Publications by authors named "Sook-Jeong Lee"

37 Publications

CSNK1G2 differently sensitizes tamoxifen-induced decrease in PI3K/AKT/mTOR/S6K and ERK signaling according to the estrogen receptor existence in breast cancer cells.

PLoS One 2021 16;16(4):e0246264. Epub 2021 Apr 16.

Department of Bioactive Material Sciences, Jeonbuk National University, Jeonju, Jeollabuk-do, Republic of Korea.

Tamoxifen (TAM) is a selective estrogen receptor modulator used for breast cancer patients. Prolonged use of tamoxifen is not recommended for some patients. In this study, we aimed to identify molecular targets sensitive to TAM using a genome-wide gene deletion library screening of fission yeast heterozygous mutants. From the screening, casein kinase 1 gamma 2 (CSNK1G2), a serine-/threonine protein kinase, was the most sensitive target to TAM with a significant cytotoxicity in estrogen receptor-positive (ER+) breast cancer cells but with only a slight toxicity in the case of ER- cells. In addition, tumor sphere formation and expression of breast stem cell marker genes such as CD44/CD2 were greatly inhibited by CSNK1G2 knockdown in ER+ breast cancer cells. Consistently, CSNK1G2 altered ERα activity via phosphorylation, specifically at serine (Ser)167, as well as the regulation of estrogen-responsive element (ERE) of estrogen-responsive genes such as CTSD and GREB1. However, ERα silencing almost completely blocked CSNK1G2-induced TAM sensitivity. In ER+ breast cancer cells, combined treatment with TAM and CSNK1G2 knockdown further enhanced the TAM-mediated decrease in phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR)/ribosomal protein S6 kinase (S6K) signaling but not extracellular signal-regulated kinase (ERK) signaling. Inversely, in ER- cells treated with TAM, only ERK and PI3K signaling was altered by CSNK1G2 knockdown. The CK1 inhibitor, D4476, partly mimicked the CSNK1G2 knockdown effect in ER+ breast cancer cells, but with a broader repression ranging from PI3K/AKT/mTOR/S6K to ERK signaling. Collectively, these results suggest that CSNK1G2 plays a key role in sensitizing TAM toxicity in ER+ and ER- breast cancer cells via differently regulating PI3K/AKT/mTOR/S6K and ERK signaling.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0246264PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8051802PMC
April 2021

Bone remodeling effects of Korean Red Ginseng extracts for dental implant applications.

J Ginseng Res 2020 Nov 27;44(6):823-832. Epub 2020 May 27.

Department of Dental Biomaterials and Institute of Biodegradable Materials, Institute of Oral Bioscience and School of Dentistry (Plus BK21 Program), Jeonbuk National University, Jeonju, Jeollabuk-do, Republic of Korea.

Background: The formation of a nanotube layer on a titanium nanotube (N-Ti) plate facilitates an active reaction between bone cells and the material surface via efficient delivery of the surface materials of the dental implant into the tissues. Studies have reported that Korean Red Ginseng extracts (KRGEs) are involved in a variety of pharmacological activities: we investigated whether implantation with a KRGE-loaded N-Ti miniimplant affects osteogenesis and osseointegration.

Methods: KRGE-loaded nanotubes were constructed by fabrication on pure Ti via anodization, and MC3T3-E1 cells were cultured on the N-Ti. N-Ti implants were subsequently placed on a rat's edentulous mandibular site. New bone formation and bone mineral density were measured to analyze osteogenesis and osseointegration.

Results: KRGE-loaded N-Ti significantly increased the proliferation and differentiation of MC3T3-E1 cells compared with cells on pure Ti without any KRGE loading. After 1-4 weeks, the periimplant tissue in the edentulous mandibular of the healed rat showed a remarkable increase in new bone formation and bone mineral density. In addition, high levels of the bone morphogenesis protein-2 and bone morphogenesis protein-7, besides collagen, were expressed in the periimplant tissues.

Conclusion: Our findings suggest that KRGE-induced osteogenesis and osseointegration around the miniimplant may facilitate the clinical application of dental implants.
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http://dx.doi.org/10.1016/j.jgr.2020.05.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7655497PMC
November 2020

Metallothionein-3 as a multifunctional player in the control of cellular processes and diseases.

Mol Brain 2020 08 25;13(1):116. Epub 2020 Aug 25.

Department of Bioactive Material Science, Jeonbuk National University, Jeonju, Jeollabuk-do, 54896, Republic of Korea.

Transition metals, such as iron, copper, and zinc, play a very important role in life as the regulators of various physiochemical reactions in cells. Abnormal distribution and concentration of these metals in the body are closely associated with various diseases including ischemic seizure, Alzheimer's disease, diabetes, and cancer. Iron and copper are known to be mainly involved in in vivo redox reaction. Zinc controls a variety of intracellular metabolism via binding to lots of proteins in cells and altering their structure and function. Metallothionein-3 (MT3) is a representative zinc binding protein predominant in the brain. Although the role of MT3 in other organs still needs to be elucidated, many reports have suggested critical roles for the protein in the control of a variety of cellular homeostasis. Here, we review various biological functions of MT3, focusing on different cellular molecules and diseases involving MT3 in the body.
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http://dx.doi.org/10.1186/s13041-020-00654-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7448430PMC
August 2020

A role of metallothionein-3 in radiation-induced autophagy in glioma cells.

Sci Rep 2020 02 6;10(1):2015. Epub 2020 Feb 6.

Neural Injury Research Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul, Republic of Korea.

Although metallothionein-3 (MT3), a brain-enriched form of metallothioneins, has been linked to Alzheimer's disease, little is known regarding the role of MT3 in glioma. As MT3 plays a role in autophagy in astrocytes, here, we investigated its role in irradiated glioma cells. Irradiation increased autophagy flux in GL261 glioma cells as evidenced by increased levels of LC3-II but decreased levels of p62 (SQSTM1). Indicating that autophagy plays a cytoprotective role in glioma cell survival following irradiation, measures inhibiting autophagy flux at various steps decreased their clonogenic survival of irradiated GL261 as well as SF295 and U251 glioma cells. Knockdown of MT3 with siRNA in irradiated glioma cells induced arrested autophagy, and decreased cell survival. At the same time, the accumulation of labile zinc in lysosomes was markedly attenuated by MT3 knockdown. Indicating that such zinc accumulation was important in autophagy flux, chelation of zinc with tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN), induced arrested autophagy in and reduced survival of GL261 cells following irradiation. Suggesting a possible mechanism for arrested autophagy, MT3 knockdown and zinc chelation were found to impair lysosomal acidification. Since autophagy flux plays a cytoprotective role in irradiated glioma cells, present results suggest that MT3 and zinc may be regarded as possible therapeutic targets to sensitize glioma cells to ionizing radiation therapy.
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http://dx.doi.org/10.1038/s41598-020-58237-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7005189PMC
February 2020

Enhanced antibacterial activity of titanium by surface modification with polydopamine and silver for dental implant application.

J Appl Biomater Funct Mater 2019 Jul-Sep;17(3):2280800019847067

Department of Dental Biomaterials and Institute of Biodegradable Material, Chonbuk National University, Jeollabuk-do, South Korea.

Background: Biofilm formation and microbial colonization on the surface of implant devices may cause dental caries and peri-implantitis. Therefore, various surface treatments have been developed to improve the antibacterial activity of titanium implant.

Methods: Silver-loaded polydopamine coating was formed by immersing pure titanium in dopamine hydrochloride/HCl buffer solution for 24 h in 50 mL silver nitrate solutions with different concentrations for 30 min. Microbial growth inhibition and microbial growth curve analyses for bacterial solutions of and incubated with the specimens were respectively conducted by counting the numbers of colonies on agar solid medium and by measuring absorbance using enzyme-linked immunosorbent assay reader.

Results: Silver nanoparticles were uniformly distributed over the whole surface of the polydopamine and silver-coated titanium specimens. The numbers of microbial colonies for both bacteria cultured with surface-modified titanium were significantly lower than those cultured with uncoated titanium. When and were cultured with surface-modified titanium, the lag phase of the growth curves for both bacteria was continually maintained, whereas the lag phase for and changed to exponential phase after 9 and 15 h, respectively, when both bacteria were cultured with uncoated titanium.

Conclusion: It was confirmed that the coating of polydopamine and silver on the surface of titanium effectively retards the microbial growth, which can cause the formation of biofilm and pathogenesis of gum disease in the mouth.
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http://dx.doi.org/10.1177/2280800019847067DOI Listing
February 2020

and Characterization of N-Acetyl-L-Cysteine Loaded Beta-Tricalcium Phosphate Scaffolds.

Int J Biomater 2018 31;2018:9457910. Epub 2018 Jul 31.

Department of Dental Biomaterials and Institute of Biodegradable Materials, Institute of Oral Bioscience and School of Dentistry (Plus BK21 Program), Chonbuk National University, Jeonju, Republic of Korea.

Beta-tricalcium phosphate bioceramics are widely used as bone replacement scaffolds in bone tissue engineering. The purpose of this study is to develop beta-tricalcium phosphate scaffold with the optimum mechanical properties and porosity and to identify the effect of N-acetyl-L-cysteine loaded to beta-tricalcium phosphate scaffold on the enhancement of biocompatibility. The various interconnected porous scaffolds were fabricated using slurries containing various concentrations of beta-tricalcium phosphate and different coating times by replica method using polyurethane foam as a passing material. It was confirmed that the scaffold of 40 w/v% beta-tricalcium phosphate with three coating times had optimum microstructure and mechanical properties for bone tissue engineering application. The various concentration of N-acetyl-L-cysteine was loaded on 40 w/v% beta-tricalcium phosphate scaffold. Scaffold group loaded 5 mM N-acetyl-L-cysteine showed the best viability of MC3T3-E1 preosteoblastic cells in the water-soluble tetrazolium salt assay test.
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http://dx.doi.org/10.1155/2018/9457910DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6091360PMC
July 2018

Editor's Highlight: A Genome-wide Screening of Target Genes Against Silver Nanoparticles in Fission Yeast.

Toxicol Sci 2018 01;161(1):171-185

Department of New Drug Discovery and Development, Chungnam National University, Daejeon 34134, Republic of Korea.

To identify target genes against silver nanoparticles (AgNPs), we screened a genome-wide gene deletion library of 4843 fission yeast heterozygous mutants covering 96% of all protein encoding genes. A total of 33 targets were identified by a microarray and subsequent individual confirmation. The target pattern of AgNPs was more similar to those of AgNO3 and H2O2, followed by Cd and As. The toxic effect of AgNPs on fission yeast was attributed to the intracellular uptake of AgNPs, followed by the subsequent release of Ag+, leading to the generation of reactive oxygen species (ROS). Next, we focused on the top 10 sensitive targets for further studies. As described previously, 7 nonessential targets were associated with detoxification of ROS, because their heterozygous mutants showed elevated ROS levels. Three novel essential targets were related to folate metabolism or cellular component organization, resulting in cell cycle arrest and no induction in the transcriptional level of antioxidant enzymes such as Sod1 and Gpx1 when 1 of the 2 copies was deleted. Intriguingly, met9 played a key role in combating AgNP-induced ROS generation via NADPH production and was also conserved in a human cell line.
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http://dx.doi.org/10.1093/toxsci/kfx208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5837777PMC
January 2018

The effect of the cwf14 gene of fission yeast on cell wall integrity is associated with rho1.

J Microbiol 2016 Feb 2;54(2):98-105. Epub 2016 Feb 2.

Department of New Drug Discovery and Development, Chungnam National University, Daejeon, 305-764, Republic of Korea.

In all eukaryotic organisms, a wide range of morphologies are responsible for critical cellular function and development. In particular, the Rho GTPases, which are highly conserved from yeast to mammals, are key molecules in signaling pathways that control cell polarity processes and cell wall biosynthesis, which are fundamental aspects of morphogenesis. Therefore, using haploinsufficiency deletion mutants of the fission yeast Schizosaccharomyces pombe, we screened the slow-growing mutants and their morphogenesis, specifically focusing on regulation of their Rho GTPases. Based on this screening, we found that the cwf14 mutant of S. pombe exhibited the slow growth and abnormal phenotypes with an elongated cell shape and thicker cell wall when compared with wild-type cells. In particular, cells with the cwf14 deletion showed excessive Rho1 expression. However, the wildtype strain with ectopically expressed Rho1 did not exhibited any significant change in the level of cwf14, suggesting that cwf14 may act on the upstream of Rho1. Furthermore, the cells with a cwf14 deletion also have increased sensitivity to β-glucanase, a cell wall-digesting enzyme, which is also seen in Rho1-overexpressing cells. Overall, our results suggest that the cwf14 plays a key role in fission yeast morphogenesis and cell wall biosynthesis and/or degradation possibly via the regulation of Rho1 expression.
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http://dx.doi.org/10.1007/s12275-016-5569-yDOI Listing
February 2016

The effect of hydrothermal spark discharge anodization in the early integration of implants in sheep sinuses.

Clin Oral Implants Res 2016 Aug 22;27(8):975-80. Epub 2016 Jan 22.

Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.

Objectives: Spark discharge anodic oxidation forms a porous oxide film on titanium implant surfaces, which may increase surface roughness and enhance early osseointegration. This study aimed to clinically and histomorphometric compare commercially-available sandblasted (RBM) implants, treated with hydrothermal anodization and placed into an animal maxillary sinus model.

Materials And Methods: Thirty 3.75 mm × 8.5 mm threaded titanium implants were placed into the maxillary sinuses of 10 sheep via an external approach, with three test groups and 10 implants per group: right side, Control = CP-titanium with RBM surface, Test group 1 = CP-titanium with RBM + anodized surface; left side, Test group 2 = Ti-6Al-7Nb with RBM + anodized surface. Schneiderian membranes were elevated but not bone grafted. Resonant frequency analysis (RFA) was measured at surgery. Animals were sacrificed after 1 month unloaded healing. Resin-embedded undemineralized ground-sections were digitised, and mean bone-implant contact (% BIC) was measured bilaterally for the best-three consecutive threads.

Results: Seven of 30 implants showed signs of failure. RFA was low at placement but did not differ between the groups (group mean ISQ values ranged from 23 to 35; χ(2)  = 0.37). RFA was not repeated at sacrifice due to implant instability. Histomorphometric analysis showed % BIC was highest for control (34.8 ± 15.7), followed by Test 1 (29.6 ± 18.1) and Test 2 implants (23.3 ± 22.7), but this difference was not statistically significant (χ(2)  = 0.3).

Discussion And Conclusions: Early integration of RBM implants placed into thin maxillary sinus walls was not enhanced by hydrothermal anodization of implant surfaces. This may be related to the initial low stability of the implants and the relatively short healing period. However, non-anodized RBM surfaces showed promising results, with % BIC values comparable to the best estimates of other studies using sinus grafting. Whether the modification of the implant surfaces through anodization with simultaneous sinus grafting would promote enhanced early osseointegration, is a subject of future research.
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http://dx.doi.org/10.1111/clr.12741DOI Listing
August 2016

Metallothionein-3 modulates the amyloid β endocytosis of astrocytes through its effects on actin polymerization.

Mol Brain 2015 Dec 4;8(1):84. Epub 2015 Dec 4.

Neural Injury Research Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul, South Korea.

Background: Astrocytes may play important roles in the pathogenesis of Alzheimer's disease (AD) by clearing extracellular amyloid beta (Aβ) through endocytosis and degradation. We recently showed that metallothionein 3 (Mt3), a zinc-binding metallothionein that is enriched in the central nervous system, contributes to actin polymerization in astrocytes. Because actin is likely involved in the endocytosis of Aβ, we investigated the possible role of Mt3 in Aβ endocytosis by cortical astrocytes in this study.

Results: To assess the route of Aβ uptake, we exposed cultured astrocytes to fluorescently labeled Aβ1-40 or Aβ1-42 together with chloropromazine (CP) or methyl-beta-cyclodextrin (MβCD), inhibitors of clathrin- and caveolin-dependent endocytosis, respectively. CP treatment almost completely blocked Aβ1-40 and Aβ1-42 endocytosis, whereas exposure to MβCD had no significant effect. Actin disruption with cytochalasin D (CytD) or latrunculin B also completely blocked Aβ1-40 and Aβ1-42 endocytosis. Because the absence of Mt3 also results in actin disruption, we examined Aβ1-40 and Aβ1-42 uptake and expression in Mt3 (-/-) astrocytes. Compared with wild-type (WT) cells, Mt3 (-/-) cells exhibited markedly reduced Aβ1-40 and Aβ1-42 endocytosis and expression of Aβ1-42 monomers and oligomers. A similar reduction was observed in CytD-treated WT cells. Finally, actin disruption and Mt3 knockout each increased the overall levels of clathrin and the associated protein phosphatidylinositol-binding clathrin assembly protein (PICALM) in astrocytes.

Conclusions: Our results suggest that the absence of Mt3 reduces Aβ uptake in astrocytes through an abnormality in actin polymerization. In light of evidence that Mt3 is downregulated in AD, our findings indicate that this mechanism may contribute to the extracellular accumulation of Aβ in this disease.
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http://dx.doi.org/10.1186/s13041-015-0173-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4670512PMC
December 2015

Identification of Rbd2 as a candidate protease for sterol regulatory element binding protein (SREBP) cleavage in fission yeast.

Biochem Biophys Res Commun 2015 Dec 3;468(4):606-10. Epub 2015 Nov 3.

Aging Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea. Electronic address:

Lipid homeostasis in mammalian cells is regulated by sterol regulatory element-binding protein (SREBP) transcription factors that are activated through sequential cleavage by Golgi Site-1 and Site-2 proteases. Fission yeast SREBP, Sre1, engages a different mechanism involving the Golgi Dsc E3 ligase complex, but it is not clearly understood exactly how Sre1 is proteolytically cleaved and activated. In this study, we screened the Schizosaccharomyces pombe non-essential haploid deletion collection to identify missing components of the Sre1 cleavage machinery. Our screen identified an additional component of the SREBP pathway required for Sre1 proteolysis named rhomboid protein 2 (Rbd2). We show that an rbd2 deletion mutant fails to grow under hypoxic and hypoxia-mimetic conditions due to lack of Sre1 activity and that this growth phenotype is rescued by Sre1N, a cleaved active form of Sre1. We found that the growth inhibition phenotype under low oxygen conditions is specific to the strain with deletion of rbd2, not any other fission yeast rhomboid-encoding genes. Our study also identified conserved residues of Rbd2 that are required for Sre1 proteolytic cleavage. All together, our results suggest that Rbd2 is a functional SREBP protease with conserved residues required for Sre1 cleavage and provide an important piece of the puzzle to understand the mechanisms for Sre1 activation and the regulation of various biological and pathological processes involving SREBPs.
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http://dx.doi.org/10.1016/j.bbrc.2015.10.165DOI Listing
December 2015

The zinc ionophore clioquinol reverses autophagy arrest in chloroquine-treated ARPE-19 cells and in APP/mutant presenilin-1-transfected Chinese hamster ovary cells.

Neurobiol Aging 2015 Dec 16;36(12):3228-3238. Epub 2015 Sep 16.

Neural Injury Research Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul, Korea; Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. Electronic address:

Arrested autophagy may contribute to the pathogenesis of Alzheimer's disease. Because we found that chloroquine (CQ) causes arrested autophagy but clioquinol (ClioQ), a zinc ionophore, activates autophagic flux, in the present study, we examined whether ClioQ can overcome arrested autophagy induced by CQ or mutant presenilin-1 (mPS1). CQ induced vacuole formation and cell death in adult retinal pigment epithelial (ARPE-19) cells, but co-treatment with ClioQ attenuated CQ-associated toxicity in a zinc-dependent manner. Increases in lysosome dilation and blockage of autophagic flux by CQ were also markedly attenuated by ClioQ treatment. Interestingly, CQ increased lysosomal pH in amyloid precursor protein (APP)/mPS1-expressing Chinese hamster ovary 7WΔE9 (CHO-7WΔE9) cell line, and ClioQ partially re-acidified lysosomes. Furthermore, accumulation of amyloid-β (Aβ) oligomers in CHO-7WΔE9 cells was markedly attenuated by ClioQ. Moreover, intracellular accumulation of exogenously applied fluorescein isothiocyanate-conjugated Aβ(1-42) was also increased by CQ but was returned to control levels by ClioQ. These results suggest that modulation of lysosomal functions by manipulating lysosomal zinc levels may be a useful strategy for clearing intracellular Aβ oligomers.
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http://dx.doi.org/10.1016/j.neurobiolaging.2015.09.006DOI Listing
December 2015

Targeting ERK1/2-bim signaling cascades by BH3-mimetic ABT-737 as an alternative therapeutic strategy for oral cancer.

Oncotarget 2015 Nov;6(34):35667-83

Department of Oral Pathology, School of Dentistry, Institute of Biodegradable Material, Institute of Oral Bioscience, Chonbuk National University, Jeonju, Republic of Korea.

To date, many different chemotherapeutic agents have been widely used as common treatments for oral cancers. However, their therapeutic effects have been disappointing, and these agents may have unwanted side effects. Among the many regulatory factors, overexpression of pro-survival Bcl-2 family members may promote resistance to chemotherapeutic drugs in many tumors. The BH3 domain-only proteins effectively antagonize their apoptotic activities. Therefore, there is substantial interest in developing chemotherapeutic drugs that directly target pro-survival Bcl-2 proteins by mimicking the BH3 domain and unleashing pro-apoptotic molecules in tumor cells. Among the numerous available small molecule BH3 mimetics, ABT-737, a potent small molecule that binds to Bcl-2/Bcl-xL with high affinity, has anti-tumor activity in a wide variety of cancer cells. However, the effects of ABT-737 on human oral cancers and the underlying molecular mechanisms have not previously been elucidated. In the present study, we observed that inactivation of the ERK1/2 signaling pathway using ABT-737 dramatically increased the expression of pro-apoptotic protein Bim via transcriptional and/or posttranslational regulation, in a cell type-dependent manner, inducing mitochondria-mediated apoptosis of human oral cancer cells. To the best of our knowledge, this is the first demonstration of the antitumor effects of ABT-737 on human oral cancers.
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http://dx.doi.org/10.18632/oncotarget.5523DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4742133PMC
November 2015

Anodisation Increases Integration of Unloaded Titanium Implants in Sheep Mandible.

Biomed Res Int 2015 8;2015:857969. Epub 2015 Sep 8.

Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.

Spark discharge anodic oxidation forms porous TiO2 films on titanium implant surfaces. This increases surface roughness and concentration of calcium and phosphate ions and may enhance early osseointegration. To test this, forty 3.75 mm × 13 mm titanium implants (Megagen, Korea) were placed into healed mandibular postextraction ridges of 10 sheep. There were 10 implants per group: RBM surface (control), RBM + anodised, RBM + anodised + fluoride, and titanium alloy + anodised surface. Resonant frequency analysis (RFA) was measured in implant stability quotient (ISQ) at surgery and at sacrifice after 1-month unloaded healing. Mean bone-implant contact (% BIC) was measured in undemineralised ground sections for the best three consecutive threads. One of 40 implants showed evidence of failure. RFA differed between groups at surgery but not after 1 month. RFA values increased nonsignificantly for all implants after 1 month, except for controls. There was a marked difference in BIC after 1-month healing, with higher values for alloy implants, followed by anodised + fluoride and anodised implants. Anodisation increased early osseointegration of rough-surfaced implants by 50-80%. RFA testing lacked sufficient resolution to detect this improvement. Whether this gain in early bone-implant contact is clinically significant is the subject of future experiments.
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http://dx.doi.org/10.1155/2015/857969DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4578837PMC
July 2016

Terrein reduces age-related inflammation induced by oxidative stress through Nrf2/ERK1/2/HO-1 signalling in aged HDF cells.

Cell Biochem Funct 2015 Oct 28;33(7):479-86. Epub 2015 Sep 28.

Departments of Oral Biochemistry, Institute of Oral Bioscience, School of Dentistry, Chonbuk National University, Jeonju, Korea.

This study investigated whether multiple bioactivity of terrein such as anti-inflammatory and anti-oxidant inhibits age-related inflammation by promoting an antioxidant response in aged human diploid fibroblast (HDF) cells. HDF cells were cultured serially for in vitro replicative senescence. To create the ageing cell phenotype, intermediate stage (PD31) HDF cells were brought to stress-induced premature senescence (SIPS) using hydrogen peroxide (H2 O2). Terrein increased cell viability even with H2O2 stress and reduced inflammatory molecules such as intracellular adhesion molecule-1 (ICAM-1), cyclooxygenase-2 (COX-2), interleukin-1beta (IL-1β) and tumour necrosis factor-alpha (TNF-α). Terrein reduced also phospho-extracellular kinase receptor1/2 (p-EKR1/2) signalling in aged HDF cells. SIPS cells were attenuated for age-related biological markers including reactive oxygen species (ROS), senescence associated beta-galactosidase (SA β-gal.) and the aforementioned inflammatory molecules. Terrein induced the induction of anti-oxidant molecules, copper/zinc-superoxide defence (Cu/ZnSOD), manganese superoxide dismutase (MnSOD) and heme oxygenase-1 (HO-1) in SIPS cells. Terrein also alleviated reactive oxygen species formation through the Nrf2/HO-1/p-ERK1/2 pathway in aged cells. The results indicate that terrein has an alleviative function of age-related inflammation characterized as an anti-oxidant. Terrein might be a useful nutraceutical compound for anti-ageing.
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http://dx.doi.org/10.1002/cbf.3145DOI Listing
October 2015

Systematic targeted gene deletion using the gene-synthesis method in fission yeast.

J Microbiol Methods 2014 Nov 20;106:72-77. Epub 2014 Aug 20.

Department of New Drug Discovery and Development, Chungnam National University, Yuseong, Daejeon 305-764, Republic of Korea. Electronic address:

Genome-wide targeted gene deletion, a systematic method to study gene function by replacing target genes with deletion cassettes, using serial-PCR or block-PCR requires elaborate skill. We developed a novel gene-synthesis method to systematically prepare deletion cassettes on a 96-well basis in fission yeast. We designed the 2129-bp deletion cassette as three modules: a central 1397-bp KanMX4 selection marker module and two flanking 366-bp gene-specific artificial linker modules. The central KanMX4 module can be used in multiple deletion cassettes in combination with different sets of flanking modules. The deletion cassettes consisted of 147 oligonucleotides (93 for the central module+25 for each of the flanking modules+4 for the joints) and the oligonucleotides were designed as ~29mers using an in-house program. Oligonucleotides were synthesized on a 96-well basis and ligated into deletion cassettes without gaps by ligase chain reaction, which was followed by two rounds of nested PCR to amplify trace amounts of the ligated cassettes. After the artificial linkers were removed from the deletion cassettes, the cassettes were transformed into wild-type diploid fission yeast strain SP286. We validated the transformed colonies via check PCR and subjected them to tetrad analysis to confirm functional integrity. Using this method, we systematically deleted 563 genes in the fission yeast Schizosaccharomyces pombe with a >90% success rate and a point-mutation rate of ~0.4 mutations per kb. Our method can be used to create systematic gene deletions in a variety of yeasts especially when it included a bar-code system for parallel analyses.
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http://dx.doi.org/10.1016/j.mimet.2014.08.005DOI Listing
November 2014

Transactivation of bad by vorinostat-induced acetylated p53 enhances doxorubicin-induced cytotoxicity in cervical cancer cells.

Exp Mol Med 2014 Feb 14;46:e76. Epub 2014 Feb 14.

Department of New Drug Discovery and Development, Chungnam National University, Daejeon, Republic of Korea.

Vorinostat (VOR) has been reported to enhance the cytotoxic effects of doxorubicin (DOX) with fewer side effects because of the lower DOX dosage in breast cancer cells. In this study, we investigated the novel mechanism underlying the synergistic cytotoxic effects of VOR and DOX co-treatment in cervical cancer cells HeLa, CaSki and SiHa cells. Co-treatment with VOR and DOX at marginal doses led to the induction of apoptosis through caspase-3 activation, poly (ADP-ribose) polymerase cleavage and DNA micronuclei. Notably, the synergistic growth inhibition induced by the co-treatment was attributed to the upregulation of the pro-apoptotic protein Bad, as the silencing of Bad expression using small interfering RNA (siRNA) abolished the phenomenon. As siRNA against p53 did not result in an increase in acetylated p53 and the consequent upregulation of Bad, the observed Bad upregulation was mediated by acetylated p53. Moreover, a chromatin immunoprecipitation analysis showed that the co-treatment of HeLa cells with VOR and DOX increased the recruitment of acetylated p53 to the bad promoter, with consequent bad transactivation. Conversely, C33A cervical cancer cells containing mutant p53 co-treated with VOR and DOX did not exhibit Bad upregulation, acetylated p53 induction or consequent synergistic growth inhibition. Together, the synergistic growth inhibition of cervical cancer cell lines induced by co-treatment with VOR and DOX can be attributed to the upregulation of Bad, which is induced by acetylated p53. These results show for the first time that the acetylation of p53, rather than histones, is a mechanism for the synergistic growth inhibition induced by VOR and DOX co-treatments.
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http://dx.doi.org/10.1038/emm.2013.149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3944441PMC
February 2014

The role of reciprocal activation of cAbl and Mst1 in the oxidative death of cultured astrocytes.

Glia 2014 Apr 24;62(4):639-48. Epub 2014 Jan 24.

Neural Injury Research Lab, University of Ulsan College of Medicine, Seoul, 138-736, Korea; Asan Institute for Life Science, University of Ulsan College of Medicine, Seoul, 138-736, Korea.

The protein kinase Mst1 (mammalian Sterile 20-like kinase 1) likely plays a role in oxidative neuronal cell death as a target of its activator, cAbl. We previously found that H2O2-induced death of astrocytes is mediated by cAbl in a metallothionein-3 (Mt3)-dependent manner. In the present study, we examined a possible role for Mst1 in the oxidative death of astrocytes. Treatment of cortical astrocytes with 170 µM H2O2 activated Mst1. Knockdown of Mst1 reduced H2O2-induced cell death, indicating that Mst1 activation contributes to astrocytic cell death. STI571, an inhibitor of cAbl, blocked induction/activation of Mst1 and H2O2-induced cell death. However, Mst1 silencing also inhibited induction/activation of cAbl, suggesting that the two kinases are regulated by a reciprocal activating mechanism. The zinc chelator TPEN blocked induction/activation of cAbl and Mst1, indicating that these phenomena are dependent on the rise of intracellular zinc. Moreover, H2O2 exposure did not increase free zinc levels in Mt3-null astrocytes, suggesting that the increased levels of free zinc were largely from Mt3. Consistent with the involvement of FoxO1/3, which may play a role in the Mst1-cell death cascade, we found an increase in the level of phosphorylated FoxO1/3 in H2O2-treated astrocytes. Moreover, inhibition of cAbl or Mst1 reversed this effect. The present results suggest the interesting possibility that cAbl and Mst1 are reciprocally activated under oxidative stress conditions in astrocytes. Both kinases appear to be regulated by changes in the levels of free zinc originating from Mt3 and contribute to oxidative cell death through a FoxO-dependent mechanism.
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http://dx.doi.org/10.1002/glia.22631DOI Listing
April 2014

Negative regulation of adipogenesis by kaempferol, a component of Rhizoma Polygonati falcatum in 3T3-L1 cells.

Biol Pharm Bull 2012 ;35(9):1525-33

Department of Bioscience and Biotechnology, Sejong University, Seoul, Korea.

Rhizoma Polygonati falcatum (RPF) has been used as a traditional herbal medicine in Asia, because of its anti-hyperglycemic, anti-triglycemic, and anti-tumor activity. In this study, we determined the anti-adipogenic potential of RPF extract and its component kaempferol in 3T3-L1 adipocytes, and the underlying molecular mechanism(s) using microarray analysis. Adipocyte differentiation of 3T3-L1 cells was significantly impaired by RPF extract and kaempferol as monitored by Oil Red O staining and quantitative measurement of lipid accumulation. Additionally, the mRNA expression of adipogenesis genes decreased on treatment with kaempferol. The role of kaempferol at the genome-wide level was further assessed by a microarray approach. Our analysis indicated that kaempferol decreased the expression of adipogenic transcription factors (Pparγ, Cebpβ, Srebp1, Rxrβ, Lxrβ, Rorα) and genes involved in triglyceride biosynthesis (Gpd1, Agpat2, Dgat2), while increasing lipolysis-related genes, such as Tnfα, Lsr, and Cel. Finally, co-transfection assays using luciferase reporter gene and reverse transcription-polymerase chain reaction (RT-PCR) analysis using peroxisome proliferator-activated receptor-γ (PPARγ) target genes indicated that kaempferol significantly repressed rosiglitazone-induced PPARγ transcriptional activity. Overall, our data suggests that kaempferol, a major component of RPF, may be beneficial in obesity, by reducing adipogenesis and balancing lipid homeostasis partly through the down-regulation of PPARγ.
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http://dx.doi.org/10.1248/bpb.b12-00254DOI Listing
January 2013

Induction of autophagy and cell death by tamoxifen in cultured retinal pigment epithelial and photoreceptor cells.

Invest Ophthalmol Vis Sci 2012 Aug 9;53(9):5344-53. Epub 2012 Aug 9.

Department of Ophthalmology, NRL Neural Injury Research Center, University of Ulsan, College of Medicine, Seoul, Korea.

Purpose: We investigated the mechanism of tamoxifen (TAM) retinotoxicity using human retinal pigment epithelial (RPE)-derived (ARPE-19) and photoreceptor-derived (661W) cells.

Methods: Cultured ARPE-19 and 661W cells were treated with 5 to 10 μM TAM, and the resultant cell death was quantified using lactate dehydrogenase (LDH) release assay. Cellular oxidative stress was determined by measuring 5-(and-6)-carboxy-2',7'-dichlorohydrofluorescein diacetate (H(2)-DCFDA) fluorescence. Changes in intracellular free zinc levels were monitored using the zinc-specific fluorescent dye, FluoZin-3 AM. Autophagic vacuole formation was assessed morphologically in ARPE-19 and 661W cells transfected with the fluorescent protein-conjugated markers, RFP-LC3 or GFP-LC3.

Results: Following exposure to TAM, both ARPE-19 and 661W cells had cytosolic vacuoles within 1 hour and underwent cell death within 18 hours. In both cell types, TAM-induced cell death was accompanied by increased oxidative stress and elevated zinc levels, and was attenuated by the antioxidant N-acetyl-L-cysteine (NAC) or the zinc chelator N,N,N'N'-tetrakis(-)(2-pyridylmethyl)-ethylenediamine (TPEN). The levels of LC3-II as well as the number of autophagic vacuoles (AVs) increased after TAM treatment. Double staining for lysosomes and AVs showed that autolysosome formation proceeded normally. Consistent with this, autophagy flux was increased. Finally, as shown in other cases of autophagic cell death, lysosomal membrane permeabilization (LMP) as well as caspase-dependent apoptosis contributed to TAM-induced cell death.

Conclusions: ARPE-19 and 661W cells were vulnerable similarly to TAM-induced cytotoxicity. Increases in zinc levels and oxidative stress, excessive activation of autophagy flux, and ultimately the occurrence of LMP and consequent caspase activation may contribute to the well-established retinal cytotoxicity of TAM.
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http://dx.doi.org/10.1167/iovs.12-9827DOI Listing
August 2012

Corrosion behavior and cytotoxicity of Mg-35Zn-3Ca alloy for surface modified biodegradable implant material.

J Biomed Mater Res B Appl Biomater 2012 May 30;100(4):911-23. Epub 2012 Jan 30.

Department of Dental Biomaterials, School of Dentistry and Post BK21 Program, Chonbuk National University, Chonbuk, South Korea.

This study was conducted to investigate the biocompatibility of Mg-Zn-Ca ternary alloy as a biodegradable material. The casting alloy underwent anodization in an alkaline electrolyte at current density 300 mA/cm(2) and frequency 50 Hz to obtain porous oxide layer. Plasma anodization film using pulse was shown to form irregular porous oxide film. As a result of corrosion test, the corrosion current was shown to decrease and the corrosion voltage was shown to increase in the anodized group, which showed the improvement of corrosion resistance after surface treatment. Sodium silicate (0.1 M) was directly oxidized due to high charges caused by spark and then formed SiO(2), and the compounds produced inside the film were shown MgO, Mg(2) SiO(4), and SiO(2.) In the histological examination in rats, all samples of the untreated group were shown to be absorbed 3 weeks later into the body. After the magnesium alloy was implanted, blood vessel expansion and tissue change were shown in the adjacent tissues. However, the changed tissues were shown to return to normal muscle tissues 4 weeks later when the alloy was completely absorbed. These results suggest that anodized Mg-35Zn-3Ca alloy has good biocompatibility in vivo and controls the absorption rate of biomaterials.
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http://dx.doi.org/10.1002/jbm.b.32652DOI Listing
May 2012

The neurosteroids, allopregnanolone and progesterone, induce autophagy in cultured astrocytes.

Neurochem Int 2012 Jan 1;60(2):125-33. Epub 2011 Dec 1.

Neural Injury Research Laboratory, University of Ulsan College of Medicine, Seoul, Republic of Korea.

Recent studies have suggested that neurosteroids such as pregnenolone, progesterone (PG) and their derivatives, have a role in activating autophagy in addition to diverse other functions. In our previous studies, we demonstrated that cellular free Zn(2+) is involved in oxidative stress-induced autophagy and autophagic cell death in astrocytes. In the present study, we examined the possibility that neurosteroids, allopregnanolone (Allo) and PG, also activate autophagy in cultured mouse astrocytes through modulation of intracellular Zn(2+). Exposure of astrocytes to 250 nM Allo or 500 nM PG caused cytosolic vacuoles to appear within a few hours of treatment onset. Live-cell confocal microscopy of astrocytes transfected with red fluorescent protein-conjugated LC3 (RFP-LC3), a marker for autophagic vacuoles (AVs), as well as transmission electron microscopy, revealed that these vacuoles were AVs. In addition, Western blots showed increases in LC3-II levels. Interestingly, mTOR and Akt were concurrently activated, and their blockade further increased LC3-II levels and caused some cell death. These results indicate that co-activation of mTOR and Akt may act to limit neurosteroid-induced autophagy and thus inhibit autophagic cell death. As in other cases of autophagy, cellular Zn(2+) levels increased after treatment with neurosteroids. The neurosteroid-induced increase in LC3-II levels was inhibited by addition of the Zn(2+) chelator TPEN. Both the increase in LC3-II levels and activation of Akt and mTOR by neurosteroids were all mediated by PG receptors, as the effects were blocked by the addition of RU-486, a PG receptor antagonist. Moreover, mutant huntingtin (mHtt) aggregates in GFP-mHttQ74-transfected astrocytes were substantially reduced by neurosteroid treatment, indicating that neurosteroid-induced autophagy may be functional. Present results demonstrate that Allo and PG activate autophagy in astrocytes. Notably, unlike several other autophagy inducers that, in excess, may cause autophagic cell death, Allo and PG are relatively non-toxic, possibly because of concurrent Akt and mTOR activation. Thus, as natural endogenous brain substances, Allo and PG may have a potential as therapeutic agents in neurodegenerative conditions in which abnormal protein aggregates are involved.
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http://dx.doi.org/10.1016/j.neuint.2011.11.015DOI Listing
January 2012

Effect of AOT-assisted multi-walled carbon nanotubes on antibacterial activity.

Colloids Surf B Biointerfaces 2012 Jan 10;89:101-7. Epub 2011 Sep 10.

Department of Dental Biomaterials, School of Dentistry, Brain Korea 21 Project, Chonbuk National University, Jeonju, South Korea.

The dispersing power of surfactant-modified multiwalled carbon nanotubes (MWCNTs) and their effect on the antibacterial activity were examined. The MWCNTs were modified using a dioctyl sodium sulfosuccinate (AOT) surfactant. UV-vis spectroscopy and transmission electron microscopy (TEM) were used to characterize the dispersion of MWCNTs in the aqueous phase. Fourier transform infrared spectroscopy confirmed the results of UV-vis spectroscopy and TEM, indicating that the AOT molecules had been adsorbed successfully onto the MWCNT surface. The highly dispersed AOT-modified MWCNTs showed strong antibacterial activity to Streptococcus mutans. The fluorescence images showed that the AOT-modified MWCNTs were capable of capturing bacteria and forming cell aggregates as well as killing them. The optical density growth curves and colony-forming units assays confirmed that the antibacterial activity of the AOT-modified MWCNTs was concentration-dependent and treatment time-dependent. This finding might be useful for applications of AOT-modified MWCNTs as an antibacterial agent to eliminate pathogens from a biocontaminated water phase.
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http://dx.doi.org/10.1016/j.colsurfb.2011.09.001DOI Listing
January 2012

Role of zinc metallothionein-3 (ZnMt3) in epidermal growth factor (EGF)-induced c-Abl protein activation and actin polymerization in cultured astrocytes.

J Biol Chem 2011 Nov 7;286(47):40847-56. Epub 2011 Sep 7.

Neural Injury Research Lab, University of Ulsan College of Medicine, Seoul 138-736, Korea.

Recent evidence indicates that zinc plays a major role in neurochemistry. Of the many zinc-binding proteins, metallothionein-3 (Mt3) is regarded as one of the major regulators of cellular zinc in the brain. However, biological functions of Mt3 are not yet well characterized. Recently, we found that lysosomal dysfunction in metallothionein-3 (Mt3)-null astrocytes involves down-regulation of c-Abl. In this study, we investigated the role of Mt3 in c-Abl activation and actin polymerization in cultured astrocytes following treatment with epidermal growth factor (EGF). Compared with wild-type (WT) astrocytes, Mt3-null cells exhibited a substantial reduction in the activation of c-Abl upon treatment with EGF. Consistent with previous studies, activation of c-Abl by EGF induced dissociation of c-Abl from F-actin. Mt3 added to astrocytic cell lysates bound F-actin, augmented F-actin polymerization, and promoted the dissociation of c-Abl from F-actin, suggesting a possible role for Mt3 in this process. Conversely, Mt3-deficient astrocytes showed significantly reduced dissociation of c-Abl from F-actin following EGF treatment. Experiments using various peptide fragments of Mt3 showed that a fragment containing the N-terminal TCPCP motif (peptide 1) is sufficient for this effect. Removal of zinc from Mt3 or pep1 with tetrakis(2-pyridylmethyl)ethylenediamine abrogated the effect of Mt3 on the association of c-Abl and F-actin, indicating that zinc binding is necessary for this action. These results suggest that ZnMt3 in cultured astrocytes may be a normal component of c-Abl activation in EGF receptor signaling. Hence, modulation of Mt3 levels or distribution may prove to be a useful strategy for controlling cytoskeletal mobilization following EGF stimulation in brain cells.
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http://dx.doi.org/10.1074/jbc.M111.245993DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3220504PMC
November 2011

Effect of β-phenylethyl isothiocyanate from cruciferous vegetables on growth inhibition and apoptosis of cervical cancer cells through the induction of death receptors 4 and 5.

J Agric Food Chem 2011 Aug 6;59(15):8124-31. Epub 2011 Jul 6.

Department of Oral Pathology, School of Dentistry, Institute of Oral Bioscience, Brain Korea 21, Chonbuk National University, Jeonju, Republic of Korea.

Cruciferous vegetables have been shown to have the possibility to protect against multistep carcinogenesis. β-Phenylethyl isothiocyanate (PEITC) is one component of these vegetables demonstrated to help fight many types of cancer. The present study examined the apoptotic effects of PEITC and its molecular mechanism in human cervical cancer cell lines (HEp-2 and KB). PEITC induced apoptosis to inhibit cell proliferation. According to the protein chip assay, PEITC increased the expression of the death receptors (DR4 and DR5) and cleaved caspase-3 compared to the DMSO treatment group. PEITC also induced caspase-8 and truncated BID. PEITC down-regulated the phosphorylation of extracellular-related kinase (ERK)1/2, whereas neither phospho-c-Jun NH(2)-terminal kinases (JNK) nor phospho-p38 MAPK was changed. The role of ERK in PEITC-induced apoptosis was also investigated using MEK inhibitor (PD98059). PD98059 increased the expression of DR4 and DR5, activated caspase-3, and cleaved PARP. In addition, PEITC decreased the phosphorylation of MEK. Therefore, the apoptotic mechanism of PEITC in cervical cancer cells involves the induction of DR4 and DR5 through the inactivation of ERK and MEK.
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http://dx.doi.org/10.1021/jf2006358DOI Listing
August 2011

Clioquinol induces autophagy in cultured astrocytes and neurons by acting as a zinc ionophore.

Neurobiol Dis 2011 Jun 8;42(3):242-51. Epub 2011 Jan 8.

Department of Biology, University of Yonsei, College of Life Science and Biotechnology, Seoul 120-749, Republic of Korea.

Recent studies have demonstrated that clioquinol, an antibiotic with an anti-amyloid effect, acts as a zinc ionophore under physiological conditions. Because increases in labile zinc may induce autophagy, we examined whether clioquinol induces autophagy in cultured astrocytes in a zinc-dependent manner. Within 1h of exposure to 0.1-10 μM clioquinol, the levels of microtubule-associated protein 1 light chain 3 (LC3)-II, a marker of autophagy, began to increase in astrocytes. Confocal live-cell imaging of GFP-LC3-transfected astrocytes showed the formation of LC3(+) autophagic vacuoles (AVs), providing a further indication that clioquinol induced autophagy. Addition of 3-methyladenine or small-interfering RNA against autophagy-related gene 6 (ATG6/Beclin-1) blocked clioquinol-induced increases in LC3-II. FluoZin-3 fluorescence microscopy showed that, like the zinc ionophore pyrithione, clioquinol increased intracellular zinc levels in the cytosol and AVs in an extracellular zinc-dependent manner. Zinc chelation with N,N,N',N'-tetrakis-(2-pyridylmethyl) ethylenediamine (TPEN) reduced, and addition of zinc increased the levels of LC3-II and LC3(+) puncta, indicating that zinc influx plays a key role therein. Moreover, astrocytes and SH-SY5Y cells expressing mutant huntingtin (mHttQ74) accumulated less aggregates when treated with clioquinol, and this effect was reversed by TPEN. These results indicate that clioquinol-induced autophagy is likely to be physiologically functional. The present study demonstrates that clioquinol induces autophagy in a zinc-dependent manner and contributes to clearance of aggregated proteins in astrocytes and neurons. Hence, in addition to its metal-chelating effect in and around amyloid beta (Aβ) plaques, clioquinol may contribute to the reduction of Aβ loads by activating autophagy by increasing or normalizing intracellular zinc levels in brain cells.
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http://dx.doi.org/10.1016/j.nbd.2011.01.009DOI Listing
June 2011

Evaluation of characteristics on titanium surface treatment for absorption of functional groups.

Chin Med J (Engl) 2010 Nov;123(21):3132-6

School of Stomatology, Binzhou Medical University, Binzhou, Shandong 264003, China.

Background: In order to bind or fix bioactive materials directly to the surface of a Ti implant, the prior binding process of functional groups (FGs, -COOH and -OH) to the implant surface is necessary. Conventional binding processes are so high-cost and complex, so it is essential to find a simple and effective procedure for Ti-FG binding.

Methods: Various electrolyte compositions and electrochemical processing were adopted in this study to develop a relatively simple and effective Ti-FG binding process. The ability of Ti-FG binding and calcium (Ca)/phosphorous (P) absorption and corrosion resistance were evaluated according to various titanium surface treatment in electrolyte involving -COOH and -OH ion by using X ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE-SEM) and potentiodynamic scan method respectively.

Results: In cases of -COOH, the anodic oxidation process (AN) showed an effective binding ability between -COOH and Ti surface. On the other hand, in cases of -OH, there were no significant differences in the result between the conditions used. In regard to the absorption of Ca and P on Ti surface, there was a minimal amount of Ca absorbed but no P was absorbed. The anodic oxidation series showed homogenous corrosion, whereas the electrolyte immersion (EL) series showed unstable corrosion. Although EL-OH showed a novel corrosion potential, the EL-COOH series showed good corrosion resistance over the anodic potential range.

Conclusions: The ability of binding between FG and the Ti surface and Ca/P absorption were strongly associated with the surface potential (ζ potential), which was dependent on the pH of the electrolyte. Accordingly, in order to achieve the effective absorption of various FGs on the Ti surface, it is needed to develop the combination process in addition to the electric affinity, relation with the ζ potential.
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November 2010

Roles of zinc and metallothionein-3 in oxidative stress-induced lysosomal dysfunction, cell death, and autophagy in neurons and astrocytes.

Mol Brain 2010 Oct 26;3(1):30. Epub 2010 Oct 26.

Neural Injury Research Center, Department of Neurology, Asan Institute for Life Science, University of Ulsan, College of Medicine, Seoul 138-736, Korea.

Zinc dyshomeostasis has been recognized as an important mechanism for cell death in acute brain injury. An increase in the level of free or histochemically reactive zinc in astrocytes and neurons is considered one of the major causes of death of these cells in ischemia and trauma. Although zinc dyshomeostasis can lead to cell death via diverse routes, the major pathway appears to involve oxidative stress.Recently, we found that a rise of zinc in autophagic vacuoles, including autolysosomes, is a prerequisite for lysosomal membrane permeabilization and cell death in cultured brain cells exposed to oxidative stress conditions. The source of zinc in this process is likely redox-sensitive zinc-binding proteins such as metallothioneins, which release zinc under oxidative conditions. Of the metallothioneins, metallothionein-3 is especially enriched in the central nervous system, but its physiologic role in this tissue is not well established. Like other metallothioneins, metallothionein-3 may function as metal detoxicant, but is also known to inhibit neurite outgrowth and, sometimes, promote neuronal death, likely by serving as a source of toxic zinc release. In addition, metallothionein-3 regulates lysosomal functions. In the absence of metallothionein-3, there are changes in lysosome-associated membrane protein-1 and -2, and reductions in certain lysosomal enzymes that result in decreased autophagic flux. This may have dual effects on cell survival. In acute oxidative injury, zinc dyshomeostasis and lysosomal membrane permeabilization are diminished in metallothionein-3 null cells, resulting in less cell death. But over the longer term, diminished lysosomal function may lead to the accumulation of abnormal proteins and cause cytotoxicity.The roles of zinc and metallothionein-3 in autophagy and/or lysosomal function have just begun to be investigated. In light of evidence that autophagy and lysosomes may play significant roles in the pathogenesis of various neurological diseases, further insight into the contribution of zinc dynamics and metallothionein-3 function may help provide ways to effectively regulate these processes in brain cells.
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http://dx.doi.org/10.1186/1756-6606-3-30DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2988061PMC
October 2010

Induction of lysosomal dilatation, arrested autophagy, and cell death by chloroquine in cultured ARPE-19 cells.

Invest Ophthalmol Vis Sci 2010 Nov 23;51(11):6030-7. Epub 2010 Jun 23.

Department of Ophthalmology, University of Ulsan, College of Medicine, Seoul, Korea.

Purpose: To characterize and investigate the mechanism of chloroquine (CQ) retinotoxicity in human retinal pigment epithelium-derived ARPE-19 cells.

Methods: Cultured ARPE-19 cells were exposed to 10 to 250 μM CQ, and cell death was quantified using a lactate dehydrogenase release assay. Autophagy was studied in ARPE-19 cells transfected with GFP-LC3. Lysosomes in living cells were stained and observed by live-cell confocal microscopy.

Results: After exposure to CQ, ARPE-19 cells developed cytosolic vacuoles within 1 hour and underwent cell lysis within 24 hours. The levels of LC3-II, beclin-1 and, p62, as well as the number GFP-LC3- and RPF-LC3-positive autophagic vacuoles (AVs), increased after CQ treatment, indicating that autophagy was activated. However, lysosomal staining revealed that almost all AVs were separate from lysosomes; thus, fusion between AVs and lysosomes was completely blocked. In addition, the levels of ubiquitinated proteins and GFP-mHttp aggregates in ARPE-19 cells were increased by CQ, providing further evidence that autophagic degradation was inhibited.

Conclusions: CQ induces vacuole formation and cell death in ARPE-19 cells. Initially, vacuoles developed from enlarged lysosomes, followed by the activation of upstream steps in the autophagy pathway and the formation of LC3-positive AVs. Because CQ blocked the fusion of AVs with lysosomes, autophagic protein degradation was inhibited, indicating that CQ-induced retinotoxicity may be caused by the accumulation of potentially toxic ubiquitinated proteins.
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http://dx.doi.org/10.1167/iovs.10-5278DOI Listing
November 2010

Metallothionein-3 regulates lysosomal function in cultured astrocytes under both normal and oxidative conditions.

Glia 2010 Aug;58(10):1186-96

Neural Injury Research Lab, University of Ulsan College of Medicine, Seoul, Korea.

Cellular zinc plays a key role in lysosomal change and cell death in neurons and astrocytes under oxidative stress. Here, using astrocytes lacking metallothionein-3 (MT3), a potential source of labile zinc in the brain, we studied the role of MT3 in oxidative stress responses. H(2)O(2) induced a large increase in labile zinc in wild-type (WT) astrocytes, but stimulated only a modest rise in MT3-null astrocytes. In addition, H(2)O(2)-induced lysosomal membrane permeabilization (LMP) and cell death were comparably attenuated in MT3-null astrocytes. Expression and glycosylation of Lamp1 (lysosome-associated membrane protein 1) and Lamp2 were increased in MT3-null astrocytes, and the activities of several lysosomal enzymes were significantly reduced, indicating an effect of MT3 on lysosomal components. Consistent with lysosomal dysfunction in MT3-null cells, the level of LC3-II (microtubule-associated protein 1 light chain 3), a marker of early autophagy, was increased by oxidative stress in WT astrocytes, but not in MT3-null cells. Similar changes in Lamp1, LC3, and cathepsin-D were induced by the lysosomal inhibitors bafilomycin A1, chloroquine, and monensin, indicating that lysosomal dysfunction may lie upstream of changes observed in MT3-null astrocytes. Consistent with this idea, lysosomal accumulation of cholesterol and lipofuscin were augmented in MT3-null astrocytes. Similar to the results seen in MT3-null cells, MT3 knockdown by siRNA inhibited oxidative stress-induced increases in zinc and LMP. These results indicate that MT3 may play a key role in normal lysosomal function in cultured astrocytes.
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http://dx.doi.org/10.1002/glia.20998DOI Listing
August 2010