Contaminant accumulation and biological responses in Atlantic cod (Gadus morhua) caged at a capped waste disposal site in Kollevåg, Western Norway

Transcriptomic profiles of brains in juvenile Atlantic cod (Gadus morhua) exposed to pharmaceuticals and personal care products from a wastewater treatment plant discharge

Pharmaceuticals and personal care products (PPCPs) are frequently detected in marine environments, posing a threat to aquatic organisms. Our previous research demonstrated the occurrence of neuroactive compounds in effluent and sediments from a wastewater treatment plant (WWTP) in a fjord North of Stavanger, the fourth-largest city in Norway. To better understand the influence of PPCP mixtures on fish, Atlantic cod (Gadus morhua) were caged for one month in 3 locations: site 1 (reference), site 2 (WWTP discharge), and site 3 (6.7 km west of discharge). Transcriptomic profiling was conducted in the brains of exposed fish and detection of PPCPs in WWTP effluent and muscle fillets were determined. Caffeine (47.8 ng/L), benzotriazole (10.9 ng/L), N,N-diethyl-meta-toluamide (DEET) (5.6 ng/L), methyl-1H-benzotriazole (5.5 ng/L), trimethoprim (3.4 ng/L), carbamazepine (2.1 ng/L), and nortriptyline (0.4 ng/L) were detected in the WWTP effluent. Octocrylene concentrations were observed in muscle tissue at all sites and ranged from 53 to 193 ng/g. Nervous system function and endocrine system disorders were the top enriched disease and function pathways predicted in male and female fish at site 2, with the top shared canonical pathways involved with estrogen receptor and Sirtuin signaling. At the discharge site, predicted disease and functional responses in female brains were involved in cellular assembly, organization, and function, tissue development, and nervous system development, whereas male brains were involved in connective tissue development, function, and disorders, nervous system development and function, and neurological disease. The top shared canonical pathways in females and males were involved in fatty acid activation and tight junction signaling. This study suggests that pseudopersistent, chronic exposure of native juvenile Atlantic cod from this ecosystem to PPCPs may alter neuroendocrine and neuron development.

The distribution of metal and petroleum-derived contaminants within sediments around oil and gas infrastructure in the Gippsland Basin, Australia

As oil and gas infrastructure comes to the end of its working life, a decommissioning decision must be made: should the infrastructure be abandoned in situ, repurposed, partially removed, or fully removed? Environmental contaminants around oil and gas infrastructure could influence these decisions because contaminants in sediments could degrade the value of the infrastructure as habitat, enter the seafood supply if the area is re-opened for commercial and/or recreational fishing, or be made biologically available as sediment is resuspended when the structures are moved. An initial risk hypothesis, however, may postulate that these concerns are only relevant if contaminant concentrations are above screening values that predict the possibility of environmental harm or contaminant bioaccumulation. To determine whether a substantive contaminants-based risk assessment is needed for infrastructure in the Gippsland Basin (South-eastern Australia), we measured the concentration of metals and polycyclic aromatic hydrocarbons (PAHs) in benthic sediments collected around eight platforms earmarked for decommissioning. The measurements were compared to preset screening values and to background contaminant concentrations in reference sites. Lead (Pb), zinc (Zn), PAHs and other contaminants were occasionally measured at concentrations that exceeded reference values, most often within 150 m of the platforms. The exceedance of a few screening values by contaminants at some platforms indicates that these platforms require further analysis to determine the contaminant risks associated with any decommissioning option.

Long-Term Influence of PCB- and PBDE-Spiked Microplastic Spheres Fed through Rotifers to Atlantic Cod (Gadus morhua) Larvae

Omnipresent microplastics (MPs) in marine ecosystems are ingested at all trophic levels and may be a vector for the transfer of persistent organic pollutants (POPs) through the food web. We fed rotifers polyethylene MPs (1-4 µm) spiked with seven congeners of polychlorinated biphenyls (PCBs) and two congeners of polybrominated diphenyl ethers (PBDEs). In turn, these rotifers were fed to cod larvae from 2-30 days post-hatching (dph), while the control groups were fed rotifers without MPs. After 30 dph, all the groups were fed the same feed without MPs. Whole-body larvae were sampled at 30 and 60 dph, and four months later the skin of 10 g juveniles was sampled. The PCBs and PBDEs concentrations were significantly higher in MP larvae compared to the control larvae at 30 dph, but the significance dissipated at 60 dph. Expression of stress-related genes in cod larvae at 30 and 60 dph showed inconclusive minor random effects. The skin of MP juveniles showed disrupted epithelial integrity, fewer club cells and downregulation of a suite of genes involved in immunity, metabolism and the development of skin. Our study showed that POPs were transferred through the food web and accumulated in the larvae, but that the level of pollutants decreased once the exposure was ceased, possibly related to growth dilution. Considering the transcriptomic and histological findings, POPs spiked to MPs and/or MPs themselves may have long-term effects in the skin barrier defense system, immune response and epithelium integrity, which may potentially reduce the robustness and overall fitness of the fish.

Fish liver damage related to the wastewater treatment plant effluents

Wastewater treatment plants (WWTPs) continuously release a complex mixture of municipal, hospital, industrial, and runoff chemicals into the aquatic environment. These contaminants are both legacy contaminants and emerging-concern contaminants, affecting all tissues in a fish body, particularly the liver. The fish liver is the principal detoxifying organ and effects of consistent pollutant exposure can be evident on its cellular and tissue level. The objective of this paper is thus to provide an in-depth analysis of the WWTP contaminants' impact on the fish liver structure, physiology, and metabolism. The paper also gives an overview of the fish liver biotransformation enzymes, antioxidant enzymes, and non-enzymatic antioxidants, their role in metabolizing xenobiotic compounds and coping with oxidative damage. Emphasis has been placed on highlighting the vulnerability of fish to xenobiotic compounds, and on biomonitoring of exposed fish, generally involving observation of biomarkers in caged or native fish. Furthermore, the paper systematically assesses the most common contaminants with the potential to affect fish liver tissue.

Effects of weathered polyethylene microplastic ingestion on sexual maturation, fecundity and egg quality in maturing broodstock Atlantic cod Gadus morhua

Microplastics (MPs) have become a global issue as they are omnipresent in the ocean. Fish ingesting MPs through feed could be affected in their physiological function, e.g., disrupted enzyme production and function, reduction of feeding and reproductive failure. This study assessed the effects of feed containing naturally weathered MPs from the Oslofjord (Norway) on the reproductive physiology of Atlantic cod (Gadus morhua). Farmed cod broodstock were fed either control (C-diet) or feeds containing 1% microplastic (MP-diet) starting nine months prior to spawning, from June until May. No major differences were found between diet groups in overall biometrics or gonad histology. Sex steroid levels (testosterone, 11-ketotestosterone and 17β-estradiol) resulted in expected profiles increasing over time without any significant differences between treatments. Gene expression levels of the steroidogenic enzyme 20β-hydroxysteroid dehydrogenase (20β-hsd) and vitellogenin1 (vtg1) showed significant differences between dietary treatments with lower expression in the control group. This can be a direct effect of MPs, but endocrine disrupting effects of potentially leachable plastic additives cannot be completely ruled out. Thus, these enzymes could be indicators of exposure to contaminants that disrupt sexual maturation by affecting the production of primarily maturation-inducing steroid. Although the concentration of MPs employed in this study may not be high enough to elicit any observable short-term biological effects, the observed gene expression suggests that long-term consequences should be considered caused by an expected increase of MPs in marine environments.

West African e-waste-soil assessed with a battery of cell-based bioassays

Soil samples randomly taken from major e-waste sites in West Africa (Nigeria, Benin and Ghana) were examined for an extensive range of organic contaminants. Cytotoxicity measurements and assessment of activation of xeno-sensing receptors from fish (Atlantic cod) were employed as a battery of in vitro biological assays to explore the quality and toxicity profile of West African e-waste soil. The concentrations of the measured contaminants of emerging concerns (CECs) and persistent organic pollutants (POPs) in the e-waste soil differs significantly from the reference soil with chemical profiles typically dominated by legacy polybrominated diphenyl ethers (PBDEs) (405.8 μgkg^-1) and emerging organophosphate ester flame retardant tris (1-chloro-2-propyl) phosphate (TCPP) (404 μgkg^-1), in addition to the short chain perfluorobutane sulfonate (PFBS) (275.3 μgkg^-1) and perfluorobutanoate (PFBA) (16 μgkg^-1). The study revealed that perfluorooctanoic acid (PFOA) occurred only in e-waste soil from Ghana and ranged from 2.6 to 5.0 μgkg^-1. Overall, non-polar e-waste soil-derived extracts had a stronger effect on COS-7 cell viability than the polar extracts and elutriates. The highest receptor activation was observed with single polar and non-polar extracts from the Nigeria and Benin sites, indicating hotspots with Er-, PPARa- and Ahr-agonist activities. Thus, the results obtained with our battery of in vitro biological assays underscored these e-waste sites as remarkably polluted spots with complex toxicity profiles of great concern for human and environmental health.

Integrative omics-analysis of lipid metabolism regulation by peroxisome proliferator-activated receptor a and b agonists in male Atlantic cod

Lipid metabolism is essential in maintaining energy homeostasis in multicellular organisms. In vertebrates, the peroxisome proliferator-activated receptors (PPARs, NR1C) regulate the expression of many genes involved in these processes. Atlantic cod (Gadus morhua) is an important fish species in the North Atlantic ecosystem and in human nutrition, with a highly fatty liver. Here we study the involvement of Atlantic cod Ppar a and b subtypes in systemic regulation of lipid metabolism using two model agonists after in vivo exposure. WY-14,643, a specific PPARA ligand in mammals, activated cod Ppara1 and Ppara2 in vitro. In vivo, WY-14,643 caused a shift in lipid transport both at transcriptional and translational level in cod. However, WY-14,643 induced fewer genes in the fatty acid beta-oxidation pathway compared to that observed in rodents. Although GW501516 serves as a specific PPARB/D ligand in mammals, this compound activated cod Ppara1 and Ppara2 as well as Pparb in vitro. In vivo, it further induced transcription of Ppar target genes and caused changes in lipid composition of liver and plasma. The integrative approach provide a foundation for understanding how Ppars are engaged in regulating lipid metabolism in Atlantic cod physiology. We have shown that WY-14,643 and GW501516 activate Atlantic cod Ppara and Pparb, affect genes in lipid metabolism pathways, and induce changes in the lipid composition in plasma and liver microsomal membranes. Particularly, the combined transcriptomic, proteomics and lipidomics analyses revealed that effects of WY-14,643 on lipid metabolism are similar to what is known in mammalian studies, suggesting conservation of Ppara functions in mediating lipid metabolic processes in fish. The alterations in the lipid profiles observed after Ppar agonist exposure suggest that other chemicals with similar Ppar receptor affinities may cause disturbances in the lipid regulation of fish. Model organism: Atlantic cod (Gadus morhua). LSID: urn:lsid:zoobank.org:act:389BE401-2718-4CF2-BBAE-2E13A97A5E7B. COL Identifier: 6K72F.

Photo-enhanced toxicity of crude oil on early developmental stages of Atlantic cod (Gadus morhua)

Photo-enhanced toxicity of crude oil is produced by exposure to ultraviolet (UV) radiation. Atlantic cod (Gadus morhua) embryos were exposed to crude oil with and without UV radiation (290-400 nm) from 3 days post fertilization (dpf) until 6 dpf. Embryos from the co-exposure experiment were continually exposed to UV radiation until hatching at 11 dpf. Differences in body burden levels and cyp1a expression in cod embryos were observed between the exposure regimes. High doses of crude oil produced increased mortality in cod co-exposed embryos, as well as craniofacial malformations and heart deformities in larvae from both experiments. A higher number of differentially expressed genes (DEGs) and pathways were revealed in the co-exposure experiment, indicating a photo-enhanced effect of crude oil toxicity. Our results provide mechanistic insights into crude oil and photo-enhanced crude oil toxicity, suggesting that UV radiation increases the toxicity of crude oil in early life stages of Atlantic cod.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) occurrence in Sparus aurata exposed to microplastic enriched diets in aquaculture facilities

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are highly stable and bioaccumulative, and microplastics (MPs; plastics <5 mm) are ubiquitous in the marine environment. In this study we report the levels of a selection of pollutants in liver and muscle of juvenile gilthead seabream (Sparus aurata) exposed to virgin and weathered MP enriched diets during three months and followed by one month of MP depuration. In general, a major concentration of pollutants in liver was observed. According to OCPs, total DDTs was two or three times higher in liver. Levels in muscle suffer higher variability between treatments and sampling periods. The MP index was negatively correlated to HCB and positively to p,p'DDT in liver. Levels of pollutants are correlated to biological parameters such as total size and total weight. Our results suggest that the bioaccumulation is subjected to the molecular structure of the pollutants and that MPs are correlated with the detoxification system.

Toxicity assessment of urban marine sediments from Western Norway using a battery of stress-activated receptors and cell-based bioassays from fish

A luciferase reporter gene-based bioassay battery consisting of stress-activated receptors from fish, complemented with traditional fish cell-based bioassays, were used to assess the toxicity of marine sediment samples from the Byfjorden area around the city of Bergen (Norway). The reporter assays covered a wide range of cellular signalling and metabolic pathways, representing different molecular initiating events in the adverse outcome pathway framework. Cytotoxicity, generation of reactive oxygen-species, and induction of 7-ethoxyresorufin-O-deethylase activity were analysed using fish liver and gill cell lines. Chemical analyses of the sediment extracts revealed complex contamination profiles, especially at the innermost stations, which contained a wide array of persistent organic pollutants, polycyclic aromatic hydrocarbons, and metals. Sediment extracts from these sites were more potent in activating the stress-activated receptors than the other extracts, reflecting their toxicant profiles. Importantly, receptor- and cell-based bioassays complemented the chemical analyses and provided important data for future environmental risk assessments of urban marine sediments.

NOD-like receptor signaling pathway activation: A potential mechanism underlying negative effects of benzo(α)pyrene on zebrafish

Benzo(α)pyrene (BaP) is one of typical polycyclic aromatic hydrocarbons (PAHs) in aquatic environments and has been shown to cause toxic effects to aquatic animals. Although the negative effects of BaP have been investigated, the potential toxic mechanisms remain uncharacterized. To explore the potential mechanisms mediating the toxic effects of BaP, zebrafish (Danio rerio) were exposed to BaP for 15 days and the toxic effects of BaP in zebrafish liver were investigated using physiological and transcriptomic analyses. After 15-day BaP exposure, zebrafish liver exhibited abnormalities including increased cytoplasmic vacuolation, inflammatory cell infiltration, swelled nuclei and irregular pigmentation. BaP exposure also induced oxidative stress to the liver of zebrafish. Transcriptomic profiles revealed 5129 differentially expressed genes (DEGs) after 15-days of BaP exposure, and the vast majority of DEGs were up-regulated under BaP treatment. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses suggest that genes related to immune response were significantly dysregulated. Furthermore, the nucleotide-binding, oligomerization domain (NOD)-like receptor signaling pathway was significantly enriched and most of the genes in this pathway exhibited enhanced expression after BaP exposure. These results partially explained the mechanisms underlying the toxic effects of BaP on zebrafish liver. In conclusion, BaP has the potential to induce physiological responses in zebrafish liver through altering associated genes.

ReCodLiver0.9: Overcoming Challenges in Genome-Scale Metabolic Reconstruction of a Non-model Species

The availability of genome sequences, annotations, and knowledge of the biochemistry underlying metabolic transformations has led to the generation of metabolic network reconstructions for a wide range of organisms in bacteria, archaea, and eukaryotes. When modeled using mathematical representations, a reconstruction can simulate underlying genotype-phenotype relationships. Accordingly, genome-scale metabolic models (GEMs) can be used to predict the response of organisms to genetic and environmental variations. A bottom-up reconstruction procedure typically starts by generating a draft model from existing annotation data on a target organism. For model species, this part of the process can be straightforward, due to the abundant organism-specific biochemical data. However, the process becomes complicated for non-model less-annotated species. In this paper, we present a draft liver reconstruction, ReCodLiver0.9, of Atlantic cod (Gadus morhua), a non-model teleost fish, as a practicable guide for cases with comparably few resources. Although the reconstruction is considered a draft version, we show that it already has utility in elucidating metabolic response mechanisms to environmental toxicants by mapping gene expression data of exposure experiments to the resulting model.

Quantitative transcriptomics, and lipidomics in evaluating ovarian developmental effects in Atlantic cod (Gadus morhua) caged at a capped marine waste disposal site

In the present study, a previously capped waste disposal site at Kollevåg (Norway) was selected to study the effects of contaminant leakage on biomarkers associated with Atlantic cod (Gadus morhua) reproductive endocrinology and development. Immature cod were caged for 6 weeks at 3 locations, selected to achieve a spatial gradient of contamination, and compared to a reference station. Quantitative transcriptomic, and lipidomic analysis was used to evaluate the effects of the potential complex contaminant mixture on ovarian developmental and endocrine physiology. The number of expressed transcripts, with 0.75 log2-fold differential expression or more, varied among stations and paralleled the severity of contamination. Particularly, significant bioaccumulation of ∑PCB-7, ∑DDTs and ∑PBDEs were observed at station 1, compared to the other station, including the reference station. Respectively 1416, 698 and 719 differentially expressed genes (DEGs), were observed at stations 1, 2 and 3, compared to the reference station, with transcripts belonging to steroid hormone synthesis pathway being significantly upregulation. Transcription factors such as esr2 and ahr2 were increased at all three stations, with highest fold-change at Station 1. MetaCore pathway maps identified affected pathways that are involved in ovarian physiology, where some unique pathways were significantly affected at each station. For the lipidomics, sphingolipid metabolism was particularly affected at station 1, and these effects paralleled the high contaminant burden at this station. Overall, our findings showed a novel and direct association between contaminant burden and ovarian toxicological and endocrine physiological responses in cod caged at the capped Kollevåg waste disposal site.

Proteomics and lipidomics analyses reveal modulation of lipid metabolism by perfluoroalkyl substances in liver of Atlantic cod (Gadus morhua)

The aim of the present study was to investigate effects of defined mixtures of polycyclic aromatic hydrocarbons (PAHs) and perfluoroalkyl substances (PFASs), at low, environmentally relevant (1× = L), or high (20× = H) doses, on biological responses in Atlantic cod (Gadus morhua). To this end, farmed juvenile cod were exposed at day 0 and day 7 via intraperitoneal (i.p.) injections, in a two-week in vivo experiment. In total, there were 10 groups of fish (n = 21-22): two control groups, four separate exposure groups of PAH and PFAS mixtures (L, H), and four groups combining PAH and PFAS mixtures (L/L, H/L, L/H, H/H). Body burden analyses confirmed a dose-dependent accumulation of PFASs in cod liver and PAH metabolites in bile. The hepatosomatic index (HSI) was significantly reduced for three of the combined PAH/PFAS exposure groups (L-PAH/H-PFAS, H-PAH/L-PFAS, H-PAH/H-PFAS). Analysis of the hepatic proteome identified that pathways related to lipid degradation were significantly affected by PFAS exposure, including upregulation of enzymes in fatty acid degradation pathways, such as fatty acid β-oxidation. The increased abundances of enzymes in lipid catabolic pathways paralleled with decreasing levels of triacylglycerols (TGs) in the H-PFAS exposure group, suggest that PFAS increase lipid catabolism in Atlantic cod. Markers of oxidative stress, including catalase and glutathione S-transferase activities were also induced by PFAS exposure. Only minor and non-significant differences between exposure groups and control were found for cyp1a and acox1 gene expressions, vitellogenin concentrations in plasma, Cyp1a protein synthesis and DNA fragmentation. In summary, our combined proteomics and lipidomics analyses indicate that PFAS may disrupt lipid homeostasis in Atlantic cod.

Expression and localization of the aryl hydrocarbon receptors and cytochrome P450 1A during early development of Atlantic cod (Gadus morhua)

The aryl hydrocarbon receptor (Ahr) is a ligand-activated transcription factor that mediates the toxicity of dioxins and dioxin-like compounds (DLCs) in vertebrates. Two clades of the Ahr family exist in teleosts (Ahr1 and Ahr2), and it has been demonstrated that Ahr2 is the main protein involved in mediating the toxicity of dioxins and DLCs in most teleost species. Recently, we characterized the Atlantic cod (Gadus morhua) Ahr1a and Ahr2a receptors. To further explore a possible subfunction partitioning of Ahr1a and Ahr2a in Atlantic cod we have mapped the expression and localization of ahr1a and ahr2a in early developmental stages. Atlantic cod embryos were continuously exposed in a passive-dosing exposure system to the Ahr agonist, benzo[a]pyrene (B[a]P), from five days post fertilization (dpf) until three days post hatching (dph). Expression of ahr1a, ahr2a, and the Ahr-target genes, cyp1a and ahrrb, was assessed in embryos (8 dpf and 10 dpf) and larvae (3 dph) with quantitative real-time PCR analyses (qPCR), while in situ hybridization was used to assess the localization of expression of ahr1a, ahr2a and cyp1a. Quantitative measurements showed an increased cyp1a expression in B[a]P-exposed samples at all sampling points, and for ahr2a at 10 dpf, confirming the activation of the Ahr-signalling pathway. Furthermore, B[a]P strongly induced ahr2a and cyp1a expression in the cardiovascular system and skin, respectively, of embryos and larvae. Induced expression of both ahr2a and cyp1a was also revealed in the liver of B[a]P-exposed larvae. Our results suggest that Ahr2a is the major subtype involved in mediating responses to B[a]P in early developmental stages of Atlantic cod, which involves transcriptional regulation of biotransformation genes, such as cyp1a. The focused expression of ahr1a in the eye of embryos and larvae, and the presence of ahr2a transcripts in the jaws and fin nodes, further indicate evolved specialized roles of the two Ahrs in ontogenesis.

Biotransformation and oxidative stress responses in relation to tissue contaminant burden in Clarias gariepinus exposed to simulated leachate from a solid waste dumpsite in Calabar, Nigeria

In this study, we have investigated biotransformation and oxidative stress responses in relation to tissue contaminant burden in the African sharptooth catfish (Clarias gariepinus) exposed to simulated leachate from a solid waste dumpsite in Calabar, Nigeria. Fish were exposed to simulated leachate, diluted to 0:0 (negative control), 1:10, 1:50, 1:100 and phenanthrene (a PAH: 50 μg/L used as a positive control) for 3, 7 and 14 days. Hepatic transcripts for cat, sod1, gpx1, gr, gst, cyp1a, cyp2d3, and cyp27 were analyzed by real-time PCR, while enzymatic assays for ethoxyresorufin O-deethylase (EROD), buthoxyresorufin O-deethylase (BROD), methoxyresorufin O-deethylase (MROD), pentoxyresorufin O-deethylase (PROD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), uridine diphospho-glucuronosyltransferase (UDPGT) and lipid peroxidase (LPO) were measured using standard methods. In addition, protein expression for CYP1A, CYP3A and metallotheionin (MT) were measured by immunoblotting. Fish muscle samples were analyzed for selected group of contaminants after 14 days exposure showing significantly high uptake of heavy metals (Cd, Hg and Pb), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), chlorophenols, organochlorine (OC) and organophosphate pesticides in exposed fish. We observed significant concentration- and time-specific increases in biotransformation and oxidative stress responses at transcript and functional (enzyme and protein) levels, that paralleled tissue contaminants bioaccumulation patterns, after exposure to the simulated leachates. Our results highlighted the potential environmental, wildlife and public health consequences from improper solid waste disposal. In addition, it also provides a scientific basis for local sensitization and inform legislative decisions and policy formulation towards sustainable environmental management of solid wastes in Nigeria and other developing countries.

Genotoxicity and oxidative damage in zebrafish (Danio rerio) after exposure to effluent from ethyl alcohol industry

In this research, the toxicological effect of untreated wastewater from of ethyl alcohol industry was evaluated on the zebrafish (Danio rerio) under experimental conditions. Fish were treated with zero, half, one and two percent of sewage effluent for 21 days. Toxic effects were monitored in liver by determining biochemical indicators, oxidative stress biomarkers, and the expression of genes involved in the detoxification. Results showed that Sod1, Gstp-1a, Gpx1a gene expressions were significantly increased in the hepatocytes after 21 days at 2.0% sewage exposure. Sewage exposure also significantly increased Gsr, Ces2 and Cyp1a, Mt1 and Mt2 gene expression in the hepatocytes of zebrafish as compared to the reference group (P < 0.01). Total cellular antioxidants, malondialdehyde (MDA) levels, aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and alkaline phosphatase (ALP) activities in fish exposed to 1 and 2% of sewage were significantly higher than the control group (P < 0.01), whereas alanine aminotransferase (ALT) was only increased in fish exposed to 2% sewage (P < 0.01). A significant decrease in gamma-glutamyl-transferase (GGT) activity in fish exposed to 2% effluent was found (P < 0.01). Catalase (CAT) activity was increased in zebrafish exposed to all concentrations of effluent. The transcriptional analysis of the detoxification-related genes and the changes in the biochemical indicators evidenced that drainage of sewage effluents from the ethyl alcohol company is a serious threat to the health of aquatic animals in the Khorram-Rood River. These results will contribute to further study on the impact of sewage effluents of the alcohol industry on aquatic organisms.

Molecular and Functional Properties of the Atlantic Cod (Gadus morhua) Aryl Hydrocarbon Receptors Ahr1a and Ahr2a

The aryl hydrocarbon receptor (Ahr) is a ligand-activated transcription factor that mediates the toxicity of halogenated and polycyclic aromatic hydrocarbons in vertebrates. Atlantic cod (Gadus morhua) has recently emerged as a model organism in environmental toxicology studies, and increased knowledge of Ahr-mediated responses to xenobiotics is imperative. Genome mining and phylogenetic analyses revealed two Ahr-encoding genes in the Atlantic cod genome, gmahr1a and gmahr2a. In vitro binding assays showed that both gmAhr proteins bind to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), but stronger binding to gmAhr1a was observed. Transactivation studies with a reporter gene assay revealed that gmAhr1a is one order of magnitude more sensitive to TCDD than gmAhr2a, but the maximal responses of the receptors were similar. Other well-known Ahr agonists, such as β-naphthoflavone (BNF), 3,3',4,4',5-pentachlorobiphenyl (PCB126), and 6-formylindolo[3,2-b]carbazole (FICZ), also activated the gmAhr proteins, but gmAhr1a was, in general, the more sensitive receptor and produced the highest efficacies. The induction of cyp1a in exposed precision-cut cod liver slices confirmed the activation of the Ahr signaling pathway ex vivo. In conclusion, the differences in transcriptional activation by gmAhr's with various agonists, the distinct binding properties with TCDD and BNF, and the distinct tissue-specific expression profiles indicate different functional specializations of the Atlantic cod Ahr's.