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Abstract
Macroscopic and microscopic currents have been recorded using human microglia isolated from fetal human brains (12-20 weeks gestation). Within a period of two days following plating of cells, inward K+ currents were small (mean amplitude of 0.3 nA at -100 mV) and outward K+ currents were not observed. For periods in excess of five days after adherence to substrate, an inactivating outward K+ current, sensitive to 4-aminopyridine, was expressed. A slowly rising current, blocked by tetraethylammonium, was also evident in a small population of human microglia. This current was activated with cell depolarization positive to +10 mV and had properties similar to those recently described for a proton current in mouse cells. In early adherent cells (days 1 or 2 after plating), treatment of microglia with interferon-gamma led to the expression of outward K+ current which was lacking in the absence of the treatment. In excised, inside-out patches, two high conductance channels were identified. A calcium-dependent K+ channel (unitary conductance of 106 pS with physiological levels of K+ across the patch) had an open probability of 0.5 with internal Ca2+ at 7 microM and the patch potential at 0 mV. In addition, an anion channel (unitary conductance of 280 pS) was transiently activated with depolarizing or hyperpolarizing steps applied from 0 mV. Characterization of the macroscopic and unitary properties of currents in microglia will have relevance to a description of putative cell functions in the human CNS. In particular, modification of cell electrophysiological properties by various activating stimuli may contribute to signalling processes in CNS pathology.
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Stariha RL, Kikuchi S, Siow YL, Pelech SL, Kim M, Kim SU. Role of extracellular signal-regulated protein kinases 1 and 2 in oligodendroglial process extension. J Neurochem 1997; 68:945-53. [PMID: 9048739 DOI: 10.1046/j.1471-4159.1997.68030945.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The relationship between extracellular signal-regulated protein kinase (ERK) activation and process extension in cultured bovine oligodendrocytes (OLGs) was investigated. Process extension was induced through the exposure of cultured OLGs to phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC), for various intervals. During the isolation of these OLGs from bovine brain, the original processes were lost. Therefore, any reinitiation of process extension via PMA stimulation was easily discemible through morphological monitoring. It was found that exposure of OLGs to PMA for 10 min was enough to induce OLG process extension 24-72 h later. Furthermore, this extension was still evident at least 1 week after the initial PMA stimulation, indicating that OLGs do not need continuous PKC activation to sustain process extension. Control and PMA-stimulated OLGs were also subjected to immunocytochemistry using an anti-ERK antibody selective for the mitogen-activated protein kinases p42 Erk2 (ERK2) and p44 Erk1 (ERK1) isoforms. ERK immunoreactivity in the nucleus was evident after PMA stimulation of OLGs but not in control OLGs. In parallel experiments, the control and PMA-stimulated OLGs were purified by Mono Q fractionation and subjected to ERK phosphotransferase assays using [gamma-32P]ATP and either myelin basic protein (MBP) or a synthetic peptide substrate based on the Thr97 phosphorylation site in MBP. These assays indicated that in PMA-treated OLGs, ERK activation was at least 12-fold higher than in control OLGs. Anti-ERK and anti-phosphotyrosine western blots of the assay fractions verified an enhanced phosphorylation of ERK1 and ERK2 in PMA-treated fractions relative to control fractions. When OLGs were pretreated for 15 min with the ERK kinase (MEK) inhibitor PD 098059 before PMA stimulation, they exhibited a 67% decrease in ERK activation as compared with cells treated with PMA alone. Furthermore, these MEK inhibitor-pretreated cells were still viable but showed no process extensions up to 1 week later. Therefore, we propose that a threshold level of ERK activity is required for the initiation of OLG process extension.
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103
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Cho KH, Kim MW, Kim SU. Tissue culture model of Krabbe's disease: psychosine cytotoxicity in rat oligodendrocyte culture. Dev Neurosci 1997; 19:321-7. [PMID: 9215877 DOI: 10.1159/000111228] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Krabbe's disease (globoid cell leukodystrophy) is a progressive cerebral degenerative disease of infancy characterized by severe myelin loss and the presence of globoid bodies in the white matter. Previous studies have suggested that psychosine is the causative agent for the pathogenesis of Krabbe's disease. In the present study, we investigated psychosine-induced injury and cell death of oligodendrocytes in enriched cultures of oligodendrocytes prepared from 3-week-old rat brain. The psychosine concentration sufficient to induce 50% cell death in oligodendrocytes was 30 micrograms/ml in the medium containing serum and 10 micrograms/ml in the serum-free medium. When oligodendrocytes were exposed to psychosine in the presence of phorbol esters, insulin, insulin-like growth factor I (IGF-I), demethylsulfoxide, or serum albumin, the survival of oligodendrocytes was greatly increased. These results indicate that psychosine cytotoxicity against oligodendrocytes is blocked by phorbol esters, insulin, and IGF-I through activation of protein kinase-C, by dimethylsulfoxide through activation of beta-galactosidase, and by albumin through its binding to psychosine.
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104
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Spiller OB, Moretto G, Kim SU, Morgan BP, Devine DV. Complement expression on astrocytes and astrocytoma cell lines: failure of complement regulation at the C3 level correlates with very low CD55 expression. J Neuroimmunol 1996; 71:97-106. [PMID: 8982108 DOI: 10.1016/s0165-5728(96)00136-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Primary fetal human astrocytes and an astrocytoma cell line, U373-MG, expressed membrane cofactor protein (CD46), CD59, and low levels of decay-accelerating factor (CD55). Astrocyte CD55 was capable of regulating C3 deposition on the cell surface; albeit at a lower level than primary human fibroblasts. Negligible complement-mediated lysis of primary astrocytes and the U373-MG cell line was observed, even when large amount of astrocyte-specific, complement-activating antibodies were bound to the cells. Blocking the function of CD59 on astrocytes resulted in a > 90% cell lysis, while equivalent lysis of fibroblasts could only be achieved with additional blocking of CD55.
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105
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Yoo AS, McLarnon JG, Xu RL, Lee YB, Krieger C, Kim SU. Effects of phorbol ester on intracellular Ca2+ and membrane currents in cultured human microglia. Neurosci Lett 1996; 218:37-40. [PMID: 8939475 DOI: 10.1016/0304-3940(96)13120-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The effects of protein kinase C (PKC) activation by phorbol ester on intracellular Ca2+ concentration ([Ca2+]i) and membrane currents in human microglia grown in culture were investigated. Treatment of microglia with phorbol myristate acetate (PMA) resulted in a large increase in [Ca2+]i in cells loaded with fura-2. The increased levels of [Ca2+]i were not altered following removal of the phorbol ester. In Ca(2+)-free medium, application of PMA did not increase [Ca2+]i. In addition, PMA application in standard Ca(2+)-solution containing lanthanum (1.8 mM) had no effect on the microglial response to PMA, suggesting that the phorbol ester actions were due to transmembrane influx of Ca2+ but not through voltage-gated Ca2+ channels. Whole-cell patch clamp measurements demonstrated that PMA potentiated an outward K+ current and inhibited an inward rectifier K+ current. This study is the first demonstration that PKC activation by phorbol ester leads to increased intracellular [Ca2+] and changes in membrane currents in human microglia.
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Kim SU, Han J, Lim YH. Revised assignment of 1H-NMR signals of artemisinic acid. PLANTA MEDICA 1996; 62:480-1. [PMID: 17252486 DOI: 10.1055/s-2006-957948] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The correct 1H-NMR assignment of artemisinic acid was achieved through COSY, HETCOR, DEPT, J-resolved, and NOESY techniques. The present experiments supplemented by molecular mechanics calculations could correct some previously misinterpreted signals, notably of H-2s, H-3s, and H-6. The results should be helpful in further work with this important artemisinin-analogue precursor.
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107
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Ogawa Y, Shimizu H, Kim SU. 2,5-Hexanedione induced apoptosis in cultured mouse DRG neurons. Int Arch Occup Environ Health 1996; 68:495-7. [PMID: 8891791 DOI: 10.1007/bf00377875] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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108
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Kim SU, Kwon HJ. Production of methyl 3-oxoartemisinate from methyl artemisinate by suspension cell culture of Mentha piperita. PLANTA MEDICA 1996; 62:359-360. [PMID: 8792672 DOI: 10.1055/s-2006-957904] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Methyl artemisinate was fed to the suspension cell culture of Mentha piperita. The biotransformation product was isolated and identified as a novel compound, methyl 3-oxoartemisinate. The Mentha cells were apparently capable of extensively oxidizing at the allylic C-3 position, to give rise to an oxo group. The conversion of the fed methyl ester of the acid reached a maximum in 48 h with 5.5% conversion. The physicochemical data of the oxo compound are presented.
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Kim YK, Son KH, Nam JY, Kim SU, Jeong TS, Lee WS, Bok SH, Kwon BM, Park YJ, Shin JM. Inhibition of cholesteryl ester transfer protein by rosenonolactone derivatives. J Antibiot (Tokyo) 1996; 49:815-6. [PMID: 8823516 DOI: 10.7164/antibiotics.49.815] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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110
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Lomovskaya N, Hong SK, Kim SU, Fonstein L, Furuya K, Hutchinson RC. The Streptomyces peucetius drrC gene encodes a UvrA-like protein involved in daunorubicin resistance and production. J Bacteriol 1996; 178:3238-45. [PMID: 8655504 PMCID: PMC178076 DOI: 10.1128/jb.178.11.3238-3245.1996] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The drrC gene, cloned from the daunorubicin (DNR)- and doxorubicin-producing strain of Streptomyces peucetius ATCC 29050, encodes a 764-amino-acid protein with a strong sequence similarity to the Escherichia coli and Micrococcus luteus UvrA proteins involved in excision repair of DNA. Expression of drrC was correlated with the timing of DNR production in the growth medium tested and was not dependent on the presence of DNR. Since introduction of drrC into Streptomyces lividans imparted a DNR resistance phenotype, this gene is believed to be a DNR resistance gene. The drrC gene could be disrupted in the non-DNR-producing S. peucetius dnrJ mutant but not in the wild-type strain, and the resulting dnrJ drrC double mutant was significantly more sensitive to DNR in efficiency-of-plating experiments. Expression of drrC in an E. coli uvrA strain conferred significant DNR resistance to this highly DNR-sensitive mutant. However, the DrrC protein did not complement the uvrA mutation to protect the mutant from the lethal effects of UV or mitomycin even though it enhanced the UV resistance of a uvrA+ strain. We speculate that the DrrC protein mediates a novel type of DNR resistance, possibly different from the mechanism of DNR resistance governed by the S. peucetius drrAB genes, which are believed to encode a DNR antiporter.
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111
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Satoh JI, Tai T, Kim SU. Differential expression of gangliosides and galactolipids in fetal human oligodendrocytes and astrocytes in culture. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1996; 93:172-81. [PMID: 8804704 DOI: 10.1016/0165-3806(96)00030-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The phenotypic expression of gangliosides and galactolipids was investigated using primary cultures of fetal human oligodendrocytes and astrocytes. These glial cells were isolated from fetal human brains of 12-18 weeks' gestation. Expression of gangliosides and galactolipids in oligodendrocytes and astrocytes was investigated by double labeling immunocytochemistry using rabbit antibodies specific for galactocerebroside (GalC, a cell type-specific marker for oligodendrocyte) and glial fibrillary acidic protein (GFAP, a cell type-specific marker for astrocyte) in combination with a panel of mouse monoclonal antibodies which react with specific gangliosides or galactolipids. A considerable number of GalC+ oligodendrocytes expressed intense immunoreactivities specific for GM3 (19%) and GM2 (45%) gangliosides. Approximately 11% of GalC+ oligodendrocytes expressed GM4 immunoreactivity, and smaller numbers of GalC+ oligodendrocytes expressed GD3 (4%), GD2 (1%), GT1b (5%) and A2B5 (3%) immunoreactivities. However, GalC+ oligodendrocytes did not express GM1, GD1a, GT1b or GQ1c. Major populations of GalC+ oligodendrocytes immunolabeled by rabbit anti-GalC antibody reacted with anti-GalC mAb (Ranscht mAb, 81%) or by anti-sulfatide mAb (O4 mAb, 91%). A considerable number of GFAP+ astrocytes expressed intense GM2 (26%) and GD2 (15%) immunoreactivities, while a smaller population expressed intense GM3 (3%), GD3 (6%) and GM4 (4%) immunoreactivities. Weak immunoreactions specific for GD1b, A2B5 and sulfatide were found in less than 1% each of GFAP+ astrocytes, while GFAP+ astrocytes did not express GM1, GD1a, GT1a, GT1b or GQ1b. These results indicate that GM3, GM2 and sulfatide are expressed in a major population of GalC+ oligodendrocytes, while GM3, GM2, GD3, GD2, and GM4 are expressed in a small but distinctive population of GFAP+ astrocytes. Our results suggest that GM4, GM1 and GD3, which are utilized as markers for adult human oligodendrocytes and myelin, are not the major ganglioside constituents in cultured fetal human oligodendrocytes.
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112
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Lee YB, Satoh J, Walker DG, Kim SU. Interleukin-15 gene expression in human astrocytes and microglia in culture. Neuroreport 1996; 7:1062-6. [PMID: 8804052 DOI: 10.1097/00001756-199604100-00022] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Interleukin-15 (IL-15) is a novel cytokine that has recently been cloned and expressed. IL-15 interacts with components of the IL-2 receptor and exhibits T-cell stimulating activity similar to that of IL-2. In the present study, we investigated the expression of IL-15 in enriched cultures of human fetal astrocytes and microglia using reverse transcription-polymerase chain reaction (RT-PCR) and immunodetection analysis. Low levels of IL-15 were expressed by unstimulated human fetal astrocytes and microglia, and treatment of astrocytes with interleukin-1 beta (IL-1 beta), interferon-gamma (IFN-gamma), or tumor necrosis factor-alpha (TNF-alpha) increased the expression of IL-15 at both the mRNA and protein level. Treatment of microglia with IFN-gamma and lipopolysaccharide (LPS) similarly increased IL-15 expression in microglia. These findings suggest that IL-15 produced by human fetal astrocytes and microglia may have a role in T cell-mediated immune responses in the human CNS.
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113
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Satoh J, Paty DW, Kim SU. Counteracting effect of IFN-beta on IFN-gamma-induced proliferation of human astrocytes in culture. Mult Scler 1996; 1:279-87. [PMID: 9345430 DOI: 10.1177/135245859600100504] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Recent clinical trials have shown that interferon beta (IFN-beta) is effective in reducing exacerbations in relapsing-remitting MS, while interferon gamma (IFN-gamma) precipitates the relapses. To investigate mechanisms underlying the beneficial effects of IFN-beta and the detrimental effects of IFN-gamma in MS, cell growth-regulatory effects of IFNs were examined in astrocyte-enriched cultures isolated from fetal brains of 12-20 weeks' gestation. Treatment with IFN-gamma (50 or 500 IU ml-1) stimulated significantly the proliferation of astrocytes in 6 out of 9 culture series examined, while IFN-beta (50 or 500 IU ml-1) inhibited the astrocytic proliferation in 3 out of 9 cultures, and IFN-alpha (50 or 500 IU ml-1) did not affect the proliferation IFN-beta and to a lesser degree IFN-alpha reduced the astrocytic proliferation induced by IFN-gamma-treatment in 8 out of 9 culture series. The counteracting effect of IFN-alpha/IFN-beta against IFN-gamma-induced astrocytic proliferation was verified by the DNA content distribution analysis of propidium iodide-labeled cells. The antagonistic effect of IFN-alpha/IFN-beta on the growth-promoting activity of IFN-gamma in cultured human astrocytes suggests that interferons serve as growth regulators of astrocytes at sites of reactive gliosis lesions of MS.
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114
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Yasuhara O, Schwab C, Matsuo A, Kim SU, Steele JC, Akiguchi I, Kimura J, McGeer EG, McGeer PL. Midkine-like immunoreactivity in extracellular neurofibrillary tangles in brains of patients with parkinsonism-dementia complex of Guam. Neurosci Lett 1996; 205:107-10. [PMID: 8907328 DOI: 10.1016/0304-3940(96)12385-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Midkine (MK) has been shown to be present in amyloid deposits in Alzheimer's disease (AD). In the present study, expression of midkine was examined immunohistochemically in brains of patients with the parkinsonism-dementia complex of Guam, lytico bodig disease (LB), using an affinity purified antibody to midkine. Positive staining was identified on some extracellular neurofibrillary tangles. The relative prevalence was somewhat less than for beta-amyloid protein (Abeta)-positive extracellular tangles. The results demonstrate that expression of MK and Abeta is not an exclusive feature of amyloid deposits in Alzheimer brain, but is also found in LB brain.
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115
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Kim SU, Song KS, Jung DS, Chae YA, Lee HJ. Production of indoxyl derivatives in indole-supplemented tissue cultures of Polygonum tinctorium. PLANTA MEDICA 1996; 62:54-6. [PMID: 17252408 DOI: 10.1055/s-2006-957797] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
A red pigment produced in the suspension, root and, shoot cultures of Polygonum tinctorium Ait. (Polygonaceae) upon feeding of indole was identified as indirubin by comparison with the authentic compound obtained from the leaves of the plant. Indole-5-D was specifically incorporated into the pigment to form indirubin-5,5'-D(2) when fed to the cultures. Tryptophan feeding did not cause the accumulation of the pigment. The dilution of the fed indole with the endogeneous indole was about zero, ten, and thirty-five percent for the suspension, root, and shoot cultures, respectively. The feeding of indole to the suspension and root cultures suppressed the biosynthesis of indigo thus resulting in the production of indirubin. However, the fed indole was equally well incorporated into indigo and indirubin in the shoot culture.
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Kim YK, Lee HW, Son KH, Kwon BM, Jeong TS, Lee DH, Shin J, Seo Y, Kim SU, Bok SH. GERI-BP002-A, novel inhibitor of acyl-CoA: cholesterol acyltransferase produced by Aspergillus fumigatus F93. J Antibiot (Tokyo) 1996; 49:31-6. [PMID: 8609082 DOI: 10.7164/antibiotics.49.31] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A new inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), designated GERI-BP002-A, was isolated from the culture broth of Aspergillus fumigatus F93 by acetone extraction, EtOAc extraction, SiO2 column chromatography and reverse phase HPLC. Spectroscopic analyses of the compound identified bis (2-hydroxy-3-tert-butyl-5-methylphenyl) methane as the structure and its molecular weight and formula to be 340 and C23H32O2, respectively. GERI-BP002-A inhibited ACAT activity by 50% at the concentration of 50 microM in an enzyme assay system using rat liver microsomes.
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Satoh J, Lee YB, Kim SU. T-cell costimulatory molecules B7-1 (CD80) and B7-2 (CD86) are expressed in human microglia but not in astrocytes in culture. Brain Res 1995; 704:92-6. [PMID: 8750966 DOI: 10.1016/0006-8993(95)01177-3] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The B7-1 and B7-2 expressed on the 'professional' antigen-presenting cells (APC) of the lymphoid system are counterreceptors for the T cell antigens CD28/CTLA-4. The B7/CD28 interaction provides a critical costimulatory signal in the decision between functional activation or clonal anergy of T cells. To investigate the biological role of B7 in the central nervous system, constitutive and cytokine-induced expression of B7 was investigated in fetal human astrocytes and microglia in culture. B7-1 expression was minimally detectable in unstimulated microglia but was increased markedly following exposure to IFN-gamma or GM-CSF. B7-2 was expressed at a high level in untreated microglia and upregulated to a small degree by exposure to IFN-gamma or GM-CSF. In contrast, B7-1 and B7-2 were undetectable in astrocytes under unstimulated or IFN-gamma/GM-CSF-treated conditions. These results indicate that both B7-1 and B7-2 are expressed in cultured human microglia but not in astrocytes.
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118
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McLarnon JG, Sawyer D, Kim SU. Cation and anion unitary ion channel currents in cultured bovine microglia. Brain Res 1995; 693:8-20. [PMID: 8653424 DOI: 10.1016/0006-8993(95)00664-c] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The use of excised patches has led to the identification and characterization of two channels not previously reported in microglia. A calcium-dependent K+ channel K(Ca) was activated in inside-out patches obtained from cultured bovine microglia and had a unitary conductance of 240 pS with symmetrical 140 mM K+ across patches. Mean open times of K(Ca) were exponentially dependent on patch potential and were increased with patch depolarization. Channel open probability (Popen) was increased with patch depolarization with either 5 mM or 140 mM internal K+ and was attributable to potential dependent enhancement of both opening frequency and mean open time. Whole cell currents showed the presence of a slowly activating K+ conductance, blocked by external TEA (at 2 mM) and likely the macroscopic correlate of the unitary K(Ca); half-maximal activation of the current occurred at +25 mV. An anion channel (unitary conductance of 325 pS with symmetrical Cl- across patches) was activated in inside-out patches with depolarizing and hyperpolarizing potential steps from 0 mV. Channel activation was not dependent on internal Ca2+. The anion currents inactivated during maintained potential steps with the time constant for inactivation faster with increased patch depolarization. The properties of the K(Ca) and anion channels in microglia membrane may have relevance to cell function in response to neuronal damage in the CNS.
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Satoh JI, Kim SU. Differential expression of heat shock protein HSP27 in human neurons and glial cells in culture. J Neurosci Res 1995; 41:805-18. [PMID: 7500382 DOI: 10.1002/jnr.490410611] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
HSP27 expression was investigated in cultured neurons and glial cells isolated from fetal human brains using immunoblotting and immunocytochemistry. Under unstressed conditions, HSP27 was identified at a high level in astrocytes (> 99%), at a low level in neurons (7%), and at a minimally detectable level in microglia (< 1%), whereas it was undetectable in oligodendrocytes. Under these conditions, HSP27 was located in the cytoplasm, fractionated into the Triton X-100-soluble phase, and composed chiefly of the basic isoform (HSP27a). After exposure to heat stress (43 degrees C/90 min), the level of HSP27 expression was not altered in astrocytes but was elevated significantly in neurons (11-21%) and microglia (4-7%) during 8-48 hr postrecovery periods, while it remained undetectable in oligodendrocytes. In addition, various human neural cell lines exhibited differential patterns of HSP27 expression under unstressed and heat-stressed conditions. Following heat shock treatment (45 degrees C/30 min), granular aggregates of HSP27 were identified in the cytoplasm of astrocytes. Under heat-stressed conditions, HSP27 was distributed within the Triton X-100-insoluble fraction associated with an increase in two more acidic isoforms (HSP27b and HSP27c). HSP27 and alpha B-crystallin were coexpressed in astrocytes under unstressed and heat-stressed conditions. When astrocytes were exposed to known HSP27 inducers, hydrogen peroxide and cysteamine reduced the synthesis of HSP27, while estradiol showed no effects. The differential patterns of constitutive and heat-induced expression of HSP27 in cultured human neurons and glial cells suggest that the cellular mechanisms by which HSP27 expression is regulated are different among various cell types in the human central nervous system.
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Moretto G, Xu RY, Monaco S, Rizzuto N, Kim SU. Expression and distribution of GAP-43 in human astrocytes in culture. Neuropathol Appl Neurobiol 1995; 21:362-7. [PMID: 7494605 DOI: 10.1111/j.1365-2990.1995.tb01071.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
By combining mRNA analysis and immunocytochemistry, we investigated the expression of the growth associated protein 43 (GAP-43) in enriched populations of astrocytes, obtained from mixed cultures of human fetal brains. Total cellular RNA was extracted from cell pellets and reverse transcribed into cDNA; cDNA was subjected to PCR amplification using primers specific for GAP-43 and PCR products were separated through polyacrylamide gels. Double immunofluorescence staining was performed on dissociated cell cultures using antibodies to glial fibrillary acidic protein (GFAP) and to GAP-43. Results showed that both transcription and translation for GAP-43 occur in cultured astrocytes. GAP-43 immunoreacting material was detected in the cell processes and diffusely in the cytoplasm of GFAP-positive astrocytes, during early stages of maintenance in vitro. In older cultures, GAP-43 immunoreactivity persisted in a large percentage of cells, with a tendency to accumulate in perinuclear areas. These observations provide evidence that GAP-43 is not restricted to neuronal cells. The close spatial association with cytoskeletal constituents, as observed in astrocytes, suggests a role for this protein in the control of cell shape, motility and adhesion processes.
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121
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Jeong TS, Kim SU, Son KH, Kwon BM, Kim YK, Choi MU, Bok SH. GERI-BP001 compounds, new inhibitors of acyl-CoA: cholesterol acyltransferase from Aspergillus fumigatus F37. I. Production, isolation, and physico-chemical and biological properties. J Antibiot (Tokyo) 1995; 48:751-6. [PMID: 7592016 DOI: 10.7164/antibiotics.48.751] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
GERI-BP001 compounds, new inhibitors of acyl-CoA:cholesterol acyltransferase (ACAT), were isolated from a culture broth of Aspergillus fumigatus F37 by acetone extraction, EtOAc extraction, SiO2 column chromatography, and reverse phase HPLC. GERI-BP001 M, A, and B inhibit ACAT activity in an enzyme assay system using rat liver microsomes by 50% at concentrations of 42, 94, and 40 microM, respectively.
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Satoh J, Kim SU. Cytokines and growth factors induce HSP27 phosphorylation in human astrocytes. J Neuropathol Exp Neurol 1995; 54:504-12. [PMID: 7541446 DOI: 10.1097/00005072-199507000-00004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
In previous studies, an enhanced expression with abnormal phosphorylation of a low molecular weight heat shock protein, HSP27, was identified in reactive astrocytes and Rosenthal fibers in Alexander disease brain. To investigate the relevance of HSP27 to the pathological change of astrocytes, phosphorylation of HSP27 was examined in astrocyte cultures isolated from fetal human brains. In unstimulated human astrocytes, HSP27 was identified in the cytoplasm and was comprised of a major unphosphorylated "a" isoform and a minor monophosphorylated "b" isoform. The level of HSP27 phosphorylation was elevated greatly after a 30 minute exposure to heat shock, sodium arsenite, interleukin-1 (IL-1 alpha and IL-1 beta), and tumor necrosis factor-alpha (TNF-alpha) with an increased expression of a diphosphorylated "c" isoform. Treatment with interferon-beta (IFN-beta), platelet-derived growth factor-AA, leukemia inhibitory factor, phorbol 12-myristate 13-acetate, and dibutyryl cyclic AMP stimulated phosphorylation of HSP27 moderately, while IFN-gamma, TNF-beta, basic fibroblast growth factor, epidermal growth factor, or fetal bovine serum did not significantly alter the level of HSP27 phosphorylation. Total amount of the HSP27 protein and its cytoplasmic localization were unaffected by any of these reagents. These results indicate that HSP27 is a constitutive protein in human astrocytes. The induction of HSP27 phosphorylation by a specific set of cytokines and growth factors suggests that HSP27 is a key cellular substrate by which signaling events are mediated in human astrocytes under normal and pathological conditions.
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Nakao J, Yamada M, Kagawa T, Kim SU, Miyao Y, Shimizu K, Mikoshiba K, Ikenaka K. Expression of proteolipid protein gene is directly associated with secretion of a factor influencing oligodendrocyte development. J Neurochem 1995; 64:2396-403. [PMID: 7539050 DOI: 10.1046/j.1471-4159.1995.64062396.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Oligodendroglial cell death in the myelin proteolipid protein (PLP) mutants can be partially rescued by the environment factor(s) supplied by the wild-type cells in vivo and in vitro. It is possible that the presence of PLP or DM-20 results in secretion of a factor or factors in the CNS influencing oligodendrocyte development. We previously showed that DM-20 mRNA is produced in G26 mouse oligodendroglioma, B104 rat neuroblastoma, and B16 mouse melanoma but not in NIH3T3 mouse fibroblast cell lines. Culture supernatants from these cell lines were added to primary glial cell cultures from embryonic day 17 mouse brain. After 4 days, the number of oligodendrocytes present in cultures with supernatants from DM-20-producing cells (G26, B104, and B16) was significantly higher than that of control cultures but not with the NIH3T3 supernatant. To investigate more directly whether the PLP gene expression is involved in this process, NIH3T3 cells (nonneural cells) were forced to produce PLP or DM-20. By addition of the supernatants from the PLP/DM-20 transformants, the number of oligodendrocytes in the mixed glial cell cultures increased. This clearly demonstrates that the expression of the PLP gene is sufficient for and directly associated with secretion of a factor, which influences the oligodendrocyte development.
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Satoh J, Kim SU. Constitutive and inducible expression of heat shock protein HSP72 in oligodendrocytes in culture. Neuroreport 1995; 6:1081-4. [PMID: 7662882 DOI: 10.1097/00001756-199505300-00002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The stress-induced HSP72 expression in bovine oligodendrocytes (OL) in culture was investigated following exposure to heat stress, oxidative stress and cytokines by immunoblotting and immunocytochemistry. Under the unstressed condition, HSP72 was expressed in a small number (3%) of OL. After exposure to heat stress, the level of HSP72 expression in OL was elevated significantly and an intense HSP72 immunolabelling was identified in almost all OL, while HSP72 was not induced by exposure to hydrogen peroxide (10 microM) or glucose oxidase (20 mU ml-1). The level of HSP72 expression was not elevated by treatment with interleuken (IL)-1 alpha (10 ng ml-1), IL-1 beta (10 ng ml-1), tumour necrosis factor (TNF)-alpha (200 ng ml-1), or TNF-beta (200 ng ml-1). Our results indicate that HSP72 is upregulated in cultured bovine OL by heat stress but not by oxidative stress or cytokines such as IL-1 and TNF.
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Moore GR, Kim SU, Chang E, Kim M. Myelin basic protein does not have a mitogenic effect on adult oligodendrocytes. Acta Neuropathol 1995; 89:431-7. [PMID: 7542424 DOI: 10.1007/bf00307648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Increased numbers of oligodendrocytes and remyelination are frequently observed in multiple sclerosis plaques. It is presumed the increased numbers of oligodendrocytes are due to cell division, but this has not been proven. The mitogens within the lesion which might be responsible for this are unknown. Since oligodendrocyte proliferation occurs in areas in which there is myelin breakdown, we undertook the present study to determine if myelin basic protein (MBP) or its breakdown products could induce oligodendrocyte proliferation. MBP, or MBP digested by the neutral proteinase plasmin, was added in three concentrations to the media of adult bovine oligodendrocytes in culture. Oligodendrocytes were identified by staining for galactocerebroside. Bromodeoxyuridine incorporation was used as a measure of cell division. Oligodendrocytes were found to divide only rarely in regular culture media, in the presence of MBP, plasmin, or MBP digested by plasmin. The results indicate that MBP is not a significant mitogen for the mature oligodendrocyte.
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