Di-ortho PCB congeners 52, 138, 153 and 180, and the mono-ortho coplanar congener 118 have been detected as a complex mixture in human tissue in Korea. This study examined the antiestrogenic effects of samples exposed to single or combination treatment of the ortho-PCB congeners. In order to determined the combined toxicity, a sample mixture (M1, M2, M3, M4, and M5) was designed based on the ortho-PCB congeners found in Korean human tissue. With the exception of PCB 52, the ortho-PCB congeners (PCB 118, 138, 153, and 180) showed weak antiestrogenic activity. The antiestrogenic activity of di-ortho PCB congeners (PCB 138, 153, and 180) was induced by the depletion of endogenous E2 as well as through the ER-dependent pathway, whereas the antiestrogenic activity of mono-ortho PCB 118 was only induced through the depletion of endogenous E2. When the MCF7-BUS cells were treated with mixtures containing the no effective concentration (10(-6) M) of the PCB congeners, M3 (PCB 118 + PCB 138 + PCB 180) and M4 (PCB 118 + PCB 138) had an antiestrogenic effect but the other mixtures (M1; PCB 52 + PCB 118 + PCB 138 + PCB 180, M2; PCB 118 + PCB 138 + PCB 153 + PCB 180, M5; PCB 118 + PCB 180) did not. Although the mechanism for the interaction between the PCB congeners is not completely understood, it was presumed that exposure to a mixture of the PCB congeners might have synergistic effects on their antiestrogenicity through the ER-independent pathway.
Bioassay-directed fractionation was performed to identify causative chemical groups of DEPs with estrogenic and antiestrogenic activities. Bioassay-directed fractionation consists of a cell bioassay (E-SCREEN) in conjunction with acid-base partitioning (F1 and F2) and silica gel column fractionation of neutral fractions (F3-F7). Crude extract (CE) of DEPs in dichloromethane (DCM) exhibited both estrogenic and antiestrogenic activity. Estrogenic activity of CE and some fractions (F1, F2, F3, F5 and F6) was induced through estrogen receptor (ER)-mediated pathways. In particular, the acid polar fraction (F2) of DEPs, which contains phenols, induced high levels of estrogenic activity compared to other fractions. The estrogenic activity of F2 (610.80 pg-bio-EEQ/g-DEPs) was higher than that of the total estrogenic activity of CE (222.22 pg-bio-EEQ/g-DEPs). This result indicates that the estrogenic activity induced by causative estrogenic fraction (F2) may be antagonized by unidentified chemicals in DEPs. On the other hand, non-polar fractions (F3 and F4) of DEPs include aliphatic and chlorinated hydrocarbon, polyaromatic hydrocarbons, and their alkyl derivatives, which play an important role in the antiestrogenic activity of DEPs. In particular, F4, which contains PAH and its derivatives, showed the highest antiestrogenic activity. Since in our previous study, dibenzo(a, h)anthracene and chrysene were identified in F4, and these chemicals have antiestrogenic activity, we assume that these chemicals are the major causative chemicals with antiestrogenic activity in DEPs. In contrast to the estrogenic activity of DEPs, antiestrogenic activity of CE was stronger than that of antiestrogenic fractions (F3 and F4) at non-cytotoxic concentrations, indicating that additive or synergistic effects by unidentified chemicals contained in DEPs occurred.
We cloned and sequenced the cytochrome P450 1A (CYP1A) gene from goldfish (Carassius auratus). It has a 1581 bp open reading frame that encodes a 526 amino acid protein with a theoretical molecular weight of 59.02 kDa. The CYP1A amino acid sequence clusters in a monophyletic group with other fish CYP1As, and more closely related to zebrafish CYP1A (91% identity) than to other fish CYP1As. Exposure to benzo(a)pyrene (BaP) by intraperitoneal injection increased biliary BaP metabolites and liver CYP1A gene expression. BaP exposure also increased CYP1A gene expression in extrahepatic organs, including intestine, and gill, which are sensitive to aqueous and dietary exposure to Arylhydrocarbon receptor (AhR) agonists. Therefore, goldfish CYP1A identified in this study offers basic information for further research related to biomarker use of CYP1A of goldfish.
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