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Convulsive status epilepticus (CSE) is a common critical neurological condition that can lead to irreversible hippocampal neuron damage and cognitive dysfunction. Multiple studies have demonstrated the critical roles that long non-coding RNA Mir155hg plays in a variety of diseases. However, less is known about the function and mechanism of Mir155hg in CSE. Here we investigate and elucidate the mechanism underlying the contribution of Mir155hg to CSE-induced hippocampal neuron injury. By applying high-throughput sequencing, we examined the expression of differentially expressed genes in normal and CSE rats. Subsequent RT-qPCR enabled us to measure the level of Mir155hg in rat hippocampal tissue. Targeted knockdown of Mir155hg was achieved by the AAV9 virus. Additionally, we utilized HE and Tunel staining to evaluate neuronal injury. Immunofluorescence (IF), Golgi staining, and brain path clamping were also used to detect the synaptic plasticity of hippocampal neurons. Finally, through IF staining and Sholl analysis, we assessed the degree of microglial phagocytic function. It was found that the expression of Mir155hg was elevated in CSE rats. HE and Tunel staining results showed that Mir155hg knockdown suppressed the hippocampal neuron loss and apoptosis followed CSE. IF, Golgi staining and brain path clamp data found that Mir155hg knockdown enhanced neuronal synaptic plasticity. The results from IF staining and Sholl analysis showed that Mir155hg knockdown enhanced microglial phagocytosis. Our findings suggest that Mir155hg promotes CSE-induced hippocampal neuron injury by inhibiting microglial phagocytosis. [ABSTRACT FROM AUTHOR]

As a noninvasive technique, ultrasound stimulation is known to modulate neuronal activity both in vitro and in vivo. The latest explanation of this phenomenon is that the acoustic wave can activate the ion channels and further impact the electrophysiological properties of targeted neurons. However, the underlying mechanism of low-intensity pulsed ultrasound (LIPUS)-induced neuro-modulation effects is still unclear. Here, we characterize the excitatory effects of LIPUS on spontaneous activity and the intracellular Ca2+ homeostasis in cultured hippocampal neurons. By whole-cell patch clamp recording, we found that 15 min of 1-MHz LIPUS boosts the frequency of both spontaneous action potentials and spontaneous excitatory synaptic currents (sEPSCs) and also increases the amplitude of sEPSCs in hippocampal neurons. This phenomenon lasts for > 10 min after LIPUS exposure. Together with Ca2+ imaging, we clarified that LIPUS increases the [Ca2+]cyto level by facilitating L-type Ca2+ channels (LTCCs). In addition, due to the [Ca2+]cyto elevation by LIPUS exposure, the Ca2+-dependent CaMKII-CREB pathway can be activated within 30 min to further regulate the gene transcription and protein expression. Our work suggests that LIPUS regulates neuronal activity in a Ca2+-dependent manner via LTCCs. This may also explain the multi-activation effects of LIPUS beyond neurons. LIPUS stimulation potentiates spontaneous neuronal activity by increasing Ca2+ influx. [ABSTRACT FROM AUTHOR]

Sevoflurane is one of the most widely used inhaled anesthetics. MicroRNAs (miRNAs) have been demonstrated to affect sevoflurane anesthesia-induced neuron damage. The purpose of this study was to investigate the role and mechanism of miR-181a-5p in sevoflurane-induced hippocampal neuronal injury. Primary hippocampal neurons were identified using microscopy and immunofluorescence. The viability and apoptosis of sevoflurane anesthesia-induced neurons were detected by cell counting kit-8 (CCK-8) assay and terminal-deoxynucleoitidyl transferase-mediated nick end-labeling (TUNEL) staining assay, respectively. The levels of apoptosis- and oxidative stress-related proteins as well as the markers in the Wnt/β-catenin signaling pathway were examined by immunoblotting. Enzyme-linked immuno-sorbent assays were performed to examine the levels of inflammatory cytokines. Luciferase reporter assay was conducted to validate the combination between miR-181a-5p and DEAD-box helicase 3, X-linked (DDX3X). Sevoflurane exposure led to significantly inhibited hippocampal neuron viability and elevated miR-181a-5p expression. Knockdown of miR-181a-5p alleviated sevoflurane-induced neuron injury by reducing cell apoptosis, inflammatory response, and oxidative stress. Additionally, DDX3X was targeted and negatively regulated by miR-181a-5p. Moreover, miR-181a-5p inhibitor activated the Wnt/β-catenin pathway via DDX3X in sevoflurane-treated cells. Rescue experiments revealed that DDX3X knockdown or overexpression of Wnt antagonist Dickkopf-1 (DKK1) reversed the suppressive effects of miR-181a-5p inhibitor on cell apoptosis, inflammatory response, and oxidative stress in sevoflurane-treated neuronal cells. MiR-181a-5p ameliorated sevoflurane-triggered neuron injury by regulating the DDX3X/Wnt/β-catenin axis, suggesting the potential of miR-181a-5p as a novel and promising therapeutic target for the treatment of sevoflurane-evoked neurotoxicity. [ABSTRACT FROM AUTHOR]

Ferroptosis is a distinct peroxidation-driven form of cell death tightly involved in subarachnoid hemorrhage (SAH). This study delved into the mechanism of deferoxamine (DFO, an iron chelator) in SAH-induced ferroptosis and inflammation. SAH mouse models were established by endovascular perforation method and injected intraperitoneally with DFO, or intraventricularly injected with the Nrf2 pathway inhibitor ML385 before SAH, followed by detection of neurological function, blood–brain barrier (BBB) permeability, and brain water content. Apoptotic level of hippocampal neurons, symbolic changes of ferroptosis, and levels of pro-inflammatory cytokines were assessed using TUNEL staining, Western blotting, colorimetry, and ELISA. The localization and expression of nuclear factor-erythroid 2-related factor 2 (Nrf2) were detected. HT22 cells were exposed to Hemin as in vitro SAH models and treated with FIN56 to induce ferroptosis, followed by evaluation of the effects of DFO on FIN56-treated HT22 cells. The regulation of Nrf2 in thioredoxin reductase 1 (TXNRD1) was analyzed by co-immunoprecipitation and Western blotting. Moreover, HT22 cells were treated with DFO and ML385 to identify the role of DFO in the Nrf2/TXNRD1 axis. DFO extenuated brain injury, and ferroptosis and inflammation in hippocampal neurons of SAH mice. Nrf2 localized at the CA1 region of hippocampal neurons, and DFO stimulated nuclear translocation of Nrf2 protein in hippocampal neurons of SAH mice. Additionally, DFO inhibited ferroptosis and inflammatory responses in FIN56-induced HT22 cells. Nrf2 positively regulated TXNRD1 protein expression. Indeed, DFO alleviated FIN56-induced ferroptosis and inflammation via activation of the Nrf2/TXNRD1 axis. DFO alleviated neurological deficits, BBB disruption, brain edema, and brain injury in mice after SAH by inhibiting hippocampal neuron ferroptosis via the Nrf2/TXNRD1 axis. DFO ameliorates SAH-induced ferroptosis and inflammatory responses in hippocampal neurons by activating the Nrf2/TXNRD1 axis. [ABSTRACT FROM AUTHOR]

The hypothalamic–pituitary–adrenal (HPA) system plays an important role in stress response. Chronic stress is thought to induce neuronal damage and contribute to the pathogenesis of psychiatric disorders by causing dysfunction of the HPA system and promoting the production and release of glucocorticoids, including corticosterone and cortisol. Several clinical studies have demonstrated the efficacy of herbal medicines in treating psychiatric disorders; however, their effects on corticosterone-induced neuronal cell death remain unclear. Here, we used HT22 cells to evaluate the neuroprotective potential of herbal medicines used in neuropsychiatry against corticosterone-induced hippocampal neuronal cell death. Cell death was assessed using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) reduction and Live/Dead assays. Hangekobokuto, Kamikihito, Saikokaryukotsuboreito, Kamishoyosan, and Yokukansan were supplied in the form of water-extracted dried powders. Exposure of HT22 cells to ≥ 100 μM corticosterone decreased MTT values. Exposure to 500 μM corticosterone alone reduced MTT values to 18%, while exposure to 10 μM Mifepristone (RU486)—a glucocorticoid receptor antagonist—restored values to 36%. Corticosterone-induced cell death was partially suppressed by treatment with RU486. At 100 μg/mL, Hangekobokuto significantly suppressed the decrease in MTT values (15–32%) and increase in the percentage of ethidium homodimer-1-positive dead cells caused by corticosterone exposure (78–36%), indicating an inhibitory effect on cell death. By contrast, Kamikihito, Saikokaryukotsuboreito, Kamishoyosan, and Yokukansan did not affect corticosterone-induced cell death. Therefore, our results suggest that Hangekobokuto may ameliorate the onset and progression of psychiatric disorders by suppressing neurological disorders associated with increased levels of glucocorticoids. [ABSTRACT FROM AUTHOR]

Uncovering mechanisms underlying epileptogenesis aids in preventing further epilepsy progression and to lessen seizure severity and frequency. The purpose of this study is to explore the antiepileptogenic and neuroprotective mechanisms of EGR1 in neuron injuries encountered in epilepsy. Bioinformatics analysis was conducted to identify the key genes related to epilepsy. The mice were rendered epileptic using the kainic acid protocol, followed by measurement of seizure severity, high amplitude and frequency, pathological changes of hippocampal tissues and neuron apoptosis. Furthermore, an in vitro epilepsy model was constructed in the neurons isolated from newborn mice, which was then subjected to loss- and gain-of-function investigations, followed by neuron injury and apoptosis assessment. Interactions among EGR1, METTL3, and VIM were analyzed by a series of mechanistic experiments. In the mouse and cell models of epilepsy, VIM was robustly induced. However, its knockdown reduced hippocampal neuron injury and apoptosis. Meanwhile, VIM knockdown decreased inflammatory response and neuron apoptosis in vivo. Mechanistic investigations indicated that EGR1 transcriptionally activated METTL3, which in turn downregulated VIM expression through m6A modification. EGR1 activated METTL3 and reduced VIM expression, thereby impairing hippocampal neuron injury and apoptosis, preventing epilepsy progression. Taken together, this study demonstrates that EGR1 alleviates neuron injuries in epilepsy by inducing METTL3-mediated inhibition of VIM, which provides clues for the development of novel antiepileptic treatments. [ABSTRACT FROM AUTHOR]

Ketamine, a noncompetitive N-methyl D-aspartate (NMDA) receptor antagonist, is widely used in pediatric clinical practice. The neuroprotective and neurotoxic effects of ketamine on brain neurons during development remain controversial. The reason may be related to the different concentrations of ketamine used in practice and the small range of concentrations used in previous studies. In this study, cultured hippocampal neurons were treated with ketamine in a wide range of concentrations to comprehensively observe the effects of different concentrations of ketamine on neurons. We demonstrated that low concentrations of ketamine (10 μM, 100 μM and 1000 μM) promoted neuronal survival (p < 0.05) and reduced neuronal apoptosis (p < 0.05) compared with those of the control group. High concentrations of ketamine (2000 μM, 2500 μM and 3000 μM) reduced neuronal survival (p < 0.05) and promoted neuronal apoptosis (p < 0.05). The p38 MAPK inhibitor SB203580 reduced neuronal apoptosis induced by high concentrations of ketamine (2500 μM) (p < 0.05). Our findings indicate that ketamine exerts a dual effect on the apoptosis of primary cultured fetal rat hippocampal neurons in vitro and that the neurotoxic effects of ketamine are related to activation of the p38 MAPK signaling pathway. [ABSTRACT FROM AUTHOR]

Vascular dementia (VaD) is the second most common subtype of dementia, but the precise mechanism underlying VaD is not fully understood. Long non-coding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) can act as a key regulator in physiological and pathological processes, including neurological disorders, but whether it is correlated with VaD has not been elucidated. In this study, we established a mouse model of VaD by the transient bilateral common carotid artery occlusion surgery. As expected, the Morris water maze showed that VaD mice had significant deficits in spatial learning and memory. MALAT1 was elevated in the hippocampus of VaD mice. Additionally, we found that microRNA (miR)-9-3p was downregulated in the VaD hippocampus. By performing a dual-luciferase report assay, we verified the binding relationship between MALAT1 and miR-9-3p. Interestingly, synapse-associated protein-97 (SAP97), a well-known gene related to synaptic functions, was found upregulated in the hippocampus of VaD mice. In vitro experiments performed on hippocampal neurons demonstrated that miR-9-3p negatively regulated SAP97 expression. The downregulation of MALAT1 in hippocampal neurons increased miR-9-3p and reduced SAP97, whereas miR-9-3p inhibition rescued the MALAT1 downregulation-mediated SAP97 reduction. In conclusion, the present study reported the alterations in the expression levels of MALAT1, miR-9-3p, and SAP97 in the hippocampus of VaD mice, suggesting that MALAT1 targets miR-9-3p to upregulate SAP97 in the hippocampus of mice with VaD. This work will be helpful for understanding the molecular mechanisms of VaD. [ABSTRACT FROM AUTHOR]

Cerebral ischemia/reperfusion (I/R) injury contributes considerably to the poor prognosis in patients with ischemic stroke. This study is aimed to delineate the molecular mechanistic actions by which sevoflurane protects against cerebral I/R injury. A rat model of cerebral I/R injury was established and pre-treated with sevoflurane, in which hippocampal neuron apoptosis was found to be repressed and the level of E2F transcription factor 1 (E2F1) was observed to be down-regulated. Then, the up-regulated expression of E2F1 was validated in rats with cerebral I/R injury, responsible for stimulated neuron apoptosis. Further, the binding of E2F1 to enhancer of zeste homolog 2 (EZH2) and EZH2 to tissue inhibitor of metalloproteinases-2 (TIMP2) was identified. The stimulative effect of the E2F1/EZH2/TIMP2 regulatory axis on neuron apoptosis was subsequently demonstrated through functional assays. After that, it was substantiated in vivo that sevoflurane suppressed the apoptosis of hippocampal neurons in rats with cerebral I/R injury by down-regulating E2F1 to activate the EZH2/TIMP2 axis. Taken together, our data elucidated that sevoflurane reduced neuron apoptosis through mediating the E2F1/EZH2/TIMP2 regulatory axis, thus protecting rats against cerebral I/R injury. [ABSTRACT FROM AUTHOR]

Ceriporia lacerata (CL) is a species of white rot fungi. In this study, we have examined the beneficial effect of CL on scopolamine-induced memory impairment in mice. A freeze-dried CL mycelial culture broth was dissolved and orally administered to scopolamine-treated C57BL/6J mice followed by behavioral tests using the Y-maze, passive avoidance, and Morris water maze tasks. CL administration at a daily dose of 200 mg/kg body weight resulted in restoration of exploration reduction and improvement of associative and spatial learning and memory impairment in scopolamine-treated mice. Concomitantly, heme oxygenase-1 was highly expressed in the hippocampal region of CL-administered mice. Moreover, the ethanolic extract of CL significantly increased the transcriptional activity of antioxidant response element and attenuated the glutamate-induced cytotoxicity in HT22 mouse hippocampal neuronal cells. These findings suggest that the CL intake can confer a beneficial effect on learning and memory presumably through protecting hippocampal neuronal cells from oxidative stress-induced damage. [ABSTRACT FROM AUTHOR]

Abnormal excessive production and deposition of β-amyloid (Aβ) peptides in selectively susceptible brain regions are thought to be a key pathogenic mechanism underlying Alzheimer's disease (AD), resulting in memory deficits and cognitive impairment. Genistein is a phytoestrogen with great promise for counteracting diverse Aβ-induced insults, including oxidative stress and mitochondrial dysfunction. However, the exact molecular mechanism or mechanisms underlying the neuroprotective effects of genistein against Aβ-induced insults are largely uncharacterized. To further elucidate the possible mechanism(s) underlying these protective effects, we investigated the neuroprotective effects of genistein against Aβ-induced oxidative stress mediated by orchestrating α7 nicotinic acetylcholine receptor (α7nAChR) signaling in rat primary hippocampal neurons. Genistein significantly increased cell viability, reduced the number of apoptotic cells, decreased accumulation of reactive oxygen species (ROS), decreased contents of malondialdehyde (MDA) and lactate dehydrogenase (LDH), upregulated BCL-2 expression, and suppressed Caspase-3 activity occurring after treatment with 25 μM Aβ25-35. Simultaneously, genistein markedly inhibited the decreases in α7nAChR mRNA and protein expression in cells treated with Aβ25-35. In addition, α7nAChR signaling was intimately involved in the genistein-mediated activation of phosphatidylinositol 3-kinase (PI3K)/Akt and Nrf2/keap1 signaling. Thus, α7nAChR activity together with the PI3K/Akt/Nrf2 signaling cascade likely orchestrates the molecular mechanism underlying the neuroprotective effects of genistein against Aβ-induced oxidative injury. [ABSTRACT FROM AUTHOR]

Purpose: In this study, we investigated the effects of different concentration of propofol on cell viability of hippocampal neurons and explored the possible mechanism. Patients and methods: Primary hippocampal neurons were cultured in vitro and treated with different concentration of propofol. MTT was used to examine the survival of neurons. Flow cytometry was used to detect the neuronal apoptosis. Western-blot analysis was used to examine the expression level of p-p38MAPK and p38MAPK. Results: We found that low concentration propofol (0.5 μM and 1 μM) promoted the cell survival rate; however, high concentration of propofol (10 μM,50 μM,100 μM,150 μM, and 200 μM) decreased the cell survival rate (P < 0.05). Flow cytometry showed that the neuronal apoptosis rate was decreased in 1 μM propofol group (P < 0.05), but was significantly higher in10μM, 100 μM and 200 μM groups in a concentration-dependent manner (P < 0.05 or P < 0.01). Western blot revealed that the propofol induced the phosphorylation of p38MAPK concentration-dependently and time-dependently. SB203580, one inhibitor of p38MAPK, increased the cell survival rate and decreased the cell apoptosis induced by high concentration of propofol. Conclusion: Low concentration of propofol improved the survival rate of neurons, while high concentration of propofol promoted the cell apoptosis and decreased the cell viability. p38MAPK pathway is involved the effect of high concentration of propofol promoted on primary hippocampal neurons viability and apoptosis. [ABSTRACT FROM AUTHOR]

This study is designed to explore the effect of electric acupuncture on the apoptosis of hippocampal neurons through the Notch3 signaling pathway. A middle cerebral artery occlusion (MCAO) mouse model was generated by thread embolization. A Y-maze was used to test cognitive function (learning and memory). The apoptosis factor caspase-3 was identified through an enzyme-linked immunosorbent assay (ELISA). TTC staining was used to evaluate the cerebral infarction area. Apoptosis of hippocampal neurons was identified by TUNEL staining and flow cytometry. The expression levels of genes and proteins related to the Notch3 signaling pathway were assessed by qRT-PCR and Western blot. It was determined that 7 days of electroacupuncture treatment improved recovery from cerebral infarction. Electroacupuncture therapy reduced the cerebral infarction area in mice and decreased the apoptosis of hippocampal neurons. The apoptosis rate of hippocampal neurons and the area of cerebral infarction were significantly lower in the electroacupuncture group than in the MCAO group (P < 0.01), while the apoptosis rate of hippocampal neurons and the area of cerebral infarction were significantly higher in the inhibitor group than in the electroacupuncture group (P < 0.01). The expression levels of genes related to the Notch3 signaling pathway were significantly increased in the electric acupuncture treatment group compared with the MCAO group (P < 0.01). The results showed that electroacupuncture inhibited the apoptosis of hippocampal neurons through the Notch3 signaling pathway, while the expression levels of genes related to the Notch3 signaling pathway were significantly higher in the inhibitor group than in the electroacupuncture group (P < 0.01). Electroacupuncture inhibited the apoptosis of hippocampal neurons in mice with cerebral infarction by stimulating the Notch3 signaling pathway and triggering corresponding protein expression. [ABSTRACT FROM AUTHOR]

Neurotrophic factors are essential to support neuronal development and to protect mature neurons from atrophy in neurodegenerative disorders. To investigate effects of the carrageenan-producing seaweed, Kappaphycus alvarezii, on the development and complexity of neuronal cytoarchitecture, ethanol extract of the seaweed was added to primary cultures of fetal rat hippocampal neurons. The neuronal morphology was observed under phase-contrast microscope and analyzed using ImageJ software. With an optimal concentration of 1 μg mL−1, the extract significantly increased axonal length, number of secondary axonal collateral branches, length of primary dendrites, and number of secondary dendritic branches by 58%, eightfold, 68%, and 2.6-fold, compared with control (p < 0.05). In Sholl's analysis, the extract also significantly increased numbers of axodendritic intersections, branching points, and branching tips. It is assumed that several kinds of lipophilic compounds provide the neurotrophic activities to enhance neurites in a robust form. Thus, the K. alvarezii may be useful as a diet supplement or pharmaceuticals for people who are prone to neurological disorders. [ABSTRACT FROM AUTHOR]

Neuroprotective and neurotrophic supports are critical for neuronal survival, outgrowth, and functional activity in the degenerating brain where oxidative stress is a leading cause of neurological disorders. An ethanol extract of the phaeophyte Undaria pinnatifida (UPE) concentration dependently increased the viability of rat hippocampal neurons in both hypoxia-induced oxidative stress and normoxic conditions. UPE, at an optimal 15 μg mL−1, significantly reduced reactive oxygen species formation, DNA fragmentation, early and late apoptosis rates, and mitochondrial membrane dysfunction against hypoxia. In addition, the most active neuroprotectant from UPE was identified as fucoxanthin (Fx) by reverse-phase high-pressure liquid chromatography (RP-HPLC) and 1H NMR. Fucoxanthinol (FxOH), a metabolite after enzymatic hydrolysis of Fx, significantly provided protection from neurite breakage and also enhanced the length of neurites in hypoxia cultures. The findings suggest that UPE and its active component Fx as well as FxOH have the ability to protect central nervous system neurons through anti-excitatory and anti-oxidative actions. [ABSTRACT FROM AUTHOR]

Epilepsy is a common chronic brain disorder and is characterized by an enduring predisposition to generate seizures. The hippocampus is especially vulnerable to seizure-induced damage. In this study, we explore the ability of long noncoding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) to influence the autophagy and apoptosis of hippocampal neurons in epilepsy and the underlying mechanism involving the PI3K/Akt signaling pathway. Seventy-two Sprague-Dawley rats were assigned to normal, sham, Ep, Ep + si-NC, Ep + si-MALAT1, and Ep + si-MALAT1 + LY groups. Fluorescence in situ hybridization kit was employed to determine the MALAT1 in the brain tissues. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blotting were performed to determine the expression of MALAT1, mRNAs, and proteins. The autophagy of hippocampal neurons was evaluated under a transmission electron microscope and their apoptosis was evaluated using TUNEL staining. We found that MALAT1 and c-Met were enriched while microRNA-101 (miR-101) decreased in rats with epilepsy. The demonstration showed that MALAT1 binds to miR-101, thus regulating c-Met. In rats with epilepsy, MALAT1 depletion mediated by anti-MALAT1 siRNA resulted in activation of PI3K/Akt signaling pathway and loss of hippocampal neurons. LY294002, an inhibitor of PI3K/Akt signaling pathway, could reverse the events caused by MALAT1 knockdown. Taken together, these findings indicate that down-regulation of MALAT1 activates the PI3K/Akt signaling pathway to protect hippocampal neurons against autophagy and apoptosis in rats with epilepsy. [ABSTRACT FROM AUTHOR]

Hypoxic-ischemic brain injury is an important cause of neonatal mortality and morbidity. Brain-derived neurotrophic factor (BDNF) has been reported to play a neuroprotective role in hypoxic-ischemic brain injury; however, the specific effects and mechanism of BDNF on hypoxic-hypoglycemic hippocampal neuron injury remains unknown. The current study investigated the action of BDNF in regulating cerebral hypoxic-ischemic injury by simulating hippocampal neuron ischemia and hypoxia. We found that BDNF, p-Trkb, and miR-134 expression levels decreased, and that exogenous BDNF increased survival and reduced apoptosis in hypoxic-hypoglycemic hippocampal neurons. The results also show that BDNF inhibits MiR-134 expression by activating the TrkB pathway. Transfection with TrkB siRNA and pre-miR-134 abrogated the neuroprotective role of BDNF in hypoxic-hypoglycemic hippocampal neurons. Our results suggest that exogenous BDNF alleviates hypoxic-ischemic brain injury through the Trkb/MiR-134 pathway. These findings may help to identify a potential therapeutic agent for the treatment of hypoxic-ischemic brain injury. [ABSTRACT FROM AUTHOR]

Neurodegenerative disorders, which affect memory, cognition, and social functions, can be treated using neurotrophic agents to support neuronal development and protect mature neurons from atrophy. We screened 34 tropical seaweed species collected from Indonesian coastal areas for their neurite-outgrowth-promoting activity (NOPA) in fetal rat hippocampal neurons in vitro. Based on the number and total length of primary neurites, red seaweeds had greater NOPA than green and brown seaweeds. The red seaweed Kappaphycus alvarezii showed the highest NOPA. Addition of the ethanol extract to the culture (1 μg mL) significantly accelerated initial neuronal maturation from stage I to stage II (70 %; P < 0.05) within 24 h and increased the number of neurites that developed multipolar characteristics (48 %; P < 0.05). These results indicate that the aquaculturable carrageenan producer K. alvarezii might be a promising source of neurotrophic compounds to enhance memory and learning. [ABSTRACT FROM AUTHOR]

The edible red alga Porphyra yezoensis is among the most popular marine algae and is of economic and medicinal importance. In the present study, the neurotrophic and neuroprotective activities of the ethanol extract of P. yezoensis (PYE) were investigated in primary cultures of hippocampal neurons. Results revealed that PYE significantly increased neurite outgrowth at an optimal concentration of 15 µg/mL. PYE dose-dependently increased viable cells, significantly accelerated the rate of neuronal differentiation in cultures, promoted axodendritic arborization, and eventually induced synaptogenesis. In addition to morphological development, PYE also promoted functional maturation as indicated by the staining of live cultures with FM 1-43. Moreover, PYE increased neuronal survivability, which was attributed to reduced apoptosis and its ROS scavenging activity. Taurine, a major organic acid in PYE (2.584/100 mg of dry PYE) promoted neurite outgrowth in a dose-dependent manner, and this promotion was suppressed by the taurine antagonist isethionic acid. The study indicates that PYE and its active component, taurine, facilitate neuronal development and maturation and have a neuroprotective effect. [ABSTRACT FROM AUTHOR]

Resveratrol is a naturally occurring phytoalexin found in red grapes, and believed to have neuroprotective, anti-oxidant, and anti-inflammatory effects. But little is known about its effect on the neural impairments induced by microglial over-activation, which leads to neuroinflammation and multiple pathophysiological damages. In this study, we aimed to investigate the protective effects of resveratrol on the impairments of neural development by microglial over-activation insult. The results indicated that resveratrol inhibited the lipopolysaccharide (LPS)-dependent release of cytokines from activated microglia and LPS-dependent changes in NF-κB signaling pathway. Conditioned medium (CM) from activated microglia treated by resveratrol directly protected primary cultured hippocampal neurons against LPS-CM-induced neuronal death, and restored the inhibitory effects of LPS-CM on dendrite sprouting and outgrowth. Finally, neurons cultured in CM from LPS-stimulated microglia treated by resveratrol exhibited increased spine density compared to those without resveratrol treatment. Our findings support that resveratrol inhibits microglial over-activation and alleviates neuronal injuries induced by microglial activation. Our study suggests the use of resveratrol as an alternative intervention approach that could prevent further neuronal insults. [ABSTRACT FROM AUTHOR]

Neurotrophic factors are essential for the differentiation and maturation of developing neurons as well as providing survival support to the mature neurons. Moreover, therapeutically neurotrophic factors are promising to reconstruct partially damaged neuronal networks in neurodegenerative diseases. In the previous study, we reported that the ethanol extract of an edible marine alga, Gelidium amansii (GAE) had shown promising effects in the development and maturation of both axon and dendrites of hippocampal neurons. Here, we demonstrate that in primary culture of hippocampal neurons (1) GAE promotes a significant increase in the number of filopodia and dendritic spines; (2) promotes synaptogenesis; (3) enhances N-methyl- d-aspartic acid (NMDA) receptor recruitment; and (4) modulates NMDA-receptor-mediated postsynaptic current. Taken together these findings that GAE might be involved in both morphological and functional maturation of neurons suggest the possibility that GAE may constitute a promising candidate for novel compounds for the prevention and treatment of neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Endoplasmic reticulum (ER) stress, implicated in various neurodegenerative processes, increases the level of intracellular Ca and leads to activation of calpain, a Ca-dependent cysteine protease. We have shown previously that S-allyl- l-cysteine (SAC) in aged garlic extracts significantly protects cultured rat hippocampal neurons (HPNs) against ER stress-induced neurotoxicity. The neuroprotective effect of SAC was compared with those of the related antioxidant compounds, l-cysteine (CYS) and N-acetylcysteine (NAC), on calpain activity in HPNs and also in vitro. SAC, but not CYS or NAC, reversibly restored the survival of HPNs and increased the degradation of α-spectrin, a substrate for calpain, induced by tunicamycin, a typical ER stress inducer. Activities of μ- and m-calpains in vitro were also concentration dependently suppressed by SAC, but not by CYS or NAC. At submaximal concentration, although ALLN (5 pM), which blocks the active site of calpain, and calpastatin (100 pM), an endogenous calpain-inhibitor protein, additively inhibited μ-calpain activity in vitro in combination with SAC, the effect of PD150606 (25 μM), which prevents interaction of Ca with the Ca-binding site of calpain, was unaffected by SAC. In contrast, SAC (1 mM) significantly reversed the effect of PD150606 at a concentration that elicited supramaximal inhibition (100 μM), but did not affect ALLN (1 nM)- and calpastatin (100 nM)-induced inhibition of μ-calpain activity. These results suggest that the protective effects of SAC against ER stress-induced neuronal cell death are not attributable to antioxidant activity, but to suppression of calpain through interaction with its Ca-binding site. [ABSTRACT FROM AUTHOR]

With the development of communications industry, mobile phone plays an important role in daily life. Whether or not the electromagnetic radiation emitted by mobile phone causes any adverse effects on brain function has become of a great concern. This paper investigated the effect of electromagnetic field on spatial learning and memory in rats. 32 trained Wistar rats were divided into two groups: exposure group and control group. The exposure group was exposed to 916 MHz, 10w/m2 mobile phone electromagnetic field (EMF) 6 h a day, 5 days a week, 10 weeks. The completion time, number of total errors and the neuron discharge signals were recorded while the rats were searching for food in an eight-arm radial maze at every weekend. The neuron signals of one exposed rat and one control rat in the maze were obtained by the implanted microelectrode arrays in their hippocampal regions. It can be seen that during the weeks 4-5 of the experiment, the average completion time and error rate of the exposure group were longer and larger than that of control group ( p < 0.05). During the weeks 1-3 and 6-9, they were close to each other. The hippocampal neurons showed irregular firing patterns and more spikes with shorter interspike interval during the whole experiment period. It indicates that the 916 MHz EMF influence learning and memory in rats to some extent in a period during exposure, and the rats can adapt to long-term EMF exposure. [ABSTRACT FROM AUTHOR]

Propofol is an intravenous anesthetic with neuroprotective effects against cerebral ischemia or hypoxia injury. However, the underlying mechanisms remain obscure. Recent years emerging evidence has demonstrated that metallothionein-3 (MT-3), a growth inhibitory factor that exists mainly in the central nervous system, exhibited neuroprotective effect in vivo. Here, we used a model of hypoxia/re-oxygenation (H/R) injury to examine the hippocampal neuroprotective effect of propofol, and explored the role of MT-3 in this action. H/R resulted in reduced cell viability and increased cell death in hippocampal neuron culture, as indicated by MTT assay and lactate dehydrogenase (LDH) release assay, respectively. Pretreatment of propofol at different concentrations (50, 150, and 250 μmol/L) reversed H/R-induced neurotoxicity and increased MT-3 mRNA and protein expressions. Moreover, propofol failed to exert neuroprotective effect when MT-3 was silenced by the transfection with the specific siRNA, suggesting that MT-3 was the crucial mediator for propofol's neuroprotective effect against H/R. In conclusion, our findings showed that propofol is neuroprotective in H/R model on hippocampal neuron cells and that it may act by up-regulation of MT-3. [ABSTRACT FROM AUTHOR]

Migraine is one of the risk factor for ischemic stroke. The purpose of this study was to examine the effect of lomerizine, a prophylactic drug for migraine, on HO-induced cell death of hippocampal neurons. Cytosolic Ca concentration was measured using fura-2 as a Ca indicator. Cell death was estimated by trypan blue exclusion. In rat-cultured hippocampal neurons, the addition of HO induced biphasic Ca elevations and cell death. The HO-induced biphasic Ca elevations and cell death only occurred when extracellular Ca was present. The biphasic Ca elevation was mediated by Ca influx through the plasma membrane, but not Ca release from the intracellular Ca store. Both the early and late phases of HO-induced Ca influx were reduced by either a T- or L-type voltage-dependent Ca channel (VDCC) blocker, lomerizine. In fact, L-type VDCC (α subunit) and T-type VDCC (α subunit) mRNA were expressed in rat hippocampal neurons. Although an L-type VDCC blocker, nifedipine, partly suppressed the late phase of Ca influx in response to HO, a T-type VDCC blocker, mibefradil, reduced both phases of Ca influx. Moreover, lomerizine and mibefradil strongly reduced HO-induced cell death, and nifedipine weakly reduced it. These findings suggest that the inhibition of HO-induced Ca influx through T-type VDCC seems to be important in the protective effect of lomerizine against oxidative stress. It is possible that lomerizine may be a useful drug for prophylactic treatment of migraine, because migraine is a risk factor for ischemic stroke. [ABSTRACT FROM AUTHOR]

A large body of evidence indicates that astrocytes play an important role in a range of brain functions through calcium (Ca2+) signaling. Experimentally evoking Ca2+ signaling is a useful technique for investigating the functions of astrocytes. However, conventional stimulation methods typically have poor spatio-temporal precision, and some are invasive. Our group has developed a technique to overcome these problems, in which astrocytes are photostimulated with a femtosecond laser. In the current study, we applied this method to a hippocampal neural network to explore astrocytic functions in detail. The results revealed that applying photostimulation to astrocytes in a cultured hippocampal astrocyte-neuron network caused the following changes: (i) Synchronous Ca2+ oscillations in neurons were induced; (ii) spontaneous Ca2+ synchrony instantaneously emerged; and (iii) high-frequency spontaneous Ca2+ synchrony was regulated. Thus, astrocytic Ca signaling evoked by photostimulation was found to modulate synchronous Ca2+ oscillations in hippocampal neurons. We propose that photostimulation with a femtosecond laser will serve as a powerful tool in investigating astrocytic functions at the network level. [ABSTRACT FROM AUTHOR]

Iron is required for neuronal function but in excess generates neurodegeneration. Although the iron homeostasis machinery in neurons has been described extensively, little is known about the influence of corticosterone on the iron homeostasis in neurons. In this study, we characterized the response of hippocampal neurons to a model of progressive corticosterone condition. We found that increasing extracellular corticosterone-induced iron accumulation killed a large proportion of neurons. Iron concentrations were significantly increased in the corticosterone-treated cells. In the hippocampal neurons, corticosterone decreased expression of ferritin and increased expression of transferrin receptor1 (TfR1), iron regulatory protein1 (IRP1), and divalent metal transporter 1. Corticosterone-induced elevation of IRP1 expression can cause increase of TfR1 and decrease of ferritin expression, which further leads to iron accumulation in hippocampal neurons and subsequently increases the oxidative damage of the neurons; it is indicated that corticosterone might be an important reason for iron deposition-caused neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

The advancement of immunocytochemistry (ICC) allows one to observe detailed spatial distribution of cellular antigens, but, with some limitations. Using conventional ICC, it is difficult to distinguish the nuclear localization from cytoplasm, as two large subcellular compartments overlap on the z-axis. In this study, we have investigated whether in situ immunostaining of 'naked' nuclei could provide an unambiguous method for detection of nuclear antigens. We have designed a protocol that efficiently lyses plasmalemma, while keeping the nuclear envelope intact. The optimal condition for lysing the plasmalemma was 0.5% Nonidet P-40 for 5 min in both neuronal and non-neuronal cultured cells. Using this protocol, we could unambiguously isolate nuclear from cytoplasmic ICC signals. Since the present protocol has been designed for immunostaining of 'naked' nuclei from cultured or isolated cells, we have coined a new term to refer to this procedure as 'immunonucleochemistry' ('INC' for abbreviation). [ABSTRACT FROM AUTHOR]

Epigallocatechin-3-gallate (EGCG), a catechin polyphenols component, is the main ingredient of green tea extract. It has been reported that EGCG is a potent antioxidant and beneficial in oxidative stress-related diseases, but others and our previous study showed that EGCG has pro-oxidant effects at high concentration. Thus, in this study, we tried to examine the possible pathway of EGCG-induced cell death in cultures of rat hippocampal neurons. Our results showed that EGCG caused a rapid elevation of intracellular free calcium levels ([Ca2+]i) in a dose-dependent way. Exposure to EGCG dose- and time-dependently increased the production of reactive oxygen species (ROS) and reduced mitochondrial membrane potential (Δ ψm) as well as the Bcl-2/Bax expression ratio. Importantly, acetoxymethyl ester of 5,5′-dimethyl-bis( o-aminophenoxy)ethane- N,N,N′ ,N′-tetraacetic acid, ethylene glycol-bis-(2-aminoethyl)- N,N,N′ ,N′-tetraacetic acid, and vitamin E could attenuate EGCG-induced apoptotic responses, including ROS generation, mitochondrial dysfunction, and finally partially prevented EGCG-induced cell death. Furthermore, treatment of hippocampal neurons with EGCG resulted in an elevation of caspase-3 and caspase-9 activities with no significant accompaniment of lactate dehydrogenase release, which provided further evidence that apoptosis was the dominant mode of EGCG-induced cell death in cultures of hippocampal neurons. Taken together, these findings indicated that EGCG induced hippocampal neuron death through the mitochondrion-dependent pathway. [ABSTRACT FROM AUTHOR]

Introducing exogenous genes into cells is one of the most important molecular techniques to study gene functions. Comparing to other type of cells, neurons are more difficult to transfect with cDNAs because they are very sensitive to microenvironmental changes. Among various gene transfer techniques, the Ca2+-phosphate transfection method is one of the most popular tools in neuroscience research because of its low cell toxicity and easiness to use. However, it is well known that the Ca2+-phosphate transfection efficiency in neurons is very low, typically in the range of 1-5%, which has limited its applications in gene functional analyses. Here we report a novel Ca2+-phosphate transfection protocol that dramatically increased the transfection efficiency by 10-fold, up to 60%, while maintaining low cell toxicity. The critical factors are the formation of homogenous snow-like precipitate with particle size about 1-3?µm and the subsequent removal of the precipitate. Using this new transfection protocol, we were able to routinely transfect single autaptic neurons in hippocampal microisland cultures and combine it with electrophysiology and fluorescent imaging methods to study gene functions. This high efficiency, low toxicity, and simple to use gene transfer method will have a broad application in gene research at the single cell level.Gene Therapy (2004) 11, 1303-1311. doi:10.1038/sj.gt.3302305; Published online 1 July 2004 [ABSTRACT FROM AUTHOR]

Epilepsy or the occurrence of spontaneous recurrent epileptiform discharges (SREDs, seizures) is one of the most common neurological disorders. Shift in the balance of brain between excitatory and inhibitory functions due to different types of structural or functional alterations may cause epileptiform discharges. N-Methyl-D-aspartate (NMDA) receptor dysfunctions have been implicated in modulating seizure activities. Seizures and epilepsy are clearly dependent on elevated intracellular calcium concentration ([Ca2+]i) by NMDA receptor activation and can be prevented by NMDA antagonists. This perturbed [Ca2+]i levels is forerunner of neuronal death. However, therapeutic tools of elevated [Ca2+]i level during status epilepticus (SE) and SREDs have not been discovered yet. Our previous study showed fast inhibition of ginseng total saponins and ginsenoside Rg3 on NMDA receptor-mediated [Ca2+]i in cultured hippocampal neurons. We, therefore, examined the direct modulation of ginseng on hippocampal neuronal culture model of epilepsy using fura-2-based digital Ca2+ imaging and neuronal viability assays. We found that ginseng total saponins and ginsenoside Rg3 inhibited Mg2+ free-induced increase of [Ca2+]i and spontaneous [Ca2+]i oscillations in cultured rat hippocampal neurons. These results suggest that ginseng may play a neuroprotective role in perturbed homeostasis of [Ca2+]i and neuronal cell death via the inhibition of NMDA receptor-induced SE or SREDs. [ABSTRACT FROM AUTHOR]

Pyrethroid modulation of sodium channels is unique in the sense that it is highly dependent on temperature, the potency being augmented by lowering the temperature. To elucidate the mechanisms underlying the negative temperature dependence of pyrethroid action, single sodium channel currents were recorded from cultured rat hippocampal neurons using the inside-out configuration of patch-clamp technique, and the effects of the pyrethroid tetramethrin were compared at 22 and 12 degrees C. Tetramethrin-modified sodium channels opened with short closures and/or transitions to subconductance levels at 22 and 12 degrees C. The time constants of the burst length histograms for tetramethrin-modified channels upon depolarization to -60 mV were 7. 69 and 14.46 msec at 22 and 12 degrees C, respectively (Q(10) = 0. 53). Tetramethrin at 10 microm modified 17 and 23% of channels at 22 and 12 degrees C, respectively, indicating that the sensitivity of the sodium channel of rat hippocampal neurons to tetramethrin was almost the same as that of tetrodotoxin-sensitive sodium channels of rat dorsal root ganglion neurons and rat cerebellar Purkinje neurons. The time constants for burst length in tetramethrin-modified sodium channels upon repolarization to -100 mV from -30 mV were 8.26 and 68. 80 msec at 22 and 12 degrees C (Q(10) = 0.12), respectively. The prolongation of tetramethrin-modified whole-cell sodium tail currents upon repolarization at lower temperature was ascribed to a prolongation of opening of each channel. Simple state models were introduced to interpret behaviors of tetramethrin-modified sodium channels. The Q(10) values for transition rate constants upon repolarization were extremely large, indicating that temperature had a profound effect on tetramethrin-modified sodium channels. [ABSTRACT FROM AUTHOR]