Antiestrogenicity of beta-naphthoflavone and PAHs in cultured rainbow trout hepatocytes: evidence for a role of the arylhydrocarbon receptor

Spawning time in adult polar cod (Boreogadus saida) altered by crude oil exposure, independent of food availability

Fish early life stages are well known for their sensitivity to crude oil exposure. However, the effect of crude oil exposure on adults and their gametes during their spawning period is not well studied. Polar cod, a key arctic fish, may be at risk for crude oil exposure during this potentially sensitive life stage. Additionally, this species experiences lower food availability during their spawning season, with unknown combined consequences. In the present study, wild-caught polar cod were exposed to decreasing levels of a water-soluble fraction (WSF) of crude oil or control conditions and fed either at a low or high feed ration to assess the combined effect of both stressors. Samples were taken during late gonadal development, during active spawning (spawning window), and in the post-spawning period. Histology analysis of gonads from fish sampled during the spawning window showed that oil-exposed polar cod were more likely to have spawned compared to controls. Oil-exposed females had 947 differentially regulated hepatic genes, and their eggs had a higher polycyclic aromatic hydrocarbon body burden compared to controls. Feed ration did not consistently affect polar cod's response to oil exposure for the endpoints measured, however, did alone result in decreases in some sperm motility parameters. These results suggest that polar cod's spawning period is a sensitive life event to crude oil exposure, while feed limitation may play a minor role for this supposedly capital breeder. The effects of adult exposure to crude oil on gamete quality and the next generation warrant further investigation.

Effects of microplastics and food particles on organic pollutants bioaccumulation in equi-fugacity and above-fugacity scenarios

Microplastics (MPs), as emerging contaminants, sorb organic pollutants from the environment or leach out additives, thereby altering the fate of co-existing pollutants to organisms. We chose equi-fugacity and above-fugacity concentrations of polychlorinated biphenyls (PCBs) as background contamination and plastic additive concentrations, respectively, to investigate the effects of MPs on PCB bioaccumulation; we compared the effects of MPs with those of food-borne particles (FBPs). Co-exposure to MPs and FBPs at both the equi-fugacity and above-fugacity PCB concentrations had no obvious toxic effects (ROS generation and cyp1a expression) on zebrafish. When the zebrafish were exposed to the equi-fugacity PCB concentrations, the PCB concentrations reached 177.7-400.5 ng/g after a 7-d uptake; the presence of MPs did not significantly enhance PCB bioaccumulation. The remaining PCB concentrations in the fish after a 4-d depuration were 58.4-125.1 ng/g; the effects of MPs were the same as those during the uptake period. However, at the above-fugacity PCB concentrations, the MPs markedly increased the PCB bioaccumulation (by 1.8-fold) to 712.9 ng/g. This is because at above-fugacity concentrations, PCBs on MPs migrate to organisms as there were high fugacity gradients. The FBPs enhanced PCB bioaccumulation in zebrafish more effectively than the MPs, even after depuration. In the presence of FBPs, PCB bioaccumulation increased by 2.8- and 4.2- fold after uptake in the equi-fugacity and above-fugacity scenarios, respectively, both of which were significantly higher than that observed for the MPs. This is probably because FBPs are easily assimilated by fish, making the associated PCBs more bioavailable. Finally, during the co-existence of MPs and FBPs, MPs facilitate the depuration of PCBs accumulated via FBP vectors; conversely, FBPs did not affect PCB accumulation via MP vectors. Thus, this study elucidated the effects of MPs and FBPs on the bioaccumulation of pollutants at equi-fugacity or above-fugacity concentrations in aquatic environments.

Liver biomarkers response of the neotropical fish Aequidens metae to environmental stressors associated with the oil industry

The Acacias River in Colombia receives large volumes of industrial effluents mostly derived from the oil industry. To contribute to the study of the possible effects of industrial wastewaters on the aquatic environment and particularly on fish populations, a native neotropical fish, Aequidens metae was used as a sentinel species. Wild specimens of A. metae were caught at three different places of the Acacias River taking as reference the point of discharge of an oil industry effluent; upstream, downstream, and at the vicinity of the discharge pipe. A fourth sampling site was chosen as a reference site away from urban settlements. Samplings were performed twice, during the rainy and dry seasons. After anesthesia animals were weighted and measured, and humanely sacrificed. Livers were extracted, frozen on site and transported to the laboratory. Condition indices were calculated. Total protein content and the detoxification 7-ethoxyresorufin-O-deethylase (EROD) enzyme activity were estimated. Histopathological alterations were also evaluated. Water quality was estimated through the measurement of several variables. Results obtained evidenced that the highest induction in EROD activity and the strongest histological alterations in liver of the monitored fish appeared during the dry seasons at the discharge site and downstream to this point.

Coastal ecosystem inventory with characterization and identification of plastic contamination and additives from aquaculture materials

In the early 1970s, studies of marine litter first appeared in the scientific literature. Fifty years later, knowledge of several coastal areas of the Atlantic, the driving forces of oyster farmers and aquaculture, is lacking. This work documents a pilot study on an Atlantic coastal area (France). This study aims to (i) characterize the abundance of macroplastics related to aquaculture tools; (ii) microplastics present in beach sediments and (iii) characterization of pollutants present on aquaculture plastics collected. First, it was observed that 70% of the plastics collected on the beach were characteristic of aquaculture materials. In sediments, MPs most found were Polyamide between 10 and 20 μm, with a total MP concentration of 397-457 MPs.kg^-1. Pipes collectors (PVC), frequently used in aquaculture, have been shown to have concentrations of dimethylphthalates and naphthalene. Waste management and support policies can then base their actions on such studies, in order to improve their knowledge.

Transcriptome responses in polar cod (Boreogadus saida) liver slice culture exposed to benzo[a]pyrene and ethynylestradiol: insights into anti-estrogenic effects

Polar cod (Boreogadus saida) is a key species in the arctic marine ecosystem vulnerable to effects of pollution, particularly from petroleum related activities. To facilitate studying the effects of those pollutants, we adapted a precision-cut liver slice culture protocol for this species. Using this system on board a research vessel, we studied gene expression in liver slice after exposure to the polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene (BaP), ethynylestradiol (EE2), and their mixtures, to map their molecular targets and examine possible anti-estrogenic effects of BaP. The exposure experiments were performed with BaP alone (0.1, 1, and 10 μM) or in combination with low concentrations of EE2 (5 nM) to mimic physiological estradiol levels in early vitellogenic female fish. Transcriptome analysis (RNA-seq) was performed after 72 h exposure in culture to map the genes and cellular pathways affected. The results provide a view of global transcriptome responses to BaP and EE2, which resulted in enrichment of many pathways such as the aryl hydrocarbon (Ahr) and estrogen receptor pathways. In the mixture exposure, BaP resulted in anti-estrogenic effects, shown by attenuation of EE2 activated transcription of many estrogen target genes. The results from this ex vivo experiment suggest that pollutants that activate the Ahr pathway such as the PAH compound BaP can result in anti-estrogenic effects that may lead to endocrine disruption in polar cod.

Exposure to hydrocarbons and chlorpyrifos alters the expression of nuclear receptors and antioxidant, detoxifying, and immune response proteins in the liver of the rainbow trout, Oncorhynchus mykiss

The development of oil and gas production together with the fruit production in nearby areas of North Patagonia, Argentina, suggests aquatic pollution scenarios which include permanent oil pollution combined with short events of pesticides application. It has been reported that oil hydrocarbons activate the aryl hydrocarbon receptor (AhR) pathway in the rainbow trout, Oncorhynchus mykiss, and that the insecticide Chlorpyrifos (CPF) interacts with these effects. Thus, it is interesting to investigate whether hydrocarbons and insecticides, applied by separate or combined, can affect fish health and reproductive signaling by acting on different nuclear receptors' regulatory pathways. To study this kind of interactions, we exposed juvenile rainbow trout to water accommodated fraction (WAF) of crude oil (62 μg L^-1 TPH) for 48 h and subsequently exposed the livers ex vivo to the insecticide Chlorpyrifos (CPF) (20 µg L^-1) for 1 h. We analyzed the mRNA expression of nuclear receptors and proteins involved in detoxifying, antioxidant, immune and apoptosis responses by qRT-PCR. We also performed histopathological analysis. WAF induced the expression of the androgen (AR) and the Liver X receptor (LXR) by 8- and 3-fold, respectively. AR induction was reversed by subsequent exposure to CPF. The progesterone receptor (PR) and glucocorticoid receptor (GR) were increased 2-fold and 3-fold by WAF respectively, while estrogen and mineralocorticoid receptors were not affected. GR was also induced by CPF with an additive effect in the WAF-CPF treatment. The antioxidant genes, gamma glutamyl transferase (GGT), superoxide dismutase (SOD1) were induced by WAF (2-3-fold). WAF upregulated the ATP Binding Cassette Subfamily C Member 2 (ABCC2, MRP2) (4-fold) and downregulated alkaline phosphatase. WAF also induced the inflammatory interleukins (IL) IL-8, and IL-6 and the anti-inflammatory IL-10, while CPF induced the inflammatory tumor necrosis factor (-α) and IL-6, and activated the intrinsic apoptotic pathway through the induction of caspases 3 and 9. Both, WAF and CPF downregulated the expression of the extrinsic apoptosis initiator caspase 8 and the inflammatory caspase 1. In conclusion, WAF hydrocarbons alter O. mykiss endocrine regulation by inducing AR, PR and GR. The subsequent exposure to CPF reverses AR, suggesting a complex interaction of different pollutants in contaminated environments, WAF hydrocarbons alter liver metabolism by inducing the expression of LXR, GR, antioxidant and detoxifying enzymes, and both inflammatory and anti-inflammatory cytokines, and causing mild hepatic steatosis. CPF activates inflammatory and stress responses associated with the induction of inflammatory cytokines together with apoptosis initiator and executioner caspases.

Polycyclic aromatic compounds (PACs) in the Canadian environment: Exposure and effects on wildlife

Polycyclic aromatic compounds (PACs) are ubiquitous in the environment. Wildlife (including fish) are chronically exposed to PACs through air, water, sediment, soil, and/or dietary routes. Exposures are highest near industrial or urban sites, such as aluminum smelters and oil sands mines, or near natural sources such as forest fires. This review assesses the exposure and toxicity of PACs to wildlife, with a focus on the Canadian environment. Most published field studies measured PAC concentrations in tissues of invertebrates, fish, and birds, with fewer studies of amphibians and mammals. In general, PAC concentrations measured in Canadian wildlife tissues were under the benzo[a]pyrene (BaP) guideline for human consumption. Health effects of PAC exposure include embryotoxicity, deformities, cardiotoxicity, DNA damage, changes to DNA methylation, oxidative stress, endocrine disruption, and impaired reproduction. Much of the toxicity of PACs can be attributed to their bioavailability, and the extent to which certain PACs are transformed into more toxic metabolites by cytochrome P450 enzymes. As most mechanistic studies are limited to individual polycyclic aromatic hydrocarbons (PAHs), particularly BaP, research on other PACs and PAC-containing complex mixtures is required to understand the environmental significance of PAC exposure and toxicity. Additional work on responses to PACs in amphibians, reptiles, and semi-aquatic mammals, and development of molecular markers for early detection of biological responses to PACs would provide a stronger biological and ecological justification for regulating PAC emissions to protect Canadian wildlife.

Toxicity characterization of surface sediments from a Mediterranean coastal lagoon

The occurrence of bioactive compounds and contaminant-associated effects was assessed by means of in vivo and in vitro assays using different extractable fractions of surface sediments from a contaminated coastal lagoon (Mar Menor, SE Spain). Sediment elutriates and clean seawater, previously exposed to whole sediment, were used for assessing the in vivo toxicity on embryo development of the sea urchin Paracentrotus lividus. Agonist and antagonist activities relating to estrogen and androgen receptors and agonist activities on aryl hydrocarbon receptor (expressed as ethoxyresorufin-O-deethylase (EROD) activities) were investigated in sediment extracts by using HER-Luc, AR-EcoScreenTM and fibroblast-like RTG-2 cell lines. Embryotoxicity effects were greater for sediment elutriates than those incubated in sediment-water interphase, implying that diffusion of bioactive chemicals can occur from sediments to sea water column, favoured by sediment disturbance events. In vitro results show the occurrence in extracts of compounds with estrogen antagonism, androgen antagonism and dioxin-like activities. Multidimensional scaling analysis classified the sampling sites into four sub-clusters according to their chemical-physical and biological similarities, relating in vitro bioactivity with the total organic carbon and known organic chemical load, with particular reference to total sum of PAHs, PCB 180, p,p-DDE and terbuthylazine. Overall, results pointed to the presence of unknown or unanalyzed biologically-active compounds in the sediments, mostly associated with the extracted polar fraction of the Mar Menor lagoon sediments. Our findings provide relevant information to be considered for the environmental management of contaminated coastal lagoons.

Benzo[a]pyrene exposure induced reproductive endocrine-disrupting effects via the steroidogenic pathway and estrogen signaling pathway in female scallop Chlamys farreri

Benzo[a]pyrene (B[a]P), as one of the typical polycyclic aromatic hydrocarbons and environmental contaminants, may cause endocrine disrupting effects and reproductive impairments in bivalves. However, the molecular mechanisms are still not fully understood. In this study, three reproductive stages (proliferative stage, growing stage and mature stage) of female scallops Chlamys farreri were exposed to B[a]P at 0, 0.38 and 3.8 μg/L. The present study determined the adverse effects of B[a]P on gonadosomatic index, circulating hormone concentrations, endocrine-associated gene expression and ovarian histology. Significant decrease in sex hormones including progesterone (P), testosterone (T) and 17β-estradiol (E2), was observed in B[a]P-treated C. farreri at growing stage and mature stage. These effects were associated with down-regulated expression of steroidogenic enzymes, including 3β-HSD, CYP17 and 17β-HSD, which were regulated by the upstream adenylate cyclase (Adcy) - protein kinase (PKA) signaling pathway. Ovarian transcript levels of estrogen receptor (ER) and caveolin-1 (cav-1) were decreased in B[a]P-treated C. farreri. Vitellogenin (Vtg), an estrogen-mediated gene involved in ovarian development, was down-regulated by B[a]P. Furthermore, ovarian histology was investigated to clarify the impairment of B[a]P on ovaries at growing stage and mature stage. Overall, the present results elucidated the anti-estrogenic mechanisms along the steroidogenic pathway and estrogen signaling pathway for the stage-dependent endocrine-disrupting effects of B[a]P. This finding provides important information regarding to the underlying molecular mechanisms of B[a]P-induced endocrine disruption in different reproductive stages of bivalves. In addition, the adverse effects should be taken into concertation during protection of bivalves germplasm resources and comprehensive evaluation of ecological risks.

Changes in Reef Fish Community Structure Following the Deepwater Horizon Oil Spill

Large-scale anthropogenic disturbances can have direct and indirect effects on marine communities, with direct effects often taking the form of widespread injury or mortality and indirect effects manifesting as changes in food web structure. Here, we report a time series that captures both direct and indirect effects of the Deepwater Horizon Oil Spill (DWH) on northern Gulf of Mexico (nGoM) reef fish communities. We observed significant changes in community structure immediately following the DWH, with a 38% decline in species richness and 26% decline in Shannon-Weiner diversity. Initial shifts were driven by widespread declines across a range of trophic guilds, with subsequent recovery unevenly distributed among guilds and taxa. For example, densities of small demersal invertivores, small demersal browsers, generalist carnivores, and piscivores remained persistently low with little indication of recovery seven years after the DWH. Initial declines among these guilds occurred prior to the arrival of the now-widespread, invasive lionfish (Pterois spp.), but their lack of recovery suggests lionfish predation may be affecting recovery. Factors affecting persistently low densities of generalist carnivores and piscivores are not well understood but warrant further study given the myriad ecosystem services provided by nGoM reef fishes.

Xenobiotic biotransformation, oxidative stress and obesogenic molecular biomarker responses in Tilapia guineensis from Eleyele Lake, Nigeria

Despite the important ecosystem and hydrological roles of coastal and inland waters, there are no established biomonitoring protocols for evaluating environmental, wildlife and human health for these coastlines in Nigeria. In the present study, contaminants tissue burden and effects at molecular and physiological levels, were investigated in Tilapia guineensis from a man-made lake (Eleyele Lake) that is used for municipal domestic water supply and compared to a reference site (Igboho Lake). Gene expression of phase I and II biotransformation systems, oxidative stress and obesogen responses were analyzed using real-time PCR, and these results were related to general health index (condition factor: CF) and muscle burden of trace metals, aliphatic and polycyclic aromatic hydrocarbons (PAHs). We observed a significant increase in phase I and II biotransformation systems, oxidative stress and obesogen responses in male and female fish from Eleyele lake compared with the reference site. Overall, our data showed significant relationships between biological responses and tissue concentrations of metals and PAHs for the Eleyele lake compared with the reference site. Given that a positive influence on genes and pathways associated with metabolic status has been previously associated with peroxisome proliferator activated receptors (PPARs), xenobiotic compounds that activate PPARs may produce changes in energy and metabolic processes, leading to obesity. The high CF (>1 = good health condition) observed, coupled with the high muscle burden of inorganic and organic contaminants in fish from Eleyele lake, suggest a potential obesogenic effect in these fishes. These findings represent co-relational evidence that the Eleyele lake is contaminated and consequently affecting biological and physiological integrity of organisms inhabiting the lake. These findings also suggest potential health risks for humans, since the lake is extensively used for domestic water supply and fisheries.

Gene expression profiles of putative biomarkers in juvenile loggerhead sea turtles (Caretta caretta) exposed to polycyclic aromatic hydrocarbons

There is evidence that polycyclic aromatic hydrocarbons (PAHs) are consistently the predominant organic contaminants in concentration found in loggerhead sea turtles (Caretta caretta) from the North and Central Adriatic Sea. Hence this study investigates the PAH toxicity to loggerheads by using a particular set of genes [i.e. CYP1B, CAT, GPX, GSTT1, SOD3, DNMT1, Epoxide hydrolase 1 (EPHX1), Poly (ADP-ribose) polymerase 1 (PARP1), Lamin-A/C isoform 3 (LMNA), Talin 1 (TLN1), Annexin A1 (ANXA1)] whose altered expression is potentially dependent on and specific for the PAH-related mechanism of action. Twenty healthy juvenile loggerheads were thus divided into high and low exposure groups (mean of ΣPAHs: 80.34 ng mL^-1 vs. 8.84 ng mL^-1, P < 0.0001) according to the median split of ΣPAHs. Interestingly, we found that the whole blood mRNA levels of each gene biomarker tested were significantly increased in high PAH-exposed turtles thus proving to be useful for the biological monitoring of PAH toxicity and hematotoxicity in sea turtles.

RNA-Seq analysis of transcriptome responses in Atlantic cod (Gadus morhua) precision-cut liver slices exposed to benzo[a]pyrene and 17α-ethynylestradiol

Polycyclic aromatic hydrocarbons such as benzo[a]pyrene (BaP) that activate the aryl hydrocarbon receptor (Ahr) pathway, and endocrine disruptors acting through the estrogen receptor pathway are among environmental pollutants of major concern. In this work, we exposed Atlantic cod (Gadus morhua) precision-cut liver slices (PCLS) to BaP (10 nM and 1000 nM), ethynylestradiol (EE2) (10 nM and 1000 nM), and equimolar mixtures of BaP and EE2 (10 nM and 1000 nM) for 48 h, and performed RNA-Seq based transcriptome mapping followed by systematic bioinformatics analyses. Our gene expression analysis showed that several genes were differentially expressed in response to BaP and EE2 treatments in PCLS. Strong up-regulation of genes coding for the cytochrome P450 1a (Cyp1a) enzyme and the Ahr repressor (Ahrrb) was observed in BaP treated PCLS. EE2 treatment of liver slices strongly up-regulated genes coding for precursors of vitellogenin (Vtg) and eggshell zona pellucida (Zp) proteins. As expected, pathway enrichment and network analysis showed that the Ahr and estrogen receptor pathways are among the top affected by BaP and EE2 treatments, respectively. Interestingly, two genes coding for fibroblast growth factor 3 (Fgf3) and fibroblast growth factor 4 (Fgf4) were up-regulated by EE2 in this study. To our knowledge, the fgf3 and fgf4 genes have not previously been described in relation to estrogen signaling in fish liver, and these results suggest the modulation of the FGF signaling pathway by estrogens in fish. The signature expression profiles of top differentially expressed genes in response to the single compound (BaP or EE2) treatment were generally maintained in the expression responses to the equimolar binary mixtures. However, in the mixture-treated groups, BaP appeared to have anti-estrogenic effects as observed by lower number of differentially expressed putative EE2 responsive genes. Our in-depth quantitative analysis of changes in liver transcriptome in response to BaP and EE2, using PCLS tissue culture provides further mechanistic insights into effects of the compounds. Moreover, the analyses demonstrate the usefulness of PCLS in cod for omics experiments.

DNA damage in marine rock oyster (Saccostrea Cucullata) exposed to environmentally available PAHs and heavy metals along the Arabian Sea coast

Molecular biomarkers are used world wide for quick assessment of the immediate effect of environmental pollution on marine ecosystems. Recently, we evaluated oxidative stress responses of marine rock oyster, Saccostrea cucullata impacted due to polycyclic aromatic hydrocarbons (PAHs) accumulated in their tissues at a few sampling sites along the coast of Goa around the region of the Arabian sea coast, India (Sarkar et al., 2017). Using a combination of partial alkaline unwinding and comet assays, we now report a comprehensive study on the impairment of DNA integrity (DI) in S. cucullata due to exposure to environmentally available PAHs and also heavy metals (Pb, Cd, Cu, Fe and Mn) along the Arabian Sea coast, Goa, India exclusively around the entire coast of Goa. First, we determined significant correlation between DI in S. cucullata and the extent of exposure to and bioaccumulation of different PAH compounds including 2-3 aromatic ring PAHs (R², 0.95), 4-6 aromatic ring PAHs (R², 0.85), oxygenated-PAHs (oxy-PAHs, R², 0.84) and total PAHs (t-PAHs, R², 0.98). Second, we observed dose-dependent decrease in DI in S. cucullata with increasing concentrations of different PAH components in oyster tissues. We substantiated our field observations with appropriate laboratory controls using benzo[a]pyrene (BaP). Third, we performed stepwise multiple regression analyses of different water quality parameters including pH, salinity, temperature, dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrite (NO₂), nitrate (NO₃), phosphate (PO₄), turbidity and also t-PAH-biota, t-PAH-water with DI as the dependent variable. Among all these parameters, only four parameters such as t-PAH-biota in combination with DO, BOD and NO₂ showed significant correlation (R¯² = 0.95) with loss in DI in S. cucullata. Based on these results, we created a map indicating the percentage of DNA damage in S. cucullata exposed to PAHs and heavy metals at each sampling location along the west coast of India around Goa, India.

Characterizing combined effects of antiestrogenic chemicals on vitellogenin production in rainbow trout (Oncorhynchus mykiss) hepatocytes

Fish are exposed to a complex mixture of endocrine disrupting compounds (EDC), some of which display antiestrogenic activity leading to suppression of estrogen receptor (ER)- mediated reproductive processes. Although the main mode of action (MoA) of these antiestrogens is to directly interfere with natural ligand binding of the ER, several other MoA have been proposed. The aim of the present study was to characterize single and combined antiestrogenic effects of the aryl hydrocarbon receptor (AhR)-agonist β-naphthoflavone (BNF) and ER-antagonist 4-hydroxytamoxifen (OHT) on vitellogenin (Vtg) protein using primary rainbow trout (Oncorhynchus mykiss) hepatocytes. Supporting transcriptional analysis of ER-responsive genes (estrogen receptor-α (er-α), vitellogenin-1 (vtg-1), eggshell zona radiata protein (zrp)) and AhR-mediated genes (aryl hydrocarbon receptor-2β, cytochrome p450-1a (cyp1a)) was performed by qPCR to characterize the antiestrogenic influence on ER- and AhR-mediated responses. Data demonstrated that both BNF and OHT significantly reduced 17β-estradiol (E2)-induced Vtg protein expression in a concentration responsive manner, whereas exposure to a mixture of these produced an additive antiestrogenic effect. The results observed at the protein level were further supported by transcriptional analysis of ER-responsive genes (er-α, vtg-1, zrp), where only E2-induced vtg-1 gene expression was significantly decreased by OHT and the mixture of OHT and BNF. E2-induced er-α and zrp gene expression was not markedly altered. The significant reduction of E2-induced vtg-1 gene expression by OHT suggested that the antiestrogenic effect of this compound may be associated with ER signaling pathway. Specific genes involved in putative AhR-ER cross-talk were also investigated, however none were directly associated with the compound anti-estrogenic MoA. Although the MoA of the single compounds and mixture were not completely characterized, the present study enhanced our knowledge of the combined toxicity mediated by antiestrogens acting through different MoA.

In silico prediction and in vivo analysis of antiestrogenic potential of 2-isopropylthioxanthone (2-ITX) in juvenile goldfish (Carassius auratus)

Previous studies have shown both anti-estrogenic and anti-androgenic activities of 2-isopropylthioxanthone (2-ITX), a well known food contaminant, in in vitro assays. However, no data are available on the anti-estrogenic potentials and risks of 2-ITX in aquatic organisms. This work evaluated the potential endocrine disrupting effects of 2-ITX at the level of estrogen receptor (ER) signaling cascade using juvenile goldfish (Carassius auratus) as model. Firstly, we investigated the ligand binding efficiency of 2-ITX to the ligand binding domains (LBD) of goldfish ER subtypes using a molecular docking approach. Secondly, we assessed the effects of 2-ITX on E2-induced hepatic expression of ERα1, ERβ1, ERβ2, and vitellogenin (VTG) in vivo. Crosstalk between ER-VTG and aryl hydrocarbon receptor 2 (AhR2)-cytochrome P4501A (CYP1A) was also investigated. Fish were injected with increasing doses of 2-ITX ranging from 2 to 10µg/g BW, and results were compared to the effect of tamoxifen, a well-known ER modulator. We observed that compared to ERβ, the interaction potentials of 2-ITX to goldfish ERα1 LBD was more stable in the inactive receptor conformation. The in silico docking simulation analysis also revealed that 2-ITX acted as agonist for the goldfish AhR2 LBDs suggesting the ability of this compound to activate the cross-talk between the ERα- and AhR-signaling pathways. In vivo experiments confirm in silico simulation predictions demonstrating that 2-ITX reduced the estrogenicity of E2 at both transcriptional and post-transcriptional levels, indicating a clear anti-estrogenic effect. Co-exposure of E2 and 2-ITX also resulted in a significant decrease of CYP1A gene expression with respect to 2-ITX alone. Results from these studies collectively revealed that the antiestrogenic property of 2-ITX can be ascribed to a combination of effects on multiple signaling pathways suggesting the potential for this environmental contaminant to affect the hormonal control of reproductive processes in fish.

Fish condition factor, peroxisome proliferator activated receptors and biotransformation responses in Sarotherodon melanotheron from a contaminated freshwater dam (Awba Dam) in Ibadan, Nigeria

The relationship between condition factor (CF), peroxisome proliferator-activated receptors (PPARs), phase 1 biotransformation (CYP1A isoforms) and contaminant burden has been studied in Sarotherodon melanotheron from a contaminated tropical freshwater dam (Awba Dam) and compared to a reference site (Modete Dam) in Southwest, Nigeria. A total of 89 fish (57 males and 32 females) was collected from Awba Dam and 95 fish (48 males and 47 females) from the reference site. In general, fish sampled from Awba Dam were bigger than reference site. Sediment samples were also collected from both sites for contaminant analysis. Expression of ppar and cyp1 isoforms was analyzed using validated real-time PCR, while CYP1A and PPAR protein levels were analyzed using immunochemical method with specific antibodies. CYP-mediated catalytic responses (EROD, MROD and BROD) were performed by biochemical methods. We observed significant increases in ppar and cyp1 isoforms mRNA in both male and female fish from Awba Dam, compared to the reference site. Catalytic activities of EROD, MROD and BROD paralleled cyp1 transcript levels. Sex-related differences in PPAR and CYP1A protein levels were also observed, showing higher CYP1A proteins in males, compared with females, and higher PPAR proteins in females compared with males. Principal component analysis (PCA) biplot showed positive relationships between biological responses (ppar isoforms), condition factor (CF) and sediment PCBs, PAHs, OCPs and heavy metal concentrations. The present study shows that S. melanotheron inhabiting Awba Dam are severely affected by different classes of environmental contaminants that target metabolic processes (PPAR) and biotransformation pathways (CYP1A) in male and female fish, compared to a reference site. Interestingly, fish from Awba Dam were exhibiting good growth (evidence by high CF values) that paralleled increases in the transcriptional activation of ppar and cyp1 isoforms, despite the high contaminant burdens, suggesting a possible contaminant-induced obesogenic effects.

Spatial and temporal variation of biochemical biomarkers in Gobius niger (Gobiidae) from a southern Mediterranean lagoon (Bizerta lagoon, Tunisia): Influence of biotic and abiotic factors

This study aims at evaluating both the influence of natural and some anthropogenic pressures on spatio-temporal variations on biomarker responses in sedentary benthic fish Gobius niger. For this purpose, variability of biotransformation enzymes and oxidative stress parameters response were studied in six stations from Bizerta lagoon as well as a reference station located in Ghar El Melh lagoon. Biomarker responses were shown to vary according to both physico-chemical parameters and anthropogenic pressures, but no influence of sex was reported. Based on multivariate analyses, the responses of biomarkers, obtained after covariate analysis in order to weigh the effect of physico-chemical parameters, allowed us to discriminate all stations, with a good classification rate for those that are highly contaminated. Altogether, this study shows the usefulness of G. niger as a sentinel species and stresses the necessity of integrating natural variables for data interpretation.

Biological impact of environmental polycyclic aromatic hydrocarbons (ePAHs) as endocrine disruptors

Polycyclic aromatic hydrocarbons (PAHs) are often detected in the environment and are regarded as endocrine disruptors. We here designated mixtures of PAHs in the environment as environmental PAHs (ePAHs) to discuss their effects collectively, which could be different from the sum of the constituent PAHs. We first summarized the biological impact of environmental PAHs (ePAHs) found in the atmosphere, sediments, soils, and water as a result of human activities, accidents, or natural phenomena. ePAHs are characterized by their sources and forms, followed by their biological effects and social impact, and bioassays that are used to investigate their biological effects. The findings of the bioassays have demonstrated that ePAHs have the ability to affect the endocrine systems of humans and animals. The pathways that mediate cell signaling for the endocrine disruptions induced by ePAHs and PAHs have also been summarized in order to obtain a clearer understanding of the mechanisms responsible for these effects without animal tests; they include specific signaling pathways (MAPK and other signaling pathways), regulatory mechanisms (chromatin/epigenetic regulation, cell cycle/DNA damage control, and cytoskeletal/adhesion regulation), and cell functions (apoptosis, autophagy, immune responses/inflammation, neurological responses, and development/differentiation) induced by specific PAHs, such as benz[a]anthracene, benzo[a]pyrene, benz[l]aceanthrylene, cyclopenta[c,d]pyrene, 7,12-dimethylbenz[a]anthracene, fluoranthene, fluorene, 3-methylcholanthrene, perylene, phenanthrene, and pyrene as well as their derivatives. Estrogen signaling is one of the most studied pathways associated with the endocrine-disrupting activities of PAHs, and involves estrogen receptors and aryl hydrocarbon receptors. However, some of the actions of PAHs are contradictory, complex, and unexplainable. Although several possibilities have been suggested, such as direct interactions between PAHs and receptors and the suppression of their activities through other pathways, the mechanisms underlying the activities of PAHs remain unclear. Thus, standardized assay protocols for pathway-based assessments are considered to be important to overcome these issues.

Peroxisome proliferator-activated receptors and biotransformation responses in relation to condition factor and contaminant burden in tilapia species from Ogun River, Nigeria

A major development in fishery science has been the Fulton's condition factor (CF) as a reliable physiological index of fish growth and health status (Fulton 1902). As a general rule, CF-value greater than 1 (>1) should be regarded as an indicator for good growth and health. Therefore, exposure of fish to contaminants in the environment will be expected to produce a reduction in scope for growth, since energy for growth will be allocated to overcome stressful conditions. In the present study, we hypothesized that tilapia species from Ogun River (Nigeria) are experiencing severe contaminant-induced obesogen effects leading to high CF (≥ 2) in fish with pathological alterations. The environmental obesogen hypothesis has related the interaction between environmental pollutants and PPAR isoform activation In this respect, peroxisome proliferator-activated receptors (PPARs) and biotransformation responses in relation to contaminant burden were investigated in a total of 1074 specimens of Tilapias species (Tilapia guineensis, Sarotherodon galileaus and Oreochromis niloticus) collected from three areas with different degrees of anthropogenic contamination and from a putative control site along the Ogun River. Liver mRNA expression of cytochrome cyp1 isoforms (cyp1a, 1b and 1c) and PPAR isoforms (ppar-α, β and γ) were analyzed using validated real-time PCR. Fish were also analyzed for CF and muscle contaminant burden (aliphatic and polycyclic aromatic hydrocarbons, organochlorine pesticides, and polychlorinated biphenyls). A significant increase in mRNA expression of cyp1- and ppar isoforms was observed in fish from polluted areas, and these results paralleled data on PCBs and PAHs tissue concentrations. Further, cyp1 isoforms showed clear sex-related differences, with higher mRNA expression in male fish than in females. Principal component analysis revealed a relationship between cyp1 isoforms, ppar-α, β, PCBs and PAHs and these interactions may suggest a crosstalk between AhR- and PPARs mediated pathways on metabolic and energetic processes. The PCA biplot also highlighted a positive relationship between ppar-γ, body weight, total length and PAHs. The CF for fish from all the sites was ≥ 2 indicating that this parameter may not be a reliable index for evaluating fish growth and health condition, especially in wild fish population exposed to complex cocktails of environmental pollutants.

17α-Ethinylestradiol (EE2) effect on global gene expression in primary rainbow trout (Oncorhynchus mykiss) hepatocytes

The potential impact of endocrine disrupting chemicals (EDCs) in the aquatic environment has driven the development of screening assays to evaluate the estrogenic properties of chemicals and their effects on aquatic organisms such as fish. However, obtaining full concentration-response relationships in animal (in vivo) exposure studies are laborious, costly and unethical, hence a need for developing feasible alternative (non-animal) methods. Use of in vitro bioassays such as primary fish hepatocytes, which retain many of the native properties of the liver, has been proposed for in vitro screening of estrogen receptor (ER) agonists and antagonists. The aim of present study was to characterize the molecular mode of action (MoA) of the ER agonist 17α-ethinylestradiol (EE2) in primary rainbow trout (Oncorhynchus mykiss) hepatocytes. A custom designed salmonid 60,000-feature (60k) oligonucleotide microarray was used to characterize the potential MoAs after 48h exposure to EE2. The microarray analysis revealed several concentration-dependent gene expression alterations including classical estrogen sensitive biomarker gene expression (e.g. estrogen receptor α, vitellogenin, zona radiata). Gene Ontology (GO) analysis displayed transcriptional changes suggesting interference of cellular growth, fatty acid and lipid metabolism potentially mediated through the estrogen receptor (ER), which were proposed to be associated with modulation of genes involved in endocrine function and reproduction. Pathway analysis supported the identified GOs and revealed modulation of additional genes associated with apoptosis and cholesterol biosynthesis. Differentially expressed genes (DEGs) related to impaired lipid metabolism (e.g. peroxisome proliferator-activated receptor α and γ), growth (e.g. insulin growth factor protein 1), phase I and II biotransformation (e.g. cytochrome P450 1A, sulfotransferase, UDP-glucuronosyltransferase and glutathione S-transferase) provided additional insight into the MoA of EE2 in primary fish hepatocytes. Results from the present study suggest that biotransformation, estrogen receptor-mediated responses, lipid homeostasis, growth and cancer/apoptosis in primary fish hepatocytes may be altered after short-term exposure to ER-agonists such as EE2. In many cases the observed changes were similar to those reported for estrogen-exposed fish in vivo. In conclusion, global transcriptional analysis demonstrated that EE2 affected a number of toxicologically relevant pathways associated with an estrogenic MoA in the rainbow trout hepatocytes.

BFCOD activity in fish cell lines and zebrafish embryos and its modulation by chemical ligands of human aryl hydrocarbon and nuclear receptors

Assessment of exposure and effect of fish to pharmaceuticals that contaminate aquatic environment is a current major issue in ecotoxicology and there is a need to develop specific biological marker to achieve this goal. Benzyloxy-4-trifluoromethylcoumarin-O-debenzyloxylase (BFCOD) enzymatic activity has been commonly used to monitor CYP3A activity in fish. In this study, we assessed the capacity of a panel of toxicologically relevant chemicals to modulate BFCOD activity in fish, by using in vitro and in vivo bioassays based on fish liver cell lines (PLHC-1, ZFL, RTL-W1) and zebrafish embryos, respectively. Basal BFCOD activity was detectable in all biological models and was differently modulated by chemicals. Ligands of human androgens, glucocorticoids, or pregnanes X receptors (i.e., dexamethasone, RU486, rifampicin, SR12813, T0901317, clotrimazole, ketoconazole, testosterone, and dihydrotestosterone) moderately increased or inhibited BFCOD activity, with some variations between the models. No common feature could be drawn by regards to their capacity to bind to these receptors, which contrasts with their known effect on mammalian CYP3A. In contrast, dioxins and polycyclic aromatic hydrocarbons (PAHs) strongly induced BFCOD activity (up to 30-fold) in a time- and concentration-dependent manner, both in vitro in all cell lines and in vivo in zebrafish embryos. These effects were AhR dependent as indicated by suppression of induced BFCOD by the AhR pathway inhibitors 8-methoxypsoralen and α-naphthoflavone. Altogether our result further question the relevance of using liver BFCOD activity as a biomarker of fish exposure to CYP3A-active compounds such as pharmaceuticals.

Biotransformation and Oxidative Stress Responses in Captive Nile Crocodile (Crocodylus niloticus) Exposed to Organic Contaminants from the Natural Environment in South Africa

In the present study, the biotransformation and oxidative stress responses in relation to chemical burden in the liver of male and female Nile crocodiles--Crocodylus niloticus--from a commercial crocodile farm passively exposed to various anthropogenic aquatic pollutants was investigated. In general, the data showed that male crocodiles consistently produced higher biotransformation and oxidative stress responses compared to females. Relationships between these responses and concentrations of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) were also observed. Specifically, the catalytic assays for EROD and BROD (not PROD and MROD) showed sex-differences between male and female crocodiles and paralleled immunochemically determined CYP1A and CYP3A protein levels; the relatively similar levels of PAHs in both sexes suggest an estrogen-mediated reduction of this pathway in females. The antioxidant system exhibited higher levels in male crocodiles with slight or significant higher values for catalase (CAT), glutathione reductase (GR), glutathione peroxidases-H2O2 (GPx-H2O2), glutathione peroxidases-Cu (GPx-Cu), total antioxidant capacity towards peroxyl radicals (TOSC-ROO) and hydroxyl radicals (TOSC-HO), total glutathione (GSH) and malondialdehyde (MDA). On the other hand, the activities of acyl-CoA oxidase (AOX) and glutathione S-transferases (GST) were significantly higher in females. Principal component analysis (PCA) produced significant groupings that revealed correlative relationships (both positive and negative) between biotransformation/oxidative stress variables and liver PAHs and aliphatic hydrocarbon burden. The overall results suggest that these captive pre-slaughter crocodiles exhibited adverse exposure responses to anthropogenic aquatic contaminants with potentially relevant effects on key cellular pathways, and these responses may be established as relevant species biomarkers of exposure and effects in this endangered species.

Detection of effects caused by very low levels of contaminants in riverine sediments through a combination of chemical analysis, in vitro bioassays, and farmed fish as sentinel

Aquatic organisms are often exposed to mixtures of low levels of pollutants whose presence and effects can pass easily unnoticed if only traditional monitoring strategies are employed. The main aim of this work was to assess the presence and effects of trace levels of pollutants in a scarcely affected area through the combination of chemical and biological approaches. Sediments were collected along a river with little anthropogenic pressure and assayed for cytochrome P450 (Cyp1a)-dependent ethoxyresorufin-O-deethylase (EROD) activity with the rainbow trout gonadal cell line RTG-2. Chemical analyses were performed in these sediments using two-dimensional gas chromatography-time-of-flight mass spectrometry. Sediment samples induced EROD activity, and chemical analyses evidenced the presence of a wide variety of contaminants in the range of nanograms per gram of dry weight. Correlation analysis between EROD induction and chemical analyses data showed an r value of 0.840 (p < 0.05). In addition, fish from a fish farm located downstream of the sampling points exhibited high hepatic EROD levels as well as an induced expression of cyp1a and cyp3a. In conclusion, only an appropriate combination of biological and chemical techniques allowed the detection of the presence of trace levels of contaminants in a theoretically nonaffected river.

Sublethal effects of aged oil sands-affected water on white sucker (Catostomus commersonii)

To investigate impacts of proposed oil sands aquatic reclamation techniques on benthic fish, white sucker (Catostomus commersonii Lacépède, 1803) were stocked in 2 experimental ponds-Demonstration Pond, containing aged fine tailings capped with fresh water, consistent with proposed end-pit lake designs, and South Bison Pond, containing aged unextracted oil sands material-to examine the effects of unmodified hydrocarbons. White sucker were stocked from a nearby reservoir at both sites in May 2010 and sampled 4 mo later to measure indicators of energy storage and utilization. Comparisons were then made with the source population and 2 reference lakes in the region. After exposure to aged tailings, white sucker had smaller testes and ovaries and reduced growth compared with the source population. Fish introduced to aged unextracted oil sands material showed an increase in growth over the same period. Limited available energy, endocrine disruption, and chronic stress likely contributed to the effects observed, corresponding to elevated concentrations of naphthenic acids, aromatic compounds in bile, and increased CYP1A activity. Because of the chemical and biological complexity of these systems, direct cause-effect relationships could not be identified; however, effects were associated with naphthenic acids, polycyclic aromatic hydrocarbons, ammonia, and high pH. Impacts on growth have not been previously observed in pelagic fishes examined in these systems, and may be related to differences in sediment interaction.

Characterization and expression of cytochrome p450 cDNA (CYP9AT2) in Chironomus riparius fourth instar larvae exposed to multiple xenobiotics

We identified and characterized a CYP9 family gene, CrCYP9AT2, from Chironomus riparius, an eco-toxicologically important model organism. The 1978 base pair (bp) length CrCYP9AT2 cDNA has an open reading frame of 1587 bp encoding a putative 528 amino acid protein. There was 267 bp 5' and 123 bp 3' untranslated region with a polyadenylation signal site (AATAAA). The putative heme-binding cysteine at position 471 and the typical p450 signature sequence of 463-FGIGPRNCIG-473 were also present. The CrCYP9AT2 transcript was present in all life stages with the highest expression in larvae. The modulation of CrCYP9AT2 was studied using real-time polymerase chain reaction after 24h exposure to cadmium chloride, benzo(a)pyrene; bisphenol A; nonylphenol; chlorpyrifos and ethinylestradiol. Significant up-regulation of CrCYP9AT2 gene was observed after exposure to Cd, B(a)P and CP. However, CrCYP9AT2 was significantly down-regulated after exposure to BPA, NP and EE.

Effects of 4-nonylphenol on hepatic gene expression of peroxisome proliferator-activated receptors and cytochrome P450 isoforms (CYP1A1 and CYP3A4) in juvenile sole (Solea solea)

The objective of the present study was to investigate the modulatory effects of the xenoestrogen 4-nonylphenol (4-NP) on hepatic peroxisome proliferator-activated receptor (PPAR) α and β gene expression patterns in relation to the detoxification pathways mediated by cytochrome P450 isoforms (CYP1A1 and CYP3A4). Waterborne 4-NP-induced effects were compared with those of 10(-8)M 17β-estradiol (E2) by using in vivo dose-response experiments carried out with juvenile sole (Solea solea). Compared to the controls, significantly higher levels of PPARα mRNAs were found in fish treated with E2 or 4-NP (10(-6)M) 3 d after exposure; the highest dose of 4-NP also caused up-regulation of retinoid X receptor α (RXRα) transcript levels. On the contrary, PPARβ gene expression was not modulated by E2 or 4-NP. Our data show that 4-NP-induced PPARα mRNA levels coincide with suppression of CYP1A1 and CYP3A4 expression similarly to E2. The results from these in vivo studies suggest the presence of cross-talk between nuclear receptor-mediated signaling pathways and PPARα that may result in modulation of CYP450 isoforms expression following 4-NP treatment in sole liver.

Impact of environmental estrogens on Yfish considering the diversity of estrogen signaling

Research on endocrine disruption in fish has been dominated by studies on estrogen-active compounds which act as mimics of the natural estrogen, 17β-estradiol (E2), and generally exert their biological actions by binding to and activation of estrogen receptors (ERs). Estrogens play central roles in reproductive physiology and regulate (female) sexual differentiation. In line with this, most adverse effects reported for fish exposed to environmental estrogens relate to sexual differentiation and reproduction. E2, however, utilizes a variety of signaling mechanisms, has multifaceted functions and targets, and therefore the toxicological and ecological effects of environmental estrogens in fish will extend beyond those associated with the reproduction. This review first describes the diversity of estrogen receptor signaling in fish, including both genomic and non-genomic mechanisms, and receptor crosstalk. It then considers the range of non-reproductive physiological processes in fish that are known to be responsive to estrogens, including sensory systems, the brain, the immune system, growth, specifically through the growth hormone/insulin-like growth factor system, and osmoregulation. The diversity in estrogen responses between fish species is then addressed, framed within evolutionary and ecological contexts, and we make assessments on their relevance for toxicological sensitivity as well as ecological vulnerability. The diversity of estrogen actions raises questions whether current risk assessment strategies, which focus on reproductive endpoints, and a few model fish species only, are protective of the wider potential health effects of estrogens. Available - although limited - evidence nevertheless suggests that quantitative environmental threshold concentrations for environmental protection derived from reproductive tests with model fish species are protective for non-reproductive effects as well. The diversity of actions of estrogens across divergent physiological systems, however, may lead to and underestimation of impacts on fish populations as their effects are generally considered on one functional process only and this may underrepresent the impact on the different physiological processes collectively.

Use of fish farms to assess river contamination: combining biomarker responses, active biomonitoring, and chemical analysis

Here we addressed the possible effects of trace levels of contaminants on fish by means of a combination of biomarker responses, active biomonitoring (ABM), and chemical analysis. In environmental studies, cytochromes P4501A (Cyp1A) and Cyp3A and related enzyme activities (7-ethoxyresorufin-O-deethylase, EROD, and benzyloxy-4-[trifluoromethyl]-coumarin-O-debenzyloxylase, BFCOD, respectively) are commonly used as biomarkers for evidencing exposure to a variety of contaminants. In a rainbow trout (Oncorhynchus mykiss) fish farm that is routinely sampled to obtain references regarding normal levels of such enzyme activities in freshwater fish, we observed a strong and punctual increase in these activities at the end of 2011. In order to shed light on the causes of this induction, we transferred some fish to a fish farm with controlled conditions and examined them using an active biomonitoring (ABM) approach. EROD activity showed a decrease of 80% from the original values after 7 days in the control farm, while BFCOD activity was also reduced after 15 days. Although not significant, a decrease in cyp1A and cyp3A mRNA levels was also observed. To determine the presence of pollutants, water and sediment samples from the river feeding the fish farm were analyzed by two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOF-MS). The screening study reflected a weak inflow of pollutants in the monitored area, which is located far from any industrial activity or densely populated cities. Trace levels of polyaromatic hydrocarbons (PAHs) and personal care products (the polycyclic musk fragrance HHCB, and triclosan) were detected in sediments, at concentrations ranging from 0.01 to 38 ng/g dry weight, and in water from 4 to 441 ng/L. The approach followed in this study proved useful as a biomonitoring technique for the early detection of trace contaminants.

Cyclopenta[c]phenanthrenes--chemistry and biological activity

Despite cyclopenta-fused polycyclic aromatic hydrocarbons (CP-PAHs) having been detected in the environment, the ability of these compounds to induce cellular and tissue responses remains poorly characterized. In this review, we look at the chemistry and biological activity of the cyclopenta[c]phenanthrenes (CP[c]Phs) as potential chemicals of concern in the process of risk assessment. The first part of the review deals with the environmental occurrence and chemistry of CP-PAHs, focusing on available methods of CP[c]Ph chemical synthesis. The most interesting structural feature of the CP[c]Ph is the presence of a pseudo fjord-region constructed by the cyclopentane ring. This compound can be treated either as a structurally similar one to B[c]Ph, or as a phenanthrene skeleton with an electrodonating alkyl substituent in the bay-region of the molecule. The second thread, providing available data on the adverse effects of CP[c]Ph compounds on cells and tissues of living organisms, mainly fish, improves our understanding of these possible environmental hazards. The data show that CP[c]Ph is less potent at inducing CYP1A gene expression in rainbow trout than benzo[a]pyrene (B[a]P), a well-known Ah-receptor agonist. Interestingly, the CP[c]Ph dependent up-regulation of CYP1A mRNA is positively correlated with the incidences of clastogenic changes in rainbow trout erythrocytes. CP[c]Ph has, comparably to B[a]P, a potential to repress expression of tumor suppressor p53, in the head kidney of rainbow trout. Furthermore, estrogen responsive genes in fish liver, ERα and VTG, are not induced by CP[c]Ph, suggesting that the compound has no endocrine disrupting potential. However, some CP[c]Phs show mutagenic activity when investigated in the Ames test, and exhibit genotoxic properties in in vitro micronucleus assay. The above characteristics suggest that CP-PAHs are chemicals of concern for which potential pathways of exposure should be further identified.

Integrated chemical and biological analysis to explain estrogenic potency in bile extracts of red mullet (Mullus barbatus)

A biological screening was performed to establish the total exposure to estrogenic compounds of red mullet (Mullus barbatus) collected at several sites along the Spanish Mediterranean coast by testing male fish bile extracts using the in vitro ER-LUC reporter gene assay. In addition, major metabolites were identified and measurements of OH-PAHs (1-naphthol, 9-phenantrol, 9-fluorenol, 1-pyrenol, 1OH-BaP and 3OH-BaP) and alkylphenols (4-n-nonylphenol (4-n-NP) and 4-tertoctylphenol (4-tert-OP)) in the same fish bile extracts were taken by gas chromatography-mass spectrometry in electron ionization mode (GC-EI-MS). Relative in vitro estrogenic potencies of the chemically quantified compounds were also tested. The highest biliary concentrations of 1-pyrenol, 9-fluorenol and 4-n-NP were found in fish from Barcelona and from the Mar Menor coastal lagoon. However, these concentrations can be considered relatively low compared to values reported in red mullet from other polluted waters in the Mediterranean Sea. The contribution of 1-pyrenol, 4-n-NP and 4-tert-OP to the total estrogenic potency measured in male fish bile was found to be negligible, indicating the presence of other estrogenic compounds in red mullet bile. Estrogenic potency in bile from male fish was markedly elevated in Mar Menor lagoon (234.8±5.7 pg E2EQ/μl), and further research will be necessary to explain whether the presence of natural and synthetic-hormones in the lagoon contributed to this finding. Values of approximately 15-16E2EQ pg/mg bile can be regarded as preliminary baseline levels of bile estrogenicity in male red mullet from the western Mediterranean Sea.

Whole spectrum of cytochrome P450 genes and molecular responses to water-accommodated fractions exposure in the marine medaka

Water-accommodated fractions (WAFs) of crude oil include chemicals that are potent toxicants in fish. Increasing oil pollution thus demands a better understanding of molecular mechanisms for detoxification, metabolism, toxicity, and adaptation of fish. Previous studies with fish show modulation of expression of key genes in relation to stress response against WAF exposure, but there is still a lack of studies on responses of cytochrome P450 (CYP) genes and changes in biotransformation upon WAF exposure. In this study, we used the full spectrum of CYP genes of the marine medaka, Oryzias melastigma, to understand their potential mode of action on WAFs-triggered molecular mechanisms. We also analyzed further CYP-involved detoxification and endogenous steroidogenic metabolism after exposure to different concentrations of WAFs over different time courses in the marine medaka. Also, detoxification- and antioxidant-related enzymes' activities were analyzed with different concentrations of WAFs. As a result, the WAF exposure induced CYP-involved detoxification mechanism but reduced CYP-involved steroidogenic metabolism in the marine medaka. These data suggest that whole CYP profiling can be a way of understanding and uncovering the mode of action particularly with respect to emerging chemicals such as WAF exposure with the new finding that WAFs have dual functions on CYP-involved metabolisms.

Screening for potential effects of endocrine-disrupting chemicals in peri-urban creeks and rivers in Melbourne, Australia using mosquitofish and recombinant receptor-reporter gene assays

Sexually mature male mosquitofish (Gambusia holbrooki) were collected from various sites around Melbourne in 2009 to evaluate the performance of gonopodial indices as a biomarker for endocrine disruption in Melbourne's waterways. The mosquitofish indices assessed were body length (BL), gonopodial length (GL)/BL ratio, ray 4:6 ratio and the absence or presence of hooks and serrae, and these varied between sites. The study was complemented by measurements of estrogenic, retinoid, thyroid and aryl hydrocarbon (AhR) receptor activities of the water. Male mosquitofish were 16.3-21.5 mm in length, and although there was a statistically significant positive relationship showing that bigger fish had longer gonopodia than small fish (r2 = 0.52, p < 0.001), there were few significant differences in GL/BL ratio of fish between sites. Measured estrogenic activity was mostly in the range 0.1-1.7 ng/L EEQ, with one site having much higher levels (~12 ng/L EEQ). Aryl hydrocarbon (AhR) receptor activity was observed in all water samples (7-180 ng/L βNF EQ), although there was no consistent pattern in the level of AhR activity observed, i.e., 'clean' sites were as likely to return a high AhR activity response as urban or wastewater treatment plant (WWTP)-impacted sites. There was no correlation between measurements of receptor actvity and gonopodial length (GL):BL ratio and BL. We conclude that the mosquitofish gonopodia only fulfills part of the criteria for biomarker selection for screening. The mosquitofish indices assessed were cheap and easy-to-perform procedures; however, there is no baseline data from the selected sites to evaluate whether differences in the morpholical indices observed at a site were a result of natural selection in the population or due to estrogenic exposure.

Aryl hydrocarbon receptor activation leads to impairment of estrogen-driven chicken vitellogenin promoter activity in LMH cells

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates most of the toxic effects of environmental contaminants. Among the multiple pleiotropic responses elicited by AHR agonists, the antiestrogenic and endocrine-disrupting action of the receptor activation is one of the most studied. It has been demonstrated that some AHR agonists disrupt estradiol-induced vitellogenin synthesis in the fish liver via a mechanism that involves crosstalk between the AHR and the estrogen receptor (ER). Chicken hepatocytes have become a model for the study of AHR action in birds and the induction of the signal and its effect in these cells are well established. However, the impact of AHR activation on estradiol-regulated responses in the chicken liver remains to be demonstrated. The aim of the present study was, therefore, to determine the effect of AHR action on ER-driven transcription in a convenient model of chicken liver cells. For this purpose, we designed a reporter construct bearing the 5' regulatory region of the chicken vitellogenin II gene and used it to transfect chicken hepatoma LMH cells. We found that β-naphthoflavone represses ER-driven vitellogenin promoter activity and that this action is mediated by the AHR. This inhibitory crosstalk between both pathways appears to be unidirectional, since estradiol did not alter the transcript levels of an AHR target gene. Besides, and highly relevant, we show that LMH cell line transfected with a reporter construct bearing the chicken vitellogenin promoter sequence is a useful and convenient model for the study of AHR-ER interaction in chicken liver-derived cells.

Inhibition of vitellogenin gene induction by 2,3,7,8-tetrachlorodibenzo-p-dioxin is mediated by aryl hydrocarbon receptor 2 (AHR2) in zebrafish (Danio rerio)

Vitellogenins are hepatically derived yolk-protein precursors required for oogenesis in all oviparous teleosts. Altered gene-regulation of vitellogenesis by environmental contaminants can have profound effects on reproductive success, and ultimately population sustainability. To better understand chemical effects on vitellogenin gene regulation, we tested the hypothesis that activation of the aryl hydrocarbon receptor 2 (AHR2) by dioxin inhibits the estrogen receptor pathway regulation of 3 vitellogenin genes (vtg1-3) in vivo, using zebrafish (Danio rerio) as a model teleost. Using an embryo-larval bioassay, embryos were either treated with 1000 pptr (parts-per-trillion, pg/mL) 17α-ethynylestradiol (EE2) alone from 6h post fertilization (hpf) to 4 days post fertilization (dpf), or pre-treated with dioxin (4-5 hpf) prior to EE2. Pre-treatment with 400 pptr 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) or 1,2,3,7,8-pentachlorodibenzo-p-dioxin inhibited the EE2 induction of vtg1, vtg2 and vtg3 by >95% (p≤0.05). In comparison, a splice-blocking AHR2 morpholino used to down-regulate ahr2 expression significantly reduced the inhibition of vtg1, vtg2 and vtg3 by 400 pptr 2,3,7,8-TCDD (20.7-27.4% rescue). These studies demonstrate that 2,3,7,8-TCDD directly inhibits the vitellogenin pathway in vivo through activation of the AHR2. This work provides evidence for AHR2 dependent cross-talk inhibition of vitellogenin genes and offers insight into anti-estrogenic reproductive effects observed in oviparous species exposed to AHR agonist contaminants.

Alternatives to in vivo tests to detect endocrine disrupting chemicals (EDCs) in fish and amphibians--screening for estrogen, androgen and thyroid hormone disruption

Endocrine disruption is considered a highly relevant hazard for environmental risk assessment of chemicals, plant protection products, biocides and pharmaceuticals. Therefore, screening tests with a focus on interference with estrogen, androgen, and thyroid hormone pathways in fish and amphibians have been developed. However, they use a large number of animals and short-term alternatives to animal tests would be advantageous. Therefore, the status of alternative assays for endocrine disruption in fish and frogs was assessed by a detailed literature analysis. The aim was to (i) determine the strengths and limitations of alternative assays and (ii) present conclusions regarding chemical specificity, sensitivity, and correlation with in vivo data. Data from 1995 to present were collected related to the detection/testing of estrogen-, androgen-, and thyroid-active chemicals in the following test systems: cell lines, primary cells, fish/frog embryos, yeast and cell-free systems. The review shows that the majority of alternative assays measure effects directly mediated by receptor binding or resulting from interference with hormone synthesis. Other mechanisms were rarely analysed. A database was established and used for a quantitative and comparative analysis. For example, a high correlation was observed between cell-free ligand binding and cell-based reporter cell assays, between fish and frog estrogenic data and between fish embryo tests and in vivo reproductive effects. It was concluded that there is a need for a more systematic study of the predictive capacity of alternative tests and ways to reduce inter- and intra-assay variability.

Estrogen receptor-hijacking by dioxin-like 3,3'4,4',5-pentachlorobiphenyl (PCB126) in salmon hepatocytes involves both receptor activation and receptor protein stability

Several hypotheses have been proposed explaining the interactions between estrogen receptor (ER) and aryl hydrocarbon receptor (AhR) signaling pathways in both fish and mammalian systems. In both piscine and mammalian systems, ligand-activated AhR may recruit basal ER (i.e. hijack) in the absence of ER ligand and bind to the estrogen responsive elements (ERE) to activate ER-responsive genes. We have evaluated, the roles of receptor activation and receptor-protein stability on dioxin-like [3,3'4,4',5-pentachlorobiphenyl: PCB 126] mediated ER-hijacking in a salmon in vitro system. Primary salmon hepatocytes were exposed to PCB126 (1, 10 and 50 nM) with or without an ER-antagonist (ICI), putative AhR inhibitor (3',4'-dimethoxyflavone; DMF) or protein synthesis inhibitor (cycloheximide; CHX). Hepatocytes were exposed for 6, 12 and 24h. The expression of genes and proteins involved in ER (ERα, ERβ and vitellogenin) and AhR (CYP1A1, AhR-repressor, AhR2-isotypes and cofactors) pathways were analysed using qPCR and immunochemical methods. PCB126 induced transcripts of ER and AhR signalling pathways that were variably influenced by protein synthesis and receptor inhibitors. CHX stimulated a coordinated recruitment of the proteasome complex, resulting in the ubiquitination and degradation of ER and AhR isoforms and downstream protein products. Interestingly, DMF produced differential effects on the AhR signalling pathway, in the presence or absence of PCB126. Overall, ER-hijacking by dioxin-like compounds and subsequent activation of ER responsive genes involves both receptor activation/deactivation and receptor-protein degradation/destabilization (stability). Given that the Per-AhR/Arnt-Sim homology sequence of transcription factors usually associate with each other to form heterodimers and bind the XRE or ERE sequences in the promoter regions of target genes to regulate their expression, the complete mechanism of interactions between dioxin-like and estrogenic compounds in vertebrate systems may require additional characterization.

Responses of conventional and molecular biomarkers in turbot Scophthalmus maximus exposed to heavy fuel oil no. 6 and styrene

Several accidental spills in European coastal areas have resulted in the release of different toxic compounds into the marine environment, such as heavy fuel oil type no. 6 in the "Erika" and "Prestige" oil spills and the highly toxic styrene after the loss of the "Ievoli Sun". There is a clear need to develop tools that might allow assessing the biological impact of these accidental spills on aquatic organisms. The aim of the present study was to determine the short-term effects and recovery after exposure of juvenile fish (Scophthalmus maximus) to heavy fuel oil no. 6 and styrene by using a battery of molecular, cell and tissue level biomarkers. Turbots were exposed to styrene for 7 days and to the diluted soluble fraction of the oil (10%) for 14 days, and then allowed to recover in clean seawater for the same time periods. cyp1a1 transcript was overexpressed in turbots after 3 and 14 days of exposure to heavy fuel oil, whereas ahr transcription was not modulated after heavy fuel oil and styrene exposure. pparα transcription level was significantly up-regulated after 3 days of treatment with styrene. Liver activity of peroxisomal acyl-CoA oxidase (AOX) was significantly induced after 14 days of oil exposure, but it was not affected by styrene. Hepatocyte lysosomal membrane stability (LMS) was significantly reduced after exposure to both treatments, indicating that the tested compounds significantly impaired fish health. Both AOX and LMS values returned to control levels after the recovery period. No differences in gamete development were observed between fuel- or styrene- exposed fish and control fish, and vitellogenin plasma levels were low, suggesting no xenoestrogenic effects of fuel oil or styrene. While styrene did not cause any increase in the prevalence of liver histopathological alterations, prevalence of extensive cell vacuolization increased after exposure to heavy fuel oil for 14 days. In conclusion, the suite of selected biomarkers proved to be useful to determine the early impact of and recovery from exposure to tested compounds in turbot.

Differences in the induction of cyp1A and related genes in cultured rainbow trout Oncorhynchus mykiss. Additional considerations for the use of EROD activity as a biomarker

Two rainbow trout Oncorhynchus mykiss fish farms were repeatedly sampled in order to observe the variability of ethoxyresorufin-O-deethylase (EROD) activity and of related genes in the liver. Fish coming from fish farm A exhibited EROD levels that could be considered as basal according to the scientific literature, however, EROD activity in fish coming from fish farm B was significantly increased. This was accompanied by augmented aryl hydrocarbon receptor (ahr) and cytochrome P4501A (cyp1A) messenger RNA expression and reduced oestrogen receptor (er) and vitellogenin (vtg) transcription. Only sediment extracts from the entry channel of fish farm B induced EROD activity in O. mykiss cultured cells, however, this induction could not be explained by the levels of polyaromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) measured in the sediments. The results of this study point out that O. mykiss cultured in fish farms could be used as sentinels for indication of pollution. In this particular work, however, no conclusive evidence has been found for a relationship between the presence of PAHs and PCBs and the observed EROD induction.

Decreased vitellogenin inducibility and 17β-estradiol levels correlated with reduced egg production in killifish (Fundulus heteroclitus) from Newark Bay, NJ

Aquatic species inhabiting polluted estuaries are exposed to complex mixtures of xenobiotics which can alter normal reproduction. We previously reported that female Atlantic killifish (Fundulus heteroclitus) from the highly contaminated Newark Bay, NJ (USA) exhibited an inhibition of oocyte development due to reduced vitellogenin (egg-yolk precursor) levels. Our hypothesis was that the inhibition of oocyte development in Newark Bay killifish is due to (1) deficient levels of circulating 17β-estradiol, and (2) a decreased sensitivity of the vitellogenin pathway to physiological doses of 17β-estradiol. In the first study, adult naïve killifish from Tuckerton, NJ (reference) were caged at Tuckerton and Newark Bay. After 1 month, males caged at Newark Bay exhibited inductions of hepatic vitellogenin and estrogen receptor α, which were transient and returned to basal levels after 2 months (p≤0.05). In the second study, fecundity and 17β-estradiol levels were measured in reproductively active adult females from Tuckerton and Newark Bay. Tuckerton females produced 140 eggs per female and Newark Bay females produced 11 eggs per female. Embryos from Newark Bay had 34% greater mortality and 28% less hatch, relative to Tuckerton. In addition, embryo mass and yolk-volume of Newark Bay embryos compared to Tuckerton embryos was 16% and 25% lower, respectively. Circulating 17β-estradiol levels in Newark Bay females (0.26 ng/mL) were measured to be 8-fold lower than Tuckerton females (2.25 ng/mL). In the third study, adult killifish from both sites were dosed with 17β-estradiol to assess the sensitivity of the vitellogenin pathway. At doses of 0.01, 0.1, 1 and 10 ng/g body weight, induction levels of circulating vitellogenin in Newark Bay males were significantly inhibited by 97, 99, 98 and 44%, respectively, compared to Tuckerton males. At doses of 0.01, 0.1, 1, 10 and 100 ng/g body weight, induction levels of circulating vitellogenin in Newark Bay females were inhibited by 89, 79, 61, 40 and 30%, respectively, compared to Tuckerton females. These differences in inducibility could not be explained by altered hepatic expression of estrogen receptors α, βa or βb. Based on the caged and dose-response studies, contaminants that down-regulate vitellogenin would interfere with its ability to be used as a biomarker for xeno-estrogen exposures. These studies demonstrate that contaminants within Newark Bay exert both estrogenic and anti-estrogenic responses which results in an overtly anti-estrogenic phenotype (reduced egg production due to inhibition of vitellogenesis).

Effects of produced water on reproductive parameters in prespawning Atlantic cod (Gadus morhua)

Produced water (PW) discharged from offshore oil industry activities contains substances that are known to contribute to a range of mechanisms of toxicity. In the present study selected reproductive biomarkers were studied in prespawning Atlantic cod (Gadus morhua) exposed to PW. The fish were exposed for 12 wk within a continuous flow-through system at realistic environmental near-field concentrations. Concentrations of polyaromatic hydrocarbon (PAH) and alkylphenol (AP) compounds were analyzed by gas chromatography with mass spectrometric detection measurement, as were PAH and AP metabolites in fish bile for verification of exposure conditions and presence of compounds in PW. A suite of reproductive biomarkers (vitellogenin, zona radiata protein, and plasma steroid concentrations) and histological alterations of the gonads were determined. Results showed that exposure to sufficiently high levels of PW produced an increase in vitellogenin levels in female fish compared to the control. Impaired oocyte development and reduced estrogen levels were also observed in PW-exposed female fish. In male fish testicular development was altered, showing a rise in amount of spermatogonia and primary spermatocytes and a reduction in quantity of mature sperm in the PW-exposed fish compared to control. Data indicate that sufficiently high levels of PW have the potential to adversely affect the reproductive fitness of cod.

Intersex and oocyte atresia in a mussel population from the Biosphere's Reserve of Urdaibai (Bay of Biscay)

Urdaibai is a Biosphere's Reserve, containing rich bivalve populations. In the present work we aimed to characterize the reproductive cycle and to study possible disturbances in reproduction in mussel populations from Urdaibai. During an annual gametogenic cycle (January 2003-March 2004) samples of gonads were collected bimonthly and gamete development (gonad index), histopathology of mantle tissue and vitellogenin-like protein levels by alkali labile phosphate (ALP) method were measured. No significant changes were detected in ALP levels out of those related to gametogenic development in females. However, severe oocyte atresia was observed in female mussels in January and March 2003. Male mussels showed low ALP values with the exception of high ALP levels in March 2003. High prevalence of hermaphrodite/intersex mussels (26%) was detected in March 2004. Hermaphrodites/intersex and oocyte atresia were not found in mussels from the nearby Abra estuary. In conclusion, these results suggest that mussels inhabiting the Urdaibai estuary could be exposed to toxic chemicals such as endocrine disruptors.

Endocrine disruption in wild populations of chub (Leuciscus cephalus) in contaminated French streams

The aim of this study was to assess endocrine disruptive effects in wild population of fish in five French rivers selected to represent different pollution contexts at two seasons (summer and fall). For that purpose, a panel of biometrical parameters (length, weight, and gonado-somatic index: GSI) and biochemical (ethoxyresorufin-O-deethylase: EROD, vitellogenin: VTG, and brain aromatase) and histological biomarkers (gonads histology) were used in chub (Leuciscus cephalus), a common cyprinid fish species. In fish from the reference site, EROD activity and VTG levels were low at the two seasons. Brain aromatase activities (AAs) were similar to other species and increased with increasing GSI and gonad maturation. Among the four contaminated sites, the Jalle d'Eysines River was the most impacted site. At this site, fish were exposed to estrogenic substances as demonstrated by the VTG induction in males and the arrest of development of the gonads that led to lower brain AA compared to fish from the reference site. In fish from other contaminated sites, EROD activity was induced as compared to fish from the reference site and some males had elevated concentrations of VTG. Moreover, the presence of aromatase-inhibiting compounds was demonstrated in the sediments of three contaminated sites, even if the precise nature of contaminants is not known. This study provides new data concerning endocrine disruption in wild fish populations inhabiting French rivers and demonstrates that measurements of in vivo and in vitro aromatase could be used as biomarkers of endocrine disruption in field studies.