Biomedical subjects

H W Lee

Publications and source records attributed to H W Lee.

At least 37 records · Page 2Linked to original sources

PubMed2002

Novel E2F decoy oligodeoxynucleotides inhibit in vitro vascular smooth muscle cell proliferation and in vivo neointimal hyperplasia.

The transcription factor, E2F, plays a critical role in the trans-activation of several genes involved in cell cycle regulation. Previous studies showed that the transfection of cis element double-stranded decoy oligodeoxynucleotides (ODNs) corresponding to E2F binding sites inhibited the proliferation of vascular smooth muscle cells (VSMCs) and neointimal hyperplasia in injured vessels. We have developed a novel E2F decoy ODN with a circular dumbbell structure (CD-E2F) and compared its effects with those of the conventional phosphorothioated E2F decoy (PS-E2F) ODN. CD-E2F ODN was more stable than PS-E2F ODN, largely preserving its structural integrity after incubation in the presence of nucleases and sera. Moreover, CD-E2F ODN inhibited high glucose- and serum-induced transcriptional expression of cell cycle regulatory genes more strongly than PS-E2F ODN. Transfection of CD-E2F ODN resulted in more effective inhibition of VSMC proliferation in vitro and neointimal formation in vivo, compared with PS-E2F ODN. An approximately 40-50% lower dose of CD-E2F ODN than PS-E2F ODN was sufficient to attain similar effects. In conclusion, our results indicate that CD-E2F ODN may be a valuable tool in gene therapy protocols for inhibiting VSMC proliferation and studying transcriptional regulation.

Animals↗

PubMed2001

Genistein prevents nuclear factor-kappa B activation and acute lung injury induced by lipopolysaccharide.

Protein tyrosine kinase (PTK) inhibitors have been proposed to reduce lung injury and lethal toxicity. The mechanisms responsible for the effects of PTK inhibitors remain obscure. The purpose of the present study was to examine whether genistein, a specific inhibitor of PTK, inhibits nuclear factor-kappa B (NF-kappaB) activation during acute lung injury induced by lipopolysaccharide (LPS) and, if so, to enumerate the effects of inhibition of NF-kappaB activation on LPS-induced proinflammatory gene products, such as cytokine-inducible neutrophil chemoattractant (CINC) and matrix metalloproteinase-9 (MMP-9), as well as neutrophil influx into the lungs. Intratracheal treatment of rats with LPS (6 mg/kg) resulted in increases in total protein and lactate dehydrogenase activity in bronchoalveolar lavage fluid and activated DNA-binding activity of NF-kappaB in alveolar macrophages and lung tissue. A 2-h pretreatment with genistein (50 mg/kg, intraperitoneally) inhibited the LPS-induced changes in lung injury parameters and the induction of NF-kappaB activation. Furthermore, these inhibitory effects of genistein correlated with a depression of LPS-induced protein tyrosine phosphorylation (approximately molecular masses of 46, 48, and 54 kD) and phosphorylation of Jun N-terminal kinase (JNK) in lung tissue. Genistein also substantially reduced the LPS-induced CINC production and MMP-9 activity and suppressed neutrophil recruitment. These results suggest that genistein attenuates LPS-induced acute lung responses through inhibition of NF-kappaB activation. In addition, NF-kappaB activation appears to be an important mechanism mediating LPS-induced CINC production and MMP-9 activity and resulting neutrophil recruitment associated with acute lung inflammation and injury.

Animals↗

PubMed2001

Structure-reactivity relationships in the pyridinolysis of N-methyl-N-arylcarbamoyl chlorides in dimethyl sulfoxide.

Nucleophilic substitution reactions of N-methyl-N-arylcarbamoyl chlorides (YC(6)H(4)N(CH(3))COCl) with pyridines (XC(5)H(4)N) have been investigated in dimethyl sulfoxide at 45.0 degrees C. A striking trend in the selectivity parameters is that they are constant within experimental errors, rho(X) = -2.25 +/- 0.03, beta(X) = 0.42 +/- 0.01, and rho(Y) = 1.10 +/- 0.06, with changing reactivities of the electrophiles (deltasigma(Y)) and nucleophiles (deltasigma(X)), respectively, and this leads to a vanishingly small cross-interaction constant, rho(XY) approximately equals beta(XY) approximately equals 0. The rate data can be expressed in the Ritchie N(+) type equation. Based on this and other results, the mechanism of nucleophile (pyridine) addition to the resonance- stabilized carbocation is proposed. It has been shown from the definition of beta(XY) (and rho(XY)) together with the Marcus equation that the high intrinsic barrier, DeltaG(0), in the intrinsic-barrier controlled reaction series is a prerequisite for such reactions in which the cross-interaction vanishes and the N(+) relationship holds.

Journal Article↗

PubMed2001

Cell cycle controlling the silencing and functioning of mammalian activators.

Naïve CD4(+) helper T (T(H)) cells respond to stimulation by terminally differentiating into two mature classes, T(H)1 cells, which express interferon gamma (IFN-gamma), and T(H)2 cells, which express interleukin 4 (IL-4). The transcriptional activators T-bet and Gata-3 mediate commitment to the T(H)1 and T(H)2 fates, respectively, including chromatin remodeling of signature genes. The cytokine IL-12 fosters growth of committed T(H)1 cells, while IL-4 fosters growth of committed T(H)2 cells. IL-12 and IL-4 also play critical roles in commitment by promoting transcriptional silencing of Gata-3 and T-bet, respectively. We now show that both T-bet and Gata-3 are induced in a cell cycle-independent manner in bipotent progenitor cells. In contrast, both lineage-restricted gene induction by the activator proteins and heritable silencing of the transcription of each activator, the hallmarks of terminal differentiation, are cell cycle dependent. We found that cells that cannot cycle remain uncommitted and bipotent in response to the most polarizing signals for maturation. These results provide mechanistic insight into a mammalian model of terminal differentiation by illustrating that cell cycle-coupled epigenetic effects, as originally described in yeast, may represent an evolutionarily conserved strategy for organizing signaling and cell fate.

Cell Cycle↗

PubMed2001

Macroscopic traffic models from microscopic car-following models.

We present a method to derive macroscopic fluid-dynamic models from microscopic car-following models via a coarse-graining procedure. The method is first demonstrated for the optimal velocity model. The derived macroscopic model consists of a conservation equation and a momentum equation, and the latter contains a relaxation term, an anticipation term, and a diffusion term. Properties of the resulting macroscopic model are compared with those of the optimal velocity model through numerical simulations, and reasonable agreement is found although there are deviations in the quantitative level. The derivation is also extended to general car-following models.

Journal Article↗

PubMed2001

Induction of cytotoxic T lymphocyte antigen 4 (CTLA-4) restricts clonal expansion of helper T cells.

Cytotoxic T lymphocyte antigen (CTLA)-4 plays an essential role in immunologic homeostasis. How this negative regulator of T cell activation executes its functions has remained controversial. We now provide evidence that CTLA-4 mediates a cell-intrinsic counterbalance to restrict the clonal expansion of proliferating CD4(+) T cells. The regulation of CTLA-4 expression and function ensures that, after approximately 3 cell divisions of expansion, most progeny will succumb to either proliferative arrest or death over the ensuing three cell divisions. The quantitative precision of the counterbalance hinges on the graded, time-independent induction of CTLA-4 expression during the first three cell divisions. In contrast to the limits imposed on unpolarized cells, T helper type 1 (Th1) and Th2 effector progeny may be rescued from proliferative arrest by interleukin (IL)-12 and IL-4 signaling, respectively, allowing appropriately stimulated progeny to proceed to the stage of tissue homing. These results suggest that the cell-autonomous regulation of CTLA-4 induction may be a central checkpoint of clonal expansion of CD4(+) T cells, allowing temporally and spatially restricted growth of progeny to be dictated by the nature of the threat posed to the host.

Abatacept↗

PubMed2001

Activation of p21(WAF1/Cip1) transcription through Sp1 sites by histone deacetylase inhibitor apicidin: involvement of protein kinase C.

We previously reported that apicidin, a novel histone deacetylase inhibitor, inhibited the proliferation of tumor cells via induction of p21(WAF1/Cip1). In this study, we determined the molecular mechanisms by which apicidin induced the p21(WAF1/Cip1) gene expression in HeLa cells. Apicidin induced p21(WAF1/Cip1) mRNA independent of the de novo protein synthesis and activated the p21(WAF1/Cip1) promoter through Sp1-3 site located at -82 and -77 relative to the transcription start site. This transcriptional activation appears to be mediated by protein kinase C (PKC), because calphostin C, a PKC inhibitor, significantly attenuated the activation of p21(WAF1/Cip1) promoter via Sp1 sites, which was accompanied by a marked suppression of p21(WAF1/Cip1) mRNA and protein expression induced by apicidin. Consistent with the transcriptional activation of p21(WAF1/Cip1) promoter by apicidin, apicidin treatment led to the translocation of PKCepsilon from cytosolic to particulate fraction, which was reversed by pretreatment with calphostin C, indicating the involvement of PKC in the transcriptional activation of p21(WAF1/Cip1) via Sp1 sites by apicidin. However, the PKC-mediated transcriptional activation of p21(WAF1/Cip1) by apicidin appears to be independent of the histone hyperacetylation, because apicidin-induced histone hyperacetylation was not affected by calphostin C. Furthermore, a PKC activator, phorbol 12,13-dibutyrate, alone induced the transcriptional activation of p21(WAF1/Cip1) promoter, p21(WAF1/Cip1) mRNA, and protein expression without induction of the histone hyperacetylation, suggesting that the transcriptional activation of p21(WAF1/Cip1) by apicidin might have been mediated by a mechanism other than chromatin remodeling through the histone hyperacetylation. Taken together, these results suggest that the PKC signaling pathway plays a pivotal role in the transcriptional activation of the p21(WAF1/Cip1) gene by apicidin.

Biological Transport↗

PubMed2001

Notch1 confers a resistance to glucocorticoid-induced apoptosis on developing thymocytes by down-regulating SRG3 expression.

We previously have reported that SRG3 is required for glucocorticoid (GC)-induced apoptosis in the S49.1 thymoma cell line. Activation of Notch1 was shown to induce GC resistance in thymocytes. However, the specific downstream target of Notch1 that confers GC resistance on thymocytes is currently unknown. We found that the expression level of SRG3 was critical in determining GC sensitivity in developing thymocytes. The expression of SRG3 also was down-regulated by the activated form of Notch1 (NotchIC). The promoter activity of the SRG3 gene also was down-regulated by NotchIC. Expression of transgenic SRG3 resulted in the restoration of GC sensitivity in thymocytes expressing transgenic Notch1. These results suggest that SRG3 is the downstream target of Notch1 in regulating GC sensitivity of thymocytes.

Animals↗

PubMed2001

Even-odd behavior of conductance in monatomic sodium wires.

With the aid of the Friedel sum rule, we perform first-principles calculations of conductances through monatomic Na wires, taking into account the sharp tip geometry and discrete atomic structure of electrodes. We find that conductances (G) depend on the number (L) of atoms in the wires; G is G(0)( = 2e(2)/h) for odd L, independent of the wire geometry, while G is generally smaller than G(0) and sensitive to the wire structure for even L. This even-odd behavior is attributed to the charge neutrality and resonant character due to the sharp tip structure. We suggest that similar even-odd behavior may appear in other monovalent atomic wires.

Journal Article↗

PubMed2001

Measurement of the rate of nu(e) + d --> p + p + e(-) interactions produced by (8)B solar neutrinos at the Sudbury Neutrino Observatory.

Solar neutrinos from (8)B decay have been detected at the Sudbury Neutrino Observatory via the charged current (CC) reaction on deuterium and the elastic scattering (ES) of electrons. The flux of nu(e)'s is measured by the CC reaction rate to be straight phi(CC)(nu(e)) = 1.75 +/- 0.07(stat)(+0.12)(-0.11)(syst) +/- 0.05(theor) x 10(6) cm(-2) s(-1). Comparison of straight phi(CC)(nu(e)) to the Super-Kamiokande Collaboration's precision value of the flux inferred from the ES reaction yields a 3.3 sigma difference, assuming the systematic uncertainties are normally distributed, providing evidence of an active non- nu(e) component in the solar flux. The total flux of active 8B neutrinos is determined to be 5.44+/-0.99 x 10(6) cm(-2) s(-1).

Journal Article↗

PubMed2001

Enzymatic activation of autotaxin by divalent cations without EF-hand loop region involvement.

Autotaxin (ATX) is a recently described member of the nucleotide pyrophosphatase/phosphodiesterase (NPP) family of proteins with potent tumor cell motility-stimulating activity. Like other NPPs, ATX is a glycoprotein with peptide sequences homologous to the catalytic site of bovine intestinal alkaline phosphodiesterase (PDE) and the loop region of an EF-hand motif. The PDE active site of ATX has been associated with the motility-stimulating activity of ATX. In this study, we examined the roles of the EF-hand loop region and of divalent cations on the enzymatic activities of ATX. Ca(2+) or Mg(2+) was each demonstrated to increase the PDE activity of ATX in a concentration-dependent manner, whereas incubation of ATX with chelating agents abolished this activity, indicating a requirement for divalent cations. Non-linear regression analysis of enzyme kinetic data indicated that addition of these divalent cations increases reaction velocity predominantly through an effect on V(max.) Three mutant proteins, Ala(740)-, Ala(742)-, and Ala(751)-ATX, in the EF-hand loop region of ATX had enzymatic activity comparable to that of the wild-type protein. A deletion mutation of the entire loop region resulted in slightly reduced PDE activity but normal motility-stimulating activity. However, the PDE activity of this same deletion mutant remained sensitive to augmentation by cations, strongly implying that cations exert their effect by interactions outside of the EF-hand loop region.

Amino Acid Sequence↗

PubMed2001

Peripheral T cells become sensitive to glucocorticoid- and stress-induced apoptosis in transgenic mice overexpressing SRG3.

Immature double-positive thymocytes are sensitive to glucocorticoid (GC)-induced apoptosis, whereas mature single-positive T cells are relatively resistant. Thymocytes seem to acquire resistance to GCs during differentiation into mature single-positive thymocytes. However, detailed knowledge concerning what determines the sensitivity of thymocytes to GCs and how GC sensitivity is regulated in thymocytes during development is lacking. We have previously reported that the murine SRG3 gene (for SWI3-related gene) is required for GC-induced apoptosis in a thymoma cell line. Herein, we provide results suggesting that the expression level of SRG3 protein determines the GC sensitivity of T cells in mice. SRG3 associates with the GC receptor in the thymus, but rarely in the periphery. Transgenic overexpression of the SRG3 protein in peripheral T cells induces the formation of the complex and renders the cells sensitive to GC-induced apoptosis. Our results also show that blocking the formation of the SRG3-GC receptor complex with a dominant negative mutant form of SRG3 decreases GC sensitivity in thymoma cells. In addition, mice overexpressing the SRG3 protein appear to be much more susceptible to stress-induced deletion of peripheral T cells than normal mice, which may result in an immunosuppressive state in an animal.

Animals↗

PubMed2001

Role of T-bet in commitment of TH1 cells before IL-12-dependent selection.

How cytokines control differentiation of helper T (TH) cells is controversial. We show that T-bet, without apparent assistance from interleukin 12 (IL-12)/STAT4, specifies TH1 effector fate by targeting chromatin remodeling to individual interferon-gamma (IFN-gamma) alleles and by inducing IL-12 receptor beta2 expression. Subsequently, it appears that IL-12/STAT4 serves two essential functions in the development of TH1 cells: as growth signal, inducing survival and cell division; and as trans-activator, prolonging IFN-gamma synthesis through a genetic interaction with the coactivator, CREB-binding protein. These results suggest that a cytokine does not simply induce TH fate choice but instead may act as an essential secondary stimulus that mediates selective survival of a lineage.

Alleles↗

PubMed2001

Suppression by a sesquiterpene lactone from Carpesium divaricatum of inducible nitric oxide synthase by inhibiting nuclear factor-kappaB activation.

Excessive nitric oxide (NO) produced by inducible NO synthase (iNOS) acts as a causative regulator in various inflammatory disease states. Carpesium divaricatum has been used in Korean traditional herbal medicine for its antipyretic, analgesic, vermifugic, and anti-inflammatory properties. We investigated the molecular mechanism for the suppression of lipopolysaccharide/interferon-gamma (LPS/IFN-gamma)-induced NO production in RAW 264.7 macrophages by the sesquiterpene lactone 2beta,5-epoxy-5,10-dihydroxy-6alpha-angeloyloxy-9beta-isobutyloxy-germacran-8alpha,12-olide (C-1), which has been identified recently as a new compound from C. divaricatum. C-1 decreased NO production in LPS/IFN-gamma-stimulated RAW 264.7 cells in a concentration-dependent manner, with an IC50 of approximately 2.16 microM; however, it had no direct effect on the iNOS activity of fully LPS/IFN-gamma-stimulated RAW 264.7 cells. Furthermore, treatment with C-1 led to a decrease in iNOS protein and mRNA. These effects appear to be due to inhibition of nuclear factor-kappaB (NF-kappaB) activation through a mechanism involving stabilization of the NF-kappaB/inhibitor of the kappaB (I-kappaB) complex, since inhibition of NF-kappaB DNA binding activity by C-1 was accompanied by a parallel reduction of nuclear translocation of subunit p65 of NF-kappaB and I-kappaBalpha degradation. Taken together, the results suggest that the ability of C-1 to inhibit iNOS gene expression may be responsible, in part, for its anti-inflammatory effects.

Animals↗

PubMed2001

F508 amino acid deletion mutation of CFTR gene in Korean lung cancer patients.

Mutations of the transmembrane conductance regulator (CFTR) gene in cystic fibrosis lead to dysfunction of the lung, pancreas, and sweat glands, etc. To investigate the possibility of the relationship between lung cancer and the mutations of CFTR gene, we determined amino acid sequences using reverse transcription-polymerase chain reaction (RT-PCR) and DNA sequencing. In this study, the deletion mutation of 508th amino acid in one of nine lung caner patients was found confirming that CFTR gene mutation exists in a Korean lung cancer patient.

Adult↗

PubMed2001

Constitutive expression of c-myb mRNA in the adult rat brain.

In this study, we demonstrated the c-myb mRNA expression in the adult rat brain using an in situ hybridization technique. We found c-myb mRNA signals in the various regions of the forebrain and midbrain including the cerebral cortex, thalamus, hippocampus, hypothalamus, superior and inferior colliculi and central gray. In the cerebellum, a diffuse signal was found in the granular layer while some positive cells were detected in the molecular layer as well. In addition, a number of cells showed intense signals in many nuclei of the medulla oblongata. The constitutive expression of c-myb mRNA in the different kinds of neural cells suggests that this gene might be involved in the normal function of these neurons.

Animals↗

PubMed2001

Purification and characterization of protein methylase II from Helicobacter pylori.

Protein methylase II (AdoMet:protein-carboxyl O-methyltransferase, EC 2.1.1.24) was identified and purified 115-fold from Helicobacter pylori through Q-Sepharose ion exchange column, AdoHcy-Sepharose 4B column, and Superdex 200 HR column chromatography using FPLC. The purified preparation showed two protein bands of about 78 kDa and 29 kDa molecular mass on SDS-PAGE. On non-denaturing gel electrophoresis, the enzyme migrated as a single band with a molecular mass of 410 kDa. In addition, MALDI-TOF-MS analysis and Superdex 200 HR column chromatography of the purified enzyme showed a major mass signal with molecular mass values of 425 kDa and 430 kDa, respectively. Therefore, the above results led us to suggest that protein methylase II purified from H. pylori is composed of four heterodimers with 425 kDa (4x(78+29)=428 kDa). This magnitude of molecular mass is unusual for protein methylases II so far reported. The enzyme has an optimal pH of 6.0, a K(m) value of 5.0x10(-6) M for S-adenosyl-L-methionine and a V(max) of 205 pmol methyl-(14)C transferred min(-1) mg(-1) protein.

Amino Acid Sequence↗

PubMed2001

Islet cell autoimmunity and mitochondrial DNA mutation in Korean subjects with typical and atypical Type I diabetes.

AIMS/HYPOTHESIS: The 1997 American Diabetes Association classification of diabetes mellitus included a subset of Type I diabetic patients who do not need insulin for several years but eventually progress to complete insulin deficiency i. e. atypical Type I diabetes mellitus. In Caucasian populations, most Type I diabetic patients have auto-antibodies against islet cells. We examined the frequency of the auto-antibodies against islet cells and mitochondrial DNA 3243 mutation in Koreans with typical and atypical Type I diabetes mellitus. METHODS: We measured plasma C-peptide level in 1870 consecutive Korean diabetic patients. Of these, 56 patients had insulin deficiency (fasting and glucagon-stimulated plasma C-peptide concentrations < or = 0.2 nmol/l and < or = 0.32 nmol/l, respectively), and they were subdivided into typical (n = 26) and atypical Type I (insulin-dependent) diabetes mellitus (n = 30) according to clinical manifestation. Islet cell antibody was measured by indirect immunofluorescence. Anti-GAD antibody and anti-ICA512 antibody were measured by radioimmunoassay. Mitochondrial DNA 3243 mutation was detected using restriction enzyme Apa-I digestion of the amplified genomic DNA. RESULTS: The overall prevalence of auto-antibodies in the typical and atypical groups was 77% and 57%, respectively. Mitochondrial DNA 3243 mutation was found in 3 out of 30 (10%) of atypical Type I (insulin-dependent) diabetic patients but not in typical Type I (insulin-dependent) diabetic patients. CONCLUSION/INTERPRETATION: Autoimmunity might not be the only cause of progressive insulin deficiency in Koreans. Mitochondrial DNA mutation is another identifiable cause but the cause(s) of insulin deficiency in the remainder of Type I diabetic patients without autoimmunity is not clear.

Adolescent↗