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Hun-Taeg Chung

Publications and source records attributed to Hun-Taeg Chung.

At least 37 records · Page 2Linked to original sources
PubMed2004

Nitric oxide inhibition of homocysteine-induced human endothelial cell apoptosis by down-regulation of p53-dependent Noxa expression through the formation of S-nitrosohomocysteine.

Hyperhomocysteinemia is believed to induce endothelial dysfunction and promote atherosclerosis; however, the pathogenic mechanism has not been clearly elucidated. In this study, we examined the molecular mechanism by which homocysteine (HCy) causes endothelial cell apoptosis and by which nitric oxide (NO) affects HCy-induced apoptosis. Our data demonstrated that HCy caused caspase-dependent apoptosis in cultured human umbilical vein endothelial cells, as determined by cell viability, nuclear condensation, and caspase-3 activation and activity. These apoptotic characteristics were correlated with reactive oxygen species (ROS) production, lipid peroxidation, p53 and Noxa expression, and mitochondrial cytochrome c release following HCy treatment. HCy also induced p53 and Noxa expression and apoptosis in endothelial cells from wild type mice but not in the p53-deficient cells. The NO donor S-nitroso-N-acetylpenicillamine, adenoviral transfer of inducible NO synthase gene, and antioxidants (alpha-tocopherol and superoxide dismutase plus catalase) but not oxidized SNAP, 8-Br-cGMP, nitrite, and nitrate, suppressed ROS production, p53-dependent Noxa expression, and apoptosis induced by HCy. The cytotoxic effect of HCy was decreased by small interfering RNA-mediated suppression of Noxa expression, indicating that Noxa up-regulation plays an important role in HCy-induced endothelial cell apoptosis. Overexpression of inducible NO synthase increased the formation of S-nitroso-HCy, which was inhibited by the NO synthase inhibitor N-monomethyl-l-arginine. Moreover, S-nitroso-HCy did not increase ROS generation, p53-dependent Noxa expression, and apoptosis. These results suggest that up-regulation of p53-dependent Noxa expression may play an important role in the pathogenesis of atherosclerosis induced by HCy and that an increase in vascular NO production may prevent HCy-induced endothelial dysfunction by S-nitrosylation.

Antioxidants↗
PubMed2004

Nitric oxide suppresses inducible nitric oxide synthase expression by inhibiting post-translational modification of IkappaB.

The expression of inducible nitric oxide synthase (iNOS) is a critical factor in both normal physiological functions and the pathogenesis of disease. This study was undertaken to determine the molecular mechanism by which nitric oxide (NO) exerts negative feedback regulation on iNOS gene expression. Isolated rat hepatocytes stimulated with cytokines exhibited a marked increase in NO production as well as iNOS mRNA and protein levels, which were significantly reduced by pretreatment of the NO donors S-nitroso-N-acetyl-D,L-penicillamine (SNAP) and V-PYRRO/NO. This effect of SNAP was inhibited when NO was scavenged using red blood cells. Pretreatment with oxidized SNAP, 8-Br-cGMP, NO2-, or NO3- did not suppress the cytokine-induced NO production. Moreover, LPS/ IFN-gamma-stimulated RAW264.7 cells, which produce endogenous NO, expressed lower levels of iNOS, IL-1beta, IL-6 and TNF-alpha mRNAs, without changes in their mRNA half-lives, than those in the presence of the iNOS inhibitor NG-monomethyl-L-arginine. The iNOS gene transcription rate exhibited an 18-fold increase after cytokine stimulation, which was significantly inhibited by SNAP pretreatment. SNAP also blocked cytokine- induced increase in NF-kappaB activation, iNOS promoter activity, nuclear translocation of cytosolic NF-kappaB p65 subunit, and IkappaBalpha degradation, which correlated with its inhibitory effect on phosphorylation and ubiquitination of IkappaB. These data indicate that NO down-regulates iNOS gene expression and NO production by inhibiting the post-translational processes of IkappaBalpha thereby preventing NF-kappaB activation. These results identify a novel negative feedback mechanism whereby NO down-regulates iNOS gene expression.

Animals↗
PubMed2004

The polymorphisms of Th1 cell surface gene Tim-3 are associated in a Korean population with rheumatoid arthritis.

The family of T-cell immunoglobulin domain and mucin domain (TIM) proteins is identified to be expressed on T cells. A member of TIM family, TIM-3 is selectively expressed on the surface of differentiated Th1 cells. TIM-3 might have an important role in the induction of autoimmune diseases by regulating macrophage activation and interacts with TIM-3 ligand to regulate Th1 responses. In the present study, we analyzed the association of the genotype and allele frequencies between rheumatoid arthritis (RA) patients and the controls without RA using large samples size at the -1516G>T, -574T>G and 4259G>T polymorphic sites of human Tim-3 gene. We further investigated the relationships between the genotypes of each single nucleotide polymorphisms (SNPs) and C-reactive protein (CRP) or rheumatoid factor (RF) levels in RA patients. The genotype and allele frequencies of the -574T>G (P = 0.001 and 0.001, respectively) as well as the 4259G>T (P = 0.001 ands 0.003, respectively) between RA patients and non-RA controls were significantly different. These results strongly suggest that -574T>G and 4259G>T polymorphism of the Tim-3 might be associated with susceptibility to RA.

Adult↗
PubMed2004

Induction of heme oxygenase-1 is involved in anti-proliferative effects of paclitaxel on rat vascular smooth muscle cells.

In this study, we evaluated the possibility that the anti-proliferative effects of paclitaxel on vascular smooth muscle cells (VSMCs) of the rat might be due to the induction of HO-1 gene expression. Treatment of the cells with paclitaxel resulted in marked time- and dose-dependent inductions of HO-1 mRNA, followed by corresponding increases in HO-1 protein expression and HO enzymatic activities. Furthermore, paclitaxel rapidly activated the JNK, ERK, and p38 mitogen-activated protein kinase pathways. A specific inhibitor of JNK, SP600125, abolished paclitaxel-induced HO-1 mRNA expression, whereas PD98059, a specific inhibitor of ERK, and SB203580, a specific inhibitor of p38, had no significant effect. Finally, the suppression of platelet-derived growth factor induced VSMC proliferation was abolished by the HO inhibitor, ZnPP, as well as by the CO scavenger, hemoglobin. These results demonstrated that paclitaxel induces the expression of HO-1 via the JNK pathway in VSMC and that HO-1 expression might be responsible for the anti-proliferative effect of paclitaxel on VSMC.

Animals↗
PubMed2004

3-Hydroxyanthranilic acid, one of metabolites of tryptophan via indoleamine 2,3-dioxygenase pathway, suppresses inducible nitric oxide synthase expression by enhancing heme oxygenase-1 expression.

Inducible nitric oxide (NO) synthase (iNOS), heme oxygenase (HO)-1, and indoleamine 2,3-dioxygenase (IDO) are simultaneously expressed in murine macrophages stimulated with interferon (IFN)-gamma and lipopolysaccharide (LPS). NO produced by iNOS suppresses IDO expression and also induces HO-1 expression. The antioxidant 3-hydroxyanthranilic acid (HA), one of metabolites of tryptophan via IDO pathway, has been previously reported to suppress iNOS expression. Because HO-1 expression can suppress iNOS expression, we investigated whether HA could suppress iNOS expression by affecting HO-1 expression in murine RAW 264.7 macrophages stimulated with IFN-gamma plus LPS. Treatment with exogenous HA dose-dependently suppressed iNOS expression and coincidently enhanced HO-1 expression. This suppressive effect of HA on iNOS expression was reversed by blocking HO-1 activity, and proven to be due to carbon monoxide (CO) produced by HO-1. In addition, either blocking of iNOS activity or addition of exogenous CO further enhanced IDO expression and activity. These results show for the first time that HA is able to suppress iNOS expression by enhancing HO-1 expression, thereby resulting in further increases in IDO expression and activity.

3-Hydroxyanthranilic Acid↗
PubMed2004

Analysis of the polymorphisms in eotaxin gene family and their association with asthma, IgE, and eosinophil.

The eotaxin gene family (eotaxin, eotaxin-2, and eotaxin-3) has been implicated in the recruitment of eosinophils, basophiles, and Th2 lymphocytes that is a central aspect of allergic diseases such as asthma. To determine whether the single nucleotide polymorphisms (SNPs) of eotaxin gene family are associated with susceptibility to asthma, we scanned 225 asthma patients and 294 non-asthmatic controls using the direct sequencing method. We further investigated the relationships among each SNP, eosinophils, and serum total IgE levels in asthma patients. Eleven SNPs were identified in the eotaxin gene family. We found that EoB179T > C (P = 0.0001), EoB275C > T (P = 0.018) of the eotaxin-2 and EoA2497T > G (P = 0.003) of the eotaxin-3 were significantly associated with the susceptibility of asthma. Furthermore, our data demonstrated for the first time that EoA2497T > G (P = 0.005) is related to serum total IgE level while EoA77C > T (P = 0.035) and EoA2497T > G (P = 0.033) are related to the peripheral blood eosinophil counts in asthma. Our results suggest that the polymorphisms of the eotaxin gene family are associated with the susceptibility of asthma and Eotaxin-3 might play the critical role for the recruitment of eosinophils and the maintenance of IgE levels.

Adult↗
PubMed2004

Inhibition of farnesyltransferase prevents collagen-induced arthritis by down-regulation of inflammatory gene expression through suppression of p21(ras)-dependent NF-kappaB activation.

Farnesylation of p21(ras) is an important step in the intracellular signaling pathway of growth factors, hormones, and immune stimulants. We synthesized a potent and selective farnesyltransferase inhibitor (LB42708) with IC(50) values of 0.8 nM in vitro and 8 nM in cultured cells against p21(ras) farnesylation and examined the effects of this inhibitor in the settings of inflammation and arthritis. LB42708 suppressed NF-kappaB activation and iNOS promoter activity by suppressing the I-kappaB kinase activity and I-kappaBalpha degradation. The inhibitor suppressed the expression of inducible NO synthase, cyclooxygenase-2, TNF-alpha, and IL-1beta and the production of NO and PGE(2) in immune-activated macrophages and osteoblasts as well as LPS-administrated mice. Furthermore, in vivo administration of LB42708 significantly decreased the incidence and severity of arthritis as well as mRNA expression of inducible NO synthase, cyclooxygenase-2, TNF-alpha, and IL-1beta in the paws of collagen-induced arthritic mice compared with controls. These observations indicate that the anti-inflammatory and antiarthritic effects of the farnesyltransferase inhibitor may be ascribed to the inhibition of I-kappaB kinase activity and subsequent suppression of NF-kappaB-dependent inflammatory gene expression through the suppression of p21(ras) farnesylation. Together, these findings reveal that the inhibitory effect of LB42708 on p21(ras)-dependent NF-kappaB activation may have potential therapeutic value for arthritis and other inflammatory diseases.

Alkyl and Aryl Transferases↗
PubMed2004

Molecular variations in Th1-specific cell surface gene Tim-3.

The family of T-cell immunoglobulin domain and mucin domain (TIM) proteins is identified to be expressed on T cells. A member of Tim family, Tim-3 (T cell immunoglobulin mucin 3) is selectively expressed on the surface of differentiated Th1 cells. Tim-3 might have an important role in the induction of autoimmune diseases by regulating macrophage activation and interacts with Tim-3 ligand to regulate Th1 responses. To determine the variation sites in the coding and promoter region of human Tim-3 gene, we performed variation scanning by direct sequencing using the genomic DNA isolated from the patients with asthma or allergic rhinitis and healthy controls without asthma and allergic rhinitis. We identified four single nucleotide polymorphisms (SNPs) including one novel SNPs (-1541C>T) and two variation sites (-1292_-1289delTAAA and -1282_-1278dupTAAAA) in the coding and promoter region of human Tim-3 gene in both the patients and healthy groups.

Asthma↗
PubMed2004

Iron chelator triggers inflammatory signals in human intestinal epithelial cells: involvement of p38 and extracellular signal-regulated kinase signaling pathways.

Competition for cellular iron (Fe) is a vital component of the interaction between host and pathogen. Most bacteria have an obligate requirement for Fe to sustain infection, growth, and survival in host. To obtain iron required for growth, many bacteria secrete iron chelators (siderophores). This study was undertaken to test whether a bacterial siderophore, deferoxamine (DFO), could trigger inflammatory signals in human intestinal epithelial cells as a single stimulus. Incubation of human intestinal epithelial HT-29 cells with DFO increased the expression of IL-8 mRNA, as well as the release of IL-8 protein. The signal transduction study revealed that both p38 and extracellular signal-regulated kinase-1/2 were significantly activated in response to DFO. Accordingly, the selective inhibitors for both kinases, either alone or in combination, completely abolished DFO-induced IL-8 secretion, indicating an importance of mitogen-activated protein kinases pathway. These proinflammatory effects of DFO were, in large part, mediated by activation of Na(+)/H(+) exchangers, because selective blockade of Na(+)/H(+) exchangers prevented the DFO-induced IL-8 production. Interestingly, however, DFO neither induced NF-kappaB activation by itself nor affected IL-1beta- or TNF-alpha-mediated NF-kappaB activation, suggesting a NF-kappaB-independent mechanism in DFO-induced IL-8 production. Global gene expression profiling revealed that DFO significantly up-regulates inflammation-related genes including proinflammatory genes, and that many of those genes are down-modulated by the selective mitogen-activated protein kinase inhibitors. Collectively, these results demonstrate that, in addition to bacterial products or cell wall components, direct chelation of host Fe by infected bacteria may also contribute to the evocation of host inflammatory responses.

Deferoxamine↗
PubMed2004

Carbon monoxide produced by heme oxygenase-1 suppresses T cell proliferation via inhibition of IL-2 production.

Heme oxygenase-1 (HO-1) catabolizes heme into CO, biliverdin, and free iron and serves as a protective enzyme by virtue of its anti-inflammatory, antiapoptotic, and antiproliferative actions. Previously, we have demonstrated that human CD4(+) T cells express HO-1 and that HO-1-overexpressing Jurkat T cells tend to display lower proliferative response. The aim of this study is to elucidate the mechanism(s) by which HO-1 can mediate its antiproliferative effect on CD4(+) T cells. Among the three HO-1 byproducts, only CO showed suppressive effect on T cell proliferation in response to anti-CD3 plus anti-CD28 Abs, mimicking the antiproliferative action of HO-1. CO blocked the cell cycle entry of T cells, which was independent of the guanylate cyclase/cGMP pathway. CO also suppressed the secretion of IL-2, and this suppressive effect of CO on IL-2 secretion mediated the antiproliferative action of CO. CO selectively inhibited the extracellular signal-regulated kinase pathway, which could explain the suppressive effects of CO on T cell proliferation and IL-2 secretion. Based on these findings, we suggest that HO-1/CO suppresses T cell proliferation and IL-2 secretion, possibly via its inhibition of extracellular signal-regulated kinase activation.

CD4-Positive T-Lymphocytes↗
PubMed2004

Overexpression of heme oxygenase (HO)-1 renders Jurkat T cells resistant to fas-mediated apoptosis: involvement of iron released by HO-1.

We recently demonstrated that heme oxygenase (HO)-1 is constitutively expressed in human CD4+CD25+ regulatory T cells and induced by anti-CD28 or anti-CD28/anti-CD3 stimulation, even in CD4+CD25- responder T cells. To study the effects of HO-1 expression on lymphocyte survival, we transfected the HO-1 gene or induced the gene to express HO-1 protein with cobalt protoporphyrin (CoPP) in Jurkat T cells. Consistently, anti-Fas antibody triggered apoptotic cell death in wild-type Jurkat T cells. Surprisingly, however, HO-1-overexpressing Jurkat T cells showed strong resistance to Fas-mediated apoptosis. In contrast, abrogation of HO-1 expression by antisense oligomer against HO-1 gene from CoPP-treated cells or depletion of iron by desferrioxamine from HO-1-transfected cells abolished the resistance. In addition, exogenously added iron rendered wild-type Jurkat T cells resistant. The resistance involved IkappaB kinase (IKK) activation via iron-induced reactive oxygen species formation, NF-kappaB activation by activated IKK, and c-FLIP expression by activated NF-kappaB. Primary CD4+ T cells induced by CoPP to express HO-1 also showed more resistance to Fas-mediated apoptosis than untreated cells. Our findings suggest that HO-1 plays a critical and nonredundant role in Fas-mediated activation-induced cell death of T lymphocytes.

Apoptosis↗
PubMed2004

The exon 4 variations of Tim-1 gene are associated with rheumatoid arthritis in a Korean population.

The family of T-cell immunoglobulin domain and mucin domain (TIM) proteins is identified to be expressed on T cells. A member of Tim family, TIM-1, is considered as a membrane protein that is associated with the development of Th2 biased immune responses and selectively expressed on Th2 cells. In the present study, we analyzed the association of genotype and allele frequencies between rheumatoid arthritis (RA) patients and the controls without RA using large samples size at 5383_5397del and 5509_5511delCAA variations of Tim-1 gene. We further investigated the relationships among these variations to C-reactive protein (CRP) and rheumatoid factor (RF) levels in RA patients. Although these factors were not associated with exon 4 variations in RA patients, the genotype and allele frequencies of 5383_5397del variation site (P = 0.015 and 0.014, respectively) as well as 5509_5511delCAA variation site (P = 0.0002 and 0.0001, respectively) in RA patients were significantly different from those in the non-RA controls. Our results strongly suggest that the variations of Tim-1 exon 4 might be associated with the susceptibility to RA.

Adult↗
PubMed2004

Stylopine from Chelidonium majus inhibits LPS-induced inflammatory mediators in RAW 264.7 cells.

Stylopine is a major component of the leaf of Chelidonium majus L. (Papaveraceae), which has been used for the removal of warts, papillomas and condylomas, as well as the treatment of liver disease, in oriental countries. Stylopine per se had no cytotoxic effect in unstimulated RAW 264.7 cells, but concentration-dependently reduced nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta), and the IL-6 production and cyclooxygenase-2 (COX-2) activity caused by the LPS stimulation. The levels of inducible nitric oxide synthase (iNOS) and COX-2 protein expressions were markedly suppressed by stylopine in a concentration dependent manner. These results suggest that stylopine suppress the NO and PGE2 production in macrophages by inhibiting the iNOS and COX-2 expressions. These biological activities of stylopine may contribute to the anti-inflammatory activity of Chelidonium majus.

Animals↗
PubMed2004

The association of TIM-3 gene polymorphism with atopic disease in Korean population.

The family of T-cell immunoglobulin domain and mucin domain (TIM) proteins is identified to be expressed on T cells. A member of the TIM family, TIM-3 is selectively expressed on the surface of differentiated T helper 1 (Th1) cells. TIM-3 might have an important role in the induction of autoimmune diseases by regulating macrophage activation and interacts with the TIM-3 ligand to regulate Th1 responses. In the present study, we analyzed the association of the genotype and allele frequencies between asthma or allergic rhinitis patients and nonatopic controls using large samples size at -1516G > T, -574T > G, and 4259G > T polymorphic sites of the Tim-3 gene. The genotype and allele frequencies of -574T > G polymorphism in asthma patients (p = 0.042 and p = 0.017, respectively) as well as allergic rhinitis patients (p = 0.008 and p = 0.003, respectively) were significantly different from those of nonatopic controls. Furthermore, the allele frequency of 4259G > T polymorphism in allergic rhinitis patients (p = 0.029) was also significantly different. Our results strongly suggest that the -574T > G polymorphism of Tim-3 might be associated with the susceptibility of atopic diseases such as asthma and allergic rhinitis.

Adult↗
PubMed2004

In vitro cytotoxicity of Mokko lactone in human leukemia HL-60 cells: induction of apoptotic cell death by mitochondrial membrane potential collapse.

We studied the effect of mokko lactone (ML) isolated from the roots of Saussurea lappa (Compositae), a plant that is used for medicinal purposes in Korea, on the induction of apoptosis in human leukemia HL-60 cells. ML was cytotoxic to HL-60 cells, and this cytotoxic effect of ML appears to be attributable to its induction of apoptotic cell death, as ML induced nuclear morphologic changes and internucleosomal DNA fragmentation and increased the proportion of Annexin V-positive cells and the activity of caspase-3. Further studies revealed that the induction of apoptosis by ML was associated with the loss of mitochondrial membrane potential. Collectively, our results suggest that apoptosis induced by ML in HL-60 cells was executed by a collapse of mitochondrial membrane potential followed by the activation of caspase-3. This is the first report on the mechanism of apoptosis-inducing effect of ML.

4-Butyrolactone↗
PubMed2004

Catalposide, a compound isolated from catalpa ovata, attenuates induction of intestinal epithelial proinflammatory gene expression and reduces the severity of trinitrobenzene sulfonic Acid-induced colitis in mice.

Certain irinoid-producing plants have been used as herbal anti-inflammatory remedies. Here we evaluated whether catalposide (CATP), a single compound isolated from irinoid-producing plant Catalpa ovata, has a potential for preventing or ameliorating diseases characterized by mucosal inflammation. Preliminary microarray-based gene expression test revealed that CATP, which alone did not significantly affect expression of any of the >8,000 genes analyzed, attenuated the expression of tumor necrosis factor-alpha (TNF-alpha)-induced proinflammatory genes including interleukin-8 (IL-8) in human intestinal epithelial HT-29 cells. Down-regulation of IL-8 mRNA accumulation was also reflected by the decreased IL-8 secretion in CATP-treated HT-29 cells. The signal transduction study revealed that CATP significantly attenuates TNF-alpha-mediated p38 and extracellular signal-regulated kinase (ERK) phosphorylation. Further, CATP reduced NF-kappaB-mediated transcriptional activation as well as Ikappa-Balpha degradation. To establish the in vivo relevance of these findings, we examined whether CATP could affect intestinal inflammation in vivo using the mouse model of trinitrobenzene sulfonic acid (TNBS)-induced inflammatory colitis. Intrarectal administration of CATP dramatically reduced the weight loss, colonic damage, and mucosal ulceration that characterize TNBS colitis. Moreover, CATP suppressed the expression of TNF-alpha, interleukin-1beta, and intercellular adhesion molecule-1 along with the inhibition of NF-kappa B p65 translocation into nucleus in TNBS colitis. Collectively, current results demonstrate that CATP may be an effective agent for the treatment of diseases characterized by mucosal inflammation.

Animals↗
PubMed2004

Roles of heme oxygenase-1 in the antiproliferative and antiapoptotic effects of nitric oxide on Jurkat T cells.

Nitric oxide (NO) has been shown to exert antiproliferative and antiapoptotic effects on human T cells. Heme oxygenase-1 (HO-1), which degrades heme into biliverdin, free iron (Fe(2+)), and carbon monoxide (CO), has also been known to have antiproliferative and antiapoptotic effects. Recent evidence suggests that HO-1 is an important cellular target of NO; whether HO-1 expression contributes to the antiproliferative and/or antiapoptotic effects mediated by NO remains to be investigated. In the present study, we examined the effects of NO on HO-1 expression and possible roles of HO-1 in T cell proliferation and apoptosis. Using human Jurkat T cells, we found that the NO donor sodium nitroprusside (SNP) induced HO-1 expression and that preincubation with SNP suppressed T cell proliferation induced by concanavalin A and apoptosis triggered by anti-Fas antibody. Suppressions of T cell proliferation and apoptosis comparable with SNP were also observed when the T cells were preincubated with the HO-1 inducer cobalt protoporphyrin. A phosphorothioate-linked HO-1 antisense oligonucleotide blocked HO-1 expression, and subsequently abrogated the antiproliferative and antiapoptotic effects of SNP. Overexpression of the HO-1 gene after transfection into Jurkat T cells resulted in significant decreases in T cell proliferation and apoptosis. The CO donor tricarbonyldichlororuthenium (II) dimer mimicked the antiproliferative effect of SNP, and the Fe(2+) donor FeSO(4) blocked anti-Fas-induced apoptosis. Taken together, our results suggest that NO induces HO-1 expression in T cells and that suppressions of T cell proliferation and apoptosis afforded by NO are associated with an increased expression of HO-1 by NO.

Apoptosis↗