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Biomedical subjects

Y J Jeon

Publications and source records attributed to Y J Jeon.

At least 37 records · Page 2Linked to original sources
PubMed1999

Protection of mice against P. aeruginosa infections by large-scale affinity-purified human IgG specific to P. aeruginosa outer membrane proteins.

In order to develop an effective means to treat Pseudomonas aeruginosa infections, we designed a large-scale process for purification of human IgG specific to P. aeruginosa outer membrane proteins (Oprs) from normal human sera. The process we developed includes affinity column chromatography using P. aeruginosa Oprs as ligands, protein A column chromatography and ultrafiltration, which enriched P. aeruginosa Oprs-specific IgG antibody by 500-fold. The purified anti-Oprs IgG was specific to the Oprs as confirmed by an ELISA competition assay and retained opsonophagocytic-killing capacity. In vivo protective efficacy of anti-Oprs IgG was evaluated by passive protection assays in mice where the 50% protective dose of anti-Oprs IgG against P. aeruginosa infections was 41 microg/kg, which was 20 times lower than that of normal serum IgG. When administered to mice 3 h after bacterial challenge, only anti-Oprs IgG afforded protection. These data demonstrate the feasibility of use of the purification process in producing functionally active target-specific human antibodies for clinical use and provide a rationale for use of anti-Oprs IgG as a valuable adjunct to treat P. aeruginosa infections.

Animals↗
PubMed1999

Suppression of the interleukin-2 gene expression by aflatoxin B1 is mediated through the down-regulation of the NF-AT and AP-1 transcription factors.

The effect of aflatoxin B1 (AFB1) on the interleukin-2 (IL-2) gene expression was investigated in thymocytes of B6C3F1 mice, Jurkat E6-1 human T-cell leukemia, and EL4.IL-2 murine thymoma. AFB1 inhibited the phorbol-12myristate-13-acetate/i6nomycin (PMA/Io)-induced IL-2 mRNA expression in the murine thymocytes and Jurkat E6-1 cells as determined by qualitative RT-PCR, while no effect was observed in the EL4.IL-2 cells. Electrophoretic mobility shift assay indicated that AFB1 treatment showed an inhibition of the NF-AT and AP-1 DNA binding in PMA/Io-stimulated thymocytes and Jurkat E6-1 cells. No effect was observed on the Oct and NF-kappaB DNA binding. Employing a reporter gene expression system with p(NF-AT)3-CAT and p(AP-1)3-CAT, treatment with AFB1 to the transfected Jurkat E6-1 cells also showed an inhibition of the PMA/Io-induced NF-AT/CAT and AP-1/CAT activities. These results suggest that suppression of the IL-2 gene expression by AFB1 is mediated through the down-regulation of the NF-AT and AP-1 activation.

Aflatoxin B1↗
PubMed1999

Induction of inducible nitric oxide synthase gene expression by Pokeweed mitogen.

The present study has characterized the expression of iNOS gene in Pokeweed mitogen (PWM)-driven murine macrophage RAW 264.7 cells. PWM significantly induced nitric oxide production in a dose-dependent manner. Quantitative reverse transcription-polymerase chain reaction analysis demonstrated that the inducible nitric oxide synthase gene expression is increased by PWM treatment. Since iNOS transcription has recently been shown to be under the control of the nuclear factor (NF)-kappaB/Rel family of transcription factors, the effects of PWM on NF-kappaB/Rel activation were examined using a transient transfection assay and an electrophoretic mobility shift assay (EMSA). Transient expression assays with NF-kappaB/Rel binding sites linked to the chloramphenicol acetyltransferase gene suggest that the PWM-induced increase in transcription is mediated by the NF-kappaB/Rel transcription factor complex. Using DNA fragments containing the NF-kappaB/Rel binding sequence, PWM was shown to activate the protein/DNA binding of NF-KB/Rel to its cognate site as measured by EMSA. Supershift EMSA showed the presence of p50 and c-Rel protein in the complex at the kappaB site. Western blot analysis of isolated nuclear fractions, using p65 and c-Rel-specific antibodies, provided further evidence that c-Rel is increased by PWM treatment. N-Tosyl-1-phenylalanine chloromethyl ketone, a potent inhibitor of NF-kappaB/Rel activation, inhibited PWM-induced nitrite generation in a dose-dependent manner. Collectively, the results of these experiments indicate that c-Rel is positively regulated by PWM to assist in the initiation of iNOS gene expression.

Animals↗
PubMed1999

Acetylaminofluorene inhibits nitric oxide production in LPS-stimulated RAW 264.7 cells by blocking NF-kappa B/Rel activation.

The mechanism by which 2-acetylaminofluorene (AAF) inhibited nitric oxide (NO) formation, in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells was investigated. The decrease in NO, as demonstrated by measurement of nitrite was found to correlate well with a decrease in inducible nitric oxide synthase (iNOS) mRNA. Since the promoter in iNOS gene contains binding motifs for NF-kappa B/Rel, AP-1, and NF-IL6 which appear to be important for LPS-mediated iNOS induction, the effect of AAF on the activation of these transcription factors was determined. Treatment of AAF to RAW 264.7 cells induced a dose-related inhibition of NF-kappa B/Rel in chloramphenicol acetyltransferase activity, while either AP-1 or NF-IL6 activation was not affected by AAF. Treatment of RAW 264.7 cells with AAF inhibited protein/DNA binding of NF-kappa B/Rel to its cognate site as measured by electrophoretic mobility shift assay. In addition, AAF treatment caused a significant reduction of nuclear c-rel, p65, and p50 protein levels, and this decrease was paralleled by the accumulation of cytoplasmic c-rel, p65, and p50. These data suggest that AAF inhibits iNOS gene expression by a mechanism involving a blockade of LPS-induced nuclear translocation of NF-kappa B/Rel.

2-Acetylaminofluorene↗
PubMed1999

Cytotoxicity of urushiols isolated from sap of Korean lacquer tree (Rhus vernicifera Stokes).

Cytotoxicities of four urushiols, congeners isolated from the sap of Korean lacquer tree (Rhus vernicifera Stokes), to 29 human cancer cell lines originated from 9 organs were evaluated. Their values of 50% growth inhibition were below 4 microg/ml, and showed cell line specific cytotoxicity. The present result is the first report on the cytotoxicity of urushiols suggesting that they would have an anticancer activity to human cancer cells.

Antineoplastic Agents↗
PubMed1999

The inhibitory effect of polysaccharides isolated from Phellinus linteus on tumor growth and metastasis.

It was previously reported that polysaccharides (PL) isolated from Phellinus linteus strongly stimulated cell-mediated and humoral immunity. This study was undertaken to investigate the immunochemotherapeutic activity of PL against tumor growth and metastasis. PL alone significantly prolonged the survival rate of B16F10-implanted mice, inhibited tumor growth in NCI-H23-implanted nude mice, and reduced the frequency of pulmonary metastasis of B16F10 melanoma. Adriamycin significantly inhibited tumor growth, but only slightly inhibited metastasis. The combination therapy with PL and adriamycin was more effective in inhibiting tumor growth, but not metastasis. PL did not induce direct toxicity in cancer cells, which is characteristic of immunotherapeutics. In conclusion, PL might be of use in immunochemotherapy of cancer because of its effective activities on tumor growth and metastasis through the immunopotentiation of the patients without toxicity.

Animals↗
PubMed1999

Activation of NF-kappaB/Rel in angelan-stimulated macrophages.

In our previous studies we showed that the primary target cell of angelan, a polysaccharide purified from Angelica gigas Nakai, is a macrophage (Han et al., 1998). In the present study we examined the effect of angelan on iNOS, IL-1beta, and TNF-alpha transcription in mouse macrophage line RAW 264.7. We show that angelan produces a marked induction of iNOS, IL-1beta, and TNF-alpha transcription by RAW 264.7 cells. Since these gene transcriptions have been recently shown to be under the control of NF-kappaB/Rel family of transcription factors, we assessed the effect of angelan on NF-kappaB/Rel using a electrophoretic mobility shift assay. Treatment of RAW 264.7 cells with angelan produced strong induction of NF-kappaB/Rel binding. Treatment of RAW 264.7 cells with angelan slightly induced AP-1 binding activity, whereas Oct binding was not affected by angelan. Angelan stimulated macrophages to activate NF-kappaB/Rel, whereas neither B-cells nor T-cells were affected by the angelan. In conclusion, we demonstrate that the stimulation effect of angelan on macrophage is mediated by specific activation of NF-kappaB/Rel.

Animals↗
PubMed1999

Photonic defect modes of cholesteric liquid crystals.

We investigate defect modes of cholesteric liquid crystals as photonic band gap materials. For normal incidence of light, cholesteric liquid crystals exhibit total reflection for the circular polarization with the same handedness as that of cholesteric helix. However, the other orthogonal component is completely transmitted. When we replace a thin layer of liquid crystal by an isotropic material as a defect, defect modes are induced for both polarizations of incident light. We analyze the wavelength and reflectivity of the defect modes in terms of the refractive index of defect layer.

Journal Article↗
PubMed1998

Down-regulation of protein kinase C: a potential mechanism for 2-amino-3-methylimidazo[4,5-f]quinoline-mediated immunosuppression.

Immunosuppressive mechanism of food-born mutagenic and carcinogenic heterocyclic amine, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), was studied in murine spleen cells. IQ suppressed the IL-2 secretion and its mRNA expression. Treatment of IQ also decreased PKC activity in both the membrane fraction and the cytosol fraction. Treatment of PMA resulted in the recovery of IQ-induced suppression of IL-2 production, but the addition of ionomycin (Io) had no effect. Subsequently, we examined the effect of IQ on the activation of NF-kappaB, AP-1, and NF-AT, which are key transcription factors for IL-2 transcription. The activation of NF-kappaB and AP-1 was markedly inhibited by IQ in PMA/PHA-stimulated cells. Meanwhile, NF-AT was not affected by IQ in PMA/Io-stimulated cells. These results suggest that the immunosuppression induced by IQ might be associated with the down-regulation of PKC and subsequent blockade of the activation of NF-kappaB and AP-1 in the IL-2 gene expression.

Animals↗
PubMed1998

The effect of 2-mercapto-5-methyl-1,3,4-thiadiazole on enzymatic synthesis of cefazolin.

The effect of unreacted residual 2-mercapto-5-methyl-1,3,4-thiadiazole (MMTD), the reagent for 3-[5-methyl-1,3,4-thiadiazole-2-yl]-7-aminocephalosporanic acid (M-7-ACA) synthesis, on the enzymatic acylation of M-7-ACA by the methyl ester of 1,2,3,4-tetrazol-1-acetic acid (MeTzAA) to produce cefazolin (CEZ) was studied. In the two-step process of synthesizing CEZ from 7-aminocephalosporanic acid (7-ACA), one of the key parameters controlling the overall CEZ yield was the ratio of MMTD to 7-ACA in M-7-ACA synthesis. The increase of the ratio showed opposing effects by increasing the M-7-ACA yield in the first step, while decreasing CEZ yield in the subsequent enzymatic reaction by the inhibitory effect of the increased content of MMTD as an impurity in the M-7-ACA preparation. It was revealed that the decrease of CEZ yield in the enzymatic reaction was caused by the selective retardation of the rate of CEZ synthesis reaction by a typical competitive inhibition, while not affecting the rate of MeTzAA hydrolysis reaction. The optimum MMTD-to-7-ACA ratio rendering the highest overall CEZ yield over 7-ACA was 1.2:1.

Catalysis↗
PubMed1998

Inhibition of NF-kappa B/Rel nuclear translocation by dexamethasone: mechanism for the inhibition of iNOS gene expression.

The decrease in NO production was found to correlate well with a decrease in inducible nitric oxide synthase (iNOS) mRNA expression as demonstrated by Northern blot analysis and quantitative RT-PCR. Since the promoter in iNOS gene contains binding motifs for NF-kappa B/Rel, NF-IL6, and Oct which appear to be important for LPS-mediated iNOS induction, the effects of DEX on the activation of these transcription factors were examined. Treatment of DEX to RAW 264.7 cells induced a dose-related inhibition of NF-kappa B/Rel in chloramphenicol acetyltransferase activity, while NF-IL6 or Oct activation was not affected by DEX. Treatment of RAW 264.7 cells with DEX inhibited DNA binding of NF-kappa B/Rel proteins to their cognate DNA site as measured by electrophoretic mobility shift assay. In addition, DEX treatment caused a significant reduction in nuclear c-rel, p65, and p50 protein contents, and these decreases were paralleled by the accumulation of cytoplasmic c-rel, p65, and p50. These results suggest that DEX may inhibit iNOS gene expression by a mechanism involving the blockade of LPS-induced nuclear translocation of NF-kappa B/Rel.

Animals↗
PubMed1998

Transforming growth factor-beta 1 (TGF-beta1) promotes IL-2 mRNA expression through the up-regulation of NF-kappaB, AP-1 and NF-AT in EL4 cells.

Transforming growth factor beta1 (TGF-beta1) has been previously shown to modulate interleukin 2 (IL-2) secretion by activated T-cells. In the present studies, we determined that TGF-beta1 induced IL-2 mRNA expression in the murine T-cell line EL4, in the absence of other stimuli. IL-2 mRNA expression was significantly induced by TGF-beta1 (0.1-1 ng/ml) over a relatively narrow concentration range, which led to the induction of IL-2 secretion. Under identical condition, we examined the effect of TGF-beta1 on the activity of nuclear factor AT (NF-AT), nuclear factor kappaB (NF-kappaB), activator protein-1 (AP-1) and octamer, all of which contribute to the regulation of IL-2 gene expression. Electrophoretic mobility shift assays showed that TGF-beta1 markedly increased NF-AT, NF-kappaB and AP-1 binding to their respective cognate DNA binding sites, whereas octamer binding remained constant, as compared with untreated cells. Employing a reporter gene expression system with p(NF-kappaB)3-CAT, p(NF-AT)3-CAT and p(AP-1)3-CAT, TGF-beta1 treatment of transfected EL4 cells induced a dose-related increase in chloramphenicol acetyltransferase activity that correlated well with the DNA binding profile found in the electrophoretic mobility shift assay studies. These results show that TGF-beta1, in the absence of any additional stimuli, up-regulates the activity of key transcription factors involved in IL-2 gene expression, including NF-AT, NF-kappaB and AP-1, to help promote IL-2 mRNA expression by EL4 cells.

Animals↗
PubMed1997

Induction of liver-associated transforming growth factor beta 1 (TGF-beta 1) mRNA expression by carbon tetrachloride leads to the inhibition of T helper 2 cell-associated lymphokines.

Acute treatment of B6C3F1 mice with a hepatotoxic dose (500 mg/kg) of carbon tetrachloride (CCl4) produced a marked but transient increase in transforming growth factor beta 1 (TGF-beta 1) mRNA expression in the liver within 24 hr. We have previously shown that an identical dose of CCl4 also produces a marked increase in serum TGF-beta 1 concentrations which peak at 48 hr and produce a marked inhibition of the anti-sRBC IgM antibody forming cell (AFC) response. Similar increases in TGF-beta 1 transcripts scripts in the liver were also induced by an acute hepatotoxic dose (600 mg/kg) of acetaminophen. No increase in TGF-beta 1 mRNA expression was detected in the spleen following treatment with either agent. Direct addition of TGF-beta 1 (0.05-1.0 ng/ml) to naive splenocyte cultures produced a marked and dose-related inhibition of the anti-sRBC IgM AFC response. Under the same conditions, TGF-beta 1 induced a marked decrease in IL-4 and IL-5 mRNA expression in sRBC-sensitized splenocytes. Concomitantly, TGF-beta 1 induced a rapid increase in NF-kappa B/Rel trans-acting factor binding within the first 24 hr post-sRBC sensitization of splenocytes. Conversely, NF-kappa B/Rel binding activity was inhibited on Days 2 through 4 in sRBC-sensitized splenocytes in the presence of TGF-beta 1. The increase in NF-kappa B/Rel binding within 24 hr following sRBC sensitization is consistent with the positive influence TGF-beta 1 exerts on Th1 cytokines such as IL-2 and IFN-gamma. Conversely the decrease in NF-kappa B/Rel binding at the later time period during the AFC response (Days 2-4) coincides with the inhibitory effects TGF-beta 1 exerted on IgM production by B cells.

Acetaminophen↗
PubMed1997

Transient CRE- and kappa B site-binding is cross-regulated by cAMP-dependent protein kinase and a protein phosphatase in mouse splenocytes.

Cyclic AMP regulates a variety of cellular responses through activation of cAMP-dependent protein kinase (PKA). The catalytic subunit of PKA, in turn, activate cAMP responsive element (CRE) and nuclear factor-kappa B (NF-kappa B) binding proteins. In this study, we demonstrated that binding activity to both CRE and kappa B sites in nuclear extracts from spleen cells is modulated by PKA in a time-dependent manner. Electrophoretic mobility shift assays showed that binding by transcription factors to either the CRE or kappa B motif was rapidly up-regulated by cAMP, with maximum binding detected at 30 min in response to forskolin stimulation of splenocytes. This was followed by a steady decline in CRE and kappa B thereafter reaching basal levels by 2 hr. This up-regulation in CRE and kappa B binding was closely associated with an enhancement of PKA activity which was maximum at 30 min following forskolin stimulation. However, unlike the binding of regulatory factors to CRE and kappa B motifs which was very transient, peak PKA activity was sustained for 2 hr. Interestingly, okadaic acid, a protein phosphatase inhibitor, prevented the decline in protein binding to CRE and kappa B motifs 2 hr following forskolin stimulation and actually produced a slight increase at 30 min. These data suggest that binding by transcription factors to CRE and kappa B sites are up-regulated concomitantly with PKA activation but subsequently down-regulated by a protein phosphatase.

Animals↗
PubMed1997

Expression of estrogen receptors in a normal human breast epithelial cell type with luminal and stem cell characteristics and its neoplastically transformed cell lines.

Although approximately two-thirds of breast cancers are estrogen receptor (ER)-positive, only a small proportion of epithelial cells in the mammary gland express the ER. The origin of the ER-positive breast cancers is unknown. Recently, we have developed a culture method to grow two morphologically and antigenically distinguishable types of normal human breast epithelial cells (HBEC) derived from reduction mammoplasty. In this report, we studied the expression of ER in these two types of cells and their transformed cell lines. The results indicate that Type I HBEC with luminal and stem cell characteristics expressed a variant ER (approximately 48 kd) by Western blot analysis. This variant ER contains a deletion in the DNA binding domain (exon 2) as revealed by RT-PCR analysis. The lack of the DNA-binding domain of the variant ER was also confirmed by the ER-estrogen responsive element binding assay, as well as by the immunofluorescence staining of the ER using anti-ER antibodies which recognize either the C-terminal or N-terminal region. In contrast, Type II HBEC with basal epithelial phenotype are ER-negative. Simian virus 40 (SV40) transformed Type I and Type II HBEC lines also expressed the variant ER. Tumors formed in athymic nude mice by in vitro transformed tumorigenic Type I cell lines, however, expressed a high level of wild type ER which was undetectable in these cells grown in vitro before and after tumor formation. Thus, there appears to be a differential ER mRNA splicing between the in vitro and in vivo mileu.

Adult↗
PubMed1996

2-amino-3-methylimidazo[4,5-f]quinoline-mediated immunosuppression involves inhibition of protein kinase C in murine splenocytes.

The effects of the food-borne mutagenic and carcinogenic heterocyclic amine, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), on the proliferation of murine spleen cells was examined. A significant and dose-related suppression of the proliferative response to concanavalin A (Con A) was observed by the treatment of IQ. IQ also decreased markedly the level of proliferative response induced by PMA and ionomycin and the IL-2 secretion by T cells. Treatment of PMA resulted in the recovery of IQ-induced suppression of IL-2 production, but the addition of ionomycin (Io) had no effect. IQ decreased PKC activity in both the membrane fraction and the cytosol fraction and inhibited the phosphorylation of MARCKS protein. These results suggest that the suppression of spleen cell proliferation induced by IQ might be associated with the inhibition of PKC activity and the subsequent IL-2 secretion of T cells.

Animals↗
PubMed1996

Attenuation of inducible nitric oxide synthase gene expression by delta 9-tetrahydrocannabinol is mediated through the inhibition of nuclear factor- kappa B/Rel activation.

delta 9-Tetrahydrocannabinol (delta 9-THC) a prototypic compound belonging to the family of agents known as cannabinoids, produces a wide variety of biological effects, including inhibition of immune function. The putative mechanism for cannabinoid biological action involves binding to cannabinoid receptor types 1 and 2 (CB1 and CB2) to negatively regulate adenylate cyclase and inhibit intracellular signaling via the cAMP cascade. In the current study, we show that delta 9-THC produces a marked inhibition of inducible nitric oxide synthase (iNOS) transcription and nitric oxide production by the macrophage line RAW 264.7 in response to lipopolysaccharide (LPS). Analysis of RAW 264.7 cell RNA demonstrated transcripts for CB2 but not CB1. Treatment of RAW 264.7 with delta 9-THC inhibited forskolin-stimulated cAMP production in a dose-related manner, verifying the expression of functional cannabinoid receptors by this cell line. iNOS transcription, which is regulated in part by the nuclear factor-kappa B/Rel (NF-kappa B/Rel) family of transcription factors, has been shown to be under the control of the cAMP signaling cascade. We demonstrate that delta 9-THC inhibits the activation and binding of NF-kappa B/Rel proteins to their cognate DNA site, kappa B, in response to LPS stimulation. LPS treatment of RAW 264.7 cells also induced the activation of the cAMP cascade, as indicated by an increase in binding of nuclear factors to the cAMP response element. Activation of CRE binding proteins was inhibited by delta 9-THC. Forskolin treatment of RAW 264.7 cells induced both kappa B and cAMP response element binding activity and was likewise inhibited by delta 9-THC. Collectively, this series of experiments indicates that NF-kappa B/Rel is positively regulated by the cAMP cascade to help initiate iNOS gene expression in response to LPS stimulation of macrophages. This activation of iNOS is attenuated by delta 9-THC through the inhibition of cAMP signaling.

Activating Transcription Factor 2↗