Effects of oil pollution and persistent organic pollutants (POPs) on glycerophospholipids in liver and brain of male Atlantic cod (Gadus morhua)

Divergent bacterial landscapes: unraveling geographically driven microbiomes in Atlantic cod

Establishing microbiome signatures is now recognized as a critical step toward identifying genetic and environmental factors shaping animal-associated microbiomes and informing the health status of a given host. In the present work, we prospectively collected 63 blood samples of the Atlantic cod population of the Southern Gulf of Saint Lawrence (GSL) and characterized their 16S rRNA circulating microbiome signature. Our results revealed that the blood microbiome signature was dominated at the phylum level by Proteobacteria, Bacteroidetes, Acidobacteria and Actinobacteria, a typical signature for fish populations inhabiting the GSL and other marine ecosystems. At the genus level, however, we identified two distinct cod groups. While the microbiome signature of the first group was dominated by Pseudoalteromonas, a genus we previously found in the microbiome signature of Greenland and Atlantic halibut populations of the GSL, the second group had a microbiome signature dominated by Nitrobacter and Sediminibacterium (approximately 75% of the circulating microbiome). Cods harboring a Nitrobacter/Sediminibacterium-rich microbiome signature were localized in the most southern part of the GSL, just along the northern coast of Cape Breton Island. Atlantic cod microbiome signatures did not correlate with the weight, length, relative condition, depth, temperature, sex, and salinity, as previously observed in the halibut populations. Our study provides, for the first time, a unique snapshot of the circulating microbiome signature of Atlantic cod populations and the potential existence of dysbiotic signatures associated with the geographical distribution of the population, probably linked with the presence of nitrite in the environment.

Environmentally realistic concentrations of chlorinated, brominated, and fluorinated persistent organic pollutants induce the unfolded protein response as a shared stress pathway in the liver of Atlantic cod (Gadus morhua)

In the North Sea and North Atlantic coastal areas, fish experience relatively high background levels of persistent organic pollutants. This study aimed to compare the mode of action of environmentally relevant concentrations of mixtures of halogenated compounds in Atlantic cod. Juvenile male cod with mean weight of 840 g were exposed by gavage to dietary mixtures of chlorinated (PCBs, DDT analogs, chlordane, lindane, and toxaphene), brominated (PBDEs), and fluorinated (PFOS) compounds for 4 weeks. One group received a combined mixture of all three compound groups. The results showed that the accumulated levels of chemicals in cod liver after 4 weeks of exposure reflected concentrations found in wild fish in this region. Pathway analysis revealed that the treatment effects by each of the three groups of chemicals (chlorinated, brominated, and fluorinated) converged on activation of the unfolded protein response (UPR). Upstream regulator analysis predicted that almost all the key transcription factors (XBP1, ERN1, ATF4, EIF2AK3, and NFE2L2) regulating the UPR were significantly activated. No additive effect was observed in cod co-treated with all three compound groups. In conclusion, the genome-wide transcriptomic study suggests that the UPR pathway is a sensitive common target of halogenated organic environmental pollutants in fish.

Bisphenol A has a sex-dependent disruptive effect on hepatic lipid metabolism in zebrafish

Bisphenol A (BPA) is an endocrine disruptor that has adverse effects on lipid metabolism. However, most of the current studies on the effects of BPA on lipid metabolism in fish have focused on middle- and short-term exposure tests. The aim of this study was to investigate the effects of long-term BPA exposure on liver lipid metabolism in zebrafish. Post-fertilization embryos were exposed to environmentally relevant concentrations of BPA for 120 days, and the changes in triglyceride (TG), total cholesterol (TC) levels, and gene expression related to liver lipid metabolism were investigated in both male and female fish. The results showed that long-term exposure to BPA led to lipid deposition in liver, and there was a sex difference. In the liver of female fish, there was higher lipid transport and synthesis at low concentration of BPA, while overall metabolic levels were increased at high concentration of BPA. In contrast, BPA showed a dose-dependent effect on the lipid deposition in male fish. The expression of mRNA of TG transport-related and lipid synthesis-related genes was significantly up-regulated and the expression of genes related to lipid catabolism, was significantly down-regulated with increasing BPA dose. Taken together, our results indicate that long-term exposure to BPA can increase lipid deposition in a gender-specific manner. This may be due to the different responses of lipid metabolism related genes to BPA in male and female zebrafish. These results will provide a new reference for a deeper understanding of the ecotoxicological effects of BPA on aquatic animals.

Effects of prenatal exposure to persistent organic pollutants on neonatal Outcomes:A mother-child cohort (Shanghai, China)

Persistent organic pollutants (POPs), known as common environmental pollutants, which have adverse effects on neurobehavioral development, are widely applied in industry and agriculture. However, evidence about neurodevelopmental toxicity of POPs in humans is limited. This study aimed to explore the relationship between prenatal exposure to POPs and birth outcome of the newborn including birth length, weight, and head circumference. In this study, 1522 mother-child pairs were included in this study and cord blood samples were collected, which were detected to determine exposure level of 37 POPs in total. After delivery, the neonatal anthropometric indices detection (birth length, weight, and head circumference) was performed. According to the multivariate linear regression, the newborn with high detection rates (≥75 percentile) of hexachlorobenzene (HCB), beta-hexachlorocyclohexane (β-HCH), p,p'-dichlorodiphenyl dichloroethylene (p,p'-DDE) in the umbilical cord blood were demonstrated negative relationship with birth head circumference after adjusting for confounding factors, but not related with birth length and weight. After confirming that there was a nonlinear relationship between HCB and birth head circumference based on sex stratification through the generalized additive model (GAM), further two-piecewise linear regression model was conducted to explore the saturation threshold effect between HCB and birth head circumference, which showed cord serum HCB concentration greater than 0.5 μg/L was negatively associated with birth head circumference in girls. Our study provided evidence for the adverse influence of HCB, β-HCH and p,p'-DDE exposure during pregnancy on the birth head circumference of offspring. Although HCB induced reduction of birth head circumference was found in girls, the mechanism of gender difference remained unclear. Further studies are needed to explore the effect of POPs on the growth and development of offspring based on in vivo or in vitro experimental models.

Sex Dependent Action of Aroclor 1254 on Basal and sGnRHa-Stimulated Secretion of LH from the Pituitary Cells of Common Carp, Cyprinus carpio L

Polychlorinated biphenyls (PCBs) affect the hypothalamic-pituitary-gonadal axis in many vertebrates, changing the hormonal regulation of reproduction. To identify one of the possible sites of action of PCBs on gonadotropin release in common carp, the direct effects of Aroclor 1254 on luteinizing hormone (LH) secretion from dispersed pituitary cells were investigated. Pituitary cells were obtained from sexually mature male and female common carp (Cyprinus carpio L.) at the time of natural spawning. The cells were incubated with different concentrations of Aroclor 1254 (5, 10, 50 and 100 ng mL–1 medium) and/or salmon gonadotropin-releasing hormone analogue (sGnRHa) at a concentration of 10−8 M. LH levels were measured in the cultured medium by the ELISA method after 10 hours of cell incubation. Incubation of male pituitary cells in the presence of tested concentrations of Aroclor did not change the basal LH secretion to the media. In the female pituitary cell incubations Aroclor (5, 10 and 100 ng mL–1 medium) caused a significant increase in LH concentrations in comparison to control incubations. In the case of sGnRHastimulated LH secretion in incubations of cells of both sexes, all the concentrations of Aroclor significantly stimulated LH release and potentiated stimulatory effects of sGnRH analogue. These results indicate that endocrine disrupters, such as Aroclor 1254, may affect reproduction in fish, acting also directly on gonadotrophs at the level of the pituitary gland, changing LH secretion.

Toxicity of Tetrabromobisphenol A and Its Derivative in the Mouse Liver Following Oral Exposure at Environmentally Relevant Levels

As typical brominated flame retardants (BFRs), tetrabromobisphenol A (TBBPA) and its derivative TBBPA-bis(2,3-dibromopropyl ether) (TBBPA-BDBPE) are ubiquitous in various environmental compartments. However, the potential health risk posed by these compounds, especially at environmentally relevant levels, remains unclear. In this study, using adult male mice, we investigated the toxicity of orally administered TBBPA and TBBPA-BDBPE at an environmentally relevant dose (57 nmol/kg body weight). After a single exposure and daily exposure, we assessed lipid metabolism homeostasis, the transcriptome, and immune cell components in the liver. We found that the single exposure to TBBPA or TBBPA-BDBPE alone increased the number of hepatic macrophages, induced alterations in the levels of lipids, including triacylglycerol and free fatty acids, and caused transcriptome perturbation. The results from the daily administration groups showed that TBBPA and TBBPA-BDBPE both significantly increased the triacylglycerol content; however, the elevation of hepatic macrophages was observed only in the TBBPA-BDBPE treatment group. This study confirmed that environmentally relevant levels of TBBPA and TBBPA-BDBPE are toxic to the liver. Our findings revealed that dysfunction of the liver is a health concern, following exposure to BFRs, even at very low concentrations. The chronic effects induced by TBBPA and its derivatives should be further investigated.

Application of quantitative transcriptomics in evaluating the ex vivo effects of per- and polyfluoroalkyl substances on Atlantic cod (Gadus morhua) ovarian physiology

Because of their global consumption and persistence, per- and polyfluoroalkyl substances (PFASs), are ubiquitously distributed in the environment, as well as in wildlife and humans. In the present study, we have employed an ex vivo organ culture technique, based on the floating agarose method, of Atlantic cod ovarian tissue to investigate the effects of three different concentrations of PFOS, PFOA (1, 5 and 25 μM) and PFNA (0.5, 5 and 50 μM), used singly and in also in combination (1×, 20× and 100×). In the 1× exposure mixture, concentrations were decided based on their proportional levels (in molar equivalents) relative to PFOS, which is the most abundant PFAS in cod liver from a 2013 screening project. To investigate the detailed underlying mechanisms and biological processes, transcriptome sequencing was performed on exposed ovarian tissue. The number of differentially expressed genes (DEGs) having at least 0.75 log₂-fold change was elevated in high, compared to low and medium concentration exposures. The highest PFNA, PFOA and PFOS concentrations, and the highest (100×) mixture exposure, showed 40, 68, 1295, and 802 DEGs, respectively. The latter two exposure groups shared a maximum of 438 DEGs. In addition, they both shared the majority of functionally enriched pathways belonging to biological processes such as cellular signaling, cell adhesion, lipid metabolism, immunological responses, cancer, reproduction and metabolism. Shortlisted DEGs that were specifically annotated to reproduction associated gene ontology (GO) terms were observed only in the highest PFOS and mixture exposure groups. These transcripts contributed to ovarian key events such as steroidogenesis (star, cyp19a1a), oocyte growth (amh), maturation (igfbp5b, tgfβ2, tgfβ3), and ovulation (pgr, mmp2). Contrary to other PFAS congeners, the highest PFOS concentration showed almost similar transcript expression patterns compared to the highest mixture exposure group. This indicates that PFOS is the active component of the mixture that significantly altered the normal functioning of female gonads, and possibly leading to serious reproductive consequences in teleosts.

Temporal transcriptome analysis in female scallop Chlamys farreri: First molecular insights into the disturbing mechanism on lipid metabolism of reproductive-stage dependence under benzo[a]pyrene exposure

Polycyclic aromatic hydrocarbons (PAHs) are one of the most widespread persistent organic pollutants (POPs) in marine environment. Benzo[a]pyrene (B[a]P), the most toxic carcinogen of PAHs, is widely studied as a representative that interferes with lipid metabolism. However, the underlying molecular mechanisms of lipid metabolism by B[a]P interference towards bivalve, one of the marine-pollution bio-indicators have not been elucidated yet, especially during gonadal development which is closely associated with lipids. In this study, female scallops Chlamys farreri were cultured with natural and 4 μg/L B[a]P exposed seawater, respectively, and a multi-stage (proliferative, growth, mature, and spawn stage) ovarian transcriptome profiling was performed to decipher the reproductive stage-dependence disturbing mechanisms on lipid metabolism caused by B[a]P in bivalves. The results revealed the potential molecular mechanism of B[a]P-induced triglycerides (TGs) accumulation, which probably resulted from the collaboration of promoting synthesis and inhibiting metabolization of TGs, notably, this mechanism also occurred at spawn stage. Correspondingly, B[a]P and TGs contents measured in ovary offered direct biochemical evidences for the interference effects and stage-dependent accumulation patterns of B[a]P. Moreover, the gene expressions of fatty acids synthesis related enzymes were down-regulated cooperatively, illustrating the molecular compensatory mechanism that reduced susceptibility from oxidative damage. And these results further emphasized the important role of prostaglandins (PGs) in immune response mediated by arachidonic acid metabolism. In addition, this study explored the underlying molecular mechanism affected by B[a]P on sterol metabolism, which possibly posed a threat to normal reproductive functions in bivalves. Taken together, our findings filled the gap of the stage-dependent interference molecular mechanisms on lipid metabolism behind bivalves, and provided a new perspective for investigating the adaptive mechanisms of bivalves under POPs stress.

Environmental effects of offshore produced water discharges: A review focused on the Norwegian continental shelf

Produced water (PW), a large byproduct of offshore oil and gas extraction, is reinjected to formations or discharged to the sea after treatment. The discharges contain dispersed crude oil, polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), metals, and many other constituents of environmental relevance. Risk-based regulation, greener offshore chemicals and improved cleaning systems have reduced environmental risks of PW discharges, but PW is still the largest operational source of oil pollution to the sea from the offshore petroleum industry. Monitoring surveys find detectable exposures in caged mussel and fish several km downstream from PW outfalls, but biomarkers indicate only mild acute effects in these sentinels. On the other hand, increased concentrations of DNA adducts are found repeatedly in benthic fish populations, especially in haddock. It is uncertain whether increased adducts could be a long-term effect of sediment contamination due to ongoing PW discharges, or earlier discharges of oil-containing drilling waste. Another concern is uncertainty regarding the possible effect of PW discharges in the sub-Arctic Southern Barents Sea. So far, research suggests that sub-arctic species are largely comparable to temperate species in their sensitivity to PW exposure. Larval deformities and cardiac toxicity in fish early life stages are among the biomarkers and adverse outcome pathways that currently receive much attention in PW effect research. Herein, we summarize the accumulated ecotoxicological knowledge of offshore PW discharges and highlight some key remaining knowledge needs.

Metabolomics Provide Sensitive Insights into the Impacts of Low Level Environmental Contamination on Fish Health-A Pilot Study

This exploratory study aims to investigate the health of sand flathead (Platycephalus bassensis) sampled from five sites in Port Phillip Bay, Australia using gas chromatography-mass spectrometry (GC-MS) metabolomics approaches. Three of the sites were the recipients of industrial, agricultural, and urban run-off and were considered urban sites, while the remaining two sites were remote from contaminant inputs, and hence classed as rural sites. Morphological parameters as well as polar and free fatty acid metabolites were used to investigate inter-site differences in fish health. Significant differences in liver somatic index (LSI) and metabolite abundance were observed between the urban and rural sites. Differences included higher LSI, an increased abundance of amino acids and energy metabolites, and reduced abundance of free fatty acids at the urban sites compared to the rural sites. These differences might be related to the additional energy requirements needed to cope with low-level contaminant exposure through energy demanding processes such as detoxification and antioxidant responses as well as differences in diet between the sites. In this study, we demonstrate that metabolomics approaches can offer a greater level of sensitivity compared to traditional parameters such as physiological parameters or biochemical markers of fish health, most of which showed no or little inter-site differences in the present study. Moreover, the metabolite responses are more informative than traditional biomarkers in terms of biological significance as disturbances in specific metabolic pathways can be identified.

Growth and metabolism of adult polar cod (Boreogadus saida) in response to dietary crude oil

The increasing human presence in the Arctic shelf seas, with the expansion of oil and gas industries and maritime shipping, poses a risk for Arctic marine organisms such as the key species polar cod (Boreogadus saida). The impact of dietary crude oil on growth and metabolism of polar cod was investigated in the early spring (March-April) when individuals are expected to be in a vulnerable physiological state with poor energy stores. Adult polar cod were exposed dietarily to three doses of Kobbe crude oil during an eight weeks period and followed by two weeks of depuration. Significant dose-responses in exposure biomarkers (hepatic ethoxyresorufine-O-deethylase [EROD] activity and 1-OH phenanthrene metabolites in bile) indicated that polycyclic aromatic hydrocarbons (PAHs) were bioavailable. Condition indices (i.e. Fulton's condition factor, hepatosomatic index), growth, whole body respiration, and total lipid content in the liver were monitored over the course of the experiment. The majority of females were immature, while a few had spawned during the season and showed low hepatic lipid content during the experiment. In contrast, males were all, except for one immature individual, in a post-spawning stage and had larger hepatic energy stores than females. Most specimens, independent of sex, showed a loss in weight, that was exacerbated by exposure to crude oil and low hepatic liver lipids. Furthermore, females exposed to crude oil showed a significant elevation of oxygen consumption compared to controls, although not dose-dependent. This study highlights the importance of the energy status of individuals for their response to a crude oil exposure.

Sex-specific alterations of lipid metabolism in zebrafish exposed to polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) mixtures exerting environmental health risk. In mammals, PCBs have been shown to disrupt metabolic state, especially lipid metabolism, and energy balance, but their effects on lipid metabolism in fish are largely unknown. The zebrafish were selected as model and both male and female adult zebrafish were exposed to different concentrations of PCBs at gradient concentrations of 0.2, 2.0 and 20.0 μg/L for 6 weeks. PCB exposure did not affect survival, but a significant inhibition of growth was observed in the males after exposure to 20.0 μg/L. The lower concentrations of 0.2 and 2.0 μg/L increased hepatic lipid accumulation to a greater extent in male fish, but the higher concentration of 20.0 μg/L did not cause significant fat accumulation in either male or female fish. In males, the expression of genes related to lipogenesis and lipid catabolism was upregulated in a concentration-dependent manner in the liver and visceral mass without liver and gonad; the effects of exposure on lipid metabolism-related genes in female fish were less pronounced. PCB exposure did not induce significant oxidative stress, but did upregulate the expression of stress- and apoptosis-related genes, mostly in male fish. The low concentrations of PCBs (0.2 μg/L and 2.0 μg/L) exerted sex-specific effects on zebrafish lipid metabolism, and male fish were more sensitive to the exposure. This study provides new mechanistic insights into the complex interactions between PCBs, lipid metabolism, and sex in zebrafish, and may contribute to a future systematic assessment of the effects of PCBs on aquatic ecosystems.

Analysis of glycerophospholipid metabolism after exposure to PCB153 in PC12 cells through targeted lipidomics by UHPLC-MS/MS

Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) that have neurotoxicity, reproductive toxicity, hepatotoxicity and immunotoxicity in both animals and humans. Few studies have focused on the changes to endogenous glycerophospholipid metabolism caused by PCB153. To evaluate the relationships between exposure to PCB153 and specific endogenous glycerophospholipid metabolism, an ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was implemented in this study. Twenty-two endogenous glycerophospholipids in PC12 cells were analyzed after exposure to PCB153 at dosages of 0.05 μg mL^-1, 0.5 μg mL^-1 or 20 μg mL^-1 for 120 h. PC(14:0/14:0), PE(16:0/18:1), PE(16:0/18:2), PS(18:0/18:1) and PI(16:0/18:1) were identified as potential biomarkers under the rules of t-test (P) value < 0.05 and variable importance at projection (VIP) value > 1. It was also found that the alterations at 0.05 μg mL^-1 and 20 μg mL^-1 PCB153 were similar at 120 h, while 0.5 μg mL^-1 PCB153 presented an opposite trend. Additionally, significant upregulation of PC, PE and PS with the same fatty acid chains of 18:0/18:2 was found after exposure to 0.05 μg mL^-1 and 20 μg mL^-1 PCB153 at 120 h. This study revealed that PCB153 exposure modulated 22 endogenous glycerophospholipids in PC12 cells and provided the basis for the further study of PCB153 on the effects of glycerophospholipids on PC12 cells.

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.

Effects of dietary crude oil exposure on molecular and physiological parameters related to lipid homeostasis in polar cod (Boreogadus saida)

Polar cod is an abundant Arctic key species, inhabiting an ecosystem that is subjected to rapid climate change and increased petroleum related activities. Few studies have investigated biological effects of crude oil on lipid metabolism in this species, despite lipids being a crucial compound for Arctic species to adapt to the high seasonality in food abundance in their habitat. This study examines the effects of dietary crude oil exposure on transcription levels of genes related to lipid metabolism (peroxisome proliferator-activated receptors [ppar-α, ppar-γ], retinoic X receptor [rxr-β], palmitoyl-CoA oxidase [aox1], cytochrome P4507A1 [cyp7α1]), reproduction (vitellogenin [vtg-β], gonad aromatase [cyp19a1]) and biotransformation (cytochrome P4501A1 [cyp1a1], aryl hydrocarbon receptor [ahr2]). Exposure effects were also examined through plasma chemistry parameters. Additional fish were exposed to a PPAR-α agonist (WY-14,643) to investigate the role of PPAR-α in their lipid metabolism. The dose-dependent up-regulation of cyp1a1 reflected the activation of genes related to PAH biotransformation upon crude oil exposure. The crude oil exposure did not significantly alter the mRNA expression of genes involved in lipid homeostasis except for cyp7α1 transcription levels. Plasma levels of cholesterol and alanine transaminase showed significant alterations in fish exposed to crude oil at the end of the experiment. WY exposure induced a down-regulation of ppar-α, an effect contrary to studies performed on other fish species. In conclusion, this study showed clear effects of dietary crude oil exposure at environmentally relevant concentrations on xenobiotic biotransformation but revealed only weak alterations in the lipid metabolism of polar cod.

QSAR Study for Carcinogenic Potency of Aromatic Amines Based on GEP and MLPs

A new analysis strategy was used to classify the carcinogenicity of aromatic amines. The physical-chemical parameters are closely related to the carcinogenicity of compounds. Quantitative structure activity relationship (QSAR) is a method of predicting the carcinogenicity of aromatic amine, which can reveal the relationship between carcinogenicity and physical-chemical parameters. This study accessed gene expression programming by APS software, the multilayer perceptrons by Weka software to predict the carcinogenicity of aromatic amines, respectively. All these methods relied on molecular descriptors calculated by CODESSA software and eight molecular descriptors were selected to build function equations. As a remarkable result, the accuracy of gene expression programming in training and test sets are 0.92 and 0.82, the accuracy of multilayer perceptrons in training and test sets are 0.84 and 0.74 respectively. The precision of the gene expression programming is obviously superior to multilayer perceptrons both in training set and test set. The QSAR application in the identification of carcinogenic compounds is a high efficiency method.

Accumulation of neurotoxic organochlorines and trace elements in brain of female European eel (Anguilla anguilla)

Xenobiotics such as organochlorine compounds (OCs) and metals have been suggested to play a significant role in the collapse of European eel stocks in the last decades. Several of these pollutants could affect functioning of the nervous system. Still, no information is so far available on levels of potentially neurotoxic pollutants in eel brain. In present study, carried out on female eels caught in Belgian rivers and canals, we analyzed brain levels of potentially-neurotoxic trace elements (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Hg, MeHg, Mn, Ni, Pb, Sn, Sb, Zn) and OCs (Polychlorinated biphenyls, PCBs; Hexachlorocyclohexanes, HCHs; Dichlorodiphenyltrichloroethane and its metabolites, DDTs). Data were compared to levels in liver and muscle tissues. Eel brain contained very high amounts of OCs, superior to those found in the two other tissues. Interestingly, the relative abundance of PCB congeners markedly differed between tissues. In brain, a predominance of low chlorinated PCBs was noted, whereas highly chlorinated congeners prevailed in muscle and liver. HCHs were particularly abundant in brain, which contains the highest amounts of β-HCH and ϒ-HCH. p,p'-DDTs concentration was similar between brain and muscle (i.e., about twice that of liver). A higher proportion of p,p'-DDT was noticed in brain. Except for Cr and inorganic Hg, all potentially neurotoxic metals accumulated in brain to levels equal to or lower than hepatic levels. Altogether, results indicate that eel brain is an important target for organic and, to a lesser extent, for inorganic neurotoxic pollutants.

The protective effect of vitamin E against changes in fatty acid composition of phospholipid subclasses in gill tissue of Oreochromis niloticus exposed to deltamethrin

The effects of deltamethrin on the fatty acid composition of phospholipid subclasses (phosphatidylchlonine (PC), phosphatidylethanolamine (PE), phosphatidylinositole (PI) and phosphatidylserine (PS)) in gill tissue of Oreochromis niloticus (Perciformes: Cichlidae) and the possible protective effect of vitamin E against deltamethrin were determined by gas chromatography. The changes in the fatty acid profile were analysed after 14 d of exposure. Treatments included Group I (fed with basal diet only), Group II (fed with vitamin E-supplemented diet), Group III (fed with basal diet and exposed to deltamethrin) and Group IV (fed with vitamin E-supplemented diet and exposed to deltamethrin). The effects of deltamethrin on PI, PE and PS were valid for the total saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs). The effect on PC was detected in total SFAs and total PUFAs. The vitamin E-supplemented diet did not show complete protective effect on fatty acid composition of the fish exposed to deltamethrin. However, the protective effect was observed in total SFAs, total MUFAs and total PUFAs in PC. In PI, protective effect was only recorded on total PUFAs. There was no protective effect in PS and PE. The results of the present study demonstrated that deltametrin exposure had harmful effects on cell membrane and treatment with vitamin E could only partially protect fish gills.

Omega-3 and alpha-tocopherol provide more protection against contaminants in novel feeds for Atlantic salmon (Salmo salar L.) than omega-6 and gamma tocopherol

Extended use of plant ingredients in Atlantic salmon farming has increased the need for knowledge on the effects of new nutrients and contaminants in plant based feeds on fish health and nutrient-contaminant interactions. Primary Atlantic salmon hepatocytes were exposed to a mixture of PAHs and pesticides alone or in combination with the nutrients ARA, EPA, α-tocopherol, and γ-tocopherol according to a factorial design. Cells were screened for effects using xCELLigence cytotoxicity screening, NMR spectroscopy metabolomics, mass spectrometry lipidomics and RT-qPCR transcriptomics. The cytotoxicity results suggest that adverse effects of the contaminants can be counteracted by the nutrients. The lipidomics suggested effects on cell membrane stability and vitamin D metabolism after contaminant and fatty acid exposure. Co-exposure of the contaminants with EPA or α-tocopherol contributed to an antagonistic effect in exposed cells, with reduced effects on the VTG and FABP4 transcripts. ARA and γ-tocopherol strengthened the contaminant-induced response, ARA by contributing to an additive and synergistic induction of CYP1A, CYP3A and CPT2, and γ-tocopherol by synergistically increasing ACOX1. Individually EPA and α-tocopherol seemed more beneficial than ARA and γ-tocopherol in preventing the adverse effects induced by the contaminant mixture, though a combination of all nutrients showed the greatest ameliorating effect.