The dose-response relationships for EROD and GST induced by polyaromatic hydrocarbons in Carassius auratus

Metabolomics identified distinct molecular-level responses in Daphnia magna after exposure to phenanthrene and its oxygen and nitrogen containing analogs

The prevalence of polycyclic aromatic hydrocarbons and their oxygenated and nitrogen containing analogs in freshwater ecosystems are of concern due to their reported toxicity to several aquatic species including Daphnia magna. This study explored the molecular-level responses of phenanthrene (PHEN), 9,10-phenanthrenequinone (PHQ), and phenanthridine (PN) as little is known about the impacts of these pollutants on the metabolic profile of D. magna. For this purpose, D. magna was exposed to three sub-lethal concentrations of these pollutants for 24 h. To assess molecular-level responses, 52 polar metabolites were extracted from individual adult daphnids, and analyzed using a mass spectrometry-based targeted metabolomics approach. Exposure to PN resulted in the most statistically significant changes to the metabolic profile of D. magna followed by PHQ, and then PHEN exposures. After PN exposure, the biochemical pathway analysis showed that all exposure concentrations shared 21 perturbed metabolic pathways. However, the number of disrupted metabolic pathways increased with increasing exposure concentrations for PHEN and PHQ. The results suggest that PN and PHQ exposures are more disruptive due to the presence of reactive functional groups when compared to PHEN exposure. For the tested concentration ranges, the findings indicate that exposure to PN resulted in non-monotonic disruptions across exposure concentrations. In contrast, exposure to PHEN and PHQ elicited perturbations that were concentration-dependent. Although the reported median effective concentration (EC50) for PN is higher than PHEN and PHQ, our data shows that metabolomics captures molecular-level changes that may not be detected by traditional toxicity metrics.

Contaminated sediment in the Detroit River provokes acclimated responses in wild brown bullhead (Ameiurus nebulosus) populations

In a previous study, adaptive responses to a single polycyclic aromatic hydrocarbon (PAH), benzo[a]pyrene (BaP), were identified in brown bullhead (Ameiurus nebulosus) captured from contaminated sites across the Great Lakes. The tumor suppressor p53 and phase I toxin metabolizing CYP1A genes showed a elevated and refractory response, respectively, up to the F1 generation (Williams and Hubberstey, 2014). As an extension to the first study, bullhead were exposed to sediment collected from sites along the Detroit River to see if these adaptive responses are attainable when fish from a contaminated site are exposed to a mixture of contaminants, instead of a single compound. p53 and CYP1A proteins were measured again with the addition of phase II glutathione-s-transferase (GST) activity in the present study. Three treatment groups were measured: acute (treated immediately), cleared (depurated for three months and subsequent treatment), and farm raised F1 offspring. All three treatment groups were exposed to clean and contaminated sediment for 24 and 96 h. Acute fish from contaminated sites exposed to contaminated sediment revealed an initial elevated p53 response that did not persist in fish after long-term contaminated sediment exposure. Acute fish from contaminated sites exposed to contaminated sediment revealed refractory CYP1A expression, which disappeared in cleared fish and whose F1 response overlapped with clean site F1 offspring. Decreasing GST activity was evident in both clean and contaminated fish over time, and only clean site fish responded to long-term contaminated sediment deliberately with increasing GST activity. Because p53 and CYP1A gene expression and GST activity responses did not overlap between contaminated fish treatment groups, our study suggests that contaminated fish have acclimated to the contaminants present in their environments and no evidence of adaptation could be detected within these biomarkers.

Different effects of continuous and pulsed Benzo[a]pyrene exposure on metabolism and antioxidant defense of large yellow croaker: Depend on exposure duration

This study aims to compare differential effects of continuous and pulsed BaP exposures on metabolism and antioxidant defense in the liver of large yellow croaker. Fish were subjected to BaP for 4 days and 36 days in three exposure regimes with the same time-averaged concentration of BaP: 4 μg/L BaP continuously, 8 μg/L BaP for 24 h every other day or 16 μg/L BaP for 24 h every 4 days. Our results showed that compared to pulsed BaP exposures, continuous BaP exposure reduced BaP metabolism (CYP1A, CYP3A and AHR transcriptional expressions, GSH content, GSH/GSSG ratio, EROD and GST activities) and antioxidant defense (T-SOD activity) on day 4, resulting to the increases in MDA and PC contents, indicating that continuous BaP exposure induced more severe oxidative damage during the early stage of exposure. But continuous BaP exposure reduced MDA and PC contents by improving BaP metabolism and antioxidant defense during the late stage of exposure. CYP1B transcriptional expression and CAT activity were unsuitable biomarkers of both continuous and pulsed BaP exposures. In conclusion, our results demonstrated differential effects of continuous and pulsed exposures on BaP metabolism and antioxidant responses, which were depend on exposure duration.

Moderate acidification mitigates the toxic effects of phenanthrene on the mitten crab Eriocheir sinensis

Freshwater acidification and phenanthrene may result in complex adverse effects on aquatic animals. Juvenile Chinese mitten crabs (Eriocheir sinensis) were exposed to different pH levels (7.8, 6.5, and 5.5) under phenanthrene (PHE) (0 (control) and 50 μg/L) conditions for 14 days. Antioxidant and transcriptomic responses were determined under stress conditions to evaluate the physiological adaptation of crabs. Under the control pH 7.8, PHE led to significantly reduced activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione S-transferase (GST), but increased glutathione peroxidase (GSH-Px), 7-ethoxyresorufin-o-deethylase (EROD) activities, and malondialdehyde (MDA) levels. However, moderate acidification (pH 6.5) changed PHE effects by increasing antioxidant enzymes. Acidification generally reduced SOD, GPx, GST and EROD activities, but increased CAT, GR, MDA. Compared with pH7.8 group, pH7.8 × PHE and pH6.5 × PHE groups had 1148 and 1498 differentially expressed genes, respectively, with "Biological process" being the main category in the two experimental groups. pH7.8 × PHE treatment caused significant enrichment of disease and immune-related pathways, while under pH6.5 × PHE, more pathways related to metabolism, detoxification, environmental information processing, and energy supply were significantly enriched. Thus, PHE had a significant inhibitory effect on antioxidant performance in crabs, while moderate acidification (pH6.5) mitigated the toxic effects of PHE. Overall, moderate acidification has a positive effect on the defense against the negative effects of PHE in Chinese mitten crabs, and this study provides insights into the defense mechanism of crustaceans in response to combined stress of acidification and PHE.

Long-Term Exposure to Phenanthrene Induced Gene Expressions and Enzyme Activities of Cyprinus carpio below the Safe Concentration

Phenanthrene (PHE) is a typical compound biomagnified in the food chain which endangers human health and generally accumulates from marine life. It has been listed as one of the 16 priority PAHs evaluated in toxicology. In order to evaluate the changes of CYP1A GST mRNA expression and EROD GST enzyme activity in carp exposed to lower than safe concentrations of PHE. Long-term exposure of carp to PHE at lower than safe concentrations for up to 25 days. The mRNA expression level and cytochrome P450 (CYP1A/EROD (7-Ethoxylesorufin O-deethylase)) and glutathione S-transferase (GST) activity were measured in carp liver and brain tissue. The results showed that PHE stress induced low-concentration induction and high-concentration inhibition of CYP1A expression and EROD enzyme activity in the liver and brain of carp. In both two organs, GST enzyme activity was also induced. However, the expression of GST mRNA was first induced and then inhibited, after the 15th day. These results indicate that long-term exposure to PHE at lower than safe concentrations still poses a potential threat to carp’s oxidase system and gene expression.

Gene expression analysis on growth, development and toxicity pathways of male Nile tilapia (Oreochromis niloticus), after acute and sub-chronic benzo (α) pyrene exposures

Benzo[α]pyrene (BaP), a lipophilic polycyclic aromatic hydrocarbon (PAH), is a contaminant widely distributed in aquatic systems. Its presence in freshwater organisms is of great concern; particularly in Nile tilapia (Oreochromis niloticus), due to its economic relevance. The aim of this study is to evaluate the effects of acute and sub-chronic BaP exposures on molecular growth/development responses, toxicity to DNA pathways and xenobiotic metabolism. Negative morphometric changes (the growth condition factor, hepatosomatic and gonadosomatic indices), the fluorescent aromatic compounds (FACs) in bile were also studied in order to understand the mechanisms of action of BaP. Genes involved in the growth hormone GH/insulin-like growth factor 1 (IGF-1) were measured, such as IGF1-2 with the growth hormone receptor gene expression GHR1-2, and the endocrine disruption biomarker vitellogenin (VTG). Acute exposure elicited changes in the GH/IGF axis, mainly in the GHR1 and in IGF1 mRNA levels without affecting the GHR2 expression. While sub-chronic exposure had less effect on both GHR and IGF genes. The most notable tissue-specific effects and morphometric endpoints were observed upon sub-chronic exposure, such as changes in key genes involved in detoxification, DNA damage, and altered reproductive morphological endpoints; showing that sub-chronic BaP doses have longer-lasting toxic effects. This study shows that sub-chronic BaP exposure may compromise the health of Nile tilapia and sheds light on the changes of the GH/IGF axis and the biotransformation of the xenobiotics due to the presence of this contaminant.

Effects of polycyclic aromatic hydrocarbons on biomarker responses in Gambusia yucatana, an endemic fish from Yucatán Peninsula, Mexico

Polycyclic aromatic hydrocarbons (PAHs) are petroleum components that, when dissolved in the aquatic environment, can disrupt normal animal physiological functions and negatively affect species populations. Gambusia yucatana is an endemic fish of the Yucatán Peninsula that seems to be particularly sensitive to the presence of PAHs dissolved in the water. Here, we examined PAH effects on gene expressions linked to endocrine disruption and biotransformation in this species. Specifically, we examined the expression of vitellogenin I (vtg1), vitellogenin II (vtg2), oestrogen receptor α (esr1), oestrogen receptor β (esr2), aryl hydrocarbon receptor (AhR) and the cytochrome P4503A (CYP3A) genes. We exposed G. yucatana to different concentrations of PAHs (3.89, 9.27, 19.51 μg/L) over a period of 72 h and found changes associated with reproduction, such as increases in hepatic expression of vtg, esr, AhR and CYP3A, mainly at concentrations of 9.27 and 19.51 μg/L. Our results also indicate that benzo[a]pyrene was probably the main PAH responsible for the observed effects. The genes examined here can be used as molecular markers of endocrine-disrupting compounds, as the PAHs, present in the environment, as gene expression increases could be observed as early as after 24 h. These biomarkers can help researchers and conservationists rapidly identify the impacts of oil spills and improve mitigation before the detrimental effects of environmental stressors become irreversible.

In vitro effects of bisphenol F on antioxidant system indicators in the isolated hepatocytes of rainbow trout (Oncorhyncus mykiss)

Bisphenol F (BPF) has been used frequently in the plastics industry and the production of daily consumer products as an alternative to bisphenol A (BPA). It was aimed herein to determine the cytotoxic effects of BPF on hepatocytes isolated from the liver of rainbow trout (Oncorhyncus mykiss) using lactate dehydrogenase (LDH) assay and antioxidant defence system indicators. The cultured hepatocytes were exposed to seven concentrations (0, 15.63, 31.25, 62.50, 125, 250, and 500 µM) of BPF for 24 h. According to the LDH assay, the percentage of cytotoxicity was increased dose dependently in the cells. The malondialdehyde content, which is indicative of lipid peroxidation, was increased significantly at BPF concentrations between 15.63 and 250 µM, whereas it remained unchanged with a concentration of 500 µM. The activities of superoxide dismutase were increased, while those of catalase were decreased with all of the BPF concentrations. Elevated levels of reduced glutathione content were determined with BPF concentrations between 15.63 and 250 µM, but decreased significantly with a concentration of 500 µM. Significant increases in the activities of the glutathione peroxidase were found in hepatocytes treated with BPF at concentrations of 31.25 to 500 µM. GST activity was only significantly increased with a BPF concentration of 250 µM. The results showed that the toxic mechanism of BPF was mainly based on cell membrane damage and oxidative stress, which have an influence on antioxidant defences. Therefore, BPF should be reconsidered as a safe alternative instead of BPA in the manufacturing of industrial or daily products.

Toxicity of Weathered Sediment-Bound Dilbit to Early Life Stages of Zebrafish (Danio rerio)

Due to high viscosity, bitumen extracted from the Alberta oil sands is diluted with natural gas condensates to form diluted bitumen (dilbit) to facilitate transport through pipelines. Dilbit that is spilled into or near a waterbody is subject to environmental weathering processes such as evaporation and interaction with sediments. This is the first study that assessed the toxicity of weathered sediment-bound dilbit (WSD) to fish early life stages. Exposure of zebrafish (Danio rerio) embryos to water-soluble fractions (WSFs) or water-accommodated fractions (WAFs) of WSD from 30 min to 120 h postfertilization resulted in pericardial edema, yolk sac edema, and incidences of uninflated swim bladder. The presence of oil-mineral aggregates (OMAs) in the WAFs greatly increased toxicity, despite all fractions having similar concentrations of dissolved polycyclic aromatic hydrocarbons (PAHs). There were greater cyp1a mRNA abundances in larvae exposed to WAFs, suggesting that there were differences in bioavailability of PAHs between fractions. However, there was little evidence that embryotoxicity was caused by oxidative stress. Results suggest that evaporation and sediment interaction do not completely attenuate toxicity of dilbit to zebrafish early life stages, and OMAs in exposures exacerbate toxicity.

Biliary polycyclic aromatic hydrocarbons and enzymatic biomarkers in Eugerres brasilianus along four tropical estuaries

Polycyclic aromatic hydrocarbons (PAH) in bile and biochemical biomarkers were evaluated in Brazilian mojarra Eugerres brasilianus along four estuaries in northeastern Brazil. Bile PAHs naphthalene, phenanthrene chrysene, pyrene and benzo[a]pyrene were lowest at Formoso River Estuarine System (FRES), an area with low population density focused on tourism. Fish sampled in Suape Estuarine Complex (SEC), where a growing industrial port complex is established indicated higher naphthalene and pyrene concentrations compared with FRES. Fish sampled in highly urbanized and populated Bacia do Pina Estuarine Complex (BPEC) and Barra de Jangada Estuarine System (BJES) indicated an increase in all PAHs compared to FRES. Activities of phase 1 Ethoxyresorufin-O-deethylase, phase 2 glutathione-S-transferase and antioxidant defense catalase were induced up to 20, 2 and 2-fold in BJES and BPEC compared to FRES. This study confirms E. brasilianus as an important sentinel species, providing baseline information for these tropical estuaries with different degrees of anthropogenic pressure.

Biotransformation in the fish Prochilodus lineatus: An organ-specific approach to cyp1a gene expression and biochemical activity

The biotransformation ability of the organism is the result of organ-specific responses. This paper presents a molecular and biochemical approach to elucidate the biotransformation mechanisms in different organs of Prochilodus lineatus induced at 6, 24, and 96 h after a benzo[a]pyrene (B[a]P) injection. The induction in cyp1a transcription showed an organ-specific intensity at every tested time time. The EROD (ethoxyresorufin-O-deethylase) activity increased rapidly (6 h) in the liver and the kidney; the gills and the brain showed an increase at 24 h; and the gills demonstrated the highest activity among all the organs tested. There was no increase in glutathione S-transferase (GST) activity or lipoperoxidation. The decreased hepatic glutathione content (GSH) may be due to its role as an antioxidant. B[a]P was detected in the bile, confirming the xenobiotic efflux from the metabolizing organs. The gills, liver, brain, and kidney of P. lineatus presented an integrated mechanism to deal with the xenobiotic biotransformation.

Differential responses in the biotransformation systems of the oyster Crassostrea gigas (Thunberg, 1789) elicited by pyrene and fluorene: Molecular, biochemical and histological approach - Part II

Pyrene (PYR) and fluorene (FLU) are among the sixteen priority Polycyclic Aromatic Hydrocarbons (PAH) of the United States Environmental Protection Agency and are both frequently detected in contaminated sites. Due to the importance of bivalve mollusks in biomonitoring programs and the scarce information on the biotransformation system in these organisms, the aim of this study was to investigate the effect of PYR and FLU at the transcriptional level and the enzymatic activities of some biotransformation systems in the Pacific oyster Crassostrea gigas, and to evaluate the histological effects in their soft tissues. Oysters C. gigas were exposed for 24 h and 96 h to PYR (0.25 and 0.5 μM) and FLU (0.6 and 1.2 μM). After exposure, transcript levels of cytochrome P450 coding genes (CYP1-like, CYP2-like, CYP2AU2, CYP356A1, CYP17α-like), glutathione S tranferase genes (omega GSTO-like and microsomal, MGST-like) and sulfotransferase gene (SULT-like), and the activity of ethoxyresorufin O-deethylase (EROD), Glutathione S-transferase (GST) and microssomal GST (MGST) were evaluated in gills. Histologic changes were also evaluated after the exposure period. PYR and FLU bioconcentrated in oyster soft tissues. The half-life time of PYR in water was lower than fluorene, which is in accordance to the higher lipophilicity and bioconcentration of the former. EROD activity was below the limit of detection in all oysters exposed for 96 h to PYR and FLU. The reproductive stage of the oysters exposed to PYR was post-spawn. Exposure to PYR caused tubular atrophy in digestive diverticula, but had no effect on transcript levels of biotransformation genes. However, the organisms exposed for 96 h to PYR 0.5 μM showed higher MGST activity, suggesting a protective role against oxidative stress in gills of oysters under higher levels of PYR in the tissues. Increased number of mucous cells in mantle were observed in oysters exposed to the higher FLU concentration, suggesting a defense mechanisms. Oysters exposed for 24 h to FLU 1.2 μM were in the ripe stage of gonadal development and showed higher transcript levels of CYP2AU2, GSTO-like and SULT-like genes, suggesting a role in the FLU biotransformation. In addition, after 96 h of exposure to FLU there was a significant increase of mucous cells in the mantle of oysters but no effect was observed on the EROD, total GST and MGST activities. These results suggest that PAH have different effects on transcript levels of biotransformation genes and enzyme activities, however these differences could also be related to the reproductive stage.

24-Epibrassinolide protects against ethanol-induced behavioural teratogenesis in zebrafish embryo

Embryonic studies have demonstrated the neurotoxic, teratogenic, and neurobehavioral toxicity of ethanol (EtOH). Although multiple mechanisms may contribute to these effects, oxidative stress has been described as the major damage pathway. In this regard, natural antioxidants have the potential to counteract oxidative stress-induced cellular damage. Therefore, the present study aimed to investigate the potential protective role of 24-epibrassinolide (24-EPI), a natural brassinosteroid with proved antioxidant properties, in EtOH-induced teratogenic effects during early zebrafish development. Embryos (~2 h post-fertilization - hpf) were exposed to 1 % EtOH, co-exposed to 24-EPI (0.01, 0.1 and 1 μM) and to 24-EPI alone (1 μM) for 24 h. Following exposure, biochemical evaluations were made at 26 hpf, developmental analysis was made throughout the embryo-larval period, and behavioural responses were evaluated at 120 hpf. Exposure to 1 % EtOH caused an increase in the number of malformations, which were diminished by 24-EPI. In addition, EtOH induced an accumulation of GSSG and consequent reduction of GSH:GSSG ratio, indicating the involvement of oxidative mechanisms in the EtOH-induced effects. These were reverted by 24-EPI as proved by the GSSG levels and GSH:GSSG ratio that returned to control values. Furthermore, exposure to EtOH resulted in behavioural deficits at 120 hpf as observed by the disrupted response to an aversive stimulus, suggesting the involvement of neurotoxic mechanisms. 24-EPI restored the behavioural deficits observed in a dose-dependent manner. The absence of effects in the embryos exposed solely to 24-EPI showed its safety during the exposure period. In conclusion, EtOH caused developmental teratogenicity and behavioural toxicity by inducing glutathione changes, which were prevented by 24-EPI.

Biomarker Effects in Carassius auratus Exposure to Ofloxacin, Sulfamethoxazole and Ibuprofen

Ofloxacin, sulfamethoxazole and ibuprofen are three commonly used drugs which can be detected in aquatic environments. To assess their ecotoxicity, the effects of these three pharmaceuticals and their mixture on AChE (acetylcholinesterase) activity in the brain, and EROD (7-ethoxyresorufin-O-deethylase) and SOD (superoxide dismutase) activities in the liver of the freshwater crucian carp Carassius auratus were tested after exposure for 1, 2, 4 and 7 days. The results showed that treatments with 0.002–0.01 mg/L ofloxacin and 0.0008–0.004 mg/L sulfamethoxazole did not significantly change AChE, EROD and SOD activities. AChE activity was significantly inhibited in response to treatment with >0.05mg/L ofloxacin and >0.02 mg/L sulfamethoxazole. All three biomarkers were induced significantly in treatments with ibuprofen and the mixture of the three pharmaceuticals at all the tested concentrations. The combined effects of ofloxacin, sulfamethoxazole and ibuprofen were compared with their isolated effects on the three biomarkers, and the results indicated that exposure to ibuprofen and the mixture at environmentally relevant concentrations could trigger adverse impacts on Carassius auratus. The hazard quotient (HQ) index also demonstrated a high risk for ibuprofen. Moreover, the present study showed that the effects of ofloxacin, sulfamethoxazole and ibuprofen might be additive on the physiological indices of Carassius auratus.

Effects of dietary fluoranthene on nymphs of Blaptica dubia S. (Blattodea: Blaberidae)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants which exert detrimental effects on living beings. Considering the health risk associated with exposure to these pollutants, their presence in food increases efforts to establish early-warning indicators of pollution. We aimed to examine the effects of environmentally relevant concentrations of fluoranthene (0.2 ng and 18 ng/g dry weight of diet) on the activities of midgut antioxidant and detoxification enzymes in Blaptica dubia. Significant changes of superoxide dismutase and catalase activities, recorded at the higher fluoranthene concentration regardless of the exposure time, suggest that they may be used as biomarkers of PAH pollution. Increased GST activity and decreased total GSH content, detected upon acute exposure to the lower concentration, indicate processes of detoxification. Reorganization of B. dubia mechanisms of defense in response to oxidative stress caused by exposure to dietary PAH point to the necessity for further examination of fluoranthene actions.

Responses of antioxidant and biotransformation enzymes in Carassius carassius exposed to hexabromocyclododecane

The ubiquitous existence of hexabromocyclododecane (HBCD) in environmental matrices has made it attractive to both field investigators as well as laboratory researchers. However, literature on the biological effects caused by HBCD on aquatic vertebrates seldom exist. This has inevitably increased the difficulty of toxicological assessment in the aquatic environment. Juvenile crucian carp (Carassius carassius) were exposed (flow-through) to different concentrations of technical HBCD (nominal 2, 20, 200 μg L^-1) for 7 days to determine the responses of antioxidant and biotransformation enzymes. HBCD was found to be increasingly bioconcentrated in the fish livers as time proceeds. Also, the contribution of α-HBCD exhibited an enhancement from 13% in the exposure solutions to 24% in crucian carp, still much lower than in wild fishes (ca. 80%). HBCD induced activities of antioxidant enzymes in most cases, as well as increased level of lipid peroxidation. In contrast to the weak response of 7-ethoxyresorufin-O-deethylase (EROD), 7-pentoxyresorufin-O-depentylase (PROD) activity was generally induced in a time-dependent manner with peaks at day 2. Phase II enzyme Glutathione-S-transferase (GST) showed a dose-dependent induction with maximums in the 20 μg L^-1 treatment at all the four timepoints of 1, 2, 4 and 7 days. Some enzymatic responses showed good associations, indicating coordinated functions. To sum up, tHBCD exposure in the present circumstance had produced an ecological stress to crucian carp. The low levels of biotransformation and slow rates of bioisomerization suggest a possible long-term toxic effect, especially around HBCD point sources.

Reuse water: Exposure duration, seasonality and treatment affect tissue responses in a model fish

Partially remediated gray (reuse) water will likely find increasing use in a variety of applications owing to the increasing scarcity of freshwater. We aimed to determine if a model fish, the goldfish, could sense reuse water using olfaction (smell), and if 30min or 7d (acute) and 60d (sub-chronic) exposures would affect their olfactory responses to natural odorants. We examined olfaction as previous studies have found that numerous chemicals can impair the olfactory sense, which is critical to carrying out numerous life-sustaining behaviors from feeding to mating. We also examined if fish olfactory and liver tissues would mount a response in terms of biotransformation enzyme gene expression, and whether treatment of reuse water with UV/H₂O₂ ameliorated adverse effects following reuse water exposure. We found that fish olfactory tissue responded to reuse water as it would to a natural odorant and that UV/H₂O₂ treatment had no influence on this. With acute exposures, olfactory impairment was apparent regardless of water type (e.g. responses of 23-55% of control), but in sub-chronic exposures, only the untreated reuse water caused olfactory impairment. The exposure of fish to reuse water increased the expression of one enzyme (CYP1A; >2.5-6.5 fold change) and reuse water treatment with UV/H₂O₂ reversed the effect. There was a seasonal effect that was likely due to changes in water quality (60d summer exposure impaired olfaction whereas spring and fall exposures did not). Overall, the data suggest that reuse water may be detected by olfaction, impair olfactory responses in fish receiving unavoidable exposures, and that exposure duration and season are important factors to consider regarding adverse effects.

Biomarkers and bioindicators of the environmental condition using a fish species (Pimelodus maculatus Lacepède, 1803) in a tropical reservoir in Southeastern Brazil

Abstract The Funil Reservoir receives a large amount of xenobiotics from the Paraíba do Sul River (PSR) from large number of industries and municipalities in the watershed. This study aimed to assess environmental quality along the longitudinal profile of the Paraíba do Sul River–Funil Reservoir system, by using biomarkers and bioindicators in a selected fish species. The raised hypothesis is that Funil Reservoir acts as a filter for the xenobiotics of the PSR waters, improving river water quality downstream the dam. Two biomarkers, the ethoxyresorufin–O–deethylase activity (EROD), measured as fluorimetricly in S9 hepatic fraction, and the micronuclei frequency (MN), observed in erythrocytes of the cytoplasm, and three bioindicators, the hepatosomatic index (HSI), gonadosomatic index (GSI) and condition factor (CF) were used in Pimelodus maculatus, a fish species widely distributed in the system. Four zones were searched through a longitudinal gradient: 1, river upstream from the reservoir; 2, upper reservoir; 3, lower reservoir; 4, river downstream of the reservoir. EROD activity and HSI and GSI had significant differences among the zones (P<0.05). The upper reservoir had the lowest EROD activity and HSI, whereas the river downstream of the reservoir had the highest EROD and lowest GSI. The river upstream from the reservoir showed the highest HSI and GSI. It is suggested that the lowest environmental condition occur at the river downstream of the reservoir, where it seems to occur more influence of xenobiotics, which could be associated with hydroelectric plant operation. The hypothesis that Funil reservoir acts as a filter decanting pollution from the Paraíba do Sul River waters was rejected. These results are novel information on this subject for a native fish species and could be useful for future comparisons with other environments.

Ras oncogene and Hypoxia-inducible factor-1 alpha (hif-1α) expression in the Amazon fish Colossoma macropomum (Cuvier, 1818) exposed to benzo[a]pyrene

Benzo[a]pyrene (B[a]P) is a petroleum derivative capable of inducing cancer in human and animals. In this work, under laboratory conditions, we analyzed the responses of Colossoma macropomum to B[a]P acute exposure through intraperitoneal injection of four different B[a]P concentrations (4, 8, 16 and 32 μmol/kg) or corn oil (control group). We analyzed expression of the ras oncogene and the Hypoxia-inducible factor-1 alpha (hif-1α) gene using quantitative real-time PCR. Additionally, liver histopathological changes and genotoxic effects were evaluated through the comet assay. Ras oncogene was overexpressed in fish exposed to 4, 8 of 16 μmol/kg B[a]P, showing 4.96, 7.10 and 6.78-fold increases, respectively. Overexpression also occurred in hif-1α in fish injected with 4 and 8 μmol/kg B[a]P, showing 8.82 and 4.64-fold increases, respectively. Histopathological damage in fish liver was classified as irreparable in fish exposed to 8, 16 and 32 μmol/kg μM B[a]P. The genotoxic damage increased in fish injected with 8 and 16 μmol/kg in comparison with the control group. Acute exposure of B[a]P was capable to interrupt the expression of ras oncogene and hif-1α, and increase DNA breaks due to tissue damage.

Modulation of erythromycin-induced biochemical responses in crucian carp by ketoconazole

The individual and combined biochemical responses of erythromycin and ketoconazole have been examined in an organism representative of the aquatic environment, crucian carp (Carassius auratus). The possible interactions between erythromycin and ketoconazole were investigated on the bioaccumulation and the expression of biotransformation enzymes 7-ethoxyresorufin-O-deethylase (EROD) and glutathione S-transferase (GST), and an antioxidant defense enzyme superoxide dismutase (SOD) in fish tissues. After 14 days of combined exposure (erythromycin + ketoconazole), the addition of ketoconazole at nominal concentrations of 0.2, 2, and 20 μg/L significantly increased the accumulation of erythromycin in fish bile; however, elevated erythromycin accumulation levels were not observed in the other test tissues. The inductions of EROD and SOD activity to erythromycin were inhibited by the combined exposure of ketoconazole in most cases; however, the GST activity returned to normal with exposure time and concentration of combined administration. From the tested pharmaceutical mixtures, it indicated that certain specific combinations may pose some perturbations in biochemical responses in fish and also provide a better understanding of the effects of toxic mixtures.

In vivo and in vitro effects of tunnel wash water and traffic related contaminants on aquatic organisms

In order to maintain the construction and safety of road tunnels, they are routinely washed. The wash water appears to be highly polluted with a plethora of contaminants in elevated concentrations. In addition, new and emerging compounds are likely to occur. The discharge water has shown acute toxic and sub-lethal effects in several organisms. In this study, ecotoxicity tests with algae (Pseudokirchneriella subcapitata) and in vitro tests with primary rainbow trout (Oncorhynchus mykiss) hepatocytes were used to characterize the effect of TWW from three different tunnels. In addition, selected N- and Cl-PAHs were tested for cytotoxicity, EROD activity and CYP1A protein production. TWW samples and/or extracts from two tunnels reduced the algal growth and induced cytotoxicity, EROD activity and CYP1A protein production in vitro. Four of the eight tested Cl- and N-substituted PAHs induced EROD activity and CYP1A protein production at micro-molar concentrations. N-PAHs were detected in samples from the tunnel wash, highlighting substituted PAHs as potentially important traffic-related contaminants.

Alterations in histology and antioxidant defense system in the testes of the lake Van fish (Alburnus tarichi Güldenstädt, 1814)

Recent reports have demonstrated gonadal abnormalities in the Lake Van fish (Alburnus tarichi) from Lake Van caused by increasing pollution. In the present study, the fish was collected from an area of Lake Van receiving mainly sewage treatment plant effluent at prespawning period (April) and from a river (Karasu) which is close to the polluted area of the lake and where the fish migrates at spawning period (May). Collected specimens were examined for testicular alterations, gonadosomatic index (GSI), condition factor (CF), and antioxidant defense system biomarkers based on comparison with a reference lake (Erçek) and a reference freshwater inlet (Memedik River). Histological examinations of the testes of fish from the polluted area and the connected river showed various alterations consisting of macrophage aggregates, vacuolation, pyknosis, germ cell degeneration, seminiferous tubule dilation, disorganization of tubules, reduced spermatozoa, and fibrosis. A lower GSI and CF were also observed. Moreover, alterations in the antioxidant system biomarkers were determined in the testis tissues of fish from the Lake Van and Karasu River, indicating oxidative stress. These results suggest that the abnormalities in the testes are causally related to the increased oxidative stress, and pollution in Lake Van may have adversely affected the reproductive health of the lake Van fish.

Bioconcentration and metabolism of ketoconazole and effects on multi-biomarkers in crucian carp (Carassius auratus)

The tissue distribution, bioconcentration, metabolism and biological effects of the antifungal medication ketoconazole were investigated in fish, crucian carp (Carassius auratus) were exposed to a series of nominal concentrations (0.2, 2 and 20 μg/L) for 14 days. The ultra-high performance liquid chromatography tandem triple quadrupole mass spectroscopy (UPLC/MS/MS) analysis was used to determine the bioconcentration of ketoconazole and its metabolites in fish. The highest tissue concentration of ketoconazole was observed in the liver with the bioconcentration factor of 257.2, which is lower than the estimated BCF value. The ability of crucian carp to metabolize ketoconazole was confirmed and the results pointed out the existence of seven metabolites likely formed via oxidation of imidazole ring and the metabolic alteration of the piperazine rings. In addition, acetylcholinesterase, 7-ethoxyresorufin O-deethylase, superoxide dismutase and glutathione S-transferase changed significantly after 3, 7 and 14 days of exposure (P < 0.05), which indicated that the accumulation and metabolism of ketoconazole in fish tissues may account for the biological effects.

Modulation of 17β-estradiol induced estrogenic responses in male goldfish (Carassius auratus) by benzo[a]pyrene and ketoconazole

The aquatic environment is challenged with complex mixtures of chemicals that may interact biochemically with each other in non-target aquatic organisms through a combination of actions, resulting in unpredictable mixture toxicity. This study focuses on the interactive effects of chemicals, including benzo(a)pyrene (BaP) and ketoconazole (KCZ), on 17β-estradiol (E2)-induced estrogenic responses in male goldfish (Carassius auratus). The possible interactions between BaP or KCZ and E2 were investigated on the expression of cytochromeP4501A (CYP1A, biotransformation enzyme) and on its corresponding catalytic activity 7-ethoxyresorufin-O-deethylase (EROD activity), as well as on the expression of CYP19 (steroidogenic enzyme) and E2 bioaccumulation in liver. Exposure to E2 caused a significant increase in estrogenic responses corresponding with the E2 bioaccumulation. When comparing results to the E2 exposure group, co-exposure to BaP resulted in an increase in the cyp1a mRNA expression and its corresponding EROD activity and a marked decrease in the E2 bioaccumulation, but the expression of aromatase was not altered. Conversely, co-treatment with KCZ significantly suppressed the E2-modulated expression of metabolism and synthesis enzymes, which were accompanied by an increase in the E2 bioaccumulation. These data suggest that the modulation of E2-induced estrogenic responses by BaP and KCZ were correlated to the alterations of E2 bioaccumulation in goldfish, leading to a combination of changes in the capacity of biotransformation and steroidogenesis. The complex interactions between chemicals with different modes of actions highlight the need for caution in determining the safety of combined pollution in the aquatic environment.

Application of molecular endpoints in early life stage salmonid environmental biomonitoring

Molecular endpoints can enhance existing whole animal bioassays by more fully characterizing the biological impacts of aquatic pollutants. Laboratory and field studies were used to examine the utility of adopting molecular endpoints for a well-developed in situ early life stage (eyed embryo to onset of swim-up fry) salmonid bioassay to improve diagnostic assessments of water quality in the field. Coastal cutthroat trout (Oncorhynchus clarki clarki) were exposed in the laboratory to the model metal (zinc, 40μg/L) and the polycyclic aromatic hydrocarbon (pyrene, 100μg/L) in water to examine the resulting early life stage salmonid responses. In situ field exposures and bioassays were conducted in parallel to evaluate the water quality of three urban streams in British Columbia (two sites with anthropogenic inputs and one reference site). The endpoints measured in swim-up fry included survival, deformities, growth (weight and length), vitellogenin (vtg) and metallothionein (Mt) protein levels, and hepatic gene expression (e.g., metallothioneins [mta and mtb], endocrine biomarkers [vtg and estrogen receptors, esr] and xenobiotic-metabolizing enzymes [cytochrome P450 1A3, cyp1a3 and glutathione transferases, gstk]). No effects were observed in the zinc treatment, however exposure of swim-up fry to pyrene resulted in decreased survival, deformities and increased estrogen receptor alpha (er1) mRNA levels. In the field exposures, xenobiotic-metabolizing enzymes (cyp1a3, gstk) and zinc transporter (zntBigM103) mRNA were significantly increased in swim-up fry deployed at the sites with more anthropogenic inputs compared to the reference site. Cluster analysis revealed that gene expression profiles in individuals from the streams receiving anthropogenic inputs were more similar to each other than to the reference site. Collectively, the results obtained in this study suggest that molecular endpoints may be useful, and potentially more sensitive, indicators of site-specific contamination in real-world, complex exposure scenarios in addition to whole body morphometric and physiological measures.

Relation between increased oxidative stress and histological abnormalities in the ovaries of Alburnus tarichi in Lake Van, Turkey

Recent studies have shown reproductively arrested gonad development in female Alburnus tarichi (Güldenstädt, 1814) (Cyprinidae) from the eastern coastline of Lake Van, Turkey, due to increasing pollution. In the reproductively arrested females (RAF), oocytes were developmentally blocked and arrested at the previtellogenic stage and gonadosomatic indices (GSI) were very low, while reproductively non-arrested females (RNF) found at the same site displayed relatively normal ovarian development and higher GSI. The present study investigated various oxidative stress biomarkers in the ovaries of RAF and RNF collected from a polluted site at Lake Van at the mid-vitellogenic phase, compared with reference fish from a non-polluted site (Lake Erçek). Ovarian total protein content, biometric indices, and histology were also evaluated. The oxidative stress biomarkers used were levels of lipid peroxidation (LPO) and glutathione (GSH), and activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione-S-transferase (GST). High levels of LPO and GSH and activities of SOD, GPx and GST were found in the ovaries of RAF compared with the reference fish. GSH content and activities of GPx and GST were also higher in the RNF. The total protein content and biometric indices decreased significantly in the RAF compared with the RNF and reference fish. The histology of the ovaries revealed atresia, melano-macrophage centers, encapsulated follicle cysts, and severe fibrosis in the RAF. The results of this study suggest that abnormalities in the ovaries of A. tarichi are causally related to increased oxidative stress as a result of pollution.

β-Naphthoflavone induces oxidative stress in the intertidal copepod, Tigriopus japonicus

β-Naphtoflavone (β-NF) is a flavonoid and enhances oxidative stress in vertebrates with little information from aquatic invertebrates as yet. In this study, we investigated the effects of β-NF on the antioxidant defense systems of the intertidal copepod Tigriopus japonicus. To measure the β-NF-triggered changes in oxidative stress markers, such as intracellular reactive oxygen species (ROS), glutathione (GSH) concentration, residual glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), and superoxide dismutase (SOD) activity, T. japonicus were exposed to β-NF (0.5 and 1 mg/L) for 72 h. Significant (P < 0.05) induction of the intracellular ROS content (%) was observed in 1 mg/L of β-NF exposed T. japonicus, compared to the negative control and H2O2-exposed group. The GSH levels were significantly increased in the 0.5 mg/L of β-NF-exposed group for 12 h and 1 mg/L of β-NF-exposed groups for 12-24 h. GPx, GST, and GR activities showed a significant increase in the 1 mg/L β-NF-exposed group, indicating that β-NF induces oxidative stress in T. japonicus. To understand the effects of β-NF at the level of transcript expression, a 6K microarray analysis was employed. Transcript profiles of selected antioxidant-related genes were modulated after 72 h exposure to 1 mg/L of β-NF. From microarray data, 10 GST isoforms, GR, GPx, PH-GPx, and Se-GPx were chosen for a time-course test by real-time RT-PCR. T. japonicus GST-S, GST-O, GST-M, and GST-D1 were significantly increased in a 1 mg/L β-NF-exposed group. T. japonicus GPx, GR, and Se-GPx mRNA levels were also significantly increased at both concentrations. Our results revealed that oxidative stress was induced by β-NF exposure in T. japonicus.

Combined use of PAH levels and EROD activities in the determination of PAH pollution in flathead mullet (Mugil cephalus) caught from the West Black Sea coast of Turkey

The aim of this study was to determine the extent of polycyclic aromatic hydrocarbon (PAH) pollution by measuring PAH levels and 7-ethoxyresorufin-O-deethylase (EROD) activities in flathead mullet (Mugil cephalus) samples caught from the West Black Sea coast of Turkey. The fish samples were caught in August 2008-2011. The levels of 13 PAHs were measured by high-performance liquid chromatography (HPLC) in the liver of fish. Most of the measured PAHs had three rings (low molecular weight). The frequencies of detection of PAHs were higher in fish samples caught from Zonguldak Harbour and Gülüç Stream Mouth than those from Sakarya River Mouth, Amasra and Kefken. EROD activities and cytochrome P4501A (CYP1A) protein level were also measured in the fish liver microsomes. Highly elevated EROD activities and CYP1A levels were measured in the mullet samples caught from Zonguldak Harbour and Gülüç Stream than those from Amasra and Kefken. The detection of PAHs in the liver of fish samples shows recent exposure to PAHs. The chemical analyses of PAHs and EROD activity results together reflected the extent of PAH pollution in the livers of fish caught from the West Black Sea coast of Turkey. The results indicate that Zonguldak Harbour is the most polluted site in the West Black Sea coast of Turkey.

Biological effects and bioaccumulation of pharmaceutically active compounds in crucian carp caged near the outfall of a sewage treatment plant

Pharmaceutically active compounds (PhACs) have been universally detected in rivers, lakes and coastal waters that are affected by effluents from sewage treatment plants (STPs). In this study, the biological effects and bioaccumulation of PhACs were assessed in crucian carp (Carassius auratus) caged in an effluent-receiving river for 21 days. Compared with control fish in the laboratory and at a reference site, a significant reduction in hepatosomatic index (HSI) and increase in the biotransformation enzymes ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) activities were observed in the fish that was caged downstream from the STP outfall. In general, the total concentrations of PhACs detected in fish tissues were in the order as follows: liver > brain > gill > muscle > bile. The bioaccumulation factors (BAFs) for PhACs were between 195 and 2782 in the major storage tissue liver. The corresponding results for both risk quotient (RQ) and enhanced integrated biomarker response (EIBR) based on laboratory and field studies, respectively, indicated that environmental risk for adverse effects to aquatic organisms were clearly higher at the downstream of the STP outfall than at the upstream.

Pollution biomonitoring in the Bizerte lagoon (Tunisia), using combined chemical and biomarker analyses in grass goby, Zosterisessor ophiocephalus (Teleostei, Gobiidae)

In this study, biological responses and contaminant levels in biological tissues were investigated in grass goby fish specimens (Zosterisessor ophiocephalus) collected from five stations in a moderately polluted ecosystem, namely the Bizerte lagoon on the north coast of Tunisia. The following biomarkers were measured: muscular acetylcholinesterase (AChE), hepatic ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), catalase (CAT), lipoperoxidation (TBARS), condition factor (CF), and hepatosomatic index (HSI). These measurements were taken in parallel with the content of Organochlorine pesticides (OCPs), Polychlorinated biphenyls (PCBs), Polycyclic aromatic hydrocarbons (PAHs) and trace metals (As, Cr, Cu, Mn, Pb, V, Zn, Ag, Cd, Co and Ni) in muscle tissue. Total PAH concentrations ranged from 20.09 ± 0.68 to 105.77 ± 42.58 ng g(-1) dw, PCB from 33.19 ± 6.25 to 126.28 ± 7.37 ng g(-1) dw, OCP from 11.26 ± 1.62 to 19.17 ± 2.06 ng g(-1) dw, and metals from 107.83 ± 1.83 to 187.21 ± 2.00 mg/kg dw. The highest levels of pollutants and biomarkers were observed at station S1, located in the Bizerte channel. Elevated EROD, GST and CAT activities, as well as TBARS levels in liver were positively correlated with tissue contaminant levels at station S1. Significant negative correlations were also found between hexachlorobenzene (HCB) and dichlorodiphenyltrichloroethane (DDTs) body burden with AChE activity in muscle at station S2. The integration of biological responses and contaminant tissue content indicated that certain areas of the Bizerte lagoon, notably station S1, are significantly impacted by various human activities, which likely represent a threat for aquatic wildlife. On the basis of these results, and due to its ecological characteristics, the grass goby appears a suitable indicator species for pollution biomonitoring in coastal marine areas along the Mediterranean Sea.

Metal-PAH mixtures in the aquatic environment: a review of co-toxic mechanisms leading to more-than-additive outcomes

Mixtures of metals and polycyclic aromatic hydrocarbons (PAHs) occur ubiquitously in aquatic environments, yet relatively little is known regarding their combined toxicities. Emerging reports investigating the additive mortality in metal-PAH mixtures have indicated that more-than-additive effects are equally as common as strictly-additive effects, raising concern for ecological risk assessment typically based on the summation of individual toxicities. Moreover, the current separation of focus between in vivo and in vitro studies, and fine- and coarse-scale endpoints, creates uncertainty regarding the mechanisms of co-toxicity involved in more-than-additive effects on whole organisms. Drawing from literature on metal and PAH toxicity in bacteria, protozoa, invertebrates, fish, and mammalian models, this review outlines several key mechanistic interactions likely to promote more-than-additive toxicity in metal-PAH mixtures. Namely, the deleterious effects of PAHs on membrane integrity and permeability to metals, the potential for metal-PAH complexation, the inhibitory nature of metals to the detoxification of PAHs via the cytochrome P450 pathway, the inhibitory nature of PAHs towards the detoxification of metals via metallothionein, and the potentiated production of reactive oxygenated species (ROS) in certain metal (e.g. Cu) and PAH (e.g., phenanthrenequinone) mixtures. Moreover, the mutual inhibition of detoxification suggests the possibility of positive feedback among these mechanisms. The individual toxicities and interactive aspects of contaminant transport, detoxification, and the production of ROS are herein discussed.

Effects of BDE-209 and its mixtures with BDE-47 and BDE-99 on multiple biomarkers in Carassius auratus

In the present study, the sublethal effects of BDE-209 and its mixtures with BDE-47 and BDE-99 on goldfish (Carassius auratus) were investigated, and the biomarkers including acetylcholinesterase (AChE) in brain, catalase (CAT), ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST) and superoxide dismutase (SOD) in liver were determined after 4 days of exposure. AChE and CAT activities were significantly inhibited by BDE-209 and the mixtures at higher dosages (≥1mg/kg), and exhibited obvious dose-response relationships. EROD, GST and SOD activities were significantly induced by BDE-209 and the mixtures in most cases. Integrated biomarker response (IBR) was calculated by combining multiple biomarkers to single value and used to quantitatively evaluate the toxicological effects of PBDEs. The order of IBR values was BDE-209/BDE-99>BDE-209/BDE-99/BDE-47>BDE-209/BDE-47>BDE-209. It suggests that IBR might be a useful tool for quantification of integrated biological effects induced by coexisted contaminants toward fish.

Tissue distribution, bioconcentration, metabolism, and effects of erythromycin in crucian carp (Carassius auratus)

In this study, the tissue distribution, bioconcentration, metabolism and biological effects of the macrolide antibiotic erythromycin (ERY) were investigated in fish using crucian carp (Carassius auratus) as a model. Crucian carp were exposed to various concentrations of ERY (4, 20, and 100 μg/L) for 28 days. The UPLC/MS/MS analysis of both water and tissue provided the bioconcentration of ERY and its metabolites in the fish body. The results from tissue samples showed that a maximum tissue concentration occurred in the muscle and that the bioconcentration factor (BCF) of 72.2 was lower than the theoretical BCF of 90.4 calculated from the octanol-water coefficient of ERY. A significant portion of the absorbed ERY was metabolized via demethylation and dehydration and observed in the form of descladinose in fish. In addition, the relevant biomarkers, including acetylcholinesterase in the brain, as well as 7-ethoxyresorufin O-deethylase and superoxide dismutase in the liver, changed significantly during 28 days of exposure (P<0.05). These results clearly indicated that ERY accumulated in fish and that similar metabolites as those observed in mammals were produced, resulting in the biochemical disturbance of biological systems.

Basal and benzo[a]pyrene-induced expression profile of phase I and II enzymes and ABC transporter mRNA in the early life stage of Chinese rare minnows (Gobiocypris rarus)

ATP-binding cassette (ABC) transporters together with phase I and II detoxification enzymes have been considered as included in a cellular detoxification system. Previous studies have highlighted the involvement of aryl hydrocarbon receptor (AHR) and Cyp1a in PAH-induced embryo toxicity. However, the response of other xenobiotic enzymes/transporters in PAH-mediated embryo toxicity is not fully characterized. In the present study, rare minnow embryos were exposed to 10 and 100µg/L BaP within 4h post-fertilization (hpf) up to 168 hpf. RNA was extracted at 24, 48, 96, and 168 hpf. The basal and BaP-induced expression of phase I enzyme genes (cyp1a, 1b1, and 1c1), phase II enzyme gene (gstm and ugt1a), and ABC transporter genes (abcb1, abcc1, abcc2, and abcg2) mRNA was determined using real-time PCR. Severe developmental defects (e.g., spinal deformities, pericardial and yolk-sac edema) were observed in the BaP treated groups. The basal expression showed that gstm was most strongly expressed, followed by abcb1, ugt1a, and abcc2, whereas cyp1a, 1b1, 1c1, and abcg2 showed weak expression. BaP significantly induced the mRNA expression of three CYP1s (cyp1a, 1b1, and 1c1) (p<0.05) and the ABC transporters (abcc1, abcc2, and abcg2) in a dose-dependent manner. However, the mRNA expression of Phase II enzymes (gstm, ugt1a) for the BaP treatments showed no significant difference with that of the controls. Furthermore, distinct induced patterns of these genes were observed during different exposure periods. Simultaneous up-regulation of the cyp and ABC transporter gene transcripts suggests that a possible involvement and cooperation in the detoxification process could provide protection against the BaP toxicity of rare minnows at the early life stage.

Evaluation of the interactive effects of lead, zinc and benzo(k)fluoranthene on crucian carp, Carassius carassius, using a multiple biomarker approach

The aim of this study was to evaluate the interactive effects of the metals lead (Pb) and zinc (Zn) and the polycyclic aromatic hydrocarbon benzo(k)fluoranthene (BkF) on crucian carp (Carassius carassius). To this end, various biomarkers in the fish [7-ethoxyresorufin-O-deethylase (EROD); superoxide dismutase (SOD); malondialdehyde (MDA) and metallothioneins (MT)] were measured after 96 h of exposure. When compared to either treatment with Pb and Zn mixtures or BkF-only treatment, the treatment with BkF combined with Pb and Zn resulted in lower responses of EROD and MT synthesis activity, and higher SOD and MDA increases. These results indicated that the co-exposure of metals and polycyclic aromatic hydrocarbons may cause more severe oxidative stress on fish. However, the effect of these interactions on EROD and MT may lead to an underestimation of the actual exposure in the field and thereby should be carefully considered.

A multi-biomarker assessment of single and combined effects of norfloxacin and sulfamethoxazole on male goldfish (Carassius auratus)

In the present study, the sublethal effects of norfloxacin alone and in combination with sulfamethoxazole in goldfish (Carassius auratus) were investigated, the biomarkers including acetylcholinesterase (AChE) in brain, 7-ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST), and superoxides dismutase (SOD) activities in liver, vitellogenin (Vtg) in serum and DNA damage in gonad were determined after 1, 2, 4 and 7 days of exposure. Brain AChE activity was significantly inhibited by norfloxacin (≥0.4 mg/L) after 4 and 7 days and the mixtures with sulfamethoxazole (≥0.24 mg/L) after 4 days of exposure, and significant concentration-response relationships were obtained. Liver EROD, GST and SOD activities were significantly increased by the individual and mixed pharmaceuticals in most cases and exhibited analogously bell-shaped concentration-response curves. Serum Vtg was increased by the highest concentration of norfloxacin and two higher concentrations of the mixtures. Higher concentrations of the test antibiotics induced significant DNA damage in a concentration- and time-dependent manner. The results indicated that selected antibiotics possesses cytotoxic and genotoxic potential against the non-target organism C. auratus.

Bioconcentration, metabolism, and biomarker responses in freshwater fish Carassius auratus exposed to roxithromycin

To investigate the distribution, bioconcentration, metabolism, and biomarker responses of macrolide antibiotic roxithromycin (ROX) in fish, crucian carp (Carassius auratus) were exposed to various concentrations of ROX (4, 20, and 100μgL(-1)) for 20d. The ROX content in different tissues was quantified using UPLC/MS/MS. The liver exhibited the highest ROX concentration followed by the bile, gills, and muscle tissues. After 15d of exposure to different concentrations of ROX, the bioconcentration factors were 2.15-38.0 in the liver, 0.950-20.7 in the bile, 0.0506-19.7 in the gill, and 0.0439-13.8 in the muscle; these results were comparable to the estimated BCF values. The metabolites formed in the bile were identified based on metabolic identification in human bile. Additionally, the biomarkers, including acetylcholinesterase in the brain, as well as 7-ethoxyresorufin O-deethylase and superoxide dismutase in the liver changed significantly after 5, 10, 15, and 20d of exposure (P<0.05). Our results suggest that ROX can accumulate and be metabolized in fish; therefore, interactions between ROX or its metabolites and the biological systems may induce biochemical disturbances in fish.

Potential environmental implications of emerging organic contaminants in Taihu Lake, China: comparison of two ecotoxicological assessment approaches

In this study, the hazard quotient (HQ) and a novel enhanced integrated biomarker response (EIBR) were applied to indirectly/directly estimate the ecotoxicological risk of emerging organic contaminants in Taihu Lake. Nine out of sixteen target compounds were detected in most sampling points at comparable concentrations (1.58-206.95 ng/L). Simultaneously, changes in multi-biomarkers were measured in caged fish for 28 days. The 0HQ results preliminarily indicated that most water areas were at significant risk for adverse effects to aquatic organisms (HQ>10). The prioritisation was then ranked and 17α-ethinylestradiol, diethylstilbestrol and 17β-estradiol were regarded as the greatest hazards. The EIBR, covering multi-biomarkers and their weighting, was applied to field study, and Zhushan Bay was suggested as the most stressful place, followed by Meiliang Bay. The HQ showed significant positive linear correlation with the EIBR (r=0.848, P<0.001), suggesting mutual consistency between the two approaches based on laboratory and field study in ecotoxicological risk assessment.

Detrimental effects of metronidazole on the liver of freshwater common carp (Cyprinus carpio L.)

The widely used antibiotic metronidazole (MTZ) was investigated for its toxic effects on the liver of the common carp (Cyprinus carpio L.). The fish were exposed to 0.1, 0.5, and 2.5 mg/L MTZ in water for 30 days, and parameters that are indicative of liver damage and oxidative stress were measured. MTZ increased liver ethoxyresorufin-O-deethylase, malondialdehyde, and glutathione levels, and elevated the activities of superoxide dismutase, catalase, aspartate aminotransferase, and alanine aminotransferase. These parameters usually showed significant differences in the 0.5 and 2.5 mg/L MTZ groups compared to the control group (p < 0.05). These findings indicated that MTZ induced oxidative stress and caused liver damage in common carp, suggesting that measures should be taken to avoid contamination of surface waters with MTZ.

Interaction of 17β-estradiol and ketoconazole on endocrine function in goldfish (Carassius auratus)

An understanding of the effects of toxic mixtures of endocrine disrupting chemicals (EDCs) on aquatic organisms is challenging as these organisms are exposed to multiple classes of contaminants in their natural habitat. The aim of the present study was to evaluate the interactions of two classes of EDCs, 17β-estradiol (E2) and ketoconazole (KTC), on endocrine function in male goldfish (Carassius auratus), including vitellogenesis, metabolic capability and serum steroid synthesis. Changes in vitellogenin (VTG) concentration, liver 7-ethoxyresorufin-O-deethylase (EROD) activity and circulating serum E2 level were examined. The expression of related genes was also determined using quantitative real-time polymerase chain reaction. Exposure to E2 caused a significant increase in VTG concentrations which corresponded with the gene expression of VTG and estrogen receptor (ER) in males, which were further elevated after combined exposure to E2 and KTC, indicative of a synergetic relationship. Exposure to E2 also resulted in a distinct increase in serum steroid biosynthesis and associated cytochrome P450 (CYP) aromatase expression after 10 days. However, these changes were inhibited by the presence of KTC, which acted as a steroidogenic inhibitor in fish. Moreover, KTC significantly decreased liver EROD activity and increased the related gene expression of CYP1A. However, these KTC-mediated metabolic reactions in goldfish were up-regulated following exposure to KTC in combination with E2. These findings reveal complex interactions on endocrine functions in male goldfish when exposed to multiple contaminations and may provide a better understanding of the effects of toxic mixtures.

Biochemical effects in crabs (Carcinus maenas) and contamination levels in the Bizerta Lagoon: an integrated approach in biomonitoring of marine complex pollution

The biochemical effects in Carcinus maenas and contamination levels in seawater and sediments of Bizerta Lagoon (northeast of Tunisia) were investigated. The levels of metals and hydrocarbons were higher in seawater and sediments in Menzel Bourguiba and Cimentery in February and July than in the other sampling sites. Differences among sites for glutathione S-transferase, catalase, acetylcholinesterase activities, and the content of lipid peroxidation and metallothioneins in two important organs which accumulated contaminants (the gills and the digestive gland) of the C. maenas were found and possibly related to differences in metal and hydrocarbon levels. The seasonal variation of biomarkers was possibly associated with chemical contamination and also with the high fluctuation of physico-chemical characteristics of the sites. The integrated biomarker response values found in the five sites is in good agreement with hydrocarbon and trace metal concentrations detected in the water and sediments of the stressful places where crabs are living.

Fuzzy logic and adaptive neuro-fuzzy inference system for characterization of contaminant exposure through selected biomarkers in African catfish

This study represents a first attempt at applying a fuzzy inference system (FIS) and an adaptive neuro-fuzzy inference system (ANFIS) to the field of aquatic biomonitoring for classification of the dosage and time of benzo[a]pyrene (BaP) injection through selected biomarkers in African catfish (Clarias gariepinus). Fish were injected either intramuscularly (i.m.) or intraperitoneally (i.p.) with BaP. Hepatic glutathione S-transferase (GST) activities, relative visceral fat weights (LSI), and four biliary fluorescent aromatic compounds (FACs) concentrations were used as the inputs in the modeling study. Contradictory rules in FIS and ANFIS models appeared after conversion of bioassay results into human language (rule-based system). A "data trimming" approach was proposed to eliminate the conflicts prior to fuzzification. However, the model produced was relevant only to relatively low exposures to BaP, especially through the i.m. route of exposure. Furthermore, sensitivity analysis was unable to raise the classification rate to an acceptable level. In conclusion, FIS and ANFIS models have limited applications in the field of fish biomarker studies.

Biochemical responses and physiological status in the crab Hemigrapsus crenulatus (Crustacea, Varunidae) from high anthropogenically-impacted estuary (Lenga, south-central Chile)

Estuarine environmental assessment by sub-individual responses is important in order to understand contaminant effects and to find suitable estuarine biomonitor species. Our study aimed to analyze oxidative stress responses, including glutathione-S-transferase (GST) activity, total antioxidant capacity (ACAP) and lipid peroxidation levels (TBARS) in estuarine crabs Hemigrapsus crenulatus from a high anthropogenically-impacted estuary (Lenga) compared to low and non-polluted estuaries (Tubul and Raqui), in a seasonal scale (winter-summer), tissue specific (hepatopancreas and gills) and sex related responses. Results showed that hepatopancreas in male crabs better reflected inter-estuary differences. Morpho-condition traits as Cephalothorax hepatopancreas index (CHI) could be used as an indicator of physiological status of estuarine crabs. Discriminant analysis also showed that GST and TBARS levels in summer are more suitable endpoints for establishing differences between polluted and non-polluted sites. These results suggest the importance of seasonality, target tissue, sex and physiological status of brachyuran crabs for estuarine biomonitoring assessment.

Contamination by metals and pharmaceuticals in northern Taihu Lake (China) and its relation to integrated biomarker response in fish

Taihu Lake is the largest shallow freshwater lake in eastern China and is suffering not only from an increasingly serious threat of eutrophication but also potential ecological risk due to the input of emerging contaminants. Active biomonitoring was conducted in Taihu Lake using transplanted goldfish (Carassius auratus) to determine the contamination by pharmaceuticals and metals and to assess the potential ecological risk. A suite of biomarkers including acetylcholinesterase, ethoxyresorufin O-deethylase, glutathione S-transferase, glutathione peroxidase and superoxide dismutase activities in fish after 7, 14, 21 and 28 days of exposure in situ, as well as pharmaceuticals and metals in water, were determined during the field exposure period. The results indicate that pharmaceuticals exist mainly in Zhushan Bay and Meiliang Bay, while metals are present mainly in Gong Bay. An integrated biomarker response (IBR) was calculated and used to evaluate the ecological risk of the polluted area of Taihu Lake. It was found that Zhushan Bay might present higher risk to fish, followed by Meiliang Bay. IBR values were in good agreement with copper and caffeine concentrations.

Biochemical response to exposure to six textile dyes in early developmental stages of Xenopus laevis

The present study was undertaken to determine the toxic effect of a lethal concentration of six different commercially used textile dyes on the 46th stage of Xenopus laevis tadpoles. The tadpoles were exposed to Astrazon Red FBL, Astrazon Blue FGRL, Remazol Red RR, Remazol Turquoise Blue G-A, Cibacron Red FN-3G, and Cibacron Blue FN-R for 168 h in static test conditions, and thus, 168-h median lethal concentrations (LC(50)s) of each dye were determined to be 0.35, 0.13, 112, 7, 359, and 15.8 mg/L, respectively. Also, to evaluate the sublethal effects of each dye, tadpoles were exposed to different concentrations of dyes (with respect to 168-h LC(50)s) for 24 h. The alteration of selected enzyme activities was tested. For this aim, glutathione S-transferase (GST), carboxylesterase, and lactate dehydrogenase (LDH) were assayed. After dye exposure, the GST induction or inhibition and LDH induction indicated some possible mechanisms of oxidative stress and deterioration in aerobic respiration processes induced by the tested dyes. Findings of the study suggest that selected biomarker enzymes are useful in understanding the toxic mechanisms of these dyes in X. laevis tadpoles as early warning indicators. Therefore, these selected biomarkers may evaluate the effect of environmental factors, such as textile dye effluents and other industrial pollutants, on amphibians in biomonitoring studies.

Biomarkers responses in muscle of Senegal sole (Solea senegalensis) from a heavy metals and PAHs polluted estuary

The biochemical responses in muscle, such as the enzymatic activities of acetylcholinesterase, lactate dehydrogenase and isocitrate dehydrogenase, were studied in sole (Solea senegalensis) collected in Huelva estuary (SW Spain), in the vicinity of a petrochemical and mining industry. The sampling sites showed different type and degree of pollution. The results demonstrated significant differences in muscle activities of AChE and IDH in Odiel and Tinto Rivers compared to control fish. LDH activity did not show any difference between sampling sites. Significant correlations were established between some biomarkers and heavy metals: AChE was correlated with Pb, Cd and Cu concentrations in water; IDH activity was correlated with Cd and Cu concentrations in water and As, Pb and Cd concentrations in sediments; LDH activity was correlated with As and Zn concentration in water and Cd concentration in sediment. Only one correlation was established between the biomarkers analysed and the concentrations of PAHs: benzo(b)fluoranthene concentration in sediment and IDH.

Reciprocal inhibiting interactive mechanism between the estrogen receptor and aryl hydrocarbon receptor signaling pathways in goldfish (Carassius auratus) exposed to 17β-estradiol and benzo[a]pyrene

In the aquatic environment, both the estrogen receptor (ER) and aryl hydrocarbon receptor (AhR) responses are established biomarkers for assessing exposure to pollutants. These receptor responses can also be affected by the presence of other classes of pollutants and may result in misinterpretation of existing pollution. In this study, we investigated the interaction between ER-vitellogenin (VTG) and AhR-cytochrome P450 1A (CYP1A) signaling pathways in goldfish (Carassius auratus) after 10 days exposure to pollutants. 17β-Estradiol (E(2)) and benzo[a]pyrene (BaP) were selected as the ER and AhR agonists, respectively. The messenger RNA (mRNA) expression of ER-VTG and AhR-CYP1A in liver was determined using quantitative real-time polymerase chain reaction (QRT-PCR). VTG, endogenous E(2) and 7-ethoxyresorufin-O-deethylase (EROD) were also studied. Exposure to E(2) and BaP alone significantly induced the gene expression of ERα-VTG and AhR2-CYP1A, respectively. Moreover, the obvious expression of related proteins was also observed. However, these inductions were significantly reduced after combined exposure to E(2) and lower concentrations of BaP (20 and 50 μg/L), indicative of a reciprocal inhibiting ER-AhR interaction. However, high concentrations (100 μg/L) of BaP did not affect the E(2)-induced gene expression. Changes in VTG protein were in accordance with the expression of VTG mRNA, and more VTG protein was observed in liver than in serum. The induced endogenous E(2) levels were suppressed by the presence of BaP. While the gene expression of CYP1A showed a concentration-dependent increase, EROD induction exhibited a bell-shaped concentration-response curve. Taken together, these results demonstrate a reciprocal inhibiting mode of ER-AhR interactions and may lead to a possible underestimation of actual exposure.

Artificial neural network modeling of biomarkers to infer characteristics of contaminant exposure in Clarias gariepinus

This study examined the potential of artificial neural network (ANN) modeling to infer timing, route and dose of contaminant exposure from biomarkers in a freshwater fish. Hepatic glutathione S-transferase (GST) activity and biliary concentrations of BaP, 1-OH BaP, 3-OH BaP and 7,8D BaP were quantified in juvenile Clarias gariepinus injected intramuscularly or intraperitoneally with 10-50 mg/kg benzo[a]pyrene (BaP) 1-3 d earlier. A feedforward multilayer perceptron (MLP) ANN resulted in more accurate prediction of timing, route and exposure dose than a linear neural network or a radial basis function (RBF) ANN. MLP sensitivity analyses revealed contribution of all five biomarkers to predicting route of exposure but no contribution of hepatic GST activity or one of the two hydroxylated BaP metabolites to predicting time of exposure and dose of exposure. We conclude that information content of biomarkers collected from fish can be extended by judicious use of ANNs.