusion: ß-Elemene improved MT in bone cancer pain through the regulation of NR2B-mediated MOPR.