Biomedical subjects

S U Kim

Publications and source records attributed to S U Kim.

At least 55 records · Page 3Linked to original sources

PubMed2000

Cisplatin-induced apoptotic cell death in mouse hybrid neurons is blocked by antioxidants through suppression of cisplatin-mediated accumulation of p53 but not of Fas/Fas ligand.

Peripheral neuropathy following cisplatin treatment is a major limiting factor in cisplatin chemotherapy of cancer patients. We investigated the pathomechanism underlying cisplatin neuropathy using a mouse dorsal root ganglion neuron-neuroblastoma hybrid cell line (N18D3) developed in our laboratory. DNA fragmentation, a characteristic feature of apoptosis, was induced in hybrid neurons following treatment with cisplatin. Accumulation of p53, Fas, and Fas ligand (Fas-L) was also demonstrated in these neurons. Preincubation with N-acetylcysteine (NAC), a precursor of glutathione, blocked cisplatin-induced apoptosis completely, whereas Trolox, a vitamin E analogue, blocked it partially. Cisplatin-induced p53 accumulation was suppressed by NAC treatment, whereas p53 accumulation was retarded by Trolox treatment. In contrast, neither NAC nor Trolox showed any inhibitory effect on cisplatin-induced Fas/Fas-L accumulation. These results suggest that the neuroprotective effects of antioxidants against cisplatin-induced neurotoxicity in hybrid neurons are mediated mainly through the inhibition of p53 accumulation but not of Fas/Fas-L accumulation by these antioxidants.

Acetylcysteine↗

PubMed2000

Haloperidol-induced neuronal apoptosis: role of p38 and c-Jun-NH(2)-terminal protein kinase.

We examined patterns and mechanisms of cell death induced by haloperidol. Cortical cell cultures exposed to 10-100 microM: haloperidol for 24 h underwent neuronal death without injuring glia. The degenerating neurons showed hallmarks of apoptosis, featuring cell body shrinkage, nuclear chromatin condensation and aggregation, nuclear membrane disintegration with intact plasma membrane, and prominent internucleosomal DNA fragmentation. Neither glutamate antagonists nor antioxidants prevented the haloperidol-induced neuronal apoptosis. The c-Jun-NH(2)-terminal protein kinase and p38 mitogen-activated protein kinase were activated within 1 h and were sustained over the next 3 h following exposure of cortical neurons to 30 microM haloperidol. Haloperidol-induced neuronal apoptosis was partially attenuated by 10-30 microM PD169316, a selective inhibitor of p38 mitogen-activated protein kinase. Inclusion of 1 microg/ml cycloheximide, a protein synthesis inhibitor, or 100 ng/ml insulin prevented activation of both kinases and subsequent neuronal death. The present study demonstrates that cortical neurons exposed to haloperidol undergo apoptosis depending on activation of p38 mitogen-activated protein kinase and c-Jun-NH(2)-terminal protein kinase sensitive to cycloheximide and insulin.

Animals↗

PubMed2000

Activation of purinergic P2X receptors inhibits P2Y-mediated Ca2+ influx in human microglia.

Purinoceptor (P2X and P2Y) mediated Ca2+ signaling in cultured human microglia was studied using Ca2+ sensitive fluorescence microscopy. ATP (at 100 microM) induced a transient increase in [Ca2+]i in both normal and Ca(2+)-free solution suggesting a primary contribution by release from intracellular stores. This conclusion was further supported by the failure of ATP to cause a divalent cationic influx in Mn2+ quenching experiments. However, when fluorescence quenching was repeated after removal of extracellular Na+, ATP induced a large influx of Mn2+, indicating that inward Na+ current through a non-selective P2X-coupled channel may normally suppress divalent cation influx. Inhibition of Mn2+ entry was also found when microglia were depolarized using elevated external K+ in Na(+)-free solutions. The possibility of P2X inhibition of Ca2+ influx was then investigated by minimizing P2X contributions of purinergic responses using either the specific P2Y agonist, ADP-beta-S in the absence of ATP or using ATP combined with PPADS, a specific inhibitor of P2X receptors. In quenching studies both procedures resulted in large increases in Mn2+ influx in contrast to the lack of effect observed with ATP. In addition, perfusion of either ATP plus PPADS or ADP-beta-S alone caused a significantly enhanced duration (about 200%) of the [Ca2+]i response relative to that induced by ATP. These results show that depolarization induced by P2X-mediated Na+ influx inhibits store-operated Ca2+ entry resulting from P2Y activation, thereby modulating purinergic signaling in human microglia.

Adenosine Diphosphate↗

PubMed2000

Anion channels modulate store-operated calcium influx in human microglia.

Recent work from this laboratory has demonstrated that purinergic-mediated depolarization of human microglia inhibited a store-operated pathway for entry of Ca2+. We have used Fura-2 spectrofluorometry to investigate the effects on store-operated Ca2+ influx induced by replacement of NaCl with Na-gluconate in extracellular solutions. Three separate procedures were used to activate store-operated channels. Platelet activating factor (PAF) was used to generate a sustained influx of Ca2+ in standard physiological saline solution (PSS). The magnitude of this response was depressed by 70% after replacement of PSS with low Cl- PSS. A second procedure used ATP, initially applied in Ca2+-free PSS solution to deplete intracellular stores. The subsequent perfusion of PSS solution containing Ca2+ resulted in a large and sustained entry of Ca2+, which was inhibited by 75% with low Cl- PSS. The SERCA inhibitor cyclopiazonic acid (CPA) was used to directly deplete stores in zero-Ca2+ PSS. Following the introduction of PSS containing Ca2+, a maintained stores-operated influx of Ca2+ was evident which was inhibited by 77% in the presence of the low Cl- PSS. Ca2+ influx was linearly reduced with cell depolarization in elevated K+ (7.5 to 35 mM) suggesting that changes in external Cl- were manifest as altered electrical driving force for Ca2+ entry. However, 50 mM external KCl effectively eliminated divalent entry which may indicate inactivation of this pathway with high magnitudes of depolarization. Patch clamp studies showed low Cl-PSS to cause depolarizing shifts in both holding currents and reversal potentials of currents activated with voltage ramps. The results demonstrate that Cl- channels play an important role in regulating store-operated entry of Ca2+ in human microglia.

Adenosine Triphosphate↗

PubMed2000

Antimicrobial activity of 9-O-acyl- and 9-O-benzoyl-substituted berberrubines.

In the course of a structure-activity relationship study on berberrubine derivatives, a series of compounds bearing 9-O-acyl-(4-6) and 9-O-benzoyl- (7) substituents was synthesized with the expectation of increasing the antimicrobial activity. One of the berberrubine derivatives, 9-lauroylberberrubine chloride was the most active against Gram-positive bacteria Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus, Bacillus subtilis as well as the Gram-negative bacterium Klebsiella pneumoniae in comparison to berberine, the currently used antibiotic in clinic. This result suggested that the presence of lipophilic substituents of certain structures and sizes might be crucial for the optimal antimicrobial activity.

Anti-Bacterial Agents↗

PubMed2000

In vitro development of reconstructed porcine oocytes after somatic cell nuclear transfer.

This study was designed to examine the developmental ability of porcine embryos after somatic cell nuclear transfer. Porcine fibroblasts were isolated from fetuses at Day 40 of gestation. In vitro-matured porcine oocytes were enucleated and electrically fused with somatic cells. The reconstructed eggs were activated using electrical stimulus and cultured in vitro for 6 days. Nuclear-transferred (NT) embryos activated at a field strength of 120 V/mm (11.6 +/- 1.6%) showed a higher developmental rate as compared to the 150-V/mm group (6.5 +/- 2.3%) (P: < 0.05), but the mean cell numbers of blastocysts were similar between the two groups. Rates of blastocyst development from NT embryos electrically pulsed at different times (2, 4, and 6 h) after electrofusion were 11.6 +/- 2.9, 6.6 +/- 2.3, and 8.1 +/- 3.3%, respectively. The mean cell numbers of blastocysts developed from NT embryos were gradually decreased (30.4 +/- 10.4 > 24.6 +/- 10.1 > 16.5 +/- 7.4 per blastocyst) as exposure time (2, 4, and 6 h) of nuclei to oocyte cytoplast before activation was prolonged. There was a significant difference in the cell number between the 2- and 6-h groups (P: < 0. 05). Nuclear-transferred embryos (9.4 +/- 0.9%) had a lower developmental rate than in vitro fertilization (IVF)-derived (21.4 +/- 1.9%) or parthenogenetic embryos (22.4 +/- 7.2%) (P: < 0.01). The mean cell number (28.9 +/- 11.4) of NT-derived blastocysts was smaller than that (38.6 +/- 10.4) of IVF-derived blastocysts (P: < 0. 05) and was similar to that (29.9 +/- 12.1) of parthenogenetic embryos. Our results suggest that porcine NT eggs using somatic cells after electrical activation have developmental potential to the blastocyst stage, although with smaller cell numbers compared to IVF embryos.

Animals↗

PubMed2000

Alcohol consumption, glutathione S-transferase M1 and T1 genetic polymorphisms and breast cancer risk.

To evaluate the potential association between GSTM1 and GSTT1 genotypes and development of breast cancer, a hospital based case-control study was conducted in a South Korean study population consisting of 189 histologically confirmed incident breast cancer cases and their 189 age-matched control subjects with no present or previous history of cancer. A multiplex polymerase chain reaction method was used for the genotyping analyses and statistical evaluations were performed by unconditional logistic regression model. The GSTM1 null genotype was significantly associated with breast cancer risk in premenopausal women [odds ratio (OR) = 2.0, 95% confidence interval (CI) = 1-3.7], but not in the postmenopausal women (OR = 0.9, 95% CI = 0.5-1.9), nor in all women grouped together (OR = 1.3, 95% CI = 0.8-1.1). The GSTT1 null genotype posed a similar risk of breast cancer with an OR of 1.6 (95% CI = 1.0-2.5) for the total breast cancer group, OR of 1.7 (95% CI = 0.9-3.2) for pre-menopausal women, and OR of 1.3 (95% CI = 0.6-2.8) for post-menopausal women. The breast cancer risk associated with concurrent lack of both GSTM1 and GSTT1 genes was 2.2 (95% CI = 1.1-4.5), and the risk increased as the number of null genotype increased (P for trend = 0.03). When the data were stratified by the known risk factors of breast cancer, a significant interaction was observed between the GSTM1 genotypes and alcohol consumption (P for interaction = 0.03). An especially remarkable risk of breast cancer was observed for alcohol-consuming premenopausal women lacking both the GSTM1 and GSTT1 genes (OR = 5.3, 95% CI = 1.0-27.8) compared to those with both of the genes. Our findings thus suggest a novel gene-environment interaction which plays an important role in the individual susceptibility to breast cancer. p6

Adult↗

PubMed2000

Chaetoatrosin A, a novel chitin synthase II inhibitor produced by Chaetomium atrobrunneum F449.

Chaetoatrosin A, a novel chitin synthase II inhibitor, was isolated from the culture broth of fungus F449, which was identified as Chaetomium atrobrunneum F449. Chaetoatrosin A was purified by solvent partition, silica gel, ODS, preparative TLC, and Sephadex LH-20 column chromatographies, consecutively. The structure of chaetoatrosin A was assigned as 1,8-dihydroxy-3(2-hydroxypropionyl)-6-methoxynaphthalene on the basis of various spectroscopic analyses including UV, IR, mass spectral, and NMR. Its molecular weight and formula were found to be 262 and C14H14O5, respectively. ,Chaetoatrosin A inhibited chitin synthase II by 50% at the concentration of 104 microg/ml in an enzyme assay system. This compound showed antifungal activities against Rhizoctonia solani, Pyricularia oryzae, Botrytis cinerea, Cryptococcus neoformans and Trichophyton mentagrophytes.

Antifungal Agents↗

PubMed2000

Phellinsin A, a novel chitin synthases inhibitor produced by Phellinus sp. PL3.

Phellinsin A, a novel chitin synthases inhibitor was isolated from the cultured broth of fungus PL3, which was identified as Phellinus sp. PL3. Phellinsin A was purified by solvent partition, silica gel, ODS column chromatographies, and preparative HPLC, consecutively. The structure of phellinsin A was assigned as a phenolic compound on the basis of various spectroscopic analyses including UV, IR, Mass, and NMR. Its molecular weight and formula were found to be 358 and C18H14O8, respectively. Phellinsin A selectively inhibited chitin synthase I and II of Saccharomyces cerevisiae with an IC50 value of 76 and 28 microg/ml, respectively, in our cell free assay system. This compound showed antifungal activity against Colletotrichum lagenarium, Pyricularia oryzae, Rhizoctonia solani, Aspergillus fumigatus, and Trichophyton mentagrophytes.

Alternaria↗

PubMed1999

Characterization of mouse peroxiredoxin I genomic DNA and its expression.

Peroxiredoxins (Prxs) are a newly defined family of anti-oxidant proteins that have been implicated, via their anti-oxidant activity, in a number of cellular functions, including cell proliferation and differentiation, protection of other proteins from oxidative damage, and intracellular signaling. We isolated genomic DNA sequences of the Prx I genes from the mouse, and characterized their molecular genetic features. Prx I was found to form a small gene family with two and three members; one functional and two pseudogenes. The Prx I-1 gene has splice donor/acceptor site sequences and five or six exons, whereas the Prx I-2 clone has several structural features characteristic of a typical retroposon found to have ORF sequences. We analyzed the expression of pseudogenes, which were not expressed on the transcription levels in the investigated organs. The functional copy of the Prx I-1 gene was expressed abundantly in liver and kidney of the adult, as well as in early developing embryos. This report, together with amino acid/nucleotide sequence similarity between human and mice, provides a basis for speculating on an even earlier event in the evolution of the Prx I gene family, i.e. the Prx I gene was well conserved in human and mice via its anti-oxidant activity.

Amino Acid Sequence↗

PubMed1999

A novel fluorescent GSH-adduct binds to the NMDA receptor.

In an attempt to develop various fluorescent probes to label glutathione (GSH) receptors, we have serendipitously synthesized a probe that binds to and antagonizes the NMDA receptor. Probe 1, a GSH adduct, displaces the competitive NMDA antagonist [3H]-CGP 39653 with a higher affinity than NMDA or cysteine in rat synaptic membranes. In recording experiments from a rat cortical 'wedge' preparation, Probe 1 reversibly blocks both NMDA- and cysteine-induced depolarization. In mixed astrocyte-neuron tissue culture preparations, Probe 1 labels parts of both cell bodies as well as processes. The present data suggest that Probe 1 binds to the NMDA receptor and antagonizes channel function.

2-Amino-5-phosphonovalerate↗

PubMed1999

Effects of Selaginella tamariscina on in vitro tumor cell growth, p53 expression, G1 arrest and in vivo gastric cell proliferation.

Selaginella tamariscina, an oriental medicinal plant, was extracted using water and several organic solvents, and each fraction was assayed for its tumoricidal effects with 3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide (MTT). Influences on expression of p53 tumor suppressor gene and induction of G1 arrest in the cell cycle were analyzed by Northern blotting and flow cytometry, respectively. The modifying effects of pulverized Selaginella tamariscina on cell turnover in the stomach were also investigated in rats given 150 mg/kg of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) by gavage and then fed a diet containing 5, 1 or 0% Selaginella tamariscina. Fractions I-V showed significant tumoricidal effects against cultured human leukemia cells whereas these fractions did not affect normal human lymphocytes. Among the effective fractions, the water-extracted fraction (V) efficiently increased p53 gene expression and induced G1 arrest. The 1% Selaginella tamariscina feeding caused a significant reduction (P < 0.05) in the proliferating cell nuclear antigen-(PCNA) labeling index of the glandular stomach epithelium as compared with the MNNG-alone group value although 5% Selaginella tamariscina feeding was only associated with a tendency for decrease. These results suggest that Selaginella tamariscina could be a candidate chemopreventive agent against gastric cancer.

Animals↗

PubMed1999

Platelet-activating factor induced Ca(2+) signaling in human microglia.

Increases in intracellular Ca(2+) concentration in human microglial cells in response to platelet-activating factor (PAF) were studied using Ca(2+)-sensitive fluorescence microscopy. In normal physiological solution (PSS), PAF-induced transient increases in [Ca2+](i) which recovered to baseline values within 200 s. Application of PAF in zero-Ca(2+) solution caused the peak response to be decreased to a value near 20% of that recorded in PSS suggesting a primary contribution of Ca(2+) influx for the [Ca2+](i) increase in PSS. To investigate PAF-induced Ca(2+) influx, the contents of intracellular stores were modulated using the SERCA blocker cyclopiazonic acid (CPA). The Ca(2+) signal induced by CPA (10 microM) in zero-Ca(2+) solution showed a peak response about 20% of the amplitude in the presence of external Ca(2+), suggesting the latter response included significant contributions from store-operated Ca(2+) entry. The influx of divalent cations with PAF or CPA was directly measured using Mn(2+) quenching of the fluorescence signal. Although both PAF and CPA induced a similar degree of Mn(2+) influx over time, the PAF effect was very rapid, whereas the CPA action was delayed and only evident about 200 s after application. Overall, the results show that the primary source of the PAF-induced increase of [Ca2+](i) in human microglia was the influx of Ca(2+) from the extracellular space and intracellular Ca(2+)-release contributed only a small part of the total Ca(2+) signal. Nevertheless, Ca(2+)-release induced by PAF (or CPA) serves as an important factor in controlling Ca(2+) entry presumably mediated by activation of store-operated-Ca(2+) channels.

Calcium↗

PubMed1999

Characterization of the murine gene encoding 1-Cys peroxiredoxin and identification of highly homologous genes.

A new type of peroxiredoxin, named 1-Cys peroxiredoxin (1-Cys Prx), reduces hydrogen peroxide with the use of electrons from unidentified electron donor(s). We have isolated the mouse gene encoding 1-Cys Prx (CP-3) and shown that it is comprised of five exons and four introns. Analysis of 5' flanking regions revealed binding sequences of several putative transcription factors such as Sp1, Pit-1a, c-Jun, c-Myc and YY1. It is noticeable that several potential Sp1 binding sites assigned the -60 through -96bp from putative transcription initiation site. The gel shift assays showed that Sp1 and Pit-1a bind specifically to each binding site in 1-Cys Prx promoter. We also isolated two highly related genes such as CP-2 and CP-5. These genes are encoded by single exons, and show 85% of nucleotide sequence homology with the CP-3. The structural features of these genes suggest that they might be intronless genes derived from the CP-3 by the mechanism involving retrotransposition. In addition, our data suggest that they are inserted to a specific site of the mouse L1 repetitive element. The 1-Cys Prx was actively transcribed in a variety of adult tissues as well as in the developing embryos. These results suggest that only the 1-Cys Prx gene might be relevant for studying the function of the 1-Cys Prx in the murine system.

Amino Acid Sequence↗

PubMed1999

Process extension and intracellular Ca2+ in cultured murine oligodendrocytes.

Previous investigations have shown that phorbol esters stimulate process extension in oligodendrocytes (OL), likely by the activation of protein kinase C (PKC). In this report, we demonstrate that treatment of OL with 4beta-phorbol-12, 13-dibutyrate (PDB; 0.1-1 microM) resulted in an increase in intracellular Ca2+ concentration ([Ca2+]i) from 94+/-2 nM (mean+/-S.E.M.) to 244+/-10 nM. This increase was produced by Ca2+ influx through a La3+-insensitive pathway. Changes in [Ca2+]i were also produced by modifying the extracellular Ca2+ concentration ([Ca2+]o) where [Ca2+]i was increased by elevations in [Ca2+]o. In parallel experiments we found that increased [Ca2+]o alone, without concurrent phorbol ester application, resulted in increased OL process extension as determined by the percent of OL with long processes (greater than 3 times the cell body diameter). These results demonstrate that increasing [Ca2+]o stimulates OL process outgrowth. Furthermore, both elevations in [Ca2+]o and PDB exposure increase [Ca2+]i, suggesting that some of the effects of phorbol esters on OL process extension are likely mediated by changes in [Ca2+]i.

Animals↗

PubMed1999

Endothelin-induced changes in intracellular calcium in human microglia.

Calcium-sensitive spectrofluorometry was used to study the effects of endothelin on levels of intracellular calcium [Ca2+]i in cultured human microglia. Both ET-1 and ET-3 induced transient, non-desensitizing, increases in [Ca2+]i in over 80% of the cells studied. The responses to either ET-1 or ET-3 were significantly diminished in amplitude and duration in Ca2+-free solution suggesting a prominent contribution of Ca2+ influx to the response. ET-1 induced changes in [Ca2+]i were not altered in the presence of the selective ET(A) antagonist BQ610 but were significantly reduced with the selective ET(B) antagonist BQ780. These results confirm the expression of ET(B) receptors on human microglia, these receptors may serve a role in a signaling pathway between microglia and endothelial cells.

Brain↗

PubMed1999

Cytokine-induced production of macrophage inflammatory protein-1alpha (MIP-1alpha) in cultured human astrocytes.

Macrophage inflammatory protein-1alpha (MIP-1alpha) is a member of a superfamily of inflammatory cytokines termed chemokines, and it has been implicated in the pathogenesis of several human diseases with inflammatory components. It has been known that MIP-1alpha plays a role in recruiting and activating mononuclear phagocytes in the central nervous system (CNS), and that astrocytes and microglia are sources of this chemokine. However, details of the regulation of MIP-1alpha production by these glial cells are not known. In the present study, expression of MIP-1alpha was determined in purified cultures of human astrocyte. MIP-1alpha mRNA levels in human astrocyte cell preparations were determined by reverse transcription polymerase chain reaction (RT-PCR) and amount of MIP-1alpha protein secreted into culture supernatants by human astrocytes was assayed by enzyme-linked immunosorbent assay (ELISA). Under the unstimulated conditions, human astrocytes did not express MIP-1alpha message or protein, indicating that human astrocytes do not constitutively carry MIP-1alpha message. Following treatment with interleukin-1beta (IL-1beta), human astrocytes demonstrated increased message and protein expression for MIP-1alpha, while other immune modulators such as interferon-gamma (IFN)-gamma, tumor necrosis factor-alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF), lipopolysaccharide, or phorbol ester (a protein kinase C activator) did not induce MIP-1alpha expression in human astrocytes.

Astrocytes↗

PubMed1999

Molecular basis for enhanced biosynthesis of clavulanic acid by a redox-cycling agent, phenazine methosulfate, in Streptomyces clavuligerus.

Phenazine methosulfate (PMS), a generator of superoxide, evoked the transcription of cas2 and cefF, ultimately resulting in the enhanced biosyntheses of clavulanic acid (CA) and cephamycin C (CMC) in Streptomyces clavuligerus. The transcriptional activation of cas2 and cefF was accompanied with that of ccaR, a regulatory gene for biosyntheses of CA and CMC. PMS or H2O2 in cell-free extract exerted a positive regulation on in vitro protein phosphorylation. The PMS-mediated activation of protein phosphorylation was significantly offset by butylated hydroxyanisole, a radical scavenger. Staurosporine, a protein kinase inhibitor, was shown to have a negative effect on PMS-promoted CA accumulation. Therefore, it is suggestive that PMS-activated transcription of cas2 and cefF is mediated by protein phosphorylation and the expression of a pathway-specific transcriptional activator as found in other streptomycetes. These experimental results present an example of the functional relationship between oxidative stimuli and secondary metabolite production in streptomycetes.

Anti-Bacterial Agents↗