PM16 Molecular Indicators for Ecological Exposure
Exhibit Hall
8:00 AM - Monday
(PM266) Molecular cloning and expression levels of CYP1A1 and 1A2 in Baikal seals.
Hirakawa, S1, Iwata, H1, Kim, E-Y2, Tanabe, S1, Miyazaki, N3, 1 Center for Marine Environmental Studies, Ehime University, Matsuyama, Ehime, Japan2 Ehime Prefectural Institute of Public Health and Environmental Science, Matsuyama, Ehime, Japan3 Center for International Cooperation, Ocean Research Institute, The University of Tokyo, Nakano-ku, Tokyo, Japan
ABSTRACT- The toxic effects of polychlorinated dibenzo-p-dioxin (PCDDs), dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) are exhibited by the modulation of transactivation of target genes including cytochrome P450 (CYP) 1A1 and 1A2 mediated by the aryl hydrocarbon receptor. To date, we have already demonstrated the contamination of PCDDs/DFs/Co-PCBs, and presence of CYP1A-like protein immunochemically detected by an anti-rat CYP1A1 polyclonal antibody in hepatic microsomal fraction of Baikal seals (Pusa sibirica). However, the validity of such immunochemical approach of isozyme-specific detection of CYP1A is still unclear due to the possible cross-reactivity of multiple CYP1A-like proteins with anti-rat CYP1A1 polyclonal antibody. Since data from immunochemical studies of CYP1A may lead to the false evaluation of expression levels of each isozyme, isozyme-specific expressions of CYP1A1/1A2 need to be clarified in Baikal seals. This study attempts to analyze the relationships between the hepatic concentrations of PCDDs/DFs/Co-PCBs and CYP1A1/1A2 mRNA expression levels in Baikal seal population. We initially performed cDNA cloning of Baikal seal CYP1A1 and 1A2. The full length of CYP1A1 cDNA and partial length of CYP1A2 cDNA were sequenced in the liver of Baikal seal. Both CYP1A1 and 1A2 mRNA levels showed significant positive correlations with most of the individual congener TEQs. Lower levels of correlations were found for 2,3,7,8-T4CDD/DF, O8CDD, PCB77, PCB169, and most of mono-ortho Co-PCB congeners, indicating preferential metabolism of 2,3,7,8-T4CDD/DF and PCB77 by induced CYP1A1/1A2, and lower induction of these CYPs by other congeners. The mRNA levels of CYP1A1/1A2 revealed significant positive correlations with expression levels of CYP1A-like protein, suggesting that expression levels of CYP1A-like protein reflect both CYP1A1 and CYP1A2 mRNA expression levels. Therefore, these results showed that both CYP1A1 and 1A2 are induced by PCDDs/DFs/Co-PCBs at transcriptional and translational levels in the liver of Baikal seals.
Key words: cytochrome P450 1A1, Baikal seal, cytochrome P450 1A2, dioxins