• Proceedings of the Korean Society of Life Science Conference
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• 2008.10a
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• pp.63.2-63.2
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• 2008

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3441-3444
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• 2010

• 한국균학회소식:학술대회논문집
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• 2015.05a
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• pp.15-15
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• 2015

Aspergillus fumigatus is a major cause of invasive aspergillosis (IA), a significant health issue worldwide with high mortality rates up to 95%. Our lab is interested in how A. fumigatus adapts to low oxygen conditions 'hypoxia', which is one of the important host microenvironments. A. fumigatus SrbA is a basic helix-loop-helix (bHLH) transcriptional regulator and belongs to sterol regulatory element binding protein (SREBP) family members. Loss of SrbA completely blocks growth in hypoxia and results in avirulence in murine models of IA suggesting an essential role of SrbA in hypoxia adaptation and virulence in A. fumigatus. We conducted chromatin immunoprecipitation sequencing (ChIP-seq) with A. fumigatus wild type using a SrbA specific antibody, and 97 genes were revealed as SrbA direct targets. One of the 'SrbA regulons' (AFUB_099590) was a putative bHLH transcriptional regulator whose sequence contained a characteristic tyrosine substitution in the basic portion of the bHLH domain of SREBPs. Therefore, we designated AFUB_099590 SrbB. Further characterization of SrbB demonstrated that SrbB is important for radial growth, biomass production, and biosynthesis of heme intermediates in hypoxia and virulence in A. fumigatus. A series of quantitative real time PCR showed that transcription of several SrbA regulons is coordinately regulated by two SREBPs, SrbA and SrbB in hypoxia. This suggests that SrbA and SrbB have both dependent and independent functions in regulation of genes responsible for hypoxia adaptation in A. fumigatus. Together, our data provide new insights into complicated roles of SREBPs in adaptation of host environments and virulence in pathogenic fungi.

• Journal of The Korean Dental Society of Anesthesiology
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• v.14 no.1
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• pp.49-56
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• 2014

Background: Propofol (2.6-diisopropylphenol) is a widely used intravenous anesthetic agent for the induction and maintenance of anesthesia during surgeries and sedation for ICU patients. Propofol has a structural similarity to the endogenous antioxidant vitamin E and exhibits antioxidant activities.13) However, the mechanism of propofol on hypoxia/reoxygenation (H/R) injury has yet to be fully elucidated. We investigated how P-PostC influences the autophagy and cell death, a cellular damage occurring during the H/R injury. Methods: The groups were randomly divided into the following groups: Control: cells were incubated in normoxia (5% CO2, 21% O2, and 74% N2) without propofol treatment. H/R: cells were exposed to 24 h of hypoxia (5% CO2, 1% O2, and 94% N2) followed by 12 h of reoxygenation (5% CO2, 21% O2, and 74% N2). H/R + P-PostC: cells post-treated with propofol were exposed to 24 h of hypoxia followed by 12 h of reoxygenation. 3-MA + P-PostC: cells pretreated with 3-MA and post-treated propofol were exposed to 24 h of hypoxia followed by 12 h of reoxygenation Results: The results of our present study provides a new direction of research on mechanisms of propofol-mediated cytoprotection. There are three principal findings of these studies. First, the application of P-PostC at the onset of reoxygenation after hypoxia significantly increased COS-7 cell viability. Second, the cellular protective effect of P-PostC in H/R induced COS-7 cells was probably related to activation of intra-cellular autophagy. And third, the autophagy pathway inhibitor 3-MA blocked the protective effect of P-PostC on cell viability, suggesting a key role of autophagy in cellular protective effect of P-PostC. Conclusions: These data provided evidence that P-PostC reduced cell death in H/R model of COS-7 cells, which was in agreement with the protection by P-PostC demonstrated in isolated COS-7 cells exposed to H/R injury. Although the this study could not represent the protection by P-PostC in vivo, the data demonstrate another model in which endogenous mechanisms evoked by P-PostC protected the COS-7 cells exposed to H/R injury from cell death.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.1
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• pp.65-74
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• 2020

The purpose of this study was to investigate the physical characteristics of marine environment, and to predict the probability of the occurrence of hypoxia in the Dangdong bay. We predicted hypoxia using the logistic regression model analysis by observing the water temperature, salinity, and dissolved oxygen concentration. The analysis showed that the Brunt-Väisälä frequency which was shallow than the deep bay entrance, was higher inside the bay due to a lesser amount of fresh water inflow from the inner side of the bay, and density stratification was formed. The Richardson number, and Brunt-Väisälä frequency were very high occasionally from June to September; however, after September 2, the stratification had a tendency to decrease. Analysis of dissolved oxygen, water temperature, and salinity data observed in Dangdong bay showed that the dissolved oxygen concentration in the bottom layer was mostly affected by the temperature difference (dt) between the surface layer and bottom layer. Meanwhile, when the depth difference (dz) was set as a fixed variable, the probability of the occurrence of hypoxia varied with respect to the difference in water temperature. The depth difference (dz) was calculated to be 5 m, 10 m, 15 m, 20 m, and the difference in water temperature (dt) was found to be greater than 70 % at 8℃, 7℃, 5℃, and 3℃. This indicated that the larger the difference in depth in the bay, the smaller is the temperature difference required for the generation of hypoxia. In particular, the place in the bay, where the water depth dif erence was approximately 20 m, was found to generate hypoxia.

• Biomolecules & Therapeutics
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• v.26 no.5
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• pp.487-493
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• 2018

Cluster of differentiation 44 (CD44), a cell surface receptor for hyaluronic acid (HA), is involved in aggressive cancer phenotypes. Herein, we investigated the role of the CD44 standard isoform (CD44s) in hypoxia-inducible $factor-1{\alpha}$ ($HIF-1{\alpha}$) regulation using MCF7 overexpressing CD44s (pCD44s-MCF7). When pCD44s-MCF7 was incubated under hypoxia, levels of $HIF-1{\alpha}$, vascular endothelial growth factor, and the $HIF-1{\alpha}$ response element-derived luciferase activity were significantly increased compared to those in the control MCF7. Incubation of pCD44s-MCF7 cells with HA further increased $HIF-1{\alpha}$ accumulation, and the silencing of CD44s attenuated $HIF-1{\alpha}$ elevation, which verifies the role of CD44s in $HIF-1{\alpha}$ regulation. In addition, the levels of phosphorylated extracellular signal-regulated kinase (ERK) was higher in hypoxic pCD44s-MCF7 cells, and $HIF-1{\alpha}$ accumulation was diminished by the pharmacological inhibitors of ERK. CD44s-mediated $HIF-1{\alpha}$ augmentation resulted in two functional outcomes. First, pCD44s-MCF7 cells showed facilitated cell motility under hypoxia via the upregulation of proteins associated with epithelial-mesenchymal transition, such as SNAIL1 and ZEB1. Second, pCD44s-MCF7 cells exhibited higher levels of glycolytic proteins, such as glucose transporter-1, and produced higher levels of lactate under hypoxa. As a consequence of the enhanced glycolytic adaptation to hypoxia, pCD44s-MCF7 cells exhibited a higher rate of cell survival under hypoxia than that of the control MCF7, and glucose deprivation abolished these differential responses of the two cell lines. Taken together, these results suggest that CD44s activates hypoxia-inducible $HIF-1{\alpha}$ signaling via ERK pathway, and the $CD44s-ERK-HIF-1{\alpha}$ pathway is involved in facilitated cancer cell viability and motility under hypoxic conditions.

• Journal of Life Science
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• v.23 no.10
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• pp.1223-1229
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• 2013

Ursolic acid (UA) a bio-active ingredient found in a variety of fruits and vegetables, and it has potent antioxidant activity. However, the role of UA in mouse embryonic stem (ES) cells is poorly understood. This study investigated the functional role of UA in regulating the development of mouse ES cells under hypoxia. Hypoxia did not exert a significant effect on the undifferentiated state of mouse ES cells. However, it induced reactive oxygen species (ROS) generation and increased the level of lactate dehydrogenase (LDH) production at 48 h of hypoxic exposure. Conversely, oxidative stress induced by hypoxia was significantly inhibited by UA ($30{\mu}M$) pretreatment. Hypoxia significantly decreased cell survival and the level of [$^3H$] thymidine incorporation, both of which recovered following pretreatment of UA. In addition, UA decreased the apoptotic effect of hypoxia by attenuating caspase-3 cleavage or by recovering cellular inhibition of the apoptotic protein (cIAP)-2 and Bcl-2 expression. We further found that UA decreased senescence-associated beta-galactosidase activity. We suggest that UA is a natural antioxidant and one of the functional modulators of hypoxia-induced survival, apoptosis, proliferation, and aging in mouse ES cells.

• International Journal of Oral Biology
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• v.39 no.2
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• pp.97-105
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• 2014

The aim of this study was to determine the beneficial effect of propofol on human keratinocytes that have undergone hypoxia reoxygenation (H/R) injury and to investigate whether autophagy is associated with the protective mechanism. Thus, we evaluated how propofol influences the intracellular autophagy and apoptosis during the H/R process in the HaCaT cells. The cultured human keratinocyte cells were exposed to 24 h of hypoxia (5% $CO_2$, 1% $O_2$, 94% $N_2$) followed by 12 h of reoxygenation (5% $CO_2$, 21% $O_2$, 74% $N_2$). The experiment was divided into 4 groups: (1) Control=Normoxia ; (2) H/R=Hypoxia Reoxygenation ; (3) PPC+H/R=Propofol Preconditioning+Hypoxia Reoxygenation; (4) 3-MA+PPC+ H/R=3-MA-Methyladenine+Propofol Preconditioning+ Hypoxia Reoxygenation. In addition, Western blot analysis was performed to identify the expression of apoptotic pathway parameters, including Bcl-2, Bax, and caspase 3 involved in mitochondrial-dependent pathway. Autophagy was determined by fluorescence microscopy, MDC staining, AO staining, and western blot. The H/R produced dramatic injuries in keratinocyte cells. In our study, the viability of Propofol in H/R induced HaCaT cells was first studied by MTT assay. The treatment with 25, 50, and $100{\mu}M$ Propofol in H/R induced HaCaT cells enhanced cell viability in a dose-dependent manner and $100{\mu}M$ was the most effective dose. The Atg5, Becline-1, LC3-II, and p62 were elevated in PPC group cells, but H/R-induced group showed significant reduction in HaCaT cells. The Atg5 were increased when autophagy was induced by Propofol, and they were decreased when autophagy was suppressed by 3-MA. These data provided evidence that propofol preconditioning induced autophagy and reduced apoptotic cell death in an H/R model of HaCaT cells, which was in agreement with autophagy playing a very important role in cell protection.

• The Journal of Korean Medicine
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• v.23 no.3
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• pp.145-163
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• 2002

Objectives: The purpose of this investigation was to evaluate the effects of Woohwangcheongsim-won and to study the mechanism for neuronal death protection in hypoxia with Embryonic day 20 (E20) cortical cells of a rat (Sprague Dawley). Methods: E20 cortical cells were dissociated in neurobasal media and grown for 14 days in vitro (DIV). On 14 DIV, Woohwangcheongsim-won was added to the culture media for 24 hrs or 72 hrs. On 17 DIV, cells were given a hypoxic shock and further incubated in normoxia for another three days. On 20 DIV, Woohwangcheongsim-won's effects for neuronal death protection were evaluated by LDH assay, propidium iodide stain and phospho-H2AX immunostain and the mechanisms were studied by Bcl-2, Bak, Bax, caspase family, PKCα, ca1pain I. Results & Conclusions : 1. This study indicated that Woohwangcheongsim-won's effects for neuronal death protection in hypoxia were confirmed by LDH assay, propidium iodide stain and phospho-H2AX immunostain in culture method of Embryonic day 20(E20) cortical neuroblasts. 2. Woohwangcheongsim-won's mechanisms for neuronal death protection in hypoxia are to reduce the membrane damage fraction, to restrain DNA truncate, to restrain inflow of cytochrome c into cellularity caused by Bak diminution, to reduce the caspase cascade intiator caspase-8 and the effector caspase-3, to reduce the calpain I activity and to increase PKCand its activity in the membrane fraction. (J Korean Oriental Moo 2002;23(3):145～163)

• Biomolecules & Therapeutics
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• v.7 no.4
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• pp.315-321
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• 1999

Since it has been known that hypoxia increases inducible nitric oxide synthase (iNOS) gene expression through hypoxia responsive element, it was possible to establish the hypothesis that nitric oxide could be a mediator of hypoxia to inhibit Cyplal promoter activity. In order to test this hypothesis, we have undertaken the study to examine the effects of hypoxia and nitric oxide on Cyplal promoter activity in Hepa I cells. Mouse Cyplal 5'flanking DNA, 1.6 Kb was cloned into pGL3 expression vector in order to construct pmCyplal-Luc. Hepa I cells were transfected with pmCyplal-Luc and were treated with $10^{-9}$ M TCDD and nitric oxide producing agents, such as lipopolysaccharide(LPS), sodium nitroprusside (SNP). Luciferase activity of reporter gene was measured from pmCyplal-Luc transfected Hepa I cell lysate which contains 2 g total protein using luciferin as a substrate. Nitric oxide producing agents, such as lipopolysaccharide (LPS), sodium nitroprusside(SNP) showed inhibition of luciferase activity that was induced by $10^{-9}$M TCDD treatment with dose dependent manner. Concomitant treatment of 1mM $N^G$-nitro-ι-arginine with $10^{-6}$~$10^{-4}$M sodium nitro-prusside recovered luciferase activity from the TCDD induced luciferase activity that was inhibited by nitric oxide producing agents. These demonstrated that nitric oxide could be a mediator of inhibitors on dioxin induced Cyplal expression in Hepa I cells.