Potential effects of perfluorinated compounds in common cormorants from Lake Biwa, Japan: an implication from the...

Contamination levels of perfluorinated compounds (PFCs), including perfluorooctanesulfonate (PFOS), perfluorononanoic acid (PFNA), perfluorooctane sulfonamide (PFOSA), perfluorohexanesulfonate (PFHS), and perfluorooctanoic acid (PFOA), were determined in the livers of wild common cormorants (Phalacrocorax carbo) from Lake Biwa, Japan. Potential effects of PFCs alone and combined effects by complex mixture of PFCs and dioxins and related compounds (DRCs) were also assessed by gene expression profiling using a cormorant oligo array. Perfluorooctanesulfonate, PFNA, and PFOSA were detected in almost all liver samples analyzed, while concentrations of PFHS and PFOA were below the limit of quantification. The microarray data analyses revealed that hepatic PFC levels were correlated with the expression of 74 genes. Real-time reverse-transcript polymerase chain reaction data demonstrated that PFOS concentration was positively correlated with mRNA levels of glutathione peroxidase 1 and glutathione S-transferase alpha 3 and negatively correlated with levels of heat shock 70-kDa protein 8 and tumor rejection antigen 1 mRNAs. These results suggest the induction of antioxidant enzymes in response to oxidative stress caused by PFCs and the suppression of molecular chaperones, leading to reduction in protein stability. Moreover, multiple regression analyses identified seven significant models in which certain genes showed expression levels altered by accumulation of PFCs and DRCs. The regression models explained associations with cytochrome P450 1A mRNA and protein expression levels, and its catalytic activity, ethoxyresorufin-O-deethylase of both PFNA and the 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalent levels. Thus, the regression models suggested the potential of PFCs to enhance toxicities of DRCs. Since mixture toxicity is an urgent issue, further study is required to understand the effects of mixtures of PFCs and DRCs in wild cormorants.