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Biomedical subjects

S Y Hwang

Publications and source records attributed to S Y Hwang.

At least 37 records · Page 2Linked to original sources
PubMed2000

Genetically engineered fibroblasts with antigen-presenting capability: efficient induction of an antigen-specific cytotoxic T-lymphocyte response and protection against tumor development in vivo.

BLK mouse fibroblasts (H-2b) were genetically engineered to express costimulatory B7.1 and interleukin-2 (BLK/IL2/B7.1). The BLK/IL2/B7.1 cells were then pulsed with an ovalbumin (OVA) epitope as a model antigen (Ag) (BLK/IL2/B7.1/OVA), and tested for the induction of OVA-specific cytotoxic T lymphocytes (CTLs) in C57BL/6 mice (H-2b). The genetically engineered fibroblasts lacking one or two of three factors (interleukin-2, B7.1, and OVA) were constructed and used as controls. Immunization with the BLK/IL2/B7.1/OVA cells induced strong cytotoxic activities against OVA-expressing EL4 (EG7) tumor cells, but not against other H-2b tumor cells, such as EL4, C1498 and B16F1 cells. The magnitude of the cytotoxic response in mice with the BLK/IL2/B7.1/OVA cells was significantly higher than the response in mice immunized with any other cell constructs. CD8+ T cells with OVA-specific cytotoxic activities were predominant in mice immunized with the BLK/IL2/B7.1/OVA cells. Furthermore, immunization with the BLK/IL2/B7.1/OVA cells significantly prolonged the survival of mice, compared with any other cell constructs, when the mice were challenged with EG7 tumor cells at 2 weeks postimmunization. Induction of antitumoral CTL immunity by the BLK/IL2/B7.1/OVA cells was independent of host Ag-presenting cells and of CD4+ T-cell and natural killer 1.1+ cell help. These results suggest that fibroblasts can be genetically modified to efficient Ag-presenting cells for the induction of an Ag-specific CTL response.

Animals↗
PubMed2000

Efficient induction of an antigen-specific, T helper type 1 immune response by interleukin-12-secreting fibroblasts.

To determine whether the paracrine secretion of interleukin (IL)-12 can efficiently convert immune responses characterized by high levels of synthesis of IL-4 and immunoglobulin E (IgE) into T helper 1 (Th1)-dominated responses, 3T3 fibroblasts were stably transfected to secrete IL-12 (480 units/10(6) cells/48 hr). Their effects on the T helper cell-mediated immune response were investigated in ovalbumin (OVA)-primed mice. Free mouse recombinant IL-12 was included as a control group. IL-12-secreting fibroblasts (3T3/IL-12) were more effective than free recombinant IL-12 at increasing OVA-specific interferon-gamma (IFN-gamma) production and decreasing OVA-specific IL-4 production in CD4+ T cells. In addition, injection with 3T3/IL-12 cells significantly increased anti-OVA immunoglobulin G2a (IgG2a) levels and decreased anti-OVA IgE levels in OVA-primed mice. This work suggests that IL-12-secreting fibroblasts can efficiently induce an antigen-specific Th1 response and may be beneficial in the treatment of diseases caused by undesirable T helper 2 (Th2)-dominated responses, including allergic diseases.

Animals↗
PubMed2000

A novel cytotoxic C-methylated biflavone from the stem of Cephalotaxus wilsoniana.

Bioassay-directed fractionation of an ethanolic extract of Cephalotaxus wilsoniana has resulted in the isolation of a novel C-methylated biflavone, taiwanhomoflavone-A (1). Its structure was elucidated on the basis of spectroscopic analysis. Taiwanhomoflavone-A is cytotoxic with ED50 values of 3.4, 1.0, 2.0 and 2.5 microg/ml, respectively, against KB epidermoid carcinoma of nasopharynx, COLO-205 colon carcinoma, Hepa-3B hepatoma, and Hela cervix tumor cells.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Inhibition of interleukin-12 production in lipopolysaccharide-activated macrophages by curcumin.

Pharmacological control of interleukin-12 production may be a key therapeutic strategy for modulating immunological diseases dominated by type-1 cytokine responses. In this study we investigated the effects of curcumin (1,7-bis[4-hydroxy-3-methoxyphenyl]-1, 6-heptadiene-3,5-dione) on the production of interleukin-12 from mouse macrophages stimulated with lipopolysaccharide. Curcumin potently inhibited the production of interleukin-12 in a dose-dependent manner. The effect of curcumin on interleukin-12 p40 promoter activation was analyzed by transfecting RAW264.7 monocytic cells with p40 promoter/reporter constructs. The repressive effect mapped to a region in the p40 promoter containing a binding site for nuclear factor kappaB (p40-kappaB). Furthermore, activation of macrophages by lipopolysaccharide resulted in markedly enhanced binding activity to the kappaB site, which significantly decreased upon addition of curcumin. These results suggest that curcumin-induced inhibition of interleukin-12 production in macrophages may explain some of the biological effects of curcumin including its anti-inflammatory activity.

Animals↗
PubMed1999

Chloromethyl ketones inhibit interleukin-12 production in mouse macrophages stimulated with lipopolysaccharide.

Interleukin-12 (IL-12) plays a pivotal role in the development of T-helper type 1 (Th1) immune response, which may be involved in the pathogenesis of chronic inflammatory autoimmune disorders. In this study, we investigated the effects of N-alpha-tosyl-L-phenylalanine chloromethyl ketone (TPCK) and N-alpha-tosyl-L-lysine chloromethyl ketone (TLCK), serine protease inhibitors, on the production of IL-12 from macrophages stimulated with lipopolysaccharide (LPS). TPCK and TLCK potently inhibited this LPS-induced IL-12 production in a dose-dependent manner. The effect of TPCK and TLCK on the IL-12 p40 promoter activation was analyzed by transfecting monocytic RAW264.7 cells with p40 promoter-reporter constructs. The repressive effect maps to a region in the p40 promoter containing a binding site for NFkappaB (p40-kappaB). A linker scan mutant of the p40-kappaB site abrogates the inhibitory effect on the p40 promoter, confirming the functional relevance of the NFkappaB site. Our results show that TPCK and TLCK inhibit NFkappaB-mediated IL-12 production in macrophages. reserved.

Animals↗
PubMed1999

Antigen-specific cytotoxicity and cell number of adoptively transferred T cells are efficiently maintained in vivo by re-stimulation with an antigen/interleukin-2 fusion protein.

In order to maintain in vivo anti-tumor efficacy of antigen (Ag)-specific T cells in adoptive immunotherapy for a prolonged period, we constructed a fusion protein (OVA/IL-2) containing ovalbumin (OVA) as a model tumor Ag, co-valently linked to murine interleukin-2 (IL-2). The OVA/IL-2 protein produced in a baculovirus expression system displayed potent IL-2 bio-activity. Immunization with the OVA/IL-2 protein after adoptive transfer of OVA-specific T cells maintained the OVA-specific cytotoxicity and cell number of adoptively transferred T cells long term in vivo, while a simple mixture of recombinant OVA (rOVA) and rIL-2 did not. The response was dependent on the injection doses and times of the OVA/IL-2 protein. Furthermore, weekly re-stimulation of adoptively transferred OVA-specific T cells with the OVA/IL-2 protein cured 70% of tumor-bearing mice. In contrast, re-stimulation with a mixture of rOVA and rIL-2 could not significantly prolong the survival period of tumor-bearing mice. These studies suggest that the co-valent linkage between IL-2 and antigen confines the effect of IL-2 to antigen-specific T cells, leading to efficient maintenance of the anti-tumor activity of adoptively transferred T cells.

Animals↗
PubMed1999

Thrombin inhibitors based on a propargylglycine template.

A series of novel arylsulfonylpropargylglycinamide derivatives was investigated as thrombin inhibitors in which the SAR was focused on substituents at the acetylenic terminus. Several compounds in this series were identified as potent thrombin inhibitors (Ki up to 5 nM) that are highly selective over trypsin and other serine proteases as well.

Alkynes↗
PubMed1999

Bioassay of biotin concentration with a Escherichia coli bio deletion mutant.

Biotin concentration was determined unequivocally with the E. coli bio mutant. The results demonstrate that this simple and efficient method can determine biotin concentration in the range of 10 pg to 50 ng/ml. The present method can also clearly distinguish biotin from its precursor and analog, dethiobiotin.

Biological Assay↗
PubMed1999

A new family of mouse genes homologous to the human MAGE genes.

The human MAGE genes are expressed in a wide variety of tumors but not in normal cells, with the exception of the male germ cells, placenta, and, possibly, cells of the developing embryo. These genes encode tumor-specific antigens recognized by cytolytic T lymphocytes. The MAGE genes are located on the X chromosome, in three clusters denoted MAGE-A, B, and C, mapping at q28, p21.3, and q26, respectively. The function of these genes remains unknown. Because mice offer many advantages for the study of genes that may be involved in embryonic development, we looked for the murine equivalents of the 12 human MAGE-A genes. Using a MAGE-A probe, we isolated 8 new murine genes that are homologous to the MAGE genes. On average, the open reading frames (ORFs) of these 8 closely related genes display a slightly higher degree of nucleotide identity with the MAGE-A ORFs than with the MAGE-B or MAGE-C ORFs. Furthermore, like MAGE-A genes, they encode acidic proteins, whereas the MAGE-B genes encode basic proteins. Accordingly, these 8 murine genes were named Mage-a1 to 8 (approved symbols Magea1 to 8). Mage-a genes were mapped in two different loci on the mouse X chromosome. Mage-a4 and Mage-a7 are located in a region that is syntenic to either Xp21 or Xq28. The 6 other genes are arranged in a cluster located in a region syntenic to Xp22. Like their human counterparts, Mage-a genes were found to be transcribed in adult testis, but not in other tissues. Expression of some Mage-a genes was also detected in tumor cell lines. Two Mage-a genes were found to be expressed in blastocysts.

Animals↗
PubMed1999

The mouse cornichon gene family.

As part of a large scale mouse Expressed Sequence Tag (EST) project to identify molecules involved in the initiation of mammalian development, a homolog of the Drosophila cornichon gene was detected as a mouse maternal transcript present in the two-cell embryo. Cornichon is a multigene family in the mouse: the new gene, Cnih, maps to mouse chromosome 10, another cornichon homolog, Cnil, maps to chromosome 14 and two additional cornichon-related loci, possibly pseudogenes, localize to chromosomes 3 and 10, respectively. Cnih encodes an open reading frame (ORF) of 144 amino acids that is 93% homologous (68% identical) to the Drosophila protein, whereas the ORF of Cnil contains two extra polypeptide regions not found in these other proteins. Transcripts of Cnih are highly abundant in the full grown oocyte and the ovulated unfertilized egg, while Cnil message is only detectable after activation of the embryonic genome at the eight-cell stage. In situ hybridization shows specific localization of Cnih transcripts to ovarian oocytes. The lack of cytoplasmic polyadenylation of the maternally inherited Cnih transcript suggests that Cnih mRNA is translated in the full grown oocyte before, but not after, ovulation. In Drosophila, cornichon is involved in the establishment of both anterior-posterior and dorso-ventral polarity via the epidermal growth factor (EGF)-receptor signaling pathway. Finding Cnih in the mammalian oocyte opens a new perspective on the investigation of EGF-signaling in the oocyte.

Amino Acid Sequence↗
PubMed1999

Curcumin inhibits Th1 cytokine profile in CD4+ T cells by suppressing interleukin-12 production in macrophages.

1 Interleukin-12 (IL-12) plays a central role in the immune system by driving the immune response towards T helper 1 (Th1) type responses which are characterized by high IFN-gamma and low IL-4 production. In this study we investigated the effects of curcumin, a natural product of plants obtained from Curcuma longa (turmeric), on IL-12 production by mouse splenic macrophages and the subsequent ability of these cells to regulate cytokine production by CD4+ T cells. 2 Pretreatment with curcumin significantly inhibited IL-12 production by macrophages stimulated with either lipopolysaccharide (LPS) or head-killed Listeria monocytogenes (HKL). 3 Curcumin-pretreated macrophages reduced their ability to induce IFN-gamma and increased the ability to induce IL-4 in Ag-primed CD4+ T cells. Addition of recombinant IL-12 to cultures of curcumin-pretreated macrophages and CD4+ T cells restored IFN-gamma production in CD4+ T cells. 4 The in vivo administration of curcumin resulted in the inhibition of IL-12 production by macrophages stimulated in vitro with either LPS or HKL, leading to the inhibition of Th1 cytokine profile (decreased IFN-gamma and increased IL-4 production) in CD4+ T cells. 5 These findings suggest that curcumin may inhibit Th1 cytokine profile in CD4+ T cells by suppressing IL-12 production in macrophages, and points to a possible therapeutic use of curcumin in the Th1-mediated immune diseases.

Animals↗
PubMed1999

Interleukin-12-secreting fibroblasts are more efficient than free recombinant interleukin-12 in inducing the persistent resistance to Mycobacterium avium complex infection.

To determine whether the paracrine secretion of interleukin-12 (IL-12) can efficiently stimulate the resistance to Mycobacterium avium complex (MAC) infection, 3T3 fibroblasts were stably transfected to secrete IL-12 (480 U/106 cells/48 hr) and their effect on MAC infection was investigated in genetically susceptible BALB/c mice, compared with that of free recombinant IL-12 (rIL-12). Injection with IL-12-secreting fibroblasts (3T3-IL-12) during intranasal infection with MAC resulted in a significant decrease in the bacterial load of the lung during the entire 10-week observation period, while rIL-12 reduced the bacterial load initially, at 2 weeks, but not by 10 weeks postinfection. Lung CD4+ T cells in mice injected with the 3T3-IL-12 cells showed a persistent T helper type 1 (Th1) response throughout the 10-week period. Furthermore, immunization with the 3T3-IL-12 cells induced and maintained significantly higher levels of cytotoxic activity and nitric oxide production by lung cells than did rIL-12 immunization. This work suggests that IL-12-secreting fibroblasts may serve as a vehicle for paracrine secretion of IL-12 for immunotherapy of MAC infection.

Animals↗
PubMed1999

Protopine from Corydalis ternata has anticholinesterase and antiamnesic activities.

While screening extracts of natural products in search of anticholinesterase activity, we found that a total methanolic extract of the tuber of Corydalis ternata (Papaveraceae) showed significant inhibitory effects on acetylcholinesterase. Further fractionation of this extract using acetylcholinesterase inhibition as the parameter screened resulted in the isolation and purification of an alkaloid, protopine. Protopine inhibited acetylcholinesterase activity in a dose-dependent manner. The concentration required for 50% inhibition was 50 microM. The anti-acetylcholinesterase activity of protopine was specific reversible and competitive in manner. Furthermore, when mice were pretreated with protopine, the alkaloid significantly alleviated scopolamine-induced memory impairment. In fact, protopine had an efficacy almost identical to that of velnacrine, a tacrine derivative developed by a major drug manufacturer to treat Alzheimer's disease, at an identical therapeutic concentration. We suggest, therefore, that protopine has both anti-acetylcholinesterase and antiamnesic properties that may ultimately hold significant therapeutic value in alleviating certain memory impairments observed in dementia.

Alkaloids↗
PubMed1998

Promoter analysis of the Drosophila genes encoding TFIIB and TATA box-binding protein.

We have analyzed the 5'-flanking regions of the Drosophila genes encoding the TFIIB and TATA box-binding proteins (TBP) and mapped the regulatory regions required for their efficient expression. We found that the 500 bp long region (-439 to +60) and the 401 bp long region (-261 to +138) are required for the efficient expression of TFIIB and TBP genes, respectively. In the TFIIB promoter region, the upstream DNA between -439 and -280 and the downstream DNA between +8 and +60 are necessary for the stimulation of promoter activity. The upstream DNA between -439 and -280 stimulates transcription in an orientation dependent manner. In the TBP promoter region, the upstream DNA between -261 and -207, and the downstream DNA between +15 and +138 are necessary for the stimulation of promoter activity. The upstream DNA (-261 to -207) required for TBP promoter activity contains a 11 bp long palindromic sequence and a DNA replication-related element sequence. Particularly, we could find that the downstream promoter regions of TFIIB and TBP genes contain the conserved nucleotide sequences, suggesting the presence of a common regulatory mechanism for the expression of these two genes.

Animals↗
PubMed1998

Augmentation of therapeutic antitumor immunity by B16F10 melanoma cells transfected by interferon-gamma and allogeneic MHC class I cDNAs.

The cDNAs for interferon-gamma (IFN-gamma) and allogeneic H-2Kd molecules were transfected into highly metastatic B16F10 melanoma cells (H-2b), and the synergistic effects of the antitumor immune responses by the doubly transfected cells (B16/Kd/IFN-gamma cells) were investigated in C57BL/6 mice (H-2b). The singly transfected B16F10 cells with either IFN-gamma or H-2Kd cDNA (B16/IFN-gamma or B16/Kd cells) were used as controls. The B16/Kd/IFN-gamma cells secreted biologically active IFN-gamma, and strongly expressed both syngeneic and allogeneic MHC class I antigens (H-2Kb and H-2Kd) on the same cell construct. Immunization with the doubly transfected B16/Kd/IFN-gamma cells induced higher anti B16F10 cellular cytotoxic responses than the single transfected B16/IFN-gamma or B16/Kd cells. Lyt-2.2 (CD8)+ T-cells were a major effector cell-type involved in the anti B16F10 responses and their cytotoxic activities were augmented in the immunized mice with the B16/Kd/IFN-gamma cells, as demonstrated by in vitro depletion experiments. The survival period of melanoma-bearing mice treated with the B16/Kd/IFN-gamma cells was significantly longer than that treated with the B16/IFN-gamma or B16/Kd cells. Furthermore, the treatment with the B16/Kd/IFN-gamma cells was capable of greatly inhibiting lung metastasis from small, established B16F10 footpad tumors. These results suggest that the augmented immunotherapeutic potentials can be achieved by the vaccination with IFN-gamma and allogeneic MHC class I genes transfected B16F10 melanoma cells.

Animals↗
PubMed1998

Potent and efficacious thienylamidine-incorporated thrombin inhibitors.

Novel thrombin inhibitors incorporating thienylamidine at the P1 position were designed and synthesized. These compounds are potent, trypsin-selective and efficacious in the rat model of venous thrombosis. The proposed P1 binding mode in the thrombin active site was confirmed by X-ray crystallographic analysis.

Animals↗
PubMed1998

Discovery of LB30057, a benzamidrazone-based selective oral thrombin inhibitor.

Systematic variation of the so-called P-pocket moiety of benzamidrazone-based selective thrombin inhibitors led to the discovery of LB30057. It is potent (Ki = 0.38 nM for human thrombin), selective (Ki = 3290 nM for bovine trypsin), and orally bioavailable (58% oral bioavailability in dogs). LB30057 was efficacious in thrombosis animal models.

Animals↗