• Environmental Mutagens and Carcinogens
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• v.22 no.3
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• pp.175-182
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• 2002

Endocrine disruptors (EDs) are the chemicals that affect endocrine systems through activation or inhibition of steroid hormone response. It is necessary to have a good system to evaluate rapidly and accurately endocrine-disrupting activities of suspected chemicals and their degradation products. The key targets of EDs are nuclear hormone receptors, which bind to steroid hormones and regulate their gene transcription. We constructed a co-expression system of Gal4p DNA binding domain (DBD)- ligand binding domain of human estrogen receptor $\alpha$ or $\beta$, and Gal4p transactivation domain (TAD)-co-activator AIB-1, SRC-1 or TIF-2 in Saccharomyces cerevisiae with a chromosome-integrated lacZ reporter gene under the control of CYC1 promoter and Gal4p binding site (GAL4 upstream activating sequence, GAL4$_{UAS}$). Expression of this reporter gene was dependent on the presence of estrogen or EDs in the culture medium. We found that the two-hybrid system with combination of the hER$\beta$ LBD and co-activator SRC-1 was most effective in the xenoestrogen-dependent induction of reporter activity. The extent of transcriptional activation by those chemicals correlated with their estrogenic activities measured by other assay systems, indicating that this assay system is efficient and reliable for measuring estrogenic activity. The data in this research demonstrated that the yeast detection system using steroid hormone receptor and co-activator is a useful tool for identifying chemicals that interact with steroid receptors.s.

• Toxicological Research
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• v.23 no.2
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• pp.135-142
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• 2007

Formononetin is an isoflavonoid phytoestrogen found in certain foodstuffs such as soy and red clover. In this study, we examined the action of formononetin with the carcinogen activation pathway mediated through the aryl hydrocarbon receptor (AhR) in MCF-7 breast carcinoma cells. Treating the cells with formononetin alone caused the accumulation of CYP1A1 mRNA as well as elevation in CYP1A1-specific 7-ethoxyresorufin O-deethylase (EROD) activity in a dose dependent manner. However, a concomitant treatment with 7,12-dimethylbenz[a]anthracene (DMBA) and formononetin markedly reduced both the DMBA-inducible EROD activity and CYP1A1 mRNA level. Under the same conditions, formononetin inhibited the DMBA-induced AhR transactivation, as shown by reporter gene analysis using a xenobiotic responsive element (XRE). Additionally, formononetin inhibited both DMBA-inducible nuclear localization of the aryl hydrocarbon receptor (AhR) and metabolic activation of DMBA, as measured by the formation of the DMBA-DNA adducts. Furthermore, formononetin competed with the prototypical AhR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), for binding to the AhR in an isolated rat cytosol. These results suggest that formononetin might be considered as a natural ligand to bind on AhR and consequently produces a potent protective effect against DMBA-induced genotoxicity. Therefore, that's the potential to act as a chemopreventive agent that is related to its effect on AhR pathway as antagonist/agonist.

• Journal of Microbiology and Biotechnology
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• v.24 no.8
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• pp.1051-1058
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• 2014

Platelet-activating factor receptor (PAFR) plays an important role in bacterial infection and inflammation. We examined the effect of the bacterial cell wall components lipopolysaccharide (LPS) and lipoteichoic acid (LTA) from Lactobacillus plantarum (pLTA) and Staphylococcus aureus (aLTA) on PAFR expression in THP-1, a monocyte-like cell line. LPS and aLTA, but not pLTA, significantly increased PAFR expression, whereas priming with pLTA inhibited LPS-mediated or aLTA-mediated PAFR expression. Expression of Toll-like receptor (TLR) 2 and 4, and CD14 increased with LPS and aLTA treatments, but was inhibited by pLTA pretreatment. Neutralizing antibodies against TLR2, TLR4, and CD14 showed that these receptors were important in LPS-mediated or aLTA-mediated PAFR expression. PAFR expression is mainly regulated by the nuclear factor kappa B signaling pathway. Blocking PAF binding to PAFR using a PAFR inhibitor indicated that LPS-mediated or aLTA-mediated PAF expression affected TNF-${\alpha}$ production. In the mouse small intestine, pLTA inhibited PAFR, TLR2, and TLR4 expression that was induced by heat-labile toxin. Our data suggested that pLTA has an anti-inflammatory effect by inhibiting the expression of PAFR that was induced by pathogenic ligands.

• International Journal of Oral Biology
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• v.38 no.1
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• pp.37-42
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• 2013

Receptor activator of NF-${\kappa}B$ ligand (RANKL) is an essential cytokine for osteoclast differentiation, activation and survival. T lymphocytes such as $T_{17}$ cells, a subset of T helper cells that produce IL-17, play an important role in rheumatoid arthritic bone resorption by producing inflammatory cytokines and RANKL. It has not yet been clearly elucidated how T cell activation induces RANKL expression. T cell receptor activation induces the activation of nuclear factor of activated T cell (NFAT) and expression of its target genes. In this study, we examined the role of NFAT in T cell activation-induced RANKL expression. EL-4, a murine T lymphocytic cell line, was used. When T cell activation was induced by phorbol 12-myristate 13-acetate (PMA) and ionomycin, RANKL expression increased in a time-dependent manner. In the presence of cyclosporin, an inhibitor of NFAT activation, this PMA/ionomycin-induced RANKL expression was blocked. Overexpression of either NFATc1 or NFATc3 induced RANKL expression. Chromatin immunoprecipitation results demonstrated that PMA/ionomycin treatment induced the binding of NFATc1 and NFATc3 to the mouse RANKL gene promoter. These results suggest that NFATc1 and NFATc3 mediates T cell receptor activation-induced RANKL expression in T lymphocytes.

• Molecules and Cells
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• v.41 no.3
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• pp.234-243
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• 2018

In recent years, the interest towards the relationship between incretins and bone has been increasing. Previous studies have suggested that glucagon-like peptide-1 (GLP-1) and its receptor agonists exert beneficial anabolic influence on skeletal metabolism, such as promoting proliferation and differentiation of osteoblasts via entero-osseous-axis. However, little is known regarding the effects of GLP-1 on osteoblast apoptosis and the underlying mechanisms involved. Thus, in the present study, we investigated the effects of liraglutide, a glucagon-like peptide-1 receptor agonist, on apoptosis of murine MC3T3-E1 osteoblastic cells. We confirmed the presence of GLP-1 receptor (GLP-1R) in MC3T3-E1 cells. Our data demonstrated that liraglutide inhibited the apoptosis of osteoblastic MC3T3-E1 cells induced by serum deprivation, as detected by Annexin V/PI and Hoechst 33258 staining and ELISA assays. Moreover, liraglutide upregulated Bcl-2 expression and downregulated Bax expression and caspase-3 activity at intermediate concentration (100 nM) for maximum effect. Further study suggested that liraglutide stimulated the phosphorylation of AKT and enhanced cAMP level, along with decreased phosphorylation of $GSK3{\beta}$, increased ${\beta}-catenin$ phosphorylation at Ser675 site and upregulated nuclear ${\beta}-catenin$ content and transcriptional activity. Pretreatment of cells with the PI3K inhibitor LY294002, PKA inhibitor H89, and siRNAs GLP-1R, ${\beta}-catenin$ abrogated the liraglutide-induced activation of cAMP, AKT, ${\beta}-catenin$, respectively. In conclusion, these findings illustrate that activation of GLP-1 receptor by liraglutide inhibits the apoptosis of osteoblastic MC3T3-E1 cells induced by serum deprivation through $cAMP/PKA/{\beta}-catenin$ and $PI3K/Akt/GSK3{\beta}$ signaling pathways.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.11
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• pp.6761-6767
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• 2013

The nuclear receptor, peroxisome proliferator-activated receptor gamma ($PPAR{\gamma}$), is expressed in various cancer cells including breast, prostate, colorectal and cervical examples. An endogenous ligand of $PPAR{\gamma}$, 15-deoxy-${\Delta}^{12,14}$ prostaglandin $J_2$ (PGJ2), is emerging as a potent anticancer agent but the exact mechanism has not been fully elucidated, especially in breast cancer. The present study compared the anticancer effects of PGJ2 on estrogen receptor alpha ($ER{\alpha}$)-positive (MCF-7) and $ER{\alpha}$-negative (MDA-MB-231) human breast cancer cells. Based on the reported signalling cross-talk between $ER{\alpha}$ and $ER{\alpha}$, the effect of the $ER{\alpha}$ ligand, $17{\beta}$-estradiol (E2) on the anticancer activities of PGJ2 in both types of cells was also explored. Here we report that PGJ2 inhibited proliferation of both MCF-7 and MDA-MB-231 cells by inducing apoptotic cell death with active involvement of mitochondria. The presence of E2 potentiated PGJ2-induced apoptosis in MCF-7, but not in MDA-MB-231 cells. The $ER{\alpha}$ antagonist, GW9662, failed to block PGJ2-induced activities but potentiated its effects in MCF-7 cells, instead. Interestingly, GW9662 also proved capable of inducing apoptotic cell death. It can be concluded that E2 enhances $ER{\alpha}$-independent anticancer effects of PGJ2 in the presence of its receptor.

• Proceedings of the PSK Conference
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• 2001.10a
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• pp.109-113
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• 2001

Oxidized low-density lipoprotein (oxLDL) has been shown to modulate transactivations by the peroxisome proliferator activated receptor (PPAR)$\gamma$ and nuclear factor-kappa B (NF$\kappa$B). In this study, the oxLDL signaling pathways involved with the NF$\kappa$B transactivation were investigated by utilizing a reporter construct driven by three upstream NF$\kappa$B binding sites, and various pharmacological inhibitors. OxLDL and its constituent lysophophatidylcholine (lysoPC) induced a rapid and transient increase of intracellular calcium and stimulated the NF-KB transactivation in resting RAW264.7 macrophage cells in an oxidation-dependent manner. The NF$\kappa$B activation by oxLDL or lysoPC was inhibited by protein kinase C inhibitors or an intracellular calcium chelator. Tyrosine kinase or PI3 kinase inhibitors did not block the NF$\kappa$B transactivation. Furthermore, the oxLDL-induced NF$\kappa$B activity was abolished by the PPAR$\gamma$ ligands. When the endocytosis of oxLDL was blocked by cytochalasin B, the NF$\kappa$B transactivation by oxLDL was synergistically increased, while PPAR transactivation was blocked. These results suggest that oxLDL activates NF-$\kappa$B in resting macrophages via protein kinase C- and/or calcium-dependent pathways, which does not involve the endocytic processing of oxLDL. The endocytosis-dependent PPAR$\gamma$ activation by oxLDL may function as an inactivation route of the oxLDL induced NF$\kappa$B signal. Short heterodimer partner (SHP), specifically expressed in liver and a limited number of other tissues, is an unusual orphan nuclear receptor that lacks the conventional DNA-binding domain. In this work, we found that SHP expression is abundant in murine macrophage cell line RAW 264.7 but suppressed by oxLDL and its constituent I3-HODE, a ligand for peroxisome proliferator-activated receptor y. Furthermore, SHP acted as a transcription coactivator of nuclear factor-$\kappa$B (NF$\kappa$B) and was essential for the previously described NF$\kappa$B transactivation by lysoPC, one of the oxLDL constituents. Accordingly, NF$\kappa$B, transcriptionally active in the beginning, became progressively inert in oxLDL-treated RAW 264.7 cells, as oxLDL decreased the SHP expression. Thus, SHP appears to be an important modulatory component to regulate the transcriptional activities of NF$\kappa$B in oxLDL-treated, resting macrophage cells.

• Molecules and Cells
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• v.41 no.8
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• pp.742-752
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• 2018

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive degeneration of dopaminergic (DAergic) neurons, particularly in the substantia nigra (SN). Although circadian dysfunction has been suggested as one of the pathophysiological risk factors for PD, the exact molecular link between the circadian clock and PD remains largely unclear. We have recently demonstrated that $REV-ERB{\alpha}$, a circadian nuclear receptor, serves as a key molecular link between the circadian and DAergic systems. It competitively cooperates with NURR1, another nuclear receptor required for the optimal development and function of DA neurons, to control DAergic gene transcription. Considering our previous findings, we hypothesize that $REV-ERB{\alpha}$ may have a role in the onset and/or progression of PD. In the present study, we therefore aimed to elucidate whether genetic abrogation of $REV-ERB{\alpha}$ affects PD-related phenotypes in a mouse model of PD produced by a unilateral injection of 6-hydroxydopamine (6-OHDA) into the dorsal striatum. $REV-ERB{\alpha}$ deficiency significantly exacerbated 6-OHDA-induced motor deficits as well as DAergic neuronal loss in the vertebral midbrain including the SN and the ventral tegmental area. The exacerbated DAergic degeneration likely involves neuroinflammation-mediated neurotoxicity. The $REV-erb{\alpha}$ knockout mice showed prolonged microglial activation in the SN along with the over-production of interleukin $1{\beta}$, a pro-inflammatory cytokine, in response to 6-OHDA. In conclusion, the present study demonstrates for the first time that genetic abrogation of $REV-ERB{\alpha}$ can increase vulnerability of DAergic neurons to neurotoxic insults, such as 6-OHDA, thereby implying that its normal function may be beneficial for maintaining DAergic neuron populations during PD progression.

• Kidney Research and Clinical Practice
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• v.36 no.2
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• pp.145-157
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• 2017

Background: Vitamin D is considered to exert a protective effect on various renal diseases but its underlying molecular mechanism remains poorly understood. This study aimed to determine whether paricalcitol attenuates inflammation and apoptosis during lipopolysaccharide (LPS)-induced renal proximal tubular cell injury through the prostaglandin $E_2$ ($PGE_2$) receptor EP4. Methods: Human renal tubular epithelial (HK-2) cells were pretreated with paricalcitol (2 ng/mL) for 1 hour and exposed to LPS ($1{\mu}g/mL$). The effects of paricalcitol pretreatment in relation to an EP4 blockade using AH-23848 or EP4 small interfering RNA (siRNA) were investigated. Results: The expression of cyclooxygenase-2, $PGE_2$, and EP4 were significantly increased in LPS-exposed HK-2 cells treated with paricalcitol compared with cells exposed to LPS only. Paricalcitol prevented cell death induced by LPS exposure, and the cotreatment of AH-23848 or EP4 siRNA offset these cell-protective effects. The phosphorylation and nuclear translocation of p65 nuclear factor-kappaB ($NF-{\kappa}B$) were decreased and the phosphorylation of Akt was increased in LPS-exposed cells with paricalcitol treatment. AH-23848 or EP4 siRNA inhibited the suppressive effects of paricalcitol on p65 $NF-{\kappa}B$ nuclear translocation and the activation of Akt. The production of proinflammatory cytokines and the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were attenuated by paricalcitol in LPS exposed HK-2 cells. The cotreatment with an EP4 antagonist abolished these anti-inflammatory and antiapoptotic effects. Conclusion: EP4 plays a pivotal role in anti-inflammatory and antiapoptotic effects through Akt and $NF-{\kappa}B$ signaling after paricalcitol pretreatment in LPS-induced renal proximal tubule cell injury.

• Journal of Microbiology and Biotechnology
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• v.32 no.8
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• pp.1017-1025
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• 2022

Bone homeostasis is regulated by constant remodeling through osteogenesis by osteoblasts and osteolysis by osteoclasts and osteoporosis can be provoked when this balance is broken. Present pharmaceutical treatments for osteoporosis have harmful side effects and thus, our goal was to develop therapeutics from intrisincally safe natural products. Fucoidan is a polysaccharide extracted from many species of brown seaweed, with valuable pharmaceutical activities. To intensify the effect of fucoidan on bone homeostasis, we hydrolyzed fucoidan using AMG, Pectinex and Viscozyme. Of these, fucoidan biotransformed by Pectinex (Fu/Pec) powerfully inhibited the induction of tartrate-resistant acid phosphatase (TRAP) activity in osteoclasts differentiated from bone marrow macrophages (BMMs) by the receptor for activation of nuclear factor-κB ligand (RANKL). To investigate potential of lower molecular weight fucoidan it was separated into >300 kDa, 50-300 kDa, and <50 kDa Fu/Pec fractions by ultrafiltration system. The effects of these fractions on TRAP and alkaline phosphatase (ALP) activities were then examined in differentiated osteoclasts and MC3T3-E1 osteoblasts, respectively. Interestingly, 50-300 kDa Fu/Pec suppressed RANKL-induced osteoclasts differentiation from BMMs but did not synergistically enhance osteoblasts differentiation induced by osteogenic agents. In addition, this fraction inhibited the expressions of NFATc1, TRAP, OSCAR, and RANK, which are all key transcriptional factors involved in osteoclast differentiation, and those of Src, c-Fos and Mitf, as determined by RT-PCR. In conclusion, enzymatically low-molecularized 50-300 kDa Fu/Pec suppressed TRAP by downregulating RANKL-related signaling, contributing to the inhibition of osteoclasts differentiation, and represented a potential means of inducing bone remodeling in the background of osteoporosis.