Expression Of NMDAR Research Articles

Prenatal diesel exhaust exposure alters hippocampal synaptic plasticity in offspring.

Diesel exhaust particles (DEPs) are major air pollutants emitted from automobile engines. Prenatal exposure to DEPs has been linked to neurodevelopmental and neurodegenerative diseases associated with aging. However, the specific mechanism by DEPs impair the hippocampal synaptic plasticity in the offspring remains unclear. Pregnant C57BL/6 mice were administered DEPs solution via the tail vein every other day for a total of 10 injections, then the male offsprings were studied to assess learning and memory by the Morris water maze. Additionally, protein expression in the hippocampus, including CPEB3, NMDAR (NR1, NR2A, NR2B), PKA, SYP, PSD95, and p-CREB was analyzed using Western blotting and immunohistochemistry. The alterations in the histomorphology of the hippocampus were observed in male offspring on postnatal day 7 following prenatal exposure to DEPs. Furthermore, 8-week-old male offspring exposed to DEPs during prenatal development exhibited impairments in the Morris water maze test, indicating deficits in learning and memory. Mechanistically, the findings from our study indicate that exposure to DEPs during pregnancy may alter the expression of CPEB3, SYP, PSD95, NMDAR (NR1, NR2A, and NR2B), PKA, and p-CREB in the hippocampus of both immature and mature male offspring. The results offer evidence for the role of the NMDAR/PKA/CREB and CPEB3 signaling pathway in mediating the learning and memory toxicity of DEPs in male offspring mice. The alterations in signaling pathways may contribute to the observed damage to synaptic structure and transmission function plasticity caused by DEPs. The findings hold potential for informing future safety assessments of DEPs.

Metformin's effect on male rats experiencing CMF-induced neurotoxicity.

Numerous cancers are treated with the chemotherapy drugs cyclophosphamide (CP), methotrexate (MT), and fluorouracil (FU). However, it should be noted that neurotoxicity is a possible side effect of chemotherapy. The pharmaceutical agent metformin (MTF) is used to control type 2 diabetes. The administration of MTF has been documented to exhibit a reduction in specific toxic effects associated with chemotherapy. The primary purpose of this research was to examine whether MTF could mitigate the neurotoxicity brought on by cranial magnetic field (CMF). A cohort of forty male rats was divided into four distinct groups, with ten animals in each. We classified them as either saline, MTF, CMF, or CMF+MTF. The rats in the experiment group received two doses of CMF via intraperitoneal injection and were also given MTF in their drinking water at a concentration of 2.5 mg/mL on a daily basis. Brain tissue was obtained for ELISA of Bax, Bcl-2, and caspase-3 expression, as well as to determine NMDA and AMPA receptor mRNA expression by real-time polymerase chain reaction (RT-PCR) analysis. Expression of AMPAR, NMDAR, Bax, Bcl-2, and caspase-3 was not notably different between the saline and MTF groups. In contrast, mRNA expression for AMPAR, NMDAR, Bax, and caspase-3 was notably upregulated in the CMF group, while Bcl-2 was downregulated. The co-administration of MTF and CMF did not mitigate these side effects. neurotoxicity was induced in rats by CMF treatment, but the elevation of the glutamatergic system and the elevation of apoptotic proteins were not prevented by the MTF co-treatment.

Impact of ketamine administration on chronic unpredictable stress-induced rat model of depression during extremely low-frequency electromagnetic field exposure: Behavioral, histological and molecular study.

In the study, we examined the effects of ketamine and extremely low-frequency electromagnetic fields (ELF-EMF) on depression-like behavior, learning and memory, expression of GFAP, caspase-3, p53, BDNF, and NMDA receptor in animals subjected to chronic unpredictable stress (CUS). After applying 21 days of chronic unpredictable stress, male rats received intraperitoneal (IP) of ketamine (5mg/kg) and then were exposed to ELF-EMF (10-Hz, 10-mT exposure conditions) for 3 days (3h per day) and behavioral assessments were performed 24h after the treatments. Instantly after the last behavioral test, the brain was extracted for Nissl staining, immunohistochemistry, and real-time PCR analyses. Immunohistochemistry (IHC) was conducted to assess the effect of ketamine and ELF-EMF on the expression of astrocyte marker (glial fibrillary acidic protein, GFAP) in the CA1 area of the hippocampus and medial prefrontal cortex (mPFC). Also, real-time PCR analyses were used to investigate the impacts of the combination of ketamine and ELF-EMF on the expression of caspase3, p53, BDNF, and NMDA receptors in the hippocampus in rats submitted to the CUS procedure. Results were considered statistically significant when p<.05. Our results revealed that the combination of ketamine and ELF-EMF increased depression-like behavior,increased degenerated neurons and decreased the number of GFAP (+) cells in the CA1 area and mPFC, incremented the expression of caspase-3, and reduced the expression of BDNF in the hippocampus but showed no effect on the expression of p53 and NMDA-R. These results reveal that combining ketamine and ELF-EMF has adverse effects on animals under chronic unpredictable stress (CUS).

Remote ischemic preconditioning protects against spinal cord ischemia–reperfusion injury in mice by activating NMDAR/AMPK/PGC-1α/SIRT3 signaling

BackgroundTo study the protective effects of delayed remote ischemic preconditioning (RIPC) against spinal cord ischemia–reperfusion injury (SCIRI) in mice and determine whether SIRT3 is involved in this protection and portrayed its upstream regulatory mechanisms.MethodsIn vivo, WT or SIRT3 global knockout (KO) mice were exposed to right upper and lower limbs RIPC or sham ischemia. After 24 h, the abdominal aorta was clamped for 20 min, then re-perfused for 3 days. The motor function of mice, number of Nissl bodies, apoptotic rate of neurons, and related indexes of oxidative stress in the spinal cord were measured to evaluate for neuroprotective effects. The expression and correlation of SIRT3 and NMDAR were detected by WB and immunofluorescence. In vitro, primary neurons were exacted and OGD/R was performed to simulate SCIRI in vivo. Neuronal damage was assessed by observing neuron morphology, detecting LDH release ratio, and flow cytometry to analyze the apoptosis. MnSOD and CAT enzyme activities, GSH and ROS level were also measured to assess neuronal antioxidant capacity. NMDAR-AMPK-PGC-1α signaling was detected by WB to portray upstream regulatory mechanisms of RIPC regulating SIRT3.ResultsCompared to the SCIRI mice without RIPC, mice with RIPC displayed improved motor function recovery, a reduced neuronal loss, and enhanced antioxidant capacity. To the contrary, the KO mice did not exhibit any effect of RIPC-induced neuroprotection. Similar results were observed in vitro. Further analyses with spinal cord tissues or primary neurons detected enhanced MnSOD and CAT activities, as well as increased GSH level but decreased MDA or ROS production in the RIPC + I/R mice or NMDA + OGD/R neurons. However, these changes were completely inhibited by the absence of SIRT3. Additionally, NMDAR-AMPK-PGC-1α signaling was activated to upregulate SIRT3 levels, which is essential for RIPC-mediated neuroprotection.ConclusionsRIPC enhances spinal cord ischemia tolerance in a SIRT3-dependent manner, and its induced elevated SIRT3 levels are mediated by the NMDAR-AMPK-PGC-1α signaling pathway. Combined therapy targeting SIRT3 is a promising direction for treating SCIRI.

Effect of Mucuna pruriens on brain NMDA receptor and tau protein gene expression in cerebral ischemic rats.

Present study aimed to assess effect of pre-treatment with Mucuna pruriens seed extract and its bioactive molecule(s) on NMDAR and Tau protein gene expression in cerebral ischemic rodent model. Methanol extract of M. pruriens seeds was characterized by HPLC, and β-sitosterol was isolated by flash chromatography. In vivo studies to observe the effect of pre-treatment (28 days) with methanol extract of M. pruriens seed and β-sitosterol on the unilateral cerebral ischemic rat model. Cerebral ischemia induced by left common carotid artery occlusion (LCCAO) for 75min (on day 29) followed by reperfusion for 12h. Rats (n = 48) divided into four groups. GroupI (control,Untreated + LCCAO)-No pre-treatment + cerebral ischemia; GroupII(β-sitosterol + Sham)-pre-treatment with β-sitosterol, 10mg/kg/day + sham-operated; GroupIII(β-sitosterol + LCCAO)-pre-treatment with β-sitosterol, 10mg/kg/day + cerebral ischemia; GroupIV(methanol extract + LCCAO)-pre-treatment with methanol extract of M. pruriens seeds, 50mg/kg/day + cerebral ischemia. Neurological deficit score was assessed just before sacrifice. Experimental animals were sacrificed after 12h reperfusion. Brain histopathology was performed. Gene expression of NMDAR and Tau protein of left cerebral hemisphere (occluded side) was performed by RT-PCR. Results revealed that the neurological deficit score was lower in groups III and IV compared to group I. NMDAR and tau protein mRNA expression in left cerebral hemisphere were upregulated in Group I, downregulated in groups III and IV. Histopathology of left cerebral hemisphere (occluded side) in Group I showed features of ischemic brain damage. Groups III and IV, left cerebral hemisphere showed less ischemic damage compared GroupI. Right cerebral hemisphere showed no areas of ischemia-induced brain changes. Pre-treatment with β-sitosterol and methanol extract of M. pruriens seeds may reduce ischemic brain injury following unilateral common carotid artery occlusion in rats.

Apoptosis of NG108-15 cells induced by fluorine combined with aluminum exposure and the effect of curcumin intervention

The mechanism by which the combination of fluorine and aluminum (FA) cause learning and memory impairment is still unclear. Curcumin is a yellow polyphenol extracted from the rhizome of the plant curcuma longa linn, which has anti-apoptotic and antioxidant functions; studies have shown that the PKC-NMDAR pathway plays an important role in the process of cell apoptosis. Based on the above, we designed an in vitro study on the role of curcumin in cell apoptosis caused by coexistence of FA. In this study, the cell viability of NG108-15 cell was detected by CCK-8; cell apoptosis was detected by AO/EB dual fluorescence staining kit; mRNA expressions of PKC and NMDAR were evaluated by qRT-PCR and protein expressions of caspase3, Bax, Bcl-2, PKC and NMDAR were evaluated by WB. Our results showed that curcumin alleviated FA-induced apoptosis of NG108-15 cells, possibly by inhibiting the increase of caspase3 protein and Bax protein, and the decrease of Bcl-2 protein, thereby upregulating the expression of PKC and NMDAR to exert neuroprotective effect.

Ghrelin Is Effective on Passive Avoidance Memory by Altering the Expression of NMDAR and HTR1a Genes in the Hippocampus of Male Wistar Rats.

Memory-dependent psychological behaviors have an important role in life. Memory strengthening in adulthood to prevent its defects in aging is a significant issue. The ghrelin endogenous hormone improves memory by targeting glutamatergic and serotonergic circuits. Also, citicoline, a memory strengthening drug in aging, is not recommended to adults due to its side effects. The current study aims to test that ghrelin treatment, like citicoline, would improve passive avoidance memory via expression of the genes encoding the N-methyl-D-aspartate receptor (NMDAR1) and the serotonin receptor 1A (HTR1α) involved in this process. Five groups of adult male rats received (1) saline (as control), (2) 0.5 mg/kg citicoline, or (3-5) 0.3, 1.5, and 3 nmol/μl ghrelin). The rats received the drugs via intra-hippocampal injection. Passive avoidance memory was determined using a shuttle box device. The latency to enter the dark chamber before (IL) and after (RL) injection and the total duration of the animal's presence in the light compartment (TLC) were evaluated. Then, the gene expression rates of NMDAR1 and HTR1α were measured by the Real-Time PCR. Ghrelin and citicoline had some similar and significant effects on passive avoidance memory, and both increased NMDAR1 and decreased HTR1α expression. Ghrelin, like citicoline, improves passive avoidance learning by altering the NMDAR1 and HTR1α expression in the hippocampus.

Activation of ephrinb1/EPHB2/MAP-2/NMDAR Mediates Hippocampal Neurogenesis Promoted by Transcranial Direct Current Stimulation in Cerebral-Ischemic Mice.

tDCS, a new, safe, non-invasive physical therapy method, is often used in motor dysfunction rehabilitation. However, the effects and underlying mechanisms of tDCS on hippocampal neurogenesis after cerebral ischemia (CI) are still unclear. This study aimed to investigate the promotive effect and mechanism of repetitive anodal-tDCS on hippocampal neurogenesis after CI in mice. The CI model in mice was established using bilateral common carotid artery occlusion (BCCAO). The pathological changes in the hippocampal CA1 region and cognitive function were assessed by hematoxylin and eosin staining and Morris water maze test, respectively. Hippocampal neurogenesis was observed by immunofluorescence staining. The levels of expression of ephrinb1, EPHB2, MAP-2, and NMDAR in the hippocampi were analyzed by qRT-PCR and Western blotting. Compared with the sham mice, the model mice showed significant neuronal damage in the hippocampal CA1 region (P < 0.01), cognitive dysfunction (P < 0.01), and endogenous hippocampal neurogenesis (P < 0.01). These results suggested that the CI model was successfully established, and that CI could promote endogenous hippocampal neurogenesis, but this hippocampal neurogenesis was unable to recover cognitive dysfunction. Compared with the model mice, the tDCS mice had ameliorated pathological damage in the CA1 region (P < 0.01), improved cognitive function (P < 0.01), increased hippocampal neurogenesis (P < 0.01), and increased mRNA and protein expression of ephrinb1, EPHB2, MAP-2, and NMDAR (P < 0.05). Repetitive anodal-tDCS can promote hippocampal neurogenesis and improve cognitive function in CI mice. The effect may be related to the activation of the ephrinb1/EPHB2/MAP-2/NMDAR signaling pathway.

Down-Regulation of NOX4 Expression in Dorsal Horn of Spinal Cord Could Alleviate Cancer-Induced Bone Pain in Rats by Reducing Oxidative Stress Response.

IntroductionCancer-induced bone pain (CIBP) is very common in patients with advanced cancer. Recent studies have shown that reactive oxygen species (ROS) can sense and regulate pain response process through spinal cord mechanism, and play a role in CIBP. NADPH oxidase (NOX) is a group of protease complexes that produce ROS. In the current study, we investigated the expression of NOX4 in the spinal dorsal horn of rats with CIBP and its related role and molecular mechanism.Materials and MethodsA rat CIBP model was established by injecting Walker-256 cells into the tibia medullary cavity, and the expression of NOX4 in spinal dorsal horn was down-regulated by injecting lentivirus into spinal cord. RT-PCR, Western blot and immunofluorescence staining were used to detect the expression of NOX4 in CIBP rats, cell localization and its effect on CIBP rats, and the effect of down-regulating the expression of NOX4 on the expression of H2O2, nitric oxide synthase nNO, antioxidant enzyme SOD, and the activity of neuro-receptor in spinal dorsal horn of rats.ResultsIn rats with CIBP, the expression of NOX4 was significantly increased, and immunofluorescence showed that NOX4 was mainly expressed in microglia in the dorsal horn of spinal cord. Down-regulating the expression of NOX4 in rats can reduce the level of H2O2 and nNO in dorsal horn tissue, and increase the expression of SOD to reduce the oxidative stress response. At the same time, down-regulating NOX4 can reduce the sensitivity of spinal cord and relieve the pain of bone cancer by inhibiting the expression of NMDAR and GABAA-γ2 in dorsal horn tissue.ConclusionNOX4 is a promising therapeutic target in CIBP, and down-regulation of NOX4 expression can alleviate CIBP in rats by reducing oxidative stress and weakening spinal cord sensitization.

The Effects of Ginsenoside Compound K Against Epilepsy by Enhancing the γ-Aminobutyric Acid Signaling Pathway.

The imbalance between the GABA-mediated inhibition and the glutamate-mediated excitation is the primary pathological mechanism of epilepsy. GABAergic and glutamatergic neurotransmission have become the most important targets for controlling epilepsy. Ginsenoside compound K (GCK) is a main metabolic production of the ginsenoside Rb1, Rb2, and Rc in the intestinal microbiota. Previous studies show that GCK promoted the release of GABA from the hippocampal neurons and enhanced the activity of GABAA receptors. GCK is shown to reduce the expression of NMDAR and to attenuate the function of the NMDA receptors in the brain. The anti-seizure effects of GCK have not been reported so far. Therefore, this study aimed to investigate the effects of GCK on epilepsy and its potential mechanism. The rat model of seizure or status epilepticus (SE) was established with either Pentylenetetrazole or Lithium chloride-pilocarpine. The Racine’s scale was used to evaluate seizure activity. The levels of the amino acid neurotransmitters were detected in the pilocarpine-induced epileptic rats. The expression levels of GABAARα1, NMDAR1, KCC2, and NKCC1 protein in the hippocampus were determined via western blot or immunohistochemistry after SE. We found that GCK had deceased seizure intensity and prolonged the latency of seizures. GCK increased the contents of GABA, while the contents of glutamate remained unchanged. GCK enhanced the expression of GABAARα1 in the brain and exhibited a tendency to decrease the expression of NMDAR1 protein in the hippocampus. The expression of KCC2 protein was elevated by the treatment of GCK after SE, while the expression of NKCC1 protein was reversely down-regulated. These findings suggested that GCK exerted anti-epileptic effects by promoting the hippocampal GABA release and enhancing the GABAAR-mediated inhibitory synaptic transmission.

Grewia tiliaefolia and its active compound vitexin regulate the expression of glutamate transporters and protect Neuro-2a cells from glutamate toxicity

AimGlutamate is a major neurotransmitter involved in several brain functions and glutamate excitotoxicity is involved in Alzheimer's disease (AD). In the current study, the neuroprotective effect of the Indian medicinal plant Grewia tiliaefolia (GT) and its active component vitexin was evaluated in Neuro-2a cells against glutamate toxicity. Materials and methodsNeuro-2a cells were exposed to glutamate to cause excitotoxicity and the neuroprotective effect of GT and vitexin were evaluated using biochemical studies (estimation of reactive oxygen species, reactive nitrogen species, protein carbonyl content, lipid peroxidation level, mitochondrial membrane potential and caspase-3 activity), molecular docking studies, gene expression and western blot analysis. Key findingsGlutamate exposure to Neuro-2a cells induced oxidative stress, loss of membrane potential, suppressed the expression of antioxidant response genes (Nrf-2, HO-1, NQO-1), glutamate transporters (GLAST-1, GLT-1) and induced the expression of NMDAR, Calpain. However, pre-treatment of cells with GT/vitexin inhibited oxidative stress mediated damage by augmenting the expression of Nrf-2/HO-1 pathway, inducing the expression of glutamate transporters and downregulating Calpain, NMDAR. Molecular docking showed that vitexin effectively binds to NMDAR and GSK-3β and thereby can inhibit their activation. GT/vitexin also inhibited glutamate induced Bax expression. SignificanceMethanol extract of G. tiliaefolia and its active component vitexin can act in an antioxidant dependent mechanism as well as by regulating glutamate transporters in mitigating the toxicity exerted by glutamate in Neuro-2a cells. Our results conclude that GT/vitexin can act as potential drug leads for the therapeutic intervention of AD.

Resection of melanocytic nevi as a potential treatment of anti-NMDAR encephalitis patients without tumor: report of three cases

The most common underlying tumor associated with anti-N-methyl D-aspartate-receptor (NMDAR) encephalitis is ovarian teratoma. Resection of the underlying tumor may decrease exposure of autoantigen and make for faster response of immunotherapy and less relapse frequency. Similar to teratoma, expression of NMDAR in human epidermal melanocytes was suspected recently. The dense melanocytes in melanocytic nevus may serve as potential autoantigens and are prone to increase relapse frequency in the tumor-negative patients. Three patients with confirmed diagnosis of anti-NMDAR encephalitis were described here. They shared common features that the screening tests for an ovarian teratoma or other tumors were all negative, while they were found to have prominent melanocytic nevi on the skin and resection of the nevi likely played a positive effect on their persistent recovery. This is a report on treatment of anti-NMDAR encephalitis patients without underlying tumor through resection of melanocytic nevi. More clinical and experimental investigations are needed to prove its validity.

The excitotoxity of NMDA receptor NR2D subtype mediates human fetal lung fibroblasts proliferation and collagen production

Studies have suggested that endogenous glutamate and N-methyl-d-aspartate (NMDA) receptor have an excitotoxity role during acute lung injury. Fibroblasts play a critical role in lung development and chronic lung disease after acute lung injury. This study aims to explore the immediate role of NMDAR activation in human lung fibroblasts. The expression of NMDAR 1 subtype (NR1) and four individual NMDAR 2 (NR2) subtypes (NR 2 A to D) was measured in human fetal lung fibroblasts (HFL-1 and MRC-5). Five NMDARs expression were all detectable in two cell lines. Although the expressions of NMDARs were different between MRC-5 and HFL-1, 1mM NMDA elicited the same trend in the downregulation of NR2A expression, the upregulation of NR2D, and the increase of cells proliferation and collagen production. Glutamate stimulation after 24-h of NMDA exposure resulted in weaker and more delayed but more prolonged iCa2+ elevation in HFL-1 than no NMDA exposed cells. NMDA increased the level of pERK1/2, cells proliferation and collagen production, whereas nonspecific NMDAR antagonist MK-801, NR2D-preferring receptor antagonist UBP141 and ERK1/2 phosphorylation inhibitor U0126 suppressed it, respectively. In conclusion, we found that NMDAR activation, NR2D in particular, is involved in human fetal lung fibroblast proliferation and collagen production through a potential ERK1/2-mediated mechanism.

Neo-adjuvant chemotherapy with cisplatin induces low expression of NMDA receptors and postoperative cognitive impairment

Whether Neo-adjuvant chemotherapy can affect patients’ postoperative brain function is not clear. In this study, we investigated the effect of preoperative cisplatin treatment on postoperative cognitive function and its possible mechanism in rats. Moreover, we also tested whether the NMDAR inhibitor memantine could attenuate cisplatin-induced alterations. 12-month-oldSprague-Dawley rats randomly received an intraperitoneal injection of either cisplatin once a week at a dose of 3mg/kg for three consecutive weeks or an equivalent volume of normal saline. After the injections, the normal saline injection group was divided into 3 groups (n=5 each): a normal saline group (group S), normal saline+pentobarbital group (group SP), and normal saline+pentobarbital+operation group (group SPO).The cisplatin injection group was divided into 3 groups: a cisplatin group (group C), cisplatin+pentobarbital group (group CP), and cisplatin+pentobarbital+operation group (group CPO).Rats in the group SP, SPO,CP and CPO were anaesthetized with sodium pentobarbital and then the SPO and CPO groups underwent a simple laparotomy operation. The effects of memantine were tested through two additional groups of rats (cisplatin+memantine group (group CM) and cisplatin+pentobarbital+operation+memantine group (group CPOM)). A Morris water maze test was performed to evaluate the spatial learning and memory ability five days after anesthesia or operation. After the test, the hippocampi were removed for detection of the expression of NMDAR by western bloting. The relevant protein expression levels of PSD95 and ERK1/2 were detected by western blot analysis. Rats treated with cisplatin had a longer mean escape latency and spent a shorter amount of time in the target quadrant than did the normal saline injection rats. Furthermore, the protein expression levels of NMDA receptors, PSD95 and ERK1/2 were decreased in cisplatin group and memantine could up-regulate their expression. These results suggest that neo-adjuvant chemotherapy with cisplatin exacerbate the postoperative cognitive dysfunction in rats, and this may be caused by a lower expression of NMDA receptors in the hippocampus. Memantine could attenuate these alterations.

Regulation of structural and functional synapse density by L-threonate through modulation of intraneuronal magnesium concentration

Oral administration of the combination of L-threonate (threonate) and magnesium (Mg2+) in the form of L-Threonic acid Magnesium salt (L-TAMS) can enhance learning and memory in young rats and prevent memory decline in aging rats and in Alzheimer’s disease model mice. Recent results from a human clinical trial demonstrate the efficacy of L-TAMS in restoring global cognitive abilities of older adults. Previously, we reported that neuronal intracellular Mg2+ serves as a critical signaling molecule for controlling synapse density, a key factor that determines cognitive ability. The elevation of brain Mg2+ by oral administration of L-TAMS in intact animals plays a significant role in mediating the therapeutic effects of L-TAMS. The current study sought to elucidate the unique role of threonate. We aimed to understand if threonate acts directly to elevate intraneuronal Mg2+, and why Mg2+ given without threonate is ineffective for enhancing learning and memory ability. We discovered that threonate is naturally present in cerebrospinal fluid (CSF) and oral treatment with L-TAMS elevated CSF threonate. In cultured hippocampal neurons, threonate treatment directly induced an increase in intracellular Mg2+ concentration. Functionally, elevating threonate upregulated expression of NR2B-containing NMDAR, boosted mitochondrial membrane potential (ΔΨm), and increased functional synapse density in neuronal cultures. These effects are unique to threonate, as other common Mg2+ anions failed to have the same results. Mechanistically, threonate’s effects were specifically mediated through glucose transporters (GLUTs). We also evaluated the effects of threonate in human neural stem cell-derived neurons, and found it was equally effective at upregulating synapse density. The current study provides an explanation for why threonate is an essential component of L-TAMS and supports the use of L-TAMS to promote cognitive abilities in human.

Changes in synaptic plasticity and expression of glutamate receptor subunits in the CA1 and CA3 areas of the hippocampus after transient global ischemia

Excess glutamate release from the presynaptic membrane has been thought to be the major cause of ischemic neuronal death. Although both CA1 and CA3 pyramidal neurons receive presynaptic glutamate input, transient cerebral ischemia induces CA1 neurons to die while CA3 neurons remain relatively intact. This suggests that changes in the properties of pyramidal cells may be the main cause related to ischemic neuronal death. Our previous studies have shown that the densities of dendritic spines and asymmetric synapses in the CA1 area are increased at 12h and 24h after ischemia. In the present study, we investigated changes in synaptic structures in the CA3 area and compared the expression of glutamate receptors in the CA1 and CA3 hippocampal regions of rats after ischemia. Our results demonstrated that the NR2B/NR2A ratio became larger after ischemia although the expression of both the NR2B subunit (activation of apoptotic pathway) and NR2A subunit (activation of survival pathway) decreased in the CA1 area from 6h to 48h after reperfusion. Furthermore, expression of the GluR2 subunit (calcium impermeable) of the AMPA receptor class significantly decreased while the GluR1 subunit (calcium permeable) remained unchanged at the same examined reperfusion times, which subsequently caused an increase in the GluR1/GluR2 ratio. Despite these notable differences in subunit expression, there were no obvious changes in the density of synapses or expression of NMDAR and AMPAR subunits in the CA3 area after ischemia. These results suggest that delayed CA1 neuronal death may be related to the dramatic fluctuation in the synaptic structure and relative upregulation of NR2B and GluR1 subunits induced by transient global ischemia.

The microRNA miR-124 suppresses seizure activity and regulates CREB1 activity.

miR-124, a brain-specific microRNA, was originally considered as a key regulator in neuronal differentiation and the development of the nervous system. Here we showed that miR-124 expression was suppressed in patients with epilepsy and rats after drug induced-seizures. Intrahippocampal administration of a miR-124 duplex led to alleviated seizure severity and prolonged onset latency in two rat models (pentylenetetrazole- and pilocarpine-induced seizures), while miR-124 inhibitor led to shortened onset latency in pilocarpine-induced seizure rat models. Moreover, the result of local field potentials (LFPs) records further demonstrated miR-124 may have anti-epilepsy function. Inhibition of neuronal firing by miR-124 was associated with the suppression of mEPSC, AMPAR- and NMDAR-mediated currents, which were accompanied by decreased surface expression of NMDAR. In addition, miR-124 injection resulted in decreased activity and expression of cAMP-response element-binding protein1 (CREB1). a key regulator in epileptogenesis. A dual-luciferase reporter assay was used to confirm that miR-124 targeted directly the 3'UTR of CREB1 gene and repressed the CREB1 expression in HEK293T cells. Immunoprecipitation studies confirmed that the CREB1 antibody effectively precipitated CREB1 and NMDAR1 but not GLUR1 from rat brain hippocampus. These results revealed a previously unknown function of miR-124 in neuronal excitability and provided a new insight into molecular mechanisms underlying epilepsy.

Hydrogen Sulfide Ameliorates Homocysteine-Induced Alzheimer's Disease-Like Pathology, Blood-Brain Barrier Disruption, and Synaptic Disorder.

Elevated plasma total homocysteine (Hcy) level is associated with an increased risk of Alzheimer's disease (AD). During transsulfuration pathways, Hcy is metabolized into hydrogen sulfide (H2S), which is a synaptic modulator, as well as a neuro-protective agent. However, the role of hydrogen sulfide, as well as N-methyl-D-aspartate receptor (NMDAR) activation, in hyperhomocysteinemia (HHcy) induced blood-brain barrier (BBB) disruption and synaptic dysfunction, leading to AD pathology is not clear. Therefore, we hypothesized that the inhibition of neuronal NMDA-R by H2S and MK801 mitigate the Hcy-induced BBB disruption and synapse dysfunction, in part by decreasing neuronal matrix degradation. Hcy intracerebral (IC) treatment significantly impaired cerebral blood flow (CBF), and cerebral circulation and memory function. Hcy treatment also decreases the expression of cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE) in the brain along with increased expression of NMDA-R (NR1) and synaptosomal Ca(2+) indicating excitotoxicity. Additionally, we found that Hcy treatment increased protein and mRNA expression of intracellular adhesion molecule 1 (ICAM-1), matrix metalloproteinase (MMP)-2, and MMP-9 and also increased MMP-2 and MMP-9 activity in the brain. The increased expression of ICAM-1, glial fibrillary acidic protein (GFAP), and the decreased expression of vascular endothelial (VE)-cadherin and claudin-5 indicates BBB disruption and vascular inflammation. Moreover, we also found decreased expression of microtubule-associated protein 2 (MAP-2), postsynaptic density protein 95 (PSD-95), synapse-associated protein 97 (SAP-97), synaptosomal-associated protein 25 (SNAP-25), synaptophysin, and brain-derived neurotrophic factor (BDNF) showing synapse dysfunction in the hippocampus. Furthermore, NaHS and MK801 treatment ameliorates BBB disruption, CBF, and synapse functions in the mice brain. These results demonstrate a neuro-protective effect of H2S over Hcy-induced cerebrovascular pathology through the NMDA receptor. Our present study clearly signifies the therapeutic ramifications of H2S for cerebrovascular diseases such as Alzheimer's disease. Graphical Abstract ᅟ.

The N-methyl-D-aspartate receptor, a precursor to N-methyl-D-aspartate receptor encephalitis, is found in the squamous tissue of ovarian teratomas.

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is the most common antibody-mediated limbic encephalitis and is associated with underlying ovarian teratoma. Previous studies suggest that expression of NMDAR on teratoma neural tissue initiates an autoimmune response to NMDAR in the brain. As some teratomas of patients with anti-NMDAR encephalitis lack neuronal tissue, we questioned if there could be an alternate mechanism of the disease. We performed immunohistochemical analyses for NMDAR and correlated its expression with histology on 10 control teratomas and 5 teratomas associated with anti-NMDAR encephalitis. Both control and case teratomas expressed NMDAR-bearing neural tissue. All 15 teratomas contained large amounts of NMDAR bearing squamous epithelium; in 2 cases this was the only tissue expressing NMDAR. NMDAR-bearing neural tissue is not the sole source of encephalitis in all patients. Furthermore, we speculate that NMDAR expression by squamous epithelium may contribute to the disease development in some patients.

Orexin-A influences mRNA expression of some glutamatergic receptor subtypes in Carassius auratus (Actinopterygii: Cyprinidae)

At date, studies are beginning to show that ionotropic glutamate receptors (iGluRs) are influenced by the orexin/hypocretin (ORX) system during the regulation of several physiological functions in mammals. In this study, we showed that the effects of ORX-A and specific glutamatergic antagonists (3-(+)-2-carboxypiperazin-4-yl-propyl-1-phosphonate, CPP/cyano-7-nitro-quinoxaline-2,3-dione, CNQX) on the expression of NMDAR (NR1) and AMPAR (GluR2) subtype genes underlie a tight relationship of the ORXergic system with iGluRs in the teleost Carassius auratus (goldfish; Linnaeus, 1758). The application of specific primers for NR1 and GluR2 permitted us to identify two partial coding sequences (cds) of 115 bp and 90 bp that were highly similar (97% and 81%, respectively) to the related sequences of the rat (Rattus norvegicus). These cds were used to carry out a semi-quantitative RT-PCR (reverse transcription-polymerase chain reaction) in which a differentiated expression pattern of NR1 and GluR2 was obtained following drug treatments. Interestingly, goldfish treated with ORX-A showed a significant (p < 0.001) up-regulation of NR1 expression (∼120%) while GluR2 was only moderately up-regulated (+45%; p < 0.05) with respect to controls. As far as CPP effects were concerned, this NMDAR antagonist strongly blocked (–72%; p < 0.01) NR1 expression while CNQX did not account for any significant variation with respect to controls. Moreover, the contextual administration of ORX-A+CPP continued to provide a blocking effect on NR1 expression, especially when compared to ORX-A-treated fish (–98%). On the other hand, ORX-A+CNQX caused an up-regulated trend even though of a lesser extent with respect to ORX-A-treated fish (–44%). Regarding GluR2, only the AMPAR antagonist moderately blocked (–38%) its expression, an effect that was completely abolished in the presence of ORX-A. Overall, results of the present study highlight, for the first time, a prevalent up-regulatory role of ORX-A on NMDAR subtype mRNA expression in fish.