Inhibition of rainbow trout (Oncorhynchus mykiss) estrogen receptor activity by cadmium

An integrative data-centric approach to derivation and characterization of an adverse outcome pathway network for cadmium-induced toxicity

Cadmium is a prominent toxic heavy metal that contaminates both terrestrial and aquatic environments. Owing to its high biological half-life and low excretion rates, cadmium causes a variety of adverse biological outcomes. Adverse outcome pathway (AOP) networks were envisioned to systematically capture toxicological information to enable risk assessment and chemical regulation. Here, we leveraged AOP-Wiki and integrated heterogeneous data from four other exposome-relevant resources to build the first AOP network relevant for inorganic cadmium-induced toxicity. From AOP-Wiki, we filtered 309 high confidence AOPs, identified 312 key events (KEs) associated with inorganic cadmium from five exposome-relevant databases using a data-centric approach, and thereafter, curated 30 cadmium relevant AOPs (cadmium-AOPs). By constructing the undirected AOP network, we identified a large connected component of 18 cadmium-AOPs. Further, we analyzed the directed network of 59 KEs and 82 key event relationships (KERs) in the largest component using graph-theoretic approaches. Subsequently, we mined published literature using artificial intelligence-based tools to provide auxiliary evidence of cadmium association for all KEs in the largest component. Finally, we performed case studies to verify the rationality of cadmium-induced toxicity in humans and aquatic species. Overall, cadmium-AOP network constructed in this study will aid ongoing research in systems toxicology and chemical exposome.

Challenges and Recommendations in Assessing Potential Endocrine-Disrupting Properties of Metals in Aquatic Organisms

New tools and refined frameworks for identifying and regulating endocrine-disrupting chemicals (EDCs) are being developed as our scientific understanding of how they work advances. Although focus has largely been on organic chemicals, the potential for metals to act as EDCs in aquatic systems is receiving increasing attention. Metal interactions with the endocrine system are complicated because some metals are essential to physiological systems, including the endocrine system, and nonessential metals can have similar physiochemical attributes that allow substitution into or interference with these systems. Consequently, elevated metal exposure could potentially cause endocrine disruption (ED) but can also cause indirect effects on the endocrine system via multiple pathways or elicit physiologically appropriate compensatory endocrine-mediated responses (endocrine modulation). These latter two effects can be confused with, but are clearly not, ED. In the present study, we provide several case studies that exemplify the challenges encountered in evaluating the endocrine-disrupting (ED) potential of metals, followed by recommendations on how to meet them. Given that metals have multiple modes of action (MOAs), we recommend that assessments use metal-specific adverse outcome pathway networks to ensure that accurate causal links are made between MOAs and effects on the endocrine system. We recommend more focus on establishing molecular initiating events for chronic metal toxicity because these are poorly understood and would reduce uncertainty regarding the potential for metals to be EDCs. Finally, more generalized MOAs such as oxidative stress could be involved in metal interactions with the endocrine system, and we suggest it may be experimentally efficient to evaluate these MOAs when ED is inferred. These experiments, however, must provide explicit linkage to the ED endpoints of interest. Environ Toxicol Chem 2023;42:2564-2579. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Toxic Effects of Cadmium on Fish

Large amounts of enriched cadmium (Cd) in the environment seriously threatens the healthy and sustainable development of the aquaculture industry and greatly restricts the development of the food processing industry. Studying the distribution and toxic effects of Cd in fish, as well as the possible toxic effects of Cd on the human body, is very significant. A large number of studies have shown that the accumulation and distribution of Cd in fish are biologically specific, cause tissue differences, and seriously damage the integrity of tissue structure and function, the antioxidant defense system, the reproductive regulation system, and the immune system. The physiological, biochemical, enzyme, molecular, and gene expression levels change with different concentrations and times of Cd exposure, and these changes are closely related to the target sites of Cd action and tissues in fish. Therefore, the toxic effects of Cd on fish occur with multiple tissues, systems, and levels.

Effects of Anthropic Pollutants Identified in Pampas Lakes on the Development and Reproduction of Pejerrey Fish Odontesthes bonariensis

Anthropic activities can seriously affect the health of the organisms inhabiting them, and the observation of any alteration in the reproduction of fish could be associated with the presence of endocrine disruptors. In this manuscript we have collected information on the adverse effects of pollutants (heavy metals, environmental steroids, and agrochemicals), present in Chascomús lake, Argentina, either at environmentally relevant and pharmacological concentrations on reproduction, embryonic development, and larval survival of pejerrey fish Odontesthes bonariensis. During development, it has been reported that 17β-estradiol (E₂) feminized and reduced larval survival, while 17α-ethinyl-estradiol (EE₂) not only feminized but also affected both embryo and larval survival. In adult male fish, treatments with EE₂ and E₂ + EE₂ were able to increase mRNA abundance of gnrh3 and cyp19a1b and decreased those of gonadotropin receptors (fshr and lhcgr). Heavy metals such as cadmium, chromium, and copper negatively affected sperm quality, diminishing the motility. Also, a decrease in the percentage of hatching rate and larval survival was also observed with the same metals, highlighting zinc as the most detrimental metal. Furthermore, all these metals altered the expression of hypothalamic and pituitary genes related to reproduction in male pejerrey (gnrh1,2,3; cyp19a1b; fshb; lhb; fshr and, lhcgr). Moreover, in all cases pyknotic cells, corresponding to the degeneration of the germ cells, were observed in the testes of exposed fish. For agrochemicals, exposure of male pejerrey to environmental concentrations of glyphosate did not cause alterations on the endocrine reproductive axis. However, male pejerrey with gonadal abnormalities such as the presence of intersex (testis-ova) gonads were found in other Pampa´s lakes with high concentrations of atrazine and glyphosate associated with soybean and corn crops near their coasts. These types of studies demonstrate that pejerrey, an endemic species with economic importance inhabiting the Pampas shallow lakes, can be used as a sentinel species. It should be noted that increased pollution of aquatic ecosystems and the effects on the reproduction of organisms can lead to a decline in fish populations worldwide. Which, added to overfishing and other external factors such as global warming, could cause an eventual extinction of an emblematic species.

Eco-Corona vs Protein Corona: Effects of Humic Substances on Corona Formation and Nanoplastic Particle Toxicity in Daphnia magna

Despite many studies on the toxicity of nanoplastic particles (NPPs) to aquatic invertebrates, the effects of ecological constituents such as humic substances (HSs) are often neglected. In our study, Daphnia magna was used to evaluate the effects of three HSs, natural organic matter (NOM), fulvic acid (FA), and humic acid (HA), on NPP toxicity and corona formation. Acute toxicities of NPPs were reduced by all HSs at environmentally relevant concentrations. NPPs elicited the upregulation of all genes related to detoxification, oxidative stress, and endocrine activity after 7 days of exposure. The presence of NOM or HA resulted in the mitigation of gene expression, whereas significantly higher upregulation of all of the genes was observed with FA. The presence of FA led to increased protein adsorption on NPPs in D. magna culture medium (eco-corona, EC) and homogenates (protein corona, PC), while there was less adsorption in the presence of HA. The highly abundant proteins identified in EC are involved in immune defense, cell maintenance, and antipredator response, while those in PC are responsible for lipid transport, antioxidant effects, and estrogen mediation. Our findings revealed the key influence of HSs on the toxicity of NPPs and provide an analytical and conceptual foundation for future study.

Effects of heavy metals identified in Chascomús shallow lake on the endocrine-reproductive axis of pejerrey fish (Odontesthes bonariensis)

Some heavy metals related to human activities were measured in the water of Chascomús lake. The maximum concentrations were: 0.23 μg/L for Cd, 4.28 μg/L for Cr, 22.09 μg/L for Cu, 2.49 μg/L for Ni, 3.24 μg/L for Pb and 210.76 μg/L for Zn. The values of Cd, Cr, Cr, Pb and Zn were above the Argentine National Guidelines for the Protection of the Aquatic life. The analysis of gonadal condition of pejerrey fish (Odontesthes bonariensis) from this lake did not revealed any reproductive damages. However, exposures with environmental concentrations of Cd, Cr, Cu and Zn under laboratory conditions of pejerrey males (14 days), caused a significant increase of the expression of the three variants of gnrh in the brain (within Cd exposure) and a decrease in cyp19a1b mRNA (within Cu exposure). Furthermore, at pituitary level, a decrease in fshb transcript levels was observed in the fish exposed to Cd and Cr and a decrease in the expression of both gonadotropin receptors at gonadal level in Zn exposure. Moreover, the gonads of the fish exposed to all the tested metals suffered structural damages showing shortness of the spermatic lobules, fibrosis, testis ova and the presence of piknotic cells. All these findings alert that heavy metals pollution affects the expression of key reproductive genes and gonadal structure of fish species that represent the predominant group of organisms and are considered sentinel species in the aquatic ecosystems.

Heavy metals accumulation and endocrine disruption in Prochilodus argenteus from a polluted neotropical river

Heavy metals are considered major pollutants of aquatic environments due to the difficulty of metabolization and the bioaccumulative potential in tissues of aquatic organisms, especially fish muscle that is often used as food worldwide. In addition to causing cell damage, some metals such as aluminium (Al), cadmium (Cd), copper (Cu), and lead (Pb) can act as endocrine disrupting chemicals in fish. The Paraopeba and Abaete Rivers are important tributaries of the upper São Francisco River basin, but the Paraopeba River receives, along its course, the discharge of many types of effluents that affect fish species, including widely consumed species such as Prochilodus argenteus. This study evaluated histological and molecular changes caused by chronic exposure to heavy metals in P. argenteus from the Paraopeba River and compared this to fish from the non-impacted Abaete River. Sampled fish from both rivers were used in histological analyses and immunohistochemical assays. The results showed increased incidence of histopathologies and changes in number and morphology of germline cells in both sexes. In addition, up-regulated expression of oestrogens-induced proteins in the liver of males were detected in polluted environment. All the alterations were related to the concentration of metals in water and fish. The high concentration of various metals observed in water and fish from Paraopeba River serves as an alert to the environmental and public health regulatory authorities.

Anti-Osteogenic Activity of Cadmium in Zebrafish

Among the many anthropogenic chemicals that end up in the aquatic ecosystem, heavy metals, in particular cadmium, are hazardous compounds that have been shown to affect developmental, reproductive, hepatic, hematological, and immunological functions in teleost fish. There is also evidence that cadmium disturbs bone formation and skeletal development, but data is scarce. In this work, zebrafish was used to further characterize the anti-osteogenic/osteotoxic effects of cadmium and gain insights into underlying mechanisms. Upon exposure to cadmium, a reduction of the opercular bone growth was observed in 6-days post-fertilization (dpf) larvae and an increase in the incidence of skeletal deformities was evidenced in 20-dpf post-larvae. The extent and stiffness of newly formed bone was also affected in adult zebrafish exposed to cadmium while regenerating their caudal fin. A pathway reporter assay revealed a possible role of the MTF-1 and cAMP/PKA signaling pathways in mechanisms of cadmium osteotoxicity, while the expression of genes involved in osteoblast differentiation and matrix production was strongly reduced in cadmium-exposed post-larvae. This work not only confirmed cadmium anti-osteogenic activity and identified targeted pathways and genes, but it also suggested that cadmium may affect biomechanical properties of bone.

Molecular characterization and expression of vitellogenin gene from Spodoptera exigua exposed to cadmium stress

In this study, we cloned a full-length cDNA encoding vitellogenin (Vg) in Spodoptera exigua. The complete Vg cDNA consists of 5694 nucleotides with a long open reading frame encoding 1761 amino acid residues. The deduced amino acid sequence shared high similarity with the Vgs of other lepidopteran insects, particularly in the C-terminal region including the GL/ICG motif, five cysteine residues and DGXR motif. We analyzed the spatiotemporal expression of Vg transcripts in S. exigua by RT-PCR and Real-time Quantitative PCR. The results revealed that Vg was expressed specifically in the female fat body and was detectable after 5th day female pupae. The maximum level of Vg mRNA appeared in 48-h-old female adults and started to decrease quickly. When exposed to cadmium (Cd) (25-100mg/kg), there was a significantly decreased Vg level in female adults. The information presented in this study suggested the Vg in S. exigua could be significantly affected by Cd pressure.

Histological changes, apoptosis and metallothionein levels in Triturus carnifex (Amphibia, Urodela) exposed to environmental cadmium concentrations

The aim of this study was to verify if the freshwater safety values established from the European Community (1998) and the Italian Ministry of Health (2001) for cadmium (44.5nM/L in drinking water and 178nM/L in sewage waters) were safe for amphibians, since at these same concentrations cadmium induced endocrine disruption in the newt Triturus carnifex. Adult male specimens of T. carnifex were exposed daily to cadmium (44.5nM/L and 178nM/L as CdCl2, nominal concentrations), respectively, during 3- and 9-months; at the same time, control newts were exposed to tap water only. The accumulation of cadmium in the skin, liver and kidney, the levels of metallothioneins in the skin and the liver, the expression of metallothionein mRNA in the liver, as well as the presence of histological alterations and of apoptosis in the target organs were evaluated. The 9-months exposure induced cadmium accumulation in all the tissues examined; moreover, histological changes were observed in all the tissues examined, irrespective of the dose or the time of exposure. Apoptosis was only detected in the kidney, whereas metallothioneins and metallothionein mRNA did not increase. This study demonstrates that the existing chronic water quality criterion established for cadmium induces in the newt T. carnifex cadmium accumulation and histological alterations in the target organs examined. Together with our previous results, showing that, at these same concentrations, cadmium induced endocrine disruption, the present results suggest that the existing chronic water quality criterion for cadmium appears to be not protective of amphibians.

Regulation of vitellogenin (vtg1) and estrogen receptor (er) gene expression in zebrafish (Danio rerio) following the administration of Cd²⁺ and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

We evaluated the individual and joint estrogenic effects of cadmium (Cd(2+)) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the zebrafish liver (ZFL) cell line, zebrafish embryo, larvae and the liver of adult zebrafish. The mRNA expression of vtg1 was inhibited by Cd(2+), but unaffected by TCDD in ZFL cells. Similar changes in the mRNA levels of ERα, ERβ1, ERβ2 and GPER (G protein coupled estrogen receptor) in ZFL cells were also observed. Deletion mutants of vtg1 gene promoters were constructed to investigate transcriptional regulation, and we found that all of the constructs failed to respond to TCDD or Cd(2+). However, after co-transfection with a vtg1 promoter-luciferase construct to the ERα, ERβ1, ERβ2 and GPER expression vectors, decreased luciferase activity was observed in the ERα co-transfection group after treatment with Cd(2+), suggesting that ERα participates in vtg1 transcriptional regulation and is affected by Cd(2+). Differences in the regulation of the mRNA levels of these genes were also observed between different developmental stages and between the livers of male and female zebrafish.

Interactive effects of chronic waterborne copper and cadmium exposure on tissue-specific metal accumulation and reproduction in fathead minnow (Pimephales promelas)

The present study was carried out to examine the interactive effects of chronic waterborne copper (Cu) and cadmium (Cd) on tissue-specific metal accumulation and reproduction in fathead minnow (Pimephales promelas). Trios (1 male: 2 female; n=5) of fish were exposed for 21days to: (i) control (no added Cu or Cd), (ii) waterborne Cu (75μg/L), (iii) waterborne Cd (5μg/L), and (iv) Cu and Cd mixture (75 and 5μg/L, respectively). Reproductive output (cumulative egg production) was significantly reduced by Cu but not by Cd. Interestingly however, no spawning occurred in fish exposed to the mixture of waterborne Cu and Cd. In general, both Cu and Cd accumulation in target tissues (gill, liver, gonad and carcass) increased significantly in fish exposed to Cu and Cd mixture, and no interaction between Cu and Cd accumulation was observed in any tissues, except in the liver where Cu accumulation was significantly reduced by Cd. The expression of female hepatic estrogen receptor genes (ER-α and ER-β) was most significantly elevated in fish exposed to Cu and Cd mixture, whereas vitellogenin gene expression was reduced maximally in the same exposure. Similarly, the hepatic expression of the metallothionein gene was most significantly upregulated in fish exposed to Cu and Cd mixture. Moreover, the circulating estradiol level in females was significantly decreased only during the co-exposure of waterborne Cu and Cd. Overall, the present study indicates that the interaction of chronic waterborne Cu and Cd exposure may elicit greater than additive effect on reproductive output in fish.

Subchronic effects of cadmium on the gonads, expressions of steroid hormones and sex-related genes in tilapia Oreochromis niloticus

Cadmium (Cd) is one of the most toxic heavy metals in aquatic ecosystem which affects fish health and aquaculture. In the present study, we examined the bioaccumulation of Cd in the gonads of tilapia via dissolved and dietary routes. We evaluated the subchronic effects of Cd on the histology of gonads, steroid hormone levels and sex-related gene expressions in tilapia. In addition, we also studied maternal transfer of Cd. Our results indicated that Cd was accumulated significantly in both ovary and testis from both exposure routes. Histopathological analysis showed that Cd induced ovary and testis injuries. Estradiol levels were significantly increased in dissolved Cd exposed female fish. In addition, the Cd exposure displayed different effects on gene expressions in gonads. In females, the estrogen receptor (ERα) was stimulated in dissolved Cd-exposed fish at 70.32 and 143.78 μg/L for 30 days and in fish at 143.78 μg/L for 60 days. Vitellogenin expression was significantly down-regulated in the ovary of dissolved Cd-exposed fish. In testis, GR expression was elevated after 60 days of dissolved Cd and dietary exposure. Furthermore, Cd level was significantly higher in the eggs than that in the fry. Our results demonstrated that both dissolved and dietary Cd exposures affected gonad development by altering steroid hormone levels and sex-related gene expressions in tilapia.

Cadmium inhibits the vitellogenesis of freshwater crab Sinopotamon henanense

Cadmium (Cd) may pose risks to freshwater organisms, including crabs that live at the interface of sediments and water column all year round. One of the major changes that occur during oocyte maturation of crabs is the production of vitellin. In the present study, the authors investigated the effects of Cd on oocyte size, vitellin level, and vitellogenin (Vtg) messenger RNA (mRNA) expression in the ovary of the freshwater crab Sinopotamon henanense. The authors studied the impacts of Cd on carbohydrate as well as on the protein metabolism, metallothionein, glutathione (GSH) synthesis, energy-related parameters, and mRNA expression of genes involved in energy metabolism. After Cd treatment, vitellin concentration, Vtg mRNA expression, and oocyte diameter decreased. Less carbohydrate and enhanced protein catabolism were found in the ovary. Adenosine triphosphate to adenosine diphosphate (ATP:ADP) ratios, reduced nicotinamide adenine dinucleotide (NADH) to oxidized nicotinamide adenine dinucleotide (NAD(+) ) ratios, mitochondrial membrane potential, and energy production-related mRNA expressions increased in the ovary after 10 d Cd treatment and decreased after 20 d. Metallothionein and GSH synthesis were up-regulated after 10 d on Cd exposure. Moreover, Cd caused a time-dependent up-regulation of malondialdehyde. The authors' findings show significant effects of Cd on vitellogenesis, which suggests that Cd slows down vitellogenesis in S. henanense because of excessive energy consumption and an activated defense system.

In vitro and in vivo studies of the endocrine disrupting potency of cadmium in roach (Rutilus rutilus) liver

Cadmium has been reported to exert estrogenic, antiestrogenic or both effects in vertebrate species. To elucidate the endocrine disrupting action of CdCl2, ex vivo and in vivo experiments were performed in roach (Rutilus rutilus). Roach liver explants were exposed to a range of CdCl2 concentrations alone (0.1-50μM) or with an effective concentration (100nM) of 17β-estradiol (E2). In addition, juvenile roach were intraperitoneally injected with CdCl2 (0.1-2.5mg/kg) with or without 1mg E2/kg. Subsequent analysis evaluated the effect of CdCl2 on vitellogenin (VTG) synthesis both at the mRNA and protein level, on estrogen receptors (erα and erβ1) and on androgen receptor (ar) mRNA expression. Ex vivo and in vivo experiments indicated that CdCl2 is strongly anti-estrogenic as, when co-exposed to E2, CdCl2 significantly inhibited VTG production as well as vtg and erα mRNA expressions. Moreover, CdCl2 compromised the E2-mediated induction of the ar mRNA expression in vivo.

Cadmium inhibits molting of the freshwater crab Sinopotamon henanense by reducing the hemolymph ecdysteroid content and the activities of chitinase and N-acetyl-β-glucosaminidase in the epidermis

Molting is an essential process during the growth of crustaceans, which is coordinated by ecdysteroids secreted by the Y-organ, molting inhibiting hormone secreted by the X-organ sinus-gland complex, as well as chitinase and N-acetyl-β-glucosaminidase synthesized by the epidermis. Cadmium is one of the toxic metals in the aquatic environment. However, the endocrine effects of cadmium on the molting of freshwater crabs and the underlying mechanisms are unknown. To investigate these, freshwater crabs (Sinopotamon henanense) were acutely exposed to 0, 7.25, 14.5 and 29 mg/l Cd for 3, 4, 5 days or in some experiments for 4 days after eyestalk-ablation. The concentration of hemolymph ecdysone and the activities of the molting enzymes chitinase and NAG were measured. Histological changes in the epidermal tissues were documented. Our results showed that eyestalk ablation increased the ecdysteroid content as well as the activities of chitinase and NAG, which were inhibited by cadmium in a concentration-dependent manner; histological examinations demonstrated that eyestalk ablation produced storage particles in the epidermal tissues, which was also reduced by cadmium in a concentration-dependent manner. Our data suggest that cadmium disrupts endocrine function through inhibiting the secretion of ecdysteroids by the Y-organ and altering with the regulation of chitinase and NAG activity in the epidermis. This work provides new insights into the mechanisms underlying the molting inhibition effect of cadmium on the crabs.

Effect of heavy metals on fish larvae deformities: A review

Heavy metals have been associated with many fish deformities in natural populations and in laboratory produced specimens as well. Deformities in general have devastating effects on fish populations since they affect the survival, the growth rates, the welfare and their external image. Although the embryonic stage in respect to heavy metal exposure has been extensively studied, there is not much information available as to what happens in fish larvae and adults. In the present article, we present the available information on the effect of heavy metals on fish larvae deformities. We also address the need for more research towards the effects of metals on the subsequent life stages in order to assess the long-term consequences of heavy metal poisoning on fish organisms and possibly correlate these consequences with the environmental contamination (use as biomarkers).

Potential role of HSP90 in mediating the interactions between estrogen receptor (ER) and aryl hydrocarbon receptor (AhR) signaling pathways

The estrogen receptor (ER) and aryl hydrocarbon receptor (AhR) are ligand-activated transcription factors involved in estrogen or xenobiotic exposure, whereas the 90-kDa heat shock protein (HSP90), which is a ubiquitously expressed molecular chaperone, is involved in the signal transduction process. Although the interactions between these pathways have been under investigation, the mechanisms are unclear and the potential role of HSP90 in these interactions has not been reported. The results of goldfish primary hepatocytes showed that exposure to PCB77 and 17β-estradiol (E2) alone induced significant protein expression of cytochrome P450 1A (CYP1A) and vitellogenin (VTG), respectively. On the other hand, the combined exposure to PCB77 and E2 led to the reduction of CYP1A and VTG compared to the single treatments. Although the AhRs and ERs were naturally induced during the co-treatment, the total amount of HSP90 binding to the receptors was not changed. Furthermore, while the HSP90 chaperon activity was blocked by the specific inhibitor (geldanamycin), reciprocal inhibition between AhR and ER pathways was not observed. These findings indicate a potential role of HSP90 where competition between AhR and ER for binding to HSP90 can occur and cause reciprocal inhibition.

Effects of maternal cadmium exposure on female reproductive functions, gamete quality, and offspring development in zebrafish (Danio rerio)

Impacts of maternal Cd(2+) exposure on female zebrafish (Danio rerio) were observed in females as well as their offspring. In females, Cd disturbed fecundity and other reproductive functions. In their offspring, it retarded gamete development and growth and influenced gene expression. There was a positive relationship between Cd(2+) contents in ovaries of females and treatment doses of 0-8.9 μM of Cd(2+). The mating rate decreased by 60 % when females were exposed to 8.9-35.6 μM of Cd(2+) for 72 h compared with the control group. It was observed that growth is delayed by one somite stage in maternal-Cd(2+) embryos compared with control embryos, which grew at the sixth-somite stage. The ceratohyal angles of larvae of Cd-exposed adults (maternal Cd(2+)) at 72 h postfertilization (hpf) appeared to have a positive response after doses of maternal Cd. In addition, approximately 30 % of 96-hpf larvae that were treated with a dose of 35.6 μM of maternal Cd(2+) appeared to have pericardial edema. At the 5-hpf stage of maternal Cd(2+) exposure, embryos showed 33 and 37 target genes, respectively, that were significantly downregulated and upregulated as shown by cDNA microarray analysis. A major effect of maternal Cd(2+) exposure on zebrafish embryo genes is that 18.9% of transcription functions were upregulated. In addition, 33.3% of transcripts relative to the function of protein biosynthesis were downregulated. These results showed that maternal Cd(2+) exposure influenced the reproduction ability of females and also caused their embryos to develop with abnormal gene expression.

Cadmium impairment of reproduction in the female wall lizard Podarcis sicula

The exposure to environmental toxicants such cadmium (Cd) is an important research area in wildlife protection. In this study, the effect of Cd oral administration on the ovarian structure and function and on reproductive performance of the Italian wall lizard Podarcis sicula was studied. In vivo, adult female lizards were randomly assigned to three groups. Cd was given with food in single dose and in multiple doses 3 days/week for 4 weeks at dose of 1.0 μg/g body weight. Following euthanasia, the ovaries were removed and analyzed for morpho-functional changes. Results demonstrated that Cd increases prefollicular germ cells number; the evaluation of the number of follicles detects significantly higher number of atretic growing follicles, whereas primary follicles remain unchanged with respect to controls. After Cd treatments, follicles are deformed by the presence of large protrusions and a general dysregulation in the follicle organization is observed. The zona pellucida is also affected. Cd causes alteration in sugar metabolism and in metallothionein gene expression. Finally, Cd administration significantly reduces clutch size and dramatically increases embryo mortality. In conclusion, data here described show that Cd induces morpho-functional alterations in lizard follicles and indicates that these are responsible for a significant impairment of oogenesis. The effects of the dose are time independent, persisting essentially unchanged regardless of single or multiple administration, so it can be concluded that even occasional, sublethal Cd contamination may significantly impair reproductive performance in these animals.

Chronic exposure to cadmium disrupts the adrenal gland activity of the newt Triturus carnifex (Amphibia, Urodela)

We intended to verify the safety of the freshwater values established for cadmium by the European Community and the Italian Ministry of Health in drinking water (5 μg/L) and sewage waters (20 μg/L). Therefore, we chronically exposed the newt Triturus carnifex to 5 μg/L and 20 μg/L doses of cadmium, respectively, during 3 and 9 months and verified the effects on the adrenal gland. We evaluated the serum concentrations of adrenocorticotropic hormone (ACTH), corticosterone, aldosterone, norepinephrine, and epinephrine. During the 3-month exposure, both doses of cadmium decreased ACTH and corticosterone serum levels and increased aldosterone and epinephrine serum levels. During the 9-month exposure, the 5 μg/L dose decreased ACTH and increased aldosterone and epinephrine serum levels; the 20 μg/L dose decreased norepinephrine and epinephrine serum levels, without affecting the other hormones. It was concluded that (1) chronic exposure to the safety values established for cadmium disrupted the adrenal gland activity and (2) the effects of cadmium were related both to the length of exposure and the dose administered. Moreover, our results suggest probable risks to human health, due to the use of water contaminated by cadmium.

Assessment and molecular actions of endocrine-disrupting chemicals that interfere with estrogen receptor pathways

In all vertebrate species, estrogens play a crucial role in the development, growth, and function of reproductive and nonreproductive tissues. A large number of natural or synthetic chemicals present in the environment and diet can interfere with estrogen signaling; these chemicals are called endocrine disrupting chemicals (EDCs) or xenoestrogens. Some of these compounds have been shown to induce adverse effects on human and animal health, and some compounds are suspected to contribute to diverse disease development. Because xenoestrogens have varying sources and structures and could act in additive or synergistic effects when combined, they have multiple mechanisms of action. Consequently, an important panel of in vivo and in vitro bioassays and chemical analytical tools was used to screen, evaluate, and characterize the potential impacts of these compounds on humans and animals. In this paper, we discuss different molecular actions of some of the major xenoestrogens found in food or the environment, and we summarize the current models used to evaluate environmental estrogens.

Host and virus protein interaction studies in understanding shrimp virus gene function

Protein-protein interaction studies have been widely used in several fields to characterize an unknown protein. This in turn helps to find out several pathways to understand a complex mechanism or discover a drug for treatment. Among the methods, yeast two-hybrid has widely been used in human, animal and plant research studies. This aspect of research has also been found useful in understanding the shrimp virus gene function. With respect to White spot syndrome virus, interaction studies have been applied to elucidate virus structure, understand the mode of entry of the virus, mechanism of virus replication and also to discover some of the host anti-viral proteins. Interaction studies on other shrimp viruses are scanty and only few reports available on Yellow head virus and Taura syndrome virus. All these findings are still in preliminary stage and lot more studies are necessary to have the clear picture. Protein interaction research on other shrimp viruses are still lacking. Considering all these, it appears that this field of research has a wide scope to understand the virulence mechanism of shrimp viruses where very little information is available till date.

Feminization of Longnose Dace (Rhinichthys cataractae) in the Oldman River, Alberta, (Canada) Provides Evidence of Widespread Endocrine Disruption in an Agricultural Basin

We sampled an abundant, native minnow (Longnose dace-Rhinichthys cataractae) throughout the Oldman River, Alberta, to determine physiological responses and possible population level consequences from exposure to compounds with hormone-like activity. Sex ratios varied between sites, were female-biased, and ranged from just over 50% to almost 90%. Histological examination of gonads revealed that at the sites with >60% females in the adult population, there was up to 38% occurrence of intersex gonads in fish identified through visual examination of the gonads as male. In the majority of intersex gonad cases, there was a large proportion (approx., 50%) of oocytes within the testicular tissue. In male dace, vitellogenin mRNA expression generally increased with distance downstream. We analyzed river water for 28 endocrine disrupting compounds from eight functional classes, most with confirmed estrogen-like activity, including synthetic estrogens and hormone therapy drugs characteristic of municipal wastewater effluent, plus natural hormones and veterinary pharmaceuticals characteristic of livestock production. The spatial correlation between detected chemical residues and effects to dace physiology indicate that multiple land uses have a cumulative impact on dace in the Oldman River and effects range from altered gene regulation to severely female-biased sex ratios.

Influence of divalent metal ions on E2-induced ER pathway in goldfish (Carassius auratus) hepatocytes

Metal ions existing in the environment could influence the estrogen pathway in aquatic animal, but the detailed mechanism is still delusive. We here showed that in male Carassius auratus hepatocytes, copper (Cu) or cadmium (Cd), did not directly induce vitellogenin (VTG) expression. Interestingly, co-exposure with Cd²⁺ (or Cu²⁺) and 17-β-estradiol (E2) greatly increased the VTG level, comparing with single treatment of E2. Meanwhile, Cd²⁺ or Cu²⁺ (but not E2) triggers HSP70 expression. But, mixture of Cd²⁺ or Cu²⁺ with E2 did not obviously raise HSP70 level. E2 also had no obvious effect on reactive oxygen species. Co-treatment of Cd²⁺ and E2 showed no obvious increase compared to single treatment with Cd²⁺. We further assume that Cd²⁺-involved oxidative stress generates misfolded proteins, resulting in the competition of HSP70 proteins from a heterocomplex (with estrogen receptor). Thus, dissociation of the heterocomplex actives the receptor-ligand binding activity and promotes the E2-induced VTG expression.

Biosensors paving the way to understanding the interaction between cadmium and the estrogen receptor alpha

Cadmium is a toxic heavy metal ubiquitously present in the environment and subsequently in the human diet. Cadmium has been proposed to disrupt the endocrine system, targeting in particular the estrogen signaling pathway already at environmentally relevant concentrations. Thus far, the reports on the binding affinity of cadmium towards human estrogen receptor alpha (hERα) have been contradicting, as have been the reports on the in vivo estrogenicity of cadmium. Hence, the mode of interaction between cadmium and the receptor remains unclear. Here, we investigated the interaction between cadmium and hERα on a molecular level by applying a novel, label-free biosensor technique based on reflectometric interference spectroscopy (RIfS). We studied the binding of cadmium to hERα, and the conformation of the receptor following cadmium treatment. Our data reveals that cadmium interacts with the ligand binding domain (LBD) of the ERα and affects the conformation of the receptor. However, the binding event, as well as the induced conformation change, greatly depends on the accessibility of the cysteine tails in the LBD. As the LBD cysteine residues have been reported as targets of post-translational modifications in vivo, we present a hypothesis according to which different cellular pools of ERα respond to cadmium differently. Our proposed theory could help to explain some of the previously contradicting results regarding estrogen-like activity of cadmium.

Cadmium, lead, and mercury in relation to reproductive hormones and anovulation in premenopausal women

BACKGROUND

Metals can interfere with hormonal functioning by binding at the receptor site and through indirect mechanisms; thus, they may be associated with hormonal changes in premenopausal women.

OBJECTIVES

We examined the associations between cadmium, lead, and mercury, and anovulation and patterns of reproductive hormones [estradiol, progesterone, follicle-stimulating hormone (FSH), luteinizing hormone] among 252 premenopausal women 18-44 years of age who were enrolled in the BioCycle Study in Buffalo, New York.

METHODS

Women were followed for up to two menstrual cycles, with serum samples collected up to eight times per cycle. Metal concentrations were determined at baseline in whole blood by inductively coupled mass spectroscopy. Marginal structural models with stabilized inverse probability weights and nonlinear mixed models with harmonic terms were used to estimate the effects of cadmium, lead, and mercury on reproductive hormone levels during the menstrual cycle and anovulation.

RESULTS

Geometric mean (interquartile range) cadmium, lead, and mercury levels were 0.29 (0.19-0.43) μg/L, 0.93 (0.68-1.20) μg/dL, and 1.03 (0.58-2.10) μg/L, respectively. We observed decreases in mean FSH with increasing cadmium [second vs. first tertile: -10.0%; 95% confidence interval (CI), -17.3% to -2.5%; third vs. first tertile: -8.3%; 95% CI, -16.0% to 0.1%] and increases in mean progesterone with increasing lead level (second vs. first tertile: 7.5%; 95% CI, 0.1-15.4%; third vs. first tertile: 6.8%; 95% CI, -0.8% to 14.9%). Metals were not significantly associated with anovulation.

CONCLUSIONS

Our findings support the hypothesis that environmentally relevant levels of metals are associated with modest changes in reproductive hormone levels in healthy, premenopausal women.

The effect of cadmium on steroid hormones and their receptors in women with uterine myomas

Cadmium (Cd) is one of the environmental metalloestrogens, and its role in uterine tissues has not yet been fully elucidated. The aim of the study was to investigate estrogenic properties of Cd in uterine tissues by analyzing the expression of estrogen receptor (ER) and progesterone receptor (PR) as well as estrogen and progesterone levels in serum and Cd concentrations in blood and tissues. The samples of tissues (leiomyoma and surrounding myometrium) collected intrasurgically and blood samples drawn from 53 women (age 39 to 52 years) with uterine myomas were thoroughly analyzed. In the study group, blood Cd concentration ranged from 0.33 to 3.5 μg/L. Cd concentration in leiomyoma tissues was twice as low [corrected] as that in surrounding myometrium (0.047 and 0.075 μg Cd/g [corrected] wet tissue, respectively), albeit the difference was not statistically significant. Cd concentrations in blood significantly correlated with Cd concentrations in tissues (leiomyoma and surrounding myometrium). The measurement of ER expression showed no difference between leiomyoma tissues and surrounding myometrium. The statistical analysis showed a significant correlation between ER expression and Cd concentration in both tissues under study. An additional statistical analysis (path analysis) demonstrated the correlation of uterine tissue levels of Cd and ER expression. However, there was no association between ER expression in both tissues and E(2) level in serum. Our results suggest a metalloestrogenic effect of Cd by way of ER stimulation in the uterus.

Effects of estrogens and endocrine-disrupting chemicals on cell differentiation-survival-proliferation in brain: contributions of neuronal cell lines

Estrogens and estrogen receptors (ER) are key actors in the control of differentiation and survival and act on extrareproductive tissues such as brain. Thus, estrogens may display neuritogenic effects during development and neuroprotective effects in the pathophysiological context of brain ischemia and neurodegenerative pathologies like Alzheimer's disease or Parkinson's disease. Some of these effects require classical transcriptional "genomic" mechanisms through ER, whereas other effects appear to rely clearly on "membrane-initiated mechanisms" through cytoplasmic signal transduction pathways. Disturbances of these mechanisms by endocrine-disrupting chemicals (EDC) may exert adverse effects on brain. Some EDC may act via ER-independent mechanisms but might cross-react with endogenous estrogen. Other EDC may act through ER-dependent mechanisms and display agonistic/antagonistic estrogenic properties. Because of these potential effects of EDC, it is necessary to establish sensitive cell-based assays to determine EDC effects on brain. In the present review, some effects of estrogens and EDC are described with focus on ER-mediated effects in neuronal cells. Particular attention is given to PC12 cells, an interesting model to study the mechanisms underlying ER-mediated differentiating and neuroprotective effects of estrogens.

Estrogenic response in male bullfrog (Rana catesbeiana) hepatocytes after single or combined exposure to cadmium (Cd) and 17beta-estradiol (E2)

Contamination by heavy metals and sex hormones in a water environment is an important health issue. In this study, we investigated the estrogenic effects of cadmium (Cd) administration alone and in combination with 17beta-estradiol (E2) on the hepatocytes of male Bullfrog (Rana catesbeiana). Their vitellogenin (VTG) expression and reactive oxygen species (ROS) were analyzed upon exposure to Cd alone or to both Cd and E2. Our results suggest that the VTG levels induced by the co-treatment of 100 nM E2 and 100 nM CdCl(2) were significantly higher than those induced by 100 nM E2 alone (p < 0.05), and were comparable to vitellogenin induction observed with 1 μM E2. A similar result was observed by western blot analysis in the culture medium of hepatocytes. Meanwhile, Cd (but not E2) increased the ROS levels. These results suggest that Cd has a cooperative effect with E2 in the induction of VTG, thus acting as an estrogenic disruptor. Cd also causes oxidative stress that occurs with the enhanced vitellogenesis.

Estrogen-like effects of cadmium in vivo do not appear to be mediated via the classical estrogen receptor transcriptional pathway

BACKGROUND

Cadmium (Cd), a ubiquitous food contaminant, has been proposed to be an endocrine disruptor by inducing estrogenic responses in vivo. Several in vitro studies suggested that these effects are mediated via estrogen receptors (ERs).

OBJECTIVE

We performed this study to clarify whether Cd-induced effects in vivo are mediated via classical ER signaling through estrogen responsive element (ERE)-regulated genes or if other signaling pathways are involved.

METHODS

We investigated the estrogenic effects of cadmium chloride (CdCl2) exposure in vivo by applying the Organisation for Economic Co-operation and Development (OECD) rodent uterotrophic bioassay to transgenic ERE-luciferase reporter mice. Immature female mice were injected subcutaneously with CdCl2 (5, 50, or 500 µg/kg body weight) or with 17α-ethinylestradiol (EE2) on 3 consecutive days. We examined uterine weight and histology, vaginal opening, body and organ weights, Cd tissue retention, activation of mitogen-activated protein kinase (MAPK) pathways, and ERE-dependent luciferase expression.

RESULTS

CdCl2 increased the height of the uterine luminal epithelium in a dose-dependent manner without increasing the uterine wet weight, altering the timing of vaginal opening, or affecting the luciferase activity in reproductive or nonreproductive organs. However, we observed changes in the phosphorylation of mouse double minute 2 oncoprotein (Mdm2) and extracellular signal-regulated kinase (Erk1/2) in the liver after CdCl2 exposure. As we expected, EE2 advanced vaginal opening and increased uterine epithelial height, uterine wet weight, and luciferase activity in various tissues.

CONCLUSION

Our data suggest that Cd exposure induces a limited spectrum of estrogenic responses in vivo and that, in certain targets, effects of Cd might not be mediated via classical ER signaling through ERE-regulated genes.

Cadmium-induced increase in uterine wet weight and its mechanism

BACKGROUND

Cadmium (Cd) increases in uterine wet weight in rodents remain unclear and there are only a few studies that examined the effects of Cd on uterine morphology. It is unknown whether Cd induces a uterotrophic effect via its interaction with the estrogen receptor (ER). In our study, we compared the effects of cadmium chloride (CaCl(2)) on uterine wet weight and morphology to those of 17beta-estradiol in Sprague-Dawley (SD) rats.

METHODS

Forty-eight SD rats (23 days of age) were ectomized and randomly divided into six groups (eight rats per group): vehicle control (sterile saline solution), positive control (17beta-estradiol, 0.03 mg/kg in peanut oil), and CaCl(2) groups (0.0064, 0.032, 0.16, and 0.8 mg/kg, respectively). The animals were treated by daily intraperitoneal (i.p.) injection for 3 days. The uteri were removed and assessed for weight, morphology, and immunohistochemical analysis.

RESULTS

Compared to the control group, the uterine wet weight, the thickness of endomerium, the thickness of the stroma and the nucleus/cytoplasm ratio in the 17beta-estradiol-treated and 0.8 mg/kg-day CaCl(2)-treated groups changed (P<0.01 or P 0.05). The endometrial gland number, the uterine epithelial cell height, and the PCNA-positive expression in 17beta-estradiol-treated rats increased compared to that of the control (P<0.01), but not in the CaCl(2) dose groups.

CONCLUSIONS

These results indicate that cadmium may induce an increase in uterine wet weight. However, this effect is not similar to that caused by 17beta-estradiol, suggesting it is not via Ca-ER interactions.

E-screen and vitellogenin assay for the detection of the estrogenic activity of alkylphenols and trace elements

The estrogenic potential of 4-nonylphenol (4-NP), 4-octylphenol (4-OP), p-t-octylphenol (p-t-OP) and three trace elements, lead (Pb), copper (Cu) and cadmium (Cd(NO(3))(2) and CdCl(2)), were compared in two different tests, a proliferation assay with estrogen receptor-positive human MCF-7 breast cancer cells (E-screen) and the induction of vitellogenin (Vtg) in juvenile goldfish (Carassius auratus). The results showed differences in the bioassays' sensitivity and potency with the following order: E-screen>Vtg. Among alkylphenols, both in vitro and in vivo, 4-NP and 4-OP showed the highest estrogen-like activity while p-t-OP was inferior. For trace elements, Pb and Cu showed estrogenic activity in vitro and they were also active in vivo. A range of estrogenicity was observed for different species of cadmium (Cd(NO(3))(2) and CdCl(2)) which showed the highest relative proliferative effect (RPE %) in vitro, when compared with the 17beta-estradiol (E(2); RPE=100%) but, Cd(NO(3))(2) was not estrogenic in vivo. The results suggest that an integrated approach using in vitro and in vivo assays is necessary for a correct risk assessment of the endocrine disrupting activity induced by environmental contaminants.

Effects of cadmium, estradiol-17beta and their interaction on gonadal condition and metamorphosis of male and female African clawed frog, Xenopus laevis

To assess interaction effects between cadmium (Cd, a putative xenoestrogen) and estradiol-17beta (E(2)) on sex differentiation and metamorphosis, Xenopus laevis were exposed to solvent-control (0.005% ethanol), Cd (10microgL(-1)), E(2) (1microgL(-1)), or Cd and E(2) (Cd+E(2)) in FETAX medium from fertilization to 75d postfertilization. Each treatment was applied to four aquaria, each with 30 fertilized eggs. Mortality was recorded and animals were sampled as they completed metamorphosis (Nieuwkoop and Faber stage 66). Gonadal sex of individuals (including >or= tadpoles NF stage 55 at day 75) was determined gross-morphologically and used to compute sex ratios. Time course and percent completion of metamorphosis, snout-vent length (SVL), hindlimb length (HLL) and weight were analyzed for each gender separately. Survival rates did not differ among treatments. The E(2) and Cd+E(2) treatments significantly skewed sex ratios towards females; however, no sex-ratio differences were observed between the control and Cd treatments or between the E(2) and Cd+E(2) treatments. Time course of metamorphosis was generally delayed and percent completion of metamorphosis was generally reduced in males and females exposed to Cd, E(2) or their combination compared to control animals. In males, but not females, the effect of Cd+E(2) was greater than that of individual chemicals. Weight at completion of metamorphosis was reduced only in females and only by the Cd+E(2) treatment. In conclusion, although Cd at an environmentally relevant concentration did not exhibit direct or indirect feminizing effects in Xenopus tadpoles, the metal and E(2) both had similar inhibitory effects on metamorphosis that were of greater magnitude in males than females.

Cadmium malignantly transforms normal human breast epithelial cells into a basal-like phenotype

BACKGROUND

Breast cancer has recently been linked to cadmium exposure. Although not uniformly supported, it is hypothesized that cadmium acts as a metalloestrogenic carcinogen via the estrogen receptor (ER). Thus, we studied the effects of chronic exposure to cadmium on the normal human breast epithelial cell line MCF-10A, which is ER-negative but can convert to ER-positive during malignant transformation.

METHODS

Cells were continuously exposed to low-level cadmium (2.5 μM) and checked in vitro and by xenograft study for signs of malignant transformation. Transformant cells were molecularly characterized by protein and transcript analysis of key genes in breast cancer.

RESULTS

Over 40 weeks of cadmium exposure, cells showed increasing secretion of matrix metalloproteinase-9, loss of contact inhibition, increased colony formation, and increasing invasion, all typical for cancer cells. Inoculation of cadmium-treated cells into mice produced invasive, metastatic anaplastic carcinoma with myoepithelial components. These cadmium-transformed breast epithelial (CTBE) cells displayed characteristics of basal-like breast carcinoma, including ER-alpha negativity and HER2 (human epidermal growth factor receptor 2) negativity, reduced expression of BRCA1 (breast cancer susceptibility gene 1), and increased CK5 (cytokeratin 5) and p63 expression. CK5 and p63, both breast stem cell markers, were prominently overexpressed in CTBE cell mounds, indicative of persistent proliferation. CTBE cells showed global DNA hypomethylation and c-myc and k-ras overexpression, typical in aggressive breast cancers. CTBE cell xenograft tumors were also ER-alpha negative.

CONCLUSIONS

Cadmium malignantly transforms normal human breast epithelial cells-through a mechanism not requiring ER-alpha-into a basal-like cancer phenotype. Direct cadmium induction of a malignant phenotype in human breast epithelial cells strongly fortifies a potential role in breast cancer.

The effects of heavy metals on embryonic development of fish (a review)

Early developmental stages of fish are particularly sensitive to water pollution. Heavy metals may affect various developmental processes during the embryonic period, which results in a reduction of offspring quantity and quality. Waterborne metals may accumulate in the gonads of spawners and adversely affect gamete production and viability, or exert direct toxic influence upon developing embryos. The egg shell does not fully protect the embryo against metal penetration, particularly during the swelling phase; thus, metals may accumulate in the egg. The results depend on metal concentration and range from developmental disturbances to death of the embryo. Metals disturb various processes of fish embryonic development and affect the development rate. Early stages just after fertilization are particularly sensitive to metal intoxication, when most disturbances and the highest embryonic mortality occur. Waterborne metals also promote developmental anomalies during organogenesis, including body malformations. Heavy metals often induce a delay in the hatching process, premature hatching, deformations and death of newly hatched larvae. All these disturbances result in reduced numbers and poor quality of the larvae, which show small body size, high frequency of malformations and reduced viability.

Effects of cadmium on estrogen receptor mediated signaling and estrogen induced DNA synthesis in T47D human breast cancer cells

Cadmium (Cd) has been shown to bind to the human estrogen receptor (ER), yet studies on Cd's estrogenic effects have yielded inconsistent results. In this study, we investigated the effects of Cd on DNA synthesis and its simultaneous effects on both genomic (mediated by nuclear ER (nER)) and non-genomic (mediated by membrane-bound ER (mER)) signaling in human breast cancer derived T47D cells. No effects on DNA synthesis were observed for non-cytotoxic concentrations of CdCl(2) (0.1-1000 nM), and Cd did not increase progesterone receptor (PgR) or pS2 mRNA levels. However, Cd stimulated phosphorylation of ERK1/2 MAPK, detectable following 10 min and 18 h of treatment. The sustained Cd-induced ERK1/2 phosphorylation was inhibited by the ER antagonist ICI 182,780, suggesting the involvement of ER. In addition, Cd enhanced DNA synthesis and pS2 mRNA levels in estrogen (10 pM estradiol) treated T47D cells. The MEK1/2 specific inhibitor U0126 blocked DNA synthesis stimulated by estradiol (E2) and the E2-Cd mixtures. These findings indicate that the ERK1/2 signaling is critical in E2-related DNA synthesis. The sustained ERK1/2 phosphorylation may contribute to the Cd-induced enhancement of DNA synthesis and pS2 mRNA in mixture with low-concentration E2.

In-vitro screening of the antiestrogenic activity of chemicals

BACKGROUND

Many chemicals have the potential to interfere with the endocrine systems of humans and wildlife, leading to adverse health effects. In the tiered testing strategies developed for regulatory hazard assessment, in-vitro screens could serve for prioritisation of compounds and for guiding subsequent testing.

OBJECTIVE

To describe in-vitro assays to detect antiestrogenic activity of chemicals.

METHODS

Antiestrogenicity was considered in this review as any inhibition or reduction of estrogen-induced processes due to interference with the normal functioning of the estrogen receptor pathway. Accordingly, in-vitro screening assays for antiestrogenicity have to consider all the possible mechanisms by which this inhibition may occur. Such assays include binding assays, cell proliferation assays, reporter gene assays, and gene activation/protein production assays.

RESULTS/CONCLUSIONS

While binding assays appear to be of limited value in assessing antiestrogenicity, assays using differentiated cells with metabolic competence and a varied receptor/regulatory factor equipment have the capability to detect various modes of antiestrogenic action.

Assessment of water pollution in the Tronto River (Italy) by applying useful biomarkers in the fish model Carassius auratus

The Tronto River (southern Marche region of central Italy) is located in an area with neighboring industrial activities and is contaminated with domestic and industrial wastewater. Water quality data analyses revealed the presence of a mixture of low levels of heavy metals and organic compounds. The effects of long-term exposure to Tronto River water on juvenile Carassius auratus were evaluated with an integrated approach using xenoestrogens biomarkers, such as vitellogenin (VTG) and ER beta-1 mRNA expression, and stress parameters (i.e., cortisol and glucose in the blood and glycogen in the liver). Treatment with Tronto River water did not induce VTG synthesis in fish and did not affect ER beta-1 mRNA expression. Moreover, cortisol titers found in the plasma of fish exposed to Tronto River water were lower than those found in the control group. Regarding energy parameters, treatment with Tronto River water induced an increase in plasma glucose and a depletion of liver glycogen reserves.The effects of Tronto River water were studied in parallel with those of 4-NP and CdCl(2). The 4-NP at the dose of 22 microg/L induced the synthesis of peripheral vitellogenin and increase of ER beta-1 titers; on the contrary, CdCl2 exposure at the concentration of 22 microg/L did not induce significant changes on plasma VTG and/or hepatic ER beta-1 levels. In addition, no significant changes in plasma cortisol levels in fish exposed to 4-NP or CdCl(2) were found. Fish exposed to CdCl(2) displayed liver glycogen depletion, but no significant increase in plasma glucose was observed. On the contrary, a 30-day exposure to 4-NP induced only a slight decrease of glycogen reserves without any changes in plasma glucose levels. In conclusion, our study demonstrated that long-term exposure of juvenile goldfish to the water of the Tronto River significantly affects both stress and energy parameters. There is evidence that pollutants, present in Tronto River water, were not able to induce xenoestrogenic effects but caused a functional impairment of the hypothalamum-pituitary-interrenal axis.

Natural arsenic contaminated diets perturb reproduction in fish

The toxicological effect of natural diets elevated in metals on reproduction in fish is poorly understood. The reproductive output of zebrafish fed the polychaete Nereis diversicolor collected from a metal-impacted estuary, Restronguet Creek, Cornwall, UK, was compared to fish fed N. diversicolor collected from a nonmetal impacted estuary, Blackwater, Essex, UK. Fish fed the metal laden N. diversicolorfor 68 days showed reduced reproductive output, characterized by reduced cumulative egg production (47%), cumulative number of spawns (30%), as well as reduced average number of eggs produced per spawn and % hatch rate. The mRNA transcript levels of the egg-yolk protein vitellogenin was also reduced 1.5 fold in the livers of female fish fed metal-laden N. diversicolor. No difference was seen between the lipid, protein, or moisture content of the two diets and no difference in growth was seen between the two fish populations. The Restronguet Creek polychaetes have elevated arsenic, cadmium, copper, zinc, lead, and silver body burdens, but the only element found to accumulate in the tissues of zebrafish fed this diet was As. The As in these N. diversicolor was found to be predominantly potentially toxic inorganic As species, 58% of total As content, which is unusual for aquatic organisms where arsenic is typically biotransformed into less toxic organoarsenical compounds. These results demonstrate that reproduction in fish is a sensitive target of exposure to a natural diet contaminated with As and this exposure route could be of significance to the health of fish populations.

In vitro study of the effects of cadmium on the activation of the estrogen response element using the YES screen

Estrogenic potential of environmental samples is frequently assessed using receptor-based functional assays. Using the yeast estrogen screen (YES) developed by Routledge and Sumpter, we assessed the ability of cadmium to activate the estrogen receptor-mediated response. No induced transcriptional activity was observed with a range of CdCl2 concentrations (1 nm-1mM). But, when combining cadmium with the model compound 17beta-estradiol, cadmium was able to significantly potentiate the induced estrogenic response for concentrations ranging from 15 nM to 1 microM. A maximal effect was observed at 0.5 microM with a ten fold reduction of the 17beta-estradiol EC50.

How cadmium could compromise the completion of the European eel's reproductive migration

The European eel (Anguilla anguilla L.) is severely threatened with extinction. Surprisingly, even though their unusual life cycle makes them particularly vulnerable to pollution, the possible contribution of contamination remains especially poorly known. Here we have investigated the possible effect of cadmium (Cd), a widespread nonessential metal, on eel reproductive capacities. Both control and Cd precontaminated female silver eels were experimentally matured and forced to swim in metal-free conditions to mimic their reproductive migration. Cd pre-exposure was found to strongly stimulate the pituitary-gonad-liver axis of maturing female silver eels leading to early and enhanced vitellogenesis. This was followed by a strong phenomenon of oocyte atresia and eel mortality. These phenomena occurred before oocytes could reach full maturation and were associated with a large entry of both vitellogenin and Cd into the ovaries. Indeed, a redistribution of previously stored cadmium, even from the low Cd levels of control eels, was observed during sexual maturation. Atresia and mortality phenomena were also associated with an overexpression of the pituitary gene encoding the growth hormone, a marker of physiological stress and energy reserves exhaustion. Significantly, these devastating effects of Cd were observed in organisms that presented liver and kidney Cd concentrations still below those observed in eels from Cd contaminated hydrosystems. Our research shows how common levels of cadmium contamination could disrupt endocrine pathways implicated in gonad maturation and subsequently impair reproductive capacity of eel future genitors.