In vivo and in vitro metabolism and organ distribution of nonylphenol in Atlantic salmon (Salmo salar)

First metabolic profiling of 4-n-nonylphenol in human liver microsomes by integrated approaches to testing and assessment: Metabolites, pathways, and biological effects

4-n-nonylphenol (4-n-NP), a typical endocrine disrupting chemical, has been so far frequently detected in various environmental mediums and editable food. However, the specific metabolic pathways in human and potential adverse effects of metabolites have not been elucidated yet. Here, metabolic profiling of 4-n-NP in human liver microsome (HLM) was comprehensively characterized by integrated approaches of testing and assessment. A total of 21 metabolites were identified using nontarget analysis with high-resolution mass spectrum, including three groups of unique phase I metabolites first determined in HLM. Seven various metabolic pathways of 4-n-NP were identified by both in silico and in vitro, and CYP1A2, 2C19, and 2D6 were the mainly participating enzymes. Two secondary metabolites with carbonyl groups on side chains (M4, M7) presented most abundant in HLM, which were also predicted to have high binding affinities towards HPG-axis-related receptors (AR, ER, and PR). ESRs (estrogen receptors) were shared core protein targets for all metabolites revealed by protein-protein interaction networks. Biological functions enrichment analysis indicated that 4-n-NP metabolites might primarily involve in ESR-mediated signaling, GPCR ligand binding, Class A/1 (Rhodopsin-like receptors) and metabolism-related pathways. These findings of 4-n-NP metabolites, pathways, and biological effects provide insightful information for its environmental exposure and risk assessment.

Reproductive Toxicity and Recovery Associated With 4-Non-ylphenol Exposure in Juvenile African Catfish (Clarias garepinus)

Although, the effects of 4-non-ylphenol (4-NP) on fish's reproductive hormones were assessed in several studies using adult models, however, the effect of this endocrine disruptor on immature fish's reproductive hormones was not addressed commonly. We aimed to study the apoptosis induction, hematotoxicity, reproductive toxicity, and the recovery associated with 4-NP exposure in juvenile African catfish [Clarias garepinus) using some hormones [17β-estradiol (E2), testosterone (T), follicle-stimulating hormone (FSH), and luteinizing hormone (LH)] and gonad histology as biomarkers. The toxic effects of 4-NP have been studied in many animal models, but there is still limited knowledge about the dose-dependent damage caused by 4-NP exposure in juvenile Clarias gariepinus. A healthy juvenile C. gariepinus was categorized into four groups (n = 3/group; three replicates in each group). The first group was the control, and the other three groups were subjected to 4-NP concentrations as 0.1, 0.2, and 0.3 mg/L for 15 days; they were left for a recovery period of another 15 days. The reproductive hormones of C. gariepinus exposed to 4-NP for 15 days exhibited significant variations between the treatment groups and the control (P < 0.05), which were evident in E2 and T-values, whereas FSH, LH, total protein, and lipid peroxidation values showed non-significant differences among all groups at P < 0.05. Such a situation referred to the fact that the 15-day recovery period was insufficient to remove the impacts of 4-NP doses in concern. The trend of dose-dependent increase/decrease was recorded for T, E2, FSH, and LH. The histopathological alterations of 4-NP treated in gonad tissues were recorded in juvenile C. gariepinus, reflecting their sensitivity to 4-NP estrogenic-like effects. Overall, our results investigate that recovery has improved the reproductive toxicity caused by 4-NP in juvenile C. garepinus. Significant variations between the treated groups and the control group (P < 0.05) were evident in hematological parameters except for hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). The parameters exhibiting significance decreased with such increased doses [red blood cells (RBCs), hematocrit (Hct), and white blood cells (WBCs)]. Similar patterns of significant variations toward the increase or decrease were recorded following the 15-day recovery period. Apoptotic frequency in erythrocytes and brain cells has increased significantly with increased 4-NP exposure, indicating that 4-NP caused cytotoxic effects, such as apoptosis in a dose-dependent manner. However, these cellular alterations greatly decreased after the 15-day recovery period.

Thymoquinone Improved Nonylphenol-Induced Memory Deficit and Neurotoxicity Through Its Antioxidant and Neuroprotective Effects

Nonylphenol (NP), a well-known endocrine-disrupter chemical, has several harmful effects on the central nervous system including neuroendocrine disruption, cognitive impairment, and neurotoxicity. Thymoquinone (TQ) is a main bioactive compound in the black seeds of Nigella sativa that has antioxidant, anti-inflammatory, and neuroprotective properties. Here, we investigated the neuroprotective effect of TQ against NP-induced memory deficit and neurotoxicity in rats. To induce memory impairment, NP (25 mg/kg) was used as gavage in male Wistar rats for 21 days. TQ (2.5, 5, and 10 mg/kg) was intraperitoneally administered in NP-treated animals. The morris water maze test was performed to assess spatial learning and memory. The hippocampal tissues were isolated from the brain for histopathological evaluation. Biochemical, molecular, and cellular tests were performed to quantify oxidant (malondialdehyde; MDA)/antioxidant (superoxide dismutase (SOD), total antioxidant capacity (TAC), and reduced glutathione (GSH) parameters) as well as markers for astrocytic activation (glial fibrillary acidic protein; GFAP) and neuronal death (alpha-synuclein; α-syn). Results showed TQ (5 mg/kg) significantly improved NP-induced memory impairment. Histological data revealed a significant increase in the number of necrotic cells in hippocampus, and TQ treatment markedly decreased this effect. The GSH and TAC levels were significantly increased in TQ-treated groups compared to NP group. The molecular analysis indicated that NP increased GFAP and decreased α-syn expression and TQ treatment did the reverse. In vitro study in astrocytes isolated from mice brain showed that TQ significantly increased cell viability in NP-induced cytotoxicity. This study strongly indicates that TQ has neuroprotective effects on NP-induced neurotoxicity through reducing oxidative damages and neuroinflammation. This study investigates the behavioral neurotoxicity induced by Nonylphenol (NP) and the protective effects of Thymoquinone (TQ) as a potent antioxidant compound using molecular, cell culture, histopathological and biochemical techniques.

The Investigation into Neurotoxicity Mechanisms of Nonylphenol: A Narrative Review

BACKGROUND

Nonylphenol (NP), a chemical compound widely used in industry, is the result of the nonylphenol ethoxylate decomposition and it is known as an estrogen-like compound. Numerous studies and researches have shown that it has many destructive functions of various organs such as the brain. This toxicant causes oxidative stress in the cortex and hippocampus cells, which are two essential regions to preserve memory and learning in the brain.

METHODS

This review examines recent findings to better understanding the mechanisms of NP neurotoxicity. We used Scopus, Google Scholar, and PubMed databases to find articles focused on the destructive effects of NP on the oxidative stress pathway and its defense mechanisms.

RESULTS

NP has potential human health hazards associated with gestational, peri- and postnatal exposure. NP can disrupt brain homeostasis in different ways, such as activation of inflammatory factors in brain especially in hippocampus and cortex, disruption of the cell cycle, changes in neuron, dendrites and synapses morphology, disruption of extra and intracellular calcium ion balance and also memory and learning disorders.

Disruptive effects of nonylphenol on reproductive hormones, antioxidant enzymes, and histology of liver, kidney and gonads in Caspian trout smolts

The endocrine-disrupting effect of pollutants such as alkylphenols has been considered a major concern during recent years. Although the effects of nonylphenol on the reproductive hormones of fish have been investigated in several studies, the effect of this endocrine disruptor on reproductive hormones of immature fish and salmonid smolts has been less addressed. The present work studied the effects of 1, 10 and 100 μg/l concentrations of nonylphenol on the levels of plasma reproductive hormones and liver antioxidant enzymes as well as on histopathology of reproductive and non-reproductive organs of male and female Caspian brown trout (Salmo trutta caspius) smolts after 21 days of exposure. The results of the present study showed that environmentally relevant concentrations of nonylphenol affected plasma levels of sex steroids; gonadotropins, phosphorus, estradiol to testosterone ratio, and also caused histopathological lesions in liver, kidney and testis tissues of immature Caspian brown trout during smolting. Nonylphenol significantly increased the levels of estradiol in plasma of both male and female smolts exposed to nonylphenol compared with the control groups. Exposure to nonylphenol decreased testosterone and FSH levels in both genders. It has also increased plasma levels of LH in females but did not affect LH levels in male fish. Liver SOD and CAT content was decreased in nonylphenol-exposed smolts. Therefore, the release of this economically valuable and endangered species into the rivers contaminated with nonylphenol should be avoided as it can have significant effects on the development and reproductive function of smolts.

The occurrence and distribution of nonylphenols and nonylphenol ethoxylates in different species of fish

The aim of this study was to analyze the accumulation of nonylphenols (NPs) and nonylphenol ethoxylates (NPEOs) in the muscles, liver, and bile of flounder (Platichthys flesus), cod (Gadus morhua), and eels (Anguilla anguilla). The flounder and cod were caught in the Gulf of Gdańsk (the Baltic Sea), while the eels were sampled in the Vistula and Szczecin lagoons (the Baltic Sea) and in the inland waters of the Masurian Lake District. NP concentrations in muscles were low in all the samples analyzed and ranged from 14.2 to 28.2 μg-1 kg ww. In contrast, a wide range of NP concentrations were observed in livers, which seemed to depend on both the species and the feeding status of the fishes. NP levels in flounder and eel livers were from three to twenty times higher than those in the muscles, but they were below the limit of quantitation (LOQ) in all the cod liver samples. The mean concentration of NPs in the liver of flounder caught in the Gulf of Gdańsk was 222 μg kg-1 ww, while in that of the eel ranged from 57 μg kg-1 ww in fish caught in the Masurian Lake District to 519 μg kg-1 ww in eels caught in the Vistula Lagoon. NPs were detected in bile in only a few eel samples, which indicated that bile analysis has limited applications for estimating NP contamination in marine fish. The NPEOs in all the samples analyzed were below the LOQ.

Mixture toxicity of copper and nonylphenol on the embryo-larval development of Rhinella arenarum

Copper and nonylphenol are two commonly found chemicals in the aquatic environment, particularly in the distribution area of the amphibian Rhinella arenarum. The current work evaluated the lethal toxicity of equitoxic and non-equitoxic binary mixtures of copper and nonylphenol on embryos and larvae of the South America toad by means of the standardized test, AMPHITOX. Joint toxicity of mixtures was assessed in several proportions of these compounds at different exposure times and was analyzed at different level of mortality effect (LC10, LC50 and LC90). Considering the LC50, the equitoxic mixture was always antagonistic independently of the exposure time and the developmental stage. Joint toxicity showed mainly an antagonistic pattern; nonetheless, some time-dependent additive interactions were observed. Regarding the LC10, synergistic interactions were found in embryos and larvae exposed to two different mixture proportions at several exposure times. This highlights the possible synergism of these chemicals at environmentally relevant concentrations. These results point out the relevance of assessing joint toxicity of environmental pollutants for environmental risk assessment.

Maternal exposure to nonylphenol during pregnancy and lactation induces microglial cell activation and pro-inflammatory cytokine production in offspring hippocampus

Recently, environmental nonylphenol (NP) exposure in the fetus and child has received increasing attention because of its potentially deleterious effects on the central nervous system (CNS). Microglia (MG), resident immune cells in the CNS, are vital to CNS homeostasis and defense against exogenous chemicals, which makes them a potentially sensitive target of NP. The present study aims to explore the effects of maternal NP exposure during pregnancy and lactation on MG in offspring hippocampus, the production of pro-inflammatory cytokines by MG, and associated underlying mechanisms. We found that maternal NP exposure increased the production of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in offspring hippocampus. Increases in both activation and number of MG were observed in offspring hippocampus. Increased phosphorylation of Akt was found to co-localize with hippocampal MG, while increased phosphorylation of c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK) were observed in offspring hippocampus. Activator protein 1 (AP-1), an inflammatory transcription factor, was also activated in the hippocampus of pups subjected to maternal NP exposure. These results suggest that maternal NP exposure might activate MG in offspring hippocampus. This activation seems to subsequently increase the production of IL-1β, IL-6, and TNF-α. Furthermore, Akt/MAPK/AP-1 signaling may be involved in this activation of MG and increased production of pro-inflammatory cytokines.

Modification of the plasma complement protein profile by exogenous estrogens is indicative of a compromised immune competence in marine medaka (Oryzias melastigma)

Growing evidence suggests that the immune system of teleost is vulnerable to xenoestrogens, which are ubiquitous in the marine environment. This study detected and identified the major circulatory immune proteins deregulated by 17α-ethinylestradiol (EE2), which may be linked to fish susceptibility to pathogens in the marine medaka, Oryzias melastigma. Fish immune competence was determined using a host resistance assay to pathogenic bacteria Edwardsiella tarda. Females were consistently more susceptible to infection-induced mortality than males. Exposure to EE2 could narrow the sex gap of mortality by increasing infection-induced death in male fish. Proteomic analysis revealed that the major plasma immune proteins of adult fish were highly sexually dimorphic. EE2 induced pronounced sex-specific changes in the plasma proteome, with the male plasma composition clearly becoming "feminised". Male plasma was found to contain a higher level of fibrinogens, WAP63 and ependymin-2-like protein, which are involved in coagulation, inflammation and regeneration. For the first time, we demonstrated that expression of C1q subunit B (C1Q), an initiating factor of the classical complement pathway, was higher in males and was suppressed in both sexes in response to EE2 and bacterial challenge. Moreover, cleavage and post-translational modification of C3, the central component of the complement system, could be altered by EE2 treatment in males (C3dg down; C3g up). Multiple regression analysis indicated that C1Q is possibly an indicator of fish survival, which warrants further confirmation. The findings support the potential application of plasma immune proteins for prognosis/diagnosis of fish immune competence. Moreover, this study provides the first biochemical basis of the sex-differences in fish immunity and how these differences might be modified by xenoestrogens.

Deriving in vivo biotransformation rate constants and metabolite parent concentration factor/stable metabolite factor from bioaccumulation and bioconcentration experiments: An illustration with worm accumulation data

Growing concern for the biological fate of organic contaminants and their metabolites and the urge to connect in vitro and in vivo toxicokinetics have prompted researchers to characterize the biotransformation behavior of organic contaminants in biota. The whole body biotransformation rate constant (k_M ) is currently determined by the difference approach, which has significant methodological limitations. A new approach for determining k_M from the kinetic observations of the parent contaminant and its intermediate metabolites is proposed. In this method, k_M can be determined by fitting kinetic data of the parent contaminant and the metabolites to analytical equations that depict the bioaccumulation kinetics. The application of the proposed method is illustrated using worm bioaccumulation-biotransformation data collected from the literature. Furthermore, a metabolite parent concentration factor (MPCF) is also proposed to characterize the persistence of the metabolite in biota. Because both the proposed k_M method and MPCF build on the existing theoretical framework for bioaccumulation, they can be readily incorporated into standard experimental bioaccumulation protocols or risk assessment procedures or frameworks. Possible limitations, implications, and future directions are elaborated. Environ Toxicol Chem 2016;35:2903-2909. © 2016 SETAC.

Experimental paradigm for in-laboratory proxy aquatic studies under conditions of static, non-flow-through chemical exposures

Endocrine-disrupting chemicals (EDCs) such as 17α-ethynylestradiol, 17β-estradiol, estrone, and para-nonylphenol have been measured in wastewater-treatment plant effluents, surface waters, sediments, and sludge and have been shown to induce liver-specific vitellogenin (vtg) messenger RNA in male fathead minnows (Pimephales promelas). The purpose of the present study was to establish minimal concentrations of select EDCs necessary to induce transcription of vtg in 48-h static renewal exposures, as measured by quantitative real-time thermal cycle amplification. Adult males were exposed to 17α-ethynylestradiol, 17β-estradiol, estrone, and para-nonylphenol. Dose-dependent increases in vtg expression were significant with all chemicals tested. The lowest concentrations of these chemicals to induce measurable vtg expression, with significant difference from respective controls, were 17α-ethynylestradiol, 2.2 ng L(-1); para-nonylphenol, 13.9 μg L(-1); 17β-estradiol, 42.7 ng L(-1); and estrone, 46.7 ng L(-1), measured as 48-h average concentrations. The present experiments were designed to frame a commonly acceptable approach for investigators who conduct static, in-laboratory proxy environmental aquatic exposures. The present study highlights the need for investigators to report in peer-reviewed submissions the observed concentration values for minimal induction levels when measuring molecular responses to chemical exposures by means of real-time polymerase chain reaction, quantitative polymerase chain reaction, or other "omic" technologies.

Migration of nonylphenol from food-grade plastic is toxic to the coral reef fish species Pseudochromis fridmani

Nonylphenol (NP) is a non-ionic surfactant used extensively in industrial applications, personal care products, and many plastics. We exposed marine orchid dottybacks (Pseudochromis fridmani) for 48h to either glass, Teflon, or two bags labeled as FDA food-grade polyethylene (PE1 and PE2) from different manufacturers. The PE2 bags leached high levels of NP into the contact water, which were taken up by the fish, and decreased short and long-term survival. Concentrations of NP that leached from the bags were consistent with 96h LC50 values determined in this study, indicating NP is the likely toxic agent. Despite being similarly labeled, the NP concentrations that leached from the bags and the resultant toxicity to the fish varied dramatically between manufacturers. This study highlights that some plastics, labeled as food-safe, can be highly toxic to aquatic animals, and could pose a greater threat to humans than previously realized. This study also highlights risks for aquatic animals exposed to increasing quantities of plastic waste.

Bioaccumulation of 4-nonylphenol and effects on biomarkers, acetylcholinesterase, glutathione-S-transferase and glutathione peroxidase, in Mytilus galloprovincialis mussel gilla

Wild marine mussels, Mytilus galloprovincialis showed a moderate bioaccumulation ability when exposed to waterborne 4-nonylphenol (4-NP), with a bioconcentration factor (BCF) of 6850 L Kg(-1) (dry weight). Kinetic and concentration-response experiments were performed and three enzymatic biomarkers in mussel gills were measured: Glutathione S-transferase (GST), glutathione peroxidase (GPx) and acetylcholinesterase (AChE). Exposure of mussels to environmentally relevant concentrations (25-100 μg L(-1)) of 4-nonylphenol significantly inhibited the AChE activity and induced the GST and GPx activities. GST induction was dose dependent whilst GPx activity showed a less consistent pattern, but in both cases the induction remained after a 10 d depuration period. Mussels seem capable of eliminating 4-NP from their tissues through a mechanism involving GST induction.

Interferences of an environmental pollutant with estrogen-like action in the male reproductive system of the terrestrial vertebrate Podarcis sicula

Nonylphenol (NP) is classified among the endocrine disruptor chemicals with estrogen-like properties. It is widely used in many industries and to dilute pesticides in agriculture, and is known to affect the reproductive system of many aquatic and semi-aquatic organisms. This study aimed to verify how NP, administered via food and water, may interfere with the reproductive cycle of a terrestrial vertebrate. Our model was the male Italian wall lizard Podarcis sicula, a seasonal breeding species that may be naturally exposed to environmental pollution. From our findings it emerges that an NP-polluted diet administered during the mating period causes in this lizard a slowdown of spermatogenesis and affects the testicular and epididymal structure, making it similar to that of the non-reproductive period. The distribution in the testis and epididymis of mRNA for steroid hormone receptors, i.e., estrogen α and β and androgen receptors, was also investigated. NP treatment inhibits the expression of AR, ERα, and ERβ-mRNA in spermatogonia and primary spermatocytes and causes a switch-off of the secretory activity of the epididymal corpus by inducing the expression of ERα.

Phenolic endocrine-disrupting chemicals and intersex in wild crucian carp from Hun River, China

This study investigated the concentrations of phenolic endocrine-disrupting chemicals (EDCs) and the incidence of ovo-testis (intersex) in wild crucian carp (Carassius carassius) sampled from the Hun River. As expected, nonylphenols (NP) and bisphenol A (BPA) were detected in all samples, and octylphenols (OP) were found in most samples. NP concentrations ranged from 1290 ± 584 to 3111 ± 2071 ng g(-1) wet weight (ww) in July and from 1132 ± 644 to 1556 ± 587 ng g(-1) ww in November; OP ranged from 6 ± 7 to 46 ± 38 ng g(-1) ww in July and from no detection to 22 ± 16 ng g(-1) ww in November; and BPA ranged from 4 ± 9 to 41 ± 24 ng g(-1) ww in July and from 6 ± 5 to 59 ± 24 ng g(-1) ww in November. Moreover, the concentrations of these compounds were higher in fish found down-stream of the sewage treatment plant (STP), and the lowest concentrations were found in fish up-stream of the STP. Concentrations of these EDCs in muscles might be correlated with the prevalence of intersex traits in wild fish, suggesting that these compounds contribute, at least in part, to the occurrence of intersex morphology. Thus, phenolic EDCs discharged from the STP pose a risk to the aquatic ecosystem in the Hun River.

A developmental hepatotoxicity study of dietary bisphenol A in Sparus aurata juveniles

Previous studies in rats have indicated that a diet enriched with Bisphenol A adversely effects metabolism and reproductive success. In rats exposed to BPA by maternal gavage, alteration in the developmental programming, higher obesity rates and reproductive anomalies were induced. Starting with this evidence, the aim of this study was to provide important insights on the effects induced by a BPA enriched diet, on the reproductive physiology and metabolism of juvenile fish, simulating the scenario occurring when wild fish fed on prey contaminated with environmental BPA. Seabream was chosen as model, as it is one of the primary commercial species valued by consumers and these results could provide important findings on adverse effects that could be passed on to humans by eating contaminated fish. A novel method for measuring BPA in the food and water by affinity chromatography was developed. Analysis of signals involved in reproduction uncovered altered levels of vtg and Zp, clearly indicating the estrogenic effect of BPA. Similarly, BPA up-regulated catd and era gene expression. A noteworthy outcome from this study was the full length cloning of two vtg encoding proteins, namely vtgA and vtgB, which are differently modulated by BPA. Cyp1a1 and EROD activity were significantly downregulated, confirming the ability of estrogenic compounds to inhibit the detoxification process. GST activity was unaffected by BPA contamination, while CAT activity was down regulated. These results collectively confirm the estrogenic effect of BPA and provide additional characterization of novel vtg genes in Sparus aurata.

Developmental toxicity and risk assessment of nonylphenol to the South American toad, Rhinella arenarum

The toxicity of Nonylphenol, an emerging pollutant, on the common South American toad Rhinella arenarum was stage and time dependent, thus Median Lethal Concentrations (LC50) for acute (96h), short-term chronic (168h) and chronic exposure (336h) were 1.06; 0.96 and 0.17mgNP/L from embryonic period (S.4), whereas for exposure from larvae (S.25), LC50 remained constant at 0.37mgNP/L from 96h to 168h, decreasing to 0.11mgNP/L at 336h. NOEC-168h for exposure from embryos was 0.025mgNP/L. The Teratogenic Potential (NOEC-lethality/NOEC-sublethal effects) was 23 times higher than the threshold value, indicating a high risk for embryos to be malformed in absence of significant lethality and representing a threat for the species conservation. By comparing with other amphibians, the early development of R. arenarum was very sensitive to NP. The results highlight the relevance of extending the exposure time and look for the most sensitive stage in order to perform the bioassays for conservation purposes.

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

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

The effect of nonylphenol on gene expression in Atlantic salmon smolts

The parr-smolt transformation in Atlantic salmon (Salmo salar) is a complex developmental process that culminates in the ability to migrate to and live in seawater. Exposure to environmental contaminants like nonylphenol can disrupt smolt development and may be a contributing factor in salmon population declines. We used GRASP 16K cDNA microarrays to investigate the effects of nonylphenol on gene expression in Atlantic salmon smolts. Nonylphenol exposure reduced gill Na(+)/K(+)-ATPase activity and plasma cortisol and triiodothyronine levels. Transcriptional responses were examined in gill, liver, olfactory rosettes, hypothalamus, and pituitary. Expression of 124 features was significantly altered in the liver of fish exposed to nonylphenol; little to no transcriptional effects were observed in other tissues. mRNA abundance of genes involved in protein biosynthesis, folding, modification, transport and catabolism; nucleosome assembly, cell cycle, cell differentiation, microtubule-based movement, electron transport, and response to stress increased in nonylphenol-treated fish. This study expands our understanding of the effect of nonylphenol on smolting and provides potential targets for development of biomarkers.

Endocrine-disrupting effects of nonylphenol in the newt, Triturus carnifex (Amphibia, Urodela)

The aim of our study was to verify whether environmental concentrations of nonylphenol influenced the adrenal gland of Triturus carnifex. Newts were exposed to 19 μg/L nominal concentration of nonylphenol throughout the periods of December-January and March-April, corresponding to different stages of the chromaffin cell functional cycle. The morphological features of the steroidogenic and chromaffin tissues, and the serum levels of ACTH, aldosterone, corticosterone, norepinephrine and epinephrine were evaluated. Nonylphenol did not influence ACTH serum levels. During the two periods examined, the steroidogenic tissue had the same reaction: the quantity of cytoplasmic lipids, and the corticosteroid serum levels, decreased, suggesting the inhibition of synthesis and release of corticosteroids. During the two periods examined, the chromaffin tissue reacted differently to nonylphenol. During December-January, the numeric ratio of norepinephrine granules to epinephrine granules, and the epinephrine serum levels, increased, suggesting the stimulation of epinephrine release. During March-April, the numeric ratio of norepinephrine granules to epinephrine granules did not change, and the norepinephrine serum levels decreased, suggesting the inhibition of norepinephrine release. Our results show that nonylphenol influences the activity of the newt adrenal gland; considering the physiological role of this gland, our results suggest that nonylphenol may contribute to amphibian decline.

Expression of catalase and glutathione S-transferase genes in Chironomus riparius on exposure to cadmium and nonylphenol

Antioxidant enzymes play important roles in the protection against oxidative damage caused by environmental pollutants by scavenging high levels of reactive oxygen species and have been quantified as oxidative stress markers. However, combining mRNA expressions of genes coding for detoxification enzymes along with enzyme activities will be more useful biomarkers of stress. Therefore, in this study the cDNA of the catalase gene from the aquatic midge, Chironomus riparius (CrCAT) was sequenced using 454 pyrosequencing. The 2139 bp CrCAT cDNA included an open reading frame of 1503 bp encoding a putative protein of 500 amino acids with a predicted molecular mass of 56.72 kDa. There was an 18 bp 5' and a long 618 bp 3' untranslated region with a polyadenylation signal site (AATAAA). The deduced amino acid sequence of CrCAT contained several highly conserved motifs including the proximal heme-ligand signature sequence RLFSYNDTX and the proximal active site signature FXRERIPERVVHAKGXGA. A comparative analysis showed the presence of conserved amino acid residues and all of the catalytic amino acids (His(70), Asn(143), and Tyr(353)) were conserved in all species. The CrCAT contained three potential glycosylation sites and a peroxisome targeting signal of 'AKM'. The mRNA was detected using RT-PCR at all developmental stages. The time-course expression of CrCAT was measured using quantitative real-time PCR after exposure to different concentration and durations of Paraquat (PQ), cadmium chloride (Cd) and nonylphenol (NP). The expression of CrCAT was significantly up regulated on exposure to 50 and 100mg/L PQ for 12 and 24h. Among the different concentrations and durations of Cd tested, significantly highest level of expression for CrCAT mRNA and catalase enzyme activity was observed on exposure to 10mg/L for 24h. In the case of NP, the highest level of CrCAT expression was observed after exposure to 100 μg/L for 24h. The expression profiles of three selected C. riparius glutathione S-transferase genes (CrGSTs) viz. CrGSTdelta3, CrGSTsigma4 and CrGSTepsilon1 was also studied on exposure to NP and were up or down regulated at different time points and concentrations. Significantly highest level of expression for CrGSTdelta3 was observed after 48 h and for CrGSTsigma4 and CrGSTepsilon1 after 24h exposure to 100 μg/L of NP. The results show that CrGSTs and CrCAT could be used as potential biomarkers in C. riparius for aquatic ecotoxicological studies.

Glutathione-S-transferase in Nereis succinea (Polychaeta) and its induction by xeno-estrogen

The need to replace or at least to reduce the use of vertebrates in toxicity tests is a timely major concern in research and industry but to date, efforts made to minimize their use are still far from complete. Increasing demands for toxicity tests put considerable pressures upon the development of future fast and efficient test methods using invertebrates. In fact, to date, few studies provide links between biochemical and cellular effects of xeno-estrogens in aquatic invertebrates. Glutathione-S-transferase (GST) activity, as a biomarker of stress exposure, was measured in the population of clamworms (Nereis succinea) from Cardiff Bay. In addition, we examined the effect of single exposure to nonylphenol (NP) on this enzymatic activity. Field study results showed a relationship between the worm's size, reproductive status, and GST activity from the field population. In addition, we show a significant increase in the GST activity at 100 μg/L NP with sex-specific responses. The xeno-estrogens, which could affect reproduction of nereid by interfering in normal endocrinological pathways, are eliminated through GST by conjugation with glutathione. This work shows for the first time that GST activity depends on sex and stage of the clamworms and also that the xeno-estrogen NP induces its activity. This study supports the use of this species as a bioindicator of aquatic pollution and lays the foundation to causally link toxic exposure with reproductive output.

Low-dose exposure to alkylphenols adversely affects the sexual development of Atlantic cod (Gadus morhua): acceleration of the onset of puberty and delayed seasonal gonad development in mature female cod

Produced water (PW), a by-product of the oil-production process, contains large amount of alkylphenols (APs) and other harmful oil compounds. In the last 20 years, there have been increasing concerns regarding the environmental impact of large increases in the amounts of PW released into the North Sea. We have previously shown that low levels of APs can induce disruption of the endocrine and reproductive systems of Atlantic cod (Gadus morhua). The aims of this follow-up study were to: (i) identify the lowest observable effect concentration of APs; (ii) study the effects of exposure to real PW, obtained from a North Sea oil-production platform; and (iii) study the biological mechanism of endocrine disruption in female cod. Fish were fed with feed paste containing several concentrations of four different APs (4-tert-butylphenol, 4-n-pentylphenol, 4-n-hexylphenol and 4-n-heptylphenol) or real PW for 20 weeks throughout the normal period of vitellogenesis in Atlantic cod from October to January. Male and female cod, exposed to AP and PW, were compared to unexposed fish and to fish fed paste containing 17β-oestradiol (E(2)). Approximately 60% of the females and 96% of the males in the unexposed groups were mature at the end of the experiment. Our results show that exposure to APs and E(2) have different effects depending on the developmental stage of the fish. We observed that juvenile females are advanced into puberty and maturation, while gonad development was delayed in both maturing females and males. The AP-exposed groups contained increased numbers of mature females, and significant differences between the untreated group and the AP-treated groups were seen down to a dose of 4 μg AP/kg body weight. In the high-dose AP and the E(2) exposed groups, all females matured and no juveniles were seen. These results suggest that AP-exposure can affect the timing of the onset of puberty in fish even at extremely low concentrations. Importantly, similar effects were not seen in the fish that were exposed to real PW.

A flounder (Paralichthys olivaceus) gill cell line as in vitro acute assay system of nonylphenol cytotoxicity

A cell line (FG cells) derived from a gill of the flounder, Paralichthys olivaceus were used to determine the cytotoxic effects of nonylphenol (NP). Cytotoxicity was measured by three endpoint systems: neutral red (NR) uptake assay, methyl thiazolyl tetrazolium (MTT) assay and cell protein assay. The result showed that NP was cytotoxic to FG cells at all tested concentrations, and toxicity increased as the concentration of NP was progressively increased. The 24 h-IC50 values of NP were 39.81, 37.76 and 38.22 μmol/L for NR uptake, MTT assay and cell protein assay, respectively. Moreover, the morphological changes of FG cells were also studied at the concentration of 30 μmol/L for 24 h. Cells morphology were markedly altered by NP observed under a scanning electron microscopy, as evidenced by swelling cells, two and more nucleolus and an increased number of lipid particles. This would suggest that the FG cell line is a suitable bioindicator for the screening of the acute toxicity of NP.

Alkylphenol metabolites in fish bile as biomarkers of exposure to offshore oil industry produced water in feral fish

The measurement of low-concentration alkylphenol (AP) exposure in fish is relevant in connection with monitoring and risk assessment of offshore oil industry produced water (PW) discharges. Detection of AP markers in fish bile offers significantly greater sensitivity than detection of AP in tissues such as liver. Recent studies revealed that gas chromatography-mass spectrometry in electron ionization mode (GC-EI-MS) enabled a selective and sensitive analytical detection of PW AP in mixtures with unknown composition. A procedure consisting of enzymatic deconjugation of metabolites in fish bile followed by derivatization with bis(trimethylsilyl)trifluoroacetamide and then separation and quantification of derivatized AP using GC-EI-MS is presented. The use of this procedure as a possible recommended approach for assessment and biomonitoring of AP contamination in fish populations living down-current from offshore oil production fields is presented.

Assessing the estrogenic potency in a Portuguese wastewater treatment plant using an integrated approach

The estrogenic potency of a wastewater treatment plant (WWTP) was evaluated using chemical and biological analyses, which showed that after the station treatment processes some of the selected endocrine disruptor compounds (EDCs) were still present in the treated effluent (e.g., bisphenol A, alkylphenols, estrone). Thus, the most common endocrine EDCs were identified and quantified and the overall estrogenicity of the treated effluent assessed by integrating the results. Male goldfish (Carassius auratus) were used as biological indicators in a 28-day experiment. Vitellogenin (Vtg), gonadosomatic and hepatosomatic indices, steroids (17beta-estradiol and 11-ketotestosterone) and histopathology were biomarkers used in fish to evaluate WWTP treated effluent estrogenicity, in combination with instrumental analyses. The results showed a significant increase (P < 0.01) in plasma and liver Vtg, which were significantly correlated (r = 0.66; P < 0.01). The gonadosmatic index was significantly (P < 0.01) reduced in exposed fish. The steroid analyses revealed significant elevations in 17beta-estradiol and depressed 11-ketotestosterone concentrations. The histological examinations show changes in exposed fish gonads, such as regressed testes and in some cases (43% to 75%) the development of ovo-testis in fish exposed to 50% and 100% treated effluent.

Importance of prey and predator feeding behaviors for trophic transfer and secondary poisoning

Hydrophobic contaminants accumulate within aquatic sediments, hence pelagic predators may have limited direct contact with such compounds, but can be exposed via their benthic prey (i.e., via dietary exposure). Here we examine the importance of feeding behaviors of both prey (sediment ingesters or noningesters) and predators (piercers or engulfers) in determining the extent of dietary exposure and toxic effects. A freshwater macroinvertebrate system was used, consisting of two predator species, a piercer (Notonecta glauca) and an engulfer (Ischnura elegans), and three prey species, a sediment noningester (Cloëon dipterum) and two sediment ingesters (Asellus aquaticus, Chironomus riparius). Predators were fed prey previously exposed to artificial sediment dosed with 30 microg/g of 14C benzophenone. The piercer predator accumulated more benzophenone from sediment ingester compared to sediment noningester prey, whereas the engulfer predator accumulated a similar concentration for all three prey species. Toxic effects, in terms of reduced feeding rate, were only observed with the engulfer feeding on sediment noningesters, probably due to the interaction between the narcotic mode of action of benzophenone and predator hunting strategy. The importance of dietary exposure in risk assessments may therefore depend on exposure pathways of prey, feeding behaviors of predators, and the contaminant's toxic mode of action.

Neural aromatase transcript and protein levels in Atlantic salmon (Salmo salar) are modulated by the ubiquitous water pollutant, 4-nonylphenol

At present, there are no known direct occurrences of nonylphenol (NP) in nature. Therefore, its presence in nature is solely a consequence of human activities. NP is generated through degradation of alkylphenol ethoxylates released mainly from textile, metal working, institutional cleansing and laundry cleaning, but few data on the amount of the release is available. These compounds have been shown to affect several biological processes, including the endocrine systems, in a wide number of species. The cytochrome P450 aromatase (Cyp19) is the rate-limiting step in estrogen production, and is known to be a potential target for endocrine-disrupting chemicals (EDCs) such as NP. Teleost fish generally have a high brain aromatase activity, and the effects of EDCs in fish brain is not thoroughly investigated. In this study, juvenile Atlantic salmon (Salmo salar) were exposed to waterborne concentrations of the synthetic pharmaceutical and xenoestrogen 17alpha-ethynylestradiol (EE2; 5ng/L) and the xenoestrogen 4-nonylphenol (NP; 5 and 50microg/L) for 72h. Brain tissue and blood were sampled from individual fish. Gene expression patterns of Cyp19 isoforms were determined by quantitative PCR, aromatase protein immunoreactivity in the brain was evaluated by immunohistochemistry and immunoblotting, and aromatase activity was analyzed using the tritiated water-release assay. Plasma estradiol (E2) and testosterone (T) levels were measured by EIA. In the brain, EE2 increased the mRNA expression of Cyp19b almost threefold compared to the solvent control, whereas Cyp19a levels were unaffected by EE2 treatment. In contrast, both NP concentrations produced significant reduction of Cyp19a expression. Immunohistochemical aromatase protein reactivity was localized in several brain regions, but no apparent quantitative effects of the exposures were observed. Immunoblotting analysis showed that EE2 and NP produced a slight increase in brain immunoreactive aromatase protein band, compared with controls. Plasma levels of E2 increased twofold when treated with EE2 and 5microg NP/L, and threefold when exposed to 50microg NP/L. In general, the present study shows that the parallel biochemical, transcriptional and cellular detection of neural aromatase for endocrine-disrupting effects from EE2 and NP may be observed at specific levels of the biological organization.

Uptake and tissue distribution of C4-C7 alkylphenols in Atlantic cod (Gadus morhua): relevance for biomonitoring of produced water discharges from oil production

The sensitivity of different tissues for assessment of chronic low-dose environmental exposure of fish to alkylphenols (APs) was investigated. We exposed Atlantic cod (Gadus morhua) in the laboratory to tritium labelled 4-tert-butylphenol, 4n-pentylphenol, 4n-hexylphenol, and 4n-heptylphenol via seawater (8 ng/l) and via contaminated feed (5 microg/kg fish per day). Measurements of different fish tissues during eight days of exposure and eight subsequent days of recovery revealed that APs administered via spiked seawater were readily taken up whereas the uptake was far less efficient when APs were administered in spiked feed. AP residues were mainly located in the bile fluid whereas the concentrations in liver were very low, indicating a rapid excretion and the liver-bile axis to be the major route of elimination. The biological half-life of APs in the exposed cod was short, between 10 and 20 h. Our study shows that in connection with biomonitoring of AP exposure in fish, assessment of AP metabolites in bile fluid is a more sensitive tool than detection of parent AP levels in liver or other internal tissues.

Elevation of inducible nitric oxide synthase and cyclooxygenase-2 expression in the mouse brain after chronic nonylphenol exposure

The present study was performed to investigate the effects of chronic administration of nonylphenol (NP) on the expression of inflammation-related genes in the brains of mice. NP was given orally by gavages at 0, 50, 100, and 200 mg/kg/d. The expression of inflammatory enzymes, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), was evaluated by immunohistochemistry and immunoblotting assays. The nitric oxide (NO) level and nitric oxide synthase (NOS) activity were also measured by biochemical analyses. The results showed that NP at a high dose (200 mg/kg/d) significantly increased the expression of iNOS and COX-2 in both the hippocampus and cortex. In parallel with the increase in iNOS expression, the NO level was significantly greater at the dose of 200 mg/kg/d, compared to the control. The activity of NOS was also increased in the brain of mice at the dose of 100 and 200 mg/kg/d. These findings demonstrate that NP may have the potential to induce the chronic inflammation or cause neurotoxicity in the mouse brain.

Sexually disrupting effects of nonylphenol and diethylstilbestrol on male silver carp (Carassius auratus) in aquatic microcosms

Based on detected nonylphenol (NP) levels in aquaculture water, this study investigated sexually disrupting effects in mature male silver carp (Carassius auratus) exposed to NP and a positive control diethylstilbestrol (DES). The combined evidences of steroid hormone (17beta-estradiol, estrone and testosterone) levels and hispathological pictures showed that NP (10 microg/L) and DES could exert estrogenic effects through indirect mechanisms [i.e. increased estrogens levels (up to two times) and decreased androgen level in serum (down to 20-30%)], which might subsequently induce vitellogenin synthesis in liver. Environmental realistic concentrations of NP might be on the verge of inducing significant estrogenic effects in male silver carps. High amounts of NP and DES might be accumulated in fish serum, and the uptake by fish was possibly responsible for their quick attenuation in experimental tank water. NP and DES might have different metabolic mechanisms, the estrogenic effects of DES were more significant than those of NP.

Distribution and fate of nonylphenol in an aquatic microcosm

An aquatic microcosm consisting of four compartments, namely surface microlayer (SM), water sediment and biota (zebra fish), was developed to investigate the distribution and fate of nonylphenol (NP) in an aquatic environment. Level III and level IV fugacity-based multimedia models were used to calculate the distribution and fate of NP. Data obtained from model calculations were in good agreement with those of the experiments. Results of the model calculations showed that 86.50% of all NP input was removed by advective outflow, while 61.99% of the remainder was distributed to the sediment phase, 34.89% to the water phase, 2.50x10(-2)% to SM and 3.13% to the biotic phase. This finding demonstrates that sediment plays a key role in the fate of NP and acts as a sink in the aquatic environment. Bioconcentration factor (BCF) of NP in the zebra fish was high and varied in different parts of the fish. The highest BCF was 1440 in the viscera. After the uptake experiment, depuration of NP in clean water indicated that, the concentration of residue NP in the zebra fish was still high. This implies that NP in fish can pose a potential threat to human health due to its bioaccumulation in the food chain.

Activation of estrogen receptor signaling by the dioxin-like aryl hydrocarbon receptor agonist, 3,3',4,4',5-pentachlorobiphenyl (PCB126) in salmon in vitro system

Available toxicological evidence indicates that environmental contaminants with strong affinity to the aryl hydrocarbon receptor (AhR) have anti-estrogenic properties in both mammalian and non-mammalian in vivo and in vitro studies. The primary objective of the present study was to investigate the interactions between the AhR and estrogen receptor (ER) in salmon in vitro system. Two separate experiments were performed and gene expression patterns were analyzed using real-time PCR, while protein analysis was done by immunoblotting. Firstly, salmon primary hepatocytes were exposed to the dioxin-like PCB126 at 1, 10 and 50 nM [corrected] and ER agonist nonylphenol (NP) at 5 and 10 microM, singly or in combination. Our data showed increased levels of ER-mediated gene expression (vitellogenin: Vtg, zona radiata protein: Zr-protein, ERalpha, ERbeta and vigilin) as well as increased cellular ERalpha protein levels after treatment with NP and PCB126, singly or in combination. PCB126 treatment alone produced, as expected, increased transcription of AhR nuclear translocator (Arnt), CYP1A1 and AhR repressor (AhRR) mRNA, and these responses were reduced in the presence of NP concentrations. PCB126 exposure alone did not produce significant effect on AhR2alpha mRNA but increased (at 1 and 50 pM) and decreased (at 10 pM) AhR2beta mRNA below control level. For AhR2delta and AhR2gamma isotypes, PCB126 (at 1 nM) [corrected] produced significant decreases (total inhibition for AhR2gamma) of mRNA levels but was indifferent at 10 and 50 pM, compared to control. NP exposure alone produced concentration-dependent significant decrease of AhR2beta mRNA. In contrast, while 5 microM NP produced an indifferent effect on AhR2delta and AhR2gamma, 10 microM NP produced significant decrease (total inhibition for AhR2gamma) and the presence of NP produced apparent PCB126 concentration-specific modulation of all AhR isotypes. A second experiment was performed to evaluate the involvement of ER isoforms in PCB126 mediated estrogenicity. Here, cells were treated with the different concentrations of PCB126, alone or in combination with ICI182,780 (ICI) and sampled at 12, 24 and 48 h post-exposure. Our data showed that PCB126 produced a time- and concentration-specific increase of ERalpha and Vtg expressions and these responses were decreased in the presence of ICI. In general, these responses show a direct PCB126 induced transcriptional activation of ERalpha and estrogenic responses in the absence of ER agonists. Although not conclusive, our findings represent the first study showing the activation of estrogenic responses by a dioxin-like PCB in fish in vitro system and resemble the "ER-hijacking" hypothesis that was recently proposed. Thus, the direct estrogenic actions of PCB126 observed in the present study add new insight on the mechanisms of ER-AhR cross-talk, prompting a new wave of discussion on whether AhR-mediated anti-estrogenicity is an exception rather than rule of action.

Effects of a branched p-nonylphenol isomer (4(3',6'-dimethyl-3'-heptyl)-phenol) on embryogenesis in Lymnae stagnalis L

The tertiary branched alkyl-chain isomers of p-nonylphenol (NP) are perceived to have more estrogenic potency than its constituent secondary and primary straight alkyl-chain isomers. Investigations with single tertiary branched isomers of NP can therefore contribute toward the elucidation of the mechanisms of toxicity and estrogenicity of NP. A single tertiary branched alkyl-chain isomer (4(3',6'-dimethyl-3'-heptyl)-phenol) was used in studies to determine its effects on embryonic growth and mortality in Lymnaea stagnalis L. Egg masses were exposed to the test compound for 20 days in a static waterborne-exposure regime with an average NP concentration of 105 microg/L and water temperature range of 18-20 degrees C. Observations were made under a microscope and pictures were taken with a digital camera to determine the various developmental stages of growth, the duration of growth in each stage, embryo hatchability, and embryo mortality. The isomer was found to cause significant delay in all stages of growth and more significantly in the Morula and Veliger stages. An increase in embryo mortality, from the third day until the end of the experiment, was observed in exposed egg masses compared to controls. The hatching success of embryos was also significantly reduced by exposure, with 81% hatchability in exposed egg masses compared to 93% in the controls, after 18 days of continuous exposure. The encapsulating jelly strand that completely covers the rows of egg masses may have prevented the isomer residues from effectively penetrating into the embryos as shown by the observed low bioconcentration factors of the isomer in egg masses during exposure, resulting in unexpectedly lower observed estrogenic effects. However, this factor was not investigated. In vivo biotransformation of some of the residues of the isomer into catechol metabolites by the embryos during exposure could also result in the reduction of its estrogenic potential. To understand more fully the extent of toxicity and estrogenicity of this isomer, in vitro estrogenic assays are recommended. It would also be necessary to investigate its estrogenic effects on embryo development after in vivo maternal exposure.

Effects of North Sea oil and alkylphenols on biomarker responses in juvenile Atlantic cod (Gadus morhua)

A consequence of oil drilling at sea is the release of produced water contaminated with e.g. polycyclic aromatic hydrocarbons (PAH) and alkylphenols. In the present study, juvenile Atlantic cod were exposed to North Sea oil, nonylphenol and a combination of the North Sea oil and an alkylphenol mixture in a flow-through system. A suite of hepatic biomarkers were analysed. Exposure to North Sea oil resulted in strong induction of CYP1A protein levels and EROD activities. Exposure to nonylphenol, on the other hand, resulted in decreased CYP1A levels and EROD activities. Thus, nonylphenol appears to down-regulate CYP1A expression in Atlantic cod. Combined exposure to North Sea oil with an alkylphenol mixture resulted in lower EROD induction, compared to that in fish exposed to North Sea oil alone. This difference was not statistically significant, but still we believe that the alkylphenols have inhibited CYP1A activities in the fish which may have compromised CYP1A mediated metabolism of other xenobiotics, including PAH. CYP3A protein levels were lower, compared to controls, in fish exposed to nonylphenol and the combination of North Sea oil and alkylphenol mixture. In contrast, the oil alone had no effect on CYP3A protein content. North Sea oil exposure, alone or in combination with alkylphenols, caused oxidative stress observed as elevated levels of GSSG content and GR and CAT activities. Interestingly, exposure to nonylphenol resulted in a marked depletion of total glutathione levels. This apparent depletion may be a consequence of increased conjugation of glutathione to nonylphenol followed by excretion. An increase in conjugation enzyme GST activity was observed in the nonylphenol exposed group, although the difference was not significant. No sign of oxidative damage, measured as lipid peroxidation, was observed in any of the exposures experiments. This study suggests that North Sea oil may lead to oxidative stress and altered CYP1A and CYP3A expression. Alkylphenols, present in produced water, resulted in decreased CYP1A and CYP3A protein expression in Atlantic cod.

Comparison of protein expression in plasma from nonylphenol and bisphenol A-exposed Atlantic cod (Gadus morhua) and turbot (Scophthalmus maximus) by use of SELDI-TOF

The overall objective of this study was to compare the expression of plasma proteins in juvenile cod and turbot after a 3 week exposure to two different chemicals known to be estrogenic: 4-nonylphenol (NP, 29 microg/L) and bisphenol A (BPA, 59 microg/L). ProteinChip) array technology in combination with surfaced enhanced laser desorption ionisation-time of flight (SELDI-TOF) was used to investigate general responses in plasma proteins. In addition, an indirect enzyme-linked immunosorbent assay (ELISA) was used to analyse two specific biomarkers of estrogenic exposure, vitellogenin (Vtg) and zona radiata protein (Zrp) in plasma. Both methods revealed clear species specific responses. In cod, 67% of significantly altered proteins showed the same response (up or down regulated) in NP and BPA exposed animals (males and females combined). The rest were either specific to NP (10%), BPA (19%) or they showed opposite responses to the two chemicals (4%). In contrast, only 20% of significantly altered proteins were common for NP and BPA exposed turbot: 60% were altered only in NP and 17% only in BPA. Furthermore, in BPA exposed cod, 77% of the responses were common for male and females, whereas turbot showed only 21% similarity for the two genders. However, NP exposed male and female turbot showed 88% similarity in responses. As gender was not determined in NP exposed cod, gender specific responses could not be determined. ELISA results supported that cod responded clearly to both chemicals as a large increase was observed in Vtg and Zrp levels. Turbot responded strongly to NP, but seemed only slightly affected by BPA. Overall, the results indicated that cod are more sensitive or respond with less specificity to estrogenic chemicals than turbot. The relatively large degree of common responses in NP and BPA exposed cod may indicate that in cod BPA have similar mode of action as NP. Generally, the results show the potential of SELDI-TOF as a tool for comparing multiple responses, and for identifying exposure as well as gender specific responses.

Effects of 4-n-Nonylphenol and Tamoxifen on Salmon Gonadotropin-Releasing Hormone, Estrogen Receptor, and Vitellogenin Gene Expression in Juvenile Rainbow Trout

Alkylphenols such as nonylphenol (NP) are one of a wide variety of environmental chemicals reported to have estrogenic effects in both in vitro and in vivo studies. Induction of hepatic vitellogenin (Vg) gene expression is widely used as a biomarker for xenoestrogen exposure in fish. However, little work has been done to characterize the molecular effects of xenoestrogens on other potential target organs such as the brain. To evaluate brain and liver effects of 4-n-nonylphenol (4-NP), juvenile rainbow trout (Oncorhynchus mykiss) were exposed to waterborne 4-NP or 17beta-estradiol (E(2)). Changes in mRNA levels of salmon gonadotropin-releasing hormone (sGnRH) and estrogen receptor alpha (ERalpha) isoforms in the brain and ERalpha isoforms and Vg in the liver were measured after 3 and 6 days of exposure, with the help of a relative RT-PCR-based quantification method. Fish were treated with increasing doses of 4-NP ranging from 0.01 to 10 microM (2.2 microg/l to 2.2 mg/l), and results were compared to the effect of E(2) or tamoxifen, a specific ER modulator. In liver, E(2) and the highest doses of 4-NP increased Vg and ERalpha long-isoform mRNA levels within 3 or 6 days of exposure, but 4-NP did not have any effect on ERalpha short-isoform transcription level. In the brain, 4-NP reduced sGnRH2 gene expression in a dose-dependent manner, but did not modify sGnRH1 or ERalpha mRNA levels.

Screening and testing for endocrine disruption in fish-biomarkers as "signposts," not "traffic lights," in risk assessment

Biomarkers are currently best used as mechanistic "signposts" rather than as "traffic lights" in the environmental risk assessment of endocrine-disrupting chemicals (EDCs). In field studies, biomarkers of exposure [e.g., vitellogenin (VTG) induction in male fish] are powerful tools for tracking single substances and mixtures of concern. Biomarkers also provide linkage between field and laboratory data, thereby playing an important role in directing the need for and design of fish chronic tests for EDCs. It is the adverse effect end points (e.g., altered development, growth, and/or reproduction) from such tests that are most valuable for calculating adverseNOEC (no observed effect concentration) or adverseEC10 (effective concentration for a 10% response) and subsequently deriving predicted no effect concentrations (PNECs). With current uncertainties, biomarkerNOEC or biomarkerEC10 data should not be used in isolation to derive PNECs. In the future, however, there may be scope to increasingly use biomarker data in environmental decision making, if plausible linkages can be made across levels of organization such that adverse outcomes might be envisaged relative to biomarker responses. For biomarkers to fulfil their potential, they should be mechanistically relevant and reproducible (as measured by interlaboratory comparisons of the same protocol). VTG is a good example of such a biomarker in that it provides an insight to the mode of action (estrogenicity) that is vital to fish reproductive health. Interlaboratory reproducibility data for VTG are also encouraging; recent comparisons (using the same immunoassay protocol) have provided coefficients of variation (CVs) of 38-55% (comparable to published CVs of 19-58% for fish survival and growth end points used in regulatory test guidelines). While concern over environmental xenoestrogens has led to the evaluation of reproductive biomarkers in fish, it must be remembered that many substances act via diverse mechanisms of action such that the environmental risk assessment for EDCs is a broad and complex issue. Also, biomarkers such as secondary sexual characteristics, gonadosomatic indices, plasma steroids, and gonadal histology have significant potential for guiding interspecies assessments of EDCs and designing fish chronic tests. To strengthen the utility of EDC biomarkers in fish, we need to establish a historical control database (also considering natural variability) to help differentiate between statistically detectable versus biologically significant responses. In conclusion, as research continues to develop a range of useful EDC biomarkers, environmental decision-making needs to move forward, and it is proposed that the "biomarkers as signposts" approach is a pragmatic way forward in the current risk assessment of EDCs.

Oral single pulse exposure of flounder Platichthys flesus to 4-tert-octylphenol: Relations between tissue levels and estrogenic effects

The accumulation of 4-tert-octylphenol and the associated estrogenic effects were studied after a single pulse exposure to flounder Platichthys flesus. 4-tert-octylphenol was administered orally in a single dose of 50 mg kg(-1) and tissue (liver, muscle and testis) and plasma concentrations of 4-tert-octylphenol as well as plasma vitellogenin were measured 3, 6, 12, 18, 24, 48, 72, 144 and 216 h after administration of the dose. Concentrations of 4-tert-octylphenol in plasma and tissues were determined by Liquid Chromatography Mass Spectrometry (LC-MS). 4-tert-octylphenol was detectable in liver, testis, muscle and plasma 3h post administration and an accumulation was observed in liver, muscle and plasma up to 12 h and in testis 18 h post administration, respectively. The maximum concentrations of 4-tert-octylphenol in liver, muscle and testis were 67, 3.2 and 6.8 microg g(-1), respectively. An increase in plasma vitellogenin levels was seen 48 h post administration and the vitellogenin level continued to increase (from <100 ng ml(-1) to 1.4 mg ml(-1)) until the end of the experiment 9 days after the administration of 4-tert-octylphenol.

The potential of ecotoxicoproteomics in environmental monitoring: biomarker profiling in mussel plasma using ProteinChip array technology

New global technologies, allowing simultaneous analysis of thousands of genes, proteins, and metabolites (so-called "omics" technologies), are being adopted rapidly by industry, academia, and regulatory agencies. This study evaluated the potential of proteomics in ecotoxicological research (i.e., ecotoxicoproteomics). Filter-feeding mussels (Mytilus edulis) were exposed continuously for 3 wk to oil, or oil spiked with alkylphenols and extra polycyclic aromatic hydrocarbons. The influence of chronic exposure on mussel plasma protein expression was investigated utilizing ProteinChip array technology in combination with surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI TOF MS). Results indicated that exposure to spiked oil had a more significant effect on protein expression in mussels than oil alone. In total, 83 mass peaks (intact or modified proteins/peptides) were significantly altered by spiked oil, while 49 were altered by oil. In exposed organisms, the majority of peaks were upregulated compared to controls (i.e., 69% in oil and 71% in spiked oil). Some peaks (32 in total) were affected by both treatments; however, the degree of response was higher in the spiked oil group for 25 of the 32 commonly affected features. Additionally, certain peaks revealed exposure- or gender-specific responses. Multivariate analysis with regression tree-based methods detected protein patterns associated with exposure that correctly classified masked samples with 90-95% accuracy. Similarly, 92% of females and 85% of males were correctly classified (independent of exposure). Results indicate that proteomics have the potential to make a valuable contribution to environmental monitoring and risk assessment.

Comparative study of the estrogenic responses of mirror carp (Cyprinus carpio) exposed to treated municipal sewage effluent (Lisbon) during two periods in different seasons

To assess the estrogenic potency of the treated domestic sewage effluent from a sewage treatment plant (STP) located in Lisbon (Chelas), 60 mirror carp (Cyprinus carpio) were exposed to different concentrations of the sewage effluent (0%, 25%, 50% and 100%) for two periods of 28 days in two different seasons (winter/spring). Vitellogenin induction in males was used as a biomarker of exposure to xenoestrogens. At the end of the experiment, blood samples were taken for vitellogenin analysis and the fish were sacrificed and dissected. Gonad samples were taken for histological evaluation of the sewage effects. The results showed an increase in vitellogenin induction in exposed fish, both males and females, depending on the different dilutions of the sewage effluent. In comparison with controls, the gonadosomatic index decreased significantly (P < 0.05) in fish exposed to 100% treated effluent. Although statistically not significant, the hepatosomatic index (HSI) was high in all exposed fish. Histological abnormalities in fish gonads were evaluated and related to the different percentages of sewage effluent. Seasonal variations found in estrogenic responses were attributed to weather influences on sewage dilution.

Juvenile sea bass biotransformation, genotoxic and endocrine responses to beta-naphthoflavone, 4-nonylphenol and 17 beta-estradiol individual and combined exposures

Juvenile sea bass, Dicentrarchus labrax L., were exposed during 2, 4, 8, and 24 h to 0.9 microM beta-naphthoflavone (BNF), 131 nM 17 beta-estradiol (E(2)), 4.05 microM 4-nonylphenol (NP), as well as to BNF combined either to E(2) or NP (maintaining the previous concentrations). Liver cytochrome P450 content (P450), ethoxyresorufin-O-deethylase (EROD), and glutathione S-transferase (GST) activities were measured in order to evaluate biotransformation responses. Genotoxicity was assessed as erythrocytic nuclear abnormalities (ENA) frequency. The effects on endocrine function were evaluated as plasma cortisol and glucose. Cortisol was not affected by xeno/estrogens tested, either in single exposure or mixed with BNF. Nevertheless, the intermediary metabolism was affected since glucose concentration increased after 4 h exposure to E(2), and after all BNF+NP exposure lengths. Moreover, a synergism between BNF and NP was thoroughly demonstrated, whereas a sporadic antagonistic interaction was found at 4 h BNF + E(2) exposure. Liver EROD and GST activities were not significantly altered by single E(2) or NP exposure. However, both compounds were able to induce EROD activity in the presence of BNF. NP single exposure was able to significantly increase liver P450 content, while its mixture with BNF displayed an antagonistic interference. Considering the xeno/estrogens single exposures, only NP induced an ENA increase; however, both mixtures (BNF + E(2) and BNF + NP) displayed genotoxic effects. Fish responses to mixtures of xenobiotics are complex and the type of interaction (synergism/potentiation or antagonism) in a particular mixture can vary with the evaluated biological response.