• Proceedings of the Korean Biophysical Society Conference
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• 2001.06a
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• pp.53-53
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• 2001

When repolarization of neuronal action potential does not decline monotonically but interrupted by additional depolarization, this prolonged depolarization phase is referred to afterdepolarization(ADP). ADP is considered to playa crucial role in the modulation of neuronal excitability, since it contributes to burst firing. We studied the ionic mechanisms underlying ADP in the soma of dentate granule cells, using rat hippocampal slice (300${\mu}{\textrm}{m}$ in thickness) prepared from 3- to 3-week-old SD rats.(omitted)

• The Korean Journal of Physiology and Pharmacology
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• v.20 no.1
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• pp.41-51
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• 2016

Adult hippocampal dentate granule neurons are generated from neural stem cells (NSCs) in the mammalian brain, and the fate specification of adult NSCs is precisely controlled by the local niches and environment, such as the subventricular zone (SVZ), dentate gyrus (DG), and Toll-like receptors (TLRs). Epigallocatechin-3-gallate (EGCG) is the main polyphenolic flavonoid in green tea that has neuroprotective activities, but there is no clear understanding of the role of EGCG in adult neurogenesis in the DG after neuroinflammation. Here, we investigate the effect and the mechanism of EGCG on adult neurogenesis impaired by lipopolysaccharides (LPS). LPS-induced neuroinflammation inhibited adult neurogenesis by suppressing the proliferation and differentiation of neural stem cells in the DG, which was indicated by the decreased number of Bromodeoxyuridine (BrdU)-, Doublecortin (DCX)- and Neuronal Nuclei (NeuN)-positive cells. In addition, microglia were recruited with activating TLR4-NF-${\kappa}B$ signaling in the adult hippocampus by LPS injection. Treating LPS-injured mice with EGCG restored the proliferation and differentiation of NSCs in the DG, which were decreased by LPS, and EGCG treatment also ameliorated the apoptosis of NSCs. Moreover, pro-inflammatory cytokine production induced by LPS was attenuated by EGCG treatment through modulating the TLR4-NF-${\kappa}B$ pathway. These results illustrate that EGCG has a beneficial effect on impaired adult neurogenesis caused by LPS-induced neuroinflammation, and it may be applicable as a therapeutic agent against neurodegenerative disorders caused by inflammation.

• Molecules and Cells
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• v.22 no.1
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• pp.51-57
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• 2006

Haloperidol is a classical neuroleptic drug that is still in clinical use and can lead to abnormal motor activity following repeated administration. However, there is little knowledge of how it triggers neuronal impairment. In this study, we report that it induced calcium ion influx via L-type calcium channels and that the elevation of calcium ions induced by haloperidol appeared to render hippocampal cells more susceptible to oxidative stress. Indeed, the level of cytotoxic reactive oxygen species (ROS) and the expression of pro-apoptotic Bax increased in response to oxidative stress in haloperidol-treated cells, and these effects were inhibited by verapamil, a specific L-type calcium channel blocker, but not by the T-type calcium channel blocker, mibefradil. These findings indicate that haloperidol induces calcium ion influx via L-type calcium channels and that this calcium influx influences neuronal fate.

• Biomolecules & Therapeutics
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• v.31 no.1
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• pp.127-138
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• 2023

Glycogen synthase kinase-3β (GSK-3β) is an important serine/threonine kinase that implicates in multiple cellular processes and links with the neurodegenerative diseases including Alzheimer's disease (AD). In this study, structure-based virtual screening was performed to search database for compounds targeting GSK-3β from Enamine's screening collection. Of the top-ranked compounds, 7 primary hits underwent a luminescent kinase assay and a cell assay using human neuroblastoma SH-SY5Y cells expressing Tau repeat domain (Tau_RD) with pro-aggregant mutation ΔK280. In the kinase assay for these 7 compounds, residual GSK-3β activities ranged from 36.1% to 90.0% were detected at the IC₅₀ of SB-216763. In the cell assay, only compounds VB-030 and VB-037 reduced Tau aggregation in SH-SY5Y cells expressing ΔK280 Tau_RD-DsRed folding reporter. In SH-SY5Y cells expressing ΔK280 Tau_RD, neither VB-030 nor VB-037 increased expression of GSK-3α Ser21 or GSK-3β Ser9. Among extracellular signal-regulated kinase (ERK), AKT serine/threonine kinase 1 (AKT), mitogen-activated protein kinase 14 (P38) and mitogenactivated protein kinase 8 (JNK) which modulate Tau phosphorylation, VB-037 attenuated active phosphorylation of P38 Thr180/ Tyr182, whereas VB-030 had no effect on the phosphorylation status of ERK, AKT, P38 or JNK. However, both VB-030 and VB-037 reduced endogenous Tau phosphorylation at Ser202, Thr231, Ser396 and Ser404 in neuronally differentiated SH-SY5Y expressing ΔK280 Tau_RD. In addition, VB-030 and VB-037 further improved neuronal survival and/or neurite length and branch in mouse hippocampal primary culture under Tau cytotoxicity. Overall, through inhibiting GSK-3β kinase activity and/or p-P38 (Thr180/Tyr182), both compounds may serve as promising candidates to reduce Tau aggregation/cytotoxicity for AD treatment.

• International Journal of Molecular Medicine
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• v.44 no.3
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• pp.939-948
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• 2019

Chemokine C-X3-C motif ligand 1 (CX3CL1) and its sole receptor, CX3CR1, are known to be involved in neuronal damage/death following brain ischemia. In the present study, time-dependent expression changes of CX3CL1 and CX3CR1 proteins were investigated in the hippocampal CA1 field following 5 min of transient global cerebral ischemia (tgCI) in gerbils. To induce tgCI in gerbils, bilateral common carotid arteries were occluded for 5 min using aneurysm clips. Expression changes of CX3CL1 and CX3CR1 proteins were assessed at 1, 2 and 5 days after tgCI using western blotting and immunohistochemistry. CX3CL1 immunoreactivity was strong in the CA1 pyramidal cells of animals in the sham operation group. Weak CX3CL1 immunoreactivity was detected at 6 h after tgCI, recovered at 1 day after tgCI and disappeared from 5 days after tgCI. CX3CR1 immunoreactivity was very weak in CA1 pyramidal cells of the sham animals. CX3CR1 immunoreactivity in CA1 pyramidal cells was significantly increased at 1 days after tgCI and gradually decreased thereafter. On the other hand, CX3CR1 immunoreactivity was significantly increased in microglia from 5 days after tgCI. These results showed that CX3CL1 and CX3CR1 protein expression levels in pyramidal cells and microglia in the hippocampal CA1 field following tgCI were changed, indicating that tgCI-induced expression changes of CX3CL1 and CX3CR1 proteins might be closely associated with tgCI-induced delayed neuronal death and microglial activation.

• Journal of Life Science
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• v.26 no.12
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• pp.1458-1465
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• 2016

We investigated the neuroprotective effect of an ethanol extract from Asparagus cochinchinensis (AC) against glutamate-induced toxicity in the HT22 hippocampal cell, which is an ideal in vitro model for oxidative stress. The neuroprotective effects of AC in HT22 cells were evaluated by analyzing cell viability, lactate dehydrogenase (LDH), flow cytometry for cell death types, reactive oxygen species (ROS), mitochondria membrane potential (MMP), and Western blot assays. In the cell death analysis, AC treatment resulted in significantly attenuated glutamate-induced loss of cell viability with a decrease in LDH release. AC treatment also reduced glutamate-induced apoptotic cell death. In the ROS and MMP analysis, AC treatment inhibited the elevation of intracellular ROS induced by glutamate exposure and the disruption of MMP. In oxidative stress-related proteins analysis, AC treatment inhibited the expression of poly ADP ribose polymerase and heme oxygenase-1 by glutamate. These results indicate that AC exerts a significant neuroprotective effect against glutamate-induced hippocampal damage by decreasing ROS production and stabilizing MMP. Thus, AC potentially provides a new strategy for the treatment of oxidative stress-related diseases.

• The Korea Journal of Herbology
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• v.30 no.3
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• pp.49-54
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• 2015

Objectives : This study investigated the neuroprotective effect of Gastodia Rhizoma-gamibang (GG) water extracts against scopolamine-induced neurotoxicity in the hippocampus of male Sprague-Dawley rats. Methods : The animals were divided into five different groups with six animals per each group. The normal group (Nor) was administered with saline, while the control group (Con) was administered with saline after scopolamine treatment. The experimental group (Exp) was administered orally GG extracts at doses of 200 mg/kg (GG1 group), 400 mg/kg (GG2 group), 1000 mg/kg (GG5 group) for 30 day after scopolamine treatment. Results : From a light microscopy study, the nuclei of neurons and glial cells in the hippocampus were more shrunken or condensed in the 30 day control group compared with normal group. In the experimental groups, proportional to the dose, recovered from neurotoxicity induced by scopolamine. The control group, the density of hippocampal neurons were reduced 17-20% compared to normal group. The densities of neurons from the CA1, and CA3 area of the hippocampus in the GG1, GG2 and GG5 groups significantly increased compared with the Con. In the experimental group, neuronal cells are recovered from scopolamine-induced damage. A number of glial cells are observed increase from GG2 and GG5 groups. The PAS-positive materials in the tissues hippocampus), was lower in the Exp than the Con. Conclusions : The present study demonstrates that Gastodia Rhizoma-gamibang extract reduces neuronal damage in the hippocampus of scopolamin-induced impairment mice.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.2
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• pp.43-49
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• 2008

Flavonoids have been shown to affect calcium signaling in neurons. However, there are no reports on the effect of apigenin on glutamate-induced calcium signaling in neurons. We investigated whether apigenin affects glutamate-induced increase of free intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) in cultured rat hippocampal neurons, using fura-2-based digital calcium imaging and microfluorimetry. The hippocampal neurons were used between 10 and 13 days in culture from embryonic day 18 rats. Pretreatment of the cells with apigenin ($1{\mu}M$ to $100{\mu}M$) for 5 min inhibited glutamate ($100{\mu}M$, 1 min) induced $[Ca^{2+}]_i$ increase, concentration-dependently. Pretreatment with apigenin ($30{\mu}M$) for 5 min significantly decreased the $[Ca^{2+}]_i$ responses induced by two ionotropic glutamate receptor agonists, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA, $10{\mu}M$, 1 min) and N-methyl-D-aspartate (NMDA, $100{\mu}M$, 1 min), and significantly inhibited the AMPA-induced peak currents. Treatment with apigenin also significantly inhibited the $[Ca^{2+}]_i$ response induced by 50 mM KCl solution, decreased the $[Ca^{2+}]_i$ responses induced by the metabotropic glutamate receptor agonist, (S)-3,5-dihydroxy-phenylglycine (DHPG, 100 $[Ca^{2+}]_i$, 90 s), and inhibited the caffeine (10 mM, 2 min)-induced $[Ca^{2+}]_i$ responses. Furthermore, treatment with apigenin ($30{\mu}M$) significantly inhibited the amplitude and frequency of 0.1 mM $[Mg^{2+}]_o$-induced $[Ca^{2+}]_i$ spikes. These data together suggest that apigenin inhibits glutamate-induced calcium signaling in cultured rat hippocampal neurons.

• Journal of Physiology & Pathology in Korean Medicine
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• v.19 no.3
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• pp.647-655
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• 2005

This study demonstrated anti-oxidative and neuroprotective effects of Rhei Rhizoma. Anti-oxidative effects were studied on BV-2 microglia cells damaged by $H_2O_2$ and nitric oxide. Neuroprotective effects were studied by using oxygen/glucose deprivation of the organotypic hippocampal slice cultures. The results obtained are as follows; The groups treated with 0.5 and 5 mg/ml of Puerariae Radix revealed significant decreases of neuronal cell death area and cell death area percentages in CA1 region of ischemic damaged hippocampus cultures during whole 48 hours of the experiment. The group treated with 50 mg/ml of Puerariae Radix demonstrated decreases of neuronal cell death area and cell death area percentages in CA1 region, but these were not significant statistically. The groups treated with 0.5 and 5 mg/ml of Puerariae Radix revealed significant decreases of neuronal cell death area and cell death area percentages in dentate gyrus of ischemic damaged hippocampus cultures during whole 48 hours of the experiment. The group treated with 50 mg/ml of Puerariae Radix demonstrated decreases of neuronal cell death area and cell death area percentages in dentate gyrus, but these were not significant statistically. The groups treated with 0.5 and 5 mg/ml of Puerariae Radix revealed significant decreases of TUNEL-positive cells in both CA1 region and dentate gyrus of ischemic damaged hippocampus cultures. The group treated with 50 mg/ml of Puerariae Radix demonstrated significant decrease of TUNEL-positive cells in CA1 region, but not in dentate gyrus of ischemic damaged hippocampus. The groups treated with 0.5 and 5 mg/ml of Puerariae Radix revealed significant decreases of LDH concentrations in culture media of ischemic damaged hippocampus cultures. The group treated with 50 mg/ml of Puerariae Radix demonstrated decrease of LDH concentrations in culture media, but it was not significant statistically. The groups treated with 0.5 and 5 mg/ml of Puerariae Radix revealed significant increases of cell viabilities of BV-2 microglia cells damaged by $H_2O_2$. The group treated with 50 mg/ml of Puerariae Radix demonstrated increase of cell viability of BV-2 microglia cells, but it was not significant statistically. The group treated with 0.5 mg/ml of Puerariae Radix revealed significant increase of cell viability of BV-2 microglia cells damaged by nitric oxide. The groups treated with 5 and 50 mg/ml of Puerariae Radix demonstrated increases of cell viabilities of BV-2 microglia cells, but these were not significant statistically. These results suggested that Puerariae Radix revealed neuroprotective effects through the control effect of apoptosis and oxidative damages.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.3
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• pp.279-286
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• 1998

It has been well documented that transient forebrain global ischemia causes selective neuronal degeneration in hippocampal CA1 pyramidal neurons with a delay of a few days. The mechanism of this delayed hippocampal CA1 pyramidal neuronal death (DND) is still controversial. To delineate the mechanisms of the DND, the effects of treatment with MK-801, an NMDA receptor antagonist, kynurenic acid, a NMDA/non-NMDA receptor antagonist, and/or cycloheximide, a protein synthesis inhibitor, on the DND were investigated in male Wistar rats. To examine the participation of apoptotic neuronal death in the DND, TUNEL staining was performed in ischemic brain section. Global ischemia was induced by 4-vessel occlusion for 20 min. All animals in this study showed the DND 3 and 7 days after the ischemic insult. The DND that occured 3 days and 7 days after the ischemia were not affected by pretreatment with MK-801 (1 mg/kg), but markedly attenuated by the pretreatment with kynurenic acid (500 mg/kg). Treatment with cycloheximide (1 mg/kg) also markedly inhibited the DND. The magnitudes of attenuation by the two drugs were similar. The magnitude of attenuation by co-treatments with kynurenic acid and cycloheximide was not greater than that with any single treatment. TUNEL staining was negative in the sections obtained 1 or 2 days after the ischemic insults, but it was positive at hippocampal CA1 pyramidal cells in sections collected 3 days after the ischemia. These results suggested that the DND should be mediated by the activation of non-NMDA receptor, not by the activation of NMDA receptor and that the activation of AMPA receptor should induce the apoptotic process in the DND.