• Proceedings of the Korean Society of Toxicology Conference
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• 2003.10b
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• pp.179-179
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• 2003

2,3,7,8-Tetrachlorodibenzo-$\rho$-dioxin (TCDD) displays high toxicity in animals and has been implicated in human carcinogenesis. Although the mechanisms of TCDD-induced carcinogenesis are poorly understood, it considered to be non-genotoxic and tumor promoter. In this study, we investigated the tumor promotion effect of TCDD on the two-stage skin chemical carcinogenesis using hairless mouse (SKH1).(omitted)

• Journal of the Korean Chemical Society
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• v.38 no.11
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• pp.819-826
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• 1994

This study described a simple, rapid and cost effective analytical technique for the ultra-trace analysis of dioxins in environmental samples. Liquid-Liquid extraction methods were used for the initial extraction and enrichment of the analyte. Subsequent clean-up procedures were achieved by using strong cation exchanger, silica and Florisil cartridges. Extracts were analysed by HRGC/HRMS-SIM. The efficiency of these analytical methods was tested by recovery and selectivity for elimination of interferences such as phenols, pesticides and PCBs in each step. The mean recovery of 1,2,3,4-TCDD spiked at 10 ppt in sea water was about 92(${\pm}$1.6)%. This analytical method was applied to Kwangyang sea water and 4.5pg/L of 2,3,7,8-TCDD was determined.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2001.11a
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• pp.112-112
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• 2001

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental toxin that activates the aryl hydrocarbon receptor (AhR) and disrupts multiple endocrine signaling pathways by enhancing ligand metabolism, altering hormone synthesis, down regulating receptor levels, and interfering with gene transcription. And TCDD-mediated gene transactivation via the AhR has been shown to be dependent upon estrogen receptor (ER) expression in human breast cancer cells. In the present study, we have examined the effect of natural estrogen, phytoestrognes and environmental estrogens on the regulation of CYP1A1 gene expression in MCF-7 human breast cancer cell line. that ER and AhR are co-expressed. pCYP1A1 -luc reporter gene was transiently transfected into MCF-7 cells. These cells were treated with various chemicals and then luciferase assay was carried out. 17be1a-estradiol significantly inhibited TCDD stimulated luciferase activity dose dependently and this inhibition was partially recovered by concomitant treatment of tamoxifen. 17beta-estradiol metabolites, 2-hydroxyestradiol and 16alpha-estriol resulted in less potent inhibitory effect than estradiol and synthetic estrogen, diethylstilbestrol (DES) showed no effect on CYP1A1 gene expression. This study demonstrated that estrogen down-regulated TCDD stimulated CYP1A1 expression via ER mediation. And we have found out that several flavonoids such as genistein, kaempferol, daidzein, naringenin, and alkylphenols such as nonylphenol, 4-octylphenol and resveratrol also inhibited TCDD induced CYP1A1 expression like estrogen.

• 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.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2003.10a
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• pp.179-179
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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 CYP1A1. 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.

• Proceedings of the Korean Society of Toxicology Conference
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• 2002.05a
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• pp.129-129
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• 2002

2,3,7,8-Tetrachlorodibenzo-p-dioxin(TCDD) a prototype of many halogenated aromatic hydrocarbons, is a ubiquitous, persistent environmental contaminant and the most powerful carcinogen categorized by IARC. Despite extensive research, the mechanisms of TCDD-induced carcinogenesis are poorly understood.(omitted)

• Proceedings of the Korea Environmental Mutagen Society Conference
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• 2004.05a
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• pp.97-97
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• 2004

• Proceedings of the Korean Society of Toxicology Conference
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• 2003.10b
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• pp.178-178
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• 2003

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a prototype of many halogenated aromatic hydrocarbons, is a ubiquitous, persistent environmental contaminant and the most powerful carcinogen categorized by IARC. It is display high toxicity in animals and is associated with several cancers in human. Although the mechanism of carcinogenesis by TCDD is unclear, it is considered to be a non-genotoxic and rumor promoter.(omitted)

• Proceedings of the Korean Society of Toxicology Conference
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• 2003.10b
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• pp.190-191
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• 2003

We investigated the effects of gestational and lactational exposures to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the differential induction of CYP1A1 in the levels of protein and gene expression in the liver and brain regions of offspring rats. For this study, pregnant Sprague Dawley rats were orally exposed to TCDD (1 or 10 ng/kg body weight/day) starting at Day 1 of gestation up to Day 20 of postpartum. (omitted)

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.121.1-121.1
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• 2003

Houttuynia cordata Thunb (HCT) is a herbal plant growing in China, Japan and Korea. According to the records of the Chinese medicine, this plant has been used as folk medicine for analgesics, beriberi, edema, hepatitis, icterus, etc. TCDD (2, 3, 7, 8 -tetrachlorodibenzo-p-dioxin), one of the notorious toxic environmental pollutants, damages various organs including liver and is regarded as an endocrine disrupter. After 7 days from TCDD (1$\mu$g/kg) injection, HCT (200 mg/kg) was administered into rats intraperitoneally for 4 weeks. (omitted)