Hak Sung Lee

Seoul National University, Sŏul, Seoul, South Korea

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Publications (51)71.26 Total impact

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    ABSTRACT: Epigalloccatechin-3-gallate (EGCG) is the main polyphenol component of green tea (leaves of Camellia sinensis). EGCG is known for its antioxidant, anti-inflammatory, antiviral, and anti-carcinogenic properties. Here, we identify EGCG as a new inhibitor of ocular angiogenesis and its vascular permeability. Matrix metalloproteinases (MMPs) and vascular endothelial growth factor (VEGF) play a key role in the processes of extracellular matrix (ECM) remodeling and microvascular permeability during angiogenesis. We investigated the inhibitory effects of EGCG on ocular neovascularization and vascular permeability using the retina oriented cells and animal models induced by VEGF and alkaline burn. EGCG treatment significantly decreased mRNA and protein expression levels of MMP-9 in the presence of 12-O-tetradecanoylphorbol-13-acetate (TPA) and tumor necrosis factor alpha (TNF-α) in human retinal pigment epithelial cells (HRPECs). EGCG also effectively protected ARPE-19 cells from cell death and attenuated mRNA expressions of key angiogenic factors (MMP-9, VEGF, VEGF Receptor-2) by inhibiting generation of reactive oxygen species (ROS). EGCG significantly inhibited proliferation, vascular permeability, and tube formation in VEGF-induced human retinal microvascular endothelial cells (HRMECs). Furthermore, EGCG significantly reduced vascular leakage and permeability by blood-retinal barrier breakdown in VEGF-induced animal models. In addition, EGCG effectively limited upregulation of MMP-9 and platelet endothelial cell adhesion molecule (PECAM/CD31) on corneal neovascularization (CNV) induced by alkaline burn. Our data suggest that MMP-9 and VEGF are key therapeutic targets of EGCG for treatment and prevention of ocular angiogenic diseases such as age-related macular degeneration, diabetic retinopathy, and corneal neovascularization.
    Molecules 08/2014; 19(8):12150-72. DOI:10.3390/molecules190812150 · 2.42 Impact Factor
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    ABSTRACT: The aim of this study was to examine the effect of standardized extract of Salvia miltiorrhiza (SME) on gene and protein expression of non-alcoholic steatohepatitis (NASH)-related factors in activated human hepatic stellate cells (HSC), and in mice with steatohepatitis induced by a methionine-choline deficient (MCD) diet. Male C57BL/6J mice were placed on an MCD or control diet for 8 weeks and SME (0, 0.1, 0.5 and 1 mg/kg body weight) was administered orally every other day for 4 or 6 weeks. HSCs from the LX-2 cell line were treated with transforming growth factor β-1 (TGF-β1) or TGF-β1 plus SME (0.1-10 μg/mL). To investigate the effect of SME on reactive oxygen species (ROS)-induced condition, LX-2 cells were treated with hydrogen peroxide (H2O2) or H2O2 plus SME (0.1-100 μg/mL). MCD administration for 12 weeks increased mRNA expression of tumor necrosis factor (TNF-α), TGF-β1, interleukin-1β (IL-1β), C-reactive protein (CRP), α-smooth muscle actin (α-SMA), type I collagen, matrix metalloproteinase-2 (MMP-2) and MMP-9. TGF-β1-induced LX-2 cells exhibited similar gene expression patterns. SME treatment significantly reduced the mRNA and protein expression of NASH-related factors in the mouse model and HSCs. Histopathological liver analysis showed improved non-alcoholic fatty liver disease (NAFLD) activity and fibrosis score in SME-treated mice. The in vivo studies showed that SME had a significant effect at low doses. These results suggest that SME might be a potential therapeutic candidate for NAFLD treatment.
    Molecules 06/2014; 19(6):8189-211. DOI:10.3390/molecules19068189 · 2.42 Impact Factor
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    ABSTRACT: In this study, mesoporous titanosilicate (MTS)/reduced graphene oxide (RGO) composite materials were prepared as a function of the RGO content and used as novel adsorbents for a mixed-solute solution of methylene blue and rhodamine B (RhB). Adsorption capacities of the composite materials were higher than those of MTS or RGO by themselves, demonstrating that adsorptive performances of the composite materials are better than the inorganic or organic materials alone. Composite material containing 20 wt% RGO (20MTSG) showed the best adsorption capacity for both contaminants where its adsorptive behavior in the mixed-solute solution can be ascribed to the unique morphology of the large layered structure of MTS and RGO, as well as many aggregates of small-sized plates. Compared to the other composite materials, 20MTSG contained an abundant edge structure of RGO, resulting in a relatively higher RhB adsorption capacity. RhB preferred the adsorption sites on RGO to the adsorption sites on MTS due to steric hindrance inside the mesopores of MTS.
    Environmental Engineering Science 03/2014; 31(3):148-155.. DOI:10.1089/ees.2013.0303. · 0.93 Impact Factor
  • Byung-Wook Kang, Jun-Min Jeon, Hak Sung Lee
    02/2014; 30(1):18-25. DOI:10.5572/KOSAE.2014.30.1.018
  • 10/2012; 28(5):595-605. DOI:10.5572/KOSAE.2012.28.5.595
  • Hak Sung Lee, Jung Ho Suh
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    ABSTRACT: Continuous biosorption process for removal of lead and copper by laboratory scale fixed-bed reactor was carried out using Ca-loadedLaminaria japonica. All biosorption processes were observed as cation exchange such as Pb2+ vs. Ca2+, Cu2+ vs. Ca2+, and Pb2+ vs. Cu2+. The affinity of lead ions towardsL. japonica was stronger than that of copper ions because the initial amount of desorbed Cu2+ in Cu-Pb system was higher than that of eluted Pb2+ in Pb-Cu system.
    Korean Journal of Chemical Engineering 04/2012; 17(4):477-479. DOI:10.1007/BF02706864 · 1.24 Impact Factor
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    ABSTRACT: Many natural compounds have been investigated as drug candidates to prevent human immunodeficiency virus (HIV) with low cytotoxicity. We tested whether ingenol from Euphorbia ingens exerts anti-HIV effects in human T cell lines. Ingenol effectively maintained high cell viability (CD50, >1 mM) in H9 and MT4 T cells. The efficacy of ingenol to inhibit HIV-1 infection was dose dependent. ED50 for 100 and 200 TCID50 of HIV-1 was 5.06 and 16.87 μM, respectively. Gag p24 antigen production in ingenol-treated MT4 cells was reduced by 24.5% on day 6 post-infection. While p24 antigen was reduced in ingenol-treated cells, levels of cytokines such as TNF-α and IL-6 and chemokines such as RANTES and MCP-1 were increased. dUTP level related to late apoptotic events was increased on day 2 post-infection of HIV by ingenol treatment, whereas expression of annexin V was unchanged. Reduced levels of iNOS and ZAP-70 after HIV infection were recovered by ingenol treatment. Ingenol helps T cells to survive longer against viremia after HIV-1 infection, without exerting cytotoxic effects. Ingenol can be considered a safe and efficacious candidate for immune-boosting therapy for AIDS patients.
    09/2011; 2(2):109-14. DOI:10.1016/j.phrp.2011.07.001
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    ABSTRACT: HIV-1 specific cytotoxic T lymphocytes (CTLs) have an important role as antiviral effector cells for controlling HIV-1 infection. To investigate CTL response during the early stage of HIV infection, we measured immunity-related factors including CD4+ T cell counts, CD8+ T cell counts, HIV-1 RNA viral loads and IFN-γ secretion according to CTL response in 78 selected primary HIV-1-infected Koreans. The CTL response was strongly induced by HIV-1 specific Gag and Nef peptides (p = 0.016) compared with induction by Tat or Env peptides. These results suggest that the major antiviral factors inducing strong HIV-specific CTL responses are associated with the Gag and Nef viral regions in primary HIV-1 infected Koreans. The relationship between viral load and CTL response showed varying correlations with time following HIV infection. CTL response was inversely correlated with viral loads at preseroconversion stage I (r = -0.224 to -0.33) and changed to a positive correlation at the preseroconversion stage II (r = 0.132 to 0.854). Finally, it changed to an inverse correlation again after seroconversion until a viral set point was established on serological profiling (r = -0.195 to -0.407). These findings demonstrate a dynamic correlation between viral load and subsequent CTL responses during early HIV infection.
    Virology Journal 09/2010; 7:239. DOI:10.1186/1743-422X-7-239 · 2.09 Impact Factor
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    ABSTRACT: We prepared La-impregnated mesoporous silicates to investigate the adsorption of tetracycline in aqueous solution. Nitrogen adsorption-desorption isotherm tests confirmed the mesoporosity of the prepared materials, resulting in a decline in surface area and pore volume along with La loading amount. In adsorption tests, however, La impregnation improved the adsorption capacity of materials for tetracycline even though the surface area and the pore volumes were lower after La impregnation. Adsorption capacities for tetracycline showed a maximum value with La loading amounts. The highest adsorption capacity for tetracycline was 303.3 mg g(-1), which was acquired from the fitting of isotherm data of 10 wt% La-impregnated mesoporous silicates to the Langmuir model. Changes in FTIR patterns of tetracycline adsorbed on La-impregnated mesoporous silicates implied that the negatively charged oxygen of the tricarbonylamide group of tetracycline chemically interacted with La hydroxide species in materials in the neutral condition.
    Environmental Technology 03/2010; 31(3):233-41. DOI:10.1080/09593330903453210 · 1.20 Impact Factor
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    ABSTRACT: Histone deacetylase plays an important role in HIV latency. Novel histone deacetylase inhibitors, CG05 and CG06, were evaluated for their roles in HIV latency using ACH2 cells. Both inhibitors were highly efficient in reactivation of provirus and exerted lesser toxicity compared with other known histone deacetylase inhibitors. Histone acetylation increased when proviruses were reactivated by the compounds. These new inhibitors may contribute to the reduction of the HIV reservoir when used in conjunction with highly active antiretroviral therapy.
    AIDS (London, England) 02/2010; 24(4):609-11. DOI:10.1097/QAD.0b013e328333bfa1 · 6.56 Impact Factor
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    ABSTRACT: We prepared Fe-impregnated mesoporous silicates to investigate the adsorption of tetracycline in aqueous solution. Mesoporous silicates with different Fe content (5, 10, 30, 50 wt%) were prepared by an incipient wetness method. Adsorption kinetics for tetracycline showed that Fe-impregnation improved the adsorption ability for tetracycline. By fitting the adsorption kinetic data to a pseudo second-order model, we obtained a maximum adsorption amount of tetracycline with Fe30SBA-15 (30 wt% Fe-impregnated mesoporous silicates) at 41.7 mg/g. The pH dependency of tetracycline adsorption exhibited a volcano curve where the maximum adsorption onto the Fe30SBA-15 sample occurred in the neutral pH region. The introduction of Fe species into the SBA-15 revived the adsorption ability for tetracycline, whereas there was no interaction between tetracycline and SBA-15, a mesoporous silicate. These results suggest that impregnated Fe species produce an effective interaction with tetracycline in an aqueous system.
    Korean Journal of Chemical Engineering 01/2010; 27(1):116-120. DOI:10.1007/s11814-009-0313-5 · 1.24 Impact Factor
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    ABSTRACT: Aiming at improving the phase behavior of the OPVCs, we have designed and synthesized a series of C60 and C70 derivatives, which showed high electron mobility, electron affinity, and good solubility. These methanofullerene acceptor materials having ethyleneoxy substituent, PCBEs, were synthesized from the reaction of fullerene C60 or C70 with each hydrizide. Device performances of OPVC using the mixture of P3HT and PCBEs as an active layer were measured under illumination of 100 mW/cm2 AM 1.5G simulated light. Pristine OPVC using P3HT:compound 3 showed 2.59% of power conversion efficiency, which is much higher than 1.65% of pristine P3HT:PCBM device. The electrochemical and photophysical properties of these methanofullerene derivatives were examined by using cyclicvoltammetry and UV-Vis spectroscopy, respectively. We revealed that ethyleneoxy substituted methanofullerenes can be used as a good candidate for acceptor materials in OPVCs.
    Journal of Nanoscience and Nanotechnology 12/2009; 9(12):7034-8. DOI:10.1166/jnn.2009.1638 · 1.34 Impact Factor
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    ABSTRACT: Resistance to metronidazole (MTZ) in Helicobacter pylori is associated with mutations in rdxA, encoding an oxygen-insensitive NADPH nitroreductase, and mutations in frxA, encoding a NAD(P)H-flavin oxidoreductase. Despite this association, the strict correlation of MTZ resistance with mutations in rdxA or frxA is still controversial. In this study, rdxA allelic replacement was used to distinguish resistance-associated nucleotide mutations from the natural genetic diversity of H. pylori. Replacement with truncated rdxA resulted in MTZ resistance, whereas replacement with missense-mutated rdxA from resistant clinical isolates failed to yield MTZ resistance. Thus, although truncation of rdxA confers MTZ resistance in G27 H. pylori, MTZ resistance found in other clinical isolates is not due to the identified amino-acid substitutions. Three of our MTZ-resistant clinical isolates expressed functional rdxA and two of these also encoded full-length frxA. Therefore, MTZ resistance can arise in H. pylori possessing functional rdxA, suggesting that other factors are involved in MTZ resistance.
    The Journal of Antibiotics 02/2009; 62(1):43-50. DOI:10.1038/ja.2008.6 · 2.04 Impact Factor
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    ABSTRACT: Helicobacter pylori causes diseases ranging from gastritis to peptic ulcer disease to gastric cancer. Geographically, areas with high incidences of H. pylori infection often overlap with areas with high incidences of gastric cancer, which remains one of the leading causes of cancer-related deaths worldwide. Strains of H. pylori that carry the virulence factor cytotoxin-associated gene A (cagA) are much more likely to be associated with the development of gastric cancer. Moreover, particular C-terminal polymorphisms in CagA vary by geography and have been suggested to influence disease development. We conducted a large-scale molecular epidemiologic analysis of South Korean strains and herein report a statistical link between the East Asian CagA EPIYA-ABD genotype and the development of gastric cancer. Characterization of a subset of the Korean isolates showed that all strains from cancer patients expressed and delivered phosphorylatable CagA to host cells, whereas the presence of the cagA gene did not strictly correlate to expression and delivery of CagA in all noncancer strains.
    Journal of clinical microbiology 02/2009; 47(4):959-68. DOI:10.1128/JCM.02330-08 · 4.23 Impact Factor
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    ABSTRACT: We designed and synthesized methanofullerene derivatives with several types of thiophenyl mono-ketone for application in organic photovoltaic cells (OPVCs) as new accepter materials. The various mono-ketones having thiophene rings were substituted onto fullerene through application of Hirch-Bingel reaction under mild condition to compete with donor materials especially P3HT [Poly(3-hexylthiophene)] for nano-networking bulk-heterojunction structure where efficient light-induced charge separation is enable by a large-area donor-acceptor interface. The newly synthesized methanofullerene derivatives were characterized through H-NMR and FAB Mass spectroscopy. The compounds were also applied in OPV cell devices with P3HT as a donor material and measured electrochemical the property and power conversion efficiency.
    Molecular Crystals and Liquid Crystals 10/2008; 492(492). DOI:10.1080/15421400802330689 · 0.49 Impact Factor
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    ABSTRACT: The feasibility of novel 1,3-diketone modified C60s (compound 1 and 2) was studied as acceptor materials in organic photovoltaic cells (OPVC). 1,3-Diketone modified fullerenes were synthesized by the addition reaction of 1,3-bis(5'-hexylthiophen-2'-yl)propane-1,3-dione with C60 in the presence of DBU (1,8-diazabicyclo[5,4,0]undec-7-ene). From this procedure two products can be prepared, which are mono- (1) and di-substituted compound (2) in the yield of 40% and 17%, respectively. OPVCs fabricated by using the mixture of P3HT and compound 1 as an active layer showed excellent power conversion efficiency of about 3.42% after annealed at 160 degrees C for 15 min and we believe that substantial improvements can be realized by nano-structured heterojunction. It was demonstrated that 1,3-diketone modified C60 (compound 1) was one of the promising candidates for acceptor materials for OPVCs.
    Journal of Nanoscience and Nanotechnology 10/2008; 8(9):4533-7. DOI:10.1166/jnn.2008.IC03 · 1.34 Impact Factor
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    ABSTRACT: Electric power equipment must be operated in the state of high reliability with its responsibility in the seamless power supply. Therefore, persistent maintenance is very important. There are many maintenance methods well known in industrial business. Among them, the reliability-centered maintenance (RCM) is a state of the art maintenance technique. This paper shows a RCM method for electric power equipments. This reliability-centered maintenance (RCM) has been applied in the fields of aerospace, nuclear power plants and rail system, etc. In this paper, we design the FMEA flow for power transformer and evaluate the importance level based on the fault information. The importance level is applied to the inspection period, fault detection method and operator selection. The results of the system are provided as a worksheet containing the information that needs to be maintained.
    Condition Monitoring and Diagnosis, 2008. CMD 2008. International Conference on; 05/2008
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    ABSTRACT: As the recent trend of the monitoring and diagnosis technique for high-voltage GIS, many power industrial companies are researching and developing on-line preventive and diagnosis system of PD (partial discharge) for GIS. In succession of high-voltage class, the demand in transmission and distribution class is increasing and the scope of its application is spreading. Thus, we developed on-line iPDM (intelligent partial discharge monitoring) system for 25.8 kV cubicle-GIS (C-GIS). We are briefly introduced the configuration of on-line iPDM system using UHF methods for effectively diagnosing the insulation condition of C-GIS. For the internal UHF sensor, we designed the novel model with high sensitivity and checked experiment results as antenna performance factor. Comparing of ERA method and UHF method, the relationship between pC-dBm is described based on experimental results. The measured data is converted to frequency domain data and we can search the frequency with peak value except external noise. And then input data of ANN (artificial neural network) model is made from normalized zero span data. Finally, our expert system can judge the risk level from PD magnitude and its cause. In this paper, we will describe the development results and the actual experience of the on-line iPDM system for C-GIS in KOREA.
    Condition Monitoring and Diagnosis, 2008. CMD 2008. International Conference on; 05/2008
  • Antiviral Research 05/2008; 78(2). DOI:10.1016/j.antiviral.2008.01.085 · 3.94 Impact Factor
  • Antiviral Research 05/2008; 78(2):A40–A41. DOI:10.1016/j.antiviral.2008.01.077 · 3.94 Impact Factor

Publication Stats

495 Citations
71.26 Total Impact Points

Institutions

  • 2011–2014
    • Seoul National University
      • • Natural Products Research Institute
      • • Department of Pharmacology
      Sŏul, Seoul, South Korea
  • 1997–2014
    • University of Ulsan
      • Department of Chemical Engineering
      Urusan, Ulsan, South Korea
    • McGill University
      • Department of Chemical Engineering
      Montréal, Quebec, Canada
  • 2009
    • Catholic University of Korea
      • Department of Internal Medicine
      Sŏul, Seoul, South Korea
  • 2008
    • The Seoul Institute
      Sŏul, Seoul, South Korea
    • Yonsei University
      • Department of Chemistry
      Sŏul, Seoul, South Korea
  • 2006
    • Harvard University
      Cambridge, Massachusetts, United States
  • 2004–2005
    • Chung-Ang University
      • Department of Systems Biotechnology
      Seoul, Seoul, South Korea
  • 1997–2005
    • Seowon University
      Seishō-gun, Gyeongsangbuk-do, South Korea
  • 2001–2004
    • Ulsan College
      Urusan, Ulsan, South Korea
  • 1989
    • Pusan National University
      • Department of Polymer Science and Engineering
      Tsau-liang-hai, Busan, South Korea