Biomedical subjects

Hyun-Mi Ko

Publications and source records attributed to Hyun-Mi Ko.

14 recordsLinked to original sources

PubMed2007

Critical role for matrix metalloproteinase-9 in platelet-activating factor-induced experimental tumor metastasis.

In this study, the roles of matrix metalloproteinase (MMP)-2 and MMP-9 in platelet-activating factor (PAF)-induced experimental pulmonary metastasis of the murine melanoma cell, B16F10, were investigated. An injection of PAF resulted in increases in mRNA expression, protein levels and the activities of both MMP-2 and MMP-9 in the lungs. The overall expression of MMP-9 was stronger than that of MMP-2. The increased MMP-9 expression was inhibited by both NF-kappaB and AP-1 inhibitors, whereas the increased MMP-2 expression was inhibited by only AP-1 inhibitors. Immunohistochemical analysis revealed that MMP-9 was expressed in bronchial epithelial cells as well as in the walls of blood vessels, whereas MMP-2 expression was observed only in bronchial epithelial cells. PAF significantly enhanced the pulmonary metastasis of B16F10, which was inhibited by both NF-kappaB and c-jun inhibitors. MMP-9 inhibitor, but not that of MMP-2, completely inhibited PAF-induced B16F10 metastasis. These data indicate that MMP-9, the expression of which was regulated by NF-kappaB and AP-1, plays a critical role in PAF-induced enhancement of pulmonary melanoma metastasis.

Animals↗

PubMed2006

Impairment of p38 MAPK-mediated cytosolic phospholipase A2 activation in the kidneys is associated with pathogenicity of Candida albicans.

In studying the mechanisms underlying the susceptibility of the kidney to candidal infection, we previously reported that the reduced production of cytokines [i.e. tumour necrosis factor-alpha (TNF-alpha)] via platelet-activating factor (PAF)-induced activation of nuclear factor-kappaB (NF-kappaB) renders the organ susceptible to the fungal burden. In this study, we investigated the possibility that pathogenic Candida albicans may evade clearance and perhaps even multiply by inhibiting elements in the signalling pathway that lead to the production of TNF-alpha. The fungal burden of pathogenic C. albicans in the kidneys was 10(4)-10(5)-fold higher than that of a non-pathogenic strain. PAF-induced early activation of NF-kappaB and TNF-alpha mRNA expression were both observed in the kidneys of mice infected with non-pathogenic strains of C. albicans, but not in mice infected with pathogenic strains. Impairment of PAF-mediated early NF-kappaB activation following infection with pathogenic C. albicans was associated with the prevention of activation of the enzyme cytosolic phospholipase A(2) (cPLA(2)) as well as the upstream pathway of cPLA(2), p38 mitogen-activated protein kinase. Collectively, these findings indicate that C. albicans exerts its pathogenicity through impairing the production of anticandidal cytokines by preventing cPLA(2) activity. This novel mechanism provides insight into understanding pathogenic C. albicans and perhaps identifies a target for its treatment.

Animals↗

PubMed2006

Platelet-activating factor induces up-regulation of antiapoptotic factors in a melanoma cell line through nuclear factor-kappaB activation.

In this study, we investigated the influence of platelet-activating factor (PAF) on the induction of apoptosis-regulating factors in B16F10 melanoma cells. PAF increased the expression of mRNA and the protein synthesis of antiapoptotic factors, such as Bcl-2 and Bcl-xL, but did not increase the expression of the proapoptotic factor, Bax. A selective nuclear factor-kappaB (NF-kappaB) inhibitor, parthenolide, inhibited the effects of PAF. Furthermore, PAF inhibited etoposide-induced increases in caspase-3, caspase-8, and caspase-9 activities, as well as cell death. p50/p65 heterodimer increased the mRNA expression of Bcl-2 and Bcl-xL and decreased etoposide-induced caspase activities and cell death. In an in vivo model in which Matrigel was injected s.c., PAF augmented the growth of B16F10 cells and attenuated etoposide-induced inhibition of B16F10 cells growth. These data indicate that PAF induces up-regulation of antiapoptotic factors in a NF-kappaB-dependent manner in a melanoma cell line, therefore suggesting that PAF may diminish the cytotoxic effect of chemotherapeutic agents.

Animals↗

PubMed2006

Platelet-activating factor-induced NF-kappaB activation enhances VEGF expression through a decrease in p53 activity.

We investigated the role of p53 in nuclear factor (NF)-kappaB dependent, platelet-activating factor (PAF)-induced vascular endothelial growth factor (VEGF) expression. Transfected NF-kappaB subunits in ECV304 cells increased the tumor necrosis factor-alpha promoter activity, which was completely inhibited by p53. Transfected p53 increased p53RE promoter activity, which was completely inhibited by NF-kappaB subunits, indicating that cross-regulation occurs between NF-kappaB and p53. PAF-induced increase in VEGF expression was correlated with decreased p53 activity. These data suggest that NF-kappaB-dependency of the PAF-induced increase in VEGF expression is due to decreased p53 activity, which is reciprocally regulated by increased NF-kappaB activity.

Cells, Cultured↗

PubMed2006

Glutamine inhibits lipopolysaccharide-induced cytoplasmic phospholipase A2 activation and protects against endotoxin shock in mouse.

Glutamine (Gln) supplementation is known to play a beneficial role in a number of settings of critical illness as well as laboratory models of endotoxin shock. We have investigated a molecular mechanism of the protective role of Gln in lipopolysaccharide (LPS)-induced shock using a mouse model. To examine the effectiveness of Gln, Gln was administered before or after LPS injection. Treatment of Gln before, but not after, LPS injection resulted in inhibition of nuclear factor kappaB activation and tumor necrosis factor alpha synthesis. In contrast, protection of animal from LPS-mediated death by Gln was observed when the Gln treatment was performed after LPS injection, suggesting that nuclear factor kappaB/tumor necrosis factor alpha signaling does not play an important role in this process. LPS injection induced phosphorylation of cytoplasmic phospholipase A2 (cPLA2), which was blocked by Gln treatment after LPS injection. Similarly, the LPS-stimulated cPLA2 activity was also inhibited by Gln treatment after LPS injection. Moreover, a cPLA2 inhibitor not only inhibited LPS-induced activation of cPLA2, but also significantly prevented LPS-mediated death. These observations indicate that Gln has a capability to inhibit cPLA2 phosphorylation and activation and suggest that Gln might be of a great therapeutic value for controlling inflammatory diseases in which cPLA2 plays an important role in the pathogenesis of the diseases.

Animals↗

PubMed2005

Platelet-activating factor induces matrix metalloproteinase-9 expression through Ca(2+)- or PI3K-dependent signaling pathway in a human vascular endothelial cell line.

Platelet-activating factor (PAF) augments angiogenesis by promoting the synthesis of a variety of angiogenic factors, via the nuclear factor (NF)-kappaB activation. Recently, we reported that PAF upregulates MMP-9 expression in a NF-kappaB-dependent manner. In this study, we investigated the signaling pathway involved in PAF-induced MMP-9 expression in ECV304 cells. Our current data indicate that the Ca(2+)- or phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathway is necessary for PAF-induced MMP-9 expression. Furthermore, PAF-induced NF-kappaB activation was blocked by selective inhibitors of Ca(2+), PI3K, or extracellular signal-regulated kinase (ERK). Our results suggest that PAF-induced MMP-9 expression, in a NF-kappaB-dependent manner, is regulated by Ca(2+), PI3K and ERK signaling pathways.

Calcium↗

PubMed2005

Modulation of the expression and transactivation of androgen receptor by the basic helix-loop-helix transcription factor Pod-1 through recruitment of histone deacetylase 1.

Androgen receptor (AR) is important in male sexual differentiation and testicular function. Here, we demonstrate the regulation of AR expression and its transactivation by the basic helix-loop-helix (bHLH) transcription factor Pod-1, the expression of which in postnatal testis reciprocally coincides with the expression of AR. Pod-1 represses the promoter activity of AR, possibly through its E-box. An AR promoter region of 169 bp, which harbors one canonical E-box, is sufficient for the Pod-1-repression and bound by purified Pod-1 proteins. Pod-1 also suppresses the transactivation of AR. Transient transfection analyses of mammalian cells show that Pod-1 represses AR transactivation in a dose-dependent manner. Furthermore, yeast two-hybrid, glutathione-S-transferase-pull-down, and co-immunoprecipitation analyses reveal that Pod-1 directly associates with AR through its N-terminal region and through the DNA binding-hinge domain of AR. Interestingly, Pod-1 recruits histone deacetylase (HDAC)-1 to inhibit both promoter activity and transactivation of AR. Overexpression of HDAC1 further inhibits the Pod-1-mediated repressions and Pod-1 directly interacts with HDAC1. Furthermore, chromatin immunoprecipitation assay reveals that HDAC1 is recruited with Pod-1 to the endogenous AR promoter and the androgen-regulated Pem promoter. Taken together, these results suggest that Pod-1, which controls AR transcription and function, may play an important role in the development and function of the testis.

Animals↗

PubMed2005

Involvement of matrix metalloproteinase-9 in platelet-activating factor-induced angiogenesis.

Platelet-activating factor (PAF) augments angiogenesis by promoting the synthesis of various angiogenic factors, via the activation of NF-kappaB. In this study, we investigated the role of the matrix metalloproteinase (MMP)-9, in PAF-induced angiogenesis. PAF increased mRNA expression, protein synthesis, and MMP-9 activity in ECV304 cells, in a NF-kappaB-dependent manner. PAF increased MMP-9 promoter activity in ECV304, which was inhibited by WEB2107, and NF-kappaB inhibitors. Transfected NF-kappaB subunits, p65 or/and p50, increased luciferase activity in the reporter plasmid MMP-9, resulting in an increase not only of MMP-9 luciferase activity, but also of mRNA expression in MMP-9. MMP-9 or NF-kappaB inhibitors significantly inhibited PAF-induced angiogenesis, in a dose-dependent manner, in an in vivo mouse Matrigel implantation model. In a parallel to the Matrigel implantation study, MMP-9 or NF-kappaB inhibitors inhibited PAF-induced sprouting of porcine pulmonary arterial endothelial cells. These data indicate that NF-kappaB-dependent MMP-9 plays a key role in PAF-induced angiogenesis.

Animals↗

PubMed2005

TNF-alpha induces the late-phase airway hyperresponsiveness and airway inflammation through cytosolic phospholipase A(2) activation.

BACKGROUND: Late-phase airway hyperresponsiveness (AHR) in asthma is considered the event leading to persistent inflammation in the lungs, but the molecular mechanisms involved in this process are poorly understood. OBJECTIVE: To examine the role of TNF-alpha in the development of a late AHR and airway inflammation in asthma. METHODS: We established a murine model of asthma with not only biphasic AHR to methacholine but also airway eosinophilia. The effect of TNF-alpha blockade was determined by using anti-TNF-alpha antibody and TNF-alpha knockout mice. Cytosolic phospholipase A(2) (cPLA(2)) mRNA expression and activity were assessed by using RT-PCR and 1-stearoyl-2-[1-(14)C] arachidonyl-sn-glycero-3-phosphocholine as the substrate, respectively. RESULTS: TNF-alpha blockade resulted in significant inhibition of the late AHR without affecting the early AHR, and reduction in airway eosinophilia and inflammation. cPLA(2) activity was increased in asthmatic lungs in a TNF-alpha-dependent way, and cPLA(2) inhibitor blocked late AHR and airway eosinophilia. TNF-alpha also stimulated the synthesis of cPLA(2) metabolites such as leukotriene B(4) and platelet-activating factor in the airway. Specific inhibitors of cPLA(2) metabolites inhibited the late AHR and airway eosinophilia. CONCLUSIONS: TNF-alpha is the proximal key cytokine capable of developing late-phase AHR and subsequent airway inflammation through expression/activation of cPLA(2).

Animals↗

PubMed2004

Administration of antisense phosphorothioate oligonucleotide to the p65 subunit of NF-kappaB inhibits established asthmatic reaction in mice.

The transcription factor, nuclear factor (NF)-kappaB, which transactivates various genes for proinflammatory cytokines and many other immunoregulatory genes, plays an important role in the regulation of various inflammatory diseases including asthma. Its increased activation has been demonstrated in the lungs after allergen challenge and in airway epithelial cells and macrophages of asthmatic patients. In the present study, we investigated whether the pretreatment with p65 antisense results in a significant inhibition of asthmatic reactions in a mouse model. Mice sensitized and challenged with ovalbumin (OVA) showed typical asthmatic reactions as follows: (1) an increase in the number of eosinophil in bronchoalveolar lavage fluid; (2) a marked influx of inflammatory cells into the lung around blood vessels and airways, and airway luminal narrowing; (3) the development of airway hyperresponsiveness; (4) the detection of TNF-alpha and Th2 cytokines, such as IL-4 and IL-5 in the bronchoalveolar lavage (BAL) fluid; and (5) detection of allergen-specific IgE and IgG in the serum. Two successive intravenous administration of p65 antisense before the last airway OVA challenge resulted in a significant inhibition of all asthmatic reactions, whereas the p65 nonsense did not produce such effects. In addition, the p65 antisense inhibition of asthmatic reaction appears to be due to the initial suppression of an allergen-specific IgE response, inducing degranulation of mast cells through the cross-linking of allergen-specific IgE. This study may provide evidence that NF-kappaB plays a critical role in the pathogenesis of asthma in mice.

Animals↗

PubMed2004

Estrogen enhances angiogenesis through a pathway involving platelet-activating factor-mediated nuclear factor-kappaB activation.

In this study, we investigated the molecular events involved in estrogen-induced angiogenesis. Treatment of the human endometrial adenocarcinoma cells, HEC-1A, with estrogen up-regulated mRNA expression and protein synthesis of various angiogenic factors such as tumor necrosis factor-alpha, interleukin-1, basic fibroblast growth factor, and vascular endothelial growth factor. The estrogen-dependent induction of the expression was blocked by the platelet-activating factor (PAF) antagonists, WEB 2170. Estrogen treatment caused the activation of nuclear factor (NF)-kappaB in HEC-1A cells and was also blocked by PAF antagonist. Inhibitors of NF-kappaB activation inhibited estrogen-induced mRNA expression and protein synthesis of the angiogenic factors. Estrogen led to a pronounced angiogenesis as assessed by a mouse Matrigel model in vivo and endothelial cell sprouting in vitro. PAF antagonists or NF-kappaB inhibitors significantly inhibited this estrogen-dependent angiogenesis. Estrogen caused phospholipase A2 (PLA2) gene and protein expression. Estrogen-induced vascular endothelial growth factor mRNA expression and sprouting were significantly inhibited by PLA2 inhibitors, suggesting PLA2 expression is the upstream pathway in the estrogen-induced angiogenesis. Taken together, these results suggest that estrogen induces the production of angiogenic factors via a mechanism involving PAF-mediated NF-kappaB activation.

Adenocarcinoma↗

PubMed2004

Essential role for platelet-activating factor-induced NF-kappaB activation in macrophage-derived angiogenesis.

Activated monocyte-macrophages have been implicated in tumor angiogenesis via their capacity to produce many potent angiogenic factors. However, the mechanisms leading to production of these angiogenic factors in macrophages remain to be elucidated. In this study, we demonstrated by use of a mouse Matrigel implantation model that mouse peritoneal macrophages induce angiogenesis. mRNA expression and protein synthesis of macrophage-derived crucial angiogenic factors such as IL-1, TNF-alpha, basic fibroblast growth factor, and vascular endothelial growth factor (VEGF) were blocked by platelet-activating factor (PAF) receptor antagonists. It was also observed that inhibitors of NF-kappaB blocked macrophage production of these angiogenic factors. Gene expression and protein synthesis of the angiogenic factors cited above were also inhibited in IkappaBalpha-mutated macrophages. VEGF is the most potent angiogenic factor in macrophage-induced angiogenesis. PAF antagonists or NF-kappaB inhibitors also inhibit the capacity of conditioned medium from LPS-stimulated human peripheral blood monocytes to induce sprouting of porcine pulmonary arterial endothelial cells. These data indicate that PAF-induced NF-kappaB activation is a common upstream pathway leading to the production of crucial macrophage-derived angiogenic factors. This will provide an important clue for a better understanding of mechanisms involved in tumor angiogenesis.

Angiogenesis Inducing Agents↗

PubMed2002

Molecular mechanisms for lipopolysaccharide-induced biphasic activation of nuclear factor-kappa B (NF-kappa B).

The nuclear factor-kappaB (NF-kappaB) is an important transcription factor necessary for initiating and sustaining inflammatory and immune reactions. The inducers of NF-kappaB are well characterized, but the molecular mechanisms underlying multiple in vivo NF-kappaB activation processes are poorly understood. The injection of lipopolysaccharide resulted in a biphasic activation of NF-kappaB during the 18-h observation period in various organs of mice. The early and late phases of NF-kappaB activation occurred at 0.5-2 h and 8-12 h, respectively. Platelet-activating factor, which is released in response to lipopolysaccharide injection, was responsible for the activation of the early phase of NF-kappaB. The early NF-kappaB activity led to the induction of proinflammatory cytokines, tumor necrosis factor (TNF), and interleukin (IL)-1beta, which are known to be efficient inducers of NF-kappaB. Using the TNF knockout and IL-1 receptor knockout mice, we found that TNF and IL-1beta had a role in the second phase activation of NF-kappaB. These cytokines did promote the synthesis of platelet-activating factor, which in turn induced the secondary activation of NF-kappaB. These observations describe a novel autoregulatory molecular mechanism for the biphasic activation of NF-kappaB.

Animals↗

PubMed2002

Nuclear factor kappaB dependency of platelet-activating factor-induced angiogenesis.

This study investigated the mechanisms of platelet-activating factor (PAF)-induced angiogenesis in a mouse model of Matrigel implantation. PAF induced a dose- and time-dependent angiogenic response. Inhibitors of nuclear factor (NF) kappaB expression or action, including antisense oligonucleotides to the p65 subunit of NFkappaB (p65 antisense) and antioxidants such as alpha-tocopherol and N-acetyl-L-cysteine, significantly reduced PAF-induced angiogenesis. In human umbilical vein endothelial cells, PAF-induced mRNA expression and protein synthesis of various NFkappaB-dependent angiogenic factors, such as tumor necrosis factor-alpha, interleukin-1alpha, basic fibroblast growth factor, and vascular endothelial growth factor (VEGF). The PAF-induced expression of the above mentioned factors was inhibited by p65 antisense or antioxidants. A significant inhibition of the angiogenic effect of PAF was achieved by anti-VEGF antibodies or soluble VEGF receptors such as KDR and flt-1 but not by antibodies against tumor necrosis factor-alpha, interleukin-1alpha, or basic fibroblast growth factor. These data indicate that PAF enhances angiogenesis through inducing NFkappaB activation, which in turn promotes the production of angiogenic factors such as VEGF.

Animals↗