• Nutrition Research and Practice
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• v.4 no.4
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• pp.276-282
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• 2010

The principal objective of this study was to evaluate the chemopreventive and therapeutic effects of a combination of all-trans-retinoic acid (RA) and knockdown of delta-like 1 homologue (Drosophila) (DLK1) on neuroblastoma, the most common malignant disease in children. As unfavorable neuroblastoma is poorly differentiated, neuroblastoma cell was induced differentiation by RA or DLK1 knockdown. Neuroblastoma cells showed elongated neurite growth, a hallmark of neuronal differentiation at various doses of RA, as well as by DLK1 knockdown. In order to determine whether or not a combination of RA and DLK1 knockdown exerts a greater chemotherapeutic effect on neuroblastoma, cells were incubated at 10 nM RA after being transfected with SiRNA-DLK1. Neuronal differentiation was increased more by a combination of RA and DLK1 knockdown than by single treatment. Additionally, in order to assess the signal pathway of neuroblastoma differentiation induced by RA and DLK1 knockdown, treatment with the specific MEK/ERK inhibitors, U0126 and PD 98059, was applied to differentiated neuroblastoma cells. Differentiation induced by RA and DLK1 knockdown increased ERK phosphorylation. The MEK/ERK inhibitor U0126 completely inhibited neuronal differentiation induced by both RA and DLK1 knockdown, whereas PD98059 partially blocked neuronal differentiation. After the withdrawal of inhibitors, cellular differentiation was fully recovered. This study is, to the best of our knowledge, the first to demonstrate that the specific inhibitors of the MEK/ERK pathway, U0126 and PD98059, exert differential effects on the ERK phosphorylation induced by RA or DLK1 knockdown. Based on the observations of this study, it can be concluded that a combination of RA and DLK1 knockdown increases neuronal differentiation for the control of the malignant growth of human neuroblastomas, and also that both MEK1 and MEK2 are required for the differentiation induced by RA and DLK1 knockdown.

• Environmental Mutagens and Carcinogens
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• v.10 no.1
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• pp.11-24
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• 1990

발생중인 계배의 날개에서 지골의 복제를 유발하는 retinoic acid(RA)가 날개의 조직발생에 미치는 영향을 알아보았다. Hamburger와 Hamilton stage 19에 도달한 계배의 wingbud 앞부분에 RA를 처리하고 처리후 24, 48, 72시간이 경과되었을 때 나타난 조직상의 변화를 조사하여 다음과 같은 결과를 얻었다. (1) RA처리는 처리부위와 인접한 조직에서 세포밀도의 감소를 초래하였으며 처리부위와 떨어진 부위에서는 오히려 세포밀도의 증가를 유발하였다. (2)RA처리는 apical ectodermal ridge(AER) 길이의 신장을 유발하였고 또한 그 위치의 전단부 쪽으로의 이동을 가져왔다. (3) 이러한 조직상의 변화는 처리후 24시간에 나타나 72시간까지 계속 되었으며, 특히 처리후 72시간에는 날개의 앞부분에서 원래의 AER외에 복제된 AER을 관찰할 수 있었다. 이러한 RA처리에 다른 조직상에서의 변화는 RA처리에 의하여 유발되는 지골복제현상이 처리후 24시간내에 시작되는 중배엽성조직 및 중배엽조직의 성장과 분화에 필수적인 AER의 변화에 기인함을 시사하고 있다.

• Korean Journal of Veterinary Service
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• v.31 no.4
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• pp.449-456
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• 2008

The differentiation of mouse embryonic stem(ES) cell into smooth muscle cells(SMC) may play a major role in cardiovascular development and under pathophysiological conditions. Therefore, in the present study, we have examined the differentiation of ES cells and its related gene expression. SMC differentiation was indicated by cellular morphology and time-dependent induction of dibutyryl adenosine 3,5-cyclic monophosphate(DBcAMP)and retinoic acid(RA) on smooth muscle ${\alpha}$-actin($SM{\alpha}A$), smooth muscle myosin heavy chain(SMMHC) gene expression. The control was undifferentiated ES cells(protein expressions represent 50-60kDaOct-4). The results of this study show that morphology of embryoid body and confirmation of $SM{\alpha}A$ expression by immunocytochemistry. Moreover, SMMHC and desmin expression was significantly increased by time dependent manner(5, 7, 15 days), in contrast to $SM{\alpha}A$ expression was slightly decreased on 15days. In conclusion, DBcAMP and RA stimulate mouse ES cells differentiation into SMC and enhanced $SM{\alpha}A$, SMMHC and desmin expression.

• Animal cells and systems
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• v.3 no.2
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• pp.207-213
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• 1999

During the differentiation of Naegleria gruberi amoebas into flagellates, the amoebas undergo sequential changes in cell shape and form new cellular organelles. To understand the nature of the signal which initiates this differentiation and the signal transduction pathway, we treated cells with four agents, PMA, retinoic acid (RA), okadaic acid, and cAMP. Retinoic acid and cAMP had specific effects on the differentiation of N. gruberi depending on the time of the drug treatment. Addition of (100$\mu$M) retinoic acid at the initiation of differentiation inhibited differentiation by blockinq the transcription of differentiation specific genes (e.g., $\beta$-tubulin). This inhibition of differentiation by retinoic acid was overcome by co-treatment with cAMP (or dbcAMP, 20 $\mu$M). Addition of retinoic acid at later stages (30 and 70 min) had no effect on the transcriptional regulation of the $\beta$-tubulin gene, however the differentiation was inhibited by different degrees. Co-treatment of cAMP at these stages did not overcome the inhibitory effect of retinoic acid. These results suggest that the role of retinoic acid as a transcriptional regulator might be conserved throughout the evolution of eukaryotes.

• Journal of Physiology & Pathology in Korean Medicine
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• v.18 no.5
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• pp.1317-1321
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• 2004

The differentiation of the sebaceous gland is remarkably species-specific and sebocytes may play crucial parts in the pathophysiologic processes and disorders of pilosebaceous unit SZ95 cell is an immortalized human sebaceous gland cell line that shows characteristics of normal human sebocytes, In this study, we investigated the effect of testosterone and the anti-androgenic effect of 13-cis-retinoic acid (13-cis-RA) on lipid synthesis in SZ95 cells. Cytoplasmic lipid droplets were shown by Oil-red staining. The majority of the SZ95 cells positively labeled with Oil-red dye, while HaCaT cells negatively labeled with Oil red dye. Total lipid level of SZ96 cells is higher 4 times than that of HaCat cells. Testosterone markedly increased 2 times lipid synthesis of SZ95 cells in compared with control. 13-cis-RA significantly inhibited lipid synthesis and cell proliferation in SZ95 cells. Combined treatment with testosterone and 13-cis-RA resulted in a lower total lipid levels than that with androgen alone. In conclusion, SZ95 cells well resembled the morphologic and functional characteritics of normal human sebocytes. This in vitro model could provide a valuable tool for the study of sebocytes with a key role in pathophysiology and differentiation of sebaceous glands.

• Clinical and Experimental Reproductive Medicine
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• v.50 no.4
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• pp.230-243
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• 2023

Objective: High temperatures can trigger cellular oxidative stress and disrupt spermatogenesis, potentially leading to male infertility. We investigated the effects of retinoic acid (RA), chitosan nanoparticles (CHNPs), and retinoic acid loaded with chitosan nanoparticles (RACHNPs) on spermatogenesis in mice induced by scrotal hyperthermia (Hyp). Methods: Thirty mice (weighing 25 to 30 g) were divided into five experimental groups of six mice each. The groups were as follows: control, Hyp induced by a water bath (43 ℃C for 30 minutes/day for 5 weeks), Hyp+RA (2 mg/kg/day), Hyp+CHNPs (2 mg/kg/72 hours), and Hyp+RACHNPs (4 mg/kg/72 hours). The mice were treated for 35 days. After the experimental treatments, the animals were euthanized. Sperm samples were collected for analysis of sperm parameters, and blood serum was isolated for testosterone measurement. Testis samples were also collected for histopathology assessment, reactive oxygen species (ROS) evaluation, and RNA extraction, which was done to compare the expression levels of the bax, bcl2, p53, Fas, and FasL genes among groups. Additionally, immunohistochemical staining was performed. Results: Treatment with RACHNPs significantly increased stereological parameters such as testicular volume, seminiferous tubule length, and testicular cell count. Additionally, it increased testosterone concentration and improved sperm parameters. We observed significant decreases in ROS production and caspase-3 immunostaining in the RACHNP group. Moreover, the expression levels of bax, p53, Fas, and FasL significantly decreased in the groups treated with RACHNPs and RA. Conclusion: RACHNPs can be considered a potent antioxidative and antiapoptotic agent for therapeutic strategies in reproductive and regenerative medicine.

• IMMUNE NETWORK
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• v.23 no.5
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• pp.37.1-37.11
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• 2023

Forkhead box P3-positive (Foxp3⁺)-inducible Tregs (iTregs) are readily generated by TGF-β1 at low TCR signaling intensity. TGF-β1-mediated Foxp3 expression is further enhanced by retinoic acid (RA) and lactoferrin (LF). However, the intensity of TCR signaling required for induction of Foxp3 expression by TGF-β1 in combination with RA and LF is unknown. Here, we found that either RA or LF alone decreased TGF-β1-mediated Foxp3 expression at low TCR signaling intensity. In contrast, at high TCR signaling intensity, the addition of either RA or LF strongly increased TGF-β1-mediated Foxp3 expression. Moreover, decreased CD28 stimulation was more favorable for TGF-β1/LF-mediated Foxp3 expression. Lastly, we found that at high signaling intensities of both TCR and CD28, combined treatment with TGF-β1, RA, and LF induced robust expression of Foxp3, in parallel with powerful suppressive activity against responder T cell proliferation. Our findings that TGFβ/RA/LF strongly generate high affinity Ag-specific iTreg population would be useful for the control of unwanted hypersensitive immune reactions such as various autoimmune diseases.

• 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.

• Development and Reproduction
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• v.2 no.1
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• pp.53-62
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• 1998

The lysosomal acid hydrolases including lysosomal acid phosphatase (LAP) are believed to play an important role in intracellular and extracellular degradation. LAP was reported to increase its activity in dedifferentiation stage during urodele limb regeneration. In the paresent study, LAP localization in the Mexican axolotl (Ambystoma mexicanum) limb regenerates was investigated by immunohistochemistry. LAP immunoreactivity with monoclonal antibody against Korean salamander (Hynobius leehii) LAP was observed mainly in the wound epidermis, blastema cells, muscle, and cartilage which were under dedifferentiation process in axolotl limb regenerates. Moreover, LAP immunoreactivity increased gradually during the early phase of lib regeneration and reached the peak level at dedifferentiation stage. However, as redifferentiation begans, LAP immunoreactivity decreased slowly to the basal level. Retinoic acid (RA) which is known to induce skeleton pattern duplication in regenerating urodele limb appears to enhance LAP immunoreactivity. In the RA-treate limg regenerates, LAP immunoreactivity was higher than in the normal regenerates. In addition, the LAP expression period was more extended in the RA treated regenerates than in the normal regenerates. These results suggest that RA is involved in the extension of dedifferentiation state in RA-treated limb regenerate.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2003.11a
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• pp.89-89
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• 2003

Exposure of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes a variety of biological and toxicology effects, most of which are mediated by aryl hydrocarbon receptor (AhR). The ligand-bound AhR as a heterodimer with AhR nuclear translocator (ARNT) binds to its specific DNA recognition site, the dioxin-responsive element (DRE), and it results in increased transcription of CYP1A1 gene. Retinoic acid (RA) regulates the transcription of various genes for several essential functions through binding to two classes of nuclear receptors, the retinoic acid receptor (RAR) and retinoid X receptor (RXR). Constitutive androstane receptor (CAR) also regulates the transcription of gene. In this study, we have examined how RAR, RXR and CAR regulated CYP1A1 in rainbow trout hepatoma cell (RTH 149) using luciferase reporter gene assay system. We did transient transfection with CYP1A1 luciferase reporter gene and treated with TCDD, all-trans RA, 9-cis RA and phenobarbital. Treatment of all-trans RA, 9-cis RA or phenobarbital decreased the TCDD induced transcription of CYP1Al. When we did transient cotransfection with CYP1A1 luciferase reporter gene and RXR, as increase of RXR concentration, the TCDD induced transcription of CYP1A1 was decreased. Transfection with CAR also decreased the TCDD induced transcription of CYP1A1 in RTH 149 cells.