Naphthalene treatment alters liver intermediary metabolism and levels of steroid hormones in plasma of rainbow trout (Oncorhynchus mykiss)

Exploring the impact of nonylphenol exposure on Litopenaeus vannamei at the histological and molecular levels

Nonylphenol (NP) is one of the common pollutants in the environment that have toxic effects on aquatic animals. Nevertheless, little is known about the possible toxicity mechanism of NP on the hepatopancreas of Litopenaeus vannamei. In the present study, the detrimental effects of NP on the hepatopancreas of the L. vannamei were explored at the histological and transcriptomic levels. The findings indicated that after NP exposed for 3, 12, and 48 h, the hepatopancreas histology was changed significantly. Transcriptomic analysis showed that a total of 4302, 3651, and 4830 differentially expressed genes (DEGs) were identified at 3, 12, and 48 h following NP exposure. All these DEGs were classified into 12 clusters according to the expression patterns at different time points. GO and KEGG enrichment analyses of DEGs were also performed, immunological, metabolic, and inflammatory related pathways, including arachidonic acid metabolism (ko00590), the PPAR signaling pathway (ko03320), and the regulation of TRP channels by inflammatory mediators (ko04750) were significantly enriched. Six DEGs were selected for validation by quantitative real-time PCR (qRT-PCR) and the results confirmed the reliability of transcriptome data. All results indicated that NP is toxic to L. vannamei by damaging the histopathological structure and disrupting the biological function. The findings would provide a theoretical framework for lowering or limiting the detrimental impacts of NP on aquaculture and help us to further study the molecular toxicity of NP in crustaceans.

Toxic effects of tire wear particles and the leachate on the Chinese mitten crab (Eriocheir sinensis)

Tire wear particles (TWPs) were considered as an important component of microplastic pollution in the aquatic environment. To understand the ecotoxicity of TWPs to crustacean, this study investigated toxic effects of TWPs and the leachate on the mitten crab Eriocheir sinensis and the accumulation of TWPs in the crabs. Although TWPs could be accumulated in various tissues (i.e., liver, gills and gut) of the crabs, exposure to TWPs or the leachate had no lethal effect on the crabs in this study. Lower concentrations of TWPs and the leachate exposure could stimulate the antioxidant defense system of the crabs, while higher concentrations could disrupt the stress defense system. In addition, the energy supply and metabolism of the crabs could also be affected by TWPs or the leachate. The transcriptomic profiles showed that the toxic mechanisms of TWPs and the leachate were not exactly the same. Similar to the results of biochemical analysis, several Gene Ontology (GO) terms and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to oxidative stress and energy metabolism were significantly regulated by both TWPs and the leachate. However, TWPs could affect the expression of genes enriched in immune-related pathways, while the leachate regulated the enrichment of some other signaling pathways including FoxO signaling pathway, insulin signaling pathway, RIG-I-like receptor signaling pathway, NOD-like receptor signaling pathway, PPAR signaling pathway and neuroactive ligand-receptor interaction. Overall, our study could provide basic biological information for assessing the ecological risk of the TWP pollution in the aquatic environment and was useful to understand the potential toxic mechanisms of the TWPs and the leachate to crustaceans.

Measurement of hair thyroid and steroid hormone concentrations in the rat evidence endocrine disrupting potential of a low dose mixture of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) have been shown to influence endogenous hormones levels in animal models, but little is known about the effects of their mixtures. For hormone measurements, hair analysis is a promising approach to provide information on long-term status of hormones. Herein we used hair analysis to assess the combined effects of 13 PAHs on steroid and thyroid hormones levels in a rat model. The PAH mixture was administered orally three times per week to female rats at doses of 0, 10, 20, 40, 80, 200, 400 and 800 μg/kg of body weight for each compound over a 90-day exposure period. Fourteen out of 36 analyzed hormones were detected in rat hair, including pregnenolone (P5), 17α-hydroxyprogesterone (17-OHP4), corticosterone (CORT), dehydroepiandrosterone (DHEA), androstenedione (AD), 3,3'-diiodo-L-thyronine (T2), 3,3',5-triiodo-L-thyronine (T3), and 3,5,3',5'-triiodo-L-thyronine (T4). The PAH mixture significantly elevated P5 and DHEA levels at the doses of 200 and 400 μg/kg but reduced T2 and T3 levels at the highest dose as compared to the control. While P5, DHEA, 17-OHP4 and AD concentrations exhibited inverted U-shaped dose responses, T2, T3 and T4 concentrations exhibited inverse linear dose responses, which are further confirmed by their relationships with hair hydroxylated PAHs (OH-PAHs) concentrations. Likewise, there were significant nonmonotonic relationships of hormone molar ratios (e.g., AD/17-OHP4 and DHEA/CORT ratios) with exposure intensity and OH-PAHs. Overall, our results demonstrate the capability of PAH mixtures to interfere with steroid and thyroid hormones in female rats.

Metabolic changes and stress damage induced by ammonia exposure in juvenile Eriocheir sinensis

The application of nitrogen fertilizers in the rice-crab co-culture system may expose juvenile Eriocheir sinensis to high ammonia concentrations within a short period of time, potentially causing death. Currently, the molecular mechanism underlying ammonia toxicity in juvenile Eriocheir sinensis remains poorly understood. This study compared the effects of 24 h exposure to different total ammonia-N concentrations (0, 10.47, and 41.87 mg/L) on antioxidant enzyme activities and tandem mass tag (TMT)-based proteomics in the hepatopancreas of juvenile Eriocheir sinensis. During the experiment, water temperature and pH were maintained at 20.4 ± 1.4 °C and 7.69 ± 0.46, respectively. Proteomic data demonstrated that Eriocheir sinensis used different metabolic regulatory mechanisms to adapt to varying ammonia conditions. The tricarboxylic acid (TCA) cycle, glycogen degradation, and oxidative phosphorylation showed marginally upregulated trends under low ammonia exposure. High ammonia stress caused downregulation of the TCA cycle and provided energy by enhancing oxidative phosphorylation, fatty acid beta oxidation, gluconeogenesis, and glycogen degradation. The detoxification of ammonia into urea and glutamine was suppressed under high ammonia stress. Finally, ammonia exposure induced oxidative stress and caused protein damage. Antioxidant enzyme activity analysis further revealed that exposure to high concentrations of ammonia may induce more severe oxidative stress. This study provides a global perspective on the mechanisms underlying ammonia exposure-induced metabolic changes and stress damage in juvenile Eriocheir sinensis.

Exposure and Recovery of the Gulf Toadfish (Opsanus beta) to Weathered Deepwater Horizon Slick Oil: Impacts on Liver and Blood Endpoints

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants that can be responsible for a variety of deleterious effects on organisms. These adverse outcomes are relatively well studied, but at concentrations rarely found in the environment. Among the documented effects of sublethal acute PAH exposure are reductions in osmoregulatory capacity and immune function, and changes in the function of critical metabolic organs such as the liver. Gulf toadfish (Opsanus beta) were exposed to control seawater (0.006 µg tPAH₅₀ /L) or water accommodated fractions of Deepwater Horizon spill oil diluted to 3 flow-through exposure regimes (0.009, 0.059, and 2.82 µg tPAH₅₀ /L) for 7 d, with a recovery period of equal duration. We hypothesized that these chronic exposures would induce the aryl hydrocarbon receptor (AhR)-mediated pathways and result in significant impacts on markers of osmoregulatory, immune, and metabolic function. We further hypothesized that measurable reversal of these impacts would be observed during the recovery period. Our results indicate that activation of cytochrome P 450 (CYP)1A1 was achieved during exposure and reversed during the recovery phase. The only significant deviations from controls measured were a reduction in plasma glucose in fish exposed to medium and high levels of PAH after 7 d of exposure and a reduction in plasma osmolality fish exposed to high levels of PAHs after 7 d of recovery, when CYP1A1 messenger (m)RNA levels had returned to control levels. Our study illustrates a disconnect between the activation of CYP1A1 in response to environmentally realistic PAHs concentrations and several physiological endpoints and supports the idea that the AhR might not be associated with mediating osmoregulatory, immune, and metabolic changes in Gulf toadfish. Environ Toxicol Chem 2021;40:1075-1086. © 2020 SETAC.

Prioritization of contaminants and biological process targets in the North Sea using toxicity data from ToxCast

The increasing number of chemicals detected in the marine environment underlines the need for appropriate prioritization strategies prior to further testing and potential inclusion into monitoring programs. Here, a prioritization strategy is proposed for chemicals detected in the North Sea over the last decade, through the development of a Concern Index (CI) using exposure and toxicity data obtained from peer-review publications and the ToxCast database, respectively. A total of 158 chemicals were ranked and the most sensitive tested assay endpoints were identified. Additionally, similar analysis was performed for the classes of chemicals and Biological Process Targets (BPTs). By first ranking chemicals currently acknowledged for their high toxicity to the aquatic environment, i.e. naphthalene, salicylic acid and simazine, the obtained results not only reinforce the risk posed by these but also promote a confident extrapolation from mammalian in vitro toxicity data to fish. Furthermore, genes targeted by the most sensitive assays, related to basic cell maintenance processes and immune defense, are highly evolutionarily conserved across species. The identification of these assays further reinforces the importance of a shift from traditional toxicity endpoints to lower levels of biological organization, allowing the detection of adverse effects at lower concentrations.

Physiological disturbances in juvenile sockeye salmon (Oncorhynchus nerka) exposed to the water-soluble fraction of diluted bitumen

Current and proposed transcontinental pipelines for the transport of diluted bitumen (dilbit) from the Canadian oil sands traverse the coastal watersheds of British Columbia, habitat essential to Pacific salmonids. To determine the potential risks posed to these keystone species, juvenile sockeye (Oncorhynchus nerka; 1+ parr) were acutely (24-96 h) or subchronically (21-42 d) exposed to 4 concentrations of the water-soluble fraction (WSF) of unweathered Cold Lake Blend dilbit (initial total PAC concentrations: 0, 13.7, 34.7 and 124.5 μg/L) in a flow-through system. Dilbit effects on iono-osmoregulation, the physiological stress response, and the immune system were assessed by both biochemical and functional assays. Hydrocarbon bioavailability was evidenced by a significant induction of liver ethoxyresorufin-O-deethylase (EROD) activity in exposed fish. Acute and subchronic exposure significantly reduced gill Na⁺-K⁺-ATPase activity and resulted in lower plasma osmolality, Cl^-, and Na⁺ concentrations. Acute exposure to dilbit resulted in a classic physiological stress response, however at 21 d of exposure, plasma cortisol remained elevated while other measured parameters had returned to baseline values. A compromised immune system was demonstrated by a 29.5 % higher mortality in fish challenged with Vibrio (Listonella) anguillarum following dilbit exposure compared to unexposed controls. Exposure of juvenile salmonids to the WSF of dilbit (at TPAC concentrations at the ppb level) resulted in sublethal effects that included a classic physiological stress response, and alterations in iono-osmoregulatory homeostasis and immunological performance.

Ecophysiology, genotoxicity, histopathology, and gene responses of naphthalene injected Colossoma macropomum (Cuvier, 1818) exposed to hypoxia

The present study aimed to evaluate the biological responses of Colossoma macropomum to naphthalene injection and subsequent hypoxia exposure, emphasizing the expression of the tumor suppressor gene tp53. Tambaquis were intraperitoneally injected with naphthalene (50 mg/kg) and, after 96 hours, the fish were transferred to respirometry chambers and, submitted to progressive hypoxia for the determination of critical PO₂. In a subsequent experiment, the fish received an intraperitoneal injection of naphthalene and were kept for 96 hours under normoxia. Successively, fish were challenged with acute hypoxia (PO₂<PO₂ crit) during 6 hours. We observed that the PO₂ crit was not affected by naphthalene injection. Moreover, hematological parameters were modulated only in response to hypoxia. Fish with naphthalene injection plus hypoxia exposure presented altered activity of the GST and CAT enzymes. Exposure to naphthalene also resulted in DNA damages, which was not influenced by hypoxia. Hypoxia accentuated the hepatic lesions caused by naphthalene, as well as it also impaired the transcription of tp53 in naphtalene injected fish, demonstrating the risks of contaminating aquatic environments, especially environments where hypoxic conditions are common and occur on a daily or on seasonal basis, as in the Amazon basin.

Growth, energy metabolism and transcriptomic responses in Chinese mitten crab (Eriocheir sinensis) to benzo[α]pyrene (BaP) toxicity

Benzo(a)pyrene (BaP) is a highly toxic polycyclic aromatic hydrocarbon and has strong affinity to suspended materials and sediments in the aquatic environment. Most crustaceans are benthic species and are easily affected by the pollution in the sediments, but there is little information on the response mechanism of crustaceans to BaP exposure. This study compared the growth and hepatopancreas transcriptomic responses of the Chinse mitten crab (Eriocheir sinensis) exposed to 0, 0.15 (BaP1) and 0.45 μg /L (BaP2) for 28 days. Crab survival and weight gain were reduced in the water born BaP in a dose-dependent way. The contents of hepatopancreas glycogen, triglyceride, total amino acids and lactic acid were all decreased after BaP exposure, indicating possible more energy consumption during detoxification. In the transcriptome analysis, a total of 106.65 million clean reads were obtained and assembled into 81,714 unigenes with an average length of 594 bp and N50 of 808 bp. Under 0.15 or 0.45 μg /L BaP exposure, 922 and 1129 unigenes in crabs were significantly expressed, annotated to 676 and 802 Gene Ontology (GO) terms respectively. The "cellular process" was the leading category for both concentrations. Thirteen significantly changed pathways were identified in both Control vs BaP1 and Control vs BaP2 groups. These pathways were divided into four different parts according to their reported functions, including metabolism, environmental information processing, organismal systems and cellular processes. Nice out of thirteen pathways in BaP1 were related to metabolism, containing amino acid metabolism, phenylpropanoid biosynthesis, monobactam biosynthesis and styrene degradation. Almost all the pathways related with the biosynthesis processes were down-regulated, while the degradation pathways were up-regulated. Seven out of thirteen pathways were classified into metabolism category in BaP2. These pathways were mostly associated with stress resistance rather than supplying energy. This study indicates that both concentrations of BaP disturbed nutrient metabolism, immune response and defense system in the crabs, while exposure to a higher concentration had a greater impact on immunity system than on metabolism. This study provides a better understanding of the underlying molecular and regulatory mechanisms in crustaceans coping with BaP toxicity.

Reproductive and developmental changes in tree swallows (Tachycineta bicolor) are influenced by multiple stressors, including polycyclic aromatic compounds, in the Athabasca Oil Sands

Mining in the Athabasca Oil Sands Region (AOSR) has contributed extensively to increased exposure of wildlife to naturally occurring polycyclic aromatic compounds (PACs), yet little is known about the toxicity of PACs to wildlife in this region. We identified reproductive and developmental changes in tree swallows (Tachycineta bicolor) breeding in close proximity to mining-related activities in the AOSR, and determined these changes in relation to the birds' exposure and accumulation of 41 PACs (parent-, alkylated-PAHs), dibenzothiophenes (DBTs; previously published), diet (carbon (δ¹³C), nitrogen (δ¹⁵N)), volatile organic compounds, and weather variables. Tree swallow pairs (N = 43) were compared among mining-related (OS1, OS2) and reference (REF1, REF2) sites. At OS2, clutch initiation was slightly advanced (2012) but reproductive success (65%) was much lower than at the other sites (≥ 79%). Fledgling production by each pair was influenced by the timing of clutch initiation (years combined); in a highly inclement brood rearing period (2013), additional influences included the nestlings' exposure to ΣDBTs, accumulation of C1-naphthalene, the trophic position of the prey in their diet (δ¹⁵N), and record-breaking rainfall. Nestlings at OS2 were significantly lighter at day (d) 9 and d14, and in poorer body condition (d9). Nestling body mass was influenced by multiple stressors that varied by site: mass of younger nestlings (d9) was related to dietary source (δ¹³C; e.g., wetlands, terrestrial fields), exposure and/or accumulation of C1-phenanthrenes, C2-fluorenes, Σalkyl-PAHs and ΣDBTs, while for older nestlings (d14), body mass was related to sex, hatch date and/or rainfall during brood rearing. The swallows' exposure and accumulation of parent-PACs, alkyl-PACs and DBTs, the timing of hatching, their diet and exposure to highly inclement rains, contributed to their reproductive and developmental changes.

Evaluation of wastewater treatment by ozonation for reducing the toxicity of contaminants of emerging concern to rainbow trout (Oncorhynchus mykiss)

Although conventional wastewater treatment technologies are effective at removing many contaminants of emerging concern (CECs) from municipal wastewater, some contaminants are not removed efficiently. Ozonation may be a treatment option for reducing the concentrations of recalcitrant CECs in wastewater, but this process may generate toxic transformation products. In the present study, we conducted semibatch experiments to ozonate municipal wastewater effluent spiked with 5 commonly detected CECs. The purpose of the present study was to evaluate whether ozonation increased or decreased biological responses indicative of sublethal toxicity in juvenile rainbow trout (Oncorhynchus mykiss) injected intraperitoneally (i.p.) with extracts prepared from ozonated and nonozonated wastewater effluent. Blood, liver, and brain tissues were collected from the fish at 72 h post injection for analysis of a battery of biomarkers. In fish i.p. injected with the extracts from nonozonated wastewater effluent, significant induction of plasma vitellogenin (VTG) was observed, but ozonation of the municipal wastewater effluent spiked with CECs significantly reduced this estrogenic response. However, in fish injected with extracts from spiked municipal wastewater effluent after ozonation, the balance of hepatic glutathione in its oxidized (glutathione disulfide [GSSG]) form was altered, indicating oxidative stress. Levels of the neurotransmitter serotonin were significantly elevated in brain tissue from trout injected with the extracts from ozonated spiked municipal wastewater effluent, a biological response that has not been previously reported in fish. Other in vivo biomarkers showed no significant changes across treatments. These results indicate that ozonation reduces the estrogenicity of wastewater, but may increase other sublethal responses. The increase in biomarker responses after ozonation may be because of the formation of biologically active products of transformation of CECs, but further work is needed to confirm this conclusion. Environ Toxicol Chem 2018;37:274-284. © 2017 SETAC.

Using cell apoptosis, micronuclei and immune alternations as biomarkers of phenanthrene exposure in yellowfin seabream (Acanthopagrus latus)

In the present study, the apoptosis and tissue changes in the spleen, as well as humoral immune-related parameters, micronuclei (MN) induction in blood cells and Ethoxyresorufin-O-deethylase (EROD) activity were investigated in yellowfin seabream (Acanthopagrus latus) after short-term exposure to phenanthrene (Phe). The fish were intraperitoneally injected with different concentrations (2, 20 and 40 mg kg^-1) of Phe and tissue and blood samples were collected 1, 4, 7 and 14 days after injection. The concentrations of Phe in the fish liver increased 4 days after the experiment. EROD activity showed a pattern consistent with Phe concentration in the liver. Apoptotic index in the spleen increased dose dependently in Phe-exposed fish. Exposure to Phe caused significant decrease in the plasma level of immunoglobulin M, phagocytic and respiratory burst activity after 4 days of exposure. The frequency of MN in the erythrocytes of the treated fish was significantly higher than control. The main pathological alterations in the spleen included the increase in melanomacrophage centers (MMCs), destroyed red blood cell and hemorrhage. The degree of tissue changes in the spleen of the exposed fish ranged from slight to moderate damage. The size and number of MMCs in the spleen were significantly higher in Phe-treated fish compared to the control. Our results showed that Phe could suppress immune responses in fish, induce cell apoptosis, histological changes in the spleen and MN formation. This may suggest those parameters consider as useful biomarkers for monitoring of the health status of fish during exposure to Phe.

Responses of immune organs after single-dose exposure to phenanthrene in yellowfin seabream (Acanthopagrus latus): CYP1A induction and oxidative stress

The effect of phenanthrene (Phe) on induction of ethoxyresorufinO-deethylase (EROD) activity and oxidative stress was examined in immune organs of yellowfin seabream Acanthopagrus latus. Fish were treated with a single intraperitoneal injection at 2, 20, or 40 mg kg^-1. The Phe concentration in spleen, EROD activity, superoxide dismutase (SOD) and catalase (CAT) activity, ascorbic acid (AsA), total glutathione (GSH), lipid peroxidation (LPO), and protein carbonylation (PC) levels in spleen and head kidney were assessed at one, four, seven, and 14 days post-injection. Dose response relationship was explored for data on day four. Phe concentration reached the highest observed level on day four, showed decline on day seven, and was undetectable at the end of trial. EROD activity in both organs followed the pattern of Phe level in all treated groups. Catalase and SOD activity at low Phe concentrations was significantly higher than controls, while LPO and PC level showed no differences from controls. In contrast, at 20 and 40 mg kg^-1, CAT and SOD activity, an indicator of oxidative stress, was significantly lower than in untreated controls, while AsA, GSH, LPO, and PC levels were higher on days 4 and 7. No parameter of any treatment group in either organ tissue showed difference from control values at the end of the experiment. The SOD and CAT activity in both organs exhibited a biphasic (initial stimulatory effect) effect, whereas other parameters showed a monophasic effect in terms of dose-response. Results suggest that Phe induced CYP1A and antioxidant responses in immune organs.

The impact of acute PAH exposure on the toadfish glucocorticoid stress response

The objective of the present study was to determine whether the polycyclic aromatic hydrocarbons (PAHs) associated with the Deepwater Horizon (DWH) oil spill impacted the stress response of teleost fish. The hypothesis was that intraperitoneal (IP) treatment with PAHs associated with the DWH oil spill or waterborne exposure to DWH oil high energy water-accommodated fraction (HEWAF) would result in the downregulation of the stress response of Gulf toadfish, Opsanus beta, a benthic marine teleost fish that resides in the Gulf of Mexico. In vivo plasma cortisol levels and adrenocorticotropic hormone (ACTH)-mediated cortisol secretion by in vitro isolated kidney tissue were measured. Toadfish at rest IP-treated with naphthalene had higher plasma cortisol compared to fluorene-treated and control fish; phenanthrene-treated fish tended to have higher plasma cortisol levels that fluorene-treated and controls. When subjected to an additional crowding stress, naphthalene and phenanthrene-treated fish were no longer able to mount a stress response compared to fluorene-treated and control fish, suggesting exhaustion of the stress response. Supporting this in vivo data, there tended to be less cortisol released by the kidney in vitro from naphthalene and phenanthrene-treated fish in response to ACTH compared to controls. In contrast, toadfish at rest exposed to 3% Slick A HEWAF did not have significantly different plasma cortisol levels compared to controls. But, exposed fish did have significantly less cortisol released by the kidney in vitro in response to ACTH. When toadfish were subjected to an additional stress, there were no significant differences in plasma cortisol or ACTH, suggesting the action of a secondary secretagogue to maintain plasma cortisol in vivo. Combined, these data suggest that in response to acute PAH exposure, there may be internalization or downregulation of the melanocortin 2 receptor (MC2R) that mediates the action of ACTH.

Assessment of immune status of yellowfin seabream (Acanthopagrus latus) during short term exposure to phenanthrene

The aim of the present investigation was to assess the immune status in yellowfin seabream (Acanthopagrus latus) exposed to different concentrations of phenanthrene (Phe) for 14days. In addition, the Phe accumulation in the fish muscle was measured during the experiment. Fish were injected with different concentrations (0, 2, 20 and 40mg/kg) of Phe and samples were taken from tissue and blood of fish 1, 4, 7 and 14days after injection. Exposure of fish to Phe caused a significant decrease in white blood cells, C3 and C4 levels, lysosomal membrane stability, lysozyme activity after 4days and antibacterial activity after 7days of the experiment. In contrast, cortisol level significantly increased after 4days. The concentration of Phe in fish muscle increased rapidly after 4days. The main tissue changes observed in the head kidney including increase in melanomacrophage centers (MMCs), empty spaces between cells and hemorrhage. The degree of tissue changes ranged from normal to moderate in Phe-treated fish. The size and number of MMCs in treated fish were significantly higher than control. In conclusion, Phe toxicity in yellowfin seabream can induce increased cortisol level, tissue changes and immune suppression.

The Effects of Petroleum Hydrocarbons on Algae Can Be Reversed in the Presence of a Primary Consumer

The ecotoxicological effects of a mixture of petroleum hydrocarbons were tested on densities of two algae, Platymonas helgolandica var. tsingtaoensis and Isochrysis galbana, and of a rotifer, Brachionus plicatilis, by single-species and customized community experiments. Test concentrations ranged from 0 to 100 mg L(-1), while five to seven treatments were assessed in triplicate within 1 month. A significant decrease in densities during single-species toxicity tests were found when concentrations of petroleum hydrocarbons were above 1.0 mg L(-1). However, equilibrium densities of algae in the customized community showed a different pattern, which increased with concentration and reached a peak at 20.0 mg L(-1). The community-based no observed effect concentration (NOEC; 1.0 mg L(-1)) was different from the NOEC derived by single-species toxic tests (0.25 mg L(-1)). This demonstrates that ecotoxicological effects on plankton as part of a community is significantly different from single-species toxicity tests owing to ecological interactions.

Linking biochemical perturbations in tissues of the African catfish to the presence of polycyclic aromatic hydrocarbons in Ovia River, Niger Delta region

Petroleum hydrocarbons including polycyclic aromatic hydrocarbons (PAHs) are a pollution issue in the Niger Delta region due to oil industry activities. PAHs were measured in the water column of the Ovia River with concentrations ranging from 0.1 to 1055.6 ng L(-1). Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy detected alterations in tissues of the African catfish (Heterobranchus bidorsalis) from the region showed varying degrees of statistically significant (P<0.0001, P<0.001, P<0.05) changes to absorption band areas and shifts in centroid positions of peaks. Alteration patterns were similar to those induced by benzo[a]pyrene in MCF-7 cells. These findings have potential health implications for resident local communities as H. bidorsalis constitutes a key nutritional source. The study provides supporting evidence for the sensitivity of infrared spectroscopy in environmental studies and supports their potential application in biomonitoring.

Aerobic metabolism and cardiac activity in the descendants of zebrafish exposed to pyrolytic polycyclic aromatic hydrocarbons

The increase of anthropogenic activities on coastal areas induces discharges of polycyclic aromatic hydrocarbons (PAHs) in aquatic ecosystem. PAH effects depend not only on their concentration and the way of contamination but also on the different developmental stages of the organism. Zebrafish were exposed to relevant concentration of pyrolytic PAHs from the first meal (i.e., 5-day post fertilization, dpf) to mature adults. Parental effect of this type of exposure was evaluated through the assessment of aerobic metabolic scope, cardiac frequency, and cardiac mRNA expression on larval and/or embryo progeny of contaminated fish. Our results suggest that cardiac frequency increased in larval descendants of fish exposed to the environmental concentration of pyrolytic PAHs (i.e., 5 ng.g(-1) of food), while a lack of effect on aerobic metabolism in 5 dpf larvae was highlighted. A surexpression of mRNA related to the cardiac calcium transporting ATPase atp2a2a, a protein essential for contraction, is in accordance with this increasing cardiac frequency. Even if cardiac development genes cmlc1 and tnnt2a were not affected at early life stages tested, complementary work on cardiac structure could be interesting to better understand PAHs action.

Novel sensor technologies towards environmental health monitoring in urban environments: a case study in the Niger Delta (Nigeria)

The Niger Delta (Nigeria) is an exemplar of a legacy of environmental pollution. Limited knowledge on spatial and temporal pollutant distributions in the region highlights the need for biomonitoring approaches to study impacts on sentinel organisms. This study evaluated whether infrared (IR) spectroscopy and multivariate analysis could detect alterations in biomolecules in samples in differing exposure scenarios, i.e., spatial and temporal using African catfish (Heterobranchus bidorsalis) or water spinach (Ipomea aquatica). Significant spectral differences between tissues isolated from African catfish based on site or season were observed; in a region where fish appeared not to be present, water spinach was used as a surrogate sentinel organism. Using one-way ANOVA, the spectral categories were significant (P < 0.0001). The applicability of IR spectroscopy to detect subtle changes in target biological molecules within sentinel organisms along with its low-cost yet high-throughput potential suggests that biospectroscopy permits real-time evaluation of environmental exposure effects.

Comparative study of 17 β-estradiol on endocrine disruption and biotransformation in fingerlings and juveniles of Japanese sea bass Lateolabrax japonicus

Estrogenic contaminants in the aquatic environment are associated with endocrine disruption and feminization in fish. The effects of endocrine disrupting chemicals (EDCs) on fish have been well documented. However, very few studies have focused on 17 β-estradiol (E2) and its effects on endocrine system and biotransformation in a single prolonged exposure. This study investigated changes in the levels of serotonin (5-hydroxytryptamine) and acetyl choline esterase (AchE) in brain, cortisol in plasma and Ethoxyresorufin-O-deethylase (EROD) activity in gill of two different size groups (fingerlings and juveniles) of Japanese sea bass (Lateolabrax japonicus) upon exposure to two sub-lethal concentrations (200 and 2000 ng L(-1)) of E2 for 30 d. The results indicate that cortisol level and EROD activity significantly increased in both groups, whereas serotonin level increased in juveniles and decreased in fingerlings due to E2 exposure. The correlation analysis revealed that E2 significantly affected the endocrine and biotransformation systems in both age groups.

Physiological effects of gasoline on the freshwater fish Prochilodus lineatus(Characiformes: Prochilodontidae)

The purpose of this work was to evaluate the effects of the water-soluble fraction of gasoline (WSFG) on the Neotropical freshwater fish Prochilodus lineatus. The WSFG was prepared by mixing gasoline in water (1:4) and animals were exposed for 6, 24 and 96h to 5% diluted WSFG or only to water. After exposure, blood was collected from the caudal vein and the gills were removed. The following parameters were analyzed: hematological (hemoglobin, hematocrit, number of red blood cells), osmo-ionic (plasma Na+, Cl- and K+ and plasma osmolarity), metabolic (total plasma proteins and glucose), endocrine (cortisol), density and distribution of chloride cells [CC] in the gills (immunohistochemistry), and branchial Na+/K+-ATPase (NKA) activity. Hemolysis was found to occur after 96h exposure to WSFG, as indicated by the decrease in the hematological parameters analyzed, followed by an increase in plasma K+. Secondary stress response was revealed by the occurrence of hyperglycemia in the three periods of exposure, despite the absence of significant increases in the plasma cortisol. The exposure to WSFG also caused an increase in the quantity of CC and in plasma Na+, after 24h, as well as in the enzymatic activity of NKA and plasma osmolarity, after 24h and 96h. These results indicate that fish exposed to the WSFG showed physiological adjusts to maintain their osmotic balance. However, the increase in the quantity of CC in the lamellae may interfere in the gas exchange impairing respiration.

Bile benzo[a]pyrene concentration and hepatic CYP1A induction in hypoxic adult tilapia (Oreochromis niloticus)

Aquatic hypoxia is a seasonal condition in some coastal and continental wetlands where co-exposure with polycyclic aromatic hydrocarbons (PAHs) pollution may be detrimental to the biota. In the present study, adult tilapia, an euryoxic fish of high economic importance, were intraperitoneally injected with benzo[a]pyrene (BaP) (20 mg kg(-1)) and then exposed to graded hypoxia to assess combined effects on some detoxification and fitness parameters. Seventy-two hours after a stepped decrease in dissolved oxygen (<2 mg L(-1)), BaP treatment resulted in a significant diminution on the biliary BaP concentration (70% of normoxic group) and an increase in blood glucose levels (2.17-fold compared with normoxic group). These effects returned to control values in the following 48 h of hypoxia exposure. BaP-induced CYP1A mRNA levels were unaffected by hypoxia, suggesting that reduced bile BaP concentration may be related with effects on protein amount or enzyme activities. LDH mRNA levels, blood lactate and hematocrit remained without change, suggesting no extreme detrimental effects for tilapia in the short-term of the BaP-hypoxia challenge. Our results indicate that BaP treatment and hypoxia targeted glucose metabolism and biliary BaP elimination, probably by favoring the storage of BaP in tilapia tissues.

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.

Temporal changes in stress and tissue-specific metabolic responses to municipal wastewater effluent exposure in rainbow trout

Sub-chronic exposure to municipal wastewater effluent (MWWE) in situ was recently shown to impact the acute response to a secondary stressor in rainbow trout (Oncorhynchus mykiss). However, little is known about whether MWWE exposure in itself is stressful to the animal. To address this, we carried out a laboratory study to examine the organismal and cellular stress responses and tissue-specific metabolic capacity in trout exposed to MWWE. Juvenile rainbow trout were exposed to 0, 20 and 90% MWWE (from a tertiary wastewater treatment plant), that was replenished every 2d, for 14 d. Fish were sampled 2, 8 or 14 d post-exposure. Plasma cortisol, glucose and lactate levels were measured as indicators of organismal stress response, while inducible heat shock protein 70 (hsp70), constitutive heat shock protein 70 (hsc70) and hsp90 expression in the liver were used as markers of cellular stress response. Impact of MWWE on cortisol signaling was ascertained by determining glucocorticoid receptor protein (GR) expression in the liver, brain and, heart, and metabolic capacity was evaluated by measuring liver glycogen content and tissue-specific activities of key enzymes in intermediary metabolism. Plasma glucose and lactate levels were unaffected by exposure to MWWEs, whereas cortisol showed a transient increase in the 20% group at 8d. Liver hsc70 and hsp90, but not hsp70 expression, were higher in the 90% MWWE group after 8d. There was a temporal change in GR expression in the liver and heart, but not brain of trout exposed to MWWE. Liver glycogen content and activities liver gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK), and alanine aminotransferase (AlaAT) were significantly affected by MWWE exposure. The glycolytic enzymes pyruvate kinase (PK) and hexokinase (HK) activities were significantly higher temporally by MWWE exposure in the gill and heart, but not in the liver and brain. Overall, a 14 d exposure to MWWE evokes a cellular stress response and perturbs the cortisol stress response in rainbow trout. The tissue-specific temporal changes in the metabolic capacity suggest enhanced energy demand in fish exposed to MWWE, which may eventually lead to reduced fitness.

Use of intestinal Pseudomonas aeruginosa in fish to detect the environmental pollutant benzo[a]pyrene

This study examined the potential of Pseudomonas aeruginosa abundance in the intestines of fish as an indicator of exposure to benzo[a]pyrene (BaP). P. aeruginosa populations were enumerated in juvenile African catfish (Clarias gariepinus) injected intramuscularly three days previous with 0, 10, 30, 40, 50 or 70mg/kg of BaP. Hepatic EROD and GST activities and biliary fluorescent aromatic compounds (FACs) 1-OH BaP, 3-OH BaP, 7,8-D BaP and BaP were quantified to investigate agreements between the new indicator and established fish biomarkers. The shape of bacterial population (logarithm of colony-forming unit) dose-response curve generally matched those of biliary FACs concentrations. Conversely, the EROD and GST dose-response curves were generally the mirror images of the bacterial population curve. Changes in intestinal P. aeruginosa population appear to be an indirect effect of BaP exposure because exposure to 0-100μg/ml BaP had no effect on P. aeruginosa populations grown on agar plates containing BaP. Using intestinal P. aeruginosa population of fish as a universal indicator of BaP pollution in aquatic environments is discussed.Conversely, the EROD and GST dose-response curves were generally the mirror images of the bacterial population curve.

Glucose metabolism in fish: a review

Teleost fishes represent a highly diverse group consisting of more than 20,000 species living across all aquatic environments. This group has significant economical, societal and environmental impacts, yet research efforts have concentrated primarily on salmonid and cyprinid species. This review examines carbohydrate/glucose metabolism and its regulation in these model species including the role of hormones and diet. Over the past decade, molecular tools have been used to address some of the downstream components of these processes and these are incorporated to better understand the roles played by carbohydrates and their regulatory paths. Glucose metabolism remains a contentious area as many fish species are traditionally considered glucose intolerant and, therefore, one might expect that the use and storage of glucose would be considered of minor importance. However, the actual picture is not so clear since the apparent intolerance of fish to carbohydrates is not evident in herbivorous and omnivorous species and even in carnivorous species, glucose is important for specific tissues and/or for specific activities. Thus, our aim is to up-date carbohydrate metabolism in fish, placing it to the context of these new experimental tools and its relationship to dietary intake. Finally, we suggest that new research directions ultimately will lead to a better understanding of these processes.

Tissue-specific metabolic changes in response to an acute handling disturbance in juvenile rainbow trout exposed to municipal wastewater effluent

The objective of this study was to evaluate the effects of municipal wastewater effluent (MWWE) exposure on aspects of both organismal and cellular stress response in rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout were exposed for 14 d (2-d static renewal) to tertiary-treated MWWE at concentrations of 0%, 20% and 90%. Following the MWWE exposure, fish were subjected to an acute handling stress and sampled at 1, 4 and 24 h post-stressor, to evaluate the fish performance to additional stressors. Organismal stress response evaluation included measuring plasma cortisol, glucose and lactate concentrations, and tissue metabolic capacity, including gluconeogenic (liver) and glycolytic enzyme activities in the liver, brain, heart and gill. No significant differences between treatments were seen in plasma cortisol, glucose or lactate concentrations after 14 d exposure to MWWE. However, MWWE exposure significantly affected plasma cortisol and glucose response to the acute secondary stressor. Acute handling disturbance enhanced liver gluconeogenic capacity in the control group, but this response was altered in the MWWE exposed groups. MWWE exposure did not affect the acute stressor-mediated enhancement of brain or gill glycolytic capacity, but significantly reduced the glycolytic capacity of liver and heart in response to a secondary stressor compared to the control group. Altogether, chronic exposure to MWWE impacts the metabolic performances to a secondary stressor challenge and this includes disruptions in tissue-specific gluconeogenic and glycolytic capacities in rainbow trout.

In vivo effects of the soluble fraction of light cycle oil on immune functions in the European sea bass, Dicentrarchus labrax (Linné)

Hydrocarbons are major contaminants that may affect biota at various trophic levels in estuaries and coastal ecosystems. The effects of accidental pollution by light cycle oil (LCO), a refined product of heavy fuel oil, on bioaccumulation, depuration processes and immune-related parameters in the European sea bass, Dicentrarchus labrax, were investigated in the laboratory after 7 days of exposure and a 2-week recovery period. Exposure of fish to the soluble fraction of LCO (1600ngL(-1)) for 7 days led to the bioaccumulation of some polycyclic aromatic hydrocarbons (PAHs) in muscles: naphthalene, acenaphthene, fluorene, phenanthrene and anthracene. After 7 days of recovery period, half-elimination of naphthalene was reported in fish muscles due to facilitated diffusive loss by the epithelium and a faster elimination rate proven by the presence of a high level of naphthalene biliary metabolites. The other bioaccumulated molecules displayed a slower depuration rate due to their elimination by the formation of hydrophobic metabolites excreted through bile or urine. Three days after the beginning of the recovery period, each contaminated fish showed severe external lesions (tissue necrosis, suppurative exudates, haemorrhagic area). The hypothesis of a possible link with inflammatory phenomenon was supported by (i) an inversion of the leucocyte sub-population percentage, (ii) a significant up-expression in the spleen of the tumour necrosis factor alpha gene, (iii) a significant increase in ACH(50). Moreover, the lack of C3 gene regulation in the spleen suggested a non-renewal of this component. The reduction of phagocytic activity and lysozyme concentration reflected immune suppression. Finally, LCO toxicity in this fish was clearly demonstrated to be related to inflammatory reaction and immune depletion.

Aroclor 1254 disrupts liver glycogen metabolism and enhances acute stressor-mediated glycogenolysis in rainbow trout

The objective of this study was to investigate the impact of short-term exposure to polychlorinated biphenyls on the acute stress response in rainbow trout. Fish were exposed to dietary Aroclor1254 (10mg kg(-1) body mass/day) for 3 days and then subjected to a 3-min handling disturbance and sampled over a 24h recovery after the stressor exposure. In the pre-stress fish, PCB exposure significantly elevated aryl hydrocarbon receptor (AhR) and cytochrome P4501A1 (Cyp1A1) mRNA abundance and Cyp1A protein expression confirming AhR activation. There was no significant effect of PCB on plasma cortisol and glucose levels, while plasma lactate levels were significantly elevated compared to the sham group. PCB exposure significantly elevated liver glycogen content and hexokinase activity, whereas lactate dehydrogenase activity was depressed. Short-term PCB exposure did not modify the acute stressor-induced plasma cortisol, glucose and lactate responses. Liver glycogen content dropped significantly after stressor exposure in the PCB group but not in the sham group. This was matched by a significantly higher liver LDH activity and a lower HK activity during recovery in the PCB group suggesting enhanced glycolytic capacity to fuel hepatic metabolism. Liver AhR, but not Cyp1A1, transcript levels were significantly reduced during recovery from handling stressor in the Aroclor fed fish. Collectively, this study demonstrates that short-term PCB exposure may impair the liver metabolic performance that is critical to cope with the enhanced energy demand associated with additional stressor exposure in rainbow trout.

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.

A proteomics based approach to assessing the toxicity of bisphenol A and diallyl phthalate to the abalone (Haliotis diversicolor supertexta)

The contamination of marine ecosystems by endocrine disrupting compounds (EDCs) is of great concern. Protein expression profile maybe a good method to help us understand the molecular mechanisms of EDCs-toxicity to aquatic organisms. In this study, the abalone (Haliotis diversicolor supertexta), was selected as the target organism. Toxicological effects of two reference endocrine disruptors: diallyl phthalate (DAP, 50microgL(-1)) and bisphenol-A (BPA, 100microgL(-1)) were investigated after a three months static-renewal exposure on abalones using proteomics to analyze their hepatopancreas tissues. Some enzyme activity parameters of hepatopancreas extracts were also performed, including Na(+)-K(+)-ATPase, Ca(2+)-Mg(2+)-ATPase, peroxidase (POD) and malondialdehyde (MDA) production. After analyzing the proteomics profile of hepatopancreas by 2D gel electrophoresis, we found that 24 spots significantly increased or decreased at protein expression level (2-fold difference) in the 2D-maps from the treatment groups. Eighteen out of 24 protein spots were successfully identified by matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF-MS). These proteins can be roughly categorized into diverse functional classes such as detoxification, oxidative stress, hormone regulating, cellular metabolism and innate immunity. In addition, the enzymatic results indicated that DAP/BPA exposure affected the oxidative stress status and the cellular homeostasis, which partly corroborated the proteomics' results. Taken together, these data demonstrate that proteomics is a powerful tool to provide valuable insights into possible mechanisms of toxicity of EDCs contaminants in aquatic species. Additionally, the results highlight the potential of abalone as a valuable candidate for investigating EDCs impacts on marine ecosystems.

Alterations in the brain monoaminergic neurotransmitters of rainbow trout related to naphthalene exposure at the beginning of vitellogenesis

The contents of dopamine (DA), noradrenaline (NA), serotonin (5HT), and some related metabolites were studied in different brain regions of rainbow trout at two different stages of sexual maturation (at the beginning of vitellogenesis), after naphthalene (NAP) administration. The effects of NAP varied according to duration of exposure, brain region and vitellogenesis stage of the trout, and were more significant during previtellogenesis. The changes observed in DA metabolism were generally stimulatory after exposure for 3 h, and either stimulatory or inhibitory (depending on the brain regions) after exposure for 3 days to NAP. NA levels were altered by NAP in various brain regions, but only during previtellogenesis. With respect to 5HT, treatment with NAP reduced levels of the amine and/or its main metabolite in most of the brain regions studied, particularly 3 h after treatment. The results suggest that NAP might interfere with the processes regulating brain monoamine metabolism, either locally or indirectly by altering steroid feedback to brain centres, and thus disrupt endocrine control of reproductive development through the brain-pituitary axis.

Physiological changes in reproductively active rainbowfish (Melanotaenia fluviatilis) following exposure to naphthalene

Naphthalene makes up a substantial fraction of polycyclic aromatic hydrocarbons (PAHs) in crude oil and is an important by-product of industry; however, few studies have investigated the toxicity of naphthalene to aquatic organisms. We examined the toxicity of increasing concentrations (0, carrier control, 130, 200 and 400microg/l) of naphthalene to adult rainbowfish (Melanotaenia fluviatilis) for 3 and 14 days to determine its potential to act as an endocrine disruptor. After exposure for 3 days, no changes in sex steroids were measured. After 14 days, a decrease of serum estradiol in females and an increase in serum testosterone in males was observed. These results suggest that naphthalene has the potential to act as an endocrine disruptor, although since no changes in plasma vitellogenin concentrations were observed in either sex, it is unlikely that naphthalene is acting as a xenoestrogen. There was a positive correlation between the incidences of deformities in larval offspring with increasing naphthalene concentrations, suggesting parental transfer of the toxicant. Egg production, hatchability and larval lengths remained unaltered, whilst few changes were measured in gamma-glutamyltranspeptidase (GTP), an enzymatic indicator of spermatogenesis. Contrary to other PAHs, hepatic ethoxyresorufin-O-deethylase (EROD) activities declined with increasing exposure concentration, suggesting that naphthalene was either having a cytotoxic effect or disrupting enzyme synthesis.

Effects of naphthalene, beta-naphthoflavone and benzo(a)pyrene on the diurnal and nocturnal indoleamine metabolism and melatonin content in the pineal organ of rainbow trout, Oncorhynchus mykiss

Polycyclic aromatic hydrocarbons (PAHs) have deleterious effects on neuroendocrine systems in teleost fish affecting, among other processes, reproductive function or stress responses. The hormone melatonin, mainly produced in the pineal organ of vertebrates, is involved in the regulation of biological rhythms as well as other important functions, and may also act as an antioxidant molecule. The effects of environmental pollutants on the endocrine and metabolic activity of the pineal organ have been studied only in mammals. We here evaluate the effects of the PAHs naphthalene (NAP) and benzo(a)pyrene (BaP) and the flavonoid beta-naphthoflavone (BNF) on the pineal organ of rainbow trout by quantifying the diurnal and nocturnal pineal content of some indoles and methoxyindoles, including melatonin. NAP mainly induced diurnal increases in the pineal content of melatonin and other methoxyindoles like 5-methoxytryptamine (5-MT), 5-methoxyindole-3-acetic acid (5-MIAA) or 5-methoxytryptophol (5-MTOL). Those increases did not occur at night, when even occasional decreases were observed compared with controls. NAP also induced some diurnal and nocturnal decreases in the levels of indolic compounds like serotonin (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA), while pineal content of 5-hydroxytryptophan (5-HTP) was first decreased (few hours after injection) and then increased (few days after injection) during the day. BaP and BNF induced strong increases in diurnal levels of melatonin, whereas other pineal compounds were unaffected. It seems that an increase of the methylation capacity of the pineal organ takes place during the day, and a decrease occurs at night. Those effects could be mediated by changes in the activity of key enzymes involved in pineal melatonin biosynthesis, maybe as a result of the alteration of the cellular phototransduction mechanisms involved in the light-induced inhibition of melatonin synthesis in the pineal photoreceptor cells. These results demonstrate for the first time that environmental pollutants can disrupt the activity of the pineal organ of teleost fish. This disruption could be a threat for the survival of the animals in their natural environment, although the increases observed in melatonin levels could play a relevant role as a toxicity-protection factor.

beta-Naphthoflavone and benzo(a)pyrene alter dopaminergic, noradrenergic, and serotonergic systems in brain and pituitary of rainbow trout (Oncorhynchus mykiss)

In the present study we evaluate for the first time the potential of the flavonoid compound beta-naphthoflavone (BNF) and the high molecular weight- Polycyclic aromatic hydrocarbon (PAH) benzo(a)pyrene (BaP) to alter brain neurotransmitter metabolism in fish. Fish of three different groups were intraperitoneally (i.p.) injected (2 microl g(-1)) with vegetable oil alone (control) or containing BNF or BaP (10 mg kg(-1)) and sacrificed 3, 24, and 72 h after treatment. Contents of dopamine (DA), noradrenaline (NA) and serotonin (5HT), as well as the amine oxidative metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole-3-acetic acid (5HIAA) were assayed in telencephalon, hypothalamus, preoptic region, optic tectum, and brain stem, as well as the pituitary. Fish treated with PAHs showed after 3h decreases in 5HT content in telencephalon, hypothalamus, preoptic region (with both BNF and BaP), and pituitary (with BaP), resulting in increased 5HIAA/5HT ratio. An increased ratio was also observed in hypothalamus 24h after BaP, and in preoptic region 72 h after BNF, in both cases due to an increased 5HIAA content. In other brain regions PAHs effects on 5-HT metabolism were less consistent. With respect to the dopaminergic system, changes induced by PAHs mainly occurred after 24 and 72 h of treatment, with increased DOPAC/DA ratio in preoptic region and brain stem. In hypothalamus, tectum, and pituitary, changes in DA metabolism showed strong variability. Finally, a decreased content of NA was evident in preoptic region (3h) and in telencephalon (24h) after both BNF and BaP treatments. Therefore, both BNF and BaP seem to act in rainbow trout brain by impairing 5HT availability at short term (3h) and increasing neuronal metabolic utilization of both 5HT and DA after 24 and 72 h. Data collected in the present study suggest that brain monoamine neurotransmitters are potential targets of BNF and BaP, and their alteration could have a role in known effects of PAHs on several neuroendocrine processes that are centrally regulated or modulated by brain monoamines.

Effects of diesel on survival, growth, and gene expression in rainbow trout (Oncorhynchus mykiss) fry

Diesel spills are all too frequent disturbances of freshwater ecosystems, largely as a result of the quantities transported and consumed. Assessing the risk that such events may pose to aquatic life remains a difficult process, because of the complexity of this hydrocarbon mixture and our limited knowledge of its toxicity. A diesel spike experiment with rainbow trout (Oncorhynchus mykiss) fry was carried out to fill this knowledge gap. Survival, growth, and gene expression changes were assessed and toxicity thresholds were determined. Whereas the biological end points were consistent in the determination of (sub)lethal doses, microarrays supplied additional information on the mechanism of toxicity (oxygen deprivation) and potential long-term effects (feminization, immune system alterations) of diesel exposure on salmonids. Hemoglobins, prostaglandins, cytochromes, and gluthathion-S-transferases were among the molecular biomarkers proposed for use in future risk assessments based on microarray results. By bridging traditional toxicity testing with recent microarray technologies, this study shows the potential of genomics tools in ecotoxicity studies as well as industrial applications, including risk assessment, in the near future.

Acute and prolonged stress responses of brain monoaminergic activity and plasma cortisol levels in rainbow trout are modified by PAHs (naphthalene, beta-naphthoflavone and benzo(a)pyrene) treatment

We have investigated if treatment with two different PAHs such as naphthalene (NAP) and benzo(a)pyrene (BaP), and the PAH-like compound beta-naphthoflavone (BNF), may modify the stress responses elicited in rainbow trout by acute or prolonged stress stimuli, and the possible involvement of brain monoamines in those responses. Two experiments (acute and prolonged stress) were performed. In the acute stress experiment, fish were i.p. injected with vegetable oil alone (control) or oil containing NAP, BNF or BaP (10 mg kg(-1)), and 72 h after injection fish were acutely stressed by chasing for 15 min. In the prolonged stress experiment, a similar group-design and injection protocol were followed, but fish were submitted to severe confinement stress by maintaining fish under high stock density (70 kg fish mass m(-3)) for 72 h. The levels of cortisol, glucose and lactate were assayed in plasma. In addition, the contents of dopamine (DA), noradrenaline (NA) and serotonin (5HT), as well as their oxidized amine metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxy-3-indoleacetic acid (5HIAA) were assayed in telencephalon, hypothalamus, preoptic region, optic tectum and brain stem, as well as the pituitary. Both acute and prolonged stress stimuli increased plasma levels of cortisol, which further increase with NAP and BNF treatments after acute stress. In contrast, cortisol levels of fish exposed to prolonged stress showed a clear tendency to decrease after the treatment with BNF and BaP. Stress stimuli also increased plasma glucose levels, which were not affected by PAHs in acute stressed fish but decreased in fish exposed to prolonged stress. Increased plasma levels of lactate in fish exposed to stress decreased after PAHs treatment in acute stress but not in prolonged stress. With respect to monoaminergic systems, major changes induced by both acute and prolonged stress were increases of the metabolites DOPAC and 5HIAA and DOPAC/DA or 5HIAA/5HT ratios in several brain regions. PAHs induced alterations in the normal responses of monoaminergic systems to stress, with dopaminergic system being the most affected after acute stress, and serotonergic system after prolonged stress. Those alterations, especially after prolonged stress, showed certain parallelism with alterations of plasma cortisol levels. Thus, results suggest that in stressed fish PAH effects on plasma cortisol levels (and its derived metabolic actions) could be in part mediated by alterations on the monoaminergic systems at the CNS of rainbow trout.

beta-Naphthoflavone and benzo(a)pyrene treatment affect liver intermediary metabolism and plasma cortisol levels in rainbow trout Oncorhynchus mykiss

To assess the effects of the polycyclic aromatic hydrocarbons (PAHs) beta-naphthoflavone (beta-NF) and benzo(a)pyrene (BaP) on liver intermediary metabolism and plasma steroid hormones, immature female rainbow trout (Oncorhynchus mykiss) were intraperitoneally injected (2 microl g(-1)) with vegetable oil alone (control) or containing beta-NF or BaP (10 mg kg(-1)) and returned to their tanks; 3, 24, and 72 h after injection, 11 fish were sampled from each group. On each sampling time, plasma hormone levels (cortisol and 17beta-estradiol) and metabolic parameters in plasma (glucose, lactate, and alpha-amino acid levels) and liver (glycogen, glucose, lactate, and alpha-amino acid levels, and HK, GK, PK, LDH, G6Pase, G6PDH, FBPase, GDH, Asp-AT, and HOAD activities) were assessed. Changes described for hormonal systems resulted in an increase in plasma levels of cortisol after 24 and 72 h of treatment with both PAHs whereas no changes were noticed for 17beta-estradiol levels. Changes in intermediary metabolism described effects in several pathways due to treatment with both PAHs. These changes can be summarized as increased glucose and lactate levels in plasma, and increased glycogenolysis and gluconeogenesis in liver after 24 and 72 h of treatment with both PAHs. Furthermore, beta-NF treatment stimulated amino acid catabolism in liver. These metabolic changes can be associated with increased levels of plasma cortisol, and suggest a different metabolic behavior depending on PAHs.