Molecular markers of endocrine disruption in aquatic organisms

Chlorinated isomers of nonylphenol differ in estrogenic and androgenic activity

Technical mixtures of nonylphenol (NP) contain over 20 p-substituted isomers. Mono- and di-chlorinated derivatives are generated during the chlorination process in water treatment. Four NP isomers (i.e. 4n-, p353-, p33-, p363-NP) and their mono- (MCl) and di-chlorinated (DCl) derivatives were tested for their estrogenic and androgenic potency using yeast estrogenic and androgenic assay. The p353-NP and 4n-MClNP isomers showed the highest and the lowest estrogenic potency, respectively. The p363-MClNP exhibits estrogenic potency comparable to the parent isomer, whereas all p-DClNP compounds displayed a decrease in the estrogenic potency. In the anti-androgenic screen, all substances exhibited a positive response; the mono- and di-chlorinated derivatives exhibit lower potency than the parent isomers. The isomer p363-NP and its corresponding mono- and di-chlorinated derivatives were almost inactive. Furthermore, all compounds were tested for anti-estrogenic and androgenic assays, but none of them showed a positive response. These results indicate that for assessing the xeno-hormone potency of chlorinated derivatives of NP, the use of pure compounds is essential because the mixtures are not representative. In fact the concentrations of NP isomers differ in technical mixtures according to the producers; after chlorination different technical mixtures can generate dissimilar ratios of chlorinated derivatives. Finally, the chlorinated derivatives of NP didn't show an increase in xeno-hormone potency compared to the parent isomers, and for this reason the many oxidized by-products generated during chlorination process mask the xeno-hormone potency of the pure chlorinated isomers of NP.

Transcriptional response of stress genes to metal exposure in zebra mussel larvae and adults

Development of stress markers for the invader freshwater zebra mussel (Dreissena polymorpha) is of great interest for both conservation and biomonitoring purposes. Gene expression profiles of several putative or already established gene expression stress markers (Metallothionein, Superoxide dismutase, Catalase, Glutathione S transferase, Glutathione peroxidase, Cytochrome c oxidase, the multixenobiotic resistance P-gp1, and heat shock proteins HSP70 and HSP90) were analyzed by quantitative Real-Time PCR in adults and pediveliger larvae after exposure to metals (Hg, Cu, Cd). A defined pattern of coordinated responses to metal exposure and, presumably, to oxidative stress was observed in gills and digestive gland from adults. A similar, albeit partial response was observed in larvae, indicating an early development of stress-related gene responses in zebra mussel. The tools developed in this study may be useful both for future control strategies and for the use of zebra mussel as sentinel species in water courses with stable populations.

Development of Atlantic cod (Gadus morhua) exposed to produced water during early life stages: Effects on embryos, larvae, and juvenile fish

Produced water (PW) contains numerous toxic compounds of natural origin, such as dispersed oil, metals, alkylphenols (APs), and polycyclic aromatic hydrocarbons (PAHs). In addition, PW also contains many different chemicals which have been added during the oil production process. In the study described here, cod were exposed to real PW collected from an oil production platform in the North Sea. This was done in order to best recreate the most realistic field-exposure regime in which fish will be affected by a wide range of chemicals. The biological effects found in this study therefore cannot be assigned to one group of chemicals alone, but are the result of exposure to the complex chemical mixture found in real PW. Since APs are well known to cause endocrine disruption in marine organisms, we focused our chemical analysis on APs in an attempt to better understand the long-term effects of APs from PW on the biology of fish. In this study, cod were exposed to several concentrations of real PW and 17β-oestradiol (E(2)), a natural oestrogen, at different developmental stages. Cod were exposed to PW either during the embryo and early larvae stage (up to 3 months of age) or during the early juvenile stage (from 3 to 6 months of age). Results showed that, in general, APs bioconcentrate in fish tissue in a dose and developmental stage dependent manner during PW exposure. However, juveniles appeared able to effectively metabolise the short chain APs. Importantly, PW exposure had no effect on embryo survival or hatching success. However, 1% PW clearly interfered with the development of normal larval pigmentation. After hatching most of the larvae exposed to 1% PW failed to begin feeding and died of starvation. This inability to feed may be linked to the increased incidence of jaw deformities seen in these larvae. In addition, cod exposed to 1% PW, had significantly higher levels of the biomarkers vitellogenin and CYP1A in plasma and liver, respectively. No similar effects were seen in cod exposed to either 0.1% or 0.01% PW.

Characterization of vitellogenin gene expression in round goby (Neogobius melanostomus) using a quantitative polymerase chain reaction assay

A growing concern over endocrine disruption in aquatic species has prompted the development of molecular assays to monitor environmental impacts. This study describes the development of quantitative polymerase chain reaction (qPCR) assays to characterize the expression of two vitellogenin (Vtg) genes in the invasive round goby (Neogobius melanostomus). Fragments from the 18SrRNA (housekeeping gene), Vtg II, and Vtg III genes were cloned and sequenced. The qPCR assays were developed to detect hepatic Vtg expression in goby. The assays detected induction of both Vtg genes in nonreproductive males following a two-week laboratory exposure to 17β-estradiol (≥1 mg/kg i.p. injection). The assays were applied to goby from Hamilton Harbour, Lake Ontario (Canada), including those from sites where feminization and intersex of goby has been documented. Both Vtg genes had significantly higher expression in females compared to males. Male reproductive goby adopt either parental or sneaker tactics; Vtg II expression was higher in sneaker than in parental males but parental and nonreproductive males did not differ from each other. The Vtg III expression was significantly higher in sneaker males followed by parental males and nonreproductive males, respectively. The Vtg II and III expression in nonreproductive males was elevated in the contaminated site with documented intersex. This assay provides an important tool for the use of an invasive species in monitoring endocrine disruption in the Great Lakes region.

Relative potencies of natural estrogens on vitellogenin and choriogenin levels in the Indian freshwater spotted snakehead, Channa punctata: in vivo and in vitro studies

The relative efficacies of three natural estrogens viz., estrone (E(1)), estradiol-17beta (E(2)) and estriol (E(3)) to induce synthesis of vitellogenin (Vg) and choriogenin (Chg) were assessed in primary hepatocyte cultures of the Indian freshwater spotted snakehead, Channa punctata. Hepatocytes were isolated from the spotted snakehead liver by a non-enzymatic protocol. Optimum culture conditions were standardized for ensuring their viability and functioning. Isolated hepatocytes were cultured for 48 h for monolayer formation and then exposed to various concentrations (0.001-10 microM) of the three estrogens. Competitive homologous ELISAs, developed and validated for spotted snakehead Vg and Chg were employed to determine the amounts of these two proteins secreted into the culture medium after 48 h of incubation. The results reveal that although all the three estrogens were effective in inducing the production of Vg and Chg in a dose-dependent manner, there were differences in their relative potencies. Of three estrogens, E(1) was the least potent and could induce synthesis of Vg and Chg only at a minimum concentration of 0.5 microM; whereas significant levels of both the proteins were quantified in culture medium by exposing the hepatocytes to E(2) or E(3) even at a concentration of 0.001 microM. All three estrogens were effective in inducing synthesis of Vg and Chg in vivo also. These results suggest the possibility of employing the above in vitro experimental design to monitor the presence of estrogens/estrogen-like chemicals in natural waters, which could interfere with the estrogen receptor system of fish. This study further points to the possibility of using Chg, in addition to Vg, as a parameter for screening various chemicals for their estrogenic activity.

Evaluation of environmental impact on natural populations of the Mediterranean killifish Aphanius fasciatus by quantitative RNA biomarkers

The Mediterranean killifish, Aphanius fasciatus (Valenciennes, 1821) represents an excellent sentinel species for analysis of environmental impact in coastal areas. Quantitative changes on liver mRNA levels of five stress-related genes--metallothionein (metal exposure), vitellogenin, (estrogenic effects), cytochrome P4501A (CYP1A, dioxin-like compounds), superoxide dismutase (oxidative stress) and HSP70 (general stress)--were tested as markers of exposure to pollutants both in natural populations and in experimental treatments with model effectors. Analysis of fish from a metal-contaminated site in the Tunisian coast (Sfax) indicated that fish presenting spinal deformities (eight times more frequent at this site than in reference sites) showed increased levels of hepatic CYP1A mRNA levels compared to non-deformed fish from the same site or from the reference Louza site, suggesting a combined impact by metals and organic pollutants. Due to the strategy used in their design, these quantitative RNA markers will likely be useful to analyze environmental impacts on other related fish species.

Effects of estrogen exposure in mussels, Mytilus edulis, at different stages of gametogenesis

Mytilus edulis were exposed to 17beta-estradiol (E2) and the synthetic estrogens ethinyl estradiol (EE2) and estradiol benzoate (EB) for 10 days. Two exposures were performed to determine their effect on vitellogenin (VTG) and estrogen receptor 2 (ER2) mRNA expression at different stages of the reproductive cycle. Significant natural variation was not observed in VTG mRNA expression, though ER2 mRNA expression displayed significantly lower values during January, February and July compared with other times of the year. A significant increase in VTG and ER2 mRNA expression was observed in mussels exposed to estrogens at the early stage of gametogenesis. In contrast, mature mussels displayed no statistically significant change in the VTG or ER2 mRNA expression. The data presented suggests that the reproductive physiology of molluscs, in terms of VTG and ER2 mRNA expression, may be susceptible to damage by environmental estrogens at certain points in their gametogenesis process.

Hepatic transcriptomic and metabolomic responses in the Stickleback (Gasterosteus aculeatus) exposed to ethinyl-estradiol

An established three-spined stickleback (Gasterosteus aculeatus) cDNA array was expanded to 14,496 probes with the addition of hepatic clones derived from subtractive and normalized libraries from control males and males exposed to model toxicants. Microarrays and one-dimensional (1)H nuclear magnetic resonance (NMR) spectroscopy, together with individual protein and gene biomarkers were employed to investigate the hepatic responses of the stickleback to ethinyl-estradiol (EE(2)) exposure. Male fish were exposed via the water to EE(2), including environmentally relevant concentrations (0.1-100ng/l) for 4 days, and hepatic transcript and metabolite profiles, kidney spiggin protein and serum vitellogenin concentrations were determined in comparison to controls. EE(2) exposure did not significantly affect spiggin concentration but significantly induced serum vitellogenin protein at the threshold concentration of 32ng/l. (1)H NMR coupled with robust univariate testing revealed only limited changes, but these did support the predicted modulation of the amino acid profile by transcriptomics. Transcriptional induction was found for hepatic vitellogenins and choriogenins as expected, together with a range of other EE(2)-responsive genes. Choriogenins showed the more sensitive responses with statistically significant induction at 10ng/l. Real-time polymerase chain reaction (PCR) confirmed transcriptional induction of these genes. Phosvitinless vitellogenin C transcripts were highly expressed and represent a major form of the egg yolk precursors, and this is in contrast to other fish species where it is a minor component of vitellogenic transcripts. Differences in inducibility between the vitellogenins and choriogenins appear to be in accordance with the sequential formation of chorion and yolk during oogenesis in fish.

Biological and molecular responses of Chironomus riparius (Diptera, Chironomidae) to herbicide 2,4-D (2,4-dichlorophenoxyacetic acid)

2,4-Dichlorophenoxyacetic acid (2,4-D) is an agricultural contaminant found in rural ground water. It remains to be determined whether neither 2,4-D poses environmental risks, nor is the mechanism of toxicity known at the molecular level. To evaluate the potential ecological risk of 2,4-D, we assessed the biological parameters including the survival rate, adult sex ratio of emerged adults, and mouthpart deformities in Chironomus riparius after long-term exposure to 2,4-D. The larvae were treated with 0.1, 1 or, 10microgL(-1) of 2,4-D for short- and long-term exposure periods. The sex ratio was changed in C. riparius exposed to only 10microgL(-1) of 2,4-D, whereas mouthpart deformities were observed as significantly higher in C. riparius exposed to 0.1microgL(-1) of 2,4-D. Survival rates were not significantly affected by 2,4-D. Furthermore, we evaluated the molecular and biochemical responses of biomarker genes such as gene expression of heat shock proteins (HSPs), ferritins and glutathione S-transferases (GSTs) in C. riparius exposed to 2,4-D for 24h. The expressions of HSP70, HSP40, HSP90 and GST levels in C. riparius were significantly increased after exposure to a 10microgL(-1) concentration of 2,4-D, whereas ferritin heavy and light chain gene expressions were significantly increased at all concentrations of 2,4-D exposure. Finally, these results may provide an important contribution to our understanding of the toxicology of 2,4-D herbicide in C. riparius. Moreover, the 2,4-D-mediated gene expressions may be generated by 2,4-D is the causative effects on most probable cause of the observed alterations. These biological, molecular and morphological parameters and the measured parameters can be used to monitor 2,4-D toxicity in an aquatic environment.

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

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

Endosulfan in vitro toxicity in Atlantic salmon hepatocytes obtained from fish fed either fish oil or vegetable oil

The composition of the feed may alter the cellular composition of an organism and thus has the potential to influence a xenobiotic response. The main aim of this study was to see if the fatty acid composition of primary hepatocytes isolated from Atlantic salmon (Salmo salar L.) obtained from fish fed either a fish oil or a vegetable oil based diet, influenced the response to endosulfan exposure in vitro. The primary cultures were exposed to six different concentrations of endosulfan (0.001, 0.01, 0.1, 1, 10 and 100 microM) for 48 h. Cell morphology as well as a molecular toolbox of 16 genes encoding stress responsive and biotransformation proteins was examined. Endosulfan exposure caused moderate cytotoxicity and steatosis in a dose-dependent manner in the hepatocytes. In general, endosulfan hepatoxicity seems to be unaffected by the fatty acid composition of the hepatocytes. Exceptions were general stress (HSP70) and markers for estrogen exposure (ZP and VTG), which appeared to be slightly less responsive in hepatocytes isolated from the vegetable oil fed fish.

Pulp and paper mill effluents induce distinct gene expression changes linked to androgenic and estrogenic responses in the fathead minnow (Pimephales promelas)

Although effluent treatment systems within pulp and paper mills remove many toxicants and improve wastewater quality, there is a need to understand and quantify the effectiveness of the treatment process. At a combined news and kraft pulp and paper mill in northwestern Ontario, Canada, fathead minnow (FHM) reproduction and physiology were examined before, during, and after a short-term (6-d) exposure to 10% (v/v) untreated kraft mill effluent (UTK), 25% (v/v) secondary treated kraft mill effluent (TK), and 100% (v/v) combined mill outfall (CMO). Although UTK exposure significantly decreased egg production, neither TK nor CMO caused any reproductive changes. The expression of six genes responsive to endocrine-disrupting compounds, stress, or metals was then examined in livers of these fish using real-time polymerase chain reaction. In female FHMs, none of the three effluents induced significant expression changes in any genes investigated. By contrast, in males there were significant increases in the mRNA levels of androgen receptor, estrogen receptor (ER) beta, and cytochrome P4501A (CYP1A) upon UTK and TK exposure but no changes in ERalpha or vitellogenin (VTG) gene expression, whereas CMO exposure significantly increased the mRNA levels of ERalpha, VTG, and CYP1A. Together, these results suggest that kraft effluent before and after biological treatment contained compounds able to induce androgenic effects in FHMs, and that combination of kraft and newsmill effluents eliminated the androgenic compounds while inducing distinct and significant patterns of gene expression changes that were likely due to estrogenic compounds produced by the newsmill.

Effects of estradiol and progesterone on the reproduction of the freshwater crayfish Cherax albidus

In this study we have investigated the role of 17beta-estradiol and progesterone in the reproduction of the crayfish Cherax albidus by using vitellogenin (VTG) as a biomarker. Early-vitellogenic (EV), full-vitellogenic (FV), and non-vitellogenic (NV) females of Cherax albidus were treated with 17beta-estradiol, progesterone, or both for 4 weeks. Levels of VTG mRNA in the hepatopancreas were detected by RT-PCR. The PCR product was sequenced and showed 97% homology with Cherax quadricarinatus VTG. 17beta-estradiol was more effective than progesterone and 17beta-estradiol plus progesterone in increasing the vitellogenin transcript in the hepatopancreas of EV and FV females. On the contrary, progesterone was more effective than 17beta-estradiol and 17beta-estradiol plus progesterone in increasing the vitellogenin concentration in the hemolymph of EV and FV females. Hepatopancreas histology and fatty acid composition of females injected with hormones showed major modifications. No effects were registered in NV females. In conclusion, 17beta-estradiol and progesterone influence VTG synthesis, although our data indicate that they act through different pathways and are not effective until the proper hormonal environment is established, as demonstrated by their inefficacy in NV females.

Modulation of salmon ovarian steroidogenesis and growth factor responses by the xenoestrogen, 4-nonylphenol

Endocrine-disrupting chemicals are known to influence organismal reproductive processes, including the production and regulation of gonadal steroids. This study evaluated the effects of a xenoestrogen (nonylphenol: NP) on salmon ovarian steroidogenesis and growth factors using an in vitro organ culture system. Ovarian tissues were cultivated for 3 and 7d with different concentrations of NP (0 (control), 1, 10 and 50 microM) dissolved in ethanol (0.1%). The mRNA expressions of steroidogenic acute regulatory (StAR) protein, P450-mediated cholesterol side-chain cleavage (P450scc), aromatase isoforms, 3beta-hydroxysteroid dehydrogenase (3beta-HSD), Cyp11beta-, Cyp17 and 21-hydroxylase, and insulin-like growth factors (IGF-1 and IGF-2) and IGF1-receptor (IGF1-R) were quantified by real-time PCR. Tissue levels of estradiol-17beta (E2), testosterone (T) and 11-ketotestosterone (11-KT) were quantified using enzyme immunoassays. Our data show that nominal NP levels produced time- and concentration-specific effects on the expression of steroidogenesis- and IGF-related transcripts in salmon ovarian tissues. Tissue levels of ovarian E2, T and 11-KT were significantly modulated after NP exposure. Interestingly, elevated ovarian E2 levels after 10 microM NP exposure at day 3 paralleled P450Arom isoforms mRNA expression at the same time interval. The expression patterns of other steroidogenic protein and enzyme genes, such as StAR, P450scc, 3beta-HSD and Cyp17 inversely paralleled this pattern, displaying consistent decreased transcript levels. These findings show that NP (an ubiquitous environmental pollutant) can produce variations in gonadal steroidogenesis and growth regulating responses with potential consequences for overt fecundity in teleosts.

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.

Comparison of six different sewage treatment processes--reduction of estrogenic substances and effects on gene expression in exposed male fish

Treated sewage effluents often contain a mixture of estrogenic compounds in low concentrations. The total combined activity of these, however, may be sufficiently high to affect the reproduction of aquatic vertebrates. The introduction of advanced treatment technologies has been suggested as a way to remove micro-contaminants, including estrogenic substances. In this study, one municipal influent was treated with six different processes in parallel on a semi-large scale in order to assess their potential to reduce substances that could contribute to estrogenic effects in male fish. The effluent from a conventional, activated sludge treatment line was compared to a similarly treated effluent with a final sand-filtering step. The addition of ozonation (15 g O(3)/m(3)), a moving bed biofilm reactor (MBBR) or both in combination was also evaluated. There was also a separate treatment line that was based on a membrane bioreactor. A small battery of hepatic estrogen-responsive genes was measured in the exposed fish using quantitative PCR. Concentrations of steroid estrogens and estrogenic phenols in the effluents were measured by GC-ECNI-MS. The ozonated effluents were the only tested effluents for which all measured biological effects in exposed fish were removed. Chemical data suggested that the MBBR technology was equally effective in removing the analyzed estrogens; however, elevated expression of estrogen-responsive genes suggested that some estrogenic substances were still present in the effluent. The membrane bioreactor removed most of the measured estrogens and it reduced the induction of the estrogen-responsive genes. However, fish exposed to this effluent had significantly enlarged livers. Given that the same influent was treated in parallel with a broad set of technologies and that the chemical analyses were combined with an in vivo assessment of estrogenic responses, this study provides valuable input into the assessment of advanced treatment processes for removing estrogenic substances.

Effects of environmental contaminants on hemoglobin gene expression in Daphnia magna: a potential biomarker for freshwater quality monitoring

Daphnia hemoglobin (Hb) is one of the widely investigated invertebrate respiratory pigment. In this study, alteration of Daphnia magna Hb was evaluated in terms of its gene expression, using four D. magna Hb open reading frames (ORFs), by exposure of various chemicals, such as nonylphenol (NP), bisphenol A (BPA), benzo[a]pyrene (B[a]P), chloropyriphos (CP), paraquat dichloride (PQ), and lead nitrate (Pb), under laboratory conditions. A Daphnia reproduction test was also conducted to test the ecotoxicological relevance of chemical-induced Daphnia Hb gene expression. Daphnia Hb gene expression increased by most of tested chemicals. Nonylphenol induced all four Hb ORFs, and an increase in D. magna hemoglobin 2 (dmhb2), dmhb3, and dmhb4 gene expression was exposure concentration dependent. Although BPA and B[a]P also induced most of the Hb genes, the degree of increase was less than two-fold compared to the control. For CP and Pb exposure, an increase in dmhb2 and dmhb4 gene expression was the most significant among the four Daphnia Hb ORFs. Each ORF might exhibit different sensitivities to chemical stress; of the four ORFs studied, an increase in dmhb2 and dmhb4 gene expression was the most significant. It seems clear that Daphnia Hb has a considerable potential as a biomarker for freshwater toxicity monitoring, as an increase in Hb gene expression seems to be correlated with a decrease in reproduction in this animal. The results suggest that Daphnia Hb could give useful information to diagnose general health conditions in a freshwater ecosystem. Considering the potential of D. magna as a biomonitoring species and the physiological particularities of its respiratory pigments, Daphnia Hb could be developed as a biomarker for ecotoxicity monitoring.

Environmental levels of atrazine decrease spatial aggregation in the freshwater mussel, Elliptio complanata

The commonly used herbicide atrazine (ATR), may cause estrogen-like alterations and, like other xenoestrogens, may alter behavior. Here effects on animal aggregation were tested in freshwater mussels exposed short-term to ecologically relevant ATR concentrations between 1.5 and 150microg/L. The aggregation index (AI), the fraction of mussels in the most densely populated tank section, was evaluated and showed higher AI at later times in both 6- and 72-h trials (p<0.001). After 72h, there was also less aggregation in estradiol- and mid-ATR-treated animals, 26% and 24% less than control, respectively (p<0.04). These data suggest that freshwater mussels tend to aggregate, that 72-h exposure to ecologically relevant ATR concentrations decreases aggregation, and that estradiol exposure has a similar effect. Given that bivalve aggregation may be related to reproduction, the results suggest that low concentrations of ATR may have ecological consequences on animal populations in this species.

Effects of diquat and fomesafen applied alone and in combination with a nonylphenol polyethoxylate adjuvant on Lemna minor in aquatic indoor microcosms

The influence of tank-mix adjuvants on pesticide toxicity remains largely unknown. Agral 90, a nonylphenol polyethoxylated tank-mix adjuvant, has been used with diquat (bipyridylium herbicide) and fomesafen (diphenyl-ether herbicide) in aquatic indoor microcosms in order to compare the toxicity of the single compounds and of binary herbicide-adjuvant mixtures to Lemna minor. Twenty-four microcosms were used and treatments were performed with substances alone or with herbicide-adjuvant binary mixtures, at two concentrations levels (44.4 and 222.2 microg/L for the herbicides, and 100 and 500 microg/L for Agral 90). Toxicity was assessed weekly for 1 month through growth measurements, as inferred from the relative frond number (RFN) and relative frond area (RFA). Concentrations of diquat and fomesafen in water and sediments were measured weekly. The herbicides showed very different behaviour in microcosms, with a rapid disappearance of diquat from the aqueous phase whereas fomesafen levels remained almost constant over time. Diquat strongly inhibited the growth of L. minor whereas fomesafen had no effect on plant growth. Presence of the adjuvant only slightly reduced the effect of the lowest concentration of diquat, probably as a result of dispersion of the herbicide at the water surface. It is concluded that tank-mix adjuvant designed to improve herbicide efficiency in the terrestrial environment did not have any effect on aquatic plants when applied to the aquatic environment.

Relationships between physiology, tissue contaminants, and biomarker responses in Atlantic cod (Gadus morhua L.)

It is generally assumed that there should be some relationship between tissue residues of contaminants and related biomarker responses in the same individual, with a possible additional modulation through physiological processes. The main basis for such assumptions originated from experimental studies, but it has been less easy to detect and quantify any such relationships in field-collected material. The aim of the current study was to clarify whether the responses of selected biomarkers (cytochrome P-4501A [CYP1A], delta-aminolevulinic acid dehydratase [ALA-D], metallothionein [MT]) could be correlated with physiological parameters and/or contaminant levels. Atlantic cod (Gadus morhua L.) were sampled over a decade at a number of locations along the Norwegian coast. The locations included both polluted and reference areas. In addition to contaminant-related responses (biomarkers), physiological characteristics were registered for each individual and the contaminant load determined. There were clear relationships between responses in all three biomarkers and tissue contaminants, but additional factors such as age or size and liver lipid or liver somatic index also contributed in multiple-regression models. The results indicated that responses in all three biomarkers reflected relevant, contaminant-related processes in the cod even though none of them provided a simple separation between polluted and pristine locations.

Vitellogenin in African sharptooth catfish (Clarias gariepinus): purification, characterization, and ELISA development

Vitellogenin (Vtg) induction in African sharptooth catfish (Clarias gariepinus) was assessed in order to develop a method for monitoring estrogenic pollution in African freshwater systems. Clarias gariepinus Vtg (Cg-Vtg) was purified from serum obtained from 17alpha-ethynylestradiol (EE2)-exposed fish and polyclonal antibodies against Cg-Vtg were raised. An enzyme-linked immunosorbent assay (ELISA) was developed and the induction and kinetics of Vtg were assessed in male fish in three different exposure trials using both natural estrogen (17alpha-estradiol [E2]) and synthetic EE2. Concentrations of EE2 in water and levels of EE2 conjugates in bile were quantified by liquid chromatography-mass spectrometry (LC-MS). In addition, co-administration of E2 and benzo[a]pyrene (BaP) were studied. Vtg was induced in all exposure trials and the maximum induction was observed 1 wk after exposure. Exposure of male C. gariepinus to 1.4, 2.7, and 13.9 microg/ml EE2 induced Vtg synthesis at all concentrations. BaP did not influence the Vtg kinetics. However, an increased rate of biliary excretion of EE2 was observed when BaP was additionally administered. In conclusion, Vtg is induced in male C. gariepinus after exposure to both E2 and EE2, rendering it a suitable biomarker for endocrine-disrupting chemicals in African freshwater systems.

Zebrafish whole-adult-organism chemogenomics for large-scale predictive and discovery chemical biology

The ability to perform large-scale, expression-based chemogenomics on whole adult organisms, as in invertebrate models (worm and fly), is highly desirable for a vertebrate model but its feasibility and potential has not been demonstrated. We performed expression-based chemogenomics on the whole adult organism of a vertebrate model, the zebrafish, and demonstrated its potential for large-scale predictive and discovery chemical biology. Focusing on two classes of compounds with wide implications to human health, polycyclic (halogenated) aromatic hydrocarbons [P(H)AHs] and estrogenic compounds (ECs), we generated robust prediction models that can discriminate compounds of the same class from those of different classes in two large independent experiments. The robust expression signatures led to the identification of biomarkers for potent aryl hydrocarbon receptor (AHR) and estrogen receptor (ER) agonists, respectively, and were validated in multiple targeted tissues. Knowledge-based data mining of human homologs of zebrafish genes revealed highly conserved chemical-induced biological responses/effects, health risks, and novel biological insights associated with AHR and ER that could be inferred to humans. Thus, our study presents an effective, high-throughput strategy of capturing molecular snapshots of chemical-induced biological states of a whole adult vertebrate that provides information on biomarkers of effects, deregulated signaling pathways, and possible affected biological functions, perturbed physiological systems, and increased health risks. These findings place zebrafish in a strategic position to bridge the wide gap between cell-based and rodent models in chemogenomics research and applications, especially in preclinical drug discovery and toxicology.

To understand chemical-induced biological responses/effects, it is important to have large-scale and rapid capacity to investigate gene expression changes caused by chemical compounds at genome-wide scale in an adult vertebrate model; this capability is essential for drug development and toxicology. Small aquarium fish with vast genomic resources, such as zebrafish, will probably be the only vertebrate models that allow for cost-effective, large-scale, genome-wide determination of gene expression net changes in the entire adult organism in response to a chemical compound. Presently, such a whole adult organism approach is only feasible in invertebrate models such as the worm and fly, and not in rodent models, hence the usefulness of such an approach has not been demonstrated in a vertebrate. By using two classes of chemicals with wide implications to human health, we showed that capturing net changes of gene expression at a genome-wide scale in an entire adult zebrafish is useful for predicting toxicity and chemical classes, for discovering biomarkers and major signaling pathways, as well as for inferring human health risk and new biological insights. Our study provides a new approach for genome-wide investigation of chemical-induced biological responses/effects in a whole adult vertebrate that can benefit the drug discovery process and chemical toxicity testing for environmental health risk inference.

Fluorescence in situ hybridization techniques (FISH) to detect changes in CYP19a gene expression of Japanese medaka (Oryzias latipes)

The aim of this study was to develop a sensitive in situ hybridization methodology using fluorescence-labeled riboprobes (FISH) that allows for the evaluation of gene expression profiles simultaneously in multiple target tissues of whole fish sections of Japanese medaka (Oryzias latipes). To date FISH methods have been limited in their application due to autofluorescence of tissues, fixatives or other components of the hybridization procedure. An optimized FISH method, based on confocal fluorescence microscopy was developed to reduce the autofluorescence signal. Because of its tissue- and gender-specific expression and relevance in studies of endocrine disruption, gonadal aromatase (CYP19a) was used as a model gene. The in situ hybridization (ISH) system was validated in a test exposure with the aromatase inhibitor fadrozole. The optimized FISH method revealed tissue-specific expression of the CYP19a gene. Furthermore, the assay could differentiate the abundance of CYP19a mRNA among cell types. Expression of CYP19a was primarily associated with early stage oocytes, and expression gradually decreased with increasing maturation. No expression of CYP19a mRNA was observed in other tissues such as brain, liver, or testes. Fadrozole (100 microg/L) caused up-regulation of CYP19a expression, a trend that was confirmed by RT-PCR analysis on excised tissues. In a combination approach with gonad histology, it could be shown that the increase in CYP19a expression as measured by RT-PCR on a whole tissue basis was due to a combination of both increases in numbers of CYP19a-containing cells and an increase in the amount of CYP19a mRNA present in the cells.

Xenoestrogen exposure and effects in English sole (Parophrys vetulus) from Puget Sound, WA

Vitellogenin, a yolk protein produced in the liver of oviparous animals in response to estrogens, normally occurs only in sexually mature females with developing eggs. However, males can synthesize vitellogenin when exposed to environmental estrogens, making the abnormal production of vitellogenin in male animals a useful biomarker for xenoestrogen exposure. In 1997-2001, as part of the Washington State's Puget Sound Assessment and Monitoring Program, we surveyed English sole from a number of sites for evidence of xenoestrogen exposure, using vitellogenin production in males as an indicator. Significant levels of vitellogenin were found in male fish from several urban sites, with especially high numbers of fish affected in Elliott Bay, along the Seattle Waterfront. Intersex fish were rare, comprising only two fish out of more than 2900 examined. Other ovarian and testicular lesions, including oocyte atresia, were also observed, but their prevalence did not appear to be related to xenoestrogen exposure. However, at the Elliott Bay sites where abnormal vitellogenin production was observed in male sole, the timing of spawning in both male and female English sole appeared altered. Sources of xenoestrogens and types of xenoestrogens present in Elliott Bay are poorly documented, but the compounds are likely associated with industrial discharges, surface runoff, and combined sewer outfalls.

Plasma vitellogenin in Morelet's crocodiles from contaminated habitats in northern Belize

Vitellogenin induction has been widely used as a biomarker of endocrine disruption in wildlife, but few studies have investigated its use in wild reptiles living in contaminated habitats. This study examined vitellogenin induction in Morelet's crocodiles (Crocodylus moreletii) from wetlands in northern Belize contaminated with organochlorine (OC) pesticides. Vitellogenin was measured in 381 crocodile plasma samples using a vitellogenin ELISA previously developed for this species. Vitellogenin was detected in nine samples, all from adult females sampled during the breeding season. Males and juvenile females did not contain detectable levels of vitellogenin; however, many of these animals contained OC pesticides in their caudal scutes, confirming contaminant exposure. The lack of a vitellogenic response in these animals may be attributable to several factors related to the timing and magnitude of exposure to endocrine-disrupting chemicals and should not be interpreted as an absence of other contaminant-induced biological responses.

Assessing and managing risks arising from exposure to endocrine-active chemicals

Managing risks to human health and the environment produced by endocrine-active chemicals (EAC) is dependent on sound principles of risk assessment and risk management, which need to be adapted to address the uncertainties in the state of the science of EAC. Quantifying EAC hazard identification, mechanisms of action, and dose-response curves is complicated by a range of chemical structure/toxicology classes, receptors and receptor subtypes, and nonlinear dose-response curves with low-dose effects. Advances in risk science including toxicogenomics and quantitative structure-activity relationships (QSAR) along with a return to the biological process of hormesis are proposed to complement existing risk assessment strategies, including that of the Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC 1998). EAC represents a policy issue that has captured the public's fears and concerns about environmental health. This overview describes the process of EAC risk assessment and risk management in the context of traditional risk management frameworks, with emphasis on the National Research Council Framework (1983), taking into consideration the strategies for EAC management in Canada, the United States, and the European Union.

Biomonitoring recycled water in the Santa Ana River Basin in southern California

The Santa Ana River (SAR) is the primary source of groundwater recharge for the Orange County Groundwater Basin in coastal southern California. Approximately 85% base flow in the SAR originates from wastewater treatment plants operated by three dischargers. An on-line, flow-through bioassay using Japanese medaka (Oryzias latipes) as a means of judging potential public health impacts was employed to evaluate the water quality of the surface water and shallow groundwater originating from the SAR. Three chronic (3-4.5 mo) exposures using orange-red (outbred, OR) and see-through (color mutant, ST-II) Japanese medaka as bioindicators were conducted to evaluate endocrinologic, reproductive, and morphologic endpoints. No statistically significant differences in gross morphological endpoints, mortality, gender ratios, and vitellogenin induction were observed in fish from SAR groundwater treatment compared to the group tested in solute reconstituted reverse osmosis-treated or granular activated carbon (GAC)-treated control waters. Significant differences were observed in egg reproduction and the time to hatch in SAR groundwater; however, total hatchability was not significantly lower. To evaluate the estrogenic activity of the surfacewater source of the groundwater, SAR surface water was evaluated for vitellogenin and gonadal histopathology in juvenile medaka with no effects observed. These results demonstrate that OR Japanese medaka may be a sensitive strain as an on-line monitor to predict potential impacts of water quality, but further studies are needed to elicit causative agents within the water mixture.

Reduced embryonic survival in rainbow trout resulting from paternal exposure to the environmental estrogen 17alpha-ethynylestradiol during late sexual maturation

Exposure of fishes to environmental estrogens is known to affect sexual development and spawning, but little information exists regarding effects on gametes. This study evaluated embryonic survival of offspring from male rainbow trout (Oncorhynchus mykiss) exposed to 17alpha-ethynylestradiol (EE(2)) using an in vitro fertilization protocol. Males were exposed at either 1800 or 6700 degree days ( degrees d) (i.e. 161 or 587 days post-fertilization (dpf)) to test for effects on testes linked to reproductive ontogeny. At 1800 degrees d, fish were beginning testicular differentiation and were exposed to 109 ng EE(2)/l for 21 days. At 6700 degrees d, fish have testes containing spermatocytes and spermatids and were exposed for 56 days to either 0.8, 8.3, or 65 ng EE(2)/l. Semen was collected at full sexual maturity in each group and used to fertilize eggs pooled from several non-exposed females. Significant decreases in embryonic survival were observed only with the 6700 degrees d exposure. In 0.8 and 8.3 ng EE(2)/l treatments, embryo survival was significantly reduced at 19 dpf when compared with the control. In contrast, an immediate decrease in embryonic survival at 0.5 dpf was observed in the 65 ng EE(2)/l treatment. Blood samples collected at spawning from 6700 degrees d exposed males revealed a significant decrease in 11-ketotestosterone and a significant increase in luteinizing hormone levels for the 65 ng EE(2)/l treatment when compared with the other treatment groups. Results indicate that sexually maturing male rainbow trout are susceptible to EE(2) exposure with these fish exhibiting two possible mechanisms of reduced embryonic survival through sperm varying dependant on EE(2) exposure concentrations experienced.

Effects of 17alpha-ethynylestradiol on hormonal responses and xenobiotic biotransformation system of Atlantic salmon (Salmo salar)

Pharmaceuticals are ubiquitous pollutants in the aquatic environment where their potential effects on non-target species like fish has only recently become subject of systematic investigations. In the present study, experiments were undertaken to examine the effects of a synthetic pharmaceutical endocrine disruptor, ethynylestradiol (EE2), given in water at 5 or 50 ng/L and sampled at days 0 (control), 3 and 7 after exposure, on hepatic phase I and II biotransformation and hormonal pathways of juvenile salmon using quantitative (real-time) polymerase chain reaction (qPCR), Vtg ELISA and 7-ethoxyresorufin O-deethylase (EROD) catalytic activity. Our data show that EE2 produced time- and concentration-specific modulation of estrogen receptor isoforms (ERalpha, ERbeta) and androgen receptor-beta (ARbeta). EE2 produced a concentration-specific induction of vitellogenin (Vtg) and zona radiata protein (Zr-protein) at day 3 after exposure. At day 7, Vtg and Zr-protein mRNA (and plasma Vtg protein) expression were significantly decreased in the group given 5 ng EE2/L, compared to dimethyl sulfoxide (DMSO) control group. In the xenobiotic biotransformation pathway, EE2 produced a significant increase of aryl hydrocarbon receptor-alpha (AhRalpha) at day 3 in the group given 5 ng EE2/L and AhRbeta was decreased at the same concentration at day 7. While CYP3A was not significantly affected by EE2 exposure, the CYP1A1, AhR nuclear translocator (Arnt) and AhR repressor (AhRR) mRNA showed an apparent EE2 concentration and time-dependent decrease. The expression of uridine diphosphoglucuronosyl transferase (UGT) and glutathione S-transferase class pi-like (GSTpi-like) mRNA were decreased after exposure to 50ng EE2/L at both day 3 and 7 after exposure. The effect of EE2 on the CYP1A1 gene expressions paralleled effect on EROD and AhRR mRNA, suggesting a direct role of EE2 in controlling cellular detoxification machinery. Interestingly, the carrier vehicle, DMSO produced significant time-dependent induction of estrogenic (ERalpha, Vtg and Zr-protein) responses, compared with blank (i.e. without DMSO) controls at day 7 post-exposure. The effect of DMSO totally underscored the observed EE2 effect at day 7 after exposure. In general, these findings support previous reports on the endocrine effects of EE2, in addition to effects on hepatic biotransformation system. In view of the data presented here and our recent studies, the use of DMSO as carrier vehicle in endocrine toxicological experimental studies should be re-evaluated.

Specific immunoassays for endocrine disruptor monitoring using recombinant antigens cloned by degenerated primer PCR

Vitellogenin (VTG) and choriogenin (CHO) are valuable biomarkers of endocrine-disrupting compound (EDC) exposure in fish. Existing immunoassays are limited to a few species, which restricts their use for the analysis of local wildlife sentinels. Using C. facetum as a relevant South American model fish, this work presents a new strategy for the preparation of antibodies to VTG and CHO, with zero cross-reactivity with fish serum components. Recombinant fragments of Cichlasoma facetum VTG (280-mer) and CHO (223-mer) were prepared by degenerate primer RT-PCR and expression in E. coli. Polyclonal and monoclonal antibodies prepared with these antigens were used to develop rapid dotblot assays for VTG and CHO. Both the polyclonal and monoclonal antibodies prepared with the recombinant antigens reacted against the native proteins adsorbed on to nitrocellulose allowing the set up of sensitive dotblot assays. The VTG assay was further validated with spiked samples and purified native VTG. Exposure experiments with several estrogenic compounds revealed the potential of C. facetum as a sensitive biomonitor that produced measurable responses at concentrations of 100 ng L(-1) of 17-beta-estradiol, 100 ng L(-1) of ethynylestradiol, and 6.6 microg L(-1) of nonylphenol. The approach described here may be applied to other native species to produce highly specific and sensitive rapid tests. It may be particularly advantageous for species that cannot be kept in captivity or when homogeneous purification of the immunizing proteins is particularly challenging. In conclusion, we present a novel approach to develop a strategy for the generation of immunoassay reagents for vitellogenin (VTG) and choriogenin (CHO), which will facilitate regional studies on the impact of endocrine-disrupting chemicals on local wildlife.

Bisphenol-A alters gene expression and functional parameters in molluscan hepatopancreas

Bisphenol-A (BPA) is a well-known xenoestrogen in mammalian systems that can affect reproduction also in aquatic organisms. In this work the possible effects of BPA were investigated in the hepatopancreas of the bivalve mollusc Mytilus galloprovincialis: mussels were injected with different amounts of BPA (3-60ng/g dw tissue) and tissues sampled at 24h post-injection. Expression of different Mytilus genes was evaluated by RT-Q-PCR: BPA exposure increased the expression of MeER2 and induced downregulation of antioxidant genes, catalase and metallothioneins. Moreover, BPA induced changes in activity of catalase, GSH transferase (GST) and GSSG reductase (GSR), and in total glutathione content. A decrease in lysosomal membrane stability and increased neutral lipid accumulation were also observed. The results were compared with those obtained with similar concentrations of 17beta-estradiol. These data demonstrate that BPA can alter gene expression, activities of enzymes involved in redox balance, and lysosomal function in molluscan hepatopancreas, a tissue involved in the control of metabolism and gamete maturation. Overall, these data indicate that BPA, at environmentally relevant concentrations, can have both estrogen-like and distinct effects in invertebrates like in vertebrates.

Tissue-specific suppression of estrogen, androgen and glucocorticoid receptor gene expression in feral vitellogenic male Mozambique tilapia

While vitellogenesis in male fish is commonly used as a biomarker of xenoestrogen exposure, very little is known about the impacts associated with this unusual protein synthesis in feral populations. To this end, a recent study showed elevated circulating vitellogenin (VTG) levels in male Mozambique tilapia (Oreochromis mossambicus) collected from the Aja but not Tengan Rivers in Okinawa, Japan. Here we investigated whether this unusual protein synthesis in male fish from the Aja River affect transcript abundance of estrogen (ER), androgen (AR) and glucocorticoid (GR) receptors in the liver, brain and testis. The detection of plasma VTG levels ( approximately 100 microg ml(-1)) in male tilapia confirmed xenoestrogenic exposure in the Aja, but not the Tengan River. This protein induction was not associated with any changes in the reproductive capacity as assessed by sperm mobility and testis histology in the Aja fish. Plasma levels of estradiol-17beta, 11-ketotestosterone and cortisol were not significantly different between fish from the two rivers. Quantitative real-time PCR revealed a significant reduction in transcript levels of ERalpha and ERbeta, GR and ARalpha but not ARbeta, in the livers of tilapia from the Aja compared with the Tengan River. There were no significant changes in any of the steroid receptor transcript levels in either the brain or testis between the two rivers. Overall, our results imply that xenoestrogen exposure and VTG synthesis may lead to disruption of liver responsiveness to sex steroids and glucocorticoid stimulation in feral male fish.

Sensitive and robust gene expression changes in fish exposed to estrogen--a microarray approach

Background

Vitellogenin is a well established biomarker for estrogenic exposure in fish. However, effects on gonadal differentiation at concentrations of estrogen not sufficient to give rise to a measurable vitellogenin response suggest that more sensitive biomarkers would be useful. Induction of zona pellucida genes may be more sensitive but their specificities are not as clear. The objective of this study was to find additional sensitive and robust candidate biomarkers of estrogenic exposure.

Results

Hepatic mRNA expression profiles were characterized in juvenile rainbow trout exposed to a measured concentration of 0.87 and 10 ng ethinylestradiol/L using a salmonid cDNA microarray. The higher concentration was used to guide the subsequent identification of generally more subtle responses at the low concentration not sufficient to induce vitellogenin. A meta-analysis was performed with data from the present study and three similar microarray studies using different fish species and platforms. Within the generated list of presumably robust responses, several well-known estrogen-regulated genes were identified. Two genes, confirmed by quantitative RT-PCR (qPCR), fulfilled both the criteria of high sensitivity and robustness; the induction of the genes encoding zona pellucida protein 3 and a nucleoside diphosphate kinase (nm23).

Conclusion

The cross-species, cross-platform meta-analysis correctly identified several robust responses. This adds confidence to our approach used for identifying candidate biomarkers. Specifically, we propose that analyses of an nm23 gene together with zona pellucida genes may increase the possibilities to detect an exposure to low levels of estrogenic compounds in fish.

Alteration of brain and interrenal StAR protein, P450scc, and Cyp11beta mRNA levels in atlantic salmon after nominal waterborne exposure to the synthetic pharmaceutical estrogen ethynylestradiol

Pharmaceuticals are ubiquitous pollutants in the aquatic environment, where their potential effects on nontarget species like fish has only recently become subject of systematic investigations. Recently, it was shown that the documented xenoestrogen nonylphenol produced variations in brain steroidogenic acute regulatory (StAR) protein, cytochrome P-450-mediated cholesterol side-chain cleavage (P450scc), and cytochrome P-45011beta hydroxylase (CYP11beta) gene transcripts of exposed juvenile salmon (Arukwe, 2005). In the present study, experiments were undertaken to examine the effect of the synthetic pharmaceutical endocrine disruptor ethynylestradiol (EE2), given in water at 5 or 50 ng/L and sampled at d 0 (control), 3, and 7 after exposure, on these key and rate-limiting brain and interrenal steroidogenic pathways of juvenile salmon using quantitative (real-time) polymerase chain reaction (qPCR). Our data, which are based on nominal exposure concentrations, show that brain and head kidney StAR and P450scc expression were modulated by EE2 in a time- and concentration-specific manner. While the StAR protein and P450scc showed EE2 concentration-dependent transcriptional increases in the brain and head kidney at d 3 after exposure, no significant effect was observed at d 7. The EE2 induced effects at d 7 were underscored because the carrier solvent (dimethyl sulfoxide, DMSO) produced significant induction of the StAR protein and P450scc in both the brain and head kidney at d 7 compared to d 3 postexposure. CYP11beta transcript was detected in the brain and head kidney, where the expression patterns were modulated by EE2 in a concentration-and time-specific manner. In the brain, DMSO produced significant changes in the CYP11beta gene expression at d 7 compared to d 3 after exposure. These changes in the levels of StAR, P450scc, and CYP11beta mRNA levels in important steroidogenic organs suggest that the experimental animals are experiencing a time-dependent impaired steroidogenesis. Thus, the StAR protein, P450scc, and CYP11beta might represent sensitive diagnostic tools for short-term and acute exposure to endocrine disrupting chemicals. In view of the present study and high concentrations of EE2 reported in effluents and surface waters from Europe and the United States, pharmaceuticals in the environment represent potentially more serious health concern both to humans and wildlife than earlier anticipated.

Immunomodulation of Mytilus hemocytes by individual estrogenic chemicals and environmentally relevant mixtures of estrogens: in vitro and in vivo studies

Endocrine disrupting compounds (EDCs) are almost ubiquitous in the aquatic environment. In the marine bivalve Mytilus the natural estrogen 17beta-estradiol (E2) and different EDCs have been recently demonstrated to affect the function of the immune cells, the hemocytes. The effects were Tamoxifen-sensitive and were mediated by rapid modulation of kinase-mediated transduction pathways. In this work we compared the in vitro effects of individual estrogenic chemicals (E2, EE: 17alpha-ethynyl estradiol; MES: mestranol; NP: nonylphenol; NP1EC: nonylphenol monoethoxylate carboxylate; BPA: bisphenol A; BP: benzophenone) on hemocyte parameters: lysosomal membrane stability (LMS), phagocytosis, lysozyme release. LMS was the most sensitive effect parameter, showing a decreasing trend at increasing concentrations of estrogens. EC50 values obtained from LMS data were utilized to calculate the estradiol equivalency factor (EEF) for each compound; these EEFs allowed for an estimation of the estrogenic potential of a synthetic mixture with a composition very similar to that previously found in waters of the Venice lagoon. Concentrated mixtures significantly affected hemocyte parameters in vitro and the effects were prevented by Tamoxifen. Significant effects of the mixture were also observed in vivo, at longer exposure times and at concentrations comparable with environmental exposure levels. The results indicate that Mytilus immune parameters can be suitably utilized to evaluate the estrogenic potential of environmental samples.

Endocrine disruption in aquatic pulmonate molluscs: few evidences, many challenges

As compared to other groups of aquatic gastropods, documented examples of endocrine disruption in pulmonates are rather limited. This is quite surprising because the endocrine control of physiological functions has been extensively studied in these animals. In the model-species Lymnaea stagnalis, the neurohormonal regulation of reproduction has been thoroughly investigated, and the primary structure of several peptides and receptors involved in endocrine processes has been established. However, the use of this knowledge has been fairly limited in the context of ecotoxicology, to investigate the effects of endocrine-disrupting chemicals. The present review summarizes the main and more recent findings on the neuroendocrine control of reproduction in aquatic pulmonate snails (Basommatophora). It then comprehensively describes selected in vivo laboratory and semi-field studies which provide evidence for possible endocrine disrupting effects of estrogenic and androgenic test compounds [e.g., ethynylestradiol, methyltestosterone (MT)], and of environmental contaminants [e.g., cadmium (Cd), tributyltin (TBT), and nonylphenol (NP), pesticides]. Finally, challenging perspectives for future research are discussed.

Analytical methods for the determination of selected steroid sex hormones and corticosteriods in wastewater

An analytical method for the determination of 12 selected estrogens, progestagens and corticosteroids is presented. The optimization of the method, including liquid chromatography separation, extraction on a solid phase, purification on a silica gel cartridge and detection by mass spectrometry, is described. Both the repeatability, with relative standard deviation ranging from 1.4 to 2.7%, and the accuracy, with recoveries ranging from 92.7 to 102.4%, were very satisfactory for ten of the target analytes. The limits of detection were lower than 1 ng/L for progestagens, androgens and corticosteroids, and ranged between 0.9 and 4.3 ng/L for estrogens. The results of the analysis of two sewage treatment plants in the area of Lyon (France) by this method reveal that all the compounds investigated are present in the effluents. The estrogen most frequently detected was estrone, with a median of 26.1 ng/L. The target progestagens were detected with concentrations ranging between 5 and 41 ng/L. Androgens were also present in most of the samples in the range 1-30 ng/L, while the corticosteroids were present only in one plant, with a median of 31.9 ng/L.

Effects of the antidepressant mianserin in zebrafish: molecular markers of endocrine disruption

Due to their environmental occurrence and intrinsic biological activity, human pharmaceuticals have received increasing attention from environmental and health agencies. Of particular, ecotoxicological concern are drugs that affect nervous- and endocrine-systems. Zebrafish genome-wide oligo arrays are used to collect mechanistic information on mianserin-induced changes in gene expression in zebrafish. Gene expression analysis in brain and gonad tissue clearly demonstrated the estrogenic activity of mianserin and its potency to disrupt normal endocrine (estrogenic) signaling, based on induction of molecular biomarkers of estrogenicity (e.g., vitellogenin1 and zona pellucida proteins). The possible mechanism underlying this estrogenic activity of mianserin is disturbance of the Hypothalamo-Pituitary-Gonadal (HPG) axis by direct interference of mianserin with the serotonergic and adrenergic systems in the brain of zebrafish. Taking into account the importance of the HPG-axis, and considering the concept of 'critical window of exposure', our results reveal the importance for more elaborate testing of endocrine disruptive effects of aquatic antidepressants at different lifestages and during longer exposure periods (e.g., life cycle studies). Although there is a low concordance between the gene expression results in this study and previous cDNA microarray hybridizations, the global mechanistic expression patterns are similar in both platforms. This argues in favor of pathway-driven analysis of gene expression results compared to gene-per-gene analysis.

Expression of heat shock protein and hemoglobin genes in Chironomus tentans (Diptera, chironomidae) larvae exposed to various environmental pollutants: a potential biomarker of freshwater monitoring

To identify a sensitive biomarker of freshwater monitoring, we evaluated pollutant-induced expression of heat shock proteins (HSPs) and hemoglobins (Hbs) genes in the larvae of the aquatic midge Chironomus tentans (Diptera, Chironomidae). As pollutants, we examined nonylphenol, bisphenol-A, 17alpha-ethynyl estradiol, bis(2-ethylhexyl) phthalate, endosulfan, paraquat dichloride, chloropyriphos, fenitrothion, cadmium chloride, lead nitrate, potassium dichromate, benzo[a]pyrene and carbon tetrachloride. We also investigated larval growth as a physiological descriptor by measuring changes in the body fresh weight and dry weight after chemical exposure. The response of the HSPs gene expression by chemical exposure was rapid and sensitive to low chemical concentrations but it was not stressor specific. Interestingly, an increase in the expression of HSPs genes was observed not only in a stress inducible form (HSP70), but also in a constitutively (HSC70) expressed form. The expression of Hb genes showed chemical-specific responses: that is, alkyl phenolic compounds increased the expression of hemoglobin genes, whereas pesticides decreased the expression. As expected, molecular-level markers were more sensitive than physiological endpoints, suggesting that gene expression could be developed as an early warning biomarker in this animal. The overall results suggest that the expression of HSP and Hb genes in Chironomus could give useful information for diagnosing general health conditions in fresh water ecosystem. The expression of Hb genes, in particular, seems to be a promising biomarker, especially in view of the potential of Chironomus larvae as a biomonitoring species and of the physiological particularities of their respiratory pigments.

Maternal exposure to estradiol and endocrine disrupting compounds alters the sensitivity of sea urchin embryos and the expression of an orphan steroid receptor

Endocrine disrupting compounds (EDCs) are known to affect reproduction and development in marine invertebrates. In previous work, we have shown that developing sea urchin embryos were sensitive to estradiol and estrogenic EDCs at environmentally relevant concentrations in a tamoxifen-sensitive manner (Roepke et al. 2005. Aquat Toxicol 71:155-173). In this study, we report the effects of maternal exposure to EDCs on embryo sensitivity and regulation of an orphan steroid receptor in sea urchin eggs. Maternal exposures were conducted by injecting female Strongylocentrotus purpuratus sea urchins initiating oogenesis with two concentrations of estradiol, octylphenol, tributyltin and o, p-DDD for 8 weeks with an induced spawning before and after the injection cycle. Developing embryos were less sensitive to estradiol following maternal exposure to estradiol, octylphenol and DDD. The steroidogenesis inhibitor, spironolactone, and the aromatase inhibitor, formestane, affected normal sea urchin development with EC50 values of 18 and 2 microM, respectively. Binding of estradiol was demonstrated in homogenates supernatants of sea urchin embryos by filtration centrifugation and column chromatography, but saturation was not reached until 4-6 hr and was highly variable. Analysis of eggs from pre- and post-injection spawns using real-time Q-PCR for the mRNA of an orphan steroid receptor, SpSHR2, shows that receptor mRNA increased in eggs with estradiol, octylphenol and tributyltin but decreased with DDD. RIA showed that estradiol may be present during gastrulation. In summary, maternal exposure to estradiol and EDCs alters embryo sensitivity and regulates the expression of an orphan steroid receptor in the egg.

Brain aromatase: new lessons from non-mammalian model systems

This review highlights recent studies of the anatomical and functional implications of brain aromatase (estrogen synthase) expression in two vertebrate lineages, teleost fishes and songbirds, that show remarkably high levels of adult brain aromatase activity, protein and gene expression compared to other vertebrate groups. Teleosts and birds have proven to be important neuroethological models for investigating how local estrogen synthesis leads to changes in neural phenotypes that translate into behavior. Region-specific patterns of aromatase expression, and thus estrogen synthesis, include the vocal and auditory circuits that figure prominently into the life history adaptations of vocalizing teleosts and songbirds. Thus, by targeting, for example, vocal motor circuits without inappropriate steroid exposure to other steroid-dependent circuits, such as those involved in either copulatory or spawning behaviors, the neuroendocrine system can achieve temporal and spatial specificity in its modulation of neural circuits that lead to the performance of any one behavior.

A Proteomic (SELDI-TOF-MS) Approach to Estrogen Agonist Screening

A small fish model and surface-enhanced laser desorption/ionization time-of-flight mass spectrometry were used to investigate plasma protein expression as a means to screen chemicals for estrogenic activity. Adult male sheepshead minnows (Cyprinodon variegatus) were placed into aquaria for seawater control, solvent control, and treatments of 17beta-estradiol (E2), methoxychlor (MXC), bisphenol-A (BPA), 4-tert-pentylphenol (TPP), endosulfan (ES), and chlorpyriphos (CP). Fish plasma was applied to weak cation exchange (CM10) ProteinChip arrays, processed, and analyzed. The array produced approximately 42 peaks for E2 plasma and 30 peaks for solvent control plasma. Estrogen-responsive mass spectral biomarker peaks were identified by comparison of E2-treated and control plasma spectra. Thirteen potential protein biomarkers with a range from 1 to 13 kDa were up- or downregulated in E2-treated fish and their performance as estrogenic effects markers was evaluated by comparing spectra from control, estrogen agonist, and nonagonist stressor-treated males and normal female fish plasma. One of the biomarkers, mass-to-charge ratio 3025.5, was identified by high-resolution tandem mass spectrometry as C. variegatus zona radiata protein, fragment 2. The weak environmental estrogens MXC, BPA, and TPP elicited protein expression profiles consistent with the estrogen expression model. Estrogen-responsive peaks were not detected in plasma from fish in the seawater, vehicle, ES, or CP treatments. No difference was found between plasma protein expression of seawater control and solvent control fish. We show that water exposure of fish to estrogen agonists produces distinct plasma protein biomarkers that can be reproducibly detected at low levels using protein chips and mass spectrometry.

Exposures to estradiol, ethinylestradiol and octylphenol affect survival and growth of Rana pipiens and Rana sylvatica tadpoles

Endocrine disrupting compounds (EDCs) are often detected in the aquatic environment and can negatively affect the health of wildlife populations. However, little is known about the sensitivity of native amphibians to EDCs. Wood frogs (Rana sylvatica) and Northern leopard frogs (Rana pipiens) were exposed to three estrogenic EDCs: estradiol (E2), ethinylestradiol (EE2), and 4-tert-octylphenol (OP). In addition, R. pipiens were exposed during two developmental stages (Gosner stages 26 and 36) to examine life-stage differences in sensitivity. Tadpoles were exposed for 2 wk to 8 nominal concentrations (0.25 microM-10 microM) of each compound. Individual mortality was recorded during the exposure period, while body weight was measured at the end of 2 wk. LC50 values were calculated, and differences in body weight between vehicle control and exposed groups were assessed. Rank order toxicity of the compounds for both R. pipiens stages and both species was OP > EE2 > E2. Gosner stage 26 tadpoles were more sensitive (LC50: E2 [5.57 microM], EE2 [3.01 microM], OP [1.36 microM]) to all three compounds when compared to stage 36 tadpoles (LC50: E2 [>10 microM], EE2 [4.17 microM], OP [2.80 microM]). Interspecies comparisons revealed R. sylvatica tadpoles (LC50: E2 [2.50 microM], EE2 [1.89 microM], OP [0.74 microM]) as being more sensitive to the three compounds than R. pipiens (LC50: E2 [4.56 microM], EE2 [2.75 microM], OP [1.42 microM]). Xenoestrogen exposure also affected tadpole body weight which may have long-term adverse effects on the rate of metamorphosis. These results provide toxicological data needed for assessing sublethal effects of estrogenic compounds on amphibian development and suggest that environmental levels of OP may pose a serious risk to the health of amphibian populations.

Endocrine disruptors in marine organisms: approaches and perspectives

Organic pollutants exhibiting endocrine disrupting activity (Endocrine Disruptors--EDs) are prevalent over a wide range in the aquatic ecosystems; most EDs are resistant to environmental degradation and are considered ubiquitous contaminants. The actual potency of EDs is low compared to that of natural hormones, but environmental concentrations may still be sufficiently high to produce detrimental biological effects. Most information on the biological effects and mechanisms of action of EDs has been focused on vertebrates. Here we summarize recent progress in studies on selected aspects of endocrine disruption in marine organisms that are still poorly understood and that certainly deserve further research in the near future. This review, divided in four sections, focuses mainly on invertebrates (effects of EDs and mechanisms of action) and presents data on top predators (large pelagic fish and cetaceans), a group of vertebrates that are particularly at risk due to their position in the food chain. The first section deals with basic pathways of steroid biosynthesis and metabolism as a target for endocrine disruption in invertebrates. In the second section, data on the effects and alternative mechanisms of action of estrogenic compounds in mussel immunocytes are presented, addressing to the importance of investigating full range responses to estrogenic chemicals in ecologically relevant invertebrate species. In the third section we review the potential use of vitellogenin (Vtg)-like proteins as a biomarker of endocrine disruption in marine bivalve molluscs, used worldwide as sentinels in marine biomonitoring programmes. Finally, we summarize the results of a recent survey on ED accumulation and effects on marine fish and mammals, utilizing both classical biomarkers of endocrine disruption in vertebrates and non-lethal techniques, such as non-destructive biomarkers, indicating the toxicological risk for top predator species in the Mediterranean. Overall, the reviewed data underline the potential to identify specific types of responses to specific groups of chemicals such as EDs in order to develop suitable biomarkers that could be useful as diagnostic tools for endocrine disruption in marine invertebrates and vertebrates.