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D W Choi

Publications and source records attributed to D W Choi.

At least 109 records · Page 6Linked to original sources
PubMed1996

Potentiation of oxygen-glucose deprivation-induced neuronal death after induction of iNOS.

BACKGROUND AND PURPOSE: Previous studies have shown that brain ischemia and other insults can induce a marked increase in inducible nitric oxide synthase (iNOS) expression in astrocytes and some immune cells, but the biological significance of this phenomenon has not been elucidated. The purpose of the present study was to determine whether this induction of astrocyte iNOS alters neuronal vulnerability to severe hypoxic insults. METHODS: Astrocytic iNOS was induced by exposure of murine cortical cultures to interferon gamma in combination with either interleukin-1 beta or lipopolysaccharide. Cultures were exposed to combined oxygen-glucose deprivation. The extracellular concentration of glutamate was measured by high-performance liquid chromatography. N-Methyl-D-aspartate (NMDA) receptor activity was assessed by measurement of 45Ca2+ influx: neuronal death was assessed by morphological examination and quantitated by measurement of lactate dehydrogenase efflux to the bathing medium. RESULTS: In murine neocortical cell cultures containing neurons and astrocytes, neuronal injury induced by combined oxygen-glucose deprivation was not reduced by the addition of the nitric oxide synthase inhibitors NG-nitro-L-arginine or LG-nitro-arginine methyl ester. However, after induction of astrocyte iNOS activity with interferon gamma plus lipopolysaccharide or interleukin-1 beta, oxygen-glucose deprivation-induced neuronal injury was markedly enhanced and nitric oxide synthase inhibitors became protective. This iNOS-mediated potentiation was associated with a large increase in both extracellular glutamate accumulation and 45Ca2+ influx into neurons. The potentiation could be blocked by MK-801 but not CNQX, suggesting critical involvement of NMDA receptor activation. CONCLUSIONS: These results support the idea that nitric oxide production mediated by induced astrocytic iNOS can potentiate NMDA receptor-mediated neuronal death consequent to hypoxic-ischemic insults.

Animals↗
PubMed1996

Overexpression of tissue inhibitors of metalloproteinase-1 and -2 in the stroma of gastric cancer.

The fundamental event of cancer invasion and metastasis is the complicated interaction of cancer cells with host cells, in which event, a number of proteases and their inhibitors are involved. Matrix metalloproteinases are the potent proteases in degrading the basement membrane and extra cellular matrix and are inhibited by specific endogeneous inhibitors, tissue inhibitors of metalloproteinases-1(TIMP-1) and TIMP-2. The expression of mRNA for TIMP-1 and -2 was investigated by Northern blot analysis in specimens taken from 27 patients with primary gastric adenocarcinoma; 25 samples from the primary site, six from the metastatic lymph nodes and two from the peritoneal fluids. The expression for TIMP-1 and -2 was compared in primary gastric cancer tissues, metastatic lymph nodes and normal gastric mucosae. TIMP-1 mRNA was overexpressed in 24 (96%) out of 25 primary cancer tissues compared with the paired normal mucosae, while TIMP-2 was in 10 (40%). In six specimens of metastatic lymph nodes, TIMP-1 and -2 were overexpressed in 6 (100%) and 4 (67%) specimens, respectively. Of two specimens prepared from the peritoneal fluids, all specimens overexpressed TIMP-1 compared with the those of primary cancer tissues, while one (50%) specimen overexpressed TIMP-2. Immunohistochemical staining was done to investigate the localization of TIMP-1 and -2, demonstrating that the immunoreactivity for TIMP-1 and -2 was clearly detected in the cytoplasm of the stromal cells. These results suggest that both TIMP-1 and -2 are overexpressed by stromal cells in most of primary and some metastatic gastric cancer tissues and that TIMP-1 and TIMP-2, produced by stromal cells, may play an important role in inhibiting the proteolytic activity of matrix metalloproteinases originated from cancer cells, in gastric cancer.

Adenocarcinoma↗
PubMed1995

BDNF or IGF-I potentiates free radical-mediated injury in cortical cell cultures.

Free radical-mediated damage to cultured cortical neurons was induced by a 24 h exposure to Fe2+ (30 microM) or an inhibitor of gamma-glutamylcysteine synthetase, L-buthionine-[S,R]-sulfoximine (BSO, 1 mM). As expected, neuronal death was blocked by inclusion of the free radical scavenger trolox during the Fe2+ or BSO exposure. However, unexpectedly, pretreatment of the cultures with BDNF or IGF-I markedly potentiated neuronal death. This growth factor-potentiated death was still blocked by trolox, but was insensitive to glutamate antagonists. Concurrent addition of cycloheximide with the growth factors prevented injury potentiation. Present findings suggest that growth factors may increase free radical-induced neuronal death by mechanisms dependent upon protein synthesis.

Animals↗
PubMed1995

Expression of the neurofibromatosis 1 (NF1) gene in reactive astrocytes in vitro.

Neurofibromin, the product of the neurofibromatosis 1 (NF1) gene, is an important tumor suppressor protein expressed most abundantly in the nervous system. Within the central nervous system, neurofibromin has been localized to neurons and oligodendrocytes but not astrocytes. As individuals with NF1 are at an increased risk for optic pathway gliomas and astrocytomas, we chose to re-evaluate the level of neurofibromin expression in primary cultures of murine cortical astrocytes under control and reactive conditions. Astrocytes under control conditions expressed low levels of NF1 mRNA and protein. Following stimulation with dibutyryl-cyclic AMP or interferon-gamma in combination with either lipopolysaccharide or interleukin-1 beta, there was a marked increase in NF1 mRNA and protein expression. These results suggest that neurofibromin may be involved in the process of reactive astrocytosis seen in response to CNS injury.

Animals↗
PubMed1995

Potentiated necrosis of cultured cortical neurons by neurotrophins.

The effects of neurotrophins on several forms of neuronal degeneration in murine cortical cell cultures were examined. Consistent with other studies, brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4/5 all attenuated the apoptotic death induced by serum deprivation or exposure to the calcium channel antagonist nimodipine. Unexpectedly, however, 24-hour pretreatment with these same neurotrophins markedly potentiated the necrotic death induced by exposure to oxygen-glucose deprivation or N-methyl-D-aspartate. Thus, certain neurotrophins may have opposing effects on different types of death in the same neurons.

Animals↗
PubMed1995

Concomitant acceleration of the activation and inactivation kinetics of the human delayed rectifier K+ channel (Kv1.1) by Ca(2+)-independent phospholipase A2.

The electrophysiologic sequelae of arachidonic acid release mediated by the major phospholipase A2 (PLA2) in electrically active tissues (i.e. the 40-kDa Ca(2+)-independent PLA2) were assessed in Sf9 cells expressing the human recombinant delayed rectifier K+ channel Kv1.1. Intracellular administration of Ca(2+)-independent PLA2 increased the rate of activation of the macroscopic current (from tau act = 6.25 +/- 0.76 ms to tau act, PLA2 = 2.78 +/- 0.78 ms at 40 mV) and resulted in channel inactivation (from no observed inactivation to tau inact = 103 +/- 6 ms at 40 mV), which were: 1) dependent on the enrichment of Sf9 cell phospholipids in esterified arachidonic acid; 2) ablated by pretreatment of the PLA2 by the mechanism-based inhibitor (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one; and 3) manifest prior to development of alterations in cellular permeability. The bidirectional effects of Ca(2+)-independent PLA2 were indistinguishable from the effects of exogenously applied arachidonic acid (AA), which specifically and reversibly increased the rates of channel activation (from tau act = 5.73 +/- 0.88 ms to tau act,AA = 1.91 +/- 0.39 ms at 40 mV) and inactivation (from no observed inactivation to tau inact = 76.6 +/- 1.4 ms at 40 mV). These electrophysiologic alterations resulted from the effects of arachidonic acid per se since Sf9 cells did not produce oxygenated eicosanoid metabolites, and neither exogenous administration nor in situ generation of other fatty acids resulted in these effects. Collectively, these results unambiguously demonstrate the role of arachidonic acid per se on Kv1.1 electrophysiologic function and suggest the importance of Ca(2+)-independent PLAs as an enzymic modulator of ion channel function in electrically active tissues.

Animals↗
PubMed1995

3-Nitropropionic acid induces apoptosis in cultured striatal and cortical neurons.

Ingestion of 3-nitropropionic acid (3-NPA) in moldy sugar cane causes brain damage in children. The mechanism of 3-NPA toxicity is thought to be inhibition of energy production, leading to ATP depletion and excitotoxicity. We exposed cultured mouse striatal or cortical neurons to 1-2 mM 3-NPA for 48 h. This exposure produced gradual neuronal degeneration characterized by cell body shrinkage and DNA fragmentation. Addition of glutamate antagonists during 3-NPA exposure did not reduce neuronal death. However, addition of the macromolecular synthesis inhibitors cycloheximide, emetine or actinomycin D markedly reduced neuronal death. Our results do not exclude that 3-NPA can induce excitotoxicity in more intact systems, but raise the additional possibility that 3-NPA may also act to induce neuronal apoptosis.

Animals↗
PubMed1995

Staurosporine-induced neuronal apoptosis.

Staurosporine, a nonselective protein kinase inhibitor, has been shown to induce apoptosis in several different nonneuronal cell types. We tested the hypothesis that staurosporine would also induce apoptosis in central neurons. Exposure of murine cortical cell cultures to 30-100 nM staurosporine induced concentration-dependent selective neuronal degeneration over the following day; at higher concentrations, staurosporine damaged glial cells as well. Staurosporine-induced neuronal death was accompanied by cell body shrinkage, chromatin condensation, and DNA laddering. In contrast, NMDA-induced neuronal death was accompanied by acute cell body swelling without DNA laddering. Staurosporine-induced neuronal death, unlike excitotoxic death, was markedly attenuated by the protein synthesis inhibitor cycloheximide; this protective effect was not reversed by a glutathione synthesis inhibitor, buthionine sulfoximine. Interestingly, the glial cell death induced by 1 microM staurosporine was markedly potentiated by cycloheximide. Staurosporine-induced neuronal death was not accompanied by an increase in intracellular free Ca2+ and was attenuated by 30 mM K+; this protective effect of high K+ was blocked by nimodipine or Co2+. Present data suggest that staurosporine can induce apoptosis in cultured cortical neurons and that this apoptosis can be blocked by raising intracellular Ca2+ or by blocking protein synthesis. Staurosporine exposure may be useful as a model for studying central neuronal apoptosis in vitro.

Alkaloids↗
PubMed1995

The inhibitory mGluR agonist, S-4-carboxy-3-hydroxy-phenylglycine selectively attenuates NMDA neurotoxicity and oxygen-glucose deprivation-induced neuronal death.

We examined the effect of two novel phenylglycine derivative drugs on excitotoxicity in murine cortical cell cultures: S-4-carboxy-3-hydroxy-phenylglycine (4C3HPG), a selective agonist of mGluRs 2/3 and an antagonist at mGluRs 1/5, and S-3 hydroxy-phenylglycine (3HPG), an agonist of mGluRs 1/5. 4C3HPG attenuated slowly-triggered NMDA-induced excitotoxic neuronal death, as well as the death induced by combined oxygen-glucose deprivation, but did not affect slowly-triggered excitotoxicity induced by AMPA or kainate. As expected, 4C3HPG also reduced NMDA-induced increases in cAMP in near-pure neuronal cultures, and the protective effect of 4C3HPG on NMDA toxicity could be reversed by adding 8-(4-chlorophenylthio)-adenosine 3':5'-cyclic-monophosphate (CPT cAMP) to the exposure medium. In contrast, 3HPG did not did not have any protective effects in these paradigms; in fact, slowly-triggered NMDA-induced excitotoxicity and the neuronal cell death induced by oxygen-glucose deprivation were potentiated. These results are consistent with the idea that the "inhibitory" mGluRs 2/3 exert a negative modulatory action on NMDA receptor-mediated excitotoxicity via reduction in neuronal cAMP levels.

Animals↗
PubMed1995

Blockade of glutamate receptors unmasks neuronal apoptosis after oxygen-glucose deprivation in vitro.

Mouse cortical cell cultures exposed to transient oxygen-glucose deprivation developed marked acute cell body swelling followed by neurodegeneration, consistent with necrosis-type death. This death was not attenuated by the protein synthesis inhibitor, cycloheximide, but was attenuated by addition of the N-methyl-D-asparate antagonist, MK-801 (dizocilpine maleate), and the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione. If the deprivation insult was extended to overcome the protective effect of glutamate antagonists, neuronal death resulted that was associated with cell body shrinkage and DNA fragmentation, and was attenuated by cycloheximide. These data suggest that oxygen-glucose deprivation can induce in cortical neurons both excitotoxic necrosis, and apoptosis dependent on new macromolecule synthesis.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1995

Profound systemic hypothermia inhibits the release of neurotransmitter amino acids in spinal cord ischemia.

Profound hypothermia induced with cardiopulmonary bypass has a protective effect on spinal cord function during operations on the thoracoabdominal aorta. The mechanism of this protection remains unknown. It has been proposed that the release of excitatory amino acids in the extracellular space plays a causal role in irreversible neuronal damage. We investigated the changes in extracellular neurotransmitter amino acid concentrations with the use of in vivo microdialysis in a swine model of spinal cord ischemia. All animals underwent left thoracotomy and right atrium-femoral artery cardiopulmonary bypass with additional aortic arch perfusion. Lumbar laminectomies were then done and microdialysis probes were inserted stereotactically in the anterior horn of the second and fourth segments of the lumbar spinal cord. The probes were perfused with artificial cerebrospinal fluid at a rate of 2 microliters/min and 15-minute samples were assayed by high-performance liquid chromatography. Group 1 animals (n = 6) underwent aortic clamping distal to the left subclavian artery and proximal to the renal arteries for 60 minutes at normothermia (37 degrees C) and group 2 animals (n = 5) were cooled to a rectal temperature of 20 degrees C before application of aortic clamps, maintained at this level during cardiopulmonary bypass until the aorta was unclamped, and then slowly rewarmed to 37 degrees C. Seven amino acids were studied, including two excitatory neurotransmitters (glutamate and aspartate) and five putative inhibitory neurotransmitters (glycine, gamma-aminobutyric acid, serine, adenosine, and taurine). Glutamate exhibited a threefold increase in extracellular concentration during normothermic ischemia compared with baseline values and remained elevated until 60 minutes after reperfusion. The increase in aspartate concentration was not significant. The extracellular concentrations of glycine and gamma-aminobutyric acid also increased significantly during ischemia and reperfusion. Hypothermia uniformly prevented the release of amino acids in the extracellular space. Glutamate levels remained significantly decreased even after rewarming to normothermia whereas glycine levels returned to baseline values. These results are consistent with a role for excitatory amino acids in the production of ischemic spinal cord injury and suggest that the mechanism of hypothermic protection may be related to decreased release of these amino acids in the ischemic spinal cord.

Analysis of Variance↗
PubMed1995

Detection of free radicals by microdialysis/spin trapping EPR following focal cerebral ischemia-reperfusion and a cautionary note on the stability of 5,5-dimethyl-1-pyrroline N-oxide (DMPO).

We have examined free radical production in a rat model of focal cerebral ischemia using microdialysis coupled with EPR analysis. A microdialysis probe was inserted 2 mm into the cerebral cortex, supplied by the right middle cerebral artery (MCA), and after a 2-hour washout period with artificial cerebral spinal fluid (ACSF), the perfusate solution was changed to ACSF containing the spin trapping agent, 5,5-dimethyl-1-pyrroline N-oxide (DMPO). No free radicals were detected by DMPO during the pre-ischemia period. Both common carotid arteries and the right MCA were then ligated for 90 minutes. Microdialysate collected every 15 min during the ischemic period demonstrated predominantly superoxide or peroxyl radical production. After release of the occlusive sutures, hydroxyl radical became apparent initially, then thiyl and carbon centered radicals appeared later in samples collected every 15 min for two hours following cortical reperfusion. Careful studies on the purification and stability of DMPO solution were performed to circumvent artifacts and spurious signals.

Animals↗
PubMed1995

The first human case of Clinostomum complanatum (Trematoda: Clinostomidae) infection in Korea.

The authors present the first human case of Clinostomum pharyngitis in Taegu, Korea. The patient was a 56-year old male who visited an otolaryngology clinic due to foreign body sensation and pain of the pharyngeal region for 3-4 days. He used to eat raw fresh-water fish. Otolaryngological examinations revealed a living worm adhered to the right posterior pharyngeal wall. The worm removed was identified as C. complanatum after morphological observations. It is likely that more attention should be paid to eating raw fresh-water fish in Korea with regards to Clinostomum pharyngitis.

Animals↗
PubMed1995

The first human case of Diplogonoporus balaenopterae (Cestoda: Diphyllobothriidae) infection in Korea.

The first human case of Diplogonoporus balaenopterae infection is reported in Korea. The patient was a 41-year old male who passed a part of cestode strobila, about 1 m long, spontaneously in his stool. He used to eat raw marine fish when he drank alcohol. The worm was identified as D. balaenopterae after morhological observations and literature review. Results of laboratory examination were within normal limits except for slight eosinophilia (6%) and extraordinarily high serum Ig E level (10,182 IU/ml).

Adult↗
PubMed1995

Mitochondrial production of reactive oxygen species in cortical neurons following exposure to N-methyl-D-aspartate.

Increasing evidence suggests that glutamate neurotoxicity is partly mediated by reactive oxygen species, formed as a consequence of several processes, including arachidonic acid metabolism and nitric oxide production. Here we used an oxidation-sensitive indicator, dihydrorhodamine 123, in combination with confocal microscopy, to examine the hypothesis that electron transport by neuronal mitochondria may be an important source of glutamate-induced reactive oxygen species (ROS). Exposure to NMDA, but not kainate, ionomycin, or elevated potassium stimulated oxygen radical production in cultured murine cortical neurons, demonstrated by oxidation of nonfluorescent dihydrorhodamine 123 to fluorescent rhodamine 123. Electron paramagnetic resonance spectroscopy studies using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a radical-trapping agent, also showed production of ROS by cortical neurons after NMDA but not kainate exposure. NMDA-induced ROS production depended on extracellular Ca2+, and was not affected by inhibitors of nitric oxide synthase or arachidonic acid metabolism. The increased production of ROS was blocked by inhibitors of mitochondrial electron transport, rotenone or antimycin, and mimicked by the electron transport uncoupler, carbonyl cyanide p-trifluoromethoxyphenylhydrazone. These data support the possibility that NMDA receptor-mediated, Ca(2+)-dependent uncoupling of neuronal mitochondrial electron transport may contribute to the oxidative stress initiated by glutamate exposure.

Animals↗
PubMed1995

Sodium channel blockers reduce oxygen-glucose deprivation-induced cortical neuronal injury when combined with glutamate receptor antagonists.

Blockers of voltage-gated Na+ channels can protect central neuronal axons from hypoxic injury in vitro but have shown limited neuroprotective effects on neurons, where substantial injury is mediated by glutamate receptors. We explored the ability of several voltage-gated Na+ channel blockers to protect murine cultured cortical neurons from injury induced by oxygen-glucose deprivation. Whole-cell recordings from neurons revealed two types of Na+ currents activated by membrane depolarization: one rapidly inactivating and the other noninactivating. Both currents were blocked by tetrodotoxin (TTX) and 5,5-diphenylhydantoin (phenytoin). Fluorescent imaging using the Na(+)-selective dye SBFI confirmed that TTX attenuated the increase in intracellular free Na+ induced by oxygen-glucose deprivation. Addition of TTX (1 microM) but not phenytoin (10-100 microM) produced a small and variable reduction in neuronal death subsequent to oxygen-glucose deprivation for 40 to 50 min. Blockade of glutamate neurotoxicity by combined addition of MK-801, 7-chlorokynurenate and 6-cyano-7-nitroquinoxaline-2,3-dione markedly reduced injury such that prolonged deprivation times (75-100 min) were needed to induce widespread neuronal death. In this setting of glutamate receptor blockade, addition of TTX, phenytoin or one of several other Na+ channel blockers--lidocaine (100 microM), QX-314 (1 mM), quinidine (100 microM) or lorcainide (10 or 100 microM)--all further reduced neuronal death. Present results raise the possibility that Na+ channel blockers may be useful in protecting gray matter from hypoxic-ischemic injury, especially when combined with antiexcitotoxic approaches.

6-Cyano-7-nitroquinoxaline-2,3-dione↗