Publications by authors named "Sun-Kyun Yoo"

9 Publications

  • Page 1 of 1

Submerged monoxenic culture medium development for Heterorhabditis bacteriophora and its symbiotic bacterium Photorhabdus luminescens: protein sources.

J Microbiol Biotechnol 2011 Aug;21(8):869-73

KAFCO Biochemistry Research Institute, Choogchung, Mokwon Uniersity, Daejeon 302-729, Korea.

Most medium formulations for improving culture of entomopathogenic nematodes (EPN) based on protein sources have used enriched media like animal feed such as dried egg yolk, lactalbumin, and liver extract, among other ingredients. Most results, however, showed unstable yields and longer production time. Many of the results do not show the detailed parameters of fermentation. Soy flour, cotton seed flour, corn gluten meal, casein powder, soytone, peptone, casein hydrolysates, and lactalbumin hydrolysate as protein sources were tested to determine the source to support optimal symbiotic bacteria and nematode growth. The protein hydrolysates selected did not improve bacterial cell mass compared with the yeast extract control, but soy flour was the best, showing 75.1% recovery and producing more bacterial cell number (1.4×10⁹/ml) than all other sources. The highest yield (1.85×10⁵ IJs/ml), yield coefficient (1.67×10⁶ IJs/g medium), and productivity (1.32×10⁷ IJs/l/day) were also achieved at enriched medium with soybean protein.
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http://dx.doi.org/10.4014/jmb.1010.10055DOI Listing
August 2011

Preparation of branched dextran microspheres of soluble interferon-alpha and its activity in vitro and in vivo.

J Microbiol Biotechnol 2011 Feb;21(2):176-82

Department of Medical Genetic Engineering, Keimyung University School of Medicine, Daegu 700-712, Korea.

The study objective was to prepare biodegradable branched dextran microspheres encapsulated with His-tagged interferon-alpha (BDM-hIFN-alpha) and evaluate its activity in vitro and in vivo. The glycidyl methacrylate derivatized dextrans (Dex-GMA) as precursor was primarily synthesized by substituting hydroxyl groups of either the branched or linear type of dextran with GMA. Dex-GMA microspheres loaded with hIFN-alpha was then prepared by the water-in-water emulsion technique. In vitro release and Western blotting experiments demonstrated the retained activity of hIFN-alpha released from branched dextran microspheres at 24 h by inducing phosphorylation of signal transducer and activator transcription-1 (STAT-1), a down-stream effector of IFN-alpha, in HepG2 cells. Animal data further revealed a peak of plasma levels of IFN-alpha in rats injected intravenously with BDM-hIFN-alpha at 10 min post-injection, but a sharp decline at 2 h. High plasma levels of neopterin, a plasma protein induced by IFN-alpha, were also detected in rats injected with BDM-hIFN-alpha at 10 min post-injection. Notably, plasma levels of neopterin remained high at 4 h, but largely declined thereafter.
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http://dx.doi.org/10.4014/jmb.1007.07060DOI Listing
February 2011

Sanguinarine induces apoptosis in A549 human lung cancer cells primarily via cellular glutathione depletion.

Toxicol In Vitro 2009 Mar 24;23(2):281-7. Epub 2008 Dec 24.

Department of Medical Genetic Engineering, Keimyung University School of Medicine, 194 Dongsan-dong, Jung-gu, Daegu 700-712, Republic of Korea.

Sanguinarine is a plant-derived benzophenanthridine alkaloid and has been shown to possess anti-tumor activities against various cancer cells. In this study, we investigated whether sanguinarine induces apoptosis in A549 human lung cancer cells. Treatment of A549 cells with sanguinarine induced apoptosis in a dose- and time-dependent manner. Treatment with sanguinarine led to activation of caspases and MAPKs as well as increased MKP-1 expression. Importantly, pretreatment with z-VAD-fmk, a pan caspase inhibitor suppressed the sanguinarine-induced apoptosis in A549 cells. Moreover, pretreatment with NAC, a sulfhydryl group-containing reducing agent strongly suppressed the apoptotic response and caspase activation to sanguinarine. However, the sanguinarine-mediated cytotoxicity in A549 cells was not protected by pharmacological inhibition of MAPKs or MKP-1 siRNA-mediated knockdown of MKP-1. These results collectively suggest that sanguinarine induces apoptosis in A549 cells through cellular glutathione depletion and the subsequent caspase activation.
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http://dx.doi.org/10.1016/j.tiv.2008.12.013DOI Listing
March 2009

Cadmium specifically induces MKP-1 expression via the glutathione depletion-mediated p38 MAPK activation in C6 glioma cells.

Neurosci Lett 2008 Aug 23;440(3):289-93. Epub 2008 May 23.

Chronic Disease Research Center, Keimyung University School of Medicine, 194 Dongsan-dong, Jung-gu, Daegu, Republic of Korea.

Cadmium is a toxic heavy metal and an environmental pollutant. Mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) is a negative regulator of the family of MAPK. In this study, we investigated the effect of heavy metals on MKP-1 expression in C6 rat glioma cells. Cadmium treatment induced MKP-1 at both protein and mRNA levels while cobalt or manganese treatment did not, suggesting the specificity. Cadmium treatment also depleted intracellular GSH and activated p38 MAPK, JNKs, and AKT. Profoundly, pretreatment with thiol-containing compounds NAC or GSH, but not vitamin E, blocked GSH depletion, 38 MAPK activation and MKP-1 expression by cadmium. Moreover, pharmacological inhibition of p38 MAPK by SB203580 suppressed the cadmium-induced MKP-1. Collectively, these results demonstrate that cadmium specifically induces MKP-1 by transcriptional up-regulation in C6 cells in a mechanism associated with the glutathione depletion-dependent p38 MAPK activation.
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http://dx.doi.org/10.1016/j.neulet.2008.05.064DOI Listing
August 2008

Improving the yield of soluble 6xHis-tagged interferon-alpha via the addition of repressor of the araBAD promoter system in Escherichia coli.

Biotechnol Lett 2008 Sep 17;30(9):1577-82. Epub 2008 May 17.

Division of Food and Biotechnology, Chungju National University, Jeungpyung, Chungbuk 368-701, Republic of Korea.

The inhibition of inclusion body formation in Escherichia coli by the addition of alpha-D-glucopyranoside or D-fucose after induction improved the purification yield of soluble recombinant interferon-alpha. When D-fucose was added after induction, more soluble 6xHis-tagged interferon-alpha could be purified compared to when methyl alpha-D-glucopyranoside was added. It was shown that, on the basis of 1 mg dry cell weight, 16.6 microg of soluble 6xHis-tagged interferon-alpha was purified when D-fucose was added after induction and 6 ml nickel-chelated agarose gel column was used. This was about 15 times greater than when induction only was performed and 1 ml nickel-chelated agarose gel was used.
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http://dx.doi.org/10.1007/s10529-008-9741-2DOI Listing
September 2008

Furfural from Pine Needle Extract Inhibits the Growth of a Plant Pathogenic Fungus, Alternaria mali.

Mycobiology 2007 Mar 31;35(1):39-43. Epub 2007 Mar 31.

Division of Food and Biotechnology, Chungju National University, Chungju, Chungbuk 380-702, Korea.

The antifungal effect of pine needle extract prepared by a distinguishable extraction method and the dry distillation method, was examined. The effect of this extract itself was insignificant. The chemical components of pine needle extract were then investigated by gas chromatographic analysis, and four chemical components, acetol, furfural, 5-methyl furfural, and terpine-4-ol, were identified. The antifungal effects of those four chemical components against Alternaria mali (A. mali), an agent of Alternaria blotch of apple, were then examined. It was observed that the minimum inhibitory concentrations (MICs) were 6.25, 0.78, 0.78, and 12.5 (mg/ml) of acetol, furfural, 5-methyl furfural, and terpine-4-ol, respectively. MICs of furfural and 5-methyl furfural had the same order of magnitude as that of an antifungal agrochemical, chlorothalonil. Although furfural itself can not be completely substituted for an antifungal agrochemical, a partial mixture of furfural and antifungal agrochemical may be used as a substitute. The use of agrochemicals for the prevention of plant disease caused by pathogenic fungus such as A. mali could be partially reduced by the application of this mixture.
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http://dx.doi.org/10.4489/MYCO.2007.35.1.039DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3763085PMC
March 2007

Leptomycin B, a metabolite of Streptomyces, inhibits the expression of inducible nitric oxide synthase in BV2 microglial cells.

Int J Oncol 2006 Dec;29(6):1509-15

Chronic Disease Research Center and Institute for Medical Science, Keimyung University School of Medicine, Jung-Gu, Daegu 700-712, South Korea.

Overexpression of inducible nitric oxide synthase (iNOS) and the resultant overproduction of NO has been implicated in neuronal inflammatory diseases. Leptomycin B (LMB), a metabolite of Streptomyces, has been identified as a specific inhibitor of CRM1 nuclear export receptor. In this study, we evaluated the effect of LMB on lipopolysaccharide (LPS)-induced iNOS expression in BV2 cells, a murine microglial cells and the associated mechanisms. LMB strongly inhibited LPS-induced iNOS protein and mRNA expressions in BV2 cells in which 10 ng/ml of LMB (18 nM) was sufficient to greatly down-regulate iNOS by LPS, suggesting the potency of LMB to inhibit iNOS. The data of iNOS promoter-driven luciferase assay further suggested that the LMB inhibitory effect was in part due to inhibition of iNOS transcription. However, LPS-induced activation of various intracellular signaling proteins, such as nuclear factor-kappaB (NF-kappaB), extracellular signal-regulated kinases (ERKs), p38s, and c-Jun N-terminal kinases (JNKs), whose activations are known to be important for iNOS expression by LPS in BV2 cells, were not affected in the presence of LMB. Together, these results suggest that LMB inhibits iNOS expression in response to LPS in BV2 microglia, and the inhibition seems to be associated with blockage of CRM1-mediated iNOS mRNA nuclear export and also in part transcriptional down-regulation of iNOS, but not through modulation of NF-kappaB and the mitogen-activated protein kinase signaling pathways.
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December 2006

Muscular cell proliferative and protective effects of N-acetylcysteine by modulating activity of extracellular signal-regulated protein kinase.

Life Sci 2006 Jul 29;79(7):622-8. Epub 2006 Mar 29.

Department of Neurology, Keimyung University School of Medicine and Institute for Medical Science, 194 Dongsan-Dong, Jung-Gu, Daegu 700-712, Korea.

N-acetylcysteine (NAC), an antioxidant and a precursor of glutathione, is currently in clinical use for various pathological conditions. No data is available as to the relationship between NAC and muscular cell proliferation or muscular degenerative disease. In this study, we assessed the effect of NAC on growth of L6 myoblasts, a rat skeletal muscle cell line, under normal or bupivacaine-treated condition. Of interest, under normal growth conditions, NAC treatment concentration-dependently increased viability, cell number, and DNA incorporation of L6 cells. Remarkably, NAC treatment for 12 to 24 h led to increased phosphorylation of ERKs, a family of mitogen-activated protein kinase known to involve in cell proliferation, in L6 cells, and specific inhibition of ERKs by PD98059, a selective inhibitor of ERKs, greatly abolished the ability of NAC to increase the number of L6 cells. More importantly, pretreatment with NAC effectively blocked decrease in the number and ERKs phosphorylation in L6 cells induced by the exposure of bupivacaine, a local anesthetic with myotoxicity. These results collectively suggest that NAC has muscular cell proliferative and protective effects and the effects by NAC appear to be, in part, mediated via increase in ERKs activation.
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http://dx.doi.org/10.1016/j.lfs.2006.02.008DOI Listing
July 2006

Inhibitory modulation of ATP-sensitive potassium channels by gallate-ester moiety of (-)-epigallocatechin-3-gallate.

Biochem Pharmacol 2005 Nov 10;70(11):1560-7. Epub 2005 Oct 10.

Department of Microbiology, Keimyung University School of Medicine, Daegu 700-712, Republic of Korea.

(-)-Epigallocatechin-3-gallate (EGCG), a major polyphenolic substance found in green tea, is well recognized to be beneficial for human health. However, it is still controversial as to what dose of this compound is indeed good for human health. Though some recent studies have interestingly reported various beneficial effects of EGCG in cell culture system, however, plasma levels of EGCG attainable by oral regular intake in humans are normally in nanomolar range. However, potential side effects of EGCG when administered parenterally at higher concentration have not been thoroughly tested. Here, we evaluated the effect of EGCG on ATP-sensitive potassium (K(ATP)) channels expressed in Xenopus oocytes. EGCG inhibited the activity of the Kir6.2/SUR1 and Kir6.2DeltaC36 channels with IC(50) of 142+/-37 and 19.9+/-1.7microM, respectively. Inhibition of EGCG was also observed in Kir6.2/SUR2A or Kir6.2/SUR2B channels. Notably, (-)-epicatechin-3-gallate (ECG), another major polyphenolic substance in green tea, was found to reduce the channel activity with greater potency than EGCG. In contrast to EGCG and ECG, which have the gallic acid-ester moiety in their own structures, (-)-epigallocatechin and (-)-epicatechin exhibited very weak inhibition of the K(ATP) channel. Collectively, these results suggest that the gallate-ester moiety of epicatechins may be critical for inhibiting the K(ATP) channel activity via the pore-forming subunit Kir6.2 and this may be a possible mechanism by which green tea extracts or EGCG may cause unexpected side effects at micromolar plasma level.
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http://dx.doi.org/10.1016/j.bcp.2005.09.005DOI Listing
November 2005