• 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.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.11
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• pp.1293-1299
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• 2017

Obesity contributes to the development of diseases, such as type II diabetes, hypertension, coronary heart disease, and cancer. In addition, oxidative stress caused by reactive oxygen species (ROS) is recognized widely as a contributing factor in the development of chronic diseases. This study was examined the antioxidant and anti-adipogenic activities of epigallocatechin-3-gallate (EGCG) in 3T3-L1 preadipocytes. 3T3-L1 cells were differentiated with or without EGCG for 6 days. The production of glutathione (GSH) and the activities of the antioxidant enzymes, such as glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD) were measured. EGCG inhibited significantly the lipid accumulation and the expression of adipogenic specific proteins including CCAAT/enhancer binding protein ${\alpha}$ and adipocyte fatty acid binding protein. The production of intracellular ROS was decreased significantly by EGCG in 3T3-L1 cells. EGCG increased the GSH production and the activities of GPx, GR, CAT, and SOD. Moreover, EGCG increased the protein expression of glutamate-cysteine ligase and heme oxygenase-1 in 3T3-L1 cells. These results suggest that EGCG increased the activity and expression of antioxidant enzymes and suppressed the lipid accumulation in 3T3-L1 cells. Therefore, the use of phytochemicals that can maintain the GSH redox balance in adipose tissue could be promising for reducing obesity.

• Biomolecules & Therapeutics
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• v.28 no.5
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• pp.443-455
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• 2020

The thioredoxin (Trx) system plays critical roles in regulating intracellular redox levels and defending organisms against oxidative stress. Recent studies indicated that Trx reductase (TrxR) was overexpressed in various types of human cancer cells indicating that the Trx-TrxR system may be a potential target for anti-cancer drug development. This study investigated the synergistic effect of auranofin, a TrxR-specific inhibitor, on sulforaphane-mediated apoptotic cell death using Hep3B cells. The results showed that sulforaphane significantly enhanced auranofin-induced apoptosis by inhibiting TrxR activity and cell proliferation compared to either single treatment. The synergistic effect of sulforaphane and auranofin on apoptosis was evidenced by an increased annexin-V-positive cells and Sub-G1 cells. The induction of apoptosis by the combined treatment caused the loss of mitochondrial membrane potential (ΔΨm) and upregulation of Bax. In addition, the proteolytic activities of caspases (-3, -8, and -9) and the degradation of poly (ADP-ribose) polymerase, a substrate protein of activated caspase-3, were also higher in the combined treatment. Moreover, combined treatment induced excessive generation of reactive oxygen species (ROS). However, treatment with N-acetyl-L-cysteine, a ROS scavenger, reduced combined treatment-induced ROS production and apoptosis. Thereby, these results deduce that ROS played a pivotal role in apoptosis induced by auranofin and sulforaphane. Furthermore, apoptosis induced by auranofin and sulforaphane was significantly increased through inhibition of the phosphoinositide 3-kinase (PI3K)/Akt pathway. Taken together, the present study demonstrated that down-regulation of TrxR activity contributed to the synergistic effect of auranofin and sulforaphane on apoptosis through ROS production and inhibition of PI3K/Akt signaling pathway.

• Journal of Life Science
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• v.29 no.4
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• pp.410-420
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• 2019

Citrus unshiu peel extracts possess a variety of beneficial effects, and studies on their anticancer activity have been reported. However, the exact mechanisms underlying this activity remain unclear. In the current study, the apoptotic effect of ethanol extract of C. unshiu peel (EECU) on human breast adenocarcinoma MDA-MB-231 cells and related mechanisms were investigated. The results showed that the survival rate of MDA-MB-231 cells treated with EECU was significantly inhibited in a concentration-dependent manner, which was associated with the induction of apoptosis. EECU-induced apoptosis was associated with the activation of caspase-8 and caspase-9, which initiate extrinsic and intrinsic apoptosis pathways, respectively, and caspase-3, a representative effect caspase. EECU suppressed the expression of the inhibitor of apoptosis family of proteins, leading to an increased Bax/Bcl-2 ratio and proteolytic degradation of poly (ADP-ribose) polymerase. EECU also enhanced the loss of the mitochondrial membrane potential and cytochrome c release from the mitochondria to the cytosol, along with truncation of Bid. In addition, EECU activated AMP-activated protein kinase (AMPK), and compound C, an AMPK inhibitor, significantly weakened EECU-induced apoptosis and cell viability reduction. Furthermore, EECU promoted the generation of reactive oxygen species (ROS), which acted as upstream signals for AMPK activation as pretreatment of cells, with the antioxidant N-acetyl cysteine reversing both EECU-induced AMPK activation and apoptosis. Collectively, these findings suggest that EECU inhibits MDA-MB-231 adenocarcinoma cell proliferation by activating intrinsic and extrinsic apoptotic pathways, which was mediated through ROS/AMPK-dependent pathways.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.5
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• pp.272-281
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• 2003

Nontraditional or alternative medicine is becoming an increasingly attractive approach for the treatment of various inflammatory disorders and cancers. Curcumin is the major constitute of turmoric powder extracted from the rhizomes of the plant Curcuma longa. Resveratrol is a phytoalexin present in grapes and a variety of medicinal plants. In this report, We investigated the effect of curcumin and resveratrol on regulatory protein of cell cycle, induction of apoptosis and MMP activity. Treatment with 75 M curcumin for 24 hrs produced morphological changing in HN-4 cells. Curcumin and resveratrol inhibited the cellular growth in HN-4 cells. Inhibition of cell growth was associated with down-regulation of cell cycle regulatory proteins. Curcumin-induced caspase-3 activation and Bax degradation were dose-dependent with a maximal effect at a concentration of 100 M. The elevated caspase-3 activity in curcumin treated HN-4 cells are correlated with down-regulation of survivin and cIAP1, but not cIAP2. Curcumin induced a dose-dependent increase of cytochrome c in the cytosol. Curcumin induced-apoptosis was mediated through the release of cytochrome c. In addition, curcumin-induced apoptosis was caused by the generation of reactive oxygen species, which was prevented by antioxidant N-acetyl-cysteine (NAC). Cotreatment with NAC markedly prevented cytochrome c release, Bax cleavage and cell death. Also resveratrol-induced apoptosis was preceded by down-regulation of the anti-apoptotic Bcl-2, cIAP1, and caspase-3 activity. However, resveratrol-induced apoptosis was not prevented by antioxidant NAC. In addition, HN-4 cells release basal levels of MMP2 when cultured in serum-free medium. Treatment of the cells with various concentrations of PMA for 24 hr induced the expression and secretion of latent MMP9 as determined by gelatin zymography. HN-4 cells were treated with various concentrations of curcumin and resveratrol in the presence of 75 nM PMA, and MMP2 and 9 activities were inhibited by curcumin and resveratrol. These findings have implications for developing curcumin-based anticancer and anti-inflammation therapies.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.32 no.3
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• pp.218-228
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• 2010

Components of dental resin-based restorative materials are reported to leach from the filling materials even after polymerization. Hydroquinone (HQ) is one of the major monomers used in the dental resin and is known as a carcinogen. Thus, carcinogenic risk of HQ leaching from the dental resin becomes a public health concern. The present study attempted to examine the carcinogenic potentials of HQ on the human epithelial cell, which is the target cell origin of the most of oral cancers. Cytotoxicity of HQ was observed above 50${\mu}M$ as measured by LDH assay, indicating a relatively low toxicity of this substance in human epithelial cells. The parameters of neoplastic cellular transformation such as cell saturation density, soft agar colony formation and cell aggregation were analyzed to examine the carcinogenic potential of HQ. The study showed that 2-week exposure of HQ showed the tendency of increase in the saturation density and the significant enhancement of soft agar colony formation at the highest dose, 50 ${\mu}M$ only. It is suggested that HQ has a weak potential of carcinogenicity. When cells were treated with HQ and TPA, a well-known tumor promoter, the parameters of neoplastic cellular transformation was significantly increased. This result indicates that the potential risk of carcinogenicity from HQ is largely dependent upon the presence of promoter. Exposure of 50 ${\mu}M$ HQ increased the time-dependent apoptosis as measured by the ELISA kit. This concentration coincides with a dose of neoplastic transformation, indicating a possible link between apoptosis and HQ-induced cellular transformation. Hydroquinone generated Reactive Oxygen Species (ROS) which was evidenced by the treatment of antioxidants such as trolox and N-acetyl cysteine and the GSH depleting agent, BSO. Antioxidants blocked the generation of ROS and the GSH depleting agent, BSO dramatically increased the ROS production. Since HQ is known to increase ROS production thru activation of transcriptional factor such as c-Myb and Pim-1, it is speculated that ROS generation by HQ plays a role in the activation of oncogene, which may lead to neoplastic transformation. In addition, ROS is involved in the alteration of signal transduction, which regulates the apoptosis in many cellular systems. Thus, ROS-mediated apoptosis may be involved in the HQ-induced carcinogenic processes. Protein kinase C (PKC) is known to play pivotal roles in neoplastic transformation of cells and its high expression is often found in a variety of types of tumors including oral cancer. PKC translocation of PKC-${\alpha}$ was observed following HQ exposure. Altered signaling system may also play a role in the transformation process. Taken together, HQ leached from the dental resin does not pose a significant threat as a cancer causing agent, but its carcinogenic potential can be significantly elevated in the presence of promoter. The mechanism of HQ-induced carcinogenesis involved ROS generation, apoptosis and altered signaling pathway. The present study will provide a valuable data to estimate the potential risk of HQ as a carcinogen and understand mechanism of HQ-induced carcinogenesis in human epithelial cells.

• Journal of Life Science
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• v.31 no.1
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• pp.37-46
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• 2021

The effects of freeze-dried powder from fresh and black garlic hot water extracts on the lipid metabolism in Sprague-Dawley rats fed a high-cholesterol diet were analyzed. The experimental group was classified into the normal group (NG), the high-fat (HF) and high-cholesterol diet group (CG), the HFC and 1% fresh garlic hot water extract powder-added diet group (FGEG), and the HFC and 1% black garlic hot water extract powder-added diet group (BGEG), respectively. The serum total lipid content was 381.52±7.30 mg/ml and 368.80±4.40 mg/ml in the FGEG and the BGEG, respectively, and was significantly lower than that of the CG. The total cholesterol and triglyceride contents of the FGEG and BGEG were also significantly lower than that of the CG. The high-density lipoprotein (HDL) cholesterol was significantly higher, and the low-density lipoprotein (LDL) and the very low-density lipoprotein (VLDL) cholesterol content was lower in the FGEG and BGEG than in the CG. The serum ALT and AST activities were significantly lower than those of the CG, and especially the BGEG was lower. The total cholesterol content and the triglyceride levels of the liver tissue were 36.0% and 14.3% lower in the BGEG than in the CG, respectively. The thiobarbituric acid reactive substance (TBARS) concentrations in the serum and the liver tissue were higher in the CG than in the FGEG and BGEG, but there was no difference between them. Based on these results, garlic extract powders significantly reduced the lipid profile and increased the antioxidant activity in rats in vivo. The black garlic hot water extract powder was more effective than raw garlic because of the total number of phenolic compounds and browning substances in the black garlic.

• Journal of Life Science
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• v.32 no.4
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• pp.310-317
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• 2022

Recently, interest in the harmful factors of particulate matter (PM), a major component of air pollution, has been increasing. In particular, PM_2.5 with a diameter of less than 2.5 ㎛ is well known to induce oxidative stress accompanied by autophagy in human lung epithelial cells. However, studies on whether PM_2.5 increases autophagy under oxidative stress and whether this process is reactive oxygen species (ROS)-dependent are insufficient. Therefore, in this study, we investigated whether PM_2.5 promotes autophagy through the generation of ROS in human alveolar epithelial A594 cells. According to our results, cells co-treated with PM_2.5 and hydrogen peroxide (H₂O₂) showed a lower cell viability than cells treated with each alone, which was associated with increased total and mitochondrial ROS production. The co-treatment of PM_2.5 and H₂O₂ also increased autophagy induction, which was confirmed through Cyto-ID staining, and the expression of autophagy biomarker proteins increased. However, when ROS generation was artificially blocked by N-acetyl-L-cysteine pretreatment, the reduction in cell viability and induction of autophagy by PM_2.5 and H₂O₂ co-treatment were markedly attenuated. Therefore, the present results suggest that PM_2.5-induced ROS generation may play a critical role in autophagy induction in A549 cells.