Accumulation features and temporal trends of PCDDs, PCDFs and PCBs in Baikal seals (Pusa sibirica)

Assessment of binding potencies of polychlorinated biphenyls and polybrominated diphenyl ethers with Baikal seal and mouse constitutive androstane receptors: Comparisons across species and congeners

The present study evaluated the binding potencies (equilibrium dissociation constant: K_D) of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) with the constitutive androstane receptor (CAR)_ligand binding domain (LBD) of the Baikal seal (bsCAR_LBD) and mouse (mCAR_LBD) using a surface plasmon resonance (SPR) biosensor. The binding affinities of individual congeners with mCAR_LBD tended to be higher than those with bsCAR_LBD but the differences were within the same order of magnitude. Notably, PBDE congeners showed higher binding affinities for both CAR_LBDs than PCB congeners. In silico docking simulations demonstrated that PBDEs had more non-covalent interactions with specific amino acid residues in both CAR_LBDs than PCBs, supporting the results of their binding affinities. Binding affinity comparisons among congeners revealed the structural requirements for higher binding; mono or di ortho-, tri meta-, and di para‑chlorine substitutions for PCBs, and di or tri ortho-, mono meta-, and di para‑bromine substitutions for PBDEs. The binding potencies of these congeners unlikely accounted for their previously reported CAR-mediated transactivation potencies, implying that their transactivation is regulated in a ligand-dependent, but a distinct manner from ligand binding. Risk assessment analysis showed that the K_D values of individual PCB and PBDE congeners were 1-4 orders of magnitude higher than their respective hepatic concentrations in wild Baikal seal population.

Unintentionally produced polychlorinated biphenyls in pigments: An updated review on their formation, emission sources, contamination status, and toxic effects

The formation, emission, environmental occurrence, and potential adverse effects of unintentionally produced polychlorinated biphenyls (PCBs) in pigments are reviewed, providing a comprehensive and up-to-date picture on these pollutants. PCBs are typically formed during manufacturing of organic pigments that involve chlorinated intermediates and reaction solvents, rather than those of inorganic pigments. Concentrations and profiles of PCBs vary greatly among pigment types and producers, with total PCB levels ranging from lower than detection limits to several hundred ppm; major components can be low-chlorinated (e.g., CB-11) or high-chlorinated congeners (e.g., CB-209). Pigment-derived PCBs can be released into the environment through different steps including pigment production, application, and disposal. They can contaminate atmospheric, terrestrial, and aquatic ecosystems, and then affect organisms living there. This situation garners scientific and public attention to nonlegacy emissions of PCBs and suggests the need for appropriate monitoring, management, and abatement strategies regarding these pollutants.

Blood vessels are primary targets for 2,3,7,8-tetrachlorodibenzo-p-dioxin in pre-cardiac edema formation in larval zebrafish

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has adverse effects on the development and function of the heart in zebrafish eleutheroembryos (embryos and larvae). We previously reported that TCDD reduced blood flow in the mesencephalic vein of zebrafish eleutheroembryos long before inducing pericardial edema. In the present study, we compared early edema (pre-cardiac edema), reduction of deduced cardiac output and reduction of blood flow in the dorsal aorta and cardinal vein caused by TCDD. In the same group of eleutheroembryos, TCDD (1.0 ppb) caused pre-cardiac edema and circulation failure at the cardinal vein in the central trunk region with the similar time courses from 42 to 54 h post fertilization (hpf), while the same concentration of TCDD did not significantly affect aortic circulation in the central trunk region or cardiac output. The dependence of pre-cardiac edema on TCDD concentration (0-2.0 ppb) at 55 hpf correlated well with the dependence of blood flow through the cardinal vein on TCDD concentration. Several treatments that markedly inhibited TCDD-induced pre-cardiac edema such as knockdown of aryl hydrocarbon receptor nuclear translocator-1 (ARNT1) and treatment with ascorbic acid, an antioxidant, did not significantly prevent the reduction of cardiac output at 55 hpf caused by 2.0 ppb TCDD. TCDD caused hemorrhage and extravasation of Evans blue that was intravascularly injected with bovine serum albumin, suggesting an increase in endothelium permeability to serum protein induced by TCDD. The results suggest that the blood vessels are primary targets of TCDD in edema formation in larval zebrafish.

Freshwater seal as a source of direct and indirect increased human exposure to persistent organic pollutants in a background area

The aim of the study is to investigate POP levels in environmental media (air, snow, soil and sediment), certain food items in the Olkhon district (Irkutsk Region, Russia) and Lake Baikal seal (nerpa) fat and meat in order to define the main pathways of elevated human exposure to POPs in the area. POP levels in soil and air samples and in almost all of the food items from the Olkhon district were comparable to levels in background areas of the Lake Baikal region. Only certain chicken eggs, large fish and blubber of nerpa pups exceeded maximum permissible levels of ΣDDTs and ΣHCHs. The combination of elevated levels of POPs in the Baikal nerpa with the use of Baikal nerpa fat (traditional nutritional habits, feed additives, as well as medicine for humans and domestic animals) results in two pathways for POPs to enter the human body: from seals it enters the human body directly, and indirectly from seals to poultry and livestock and then to the human body. Several scenarios of human exposure to POPs including the incidental ingestion of soil, inhalation of air, and ingestion of food were considered. The largest part of POPs enters the human organism through chicken eggs followed by fish and cow's milk in the scenario without the consumption of nerpa meat and blubber. The high consumption rate of fish as well as the consumption of the fat of nerpa pups or melted fat of nerpa increases the daily intake of POPs 1.3-11 times. The indexes of non-cancer risk and total cancer risk were assessed for residents of the Olkhon district and compared with indexes of risk for the average population of Irkutsk Region. Limiting the use of nerpa fat and meat as food and feed supplement reduces the potential human health risk.

In vitro assessment of effects of persistent organic pollutants on the transactivation of estrogen receptor α and β (ERα and ERβ) from the Baikal seal (Pusa sibirica)

To assess the effect of exposure to persistent organic pollutants (POPs) on the estrogen receptor (ER) signaling pathway in Baikal seals (Pusa sibirica), we investigated the molecular characterizations and functions of two Baikal seal ER (bsER) isoforms, bsERα and bsERβ. The bsERα and bsERβ cDNA clones isolated have an open reading frame of 595 and 530 amino acid residues, respectively. The tissue distribution analyses of bsER mRNAs showed that bsERα transcripts were primarily found in the ovary and uterus, and bsERβ in the muscle in wild Baikal seals. The immunofluorescence staining assay showed that 17β-estradiol (E₂) treatment promoted the nuclear translocation of in vitro-expressed bsERα. Transient transfection of bsERα in U2OS cells enhanced the transcription of pS2, an ER target gene of E₂. We then measured bsER-mediated transactivation potencies of POPs in an in vitro reporter gene assay system, in which a bsERα or bsERβ expression vector was transfected into COS-1 cells. For comparison, transactivation potencies of POPs on mouse ERs (mERα and mERβ) were also evaluated in the same manner. Results showed significant dose-dependent responses of bsERs and mERs when treated with p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT), and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE). bsERs and mERs showed no response when exposed to polychlorinated biphenyls (PCBs) or 2,3,7,8-tetrachlorodibenzo-p-dioxin. Comparison of the dose-response curves of DDTs across species (bsERs vs. mERs) showed that bsERα had a response similar to mERα, but bsERβ was less sensitive than mERβ. Comparing the lowest observable effective concentrations of p,p'-DDT (2.8 μM) and p,p'-DDE (10 μM) for in vitro bsERα-mediated transactivation with their hepatic concentrations in wild Baikal seals indicated that some individuals accumulated these compounds at levels comparable to the effective concentrations, suggesting the potential disruption of the bsERα signaling pathway in the wild population by these compounds. Co-transfection experiments with bsER and the aryl hydrocarbon receptor (AHR) suggested that high accumulation of estrogenic compounds exerts a synergistic effect with dioxin-like congeners on ER signaling through AHR activation in the wild seal population.

In Vitro and In Silico Evaluations of Binding Affinities of Perfluoroalkyl Substances to Baikal Seal and Human Peroxisome Proliferator-Activated Receptor α

In this study, we assessed the binding affinities of perfluoroalkyl substances (PFASs), including perfluoroalkyl carboxylates (PFCAs) and perfluoroalkyl sulfonates (PFSAs), to the ligand-binding domains (LBDs) of Baikal seal ( Pusa sibirica; bs) and human (h) peroxisome proliferator-activated receptor alpha (PPARα). An in vitro competitive binding assay showed that six PFCAs and two PFSAs could bind to recombinant bs and hPPARα LBD proteins in a dose-dependent manner. The relative binding affinities (RBAs) of PFASs to bsPPARα were as follows: PFOS > PFDA > PFNA > PFUnDA > PFOA > PFHxS > PFHpA > PFHxA. The RBAs to bsPPARα showed a significant positive correlation with those to hPPARα. In silico PPARα homology modeling predicted that there were two ligand-binding pockets (LBPs) in the bsPPARα and hPPARα LBDs. Structure-activity relationship analyses suggested that the binding potencies of PFASs to PPARα might depend on LBP binding cavity volume, hydrogen bond interactions, the number of perfluorinated carbons, and the hydrophobicity of PFASs. Interspecies comparison of the in vitro binding affinities revealed that bsPPARα had higher preference for PFASs with long carbon chains than hPPARα. The in silico docking simulations suggested that the first LBP of bsPPARα had higher affinities than that of hPPARα; however, the second LBP of bsPPARα had lower affinities than that of hPPARα. To our knowledge, this is the first evidence showing interspecies differences in the binding of PFASs to PPARαs and their structure-activity relationships.

Lake sediment records of persistent organic pollutants and polycyclic aromatic hydrocarbons in southern Siberia mirror the changing fortunes of the Russian economy over the past 70 years

Persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) have previously been detected in the surface sediments, water, and endemic organisms of Lake Baikal, a UNESCO World Heritage Site. The Selenga River is the primary source of freshwater to Lake Baikal, and transports pollutants accumulating in the Selenga River basin to the lake. Sources of POPs and PAHs in the Selenga River basin grew through the 20th century. In the present study, temporal changes in the concentrations of PAHs and POPs were reconstructed from two lakes in the Selenga River basin over the past 150 years using paleolimnological techniques. Increased concentrations in PAHs and PCBs were recorded initially in the 1930s. The 1940s-1980s was the period of greatest exposure to organic contamination, and concentrations of dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCBs), hexachlorocyclohexanes (HCHs) and many PAHs peaked between the 1960s and 1980s in the two lakes. Declines in concentrations and fluxes were recorded for most PAHs and POPs in the 1980s and 1990s. Temporal trends in concentrations of total and individual compounds/congeners of PAH, PCBs, and polybrominated diphenyl ethers (PBDEs) indicate the contribution of both local and regional sources of contamination in the 20th and 21st centuries. Temporal variations in contaminants can be linked to economic and industrial growth in the former USSR after World War II and the economic decline of Russia in the late-1980s and early-1990s, as well as global trends in industrialization and development during the mid-20th century.

In Vitro Assessment of Activation of Baikal Seal ( Pusa sibirica) Peroxisome Proliferator-Activated Receptor α by Polybrominated Diphenyl Ethers

We investigated the Baikal seal ( Pusa sibirica) peroxisome proliferator-activated receptor α (bsPPARα) transactivation potencies of polybrominated diphenyl ethers (PBDEs) using an in vitro bsPPARα reporter gene assay. BDE47, BDE99, and BDE153 induced bsPPARα-mediated transcriptional activities in a dose-dependent manner. To compare bsPPARα transactivation potencies of PBDEs, perfluorooctanoic acid (PFOA)-based relative potencies (REPs), a ratio of 50% effective concentration of PFOA to the test chemical, were determined. The order of REPs of PBDEs was BDE153 (13) > BDE99 (8.1) > BDE47 (6.6) > PFOA (1.0) > BDE100, BDE154, and BDE183 (not activated). PBDEs with two bromine atoms at the ortho position showed higher bsPPARα transactivation potencies than those with three bromine atoms. Comparison of the lowest-observed-effect concentration in bsPPARα reporter gene assays revealed that BDE99 was 7-fold more potent than CB99, a polychlorinated biphenyl congener with the same IUPAC number, indicating that brominated congeners could more efficiently activate bsPPARα than chlorinated congeners. The REPs of PBDEs for bsPPARα transactivation were approximately 7- to 13-fold higher than those of perfluorochemicals (PFCs), suggesting that the effects of PBDEs on the bsPPARα signaling pathway may be superior to those of PFCs. This study provides the first evidence that PBDE congeners activate PPARα in vitro.

Accumulation and temporal changes of PCDD/Fs and dioxin-like PCBs in finless porpoises (Neophocaena asiaeorientalis) from Korean coastal waters: Tracking the effectiveness of regulation

Temporal trend studies are useful to evaluate the effectiveness of regulations on local pollutants. The emission of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) has been regulated by the Korean government in accordance with the Stockholm Convention. The accumulation and temporal trends of PCDD/Fs and dioxin-like PCBs were investigated in finless porpoises (Neophocaena asiaeorientalis) collected in Korean waters. Median concentrations of PCDDs, PCDFs, non-ortho PCBs, and mono-ortho PCBs were 1.0, 1.1, 0.1, and 1.8pgTEQ/g lipid weight, respectively, which were lower than threshold values for marine mammals. Age- and sex-dependent accumulation patterns were found for PCDFs and DL-PCBs. Temporal trends in finless porpoises collected between 2003 and 2010 showed significant reduction rates of 57%, 54%, 69%, and 60% for PCDDs, PCDFs, non-ortho PCBs, and mono-ortho PCBs, respectively. Our results suggest that the regulations on dioxin-like contaminants have been effective for marine mammals in Korea.

In Vitro and in Silico Analyses for Predicting Hepatic Cytochrome P450-Dependent Metabolic Potencies of Polychlorinated Biphenyls in the Baikal Seal

The aim of this study was to understand the cytochrome P450 (CYP)-dependent metabolic pathway and potency of polychlorinated biphenyls (PCBs) in the Baikal seal (Pusa sibirica). In vitro metabolism of 62 PCB congener mixtures was investigated by using liver microsomes of this species. A decreased ratio of over 20% was observed for CB3, CB4, CB8, CB15, CB19, CB22, CB37, CB54, CB77, and CB105, suggesting the preferential metabolism of low-chlorinated PCBs by CYPs. The highly activated metabolic pathways in Baikal seals that were predicted from the decreased PCBs and detected hydroxylated PCBs (OH-PCBs) were CB22 to 4'OH-CB20 and CB77 to 4'OH-CB79. The total amount of OH-PCBs detected as identified and unidentified congeners accounted for only a 3.8 ± 1.7 mol % of loaded PCBs, indicating many unknown PCB metabolic pathways. To explore factors involved in CYP-dependent PCB metabolism, we examined the relationships among the structural and physicochemical properties of PCBs, the in silico PCB-CYP docking parameters, and the in vitro PCB decreased ratios by principal component analysis. Statistical analysis showed that the decreased PCB ratio was at least partly accounted for by the substituted chlorine number of PCBs and the distance from the Cl-unsubstituted carbon of docked PCBs to the heme Fe in CYP2A and 2B.

Enzymatic characterization of in vitro-expressed Baikal seal cytochrome P450 (CYP) 1A1, 1A2, and 1B1: implication of low metabolic potential of CYP1A2 uniquely evolved in aquatic mammals

This study aimed to elucidate the catalytic function of cytochrome P450 (CYP) 1 enzymes in aquatic mammals. Alkoxyresorufin O-dealkylation (AROD) activities including methoxy- (MROD), ethoxy- (EROD), pentoxy- (PROD), and benzyloxyresorufin O-dealkylation (BROD), and 2- and 4-hydroxylation activities of 17β-estradiol (E2) were measured by using yeast-expressed Baikal seal (Pusa sibirica) CYP1A1, 1A2, and 1B1 proteins. Heterologous protein expression of the Baikal seal CYP1s (bsCYP1s) in yeast microsomes was confirmed by reduced CO-difference spectra and immunoblotting. Heterologously expressed human CYP1 enzyme (hCYP1) activities were simultaneously measured and compared with those of bsCYP1 isozymes. Recombinant bsCYP1A1 protein showed the highest Vmax of EROD, followed by MROD, PROD, and BROD, similar to that of hCYP1A1. Vmax/Km ratios of all AROD activities catalyzed by bsCYP1A1 were lower than those catalyzed by hCYP1A1, suggesting less potential for AROD by bsCYP1A1. Enzymatic assays for bsCYP1A2 showed no or minimal AROD activities, while hCYP1A2 displayed MROD and EROD activities. bsCYP1B1 showed an AROD profile (EROD>BROD>MROD>>PROD) similar to that of hCYP1B1; however, Vmax/Km ratios of all AROD activities by bsCYP1B1 were higher. Yeast microsomes containing bsCYP1A1 and 1B1 and hCYP1A1, 1A2, and 1B1 metabolized E2 to 2-OHE2 and 4-OHE2, whereas bsCYP1A2 showed no such activity. Comparison of 4- and 2-hydroxylations of E2 by CYP1As suggests that bsCYP1A1, hCYP1A1, and 1A2 preferentially catalyze 2- rather than 4-hydroxylation. As for CYP1B1, the Vmax/Km ratios suggest that both Baikal seal and human CYPs catalyze 4- rather than 2-hydroxylation. Interspecies comparison showed that bsCYP1B1 has higher metabolic potencies for both E2 hydroxylations than does hCYP1B1, whereas the activity of bsCYP1A1 was lower than that of hCYP1A1. Messenger RNA expression levels of bsCYP1s in the liver of Baikal seals indicated that bsCYP1A1 and 1A2 enzymes contributed to 16.2% and 83.7% of total CYP1s, respectively; bsCYP1B1 accounted for only 0.06%. Addition of anti-human CYP1A1 antibody in seal liver microsomes suppressed EROD activity more than did anti-human CYP1A2 antibody. Therefore, EROD may be catalyzed by hepatic bsCYP1A1 but not bsCYP1A2, consistent with the results of yeast-expressed bsCYP1A1 and 1A2. In silico substrate-docking models of bsCYP1s suggested that the defect in bsCYP1A2 enzymatic activities may be accounted for by the Pro substitution of highly conserved Thr in the I-helix, which is involved in formation of a hydrogen bond with the hydroperoxy intermediate on the heme. This Thr-Pro substitution is evolutionarily conserved across aquatic mammals and could explain their lower metabolic potential for persistent organic pollutants.

Toxicological assessment of polychlorinated biphenyls and their metabolites in the liver of Baikal seal (Pusa sibirica)

We have previously reported that high accumulation of dioxins and related compounds induced cytochrome P450 (CYP 1s) isozymes in the liver of wild Baikal seals, implying the enhanced hydroxylation of polychlorinated biphenyls (PCBs). The present study attempted to elucidate the residue concentrations and patterns of PCBs and hydroxylated PCBs (OH-PCBs) in the livers of Baikal seals. The hepatic residue concentrations were used to assess the potential effects of PCBs and OH-PCBs in combination with the analyses of serum thyroid hormones, hepatic mRNA levels, and biochemical markers. The hepatic expression levels of CYP1 genes were positively correlated with the concentration of each OH-PCB congener. This suggests chronic induction of these CYP1 isozymes by exposure to PCBs and hydroxylation of PCBs induced by CYP 1s. Hepatic mRNA expression monitoring using a custom microarray showed that chronic exposure to PCBs and their metabolites alters the gene expression levels related to oxidative stress, iron ion homeostasis, and inflammatory responses. In addition, the concentrations of OH-PCBs were negatively correlated with L-thyroxine (T4) levels and the ratios of 3,3',5-triiodo-L-thyronine (T3)/reverse 3,3',5'-triiodo-L-thyroninee (rT3). These observations imply that Baikal seals contaminated with high levels of OH-PCBs may undergo the disruption of mechanisms related to the formation (or metabolism) of T3 and T4 in the liver.

Blood levels of polychlorinated biphenyls and their hydroxylated metabolites in Baikal seals (Pusa sibirica): emphasis on interspecies comparison, gender difference and association with blood thyroid hormone levels

We have previously demonstrated that Baikal seals (Pusa sibirica) are still being exposed to polychlorinated biphenyls (PCBs), and the population is at risk. In the present study, we measured the residue levels of PCBs and their hydroxylated metabolites (OH-PCBs) in the blood of Baikal seals and assessed the impact of OH-PCBs on the thyroid function. Blood concentrations of PCBs and OH-PCBs were in the range of 2.8-130 ng g(-1)wet wt. and 0.71-4.6 ng g(-1)wetwt., respectively. Concentrations of higher-chlorinated OH-PCBs (hexa- to octa-PCBs) were more than 70% to total OH-PCB concentrations, indicating Baikal seals are mostly risked by higher-chlorinated OH-PCBs. High levels of 4OH-CB146 and 4OH-CB187 and low levels of 4OH-CB107/4'OH-CB108 found in Baikal seals were different from those in other phocidae species, suggesting the unique drug-metabolizing enzyme activities and/or contamination sources in this species. Concentrations of some OH-PCBs in males were significantly higher than those in females. These results suggest that these isomers may be preferentially transferred from mother to pup via cord blood. However, concentrations of almost all the isomers were not significantly correlated with the levels of blood total T3 and T4, implying less impact of PCB-related compounds on the thyroid hormone circulation.

Maternal-to-fetal transfer and concentration profiles of PCB congeners for Steller sea lions (Eumetopias jubatus) from Hokkaido, Japan

The concentrations of PCB congeners in the blubber and liver of mother Steller sea lions (Eumetopias jubatus; SSLs) and their fetuses from the coast of Hokkaido, Japan in 2008, 2010 and 2012 were analyzed by HRGC-HRMS, in order to elucidate PCB congener profiles and maternal-to-fetal transfer of PCBs in SSLs. ΣPCBs in the fetuses were 1400 ± 660 (the mean ± SD) ng/g-fat in the blubber and 570 ± 320 ng/g-fat in the liver, respectively. There was a concern that SSLs had been contaminated by PCBs during the fetal period. The concentrations of the major congeners in the blubber and liver were a correlation between the fetus and mother (blubber: r=0.9934, liver: r=0.9160; P ≦ 0.05). The results indicated that PCBs in the fetuses came from the mothers. #177 and #199 showed no correlations between the fetus and the mother in the blubber and liver. This indicated a selective capture by some natural protector such as the placenta.

Concentration profiles of PCB congeners in the blubber and liver of Steller sea lions (Eumetopias jubatus) from the coast of Hokkaido, Japan

The concentrations of PCB congeners in the blubber and liver of male and female Steller sea lions (Eumetopias jubatus; SSLs) collected from the Shakotan Peninsula and the Nemuro Strait, Hokkaido, Japan in 2008 and 2010 were measured by HRGC-HRMS, in order to express the concentration profiles in SSLs at these regions. #153 predominated in both organs, followed by #138, #99 and #118. In males, #28 and #31 were concentrated particularly in the blubber, while #177 and #199 were accumulated specifically in the liver. The differences in these concentration profiles might be expressed by the differences in the organs and their functions. The concentrations of #99, #118, #138, #153, and #180 in the blubber appeared to correspond significantly with the differences between genders. The details of the surveys on PCB congeners in SSLs could clarify the differences in the residue levels of individual congeners for organs and genders.

Temporal trends (2004-2009) of imposex in rock shells Thais clavigera collected along the Korean coast associated with tributyltin regulation in 2003 and 2008

We investigated the temporal trend in contamination of butyltin compounds (BTs) along the Korean coast using imposex and tributyltin (TBT) burden in gastropods (Thais clavigera) as a biomonitor. Thais clavigera were collected from 26 locations with different shipping activities between 2004 and 2009 after restrictions on TBT-based antifouling paints were imposed in Korea. In the present study, imposex indices and TBT tissue concentrations significantly decreased over time from 2004 to 2009, confirming the effectiveness of TBT regulation. However, imposex in 2009 samples was still found. Significantly high imposex indices and TBT tissue residues were found in large ports containing commercial and ferry services compared with small ports and background areas. Imposex indices in background areas had decreased to zero, suggesting recovery from imposex caused by BT contamination. These results suggest that recovery from TBT contamination occurs faster in areas with very low maritime activities than areas with high maritime activities.

Accumulation of PAHs and synthetic musk compound in minke whales (Balanoptera acutorostrata) and long-beaked common dolphins (Delphinus capensis) from Korean coastal waters

Information on the occurrence and accumulation profiles of polycyclic aromatic hydrocarbons (PAHs) and synthetic musk compounds (SMCs) in marine mammals is scarce. In the present study, we recorded the concentrations and profiles of PAHs and SMCs in liver tissue and blubber from minke whales and common dolphins from Korean coastal waters. The overall concentrations of PAHs and SMCs in blubber from both cetacean species were approximately three to five times higher than those in liver tissues. Residue levels of PAHs were lower, whereas levels of SMCs were relatively higher than those reported in other studies. Lack of species- and sex-dependent differences in the concentrations of PAHs and SMCs were found. Naphthalene and 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-r-2-benzopyran (HHCB) were predominant compounds in all the samples for PAHs and SMCs, respectively. The concentrations of PAHs and SMCs were significantly correlated with each other, but were not correlated with body size of cetaceans. The present data provide valuable information on the exposure of Korean cetaceans to PAHs and SMCs.

Analysis of thyroid hormones in serum of Baikal seals and humans by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunoassay methods: application of the LC-MS/MS method to wildlife tissues

Thyroid hormones (THs) are essential for the regulation of growth and development in both humans and wildlife. Until recently, TH concentrations in the tissues of animals have been examined by immunoassay (IA) methods. IA methods are sensitive, but for TH analysis, they are compromised by a lack of adequate specificity. In this study, we determined the concentrations of six THs, L-thyroxine (T(4)), 3,3',5-triiodo-L-thyronine (T(3)), 3,3',5'-triiodo-L-thyronine (rT(3)), 3,5-diiodo-L-thyronine (3,5-T(2)), 3,3'-diiodo-L-thyronine (3,3'-T(2)), and 3-iodo-L-thyronine (3-T(1)), in the serum of humans (n = 79) and wild Baikal seals (n = 37), by isotope ([(13)C(6)]-T(4))-dilution liquid chromatography (LC)-tandem mass spectrometry (MS/MS), and compared the TH levels with those measured by an electrochemiluminescent immunoassay (ECLIA) method. T(3) and T(4) were detected in all serum samples of both humans and Baikal seals, whereas T(1), 3,3'-T(2), and 3,5-T(2) were below the limit of detection (LOD). rT(3) was detected in Baikal seal sera at concentrations higher than T(3) in 28 seal samples, indicating an anomaly in deiodinase activity in Baikal seals. In humans, regression analyses of TH concentrations, measured by ECLIA and LC-MS/MS methods, showed significant correlations for T(4) (r = 0.852) and T(3) (r = 0.676; after removal of a serum sample with abnormal T(3) levels). In Baikal seals, a low correlation coefficient (r = 0.466) for T(4) levels and no correlation for T(3) levels (p = 0.093) were found between ECLIA and LC-MS/MS methods. These results suggest that interference by a nonspecific reaction against anti-T(3) and anti-T(4) antibodies used in the ECLIA can contribute to inaccuracies in TH measurement in Baikal seals. When the relationship between concentrations of THs in sera and dioxin-like toxic equivalents in blubber samples of Baikal seals (n = 19) was examined, a significantly negative correlation was found for serum T(4) levels measured by the LC-MS/MS method, but not for those measured by ECLIA. Thus, our results indicate that the LC-MS/MS method is more reliable and accurate for the elucidation of alteration in circulating TH levels in wildlife, as caused by environmental and physiological factors.

Identification of major dioxin-like compounds and androgen receptor antagonist in acid-treated tissue extracts of high trophic-level animals

We evaluated the applicability of combining in vitro bioassays with instrument analyses to identify potential endocrine disrupting pollutants in sulfuric acid-treated extracts of liver and/or blubber of high trophic-level animals. Dioxin-like and androgen receptor (AR) antagonistic activities were observed in Baikal seals, common cormorants, raccoon dogs, and finless porpoises by using a panel of rat and human cell-based chemical-activated luciferase gene expression (CALUX) reporter gene bioassays. On the other hand, no activity was detected in estrogen receptor α (ERα)-, glucocorticoid receptor (GR)-, progesterone receptor (PR)-, and peroxisome proliferator-activated receptor γ2 (PPARγ2)-CALUX assays with the sample amount applied. All individual samples (n = 66) showed dioxin-like activity, with values ranging from 21 to 5500 pg CALUX-2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent (TEQ)/g-lipid. Because dioxins are expected to be strong contributors to CALUX-TEQs, the median theoretical contribution of dioxins calculated from the result of chemical analysis to the experimental CALUX-TEQs was estimated to explain up to 130% for all the tested samples (n = 54). Baikal seal extracts (n = 31), but not other extracts, induced AR antagonistic activities that were 8-150 μg CALUX-flutamide equivalent (FluEQ)/g-lipid. p,p'-DDE was identified as an important causative compound for the activity, and its median theoretical contribution to the experimental CALUX-FluEQs was 59% for the tested Baikal seal tissues (n = 25). Our results demonstrate that combining in vitro CALUX assays with instrument analysis is useful for identifying persistent organic pollutant-like compounds in the tissue of wild animals on the basis of in vitro endocrine disruption toxicity.

Occurrence and accumulation features of polycyclic aromatic hydrocarbons and synthetic musk compounds in finless porpoises (Neophocaena phocaenoides) from Korean coastal waters

Reports of the occurrence and accumulation patterns of polycyclic aromatic hydrocarbons (PAHs) and synthetic musk compounds (SMCs) in marine mammals are scarce. In this study, the concentrations and accumulation profiles of PAHs and SMCs were determined in blubber from finless porpoises in Korean coastal waters. Total concentrations of PAHs and SMCs ranged from 6.0 to 432 (mean: 160) ng/g lipid weight and from 17 to 144 (mean: 52) ng/g lipid weight, respectively. Residue levels of PAHs were lower than those reported from other studies, while residue levels of SMCs were relatively higher than those reported in other studies. Naphthalene was the most abundant PAH and HHCB was the dominant SMC observed in finless porpoises. The concentrations of PAHs and SMCs were not correlated with each other, but were significantly correlated within the same chemical groups. No correlations were found between body size and residue levels of PAHs and SMCs.

Integrative assessment of potential effects of dioxins and related compounds in wild Baikal seals (Pusa sibirica): application of microarray and biochemical analyses

We have previously indicated that accumulation of chlorinated dioxins and related compounds (DRCs) induced cytochrome P450 (CYP) 1A1, 1A2 and 1B1 isozymes in the liver of wild Baikal seals (Pusa sibirica). Here we attempt to assess the potential effects of DRCs triggered by the induction of these CYP1 isozymes in this species, using an integrative approach, combining gene expression monitoring and biochemical assays. To screen genes that may potentially respond to the exposure of DRCs, we constructed a custom cDNA oligo array that can target mRNAs in Baikal seals, and monitored hepatic mRNA expression levels in the wild population. Correlation analyses between the hepatic total 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents (TEQs) and mRNA levels supported our previous findings that high accumulation of DRCs induces the transcription of CYP1A1, CYP1A2 and CYP1B1 genes. In addition, our integrative assessment indicated that the chronic exposure to DRCs may alter the hepatic transcript levels of genes related to oxidative stress, Fe ion homeostasis, and inflammatory responses. The expression levels of CYP1A2 showed significant positive correlations with levels of malondialdehyde, a biomarker of lipid peroxidation, and of etheno-dA, a DNA adduct, suggesting that the lipid peroxidation may be enhanced through the production of reactive oxygen species (ROS) triggered by CYP1A2 induction. Moreover, there was a positive correlation between heme oxygenase activities and malondialdehyde levels, suggesting the prompted heme degradation by ROS. Fetuin-A levels, which are suppressed by inflammation, showed a significant negative correlation with TEQ levels, and hepcidin levels, which are conversely increased by inflammation, had significant positive correlations with malondialdehyde and etheno-dA levels, implying the progression of inflammation by DRC-induced oxidative stress. Taken together, we propose here that wild Baikal seals may suffer from effects of chronic exposure to DRCs on the induction of CYP1 isozymes, followed by increased oxidative stress, heme degradation and inflammation.

Contamination status and accumulation features of PCDDs, PCDFs and dioxin-like PCBs in finless porpoises (Neophocaena phocaenoides) from Korean coastal waters

Data on the concentrations and accumulation profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in cetaceans are scarce. In this study, concentrations and accumulation profiles of PCDD/Fs and DL-PCBs were measured in the blubber of finless porpoises (Neophocaena phocaenoides) collected from Korean coastal waters. Total dioxin-like toxic equivalent (TEQ) concentrations (6.5-31 pg/g lipid weight) in finless porpoises were lower than those reported for cetaceans and pinnipeds from other countries. Significant gender-specific differences were found in the concentrations and accumulation profiles of PCDD/Fs and DL-PCBs and this difference was associated with maternal and lactation transfer of contaminants from mature females to their fetus. All of the PCDD/F homologue groups were detected in all of the samples and the proportions of PCDFs were higher than those of PCDDs. The dominant congeners found in finless porpoise blubber were 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF and OCDD for PCDD/Fs and PCB 118 for DL-PCBs. The accumulation profiles of PCDD/Fs in finless porpoise in our study were different from those found for cetaceans from other countries. Total TEQ levels in finless porpoises in Korea were below the suggested threshold values for adverse health effects in marine mammals.

Perfluorinated compounds in minke whales (Balaenoptera acutorostrata) and long-beaked common dolphins (Delphinus capensis) from Korean coastal waters

This is the first study to report the concentrations and accumulation profiles of PFCs in marine mammals from Korea. The concentrations and profiles of 10 PFCs in the liver of minke whales and common dolphins from Korean coastal waters were recorded in this study. The mean concentrations of PFOS and PFUnDA were 3-20 times higher than that found for other PFCs analyzed. The concentrations of PFOS in cetaceans from Korea were relatively lower than those reported in other countries. Inter-species differences in the concentrations of PFOS, PFOSA and PFNA were found between two cetacean species, while no difference was observed in the concentrations of PFDA, PFUnDA and PFDoDA between the species. The dominant PFC compounds found in cetaceans were PFUnDA and PFOS, accounting for 70-80% of the PFCs. The accumulation profiles and correlation analysis indicated that two cetacean species have different exposure routes and metabolic capacity for PFCs.

Concentrations and accumulation features of PCDDs, PCDFs and dioxin-like PCBs in cetaceans from Korean coastal waters

Despite several studies that report accumulation of polychlorinated biphenyls (PCBs) and DDT in marine mammals worldwide, very few have examined polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like PCBs. In particular, no earlier studies have reported concentrations and accumulation profiles of persistent organic pollutants (POPs) in marine mammals from Korea. In this study, concentrations and accumulation features of PCDD/Fs and dioxin-like PCBs were measured in liver and blubber of minke whales and long-beaked common dolphins collected from Korean coastal waters. The concentrations of PCDFs and dioxin-like PCBs in blubber were 3-10 times higher than the concentrations measured in liver, but PCDDs were higher in liver than blubber. Total toxic equivalent (TEQ) concentrations in blubber of minke whales and common dolphins from Korean coastal waters were similar to, or higher than those reported for cetaceans and seals from other countries. Homologue and congener profiles of PCDD/Fs were different between livers and blubbers, while the profiles of dioxin-like PCBs were similar between the tissues. Concentrations of PCDD/Fs and dioxin-like PCBs in liver and blubber of dolphins were significantly higher than those measured in whales, due to differences in habitat and diet. The relative contribution of individual chemical groups to total TEQs was different between the two cetacean species, suggesting different exposures and metabolic activity. The TEQ levels in minke whales did not exceed the threshold level suggested for immunomodulation, while TEQs in all dolphin samples exceeded the suggested threshold level, implying potential adverse health effects from exposure to PCDD/Fs and PCBs.

Temporal trend of butyltins in seawater, sediments, and mussels from Busan Harbor of Korea between 2002 and 2007: tracking the effectiveness of tributylin regulation

Butyltins were determined in seawater, sediments, and mussels (Mytilus edulis) collected from Busan Harbor, the largest commercial harbor in Korea, to assess the contamination status and the effectiveness of tributylin (TBT) restriction. TBT concentrations were found to be 7.6 +/- 8.3 ng Sn/L in seawater, 387 +/- 606 ng Sn/g dry weight (wt) in sediments, and 322 +/- 167 ng Sn/g dry wt in mussels, and are comparable to those in the largest harbors worldwide. TBT levels were highest at locations near shipyards and related facilities. Busan Harbor was characterized by the long-term history of butyltin contamination, based on the lowered TBT/DBT ratios in environmental matrices. The temporal trend of TBT levels decreased significantly in seawater and mussels from 2002 to 2007, probably as a consequence of the legislative action in Korea (MOE Regulation 154/2000). However, TBT in sediments did not show any trend, suggesting a long half-life for TBT, about 17 years, in sediments.