Publications by authors named "Yongseok Han"

Isotropic InP/ZnSe/ZnS quantum dots (QDs) are prepared at a high reaction temperature, which facilitates ZnSe shell growth on random facets of the InP core. Fast crystal growth enables stacking faults elimination, which induces anisotropic growth, and as a result, improves the photoluminescence (PL) quantum yield by nearly 20%. Herein, the effect of the QD morphology on photophysical properties is investigated by observing the PL blinking and ultrafast charge carrier dynamics.

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Diabetes-mediated hyperglycemia is a major risk factor for renal fibrosis, resulting in the development of chronic kidney diseases. To address this issue, the effect of melatonin, which has an antioxidative potential, on renal fibrosis in human renal proximal tubule epithelial cells under high glucose conditions was investigated. Under high glucose conditions, the generation of reactive oxygen species was drastically increased in human renal proximal tubule epithelial cells, which lead to the inhibition of cell proliferation, enlargement of cell size, reduction of cell survival, and suppression of antioxidant enzyme activities.

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Background/aim: Anti-cancer drug resistance restricts the efficacy of chemotherapy in malignant tumors. Casein kinase 2α (CK2α) is highly expressed in 5-fluorouracil (5FU)-resistant colorectal cancer (CRC) cells. We hypothesized that inhibition of CK2α might reduce CRC resistance to 5FU.

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Ischemic injury is a major risk factor for fibrosis. However, the precise mechanisms by which fibrosis is regulated and induced under ischemic oxidative stress conditions are unknown. To address this, we investigated the effect of melatonin on ischemia-induced fibrosis.

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Despite the therapeutic effect of mesenchymal stem cells (MSCs) in ischemic diseases, pathophysiological conditions, including hypoxia, limited nutrient availability, and oxidative stress restrict their potential. To address this issue, we investigated the effect of melatonin on the bioactivities of MSCs. Treatment of MSCs with melatonin increased the expression of peroxisome proliferatoractivated receptor gamma coactivator-1 alpha (PGC-1α).

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Mitochondria are considered to be the powerhouses of cells. They are the most commonly damaged organelles within dopaminergic neurons in patients with Parkinson's disease (PD). Despite the importance of protecting neuronal mitochondria in PD patients, the detailed mechanisms underlying mitochondrial dysfunction during pathogenesis and pathophysiological progression of PD have not yet been elucidated.

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Anti-cancer drug resistance is a serious issue for patients with colorectal cancer (CRC). Although recent studies have shown the mechanism by which CRC cells become drug resistant, novel strategies for overcoming this drug resistance have not yet been developed. To address this problem, we characterized 5-fluorouracil (5FU)-resistant CRC cells after treatment with 5FU, and focused on the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) in these cells.

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Although autologous human mesenchymal stem cells (hMSCs) are a promising source for regenerative stem cell therapy in chronic kidney disease (CKD), the barriers associated with pathophysiological conditions limit therapeutic applicability to patients. We confirmed that level of cellular prion protein (PrP) in serum was decreased and mitochondria function of CKD-derived hMSCs (CKD-hMSCs) was impaired in patients with CKD. We proved that treatment of CKD-hMSCs with tauroursodeoxycholic acid (TUDCA), a bile acid, enhanced the mitochondrial function of these cells through regulation of PINK1-PrP-dependent pathway.

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Object: The purpose of this study was to explore whether melatonin could protect mesenchymal stem cells (MSCs) against ischaemic injury, by inhibiting endoplasmic reticulum (ER) stress and autophagy both in vivo and in vitro.

Materials And Methods: To confirm the protective effect of melatonin against ER stress in MSCs, markers of cell viability, apoptosis and autophagy were analysed. To further investigate the regenerative effect of melatonin-treated MSCs in ischaemic tissues, a murine hindlimb ischaemic model was established.

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Although mesenchymal stem cell (MSC)-based therapy is a treatment strategy for ischemic diseases associated with chronic kidney disease (CKD), MSCs of CKD patients undergo accelerated senescence, with decreased viability and proliferation upon uremic toxin exposure, inhibiting their utility as a potent stem cell source for transplantation therapy. We investigated the effects of melatonin administration in protecting against cell senescence and decreased viability induced by pathophysiological conditions near the engraftment site. MSCs harvested from CKD mouse models were treated with H O to induce oxidative stress.

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Mesenchymal stem cells (MSC) could be a candidate for cell-based therapy in chronic kidney disease (CKD); however, the uremic toxin in patients with CKD restricts the therapeutic efficacy of MSCs. To address this problem, we explored the effect of pioglitazone as a measure against exposure to the uremic toxin -cresol (PC) in MSCs. Under PC exposure conditions, apoptosis of MSCs was induced, as well as PC-induced dysfunction of mitochondria by augmentation of mitofusion, reduction of mitophagy, and inactivation of mitochondrial complexes I and IV.

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Melatonin suppresses tumor development. However, the exact relationship between melatonin and cancer stem cells (CSCs) is poorly understood. This study found that melatonin inhibits colon CSCs by regulating the PrP -Oct4 axis.

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Mesenchymal stem cells (MSCs) are widely used in transplantation therapy due to their multilineage differentiation potential, abundance, and immuno-modulating ability. However, the risk of allograft rejection limits their application. Here, we proposed a novel method to facilitate MSC transplantation with enhanced applicability and efficacy.

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Background/aims: Stem cell transplantation has emerged as a promising therapeutic strategy, but the exact mechanisms by which stem cells exposed to hypoxic conditions increase the survival rate and rescue ischemic injury at the graft site are not well known. In this study, we aimed to determine if c-Met-activated mesenchymal stem cells (MSCs) pre-exposed to hypoxia promote therapeutic efficacy when transplanted to ischemic models, and whether c-Met interacts with cellular prion protein (PrPC) present in the ischemic tissue.

Methods: Western blot analysis was performed to determine the expression levels of PrPC, C-caspase-3, and C-PARP-1, as well as the phosphorylation of Akt, p38, JNK, and BAX.

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Background/aim: Drug resistance restricts the efficacy of chemotherapy in colorectal cancer. However, the detailed molecular mechanism of drug resistance in colorectal cancer cells remains unclear.

Materials And Methods: The level of cellular prion protein (PrP) in oxaliplatin-resistant colorectal cancer (SNU-C5/Oxal-R) cells was assessed.

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Mesenchymal stem cells (MSCs) could be a promising solution in the treatment of various diseases including chronic kidney disease (CKD). However, endoplasmic reticulum (ER) stress induced by ischemia in the area of application limits the integration and survival of MSCs in patients. In our study, we generated ER stress-induced conditions in MSCs using -cresol.

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Cellular prion protein (PrPC) can replace other pivotal molecules due to its interaction with several partners in performing a variety of important biological functions that may differ between embryonic and mature stem cells. Recent studies have revealed major advances in elucidating the putative role of PrPC in the regulation of stem cells and its application in stem cell therapy. What is special about PrPC is that its expression may be regulated by hypoxia‑inducible factor (HIF)‑1α, which is the transcriptional factor of cellular response to hypoxia.

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-Cresol, found at high concentrations in the serum of chronic kidney failure patients, is known to cause cell senescence and other complications in different parts of the body. -Cresol is thought to mediate cytotoxic effects through the induction of autophagy response. However, toxic effects of -cresol on mesenchymal stem cells have not been elucidated.

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Background: Glucose-regulated protein (GRP78), also known as immunoglobulin heavy chain binding protein and as heat shock 70 kDa protein 5, is present in the endoplasmic reticulum (ER) membrane. GRP78 is generally expressed at low concentrations, but is increased by physiological stress. GRP78 is thought to protect against tissue or organ damage under pathological conditions, such as neurotoxic stress, myocardial infarction, or arteriosclerosis.

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Mesenchymal stem cells (MSCs) are promising candidates for stem cell-based therapy in ischemic diseases. However, ischemic injury induces pathophysiological conditions, such as oxidative stress and inflammation, which diminish therapeutic efficacy of MSC-based therapy by reducing survival and functionality of transplanted MSCs. To overcome this problem, we explored the effects of melatonin on the proliferation, resistance to oxidative stress, and immunomodulatory properties of MSCs.

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Although mesenchymal stem cells (MSCs) are a promising cell source for regenerative medicine, ischemia-induced endoplasmic reticulum (ER) stress induces low MSC engraftment and limits their therapeutic efficacy. To overcome this, we investigated the protective effect of tauroursodeoxycholic acid (TUDCA), a bile acid, on ER stress in MSCs in vitro and in vivo. In ER stress conditions, TUDCA treatment of MSCs reduced the activation of ER stress-associated proteins, including GRP78, PERK, eIF2α, ATF4, IRE1α, JNK, p38, and CHOP.

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Mesenchymal stem cells (MSCs) are 'adult' multipotent cells that promote regeneration of injured tissues in vivo. However, differences in oxygenation levels between normoxic culture conditions (21% oxygen) and both the MSC niche (2-8% oxygen) and ischemic injury-induced oxidative stress conditions in vivo have resulted in low efficacy of MSC therapies in both pre-clinical and clinical studies. To address this issue, we examined the effectiveness of hypoxia preconditioning (2% oxygen) for enhancing the bioactivity and tissue-regenerative potential of adipose-derived MSCs.

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Background: Elevated production of reactive oxygen species (ROS) is observed in various cancer types and pathophysiological conditions. In cancer cells, ROS induce cell proliferation, genetic instability, and a malignant phenotype. Ginsenoside Rg3 is the main pharmacologically active component in ginseng and has been reported to have an antioxidant effect.

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Background: The putative functions of the cellular prion protein (PrP(c)) are believed to be associated with cell signaling, differentiation, survival, and cancer progression. With respect to cancer development and progression, elevations and mutations of PrP(c) expression have been shown to increase the risk for malignancy and metastasis in breast and colorectal cancer. Since both natural supplements and direct regulation of PrP(c) expression contribute to inhibition of cancer progression and growth, we hypothesized that knockdown of PrP(c) could lead to an enhanced synergic effect on the inhibition of cancer growth by fucoidan.

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