• Toxicological Research
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• v.22 no.4
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• pp.423-429
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• 2006

Recent reports on the photocarcinogenicity and photogerotoxicity of many compounds led to an increasing awareness for the need of a standard approach to test for photogenotoxicity. The comet assay has been recently validated as a sensitive and specific test system for the quantification of DNA damage. Thus, the objectives of this study are to investigate the utility of photo-comet assay for detecting photo-mutagens, and to evaluate its ability to predict rodent photo-carcinogenicity. Photo-comet assays were performed using L5178Y $Tk^{+/-}$ mouse lymphoma cells on five test substances (8-methoxypsoralen, chlorpromazine, lomefloxacin, anthracene and retinoic acid) that demonstrated positive results in photocarcinogenicity tests. For the best discrimination between the test substance-mediated DNA damage and the undesirable DNA damage caused by direct UV absorption, a UV dose-response of the cells in the absence of the test substances was firstly fnalized. Out of 5 test substances, positive comet results were obtained for chlorpromazine, lomefloxacin, anthracene and retinoic acid while 8-methoxypsoralen found negative. An investigation into the predictive value of this photo-comet assay for determining the photocarcinogenicity showed that photo-comet assay has relatively high sensitivity. Therefore, the photo-comet assay with mammalian cells seems to be a good and sensitive predictor of the photocarcinogenic potential of new substances.

• Development and Reproduction
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• v.13 no.3
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• pp.155-161
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• 2009

It has been reported that ganglioside GT1b is expressed during neuronal cell differentiation from undifferentiated mouse embryonic stem cells (mESCs), which suggests that ganglioside GT1b has a direct effect on neuronal cell differentiation. Therefore, this study was conducted to evaluate the effect of exogenous addition of ganglioside GT1b to an in vitro model of neuronal cell differentiation from undifferentiated mESCs. The results revealed that a significant increase in the expression of ganglioside GT1b occurred during neuronal differentiation of undifferentiated mESCs. Next, we evaluated the effect of retinoic acid (RA) on GT1b-treated undifferentiated mESCs, which was found to lead to increased neuronal differentiation. Taken together, the results of this study suggest that ganglioside GT1b plays a crucial role in neuronal differentiation of mESCs.

• Animal cells and systems
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• v.4 no.2
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• pp.145-150
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• 2000

Retinoic acid (RA) evokes pattern duplication in the regenerating salamander limb. Interestingly, it also enhances dedifferentiation in the regenerate by the morphological, histological and biochemical criteria. To examine whether there is any correlation between the RA-evoked pattern duplication and de novo protein synthetic profile in the regenerating salamander limb, especially during dedifferentiation, we analyzed stage-specific protein synthesis pattern in the normal and RA-treated regenerating limbs by metabolic labeling followed by two-dimensional gel electrophoresis. In the regenerating limbs without RA treatment, a few hundred kinds of proteins were found to be synthesized at the stage of wound healing and the total number of protein synthesized increased greatly as regeneration proceeded. The same trend was also observed in the RA-treated regenerating limbs. Interestingly, some protein spots were noted to be either newly synthesized or highly expressed by the RA treatment especially at the stage of dedifferentiation. The results shows that the enhancement of dedifferentiation state after the RA treatment correlates well with the protein synthesis profile, and suggest that those proteins are important for the RA-evoked pattern duplication in the regenerating limbs of salamander.

• Clinical and Experimental Pediatrics
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• v.54 no.3
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• pp.95-105
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• 2011

Since the successful introduction of all-trans-retinoic acid (ATRA) and its combination with anthracycline-containing chemotherapy, the prognosis for acute promyelocytic leukemia (APL) has markedly improved. With ATRA and anthracycline-based-chemotherapy, the complete remission rate is greater than 90%, and the long-term survival rate is 70-89%. Moreover, arsenic trioxide (ATO), which was introduced for APL treatment in 1994, resulted in excellent remission rates in relapsed patients with APL, and more recently, several clinical studies have been designed to explore its role in initial therapy either alone or in combination with ATRA. APL is a rare disease in children and is frequently associated with hyperleukocytosis, which is a marker for higher risk of relapse and an increased incidence of microgranular morphology. The frequency of occurrence of the promyelocytic leu-kemia/retinoic acid receptor-alpha (PML/$RAR{\alpha}$) isoforms bcr 2 and bcr 3 is higher in children than in adults. Although recent clinical studies have reported comparable long-term survival rates in patients with APL, therapy for APL in children is challenging because of the risk of early death and the potential long-term cardiac toxicity resulting from the need to use high doses of anthracyclines. Additional prospective, randomized, large clinical trials are needed to address several issues in pediatric APL and to possibly minimize or eliminate the need for chemotherapy by combining ATRA and ATO. In this review article, we discuss the molecular pathogenesis, diagnostic progress, and most recent therapeutic advances in the treatment of children with APL.

• IMMUNE NETWORK
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• v.22 no.4
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• pp.36.1-36.12
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• 2022

Dexamethasone (DEX) was the first drug shown to save lives of critically ill coronavirus disease 2019 (COVID-19) patients suffering from respiratory distress. A hyperactivated state of neutrophils was found in COVID-19 patients compared to non-COVID pneumonia cases. Given the beneficial effects of DEX in COVID-19 patients, we investigated the effects of DEX and of other immunomodulatory drugs vitamin D3 (VD3) and retinoic acid (RA) on neutrophil function. DEX, but not VD3 or RA, significantly inhibited all tested aspects of neutrophil function, e.g., degranulation, intracellular ROS production, CXCL8 release and NETosis. Interestingly, RA displayed the opposite effect by significantly increasing both CXCL8 and NET release by neutrophils. Taken together, these data suggest that the lower COVID-19 mortality in DEX-treated patients may in part be due to the dampening effect of DEX on the inflammatory neutrophil response, which could prevent neutrophil plugs with NETS in the lungs and other inflamed organs of patients.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.6
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• pp.848-858
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• 1995

The present study was conducted to investigate the effect of dietary vitamin A on the antioxidant status in ethanol-treated rats. Weaning rats were fed a basal diet until they reached about 160-180g body weight. Thereafter, four experimental groups were fed a liquid diet containing 36% ethanol of total calorie and four pair-fed groups were fed isocaloric sucorse instead of ethanol. Additionally, the liquid diet contained adequate amount of ${\beta}-carotene$, retinyl acetate, or 13-cis-retinoic acid except vitamin A deficient diet. The rats were sacrificed after 7 weeks of feedng periods. Significant decrease in hepatic vitamin E content was found in rats treated with chronic ethanol. However, dietary supplementation of retinyl acetate modified the change to some extent. Total vitamin C content of liver increased in vitamin A-deficient or ${\beta}-carotene$ groups with ethanol feeding. The ratio of reduced/oxidized vitamin C increased in the plasma and liver of ${\beta}-carotene$ group with ethanol feeding. Chronic ethanol intake did not change the total glutathione content of rat liver, but increased reduced glutathione(GSH)/oxidized glutathione(GSSG) ratio. This increase in hepatic GSH after chronic ethanol treatment. The changes of Se content in plasma and liver was not consistant. Fe content of liver increased by ethanol treatment, but this increase reduced in rats fed dietary retinyl acetate or 13-cis-retinoic acid. Fe content of plasma increased in vitamin A-deficient and ${\beta}-carotene$ supplemented groups with ethanol intake.

• BMB Reports
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• v.33 no.5
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• pp.402-406
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• 2000

In order to understand the role of AGP on the differentiation of promyelocytic leukemia cells, the AGP expression and its relation to cytokines were investigated during granulocytic or monocytic differentiation of HL-60 cells. When HL-60 cells were treated with all-trans-retinoic acid (ATRA) for 5 days, the cells were fully differentiated into granulocytes, and the AGP mRNA and protein levels were continuously increased up to 5 days in a dose- and time- dependent manner. However, in the case of the monocytic differentiation of HL-60 cells by tetradeanoyl phorbol acetate (TPA), the AGP gene expression was not induced. In addition, $IL-1{\alpha}$, $IL-1{\beta}$, IL-6 and $TNF-{\alpha}$ mRNAs were also enhanced during granulocytic differentiation. These cytokine transcripts showed a peak level 3 days after the ATRA treatment. It decreased gradually thereafter. However, direct addition of recombinant cytokines ($IL-1{\beta}$, IL-6 and $TNF-{\alpha}$) and dexamethasone to the HL-60 cell cultures showed no AGP induction. These findings suggest that the AGP and proinflammatory cytokines are expressed in ATRA-treated promyelocytic cells. However, these cytokines do not act as autocrine inducers on AGP expression. This fact implies that the AGP expression during granulocytic differentiation of HL-60 cells is induced through a signal pathway different from hepatocyte signaling in inflammation.

• IMMUNE NETWORK
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• v.1 no.1
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• pp.36-44
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• 2001

Background : Peritoneal metastasis is one of the maj or types of the stomach cancer recurrence and the role of the adhesion molecules is thought to be very much important in this event. Retinoic acid (RA) has been known to induce the growth inhibition and differentiation of various malignancies, and apoptpsis and the change of expression of adhesion molecules have been reported to be involved in the action of RA. Methods : We studied the adhesion abilities of SNU-1, SNU-5, and SNU-6 cells to the peritoneal endothelial cells as well as the expression of the adhesion molecules (CD44, ICAM-1) in Western blot analysis. And also we studied the expression of apoptosis and the change of expression patterns of the various isoforms of CD44 and the change of the adhsion abilities of the cell line cells after RA treatment. Results: CD44 was expressed in SNU-5 and -16, together with an isoform in SNU-16. ICAM-1 was not expressed in any of the cell line cells tested. After the treatment of RA in the concentration range of $1-5{\times}10^{-5}M$ to three stomach cancer cell lines, growth inhibition, apoptosis and the change of expression of the CD44 were noted. After RA treatment, the expression of CD44H was weakly increased in SNU-1, and was markedly increased in SNU-5. In SNU-16, the expression of CD44H was decreased while that of CD44E were markedly increased. The adhesibility of cells to peritoneal cells was increased in relation with the increase of the CD44H expression, which shows the fact that the adhesibility of tumor cells to peritoneal mesothelial cells is mediated by CD44H recognizing hyaluronic acid. Conclusion : RA induces growth inhibition of stomach cancer cell line cells and increase the adhesiblity of stomach cancer cell line cells to peritoneal mesothelium. It is believed that RA decreases the metastatic ability of stomach cancer cells by upregulating the CD44H expression.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2003.10a
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• pp.102-102
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• 2003

Embryonic stem (ES) cells proliferate extensively in the undifferentiated state and have the potential to differentiate into a variety of cell types in response to various environmental cues. The generation of functional dopaminergic neurons from ES cells is promising for cell replacement therapy to treat Parkinson's disease. We compared the in vitro differentiation potential of pluripotent human embryonic stem (hES, MB03) cells induced with basic fibroblast growth factor (bFGF) or retinoic acid (RA). Both types of treatment resulted in similar neural cell differentiation patterns at the terminal differentiation stage, specifically, 75% neurons and 11% glial cells. Additionally, treatment of hES cells with brain derived neurotrophic factor (BDNF) or transforming growth factor (TGF)- $\alpha$ during the terminal differentiation stage led to significantly increased tyrosine hydroxylase (TH) expression, compared to control (P<0.05). In contrast, no effect was observed on the rate of mature or glutamic acid decarboxylase-positive neurons. Immunostaining and HPLC analyses revealed the higher levels of TH (20.3%) and dopamine in bFGF and TGF-$\alpha$ treated hES cells than in RA or BDNF treated hES cells. The results indicate that TGF-$\alpha$ may be successfully used in the bFGF induction protocol to yield higher numbers of functional dopaminergic neurons from hES cells.

• Proceedings of the KSAR Conference
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• 2003.06a
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• pp.75-75
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• 2003

Since the establishment of embryonic stem cell, pluripotency of the cells was known to allow differentiation of the cells into various cell types consisting whole body. Several protocols have been developed to induce expression of specific genes.. However, no precise protocol that will generate a single type of the cells from stem cells has been reported. In order to produce cells suitable for transplantion into brain of PD animal model, which arouse due to a progressive degeneration of dopaminergic neurons in midbrain, human embryonic stem cell (hESC, MB03) was transfected with cDNAs cording for tyrosine hydroxylase (TH). Successful transfection was confirmed by western immunoblotting. Newly transfected cell line (TH#2/MB03) was induced to differentiate by the two neurogenic factors retinoic acid (RA) and b-FGF. Exp. I) Upon differentiation using RA/ascorbic acid (AA), embryoid bodies (EB, for 4days) derived from hES cells were exposed to RA (10$^{-6}$ M)/AA (50 mM) for 4 days, and were allowed to differentiate in N2 medium for 7, 14, 21, or 28 days. Exp. II) When bFGF was used, neuronal precursor cells were selected for 8 days in N2 medium after EB formation. After selection, cells were expanded at the presence of bFGF (20 ng/ml) for another 6 days followed by a final differentiation in N2 medium for 7, 14, 21 or 28 days. By indirect immunocytochemical studies, proportion of cells expressing NF200 increased rapidly from 20% at 7 days to 70 % at 28 days in RA/AA-treated group, while those cells expressing NF160 decreased from 80% at 7 days to 10% at 28 days upon differentiation in N2 medium. However, in differentiation by RA/AA treatment system, there was a significant increase in proportion of neuron maturity (73%) at day 14 after N2 medium. TH#2/MB03 cells expressing TH are >90% when matured at the absence of either bDNF or TGF-$\alpha$. These results suggested that TH#2/MB03 cells could be differentiated in vitro into mature neurons by RA/AA.