• BMB Reports
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• v.37 no.2
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• pp.185-191
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• 2004

Tissue transglutaminase (tTGase) regulates various biological processes, including extracellular matrix organization, cellular differentiation, and apoptosis. Here we report the protective role of tTGase in the cell death that is induced by the tumor necrosis factor $\alpha$ (TNF-$\alpha$) and ceramide, a product of the TNF-$\alpha$ signaling pathway, in human neuroblastoma SH-SY5Y cells. Treatment with retinoic acid (RA) induced the differentiation of the neuroblastoma cells with the formation of extended neurites. Immunostaining and Western blot analysis showed the tTGase expression by RA treatment. TNF-$\alpha$ or $C_2$ ceramide, a cell permeable ceramide analog, induced cell death in normal cells, but cell death was largely inhibited by the RA treatment. The inhibition of tTGase by the tTGase inhibitors, monodansylcadaverine and cystamine, eliminated the protective role of RA-treatment in the cell death that is caused by TNF-$\alpha$ or $C_2$-ceramide. In addition, the co-treatment of TNF-$\alpha$ and cycloheximide ecreased the protein level of tTGase and cell viability in the RA-treated cells, supporting the role of tTGase in the protection of cell death. DNA fragmentation was also induced by the co-treatment of TNF-$\alpha$ and cycloheximide. These results suggest that tTGase expressed by RA treatment plays an important role in the protection of cell death caused by TNF-$\alpha$ and ceramide.

• Journal of Life Science
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• v.25 no.3
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• pp.285-292
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• 2015

Citrus peel (CP) is used as a traditional herb with diverse beneficial pharmacological activities, such as anti-inflammatory, anti-oxidant, and anti-allergic effects. However, the anti-obesity effects of citrus peel are poorly defined. The aim of this study was to evaluate ethanol extracts of citrus peel (EECP) for its adipocyte differentiation and adipogenesis in 3T3-L1 preadipocytes. The aim of this study was to evaluate an EECP for its adipocyte differentiation and adipogenesis in 3T3-L1 preadipocytes. Treatment with EECP significantly suppressed the terminal differentiation of 3T3-L1 preadipocytes in a dose-dependent manner, as confirmed by a decrease in lipid droplet number and lipid content and an accumulation of cellular triglyceride. EECP exhibited potential adipogenesis inhibition and downregulated the expression of pro-adipogenic transcription factors, such as sterol regulatory elementbinding protein-1c (SREBP-1c), peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT/enhancerbinding proteins α (C/EBPα) and C/EBPβ, and adipocyte expressed genes, such as adipocyte fatty acid binding protein (aP2) and Leptin. In addition, EECP treatment effectively activated the AMP-activated protein kinase (AMPK) signaling pathway; however, compound C, a specific inhibitor of AMPK, significantly reduced the EECP-induced inhibition of adipogenesis. Taken together, these results indicate EECP showed strong anti-obesity effects through the AMPK signaling pathway, and further studies will be needed to identify the active compounds that confer the anti-obesity activity of EECP.

• Korean Journal of Poultry Science
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• v.50 no.4
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• pp.283-291
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• 2023

Long-chain fatty acids (LCFAs) are vital in cellular compartments, primarily regulating lipid metabolism. Fatty Acid-Binding Proteins (FABPs) facilitate LCFA transport, lipid synthesis, storage, and act as signaling molecules influencing various pathways, including inflammation. FABP4, in particular, is linked to vascular and cardio-related diseases, and it plays a role in macrophage-mediated inflammatory responses. Previous studies have identified FABP4 as not only a representative biomarker for lipogenesis but also as having correlations with immune responses. This study aims to investigate the regulation of the chicken FABP4 (chFABP4) gene by toll-like receptor 3 (TLR3) activation and determine the signaling pathways that are involved in chFABP4 transcriptional regulation. We analyzed the transcriptional regulation of chFABP4 in TLR3-stimulated DF-1 cells. The results showed that chFABP4 was up-regulated upon stimulation with polyinosinic-polycytidylic acid (PIC), a TLR3 ligand. Notably, chFABP4 transcription was independently regulated in the NF-κB signaling pathway. It was up-regulated in p38 inhibition, demonstrating that the p38 signaling pathway might suppress the transcription of chFABP4 within TLR3-activated DF-1 cells. In contrast, chFABP4 expression was down-regulated in JNK signaling pathway inhibition, suggesting the positive regulation of JNK signaling pathway for chFABP4 transcription in DF-1 cells in response to TLR3 activation, consistent with findings in macrophages. MEK pathway inhibition resulted in a similar regulation to NF-κB signaling. These results suggest that each MAPK contributes differentially to the transcriptional regulation of chFABP4 by in DF-1 cells in response to TLR3 activation.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.26 no.3
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• pp.254-261
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• 2000

The present study has attempted to look into the mechanism of ras-induced carcinogenesis in a human epithelial cell system. Human epithelial cells immortalized with Ad12-SV40 hybrid virus were used to assess carcinogenic potential of the ras-oncogene. Cells transfected with pSV2-ras showed characteristics of cellular transformation. The transformation parameters such as cell density, soft-agar colony formation, and cell aggregation were significantly increased in the cells expressing ras oncoprotein. In addition, the duration required for the appearance of foci was shortened in the ras-transfected cells. Consistent with other reports, our results demonstrated an evidence that the ras-oncogene induced the cellular transformation of human epithelial cell system. When a high concentration of glucocorticoid was added into the media, transformation process was accelerated. It is speculated that glucocorticoid may provide an advantageous environment for the proliferation of the transformed cells. The induction of the intracellular free calcium concentrations following agonist treatment was significantly lower in the transformed cells than in the control cells. These effects were more manifested in the presence of extracellular cacium, indicating that the transformation process may alter the influx pathway of extracellular calcium. The induction of $IP_3$ following agonist treatment was also lower in the transformed cells than in the control cells. Thus, it is suggested that phospholipase C-coupled pathway was down-regulated in the process of the ras-induced transformation. While the levels of $TGF-{\beta}_1$ and PAI-2 mRNAs were decreased, the level of fibronectin mRNA was increased. The results indicate that mechanism of the ras-induced transformation may be associated with the altered expressions of growth regulatory factors. The present study demonstrates an evidence that the ras-induced cellular transformation may be associated with alteration of signal transduction and growth regulatory factors. The study will contribute to improve the understanding of molecular mechanism of epithelium-derived cancers including oral cancer.

• Journal of Photoscience
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• v.3 no.1
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• pp.1-7
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• 1996

When cucumber (Cucumis sativus L.) cotyledon discs were floated on $\delta$-aminolevulinic acid, oxyfluorfen, or rose bengal solution under light condition following 20 h dark incubation, rapid electrolyte leakage from the tissues occurred. The electrolyte leakage from the tissues was dependent on the compounds treated, their concentrations, and the duration of light exposure to the tissues. Dark incubation before exposure to continuous white light enhanced electrolyte leakage from the tissues treated with the compounds and reduced lag period for the activity of the compounds. Electrolyte leakage from the treated tissues was greatly influenced by the light intensity to which they were exposed. Higher light intensities stimulated electrolyte leakage and reduced lag period. Porphyrin biosynthesis inhibitors, gabaculine and 4,6-dioxoheptanoic acid, completely inhibited electrolyte leakage from the oxyfluorfen-treated tissues. Protection against the activity of $\delta$-aminolevulinic acid from electrolyte leakage was complete with 4,6-dioxoheptanoic acid, but not with gabaculine. However, gabaculine and 4,6-dioxoheptanoic acid gave no such protection against rose bengal activity. In summary, our results indicate that $\delta$--aminolevulinic acid, oxyfluorfen, and rose bengal exert their effects by causing electrolyte leakage from the treated tissues in a similar manner, except that oxyfluorfen has an apparent lag period for its action on electrolyte leakage increase. All above compounds require preincubation of treated tissues in darkness and subsequent light exposure with a high intensity for their maximal activities. Our results also support that in the presence of light, $\delta$-aminolevulinic acid and oxyfluorfen cause cellular damage through the indirect generation of singlet oxygen from accumulated tetrapyrroles of porphyrin pathway, whereas rose bengal causes cellular damage through the direct generation of singlet oxygen.

• Korean Journal of Biological Psychiatry
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• v.8 no.1
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• pp.3-19
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• 2001

Recent basic and clinical studies demonstrate a major role for neural plasticity in the etiology and treatment of depression and stress-related illness. The neural plasticity is reflected both in the birth of new cell in the adult brain(neurogenesis) and the death of genetically healthy cells(apoptosis) in the response to the individual's interaction with the environment. The neural plasticity includes adaptations of intracellular signal transduction pathway and gene expression, as well as alterations in neuronal morphology and cell survival. At the cellular level, repeated stress causes shortening and debranching of dendrite in the CA3 region of hippocampus and suppress neurogenesis of dentate gyrus granule neurons. At the molecular level, both form of structural remodeling appear to be mediated by glucocorticoid hormone working in concert with glutamate and N-methyl-D-aspartate(NMDA) receptor, along with transmitters such as serotonin and GABA-benzodiazepine system. In addition, the decreased expression and reduced level of brain-derived neurotrophic factor(BDNF) could contribute the atrophy and decreased function of stress-vulnerable hippocampal neurons. It is also suggested that atrophy and death of neurons in the hippocampus, as well as prefrontal cortex and possibly other regions, could contribute to the pathophysiology of depression. Antidepressant treatment could oppose these adverse cellular effects, which may be regarded as a loss of neural plasticity, by blocking or reversing the atrophy of hippocampal neurons and by increasing cell survival and function via up-regulation of cyclic adenosine monophosphate response element-binding proteins(CREB) and BDNF. In this article, the molecular and cellular mechanisms that underlie stress, depression, and action of antidepressant are precisely discussed.

• Biomolecules & Therapeutics
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• v.19 no.3
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• pp.282-287
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• 2011

Sirt1, a nicotinamide adenine dinucleotide ($NAD^+$)-dependent histone deacetylase, is known to deacetylate a number of proteins that are involved in various cellular pathways such as the stress response, apoptosis and cell growth. Modulation of the stress response by Sirtuin 1 (Sirt1) is achieved by the deacetylation of key proteins in a cellular pathway, and leads to a delay in the onset of cancer or aging. In particular, Sirt1 is known to play an important role in maintaining genomic stability, which may be strongly associated with a protective effect during tumorigenesis and during the onset of aging. In these studies, Sirt1 was generated in stably expressing cells and during the stimulation of DNA damage to examine whether it promotes survival. Sirt1 expressing cells facilitated the repair of DNA damage induced by either ionizing radiation (IR) or bleomycin (BLM) treatment. Fastened damaged DNA repair in Sirt1 expressing cells corresponded to prompt activation of Chk2 and ${\gamma}$-H2AX foci formation and promoted survival. Inhibition of Sirt1 enzymatic activity by a chemical inhibitor, nicotinamide (NIC), delayed DNA damage repair, indicating that promoted DNA damage repair by Sirt1 functions to induce survival when DNA damage occurs.

• Animal cells and systems
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• v.11 no.2
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• pp.129-134
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• 2007

The initiation of eukaryotic DNA replication requires assembly of the pre-replicative complex (Pre-RC) through the concerted action of Orc, Cdc6, Cdt1 and Mcm2-7 complex during G1 phase. The pre-RC assembly licenses individual replication origins for the initiation of DNA replication and sufficient number of the pre-RC is essential for proper progression of S phase. However, it is not well known how cells recognize the completion of the pre-RC assembly before G1-S transition. In order to understand the cellular responses to the defects in pre-RC assembly, we depleted the known components of pre-RC proteins using the small interference RNAs in HeLa cells. Although the defects of pre-RC assembly by the depletion of the pre-RC proteins such as Orc2, Cdt1, Mcm2 & Mcm10 did not elicit the activation of Chk1- or Chk2-dependent checkpoint pathways, these cells still showed significant decrease in the cellular level of Cdc25A proteins. These results suggests that a novel checkpoint pathway exist in HeLa cells, which is not dependent upon Chk1 or Chk2 proteins and play essential roles in the cellular responses to the defects in the pre-RC assembly. Also, among those four proteins tested in this study, the depletion of Mcm10 and Cdt1 proteins significantly increased the apoptotic cell death in HeLa cells, suggesting that these proteins not only play roles in the pre-RC assembly, but also are involved in the checkpoint responses to the defects in the pre-RC assembly.

• Molecular & Cellular Toxicology
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• v.1 no.2
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• pp.137-141
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• 2005

The critical role of folate in the remethylation pathway for methionine synthesis from homocysteine has been well documented. Hyperhomocysteinemia resulting from inadequate folate nutrition has been implicated in increased incidence of macrovascular diseases, colorectal cancer, neural tube defects, etc. Chronic exposure to ethanol impairs folate nutrition and one-carbon metabolism in the liver, which often results in fatty liver due to a defective remetylation process. This study was carried out to investigate the chronic effects of moderate levels of alcohol and dietary folate on plasma homocysteine levels, and on histopathology and biochemical functions of the liver. Rats were raised on experimental diets with three levels of folate (0, 2, 8 mg/kg diet), and 50% ethanol (1.8 ml/kg body weight) was administered intragastically by intubation tubes three times a week for 10 weeks. Plasma homocysteine concentrations were found to be significantly influenced by dietary folate intake and alcohol administration. Among all treatment groups, plasma homocysteine levels were the highest in the animals receiving a combined treatment of folate deficient diet and alcohol administration. Plasma homocysteine concentrations were negatively correlated with folate concentration in the plasma (p<0.01) and liver (p<0.05). Among alcohol treated rats, increase in plasma homocysteine values due to macrovascular and microvascular fatty changes and spotted necrosis were observed more frequently in folate-deficient animals diet than those on folate-adequate and folate supplemented diets in alcohol-treated rats. These results indicate that folate supplementation above the recommended level might be beneficial in the prevention of alcohol-related hyperhomocysteinemia and abnormal histologic changes in the liver.

• Animal cells and systems
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• v.6 no.1
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• pp.69-74
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• 2002

Recent evidence has suggested that trunk neural crest cell generally assumed to have equivalent differentiation potentials, demonstrate differentiation bias along the anterior/posterior axis. In amphibian and fish, neural crest cells give rise to three chromatophore types, melanophores, xantho-phores, and iridophores. Each pigment cell type has distinct characteristics but there is speculation about the cellular plasticity that exists among them. Neural crest cells migrate along specific routes, ventromedially and dorsolaterally. Neural crest cells that travel dorsolaterally are the first cells to begin migration in the axolotl and are the major contributors to the visible pigment pattern. Many factors and mechanisms that are responsible for guiding migratory neural crest cells along potential pathways or determining their fate remain unknown. A single lineage of the crest, which becomes restricted to one of the three pigment cell types, gives us the opportunity to examine the existence of neural crest stem cell populations and cellular plasticity. Study presented here showed results from recent in vitro studies designed to identify parameters influencing differentiation events of individual neural crest-derived pigment cell lineages. Melanophore production from neural crest explants originating from different levels along the anterior/posterior axis of wild type-axolotl embryos were compared and demonstrate that the differentiation of melanophores is enhanced in subpopulation of neural crest treated with forskolin. Forskolin (an adenylate cyclase activator) increases intracellular CAMP concentration and eventually activates the protein kinase-A signaling pathway. Melanophore number, melanin content, and tyrosinase activity in explants taken from the anterior-most region of the crest increased significantly in response to forskolin treatment. This study suggests implications of region specific influences and developmental regulation in the development of pigment pattern.