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- 저자 : Thuruthippallil, Leena Mol (검색결과 2 건)
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Thuruthippallil, Leena Mol,Kubota, Akira,Kim, Eun-Young,Iwata, Hisato American Chemical Society 2013 Environmental science & technology Vol.47 No.12
<P>Our line of papers revealed that the common (great) cormorant (<I>Phalacrocorax carbo</I>) possesses two isoforms of the aryl hydrocarbon receptor (<I>cc</I>AHR1 and <I>cc</I>AHR2). This paper addresses in vitro tests of the <I>cc</I>AHR signaling pathways to solve two questions: (1) whether there are functional differences in the two <I>cc</I>AHR isoforms, and (2) whether a molecular perturbation, cytochrome P450 1A (<I>cc</I>CYP1A) induction, in the population-level can be predicted from the in vitro tests. The transactivation potencies mediated by <I>cc</I>AHR1 and <I>cc</I>AHR2 were measured in COS-7 cells treated with 15 selected dioxins and related compounds (DRCs), where <I>cc</I>AHR1 or <I>cc</I>AHR2 expression plasmid and <I>cc</I>CYP1A5 promoter/enhancer-linked luciferase reporter plasmid were transfected. For congeners that exhibited dose-dependent luciferase activities, 2,3,7,8-tetrachlorodibenzo-<I>p</I>-dioxin (TCDD) relative potencies (REPs) and induction equivalency factors (IEFs) were estimated. <I>cc</I>AHR1-IEF profile was similar to WHO avian TCDD toxic equivalency factor (TEF) profile except for dioxin-like polychlorinated biphenyls that showed lower IEFs in <I>cc</I>AHR1-driven reporter assay. <I>cc</I>AHR2-IEF profile was different from WHO TEFs and <I>cc</I>AHR1-IEFs. Notably, 2,3,4,7,8-PeCDF was more potent than TCDD for <I>cc</I>AHR2-mediated response. Using <I>cc</I>AHR1- and <I>cc</I>AHR2-IEFs and hepatic DRC concentrations in the Lake Biwa cormorant population, total TCDD induction equivalents (IEQs) were calculated for each <I>cc</I>AHR-mediated response. Nonlinear regression analyses provided significant sigmoidal relationships of <I>cc</I>AHR1- and <I>cc</I>AHR2-derived IEQs with hepatic <I>cc</I>CYP1A5 mRNA levels, supporting the results of in vitro <I>cc</I>AHR-mediated TCDD dose–response curves. Collectively, our in vitro AHR reporter assay potentially could be an alternative to molecular epidemiology of the species of concern regarding CYP1A induction by AHR ligands.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2013/esthag.2013.47.issue-12/es401155g/production/images/medium/es-2013-01155g_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es401155g'>ACS Electronic Supporting Info</A></P>
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Mol, Thuruthippallil Leena,Kim, Eun-Young,Ishibashi, Hiroshi,Iwata, Hisato American Chemical Society 2012 Environmental science & technology Vol.46 No.1
<P>Our previous studies have detected high levels of dioxins and related compounds (DRCs) including polychlorinated dibenzo-p-dioxins (PCDDs), furans (PCDFs), and coplanar PCBs (Co-PCBs) in the black-footed albatross (BFA), Phoebastria nigripes, from the North Pacific region. We have also cloned two aryl hydrocarbon receptors, AHR1 and AHR2, of the BFA. To evaluate the sensitivity to DRCs in the BFA and to assess the status of cytochrome P450 1A (CYP1A) induction in the wild population, this study investigated the mRNA expression levels of BFA AHR1 and AHR2 and also the transactivation potencies of each AHR by 15 selected DRC congeners. Quantitative real-time PCR of BFA AHR mRNAs showed that hepatic AHR1 is more highly expressed than AHR2. Transactivation by graded concentrations of individual DRCs was measured in COS-7 cells, where BFA AHR1 or AHR2 was transiently transfected. For congeners that exhibited AHR-mediated dose-dependent activities, 50% effective concentration (EC(50)) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) relative potencies (REPs) were estimated. Based on the estimates of the REPs, TCDD induction equivalency factors (IEFs) were determined. For BFA AHR1, PeCDF was equipotent to TCDD, but other congeners exhibited lower IEFs. For BFA AHR2, PCDD/F congeners except OCDD/F showed IEFs 1.0. Using BFA AHR1- or AHR2-IEFs and hepatic concentrations of DRCs in North Pacific BFAs, TCDD induction equivalents (IEQs) were calculated. We further constructed nonlinear regression models on the relationships between BFA AHR1- or AHR2-IEF derived total IEQ or WHO-TEF derived total TEQ and ethoxyresorufin-O-deethylase activity (EROD) in the liver of wild BFAs. The results indicated that the relationships of BFA AHR1- and AHR2-based IEQs and EROD were predictable from BFA AHR1- and AHR2-mediated transactivation by TCDD, respectively. Collectively, these results suggest that the in vitro assay incorporating the AHR of species of concern would be a useful tool to predict the sensitivity to DRCs in the species and CYP1A induction in the wild population.</P>
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