Mutation analysis of ras gene in the liver of European eel (Anguilla anguilla L.) exposed to benzo[a]pyrene

The effects of different temperatures in mercury toxicity to the terrestrial isopod Porcellionides pruinosus

Climate changes and metal contamination are pervasive stressors for soil ecosystems. Mercury (Hg), one of the most toxic metals, has been reported to interact with temperature. However, compared to aquatic biota, little is known about how temperature affects Hg toxicity and bioaccumulation to soil organisms. Here, toxicity and bioaccumulation experiments were replicated at 15 °C, 20 °C, and 25 °C to understand how sub-optimal temperatures affect the toxicokinetics and toxicodynamics of Hg via soil. Genotoxicity and energy reserves were also assessed to disclose potential trade-offs in life-history traits. Results underpin the complexity of temperature-Hg interactions. Survival was determined mainly by toxicokinetics, but toxicodynamics also played a significant role in defining survival probability during early stages. The processes determining survival probability were faster at 25 °C: General Unified Threshold of Survival (GUTS) model identified an earlier/steeper decline in survival, compared to 20 °C or 15 °C, but it also approached the threshold faster. Despite potentiation of Hg genotoxicity, temperature promoted faster detoxification, either increasing toxicokinetics rates or damage repair mechanisms. This metabolism-driven increase in detoxification led to higher depletion of energy reserves and likely triggered stress response pathways. This work emphasized the need for comprehensive experimental approaches that can integrate the multiple processes involved in temperature-metal interactions.

Antioxidant and antigenotoxic potential of Morinda tinctoria Roxb. leaf extract succeeding cadmium exposure in Asian catfish, Pangasius sutchi

The present study investigated the protective effect of methanolic leaf extract of Morinda tinctoria. Roxb (MEMT) (200 mg/kg) via feed in supplementation with standard compound silymarin (400 mg/kg). M. tinctoria (Roxb.) belonging to Rubiaceae, is an evergreen shrub indigenous to unfarmed lands of tropical countries. It is considered as an essential traditional medicine attributing for the potential antioxidant and anti-inflammatory properties. The enhancements of antioxidant and antigenotoxic status in different tissues of cadmium (Cd) intoxicated Pangasius sutchi were evaluated by using various antioxidant assays (superoxide dismutase (SOD) and catalase (CAT) and lipid peroxidation) in addition to micronuclei (MN), binuclei (BN) and comet assay. The cadmium toxicated fish showed a significant (p < 0.001) increase in lipid peroxidation (LPO) activities in liver, gills, muscle and kidney whereas significant (p < 0.001) decline were observed in superoxide dismutase (SOD) and catalase (CAT) contents in all fish tissues. The results also revealed that, Cd exposure induced the formation of genotoxic endpoints like MN, BN, notched nuclei, kidney shaped nuclei and DNA damage in the fish erythrocytes. Maximum of 26.8% MN frequencies and maximum of 66.74% tail DNA damage were observed on the 7th day of Cd exposure. A time-dependent significant increase (p < 0.001) in the frequencies of MN, BN and tail DNA damage were observed in all treated groups against the control which started to decline from 14th day onwards. There was a decline in the LPO content, frequencies of MN, BN and percentage of tail DNA in contrast to significant elevation in SOD and CAT content in all tissues due to the combined treatment of M. tinctoria feed and water borne Cd exposure. It can be concluded from our observations that, supplementation of M. tinctoria leaf extract through feed alone produced enhanced antioxidant and antigenotoxic status in cadmium treated fish by diminishing oxidative stress and genotoxicity effects in a time dependent manner.

Susceptibility of polar cod (Boreogadus saida) to a model carcinogen

Studies that aim to characterise the susceptibility of the ecologically relevant and non-model fish polar cod (Boreogadus saida) to model carcinogens are required. Polar cod were exposed under laboratory conditions for six months to control, 0.03 μg BaP/g fish/week and 0.3 μg BaP/g fish/week dietary benzo(a)pyrene (BaP), a reference carcinogen. The concentrations of the 3-OH-BaP bile metabolite and transcriptional responses of genes involved in DNA adduct recognition (xpc), helicase activity (xpd), DNA repair (xpf, rad51) and tumour suppression (tp53) were assessed after 0, 1, 3 and 6 months of exposure, alongside body condition indexes (gonadosomatic index, hepatosomatic index and condition factor). Micronuclei and nuclear abnormalities in blood and spleen, and liver histopathological endpoints were assessed at the end of the experiment. Fish grew steadily over the whole experiment and no mortality was recorded. The concentrations of 3-OH-BaP increased significantly after 1 month of exposure to the highest BaP concentration and after 6 months of exposure to all BaP concentrations showing the biotransformation of the mother compound. Nevertheless, no significant induction of gene transcripts involved in DNA damage repair or tumour suppression were observed at the selected sampling times. These results together with the absence of chromosomal damage in blood and spleen cells, the subtle increase in nuclear abnormalities observed in spleen cells and the low occurrence of foci of cellular alteration suggested that the exposure was below the threshold of observable effects. Taken together, the results showed that polar cod was not susceptible to carcinogenesis using the BaP exposure regime employed herein.

Intra and extracellular effects of benzo [α] pyrene on liver, gill and blood of Caspian White fish (Rutilus frissi kutum): Cyto-genotoxicity and histopathology approach

Southern parts of the Caspian Sea have been faced with a diverse range of oil pollutants. Therefore, this study was designed to evaluate the effects of relevant environmental concentrations of benzo[α]pyrene (BαP) on liver, gill, and blood of Caspian White fish. To this end, 150 fingerling fish (6.5 ± 0.8 g) were exposed to under, near and over environmental concentrations of BαP (i.e. 50, 100, and 200 ppb, respectively) and two control groups for 21 days. Following exposure to BαP, generally, DNA damage increased in the liver and gill cells as well as the frequency of micro- and bi-nucleated erythrocytes in a time and concentration-dependent pattern. In addition, the liver and gill tissues displayed several histopathological lesions. Together, the findings are warning the health status of the Caspian Sea due to an ever-increasing concentration of BαP through using Caspian White fish as an ecological model.

Severe damages caused by Malathion exposure in Colossoma macropomum

The increase in pesticide use in response to agricultural demands poses a risk to non-target organisms, including fish. Integrated analysis of biochemical, histopathological and genetic parameters in fish exposed to Malathion insecticide provide information on the toxicity mechanisms of this pesticide, which is classified as a probable carcinogen for humans. The present study assessed the biological responses of Colossoma macropomum after exposure to Malathion. We started determining the lethal concentration, which is the concentration capable of killing 50% of the subjects in an acute toxicity test (LC₅₀-96 h), which was 15.77 ± 3.30 mgL^-1. The fish were, then, exposed to Malathion during 96 h at a sublethal concentration, 7.30 mgL^-1. Overall, we observed an increased activity of biotransformation and antioxidant enzymes, which reduced production of mitochondrial reactive oxygen species after 96 h exposure, as well as kept constant the mitochondrial respiration, Acetylcholinesterase activity and DNA damage. However, fish exposed to insecticide presented severe gill histopathological damage and increased expression of proto-oncogene ras. Taken together, the results suggest that, after four days of exposure to the Malathion, C. macropomum efficiently activates its defense mechanisms, suggesting that the basal response mechanisms are responsive. On the other hand, histopathologic damages evidenced the adverse effects of Malathion on fish, since it promoted gill necrosis and increased the expression of ras oncogene that is directly related to tumorigenesis events.

Steroid androgen 17 alpha methyltestosterone used in fish farming induces biochemical alterations in zebrafish adults

The 17 alpha methyltestosterone (MT) hormone is fed to Oreochromis niloticus larvae in fish farms with the purpose of inducing sex reversal. The aim of this study was to evaluate the toxicity and sub-lethality of MT (99.9% purity) and cMT (a commercial MT with 90% purity) in zebrafish (Danio rerio) adults, where the animals were exposed to concentrations of 0, 4, 23, 139, 833 and 5000 µg/L for 96 hours. Genotoxicity was evaluated by micronucleus test (MN), nuclear abnormalities (NA) and comet assay. A low genotoxic potential of MT was showed, inducing micronucleus, nuclear abnormalities and DNA damage in Danio rerio, depending on the use of MT or cMT, gender and tested concentrations. In the sub-lethality trials, there was a basal difference in the activity of the enzymatic biochemical markers for males and females, while the Glutatione S transferase (GST) activity decreased in all analyzed tissues, and for males the enzymatic activity decreased only in the intestine. Results suggest that MT has a toxic potential to fish because it alters enzymatic metabolic pathways and may pose a risk to the ecosystems.

Gene expression, genotoxicity, and physiological responses in an Amazonian fish, Colossoma macropomum (CUVIER 1818), exposed to Roundup® and subsequent acute hypoxia

Roundup® (RD) is a glyphosate-based herbicide used to control weeds in agriculture, and fishponds. In the Amazon, hypoxia is a natural phenomenon in flooded areas. Beyond the challenge of hypoxia, fish need to cope with the use of pesticides as RD that increases in the aquatic environment through the leaching of agricultural areas, and in aquaculture fish tanks. Thus, there is a need to better understand the combined effects of hypoxia and RD contamination for aquatic biota. The aim of this study was to investigate the effects of Roundup® (RD) and subsequent acute hypoxia in the gene expression, genotoxicity, histological and physiological responses of Colossoma macropomum. Fish were individually exposed to four different treatments during 96 h: normoxia (N), hypoxia (H), RD plus normoxia (NRD), and RD plus hypoxia (HRD) (RD concentration represents 75% of LC50 - nominal concentration 15 mg L-1 to C. macropomum). HRD fishes presented down-regulation of hif-1α gene and ras oncogene, while NRD fish presented overexpression of ras; no difference occurred in hif-1α gene expression in both normoxia treatments. The glutathione-S-transferase and catalase activities increased in HRD fish liver compared to NRD. Otherwise, there was no difference in lipoperoxidation (LPO) between all treatments. Genetic Damage Index, measured throughout comet assay in erythrocytes of all treatments, presented similar values, excepted by fish exposed to NRD. As regard as hypoxic exposure, hypoxic fish presented significantly lower values, compared to HRD fishes. An increase in liver histological injuries occurred in H and HRD fish groups. In conclusion, we may affirm that C. macropomum is sensitive concerning RD contamination and that this sensitivity increases when combined with hypoxia.

Long-term exposure of Daphnia magna to carbendazim: how it affects toxicity to another chemical or mixture

Aquatic organisms might be exposed episodically or continuously to chemicals for long-term periods throughout their life span. Pesticides are one example of widely used chemicals and thus represent a potential hazard to aquatic organisms. In addition, these chemicals may be present simultaneously in the environment or as pulses, being difficult to predict accurately how their joint effects will take place. Therefore, the aim of the present study was to investigate how Daphnia magna (clone k6) exposed throughout generations to a model pesticide (the fungicide carbendazim) would react upon an exposure to another chemical compound (triclosan) and to a mixture of both chemicals (carbendazim and triclosan). Responses of daphnids continuously exposed to carbendazim and kept in clean medium will be compared using immobilization tests and the comet assay (DNA integrity). The results showed that triclosan presented similar toxicity to daphnids exposed for 12 generations (F12) to carbendazim (similar 48-h-LC₅₀ values for immobilization data), when compared with daphnids kept in clean medium. However, at subcellular level, daphnids previously exposed to carbendazim for 12 generations (F12) showed different responses than those from clean medium, presenting a higher toxicity; a general higher percentage of DNA damage was observed, after exposure to a range of concentrations of triclosan and to the binary combination of triclosan + carbendazim. The patterns of toxicity observed for the binary mixture triclosan + carbendazim were generally similar for daphnids in clean medium and daphnids exposed to carbendazim, with a dose level deviation with antagonism observed at low doses of the chemical mixture for the immobilization data and a dose ratio deviation with synergism mainly caused by triclosan for DNA damage. With this study, we contributed to the knowledge on long-term induced effects of carbendazim exposure, while looking at the organismal sensitivity to another chemical (triclosan) and to a mixture of carbendazim and triclosan using lethality as an endpoint at the individual level and DNA damage as a subcellular endpoint.

Uranium mining wastes: The use of the Fish Embryo Acute Toxicity Test (FET) test to evaluate toxicity and risk of environmental discharge

Active and abandoned uranium mining sites often create environmentally problematic situations, since they cause the contamination of all environmental matrices (air, soil and water) with stable metals and radionuclides. Due to their cytotoxic, genotoxic and teratogenic properties, the exposure to these contaminants may cause several harmful effects in living organisms. The Fish Embryo Acute Toxicity Test (FET) test was employed to evaluate the genotoxic and teratogenic potential of mine liquid effluents and sludge elutriates from a deactivated uranium mine. The aims were: a) to determine the risk of discharge of such wastes in the environment; b) the effectiveness of the chemical treatment applied to the uranium mine water, which is a standard procedure generally applied to liquid effluents from uranium mines and mills, to reduce its toxicological potential; c) the suitability of the FET test for the evaluation the toxicity of such wastes and the added value of including the evaluation of genotoxicity. Results showed that through the FET test it was possible to determine that both elutriates and effluents are genotoxic and also that the mine effluent is teratogenic at low concentrations. Additionally, liquid effluents and sludge elutriates affect other parameters namely, growth and hatching and that water pH alone played an important role in the hatching process. The inclusion of genotoxicity evaluation in the FET test was crucial to prevent the underestimation of the risks posed by some of the tested effluents/elutriates. Finally, it was possible to conclude that care should be taken when using benchmark values calculated for specific stressors to evaluate the risk posed by uranium mining wastes to freshwater ecosystems, due to their chemical complexity.

The comet assay in Folsomia candida: A suitable approach to assess genotoxicity in collembolans

The present study shows the comet assay technique being successfully applied for the first time to one of the most widely used soil organisms in standardized ecotoxicological tests, Folsomia candida, providing a step forward in assessing the genotoxicity induced by xenobiotics. Because collembolans have a high content of chitin, a new methodology was developed in which the heads of the collembolans were separated from the rest of the body, allowing the hemolymph to leak out. This procedure allows the cells to be released, and after lysis the genetic material is available for the comet assay. Among other key procedures, the use of 30 organisms (20- to 22-d-old adults) per replicate and the correct amount of cells with genetic material (translated as 10 μL of suspension) applied on the agarose gel were determinants for the success of the results obtained. The methodology was validated by exposing F. candida to a representative metallic element (cadmium) and a representative of organophosphates, the insecticide dimethoate, for a shorter time period of 10 d, compared with the 28 d for the International Organization for Standardization 11267 method. Within this method, the relatively low percentage of DNA damage (30%) observed in controls and the significant increase in terms of percentage of DNA damage for almost all the concentrations of dimethoate and Cd (reaching 52% and 56% of damage in the highest concentrations, respectively) confirmed the genotoxic effect of both compounds and validated this technique. The comet assay proved to be a sensitive technique to detect DNA strand breaks in collembolans' cells. Environ Toxicol Chem 2017;36:2514-2520. © 2017 SETAC.

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

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

Multigenerational effects of carbendazim in Daphnia magna

Carbendazim is a fungicide largely used in agriculture as a plant protection product. As a result of agricultural runoffs, drainage, and leaching, it reaches surface waters at concentrations possibly hazardous to aquatic communities. Because of potential and continuous release of carbendazim to aquatic systems, long-term exposure to aquatic organisms should be addressed. To fill the knowledge gap, the present study evaluated the responses of multiple generations of Daphnia magna (clone K6) to an environmentally relevant concentration of carbendazim (5 μg/L). Twelve successive generations were evaluated, and the effects in these offspring were compared with those from a control population. Neonates' fitness was assessed through immobilization, reproduction, and feeding activity tests, along with the comet assay for in vivo DNA damage evaluation. Recovery from long-term exposure was also assessed. In the F5 generation, the results revealed that when daphnids were re-exposed to carbendazim, DNA damage was higher in daphnids continuously exposed to carbendazim than those from clean medium. After daphnids were moved to a clean medium, a low recovery potential was observed for DNA damage. Daphnids exposed continuously for 6 generations (F6) to carbendazim displayed an increase in feeding rates when re-exposed to carbendazim compared with F6 daphnids reared in clean medium. Continuous exposure of daphnids to carbendazim induced a significant increase in DNA damage from the F0 to the F12 generation. Deleterious effects of the multigenerational exposure to carbendazim were more prominent at a subcellular level (DNA damage) compared with the individual level. Environ Toxicol Chem 2017;36:383-394. © 2016 SETAC.

Ecotoxicity and genotoxicity of cadmium in different marine trophic levels

Cadmium ecotoxicity and genotoxicity was assessed in three representative species of different trophic levels of marine ecosystems - the calanoid copepod Acartia tonsa, the decapod shrimp, Palaemon varians and the pleuronectiform fish Solea senegalensis. Ecotoxicity endpoints assessed in this study were adult survival, hatching success and larval development ratio (LDR) for A. tonsa, survival of the first larval stage (zoea I) and post-larvae of P. varians, egg and larvae survival, as well as the presence of malformations in the larval stage of S. senegalensis. In vivo genotoxicity was assessed on adult A. tonsa, the larval and postlarval stage of P. varians and newly hatched larvae of S. senegalensis using the comet assay. Results showed that the highest sensitivity to cadmium is displayed by A. tonsa, with the most sensitive endpoint being the LDR of nauplii to copepodites. Sole eggs displayed the highest tolerance to cadmium compared to the other endpoints evaluated for all tested species. Recorded cadmium toxicity was (by increasing order): S. senegalensis eggs < P. varians post-larvae < P. varians zoea I < S. senegalensis larvae < A. tonsa eggs < A. tonsa LDR. DNA damage to all species exposed to cadmium increased with increasing concentrations. Overall, understanding cadmium chemical speciation is paramount to reliably evaluate the effects of this metal in marine ecosystems. Cadmium is genotoxic to all three species tested and therefore may differentially impact individuals and populations of marine taxa. As A. tonsa was the most sensitive species and occupies a lower trophic level, it is likely that cadmium contamination may trigger bottom-up cascading effects in marine trophic interactions.

Toxicity of tributyltin (TBT) to the freshwater planarian Schmidtea mediterranea

The freshwater planarian Schmidtea mediterranea, one of the best characterized animal models for regeneration research and developmental biology, is being recognised as a useful species for ecotoxicological studies. Sensitive endpoints related to planarians' behaviour and regeneration can be easily evaluated after exposure to environmental stressors. In this work the sensitivity of S. mediterranea to a gradient of environmentally relevant concentrations of TBT was studied using multiple endpoints like survival, locomotion, head regeneration and DNA damage. In addition, a feeding assay based on planarian's predatory behaviour was performed. Results indicated that TBT is toxic to planarians with LC50's of 1.87 μg L(-1) Sn and 1.31 μg L(-1) Sn at 48 h and 96 h of exposure respectively. Sub-lethal exposures to TBT significantly reduced locomotion and feeding, delayed head regeneration and caused DNA damage in planarians. The behavioural endpoints (feeding and locomotion) and head regeneration were the most sensitive parameters followed by DNA damage. Similar to other aquatic model organisms, S. mediterranea showed high sensitivity towards TBT exposure. Based on our results, and though further research is required concerning their sensitivity to other pollutants, the use of freshwater planarians as a model species in ecotoxicology is discussed.

Genotoxic potency of mercuric chloride in gill cells of marine gastropod Planaxis sulcatus using comet assay

In vivo and in vitro exposures were used to investigate the genotoxicity of mercuric chloride (HgCl2) to the marine snail, Planaxis sulcatus. The comet assay protocol was validated on gill cells exposed in vitro to hydrogen peroxide (H2O2, 0-50 μM). Snails were exposed in vivo for 96 h to HgCl2 (10, 20, 50, and 100 μg/l). Our results showed significant concentration-dependent increase in the tail DNA (TDNA) and olive tail moment (OTM) in exposed snails for all doses compared with controls. In vitro exposure to HgCl2 (10-100 μg/l) resulted in significantly higher values for TDNA at all concentrations. Our results showed that DNA damage increased in the gill cell with increasing exposure time. This study demonstrates the usefulness of comet assay for detection of DNA damage after exposure to HgCl2 and the sensitivity of marine snail P. sulcatus as a good candidate species for metal pollution.

Ecotoxicity and genotoxicity of a binary combination of triclosan and carbendazim to Daphnia magna

In the environment, chemical substances appear as complex mixtures and consequently organisms are exposed to a variety of chemicals from different sources (e.g. wastewater treatment plants, agriculture runoffs). When studying chemical mixtures, there are two conceptual models usually used to predict toxicity: the Independent Action (IA) and Concentration Addition (CA) models. However, deviations from these reference models can occur as synergism or antagonism, dose ratio or dose level dependency. The aim of the present study was to investigate the effects of triclosan and carbendazim, and their binary mixture to Daphnia magna. With this purpose, immobilisation, feeding inhibition, and reproduction were assessed as main ecotoxicity endpoints. In addition, in vivo genotoxicity of both chemicals was investigated using the comet assay. In the single exposure, carbendazim was more toxic to D. magna than triclosan. When daphnids were exposed to both single compounds, DNA damage was observed. Concerning mixture exposures, different endpoints followed different patterns of response, from additivity: IA model (feeding inhibition and reproduction data), to deviations that indicate interaction between chemicals inside the organism: dose level dependency (immobilisation data) and dose ratio dependency (DNA damage). This study showed that additivity does not rule the dose-effect relation in chemical mixtures of carbendazim and triclosan and interactions between both chemicals might induce generally higher toxicity than predicted based on single chemical exposures.

New ternary bipyridine–terpyridine copper(ii) complexes as self-activating chemical nucleases

New copper complexes with an impressive DNA cleaving ability in the absence of any exogenous oxidants or reductants.

Biomonitoring a human population inhabiting nearby a deactivated uranium mine

Environmental exposure to uranium and its daughter radionuclides, has been linked to several negative effects such as those related with important physiological processes, like hematopoiesis, and may also be associated with genotoxicity effects. Herein, genotoxic effects, immunotoxicity, trace elements and C reactive protein (CRP) analyses, were performed in peripheral blood samples collected from individuals of a population living near a deactivated uranium mine. C reactive protein analysis was performed to exclude candidates with active inflammatory processes from further evaluations. DNA damage and immunotoxicity (immunophenotyping and immune cell counts) were evaluated by comet assay and flow cytometry, respectively. Significant DNA damage was observed in the peripheral blood samples from volunteers living in the Cunha Baixa village. A significant decrease of NK and T lymphocytes counts were observed in the individuals from the Cunha Baixa village, when compared with individuals from the reference site. Uranium and manganese levels were significantly higher in the Cunha Baixa village inhabitants. On the other hand, zinc levels were significantly lower in those individuals when compared with the volunteers from the control village. Results suggest that inhabitants from Cunha Baixa have a higher risk of suffering from serious diseases such as cancer, since high DNA damages were observed in peripheral blood leukocytes and also decreased levels of NK and T cells, which play an essential role in the defense against tumor growth.

Metal bioaccumulation, genotoxicity and gene expression in the European wood mouse (Apodemus sylvaticus) inhabiting an abandoned uranium mining area

Genotoxic effects caused by the exposure to wastes containing metals and radionuclides were investigated in the European wood mice (Apodemus sylvaticus). The animals were captured in the surroundings of an abandoned uranium mining site. DNA damage was assessed by comet assay; gene expression and single nucleotide polymorphisms (SNPs) were assessed, respectively, by Real-Time PCR and melt curve analysis. The bioaccumulation of metals in the liver, kidney and bones was also determined to help clarify cause-effect relationships. Results confirmed the bioaccumulation of cadmium and uranium in organisms exposed to uranium mining wastes. P53 gene was found to be significantly up-regulated in the liver of those organisms and SNPs in the Rb gene were also detected in the kidney. Our results showed that uranium mining wastes caused serious DNA damage resulting in genomic instability, disclosed by the significant increase in DNA strand breaks and P53 gene expression disturbance. These effects can have severe consequences, since they may contribute for the emergence of serious genetic diseases. The fact that mice are often used as bioindicator species for the evaluation of risks of environmental exposure to humans, raises concerns on the risks for human populations living near uranium mining areas.

Transcriptional responses of cancer-related genes in turbot Scophthalmus maximus and mussels Mytilus edulis exposed to heavy fuel oil no. 6 and styrene

Recent spills in European waters have released polycyclic aromatic hydrocarbons, important components of heavy fuel oil, and the hydrocarbon styrene. Heavy fuel oil and styrene are classified as potentially genotoxic and carcinogenic. Here we investigate transcription of genes involved in cancer development in the liver of juvenile turbots and in the digestive gland of mussels exposed to heavy fuel oil and to styrene and after a recovery period. In turbot, oil produced a significant up-regulation of p53 and gadd45α after 14 days exposure. cyclin G1 was up-regulated after 7 days treatment with styrene. In mussels, ras was down-regulated in both treatments after the recovery periods. No mutations in ras hotspots were detected in exposed mussels. gadd45α was up-regulated after the recovery period of the styrene experiment. Overall, transcriptional responses differed in mussels compared to turbot. Turbot responded to hydrocarbon exposure by triggering cell cycle arrest (p53) and DNA repair (gadd45α).

Evaluation of the sensitivity of genotoxicity and cytotoxicity endpoints in earthworms exposed in situ to uranium mining wastes

Earthworms were exposed for 56 days to a contaminated soil from an abandoned uranium mine and to the natural reference soil LUFA 2.2. The exposure occurred in situ: the containers with contaminated soil were placed near the mine pit; the containers with reference soil were placed in a reference site. For the assessment of metals bioaccumulation, DNA damages, cell-to-cell variation in DNA content, Median Fluorescence Intensity (MFI), coelomocytes frequency and proliferation, organisms were sampled after 0, 1, 2, 7, 14 and 56 days of exposure. For the assessment of radionuclides bioaccumulation, animals were sampled after 0, 14 and 56 days of exposure. As for growth, organisms were sampled after 0, 14, 28 and 56 days of exposure. The reproduction assay was performed according to the OECD (2004) guideline. DNA damages were assessed by comet assay and flow cytometry was used to determine cell-to-cell variation in DNA content, Median Fluorescence Intensity (MFI), coelomocytes frequency and proliferation. Results have shown a myriad of effects in the organisms exposed to the contaminated soil, namely: the inhibition of reproduction, growth reduction, DNA damages, cytotoxicity, changes in eleocytes fluorescence intensity, coelomocytes proliferation and bioaccumulation of metals and radionuclides. Our results showed that the evaluation of genotoxicity and cytotoxicity endpoints, along with other parameters at an individual level in standard reproduction assays conducted in situ, are important to improve the risk assessment process of areas contaminated with uranium and other radioactive mining wastes.

Tissue-specific expression of p53 and ras genes in response to the environmental genotoxicant benzo(α)pyrene in marine mussels

Marine mussels can develop hemeic and gonadal neoplasia in the natural environment. Associated with these diseases are the tumor suppressor (TS) p53 and the proto-oncogene ras coded proteins, both of which are highly conserved among molluscs and vertebrates. We report, for the first time, tissue-specific expression analysis of p53 and ras genes in Mytilus edulis by means of quantitative RT-PCR. A tissue-specific response was observed after 6 and 12 days exposure to a sublethal concentration of a model Polycyclic Aromatic Hydrocarbon (PAH), benzo(α)pyrene (B(α)P). This sublethal concentration (56 μg/L) was selected based on an integrated biomarker analysis carried out prior to gene expression analysis, which included a 'clearance rate' assay, histopathological analysis, and DNA strand break measurements. The results indicated that the selected concentration of B(α)P can lead to the induction of DNA strand breaks, tissue damage, and expression of tumor-regulating genes. Both p53 and ras are expressed in a tissue-specific manner, which collaborate with tissue-specific function in response to genotoxic stress. The integrated biological responses in Mytilus edulis strengthen the use of this organism to investigate the fundamental mechanism of development of malignancy in invertebrate which could be translated to other organisms including humans.

Genotoxic endpoints in the earthworms sub-lethal assay to evaluate natural soils contaminated by metals and radionuclides

Eisenia andrei was exposed, for 56 days, to a contaminated soil from an abandoned uranium mine and to the natural reference soil LUFA 2.2. The organisms were sampled after 0, 1, 2, 7, 14 and 56 days of exposure, to assess metals bioaccumulation, coelomocytes DNA integrity and cytotoxicity. Radionuclides bioaccumulation and growth were also determined at 0 h, 14 and 56 days of exposure. Results have shown the bioaccumulation of metals and radionuclides, as well as, growth reduction, DNA damages and cytotoxicity in earthworms exposed to contaminated soil. The usefulness of the comet assay and flow cytometry, to evaluate the toxicity of contaminants such as metals and radionuclides in earthworms are herein reported. We also demonstrated that DNA strand breakage and immune cells frequency are important endpoints to be employed in the earthworm reproduction assay, for the evaluation of soil geno and cytotoxicity, as part of the risk assessment of contaminated areas. This is the first study that integrates DNA damage and cytotoxicity evaluation, growth and bioaccumulation of metals and radionuclides in a sub lethal assay, for earthworms exposed to soil contaminated with metals and radionuclides.

Biomarkers as a tool to assess effects of chromium (VI): comparison of responses in zebrafish early life stages and adults

The present work aims to compare the sensitivity of embryos and adult zebrafish to chromium (VI) (as potassium dichromate) focusing on biomarkers (cholinesterase, glutathione S-transferase and lactate dehydrogenase) as endpoints. Zebrafish eggs showed less sensitivity to Cr (VI) (96 h-LC50=145.7 mg/L) than adults (96 h-LC50=39.4 mg/L) probably due to the protective action of the chorion. However, biomarkers were much more responsive in larvae than in adults and gave clear indications about Cr (VI) mode of action: it seems to be neurotoxic (inhibited cholinesterase), to inhibit glutathione S-transferase activity and to interfere with cellular metabolic activity (changes in lactate dehydrogenase activity) in larvae. In adults, only glutathione S-transferase was responsive, showing a clear inhibition. The responsiveness of the analyzed biomarkers in larvae reinforces the idea of the usefulness of early life stage assays in the assessment of chemicals effects. Moreover, early life stage assays also contributed with relevant information regarding anomalies in larvae development and behavior. Further research should focus on the use of biomarkers to assess long term effects which are ecologically more relevant.

In vivo genotoxicity and stress defences in three flatfish species exposed to CuSO4

We have used the comet assay to analyse, after 3h, 24h and 6 days, the genotoxic effect in vivo of applying a single intraperitoneal injection of CuSO4, at a concentration of 2mg/kg, to adult specimens of Solea senegalensis, Dicologlossa cuneata and Scophthalmus rhombus. Metals content (Cu, Zn and Cd) in liver was also measured. The activity of key stress defences was evaluated by analysing antioxidant enzyme activity (catalase (CAT), superoxide dismutase (SOD), total glutathione peroxidase (t-GPX), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH)), metallothionein (MT) and heat shock proteins (HSP70 and HSP60). The results show that CuSO4 intake generates high and cumulative levels of genotoxicity throughout the 6 days in all 3 species. After 6 days, metals content detected in specimens showed significant differences from controls. Inter-species differences were detected in enzyme activity (P<0.05). A clear response to CuSO4 was detected only in S. rhombus, with an increase of MT and a decrease of HSPs. Variations in antioxidant defence levels and their comparative responses to the stress-inducing agent are discussed.

Are endocrine disruptors among the causes of the deterioration of aquatic biodiversity?

Exposure to environmental pollutants such as endocrine-disrupting compounds (EDCs) is now taken into account to explain partially the biodiversity decline of aquatic ecosystems. Much research has demonstrated that EDCs can adversely affect the endocrine system, reproductive health, and immune function in aquatic species. These toxicological effects include 1) interference with normal hormonal synthesis, release, and transport, 2) impairment of growth, development, and gonadal maturation, and 3) increased sensitivity to environmental stressors. Recent studies also have confirmed that EDCs have carcinogenic and mutagenic potential. In essence, these changes in physiological and biochemical parameters reflect, to some extent, some phenotypic characteristics of the deterioration of aquatic biodiversity. At present, evidence at the molecular level shows that exposure to EDCs can trigger genotoxicity, such as DNA damage, and can reduce genetic diversity. Field studies have also provided more direct evidence that EDCs contribute to the population decrease and biodiversity decline. Evolutionary toxicology and multigenerational toxicity tests have further demonstrated that EDCs can damage an organism's offspring and eventually likely lead to loss of evolutionary potential. Taken together, these results provide some basis for understanding the relationship between variety deterioration and EDC exposure. It is conceivable that there is a causal association between EDC exposure and variety deterioration of aquatic organisms.

Genetic, biochemical, and individual responses of the teleost fish Carassius auratus to uranium

Carassius auratus were exposed for 96 h to different concentrations of uranyl nitrate (corresponding to 0, 100, 450, and 2,025 microg U L(-1)) and killed after different postexposure periods (0, 48, and 96 h) to assess uranium bioaccumulation, peroxisome proliferation (catalase [CAT]), lipid peroxidation (thiobarbituric acid reactive substances [TBARS]), and DNA integrity in erythrocytes (comet assay). In addition, feeding behaviour was recorded as a general response to toxicant exposure. Results provided evidence of uranium bioaccumulation in muscle of C. auratus after exposure to the highest concentrations (450 and 2,025 microg U L(-1)). This tissue was able to depurate uranium to control levels 96 h after exposure ceased. However, no perturbations in feeding behaviour or cell damage were observed in the tested organisms, except for the apparent irreversible inhibition of CAT activity immediately after exposure in the highest concentration tested. Data on DNA integrity (comets) showed that waterborne uranium exposure was able to induce genotoxicity in C. auratus erythrocytes because fish exposed to all concentrations exhibited higher DNA damage than controls 96 h after exposure. No DNA damage repair was apparent throughout the postexposure period, which was contrary to a recovery scenario. This experiment provides evidence of uranium's ability to induce physiologic impairment and genotoxicity in freshwater fish at environmentally relevant concentrations.

Anchoring novel molecular biomarker responses to traditional responses in fish exposed to environmental contamination

The responses of Dicentrarchus labrax and Liza aurata to aquatic pollution were assessed in a contaminated coastal lagoon, using both traditional and novel biomarkers combined. DNA damage, assessed by comet assay, was higher in both fish species from the contaminated sites, whereas levels of cytochrome P450 1A1 gene expression were not significantly altered. The liver histopathological analysis also revealed significant lesions in fish from contaminated sites. Alterations in ras and xpf genes were analysed and additional pollutant-responsive genes were identified. While no alterations were found in ras gene, a downregulation of xpf gene was observed in D. labrax from a contaminated site. Suppression subtractive hybridization applied to D. labrax collected at a contaminated site, revealed altered expression in genes involved in energy metabolism, immune system activity and antioxidant response. The approach and results reported herein demonstrate the utility of anchoring traditional biomarker responses alongside novel biomarker responses.

The effects of contaminants in European eel: a review

European eel (Anguilla anguilla (L.)) stocks are in decline in most of their geographical distribution and their status is considered below safe biological limits. Recently, there is an increasing awareness that spawner quality might be an essential element in the decline of the species since pollution by bioaccumulating chemical substances may have a large impact on the reproduction success of the eel. This review gives an overview of the literature on the effects of contaminants on the European eel and on the consequences on the biology and fitness of the eel in order to document the role of pollution in its decline. A variety of contaminants have been found to affect the eel. These contaminants may cause disturbance of the immune system, the reproduction system, the nervous system and the endocrine system and effects were reported on several levels of biological organization, from subcellular, organ, individual up to even population level. More extensive research is needed in order to evaluate how pollutants are detrimental to eel populations. Getting a comprehensive overview of the quality (including contamination levels, biomarker responses, lipid content and condition) of the silver eel population all over Europe seems to be an essential and urgent objective for the European eel management.

Transcript profiling and DNA damage in the European eel (Anguilla anguilla L.) exposed to 7,12-dimethylbenz[a]anthracene

The molecular responses induced during and after an acute exposure to 7,12-dimethylbenz[a]anthracene (DMBA) were analysed in liver, gill and blood cells of juvenile Anguilla anguilla with the aim of developing molecular biomarkers of environmental PAH pollution. Changes in the mRNA expression levels of the cell cycle checkpoint-related rad1 gene and the mRNAs of differentially expressed genes by suppression subtractive hybridization (SSH) were analysed in the liver, and related to well-established biomarkers: cyp1A1 mRNA expression and assessment of the DNA integrity using the comet assay and flow cytometry. DMBA exposure resulted in increased cyp1A1 mRNA levels, suggesting that cyp1A1 might be involved in the metabolism of DMBA. Global DNA damage, detected by the comet assay, was observed in the three tissues analysed but only blood cells showed chromosomal lesions as analysed by flow cytometry. Although DNA damage was found in the liver, no induction in rad1 gene was observed in this organ. The global SSH approach revealed that mRNAs of genes related to xenobiotic metabolism, immune processes and cytoskeleton dynamics were differentially expressed in DMBA-exposed eel livers, highlighting the complexity in the response observed in fish exposed to a genotoxic agent and providing directions for new biomarker development.

Effect of broccoli (Brassica oleracea) and its phytochemical sulforaphane in balanced diets on the detoxification enzymes levels of tilapia (Oreochromis niloticus) exposed to a carcinogenic and mutagenic pollutant

Tilapia fish (Oreochromis niloticus) were fed with enriched diets containing broccoli and its phytochemical sulforaphane over 30 d. The levels of cytochrome P450, superoxide dismutase, catalase, lipid peroxidation and glutathione-S-transferase activities were measured. Basal value of cytochrome P450 activity was significantly increased as consequence of the broccoli and sulforaphane enriched diets, while no statistically significant changes were found on catalase and lipid peroxidation activities. After benzo(a)pyrene exposure, the cytochrome P450 activity increased to higher levels in the fish feed with broccoli and sulforaphane when compared with the control fish. Activities of antioxidant enzymes also varied but without significant difference with the control fish. Supported by the lower concentrations of BaP metabolites in bile from fish fed with broccoli or with sulforaphane enriched diets (indicating a better xenobiotic elimination) the cytochrome P450 induction could be considered beneficial for the detoxification because this transformation is the first step for PAH elimination by the phase II system. The protection of aquaculture organism against pollution effects by designing special diets able to modulate the enzymes involved in the phase-I and phase-II detoxification mechanism are discussed.

Ras gene in marine mussels: a molecular level response to petrochemical exposure

Mussels are susceptible to numerous toxicants and are often employed as bioindicators. This study investigated the status of the ras proto-oncogene in Mytilus galloprovincialis following petrochemical exposure. A M. galloprovincialis homologue of the vertebrate ras gene was isolated, showing conserved sequence in regions of functional importance and a high incidence of polymorphic variation. Mutational damage was investigated in mussels chronically exposed to the water-accommodated fraction of #4 fuel-oil (WAF), and in mussels collected along the NW coast of Portugal in sites with different levels of petrochemical contamination. A ras gene point mutation was identified in the codon 35 of one individual exposed to 12.5% WAF. No mutations were detected in mussels from the WAF control or environmental samples. This represents the first report of a ras gene mutation, experimentally-induced by petrochemical exposure, in an invertebrate species.